Open File Report No. 79-2 EVALUATION of the MINERAL RESOURCES of the PIPELINE CORRIDOR PHASES I and I1

Home , Geology of Yukon, Gold mining in Alaska, Talkeetna Formation

Evaluation of the mineral resources of the pipeline corridor, phases i and ii

Item Type Technical Report

Authors Robinson, M.S. and Metz, P.A.

Citation Robinson, M.S. and Metz, P.A., 1979, Evaluation of the mineral resources of the pipeline corridor, phases i and ii: University of Alaska Mineral Industry Research Laboratory Open File 79-2, 272 p.

Publisher University of Alaska Mineral Industry Research Laboratory

Download date 11/10/2021 10:10:17

Link to Item http://hdl.handle.net/11122/2135 Open File Report No. 79-2 EVALUATION OF THE MINERAL RESOURCES OF THE PIPELINE CORRIDOR PHASES I AND I1

M.S. Robinson G P.A. Metz 1979 EVALUATION OF THE MINERAL RESOURCES OF THE PIPELINE CORRIDOR

PHASE I AND I1

Final Report

Submitted. to U.S. Bureau of Mines Alaska Fie1 d Operations Center Juneau, A1 aska

Grant No. 601 66180 June 1, 1979

Submitted by Mark S. Robinson and Paul A:Metz Mineral Industry Research Laboratory University of A1 as ka Fairbanks, Alaska 99701 CONTENTS Page Introduction 1 Summary and Conclusions .

I_. . I SectionI. Geology and Mineral Resources of the Valdez .-.7 I ::: quadrangle Previous Investigations 11 .,- Regional Geology and Petrology . 11 Structural Geology 20 Geochemistry 21 Mining Activity and Economic Geology 23 References Cited 26 Bibliography 2 9 Section 11. Geology and Mineral Resources of the Gul kana quadrangle Previous Investigations Regional Geology and Petrology Structural Geology Geoc hemi s try Mining Activity and Economic Geology References Cited Bi bl iography Section 111. Geology and Mineral Resources of the Mt. Hayes quadpang1 e ------Previous Investigations 44 Regional Geology and Petrology 45 Structural Geology 52 Geochemi stry 53 Mining Activity and Economic Geology 55 References Cited - 60 Bibliography 64 .Section IV. Geology and Mineral Resources of the Big Delta quadrangle Previous Investigations 6 9 Regional Geology and Petrology 69 Structural Geology 7 0 . Geocherni stry 7 1 Mining Activity and Economic Geology 71 References Cited 74 Bi bl iography 7 5 Page

Section V. Geology and Mineral Resources of the Fairbanks quadrangle Previous Investigations Regional Geology and Petrology Structural Geology Geochemistry Mining Activity and Economic Geology References Cited Bi bl iography Section VI. Geology and Mineral Resources of the Livengood quadrangl e Previous Investigations 95 Regional Geology and Petrology 95 Structural Geology 1 00 Geochemistry 1 02 Mining Activity and Economic Geology 1 04 References Cited 110 Bi bl iography ,112 -- . . Section VII. Geology and Mineral Resources of the Tanana -_.p ad quadrangl e L. Previous Investigations Regional Geology and Petrology Structural -Geo1ogy Geochemistry - -- - Mining Activity and Economic Geology References Cited Bi b1 iography Section VIII. Geology and Mineral Resources of the Bettles quadrangle Previous Investigations 125 Regional Geology and Petrology 125 Structural Geology 127 I , . Geochemistry 1 28 Mining Activity and Economic Geology - 129 References Cited 131 I Bi bl iography 132 i,

!- I t . . iii 1r Page

Section IX. Geology and Mineral Resources of the Wiseman quadrangle 4- Previous Investigations 134 Regional Geology and Petrology 134 Structural Geology 136 Geochemistry 137 Mining Activity and Economic Geology 137 References Cited '1 40 Bi bl iography 142 Sections X. Geology and Mineral Resources of the Chandalar quadrangle Previous Investigations Regional Geology and Petrology Structural Geology Geochemistry Mining Activity and Economic Geology References Cited Bi bl iography Section XI. Geology and Mineral Resources of the Philip Smith Mountains quadrangle Previous Investigations 156 Regional Geology and Petrology 157 Structural. Geo1 ogy 166 Geochemistry 167 Mining Activity and Economic Geology 169 References Cited 173 Bi b1 iography 175 Section XII. Geology and Mineral Resources of the Sagavanirkto k quadrangle Previous Investigations 177 Regional Geology and Petrology 178 Structural Geology 185 r.' Geoc hemi s try

,..I .I Mining Activity and Economic Geology 186 References Cited 189 Bibl iography 190 - I ! 5 List of Tables Page j: j: - k- Tab1 e 1. Val dez Quadrangle; Rock Sarnpl e Descriptions 193 - I? -: and Trace Element Concentrations

,?a ,?a 1;: 1;: Tab1 e 2. Val dez Quadrangle ; Stream Sediment Sampl e 195 . Trace El ement Concentrations i;;i- t., Table 3. MIRL Rock Samples, Chugach Terrane, 1976, 196 1eve1 s of Detection and Threshold Val ues / ma- 1.; 1.; - , -,' Table 4. MIRL Stream Sediment Samples, Chugach Terrane, 197 1976, Levels of Detection and Threshold Values 1; 1; Table 5. Gul kana Quadrangle; Rock Sample Descriptions and 1 98 , - Trace El ement Concentrations

I.'. . i .'. Table 6. MIRL Rock Samples, Amphi theatre Terrane, 1976, 200 9.. I,<. ,. ,., Levels of Detection and Threshold Values

Tab1 e 7. Mt. Hayes Quadrangle; Rock Sampl e Descri ptions 201 . and Trace Element Concentrations Table 8. Mt. Hayes Quadrangle; Stream Sediment Sample, 204 Trace Element Concentrations Table 9. MIRL Rock Samples, Birch Creek Terrane, 1976, 205 Levels of Detection and Threshold Values Table 10. MIRL Stream Sediment Samples, Birch Creek Terrane, 206 1976, Levels of Detection and Threshold Values Table 11. MIRL Rock Samples, Amphitheatre Terrane, 1976, 207 Level s of Detection and Thresh01 d Values I i Table 12. Big Delta quadrangle; Rock Sample Descriptions 208 and Trace Element Concentrations - Table 13. Big Delta Quadrangle; Stream Sediment Sample 209 1, Trace Element Concentrations Table 14. MIRL Rock Samples, Birch Creek Terrane, 1976, 21 0 I.L-' Levels of Detection and Threshold Values - . . Table 15. MIRL Stream Sediment Samples, Birch Creek Terrane, 21 1 1976, Levels of Detection and Threshold Values List of Tables Page

Table 16. Fairbanks Quadrangle; dock Sample Descriptions, - 212 and Trace El ement Concentrations Table 17. MIRL Rock Samples, Birch Creek Terrane, 1976, 21 4 Levels of Detection and Threshold Values Tab1 e 18. Livengood Quadrangle; Rock Sample Descriptions, 21 5 -__and Trace Element Concentrations Table 19. MIRL Rock Samples, Birch Creek Terrane, 1976, 230 Levels of Detection and Threshol d Values Table 20. MIRL Rock Samples, Rampart Terrane, 1976 231 Levels of Detection and Threshold Values Tab1 e 21. Tanana Quadrangle; Rock Sampl e Descriptions and 232 Trace Element Concentrations Tabl e 22. Tanana Quadrangle; Stream Sediment Sample Trace Element Concentrations Table 23. MIRL Rock Samples, Kanuti Terrane, 1976, Levels of Detection and Threshol d Values Table 24. MIRL Stream Sediment Samples, Kanuti Terrane, 1976, 23 5 Level s of Detection and Threshol d Val ues Table 25. Bettles Quadrangle; Rock Sample Descriptions and 236 Trace Element Concentrations Table 26. Bettles Quadrangle; Stream Sediment Sample Trace Element Concentrations Table 27. MIRL Rock Samples, Kanuti Terrane, 1976, 239 Levels of Detection and Threshold Values - Table 28. MIRL Stream Sediment Samples, Kanuti Terrane, 1976, 240 Levels of Detection and Threshold Values Table 29. Wf seman Quadrangle; Rock Sample Descriptions and 241 Trace El ement Concentrations Table 30. Wiseman Quadrangle; Stream Sediment Sample 243 Trace El ement Concentrations List of Tables Page

Table 31. MIRL Rock Samples, Brooks Range Terrane, 1976, 244 Levels of Detection and Threshold Values - Table 32. MIRL Stream Sediment Samples, Brooks Range Terrane, 245 1976, Levels of Detection and Threshol d Values Table 33. MIRL Rock Samples, Brooks Range Terrane, 1977,, 246 Level s of Detecti on and Threshold Values ,/ ,-- Table 34. MIRL Stream Sediment Samples, Brooks Range Terrane, 247 1977, Levels of Detection and Threshold Values Table 35. Chandalar Quadrang1 e; Rock Sample Descriptions and 248 Trace Element Concentrations Table 36. Chandalar Quadrangle; Stream Sediment Sample 249 Trace El ement Concentrations Table 37. MIRL Rock Samples, Brooks Range Terrane, 1976, 250 Levels of Detection and Threshold Values Table 38. MIRL Stream Sediment Samples, Brooks Range Terrane, 251 1976, Levels of Detection and Threshold Values Tab1 e 39. MIRL Rock Samples, Brooks Range Terrane, 1977, 252 Levels of Detection and Threshold Val ues Table 40. MIRL stream Sediment Samples, Brooks Range Terrane, 253 1977, Levels -of- Detection and Threshol d Values Table 41. Philip Smith Mountains Quadrangle; Rock Sample 254 Descriptions and Trace Element Concentrations Tab1 e 42. Phi 1ip Smith Mountains Quadrangle; Stream Sediment Sampl e Trace El emen t Concentrations r - 258 I? . Table 43. Philip Smith Mountains Quadrangle; U.S.G.S. Stream Sediment Sample Trace El ement Concentrations Table 44. U.S.G.S. Stream Sediment Samples, Brooks Range 260 Terrane, Levels of Detection and Threshol d Values Table 45. MIRL Stream Sediment Samples, Brooks Range Terrane, 261 1 i: 1977, Levels of Detection and Thresh01 d Values List of Tables Page

Tab1 e 46. MIRL Rock Samples, Brooks Range Terrane, 1977, 262 Levels of Detection and Thresh01 d Values Table 47. MIRL Stream sediment' Samples, Brooks Range Terrane, 263 . 7976, Levels of Detection and Threshold Values Table 48.' MIRL Rock samples, Brooks Range Terrane, 1976, 264 -_Level s of Detection and Threshold Values ..,

Summary and ~onclusi ons

The 800 mi 1e 1ong trans-A1 as ka pipe1 ine crosses. fourteen of . the 1 :250,000 U. S. Geological Survey quadrangles . Accofding to the U.S. Bureau of Land Management, Land Status Map, dqted March 1974, the Federal pipe1 ine corridor includes approximately 7500 square mi 1es. The pipe1 ine transects most of the. major geologic features of south central, interior and northern Alaska. From Valdez to Prudhoe Bay, the pipe1 ine crosses the following physiographic and structural features: ,-

1. Chugach Mountains ' 2. Copper River Basin 3. Alaska Range 4. Middle Tanana Basin 5. Yukon Tanana Uplands 6. Yukon Basin 7. Brooks Range 8. North Slope Basin The general geology of the Pipe1 ine Corridor is summarized by the individual 1 :250,000 quadrangles. Each quadrangle description includes the foll owing information: 1 ) previous investigations,

2) regional eo1 ogy and petrology, ' 3) structural geology, 4) geochemistry, 53 mining activity and economic geology, 6) references cited, 7) bi bl iography. Several geologic terranes were defined in this investigation to facilitate the analysis of th& geological and geochemical data. These terranes were defined on the basis of similarities in the rock type, age, and structural form of the major rock units. From-south to north these terranes are: 1. Chugach 4. Rampart 2. Amphitheatre 5. Kanuti 3. Birch Creek 6. Brooks Range Although these terranes may be congruent in part with metamorphic be1 ts and physiographic provinces prey i ously defined, - they shoul-d not be confused with these other subdivisions. The terranes are named for major defined stratigraphic or physiographic units. The Chugach terrane extends from Valdez to the Border Ranges fault; the Amphi- theater terrane from the Border Ranges fault to the Denali Fault; the Birch Creek from the Denali Fault to Washington Creek; the Rampart from Washington Creek to the Ray River; the Kanuti from the Ray River to the Jim River, and the Brooks Range from the Jim River to Galbraith Lake. The major geochemi ca1 sampl i ng for this examination terminated at Galbrai th Lake therefore no terrane was established for the North Slope Basin.

The Chugach terrane is composed primarily of metamorphosed sedimentary and volcanic rocks, principal ly greenstones, of Cretaceous age. The Amphitheater terrane is dominated by mafic y~lcanicand fel sic igneous rocks of various compositions. ,The .igneous rocks are interbedded with and intrude sedimentary rocks and the entire sequence . is metamorphosed in part. Rocks of the Birch Creek terrane are primarily Yukon-Tanana Uplands Schist. The dominant rock types include; mica schists, quartz mica schist, micaceous quartzites, and gneisses of various compositions. The Rampart terrane consists of Paleozoic, principal 1y Permian, sedimentary zind maf ic igneous rocks. The Kanuti terrane is the most heterogeneous of the terranes and includes upper Precambrian(?) or 1ower Paleozoic metamorphic rocks and Paleozoic and Mesozoic sedimentary and vo1 canic rocks. Maf i c- u 1tramafic complexes and 1arge, fel sic plutonic complexes a1so occur in the Kanuti terrane. The Brooks Range terrane contains a wide variety .of rock types that include; medidm-grade metamorphic rocks, conglomerates, sandstones, shales and 1imestones of various compositions. Rock and stream sediment samples were grouped by terrane and the sample means, variances and standard deviations were cal- cul ated .for each element analyzed. Anomalies were defined as those elemental values that were greater than 1.645 standard deviations from the mean. The sample data and statistical reduction are included in Appendix A to this report. A simplified one-way analysis of variance was done on the sample data in an effort to determine if there is a significant difference in the variances of the concentrations of the trace elements between adjacent terranes. F-statistics were calculated for each of the 42 elements that were analyzed for. Using a hypothesis'-that there is no difference in the variance between terranes, it was found that the ratio of the variances of several of the elements exceeded the crit'ical value of the F-statistic and therefore it has been shown that there is a , difference in the variance of several elements. The following table summarizes the F-statistic test results and indicates which elements show a difference in their variances. Chugach terrane Rampart terrane Ca,Fe,K,Mg,Mn,Na,Ti Ca,K,Mn,Na,Ti Amphi theater terrane Kanut i terrane A1 ,Ca,Fe,Mg,Na,Ti Ca,K,Mg,Mn,Na,Ti Birch Creek terrane Brooks Range terrane Ca,Fe,K,Mg,Mn,Na The F-statistic test is somewhat misleading .in that it tests only for a difference in the variance, and not necessarily a difference in the mean value of the concentrations in a particular terrane. TO illustrate the misleading nature of results of the F-statistic, one can examine the threshold values for the various elements in different terranes. The following tab1 e i1 lustrates the problem quite we1 1: Chugach terrane* Amphi theater terrane* thresh01 d values threshold values /, Confidence 1 evel s Conf i dence 1evei s Element Element 'm

*Rock sample threshold values from Table 3 and Table 11, Appendix A.

By examining the figures in the above table, it can be seen that there is a difference in the mean value of the concentrations between the two terranes for these elements, and differences between other elements also occur. The reason that the F-statistic was not sensitive to the differences in mean value concentrations is that although one terrane may have a higher or lower mean trace element concentration, the variabi7ity of the trace element content is low. Sample descriptions, trace element l evel s of detection, and threshold values for samples collected during this study may be found in Appendix A to this report. The threshold values for the 90%, 95% and 98% confidence intervals were derived from a statistical analysis of the raw geochemical data. Sample means, variances and standard deviations were calculated at the arithmetic mean plus 1.645 x standard deviation, 2.0 x standard deviation, and 2.33 x standard deviation for the 90%, 95%, and 98% confidence intervals respectively. It should be noted that sample analyses from the 1976 and 1977 field seasons have different l evel s of detection and therefore may not -be cornpatable. Each years' geochemical analyses were treated as separate data sets and the anomalous concentrations in Appendix A represent .va7ues at the 90%, 95%, and 98% confidence. levels of each data set. 524 of the 1,196 samples collected contain weakly anomalous, anomalous, and strongly anomalous concentrations in at least one element, and many of the anomalous samples were anomalous in several 'elements. The fo7lowing is a tabulation of the number of samples from within and without the pipeline corridor from each terrane and the number of samples with one or more anomalous elements. . - 1. Chugach a. Total number of samples 70 b. Number of anomalous samples 28 2. Amphi theatre a. Total number of samples 89 b. Number of anomalous samples 23 3. Birch Creek a. Total number of samples 186 b. Number of anomalous .84 4. Rampart a. Total number of samples 301 b. Number of anomalous samples 120 5. Kanuti \ '\. a. Total number of samples . 130 b. Number of anomalous samples 67 6. Brooks Rmge a. Total number of 'samples 420 b. Number of anomalous samples 202

The known mineral occurrences as defined by E.H. Cobb of the U.S. Geological Survey, and all of the mineral occurrences found during this study in the pipeline corridor have been plotted on the base maps of each of the 1 :63,360 quadrangles. Mineral deposit information on each occurrence has been collected and entered in the U. S. Bureau of Mines Mineral Availability System(MAS) format and can be found in Appendix B to this report.

According to E.H. Cobb, the following mineral resources have been identified in the past in the pipeline corridor: 1. Antimony 8. Molybdenum 2. Bismuth 9.. Nickel 3. Chromium 10. Nuclear fuels (uranium, thorium) 4. Clay 1.7. Phosphste 5. Coal 12. Silver 6. Gold 13 .' Tungsten 7. Lead 14. Zinc The following mineral resources have been identified by M. I. R. L. personnel during the current study: 1. Antimony 6. Lead 2. Barite 7. Molybdenum - 3. Chromium 8. Nickel 4. Coal 9. Phosphate 5. Copper 10.. Zinc No mineral deposits of obvious economic significance were found fn the pipeline corridor during the current study, however, several mineral occurrences that were found during field work indicate that some rock units in the corridor and trending through the corridor have high mineral potential and may contain significant mineral resources. The commodities that have been produced in the study - area include antimony, coal, copper, gold, sand and gravel and silver. The geologic potential for future production can be qualitatively estimated by the examination of the geologic environments and corresponding rock units that are found in the corridor. There is great diversity of rock types and geologic environments along the pipe1 ine route. Most geologic time periods from the upper Precambrian to the Tertiary are represented in the stratigraphic record. -- --- Stanton (1972) and others have developed a number of ore mineral and rock associations which relate mineral deposits to the rocks which enclose or include them. Some of these associations not only define the type of rocks that enclosed a particular type of ore but in some cases the associations can be limited to specific periods of geologic time. These well defined tectonic and depositional - environmental associations can then be util i zed in both regional exploration and site specific eval uations of mineral occurrences. With the exception of the sedimentary iron and manganese association, all the major ore associations of Stanton (1972) are found within the study area. Examples of these associations are given in Table I. Not all of the ore mineral associations are equally distributed through geologic time, therefore depending on the age and type of rscks that occur, some mineral commodities will not have the same probability of occurring as others. TABLE I Known Rock and. Ore Mineral Associations in and along the pipe1 ine corridor Ore Associations (after Stanton, 1972) -- I. Ores in Igneous Rocks Ores of Mafic and Ultramafic Association: a) Bernard Mountain chromi te occurrence, Val dez quadrangle b) Caribou Mountain chromi te and asbestos occurrences, Bettl e quadrangle ,-- Ores of Felsic Association: a) Wi7 bur Creek copper porphyry occurrence, Livengood quadrangle . b) Hess Creek copper porphyry occurrence, Livengood quadrangle 11. Stratiform sulfides of marine and marine- . . volcanic association a) Midas Copper Mine(?), Valdez quadrangle b) Wi 1low Mountain copper occurrence,

Valdez quadrangle ' c) Hogan ' s Hi11 copper occurrence, Gul kana quadrangle !. d) Barite occurrences of the Atigun River area, Philip Smith Mountains quadrangle 111. Ores of Vein Association a) Gold-quartz veins of the Valdez district, Val dez quadrangl e b) Gold-quartz veins of the Mt. Tiekel area, Val dez quadrangl e c) Gold-quartz veins of the Gunnysack Creek area, Mt. Hayes quadrangle d) Gold-quartz veins of the Tenderfoot district, Big Del ta quadrangl e e) Gold-quartz and base metal sulfide veins of the Pedro Dome-Cl eary Summit area, Livengood quadrangl e f) Base metal sulfide veins of the Shorty Creek area, Livengood quadrangl e . g) Base metal veins of the Wiseman area, Wiseman quadrangle -. -.. IV. Ores of Sedimentary Affi 1iation Placer Deposits

a) Go1 d placer deposits of the Val dez district, Val dez quadrangle b) Gold placers of the Tenderfoot district, Big Delta quadrangle c) Gold placers of the Pedro Dome-Cleary Summit area, Fairbanks and Livengood quadrangles d) Gold placers of the Livengood area, . Livengood quadrangle e) Gold placers of the Niseman area, Wi seman quadrangle V; Ores of. Metamorphic Affi 1i ation a) Di ssemi na ted sulfide occurrence near Wiseman, Wiseman quadrangle b) Contact metamorphic tungsten occurrences near Gilmore Dome, Fairbanks quadrangle

The geologic potential for future production may also be estimated in a semi-quantitative manner.. Appendix B indicates that there are approximately 150 claim groups or prospects within the pipeline corridor. In addition, this examination has delineated 50 additional mineral occurrences. If the number of occurrences that trend into the corridor are added to this figure, there are over 400 mineral occurrences in or approximate to the study area. Bailey (1964) estimates that the discovery of a single ore body in western Canada in 1964 required the examination of at least 461 prospects. These estimates are based solely on the geotechnical and economic feasibility of a mining operation. The number of mineral' occurrences within the study area is approaching this figure, thus we might expect one of these occurrences to become a viable mining - operation all other things being equal to Bailey's model. However, it should be noted that most of the mineral occurrences in the pipe1 ine - corridor are occurrences or geochemical anomalies and are not necessarily prospects or ore bodies. This estimate does not indicate which mineral occurrences or even which commodities may be produced. There are many factors that will affect the economic via'bility of a mining operation within the study area, such as supply and demand of the various commodities, the avai labi 1i ty of transportation and energy, the final classification of the land, and the levels of state mining taxation. These 'variables are beyond the scope of this investigation. Finally, we may compare historic productions in the rest of the world and Alaska and extrapolate the potential for future production in Alaska based on current production in other parts of the world. Many of the historic precious metal mini,ng distrirts of the world have In recent years become major base metal .producers. Sme examp1 es of . these districts are the porphyry copper. districts of Csnsda, Chile, Iran, Peru, Spain, Turkey., pnd the U.S.; the Cu-Pb-Zn provinces of Australia, Canada, Ireland, and the U.S. These distr.icts have had major historic gold and silver productions. The significant gold and silver pr~ductionin the Fairbanks, .Livengood and Wiseman areas may be an indication of future base. metal resource 'areas. REFERENCES CITED

I I Bailey, P.A: , 1964, Methods, costs, land requirements. and.organization -. in reglonal exploration. for base metqls, AIME Alaska -Section

<. a." Meeting, Fairbanks, A? aska, March 38-21, 1964, 31 p. 73 SL Ferrians, 0. J., 3r. , 1971, Prel imi nary engineering geologic map of I, . . the proposed trans-A1 aska pi pel ine route: U.S. Geol . Survey -1 open-file rept. .

*.. Kachadoorian, R., 1971, Preliminary engineering geologic map of the -* -.I--" proposed tran-A1 as ka pipel ine route: U. S. Geol . Survey openlf il e rept.

b Stanton, R. L., 1972, Ore petrology, McGraw-Hill Book Company, New York, - .. New York, 713 p. -. Weber, F.R., 1971, Preliminary engineering geologic map of the proposed trans-A1 aska pipel ine route: U .S. Geol . Survey open-fi le . rept. Val dez Quadrangle

Previous Investigations - Two non-scientif ic reconnaissance expeditions by the United States Army, one in 1885 under Lt. Henry T. Allen and another in 1891 under Lt. Frederick Schwatka, were the first 'American pene- . trations into the Valdez quadrangle and the Copper River region. The Copper River military expedition in 1898 and 1899, directed by Capt. W. R. Abercrombie, produced the first geologic reports on the - region. One leg of the expedition under Frank C. Schrader went from Valdez across the Valdez Glacier to Klutina and returned to Valdez via the Copper, Tasnuna, and Lowe Rivers. The first geologic surveys and geologic maps of the Copper River region were made by Schrader and Spencer in 1901 and Menden- ha1 1 in 1902. Subsequently, numerous surveys and mineral investi - gations were conducted in the region, highlighted by the work of Fred H. Moffit. All of these men were with the U.S. Geological Survey. Recent work includes regional studies (Berg, Jones, and Richter, 1972), geologic mapping (Nichols and Yehle, 1972; Ferrians and Kachadoorian, 1971 ) geochronol ogy (Marvin , 1974), structural geology (Andresean, et. al. 1964; Barnes, 1967; Gedney, 1970; Berg, 1973; Freeland and Dietz, 1973; MacKevett and Plafker, 1974; Richards, 1974; and Brogan, et. a1 ., 1975) and mineral resources (Berg and Cobb, 1967; Heiner, Wolff and Grybeck, 1971 ; Cobb, 1972, 1973; Bottge, 1974; and Mull igan, 1974). The quadrangle has not been completely mapped on any scale nor has there been any major regional geochemical investigations in the area.

Regional Geology and Petrology The predominant geological feature of the Valdez quadrangle is the Chugach Mountains which forms a major physiographic province in south-central Alaska. Rocks of the Chugach Range are composed primarily of a thick sequence of graywacke, shale, and volcanic rocks of Jurassic and Cretaceous age that have been metamorphosed from the zeolite to lower greenschist facies. The north-flank of the Chugach Range contains minor volumes of sandstones, shales, and volcanic rocks of Permian age that have been metamorphosed from the greenschist and blueschist facies to the granul ite facies. These rocks are in turn overlain by sedimentary and volcanic sequences that range from Triassic through Quaternary in age. The sedimentary metamorphic and volcanic rocks are intruded by igneous rocks that range from dunite to granite in composition and range from Jurassic to Quaternary in age (Moffit, 1938; MacKevett and Plafker, 1974; Metz, 1975). The Border Ranges Fault is the major structural feature in the region and it can be traced along the north-flank of the Chugach Mountains from the St. Elias Mountains to the southwest end of Kodiak Island, a distance 0.f approximately 1,000 kilometers (625 miles). The fault has been interpreted as a possible Mesozoic plate boundary and is marked by numerous occurrences of ul tramafic rocks north and west of the fault. North and west of the Chugach Mountains the Gravina-Nutzotin terrane and the A1 aska-Aleutian Ranges form a high temperature, low pressure metamorphic belt that para1 lels the Chugach Mountains. Prel iminary evidence indicates that the Gravina-Nutzotin belt formed as a result of a middle and upper Mesozoic thermal event. The existence of the 1ow temperature-high pressure metamorphic belt of the Chugach Mountains and the high temperature-1 ow pressure metamorphic be1 ts of the A1 aska Range provides additional evidence of major underthrusting from the south and southeast during the upper Mesozoic (Reed and Lamphere, 1973; Metz, 1975). The oldest rocks in the Valdez quadrangle are Permian(?) or upper Palezoic regionally metamorphosed graywacke, shale, limestone, volcaniclastics and basalt that contain greenschist and blueschist facies , mineral assemblages (Metz, 1975). These rocks were originally designated as the Strelna Formation and were assigned a Mississippian age (Moffit and Mertie, 1923, Moffit, 1938). The rocks have subsequently been correlated with the Permian(?) and Permian Skolai Group of Smith and MacKevett (1970) and with the Mankomen Formation (Churkin, 1973: MacKevett and Plafker, 1974). At the type local ity, the Strelna Formation includes metamorphosed gabbro, chert, silicified limestone, basalt, shale and tuff. Moff i t and Mertie (1923) reported the fo1 1ow5 ng parti a1 reference section of the Strelna Fomation in the Nugget Creek valley. Feet Meters Fined-grained basalt Water-laid and subaerial tuff Fine-grained basalt Shaly, argillaceous beds Si 1i ceous beds F i ne-grai ned basal t Si 1i ci f i ed 1imestone Gabbro with some tuffaceous beds Chert Gabbro Total 3,845 1,172 . Rocks of the Strelna Formation have been studied in some detail in the Bernard Mountain area, about 8 kilometers '(5 miles) south of the Tonsina Roadhouse, Mile 79 on the Richardson Highway. At Bernard Mountain, the Strelna Fomation is represented by a . . i I:: complex sequence of weakly metamorphosed slate, greenstone, arkosic sandstone and marble. The slate unit of Hoffman (1974), consists of about 65% dark-gray to black sl ate containing we1 1-developed seri - cite and chlorite grains that para1 lel the slaty cleavage. The slate a1 so contains accessory magnetite, pyrite, apatite and hematite. The remaining 35% of the slate unit is composed of medium-to dark-gray phyll i te. Petrographical ly, the phyll i te consists of 70% to 90% clay and silt-sized grains of sericite and chlorite, and 10% to 30% strained quartz. Accessory magneti tea pyrite, zircon, and sphene are also present. Minor amounts of graywacke sandstone and siltstone are also present in the slate unit. The graywacke is poorly sorted and consists of angular and , subangular grains of quartz, plagioclase and 1i thic fragments set in gray, clay matrix. The plagioclase is partially altered to clay minerals and the quartz grains are strained. The lithic fragments are composed of s ha1 e and minor volcanic rock fragments (Hoffman, 1974). The greenstone unit of the Bernard Mountain area is composed of weakly metamorphosed basalt, vol cani cl astics and agglomerates. The basalt is typical ly dark-green to reddish-brown, f ine-grained and massive. Petrographically, the basalt is composed of 10% to 40% phenocrysts of augi te-diopside, plagiocl ase (Anl 0), and 01 ivine, and amygdules of calcite, quartz, chlorite and epidote are common. The phenocrysts and amygdules are set in a cryptocrystal- 1ine groundmass that comprises as much as 50% of the rock locally. The vo1caniclastics of the greenstone unit are composed of a poorly sorted mixture of angular volcanic rock fragments composed of angular grains of plagioclase, chlorite, calcite and epidote along with scattered grains of a1 tered pl agioclase, pyroxene and quartz that are set in a. cryptocrystal 1i ne matrix. The agglomerates of this unit are mainly 1ight-to dark-green rocks composed of angular rock fragments 10 to 50 centimeters (4 to 127 inches) in diameter. The rock fragments are set in a fine-grained matrix of volcanic rock fragments (Hoffman, 1974).

I I The arkosic sandstone unit is composed chiefly of arkosic 1 I sandstone with minor phyll i te and marble. The arkosic sandstones are weakly metamorphosed and consist of gray to white, poorly - 1- sorted, medium-to coarse-grained, massive sandstone. Petrographi - I cally, the arkose is composed of 20% to 50% angular and subangular quartz grains, 20% to 50% plagioclase and 5% to 20% lithic fragments set in a matrix of silty-clay. The phyllites are typically black, very fine-grained rocks with we1 I -developed, cl ose-spaced cl eaveage. I-, Fine-to medium-grained, highly recrystal 1ized marble is' fairly common in the Bernard Mountain area and generally consists of 1ight- gray to white, non-fossil iferous, homogeneous marbl e composed of a mosaic of anhedral , twinned calcite grains (Hoffman, 1974). The correlative Skolai Group has not been mapped in the Valdez quadrangle, however, the type section defined by Smith and MacKevett (1970) is only a few kilometers to the east in the McCarthy C-4 14 ' quadrangle. The Skolai Group is divided into two formations and several members. The older Station Creek Formation is divided into two informal members while the younger Hansen Creek Formation includes the Golden Horn Limestone Lentil. The volcanic flow member, the lower member of the Station Creek Formation, is composed of approximately 1,200 meters (3,937 feet) of basalt and basaltic andesjte flows. The rocks are altered and contain abundant amygdule fillings of albite, chlorite, calcite, quartz and zeol i tes. Other cons ti tuents include prehni te, pumpel 7yi te, actinol i te, biotite, cl inozoisi te, hematite, sphene, and ilmenite. The mineral assembl ages may indicate a transi ti onal A1 pine to Barrovi an metamorphic . sequence. The metavol canic rocks have a chemical composi ti on of. undersaturated 01 ivine tholeite of Yoder and Ti 1ley (1962) (Smith and MacKevett, 1970). Overlying the volcanic flow member of the Station Cveek For- mation is the volcaniclastic member composed of a heterogeneous mixture of volcaniclastic rocks ranging from coarse volcanic breccia to de1 icately laminated volcaniluti te. Fine-grained volcanic1astics are more prevalent near the top of the member and the upper 150 meters (492 feet) is nearly a1 1 volcanic si1 tstone and volcaniluti te. .?, . * <$ The contact with the underlying flow member is gradational through j..'-3 several thousand meters. The volcaniclastic rocks range from mafic 3 to intermediate in composition. Petrographical ly , the volcani- cl astics are dominantly coarse tuff-breccia, thin-bedded graywacke, and volcanilutite that contains glassy clasts which have been recrystallized to mosaics of xenoblastic quartz and feldspar. The groundmasses have been recrystal 1ized and contain chlorite, epidote, and calcite. The other constituent minerals include a1 bi te, sericite, pumpel lyite, prehoi te, sphene, augi te, hornblende, potassium feldspar and opaques (Smith and MacKevett, 1970). - --- The Early Permian Hansen Creek Formation conformably and gradatf onally over1 ies the Station Creek Formation. The formation consists of a mixture of thin-bedded chert, black shale, sandstone, carbonaceous biocl astic 1imestone, and minor conglomerate. Chert is the dominant rock type near the top of the formation and is commonly red, black, and green. The chert forms beds -ranging Up to 15 centimeters (6 inches) thick. Petrographically, the chert is composed of a poorly crystalline matrix of quartz and chalcedony containing si 1ica-fil led radiolarian tests, sponge spicules and detrital grains of muscovite, chlorite, feldspar, and quartz (Smith and MacKevett, 1970). The Golden Horn Limestone Lentil conformably overlies rocks of both the Station Creek Formation and the Hansen Creek Formation. Maximum thickness of the Golden Horn Limestone is about 270 meters (886 feet). Individual beds range up to 3 meters (10 feet) thick and can be traced laterally for only several hundred meters. The limestones are mainly bioclastic grainstone, packstone, wackestone; and minor arkose occurs locally. The bul k of the bioclastic material is crinoid stems, brachiopod she1 1s, and bryozoan fragments. The unit has been assigned an Early Permian age (Smith and MacKevett, 1970). , . Unconformably overlying the Strelna Formation and its correlative rocks is the Nikolai Greenstone. The unit consists of approximately 1,000 meters (3,281 feet) of altered basalt containing primary plagioclase, augite, re1 ict 01 ivine, opaques, sphene, and apatite and secondary chlorite, epidote, clay minerals, calcite, serici te, prehni te, ferruginous serpentine minerals, pumpel lyi te, quartz, native copper, and zeol i tes. The Nikol ai Greenstone contains abundant amygdules that are f i 11ed with quartz, calcite, chlorite and native copper. The unit has a wide geographic distribution in the Wrangell Mountains area and in the western Yukon Territory. The age of greenstone has been establ ished stratigraphically as Middle or early Late Triassic (MacKevett 1970, 1971 ). The Chitistone Limestone disconformably overlies the Nikolai Greenstone and consists of 1imestone, do1 omi te, and minor chert. Moffit (1938) did not differentiate between the Chi tistone Limestone and the overlying Nizina Limestone in the Valdez quadrangle. Armstrong and others (1970) described the Chi tistone Limestone in detail, however. their work was concentrated on exposures in the McCarthy quadrangle. The mudstones and wac kestones of the Chi ti stone Limestone are dark greenish-gray, dark-gray, or dark-medium gray on unweathered surfaces and gray to brown on weathered surfaces. In addition to calcareous mud the matrices contain pyrite, iron oxides, quartz, chalcedony and clay . minerals. The packstones and grainstones are medium-gray to medium dark-gray and are composed of 1ime pel 1ets, ooids, and bioclastics. The crystal 1i ne carbonates incl ude dolomi te, do1 omi tic 1 imestone and 1 imestone. The crystalline rocks range from light-to medium gray on fresh surfaces to 1ight.-brownish-gray on weathered surfaces. These rocks are composed of interlocking carbonate grains with minor opaques and clay minerals. Chert is associated with the wackestones and occurs as grayish-black lenses and nodules. Armstrong and others (1970) feel that the Chi tistone Limestone resulted from deposition in an intertidal and supratidal deposi-- tional environment. This interpretation indicates that a low energy restricted marine environment was present during the Late Triassic. Gradationally overlying the Chitistone Limestone is the Nizina Limestone. The unit consists of fine-grained, dark greenish-gray grainstone, mudstone, and wackestone that weather brownish-gray. The Nizina Limestone ranges in thickness from 100 'to 380 meters (328 to 7,247 feet) and occurs in beds from 15 centimeters to a meter thick (6 inches to 3 feet). The mudstones and wackestones are composed primarily of pel lets 0.05 to 0.2 mil 1imeters in diameter of lime mudstone and fossil fragments with minor quartz, plagioclase, and opaque mineral s. Matrix material consists of carbonaceous matter, silica and clay minerals. Chert is present in the form of dark-gray or black lenses and nodules. The Nizina Limestone has been assigned a Late Triassic age. The McCarthy Formation conformably overlies the Nizina Lime- stone and is divided into two informal members. The lower member conformably overl ies the Nizf na Limestone and includes approximately 300 meters (984 feet) of calcareous, carbonaceous shale, impure 1 imestone and impure chert. The rocks are dark-gray, dark greenish- gray, or grayish-black on fresh surfaces and weather dark-brown. The shales are composed of calcite, carbonaceous materi a1 , c1 ay mineral s, chl ori te, quartz, chalcedony, do1 omi te, pyrite and secondary iron mineral s. The cherts are chal cedoni c rocks with minor carbonaceous' material, quartz, plagioclase, dolomite, pyrite, apatite, bioti'te and fragments of radiolaria tests and sponge spicules. The limestones are wackestones composed of grains of bi oclastic calcite in a matrix of calcareous mud. The unit has been assigned a Late Triassic or Early Jurassic (?) age based of pelecypods of the genus Monotis (MacKevett, 1971 ). The upper member of the McCarthy Formation gradationally overl ies the 1ower member and includes approximately 600 meters (1,970 feet) of chert, spicul ite, shale, and impure limestone. The rocks are dark-gray and weather dark yellowish-brown. The chert and spicul i tes are chal cedonic rocks containing cl asts of calcite, quartz, plagioclase, do1 omi te, apatite, carbonaceous matter, pyrite, hematite, potassium feldspar, i lmeni te, leucoxene, chlorite, biotite and clay minerals. The cherts and spiculites grade into impure limestones as the calcite content increases. The shales are composed of clay minerals, quartz, chalcedony, calcite, carbonaceous matter, plagioclase, dolomi te, opaque minerals, and carbonate flourapatite. These quiet water sediments may range in age from latest Triassic through Early Jurassic (MacKevett, 1971 ). Moffit (1938) defined a tuffaceous shale sequence that he considered correlative with the Middle Jurassic Tuxedni Group of the Matanuska Valley and Cook Inlet areas. The sequence includes approximately 200 meters (656 feet) of sandstone, shale, and conglomerate with a large fragmental volcanic component. - The sandstone contains quartz, feldspar, and biotite with calcareous cement. -The conglomerate is composed of pebbl es and cobbl es of argi 11 i te, diori te, greenstone, and quartz in a tuffaceous matrix. The stratigraphic position of the unit is in doubt due to apparent fault contacts. The age assignment of the unit was made based on pelecypods of the genus Inoceramus. - In the Stuck Mountain and Willow Mountain areas, there is a thick sequence of metamorphosed vol canic flows, vol caniclastics and sedimentary rocks of Jurassic (?) age (Ferrians and Kachadoorian, 1971). The contact with the Strelna Formation to the south is covered and the stratigraphic position is not definitely known. The rocks are andesi ti c or basal tic in composition and contain .chlorite, plagioclase, calcite, quartz and epidote. Intercalated ni th the volcanics and volcanic1astics are red and green cherts. The volcanic and sedimentary rocks contain abundant di ssemi nated pyrite and minor chalcopyrite locally. The rocks are highly fractured and contain anastomosing quartz veins. The tuffaceous shale sequence of Moff i t and the above sequence may. be correlative and both may be correlative with the Nizina Mountain Formation of MacKevett (1 969). Stratigraphical ly above the Nizina Mountain Formation is the Kotsina Conglomerate, however the contact between the two units is indef ini te (Imlay and Detterman, 1973). Moffi t (1 938) described the unit as 600 to 800 meters (1,970 to 2,625 feet) of massive, dark, pebble- to boulder-conglomerate. The predominant pebbles include greenstone, 1imestone, granodiori te, and quartz and are included in a shaly and arkosic matrix. The unit was assigned to the Middle Jurassic based on fossil fragments. .The Kotsina Conglomerate is unconformably overlain by a sequence of sandstone, shale, conglomerate, and 1imestone, 1200 meters (3,927 feet) thick. Moffit (1938) mapped this sequence and assigned it to the Jurassic or Cretaceous. These rocks are probably correlative with the Root Glacier Formation of MacKevett (1969). The shales, mudstones, and siltstones are composed of clasts of quartz, calcite, and plagioclase set in a microcrystal 1ine matrix. The sandstones include graywacke, wacke, and areni te and are composed of quartz, plagiocl ase, cl inopyroxene, biotite, potassium feldspar, hornblende, calcite, opaque minerals and lithic fragments. The impure limestones are detrital rocks with calcite cement. The Root Glacier Formation has been assigned to the Late Jurassic based on pelecypods of the genus Buchi a (MacKevett, 1971 ). The Kennicott Formation unconformably overlies the Jurassic and older rocks of the Wrangell Mountains area. The unit includes 30 meters (98 feet) of basal conglomerate and approximately 180 meters (590 feet) of sandstone, siltstone, and shale. The pebbles and boulders of the conglomerate are predominantly dark greenish-gray greenstone of the Nikolai Greenstone set in a matrix of coarse-grained sands tone. The sandstones are fel dspathi c wacke, areni te, and arkosic wacke. The we1 1 sorted, subangul ar clasts include quartz, plagioclase, glauconi te, chert, opaque minerals, chlorite, biotite, calcite, epidote, and garnet. The matrix consists of chlorite, chalcedony, sericite, calcite, secondary iron minerals, montmori 1- 1onite, kaol i nite, and zeol i tes. The siltstones are finer grained equivalents of the sandstones. The shales are composed of clay minerals and quartz. The formation has been assigned an A1 bian age based on the ammonite Brewericeras hulenense (Anderson) (MacKevett, 1971). South of the Border Ranges Fault the Chugach Mountains are composed of a thick flysch-like sequence of rocks known .as the Val dez Group. The sequence includes interbedded sl ate and graywacke, volcanic flow rocks, and minor conglomerate. The graywacke is I ight-to rnediur-gray, fine-to coarse-grained, feldspathic wacke composed of subangul ar cl asts of pl agiocl ase, quartz, sericite, chlorite, and biotite. The slate is a very fine. grqined rock that has incipient-to well -developed cleavage (MacKevett and Plafker, 1974). The rocks have been metamorphosed to the lower greenschist facies and have been highly deformed locally. Veinlets of quartz less than 2 centimeters (.8 inches) wide ape present in two prominent trends, one para1 lel to east-west cleavage planes and one in a north- south direction, parqllel to a major joint set. The Valdez Group is assigned a Late Cretaceous age based on fossils collected in the Valdez area (Moffit, 1914) and in the Turnagain Arm area (Park, /' 1933; Clark, 1972). Unconforrnably overlying the Cretaceous rocks north of the Borders Range Fault is a sequence of 300 to 600 meters (984 to 1,970 feet) of sandstone, conglomerate, shale, clay and coal (Moffit, 1938). This sequence is correlative with the Frederika Formation of MacKevett (1970). The unit gradational ly under1 ies and is intercalated with flows of the Wrangell Lava. The conglomerates range from pebble-to boul der-congl omerates and are composed of cl asts of greenstone of the Ni kol ai Greenstone, volcanic rocks of the Wrangell Lava, chert, quartz, granitic rocks, shale and 1imestone. The matrix is poorly sorted, calcite-cemented, arkosic sandstone. The sandstones are 1ight-brown, buff, and I ight greenish-brown feldspathic and arkosic wackes. They are composed of poorly sorted, angular grains of quartz and plagioclase set in a matrix of chlorite, and clay minerals. The sandstones have calcite and silica cement and contain minor potassium- feldspar, biotite, magnetite, ilmenite, apatite, pyrite, and hematite. The siltstones and shales are 1ight-to dark-gray and weather to various shades of brown. The si1 tstones are compositional ly fine- grained equivalents of the sandstones while the shales are composed primarily of quartz and clay minerals with minor biotite, muscovite, and opaque minerals. Lignite is present locally and occurs as finely laminated dark-gray to black layers that grade into carbonaceous shale. A Tertiary age has been assigned to the formation based on abundant plant material (MacKevett, 1971 ). Intrusive rocks in the quadrangle range in composition from- dunite to granodiorite. Ul tramafic rocks are present north of the Borders Range Fault and have been mapped in the Valdez quadrangle at Spirit Mountain (Herreid, 1970), Bernard Mountain (Hoffman, 19741, and at Chitina (Metz, 1975). At Spirit Mountain, an intrusive complex composed of quartz diori te, hornbl endi te, peri doti te and gabbro intrudes the grajwacke, greenstone, slate, and 1imestone of the Strel na Formation. Herreid (1970) describes the quartz diorite and hornbl endi te as a. 11 Fine to medi urn-grained, medi um-dark-gray to greeni sh-bl ac k rock composed of widely varying proportions of serici tized oligocl ase-hornbl ende- quartz-phl ogopi te-cl inopyroxene with accessory sphene and zircon." The peridotite occurs as an unbanded, medium-to coarse-grained, black dike rock composed oP antigorite after olivine, fosterite, tremolite, and diopslde, with massive and disseminated nickel sulfides. The gabbro is a medium-grained rock composed of 101 ivine, pyroxene, garnet, and magnetite (Herreid, 1970). Hoffman (1 974) described in detail the Bernard Mountain ultramafic complex that crops out about 8 kilometers (5 miles) south of Tonsina. The complex includes dunite, clinopyroxenite, and horn- blendite. Dunite comprises the bulk of the ul tramafic body and generally occurs as a green to olive-green, fine-grained and massive rock. Major mineral constituents include: olivine, enstatite and chromite. .The ultramafic body consists of about 75% dunite, 15% harzbergitic dunite and 5% harzbergite. The remaining 5% of the rocks in the complex are chromite bearing. The complex exhibits local zonation, however it a1 so contains characteristics of a1 pine-type ul tramafic bodies. Hoffman (1974) has classified the Bernard Mountain complex as an alpine-type ul tramafic that was emplaced in the late Mesozoic or early Cenozoic between the Permian(?) Strelna Formation to the south and a Jurassic amphibolite and granulite terrane to the north. Approximately 2 kilometers (1.25 mi 1es) northwest of Chi tina a serpentinite body 4 kilometers (2.5 miles) long and several hundred meters wide occurs in an east-west striking fault zone that dips to the south. The ultramafic body is associated with granulites and amphi bol i tes that .occur south of the fault zone and with blueschist facies metamorphic rocks of the Strel na Formati on that occur both north and south of the fault zone. The ultramafic is composed of , serpentine after 01 ivine and cl inopyroxene (Metz, 1975; 1976). Numerous small plutons of Tertiary and Quaternary age intrude the Paleozoic and Mesozoic rocks in the Valdez quadrangle. Most of the plutons are less than a few hundred meters in diameter, however several plutons are up to 16 kilometers (10 miles) across. They range in composition from quartz diorite to granodiori te. The largest body of quartz diorite is located at Spirit Mountain and has been described previously (Herreid, 1970). Two small bodies of a1 tered granodiorite and quartz diorite occur near Chitina and are composed of sericite after potassium feldspar, quartz, and plagioclase. One of the bodies contains north-south strikinq quartz veins that contain minor gold mineralization. The pluton has Leen dated at 45.5g.4 m.y. BP (Metz, 1975). The Wrangell Lava (Mendenhall, 1905) conformably over1 ies the Frederi ka Formation however some of the older flows are 'intercalated with the Miocene rocks. The lavas are a subaerial sequence of flow, pyrocl astic, vitrophyre, and congl omerqte with a total thickness of approximately 1,500 meters (4,921 feet). Individual flows range from 0.3 to 8 meters (1 foot to 26 feet) thick and are composed of andesi te, basal tic-andesi te, rhyodaci te, and basalt. The andesites and basa.1tic andesi tes. are the predominant rock types and are dark-gray to greenish-gray on fresh surfaces and medium-brown on weathered surfaces. The rocks are composed of sodic labradorite, calcic andesine, augite, hypersthene with minor pigeoni te, olivine, magnetite, hornblende, biotite, quartz, and glass. Secondary minerals occur .as amygdules and include; calcite, chlorite, siderite, ankerite, and zeolites. The rhyodacites are light-gray or buff on fresh surfaces and weather light-brown. The rocks are porphyritic. in part with plagioclase phenocrysts to 2.5 mil 1imeters (0.1 inches) in length. -The groundmass is composed of quartz, biotite, potassium feldspar, magnetite, ilmenite, glass, sphene, and zircon. Secondary minerals include chlorite, calcite, clay minerals, leucoxene, sericite, chalcedony, and iron oxides. The vitrophyre occurs as lava domes . composed of green-to black rocks that contain quartz and plagioclase phenocrysts in a glassy groundmass. The pyroclastic rocks are light- brown to red- brown tuffs and volcanic breccias. The conglomerate occurs in lentils and is similar in composition to the conglomerate of the Fredericka Formation. The Wrangell Lavas range from Miocene to Holocene in age (MacKevett, 1971 ) . A1 though there is a great lithologic diversity in the geology of the Valdez quadrangle only the Strelna Formation, the tuffaceous shale unit of Moffit and its correlatives, the Valdez Group and the mafic and ultrarnafic rocks of the Bernard Mountain complex have been mapped in the corridor. All of the units in the quadrangle including those in the corridor have not been napped in detail.

Structural Geology The Border Ranges Fault (MacKevett and Pl af ker, 1974) domi nates the structural geology of the rocks in the Valdez quadrangle. The fault has been interpreted as representing a Mesozoic plate boundary that seperates a northern block, composed predominantly of Paleozoic and Mesozoic metamorphic rocks, from a southerly block composed of . flysch-like sediments of late Cretaceous age. The Border Ranges Fault can be traced from the St. El ias Mountains on the east, to the southwest end of Kodiak Island, a distance of about 1,000 kilometers (625 rniles)(MacKevett and Plafker, 1974). The fault was first recognized by Capps (1937) on Kodiak Island, where a large, vertical, northeast-striking fault separates a greenstone-schist complex on the north from a thick sequence of graywacke, slate and argillite of Meso- zoic age on the south. Later workers also recognized the fault further to' the east and Moff i t (1 914) del ineated the contact between the upper Paleozoic rocks and the Valdez Group rocks in the Copper River Region. Although Moffit did not map the contact as a fault, he interpreted the contact as a fault locally. MacKevett and Plafker interpret the tectonic implications of the Border Ranges Fault as follows: "The Border Ranges Fault is interpreted to mark a plate- boundary that developed new the close of the Mesozoic or in the early Tertiary. During this time, the deep-water deposits of the Val dez Group buck1 ed against, and probably local 1y were subducted beneath, terrane underlain by an upper Pa'leotoic island. arc that previously had accreted to the continent. The island arc terrane is believed to have formed directly on the oceanic crust (Richter and Jones, 1971; Jones and others, 1971 ) . Its superjacent rocks consist of subaeri a1 volcanic rocks and widespread fossi 1iferous, largely clastic, Mesozoic rocks that were deposited on the continental shelf or in shallow epicontinental marine embayments. Some of these rocks are coeval with the Valdez Group. The Val dez Group ref1 ects rapid turbidi te- type sedimentation, probably largely on oceanic crust in a deep marginal trench. Activity of the Border Ranges Fault apparently waned after the early Tertiary, with subsequent up1 ift and emergence of the Valdez Group and its accretion to the continental margin. However, at least local post-early Tertiary activity on the fault cuts Tertiary rocks near the Matanuska Glacier." Rocks of the Strelna Formation have a general east-west strike and dip moderately to the north, small-scale folds with northeast- trending axes are transected by a s trongl y-devel oped nort h-south cleavage. Abundant quartz stringers cut the greenstones and slates of the Strelna Fornation. Although some of the stringers are parallel to the north-south cleavage, the bulk appear to be east- west striking. The structure of the rocks in the Valdez Group is similar to that of the Strelna Formation. The rocks have an average east-west strike and dip moderately to the north. Minor folds are present locally and indicate that the almost constant northward monoclinal dips are the result of compressed folds overturned to the south - r rooks and others, 191 1).

Geochemistry Geochemical reconnaissance in the Valdez quadrangle during the present study consisted of the collection of 46 rock samples and 23 stream sediment samples (See Tables'l and 2, Appendix A) along the pipe1 ine corridor between the Alyeska Pipe1 ine Terminal , south of Valdez and Willow Mountain on the north. Statistical analysis ,of the geochemical data has shown that 28% of the rock samples collected are strongly anomalous (98% confidence level) in at least 1 element, 13% of the rock samples contqin anomalous (95% confidence level) , concentrations of at least one element, and 24% of the rock samples were weakly anomalous (90% confidence level ) in at least one element. Sixty-one percent of the stream sediment samples collected contain weakly anomalous, qnomalous and strongly anomalous concentrations of at least one element. Most of the samples collected contain anomalous concentrations of more than one element and several samples were anomalous in more than 8 elements. Threshold values (See Tables 3 and 4, Appendix A) for the 90%, 95%, and 98% confidence intervals for each element were derived Prom a statistical analysis of the raw data and the calculation of concentrations of the elements at the arithmetic mean plus: 1.645 x standard devlation, 2.0 x standard deviation, and-. 2.33 x standard deviation for the 90%, 95% and 98% confidence levels respectively. Where the analystica? variabi 1i ty is zero or near zero, the threshold values for the confidence levels are either the detection level or nearly the same value. Samples of graywacke and metagraywacke in the southern part of . the quadrangl e contain strongly anomalous concentrations of bismuth, antimony, potassium, yttrium, zirconium, and phosphorous. The strongly anomalous values in the area seem to be related to small fractures, shear zones and quartz veins that may have formed during a regional metamorphic event that has metamorphosed the rocks in the region to the upper zeolite and lower greenschist facies. To the north, near Wortmann Creek, samples of metagraywacke and slate with quartz veining contain strongly anomalous concentrations of barium, gall ium, molybdenum, titanium, zinc, lead and silver. A stream sediment sample from Sheep Creek contains strongly anomalous concentrations of molybdenum, 1ead and zinc, and anomalous concentrations of .chromium, iron and nickel. A1 though no mineral i- zation was found in the area during the current study, several claims were staked in the past near the mouth of Sheep Creek. This area clearly needs further work to determine the bedrock source of the anomalous metal values. A sample of interbedded graywacke and slate near the mouth of Cascade Creek contains strongly anomalous concentrations of calcium, chromium, copper, iron, manganese, nickel and scandium. The - chromium, copper, nickel and iron association suggests that there may be an unknown mafic or ultramafic igneous rock component in the area. . A sample of graywacke collected near mile 40 of the Richardson Highway contains strongly anomalous concentrations of silver. Stream sediment samples from the area also contain high silver values. Moffi t (1935) describes a gold-quartz lode at Mile 40 of the Richardson Highway known as the Townsend and Holland prospect. The gold mineralization is contained in at least two veins that cut shattered slate. The anomalous silver values in the rock and stream sediment samples from the area are probably related to gold-quartz vein mineral ization. Moffi t (1 935) syggests that the. go1 d quartz veins in the region are genetically related to the intrusion of granite and quartz diorite dikes .that are you.nger thrn the abundant . small quartz veins that are developed .in the slate snd graywscke. The presence of intrusive rocks in the region may explain the scattered anomalous concentrations of tin, potassium, zirconium, and gallium, in both stream sediment samples and samples of slate and graywac ke . Samples of chert and metavolcanic rocks collected in.the Willow Mountain area contain abundant disseminated pyrite. The 'metavol canics.. are probably altered basalt and contain strongly anomalous concentrations. of. barium, bismuth, gallium, phosphorous, antimony, tin, . zinc and zirconium. Although no significant mineralization was found in the Willow Mountain area during the current study, the region .clearly needs further work to fully assess its resource potential.

Mining Activity and Economic Geology Prospecting in the Val dez -quadrang1e has been underway since the early days of the Klondike stampede. As early as 1897 some of the streams in the Valdez area were known to contain gold-bearing gravels and some were mined. Mining and prospecting in the Valdez area continued at a' slow pace until 1910 when the Cliff Mine, located about 10 kilometers west of Valdez became productive and stimulated the search for other gold-quartz veins in the region. In a short time, about 30 promising lodes had been found, and by 1914 nine mills of various types were in operation in the Port Valdez district. At least two distinct types of lode deposits are known in the area. The geld quartz veins are mainly fissure-type veins that show little if any alteration of the-wall-rock. Locally, the country rock near the veins is impregnated with pyrite and arsenopyrite and some alteration is present. The mineralogy of gold-quartz lodes is fairly simple and includes gold, quartz, calcite, and minor pyrite and arsenopyrite. The other type of deposit known in the area is characterized by the copper deposit at the Midas Mine on Solomon Gulch, south of Valdez. The Midas Mine has produced over 1,000,-000 pounds of copper and therefore is one of the major copper producers in the Prince William Sound area. The original claims at the Midas Mine were located in 1901 and by 1911 considerable development work had been done on the property. The mineralization at the Midas, known as the Jumbo lode is restricted to narrow veins adjacent to a shear zone in the slate and graywacke. The veinsxut the foliation in the mine area. High-grade mineral ization is composed of pyrite, wi th small er amounts of pyrrhotite, chalcopyrite, sphalerite and minor galena. Samples collected by A. W. Rose (1965) and by M. W. Jasper (1953) contained copper concentrations as high as 5%. The Jumbo lode is in close proximity to a fairly large greenstone body and the copper mineral i zati on may be re1 ated to the greenstone. The Cliff Mine, located about 8 kilometers (5 miles) west of Valdez, near Shoup Bay, was the most productive gold-quartz lode in the Valdez district. The property was located in 1906 and the first production occurred .in the spring of 1910. 'The ore body at the Cliff Mine is fairly typical of the gold-quqrtz .lodes in the Valdez area. The mineral ization is found In several persistant fissure veins thqt trqnsect the foliation of schistose graywacke (Johnson, 1922; in Brooks, 1922). The metasediments and metavolcanic rocks of. the Valdez district contain a we1 1-developed cleavage that early investigators recognized. The north-south cleavage is

parallel to many of' the gold-quartz veins of the region. The fissure-' vein system at the Cliff Mine was traced underground for 275 meters (825 feet) and varied from 15 centimeters to a meter (6 inches to 3 feet) wide. The ore is contained In bluish-white quartz with minor amounts of calcite, a1 bi te, chlorite and brownish-weathering carbonate. The ore contained only about 3% to 5% sulfides including pyrite and arsenopyrite with minor sphalerite and galena. The gold for the most part was free milling and early reports (Brooks, 191 1) indicate the average gold content was approximately 2 ounces per ton. Ore shoots containing up to 10 ounces per ton gold were known. Several mining operations in the Mineral Creek and Valdez Glacier area produced gold and minor silver. The deposits are similar to the gold-quartz veins in the Shoup Bay area and are generally fissure veins cutting slate, argill i te and metagraywacke. Placer gold was known in the Valdez district as early as 1897, however, only limited production from relatively small placers on Mineral Creek, Gold Creek, Solomon Gulch, and from the Lowe River has occurred. The deposits appear to be of fluvioglacial origin and no large commercial deposits are known in the Valdez district. North of Valdez in the Mt. Tiekel area, gold lodes have been known since the early3ays and are mainly quartz veins, closely associated with quartz diorite and quartz diorite porphyry that cut argill ite, graywacke, quartzite, and minor 1imestone of the region. Several promising prospects were found on Hurtle Creek, however only minor production has occurred. The quartz veins on Hurtle Creek exhibit several generations of quartz. Near the margins of the veins, the quartz is mainly mil ky-white, bull quartz with 1ittle mineraTi- zation. Near the center of most of the larger mineralized veins, a zone of vuggy quartz containing sulfides and gold is usually .present. The sulfide minerals include pyrite, aresonpyri te, galena, sphalerite and chalcopyrite. Gold usyally occurs as free gold and is generally free milling. Assays of high-grade ore-from the Wetzl er claims on Hurtle Creek ran as high as 7 ounces of gold and 12 ounces of silver per ton. However, gold contents of less than 1 ounce are the rule. Northeast of Mt. Tiekel near the head of.Fivemile Creek at Chitina, a mineralized quartz diorite intrusive contains disseminated arsenopyri te and gold (Metz, 1975). Quartz veins near the margins of the quartz diorite also contain gold-bearing mineral ization. Assays range between 0.18 and 3.0 ounces per ton gold and up to 4.2 ounces per ton silver. Other mineralized intrusives occur in the Chugach Range and there is a high probabil i ty that unknown mineral ized stocks and si 11s are present in the region. South of Tonsina, at Bernard Mountain, the dunite contains segregations and discontinuous pods of chromite. The chrome does not appear to be of economic tenure at. this time. Minor concentrations of chalcopyrite occur in the cl inopyroxeni te in the mafic-ul trarnafic complex, however the copper concentrations do not appear to be significant. 0 At Spirit Mountain, Herreid (1970) sampled a peridotite dike that ran 0.88% nickel and 0.89% copper, however the mineralized body is relatively small. The Spirit Mountain occurrence is similar to the mafic and ultramafic complex at Bernard Mountain however the economic potential of these occurrences is limited by their small size.

The Jurassic or younger volcanic rocks of the quadrangle contain zeolite minerals. The economic potential of these rocks is indeter- minate at this time but they are important targets for future examinations. , 1 REFERENCES CITED ! L- I Andreasen, G.E., Grantz, Arthur, Zietz, Isidore, and Barnes, D.F., 1964, Geologic interpretation of magnetic and gravity data in i -., ir.<.i'- the Copper River, Alaska: U.S. Geol . Survey Prof. Paper 316-H, p. 135-153.

I:'

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Mortln, G. C., 1920, The AIosLon mining industry in 1918: U.S. Geol. Swvey Moffit, F. H., 1954, Geology of tho Prince Vtilliam Sound region, AloJo: U.S. Bull. 7l2, p. 11-52. kxvey Bull. 989-E, p. 23-310.

Mortin, G. C., 1926, Th kwoic rtrotigrophy of Alosko: U.S. Gcol. Surrey Moxhom, R. M., ond Nelson, A. E., 1952, Re~~~issoncefor :~diwcti*e &-in bull. 776, 493 p. in w~h-centrol Alosb, 1947-49: U.S. +I. knyCirc. 184, 14 p.

Morrin, R. F., 1974. A tobulotion of K-Ar, Rb-5, ond Pb-alphi oges obtoimd from Mulligen. J. J., 1974, Mint101 reuwrcws of the tmm-Al& pipclim corridor: moteriols within the United Stotn (including Almb ond Horaiil during the U.S. &.Mms Inf. Circ. 8626, 24 p. yews 1965 through IW8: U.S. Geol. Suwy opcn-file report, 245 p. VALDEZ QUADRANGLE Cont. 32 , Notiowl Roeorch Council, Committee on the Alorko Eorthquoke. 1973, Smmuy ond Pops, Allen J., 1969, Stroin onolylis of hotizontol crust01 mavrments in Alosko bored reccmmedotions; includiq index to series in the collmction The Greot Almko on triongulotion survep before ond ofter the Prince VIilliom bud eorthqwke of Eorthqurke of 1964, No. B, 291 p., Notl. Aod. Sci., Washington, D.C. Morch 27, 1964, in Th. Prince Williom Sound, Alaska, sorthguoke of 1964 and aftershocks, v. 3,T. 99-111: U.S. Gost ond Gdtic SWVV. Nomn, J. W., and Kernodle, D. R., 1973. Field woter-quolity informtion olong he prqased trans-Alosko piplitu corridor, Sefitemb.r 1970 through September Pope, AIlm J., 1972, Stmin omlysir of horizonhl uurtol movements in A~&O based 1972: U.S. Gwl. Survey open-file rept., 22 p. on nioqulotion surveys hiore and after th. northquake, in Th Grmt AIOSIIO Eorthqwke 01 1964. ssirnrology ond +aye p. 435-447:-Norl. Aced. Sci., Noumon, J. W.. odKerdle, D. R., 1974, Aquotic organisms (ran selected sites Washington, D.C. along the popwed tronrAloska pipelinn corridor, September 1970 to September 1972: U.S. Geol. Survey opsn-file report, 23 p. Pat, Austin. ond Mop, L. R., 1971, Glocier doamd lobes ond ohtflMdr in AIake: U.S. Geol. hrwy ydrd. Inv. Atla MA-455, 10 p., 3 sheen. Nichols, D. R.. ond Yrhle. L. A.. 1961, Amlysea af ~OIond wotn ham hro miner01 springs in the Coppn Riwr bosin, Alorko, in Geolqicol Survey research Par, Aurtin, 1967, Effects of th. March 1964 Alosko eorthqwh on glocierr: U.S. 1961: U.S. Grol. knvey Prof. Pow 424-D, p. m91-0194. Geol, Survey Prof. Pwr 544-D, p. Dl-DU.

Nichols, D. R.. and Yehle. L. A., 1969, Enginwring geologic mop of h wul- Richards, H. Glenn, 1974, Tectonic evolution of At&: Am. AnOe. Peholem rmtnn Cwwr River b$in. Almko: U.S. Gaol. Survey Misc. Gcol. Inv. Geologists Bull., v. 58, n. 1, p. 79-105. / ~opi-szi,' i ,bet, I~OI.. 1:125,OM). Richter, Domld, ond Herreid, Gwdon, 1963, Magnetic dnomalks in Alosko, in Nichols, 0. 1.. 1960, Slump rtmturn in Pleistocene loke redinwnh in Geologicol Alosko Division of Mines adMiwrols Report for tha yeor 1963: ~un.ou~~loh, Surrey research 1960: U.S. Gcol. Survey Prof. Paper 400-8. p~B353-B354. p. 53-55.

OvwhacL, R. M., 1920, Nickel deposits in thIan Copper Rive* wllcy: U.S. Rohn, br,I9W, A reconwirronce of the Chitino Rivw ond th SLoloi Mountains. Geoi. Survey Bull. 712,.p. 91-98. ALsko: U.S. Geol. Survey 21st Ann. Rapt., pt. 2, p. 3W-440.

. pock^, Duone R., bgon, George E., ond SMM. 0. I..1975, New dota on b. A. W., 1965, Geology ond mimolizotion ol the Midor miw ond Sulphide ploh tectonics of Alosko: TectplDphpin, v. 29, p. 87-102. Gulch oreos ruw Voldez. Alosko: Alaska Div. Minesond Mimrolr hl. Rept. IS, 21 p. Poge, Robert A., Blockford, Michoel E.. ond Bench, Bolbara, 1974, Seismicity in the vicinity af Voldez. Alosko (abs.): EOS (Am. w.Union Trom.), Rose, Arthur, 1%4, Midas mine-Sulfid. Gulch robs.), in Alosko Division of Mins V. 55, n. 4, p. 347. ond Minerals, Report for the yeor 1964: ~uneou,~ioslo,p. SO.

Porkin, Ernest J., 1969, Horizontal crustal movements determined from wrveys after benboum, bmnG., 1974, Theory of worping of wulhern Alako before Alasko the Alakon aqrthqwk of 1964, in The Prince William bund, Alosko, eorth- eorthquoke, 1964: kw. Genphp. Reworth, v. 79, n. 23, p. 32BW3OI. qwke of 1964 ond ofterrhockr, "73, p. 35-49: U.S. Coost ond Geodetic Sfvey. khradu, F. C., ond Sptncer, A. C., 1901, Tha geology ond minerol resouem of a portion of h Copper River district, Almko: U.S. Geol. Survey *c. Porkin, Gnut J.. 1972, Horitontol ctwtol movements, in Th. dreot Alosko Eorth- PJ., 94 p. guoLr 01 1964, rri,mulqy ortd ~uhy,p. 419-4z: ktl. Aawl. Sri., V#oshingt~, D. C. $cheder, F. C., 1900, A r.comoiuonce of o port of Prince Williom Sound ond the Cop~rRiver disnict, Almko, in 1898: U.S. Gaol. Survey 20th Ann. Rept., pt. 7, p. 341-423. Pwrn, William H., 1971, Arctic piplininp; tough, costly, but kosible: UMR bw., , n. 2, p. 53-59. ~iielt,W. E, Goerirg, J. J., 04 Hood, D. W., 1973, Guda oil phyrotoricity Pierce, H. C., 1916, Exploration ai Spirit Mountoin nickel ixoapect, bnyon Gcek, . studies (with commentrl, in Environment01 shdin of Port VaIdez; hydm~~~lbon . lower Copper River region, Aloska: U.S. Bur. Mines Rept. Inv. 3913, 8 p. invalvment: Alosko unit: ht. kina Sci. &CM. Pub. 3, p. 413-446.

Pietsch, D. D.. Shingle, J. H.. McDcrrmn, W., et 01.. 1975. The trans-Almkb Slott, Rog.r, M., 1971, Texture of ice-cored depaih from hn Alosbn wlley pipelin, in Mplowir, Jmn, ed., L. ptrole et Ie mr orctiques; poblemn glaciers: bur. kd. Pet~ology, v. 41, p. 828-834. et perrpec?rvcs, p. 3CQ-317: . Cntre Etud. Pra., Poris. Small, James I.,ond Whrton, Lorrence C., 1969. Verticol diaplocemmh deter ' Plofker. Georg., 1971, Parible future petroleum resources of Pocific-morgin mined by swvep ofhr th. Aloskon wthquoke of Worch 1964, in The Prinu krtiory &%in, Alosko in Future petroleum prorimes of the &itad Sbtei: WilJiom bud, Alako, eorthquoke of 1964 ond ofterrhocks, v.3, p. 21-33; lhir geoiogy old po~e~o~,v. 1: Am. knoc. Patrolem Geoiogisb km. 15. U.S. Coat and Gdtic Suvey. p. 120.135. Smoll, kmn 8.. ond Wharton, Lowrence C., 1972. Vertical displocemenn. in Plofker, Georg., Kochodw.iw, ReJm, EckeI, Edwin B., et ol., 1972, Effects on The Greot Aloskon Earthquake of 1964, seivaology and gmdny: ~otl.Sicod. Mrious communities, in Th. Great Alako Eotthqwke of 1964, Geology, Sci., Woshington, D.C., p. U9-461. Porn A-8, p. 489-53x Notl. Ad. Sci., Washington, D.C. Smith, J. P., 1927, Wper Triosric 'norin inwrtebrote founos of North hrico: Plofker, Gmgc, 1971, The Aloskon eorthqwke of 1964 and Chileon eorthqwke of U.S. Geol. Surwy Prof. Popr 141, 262 p. 1960; implicotiorn for are tectonics (oh.), in Oceon floor rpceoding. 4: Internot. Union Geodesy ond Geophpics, 1sh Gm. Awn. &s., Moscow, Smith, P. S., 1926, Mineml industry of PJmko in 1924: U.S. Geol. Survey &It. p.51. . 783, p. 1-30. Plofku, Gewgc, 1972, Aloskon .orthqwke of 1964 and Chileon aorthquoke of 1960; Smith, P. S., 1929, Mineral industry of Almko in 1426: U.S. *I. Surwy Bull. itnplisotiom for orc tectcnia: h.Geophyt. Rneorch, v. 77, n. 5, 797, p. 1-50. . p. 901-925. Smith, P. S., 1930 Mineml industry of AI& in 1927: U.S. hi. %wy Bull. PloRer, ii.org., I977 Teotonicr. in Th. Great Alorko Emthquoke of 1964, polopy, 810, 1. 1-64:. Porn A-8, p. 47:122: Notl.7cod. Sci., Washington, D.C. Smith, P. S., 1?30, Minwol industry of Alosko in 1928; U.S. Gaol. Survey Bull.. PIoRa, Gecrw, 1972, Tectonics, in The Grwt Almko Earthquake of 1964, -is- 813, p. 1-72. molqy ond gday. p. 113-m: MI. hd. ki., Wahingtm, D.C. Smith, P. S., 1932, Mineral inkarty of Alasko in 1929: U.S. G-1. SUW &ll+ PIoRn, G.orge, ond MocNail, F. I., 1%. St~otigrophicaignificann of Tertiory 824, p. 1-81. forriis from th Orco Group in the P~inceWillbm regim Almko, in Geologicol Survey resmch 1966: U.S. Gal. Suvey Prof. Pop- 550-87 Smith, P. S., 1933, Miner01 industry of Alorko in 1931: U.S. -1. Survey Bull. p. 862-868. 844-A, p. 1-82.

PIoRN, George, and Mom, L. R.. 8965, Tectonic deformation, suboqwow slides Smith, P. S., 1933, Mimol industry of Alosb in 193& U.S. Gal. Suwy bll. ond destructive -on% oswcioted with th. Aloskon hrch 27, 1964 eorthqwke: 836, p. 1-83. on interim gcolosie ewiwtion: U.S. Geol. Survey open-file rep,., 19 p. Smith, P. S., 1934, Minml industry of Aloh in I=: U.S. hl. %NVBull. PlolLer, Gcwge, Kochodoorian, ReJen. Eckel, E. I.,ond Mop, L. R., 1969, 857-A, p. 1-91. Effects of rheorthqwkr of Worth 27, 1964. on various comnunitiu: U.S. Gd. Survey Prof. Pop 542-G, p. GI-GSO. Smith, P. 5.. 1934, Miml industry of Alobo in 1933: US. Gaol. Emy Bull. *A, p. 1-94. PIoRer, Gag., 1969, Tactonio of th Motch 27, 1964, Alor+o eorthquoke: U.S. Gcol. Suvey Prof. Pop 54371, p. 11-174. VALDEZ QUADRANGLE Grit. 33

Smith, P. 5.. 1936, Mineral industry of Alorko in 1934: U.S. Gml. Swvey Bull. U.S. Gcologiwl Survey, 1964, Ge~logicolSurvey rwrsh 1964: U.S. Geol. &&A. p. 1-91. Survey Prof. Pow 501-A, p. AI-A367.

Smith, P. S., 1937, Mi~rolindustry of AIoJIo in 1935: U.S. Geol. Survey &It. U.S. Geological Suvey, 1965. Ge~logicolknvey R~M& 1%5: U.S. 601. 86U-A. p. 1-95. Survey Prof. Poper 525-A, p. At-A376.

Smith, P. 5.. 1938, Mimrol industry of Alorko in 1936: U.S. Gcol.-Sumy Bull. U.S. Geologic01 Swvey, 1966, Ge~logicolSurvey r-rch 1%: U.S. GeoI. 697-A, p. I-IW. Swvey Prof. Popr 550-A, p. AI-MU.

Smith, P. 5.. 1939, Arm1 geology of Alorko: U.S. Gwl. Swvey Prof. Poper 192, U.S. GeOlogicol Swvey, 1967. Geologicof Survey renard 1967: U.S. Geol. 100 p. Survey Prof. Popu 57%. p. AI-Ui7.

Smith, P. 5.. 1939, Mirrrol industry of Alorko in 1937: U.S. Geol. Swey Bull. U.S. Geologiwl Surwy, 1972, Geological Surwy ;enarch 1972: U.St 601. 910-A, p. 1-113. Survey Prof. Poper BmA, p. AI-A32O.

Smith, P. 5.. 1939, Mineral industry of Alako in 1938: U.S. Geol. Suwy Bull. U.S. Geologicol Survey, 1973, Gcologicbl Surwy remrch 1973: U.S. 601. 917-A. p. 1-113. Suvey Prof. Papr 850, 366 p.

Smith, P. 5.. 1941, Minerol industry of Alorko in 1939: U.S. Geol. Survey bull. U.S. Geological Swwy, 1973, Unitd Stoles Grolopieol hnv Almko prq)rm,. 926-A, p. 1-106. 1973: U.S. Geol. Swwy Circ. 683, 56 p.

Smith, P. 5.. 1941. Post l&gol

Smith, P. 5,. 1942, Minnol industry of Aloha in 1940: U.S. Cml. Suvey 8ull. Von Alrtim, R. E., ond Block, R. F., 1946, bppr d8psih of tk. KoIIino- 93-A, p. I-ICP. Kuskulono dimict, AImko: U.S. Gml. Suwy Bull. 947-G, p. 121-141.

Smith. P. 5.. 1942, Occwr*ncer of laolybd.nmnminrols in Aladro: U.S. -1. Van Wonmr, J. 0.. Dories, J., and G*druy, I.., 1974, himicity and pl~h hnwy Bull. 926-C, p. 161-210. tectonics in south-centrol Alorko: kiwl. Soe. Amaiw Bull., v. 64, n. 5, p. 1467-1475. Smith, 5. S., 1913. Report of the Mine Inspector for the Territory of Alorko to tha - koetory of thc Interior for the liscol yew ended June 30, 1912: Washington, Woller, R. M., 1966, Effech of the March 1964 Alosko earthquake on the hydrology D.C., 24 p. of south-central Alaska: U.S. Geol. Survey Prof. Pwr 544-A, p. AI-A28.

Smith, 5. S., 1914, Report of the mine inrpector for th territory of Alorko to th. Wdow, klmuth, Jr., ond othn, 1953, Pc.fimimrlaunmory of r.wnmi~~cefor Seuetory of the Interior for the Ihwl yeor eddJune 30. 1914: Wohington, wonium and lhwrium in Alorka. 1952: U.S. Gaol. Survey Cite. 2f8, 15 P. D.C., 36 p. Whitten, Chorler A., 1972, Introduction; on evoluotim of the gmdetic ond photo- Smith, 5. 5.. 1917, The mining industry in the Territoty of Alorko during the prommetric survep, in Th. Greot Alosko Eorthqwke of 1964, vbnmlogy ond colendot yeot 1915: U.S. Bw. Mimr Bull. 142. 66 p. gmdery, p. 415-41~ktl. Awd. ki., Washington, D.C.

Smith, 5. S., 1917, The ~niningindustry in the Territory of Alaska during the Wilne, Milton A., ond McGlrmon, J. A., 1973, Prince Willion, Sound, Alasko, o colendor yeor 1916: U.S. br. Miner Bull. 153, 89 p. volcomgenic mosriw sulfide province (oh.): Gml. bc. Ammriw A~I.. V. 5, . n. 7, p, 86.5. Sterem, A. E., ond Milne, W. G., 1974. A study of wismic risk new pipelin. corridors in northwestern bnodo ond Nntern Alosko: bradion bu. Eotth ki., v. 11, n. 1, p. 157-164.

Stewort, 0. O., 1921; Annwl report of the Territorial Mino Inspector to the Govermr of Alorho, 1920:. Juneou,. R p. Stewart. B. D.. 1923. Anaiual rapt of th. Mine Impectof to the Gorermr of Almko, 1922: Juneou, Alorko, 175 p. ---- .- Stewart, B. D., 1924, Annvol report of the Mim Impector to th. Govermr of Alosko, 1923: Juneau, Alorka. 109 p.

Stewart, B. D., 1931, Report on cooprotion behw th. Territory of Alosko ond the United Stohr in making mining inrestigatiom end in the inspection of mim for the biennium ending Morch 31, 1931: Juneou, Alako. 145 p.

Stewart, B. D., 1933, Mining invatigotiom ond mine inspection in Alorko, includiw osrirtonc* to prospectors, biennium ending Morch 31, 1933: Juneou, Alorko, 192 p.

Sykn, Lynn R., 1971, Ahenhock zones of Qraot eorthqwkes, seismicity gop, ond mthqwke prediction for Alorko and the Alwtiom: bur. Geophp. Reseoreh, v. 76, n. 32, p. 8021-8041.

Ton, R. S., and Martin, Lowence, 1912, The earthquokn ot Yokutot Boy, Alorko, with o preface by G. K. Gilbert: U.S. Gcol. Swvmy Prof. Poper 69, 135 p.

Twnhofel, W. S., 19.53. Potential Alakon mineral rewwcu for propad electre- chmicol ond electrometollurgicol indwbin in the upper Lynn bml arm, Alorka: U.S. Gml. Swwy Circ. 252, 14p.

U.S. breou of Mimr, 1967, Production potenliol of known gold depain in th Ulited Stater: U.S. &. Minn. Inf. Circ. 8331. 24 p.

U.S. Grologisol hnvey, 1899, MOW ad dnuiptiom oi routes of exploration in I AlosLo in 1898, with gen+rol informotion concerning the Territory: U.S. Gml, Suwy Sp.c. Pub., 138 p.

U.S. Geologiwl Swv*y, 1961, Geologicol Suvey r.l.or&, 1961, rymprir of g.ologic ond wologic mulls: U.S. &I. Survey Ptof. P-r 424-A, p. AI-AI94. Gul kana Quadrangle

Previous ~nvestigations -. 7. ;;...i , G, . ,, 'A. Early investigations in the area include the Copper River mil itary expedition in 1898 and 1899 and a trqverse by Mendenhall (1905). Recent work includes regional studies (Berg, Jones and Richter, 1972; Grantz,.Jones, Lanphere, 1966), geologic mapping (Nichol s and Yehle, 1969; and Ferrriano, 1971 ) , geochronology (Marvin, 1974; and Grantz, Jones and Lanphere, 1966), structural j geology (Andreasen et al, 1964; Barnes, 1967; Gedney, 1970; Berg; 1973; Freeland and Dietz, 1973; Richards, 1974; and Brogan et a1 , 1975) and mineral resources (Berg and Cobb, 1967; Richter and Matson, 1968; Heiner, Wolff and Grybeck, 1971; and Mulligan, 1974). The quadrangle has not been completely mapped on any sca'le nor has there been any major regional geochemical investigations in the area.

Regional Geology and ~etroiogy The rocks in the southern part of the Gul kana quadrangle are domi nately metavol canic and metasedimentary rocks of Jurassic age. The volcanic rocks are general fy a1 tered andesi te and basalt flows, tuffs and breccias that have been regionally metamorphosed to the lower greenschi st facies. The greenstones are f ine-grained rocks containing chlorite, sodic plagiocl ase, calcite, quartz and egidote. The metavolcanics are interlaminated and interbedded with volcano- clastfcs and cherts. The Jurassic rocks have been tentatively correlated with the Talkeetna Formation of lower Jurassic age. The entire sequence is highly fractured and jointed and is cut locally by randomly oriented quartz veinlets. The volcanic rocks contain disseminated pyrite and euhedral cubes of pyrite to 10 millimeters (0.4 inches) on an edge are present locally. Minor chalcopyrite is also present. To the north, sedimentary rocks of the Copper River Basin - dominate the geology. Rocks of the Matanuska Formation, of upper Cretaceous age are also present. The Matanuska Fomation has been . traced from the lower Matanuska Valley to the Copper River region (Grantz et al, 1960). The unit is composed of a thick sequence of dark-gray siltstone and shale interbedded. with 1ight-colgred sandstone and conglomerate, all of marine origin. The shale and siltstone are general ly dark-gray to bl ac k, thin-bedded, nodular shale and siltstone. The sandstones are main1 y we1 I -indurated, f ine-grained, thinly laminated micaceous and f1 aggy sandstones that are arkosic in part. Conglomeratic sandstone beds occur throughout the' sequence. Unconformably overlying the rocks of the Matanuska Fomation is a sequence of non-marine sedimentary rocks known as the Gakona Formation, of Eocene age. The Gakona Formation. is com osed of a basal section of coarse conglomerate that is overlain 1y a sequence of sl ightly indurated clayshale containing I igni tic coal. . The base of the Gakona Formation is. marked by a greenish conglomerate layer composed of rounded pebbles of quartz and greenstone set in a feldspathic sandstone matrix. The overall thdckness of the Gakona Formation, robably does not exceed 600 meters (2,000 feet) (Andreason et al, 1964! .

~ocksalong the northern margin of the Copper River asi in are , part of a sequence of weakly metamorphosed basalt, andesite and tuffaceous rocks of the Amphitheatre Group of middle-to late Triassic age. Rocks of the Amphitheatre Group have been traced from the Gakona River westward to the Susitna River, a distance of about 160 kilometers (100 miles). The Paxson Mountain Basalt is the dominant rock found in the Paxson Mountain area and generally consists of green to 01 ive-green basalt with mi nor maroon amygdal oi dal basalt near the base of the unit. Locally, dark-green to olive-green basalts occur higher in the volcanic sequence and form massive, resistant outcrops with few amygdul es. The basalt is entirely recrystal 1ized and plagioclase feldspar is completely a1 tered to a1 bite and primary . augite has been altered to chlorite and actinolite. Locally, in the Paxson Mountain Basalt, zones of amygduloidal basalt are present. The amygdules contain a wide variety of minerals including epidote, pumpel lyi te, prehni te, quartz, calcite, 1aumonti te, cl inozoi si te and albite. The total thickness of Paxson Mountain Basalt is not known; however, a maximum of 3,000 meters (10,000 feet) of basalt is exposed in the Paxson Mountain area (Stout, 1976). he Tangle LaKes Formation (Stout, 1976) at its type locality, on the south 7imb of 2heJnphitheatre syncline near Tangle Lakes consists of about 4,000 meters (1 1,500 feet) of andesite, agglomerate and siliceous tuff. About 1,000 to 1,500 meters (3,000 to 4,000 feet) of the Tangle. Lake Formation consists of diabase and diorite sills. Near the base of the Tangle Lakes Formation several thousand meters of we1 1-bedded, siliceous tuff. and tuffaceous sediments crop out. Petrographical ly, the tuffs and tuffaceous sediments consist .of alter- nating sil iceous layers and layers composed of pl agioclase feldspar. Agglomerate layers consist of angular volcanic c'lasts to a meter (3 feet) in diameter. Clasts of andesite, siliceous .tuff, agglomerate and tuffaceous limestone are set in a light-to dark-green aphanitic groundmass. Near the top of the section, a sequence of andesite flows are interbedded with chert, black-sil iceous argill ite and shale and are interbedded with thln tuff aceous 1imestone and dolomi tic 1 imestone. At the very top of the Tangle Lakes Formation is a distinctive pillow andesi te sequence about 500 meters (1,500 feet) thick. This sequence marks the top of the Tangle Lakes Formation and contains we1 1-developed, nested pi1 lows locally. Overlying the Tang1 e Lakes Formation is a thick, approximately 6,000 meters (18,500 feet, ) sequence of interlayered green- basalt and amygdaloidal. basalt known as the Boulder Creek Volcanics. The Boul der Creek Vol canic sequence bears a strong resembl ance to the Paxson Mountain Basalt. Amygdaloida? members range from.thin I ayers *-. with less than 10% amygdules, to layers containing up to .75% amydules ..4 !.. y. filled with epidote, quartz, pumpel lyite, chlorite, prehnite and .,.5; calcite. . . . The greenstones at Hogan's Hi1 I, in the central part of the quadrang1e are a1 tered. basal tic or andesi ti c volcanic rocks that are cut by a stockwork of anastomozing quartz veins. .The greenstones are completely shattered and cut by numerous transecting fracture ' systems. Petrographically, the greenstones are composed of a fine- to medium-grained intergrowth of chlorite, epidote, plagioclase feldspar, quartz, sphene, actinol ite and amphibole (hornblende?). The rocks exhibit a we1 7-developed foliation locally.. .

Structural .Geology The structural geology of southcentral Alaska in general and in the Gulkana quadrangle in particular may be the result of interaction between the North American Plate and the Pacific Plate, from the late Paleozoic to the Tertiary. Richter and Jones (1973) summarized the structure and tectonic hi story of southern Alaska as follows: "The eastern A1 aska Range and -contiguous terrane to the south and southwest have acted as a fairly co- .hesive block that, until late Cenozoic time, responded to variable rates of tectonic stress mostly directed northward. Tn general, these stresses have been relieved by rupture in the pre-Jurassic rocks and by - plastic deformation-in the thick basinal Jurassic and Cretaceous strata." Richter and Jones go on to say:

"Three distinct types of faulting have been _ recognized in the post-middle Triassic rocks: I) north- to northwest-trending high-angle reverse and normal faul ts generally with the southwest. bl ock down; 2 low-angle thrust faults with northeast dip; and 3 1 1inear, northwest-trending , ri ght-1 ateral strike- slip faults." East and northeast-stri king faults, faul t blocks and large open folds dominate the structure in the west-central part of the quadrangle, and northwest-to west-trending folds are restricted to the Triassic and older rocks. Thrust faults are known in the region and , are usually associated with isocl inal -to overturned folds. Local ly, the greenstone sequences are highly fractured and are cut by several 1 - 37 I distinct joint sets. At ~ogpn'sHill, in the north-central part of the quadrangle, the. greenstones are.h.ighly fractured an4 are cut by 1 7: many quartz veins. I Geochemistry Geochemical reconnaissance in the Gul kana quadrangle during the current study consisted of the collection of approximately 30 rock samples .(see Tab1 e 5, Appendix A) from the northern part .of the quadrangle. The sampling was centered in an qrea of the inner pipe1 ine -, corridor between Hogan's Hill and Paxson Lake. ,The rocks of the region . are dominantly a1 tered, mafic volcanic rocks of the Amphitheatre Group and rnafic to silicic intrusive rocks of Mesozoic age. Statistical analysis of the geochemical data has shown that 73% of the samples col1 ected contained weakly anomalous, anomalous and strongly anomalous trace element concentrations in atleast one element. The threshold values (see Table 6, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0 x standard deviation,.and 2.33 x standard deviation, for the 90%, 95% and 98% confidence levels, respectively. Where the analytical variability is zero or near zero, the threshold values f~rthe confidence levels are either the detection level or nearly the same value. .Trace element geochemistry of the rocks in the region reflect the mafic volcanic nature of much of the bedrock. Strongly anomalous concentrations of copper, chromium, cobalt, magnesium, nickel and titanium are commonly associated with the a1 tered basalt, andesi te and tuffaceous rocks in the area. No ultramafic rocks are known to occur in the pipeline corridor. The chromium and nickel values are thought to be tied up in silicate minerals. Sporadic occurrences of chalcopyrite, malachite and minor azurite were found during the course of field work in the Hogan's Hill area, however the copper concentrations are relatively low and do not appear to be of signi- f icance. The chalcopyri te occurs with. abundant pyrite in a stockwork of anastornozing quartz veins that cut a1 tered basalt. The quartz vein material also contains zinc, silver and go1d.values along with minor concentrations of molybdenum, tin,. tungsten and cobalt. This area clearly needs further work to deternine the potential for economic mineralization.

Minjng 'Activity ' and Economic 'Geology

I Mining in the Copper River region began as early as 1900, when gold-bearing gravel s were located in the Chistochina district. The first locations in the area were made in 1898 on the Chisna River,

-: a and production from the district has continued. to date.. A total of about 141,000 ounces of gold'has been produced ,from the placers in the area. Gold was discovered in the Nelchina area in about 1914, -. however, the bulk of gold production from the region has .come from -" the Chistochina area. Lode deposits in the Nelchina district have .. 'id been prospected for gol'd, silver, manganese and chromite. The gold lodes are mainly gold quartz veins that contain minor chalcopyrite, -. galena and sphaleri te. Only minor production from the gold. quartz -. vein deposits has occurred in the district. Rocks along the northern margin of the Copper River. basin are - - mainly part of a east-southeast trending belt of greenstone and . chert of the Amphitheatre Group. The Amphitheatre Group basalts and other metavol canic rocks in the region contain low-grade copper mineral izatian locally. The copper occurrences are generally restricted to fracture veins and mineral ized breccia zones in the metavol canics . Minor concentrations of chal copyri te, borni te, chalcocite and chrysocol la are known. However, none appear to be of significance. Metavolcanic rocks near Hogan's Hi1 1 , in the north-central part of the quadrangle contain abundant pyrite and minor chalcopyrite, general ly restricted to a stockwork of anastornozing quartz veins. Minor .gold and silver values were also detected in samples of the vein material, none appear to be significant. - REFERENCES CITED

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GUCKANA QUADRANGLE 6nt. 42

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U.S. Gcologicol Survey, 1965, Geologicol Survey Research 1965: U.S. Geol. Survey Proi. Popr 525-A, p. AI-W76.

U.S. Gcologicol Survey, 1967, Geological Survey Rauorch 1967: U.S. Geol. Survey Proi; Poper 575-A, p. AI-AJ77.

U.S. Grologicol Surrey, 1969, G*ologicol Surrey rcworch 1969: U.S. Geal. Survey Prof. Popr 65C-A, AI-A425. ~ountHayes quadrang1 e

Previous ' In3estigations The Mount Hayes quadrangle has been the site of extensive geologic investigations since about 1896 when J. E. Spurr and F. C. Schrader of the U. S. Geological Survey traversed the area enroute to the Yukon gold district. A. H. Brooks (1903-1923) also of the . U. S. Geological Survey contributed much to the description of the mining activity throughout most of A1 as ka. Brooks a1 so conducted , basic geologic investigations in the region. F. H. Moffit (1912, 1954) conducted detai 1ed geologic investigations in the central Alaska Range, and his early work in the Alaska Range has served as a base upon which most of the 1ater investigators have built His later work resulted in a better understanding of the bedrock geology and mineral deposits of the region. Geologic reconnaissance by S. R. Capps, of the Geological Survey, to the west in the Bonni- field district, tied together many of the regional investigations conducted in the Alaska Range. Detailed work by C. Wahrhaftig and C. A. Hickcox (1955) of the U. S. Geological Survey in the Jarvis Creek area, centered on the Tertiary coal-bearing sequence there. Geologic investigations by T. L. Pewe and W. Holmes (1964, 1965) of the Geological Survey in the northern part of the Mt. Hayes quadrangle have resulted in two, 30 minute geologic maps with a scale of one inch equals one mile. Detailed geologic investigations by L. G. Hanson (1963) of the University of Alaska, centered in the Rainbow Mountain area of the Central Alaska Range. Later work by G. C. Bond (1965), Petocz (1 969) and Gebhardt (19721, all of the University of Alaska have led to a better understandicg--~f_the geology and stratigraphy of this part of Alaska. In the early 19601s, the Alaska State Division of Geological and Geophysical Surveys initiated the first of a series of geologic investigations in the Mount Hayes quadrangle. The state investigations are generally resource oriented programs in areas that may have good potential for hard-rock mineral deposits. Work by A. W. Rose and R. H. Saunders (1965) near Paxson was undertaken to evaluate the bedrock geology and known hardrock mineral deposits of the area. Later work by A. W. Rose (1 966) in the Arnphi theatre Mountains outlined the geology of the area and investigated many of the geo- chemically anomalous areas that had been out1 ined during previous investigations. Still later work by A. W. Rose (1.966, June) in the Eureka Creek and Rainy Creek areas resulted in a fairly detailed map of this part of the Alaska Range as well as baseline geochemica7 data related to the mineral occurrences in the area. Similar work in the upper Chistochina River area by A. W. Rose (1 967) has resulted in a bedrock geologic map of the area as well as some fairly detailed descriptions of the mineral occurrences in the region. Recent work by Smith (1972) in the western part of the Mount Hayes quadrangle has lead to a better understanding of the rocks in the Maclaren metamorphic be1 t, and other work by Smith and Turner (1 974) has resulted in a pal eo-reconstruction of central Alaska wi.th imp1 icqtions as to be possible offset along the Denali fault. Work by.3. H. Stout et a1 (1973) in the central Alaska Range has shown evidence of Quaternary movement along the McKinley Strand of the Denali Fault. Other work by Stout (1976) hqs resulted in a better understanding of the geology, structure and mineral deposits of the Eureka Creek area in the east-central Alaska Range.

Regional Geology and Petrology The oldest rocks to cropout in the northern part of the Mount Hayes quadrangle consist of metasedimentary and rnetaigneaus rocks of the Birch Creek Schist unit of Precambrian or early Paleozoic age. The Birch Creek Schist occupies an extensive area north of the north-flank of the Alaska Range and is composed of quartz-mica schist, quartzite, micaceous quartzite, gneiss, amphi bol i te with minor slate, phyl 1i te and crystal 1ine 1imestone. The metamorphic rocks .have been subjected to at least two metamorphic events and range in grade from the greenschist to the amphibolite facies of metamorphism. The quartz-mica schists of the region vary greatly in composition and show a wide range in the degree of metamorphism. Moffit (1942) describes the schists. and gneisses of the region as follows: "They occur in great variety, as would be expected in view of their origin, and show a wide rang? in degree of metamorphism. The colors are dominantly gray in varying shades but include-green and black and segregatons of pink and lavendar. Some of the more siliceous varieties have a bright silvery aspect, but the darker grays are more common. The texture grades from that of fine slate with planer cleavage and consti tyent minerals so small as to be unidentifiable in the hand speciman, to that of coarse, crinkly schist and gneiss with easily recognizable mineral components. Garnet is a common constituent of the schist and occurs in bodies of all sizes from tiny, well crystal- lized grains hardly visible with a hand lens to imperfect crystals almost an inch in diameter. Other metamorphic minerals are present also, such as hornblende, which occurs in one locality in thin blades several inches long associated with great numbers of tiny red g3rnets.I' The schists of the region are typically pelitic schists. In general, they are garnetiferous quartz muscovite and biotite schists of polymetamorphic character. One phase of metamorphi sm is represented by euhedral grains of muscovite parallel to the S1 plane and a second (later?) phase that defines an S2 plane that transects the earlier S1 foliation. The S2 foliation contalns subhedral, faintly pleochroic biotite laths. Higher-grade rocks in the northern part of the quadrangle include calcic amphi bol ite, hornblende schist and, gneissic rocks of various compositions. The amphi bol ites are predominantly fine-to medium grained, subidioblastic to granular calcic amphf bol i tes. Petrographically, the amphibolite is composed of up to 60% actinoli tic hornblende, 10% to 15% plagioclase (Anl to Anl0), 10% quartz, 5% biotite, 5% chlorite, 2% cl inozoisi te, and accessory sphene and calcite. Local ly, fine to medium-grained quartz biotite hornblende schist is present. The schist contains up to 40% quartz, 25% biotite, 15% p?agioclase, 10% clinozoisite, 5% hornblende and minor chlorite, sphene and calcite. Gneissic rocks west of Donnelly Dome are coarse-grained gneissic granitic rocks that Moffit (1942, 1954) be1 ieves represent metamorphosed intrusives. About 5 miles southeast of Donnelly Dome in the Mount Hayes C-4 quadrangle, a sequence of Tertiary rocks crop out. The Tertiary section lies between the drainage of the Delta River on the west and Jarvis Creek on the east. Wahrhaftig and Hickcox (1955) of the U. S. Geological Survey conducted detailed geologic investigations in the area between 1946 and 1951. The Tertiary sequence is composed of a basal section, 152 meters (500 feet) thick, composed of micaceous sandstone and quartz conglomerate, derived from a southerly source area (Wahrhaftig and Hickcox, 1955). The basal section is overlain by a middle unit composed of 137 to 213 meters (450 to 700 feet) of buff, arkosic sandstone, from a northerly source area. The arkosic rocks are interbedded with shale and coal. The upper unit, about 275 meters (900 feet) thick, is composed of dark-gray claystone, sandstone and thin-bedded coal. In detail, the basal sandstone and conglomerate sequence is coarsest and thickest in the southwestern most exposures, and thins rapidly to the west and north. The conglomerate generally occurs in well bedded layers and consists of pebbles of quartz, chert, and subordinate amounts of rhyolite, granite and schist. The middle stratigraphic unit contains a coal- bearing zone that ranges between -3 and 15 meters (1 foot and 50 feet) thick. The zone contains coal interbedded with well cemented orange- weathering -shale and shaly sandstone. The upper 122 meters (400 feet) of the middle unit is composed of medium-to coarse-grained, buff, arkosic sandstone, in beds 3 to 15 meters (10 to 50 feet) thick and a zone of gray to brown, silty claystone that contains lenticular coal beds to 15 centimeters (6 inches) thick. Iron-carbonate concretions of 1.8 meters (6 feet) in diameter are known in the claystone zone. The arkosic nature of this zone indicates that the sandstones were derived from a fel dspathi c terrane and Wahrhaftig (J 955) be1 ieves that the granite of Granite Mountain, northeast of Jarvis Creek, may be the ultimate source of the detrital 'material in the middle section. About 3 to 6% of the middle unit is coal. The upper stratigraphic unit of the coal-bearing sequence consists predominantly of dark-gray claystone and siltstone in beds 1.5 to 18 meters (5 to 60 feet) thick, i nterbedded with dark-gray sandstone, coal and bone. The sandstone occurs in lenticular beds 1.5 to 6 meters (5 to 20 feet) thick and contains concretions locally. The coal in the upper unit occurs in beds ranging from 8 centimeters to 2 meters (3 inches to 7 feet) thick. About 10% of the upper nit is coal. One exposure of the coal-bearing sequence qt Jarvis Creek contains 30 coal beds ranging between 0.3 and 2 meters (1 and 7 feet) thick. Another exposure contains 14 coal beds between 0.3 and 2 meters (1 and 7 feet) thlck. According to Wahrhafti g and Hi ckcox (1 955), between 100,000 and 300,000 tons of strippable coal reserves are present in the Jarvi s Creek .deposi t . The intrusive rocks between Jarvis Creek and the Gerstle River to the east are dominantly coarse-grained granodiori tic rocks composed of hornblende, bioti tea quartz and feldspar. The intrusive rocks are probably Cretaceous in age but may be as old as Jurassic (Wahrhaftig and Hickcox, 1955). Other intrusives of the north flank vary from granite to diorite in composition and include quartz monzonite, granodiorite and quartz diorite. To the east in'the Johnson River area, quartz monzonite is a common intrusive rock, and gneissic quartz monzonite is present locally. Most of the granitic rocks in the area are characteristically coarsely porphyritic and some peg- matitic phases are known. The metamorphic rocks between Jarvis Creek and the Denali Fault to the south, are mainly interlaminated quartz muscovite schist, micaceous quartzite and hornblende schist. The metamorphic sequence also contains recrystallized limestone and greenstone. The schists of the region are highly variable in nature. They range from massive to f issi le and are highly contorted. Thinly laminated, garnetiferous, . quartz muscovite schist is the dominant rock type in the area, although locally, green, red, brown and gray phyllite constitute the bulk of the rocks. The micaceous quartzites of the region are mainly fine-to medium-grained micaceous quartzites in which muscovite laths define a rudimentary fol iation .--The metamorphic sequence a1 so contains "slaty" schist and rnetagraywacke. Rocks that constitute the bulk of the metamorphic sequence are be1 ieved to be metamorphosed clastic sediments (Moffit, 191 1), although recent work seems to indicate a marked pelagic sedimentary component as well as rocks with volcanic .affinities. Metamorphosed volcanic rocks north of the Penali fault are sill- like bodies of greenstone. The greenstones are probably metamorphosed basalt si 11s and dikes that intruded the schist-quartzi te countryrock and were subsequently metamorphosed by a late metamorphic event. The greenstones north of the Denali Fault are markedly different than the greenstones of the Amphitheatre terrane to the south. The major difference is that the greenstones to the north are clearly intrusive wh.ile those to the south occur as flows (F. Weber, U. S. Geological Survey, personal communication, 1973). South of the McKinley Strand of the Denali Fault system and north of the Hines Creek Strand, the rocks are characterized by a pre- Mississippian sequence of phyll ite and calc-phyll ite with minor schist and liwestone. The rocks in the wedge-shaped area between the McKinley Strand and the Hines Creek Strand are in fault contact with the medium-grade metamorphic rocks of the Birch Creek schist terrane to the north and are also -in fault contact with the Pennsylvanian Rainbow Mountain Sequence to the south. A similar sequence of metamorphic rocks is present south of the McKinley .strand, a1 though the southerly metamorphic sequence is composed of schist, subordinate calc-phyll ite and 1imestone (Hanson, .1963). The phyl lites and calc-phyll i tes of the region are very fine- grained, locally porphyroblastic phyl 1ites that contain apparent equil i brium metamorphic mineral assemblages consisting of serici te- chlori te-al bite-quartz; stilpnomelane-chlori te-quartz-al bi te; and serici te-chlori te-calci te-a1 bi te-quartz. The calc-phyll i tes on the other hand are characterized by mineral assemblages containing ch1 ori te-carbonate-a1 bi te-quartz; sti1 pnomel ane-seri ci te-carbonate- a1 bi te-quartz. The phyll i tes and cal c-phyl 1i tes are probably metamorphosed sedimentary rocks and contain evidence of one and sometimes two deformational events. The schists of the area are polymetamorphic rocks that are metamorphosed igneous and sedimentary rocks. The schists are typical greenschist facies rocks and are characterized by mineral assemblages containing chlorite-calcite-albite-actinolite-quartz; clinozoisite- quartz-a1 bi te-chlorite-actinol i te; and stil pnomelane-actinol i te- calci te-cl inozoisi te-chlori te. The schists ranges from fine-to medium- grained, granul ar-to granobl astic rocks in which some layers appear to reflect re1 ict .igneous textures (Hanson, 1963). Recrystall ized 3 imestone and impure marble are rare in the area, however, carbonaceous marbles containing calcite, chlorite, sericite, quartz, and albite are present locally. Marble composed of sericite- quartz, chlorite, albite and calcite, and marble composed of albite, quartz and calcite are also present. Hanson (1963) believes that the rocks that constitute the finely laminated pre-Mississippian metamorphics were derived from a succession of interlaminated argil laceous, ca1 c-argi 11 aceous and impure carbonate rocks, and the massive greenschi st facies rocks containing re1 ict phenocrysts were derived from basic igneous rocks. The pre-Mississi ppian metamorphic sequence of Hanson (1 963) has been tentatively correlated with similar rocks to the west across the Deltq River. Southeast of the Miller Roadhouse a fairly large body of quartz diori te ~ntrudesthe pre-Mi ssi ssi ppian metamorphic sequence to the north and the Rainbow Mountain sequence of Pennsylvanian and Permian age to the south. The quartz diorite is characteristically a medium- to coarse-grained, porphyritic, a1 tered hornblende quartz diori te. The intrusive rocks appear to have been propolyti zed. Petrographi - tally, the intrusive is composed of 207; quartz, 50 to 60% plagioclase feldspar (Anl to An30), and secondary minerals incl ude epi dote, chlorite, csrbonate and some clay minerals. The sge of the uartz diorite body is uestionable, however, a K-qrgon age obtqine1 by Kleist (1971) in9 icated qn age of 515 1-75 milllon years B.P. Kleist believes that the alteration of the quartz diorite has resulted in a spurious age deteminqtion. Hanson (1 963) obtained a K-argon age date of 105 million years B.P.. for similar rocks about 4 miles east of the Mil 1er. Roadhouse local i ty. East of the Miller Roadhouse locality a fairly large body of serpentinized peridoti te and duni te is present. The u1 tramafic body is el ongate in a northwest-southeast direction, subparall el to the trend of the Denali Fault. The ul tramaf ic rocks occur in two distinct types. One type, includes di kes and si11 s of peridoti te that intrude the phyllite and schist of the pre-Mississippian metamorphic sequence. The other type includes a large mass ,of serpentinized peridotite and dunite that is surrounded by quartz diori te. The ultramafic dikes and sills average 2 to 3 meters (5 to 10 feet) thick although some bodies may be as much as 60 meters (200 feet) thick. The dikes and sills are general ly a1 1igned para1 ?el and subparal 1el to the Denal i Fault system, however, some strike west and southwest (Hanson, 1963). Petrographically, the peridotites in the sills and dikes consist of 01 ivine (Fo70), enstati te (En 90-95)' and antigori te. Minor chrysotil e, i ddingsi te, magneti te and diopsi tic pyroxene occur, accompanied by accessory carbonate, chlorite, chromi te and phl ogopite. The large ultramafic mass to the southeast is surrounded by quartz diorite. The ultramafic has been described by Kleist (1971 ) as a "dunite intrusion" and is about 2.4 kilometers (1 1/2 mile) long and 0.5 kilometers (1/3 mile) wide in outcrop. The margins of the ultramafic body are highly serpentinized and some chrysotile asbestos is present. The age of the ultramafic bodies is questionable, however, Kl eist (1971 )-be1 ieves them to be post-Cretaceous and therefore younger than the quartz diori te of the area. However, Stout (1965), feels that the age, though questionable, is pre- Tertiary, based on the presence of dunite and peridotite clasts in ~ertiary(?)conglomerates near Ann Creek, just west of the Delta River . South of Canwell Glacier, a thick section of Pennsylvanian sedimentary and volcanic rocks crops out. The sequence, east of the De1 ta River is collectively mapped as the Rainbow Mountain Sequence, and west of the Delta River, the same sequence has been recognized and mapped as the Tetelna Complex as far west as Broxson Gulch. Stout (1965) originally defined eight informal formations on the basis of lithologic differences. The formqtions are, from oldest to youngest: 1. Andesitic flow unit 2. Interbedded siliceous tuff and tuffaceous limestone unit 3. Siltstone and mudstone unit 4. Crystalline limestone unit 5. ~raywackeand dark tuffaceous sandstone unit 6. Dacite quartz porphyry 7. Calcareous shale and sil tstone unit 8. Volcanic breccia.and dacitic tuff . (after Stout, 1976) The entire sequence may be as thick as 3,000 meters (10,000 feet). However, Rowett (1969) believes that there is an aggregate thickness of 2,500 meters (8,000 feet). Rocks that constitute the andesi tic flow unit consist generally of thick bedded porphyritic andesite interbedded with minor porphyritic dacite and crystalline tuff. The dacitic vo1 canics occur in beds between 3 and. 15 meters (1 0 and 50 feet) thick and have an aggregate thickness of less than 65 meters (200 feet). The andesitic volcanics are highly altered and contain actinolite, chlorite and epidote. Petrographically, the andesite flow unit is characterized by phenocrysts of actinol itic hornblende up to 3 mill i- meters (0.10 inches) in length and plagioclase laths less than 1 millimeter (0.04 inches) in length, that define a relict trachytic texture. Conformably overlying the volcanic flow unit is approximately 370 meters (1,200 feet) of horizontally bedded, interbedded, chert and limestone. The chert and limestone unit consists of uniformly bedded chert interbedded with clastic 1imestone. The cherts vary in color from white to black to green and occur in beds from 0.15 to 0.60 meters (1/2 to 2 feet) thick. Total thickness of this unit is less than 45 meters (150 feet). Next, a complexly folded and faulted sequence of siltstone and mudstone about 225 to 325 meters (700 to 1,000 feet) thick is present. Bedding over much of the sequence is nearly obliterated due to severe deformation. Overlying the siltstone and mudstone unit is a sequence of structurally thickened crystal 1ine 1imestone. Stout (1 965) feels that about 275 meters (900 feet) of section may be present. The 1 imestone occurs in a well-bedded sequence and is interbedded with recrystal 1ized terrigenous limestone and sil iceous siltstone. Conformably overlying the crystal?ine 1imestone unit is a sequence of rocks composed of 1i thic graywacke and tuffaceous sandstone. The graywacke unit is at least 220 meters .(700 feet) thick and is highly deformed and a1 tered locally.

Overlying the graywqcke sequence is 4 unit composed of at least 180 meters (500 feet) of dacite quartz porphyry The dacite porphyry is characterized by calcic 01 igoclase (An25), quartz, sericite and chlorite. Late calcite pervades the entire rock and is locally a major constituent. Pseudomorphs of chlorite after amphi bo1 e and pyroxene are common. Euhedral phenocrysts of quartz up to 4 millimeters (0.16 inches) in diameter are set in very fine-grained groundmass of chlorite and pl agioclase. Phenocrysts of pl agiocl ase and pyroxene qre also known. Next, approximately 600 meters. (2,000 feet) of cal careous shale, thi n-bedded tuff, tuff breccia and I i thic graywacke over1 ie the dacite porphyry unit. Pervasive carbonate a1 teration (calci Pication) is a characteristic feature of the tuff and tuff breccia. The upper part of this unit is composed of thin-bedded, dark, calcareous siltstone and shale interbedded with lithic graywacke. The beds range from lO centimeters to a meter (4 inches to 3 feet) thick and comprise about 350 meters (1,100 feet) of section (Stout, 1965). The top of the unit consists of thick bedded, massive, lithic graywacke and one andesitic flow about 15 meters (50 feet) thick. The youngest unit in the Rainbow Mountain sequence and Tete'lna Complex is a thick sequence of volcanic breccia and fine-grained pyroclastics, overlain by a quartz lqtite flow. The quartz Iatite is characterized by abundant quartz phenocrysts in a f i ne-grained groundmass, and by a lack of mafic minerals. The remainder of the unit consists of hard, silicified, multi-colored volcanic breccias interbedded with feldspathic graywacke. East and south of Rainbow Mountain, the rocks include a sequence of altered Mississippian(?) sedimentary and pyroclastic rocks of McCall um Creek Sequence. Lithological ly, the McCal lum Creek Sequence is similar to the Rainbow Mountain Sequence and is differentiated by fossil content. The McCallum Creek Sequence is separated from the Rainbow Mountain Sequence by a high-angle fault. South of Rainbow Mountain in the Phelan Creek area, a Tertiary coal-bearing section is well exposed where McCallum Creek and Phelan Creek have cut deep canyons through the Tertiary sequence. The base of the Tertiary section is exposed sourh of College Glacier, where the sequence unconformably overlies the daci tic tuff member of Stout (1965). The rocks exposed in Phelan Creek have been broken into two groups. The 1ower group incl udes beds of buff-col ored congi omerate, with clasts up to 13 centimeters (5 inches) in diameter, composed of dacitic tuff, andesite tuff, granodiorite, diabase, mafic and leuco- cratic gneiss, porphyritic andesi te and quartz diori te. The source of the materid that constitutes the bulk of the conglomerate unit was probably derived from a local source area. Minor interbeds of grit, sandy shale and sandstone are also present in the lower unit. The upper unit consists of buff-colored, sandy shale and sandstone. Coal seams are present in the lower part of the upper unit and are assoc~atedwth sandy shale and soft clays. The lowest coal bed in the section is about 75 centimeters (30 inches) thick and Is separated from a 60 centimeter (2 foot) thick seam by 3 meters (6 feet) of sandy shale. Several other coal seams are exposed in the lower 25 meters (80 feet) of the upper unit. The coal is lignitic in grade and appears to occur in lenticular bodies. Moffit (1954) believes that the coals do not extend over a large area. West of the Delta River near Eureka Creek, similar Tertiary, coal -bearing rocks are present. However, the basal conglomerate sequence in this area contains coal -bearing sandstones. At one local ity, at least 30 meters (100 feet) of dunite conglomerate is present and unconformably over1 ies the upper part of the Tetel na Complex (stout, 1976). South of the Rainbow Mountain area near Summit Lake and Paxson, a sequence of weakly metarncrphosed basalt, andesi te and tuffaceous rocks crop out. The rocks, first mapped by Moffit (1911)., are part of the Amphitheatre Group of Middle to Late Triassic age. Rocks of the Amphitheatre Group can be traced from the Gakona River westward to the Susitna River a distance of about 160 kilometers (100 miles). The best exposure of the rocks that constitute the bulk of the group are present in the Amphitheatre Mountains north of the Denali Highway and west of Paxson. The rocks in the Paxson area are mainly dark-green, massive, f ine-grained basalt. Some exposures contain hornblende phenocrysts and vesicles. Amygdules of epidote, calcite and chlorite are fairly common. Individual units are rarely discernible, however, most of the unit is be1 i eved to occur as f 1ows (Rose and Saunders , 1965). Petrographically, the metabasal t (greenstone) of the Amphi- theatre Mountain area is a fine-to-medium grained, porphyritic, chlori tized basalt that contains a relict ophitic to subophi tic texture and pseudomorphs of ca1 cite after pl agioclase. Amygdul es of calcite, chlorite and epidote are common. Locally, fine-grains of muscovite pervade the entire rock and form an incipient foliation. \

Structural Geology The structural geology of the Mount Hayes quadrangle is dominated by the Denali Fault, a major right-lateral strike-slip fault, that separates a Paleozoic block from a Mesozoic block that dominate the geology of southern Alaska. North of the Denali Fault, the metamorphic rocks of the Birch Creek schist terrane are polymetarnorphosed, and structurally complex. The metamorphic grade of the rocks in the Birch Creek schist terrane appears to increase to the north, away from the Denal i Fault. Rocks near the fault are generally lower greenschist facies grade while those to the north are upper greenschist and lower amphibolite facies grade. The structural style present in the northern tectonic block is typl- cal 1y isocl i na1 to overturned folding with superimposed open-upright folding oblique to the strike of the isoclinal folding. - The coql- bearing formation near Jarvis Creek occupies an oval -shaped depression, in the Birch Creek schist, whose major axis trends north-northwest; In the northern part of the basin, small anticlines and synclines are present. Faulting in the area has resulted in the displacement of coal seams about 30 to 45 meters (100 to 150 feet) in the Little Gold Creek area (Wahrhaftig and Hickcox, 1955). Some faults in the Tertiary basin can be traced into the surrounding Birch Creek Schist. Just north of Donne1 ly Dome, a northwest-trending high-angle faql t can be traced from the north-flank of Donnelly Dome to the southeast as far as Jarvis Creek. No apparent 1 ateral offset exists, however, the southern block is upthrown relative to the northern block. The dominant tectonic feature of central Alaska is the Denali Fault. The Denal i Fault, a major right-lateral strike-slip fault, can be traced from the Bering Se8 to southeast A1 aska, a distance of more than 3,000 kilometers (2,000 miles). Offset along this fault has been postulated to be as 1i ttle as 80 kilometers (50 miles) (Brew and others, 1966), and as much as 425 kilometers (265 miles)(Forbes et a1 , 1974). The Denal i Fault in central Alaska is divided into two major strands. A northern strand, the Hines Creek Strand, was first recognized and described by Wahrhafti g (1 958), and a southern strand, the McKinley Strand, named by Arthur Grantz (1966), has long been recognized as a major fault in the central Alaska Range. The two strands merge in the Canwell Glacier area, east of the Oelta River. Evidence of holocene movement along the McKinley Strand (Stout et a1 , 1973) indicates that right lateral movements of between 5 and 60 meters (1 6 and 197 feet) have occurred since the end of the Pleistocene. Rocks south of the Denali Fault are complexly folded, thrust faulted and displaced along high-angle normal faults. Rocks of the Amphi theatre Group are folded into 1arge east-west trending open folds that plunge to the west at a low angle. Locally, near Broxson G~lch,west of the Delta River, these folds are truncated against the western extension of the Broxson Gulch Thrust Fault. Smith (1974) believes that the east-west open folds are terminated at the structural discontinuity between the Triassic rocks and the lower Jurassic rocks of the southern Alaska Range. If Smith is correct, the east-west folding occurred sometime in Middle or Late Triassic. Another folding event in the pre-late Jurassic has resulted in northwest and west-trending folds throughout the south-central A1 as ka Range. Evidence for a post-01 igocene folding event in the Eureka Creek area consists of folded beds of coal-bearing sandstones and conglomerates. High-angl e faulting has been active throughout the region.

Geochemistry - Geochemical reconnaissance in the Mt. Hayes quadrangle during the current study consisted of the collection of 42 rock samples and 20 stream sediment samples (see Tables 7 and 8, Appendix A) from the pipeline corridor between Paxson and Big Delta. Statistical analysis of the geochemical data has shown that 55% of the rock samples collected and 50% of the stream sediment samples collected contain weakly anomalous, anomalous and strongly anomalous concentrations of atleast one element. Threshold values (see Tables 9,10, and 11, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean, plus: 1.645 x standard deviation, 2.0 x stqndard deviation and 2.33 x standard deviation, for the 90%, 95% and 98% conftdence levels respectively. Where the analytical variability is zero or near zero, the threshold values for the confidence levels are either the detection level or nearly the same value. The rocks in the Mt. Hayes quadrangle have been assigned to two geologic terranes. Rocks south of the Penal i Faul t have been grouped with the greenstones of the Amphitheater Group. Trace element geochemistry of the rocks in the Rainbow Mountain sequence may have been over-shadowed by lumping them with the greenstone terrane to the south. The greenstones have a high background trace element content and therefore the threshold values for the various elements would be higher then those in nongreenstone terranes. The statistical analysis would be somewhat insensitive to the elemental concentrations 'of the rocks in nongreenstone terranes. Rocks north of the Denali Fault in the Mt. Hayes quadrangle have been grouped with rocks of the Birch Creek Schist terrane. The trace element geochemistry appears to be compatable with the threshold values obtained. Intrusive igneous rocks collected in the Rainbow Mountain area range from quartz monzonite to hornblende diorite in composition and contain disseminated sulfide mineralization locally. Strongly anomalous concentrations of silver, bismuth, phosphorous, lead, antimony and zinc were detected in samples of altered diabase and weakly anomal ous concentrations of chrome and nickel were detected in samples of lithic tuff of the Rainbow Mountain Sequence. No mineral ization of obvious significance was found during the current study in the Rainbow Mountain area, however, the mineral resource potential of the area may be high. , Samples of gneissic quartzite with chalcopyrite coll ected near the south margin of Canwell Glacier contain copper concentrations as high as .14% and zinc concentrations to 110 ppm. The quartzite occurs in close proximity to a highly altered dioritic intrusive that contains disseminated pyrite. The quartzite is hornfelsed and the copper and zinc concentrations may be the result of contact metamorphism. North of the Denali Fault the metamorphic rocks of the Birch Creek Schist terrane contain scattered anomalo~sand strongly anomalous metal concentrations. Samples of quartz muscovite schist from several localities contain anomalous molybdenum concentrations in excess of 18 ppm. No molybdenite was found during this study and the source of the molybdenum is not known. Samples of arnphiboljte from several I ocal i ties contain strongly anomalous concentrations of ca9 cium, iron, titanium, vanadium, tungsten and zinc. The amphi bol i tes may be metamorphosed basalt and the high metal values may reflect their mafic igneous rock parentage. Mining Activity and Economic Geology Placer gold deposits and lode deposits of gold, silver, lead, zinc, copper, nickel, molybdenum and coal are known In the Mt. Hayes quadrangle. Prospecting in the region began in the 1890!s and has continued to date. The gold placer deposits of the Chistochina district, in the southeastern part of the Mt. Hayes quadrangle were first discovered in about 1898 when gold placers were found on the Chisna River. Later, placers were found on Slate Creek and on Miller Gulch and several other creeks 'in the area. Extensive mining activities and production occurred in the district between 1900 and 1942. Only' minor sporadic production has occurred since 1942. Total production from the Chistochina district up to 1959 is about 141,000 ounces of gold (Koschmann and Bergendahl , 1968). Most of the Mt. Hayes quadrangle was prospected for gold in the early days, however only minor occurrences of placer deposits are known outside of the Chistochina .district. Minor placer deposits in the Jarvis Creek area, southeast of Donnelly Dome were discovered in the early days, however, the deposits on Little Gold Creek were not of an economic nature and little work was done. The Mt. Hayes quadrangle contains a great variety of hardrock mineral deposits. None of the deposits have had much production, however the potential for locating .unknown doposi ts is high. A disseminated molybdenum occurrence is present in the northwestern part of the Mt.- Hayes quadrangle, near Ptarmigan Creek. The molybdenum mineral ization accompanied pos t-intrusive quartz veining along zones of faulting and fracturing in a granodiorite pluton that underlies Molybdenum Ridge. The pluton intrudes the Birch Creek Schist countryrock, and is generally a medium-grained, idiomorphic granodiori te. The molybdenum mineral ization occurs in numerous white-to glassy quartz stringers and also in an aplite dike. Locally, the veins are abundant and constitute smal I stockwork-type bodies within the granodiori te. Several of the quartz stringers carry arsenopyrite and gold and are apparently later than the molybdenurn- bearing stringers (Joesting , 1942). No obviously economic mineral i - zation was found in the Ptarmigan Creek area by Henry R. Joesting . (1 942) of the Alaska Department of Mines, however, the only exposure of molybdenum-bearing veins in the area occurs in the canyon walls of Ptarmigan Creek. It is possible that undiscovered zones of of mineralization exist in the qrea and further work is -clearly needed. The coal deposit at Jarvis Creek, southeast of Donnelly Dome has produced a few hundred tons of coal for heating purposes in the past, and is now idle. The coal field occupies an area of about 16 square miles and is underlain by schist and quartzite of the Birch Creek Schist unit. The coal-bearing sequence has been warped into an oval- shaped basin with the major axis trending to the northwest (Wahrhaftig 56 and Hickcox, 1955). Dips in the Tertiary sequence are as high as 30" but average between 5" and 10". The coal occurs. in beds to 3 meters (10 feet) thick, however, seams less than 2 meters (5 feet) thick predominate. Reserve estimates, based on surface exposures and dri1 I ing data obtained from 4 U. S. Bureau of Mines drill ing program, indicate that there may be as much as 25,000 tons of measured reserves with a stripping ratio of 3 to 1; as much as 50,000 tons of indicated reserves with. a stripping ratio of 3.5 to 1 ; and inferred reserves of 300,000 tons of coal with a stripping ratio of 4 to 1. Exploration of the basin continues to date, however, the results of the exploration are not known. South of Jarvis Creek, near the Rapids Road House, Gunnysack Creek has cut a deep gorge through the Birch Creek Schist countryrock. About 0.8 kilometers (1/2 mile) above the mouth. of Gunnysack Creek, a large quartz vein cuts the schist and strikes S33"W and dips about 70°NW (Capps, 1912). The vein is irregular and -branching and as much as 6 meters (20 feet) thick. The vein material is vuggy bull quartz that is heavily iron-stained locally. A 9 meter (30 foot) long tunnel along the footwall of the vein revealed a stockwork of quartz stringers and several initially high gold assays were reported, however, later tests indicated only non-economic gold values. South of the Denali Fault, and on the south margin of Canwell Glacier, some interesting nickel -copper deposits are present. The nickel-copper mineral ization is associated with a1 tered serpentinite bodies with complex structural and contact relationships with gneissose granitic rocks, phyll ite, calc-phyll i te and volcanic rocks of the Rainbow Mountain Sequence (Forbes, unpublished data). At one 1ocal i ty, small bodies of sul f ide-bearing di ke-rock containing pyrrhoti te(?) and -chalcopyrite are present. The dike appears to parallel the contact between the gneissic granite and granite of the area. Polished section examination of the rocks revealed that the pyrrhotite(?) may in fact be pentlandite. Residual soils near the nickel -bearing zones contain garnieri te, a common weathering product in nickel-bearing rocks. The Emmerick rospect, about 2.4 kilometers (1.5 miles) east of the Richardson Hig Eway, consists of nine nickel-bearing lenses. The massive lenses range from 10 to 60 centimeters (4 to 24 inches) thick; and one lense 2.5 meters (8 feet) wide consists of basic igneous rock with sulfides disseminated throughout. The narrower lenses are mainly massive sulfides consisting of pyrrhoti te-pentlandi te, chalcopyrite and pyrite. Assays of the mineralized rock range between .38% and 14.02% nickel, and up to 1.46% copper (Saunders, 1961 ) . The assay values are somewhat sporadic, and the nickel - bearing lenses are small. However, the occurrence of nickel and copper mineral ization in the region is significant and deserves further investigation. The potential for finding other nickel and copper deposits in the area seems high. West oT the Delta River near the toe of Maclaren Glacier, Thomas E. Slick of Fairbanks, has staked 16 unpatented claims on a mineral show, known as the Kathleen-Margaret (K-M) prospect. The prospect is located along the west side of the Maclaren Glacier at an elevation of 1,300 meters (4,000 feet). The principal rock types in the area consist of greenstones, 1imestone, diori te, and a daci te porphyry dike. The mineral occurrence consists of a mineralized quartz vein in limestone. The vein is as much as 6 meters (20 feet) wide and can be traced for 80 meters (260 feet) vertically. The primary ore mineral is bornite and minor pyrite occurs locally. Ore reserves in the quartz vein may be as high as 6,500 tons of ore averaging about 5% copper and about 0.06 ounce per ton gold (C. F. Herbert, 1962). No other deposits of this type are known in the immediate area, however the probability of finding other mineralized zones in the Maclaren River area and to the east in the Amphi theatre terrane seems high. Several mineralized zones west of the Maclaren Glacier on the West Fork of the Maclaren River are similar to the K-M occurrence and may be genetically related. East of the Maclaren Glacier a variety of mineral occurrences are present. Rose (1966) describes several mineralized zones in the Broxson Gulch area, none of which appear to be significant finds. One occurrence of chrysotil e asbestos vei nl ets in a serpentinized peridotite intrusive near Broxson Gulch does not appear to be significant, however the occurrence does suggest that other asbestos deposits may occur associated with the ultramafic bodies in the central Alaska Range, south of the Denali Fault. Several nickel- copper deposits in the Eureka Creek area are associated with Tertiary(?) ul tramafic bodies. One locality near the head of Rainy Creek consists of disseminated chalcopyrite in a 1ight-colored gabbro porphyry (Stout, 1976). This deposit, like several others in the area, seems to be associated with the ultramafic belt and also with low- angle faulting (Stout, 1976). There are a variety of mineral occurrences in the Rainbow Mountain area. Vein deposits containing chalcopyrite, galena, pyrite and gold and silver values were found at many localities on Rainbow Mountain by Hanson (1963). The veins generally trend to the northwest and dip at a near vertical angle. Hanson (1963) be1 ieves that the quartz veins north of the Rainbow Mountain fault are related to the thrust fault set in the area and may ultimately prove to . have been the avenues for mineral izing fluids. Brecciated carbonate veins are also known in the area. ~orbesand Regan (1963, unpu bl i shed) describe the occurrence of several different types of mineralized zones in the region. One type consists of mineral ized congl omerate. The conglomerate contains disseminated pyrite and chalcopyrite and some go1 d values. Another type of mineral ization in the area consists of disseminated sulfide mineralization in a silicified granodiorite. No significant deposits of this type are known, however the occurrence indicates a relatively high probabi 1ity of finding other mineralized intrusives in the area. A body of dunite crops out north of Rainbow Mountain near the Canwell Glacier. The duni te contains crysoti le asbestos veinlets and traces of chromites. No commercial deposits have been found (Hanson, 1963). South of Rainbow Mountain on Phelan Creek a Tertiary coal- bearing sequence contains coal beds up to 76 centimenters (30 inches) thick. The coal occurs interbedded with sandy shales and soft clays. The coal is generally lignite in grade and has been correlated with other Tertiary coal-bearing sequences of the southern Alaska Range. The occurrence of coal at Phelan Creek does not appear to be economic. Rocks of the Amphitheatre Group of Triassic age crop out in an east-southeast trending belt, that extends from the Susitna River eastward to at least the Gakona River. The Amphitheatre basalts and other metavol canic rocks of the region contain 1ow-grade copper mineralization at many localities. According to Rose and Saunders (1965) about a dozen occurrences of copper minerals are found on Paxson Mountain and several other occurrences southwest of Paxson Lake are known. The copper occurrences on Paxson Mountain are generally restricted to fracture veins and mineralized breccia zones in the basalts of the Amphitheatre Group. The copper minerals found in the veins and breccias are mainly chalcopyrite, borni te, chalcocite and chrysocol la as we1 1' as malachite and azurite. Locally, vesicles in the basalt contain sulfide minerals, however this type of mineralization is of low grade and generally restricted in occurrence. A mineral ized zone that occurs about 11 kilometers (7 miles) west of Paxson on the Denali Highway, is generally restricted to veins and pods of quartz less than 2.5 centimeters (1 inch) wide that cut unmineral ized metabasal t. One grab sample from the quartz veins contained visible chalccpyrite, bornite and chalcocite, and ran about 1.38% copper (Rose and Saunders, 1965). The vein material a1 so contained a trace of gold and 0.3 ounce per ton silver. The zone of mineral ization is small and discontinuous, however the occurrence does indicate the possibility of finding larger deposits in the region. Recent exploration activity by mineral companies north and east of the Denal i Fault has indicated an area that has high potential for base metal sulfide deposits. A number of large claim blocks have been staked in the region. The mineral exploration seems to be centered in Paleozoic metamorphic rocks between Dry Tok Creek and the West Fork River. About 160 kilometers (100 miles) west of this area, near Wood River, mineral exploration activity has outlined an area that contains metamorphosed volcanogenic massive sulfide deposits. The rocks in the Mt. Hayes quadrangle that are currently of interest are probably the eastern extension of the Wood River belt and may contain similar mineral ization. In summary, the Mount Hayes quadrangle has been the'site of intensive prospecting since the early 1900's. The region contains 1. a wide variety of mineral deposits and a diverse suite of rocks, that are favorable targets for future mineral exploration. The I probability of finding unknown ore deposits in the region seems high.

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+ - Smith, ?. S., 1926, Mineral industry of Alaska in 1924: U.S. Gcol. Surrey Bull. $toq,, Jomer H., body, John 8.. and Lllcndcr, Jonalhon, 1972, affilerrnry me.- 763. p. 1-30. mcnt on the Dcmii Ioult in the Dels River ore., AIo~koIODS.~, in Cordilleton Sect., 68th Ann. Mlg.: Geol. Soc. Amoico Am., v. 4, n. 3.T. 243. Smith, P. S., 1929, Mcneral industry of Alorke in 1926: U.S. Geol. Swrcy bI1. 797, p. 1-50. Stout, J. H., body, J. 8.. Vleber, F., et al., 1973, Ewdence for Q#terno:y movement on the McKinley Strand nf the Demli fault ~n the Delta River or-. Alorko: Smith, P. S., 1930. Mincrol lndvstry of Alosko in 1927: U.S. Gcol. Survey Bull. Geol. kc. America Bull., v. 84, n. 3, p. 939-947. 810, p. 1-64, ' Tocngcs. A. L., and Jolley, T. R., 1949, lnvertigo~ionof cool acporitr an lou:n- Smith, P. 5.. 1730, Mineral industry of Alosko in 1928: U.5. Gsol. Survey bII. central AI~skaond the Kenai Peninrulo: U.S. Bur. Mine5 Rapt. Inv. ~520, 37 p. 813, p. 1-72. Turner, D. L., Smil!t, T. E., and Forbes, R. B., 1974, Geochrorulogy of of!w? along Lnith, P. S., 1937. Mintrol industry of Alorko in 1929: U.S. Geol. Surrey Bull. the Denoli Rvlt system in AlorLo (obr.), in Cwdilleron kt., 70th Ann. Mrg.: 824, p. 1-81. Geol. kc. Americm Abs., v. 6, n. 3. pT2b8-269.

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Wohrhoftig, C., Turner, 0. L., Weber, F. R.. et 01.. 1975, Notwe ond liming of movement on Himr Creek strand of Denali fovlt system, Alaska: Geology (buldtr), v. 2, n. 8, p. 463-466.

Wohrhoflig, Clyde, ood Hickox, C. A., 1955, Geology ond cool deporitr, jorvis Creek cool lield, Alorko: U.S. Gcol. Surrey &It. 989-G, p. 353-367.

Werfield, R. S., 1973, Rotary drilling fw rrrippoble -I in tk Jorvir-Creek -1- field. AloAa: U.S. But. Miner open-file rept. 7-73, 32 p.

Weber, F. R., 1971, Pr.liminwy engineering geologic maps of thc propaed trom- Alorko piplinc route, Fairbonks ond Big Della quodrangler: U.S. Geol. Suvry open-file mop, 2 rketr, rcolc 1:125.000.

Weber, F. 11.. 1971, Pmliminory enpineering geologic mops of the propomd trow- Alorko pipline route, Mt. Hay- qdrongle: U.S. Geol. Survey open-file mop, 2 ~heetr, rcole 1:125,000.

Wedo*. Helmuh, k., Killem, P. L., and others, 1954. Recomoirlonu Fw rodio- octiuc deposits in emiern interiw Alorko, 1916: U.S. Geol. Swwy Circ. 331, 3 P-

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Wimmln, N. L., 1923, Flocer mining in Alorko in l-2, in Stewrt, 8, D., Annwl reps* of lhe Mines Inswstor to the Governor of ~10x0,1922: Juneov, Alorko, I p. 23-56.

Wimrnler. N. L., 1924, Placer mining in AIosko in 1923, in Stewort, 0. D., Annwl report of the Mine Inspector to the Corernor of ~losG,1923: Juncou, Alaska. p. 14-54.

Wolie, J. A., 1970, Biatrotigrophr of mmxlrine Twliofy of mthrn Pocific basin (As.), in lntermrional rymporim on Arctic geology, 2nd: Am. Am. -5 ~ctc~lezGeologirtr Bull., v. 54, p. 2512-2513. Big Delta quadrangle

Previous Investigations The rocks in the Big Delta quadrangle have been the subject of geologic investigations since 1898, when A. H. Brooks of the U. S. Geological Survey trave?led down the Tanana River. In 1903, the U. S. Geological Survey, Alaska Mineral Resource Division was established and a systematic study of the geology of the Yukon-

Tanana region began. ' J. B. Mertie of the U. S. Geological Survey initiated his work in the region in 1911. His work culminated in the publication of U. S. Geological Survey Bulletin 872, "The Yukon- Tanana Region, A1 aska. " Several other workers, including Prindl e (1 913), Chapin (1914) and Mertie (1913-1937) produced papers describing mining activities and geology of the region. Recent work in the Big Delta quadrangle is genera1 Jy restricted to work by the U.S. Geological Survey as part of their AMRAP (Alaska Mineral Resource' Appraisal Program) program. Work by R.D. Reger and T.K. Bundtzen (1977) of the Alaska Division of GEological and Geophysical Surveys in the Tenderfoot Creek area has shown that the localization of gold-bearing porphyry bodies of the region may be controlled by northwest trending lineaments.

Regional Geology and Petrology

The geology of the rocks in the Big Delta quadrangle is dominated by a Precambrian or lower Paleozoic metamorphic complex known as the Birch Creek Schist (Mertie, 1937). The Birch Creek Schist, as Mertie described it, consists of a complexly deformed metamorphic sequence containing quartz muscovite schist, quartz mica schist, fel dspathic shcist, chlorite schist and minor carbonaceous schist, calcareous schist, and limestone. Recent work by Forbes et a1 (1968) and Swainbank (1970) has shown that the Birch Creek Schist also contains a wide variety of gneisses, ca1 c-mangesian schist, phyll i te, calc phyll ite, amphibol ite and eclogite. The schists of the region are typically pel i tic schist, that appear as 1ight-to medium-gray, garneti ferrous, quartz muscovite and quartz biotite schist that contain quartz, 01 igocl ase, potassi urn fe1 dspar, garnet, cl inozoisi te, epidote and musc~viteand biotite. Locally, the schists contain actinol itic hornblende and staurol i te. The metamorphic grade of the schists ranges from the lower greenschist facies to the almandine amphi bol i te faces. Retrograded metamorphic rocks are-common throughout the Yukon-Tanana Uplands. Rocks in the eastern part of the quadrangle, are generally higher grade metamorphic rocks than those to the west. Quartz, biotite gneiss and augen gneiss are common. The

' quartz biotite gneiss is characteristical ly, medium-grained, 1ight- gray to medium-1 ight-gray , very quartzi tic, porphyrobl astic gneiss and orthognei ss. Dark greeni sh-gray hornblende gneiss commonly borders augen gneiss. Locally, where the gneiss is pyroxene hornfels facies grade it contains sil limanite, cordieri te and diopside. Heteroblastic augen gneiss and biotite gneiss is commonly found throughout the region. The augen gneiss is generally medium 1iaht-gray, medium-to coarse-grained gneiss with potassium feldspar augens to 10 centimeters (4 inches) in diameter.. Petrographically, the augen gneiss is composed of quartz, orthoclase, albite, muscovite and biotite with accessory apatite, zircon, garnet and magnetite. Retrograde minerals include sericite, chlorite, calcite and iron oxides. Plutonic rocks in the Big Delta quadrangle range from granite to diorite in composition. Quartz monzonite is the most common plutonic rock found and several distinct varieties have been recognized. One variety is 1ight-gray, coarse grained porphyritic, biotite quartz monzonite, with large potassium feldspar phenocrysts. Other varieties contain small feldspar phenocrysts and traces of secondary hornblende. Local ly, 1ight-gray, medium-grained quartz monzoni te containing serici te and perthi te is present. Diori te i ntrusives, characteristically a medium-gray to medium dark-gray, fine- to medi um-grained, hornblende diori te containing abundant red-brown biotite occur l ocal ly. Fine-to coarse-grai ned, greenish- black and 1ight greenis h-gray, serpentized peridoti te, crops out near the upper Sal cha River. The peridoti te contains serpentine, talc, actinocite, chlorite, brucite and magnetite. Locally, massive amphi bole-chlorite-magneti te rocks are present. Florence Weber, (personal communication, 1978), of the U. S. Geological Survey, be1 ieves that the ultramafic rocks may represent remnants of thrust sheets that were rafted from the south some time in the upper Paleozoic. Recent work by the U. S. Geological Survey in the upper Salcha River area has shown that the ultramafic bodies are intimately related with cherts that yield a Permian age frcm radiolarians.

Structural Geology The structural geology of the rocks in the Big Delta quadrangle is dominated by thrust faults, strike-slip faults, normal faults, isoclinal overturned folding and open, upright folds. Rocks of the Birch Creek Schist unit have been affected by at least two pulses of metamorphism. The first pulse is associated with a complete recrystall ization of the parent rock. The recrystall ization is associated with isocl inal overturned folds about northwest-trending axes, and high-grade metamorphic minerals, including sill imanite and staurol i te, are devel oped local ly. The second metamorphic pul se mainly a retograde event, is associated with open, upfight folds about northeast-trending axes, and is usually signaled by the presence of sericite, chlorite and calcite. Near the east-central part of the quadrangle, gneissic rocks are present in what may be a gneiss dome. The gneiss dome is composed of quartz-biotite gneiss and is surrounded by a border zone of si11 imanite gneiss and amphi bol i te (F. Weber, U. S. Geological Survey, Personnal Comm. , 1978). Several 1arge northeast-trending, left-lateral faults cut the rocks in the central part of the quadrangle. One such fault that para1 lels the valley of Shaw Creek is known as the Shaw Creek Fault. Supporting evidence for a 40 kilometer (25 mile), left-lateral off-set on the Shaw Creek Fault, rests on an off-set hornblende quartz monzonite pluton and on an off-set sillimanite gneiss body (F. Weber, Personnal Comm., 1978). Several other large faults cut the rocks of the quadrangle, however, they are less perfectly known.

Geochemistry Geochemical reconnaissance in the Big Delta quadrangle during the current study consisted of the collection of 7 rock samples and 14 stream sediment samples (see Tables 12 and 13, Appendix A) between Big Delta and Shaw Creek. The bedrock in the region is dominated by gneisses of various compositions and calcic amphibolites, all of the Birch Creek Schist Formation. Statistical analysis of the trace element geochemistry of the rock and stream sediment samples . collected has shown that 43% of the rock samples contain strongly anomalous concentrations of at least one element, and 36% of the stream sediment samples contain weakly anomalous and strongly anomalous concentrations of at least one element. Threshold values (see Tables 14 and 15, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0 x standard dev.iation, and 2.33 x standard deviation, for the 90% 95% and 98% confidence levels respectively. Where the analytical variability is zero or near zero, the threshold values for the confidence levels are either the detection level or nearly the same -value. None of the rock samples collected in the quadrangle contain metal concentrations of significance, however recent work by the U.S. Geological Survey may show that rocks in the region have good mineral resource potential and may contain metal concentrations of unknown size and distribution. One stream sediment sample collected near Gold Run Creek contained 320 ppm lead. No bedrock source for the high lead value was found and further work is needed.

. Mining Activity and Economic Geology Mining in the Big Delta quadrangle has been limited to several placer deposits in the Tenderfoot Creek, Michigan Creek, and Salcha River areas and to several hardrock gold-quartz veins near Tibbs Creek. Mining in the Richardson district has been underway since .gold was discovered on Tenderfoot Creek in 1905. Deep placers were also found on Banner Creek, Democrat Creek and Buckeye Creek soon after the initial find on Tenderfoot Creek. Total production for the Richardson district by the end of 1930, totaled more than $1,329,900 (Saunders, 1965). Only a few small operations are active in the Richardson district today. The source of the gold in the placers may be gold-quartz veins that cut the schist-gneiss country rock. Locally, rhyolite porphyry of probable. Tertiary age, cut the gneissic rocks and contain anomalous go1 d concentrations. Recent work by the A1 as ka Division of Geological and Geophysical Survey has shown that the rhyol ite porphyry may, upon weathering, result in residual gold placer deposits (Bundtzen and Reger, 1977). Several rhyol i te porphyry occurrences are known in the southeastern part of.the quadrangle, however, only minor disseminated su1 f ides are known. Several go1 d quartz veins are known in the Tibb's Creek area and minor production has occurred. The Tibb's Creek occurrences are active and some placer mining has occurred downstream from the rhyolite porphyry outcrops. Near the head of Black Bear Gu~c~,a tributary of the North Fork of the Salcha River, a 1imestone bed containing nickel concentrations as high as .28% can be traced for almost eight miles. The bedrock in the area is dominantly quartz-muscovi te schist, quartz biotite gneiss and ultramafic rocks of the Big Salcha ultramafic body. The 1imestone is overlain to the south by ultramafic rocks and contains secondary nickel mineralization. The secondary nickel minerals may be the result of leaching of nickel from the overlying ultramafic rocks and redeposition in the limestone, or the result of weathering of primary nickel sulfides in the limestone (Saunders, 1954). Florence Weber of the U. S. Geological Survey feels that the secondary mineral ization may have resulted from leaching of the ul tramafic body and redeposition by some sort of spring system within the ultramafic- 1 imes tone sequence. In the early 1930is, gold-bearing quartz veins were discovered in the Tibbs Creek area. The area was subsequently staked and by 1941, about 400 meters (1,300 feet) of underground work had been done. The gold-bearing quartz veins are concentrated in a zone of intense shearing along the contact between granite and gneissic schist. The quartz veins vary from a few centimeters to 2 meters (few inches to eight feet) wide and consist of quartz, pyrite, arsenopyrite and stibnite. Work by the U. S. Bureau of Mines has shown that the gold content in the vein material decreases appreciably with an increase in the sulfide content. Premineral and post-mineral faulting is evidenced in the area and cross-faults displace the veins a few centimeters to a meter (ir~chesto several feet) locally. Total production from the Blue Lead was about 132 ounces of gold and 25 ounces of silver. The vein material averages about 0.88 ounces of gold per ton. The potential for finding other mineralized veins in the area seems high. Recent work by the U. S. Geological Survey and by the Alaska Division of Geological and Geophysical Surveys, has shown that rocks along the north-flank of the Alaska Range may be correlateable with similar rocks in the Big Delta quadrangle (Wyatt Gilbert, ADGGS, 7 3 personal comm., 1977). The Totatlanika Schist and Keevy Peak For- mations in the Alaska Range are the host for significant mineral i- zation of volcanogenic lead and zinc affinities. If the rocks in the Big Delta quadrangle are equivalent to the rocks on the north-flank, there may be good potential for flnding similar mineralization in the Big Delta quadrangle. REFERENCES CITED

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Stewm, Anne E., ond Milne, W. G., 1973, Seismicity studies in the hbckenzia Volley, Yukon Territory, ond eostern Almko (obs.): EOS Om. Geophys. Union Trons.), v. 54, n. 3, p. 143.

Stevens, A. E., ond Milne, W. G., 1974, A study of seismic risk ncor pipeline mridars in northweltern Conodo ond rostern Alosko: bnodion kur. Eotth Sci., v. II, A. I, p. 147-164.

Sbut, Jomes H., body, khn 8.. and Collender, kmlhon, 1972, Quoternary movement on the Demli foult in the Delto River areo, Alaska (obs.), in Cwdilleron Sect., 68th Ann. Mtg.: Geol. hc. herico Abr., v. 45. 3, p. 243.

Sbut, J. H., body, J. 8.. Weber, F., et ol., 1973, Evidence for OU0ternory movement on the McKinley Strond of the Dcnoli fovlt in the Delto River oleo. Alosko: Geol. Soc. Amoico Bull., v. 84, n. 3, p. 939-947.

Ths, B. I., 1970, Reconaoissonc~of the gold-bcoring qwrtx veins in the Tibbr Geek oleo, Goodposter River, Big Delta quodronglc, cent101 Alosko: U.S. 8w. Mines open-file rept. 14-70, 12 p.

U.S. Geologicol Survey, 1899, hbpr ond descri?tions of routes of cxpiorotion in Alosko in !8PB, with genool informotion concerning the Territory: U.S. Geol. Surrcy 4rc. Pub., 138 p.

U.S. Geologicol Surrey, 1962, Gtologicol Swvcy rescorch 1962: U.S. Geol. Swny Prof. Poper 450-A, p. Ai-A257.

U.S. Gcologicol Surcy, 1963, Geologicol Survey rescorch 1963, sumnory of invrsti- gotiom, pepwed by mtmbers 01 the Comervotion. Geologic, and Woter Rcuruca Divisions: U.S. Geol. Surrcy Pmf. Pops 475-A, p. AI-A300. Fairbanks Quadrangle

Previous Investigations The Yukon-Tanana region has been the site of extensive geologic investigations since J. E. Spurr (1897) traversed Chi1 koot Pass into the headwaters of the Yukon River and then travelled down the Yukon to Nulato. In 1898, A. H. Brooks, ascended the White River to its headwaters, portaged to the Tanana River and then travelled down the Tanana River to its mouth. With the establishment of the Division of Alaskan Mineral Resources by the U. S. Geological Survey in 1903, a systematic study of the geology and mineral resources of the Yukon- Tanana region began. The ini tal investigations of the Fairbanks district began in 1903, under the direction of Alfred H. Brooks. L. M. Prindle (1913) and others with the U. S. Geological Survey, conducted some detailed work, however, most of their work was of a regional nature. In 1911, J. B. Mertie, began intensive geologic investigations of the Yukon-Tanana Region that continued through 1936 and culminated in the publication of U. S. Geological Survey Bu1 letin 872, The Yukon-Tanana Region, A1 aska. This work summarized a11 of the known geology of the region and is still the single best pub1 ication on the geology of the Yukon-Tanana Uplands area. Durin the interim, Prindle (1913), Chapin (1914) and Mertie (1913-1 9303 produced several papers describing the lode deposits and mining activity in the Fairbanks district. The most comprehensive study of the lode deposits in the Fairbanks district was produced by J. M. Hill (1933). This study includes a brief description of the local geology and detailed descriptions of the various mining properties as well as comments on the general economic conditions affecting the mining operations. Work by Sandvik (1964) discussed the distribution of ore deposits and metals in central Alaska. Detailed geologic investigations by R. B. Forbes and J. M. Brown (1961) and J. M. Brown (1962) centered in the Cleary Summit area, and was the first real definitive work that further clarified the outcrop pattern, structure, and petrography of the calc-magnesian rocks and the surrounding pelitic schists of the area. Later work by Forbes et a1 (1968) in the Pedro Dome - Cleary Summit area, examined the gold-gradients in relation to the intrusive bodies and surrounding metamorphic rocks. A companion project by Pi1 kington et a1 (1969) resulted in a detailed examination of the gold mineralization in the same area.

Work by R. C. Swainbank (1971 ) and R. C. swainbank and R. B. Forbes (1975) on the eclogitic rocks from the Fairbanks district has resulted in a better understanding of the tectonic framework and origin of many of the metamorphic rocks found in the area. Work by J. M. Bri tton (1970) has resulted in a detailed study of the rocks that constitute the Pedro Dome pluton. Work by G. A. Furst (1968) described the olivine basalts that occur in the Fairbanks area. Recent work by 7. Pewe et a7 (1975 and 1976) on the geology of the Fairbanks area has resulted. in a series of reconnaissance geologic maps for the area.

Regional Geology and Petrology The rocks that crop out in the Fairbanks quadrangle dominate the geology of the Yukon-Tanana Up1 ands area. The rocks range from Precambrian(?) to Recent in age and are represented by sedimentary, metasedimentary, plutonic, volcanic and metavol canic rocks. The intrusive rocks are generally of two types; Paleozoic(?) ul trabasics and acid intrusives of Jura-Cretaceous and Cretaceous age. The volcanic rocks are mainly olivine basalt of Middle Tertiary(?) age. The metasedimentary rocks are metasil tstones, phyll ites, eclogi te, marble, quartzite, calc-magnesian schist and pelitic schist. The meta- VO~canic rocks may be represented by arnphi bo1 i te, quartz feldspathic schist and greenstone. The Birch Creek Formation was first described by Spurr (1896). The type locality for the Birch Creek "Schist" is located near the headwaters of Birch Creek, northeast of Fairbanks. At it's type 1ocal i ty, the unit is composed of quartz muscovi te schist, quartz mica schist, mica schist, feldspathic schist, chlorite schist and a minor proportion of carbonaceous schist, calcareous schist, and crystal 1i ne 1imestone (Mertie, 1937). Recent work by Swainbank (7971) and others has shown that the Yukon-Tanana Uplands in genera1 and the Birch Creek schist in particular contains a wide variety of gneisses, calc-magnesian schist, phyllite; amphibol ite and eclogite. Rocks in the Fairbanks district proper that are members of the Birch Creek Schist crystalline terrane have been divided into at least two sequences that may be in thrust(?) contact (Forbes et a1, 1968). The lower and older sequence, exposed in what may be a structural window, are mainly eclogi tes, garnet amphi bol i tes and cal c-magnesian rocks containing cl i nopyroxenes and amphi Do1 es. The upper sequence is composed of younger(?) pel itic schist, crystall ine schist, micaceous quartzite, quartzite and calc-rnagnesian schist. The peli tic schists are typical ly garnetiferous quartz muscovite and biotite schists that show signs of at least two phases of metamorphism and possibly a third retrograde event.- Two phases of muscovite are present in the pelitic schists. The first phase consists of euhedral grains parallel to the primary S plane and a second (later) phase that defines an Sp plane that 1ransects the earlier S foliation. The S2 foliation also contains subhedral , faintly p 1 eochroic biotite laths (Brown, 1961 ). Locally, the pelitic schists contain deeply absorptive biotite rosettes and may represent late hornfelsing of the schists (Swainbank, 1971 ). Tour- maline is a common accessory mineral along with rutile, apatite and sphene. The quartz fabric of these rocks is dominantly granoblastic and may contain untwi nned pl agiocl ase porphyrobl asts of a1 bi te-01 igoclase composition. The presence of faintly pleochroic chlorite (pennine) usual ly signals retrograded rocks. The quartzites and micaceous quartzites of the area are present in both the upper and lower plate(?) sequences, however, it is the dominant unit in the upper plate sequence. These rocks are predominantly fine-to medium- grained quartzites with variable contents of quartz, muscovite, ' biotite, garnet, and chlorite. Accessory apatite, magnetite and zircon are common. The growth of chlorite (pennine) in the upper ,, plate(?) sequence appears to be related to stable mineral development during the metamophic process, however, the growth of chlorite in the quartzites and micaceous quartzites of the lower plate(?) sequence appear to be in response to a retrograde event. The calc-magnesian rocks of the Fairbanks district, genera1 1y Occupy the lower plate sequence and have been broken into three calc- magnesian variants by Swainbank and Forbes (1975). One variant, a garnet-clinopyroxene rock, essentailly an eclogite varies from massive types to mylonitic bands and contain pale-pink garnets that exhibit reaction rims of bl ue-green amphibole. Omphaci tic pyroxene is the dominant c1 i nopyroxene and a1 bi tic pl agiocl ase usually occurs in untwinned grains and is only found in the mylonitic varieties and is usually associated with garnet, clinopyroxene and chlorite. Quartz generally occurs in granoblastic aggregates and calcite occurs as an essential phase along with clinopyroxene and garnet (Swainbank and Forbes, 1975). Accessory apatite and sphene are also present. Calc-magnesium rocks composed predominantly of garnet, clinopyroxene and amphibole make up the second variant. This variety usually occurs in fine laminations, a1 though massive varieties are common. The clinopyroxene is usually light-green and the amphibole may be a highly absorptive variety of hornblende. Plagioclase tends to be more calcic in these calc-mangesian rocks and generally ranges from a1 bi te to 01 igoclase in composition. Muscovite, when present, marks at least two pulses of metamorphism, one represented by an earl i er synkinematic fabric and the other by transecting shear planes. Calcite tends to be more abundant than quartz and clino- .zoisi te is a common mineral ccnsti tuent. Accessory tourmal ine, orthite and graphite are also present. Rocks of the third group are generally composed of garnet and amphibole and occur with massive fabrics and varieties that have only incipient foliation. Garnet porphyroblasts up to 8 millimeters (.3 inches) in diameter are common and exhibit euhedral overgrowths on subpoi ki 1oblastic cores (Swainbank and Forbes, 1975). Muscovite and biotite are present in a primary synkinematic fabric and late muscovite marks a discordant Sp plane. Cl inozoisi te seems to be restricted to certain compositional layers and sphene, rutile, and apatite are common accessories. The calc-magnesian. schists of the upper plate(?) sequence occur in thin, conformable layers or lenses and are relatively rare within 1 the sequence. The upper plate sequence also contains greenschists, epidote amphi bol i tes, calc-mica schists and impure marbles. The intrusive rocks of the Fairbanks district for the most part range from quartz diorite to granodiorite in composition. The largest pluton in the area extends from Pedro Dome west-southwest approximately 4.8 kilometers (3 miles) to the head of Moose Creek No. 2. Several small intrusives of the same general composition are known in the district. The plutons are elongate in outcrop pattern and the direction of elongation is generally parallel to the structural fabric of the area (Britton, 1969). The plutons are predominantly fine- to medium-grai ned hypidiomorphic-granular quartz diorite and grandiorite although allotriomorphic-granular textu.res are known. Petrographically, the rocks are composed of up to 45% plagioclase feldspar (An86 to An30) in subhedral to euhedral grains, 10 to 20% subhedral biotite and 8 to 12% pyroxene, that includes major augite and trace hyperthene in subhedral grains that often have reaction rims of hornblende. Accessory magnetite, apatite, zircon and pistacitic epidote are common. Quartz monzonite stocks and dikes are common in the Pedro Dome area. The dikes and stocks cut the quartz diorite and granodiorite locally. The quartz monzoni te is composed of phenocrystal to gl omeroporphyri tic quartz, potassium feldspar and pl agioclase. Petrographical ly, the quartz monzonite consists of up to 36% plagioclase (An4, to up to 38% quartz with accessory hornblende, magnetite, apatite, sphene, and zircon. Epidote, clinozoisite and calcite may also be present due to a1 teration. Locally, intrusive rocks in the Pedro Dome - Cleary Summit area have been highly altered. At several localities, the feldspars have been totally altered to clays and accessory magnetite has been altered to ferrugenous material. North of Pedro Dome, the rocks are intensely altered and combined sodium and potassium contents as high as 13% have been detected.

- -- -- . - At several locations in the Fairbanks area, Tertiary volcanic rocks are present. The volcanics are chiefly basal tic in composition. Furst (1968) found that the Fairbanks basalts are transitional between tholeiitic and alkali basalts. The basalts occur as flows and breccias and are characterized by pillows, pillow breccias and col umnar basal ts. The pi 1lows were be1 i eved to have formed during the extrusion of the basalt in a subaqueous environment. Petro- graphically, the basalts are composed of 9 to 15% olivine, 20 to 49% pl agiocl ase feldspar (AnS0 to Ane3), 5 to 20% ti tani feroui augite, 17 to 20% glass and up to 5% magnetite. Rocks near the head of Big ElDorado Creek in the pipeline trench are composed of pelitic schist, quartzite, micaceous quartzite and minor phyll ite. Locally, the metamorphic rocks are highly sheared and shattered. The rocks are deeply weathered and heavily iron- stained where shear zones and faults are present. The ironstaining is probably related to local mineral ization, however, only minor sulfide mineralization was found during this investigation. The area is spatially related to the highly mineralized zone near Pedro Dome, to the northeast, and does contain known mineral occurrences. Between Big El Dorado Creek and Goldstream Creek, the rocks are highly variable in nature. The dominant rock type in the area is a chl ori te-bearing, garnetiferous , quartz mica schist. Minor interlaminations of calc-magnesian rocks, including: garnet amphibol i tes, impure marbles, and ec1 ogi tes, are present. The metamorphic sequence is cut by quartz diorite-and quartz monzonite dikes that are highly altered and are probably genetically related to the Pedro Dome quartz diorite stock. The faults and shear zones.of the area generally para1 lel the major fold axes, a1 though discordant fracture systems are known. Superimposed fold axis demonstrate the polymetamorphic nature of the metamorphic rocks in the region. , The rocks present between Goldstream Creek and the head of Engineer Creek, are for the most part pel itic schist and quartzite. At one locality, opposite the confluence of Little Blanch and Engineer Creeks, a highly sericitized intrusive rock is present. The quartz monzonite(?) is altered and is now a rock that is composed of clay minerals and muscovite and contains pyrite cubes to 10 mi 11imeters (0.4 inches) across. Local ly, the cl ay-muscovite rock contains large, up to 10 millimeters (0.4 inches), arsenopyrite grains that may be crystals. Anomalous metal concentrations were found in these rocks. A roadcut on Hill 1558, northeast of Engineer Creek locality, contains similar rocks, but with small .blebs of pyrite. Near the head of Engineer Creek and to the east, the bedrock is composed of a monotanous sequence of interlaminated quartz-muscovite schist and micaceous quartzite. The schist is characteristically a fine-to medium-grained, garnetiferous quartz muscovite schist. The quartzite layers are generally finely laminated to massive, however, unfol iated beds up to 0.5 meters (1.6 feet) thick of fine-grained micaceous quartzite are known.

Structural Geology Rocks of the Fairbanks district have been affected by at least two major deformational events. The first metamorphic event is associated with a complete recrystallization of the parent rock and with the development of high-grade metamorphic minerals, while a later phase of metamorphism, appears to have been mainly a retrograde event. The early recrystallization is associated with west northwest-trending folds, while the later phase is associated with folding about northeast-trending axes. Fold styles associated with the early recrystal 1 ization appear to be isocl inal and overturned to the northeast. Some folds are recumbent and arcuate (Swainbank and Forbes, 1975). The northwest-trending folds appear to be overturned and (or) recumbent, with axial planes usually dipping south. The degree and direction of overturning is variable and related to the superimposed northeast-trending structures (Swainbank and Forbes, 1975). A major structure in the northwestern part of the quadrangle that appears to have a close genetic relationship with the gold mineralization in the Cleary Summit - Pedro Dome Area was first recognized by Prindle (1913). The Cleary Anticline is a northeast-trending, arcuate, asymmetrical structure that is slightly overturned to the northwest. Fracturing along the axial trace of the anticlinal structure seems to have localized and controlled the emplacement of quartz vei n systems. Swainbank and Forbes (1975) believe that the quartz schist, micaceous quartzi te, pel i tic schist terrane of the Fairbanks -area i s in thrust(?) contact with the underlying and older eclogite-bearing terrane. The structural style present in the rocks of the lower sequence is isoclinal recumbent folding about north to northwest- trending axes. Later folding has superimposed open folds, about northeast-trending axes, on the earlier i socl inal to recumbent structures. Microstructures in the rocks of the eclogi te- bearing terrane also reflect the polymetamorphic history.

Geochemistry Geochemical reconnaissance in the Fairbanks quadrangle during the current study consisted of the collection of 40 rock samples (see Table 16, Appendix A) from the inner pipeline corridor by M. I.R.L. personnel and U.S. Bureau of Mines personnel during the 1976 field season. Statistical analysis of the geochemical data has shown that 30% of the rock sampl es col lected contain weakly anomalous, anomalous and strongly anomalous concentrations of at least one element. Thres- hold values (see Table 17, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0'~standard deviation, and 2.33 x standard deviation for the 90%, 95% and 98% confidence levels respectively. Where the analytical variability is zero or near zero, the threshold values for the confidence levels are either the detection level or nearly the same value. Samples of altered schist and quartzite, collected just north of Si1 ver Gulch, near Goldstream Creek, contain strongly anomalous concentrations of silver, tin, phosphorous and sodium, that may be related to numerous quartz veins that cut the schist-quartzite countryrock. Samples of schist and quartzite collected near Murphy Dome Road contain anomalous and strongly anomalous molybdenum, zinc and chrome and nickel values. The rocks are highly artered and cut by many quartz veinlets. East of the Murphy Dome locality, at the Silver Fox Mine, a stockwork of thin quartz veins cut quartz diorite of the Pedro Dome intrusive. The quartz veins contain some disseminated molybdeni te. The Silver Fox Mine locality a1 so contains lead- silver-zinc mineralization in shear and gash zones near the contact between the schist-quartzite country rock and the Pedro Dome stock. The anomalous molybdenum and zinc values at the Murphy Dome locality 84 may indicate the presence of Silver Fox type mineralizaton in the area. Southeast of Goldstream Creek near the head of Engineer Creek, samples of highly altered rocks, that appears to be a sericitized quartz monzonite contains anomalous concentrations of tungsten, arsenic, zinc and lead. -

Mining Activity and Economic Geology The first actual gold discoveries in the Fairbanks quadrangle took place in the early 1870's when gold was found on the Tanana River. The first deposits exploited in the region were found on Faith, Hope and Charity Creeks and were originally located in 1898. The first placers found in the Fairbanks area proper were found by Felix Pedro in 1902 on Pedro Creek about 19 kilometers (12 miles) north of the Fairbanks town site. The stampede that ensued the discoveries resulted in the establ ishment of the trade center near the confluence of the Chena River and the Tanana River, that subsequently became the town of Fairbanks. Placers of the Fairbanks district have yielded about 7,239,000 ounces of gold up to 1959 (Koschmann and Ber~endahl, 1968). Lode gold production in the Fairbanks district began as early as 1910 and continues to date. The history and production from lode deposits was summarized by Bruce I. Thomas (1 973) as follows: The 1902 discovery of the rich gold-placer deposits . and the subsequent rapid development of placer mining stimulated the search for the bedrock sources of placer gold in the*Fairbanks mining district. The first gold quartz claim was made shortly- afterward. The gold- bearing quartz veins were not bonanzas, and lode mining developed slowly. The first stamp mill was built in 1909, and the first lode gold was produced in 1910. In 1913, six mills were operating, and more than 12,000 tons of gold ore was milled. Gold mining declined during World War I, and from 1915 to 1923, the mining of lode-gold deposits continued at less than 2,000 tons per year. Completion of the Alaska Railroad in 1923 provided a direct bulk-freight route from the coast to Fairbanks. Lode mining increased to 5,000 to 6,000 tons per year in the 1930's. The increase in the price of gold from $20.67 to $35.00 per fine troy ounce in 1934 resulted in an annual production of over 11,500 fine' troy ounces by the late 1930's. During this period, production of lode gold exceeded the gross production from all placer mines in the district except that of dredges. In 1942, the production of lode gold was stopped by executive order that closed gold mines. After World War 11, attempts were made to resume operations at some of the mines, but in most cases, increased costs made mining unprofitable. At various times during the past several years, one and sometimes two lode mines have operated for short periods, but at no time at a scale comparable with that prior to 1942. The total production from lode-gold deposits in the district is about 241,000 fine troy ounces from ore that averaged about 1.32 fine ounces per ton. The most productive sources of lode gold are veins a few inches to 3 feet wide. A1 though there have been as many as 10 to 12 mines operating in the district at one time, the largest single mine produced about 40 tons of ore . per 24- hour day. The general character of the gold lodes, after Hill, (1933) consist of fissure veins, that cut various types of sch-ists, and usually in close proximity to intrusives of sil icic-to intermediate composition. Veins ranging from 5 centimeters to a meter (2 inches to 3 feet) wide have been the most productive. However, zones of closely spaced quartz vein1 ets have been found and were rich enough to be mined over widths of 2 to 4 meters (8 to 12 feet). At several localities, namely the Ryan lode on Ester Dome, and at the Zimmerman lode, silicified schist over widths of 12 to 23 meters (40 feet to 75 feet) have been found and exploited to some degree. The principal veins in the Pedro Dome - Cleary Summit area strike between N60°M and due west and dip between 45" and 80" south. A few of the veins strike N25OE to N45OE and dip 70" to 75O north west. Hill (1933) recognized at least four phases of silica (quartz) deposition in the region. The earl iest episode introduced coarsely crystalline white quartz that is barren of metal1 ic minerals. This quartz was later brecciated and crushed by faulting along the veins. Next, a fine-grained quartz was introduced and was accompanied by some free gold and pyrite. Continued faulting and fracturing along the vein systems resulted in more brecciation and was accompanied by fine-grained quartz and sulfides with free gold. The final pulse according to Hill (1933) was a reactivation of the faulting and the introduction of barren quartz. Sandvik (1967) also recognized four pulses of mineralization in the Pedro Dome - Cleary Summit area. The first phase was characterized by the emplacement of barren quartz . veins, the second by the emplacement of quartz veins containing arsenopyrite, pyrite and gold, the third and most productive (Forbes et a1 , 1968) pulse of mineral ization consisted of quartz-sti bnite- gold f arsenopyrite and antimony sulfosalt veins. The fourth and final phase of mi neral i zati on consists of quartz-s tibni te veins with little or no gold. The phase three veins of Sandvik (1967) have been .further subdivided into three distinct mineral assemblages (Forbes et al, 1968). The most typical assemblage contains jamesoni te, stibni te and gold and is characterized by the Kowalita vein near the Keystone Mines property, east of Cleary Summit. The next most important assemblage contains quartz, jamesonite, freibergite, galena and stibnite and contain significant gold values. This assemblage is characteristic of the vein at the Keystone property. The third assemblage consists of galena, sphaleri te, tetrahedri te, pyrite quartz veins with subordinate gold values. This assemblage is restricted to fissure veins that cut the Pedro Dome quartz diorite stock at the Silver Fox Mine. Active mining of the gold-quartz lodes and lead-silver veins in the Pedro Dome - Cleary Summit area continues to date. The potential for finding undiscovered veins in the region seems high. Some of the previously uneconomic vein deposits may become mineable with improved mining methods and an increase in the price of gold - and silver. Several small tungsten deposits near Gilmore Dome, north of Fairbanks have produced in the past and one deposit on Gilmore Dome is being mined. The tungsten deposits are localized in 1imy layers within the Birch Creek Schist. The deposits near Gilmore Dome are located near the contact with the Gilmore Dome quartz diorite stock. The intrusion of the quartz diorite stock in the Cretaceous has altered the country rock and has produced calcite-epidote skarns and calcite-diopside skarns that are closely associated Mith the tungsten mineral iza tion. In summary, the Fairbanks district has produced in excess of 7,000,000 ounces of placer gold and over 200,000 ounces of gold from hard rock deposits. The potential for finding unknown gold and silver deposits and deposits of tungsten in the Fairbanks district seems high. REFERENCES CITED

Bri tton, J.M., 1970, Petrology and petrography of the Pedro Dome plutons, Alaska: Unpublished M.S. thesis, University of Alaska, 52 p. Brown, J.M., 1962, Bedrock geology and ore deposits of the Pedro Dome area, Fairbanks mining district, Alaska: Unpublished M.S. thesis, University of Alaska. Chapin, T., 1914, P7acer mining in the Yukon-Tanana region: U.S. Geol. Survey Bull. 592, p. 357-362. Forbes, R. B., Pi1 kington, H.D, , and Hawkins, D.B., 1968, Gold gradients and anomalies in the Pedro Dome - Cleary Summit area, Fairbanks district, Alaska: U.S. Geol. Survey open-file report 325, 43 p. Furst, G.A. , 1968, Geology and petrology of the Fairbanks basal ts, Fairbanks, Alaska: University of Alaska M.S. thesis (unpublished) 53 p. Hill, J.M., 1933, Lode deposits of the Fairbanks district, Alaska: U.S. Geol. Survey Bull. 849-0, p. 19-163.

Koschmann, A.H., and Bergendahl , M. H. , 1968, Principal gold-producing districts of the United States:. U.S.. Geol. Survey Prof. Paper 610, 283 p. Mertie, J.B., 1913, Igneous rocks (of the Circle quadrangle, Alaska): U.S. Geol. Survey Bull. 538, p.36-48. Mertie, J .B., 1937, The Yukon-Tanana region, Alaska: U.S. Geol . Survey Bull. 872, 276 p. Pewe, T.L., Bell, J.W., Forbes, R.B., and Weber, F.R., 1976, Geologic map of the Fairbanks D-2 quadrangle, Alaska: U.S. Geol . Survey Map I, 829-A. Pewe, T.L., Bell, J.W., Forbes, R.B.3 and Weber, F.R., 1976, Geologic map of the Fairbanks 0-2 NE quadrangle, Alaska: U.S. Geological Survey Map 1-950. Pewe, T.L., Bell, J.W., Forbes, R.B., and Weber, F.R., 1976, Geologic map of the Fairbanks D-1 SW quadrangle, Alaska: U.S. Geological Survey Map 1-949. Pewe, T.L., Bell, J.W., Forbes, R.B., and Weber, F.R., 1976, Geologic map of the Fairbanks D-2 SE quadrangle, Alaska.

Pewe, T.L.9 Bell, J.W., Forbes, R.B., and Weber, F.R., 1975, Geologic map of the Fairbanks 0-2 NW quadrangle, Alaska: U.S. Geological Survey Map 1-907. - I -

I Pi1 ki ngton, H.D. , Forbes, R. B. , Hawki ns, D. B. , Chapman, R.M. , and Swainbank, R.C., 1969, Preliminary investigation of the gold mineralization in the Pedro Dome - Cl eary Summit area, Fairbanks %, district, Alaska: U.S. Geol. Survey open-file rept., 47 p. Prindle, L.M., and Katz, F.J., 1913, Geology of the Fairbanks .. . district, in Prindle, L.M., A geologic reconnaissance of the Fairbanks quadrangle, Alaska: U. S. Geol . Survey Bull. 525, 1 p. 59-152.

I I. Sandvik, P.O., 1964, Relations of structure to mineral deposition at the Grant Mine, Ester Dome, Alaska: Unpublished B.S. thesis, University of Alaska, 28 p. Spurr, J. E., 1897, Geology of the Yukon gold district, Alaska in Eighteenth Annual Rept. of the U.S. Geol. Survey. Swainbank, R.C. , 1971, The geochemistry and petrology of eclogi tic rocks near Fairbanks, A1 aska: Unpubl ished Ph.D. dissertation, University of A1 aska. Swainbank, R.C., and Forbes, R.B., 1975, Petrology of the eclogitic rocks, Fairbanks district, Alaska, -in Contributions to the 1. geology of the Bering Sea region: Geol. Soc. Amer. Spec.

I, Paper 151, p. 77-123. .- Thomas, B. I., 1973, Gold lode deposits, Fairbanks mining district, I I I central Alaska: U.S. Bureau of Mines Inf. Circ. 8604, 16 p.

I FAIRMNKS QUADRANGLE 89

AloJlo Deportment of Miner. 1945. Report of the Commissioner of Mines to the Ihfnes, F. F., 1967, Gal resources of Alaska: U.S. Gcol. Suwcy Bull. 1242-0, Governor for the tw biennia ended December 31, 1944: Juneau, Alaska, 48 p. p. 01-83.

Alosko Department of Mines, 1944, Report of the Commissioner of Mines for the &rg. E., Van Wormer, J. D., and Bloom, N., 1911, Microcorthqucrkes in the biemium ended December 31, 1946: Juneou, Alaska, 50 p. Fairbanks area, Alorka, 'b" slopes and Vp/Vs rations lobs.l, Spnpanu. on forerunnerr of strong corthquakcs 8: Intetnot. Union &odesy and Geephy&s, Alorka Deparknrnt of Mines, 1948, Report of the bmmisioncr of Miner for the 15th On. Assem. Abr., Moscow, p. 28. bienniun ended December 31, 1948: Juneau, Alosko, 50 p. hrg, Edwrd, 1971, Gmlol deformation propopation: Alaska Univ. Gcophyr. Inst. Alosko Deportment of Mines. 1952, Report of the Commissioner of Mines for the Rept. UAG R-222, 22 p. biennium ended Oecembar 31, 1952: Juneau, Alasko. M p. &rg, Edwrd, 1972, Gwtal structwe in Aloska, in The Great Alasko Earthquake AIesko Deportment of Minn, 1957, Reprt of the Canmi,sioner of Mines for tha of 1964, seiwlogy and geodesy: Notl. Acox Sci., Washington, D.C., biennium ended December 31, 19%: Juneou, Alaska, lC3 p. p. 8-19.

Alosko Department of Miner, 1958, Report of the bmmissioner'of Miner for the &rg. Edward. 1973, Gustol strvctwe in Alosko, in The structure of the Earth's bienniun ended Cecember 31, 1958, 83 p. crvrt bmed on seismic &to: Tecmnophyrics,~. 20, n. 1-4, p, 165-182.

Alaska Deparhnent of Mine,, 1950, Rcpwt of the Commissicner of Mines for the kg, H. C., and Cohb, E. H.. 1967, hto~~iferoulode deposik-of Ahko: U.S. bienniwn ended December 31, 1950, Juneau, AloAo 57 p. Ccol. Surrey Bull. 1244, 254 p.

Alako Division of Geological and Geophysical Surveys, 19T3, Annuol report 1972: Blosinq, 1. J., and hilt,, H. C., 1975, Post climate of AlasCo and northwestern I~clunay.AlmLo, 57 p. Can& UI ~ecmtsu~tedism ~teuti*: AIQICO ki. Cod. PVOC. 24, p. 49-58.

Alasko Division of Ceologicol and Gecphysical Surveys. 1973, Annval Report 1972: Brqon. Gorge E., Cliff. Uoyd 5.. Dowings. Morio~iaE., st el., 1975, Actin Anchorage, AIaka, 57 p. faults of Alosko: Tectonophysics, v. 29, p. 73-85.

Alaska Division of Geologicol ond Geophysical Survey, 1974, Annual Report 1973: Brooks, A. H., and bpps, 5. R.. 1924, The Alaskan mining industry in 1922: Ancbrogc, Alaska, 59 p. U.S. Geol. Swvey Bull. 755, p. 3-49.

Alorka Dirision of Mines and Geology, 1968, Repwt for the year 1968: College. Brmks, A. H., and Martin, 6. C., 192!, The Aloskon mining idustry in 1919: Alorko, 67 p. U.S. Gcol. Survey Bull. 714, p. 59-95.

Alosko Division or Miner and Minrols, 1959. Repon of the Diririon of Mines Brooks, A. H., 1900, A reconnoinonce in the White ond Tanona river basins, and Minerals for the yew 1959: Juneou, Alosko, 80 p. Alorka, in 1898: U.S. Geol. Surrey 20th Ann. Rep)., pl. 7, p. 425-494.

Alasko Diririon of Mimes and Mincrols, 1960, Report for the year 1960: Juneau, Brooks, A. H., 1903, Placer gold mining in AIosko in 1902: U.S. Gol. Survey Alaska, 88 p. Bull. 213, p. 41-48.

Alorko Diririon of Mines and Minerals. 1962. Report fw the yeor 1962: Juneau, bwks, A. H., 1905, Plocer mining in Alorko in IMY: U.S. *I. Survey &I!. Alaska, 119 p. 259, p. 18-31.

Alosko Divisian of Mines and Minerals, 1963, Report fw the yeor 1963: Juneau, Brooks, A. H., 1907, The mining indushy in 1904: U.S. Gol. Surrey Bull. Alosko, E7 p. 314, p. 19-39.

Alorko Division of Mines and Minerals, 1966. Report for the year 1966: Juneou, &ks, A. H., 1908, The mining industry in 1907: U.S. Gal. Survey 6~11. 345, Alorka, 115 p. p. 30-53.

AIo3ko Division of Mines and Minerals, 1967, Report for the year 1967: College, Brooks, A. H., 1909. Mineral resource* of Alosko. in U.S. Geulogicol Survey, AlaJo, 98 p. Papers on the conservotion of minerol rcsovrces (reprinted from report of the National Canserration bmmirrion, February, 19091: U.S. Geol. Survey Alaska Geology Branch, U.S. Geological Sutvcv, 1972, The status of mine-ol Bull. 394, p. 172-207. resource iniormotion on the major iond withdrorol, of thAlosko Notirc Claim ktilcment Act of 1971: U.S. Geol. Survey opcn-file rept., 164 p. kookr, A. H., 1909, The mining industry in 1908: U.S. Geol. Surrey Bull. 379, p. 21-62. Anderwn, C;. S., 1970, Hydrologic reconnoissonce of the Tonono basin, central Alaska: U.S. Geal. Surrey Hydrol. In". Atlas HA-319, 4 Jleets. Brooks, A. H., I9IO. Tho mining industry in 1909: U.S. Gcol. Surrey Bull. 442, p. 20-46. Anderson, 1. A., and Johnson, G. R., 1970, Application of magnetic ond clectricol resistivity methods to invotigotiom in the Foirbonks dishict, &ooks. A. H., 1911, Geologic features of Aloskon metolliierow lodes: U.S. Geol. Aloska. in Geologicol Survey re%eorch1970: U.S. Geol. Survey Prof. Surrey Bull, 480, p. 43-93. Paper 7=C, p. C107-C113. Brooks. A. H., 1911. The Mount McKinley region, Alaska, with descriptions of the Andreosen, G. E., Wohrhoftig, Clyde, ad Zictz, Isidore, 1964, Aeromognetic igneous rocks and of the Bonnilicld and Kontishn. distticts, by L. M, Prindle: reconmiaonce pf the cost-central Tonono Lowland, Alosko: U.S. Geol. U.S. Gol. Suvey Prof. P-r 70. 234 p. Swrey Geophya. Inv. Map GP-447, 3 p., 2 sheets, rcole I:125,MK). Brooks, A. H., 1912, The mining indurhy in 1911: U.S.-Geol. Survey Bull. 520, Andreusen, G. k.. 1960. Totol intensity oar-netic profiles of the Minchvmina p. 17-4. area, Alosko: U.S. Gal. Survey open-file rept., 3 sheets. Brooks, A. H., 1914, The Aloskon mining indutry in 19:3: U.S. Gaol. Swrey Pnnonymou, 1974, Mvltimodal tronqormtion ond utility corridor system in Aloska; Bull. 592, p. 45-74. a p6limi~ry,conceptual onolpir: U.S. Dept. lntetia Bur. Land Manage- m.nt, 77 p. Brooks, A. H., 1915, The Alorkmn mining industry in 1914: U.S. Gml. Survey &It. 622. p. 1548. Anonymous, 1974. Mullimodal honrportotion and utility corridor ryrtem in Alaska; genrolized description of tk 40 primory cerridors, locat:om, mod-, kooks, A. H., 1916, Antimony deposits of Alosko: U.S. Geol. Survey @dl.649, identifying agencies, purposes, environmmtol impacts, and smtw of lands 67 p. crowd: U.S. Dept. Interior, kt. Lond Monagement. I84 p. Brds, A. H., 1916, The Aloska mining induny in 1915: U.S. Geol. Swny bin. H. F., 194, Alosko's minerals os a basis for industry: U.S. Bur. Mines Bull. 442. p. 16-71. Inf. Circ. 7379. 89 p. kooks, A. H., 1918, The Alaska mining industry in 1916: U.S. Geol. Survey Barnes, D. F.,' and hkccorthy, G. R., 1964, Prelimimry repat on tests of the Bull. 662, p. 11-62. opplicotion of ~eophysicolmethods to Arctic ground-wter problem: U.S. Geol. Survey open-file rept., 32 p. Brooks. A. H., 1919, Alosko's minerol supplies, in Mcbskey, H. 0.. and &,chord, E. F., Our mineral supplies: U.S. Gol. Swvey Bull. 666, Bornes, D. F.. 1961. Covity low ot Minto Flars, Alaska, in Geophysical Survey p. 89-102. research 1961: U.S. Grol. Swvay Prof. Popr 424-D, p. D254-D257. Brooks, A. H., 1921, The future of AloJIo mining: U.S. &I. Survey Bull. 714, Earner, D. F., 1967, Four peliminory gravity maps of ports of AIorka: U.S. Geol. p. 5-57. Surrey Ophfilc rept.. 5 p. Brooks, A. H., 1922, The Alaska mining industry in 1920: U.S. Gaol. Surwy Cobb, E. H., 1972, Matollic rninffol resources mp of the Foirbanb qw&ongle, hll. 722, p. 7-67. Alorko: U.S. Gaol. Survey Mirc. Field Studies Mop MF-410, I sheet, real. 1:250,WO. &ooks. A. H., 1923, The Alo&o mining indurtry in 1921: U.S. Geol. Survey hll. 739, p. 1-44. W,E. H., 1973, Placer deposits of AIosLo: U.S. Ccol. Surrey Bull. 1374, 213 p.

Brooks, A. H., 1925, Alosko's miner01 rcmvrces ond podwtion, 1923: - U.S. Gal. Cerbin, 5. W., ond &own, C. S., 1971, h wink, thcrml regime of &Idstreom Svvey Bull. 773, p. 3-52. Geek. Alosko lobs.): Almko Sci. bnf., Proc., n. 22, p. 163.

Bra~e.W. P.. 5obb. E. E., and King, E. R., 1970, Geolooic interprctotiorn of kt,C. C., ond Eltnmth, C. E., IW9, Water s pply of the Yukon-Tonana ~econmir%onceorromogr*tic surrey of rorthaalern.Alosko: U.S. Gal. Surwy region, 1907-1908: U.S. hl. Surrey &I). 379, p. 201-228. &I\. 1271-F, p. FI-~14. Covert, C. C., end Ellworth. C. E., 1909, Wote,-suppll imstigotionr in the bond, W. M., 1966, A geochemical investigation of the Ncmm Highwy oreo, Yukon-T-m region, AloJlo Ikirhnks, Circle, and R-;I dist*icts): U.S. sentrol Alosko: Alasko Div. Mims and Mineral, Gmchem. Rept. 10, 13 p. Geol. Surrey Woler-Supply Papec 228, 108 p.

Byffs. F. M., h., 1957, Tungsten &pasib in the FoirtanCI district, UolLo: U.S. brert, C. C., IW, Woter wpply of the F-irbonks district, 1907: U.S. &I. &I. Swvey &I!. 1024-1, p. 179-216. Suvry Bull. 345, p. 198-205.

Cappr, 5. R., 1911, Mineral resources of the Bmnifield region: U.S. G-I. Surwy Doris, J. A., 1923. Lode mining in the Fairbanks dbhict, Al~do, in Stewart. 1:0., Bull. 480, p. 218-235. Anna ol repat of the Min lny~ctmto the Chmw of Alo$a, 1922: luruou, AloAa. p. 1-113. Copps, 5. R.. 1912, The Bonnifield tegion, Alaska: U.S. Geol. Surwy Bull. 5M, 64 p. Day. Povl 5.. G yc, Genge, Dobey, Potrick L., et 01 ., 1974, Drrelopmnts in Alaska in 1973: Am. Assoc. Petroleum Geologistj hll., v. 53, n. 8, bpps, 5. R., 1919, The Kotirhm region, AloLo: U.S. Geol. Survey h11. 687, p, 1506-1517. 116 p. Dingma, 5. Lnmence, 1973, Effects of permofiort on skeom now chorocterirtics in *I, S. R., 1924, Gcolwy and minenol rcsornce%of tltc region hoverred by tlw the discontinuour pctmabost zone of cenhoi Alo*a,~ Pctmaf~o:t: Nwth Alaska Railroad: U.S. Geal. Survey &Il. 755, p. 73-150. Amrison Crul?,ibution, Scsond Internal. bnf.; grovndwter in permhost arms, p. 447-458: Notl. Pcod. Sci., Washington, D.C. Copp, 5. R., 1933, Mineral investigatiom in the AIorko Railroad bell, 1931: U.S. &I. Survey Bull. 844-8. p. 119-135. Oobro~ln~,frnrf. Schmall, H. R., and Yehle, L. A., 1969, Golog'c envir-ntol foctwr ~elotedto TAPS (Itom-AlmLo Pipeliw Sys~nn) Ira Voldcl to hitbonk%. -5, 5. R., 1940. Geology el tkAIo,ko Roilrood legion: U.S. Geol. Swvcy Alosko: U.S. Gsol. surrey open-file rapt., I sheet. &Ill. 907, 2M p. haldson, D. E., 1972, Thc distribution of baron in AIoskon waters bbr.'*: Alosko Cwtct, CloLrc, 1d.l. 1974. Unilud Stoles Grologicol Surrer Alorbo Ptogr~m, ki. hi, PIOC. 23, p. 80. 1974: U.S. Gcol. Swvey Cir. 700, 63 p. Eokin, H.'M., 1915. Mini- in the Foiibonks dishicl: U.S. Geol. Survey Bull. Cedarstrm, D. J., and Tibbitts, G, C., Ji., !%I, Jet drilling in the FoirbonLs 622, p. 229-238. or-, Alorko: U.S. Geol. Survey Wotst-Sqply Poper 1539-8, p. 61-828. Ebbley, Namon, Jr., ond Vhight, W. 5.. 1948, Antimony deposits in PIosko: Ccdersha, 0. J., bhnston, P. M., and Subitsky, Seymour, 1953, Occurtence U.S. Bur. Mines Rept. In*. 4173. 41 P. and d*rclopmcnt of pound wter in permafrost regions: U.S. Geol. Survey Circ. 275. 49 p. Eckhwt. R. P., 1953, Cloy, nor Nemrp: U.S. Geul. Surrey open-file rept., 6 p.

Cedelarstwm, 0. J., WohrhRig, Clyde, and aarnes, F. F., 1950, Gound rater Ellswatth, C. E., ond Davenport, R. W., 1913, Flo:er mining in the Yd,on-Tonone in the vicinities of Herly ond the!, Alosko: U.S. Geol. Surrey open-file region: U.S. Geol. Surrey Bull. 542, p. 203-222. rept., 4 p. Ellsworth, C. E., and Dorenpnt. R. VI., 1913, Wotcr supply of tk Yukon-Tomm Cedersttan, D. J.. 1952. Summory of ground-water derelqxnent in PIaJo, 1950: ragion, 1912: U.S. Geol. Suvey h11. 542, p. 223-278. U.S. Geol. Survey Ci

Cloud, Williom K., and Scott, Nino H.. 1972, Distribution of intensity, in Forte?, Helen L., Webat. flwencs R., Folbes, Robert 8.. et 01.. 1973. Regional The Great Alosko Eorthqwk. of 1964, rciunology ond geodesy, p. 65-103: Nutl. snology of Yukon-lanono upland, Alorko, in Arctic Gealogy: Am. Pwc. Pcod. Sci.. Washington, D.C. Cetcoleum Gcologirts Mtm. 19, p. 388-3957 FAIRBANKS QUADRAINGLE Cont. 9 1

hecbnd, Gcorpe L., ond C:ctz, Robert J., 1973, Rorstbn hiltwy ol Aloskun Lomke, R. 0.. 1972, Floods in the rmer of I971 in soqth-cewrol hlnCo: U.S. tectonic blocks: Tecromphpicr. v. 18, n. 3-4, p. 379-384. Gcol. Swvcy open-tile rep)., 88 p.

Goskin. OddA.. ond Stonlev, Leonwd E.. 1973. Control pi culvert kirp. Langc, G. Rubctt, 19-73. Investigolions of tompliy prenniolly hoxenal1ur;ol b Pc*mhmt; Nwth haicon Conbibution, Second Inlctnot. Conf.; hinciples grrvel by core dtilling, in Pe,molrost; North Amcricom bntrhtion. Second 3 comtructim in permfrost regions, p. 629-636: Fbtl. Acad. ki.; Internot. Conf.; survtrinTor-d pwdicting pemmohost conditions, p. 535-541: Woshinpt-, D.C. Narl. Acad. Sci.. Vtoihiqtoa, D.C.

G.d-y, Lo*~y,ond Von VJofmer. kmn 1974, b Alosko; remote sensing of bthrom, Gnest ti., 1972, Nimbv, IV view 01 the mior sl~uctwolkaturer of Alorkor seismic kzrvd+: Gcotimes. v. 19, n. 2. p. 15-17. Science, v. 175, n. 4029, p. 1423-1427.

Gakcy, L.. Shopi*~, L., Von Wwm, 0.. and Webar, f., 1972. Cotrebtion bthrom, Frmst H., 1973. Tecronic frnnewo.L of northan end central Aldo. lh or epicmtus 4th agpcd fovlrr, east-cmtrol Alml~o, 1968-1971: U.S. Gcd. Arctic Geology: Am. Aswc. Petrolem Geologish Mrm. 19, p. 351-b0. - . !%ray ope-(ik ~rpi.. 7 p. btkmn, Ernest H., 1970, Tectonic homework of northern and cmtrol Aldo fa6s.1. in Intermtiom1 sym+msivn M Arctic geology, 2nd: Am. kloc. PeltofeuW~ t.orp.. Worren, 1973, PrPlysh of the propod Little Clmo Rircr. corthfilled -Gtolgish bull., r. 54, p. 2493. navetention k.foiibonks, Alosko, in Permofroar: Florth Americon Contrihution, Second Intnnoi. Conf.; Principle, of &huction in.permaffort regions, p. 152-US: &+I.&ad. ki., Woshingbn, D.C. ' lincll, Kenneth A.. 1973. Lonp~tnmeffech of vegabtive core on pew~hol) s~bilityin on ore0 of dicontinuous ptmofrosi, in Permofrat; Wth Amcricon h.A, 1920. -isan of rnm~hodrof goMr.corry from block lond: U.S. bntribuion, Second Internor. Conf,; Principles% romtwctia, in pe~mftat LH. Minn Rep(. In*. 2192. 4 p. regions, p. 688-693: Notl. Arod. Sci., Vloshiqton, D.C. -

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tbr)... J. W.. Millr. M. H., ond Chopmon, 9. M.. 1975, I):unulb, in &&I. &hr, E, W., 1957, Chrmicol cho,ockr of public mter supplies d lhb Ierger citiu. D. A.. ond Pmt, W. P., (&I.), United 5htu mimol remrcn: U.S. Geol. in Alaka, tbroii, ord Pucrm Rico, 1954: U.S. Ge~l.Surry Wot~-Suppl~ Lr-y Pd. Popr 820, p. 95-98. Popr IP6&A, p. 1-39.

HarL;m, D. 8.. end fo.ber, R. 0.. 1971, Investigation of gold minerolirotion along Luthin, J. N.. ond Gqmn, G. L.. 1974, kil noistwe~gemriorrtmpwohwa , o pDrt of h filiin Hig-, RirSonks dkwicr, Aloh: U.S. Geol. Sur-y relotiomhips in cenml Almka: bur. Hydrology. r. 23, n. 3-4. p. 233-2%. . opw-lila rep*., 6.5 p. Mpddres, A. G-. 1918. Gold placers nor tb Nemm coal field: U.F. Gcol. kyw. hs3.. 1972. NOrth Slop* oil; physic01 and political problems: Rof. Surwy Lll. 662, p. 363-4U2. Geogtqhy. v. 24, p. 17-22. Motone, Kevin, 1965, Mercury in Alosko, in U.S. beau of Minu, Mercury . M&, F. F., end Covert. C. C., 19119, Wote~-suppIy investigations in Alosko, potentiof of thUnired Swn: U.S. Bu. Mins Inf. CLc, 8252, p. 31-59. 15;6-7 (NCM ond Koupok regionr, Se-d ?winrub; f-iabaks dirtricl, Yvbn-Tonom region): U.S. Gcol. Survey Vloter-Supply Paper 218,-156 p. Maloney, Williom, 1916, Repart of the Territorial Mine Inapectw to the Goarm of Plasb fa tkcyw R15: hcou, ~Iorbo, Y p, Rill. J. M., 1933, M &posits of !he Frirbonksdirhict. AIosLo: U.S. Geol. Surey aull. 8494. p. 19-163. Mol-y, William, 1917, Rcpwr of Williom Maloney, Tcrrit~iolMine lmprctor to th Governor of AtruLo fw the ,cw 1916: Junew, AIosLo 86 p. Hilt. 1. P., and Wermr. M. A*. 1972, Chemicol composition of sedimentor). rocks in Llosto, Idollo. argon wd Wmhi.gton: U.S. Cgl. Surrey hoi. Poper Mulomy, Williorn, 1918. Rep8 of the Ter~itcuiolMine lnspcw to tho. Governor of 771. 319 p. AlolLo fo~the yw1917: Junou. A!olLa 50 p.

Hoekstro. P., Sc~han*,P. V.. and Deloney, A?. 1975, Ground and oirborne Mutin, G. C., W19. Re AlaLon mining industv in 1917: U.L. Geot. Sure* ' seritivilr surveys d pcwnafrbrt **or Foirbonk~. AIasho: Geophysics. v. 40. bll. 692, p. 11-42. m. 4, p. MI+%. ' Martin. G. C.. 1919. The MMno coal Rcld. Aloako? U.S. Geol. Wvey bll 664. tbllick, Arthue, 1936. Th. Tertiary floras of Alab, with o chapter on he geology n P. d rh* 7ertky -sits, by P. 5. kith: U.S. Gaol. Survey Plof. Poper 182, I65 p. Matin, G. C.. 1920, The Afdon mlnimg industry in 1918: U.S. Gal. Surrey Bull. 712, p. 11-52. Holmes, G. W.. fap:ler, 1967, locotion of pingolikr muds &sh,rred ffmtiH pund, born aerial rocowisrance, ond on ocriol photographs in interior Morvin, R. F., 1974. A tabulation 4 K-A*, Rb-S, ond Pb- ogcs obmined from AlaLo: U.S. Cwl. knvq opm-file rcpt.. I3 p. motwiols within tht Uliicd Sh~tes(imlding AbsLo and Haniil doti- the pon1969 &rough 1971: U.S. Gcol. bur open-file rept., 193 p. +ins, 0. M.. blskom, I. N. V., and othm, l9S5, Pewft~~tand rand row in Ahko: U.S. Gwl. kr~yRof. Popr 243-F, p. 113-146. Marvin, I.F., W74, A &btia of K-Ar, Rb-5, und s&alph opn &loid . . han mslniols within the lhiled States (including AloBa ond Woroiil during the ye" 19% tk~ylh1964: US. Gco!. Survey own-filr report, 174 p.

Motthrm, Jahn,V., L., 1974, Wisconrin envmnlof interior *loAo: Pollen ond Jodng, H. R., 1943. Supplcnunt m PompLImt No. I- Strategic mineml occu- . mocrofossil onolysis of o 27 mckr core from the Irobclla~Bosinfkirbonkc, ~lakok #ewes in i*nk ClorLn: AIorko O+p(. Mimas P-h. 2, 28 p. bdinJaw. Eovih ki., v. II, n. 6, p. 828-841.

- Kddow2an. R&, 1960, bginening and suRcial -logy of the Ncmno-Rex McGuimu, C. I.., 1963, Throle of ground vakr in thmtid rotel siluotion: woo, ALslor US. -1. Erwl Misc. -1. hv. Mop 1-307, Isheet, U.S. Geol. Survey Wokr-Supply Papn 1800, 1121 p. xole 1~,350. Mutir, J. B., b., 1918, lode mining in the foirbanln district: U.S. Geol. b. L., and Slowher, Chorlw YI., 19i3. Recbge of o centrol Alorko Swray Bull. 662, p. 403-424. - hk. by dpw4C01tgtoundrotn, in Permoirost; North Prruricon Contribution, I.& Inmro). Con1.j promd*oh;-fn pmnftost orws, p. 458-462: Notl. Mertie, J. 8.. k., 1937. The Yukon-Tormm region. AlasLm: U.S. Geol. Suvey Ad. Sci., Woshiqton, D.C. Bull. 872. 276 p.

)br, bovgbr L., brlmn. W.rr K.. and &own, C. Edvmd, 1973. Grandwoter Miglioccio, Ralph R., end hamy, James Y'., 1430. 6ginecring geotqic ond pw* poswes dipcent to svhndic slreom. in Pe,~f,d; North Amlicon CM- sAufocr loil in~esti~tionfw tronr-AlosLo pipeline sphm !&,), 2 lnlermt;oml kibutekn, Seed Met-. Conf.; qroundrocz inpemofcost meor, p. 453-4582 sympmim on Arctic -lagy, 2nd: h. kroe. Petroleum C+olg)kts Buff., &I(. hd. ki.. Washington, D.C. v. 51, p. 24%. Kill~a. P. L., d ndrtie, J. I),, Jr.. 1951, Antinomy ore in the Feirbonks Millw. D. J.. Pop. T. C., and Gcyc, George, 1959, GeoIan of porstble. I dilhist Aloxka: U.S. Geol. hvey~pn-file ?cpt., 43 p. pet~oku.prorimes in Absko. .with on odtedbibliogqhy by E. H. Cobb: U.S. Gcol. hyBull. 1094. I31 p. KoKhrorm, A. H., and Eergcndohl, M. H., 1968, Primipol gold-poducing dirbicts of the Unitcd Yom: U.S. GroI. krcy Ptol. Popr 610. 283 p. Miller. M. H., 1973, himony, in bobst, D. A., and htt. W. C.. (ds.1, Ulitrd , I 5totn mincral.rewuen: U.S. Ceol. Swrcy Plol. Pow 810. p. 15-50. FAIRBANKS QUAORANGLE Cont. 92

MoeAing, brold J., 1973, An overview of the trom-Aloshn pipeline; engineering and Prindlc, L. M., ond Kon, F. J., 1913, Geology of tk Foirbonks district, in enriromcntol geology problems, Gcolopy, seismicity, and envi,onmeitol impoct, Prindle, L. M., A geologic reconnaisurnca of the Foirbnks qradrongle, Alorko: p. 405-4W: Asroc. Eng. Geology, La Angeles. U.S. Geol. Swvey 8~11. 525, p. 59-152. ' Motfit, F. H., 1927. Minerol industry in Alosko in 1925: U.S. Gwl. Survey Bull. Prindlc, 1. M.. 1904, Gold placer* of the fuirhonks district, Alaska: U.S. Geal. 792. p. 1-39. Surrey Bull. 225, p. 64-73.

Moifit, F. H., 1933, Mining developments in the Totloniko ond Tototloniko bsimr Prindle, L. M., 1905, Th. gold plocets of the Fortymile, Birch Geek, ond Foirhanlu V.S. Gal. Surrey Bull. 836, p. 339-345. ~egiora, AIosko: U.S. Geol. Swrey Bull. 251. 89 p.

Mulligon, J. J., 1974, Mi~rolIe%MC81 of the trons-Alosko pipeline corridor: Ptindle, L. M,, 1906, Yukon plocer fields: U.S. Geol. Swvey Bull. 266, p. IW-127. U.S. Bur. Mines Inl. Circ. 8626, 24 p. Prindlc, L. M., 1907, The Bomifield ond Kontishm regions, Afosko: U~S,kol. National Research Council, Committee on the Alosko Eorthqwke, 1973, Surnmory ond Survey Bull. 314, p. 205-226. remmmendcrtiom; including index to *ria in the collection The Greot Alolko Eonhqwke of 1964. No. 8, 291 p., Notl. Acod. Sci., Washington, D.C. Prindle, L. M., 1908, Occunence of gold in the Yukon-Tonono region: U.S. Grol. Suvey Bull. 345. p. 179-186. Nowmn. 1. W., ond Kcrnadle, D. R., 1973, Field woter-qwlity informotion olong the propored trom-Atosko pipeline corridor, September 1970 through SeplmLr Prindle, 1. M.. 1908, The Fairbanks and Rampart qucdronglaa, Yulron-Tonono reqion, 1972: U.S. Geol. Suwy open-file rep)., 22 p. Alasko, with o seclion on the Romport plocen, by F. L. Kss. and o pawr on the water supply of the Foirbonks region, by C. C. Covert: U.S. Geol. Svrwey Noaman, J. W.. old Kntadlr. 0. R., 1975. Aqtmlic mpwukrn lmm ,clrctvd sites 81,ll. 337, 107 p. olong the proposed trom-Alorko pipeline corridor, September 1970 though kptcmber 1972: U.S. Geol. Swvey ape<,-file r-t, 23 p. Pridle, L. M., 1910. Awitcrour quart2 reins in lk Faitbonks di'trirt: U.5. Geol. Surrey Bull. 442, p. 210-229. Overbeck, R. M., 1918, Lode depo~ihnear tk Nenona cool field: U.S. Gcol. Survey Bull. 662, p. 351-362. Ptindle, L, M., 1913, A reconnairvrnce ol thc Fairbonkr qworongle. Al~~ko, with a detailed description of the Fairbanks district, by L. M, Prindle ond F. J. Pocker, Dun** R., Brogon, George E., and Stone, Dorid 8., 1975, New data on Kotz, and on occount of lode mining nor Foirbonks, by P. 5. Smith: U.S. plote tectonic$ of Alosko: Tectomphysics, v. Z?, p. 87-102. ' Gcol. Survey Bull. 525, 220 p.

Pwn, William H., 1971. Arclic pipelining; tough, costly, but leoriblr.: UMR kvr., Purington, C. Vt., 1905, Metlmds and costs of ond plocer mining in Alosko: n. 2, p. 53-59. U.S. Geol. Surrey Bull. 263. 273 p.

Petthorn, Howord C., 1973, Stability of on underground rmm in frozen grovel, in Richards, H. Glenn, 1974, Tectonic evolution of Alako: Am. hoc. Pehoiem Prrmolrost; North American Contribution, kcond Internot. Conf.; Principles 3 Geologists Bull:, v. 58, n. I, p. 7949. construction in permfrost rcgiom, p. 6M)-706: Natl. Acod. Sci., Washington, D.C. Rortvedt. J. 0.. ond others, 1972, Summary of fldin the United Stotes durina 1967: U.5. GmI. Survey Woter-Supply Poper I8BPC. p. CI-CIIS. Pewe, 1. L., ond others, 1953, Multiple glaciation in Aloslo, 0 prog~essreport: U.S. Geol. Svrrey Circ. 289, 13 p. Rutledgr, F. A., Thorne, R. L., Kcrm, VI. H,, and ~ulligon, J. 1.. 1953, Preliminary repoct: Nonmetallic deposits accessible to the AIosLo Railroad os o Pere, 1. L., ond Poise, R. A., 1963, Fcwt heaving of pi1.s with on cromple from ~ouiblesource of row motcriolr for thc construction indurtry: U.S. Bu. Mines FoirhonLr, Aiosko: U.S. Gcol. Survey Bull. 1111-I, p. 333-407. Repr, lor. A932, 129 p.

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Wimmler, N. L., 1924, Ploccramining in Alorko in 1923, in Stcwrt, 8. D., Annual report of tk Mine lnrpctor to the Covermar of Alorko, 1923: Juneau, Alorko, p. 14-54.

Womii, O., Jr., and Letcullon, R. a,, 1975, Setting o problem of-aetting: Nwth. Eng. (Foirbanks), v. 7, n. I, p. 4-10. Liv.engood Quadrang 1e

Previous Investigations The Livengood quadrangle has been the site of extensive geological investigations since about 1899, when Alfred H. Brooks and others of the U. S. Geological Survey traversed the area. Much of the early 1i terature on the quadrangle describes the mineral resources and mining activities that were in progress within the Yukon-Tanana region. Recent work in the quadrangle by Chapman and others (1971), has resulted in a regional geologic map and basic resource information. Work by Forbes et a1 (1968) and Pilkington et a1 (1969) on the gold mineral ization near Cleary Summit, north of Fairbanks, has added much to the understanding of these gold deposits and to the basic geologic framework of the area. Recent work by Weber, Churkin, and Chapman, (in press) has added new information and resulted in the reassignment of the age of some Paleozoic rocks within the quadrangle. Recent geophysical work by Gedney et a1 (1972) and Packer et a1 (1975) have added information on seismicity and earthquakes within the area.

Regional Geol ogy and Petrology Rocks in the Livengood quadrangle have complex structural relationships. Precambrian(?) or lower Paleozoic polymetarnorphic schist, phyll ite and quartzite sequences are juxtaposed with Mesozoic sedimentary rocks across several large northeast-trending thrust faults and high-angle normal faults near the central part of the quadrangle. . A north trending high-angle norrcal fault near the Tolovana River marks the boundary between an upthrown eastern block composed dominantly of Mesozoic rocks and a western, downthrown block of dominantly Paleozoic rocks. Rocks of the Permian Rampart Group crop out northwest of Livengood. This sequence of interbedded tuff, tuff breccia, argil- 1 ite, minor chert and sedimentary rocks is cut by several northeast trending, high-angle normal faults. A small graben-1 i ke basin between the valleys of Hess and Isom Creeks contains interbedded, coarse-grained chert-pebble conglomerate, lithic sandstone, sandstone and shale believed to be Tertiary in age. The Rampart Group was first described by Spurr (1898). Later work by Mertie (1937), Brosge et a7 (1969), and Chapman, Weber and Taber, (1971) has described the Rampart Group at its type locality near Rampart, Alaska. The Rampart Group at its type locality consists mainly of bedded volcanic and sedimentary rocks of Permian age (Brosge et al, 1969). Early workers assigned a Mississippian age to these rocks based on paleontologic data, but recent work has shown these fossils to be Permian. Intrusive rocks found within the volcanic and sedimentary sequences have .been dated by K-Ar methods at 205+6 mi 11 ion years B.P. (Brosge et al, 1969), therefore the Rampart ~roup-is atleast Triassic in age. The Rampart Group as Plertie (1 937) described it, consists of basaltic and andesitic flows, basaltic, andesitic and rhyolitic tuffs and tuff breccias and a smaller amount of interbedded chert, shale, argillite and sandstone. The apparent lithologic sequence, at the type locality, consists of; dark greenish-gray lithic tuff

and tuff breccia interbedded with siliceous argill ite and minor , limestone. Overlying the basal tuff unit is a sequence of brown- weathering volcanic breccia containing cl asts of argi 11 i te and 1imestone. Next, a sequence of greeni s h-gray s ha1 e, dark-gray chert and interlayered basalt and lithic tuff is present, which is in turn overlain by an a1 tered sequence of chl ori tic, greeni sh-gray vitric tuff. A suspected fault separates this lower package of rocks from a somewhat different overlying sequence. The upper package of rocks consists of a basal unit of medium- to dark-gray, very fine-grained lithic wacke and siltstone, with shaly partings and a few silty concretions. A covered interval obscures the relation between the upper basal sequence and an overlying sequence of andesitic, basaltic and mafic-rich intrusive rocks of Triassic age. Next, a thick sequence of yellow chert and orange- weathering, sheared volcanic breccia is present which is in turn overlain by greenish-gray mottled siltstone and chloritic sandstone, which is interbedded with fine-grained crystalline pyroxene andesite. Rampart Group rocks present in the pi pel ine corridor general ly consists of interbedded argillite, metasiltstone, fine-grained lithic sandstone, crystal -1 i thic tuff and tuff breccia of basal tic composition, sill-like and clearly intrusive bodies of hornblende diorite, and basalt, dacite and diabase dikes that cut all of these rocks . The tuff sequences generally consist of highly a1 tered, crystal - lithic tuff that contain fragments of volcanic and sedimentary rocks, plagioclase laths and augite. The rocks are highly chloritized and at some localities, chlorite makes up as much as 30% of the rock. The volcanic rock fragments generally are rounded and subrounded clasts that contain subhedral plagioclase grains and minor augite, set in a matrix of glass and chlorite. A typical model composition for the lithic tuff is; 30 to 40% volcanic rock fragments, 15 to 30% chlorite, 5 to 10% quartz, 0 to 20% glass, up to 30% calcite locally, and up to 25% plagioclase that ranges from andesi ne to 1abradori te in composition. Minor amounts of hornbl ende, serici te and sedimentary and metamorphic rock fragments are present. A1 teration varies in intensity, but generally the rocks are highly chloritized and much of the plagioclase exhi bits signs of sericitization. Locally, the plagioclase laths have been completely altered and pseudomorphs of calcite and chlorite or calcite and sericite after plagioclase are present. The tuff sequences are commonly well-bedded and where in contact with interbedded sedimentpry rock sequences, 1ittle or no zone of alteration is present. The contacts between the layers of tuff and tuff breccia and the sedimentary rocks are sharp and little inter- mixing was observed. However, tuff breccia layers contain fragments and clasts of sedimentary rocks locally. Some flow structures ape present and where elongate clasts and mineral grains are present, they tend to a1 1ign themselves para1 7e'I to bedding. Sedimentary rocks interbedded with the tuff and tuff breccia 1ayers include shale, si1 tstone and medium-grained 1i thic sandstone. Locally, the shale and siltstone are weli indurated and resemble argillites and meta-siltstone. The lithic sandstone units contain some sericite and chlorite which probably represents incipient effects of regional metamorphism. Hypabyssal intrusives occur throughout the Rampart terrane and include sill-like bodies of chloritized hornblende diorite that appear to be in conformable contact with the enclosing tuffs and sedimentary rocks, and probably represent flows and or shallow intrusions. The contact zones between the sill-1 i ke intrusive bodies and the tuffs and sediments do not show much hornfelsing, and the contacts are sharp and distinct. The diorites are characteristically fine-to medium-grained, altered, hornblende diorite with an average modal composition of; 25 to 40% plagioclase, 20 to 30% hornblende, 20 to 25% chlorite, generally less than 5% potassium feldspar, minor quartz and accessory calcite, serici te, apatite, sphene, and augite(?). Many of the sill-like bodies have been highly altered with major chloritization and some saussuritization. The clearly intrusive bodies of hornblende diorite crop out on many of the hill-tops north of Hess Creek. Compositionally, this variety of diorite is similar to that occurring in the sill-like bodies, however, maf ic-rich zones of hornblende diori te or gabbro are present local ly. Magnetite contents of these rocks may reach as much as 10%. Unlike the first variety of hornblende diorite, the contact zones surrounding the clearly intrusive variety show marked alteration. North of Hess Creek a sequence of interbedded quartz-chert, volcanic-pebble conglomerate, sandstone, crystal -1 ithic tuff and tuff breccia crop out. This sequence of rock is. believed to be Tertiary in age (Chapman et al, 1971). The lithic tuff and tuff breccias are similar to those that constitute the bulk of the rocks in the Permian Rampart Group. The rocks in the Tertiary sequence are we1 1 bedded. The sands tones are commonly f i ne-to medi um-grai ned, 1 ithic sandstones that contain abundant volcanic and metamorphic rock fragments. Some crossbeddi ng and graded bedding is present. within the sedimentary sequences. Tertiary rocks that crop out about 13 kilometers (8 miles) north of Hess Creek do not contain interbedded tuffs or tuff breccias. This package of rocks contajns quartz-chert, volcanic pebble congl omerate, interbedded with medium- to coarse-grai ned 1i thic sandstone, very fine-grained, dark-gray shale and siltstone. The coarse-grained sands tone contains abundant carbonaceous material . Thin zones of graphitic material generally less than 0.5 meter (1.5 feet) thick are i nterbedded with the sandstone and conglomerate sequence. This material, analyzed by Dr. P. D. Rao (Mineral Industry Research Laboratory at the University of Alaska) is graphite, and probably represents upgraded coal. The conglomerate layers within this sequence of rocks generally consist of rounded to subrounded pebbles of chert, quartz and sandstone and volcanic rock fragments that range up to 4 centimeters (1.6 inches) in diameter set in a matrix of coarse-grained calcareous wacke. Some crossbedding and what appear to be channel. structures are present. Elongate pebbles within the conglomerate layers tend . to be alligned parallel to bedding. A typical modal composition for the conglomerate is 30% sandstone rock fragments, 15% chert pebbles, 10% volcanic rock fragments, 40% quartz pebbles and 5-10% calcareous wacke matrix. Interbedded with the 1 i thic conglomerates are coarse-grained, calcareous, quartz-pebble conglomeratic sandstones. These sandstones are composed of angular to subangular grains of quartz and plagioclase as well as sandstone and volcanic. rock.fragments. Lower Paleozoic rocks near Livengood consist of a thick sequence of interbedded chert, thin-bedded 1imestane and thin layers of shale and siltstone. .This sequence, the Livengood Chert, was first described by Mertie (1926). and consists predominantly of chert and chert-breccia at its type locality near Livengood. The chert occurs in a great variety of colors ranging from red to gray and green to black. Local ly, thin zones of si1 icified 1imestone and dolomi tic 1imestone are interbedded with the chert. Fossi 1 evidence coll ected from shaly interbeds within the unit have shown conflicting evidence as to the age of this unit. Mertie (1937) and R. M. Overbeck of the Geological Survey collected fossils near upper Lost Creek, north of Livengood. These fossi 1s, mostly crinoid stems and bryozoans, yielded an indicated age of Mississippian. Recent work by Chapman and Weber . (in press) north of Livengood near Lost Creek, has shown these rocks to be upper(?) Ordovician in age, based on graptolites found in a thin shaley unit within the chert sequence (Florence Weber, U. S. Geological . Survey, personal communications, 1977). The rock sequences in which Mertie found his fossils may indeed be Mississippian. This sequence has been reassigned to a new group and is no longer considered to be part of the Livengood Chert unit (Weber, persona1 communication, 1977). The rocks themselves are highly variable in nature. At many localities within the Fipeline Corridor, highly fractured sequences of chert, shale and thin-bedded limestone that contain calcite veins are present. The siliceous limestone beds found interbedded with the chert sequence appear to be devoid of fossils. Locally the limestone is recrystallized and silicified. Rocks east of the Tolovana River consist of interbedded dark- gray to black shales, metasi 1 tstones, subordinate slate and coarse- grained, pebble-to cobbl e-congl omerate. We1 1 indurated rocks resembling argillites are present just east of the Tolovana River, near Shorty Creek. This sequence of rocks is a well-bedded unit of dark-gray to black rnetasiltstone and argill i te that is highly fractured 1 ocal ly and shows some i socl i nal overturned folding . The- isoclinal overturned fold axes trend northwest and dip slightly to the east. The argillaceous rocks are highly fractured and pencil cleavage is developed locally. Interbedded with the argillite is a thick sequence of coarse-grained pebble-to cobble-conglomerate. The conglomerates contain clasts of greenstone, quartzite, dark-gray 1 imestone, sandstone, chert, sil tstone and minor dark-gray slate (Chapman, 1971). The matrix in these rocks is commonly coarse-grained 1 ithic wacke that is calcareous in part. Bedding is well developed and generally dips to the southeast. This package of rocks is believed to be either Cretaceous or Jurassic in age, (Chapman et al, 1971) based on scant paleontologic data. Paleozoic rocks west of the Tolovana River dip generally to the northwest while the Mesozoic rocks east of the Tolovana River dip southeast. A high-angle normal fault in the valley of the To1 ovana has been mapped by Chapman et a1 , (1971 ). The western block is down-dropped relative to the eastern block. Intrusive rocks east of the Tolovana River near the head of Wi 1 bur Creek consist of 1 ight colored, fi ne-to medium-grained, a1 tered intrusive rocks that vary from monzonite to quartz nonzonite in composition. - The intrusive rocks occur in di kes and as small i ntrusive bodies that intrude the metasi 1 tstone countryrock. The rocks are highly fractured and many quartz and calcite veinlets cut the metasil tstones east of Wilbur Creek. Near the head of Slate Creek and farther to the east near Globe Creek a thick sequence of Mesozoic rocks composed primarily of shale, si 1 tstone, quartzite, and medium- grained quartzose sandstones is present. This sequence of rocks is wei 1 bedded and exhibits graded bedding, flow casts and rill-marks (Chapman et al, 1971 ). The shales generally consist of medium-gray, very fine-grained rocks that are clayey in part. Medium-gray, fine- to coarse-grained lithic wacke in beds of variable thickness grade 1 oca1 ly into conglomerate and shale. Medium-to coarse-grained quartzose sandstones near Globe Creek have been metamorphosed to at least the lower greenschist facies of metamorphism. These rocks contain abundant muscovi te in the interstices between rounded to subrounded grains of quartz, potassium-fe1 dspar and plagioclase. Incipient epidote is also present. At Globe Creek an extensive section of Tolovana limestone crops out. This unit, first described by Brooks and Randle .(1902), is a light-to medium-gray, finely-crystalline, thick and massively bedded, dolomitic limestone that is locally recrystallized and silicified. The true thickness of the unit is unknown, but may be several thousand meters (feet) (Chapman et al, 1971). The rocks of the Tolovana Lime- stone unit within the Pipeline Corridor are highly fractured and recrystal 1ized si 1iceous-dolomi tic 1imestone and recrystal 1ized 1imestone that contain abundant calcite and quartz vein1 ets. Fossils are rare within this unit, but those collected by Chapman et a1 (1971), chiefly corals, stromatoporoids and amphipora indicate a Silurian or Devonian age. Just northwest of Globe Creek, near Pump Station Number 7, the rocks are dark-green to black, medium-grained greenstones. The hetamorphic grade of the rocks in this area is higher than the metamorphic grade of the rocks to the west. The greenstones have well-developed epidote and are probably upper greenschi st facies rocks. Metamorphosed sedimentary rocks found in the area also exhibit .a higher metamorphic grade than the rocks to the west. Quartzite units to the west show only incipient development of muscovite, while similar rocks near Pump Station 7 contain well-developed muscovite, epidote and incipient hornbl ende. Interbedded with the quartzite are dark, very-fine grained argillites. The argillites contain muscovi te and incipient hornblende and an incipient fol iation is present locally. All of the rocks in this area are highly fractured and contain quartz and calcite veinlets. Southeast of Globe Creek, an interbedded sequence of argil 1ite, slate, quartzite, sil tstone and 1imestone crops out. The argill ite and slate are generally medium to very dark red or maroon, but sometimes range to light-gray to grayish-green in color. They are moderately well bedded in thin, fissile or chunky layers and form a distinctive unit throughout the area (Chapman et al, 1971). Thin qayers of gray to very dark-gray, f inely-crystal1 ine limestone are interlaminated with the argill ites and slates. The limestones are devoid of fossils. Rocks near Washington Creek, south of Globe Creek, consist of interlaminated micaceous quartzite, quartz muscovite schist, argill i te and minor phyll ite. Minor slate interbeds are also present. Fossil evidence found in less metamorphosed sections consist of specimens of Oldhamnia, which indicate a Cambrian age (Churkin and Brabb, 1965). A1 though Mertie (1937), first identified these fossils and assigned the rocks to the Mississippian. This package of interlaminated quartz muscovite schist, micaceous quartzite, phyllite, slate and subordinate argillite is present southeast of Washington Creek and as far south as the Chatanika River. South of the Chatanika River, the rocks are much the same as those near Washington Creek. However, this package of rocks appears to have been subjected to some thermal metamorphism, possibly resulting from the intrusion of the Pedro Dome quartz diorite stock. The rocks in this area are highly altered locally, and contain abundant muscovite, biotite, epi dote, hornbl ende and sibordinate garnet. Veinlets of quartz and calcite are common and highly-altered sequences of rocks contain muscovite, while some small intrusive dikes show signs of sericitic alteration.

Structural Geology The structural geology of the rocks in the Livengood quadrangle is dominated by northeast trending thrust faults and high-angle normal faults. Fold sytles in the rocks southeast of Globe Creek are isoclinal to recumbent, overturned to the northeast, while those north- . west of Globe Creek are isocl inal , overturned to the northwest. Several large linear features that may be faults are present in the northwestern part of the-quadrangle. South of the Chatanika River the rocks exhibit at least two phases of metamorphism and two distinct structural trends. The earliest metamorphic pulse, up to almandine amphi bo1 ite grade, is probably early Paleozoic and is apparently associated with isoclinal recumbent folding about northwest-trending axes, while the later phase, probably mid Mesozoic, appears to be retrograde to upper greenschist facies, and is associated with open upright folds about northeast- trending axes. Euhedral overgrowths on subhedraf poi kilobl astic garnets in the vicinity of Pedro Dome may be evidence for a later, possibly late Mesozoic, thermal event (Swainbank and Forbes, 1975). Several large thrust faults mapped by Chapman and others (1971) north and west of Globe Creek, separate the lower Paleozoic or Pre- cambrian schist, grit and quartzite sequence to the southeast from a Mesozoic terrane composed of metasiltstone, argill ite, metagraywacke and minor. greenstone, to the northwest. The northeast-trending thrust faults and associated high-angle nomal faults are marked by several mafic and ultramafic bodies northwest of the zone of overthrusting. Northwest of a high-angle normal fault, known as the Beaver Creek Fault (Chapman and others, 1971 ) metasil tstone, argill ite, metagraywacke and pebble-to cobble-conglomerate are isoclinally folded and folds are overturned to the northwest. This Mesozoic sequence of rocks is recrystallized, and some low-grade metamorphic minerals are present. Just east of the Tolovana River a prominent escarpment parallel to the river valley is present. Chapman and others (1971 ) have mapped a large north-trending normal fault along the escarpment and the eastern, dominantly Mesozoic, block is upthrown relative to the western, dominantly Paleozoic block. In the vall ey of the Tolovana River an east northeast-trending serpentini te body is present. Chapman (1 971 ) be1 ieves that the serpentinite may be cut by the fault mapped on the Tolovana escarpment and the body is offset not more than 1.6 kilometer (1.0 miles) (F. Weber, U. S. Geological Survey, personal communications, 1977). Northwest of Livengood a fault known as the Victoria Creek Fault is present. The fault trends about N80°E and can be traced for about 80 kilometers (50 miles). The Victoria Creek fault separates a Cambrian sequence of quartzite and grit from a lower Paleozoic sequence of chert, dolomite and recrystallized limestone near Liven- good. Northwest of the Victoria Creek Fault, Chapman and others (1971) have mapped another high-angle normal fault that is subparallel to the Victoria Creek Fault. In the northeastern part of the Livengood quadrangle, this fault separates a Cambrian sequence of grit, quartzite, slate, argillite and chert from a mid-Paleozoic sequence of chert, 1imestone, clastic rocks and minor volcanics. The presence of the fault to the southwest is marked by a similar discontinuity in rock type. A strong linear feature is present in the valley of Hess Creek. This feature can be traced for about 72 kilometers (45 miles) and trends sub-parallel to the Victoria Creek Fault. No offset or discontinuity in rock types has been found on opposite sides of this 1inear. The rocks are part of a thick sequence of interbedded sedimentary and volcanic rocks of the Permian Rampart Group. Another strong linear feature sub-paral lel to the Hess Creek lineament is present in the valleys of Isom and Rogers Creeks. Rocks present on both sides of this linear are also part of the Ranpart Group and no offset or discontinuity can be determined. Just south of Isom Creek, a we1 I-bedded sequence of volcan'ics and associated argillite and lithic wacke is highly folded and fractured. Small scale folds are abundant and fold axes generally trend northeast.

Geochemistry Geochemical reconnaissance in the Livengood quadrangle during the current study consisted of the collection of 369 rock samples [see Table 18, Appendix A) from the inner pipeline corridor between Goldstream Creek, north of Fairbanks, and the Yukon River. Statistical analysis of the geochemical data has shown that 48% of the samples co1 lected contain weakly anomalous, anomalous and strongly anomalous concentrations of at least one element: Threshold values (see Tables 19 and 20, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0 x standard deviation, and 2.33 x standard deviation for the 90%, 95% and 98% confidence levels respectively. Where the analytical variability is zero or near zero, the threshold values for the confidence 1eve1 s are either the detection level or nearly the same value. Bedrock south of the Chatanika River consists mainly of quartz mica schist and micaceous quartzite that are cut by quartz veins and granitic dikes and plugs. The schists and quartzites are altered to varying degrees and contain sporadic potassium, sodium and boron anomalies that may be the result of hydrothermal a1 teration or contact metamorphic effects associated with the intrusion of the granitic bodies. Combined sodium and potassium concentrations as high as 13%are known in samples of granite and what UrS. Bureau of Mines personnel have identified as alaskite. Minor silver and arsenic values were also detected in the granitic rocks. The rocks throughout the area are shattered and cut by faults at many localities. Limonite staining, probably associated with the alteration of pyrite and other iron-bearing minerals, is common, a1 though no sulfide mineralization was found during the current study. North of the Chatani ka River and south of Washington Creek, the bedrock consists 103 of a monotonous sequence of quartz mica schist and quartzite. Locally, quartz veins cut the schist and quartzite oblique to the foliation and contain strongly anomalous gold and silver values. Anomalous , molybdenum concentrations are also present locally. The rocks between Washington Creek and Slate Creek consist of banded slate, quartz mica schist, meta-siltstone, mafic intrusive rocks, and massive 1 imes tone. The maf ic intrusi ves contain anomalous and strongly anomalous concentrations of strontium and weakly anomalous concentrations of calcium and molybdenum. North of Slate Creek, the shale, slate, graywacke and lithic conglomerate countryrock has been intruded by quartz porphyry and rhyol i te porphyry dikes and a small granitic 'plug . Samples of the intrusive rocks contain visible sulfides including pyrite, chalcopyrite and minor molybdenite. Copper concentration found in samples of the mineralized intrusive were as high as 520 ppm. Zinc concentrations of 1000 ppm and molybdenum values of 12 ppm were also detected. North of Wi 1 ber Creek and south of Shorty Creek the metasiltstone countryrock is cut by sulfide- bearing veins locally. The vein material contains clots and kidney- shaped zones of massive sulfides as much as 5 inches thick. The sul f ide mineral ization consists of arsenopyrite(?) , sti bni te, galena, and chalcopyrite. Strongly anomalous concentrations of cobalt and bismuth suggest the presence of other unrecognized mineral phases. Northwest of the Tolovana River, black chert of the Livengood Chert is intensely shattered and contains strongly anomalous concentrations of copper, zinc and molybdenum. The chert is cut by randomly-oriented quartz vei nl ets and contains tourquoise(?) and faustite. No primary sulfide mineralization was found during the current study. Scattered, weakly anomalous and strongly anomalous concentrations of calcium, molybdenum, titanium, vanadium, magnesium and gal 1 ium were detected in samples of metasil tstone and chloritized diorite between Lost Creek and Erickson Creek. No mineralization of obvious significance was found during the current study. North of Erickson Creek, the bedrock consists of metasiltstone and sill-like bodies of diorite. Locally, the siltstone contains strongly anomalous concentrations of zinc and copper, no sulfide minerals were seen however. Near Hess Creek, samples of a1 tered hornblende diorite contain strongly anomalous concentrations of copper, bismuth, titanium, vanadium and gal 1 ium. The copper values are contained in disseminated chalcopyrite and range up to 2800 ppm. Minor molybdenum values were also detected. North of Hess Creek rocks of the Rampart Group dominate the bedrock geology. The lithic tuffs of the region contain weakly anomalous concentrations of calcium, molybdenum and titanium. The volcanic rocks a1 so contain strongly anomalous concentrations of gallium, magnesium, scandium and yttrium. Locally, argillites that are interbedded with the volcanic rocks contain barium concentrations as high as 4%. 104 North of the Yukon River, the volcanic sequences seem to be more maf ic rich and scattered, strongly anomalous concentrations of nickel and chrome were detected. No mineralization was found during the current study however.

Mining Activity and Economic Geol ogy Felix Pedro discovered gold in the Fairbanks district on Pedro Creek, north of Fairbanks in 1902 and active mining has been in progress since that time. Gold was discovered in the Tolovana district in 1914 when workable placers were found on Livengood Creek, near the town of Livengood. The placer gold deposit on Livengood Creek is being actively mined and about 1,000,000 ounces of gold may remain in the deposit (B. Thomas, personal communications, 1977). Placer mining in the Fairbanks district has produced about 7,239,000 ounces of gold from 1903 through 1959, and gold production in the Tolovana district has amounted to about 375,000 ounces of gold up to 1959 (Koschmann and Bergendah1 , 1968). Active placer mining continues in both districts. The source of the placer gold deposits is believed to be lode go1 d deposits of gold-quartz and gold-quartz-sulf ide vein affinities, that are closely associated with small intrusive bodies found throughout the terrane. The placer deposits occur as bench deposits, as abandoned channel deposits, and also as active stream channel deposits. Production from 1ode gold, antimony, lead, silver and tungsten deposits has occurred in the Fairbanks district. Lode deposits of gold and silver are generally vein deposits be1 ieved by some investigators (Forbes et a7, 1969) to be associated with small granite, diorite and quartz diorite stocks that occur throughout the Yukon- Tanana Ilplands. The veins are of several definite types and include gold-quartz veins, gold-stibnite-quartz veins, sulfide-quartz veins and gold-sulfide-quartz varieties. Podiform deposits of stibnite occur commonly associated with shear zones and some quartz veins. Production of antimony has taken place from these deposits. Tungsten deposits, c1 osely associated with small intrusive bodies found throughout the Yukon-Tanana Uplands, occur near thin, discontinuous beds of limestone or calcium-rich layers within the Birch Creek Schist. Several small tungsten deposits near Gi lmore Dome, north of Fairbanks, have produced in the past and one deposit on Gilmore Dome is currently being mined. The tungsten lodes of the Gilmore Dome area are locallized near the contact with the Gilmore Dome quartz diorite stock. The scheelite mineral ization is concentrated in 1imy layers within the schist- quartzite country-rock and may represent remobilization of sedimentary tungsten (Metz, 1977). Contact metamorphic rocks consist of calcite- epidote s karn and cal ci te-diopside skarn and are closely associated with the tungsten deposits. Work by the U. S. Bureau of Mines at the Col bert Lode on Gilmore Dome has resulted in the discovery of about 20,000 tons of high grade ore averaging 3.29% WO .(U.S.B.M., 1943- 1945). There are other tungsten lodes known in ? he Cleary Sumit area, and the probability of finding other such tungsten deposits in the region seems high. On the north-flank of Murphy Dome and south of the Chatanika River many small quartz veins and shear zones were found during the examinations of the pipeline excavation. The veins and zones of shearing are heavily iron stained locally. No sulfide minerals or visible gold were seen in these rocks, however, analysis of rock. samples revealed anomalous concentrations of si 1ver, go1 d, molybdenum, nickel, lead, tungsten and zinc. An extensive zone of potassic alteration surrounds the Pedro Dome quartz diorite stock. Combined sodium and potassium concentrations of the rocks north Pedro Dome in the altered zone are as high as 13%. The extensive shearing and quartz veining in the rocks near Murphy Dome is probably spacially and genetically related to the intrusive activity. Sandvik (1967) believes that there were at least four distinct periods of mineral ization in the Fairbanks district. The first phase of mineral ization is characterized by barren quartz veins. The second phase of mineralization consists of quartz-arsenopyrite- pyrite-gold veins that are post quartz monzonite, of the Cleary area, in age. The third generally high-grade phase of mineralization belongs to the quartz-sti bni te-gold-arsenopyri te and antimony sulfosal ts veins. The fourth and final phase of mineralization consists of quartz and stibnite with little or no gold.

Several small lode mining operations were in production in the , Cleary Summit area in 1977. One vein, known as the Kawalita vein is located near the Keystone Mines property, northeast of Cleary Summit and has been described as a typical Bonanza type vein by Sandvi k (1967). The vein systen contains abundant free gold and trace sulfosalts. The footwall of the vein is marked by lenses of stibnite that lie along the contact. Forbes et a1 (1968) reported that vein material from the Kawal ita assayed between 10.6 and 238 ppm gold, with a weighted average grade of 74 ppm for the entire width of the vein. Assays as high as 100 ounces of gold per ton are known from this high-grade ore shoot (Rudy Vetter, owner, personal communication, 1977). Forbes et a1 (1968) have shown that the wall-rock in both the footwall and the hanging wall contain anomalous gold concentrations that extend at least five feet into the country-rock. Another mineralized zone on Willow Creek, just north of Pedro Dome, is being developed and some ore was shipped in 1977. The zone contains a distinctly different type of minerali'zation then that of the Kawalita vein. The Willow Creek deposit is a highly mineralized shear(?) that can be traced for almost 0.8 kilometers (0.5 miles). The mineralized material is predominantly quartz, carbonate, clay and sulfide mineral ization. The mineral ized zone is marked by intense shattering of the schist-quartzite-marble-countryrock. One section of the mineralized zone does not appear to be a vein, rather it appears to be either a replacement deposit in a limy layer in the schist- quartzite countryrock or a metamorphosed syngenetic carbonate-hosted accumulation of sulfides. .Similar zones of mineralization are known on Chatham Creek and at one locality, northwest of Pedro Dome. The mineral ization consists of thinly 1aminated and rhythmi cal ly banded marmatitic sphaleri te, galena, stibnite, pyrite and locally massive antimony sulfosalts, that are probably jamesonite and boulangerite. Trace gold, and up to 80 ounces of silver per ton have been reported from high-grade galena samples. The Cleary Summit-Pedro Dome area has long been recognized as a highly mineralized district. The probabi 1i ty of finding unknown veins and mineralized zones in the region seems high. It is also possible that mining of many of the previously uneconomic deposits in the region may become economically feasi bl e in the future. North of the Chatanika River, the country-rock is. much the same as that south of the Chatani ka only with a different structural grain. The rocks south of the Chatanika River exhibit at least two distinct phases of deformation while those to the northwest do not. The schist-quartzite country-rock near Pedro Dome exhi bits evidence that the rocks were affected by a late Mesozoic thermal event that may by related to the intrusive activity and mineralization. No mineral ization of significance was found in the pipe1 ine corridor between the Chatanika River and Globe Creek. At Globe Creek an extensive outcrop of Tolovana Limestone is present in the pipe1 ine right of way, as well as on the Elliot Highway. The limestone is characteristically a low magnesian limestone. Quartzite and some dolomitic limestone are present in close proximity to the limestone occurrence. The Tolovana Limestone and associated rocks may represent and important source of raw materials for the production of Portland cement if the feasibility of such an industry should come about in the interior. Near Globe Creek, medium-grained greenstones are present. .The rocks are probably metamorphosed mafic igneous rocks and samples of the greenstone contain anomalous concentrations of silver, gold, tin and tungsten. No anomalous nickel or copper values were detected, and no sulfide minerals were found during this study. The probability of finding significant metal concentrations associated with these metaigneous rocks seems low. North of Globe Creek, the country-rock consists of a Mesozoic sequence of shale, sil tstone, quartzite and sandstone. No anomalous metal concentrations were detected during this study a1 though the bedding surfaces of the shale and siltstone members are often coated with subhedral crystals of pyrite or marcasite. Some small quartz and calcite veinlets cut these rocks, however only pyrite was found in the veinlets. Near Wilbur Creek, the Mesozoic rocks become more cl astic in character and congl omeratic layers constitute a major portion of the rock sequence. The sedimentary rocks are intruded by dikes and a small intrusive body composed of f ine-to medium-grained monzoni te and quartz monzoni te. The intrusive rocks exhibit varying degrees of alteration and disseminated sulfide mineralization occurs throughout the dikes and intrusive bodies. The sulfides are dominantly pyrite, chalcopyrite, and molybdeni te. Copper concentrations as high as .052% and molybdenum concentrations as high as 12 ppm were detected. Minor lead and zinc concentrations were also detected. The intrusive rocks near Wilbur Creek appear to have a rather 1imited extent and the probability of this occurrence being of economic tenor seems 1ow. Northeast of the Wilbur Creek occurrence, similar intrusive.rocks crop out. The intrusives are heavily ironstained and intensely fractured. No visible sulfides were detected, however the rocks do contain manganese concentrations as high as 1.7%, lead concentrations as high as 397 ppm and zinc concentrations as high as 460 ppm. The high manganese content is probably related to a heavy coating of pyrolusite(?) that occurs locally. The rocks in this area seem to have a moderate potential and further work is needed. The rocks between Wilbur Creek and Shorty Creek are composed of very fine- grained, siliceous metasiltstones that are fractured and sheared. Locally, the metasiltstones are cut by numerous quartz-sulf ide veins. The veins cut the metasil tstone obl ique to the bedding surfaces and generally strike northeast with a southerly dip. The sulfides that constitute most of the vein material are present as clots and kidney- shaped concentrations as much as 13 centimeters (5 inches) thick. Major arsenopyrite, stibnite, galena, and chalcopyrite constitute the bulk of the vein material and secondary scorodite and malachite are also present. Boron concentrations as high as 300 ppm, bismuth concentrations as high as 610 ppm and cobalt concentrations as high as .43% were detected in vein material. Copper values as high as .21%, nickel values as high as .17% and antimony values as high as .05% were detected in high-grade samples of sulfide-bearing vein material. The v'eins found during the examination of this area are small, however the potential for finding other such mineral ized vein- systems in the area seems high. A "porphyry" prospect belonging to B.P.' Minerals, Co. near the head of Shorty Creek was actively drilled in the early part of the 1970's. A claim block consisting of at least 44 claims was staked, however, the results of the drilling and the present status of the claim group is not known. It is possible that the intense shearing and shattering of the metasiltstones and the mineralized vein systems in the area are somehow related to the intrusive activity. West of the Tolovana River, the bedrock is different than that east of the Tolovana, and is composed primarily of chert, dolomitic 1imestone and highly a1 tered vol canics . Northwest of the Livengood- Manley Hot Springs Road, the black chert member of the Livengood Chert unit is intensely shattered. The zone of fracturing can be traced for about 300 meters (1,000 feet) and is of interest because the fractures are coated with tourquoise(?) and faustite, which is essentially a zinc equivalent of tourquoise. Samples from the area have produced somewhat confl icting geochemical responses. Samples 108 collected by the U. S. Bureau of Mines in the area contained anomalous copper values as high as 680 ppm and molybdenum concentrations as high as 41 ppm. Samples collected during this study from the same area contained only minor anomalous concentrations of zinc, silver, tin and phosphorous. The copper and zinc are obviously of a secondary nature and the source of the metals is unknown. Further work is needed in the area to determine if there is a relationship between the secondary copper and zinc mineralization in the cherts, and a sequence of saussuritized dacitic volcanics that are in contact with the cherts to the north. The presence of mineralization in the associated chert and volcanics indicate an area that has a moderate to high probabi 1ity of containing metal concentraticns of unknown size and distribution. Just south of Lost Creek, an extensive zone of silicified dolomite, dolomitic 1imestone, chert, siltstone and dacitic volcanics is present. The chert and siltstone members are highly sheared and cut by many small quartz stringers locally. The rocks in the area contain anomalous concentrations of si 1ver, gold, molybdenum, tin, tungsten and lead. No mineralization was visible in these rocks,, ' however, the area does contain the anomalous metal concentrations and needs further work. North of Lost Creek, the bedrock is composed of interbedded gray, black, green, red, white and brown chert, siltstone, shale and sandstone. The sediments are cut by dikes that range from trachyte to basalt in composition. Locally, coarse-grained intrusive rocks composed of maf-ic-rich diorite are also present. The intrusive rocks contain minor disseminated sulfides. Minor pyrite and magnetite are present in the mafic-rich phases. None of the sulfide or magnetite accumulations in the area appeared to be of significance. North of Lost Creek near Erickson Creek, the character of the bedrock changes and rocks of the Permian Rampart Group are present. The rocks generally consist of interbedded tuff, tuff breccia and argil lite with minor chert and sedimentary rocks. The Rampart Group also contains a marked intrusive igneous rock component that generally consists of medium-to coarse-grained hornbl ende diorite. At an occurrence just south of Hess Creek, a sequence of meta-siltstone and shale has been intruded(?) by a sill-like body of hornblende diorite that contains as much as 70% disseminated sulfides. The sulfide mineralization is composed of pyrite and chalcopyrite, and copper values as high as 0.28% were detected in selected samples. The diori te at this locality is a medium-to coarse qrained hornblende diorite porphyry that is sausseritizied and sericitized. Secondary quartz veins are abundant and cross-cut the diorite extensively. The diorite contains secondary biotite after hornblende and some of the diori te is highly ch1 ori tized. The mineralized intrusive rock near Hess Creek does not appear to be of economic tenor, however the occurrence of the porphyry-type mineralization in rocks of the Rampart Group indicates that the terrane may have good mineral potential and may contain copper porphyry type deposits . North of Hess Creek, clearly intrusive forms of hornblende diorite crop out. The intrusives contain up to 10%magnetite, and are extremely chloritized. No sulfide minerals were found during the current study. The genetic re1 ationship between the c1 early intrusive , L diorites north of Hess Creek and the sill-like forms that occur throughout the Rampart terrane is not known. The clearly intrusive forms may also have some -potential for copper porphyry-type mineral i- zation. North of Hess Creek, argillite beds within the volcano- sedimentary sequence contain up to 4% barium. Samples of tuff and tuff breccia from the area contain anomalous concentrations of chrome, molybdenum, vanadium, tungsten and silver. No mineralization was found during the present study however. South of Isom Creek, a sequence of rocks that are thought to be Tertiary in age i s present and consists of interbedded conglomerate, lithic sandstone, graphite layers, dikes of various compositions and minor siliceous siltstone and sandstone. The sequence is probably correlatabl e with simil ar Tertiary rocks that are known along the Yukon River to the west and to the north in the Fort Ham1 in Hi1 1s. The rocks occupy a graben-like structure outlined by a lineament in Hess Creek and by a similar lineament in the Isom-Rogers Creek valleys. To the west, Tertiary rocks are the host for the coal deposits at the Drew Mine, near the mouth of Hess Creek. If these rocks are correlatable, the Tertiary(?) rocks found in the Pipeline Corridor may contain similar deposits. No above background uranium concentrations were detected, in the Tertiary rocks however further work is needed to fully evaluate the uranium potential of this area. Just south of Isom Creek a large shear zone(?) about 15 meters (50 feet) wide is present. The material in the shear zone contains sphalerite, pyrite and minor galena. Zinc concentrations as high as .21% and lead concentrations to 300 ppm were detected. Minor nickel and chrome values were also present. In summary, the rocks of the Livengood quadrangle have good mineral potential and may contain a variety of mineral deposit types. The complex structural and geologic framework of the rocks coupled with the heavy forest cover over most of the region will complicate most exploration programs. However, the probability of finding still undiscovered deposits seems high. REFERENCES CITED

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Alaskan Geology banch, U.S. Geologicol Survey, IPR, The rlotur of miner01 book, A. H., 1909, The mining industry in 1908: U.S. Geol. knvey &!I. 379, resovrce inforhotion on the major land withdrowols of the AIosko Native Claim p. 21-62. Settlement, Act oi 1971: U.S. Gaol. Survey open-file rept., 164 p. &wkr, A. H., 191 1, Geologic fcotufer of Aloskan melolliferow lodes: U.S. Gaol. Anderwn, G. 5.. 1970, Hydrologic reconr.oiaonce of the Tomno basin, centrol Survey Bull. 480, p. 43-93. Alosl: U.S. Geol. Survev Hydrol. Inv. Atlos W-319, 4 sheen. hooks, A. H., 1911, The mining industry in 1910: U.S. Geol. Surrey Bull. LBO, Anderson,. L. A., ond Johnson, G. R., 1970, Induced polorirotion ond resistivity p. 21-42. . survep on Cleory Summit, Aloska. Geologicol Survey research 1970: U.S. Geol. Swvey Prof. Paper 700-0, p. 0125-DI28. Brooks, A. H., 1911, The Mount McKinlcy region, Alako. with docriptiom of the igneous rocks and of the bnnilield ond Kontishm dirtrich, by 1. M. Prindler. Andreoren, G. E., 1960, Total intensity oetomgnetic rmp of the Yukon Flats- U.S. Geol. Surrey Prof. Paper 70, 234 p. Kondik wee, Alaska: U.S. Geol. Swvcy open-file rept., 0 sheen. Brooks, A. H., 1912, Thc mining indurtry in 1911: U.5. Gtol. Survsy Bull. 520, Anonpour, 1974, Mullirnodol t~onrportotionond utilitr corridor systems in Alosko; p. 17-44. 0 pelirninory, conccptuai onolysir: U.S. Dept. Interior, Bur. Lond Monoge- mnt, 77 p. Brooks, A. H., 1914, The Aloskon mining industry in 1913: U.S. Geol. Survey Bvll. 592. p. 45-74. Anonpour, 1974, Multimodal tramportotion and vtility cwridor %*terns in Alosko; generalized description of the 40 primory corridors, locotiom, modes. identifying books, A. H., 1915, The Alaskan mining industry in 1914: U.S. Geol. Survey agencies, purpws, cnrironnenlol impoch, and rtotus of lands ctorwd: U.S. Bull. 622, p. 15-68. Dept. Interior Bur. Lond Msnogemenl. 184 p. @rooks, A. H., 1916, Antirony depolih of Aloska: U.S. Gcol. SLrvey &I!. 649, bin, H. F., 1946, Alaska's minrals as o boris lor indurtry: U.S. Bur. Minas lnf. 67 p. Circ. 7379, 89 p. &wks, A. H., 1916, Pr~lirnimryreport on the Tolowm district: U.S. teol. Suvey Bull. 642. p. 201-209. QUADRANGLE Cont.

Brwks, A. H., 1916, Thc Alaska mining industry in 1915: U.S. Gcol. Survey Bull. Childcrs. J. M., Meckel. J. P., ond hdsrron, G. S., '1972. Fldof August 642, p. 16-71, 1967 in cost-central Algrko, with o section on V4eothcr features catr$uting lo the floods, by E. D. Diem.,: U.S. Geol. Surey Water-Supply Poper laBO-A, &wks, A. .H., 1918. The Aiorko mining industry in 1916:. U.S. Geol. Surrey Bull. p. Al-An. 662, p. 11-62. Childers, J. M., 1972, Chonnal erosion swveyr olong propmcd TAPS route, Alo~ko, books, A. H., 1919, Alosko's mineral supplier, in hkCoskey, H. D., ond Burchord, July, 1971: U.S. Gwl. Surwy open-file rept.. 7Y p. E. F., Our minerol supplies: U.S. Geol. f;rvey Bull. 666, p:89-102. Childos, J. M., 1974, Flood survey, olong TAPS route, Alosko: U.S. Geol. Svrrey books, A. H., 1921, Thc future of Alosko mining: U.S. Gtol. hyBull. 714, open-file report, 16 p. p. 5-57. Churkin, Mickel, Jr.. ond Brobb, E. E.. 1965, Occwrence and strotigrophic sign;- &wkt, A. H., 1922, The Alaska mining industry in 1920: U.S. GMI. Survey bull. ficonce of Oldhomio, o Combrion boce fossil, in east-centrol Alosko, in 722, p. 7-67. ~eolo~ico~~urveyrese~rch1965: U.S. Geol. Svrvey'Prof. Popcr 52W, p. D120-D124. &ooks, A. H , 1923, The Aloskon mining ind~tryin 1921: U.S. Geol. Survey bII. 739, p. 1-44. Chwkin, Michorl, h., 1973, Poieoroic bnd Recdrion rocks OF Atosko ond heir role in in structural evolution: U.S. 6-1. Survey kof. Powr 740. 64 p. hooks, A. H., 1925, Alosko's mineral resources ond production, 1923: U.S. Geol. Survey Bull. 773. p. 3-52. Cobb, E. H., 1972, Metollic minnol resources mop of the Livengood qwdrongle, Alaska: U.S. Geol. Surrey Misc. Field Studies Map MF-413, 2 Acts, Brosgs, W. P.. ond Conrodi, Artlaur, Jr., 1971, hgnctic susraptihilitin of cryrtol- scale I:250, OM). line rock sompler, Ydon Rivet-Porcupine Rirer area, cost-central Alorko-. U.S. Gaol. Sewcy nprn-lila ,~pt., 8 p. Cobh, E. H., 1973, Plncet drposihoI ALorko: U.S. Gcol. krry Irrll. 1374. 213 p. Brag., W. P., &obb, E. E., ond King, E. R., 1970, Geologic interpretation of teconnoiuoncm oernognelic survey of northtortarn Alaako: U.S. Gsol. Survey Collier, A. J., 1903, Cwl rcsovrca of the Yukon bosin, Alorko: U.S. Gcol. Bull. 1271-F, p. Fl-Fl4. Survey Bull. 213, p. 276-283.

kosge, W. P., Lonphae, M. A., Reiso, H. N., and Chopmon, R. M., 1969, Collier, A. J.. 1903. The cool resources of the Yukon. doh: U.S. Geol. Swrey Proboblc Permion age of the Rornpsrt Grovp, ccntrol Alosko: U.S. Gcol. bull. 218, 71 p. Survey Bull. 1294-8, p. 81-818. Collier, A. J., 1903, The Glenn Gesk pold-mining district, Alosko: V.S. &ol. Burond. W. M., 1965, A geochemicol inmtigation between Chotoniko and Circle Survey hll. 213, p. 49-56. Hot Springs, Alosko: Alorko Div. Mines ond Minerols Geochem. Rept. 5, II p Collier, A. J., 1905. Recent developmenn in Aloskan tin dcposih: U.S. Geoi. Burond, W. M., 1966, A geochemicol invcstigotion of rtrmm sediments in the Elliott Swvey Bull. 259, p. 120-127. Highwy area, Alosko: Alosko Div. ond Mincrolr Geochcm. Repr. 11, 30 p. Covert, C. C., ond Ellsworth, C. E., 1909, Woter supply of the Yukon-Tonono region, 1907-1908: U.S. Cool. Survey &I!. 379, p. 2C1-228. Burond, W. M., 1968, Geochrmicoi invertigotiom of selected arcor in the Yukos- Toncrno region of Alosko, I965 ond 1966: Alaska Div. Miner ond Minerals Corer,, C. C., cnd Ellsworth, C. E., 1909, Woter-supply inrestigotions in the Gtochm. Rep?. 13, 51 p. Yukon-Tonom region. Alesko (Foirbonks, Circle, and Romparc districts); U.S. Gcol. Survey Woter-Supply Paper 228, 108 p. Byers, F. M., Jr., 1957, Tungsten deposits in the FoirborJrs distrid, AIosko: U.S. Geol. hvey Bull. 1024-1, p. 179-216. Covert, C. C., 1908, Wotsr supply of the Foirbonks district, 1907: U.S. Gaol. Suvcy Bull. 345, p. 19E205. Cody, W. M.. Wolloce, R. E., Hoare, J. M., ond Webber, E. J., 1955, The central Ku$kokvim region, Alorko: U.S. Geoi. Svrrcy Ptof. Poper 268, 132 p. Dovis, J. A., ond Gross, khn, 1920, Recovery of gold from o magnetic block umd: U.5. Bur. Mines Rept. Inr. 2158, 5 p. Copps, 5. R, 1924, Geology ond miner01 rerovrcrs of the region tmvened b" the Alosho Roilrwd: U.S. Gal. Surrey 6uII. 755, p. 73-150. Doris, J. A., 1923, Lode mining in tk Foirbonks district, AIoska, in Srcmrt, B. 0.. Annwl report of the Mine Inspector m the Governor of ~lorkoT19?2: JuMou, Copps, 5. R., 1933, Minctol investigations in the.Alosko Roiltwd belt, 1931: U.S. Alosko, p. 88-113. Geol. Swue, Bull. 844-5, p. 119-135. Doy, Poul S., Gryc, George, Dobey, Patrick L., el ol., 1974, Developments in Copps, S. R., 1940, Geology of the Alaska Roilrood region: U.S. Gcol. Surwy Alorko in 1973: Am. Assoc. Petroleun Geologists 6uII., u. 58, n. 8, Bvll. 907, 201 p. p. 15M-1517.

Clspin, Thmdor*, 1914, Looe mining mar Feirbonks: U.S. Geol. Survey Bull. 592, Dectermon, Rovert L., 1973, Mesozoic sequence in Arctic Alosko, 3 Arctic Geology: p. 321-355. Am. Assc. Pct,olevm Geologisn Mem. 19, p. 376-387.

Chopin, Theodore, 1914. Plocer mining in the Yukon-Tonono region: U.S. Geol. Eokin. H. M., 1912, The Romport Hot Springs region: U.S. Survey Bull. Surrcy bll. 592, p. 357-562. 520. p. 271-2e6

Chopin, Thedose, 1919, Mining in the Fairbonks district: U.S. Gcol. Survey Bull. Eokin, H. M., 1913, A geologic reconnaisronce of o port of the Romport qwdrongl., 692. p. 321-327. Alosko: U.S. Geol. Swvey Bull. 535, 38 p. .

Chapmon, R. M., and Foster, R. L., 1969, Lode miner and prospects in the Foirbonks Eokin, H. M., 1914, Minerol resoucm of the Yukon-Koyvkuk tagion: U.S. &ol. district, Alosko: U.S. Gel. Survey Prof. Pep625-D, p. Dl-DZ5, Swvey Bull. 592. p. 371-384.

Chapman, R. M., ond ShocLletle, H. T., 1960, Geochemicol exploration in Alosko, Eokin, H. M., 1915, Mining in th. Foirbonb district: U.S. G-I. Swey hll. in Gcologicol Survey rrreorch 1960: U.S. Geol. Survey Prof. Poper 4W-8, 622, p. 229-238. -p. 8104-8107. Eokin, H. M., 1915, Tin mining in Alosko: U.S. Gsol. Sutv*y Bull. 612, Chapman. R. M., and Weber, F. R., 1972. Geochemicol omlyso of bedrock ond p. 81-94. rttmrn sediment sompler hathe Livengood qwdrongle, Alosko: U.S. Gcol. Surrey own-file rtpt., 2 rheeh. Eakin, H. M., 1916, The Yukon-Koyukuk region, Alosko: U.S. Geol. Survey Bull. 631, 88 p, Chpmn, R. M., Wcber. F. R., and Tober, Bond. 1971, P~elimimr~geoiegic map of the Lirengd quadrangle, Alorko: U.S. Gaol. Suvey open-rile mop, Ebbley, Fiamn. Jr., and Wright, W. S., 1948, Antimony &paits in Almko: U.S. 2 shch. rcole 1:250,000. Bw. Mines Rept. Inv. 3173. 41 p.

Childers, J. M., ond Lomke, R. D., 1973, Flood survey ot proposed TAPS crossing Ellsworth, C. E., ond Dovenporr, R. W., 1913, Placer minins in the Yukon-Tonono of Yukon River nmr Stevens Village. Alosko: U.S. Geol. Survey open-file rqion: U.S. Gaol. Swuey Bull. 542, p. 203-222. rept., 12 p. Ellswth, C. E.. ond Davenport, R, W., 1913, Woter supply of the Yukon-10-0 region, 1912: U.S. Geol. Survey Bul!. 542, p. 223-278. LIVENGOOD QUADRANGLE cant. 114

~lls&th, C. E., and Davenport, R. W., 1915, lurfoce rater supply of the Yukon- Hill, J. M.. 1933. We deposits of the Foirbanks district, Alosko: U.S. Gcol. Tonono region, Alaska: U.S. Geol. Survey Water-Supply Popr 342, 343 p. Surrey Bull. 849-8, p. 19-163.

Ellsath. C. E., and Porker, G. L., 1911, Place: mining in the Yukon-Tonom Hill, 1. P., and Werner, M, A,, 1972, Chemical composition of sedimentary rocks In region: U.S. Geol. Survey Bull. 480, p. 153-172. Alosko, Idoh, Oregon, and Wmshington: U.S. Geol. krvey Prof. Poper nl, 319 p. Ellsworth, C. E., and Porker, G. L., 1911, Woter supply of the Yukon-Tamno region, 1910: U.S. Geol. Survey Bull. 480, p. 173-217, Hollick, bathur. 1930, The +per Cretoc.our floras of Alasko, with m bscription of the plant-bearing beds, by G. C. Martin: U.S. Geol. Survey Prof. Poper 159, Ellsworth. C. E., 1910. Plocer mining in the Yukon-Tawno region: U.S. Gwl. 123 p. Survey Bull. 442, p. 230-245. Holmes, G. W., compiler, 1967, Locotion of pingolike mounds obruved from the Ellswath, C. E., 1910, Woter supply of the Yukon-Tomno region, 1909: U.S. Geol. ground, from aerial tcconrmisronce, and on aerial photographs in ideriw Alaska: Surrey Bull. 442, p. 251-283. U.S. Geol. Survey open-file rept., 13 p.

Elhwth, C. E., 1912, Placer mining in the Foirbanks and Circle districts: U.S. Holmer, G. W., Hopkin., 0. M., and Foster, H. L., 1968. Pingoer in central Geol. Survey Bull. 520, p. 240-245. Alosko: U.S. Geol. Survey Bull. 1241-H, p. HI-WO.

Ellsworth, C. E., 1912, Woter supply of the Foiiwnks, folchnket, and Circle districn: tbpkins, D. M., Korlstrom, T. N. V., and others, 1955, Pernnhat and grdwter U.S. Geol. Surrey Bull. 520, p. 246-270. in Alosko: U.S. Geol. Survey Prof. Paper 266-F, p. 113-iP6.

Emmett, W. W., 1972, Tlr hydraulic gmmrtty nf meAlorkntl stwarns lowtk of the bcknnh, Alhert H., 1973, The impact of new hilhroIs span wildones orrot: Yukon River: U.S. Geol. Survey open-file rept.. 102 p. Arctic, v. 26, n. I, p. 68-73.

Ferrions, Oscar J., Jr., and Kochodwrion, Reuben, 1973, Permfroat-rhted Jwrting, H. R., 1942, Srrotegic mineral occutrenses in interior Alaska: Alosko Dcpt. tngineerning problem^ and the trans-Alosko pipeline (0br.l. in Cordilleran Sec- Mines Pomph. 1, 46 p. tion, 69rh Ann. Mtg.: Geol. Sac. America Abr., v. 5, n!l, p. 41-42. besting, H. R., 194.3, Supplement to Pamphlet No. 1 - Stmtegic mineral occunencss ' Forbes, R. B., Pilkington, H. D., odHawkins, 0. 8., 1968, Goldgredients and in interior Alosko: Alorko Dcpt. Mines Pomph. 2, 28 p. amolie%in the Pcdro Dame-Cleory Summit oreo, Foirbonls distrkt, Alaska: U.S. Geol. Survey open-file rcpt.. 43 p. Job-n, B. L., 1910, Occurrence of wolfromite ond cosritoite in the gold plocua of Deodvwd Crcck. Birch Getk district: U.S. Geol. Swrey Bull. 42. Foster, Hclen L., Brobb, Eorle E., Webet, Florence R., et ol., 1970, Regioml p. 246-250. geology 01 Yukon-Tonono uplord, Alaska febbr.). ;n Inrerwtioml r)mpo,ivm on kctic geology, 2nd.. Am. Asloc. Petroleum Gcorqists hll., v. Y, Kochodwrion, Reuben, 1971, Prelimimry engineeriqj geologic mops of the proposed p. 2480-24a1. trom-Alaska pipeline rwte, Livengood and Tonam quodrongies: U.S. Geol. Survey open-file mop, 2 sheets, scale I:IZS,MX). Foster, Helen L., Webcr. Florence R., Fwbcr, Robert 8.. et ol., 1973, Rcgioml geology nf Yukon-Tonono upland, Alosko, in Arctic Geology: Am. Assac. KiIl.cn, P. L., and Mertie, J. 8.. Jr., 1951, Antimony ore in the Foirbonks dis- Petroleum Geologists km. 19, p. 388-39s trict, Alosko: U.S. Geol. Surrey open-tile rept., 43 p.

Foster, R. L., and Chopmon, R. M., 1967, Locations and descriptions of lode Koschmonn, A. H.. ad&rgendohl, M. H., 1968. Principrl gold-p~oducin~dishicn prospects in the Liur;u)wd area, emt-centrol Alosko: U.S. teal. Survey open- of thc United Stotes: U.S. Geol, Survey Prof. Popr 610, 283 p. file rept., unpaged. Lathram, Ernest H.. 1972, Nimbvr IV vier of the moia ~tructurolieaturer of Alosko: Foster, L. L., 1967. Tectonic inclusions from a ~rpentinite,east-central Alosko, in Science, v. 175, n. 4029, p. 1423-1427. Gcologicol Surrey researclt 1967: U.S. Geol. Survey P~of. Paper 575-0. - . p. D120-Dl22. Lothrom, Ernest H., 1973, Tectonic frorncwrk of northern and cnntvol Alosko, in Arctic Geology: Am. Anoc. Petroleum Geologists Mcm. 19, p. 351-360- Faatsf, R. L., 1968, Dercriptions of the Ruth Getk. Lillian Creek, Griffin, Old Smoky, Sunshine No. 2,' and Olive Creek lode prospects, Livengood dirtricf, Lathram, Ermst H., 1970, Taotmic fromrrork of mrthern and central AImCo (obs.), Alorko: U.S. Gcal. Surrey open-file rept., 21 p. in International syh~pa~iumon Arctic geology, 2nd: Am. &wc. Petroleum . &ologirts Bull,, v. 54, p. 2493. Foster, R. L., 1968, Potcnliol for lode deposits in the Livengood gold placer dbtrict, east-central A(orko: U.S. Ged. Surrey Civc. 590. 18 p. Modonno, kmcr A., t973, Zeolite occwrences of Alosko: Morter's, Alaska.

Foster, R. L., 1969, Nickelilerous serpentinit. near Bsorer Geck, east-central Molone, Kevin, 1962, Mercury occurrences in Alosko: U.S. 8ur. Mines Inf. Circ. Alorka, in Some shorter mineral rcsowcc invertigotion in Alosko: U.S. Geol. 8131, 57 p. Survey C~C. 615, p. 2-4. Molo~,Kevin, 1965, Mcrcvry in Alo$ko, in U.S. Bureau of Mines, Mercury Freelond, George L., and Dictz. Robert I., I9i3, Rotation history of AIwhmn potcntiol of the United States: U.S. sr. Mines Inf. G:c. 8252, p. 31-59. tectonic blocks: lcctonophysiu. v. 18, n. 3-4, p. 379-389. Maloney, Williom, 1916, Report of the Territorial Mine Inspector m the Govera Gedney, I., Shcpiro, L.. Van Wormer, D.. and Webcr, F., 1972. Correlation of of Alorlo for the year 1915: Juneau. Alorko, 36 p. epicenters rirh mopped faults, colt-cmhol AIoILo, 1968-197): U.5. Gsol. Surrey open-file rept.. 7 p, Maloney, William, 1917, Report of Williom hloney, Tenito~iolMine lnspctor to th Governor at Alaska for thc yeor 1916: Juneau, Alo&o. 86 p. Holler, J. W., Miller. M. H., ond Chapmon, R. M., 1973, Bismuth, in bobst, D. A., and Pratt, W. P., tedr.1, United Stmtes mineral resowcn:-U.S. Gcol. Maloney, William, 1918, Report of thTerritorial Mine Inspector 10 the Corernor . Surrey Prof. Poper 820, p. 95-98. of Alosko fw the yeor 1917: Juneau, Alosko, 50 p.

Hawkins, 0. 8.. and Forbes. R. 8.. ,1971, Invertigotion of gold mineralization qlong *tin, G. C., 1919, The AlaJion mining industry in 1917: U.S. G-1. Suriy o part of the Elliott Highwy, Fairbanks district, Alasko: U.S. Geol. Surrey Bull. 692, p. 11-42. open-file tept., 65 p. Mattin, G. C., 1920, The Alorkan mining indmtry in 1918: U.S. G-1. Surey hyn,nn, kmet 8.. 1972, North Slops oil; physical and political problerm: Ptof. Bull. 712, p. 11-52. Geography, v. 24, p. 17-22. Moltin, G. C., 1926, The Mesozoic stratigraphy of Alaska: U.S. Geol. Surwv Hnshv, F, F., and Covert, C. C., 1908, Water-supply investigations in Alasko, Bull. 776, 493 p. 1905-7 (hond Kougorok regiom. Scwrd Penimulo; Foirbonks districf, Yukon-Tonow region): U.S. Geol. Survey Water-Supply Popn 218, I56 p. Irbtako, J. J., and freeman, V. I,., 1963, Surmory of rccommir~ncrfw umiun in Alasko, 1955: U.S. Geol. Sutva), Bull.' 1155, p. 33-49. Hss, F. L., and Gfoton, L. C., 1905. The occurrence and distribution of tin: U.S. Geol. Surrey Bull. 260, p. 161-187. hkrti., J. B., Jr., 1918, Lode mining in tha Foirbanks district: U.S. Gcol. Sur- vey null. t.52. p. dm-424. ks, F. L., 1908. Placers a{ the hpon region, in Prindle, L. M., The Fairbonks and Ramport qurdrongles, Yukon-Towm regionT Alosko: US. Geol. Survey Mertie, J. B., k., 1918, The s~ldplocers of the Tolo~mdistrict: U.S. Gaol. Bull. 337, p. 65-98. S~IV~Yad. t.52, p. 221-277.

Hop, F. L., 1912, Tin ~csowc~sof Alorko: U.S. Geol. Surrey Bull. 520, p. 89-92. Mertie, J. B., 1919, Chromite depain in Alaska: U.S. Geol. SUIV.~ Bull. 692, p. 265-267.

Tanana Quadrangle

I Previous Investigations- Geologic investigations in the Tanana Quadrangle began as early as 1898 when geologists of the U. S. Geological Survey traversed the area- Recent work on the bedrock geology of the region include work by Chapman et a1 (1972); Detterman (1973); Foster et a1 (1973); Patton and Riller (1970) and Churkin (1973); all of the U. S. Geo- logical Survey. Regional geophysical surveys in the quadrangle include work by Brosge et a1 (I 970) ; and two open file reports by the U. S. 'Geological Survey (1973) on a~romagneticsurveys conducted in the quadrangle. Papers by Detterman (1973) and Patton (1973) are the latest works on the tectonics of the region-

Regional Geology and Petrology

The regional geology of the northeastern portion of the Tanana . quadrangle is much the same as that of the northwestern part of the Livengood quadrang1e. Interbedded sequences of tuff, tuff breccia, and argill ite of the terrnian Rampart Group, crop out north and east of the Ray River. North of-, a thick sequence of ' slate, quartzite, schist and phyllite is present. This sequence is believed to be upper Paleozoic in age (Chapman and Yeend, 1972). The phy11 ites are interbedded with very-f ine grained, micaceous metasil tstone, slate, and minor quartzite, and are general ly very fine grained, dark-gray to black phyllites that contain pods and irregular veinlets of quartz. Patton and Miller (1970) correlate this . . unit with similar rocks to the north near the Kanuti River. The phyllites of the Kanuti River region have been correlated

.with plutonic and metamorphic rocks of the Kokrines '- Hodzana highlands area complex to the west (Patton and Miller, 1970). The phyllite terrane in the Tanana Quadrangle is intruded and altered . . by granitic intrusives of Mesozoic age (Patton and Miller, '1970). . . Structural Geology The structural geology of the rocks in the Tanana quadrangle is dominated by the Kaltag Fault. This major right-lateral , stri ke-sf ip fault has been mapped by Chapman and others (1975) and is be1 ieved to follow the structural low occupied by the Yukon River. The fault Is a major structural break and can be traced for about 440 kilometers (275 miles) across west-central A1 aska. The eastern extension of the fault into the Livengood quadrangle has not been identified. However, several large northeast trending faults and strong 1ineaments in the Livengood quadrangle at Beaver Creek, Victoria Creek, Hess Creek, Isom-Rogers Creeks, and the Porcupine lineament north of the Yukon Flats may be the eastern extension of the Kal tag Fault (Florence Weber, Personnal Communications, 1977). Evidence of Quaternary movement along traces of the fault west o.f Tanana have been found. The phyllite units in the Tanana D-6 quadrangle are highly folded and sheared. A strong fo-liation is developed and quartz stringers and pods are present along fractures within phyllite sequence. The folding produces a highly variable fol iation generally stri king between 020" and 11 5" and dipping 25 to 40 degrees to the southwest. At one local i ty, small crenul ations were found indicating secondary folding at 370" and dipping 22" south.

Geochemistry Geochemical reconnaissance in the Tanana quadrangle during the current study consisted of the collection of 12 rock samples (see Tables 21 and 22, Appendix A) from the inner pipeline corridor. The sampling was concentrated in an area where the bedrock is dominated by dark gray phyllite. Statistical analysis of the geochemical data has shown that 58% of the samples collected contain weakly anomalous, anomalous and strongly anomalous concentrations of at 1east one element. Threshold values (see Tables 23 and 24, Appendix A) for each element were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0 x standard deviation, and 2.33 x standard deviation for the 90%, 95% and 98% confidence levels respectively. Where the analytical variabi 1i ty is zero or near zero, the threshold values for the confidence levels are either the detection level or nearly the same value. The phyll i tes that crop out north of 5 Mile Camp contain strongly anomalous concentrations of zinc and copper. No sulfide mineralization was found during the current study, and further work is clearly needed in the area.

Economic Geology and Mining Activity Gold was first discovered in the Rampart District in about 1882. No significant production occurred until about 1896 when rich gold placer deposits were discovered on Little Minook Creek, south of Rampart. Gold placers of the Rampart district have produced about 86,800 ounces of gold up to 1959 (Koschmann and Bergendahl, 1968) and active placer mining is continuing in the region.. Many of the placer deposits in the Rampart District contain accessory tin, cinnabar, pyrite, galena, barite and scheel i te (Waters, 1934). Coal was discovered about 32 kilometers (20 miles) northeast of Rampart in 1897, when Oliver Miller found several coal seams on the Yukon River, opposite the mouth of Hess Creek. This locality, later known as the Drew Mine, produced about 1,200 tons of coal up to 1903. The coal occurs in a thick section of Tertiary sedimentary rocks ' composed of sandstone, conglomerate, shale and coal, believed to be Pliocene(?) in age. A similar deposit occurs on Lower Minook Creek, south of Rampart. 120 REFERENCES CITED

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Miller, T. P., brnes, Ivan, and Potton, W. W., Jr., 1973. Geolcgic setting ond Smith, P. 5.. U.S. Geol. chtmicol chorocteristicr oi hot springs in central and western Alasko: U.S. 797, p. Geol. Survey open-iile rrpt.. 19 p. Smith, P. S., 1930, ~inrolindustry of Alaska irl 1927: U.S. Geol. Svrrmy &I!. Miller, T. P., 1973, Distribution old chemical armlyrs of thetmol spin9 in Aloska: 810, p. 1-64. U.S. Geol. Swvey open-file rept., 1 sheet. Smith, P. S., 1930, Miocrol industcy of Alarka in 1921: U.S. Geol. Survey &I). Mocning, Harold J., 1973, An overview of the trom-Alako pipeline; engineering and 813, p. 1-72. mviromentol geology problems, in Geology, seismicity, and environmental impact, p., 405-409: Assoc. ~ng~~colo~~,Lor Angeles. Smith, P. S,, 1932, Mincrol industry of Alasko in 1929: U.S. Grol. Survey Bull. 824. p. 1-81. Moffit, F. H., 1927, Mineral industry in Almko in 1925: U.S. Gaol. Swvey &It. 752, p. 1-39. Smith, P. S., 1933, Mineral indmrry of Alosko in 1931: U.S. Gml. Survey &!I. BLP-A, p. 1-82. Moxhmn, R. M., 1954, Rcco~oiuoncefor rodiooctive deposits in the Monley Hot Spingrdompurt district, east-centrol Alosko, 1948: U.S. Geal. Sw*ey Circ. Smith, P. 5.. 1933, Mineml indvstry of Alorko in 1930: U.S. Geol. Survey &fI. 317, 6 p. 836, p. 1-83.

Mullipn, J. J., 1974, Mineral resources of the tram-Alaska pipeline cotridw: U.S. Smith, P. S., 1934, Mineral indurtry of Aloako in 1952: U.S. Geol. Surcy &I!. &a. Mims Inf. Citc. 6626, 24 p. 857-A, p. 1-91. TANANA QUADRAN

Smitk, P. S., 1934, Mineral indurhy of Alosko in 1933: U.S. Gcol. Swvay bII. Thorne, R. L., ond Wright, W. S., 1958, kmpfing nnthwh and rsrulh at the &4-A, p. 1-94. Sullivon Creek tin ploccr deposih. hnley Hot Spills, Tolty, Alaska: U.S. Bur. Mines Rept. Inv. 4346, 8 p. Smith, P. S., IPM. Mineral industry of AIMLO in 1934: U.S. Geol. Survey bll. &%A, p. 1-91. U.S. Geologicol Surrey, 1899, Mops and descriptions of routes of exploration in Alorka in 1898, with general iniomtia, concerning the Territory: U.S. Gal. Smith, P. S., 1937, Mineral indrwtry of Alasko in 1935: U.S. Geol. Survey Bull. Surrey Spec. Pub., 138 p. 880-A. p. 1-95. U.S. Geological Survey, 1960, Geologiwl Svrvey rescorch, 1960, synopsis of Smith, P. S., 1938, Minerol industry of Alosko in 1936: U.S. Geol. Survey bII. geologic fnults: U.S. Geol. Survey Ptof. Paper 400-A, p. A1-At%. 897-A,p.I-107. . U.S. Geological Surrey, 1%2, Geological Survey research 1962: U.S. Geol. Smith. P. S., 1939, Areal geology of Aloska: U.5. Geol. Survey Plol. Paper 192, Survey Proi. Poper 4501~, p. Al-A257. • 100 p. U.S. Geological Survey. 1963, Geologicol Surrey research 1963. summery of inves- Smith, P. S., 1939. Mineral indwtry of Alasko in 1937: 2.S. Gaol. bvey Bull. tigotion, prepored by members of the Conservation, Geologic, ond 'ffoter Rr- 910.A, p. 1-113. sources Divisiom: U.S. Geol. Survc", Prof. Paprr 475-A, p. Al-A300.

Smith, P. S., 1939, Minemi industry of Alaska in 1938: U.S. Garrl. Survey Bull. U.5. G~O~OQ~CO~Survey, 1964, tcaiogicol hv8y te~ch1961:. U.5. hi. 917-A, p. 1-113. Survey Pvof. Paper 501-A, pr At--7.

Smith, P. S., 1941, Fineness of gold from Alaska placers: U.S. Gaol. hrvey Bull. U.S. Gaolog~colSurvey, 1969, Grologicol Sv~reyresearch 1969- U.S. Geol. 910-C, p. 147-272. Suvuy Prof. Pupvr 6504, p. Al-A425.

Smith, P. 5.. 1941, Minctol industry ol Alosko in 1939: U.S. Gaol. Surey bll. U.S. Geolqicol Survey. 1%9. U.S. Ccologicul Surey he.- metolr prwiyom po- 926-A. p. 1-105. grers reports, 1968 - Field studies: U.S. Geol. Swvey Circ. 621, 35 p.

Smith, P. 5.. 1941. Past lode-gold production from Alosko: U.S. Gsol. Survey U.S. G~ologicolSurrey, 1972, Geological Swrey research 1972: U.S. Ge~l. , Bull. 917-C. p. 159-212. Survey Prof. Popar 8WA. p. AI-A320.

hith, P. 5.. 1942, Minool industry of Alosko in 1940: U.S. Geol. Swvey Bull. U.S. Geologicol Suvey, 1973, Aermognetic survey, Tomw A-1, A-2, A-3, A-4, 9334, p. I-!@. A-5, A-6, 51, 52, 53. E-4. 9-5, 8-6, C-I, C-2, C-3, C4, C-5, C-6. 0-1, D-2, 0-3, 0-4, 0-5, 0-6, ord ports of Kontishno Rirer D-I, 0-2, 0-3, Smith, 5. S., 1914, Report of the mine invector for the Territory of AImko to the D-4. 0-5 quod.ongles, northeast Alosko: U.S. Geol. Svrey open-file mop, Srctrtary of the Inletior for the lirml year ended June 30, 1914: Washington, 19 shats, %ole 165,360. D.C., 36 p. U.S. Geological Swvey, 1973, Aeromagnelic wrvcy, Tomm gucdrmngle, wthemt Smith, 5, 5.. 1917, The mining iniur~ryin the Territory of AImsko durins the Almka: U.S. Geol. Survey open-file mop, I sheet, scole 1:25G,UX). colrndar year 1915: U.S. Bur. Miner Bull. 142, 66 p. U.S. Geological Survey, 1973, Geologicol Surrey mcorch I9n: U.S. Geol Smith. 5. S., 1917, The mining industry in the Territory of AlmLo during the Surrey Prol. Poper 850, 366 p. wicndcrr yeor 1916: U.S. Bur. Mines bil. 153, 89 p. U.S. Gcoiogicol Survey, 1973, United Stoles Gcologicol Survey Alosko proprom. Spvrr, J. E., 1898, Gsolgy of the Yukon gold district, AInrko, with on introduc- 1973: U.S. GeoI. Survey Circ. 683. 56 p. !or) choptcr on ti?e iristary and conditions of tkdirrrict ro 1897. by H. B. Goodrich: U.S. Geol. Survey 16th Ann. Rept.. pt. 3, p. 87-392. Woring, G, A., 1917. Mineral springs of Alusko, with a chopte. on the :hemica1 ciurrocter of some wrfocr rotsrs 01 Alosko, by R. 8. Dole cnd A. A. Chmhcrs: Stevens, A. E.. and Milne, W. G., 1974, A %tudy01 seismic risk mar pipeline U.S. GcoI. Survey Water-Supply Popcr 418. 118 p. corridors in northwestern Conodo and sostern Alorko: Conadion Jour. Earth Sci., v. 11, n. 1, p, 117-164. Waters, A. E., jr., 1934, Placer concentrates of the Romport ond Hot Spring dirtrich: U.S. Geol. Survey Bull. W-0, p. 227-246. Stevens, Anne E., ond Milne, W. G., 1973. Seisniicity rtudiar in the lvbckenzia Volley, Yukon Territory, and costern Alwho (obs.): EOS iAm. Geophys. Wayiond, R. G.. 1961, Toffy tin-&It, Manley Hot Spring district, &Iosko: U.S. Union irons.), v. 54, n. 3, p. 143, Geol. Survey 6~11. 1058-1, p. 363-414. ' Sterort, 3. 0.. and Dyer. 6. W., 1922, hnwl report of the Tctritwioi Mine Wcdow, Helmuth, Jr., Killeen, P. I.,end otkrs. 1954, iieconnoissunce for rodio- Inspector to the Governor of Aloslo, 1921: Juneou, Alorho, 96 p. active dcpmitr in eastern interior Alosko. 1946: U.S. G-I. Surrey Ckc. 331, 3.5 P. Sterort, B. D., 1923, Annuol report of the Mine Inspector to the GOWCIW of Almka, 1922: Junwu, Aloskn, 175 p. Wedor, Hclmuth, Jr., Whife, M. G., and Jhxhom, R. M., 1952. lntnim rewt on on opproisol of the uronium posribilities of Aloska: U.S. Gaol. Survey Stewart, 8. D., 1931, Report on cooperorion between the Territory 01 4loslo ond the open-rile rept., 123 p. Wiled Stoles in m~kingmining inve~tigotionsond in the inspection of mines for the biermim ending Morc.6 31, 1931: Jwrcou, Alorko, 145 p. White, M. G., Stevens, J. M., ond Marrko, I. J.. 1963, Rodimeftic ttoverse along th. Yvkon River from Fort Yukon ro Ruby, Alosko, 1949: .U.S. Seal. Sterort. 8. D., 1933, Mining investigatiora and mine inrwcrion in Alasko, insludinp Survey Bull. 1155, p. 82-89. oasiitowt to prospecrwr, biemiun ending Merch 31, 1933: Junwu, AIesko, 192 p. William, J. R., 1964, Geologic ~econnoisronceof the Yukon flon Cenozoic boain, Alorka: U.S. Gcol. Suvey open-lilt rept., 19 p. Stcroft. 8. D., 1941. Report of thc Commissioner of Miner to the Govetnor of Alosko lor thc biennium ended Drcember 31, 1940: Juneau, AIasko, 92 p. Wimmlcr, lu. L., 1923, Placer mining in AlwLo in 1922, in Stevort, 8. D., Annual report 01 the Mine Inspector to thc G0n.r~;TAlasko, 19.12: Juneau, Thanas, 8. I., ond Wtight, W. 5.. 1948, Investigation of Mo~elockGcek tin Aloako, p. 23-56, plocer dcporik, fort Gibbon dishict, Alosko: U.S. Bur. Miner Rept. Inv. 4322. 8 p. Wimmler, N, L.. 1924, Placer mining in Alosko in 1923, in Stewort, 8. D., Annuol rep1of the Mine lmp~ctorto tk Gorcrnora Alo~ko. 1923: Juneou. Thol~~,8. I., ond \Wight, W. 5.. 1948, Inrestigotton ol the Toziwon Creek tin AlmLo. p. 11-54: placer deporitr, Fort G;bbon distfict, Alosko: U.S. Bur. Mines Rept. Inv. 4323, ll p. Yecnd, \Vorr.n, 1971, Glociotion ol the Ray Mounmins. centrol Alo,lro. in Geologi- cal Survey research 1971: U.S. Geol. Surrey Prof. Poper 750-D. 0122- Thomor, 8. I., 1957, Tin-bewing placer deposin near Tafty, Hot Springs dirtrict, 0126. centrol Aloska: U.S. Bu. Mines Rept. Inr. 5373. M p.

7homor. 8. I., 1965, P~elimgmryinvertigotion 01 limestone. quartzite. onddolaila rcrwccr nem the proposed Rapart Dom in central Alosko: U.S. Bur. Miner open-fils 1ept. 9-65, 11 p.

Th-. 8. 1.. 1965, Reconmirxmce rompling of the Amct mongonese proapec*, Tanma qvodtongle, centrol AlosLo: U.S. Bur. Mines opcn-file rep!. 1045, 8 P. Bettles Quadrangle

Previous Investigations Geologic investigations along the upper Koyukuk and Chandalar Rivers in north-central Alaska began as early as 1899 when F. C. Schrader of the U. S. Geological Survey conducted reconnaissance geologic investigations. The Kanuti River area in the south-central part of the Bettles quadrangle was first visited by W.C. Mendenhall (1902) ,of the Geological Survey. The first definitive work in the area was done by A.G. Maddren (1913) of the U. S. Geological Survey, who visited most of the important mining districts north of the Yukon River and reported on the regional geology and nining activities throughout the area. Maddren (1 91 3) recognized the complex geology present in the quadrangle and his work combined with that of other workers served to describe the regional geology of the'area. Recent work by Patton and Miller (1973) has resulted in a reconnaissance geologic map of the quadrangle and some regional geochemical data has been co1 1ec ted. Prel iminary geologic investigations by Patton and Mil 1er (1970) in the Kanuti River area have del ineated several areas with high mineral potential. Detailed geologic mapping and geochemical sampl ing by Herreid (1969) near Si thylemenkat Lake in the south-central part of the quadrangle has outlined areas that contain high concentrations of nickel, cobalt, chromium, and iron. Herreid (1969) also produced detailed petrographic descriptions of many of the rocks found throughout the region. Geophysical - investigations by Lathram (1972), Barnes (1967, 1971), Gedney et a1 (1972), and Packer et a1 (1975) have resulted in a better understanding of the tectonics of the region and work by Lathram (1973), Detterman (1973)', and Patton (1973) has led to a better understanding of the bedrock relationships and the tectonic framework of the region.

Regional Geology and Petrol ogx The Bettles quadrangle is situated on the eastern extension of . the Kokrines - Hodzana Highlands areas of the upper Yukon - Koyukuk province, in north-central Alaska. The region is dominated by a crystal 1i ne terrane composed largely of metasedimentary and metaigneous rocks that have been intruded by Mesozoic granitic rocks and mafic and ul tramafic bodies of either Paleozoic or Mesozoic age. The metasediments are chiefly pelitic schists and quartzites with subordinate calc-schist, quartzo-feldspathic schist, and phyll ite of lower Paleozoic or Precambrian age. Carbonate layers within this sequence of rocks contain fossi'l s that are mid-Paleozoic in age and the metasedirnents are believed to interfinger locally with Devonian carbonates (Patton and Mil ler, 1970). The metasedimentary rocks present in the pipeline corridor are generally quartz-muscovite schist and orthoquartzi tes that ran e from the greenschist facies to lower amphibolite facies grade Patton and Miller, 1973). Locally, near the contact with Mesozoic granitica bodies, the schist and quartzite country rock has been upgraded to the pyroxene hornfel s facies. Euhedral andal usi te and cordieri te grains are present localfy (Patton and Miller, 1973). ~t several localities in the east-central part of the quadrangle, an ophiol i te-1 ike assemblage of a1 tered pi1 low basa?t, diabase, gabbro, serpentinized peridoti te and duni te, and bedded chert is present (Patton and Miller, 1970). This assemblage of rocks may reflect a major structural hinge, that marks the southern edge of the Yukon- Koyukuk basin. Payne (1955) and later workers have long recognized the wedge- like Yukon Geosyncline that is bounded on the south by the Ruby Geanticline and on the north by the Brooks Range Geanticline and the Kobuk Trough. A be1 t of mafic and ultramaf ic complexes that parallels the southern margin of the Yukon Geosyncl ine can be traced from the upper Melozitna River west of the Bettles quadrangle to Caribou Mountain, in the east-central part of the quadrangle, a distance of about 104 kilometers (65 miles) (patton and Miller, 1970). Two rcafic-ultramafic complexes along the southern margin of the Yukon Geosyncl ine have received some detailed examinations. One complex, located southwest of the pipe1 ine corridor, near Sithylemenkat Lake, was described by Patton and Miller (1970) as an area with good mineral potential, and as a result, Gordon Herreid (1969) of the Alaska Division of Geological and Geophysical Surveys conducted detailed mapping and geochemical sampling in the area. The Sithylemenkat Lake complex is composed chiefly of gabbro, diabase, basalt, diori te, peridcti te, pyroxeni te, greenstone, and minor metamorphic rocks of greenschist facies grade. The 01 ivine-bearing rocks are moderately-to highly serpentized and local 1y sheared. Some cross-fiber asbestos veinlets, about 3 mi7 l imeters (0.72 inches) wide are present (Herreid, 1969). No sulfide mineralization or chromi te accumulations of significance were found. The mafic-ultramafic complex at Caribou Mountain, just south of Old Man Pipeline Camp, is situated within the Kanuti-Hot Springs granitic batholith. The rocks within the mafic-ul tramaf ic complex consist primarily of harzbergites and duni tes. Local 1y , these rocks are serpenti ni zed. The contact between the Caribou Mountain complex and the surrounding granitic rocks is possibly a fault contact (Patton and Miller, 1970). Herreid (1969), be1 ieves that the mafic-ul tramafic complexes formed during the Jurassic when steep thrust faults were active on the southern hinge-zone of the Yukon Geosyncl ine, and the faults tapped deep zones of mafic and u1 tramafic magmas, that subsequently were intruded and tectonically mixed. Patton and Miller (1566) have mapped similar mafic-ultramfic complexes to the north in the Hughes Quadrangle, and believe that the complexes were emplaced along steep thrust faults along the northern margin of the Yukon Geosyncline. 127 The Kanuti-Hatsprings plutonic complex is composed mainly of coarse-grained, porphyritic biotite granite and medium-to coarse- grained, porphyritic quartz. monzoni te. The complex, dated at 106 mi1 1 ion years B. P. , is be1 i eved to have formed penecontemoraneous ly with the uplift of the margins of the Yukon Geosyncline (Herreid, 1969). Rocks north of the Kanuti-Hot Springs plutonic complex consist mainly of Paleozoic phyllite and schist, that are probably correlatable with the metamorphic rocks south of the Kanuti complex. The phyllite units are generally dark-gray to black phyllite with subordinate f ine-grained metagraywacke. The schist units are dominantly quartz-muscovite schist, chlorite schist, quartz-feldspathic schist and subordinate quartzite, a1 1 of greenschi st and lower amphi bol i te facies. North of Prospect Creek, in the northeastern part .of the quadrangle, upper Paleozoic or Mesozoic mafic volcanic and plutonic rocks crop out. This sequence of rocks is composed mainly of basalt, diabase, and gabbro, all of which have been metamorphosed. The metavol canic and metapl utonic rocks contain we1 1-developed epidote that probably represents a lower greenschist facies metamorphic event. Locally, throughout the Kanuti terrane bodies of fel sic igneous rocks are present. These felsic rocks occur as flows, breccias, and tuffs, and have been dated at 58 + 7 million years B.P. (Patton and Miller, 1973). The felsic rocks ~ommonlycontain disseminated sulfide mineral ization and upon weathering, produce promi nant gossan zones. Near the northeast corner of the Bettles quadrangle, Mesozoic sedimentary rocks are present. This sequence of rocks is composed of massive pebbl e-to cobbl e-congl omerate and minor sandstone. The conglomeratic units have been broken into two members, one that has igneous pebbles and one that is composed of volcanic graywacke and mudstone. The sequence of rocks was first described by Mendenhall (1902), who assigned it to the Bergman Series of probable Cretaceous age.

Structural Geology The structural geology of the Bettles quadrangle is dominated by tectonic events associated with development of the Yukon Geo- sync1 ine (Lathram, 1973). The Yukon Geosyncl ine is bounded on the south by the Ruby Geanticline and on the north by the Brooks Range Geanticline and the Kobuk Trough. The convergence of the genanti- CIina1 structures forms.the recumbant "Vt' shaped Yukon Geosyncl inal trough, whose apex falls in the Bettles quadrangle. Lathram (1973) feel s that interaction between two continental masses in the Paleozoic and Mesozoic resulted in the down-warping or subsidence of the margins of the continental masses and subsequent eugeosync 1 i nal depos i ti on. Deposit ion in the Yukon Geosyncl i ne during the Mesozoic was controlled by uplift and erosion of the marginal fold be1 ts and resulted in the deposition of the Mesozoic sedimentary sequence seen in the area today. The Lower Paleozoic or Precambrian schist belt that parallels the south flank of the Brooks Range and the schist terrane in the Kanuti River area may be the remnants of the,old marginal fold belts (Lathram, 1973). Deep-seated faulting associated with the down-warping of the continental margins and intrusion of mafic and ul tramafic magmas along the faults is marked by a thin belt of mafic and ultramafic complexes along the south flank of the Brooks Range and also the northern margin of the Kokrines - Hodzana Highlands (Herreid, 1969). Patton and Miller (1973) have mapped thrust fault contacts between several of the ul tramaf ic bodies and associated maf ic volcanic assemblages. The thrusts are mapped as over-thrust from the north. The Mesozoic and Tertiary volcanic and sedimentary rocks found within the Yukon Geosynclinal sequence are folded and faulted and only regional geologic mapping has been done over most of the area.

Geochemistry Geochemical reconnaissance in the Bettl es quadrangle during the current study consisted of the collection of 55 rock and stream sediment samples by M. I .R.L. personnel between the Ray River on the south and the south fork of the Koyukuk River on the north. Seventy-three percent of the samples collected contain weakly anomalous, anomalous and strongly anomalous concentrations of at least one element (see Tables 25 and 26, Appendix A). Threshold values (see Tables 27 and 28, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw geochemical-data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0 x standard deviation, and 2.33 x standard deviation for the 90%, 952 and 98% confidence levels respectively. Where the analytical variability is zero or near zero, the threshold values are either the detection level or nearly the same value. Rocks of the Caribou Mountain mafic-ultramafic complex contain strongly anomal ous concentrations of cobalt, chrome, magnesium, nickel, lead, tin, copper and zinc. The cobalt, copper and magnesium values in rocks of the Caribou Mountain Complex are about average for mafic and ultramafic rocks, and high chrome and nickel' values have been detected in chromi te-rich harzbergites and duni tes. Samples of biotite granite and quartz monzonite from the Kanuti- Hot Springs plutonic complex contain strongly anomalous concentrations of sodium and strontium which are commonly associated with these rock types. Samples of quartz muscovite schist and chlorite schist collected near Bonanza Creek contain strongly anomalous concentrations of si 1ver and lead, and weakly anomalous concentrations of zinc and vanadium.

Mining Activity 'and Economic Geology Placer gold was first discovered in the Koyukuk district sometime between 1895 and 1900, on the sand bars of the Koyukuk River (Koschmann and Bergendahl , 1968). Total gold production in the district through 1959 has been estimated to be about 278,000 ounces (Koschmann and Bergendahl, 1968). Most of this production, however, is from the Wiseman area. The U. S. Bureau of Mines reports about 5,300 ounces of gold production from the Bettles quadrangle proper. No production from lode gold or base-metal deposits has-occurred in the quadrangle. I The mafic-ul tramafic complexes along the southern margin of the Yukon-Koyukuk geosyncline are alpine peridotites composed of harzbergi tes and duni tes. The maf ic-ul tramaf ic compl ex at Caribou Mountain, just south of the Kanuti River, is believed to be Jurassic in age (Patton and Miller, 1970) and is situated in the center of the Kanuti-Hot 'Springs granitic bath01 i th of Cretaceous age. The harzbergites and dunites exhibit varying degrees of serpentinization. The serpentinization may be in response to the intrusion of the granitic complex. -This situation is highly favorable for the development of asbestos. Hydrothermal fluids from the granites may have migrated away from the intrusives due to a positive water gradient that usually accompanies this type of intrusion. The fluids would be drawn toward the ul tramafics, which usual ly have negative water gradients, thereby providing an avenue for the migration of fluids and subsequent serpentinization of the olivine-bearing rocks. Cross-fiber asbestos veinlets to 4 millimeters (0.16 inches) in length were found during the current study, however further reconnaissance is needed to evaluate fully the asbestos potential of the area. Chromite and magnetite accumulations in the ul tramafic body at Caribou Mountain are generally restricted to very thin, discontinuous layers generally less than 5 millimeters (0.12 inches) thick. The potential for finding economic quantities of chromite in this ultramafic body seems low. Patton and Miller (1 970) indicate that the average chromium value was less than .26%. The stream sediment geochemistry of the area indicated that stream sediment sampling may be useful in del ineating unknown and undiscovered u1 tramafic bodies. Tertiary volcanic rocks that consist of rhyol i tic-flows, tuffs and breccias are closely associated with the Mesozoic granitic batholith of the eastern extension of the Kokrines - Hodzana Highlands area. The volcanic rocks are the host for disseminated copper, lead and zinc mineralization locally. One such locality near the head of the Kanuti River contains lead concentrations as high as 2%, zinc concentrations as high as 0.3% and silver concentrations as high as 1 ounce per ton. The volcanic rocks are mainly sericitized and sil icified rhyol ites and rhyolite breccias. The rhyolite breccias generally consist of angular fragments of quartz and felsic rock fragments set in a groundmass of cryptocrystalline quartz and sericite. Galena and sphalerite occur in grains as much as 5 millimeters (0.2 inches) in diameter and are disseminated in a pyritic zone about 100 meters (300 feet) long (Patton and Miller, 1970). The rhyolite rests on and probably intrudes the Cretaceous biotite quartz monzonite of the Kanuti batholith. The rhyolite zone is highly oxidized and heavily iron-stained and is permeated by 1imonite. Patton and Mil 1er (1970) feel that deposits of this type are favorable targets for exploration in north-central A1 aska. Similar deposits are located near Indian River, 120 kilometers (75 miles) southwest , of the Kanuti area, where lead, zinc and silver mineralization also occurs. In the extreme northeastern corner of the Bettles quadrangle, the Jim River pluton is in contact with a sequence of mafic volcanic and intrusive rocks of Mesozoic age. The mafic rocks are altered and are greenstones. Locally, the greenstones contain abundant pyrite. Stream sediment samples collected by the U. S. Geological Survey along the Jim River contain anomalous concentrations of lead and copper. On their regional geologic map of the Bettles quadrangle, Patton and Miller (1973) have mapped the contact between the Jim River granitic pluton and the mafic igneous rocks in the valley of the Jim River. The favorable geologic setting and anomalous stream sediment geochemistry indicate an area that may have potential for base-metal sulfide accumulations. Rocks of the Bergman Group in the northern part of the Bettles quadrangle exhibit low radiation levels when tested with a scintillometer. The conglomerate at one locality near the Middle Fork of the Koyukuk River, consists of interbedded cobbl e-to boulder conglomerate and bl ack-to dark-gray, thin-bedded, fissi le shale. The shale interbeds contain some carbonaceous material that was probably plant material. The source of the sediments that constitute the bulk of the Bergman Group was probably the fold belts that flank the Yukon Geosyncl inal basin. No significant urani um concentrations were found during this study, however there may be moderate potential for the development of secondary uranium concentrations in the Bergman Group rocks . REFERENCES CITED

Barnes, D. F., 1967, Four prel iminary gravity maps of part of Alaska: U.S. Geol. Survey open file rept., 5 p. Barnes, D. F., 1971, Prel-iminary Bouguer anomaly and specific gravity maps of Seward Peninsula and Yukon Flats, Alaska: U.S. Geol. Survey open-file rept., 11 p. Detterman, R.L. , 1973, Mesozoic sequence in arctic A1 aska fi Arctic Geology: Am. Assoc. Petroleum Geologists Mem. 19, p. 376-387. Gedney , L ., ha pi ro , L. , Van Wormer, D. , and Weber, F. , 1972, Correlation of epicenters with mapped faults , east-central Alaska, 1968-1971: U.S. Geol. Survey open-file rept., 7 p.

Herreid, Gordon, 1969, Geology and geochemistry near Sithylemenkat I Lake area, Bettles quadrangle, Alaska: Alaska Div. Mines and Geology , Geol . Rept. 35, 22 p. Koschmann, A. H., and Bergendahl , M.H., 1968, Principal gold-producing districts of the United States: U.S. Geol. Survey Prof. Paper 610. Lathram, E.H., 1972, Nimbus IV view of the major structural features of Alaska: Science, v. 175, no. 4029, p. 1423-1427. Lathram, E. H. , 1973, Tectonic framework of northern and central Alaska, -in-~rctic ~eolo~~: Am. Assoc. Petroleum Geologist Mem. 19, p. 351-360. Maddren, A.G., 1913, The Koyukuk-Chandalar region, Alaska: U.S. Geol. Survey Bull. 532, 11 p. Mendenhal 1, W. C. , 1902, Reconnaissance from Fort Ham1 in to Kotzebue Sound, Alaska, by way of Da1 1 , Kanuti , A1 1en, and Kowa k Rivers : U.S. Geol. Survey Prof. Paper 10, 68 p. Packer, D.R., Brogan, G.E., and Stone, D.B., 1975, New data on plate tectonics of Alaska: Tectonophysics, v. 29, p. 87-102. Patton, W. W., Jr., 1973, Reconnaissance geology of the northern Yukon- Koyukuk province, Alaska: U. S. Geol . Survey Prof. Paper 774-A, p. A1-A17. Patton, W.W., Jr. and Miller, T.P., 1973, Analyses of stream-sediment samples from the Bettles and the southern 'part of the Wiseman quadrangle, Alaska: U.S. Geol. Survey open-file rept., 52 p. Payne, T.G., 1958, Mesozoic and Cenozoic tectonic elements of Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-84, scale 1 :84, scale 1 :5,000,000. BETTLES QUADRANGLE

Alorkon Geology Bronch, U.S. Geological Survey, 1972, The stotusof mineral Gedney, L., SFpiro, L., Van Wormer, D., and Weber, F., 1972. Correlation oi terwrce infamatian on the mojor land withd~orolrof the Alosko Nofive Claims epicenters wtth mopped foultr, ant-cmtrol Almka, 1968-1971: U.S. Geol. Survey Settlement Act of 1971: U.S. Geol. Swvey open-fils rcpt., 164 p. open-file rept., 7 p.

Andrearen, G. E., 1960, Total intensity oeromogntic profiles of Kobuk River, Hoynm, kmes 8.. 1972. North Slope oil; phpicol and politico1 problemr: Prpf. Alaska: U.S. Gaol. Survey open-file rep*., 5 rhcetr. Gmgrophy, v. 24, p. 17-22. hnymovs, 1W4, Multimodol trnnrportotion and utility ronidor systems in Alosko; o Hartcid. Gotdon, 1968, Geology ond geochemirtry near Sithylemenkot bke, Botlles preliminary. conceptwl analysis: U.S. Dept. Interior, Bur. Lond hbnagnnent, quadrangfe, Alaska Cobs.), in Alaska Division of Mno ond Geology, Report for ?7 P. the yeor 1968: College, ~zko,p, 22-23.

Anonymus, 1974, Multimodol tronsportotion and utility cwridor systems in Alaska: Hcrreid, Gordon, 1969, Geology and geochemimy of the Sithylemrnkor Lake area. genetalized description ol the 40 primwy cortidors, locotionc, modes, identifying &ttlcs quodtongle. Alasko: AImko Div. Miner end Geelogy Gaol. kept. 35. 22 p. agencies, purposes, environmental impoctr. adslohn of l.onds crowd: U.S. Dept. Interior, Bur. Land Monogement, I84 p. Hollick, Arthur, 1936, The Tertiary flwas oi Alorko, with 0 chapter on the geology oi the Tertiary dsporih, by P. 2. Smith: U.S. Geol. Swrey Prof. Paper 182. 16 p. Barnes, D. F., 1967, Four peliminory gravity maps of ports of Alorka: U.S. Gaol. Svrvcy open-file rept., 5 p. hckmn, Albert H., 1973, The impocl of new higkys qnrildcrmrr orem: Arctic, v. 26, n. I, p. 68-73. Borner. D. F., 1971, Preliminary Bougver anomaly ond specific gravity mop of Scwrd Penimulo and Yulron Flab, Alarko: U.5. Gaol. Surrey open-file rep,., KocWowion. Reuben, 1971, Prelimimry engintaring moprof the prowred I1 p. t,cusr-Alq~rC~~ pi^,, lirov ~cta~ta., Bttlv\ rrvrl R..u.*s q~w~O~~w~~~I~.r~81.:. CIwsl. ;*ZW~ operrlila mop, 2 sheets, scale l:125,WO. 8~111, Cclru~J. W71, Cesnlol rtenr. !sun in Alu.Co, ill Ilu. rt

&ospe, W. P., ond Cwnrodi, kthur, k., 1971, kgnetic susuptibilitiar d crYstol- Mctzko, J. J., ord F.eemon, V. L., 1963, Summary of reconnoissonce kr woniun line rock samples, Yukon River-Porcupine River oreo, east-central Alosko: U.S. in Alorko, 1955: U.S. Geol. Survey b11. 1155, p. 33-49. Geol. Swrey open-file rcpt., 8 p. Mendenhall. W. C,, 1902, Reconnoirsance from Fort Homlin to Kotxebue Sound, Braage, W. P., Brobb, E. E., and King, E. R., 1970, Geologic interpretation ol Alo~ko, by my of Doll, Kanuti, Allen, odKmmk rivers: U. S. Geol. Swrey reconnoisxl-ce oetomognetic svrrey or northeastern Alaska: U.S. Geol. Survey Proi. Paper 10, 68 p. Bull. 1271-F, p. F1-F14. Miglioccio, Ralph R.. and Rooncy, Jomcr W., 1970, Engineering qeologic and Carlei. Claire, (cd.), 1974. United Stotn Gcoiogicol Surrey Alarko Progrom, 1974: subsuriocs soil inr~rtigotionlor trom-Alntka pipeline system lobs,), in Internotionol U.S. Gaol. Survey Circ. 703, 63 p. sympasivm on kctic geology, 2nd: Am. A,loc. Petrolevm ~eolo~is~bll., v. 54, p. 2496. Cederrtrom, D. J,, 1952, Summary of giound-voter dcrelopment in Alosko, 1950: U.S. Geol. Survey Circ. 169, 37 p. Miller, 1. F., brnes, Ivon, ond Patton, W. W., Jr., 1973, Geologic sewing ond chcmicol charoctcristics of hot tp~ingsin central end restem Alosko: U.S. Geol. Childers, J, M , 1972, Chonncl erosion surveys olong proporrd TAPS route, Alasko, Surrey open-iile rept., 19 p. July, 1971: U.S. Geol. Survey opcn-file rept., 79 p. Miller, T. P., 1973. Distribution and chcmicol anoiyses of therml springr in Alo,ko: Childns, J. M., 1974, Flwd surveys along TAPS route, Alosko: U.S. Gaol. knvay U.S. Geal. Survey open-file rept., 1 sheet. open-file rept., I6 p. hning, Homld J., 1973, An overvie*, 06 the Worn-Abrko pipeline; engineering and Cobb, E. H.. i972, Metollic minoal resource mp of the &nlsr quadrangle, rnvitonmental geology prabicms, in Geology, scimicity, od envitonmcotol impocl, Alosko: U.S. Geol. Survey Mirc. Field Studies hkp MF-387, I sheet, scale p. 405-409: Arsoc. Eng. ~eolo~j;Lor Angalo. I:25O,WO. Mulligon. J. J., lV4, Mineral resources of the Irons-Alosko pipeline corridor: Cobb, E. H., 1973, Placer deposits of Alasko: U.S. GMI. Swwy b11. 1374. 213 p. U.S. &I. Mine Inf. Circ. 8626. 24 p.

Dettermn, Robert L., 1973, Mesozoic sequence in Arctic Alorko, 2 Arctic Geology: Nolioml Research Council, Cmmittce on th. Alaska Eorthqwke, 1973. Sumnary Mh Am. Asmc. Petroleum Gtoiogistr hm. 19, p. 376-387. rccammendotions: including index to series in Le collection The Geeat Alasko Earthquake or 1964, No. 8, 291 p., ktl. Aced. Sci., V4ushington, D.C. Eokin, H. M., 1914, Minnol rcroucer of the Yukon-Koyukuk region: U.S. Gsol. Surrey Bvll. 592. p. 371-384. Nournan, J. Vl., and Kernodle, D. R., 1973, Fkld water-guolity information along the ptoposcd Tmns-Alaska pipeline corridor, September 1970 through September Eokin, H. M., 1916. The Yukon-Koyukvk trgion, AIosLo: U.S. Geol. Surwy 1972: U.S. Gcol. Surrey open-iile rept., 22 p. Bull. 631, 88 p. Noumon, J. W., and Kernodle, D. R.. 1974, Aquatic organisms from selected siws Ferrimw, Chtar J., Jr.. and Kochodwrion, Reuben, 1973. Permahat-relored along the proposed tmnr-Atosko pipeline cwridar. September 1970 to kptembn engineering problems ond tk tfom-Alosko pipeline (obs.), Cordille~onSection. 1972: U.S. Geol. survey open-tile report, 23 p. 69th Ann. Mtg.: Geol. be. funerico Ah., v. 5, n. I, p. 41-42. Nelson, A. E., West. W. S., ond Matzko, J. I., 1954, Reconnoisurnce fw Forcer, Helen L., &ebb, Eorlc E., Wcber, Florence R., el 01.. 1970, Regional radiooctive deporitr in eostarn AIoska, 1952: U.S. GeoI. Survey Cils. 348. 21 p. geology oi Yukon-Tonom upland. Alaska, in kctic Geology: Am. hoc. Pehoieum Geologilh Mcm. 19, p. 388-395T Orcrrtreet, W. C., 1967, Th. geologic occurence of manoaite: U.S. Goal. Swry Prof. Paper 530, 327 p. Freeland, George L., and Dietz, Robert S., 1973, Rotation history oi Aloskon tectonic blacks: Tectonophyrics, r. 18, n. 3-4, p. 379-389. BETTLES QUADRANGLE Con*.

Pocket, Dmne R., Brogan, George E., and Stone, David B., 1975, New doto on U.S. Geological Svtvey, 1973. G.ological Surrey rtscwch 1973: U.5, Gcol. Survey ~lotetectoniu of Alosko: Tectomphysicz, v. 29. p. 87-102. Prof. Poper 850, 366 p.

Potton, W. W., JI., ond Miller, 1. P., 1970. Preliminary geologic inwstigotiom in U.S. Geologicol Sutrcy, 1973, United Stater Geala~icolSurvey Alosko program. Im: the Konuti River region, Alaska: U.S. Gcol. Survey &!I. 13l2-J, p. JI-JIO. U.S. Geol. Swvey Circ. 683. 56 p.

Potran, W. W., Jr., ad Miller, 1. P., 1973, Analper of stteam-redirncnt mplas Wadow, Htlmuth, it., and others, 1953, Prelimirwrry sunmy of reconmismnc. for imm the Bettles and the southern port of the Wiseman quadrangles, AImka: uranium and thwium in Alaska, 1952: U.S. Geol. Swvey Circ. 248. 15 p. U.S. Gwl. Swrcy qw-file rept., 52 p. Wadow, Helmuth, k., Vthite, M. G.. and Morham, R. M., 1952, Interim report on Potton, W. W., Jr., ond Miller, 1. P., 1973. Bedrock geologic mop of &tries an opptaisol of the wonium porsibilitiea of Alaska: U.S. Geol. Swvey open-file - and southern port of Wisemon qwdrongler, Alaska: U.S. Geol. Survey Mirc. rept., 123 p. Field Stdier Mop MF-492, I rhcet, sale I:250,MW). William, J. R., 1964, Geologic reconnoiswnce of th. Yvkon Flon Cenozoic basin, Potton, W. W., Jr., 1973, Reco~oiswrnsegeology of the -them YvkorrKoyukvk pro- Alaska: U.S. GeoI. hvey open-file rept., I9 p. vince, Alosko: U.S. Geol. Survey Prof. Papet 774-A, p. AI-A17. ,.. Peorn, Will;om H., 1971, &'tic pipelining; tough, ccntly, but l-sible: UMR hr., n. 2, p. 53-59.

1 Plehch, D. D., Shingle. J. H., McOermon, W., at 01.. 1975, The trons-Alaska I pip~listv., ivt h%tIattgtir,J~wt, it. wta*>lv ~t 1,. ot,, tiqa,~\; l~~dtlvetw~~ rt porpectivcr,- p. 302-317: Centre Etud. Arct., Paras.

Red, I. McK., 1938, Upper Koyukvk ,cgion. Alolko: Alosko Dept. Mines unpublished report, 169 p.

Richards, H. Glenn, 1974. Tectonic erolution of Alosko: Am, Anoc. Pctmleum Geologi,tc Bull., v. 58, n. I, p. 79-105.

Schrodu. F. C., 19M), Preliminary report on o reconmissonce olong the Chandol~r ond Koyukul. Riretr, Alasb, in 1899: U.S. Gcol, Survey 2lrt Ann. Rcpt., pt. 2, p. 441-486.

Srhroder, F. C., 1904, A recomoirmnce in northern Aloska ocroas the Rocky hkwntoint, along Koyukuk, John, Awktuvuk, and Colville rivers and the Arctic coort to Cope Lisburne, in 19M, with mtes by \V. J. Pete,,: Geol. Survey Prof. Paper 20, I39 p.

Smith, Nath, and &rg, Richard, 1973, Encountering moeire ground ice during rood construction in central AI~sko, in Permfrost; Nwth Amsrioon Conttibvtion. Second Internot. Conf.; Principles o~comtrustionin permofcost regions, p. 730-73: Notl. Acod. Sci., Washington, D.C.

Smith, P. S., and Mertie, J. B., Jr., 1930, Geology and mineral resources of northwestern Alosko: U.S. Gcol. Survey hll. 815, 351 p.

Smith, P. 5.. 1912, Th? Alotno-Nwtok region: U.S. Gcol. Survsy bll. 520, p. 315-338. i . Smith, P. 5.. 1913, The Nootok-Kobuk region, Alaska: U.S. Geol. Survey Bull. 536, 160 p.

S-ith, P. S., 1939, A~colgeology of AIosLo; U.S. Gcal. Surrey Pro(. Paper 192. IW p.

Stevenr, A. E., and Milne, Vf. G,, 1971, A study of seismic risk neor pipeline corridors in northwestern Conodo and rortern Alaska: Conadion Jnw. Eorth Sci., u, 11, n. 1, p. 147-164.

Stevens, Anne E., and Milne, W. G.. 1973. Seismicity studio in the Mockenzie Volley. Yukon Teiritwy, and eastern Alaska iahs.1: EOS (h.Geaphys. Union 1lons.i. v. 54, n. 3, p. 143.

U.S. Geological Sdvey 1973. Atromognetic surrey, eastern port of Bettles quadrangle. northeast Alaska: U.S. Geol. Survel open-file mop, I sheet, scale I:250, MKI.

U.S. Geological Swvey, 1969, Geologicol Survey rerewch 1969: U.S. Gwl. Survey Prof. Paper 650-A, p. AI-AI25.

.. U.S. Geological Survey, 1969, U.S. Geological Survey heavy metois pogrom . progress reporh, 1968 - Field studies: U.S. Gco!. Surrey Circ. 621, 35 p. U.S. Geological Survey, 1971, Geological Surrey msorch 1971: U.S. Gaol. Swrey Prof. Popr 750.A. p. AI-A418.

U.S. Geological Survey, 1973, Aeromognetic sucrey, &ttlcs A-I, A-2, A-3. A-4, 6-1. 8-2, &I,C-I, C-2, C-3, 0-1. D-2, 0-3, end port oi 8-4 quodrongles, northeast AIasko: U.S. Geol. Swvry open-file maps, I4 sheets, scale 163,360. W i seman Quadrangle

Previous Investigations Geologic investigation of the Wi seman quadrangle began as early as 1899, when Schrader (1900) of the U. S. Geological Survey conducted reconnaissance geologic investigations along the Chandal ar and Koyukuk Rivers. Brooks (1904) discussed the early mining activities in the area and described the gold placer deposits found along the Middle Fork of the Koyukuk River at Tramway Bar, about 48 kilometers (30 miles) above Bettles. Smith and Mertie (1930) discussed the mineral resources of northwest A1 aska and described the coal deposits and gold placers at Tramway Bar. Smith (1926- 1942) compiled information on many of the mining activities and mineral production in Alaska. Brosge (1960) described .a sequence of metasedimentary rocks that occurs along the south-flank of the Brooks Range. Payne (1955) defined the major tectonic features of north-central Alaska, including the Brooks Range Geanticline, Kobuk Trough and Yukon Geosyncl ine, that dominate the tectonic hi story of northern A1 aska. Barnes (1 967) conducted regional gravity studies in the area and later work by the U.S.G.S. (1973) resulted in aeromagnetic maps at various scales, for the eastern part of the quadrangle. Recent work by Brosge and Reiser (1971) and Brosge et a1 (1970) on the bedrock geology in the quadrangle has resulted in a reconnaissance geologic map of the quadrangle and work by Brosge and Reiser (1970) has resulted in regional geochemical investigations throughout the quadrangle. Work by Lathram (1973), Detterman (1973), Brosge and Dutro (1973) and Churkin (1973) has resulted in tectonic reconstructions and a better understanding of the history of the Precambrian (?) , Paleozoic and Mesozoic rock sequences present in no-rthern Alaska. Work by the U. S. Geological Surveys is continuing in an effort to evaluate the resource potential of the rocks in the region.

Regional Geology and Petrology The regional geology of the Wiseman quadrangle is dominated by a Precambrian (?) to Cretaceous sequence of carbonate, shale, conglomerate, chert, schist, phyllite, calc-schist and meta-igneous rocks. The entire sequence has been folded, faul ted and metamorphosed in part. Structural thickening of the sequence has occurred as a result of imbricate thrust faul tin9 and isocl inal folding of the rocks along the south-flank of the Brooks Range. ' A thick sequence of massive and interbedded, pebble-to cobble conglomerate and shale, crops out in the southernmost part of the Wiseman quadrangle. The conglomerate unit has been broken into two distinct members, one that is composed dominantly of igneous rock clasts and one that is composed of volcanic rock and mudstone clasts. Both members have a wacke matrix and some iron cement. This sequence has been assigned to the Bergman Group of probable Cretaceous age, by Mendenhall (1902). Brosge and Reiser (1964) have mapped similar Bergman Group rocks to the east in the Chandalar quadrangle. North and east of the Middle Fork of the Koyukuk River, a f ai rly thick sequence of interbedded meta-igneous -rocks (greenstones) and chert of probable Mesozoic age crops out. The greenstones are dominantly metabasal t, metadiabase and metagabbro , and we1 1 developed pi 11ow .structures are present locally. The greenstones contain clots of chlorite and epidote, and probably represent a lower greenschist facies metamorphic event. The greens tone-chert sequence near the Koyukuk River may be correlatable with similar greenstone sequences to the west along the south-flank of the Brooks Range. A thick sequence of greenstones in the Angayucham Mountains, near Walker Lake, may occupy a similar structural and or stratigraphic position as those at Cathedral Mountain near Coldfoot, in the southern Wiseman quadrang1 e. Fri tts (1970) described the greenstone sequence in the Angayucham Mountains as a weakly-metamorphosed sequence of a1 tered pi 11 ow basal ts and interbedded phyl? i te, chert and 1imestone of probable Devonian age. Recent work by the U. S. Geological Survey on chert samples from the Angayucham Mountains has shown the cherts to be Triassic in age (Donald G. Grybeck, U.S. Geological Survey, personal communicati on, 1977). The greenstone sequence at Cathedral Mountain is a we1 1-bedded sequence of weakly-to moderately metamorphosed pillow basalt, interbedded with dark gray-to black chert. Clastic rocks of Cretaceous age are in contact with the greenstone sequences in both areas. The contact between the Cretaceous clastic rocks and the greenstones in the Angayucham Mountains has been described as a thrust fault contact, with the Cretaceous clastic sequence thrust over the greenstones from the south (Fritts, 1970). The contact between the Cretaceous clastic sequence (Bergrnan Group rocks) and the greenstone sequence at Cathedral Mountain is obscurred by over- burden, and the contact relationships are uncertain. On the north-flank of Cathedral Mountain, a sequence of graywacke sandstone and subordinate quartzose sandstone and quartzite is present. This sequence contains isolated bodies of greenstone that may be equivalent to the greenstones to the south. The age of these ~ocksis uncertain and may be Paleozoic or Mesozoic. North of the Rosie Creek Pass, just north of Cathedra1 Mountain, a fairly thick sequence of dark-gray to black phyllite and subordinate fine-grained metagraywacke crops out. The structural and stratigraphic relationships between this unit and the graywacke to the south is unknown. The age of these rocks is uncertain, but they are probably Devonian or late Paleozoic (Patton and Miller, 1973). North of Slate Creek and Twelvemile Creek, in the eastern Wiseman quadrangle, a thick sequence of metamorphic rocks with complex structural and stratigraphic re1 ationships is present. This sequence of rocks, composed of phyll i te, quartz-feldspathic schist, marbl e, calc-schi st, micaceous marble, quartzite and slate, is complexly folded and faulted and is cut by large quartz veins at several localities. At one locality, just south of Minnie Creek, a good exposure of graphitic, quartz, muscovite schist is present. The rocks range from a medium-to coarse grained, graphitic, quartz, muscovite schist to a micaceous quartzite. Locally the schist contains as much as 10% sulfide mineralization. Large boudins and lenses of optically-clear smokey quartz to 15 centimeters (6 inches) thick are present. This metamorphic sequence may represent the eastern extension of the "schist beltn of the western Brooks Range. North of Wiseman, in the area of Vermont Dome and the Hammond River, a sequence of schist, phylli te, quartzite, slate, and grit is present. These rocks are of a lower metamorphic grade than the schists and quartzites to the south. The phyll ite units in this sequence are generally dark-gray to black phyllite with abundant quartz stringers. Inter1aminated slate sequences are black, thinly laminated slate with locally abundant pyrite. North of the Hammond River, a thick sequence of highly deformed and tectonical ly thickened 1imestone, schistose marble, dolomite, micaceous-sil ty 1ime- stone, slate, phyllite and siltstone is present. This package of rocks forms the southern be1 t of the core of the Brooks Range province. Imbricated thrust faulting coup1 ed with hi gh-angl e reverse and normal faulting of the sequence has complicated the stratigraphic relationships betweeen the rock units. The lowest most unit recognized in the central Brooks Range Devonian sequence is- the Skaji t Limestone of middle Devonian age. The Skaji t Limestone unit is composed predominantly of 1ight gray, thin-to massively bedded, locally carbonaceous, dolomi tic 1 imestone; and includes minor chlorite schist, muscovite schist and marble (Chipp, 1972). Overlying the Skajit Limestone to the north is an unnamed sequence of limestone, siltstone and sandstone of late Devonian age, that grades upward into a sequence of 1imestone, quartzite, and conglomerate of latest Devonian age.

Structural Geol ogy The structural geology of the rocks in the Wiseman quadrang1 e is dominated by large-scale isocl inal to overturned folds, thrust faults, high-angle faults and small-scale folds. Miogeosyncl inal deposition during the Paleozoic near the core of the present day Brooks Range resulted in the deposition of a thick sequence of 1 imestone, si1 ty 1imestone, si1 tstone and shale. Pene- contemporaneous volcanic activity deposited basal ts, rhyol i tic volcanics and tuffs of various compositions within the 1imestone- shale sequence. Subsequent regional metamorphism of the sequence has transformed the volcanic rocks into quartz muscovite schist, quartz feldspathic schist, meta-rhyol i te and greenstone, and has transformed the sedimentary rocks into marbles, rnetasil tstones, grits and phyll i te. Foreshortening of the entire sequence has resulted from the development of imbricate thrust faulting a1 ong the south-flank of the Brooks Range. The thrust faulting has superimposed the rocks in structural rather than depositional sequences. Oceanic volcanism along the south-flank of the Brooks Range during the Mesozoic produ-ced a fairly thick sequence of pillow basalts and inter-bedded limestone and chert that can be traced i ntermi ttantly from the western Brooks Range, near Wa1 ker Lake, at least as far as the Middle Fork of the Koyukuk River in the eastern Wiseman quadrangle. High-angle faulting has been active throughout the Brooks Range province and has added to the complexity of the geology in the region.

Geochemistry Reconnaissance geochemical investigations in the Wiseman quadrangle during this study consisted of the collection of 69 rock and stream sediment samples. Fifty-nine percent of the samples contained weakly anomalous, anomalous, and strongly anomal ous concentrations of at least one element (see Tables 29 and 30, Appendix A). Threshold values for the various elements (see Tables 37, 32, 33, and 34, Appendix A) were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.0 x standard deviation, and 2.33 x standard deviation for the 90%, 95%, and 98% confidence levels respectively. Where the analytical variability is zero or near zero, the threshold values for the confidence levels are the detection level or nearly the same value. Samples of greenstone and gabbro from the Cathedral Mountain area contain weakly anomalous copper concentrations, anomalous concentrations of iron and titanium and strongly anomalous concentrations of chromium and magnesium. The anomalous values may reflect the normal high background metal content of these mafic igneous rocks. Sporadic anomalous concentrations of manganese, iron and sodium occur in samples of schist and iron-stained quartz vein material. No base metal anomalies of significance were found in the schist and quartzite countryrock near Wiseman, however the area needs further work.

Mining Activity and Economic Geology Placer gold was first discovered in the Koyukuk d.istrict on the bars of the Koyukuk River, some time between 1895 and 1900. The first major placers were discovered on Myrtle Creek and on the Hamond 138 River, around 1899 and 1900 respectively (Cobb, 1973). Placer gold production for the district through 1961 amounted to about 270,000 ounces of gold. Most of the production has been restricted to an area within about a 32 kilometer (20 mile) radius of Wiseman. Lode production in the Koyukuk district has been small, and generally restricted to production of antimony from stibnite- quartz veins that cut the crystalline schist country-rock throughout the region. Mining activity in the region today consists mainly of small, gold placer operations on many of the old producing creeks. One large operation on Mascot Creek, west of Wiseman, was in operation- in 1977. No known lode mining was in progress in 1977. The metamorphic roc'k sequence between Wiseman on the north and Twelvemile Creek on the south, in the Pipeline Corridor, has been correlated with a similar sequence of rocks in the western Brooks Range (Grybeck et al, 1977). The metamorphic sequence in the western Brooks Range has been interpreted as resulting from penecontemporaneous miogeosyncl inal sedimentation and volcanic activity sometime in the early Paleozoic (Thomas E. Smith, Univ. of Alaska, personal communication, 1977). The metamorphic rocks in the western Brooks Range are the host for the metamorphosed volcanogenic massive sulfide deposits of the Ambler mining district. This sequence of metamorphic rocks is composed of marble, metasil tstone, grit and phyl 1ite of sedimentary origin and quartz-muscovi te schist, quartz- feldspathic schist, meta-rhyol i te and -greenstone of volcanic origin. The known massive sulfide deposits of the Ambler district are for the most part restricted to the meta-volcanic rocks. Rocks in the Pipe1 ine Corridor that have been correlated with rocks of the Ambler district -are composed of a relatively thick sequence of phyll ite, marble, calc-schist, quartz-feldspathic schist, quartz- muscovite schist and quartzite wi th compl ex structural and stratigraphic re1 ationshi ps. This metamorphic sequence is complexly folded and faulted and north-vergent i socl inal overturned fo1ds dominate the structure of the region. At Minnie Creek, southwest of Wiseman, a sequence of graphitic quartz-muscovite schist and micaceous quartzite is present. These rocks contain disseminated sulfides, that constitutes as much as 10% of the rock. The sulfide mineralization consists of major pyrrhotite with minor chalcopyrite, sphal erite and galena. No massive sulfides were found during this investigation, however, the nature of the disseminated sulfide mineralization and the country-rock in the Wiseman area are similar to the "countryrock schist" of the Ambler district (Thomas E. Smith, Univ. of Alaska, personal comm., 1977). The possibility of finding volcanogenic massive sulfide deposits in the Wiseman area seems good. More work is needed in the Wiseman area and to the west in the Wiseman quadrangle to further understand the stratigraphy and structure of the rocks and their relationships to the volcanogenic massive sulfide deposits of the southern Brooks Range schist belt. North of Wiseman a schist, phyllite, quartzite, slate and grit sequence contains di sserninated sulfide mineral ization local ly. No significant mineralization was discovered during this study. This metamorphic sequence is similar to the package of rocks south of Wiseman but of a lower metamorphic grade. The disseminated sulfides found in the area consist of well-developed cubes of pyrite on the parting surfaces of a slate unit, and only minor blebs of pyrite in a quartz muscovite schist. At Vermont Dome, a northeast-trending zone of quartz veining is about 100 meters (300 feet) wide and contains at least five veins up to 2.4 meters (8 feet) wide. The U. S. Geological Survey has identified stibnite in the vein material, prior to this study, -however, no sulfides other than pyrite were found.during the present study. The veins are composed of bull quartz and large euhedral quartz crystals to 7.6 centimeters (3 inches) ' inches in diameter are present. The vein material also contains large clots of chlorite and muscovite that are generally restricted to the vugs and open-spaces of the veins. Most of the Creeks in the Viseman area have been prospected for gold placers in the past and many have produced gold. At several localities above gold-bearing creeks, quartz veins of various sizes have been found. The veins are typical open-space filling type veins that are probably the source of the gold in the creeks. One vein above Confederate Gulch, north of Wiseman, contains euhedral pyrite octahedrens and no other sulfides. A stibnite-quartz vein is present on Smith Creek, northwest of Wiseman. The vein is composed of stibnite and quartz and little more. About 20 tons of stibnite has been mined from the vein, some of which was recovered by ground sluicing the surface exposure of the vein, in the creek bottom. Several stibnite-quartz veins are known in the Wiseman area and the probability of finding undiscovered antimony resources in the Wiseman area seems high. South of Wiseman, calc-schist and marble layers in the metamorphic sequence contain scheelite. The extent of the tun sten mineral ization is unknown (WGM, Inc., personal comm., 19777. I ~I> REFERENCES CITED I Barnes, D.G., 1967, Four preliminary gravity maps of parts of Alaska: U.S. Geol. Survey open-file rept., 5 p. 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U.S. Geological Surrey, 1960, Geologicol Survey rcseorch, 1960, synopsis of geologic results: U.S. Geal. Survey Prof. Poper 4M#, p. At-A136.

U.S. Geologicof Survey, 1963, Gcologicol Survey research 1963, summary of inrestigotions, prepoted by membos of the Conservation. Geologic. and Wotct Resources Divisions: U.S. Geol. Sutvey Prof. Pops 475-A, p. AI-A300.

U.S. Geologicml Survey, 1965, Geologicol Survey Reseo~ch1965: U.S. Geol. Survey Prof. Popa 525-A, p. AI-A376.

U.S. Gao)ogisoy Survey, 1966, Geologicol Svtvcy rercorch 1966: U.S. Gml. Survey Prof. Paper 55&A, p. AI-,4385.

U,S. Gaologicol Swvey, 1969, Geologicol Survey rereorch 1969: U.S. Geol. Surrey Prof. Poper 650-A, p. AI-A425.

U.S. Geological Swrcy, 1969, U.S. Geological Survey kmy mdols program pr-rers rspwn, 1968 - Field studies: U.S. Geol. Survey Circ. 621, 35 p. -. U.S. Geologicel Surwy, 1971. Geological Survey rerearch 1971: U.S. Gcol. Surrey Prof. Poper ?SO-A, p. Af-MIS.

U.S. Gealogicol Survey, 1973, Acronognctic survey, sostern port of Wiremon qdrongle, nwtheost Alosko: U.S. Gtol. Survey open-lilt tmp, I ,bet, SM~(:?-50,000. Chandal ar Quadrangle

Previous Investigations - Geologic investigations and topographic mapping in the Chandalar quadrangle began as early as 1899 when Schrader (1900) traversed the Koyukuk and Chandalar Rivers. Gold production in the Chandalar district began as early as 1906 with the discovery of placer gold deposits on Big Creek and St. Mary's Creek, east of Chandalar Lake. Brooks (1 907-1 923) described much of the mining activity in the Chandalar region. These reports served as a base from which Mertie (1925) produced the first regional geologic maps of the area. Later work by Mertie (1930) to the east near the Sheenjek River, was the first geologic work done in the eastern part of the quadrangle. Maddren (1913) of the U. S. Geological Survey conducted geologic investigations a1 ong the upper Koyukuk and Chandalar Rivers and compiled geologic information obtained by previous investigators in the region. Maddren's work resulted . in one of the most comp7ete descriptions of the bedrock geology and mining activity in the Chandalar district. Recent work by Brosge and Reiser (1964) has resulted in a geologic map and structural section of the Chandalar quadrangle. Some regional geochemical investigations have been conducted in conjunction with the mapping programs. Detai 1ed geologic investigations by Chi pp (1 970) were conducted in the area near the Mikado Lode, a gold-quartz vein deposit, just east of Chandalar Lake. Chipp (1 970) described the bedrock geology and conducted geochemical sampling.of the area and presents a structural interpretation of the rock sequences near Chandal ar Lake. Recent work by Lathram (1971) on the tectonics of northern Alaska has provided the basic tectonic framework of the region and has produced the base upon which Churkin (1973) and others have made pal eo- tectonic reconstructions and have developed models of the depositional history of northern A1 aska from the middle Cambrian through the Cretaceous. The reconstructions are based on 1i tho- environmental interpretations from oil well logs and measured sections throughout the area. Packer et a1 (1975) present new data on the seismicity of the area. Alaska State Division of Geological and Geophysical Surveys work in the eastern Chandalar quadrangle describes some contact metasomatic orphyry" deposits near the Mathews River (Wiltse, 1975,

Regional Geology and Petrology The regional geology of the Chandalar quadrangle is dominated by a Precambrian (?) to Tertiary-sequence of metasedimentary and metaigneous rocks, cl astic sedimentary rocks and intrusive igneous rocks of varying composition. The metamorphic.rock sequences are folded, faulted and structural 1y thickened. Imbricate thrust faulting along the south-f lank of the Brooks Range, coup1 ed with questionable stratigraphic relationships between rock units add to the complexity of the geology and to the uncertainty of the.stratigraphic position of the various rock units. Rocks in the southeastern part of the quadrangle are dominantly intrusive rocks that vary from granite to diorite in composition. Several 1arge bath01 i thic complexes are present and the intrusive rocks have a gneissic texture and are sheared and crushed locally (Maddren, 1913). The granitic rocks are generally medium-to coarse- grained, porphyritic biotite granite acd gneissic granite that are chl oritized. Gneissic quartz monzoni te and granodiori te are present locally and contain secondary epidote and calcite. A potassium argon age determination of 101+5 mi11 ion years B.P. was obtained from the granite of the Hodzana Piuton in the southwestern corner of the quadrangle. The Hodzana Pluton is in contact with a unit composed predominantly of andesi te-to daci te flows, pyroclastics and diori tic intrusives believed to be Devonian in age. The volcanics are predominantly pyroxene andes i te and hornbl ende andes i te. The intrusive rocks are mainly pyroxene diorite and some gabbroic rocks occur locally. This unit crops out in a thin belt that can be traced from the Mosquito Fork River in the southwest corner of the quadrangle to Caro, near the confluence of Flat Creek and the Chandalar River, in the south-central part of the quadrang.le, a distance of about 96 ki1 ometers (60 mi les) . Rocks of the Cretaceous Bergman Group have been recognized along the Mosquito For-k River. The Bergrnan Group in the Chandalar quadrangle is characterized by a sequence of pebble-to cobble-conglomerate and i nterbedded f el dspathi c graywac ke. The congl omerate is composed of pebbles and cobbles of quartz, quartzite, schist, slate, black and red chert and minor volcanic rock fragments. Fossils found in the Wi seman quadrangle in Bergman Group rocks are A1 bian in age and plant fossils of late Cretaceous age have also been recognized (Brosge and Ref ser, 1964). The conglomerates occur in smal I , discontinuous outcrops in close proximity to the Devonian volcanics and Cretaceous granitic complexes to the south. The conglomerates stri ke east-west and dip an average of 30" south. Just north of the South Fork of the Koyukuk River, sma'll, discontinuous bodies of green, schistose, hornbl ende diori te and pyroxene diorite of probable Devonian age crop out. The diorite plugs and sills are in contact with black phyll ite and slate that are interbedded with fine-grained quartzite. Schistose graywacke and 1 ithic graywacke are present 1oca11y. North of the South Fork Flats and south of Slate Creek a sequence of red, black; green, gray and white chert and siliceous argillite is present. The chert is a radiolarian chert locally and is be1 ieved to be late Devonian in age (Brosge and Reiser, 1964). Recent work in the Western Brooks Range by the U.S. Geological Survey has shown that cherts in the Angayucham Mountains may be correlatable with those near the South Fork River, and are Triassic in age. North of Slate Creek in the western Chandalar quadrangle, a fairly thick sequence of metamorphic rocks is present. The metamorphic rocks consist of-quartz muscovite schist, quartz feldspathic schist, ca1 c-schist, rnicaceous marble, marble, quartzite, slate and phyll i te. This sequence is probably equivalent to Chipp's upper plate sequence near Chandalar Lake (Chipp, 1970). Chipp has subdivided his sequence into several mappable units. The lowest most unit is the Mikado Phyllite and is composed of dark-gray, fine- grained phyllite with quartz segregations generally less then 5 millimeters (0.20 inches) thick (Chipp, 1970). Petrographically, the phyll ite is composed of about 35% quartz, 40% muscovite, 10% chlorite and 15% opaques. Interlaminated with the phyllite layers are sequences of quartz-muscovi te schist and schi stose quartzite. The dominant rock type in the schist interlaminations is slightly carbonaceous, quartz, muscovite schist with minor chlorite and rare a1 bi te. The upper most unit of Chi pp' s upper plate sequence is a sequence of interbedded schistose quartzite, quartzite schist and minor phyll ite. The schistose quartzite generally consists of about 90% quartz and minor muscovite, chlorite, and trace apatite, sphene, epidote and albite. Just south of Sukakapak Mountain the character of the schist sequence changes and calcareous schist and marble becomes a prominant member of the rock sequence. The calc-schist is generally a brown- weathering, thin-bedded, calcite-muscovite-quartz-chlori te schist and schistose marble. A few beds of noncalcareous schist and phyllite occur locally. Another prominant rock sequence in the Sukakapak Mountain area is a sequence of schist, phyllite, quartzite, slate and grit. The grit unit is general 1y a gritty sandstone that locally grades to conglomerate. Minor siltstone is also present. North of Sukakapak Mountain, the Skajit Limestone unit of upper Devonian age constitutes a major part of the rock sequence. The Skajit Limestone is represented by about 606 meters (2000 feet) of section composed of crystalline and semicrystalline limestone that is dolomitic in part. The limestone ranges in color from white or light-gray to red and brown, where weathering of iron minerals in the 1imestone has produced the red-brown coloration. The 1imestones are thin- to massively-bedded and are 1ocal ly carbonaceous. The 1imestone sequence contains minor interbeds of calc-schis t, muscovite schist, chi orite schist and marble. The sequence may -a1 so contain some mafic dikes and volcani-clastics locally. .The entire sequence is folded, faulted, metamorphosed and structurally thickened in part by imbricate thrust faulting. Overlying the Skajit Limestone to the north is an unnamed sequence of slate, phyll ite, shale and siltstone with minor schistose sands tone. The contact between this sequence and the underlying Skajit Limestone is be1 ieved to be gradational (Gryc et a1 , 1976), however, local unconformities may exist. A sequence of calcareous . and noncal careous s i 1ts tone, slate, phyll i te and ca1 careous gritty sandstone with minor black 1imestone interbeds is in unconformable contact with the unnamed slate-phyllite unit overlying the Skajit Limestone. .

1, IC The plutonic rocks in the central Chandalar quadrangle occur I in subparallel northeast-trending belts. An igneous complex north ._ , and east of Twin Lakes is composed of gneissic, chloritized, biotite granite, quartz monzani te and granodiori te. Minor hornblende granite with secondary epidote and calcite occurs locally. , A narrow be1 t of hornbl ende granodiori te porphyry intrusives east of Mathews River can be traced to the northeast as far as Thru Creek in the north-central part of the quadrangle, a distance of about 48 kilometers (30 miles). The granodiori te bodies are.genera1 ly composed of f ine-to medium-grained hornblende granodiori te, with hornblende phenocrysts to 5 mi 11imeters (0.2 inches) in length. The margins of the intrusives are highly sheared and locally the shearing and pervasive metamorphism has transformed the granodiori te into quartz-chl ori te-muscovi te schist (Wil tse, unpubl ished data, 1975). Where the granodiori te intrudes 1 imestone and calc- schist, the calcium-rich rocks have been thermally and hydrothermally a1 tered and calc-si1 icate hornfel s skarns are developed. We1 1- developed epidote and garnet appear to have selectively replaced the 1imy country rock (Wil tse, unpublished data, 7975). - - A northeast-trending belt of greenstone and greenschist is present in the Mount Snowden area and extends to Your Creek in the north-central part of the quadrangle. The greenstones generally occur in isolated bodies of dark-green, fine-to medium-grained, schistose, hornblende diorite and pyroxene diorite and also as a?tered andesi tic flows. The greenstones contain secondary calcite, epidote and chlorite that probably represent a lower greenschist facies metamorphic event. Similar greenstones in the Christian quadrangle to the east have been dated at 168+8 million years B.P. (Reiser et a1 , 1965). The greenstones vary in grain size and texture but are generally composed of. actinolite, cl inozoisi te and epidote with mi nor calcite, chlorite, sphene and quartz. Textural 1y the greenstones range from aphani tic to granobl astic and b1 astoporphyri tic with actinol i te phorphyroblasts to 5 mill imeters (0.02 inches) in length. Small segregations of a1 bi te with minor calcite, quartz, epidote, cl inozoi site, sphene and chlorite occur throughout the greenstones (Chipp, 1970). Discontinuous sequences of Kanayut Conglomerate of upper Devonian age and Kayak Shale of lower Mississippian age crop out in the northwest corner of the Chandal ar quadrangle. Associated with the upper Devonian rocks are the lower members of the Lisburne Group of 1ower Mississippian age. Structural Geology The structure of the rocks in the Chandalar quadrangle is dominated by northeast and east-trending large scale fold belts and imbricate thrust faulting. The thrust faulting has superimposed rnetasiltstone, marble, black slate, grit and calcareous schists in structural rather then depositional sequences (Mi 1tse, unpublished data, 1975). At least two metamorphic events have affected' the rocks in the western Chandal ar quadrangl e. The polymetamorphi c character of the rocks is exhibited by isoclinal overturned folding and a smaller pervasive structural event that produced crenul ations , quartz boudi ns and stringers whose strike is oblique to the regional strike of the major structures. Locally, small generally less than 5 centimeters (2 inches) wide premetamorphic quartz veins are enfolded with schist and quartzite and ptygmatic folding is we11 developed. Brosge and Reiser (1964) believe that one pulse of metamorphism affected -the rocks in the region some time in the early Paleozoic, and have dated samples of schist at 465+74 mill ion years B.P. and 520 million years B.P. This metarnorphicevent is believed to be related to the isoclinal overturned folding present throughout the terrane. Another event sometime in the Cretaceous is believed to be related to a more pervasive metamorphic pulse that produced small crenulations and a secondary cleavage that strikes obliquely to the regional strike of the country rock. This event has been dated at ' 103 million years B.P. and 100 mill ion years B.P. (Brosge and Reiser, 1964). -

Geochemistry Approximately 71 rock and stream sediment samples were collected in the Chandalar quadrangle during this study by M. I.R.L. personnel. S i xty-f ive percent of the sampl es were weakly anomalous , anomal ous and strongly anomalous in at least one element (see Tables 35 and 36, Appendix A). Threshold values (see Tables 37, 38, 39 and 40, Appendix A) for the 90%, 95% and 98% confidence intervals for each element were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.045 x standard deviation, 2.0 x standard deviation, and 2.33 x standard deviation for the 90%, 95% and 98% confidence levels respectively. Where the analytical variability is zero -or near zero, the threshold values for the confidence levels are either the detection level or nearly the same level. Sporadic base metal anomalies were detected in stream sediment samples in the quadrangle. One stream sediment sample'from Nugget Creek in the Chandal ar B-6 quadrangle contains strongly anomalous concentrations of zinc in excess of 1,000 ppm. The area has been prospected in the past and gold placers in the area have produced gold. Schrader (1904) reported the discovery of galena near the head of Nugget Creek, however no other lode mineral occurrences have been reported in the area. Samples of phyll ite and metasiltstone from the area south of Mt. Snowden contain weakly anomalous concentrations of copper and strongly anomalous concentrations of copper arid zinc. The phyll ite contains disseminated pyrite and is heavily iron-stained locally. The bedrock in the area consists of phyll i te, metasi 1tstone, calc-schist and porphyroblastic schist, and further work is clearly needed to ful ly evaluate the areas mineral resource potential.

Mining Activity and Economic Geology Placer gold was first discovered in the Chandalar quadrangle in 1899 or 1900, when rich placers were found on Gold Creek, a tributary of the Middle Fork of the Koyukuk River. Gold Creek, and Linda Creek and Magnet Creek which are tributaries of Gold Creek have produced at least 19,600 ounces of gold through 1968 (U. S. Bureau of Mines). The richest ground on Gold Creek occurs where diorite dikes and resistant units in the schist produce constrictions in the vall ey walls. . One such constriction, near the mouth of Magnet Creek is the sight of the richest accumulation of gold in the area. The ground in Gold Creek is fairly shallow, although ground as much as 30 meters (100 feet) deep is known in'an abandoned stream channel near Linda Creek. Five miles northeast of Gold Creek, on Emory Creek, minor production from gold placers has occurred. Only about $10,000 in production has been reported from the shallow placers there. Placer gold was discovered on Big Creek, a tributary of the North Fork of the Chandalar River, in 1906. Big Creek has yielded about 15,000 ounces of gold, of which about 10,000 ounces has been produced from 1950 with the introduction of mechanical equipment. Other creeks in the Chandalar Lake area that have had past production include: Little Squaw Creek; Big Squaw Creek; Tobin Creek; Little McClellan Creek; St. Mary's Gulch and Woodchuck Creek. Bedrock depths in the creeks ranges from 0 to 30 meters (0 to 100 feet) and exceeds 30 meters (100 feet) locally. Total production from the placers in the area has been about 40,000 ounces of gold (Heiner and Wolff, 1968). About 1908, several go1 d-bearing quartz veins were discovered near the head of Tobin Creek. By 1913, a shaft 30 meters (100 feet) deep had been sunk and approximately 150 meters (500 feet) of tunnel had been driven on the Mikado Property. One of the tunnels cross cut a 12 meter (40 foot) wide shear zone. The shear zone appears to be a sheeted shear system that contains discontinuous gold values and minor concentrations of arsenopyri te, sphalerite, galena, stibnite and pyrite. A 100 ton per day mi11 has been erected on site and only sporadic production has taken place to date. Several other gold quartz veins in the area have received some attention but none have produced any ore. A northeast-trending belt of hornblende granodiorite intrusives and associated copper mineralization is present along a line from Wiehl Mountain to Thru Creek, in the north-central part of the quadrangle. The copper mineral ization has received considerable attention since the early 1960's, and no production has occurred. Nil tse (unpublished data, 1975) be1 ieves that these deposits are pyrometasomatic skarn deposits that are.genetical1y associated with the hornblende granodiori te bodies. The su1 fide mineral ization is primarily restricted to pyrite and chalcopyrite that occur as disseminated grains throughout the intrusives and a1 so as enriched zones near the contact with the 1imy country rock. High-grade pods of massive magnetite and concentrations of chalcopyrite that constitute as much as 15%of the rock are present locally. Since 1960, at least 15 claim groups have been staked on similar deposits and the probability of finding other deposits of this type in the western Chandal ar quadrangle seems high. A shear zone that marks the contact between dark-gray phyllite and a massive limestone unit that constitutes the bulk of the rocks in the Mount Snowden area can be traced for at least 3.2 kilometers (2 miles). The zone of shearing contains discontinuous segragations of pyrite and chalcopyrite. No mineral ization of obvious significance was found however. Just south of Mount Snowden, a fairly large body of greenstone crops out. The greenstone body is gabbroic inpart and contains disseminated pyrite and chalcopyrite. The sulfide mineralization does not appear 'to be of an economic nature, hcwever, other greenstones in the region may contain similar mineralization. Phyl 1i tic rocks south of Mount Snowden are polymetamorphosed siltstcnes and mudstones that contain disseminated pyrite. The pyrite occurs in rudimentary cubes and as blebs that are all igned in layers parallel to the dominant foliation. No other sulfide minerals were recognized in the phyllites, however, further work is needed in the area to fully assess the true mineral potential. REFERENCES CITED

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Alssko Division of Mines and Minerols, 1964, Report for the yeor 1964: Juneau, . Erokr, A. H., 1915, The Aloskon mining industry in 1914: U.S. Gcol. Survey Bull. AIorLo, I07 p. 622. p. 15-68.

Alaskon Geology Bronch, U.S. Geological Surrey, 1972, The statr. of mineral books, A. H.. 1916, Antimony drporill of Alosko: U.S. Grol. Swwy Eull. 649, resource iniormotion on the mojo, lond withd,owols of the Alorks Native Claims 67 p. Settlement Act of 1971: U.S. Gcol. Surrcy open-file rapt., I64 p. Btooks. A. H., 1916, The AIosko mining indwtty in 1915: U.S. Geol. Surrey Bull. Andreasen, G. E., 1960. Total intensity oerwmgntic mop of the Yukon Flats- 662, p. 1142. Kondik oreo. Alorbo: U.S. Geol. Surrey open-file rcpt., 8 #heels. Brooks, A. H., 1922, The Alako nining industry in 1920: U.S. Gaol. Swrcy Bull. Ancnymorn, 1974, Mvlfimodoi tronsportotion ond utility corridor sysbmr in Alosko; 722, p. 7-67. 0 ptelimiwry, conceptual onolysis: U.S. Dept. Inte,ia, Bur. Lond kbnegement , 77 p . &arks, A. H., 1923. The AloJIon mining induttiy in 1921: U.S. Geol. Survey Bvll, 739, p. 1-44. Anonymous, 1974, Multimodol tranrportotion and utility corridor syrtarns in Alorko; gencrolized description of he 40 primor). cortidors. locotiom, modes, identifying bosge. W. P., and Canradi, Arthm, JI., 1971, Magnetic swcepti~iliticrof cry~tol- ' ogencim, pwpmer, enviro~entolimpacts, and status of londr crossed: U.S. lim rock somplcs, Yukon River-Porcupine River oren, cat-cemral Aloska: U.S. Dept. Inferior, Bur. Land kbnagement, 184 p. Geol. Survey open-file rep,.. 8 p.

Barnes, D. F., 1967, Four preliminary gravity mops of pare of Alosko: U.S. Geal. loqe, William P., and Dutro, J. 4.. h., 1970, Polcozoic of wrthern and centrol Surrey open-file rcpt., 5 p. Alorka (obs.), in Internotiowl symposium on Arctic Geology, 2nd: Am. Puroc. Petroleum ~eoG~istsBull., r. 54, p. 2453. Borner. 0. F., 1971, P,elirninwy Bovpver onemoly od yxciiic gravity mops of krord Peninsula and Yukon Flols, Alaska: U.S. Geol. Survey open-file bagc, W. P., and Rciter, H. N., 1964. Geologic map and section of the rcpt., I1 p. Chondolor quodronglc. AImko: U.S. Geol. Survey Misc. Gwl. Inv. Map 1-375, I sheet, scale 1:250,0W. Bales, R, G., ond Wedor, Hclmuth, Jr., 1953, Preliminary sumnary review of thorium-beoring mineral occurrences in Aloska: U.S. Geol. Swrey Circ. bolge, W. P., ond Reircr, H. N., 1970. Chemical omlyses of stream Kdiment 2a2, I3 p. vrrnplcs ham the Chondolor and r;ost.cn Wi8cmm quodrongies, Alosko: U.S. Gcd. Sorvcy wen-Iilc iept., 56 p. Berp, Edrprd, 1973, Crvrtal shucture in AIa~ko, in The rtrustute of the Eorth'r crust bared on seismic data: ~ectonoph~sirs,-v. 20, n. 1-4, p. 165-182. Brosge, W. P., 04Raiser, H. N.. 1972, Geackmical rscowc,i~ronce in the Wiremon and Chandolor dirtrictr and odjocent region, southern Btooks Range, AloPo: U.S. brg, H. C., and Cobb. E. H., 1967, Metollifrrou, lode deposits of Al~rk: Gco). Surrey Prof. Poper 7W. 21 p. U.S. Geol. Survey Bull. 1246, 254 p. bag.. W. P., and Toill*ur, I. L., 1970, Depolitioml history of norrhun Alosko Blasing, T. J., and Frills. H. C., 1975, Post climate of Alaska and mcth.rertern (with dircuuion), in Proceedings of the gmlqicol rcmimr on the North Slope of bnodo os rcconstruclcd hom tree rings: Alorho Sci. Conf. Pmc. 24, p. 48-58. Almka: Am. AISTC.Petroleum Gcologirn. Lor Angeles, p. DI-DIE. CHANDALAR CUADRANGLE Cont.

&osgs. LV. P., kabb, E. E., and King. E. R., 1970, Geologic interpretation of Lathram, Ernest H., 19T2, Nimbus IV view of the mim structural fcoturer ol Alosko: reconmir>oncc oeromognetic survey or mrtheostcrn Alosko: U.S. Grol. Survey Science, v. 175, n. 4029, p. 1423-1427. &If. 1271-F, p. F1-F14. Lothrom, Ernest H., 1973, Tectonic fromewrk of northern and central AlosL~, in &age, W. P.. 1960, Melosvdimentwy tocks in the south-c;ntrol Cooks Range, Alosko. Arctic Geology: Am. Assoc. pet role^ Geologists Mom. 19, p. 351-560.- -in Gmlogicol Survey reseorch 1960: U.S. Geol. Survey Prof. Pope. 400-8, p. 8351-8352. bthrom, Emot H., 1970, Tectonic homerrork of mhem ond cenhol Alaska lobs.), in Internotiowl rymparim on Arctic geology, 2nd: Am. Auoc. Petroleum Childerr, J. M., Meckel, J. P., and Anderson, G. 5.. 1972, Floods of Augvrt %ologirts Bull., v. 54, p. 2493. I967 in cost-centrol Alorko, with a section on Weotha leoturn contributing to the floods, by E. D. Diemer: U.S. Geol. Survey Water-Supply Pgpr Moddren, A. G., 1910, The Koyukuk-Chondolor gold region: U.S. Gcol. Surrey 1880-A, p. AI-A77. Bull. 442, p. 284-315. P

Childerr, J. M., 1972. Channel erosion surveyr along proposed .TAPS route, kddren, A. G., 1913, The Korukuk-Chondolor region, Alosko: U.S. Geol. Surrey Alorka, July, 1971: U.S. Gcol. Survey open-lile tcpt., 79 p. 8~11. 532, 119 p.

Childnr, J. M., 1974, Flood surveys olong TAPS route, AlorLa: U.S. Gcol. klonry, wiliom, 1917, Report of William klorny, Tenitoriol MiM Impecto, to the

Surrey open-lile report, I6 p. bverw 01 Alasko for the year 1916: Juneau, Alako, 86 p. -'

Chipp, E. R., 1969, Summory of the Chandolor ore. (obs.), in Aiorko Division of her, B. L., 1970, Fmminfcroi biostrotiprophy and Corbniferous microfocier, Miner and Geology, Report for the yeor 1969: bllegc,~lorko, p. 9-10. northern Alorko ond Yukon (obr.1. in lnternotiowi symposium on Arctic geology, 2nd: Am. Atmr. Prt*ol.*wn GmlmFtr RIII., v. 54, p. 3494. Chipp, E. R., 1970, Gtolngy old yeoclwmirt*y ol IIICClurndolo~ oleo. Bods Rony, Alorbo: Alosko Div. Mints end Gfolwr Gcol. Rcpt. 42, 39 p. Monhall, Robert, 1934, R.connoisronce of the northem KoyukuC Volley, AloJo: U.S. Geol. Swvel bull. 6444, p. 147-164. Churkin. Michnel. Jr., 1973. Polemoic ond Ptecombrian rocks of Alosko ond their fole in its structutol evolution: U.S. Geol. Survey Prof. Popcr 740, 64 P. Martin, G. C.. 1919, The Alorkon mining industry in 1917: U.S. Gtol. Swrey &!I. 692, p. 11-42. Co&, E. H.. 1972, Mctollic minetol (irrvrcer map of lhc Chnndoi~rqvodrongle, Alosho: U.S. Geol. Surrey Misc. Field Studies Mop .MF-JS7, I ~hect,rcole Mcttin, G. C., 1920, The AlosLa~~mining industry in 1918: U.S. Gtol. Su:rey Bull. I:25O,WO. 712, p. 11-52.

Ccbb, E. H., 1973, Placer depolin oi Almsko: U.S. Geol. Survey Bull. 1374, Mcrtie, J. 8.. +., 1923, The occvrrcnce of mctolliferous deposits in the Yukon ood 213 p. Kushokwim regions: U.S. Gcol. Survey Bull. 739, p. 149-165.

Detlcrmon, Robert L., 1970, Sedimentmy history of the bdlerochit and Shublik Mertie. J. B., Jr., 1925, Geology ond gold plucos of )he Chordelor district: U.S. formations in wrthaostern Alorio, in Proceedings of the geologicol rrmiwr on Geol. Survey Bull. 773, p. 215-263. the North Slope of Alosko: Am. Lac. Petroleum Geolqlisn Pociiic hc., Los Angeles, p. 01-05. Mcrtie, J. 8.. Jr., 1930, The Chondolor-SheenjeL district: U.S. Geol. Survey MI. 810, p. 87-139, Dettermon, Robevt L., 1970, Mesozoic sequence in Arctic Alasko (obs.1, in Intet- wtionol symposium on Arctic geology, 2nd: Am. AIM. Petroleum C%logirts Migliaccio, Rolph R., and Rmney, Jomcr W., 1970, Enpineering geologic and Bull., v. 54, p. 2477. rubsvrfoce roil invertigotion for trors-Alosko pipeline system !sol.;, in Interwtiomi symporium on Arctic geology, 2nd: Am. Assoc. Petroleum ~l;olo~ir~&ll.,r. 54, Dettermcn, Robert L., 1973, Merozoic sequence in Arctic Alosko. 2 Arctic geology: p. 2496. Am. Assoc. Petrolevm Geologistr Mem. 19, p. 376-387. Mocning. &told J., 1973, An overview of the tmnr-Alosko pipeline; engineering end Dutro; J. T,, Jr., and Atrnrrrong, A, K., 1970, Biatrotigrophy of Corbonifoour of enrironmcntol geology problems, in Geology, seismicity. cnd environmental notthem Alorko iobs.), in lntsrnotionol symposium on Arctic geology, 2nd: Am. impoct, p. 405-409: Asroe. Eng~Geology, bs Angeles. Assac. Ptnoleum Geolo~stsBull., v. 54, p. 2478. Moflit. F. H., 1927, Mineral inourtry in Alosko in 1925: U.S. Gtol. Survey Sull. . Fcrrions, Oscar J., Jt., ond Kochadoorion, Reuben, 1973, Parmofrosr-reloted 792, p. 1-39. engineering p<00lcml and the frmnc-Alorkc pipeline (obs.1, in Cordilleran Section, 69th Ann. Allg.: Geol. Soc. Americo Abs., v. 5, n. I,p. 41-42. Mull, C. G., ond Monqus, M. D., 1972, Itkilyoriok Formotion; new Mieircippion famation of Endicott Group, Arctic Slope of Alosb: Am. &sac. Petroleum Fcaeland, George L., ond D:stz, Robert S., 1973, Rotation history of Aloskon G~ologistsBoll., v. M, n. 8, p. 1364-1369. tectonic blocks: Tectowphysio, v. 18, n. 3-4, p. 379-389. Mulligon, J. J., 1974, Mineral roouccr of the tconr-Alarko p;p.linc corridor: U.S. Fracmon, V. I.., 1963, Exomi~tionoi uronivm prospects, 1956: U.S. Gcol. Survey Bur. Mims Inf. Cirs. 8626, 24 p. h11. 1155, p. 29-33. Notion01 Resaofch Council, Committee on the Alosko Eorthquoke, :973, Summary ond Gryc, Georse, 1970, History 01 petroleum explwotion in northern Alosko (with recommen&lionr; including index to series in the collection The Grebt Absko discussionl, 2 Ptoccedingr oi the geologicol seminor on the North Slope of Ewthqwke of 1964, No. 8, 291 p., ktl. Acod. Sci., ':Joshinqton, D.C. AIosko: Am. Assoc. Petrolevm Geologists. p. Cl-ClO. Nomn. J. W., ond Kemodle, D. R., 1973, Field rrter-quality inlormation olong l-bmilton, Tl~omorC., 1974, Rodiorosbov~chronology oi Alosho; o plogrrss report the p~opcsed t~ons-Alosbpipeline corridor, September 1970 throu(;i September (oh.): Gcol. Soc. Amcrico Abs. Programs, v. 6, n. 7, p. 774. 1972: U.S. Geol. Swvey open-file rept., 22 p.

Haynes. Jomo 8.. 1972, North Slope oil; physicol ond political problems: Prof. Noumon. J. W., and Kernodle, D. R., 1974, Aquotic mconirms lrm selected sites - Geography, v. 24, p. 17-22. along the propored Irons-AlosLo pipeline corridor. kptdr I970 to Saptember 1972: U.S. GeoI. Survey open-file report, 23'p. Hollick, Arthur, 1936, The Ttrtiory flwor of Alosko, with a chopref on the geology of the Tettiory deposits, by P. 5. Smith: U.S. Geol. Swvey Prof. Popr 182, Nelum, A. E., West, W. S., ond Motzbo, J. 1.; 1954, Reconmissonce !w radio- 165 p. active deposits in eortern Alosko. 1952: U.S. Geof. Surrey Circ. 348; 21 p.

Jockman, Albert H., 1973. The impact of new highway, upon wilderness oteos: Orth, Domld J., 1970, North SIopc geographic wmcs soutcer for ~eologicmen- Arctic. v. 26, n. I, p. 68-73. clotwe, in Proceedings of the geologicol semi- on the North Slope oi Alorko: Am. ASSOT.Petro!em Geologists. Pocilic Sec., Cos hgeles, p. RI-RIG. Jooting, ii. R., 1942, Strategic miner01 occur~enccsin interior Alorko: Alosko Dept. Mines Pomph. 1, 46 p. Orerst~cet, W. C., 1967, The geologic occurrence of monazite: U.S. Gcol. Surrey Pzol. Paper 530, 327 p. Joesting, H. R., '194, Supplement to Pamphlet No. I - Strategic mincrol occurrences in interior Alako: Ilosko Dept. Mines Pomph. 2, 28 p. Packer) Dmne R.. Erogon, Geotge E., on2 Stone, Dorid 8.. 1975, Kc- doto on plole tectonicr o! Alosko: Tectomphysin, r. 29, p. 67-102. Kochodowion, Reuben, 1971, P~climinoryengimering geologic mops of the proposed Irons-Alaska pipeline route, Wiremon and Chondolor qwdaonglo: U.S. Geol. Pcorn, Williom H., 1971. Acctic pipelining; tough, costly, but feosibie: UMi! hr., Swrey open-file mop, 2 sheen, uolt I:125,OM). n. 2, p. 53-59.

Koschnn, A. ti., ord firgcndohl, M. H., IW8. Ptincipol gold-producing districts Pietsch, D. D., Shingle. J. H., McDcrmon, W., et 01.. 1975, Th tram-Alaho of the United Slutas: U.S. Geol. L!wy Prof. Pmpcr 610, 283 p. pipeline, 2 Moloutie, Jeon, cd., Le petrole et Ir gos otctiqies; prociemes st perrpecttrer, p. 302-317: Centrs Etd. Arc!., Poris. 155 C HANDALAR QUADRANGLE Cant.

Reed, I. McK., 1938. *per Koyukuk region, Alaska: Alosko Dtpt. Minr unpub- Tmilleur, I. 1.. ond iLosge, W. P., 1970, Tectonic history of nvtharn Plosko (with lished report, 169 p. discurtion), in Proceedings of the geological semi-, on the North Slope of Alarka: Am. ~ssoc.~etrolevmGeologists Pocific kc., Los Angeler, p. El-i20. Richavds, H. Ghn, 1974, Tectonic evolution of Alasko: Am. Asroc. Petrola~m Geologists Bull., r. 58, n. I, p. 79-105. Toillcur, Irvin L., and &orge, VIilliam P., 1971, Cwks Ronge aojen, A~cticAlarko *, (obs.1: &I. kc. America Abt., v. 3, p. 415. Schroder, F. C., 1900, Prelirnimry report on o recerno~eoncealong the Chowhlor and Koyukvk Riwen, Almko, in 1899: U.S. Gcol. Survey 21st A&, Rept., U.S. GeolOgic~lSurvey, 1960, Geologicol Surrey rescorch 1960. synopsis of gaolqic .- pt. 2, p. 441-486. resvltr: U.S. Geol. Survey Rof. Popcr 4WA, p. AI-A136. Schroder, F. C., 1904. A *cconnois%oncein northern Alorko across the Rocky U.S. Geological Survey, 1961, Geological Survey reseorch, 1961, synqnir of g*oIoSi~ Mmtoim, olong Koyvkuk, John, Anoktuvuk, and Colvillc rivers and the and hydrologic results: W.S. Geol. Survey Prof. Paper 424-b, p. 41-AI94. Arctic cwst to tvpe Lisburne, in I9M. with mtes by W. J. Psrcn: Geol. Surrey Pmf. Paper 20, 139 p. U.S. G~logiC~lSurvcy, 1963, Geologicol Survey research 163, sunmoty of invnti- .,, gofions, prepared by members of the Can%eruotiom, Geologic. and Vloter R.roucms Smith, North. ond kg, Richrd, 1973, Encountering mossire ground ice during Divisiorn: U.S. Gcol. Surrey Prof. Poper 4754, p. AI-A3M). rood conshuctim in central Alolko, in Ptrmobost; Nnth Amcrican Contribution, kcond Intermt. bnf.; Princoples o~constructionin permofrat regions, U.S. Geologicol Survey, 1968, Geologicoi Surny research IWB: U.S. G-I. krv p. 750.736: Notl. Acod. Sci., Workingten, D.C. Prof. Paper 6aA, p. A(-A3n.

Smith, P. S., 1926, Minerol industry of Alako in 1924: U.S. Geal. Surrey Bull. U.S. Geological Survey, 1969, Gcologicol Survey reseorch 1969: U.S. Geol. Survey 783, p. 1-30. Pnaf. Pnprv 65C-A, p. Al-A425.

Smith, P. S., 1929, Minetul indurhy of Alorko in 1926: U.S. Geol. Surrey &II. U.S. Geologicol Surcy, 1969. U.S. Geological Survey heary nutols pogrom psqrrn 797, p. 1-50. reporrr, 1968 - Field studies: U.S. Geol. Survey Circ. 621, 35 p.

Smith, P. 5.. 1930, Minetol industry of Alosko in 1927: U.S. Gcol. Sutvey Bull. U.S. Ceologicol Swrey, 1973, Aeromgneric swvey, Chandalor A-4, A-5, Ad, B-4, 810, p. 1-54. 8-5, 84, C-4, C-5, C-6, D-a, D-5, D-6 qwdronglcs, mrthrort Alorko: 0.5. Geol. Survey opm-file mops, 12 ~heetr, scale 1.+3,%0. Smith, P. 5.. 1930, Mineral indu$try of Alosko in 1928: U.S. Ceol. Swvay Bull. 813, p. 1-72. U.S. Geologicoi Surrey, 1973, Aeromagntic survey, western half of Chondoln qvodrongle, rortltaort Alosko: U.S. Geol. %rey open-file mop, I sheet, scale Smith, P. S., 1932, Mineral indvstry of Aloskn in 1929: U.S. Geol. Survey Bull. 1:250,000. 824, p. 1-81. U.S. Geological Survey, 1974. Aeromognetic mop of eastern hoif of tk Chondolor Smith, P. S., 1933. Mitlcrol indurtty of Alorko in 1931: U.5. Gcol. Surrey Bull. qwJrongle, northeastern Alosko: U.S. Geol. Surrey open-fife mop. I sheet. 844-A, p. 1-82. scale i:Z5O,MX).

Smith, P. S., 1933, Mineml indvrtry of Alosko in 1930: U.S. Gcol, Survey Bull. U.S. Ccoloqicol Smvey, 1974, Ce

Smith, P. 5.. 1938, Minerol industry of Alaska in 1936: U.5: Geol. Svvey &,II. White, M. G., 1952, Rd;ooctirity of rclecled rocks and placer concmtrotas horn 897-A, p. 1-107. norrheostcrn Alasko: U.S. Gcol. Survey Circ. 195, 12 p.

Smith. P. 5.. 1939, Praal geology of Alorka: U.S. Geol. Surrey Prof. Poper 192, Williams, J. R., 1962, Geologic reconnoisonce of the Yukon Flab district. Alaska: I00 p. U.S. Geol. krrrey Bull. Illl-H, p. 289-331.

Smith, P. S., 1939, Mincrol indurlry ot Alorko in 1937: U.S. Geol. Swvcy Bull. Williamr. J. R., 1964, Geologic rcmnnoissncr of the Yukon Flats Cenozoic bmin, 9104, p. 1-113. Alaska: U.S. Geol. Sutrer open-file rept., I9 p.

Smith, P. S., 1939, Minefa1 industry of Alab in 1938: U.S. Geol. Survt), Bull. Wimmler, N. L., 1923, Plocer mining in Alasko in 1922, 5 Sterort, 8. 0.. Aonwl 917-A, p. 1-113. report of the Mine Inspector to tk Gover~rof Alako, 1922: Juneau. Alaska, p. 23-56. Smith. P. 5.. 1941. Fineness of gold from AIosko placers: U.S. Geol. Surrry &II. 9104, p. 147-272. Wimmler, N. L., 1924, Plocer mining in Alosko in 1923,k Ste~rt,0. 0.. Annwl report of tk Mine Inspector to the Gorerror of Alaska, 1923: Juneau, Alako. Smith, P. S., 1941, Mincrol industry of Alosko in 1939: U.S. Gool. Surrey bll. p. 14-54. 926-A, p. I-I@.

Smith. P. 5.. 1941. Post lode-gold podvetion fra Alarko: U.S. Geol. Swrey BuU. 917-C, p. 159-212.

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Smith, 5. S., 1917, Tk mining industry in the Tuqitory of AlosLo dwing the -lendor yeor 1916: U.S. &I. Mines Bull, IS, 89 p.

Slerens, A. E., and Milne, W. G., 1974, A study of seismic risk near pipelin. cwridors in northnstern bm& and eastern Alarko: Conodion Jour. Eorth Sci., v. II, n. I, p. 147-164.

Sterort, 8. D.. 1933. Mining invedigationr and mine inspection in Alosko, inCldicQ assistance to prorpecrots, biennium ending MDtch 31.. 1933: Juneau, AIosiro, 192 p. Phil ip Smith Mountains Quadrangle

Previous Investigations Detailed geologic investigations in the Phi 1ip Smith Mountains quadrangle began as early as 1901 when F. C. Schrader of the U. S. Geological Survey traversed the area between Bettles and Barrow. Earlier work by several groups of explorationists along the northern coast of Alaska began as early as 1826 when the Earl of Bathhurst, Sir John Frank1 in decended the MacKenzie River to its mouth and explored westward to about the 149th degree of 1ongi tude (Schrader, 1304). Later work by Dease and Simpson around 1837 surveyed the general geography of the region. Their surveys also described some first geologic observations made during their traversing. Work by Leffingwell (1919) in the Canning River region contributed much to the early geographic and geologic information of the area. Detailed descriptions of permafrost conditions and periglacial processes that are active in the high arctic are included in Leffingwell 's work. Geologic investigations in the region continued at a slow pace until about 1940 when the U. S. Geological Survey and the Department of the Navy undertook a program to evaluate the gas and oil potential of Naval Petroleum Reserve #4, now known as National Petroleum Reserve Alaska. Recent work by Bowsher and Dutro .(1957) of the U. S. Geological Survey in the Shainin Lake area has resulted in a better understanding of the stratigraphy and structure of the rock units in the region. Detailed geologic investigations east of Shainin Lake in the Shaviovi k and Sagavanirktok Rivers region by Keller et a1 (1 961 ) has resulted in detailed descriptions of the Mississippian to recent geologic section present in the 2rea. The detailed rock descriptions contained in their report serve as a base for much of the later work in the area. Geologic mapping and sampling by Patton and Tailleur (1964) in the Killik-Itkillik region, east of Shainin Lake has resulted in a regional geologic map and detailed stratigraphic data for the rocks in the area. Brosge et a1 (1962), produced the first good synthesis of the geologic setting and bedrock geology of the region between Gal braith Lake and the Canadian border. Detailed geologic work by Porter (1965), in the Anaktuvak Pass region contributed much to the understanding of the geologic history and structural evolution of the rock sequences on the north-flank of the Brooks Range. Detailed mapping and structural interpretations by Reed (1968), in an area of the northeast Brooks Range near Peters Lake, Pesulted in a good treatment of the bedrock geology of the area. Geologic investigations, by Tourtelot and Tailleur (1971), on the Shublik Formation in northern Alaska described the unit, and it's depositional and diagenetic history as well as it's trace and major elemental compositions. Similar work by Wood and Armstrong (1975) on the Lisburne Group limestones resulted in the most complete description of the Lisburne Group, its stratigraphy and its diagenetic history. Armstrong and Mamet (1 975), have studied eight carboniferous stratigraphic sections in north-east Alaska and have described the biostratigraphy of these rocks. .Detterman et .a1 (1 975) conducted detai led investigations of the post-carboni ferous rocks in northeastern Alaska that resuTted in a complete description of these rock units.

Regional Geology and Petrol ogy The north-central Brooks Range in the Philip Smith Mountains quadrangle is underlain by a thick sequence of highly deformed marine and non-marine detrital sedimentary and marine carbonate rocks of Paleozoic and Mesozoic age (Porter, 1965). The oldest rocks that crop out in the southern Philip Smith Mountains quadrangle consist of discontinuous outcrops of the middle and upper Devonian Skajit Limestone. The Skajit Limestone is represented by at least 610 meters (2,000 feet) of thin-to massive- bedded, 1ight gray to red-brown, recrystal 1ized 1imestone and do1 omi tic 1imestone. Chert constitutes a major portion of the Skajit Limestone in the Philip Smith Mountains quadrangle, unlike the Skajit Limestone in the Chandalar quadrangle, where chert is lacking and slate and minor sandstone make up a major part of the sequence. Unconformably overlying the Skajit Limestone in the southern part of the quadrangle is a sequence of silty shale, siltstone and sandstone that make up the lowest member of the Hunt Fork Shale. The shale and si1tstone are generally dark-gray and weather dark yellow to red. The sandstones are characteristically gray-green, thin-bedded, very fine-grained, calcareous sandstones. Locally, beneath the lower member of the Hunt Fork Shale is an unnamed unit that is composed of brown to orange, gray and black, shale, sandstone, siltstone, conglomerate and limestone that may contain reef structures (Brosge et al, 1977). Minor shaly limestone, conglomeratic l imestone, red and green shale, and phyl 1ite are also present. At it's type section on Fire Creek, about 40 kilometers (25 miles) east of the Killik River, the Hunt Fork Shale is about 970 meters (3,200 feet) thick, the lowest 240 meters (800 feet) constitutes the 1owest member. The lowest member of the Hunt Fork Shale grades upward into a sequence of rocks composed of about 300 meters (1,000 feet) of silty shale and siltstone. The shale is generally gray to greenish-gray, dark yellow-red weathering shale with dark-gray silty-concretions to 10 centimeters (4 inches) in diameter. Conformably overlying the shale-slate member is a sequence of about 379 meters (1,250 feet) of clay shale, siltstone and silty shale. The lower 76 meters (250 feet) of this member is distinctive because of the nonresistant nature of the clay shale horizons. The clay shales weather easily and usually form areas of lower topographic expression. The soils produced from the weathered clay shale is characteristically bright red, and are easily recognized. A characteristic feature of the Hunt Fork Shale is the relative abundance of anastornozing quartz veins. Pyrite and marcasi te crystals are common with small amounts of galena (Chapman et a1 , 1964). Fossil marine brachiopods, pelecypods, gastropods and fish teeth found in the Hunt Fork Shale are mid Devonian in age (Chapman et a1 , 1964). Conformably overlying the Hunt Fork Shale is the Kanayut Con- glomerate, a dominantly non-marine sequence of interbedded chert pebbl e to cobble conglomerate, sandstone and shale. The Kanayut conglomerate has been subdivided into three members at it's type locality near Shainin Lake. The overall extent of the Kanayut conglomerate is not known, however, it has been recognized as far west as Feniak Lake in the western Brooks Range and as far east as the Sheenjek River in the eastern Brooks Range. The total stratigraphic thickness of the Kanayut probably does not exceed 1,515 meters (5,000 feet). The unit apparently thins to the south, where Kayak Shale of lower Mississippian age 1ies directly on middle Devonian sandstones and shales possibly of the Hunt Fork Shale. The Kanayut also thins to the north, where it is not recognized in the northern belt of Paleozoic rocks. It may be absent or may be equivalent to a thin conglomerate unit named the Keki ktuk Conglomerate (~rosgeet al, 1962). The lowest member of the Kanayut Conglomerate is composed of thin-bedded, fine-grained sandstone and interbedded shale. The sandstone is general 1y an 01 ive-gray, red-brown weathering, quartzose sandstone that is cross-stratified and occurs in beds less than 0.3 meters (1 foot) thick. The intercalated shale is mainly composed of thin- bedded and cross-bedded, dark-green to black, platy, silty shale and shale. The contact between this lower unit of the Kanayut Conglomerate and the underlying Hunt Fork shale is conformable and appears to be gradational (Chapman et al, 1964). The maximum stratigraphic thickness of this lower unit is about 545 meters (1,800 feet), near Red Rock Mountain, southeast of Anaktuvak Pass (Porter, 1965). The middle member of the Kanayut Conglomerate constitutes the bulk of the unit and is characterized by the presence of conglomerate beds. The middle member exposed at Shainin Lake is composed of about 311 meters (1,026 feet) of conglomerate, sandstone and shale that are interbedded in a possible cyclic pattern throughout the member (Porter, 1965). Porter (1965) describes the cyclic sedimentation as a fining upward sequence of conglomerate tocoarse sandstone to shale. Near the top of the conglomerate member (middle member) the amount of conglomerate decreases and is replaced by cross-bedded, platy sandstone. The conglomerate layers do not persist laterally for great distances, and generally are lensoid in shape with thicknesses ranging from 0.3 to 10 meters (1 to 30 feet) (Porter, 1965). Eighty-five percent of the pebbles in the conglomerates are composed of chert ranging to 5 centimeters (0.2 inches) in diameter. The chert varies widely in color with gray, white, black, bluish green, ye1 lowish brown, and red varieties known. White quartz-pebbles make up about 5% of the pebbles and the remaining 10% of the pebbles are composed of quartz sandstone, argi 11 ite and chert breccia. The pebbles lie in definite layers or are scattered throughout a finer- grained matrix of coarse-grained, quartz sandstone that constitutes between 50 and 80% of the rock. The primary cementing agents are silica and iron oxide. Where silica is the cementing agent, the rock is extremely competent and cross-grain fracturing occurs. The sandstones of the middle member of the Kanayut Conglomerate range from poorly bedded units to we1 1-bedded layers of brownish-gray to 1ight 01 ive-gray, medium-to coarse-grained, thin-bedded to massive, locally ferruginous quartzose sandstone. Local ly, thin beds of black pyritic shale containing plant fragments are present (Porter, 1965). The upper part of the Kanayut Conglomerate, known as the Stuver Member, consists mainly of conglomerate and sandstone. At it's type locality near Shainin Lake, the Stuver Member is composed of between 25 and 50% shale and 50 to 75% fine-grained sandstone and sil tstone, and no conglomerate layers are present. The sandstone is usually massive and poorly bedded near the base of the member, and becomes well-bedded near the top of the section. The sandstone is normally a fine-grained, 1i ght gray, ye1 1ow-weathering sandstone. Shale interbeds are typical ly brownish-gray-to 01 ive gray or black, platy shale. Raindrop impressions, mudcracks, ripple marks and worm trails are found on the bedding surfaces as well as we1 1 preserved plant fossils. The sandstones and shales of the Stuver Member are gradational with the underlying conglomerate member. As much as 300 meters (1,000 feet) of Stuver Member rocks are present in the Anaktuvak Pass area and about 260 meters (860 feet) of section is represented at it's type locality near Shainin Lake, therefore Porter (1965) feels that the Stuver Member thickens to the southwest, which is the case for the entire Kanayut Conglomerate sequence. Unconformably overlying the Kanayut Conglomerate is the Kayak Shale of lower Mississippian age. Bowsher and Dutro (1957) subdivided the Kayak Shale into five informal members near Shainin Lake. Total thickness of the Kayak Shale is about 290 meters (960 feet). However, due to it's incompetent nature, the shale is extremely deformed. The basal sandstone member consists of about 40 meters , (130 feet) of poorly-bedded, grayish-brown si 1tstone and a more competent medium-gray to brown-gray , very f i ne-grai ned quartzose sandstone. The sandstones are ripple marked and worm trails are present locally. The lower black shale member overlying the basal sandstone, is grayish-black, hard, fissile, yellow-weathering shale. The shale contains a strong, we1 1 developed axial -plane cleavage (Porter, 1965). The argillaceous 1imestone member of the Kayak Shale is a bl uish-gray, coarsely crystal 1ine, argillaceous, bioclastic 1ime- stone. The total thickness of the limestone member is about 30 meters (1 00 feet). Intercalated shale horizons contain abundant 1imonite that gives the rock a red-ye1 low coloration. The upper shale member is composed of dark-gray, calcareous shale and medium-dark gray, sl ightly argill aceous, bi ocl astic 1imestone that weathers dusty red and reddish brown, and is about 43 meters (141 feet) thick. Conformably overlying the upper shale member is a very distinctive, reddish weathering, ferruginous, fine-to medium-grained biocl asti c 1irnestone. The limestone layer ranges between 0.3 and 5 meters (1 and 15 feet) thick and is an easily recognized unit marking the upper limit of the Kayak Shale. Unconformably overlying the Kayak Shale in northern A1 as ka are rocks of the early and late Mississippian Lisburne Group. The Lisburne Group was first described by Schrader (1904) as the Lisburne Formation, and has since been upgraded to the group status. The Lisburne Group is subdivided into three formations, the Wachsmuth Limestone of early Mississippian age and the Alapah Limestone of late Mississippian age and the Wahoo Limestone of Pennsylvanian and Permian age. The Wachsmuth Limestone has been subdivided into four members at it's type locality near Shainin Lake. The lowest member of the Wachsmuth Limestone at Shainin Lake is a unit that is much the same as the upper part of the underlying Kayak Shale and consists of dark-gray to 01 ive-gray, fine-grained, shaly, argi 11aceous, nodular 1imestone and shale. The dominance of the carbonate content of this member is the marked difference between this unit and the underlying Kayak Shale. This sequence of rocks probably represents a continuation of quiet, open-water marine sedimentation that persisted during the deposition of the Kayak Shale (Wood and Armstrong, 1975). The shaly 1imestone member of the Wachsmuth Limestone is about 6 meters (18 feet) thick at the type 1ocal i ty. Conformably overlying the shaly member of the Wachsmuth Limestone is a richly fossiliferous member that is composed of medium-to dark-gray, medi um-to coarse-grained, crinoidal 1imestone in which the bioclastic content is as high as 20%. The crinoidal 1imestone member of the Machsmuth Limestone is about 55 meters (180 feet) thick at its type locality and l.ike the entire Wachsmuth Limestone member, it thins to the northeast and is entirely absent in the Peters Lake section, in the Romanzof Mountains (Reed, 1968). Conformably overlying the crinoidal 1imestone member of the Wachsmuth Limestone is a fairly thick sequence of light-gray to white, medium-to coarse-grained, sl ightly argillaceous, bioclastic, dolomitic limestone, that is about 171 meters (564 feet) thick at the type locality at Shainin Lake. locally within the member, thin, discontinuous layers of chert are present. The dolomitic phase of the middle member of the Wachsmuth Limestone has been recently interpreted as resulting from sedimentation in a sabkha-type environment near the margin of a semi-restricted marine stable platform, sometime in the early Mississippian (Armstrong et a1 ,1975 p. 1). The chert of this member is usually present throughout the section, however, the amount of chert appears to decrease toward the top of the section. Locally, in the lower quarter of the middle member, the chert constitutes as much as 40 to 50% of the section. The upper banded chert member of the Wachsmuth Limestone is a 130 meter (429 foot) thick section of thin-banded limestone and chert. The chert is usually a thin-bedded, light-gray to dark-gray, thin laminated to nodular chert. Minor .do1omi tic 1imestone layers a1 so occur, interbedded with medium-gray to 1ight-gray, f ine-to medi urn-grained, evenly and irregularly bedded, bioclastic 1imestone (Patton, 1957). Fossils are fairly common in a1 1 of the members of the Wachsmuth Limestone and include crinoids, brachiopods, rugose corals , colonial corals, cephalopods and bryozoans. Total thickness of the unit at the type local ity is about 373 meters (1,230 feet), and about 409 meters (1,350 feet) of Wachsmuth Limestone has been measured to the west near Anaktuvak Pass (Porter, 1965). The entire Wachsmuth Limestone is absent to the east near Peters Lake (Reed, 1968). In two measured sections south of Shainin Lake, the banded limestone-chert member may be as much as 90 meters (300 feet) thinner than at Shainin Lake (Brosge et al, 1962). Therefore, the Wachsmuth Limestone unit appears to thin to the east and south. Conformably overlying the Wachsmuth Limestone is the Alapah Limes- stone, the late Mississippian component of the Lisburne Group. The Alapah Limestone has been subdivided into nine members at Shainin Lake. Most of the member can be recognized to the east, however, many investigators have lumped the members into three units for ease of geologic mapping. The lower four members of the Alapah Limestone unit at Shainin Lake have been lumped by Porter (1965) and others into a lower Alapah member that is composed of a thick section of limestone and chert. The lower part of this member consists of a basal sequence of dark-gray, fine-grained shaly 1imestone and minor interbedded black chert, overlain by a thick sequence of dark-gray, fine- grained, argi 11 aceous, massive and thin-bedded, cherty, bioclastic 1 imestone. Next, a sequence of 1ight brown to gray, fine-to medium- grained, fossil iferous 1imestone is present. The 1imestones exhibit a coarsening upward habit, with f i ne-grained 1imestone grading into medium-grained 1imestone near the top of individual 1imestone beds. This sequence is in turn overlain by a member that is composed of brownish-gray, fine-to medium-grained bioclastic 1imestone. The middle member of the Alapah Limestone is composed of about 76 meters (250 feet) of non-resistant, dark-gray, calcareous shale and grayish- black chert. Mi-nor interbeds of dense, hard, dark-gray, platy limestone that is interbedded with light olive-gray shale and dark-gray argillaceous phosphorite (Porter, 1965). The 1imestones contain well - developed cross-1 aminations. The upper 1umped unit of the A1 apah Limestone consists of the upper four members of the Alapah at its type 1ocal ity. The upper member is composed of 1ight-gray, f ine-grained 1imestone with interbeds of dark-and 1 ight-gray, thin-bedded chert and thick bedded, 1ight gray, fine-grai ned 1imestone that contains abundant brachiopods and a coral assemblage including 1ithostrotionel la. This unit is wide-spread and quite distinctive and is invariably found a short distance above the base of the upper member (Porter, 1965). Gigantoproductus, a productid brachiopod, is quite common near the top of the upper limstone member. Specimens of Gigantoproductus to 10 centimeters (4 inches) across have been found in the Galbraith Lake area, in a thin limestone bed believed to be part of the upper 1imestone member of the Alapah Limestone. Total thickness of the Alapah Limestone at the type locality near Shainin Lake is about 294 meters (970 feet) (Bowsher and Dutro, 1957), and it is about 704 meters (2,325 feet) thick near Anaktuvak Pass. The unit thins to the east near Galbraith Lake, where about 182 meters (600 feet) of Alapah Limestone is present and then thickens to the east near Wahoo Lake, where 590 meters (1,947 feet) of section is present. The Alapah thins northward along the northeast front of the Broo.ks Range (Brosge et al, 1962). Conformably overlying the A1 apah Limestone in the northeastern Brooks Range is the Uahoo Limestone of Pennsylvanian and lowest Permian age (Armstrong, 1970). The Wahoo Limestone is absent near Gal brai th Lake and thickens to 414 meters (1,367 feet) in the eastern- most Brooks Range. Brosge et a1 (1962) have subdivided the Wahoo into two informal members, the upper member and a lower member. The lower member of the Wahoo 1imestone is characteristical ly a medium- gray, fine-to coarse-grained, 1imestone with minor chert. The upper member of the Wahoo Limestone is similar in composition to the .basal crinoidal limestone member of the Wachsmuth Limestone. The rocks commonly consist of coarse-grained crinoidal 1imestone with minor' interbeds of shale and thin-bedded shaly limestone. The upper member is distinguished from the lower member by a zone of black nodular chert that occurs at the base of the upper member. Dolomite is lacking in both members, and coarse-grai ned, 1imestone constitutes as much as 65% of the upper member. At Galbraith Lake, the upper member of the Wahoo Limestone is missing and rocks of the Permian Si ksi kpuk Formation rest unconformably on rocks of the lower member. The upper beds of the lower member are pyritic, where they under1 ie rocks of the Si ksikpuk Formation. Disconformably overlying rocks of the Mississippian Lisburne Group and disconformably underlying rocks of the Triassic Shubl i k Formation is a Permian sequence of shale, siltstone and minor chert known as the Si ksi kpuk Formation. At the type locality on Skimo Creek, west of Chandler Lake, the Siksikpuk Formation consists of about 107 meters (354 feet) of variegated green, gray and dark-red, calcareous, cherty, locally ferruginous, shale and siltstone. The shale and siltstone occur in beds that vary from thin and fissile to massive beds as much as 15 centimeters (6 inches) thick. The unit is easily recognizable because it weathers a characteris tic red- yellow color. Minor limestone interbeds occur in the section and calcareous cannon-ball concretions are found in and interbedded with the shale and chert. The Siksikpuk Formation in the Galbraith Lake area is at least 181 meters (600 feet) thick and probably as much as 300 to 600 meters (1,000 to 2,000 feet) of section may be present (Brosge et a1, 1962). Structural thickening, crumpling, thrust faulting and isoal inal overturned folding in the Atigun Canyon area . has obscured the true thickness of the Siksikpuk Formation. The lower part of the Si ksi kpuk Formation is richly pyritic and thin zones and concretions of pyrite are present, Bladed barite concrcetions and discontinuous zones of barite are present throughout the Atigun Canyon section. Stratigraphically, the Si ksi kpuk Formation is equivalent to the Echooka Formation, the lowest formation in the Sadlerochit Group. The Echoo ka Formation is not recognized in the Gal brai th. Lake section and the Siksi kpuk is considered the lower member of the Sadlerochit Group. The rocks of the Siksikpuk Formation contain an abundant assemblage of fossils including brachipods, corals, and some gastropods, that yield an early Permian.age (Brosge et al, 1962). East of the Sagavanirktok River, the Siksikpuk Formation is not recognized (Yochelson and Dutro, 1960) and the lower member of the Sadlerochi t Group that is recognized is the lower part of the Echooka Formation. The Echooka Formation is equivalent in age to the Siksikpuk Formation but differs lithologically. The Echooka Formation has been subdivided into two members; the Joe Creek Member, composed of about 112 meters (371 feet) of thin-bedded, poorly indurated, calcareous, 1imy sil tstone and shale, minor chert interbeds and some quartzose sandstone occurs locally. The sandstones are glauconitic in part and generally consist of detrital quartz and some calcite. The lower 60 meters (200 feet) of the Joe Creek Member is predominantly a dus ky-ye1 1ow, calcareous muds tone and calcareous siltstone. The rest of the Echooka Member is dominantly quartzose sands tone, quartzite and quartzi tic si 1tstone. The upper member of the Echooka Formation, the Ikiakpaurak Member, is composed predominantly of orthoquartzite, quartzitic sandstone and siltstone. The Ikiakpaurak Member is about 85 meters (280 feet) thick at its type locality and is composed of dark, quartzose sandstones and siltstones that are interbedded with minor orthoquartti tes, that are glauconitic in part. The Ikiakpaurak Member is not recognized in the Gal braith Lake section (Detterman et a1 , 1975). Conformably and locally unconformably overlying the Echooka Formation is' the Ivashak Formation, an early Triassic sequence of silty shale, siltstone, massive sandstone and shale, that is considered the upper formation of the Sadlerochit Group. The Ivashak Formation has been subdivided into three members. The lowest member, the Kavi k Member, is composed of thinly laminated to thin bedded, silty shale and siltstone that are composed for the most part of a1 ternating layers of detrital quartz grains and dark bands of sericitic clay. Quartz constitutes as much as 40% of the rock. Conformably overlying the Kavik Member is the middle, Ledge Sandstone Member of the Ivashak Formation. The Ledge Sands tone Member commonly forms prominant hogback ridges and questas, due to its resistant nature. The Ledge Sandstone. is composed of 58 meters (190 feet) of medium- grained, massive, quartz arenite. The arenite is composed of 30 to 40% chert fragments and 50 to 60% quartz in subrounded and we1 1-rounded grains. Minor detrital tourmal ine, pl agioclase feldspar, zircon and pyrite are also present. Locally, the sandstone is conglomeratic and the conglomerates occur in well defined zones in the upper part of the member. The conglomerates are composed of subangular to well-rounded granules and pebbles of quartz and chert up to 2.5 centimeters (1 inch) in diameter. A few thin siltstone and silty shale beds are intercalated with the sandstone beds. The upper 33 meters (110 feet) of the Ivashak Formation is composed of thin-bedded to massive, siliceous sil tstone and minor silty shale and argillaceous sandstone of the Fire Creek Member (Detterman et a1 , 1975). The siltstones are predominantly composed of 40 to 80% mineral grains in a siliceous clay matrix. The mineral grains are all well-rounded and are composed of 40 to 60% quartz and as much as 20% chert. Calcite and pyrite occur locally and minor garnet and zircon are present (Detterman et a1 , 1975). Recent work by Detterman (1976) on rocks of the Permian and lower Triassic Sadlerochit Group has shown that at least some of the rocks of Permian age in the north eastern Brooks Range are volcanic rocks. At two localities, one on the Ivishak River and the other near Porcupine Lake, Detterman (1976) has identified tuffs, volcanic breccias and flows that exhibit some pillow structures. The tuffs near the Ivishak River are 1ight-to dark-green, fine-grained, amygdaloidal flows. The section near Porcupine Lake is part of a major thrust complex that rests on lower Cretaceous strata (Detterman, 1976). The vol canics are 1ight grayish-green, fine-to medium-grained flows. Dutro et a1 (1977) have shown that some of the rocks of the upper Devonian sequence in the central Brooks Range i ncl ude vol canocl astic rocks and flows and include mafic pillow lavas that Dutro be1 ieves marks the onset of deeper water deposition in Frasnian (late upper Devonian) time. Sporadic volcanic activity from the Devonian to the Permian in north-central Alaska may have resulted in the deposition of tuffaceous sedimentary rocks as well as still unrecognized volcanic sequences within the predominantly marine sedimentary sequence. Tailleur (personal communication, 1977) be1 ieves that much of the shale and siltstone present in the northcentral Brooks Range may in fact be tuffaceous sedimentary rocks. Conformably overlying the Fire Creek Siltstone Member of the Sadlerochit Group in northeastern Alaska is the Shublik Formation of middle and late Triassic age. The Shublik Formation has been informally subdivided into three members, based on changes in lithology. The basal siltstone member is composed of 21 meters (70 feet) of thin-bedded, organic-rich, phospathic siltstone. Phosphatic concretions and -grains with quartz nucl ei are fairly common, and detrital grains of plagioclase and serici te are present. The middle member of the Shubl i k Formation is composed of 100 meters (300 feet) of thin-to thick-bedded, 1ight-gray, silty, fossiliferous 1imestone and dolomite. The limestone is phosphatic in part and contains small phosphate pebbl es and green-gray and black chert grains. Local ly, chert layers are interbedded with thin interbeds of silty shale. The remaining 27 meters (90 feet) of the Shubl i k Formation, at the type locality, is composed of a very soft, incompetent, sequence of fissile, calcareous shale. The shale contains 1imestone and phosphatic concretions. Local ly, the Shubl i k Formation near Gal brai th Lake, in . Atigun Canyon, is represented by a sequence of folded and faulted, highly fractured, silty shale, chert and 1imestone. The contact with the underlying Siksikpuk Formation may be a fault and local discon- formable relationships are present. Conformably and locally unconformably overlying the Shubl i k .Formation in northeastern Alaska is the Kingak Shale of lower to upper Jurassic age (Detterman et al, 1975). The Kingak Shale is not recognized east of the Lupine River, and apparently thickens and thins irregularly over short distances. Near the Canning River, as much as 900 meters (3,000 feet) of section that is most likely Kingak Shale is present (Detterman et a1 , 1975). However, folding and fatilting of the rocks in the area may have resulted in structural thickening of the incompetent shaly horizons. The lower part of the Kingak Shale is represented by at least 181 meters (600 feet) of very fissile paper shale that decomposes into small fragments generally less than 2 centimeters (1 inch) in diameter. Overlying the fissile shale interval is a thin tone of clay shale that is inturn overlain by a section of fissile shale and siltstone about 303 meters (1000 feet) thick. The siltstone is composed of 70 to 80% rounded quartz grains and siderite constitutes as much as 10% of the siltstone.' Minor detri tal grains of plagioclase, zircon, pyrite, glauconite, and phosphate are present. The matrix of the siltstone is mainly ,, si1iceousclay. Rocks believedto bepartof theKingakShaleinthe . Atigun Canyon area, near Galbraith Lake, are mainly dark gray to black, fissile shale that disconformably overlie the upper limestone member of the Shublik Formation. Fossil fragments were found in rocks believed to be Kingak Shale, however no definitive fossil identifi- cations have been made. Disconformably overlying rocks of Shublik Formation, Kingak Shale and Ivashak Member of the Sadlerochit Group in northern Alaska is a lower Cretaceous sequence of quartz arenite, clay shale and graywacke sandstone, known as the Kongakut Formation. The contact between the Kongakut Formation and the underlying strata marks a major early Cretaceous unconformi ty in northern Alaska (Detterman, 1975). The Kongakut Formation has been subdivided into one formal and three informal members, The clay shale member is the lowest member of the Kongakut Formation and is composed of 106 meters (350 feet) of clay shale. Conformably overlying the clay shale member is the Kemik Sandstone Member, a sequence of very fine-grained quartz arenite with minor amounts of glauconite, phosphate, serici te, and zircon. Overlying the Kemik Sandstone Member is the pebble shale member that is 158 meters (520 feet) thick. The pebble shale rtember contains a section of about 53 meters (175 feet) of highly manganiferous beds of silty shale. The manganese beds are uniformly black with small pel lets and thin beds of manganese carbonates (Detterman et al, 1975). Conformably overlying the pebble shale member is the siltstone member composed of a thick sequence, 291 meters (690 feet), of thin-bedded sil tstone with minor interbeds of sands tone. The Okpikruak Formation, named by Gryc et a1 (1951, p. 159) is exposed along the Okpikruak River in the Chandler River area west of Anaktuvak Pass, and is present in the Atigun Canyon area. The formation was extended to the eastern Brooks Range by Detterman (1963, p. 195), who defined the base of the Okpi kruak Formation as the base of the Kemik Sandstone Member of the Kongakut Formation, therefore the two formations are at least in part equivalent correlatable units. In the Atigun Canyon area, the unit is composed of several hundred meters (feet) of clay shale and minor siltstone and fine-grained sandstone. Unconformably overlying rocks of the Okpi kruak Formation and

I rocks of the Kongakut Formation is a fairly thick sequence of marine sandstone, si 1tstone, s haly 1imes tone, clay s ha1 e and conglomerate of the Fortress Mountain Formation of lower Cretaceous age. The conglomerate and sandstones are typically graywacke-type sedimentary rocks that contain abundant clasts and fragments of black and green chert, feldspar and angular mafic igneous rock fragments, all set in a green mudstone matrix (Keller et a?, 1961). At it's type section, the Fortress Mountain Formation is about 3,000 meters (10,000 feet) thick, however, the type locality is probably the thickest section of Fortress Mountain Formation exposed on the north-flank of the Brooks Range, and exposures of 1,500 meters (5,000 feet) of section are common. The Torok Formation of lower Cretaceous age is be1 ieved to be the lateral equivalent of the Fortress Mountain Formation (Keller et a1 , 1961 ) . The Torok Formation is predominantly dark-gray and dark-bluish-gray, fissile to platy, soft, silty shale and clay shale. Locally, lenticular bodies of sandstone, as much as 242 meters (800 feet) thick, occur in the shale sequence. The base of the Torok Formation is not exposed, however, 1,820 meters (6,000 feet) of section is present at the type locality. Kel ler et a1 (1961) be1 ieve that a lateral facies change and major i nterfi ngering between the two formations accounts for the lithologic differences between the two units. Unconformabl y overlying rocks of the Kongakut Formation, Torok Formation and Fortress Mountain Formation in the northern foothills belt of the Brooks Range are rocks of the Nanushuk Group of early Cretaceous age. The Nanushuk Group contains both marine and non- marine rocks and has been subdivided into two formations. The Tuktu Formation is a marine sequence of interbedded, thin-bedded, fine- grained, greenish-ye1 low, calcareous sandstone; dark si ltstone and shale. The sandstone-contains abundant so1 e markings, mainly flute casts, skip and drag marks, and flame structures, all of which are suggestive of deep water turbidi te deposition. The Tuktu Formation may be as thick as 515 meters (1,700 feet), but exposures of about 212 meters (700 feet) thick are common. Conformably overlying the Tuktu Formation are rocks of the non-marine Chandler Formation. The Chandler Formation is composed of 1,447 meters (4,775 feet) of cycl ically deposited polymictic conglomerate, salt and pepper sandstone, siltstone and shale. The sequence is entirely non-marine and contains

, abundant features of fluvial deposition including; cut and fill structures, crossbedding, channel deposits, and f ine-grained shaly siltstones containing abundant plant fragments. The shaly siltstones are interpreted as being overbank fluvial deposits. Coal is a fairly common feature in the Chandler Formation.

Structural Geology The structural geology of the rocks in the Philip Smith Mountains quadrangle is dominated by imbricate thrust faults; high-angle normal , faults; anticlines and synclines of various sizes; and large, tight, overturned folds. Thrust faulting throughout the north-flank province of the Brooks Range has juxaposed rock units into structural rather than depositional sequences. Rock units that contain a large percentage of incompetent rock such as shales and siltstones have reacted differently- to the regional stresses than the rock units with more competent rocks such as cherts, sil icificed 1imestone and conglomerate. Incompetent rocks make up the bulk of the Kayak Shale, Hunt Fork Shale and Si ksi kpuk Formation. These units have been compressed into tight folds and are cut by many small faults. The shale horizons also tend to localize faults parallel to their bedding (Porter, 1965). Porter (1965) be1 ieves that the shale sequences have acted as lubricating zones that decrease the frictional resistance of faulting. The Kanayut Conglomerate on the other hand is a fairly competent rock unit and has been folded into antic1 ines and synclines of various sizes. Locally, the folds are overturned, and in the Atigun River valle , spectacular overturned folds about one thousand meters (3,000 feetf in amplitude are present. The Lisburne Group 1imestones are general 1y competent rocks that are a1 so folded into 1arge-sca1 e structures. The 1imes tones do exhibit extensive deformation where stresses on the rocks cause them to react plastically. Locally, rocks of the Lisburne Group have been tightly folded and large north-vergent folds are present. Subsequent thrust- faulting along the axial trace of one such overturned fold, in Atigun Canyon, has thrust older rocks of the Mississippian Lisburne Group over rocks of the Si ksi kpuk Formation of Permian age. Porter (1965) believes that the Hunt Fork Shale may represent the base of a zone of, de'col lement involving the late Paleozoic section of north-central Alaska. The predominence of east-west stri king structures in the Philip Smith Mountains quadrangle indicates that the major tectonic pressures were directed in a north-south direction. The presence of north vergent structures throughout the region may indicate that most of the tectonic stresses were released to the north (Porter, 1965).

Geochemistry Geochemical reconnaissance in the Phil ip Smith Mountains quadrangle during the current study consisted of the colletion of 85 rock and stream sediment samples (see Tables 41 and 42, Appendix A) by M. I. R. L. personnel and coll ection of 109 stream sediment samples by U.S. Geological Survey personnel as art of an AMRAP study of the quadrangle (see Table 43, Appendix A!. Fifty-five percent of the samples collected by M. I. R. L. personnel contain weakly anomalous, anomalous, and strongly anomalous concentrations of at least 1 element and 70% of the stream sediment samples collected by the U.S. Geological Survey contain weakly anomalous, anomalous and strongly anomalous concentrations of at least one element. The geochemical analyses conducted by the U.S. Geological Survey Laboratory on their samples and the analyses conducted by the U,S. Bureau of Mines Laboratory in 1976 and 1977 on the samples collected by M. I.R.L. were found to be incompatable with each other, in that the detection levels for the various elements differ, in some cases, by orders of magnitude. Therefore, each set of data was treated as a seperate sample set for the statistical analysis. Threshold values (see Tables 44, 45, 46, 47, and 48, Appendix A) for the various elements in each data set were derived from a statistical manipulation of the raw geochemical data and the calculation of concentrations of the elements at the arithmetic mean plus; 1.645 x standard deviation, 2.00 x standard deviation, and 2.33 x standard deviation for the 90%, 95% and 98% confidence levels respectively. Where the analytical variability is zero or near zero, the threshold values for the confidence levels are the detection level or nearly the same value. Due to the incompatability of the sample analyses and detection level variability, many samples that would normally be considered weakly anomalous, anomal ous or strongly anomalous in one data set, are not weakly anomalous, anomalous or strongly anomalous in the other data sets. The incompatabil i ty problem has resulted f n an uncertainty as to what elemental concentrations are truely anomalous. The northern foothills of the Brooks Range are underlain by marine and non-marine clastic sedimentary rocks of various compositions. The rocks contain abundant organic material and re1 atively high background radioactivity measurements were detected with a hand-he1 d scintil lometer. No significant uranium concentrations were found during this study, however the rocks of the northern foothills be1 t may have -- some potential for uranium accumulations. Locally, stream sediment samples collected by the U.S. Geological Survey, along the north-flank of the Brooks Range contain greater than 2,000 ppm manganese. The manganese anomalies may represent the presence of thin-bedded ,- manganese or manganese nodules in the pebble shale member of the Kongakut Formation. Detterman et a1 (1975) have reported manganese concentrations as high as 5% and minor lead and copper values in rocks of the pebble shale member of the Kongakut Formation. In the Atigun Canyon area, rocks of the Shublik Formation contain strongly anomalous concentrations of barium, phosphorous and strontium. Barium concentrations as high as 3% and strontium concentrations 1,000 ppm are probably related to barite and minor celestite in these rocks. Phosphorous concentrations as high as 21 were a1 so detected. Rocks of the Si ksi kpuk Formation are predominantly black shale and carbonaceous chert that contain barite and pyrite concentrations 1oca11y. Samples of pyritic shale and mudstone from the Si ksikpuk unit contain strongly anomalous concentrations in as many as 23 elements including; silver, arsenic, gold, bismuth, cadmium, cobalt, molybdenum, nickel, lead, vanadium, tin, tungsten and zinc. No obviously significant metal 1ic and non-metal1 ic mineral ization is known in rocks of the Si ksi kpuk Formation. However, the high background of metal values, and the presence of bedded barite in rocks of the Siksikpuk Formation in the Atigun Canyon area, strongly suggest a high probably for the occurrence of significant base metal and barite deposits in these rocks and equivalent formations in northern Alaska. Rocks of the Li s burne Group contain sporadic anomalous concentrations of barium and magnesium. The barium is associated with barite and the magnesium is thought to result from dolomitic phases in the 1imestone. No anomalous metal values were detected in rocks of the Lisburne Group during this study. Stream sediment samples from streams draining rocks of the Kanayut Conglomerate contain anomalous and strongly anomalous concentrations of manganese, nickel, chrome, phosphorous, 1ead, bismuth, and iron. The bedrock source of the anomalous elemental concentrations is not known.

Mining Activity and Economic Geology Remoteness and the lack of adequate infrastructure in the past have limited the amount of mineral exploration in the Philip Smith Mountains quadrangle. The only known mineral claims in the quadrangle are located near the head of the Wind River, where massive sulfide float samples were found. The U. S. Geological Survey also reports the presence of mineralized quartz veins in the area between the Middle Fork of the Chandalar River and the Wind River. The vein and stockwork deposits contain chalcopyrite, galena and sphal eri te (Grybeck, 1977). Stream sediment samples collected by the U. S, Geological Survey during their AMRAP program in the Wind River area contain anomalous concentrations of lead, zinc, copper, barium and vanadium. The bedrock in the area has been mapped (Brosge et al, 1977) as part of the Hunt Fork Shale unit, of mid and upper Devonian age. Some exposures of Skajit Limestone are also known in the area. Rocks mapped as Hunt Fork Shale in the Pipeline Corridor are mainly shaly siltstones that are phyllitic locally. These rocks contain numerous anastomozi ng quartz veins and Chapman (1964) has reported the presence of pyrite and marcasite crystals and minor galena in some of these quartz veins. No sulfide minerals were seen in Hunt Fork Shale in the Pipe1 ine Corridor, however, stream sediment samples collected by the U. S. Geological Survey, and by M. I.R.L. personnel during this study, contain anomalous concentrations of zinc, copper, vanadium, barium, lead and silver. The massive sulfide occurrences in the Wind River area, coupled with the anomalous stream sediment geochemistry in areas where the bedrock is known to be Hunt Fork Shale indicate that the Hunt Fork Shale may contain stratabound or stratiform massive sulfide deposits of copper, lead, zinc, vanadium and barium affinities, and may also have some potential for vein type mineral deposits . Rocks of the Kanayut Conglomerate reflect a' change in depositional environment from the open-marine deposition of the Hunt Fork Shale to an environment of deposition characteristic of near shore and deltaic conditions. Most of the Kanayut Conglomerate is considered non-marine and the source of the sediments that constitute the bu1 k of the unit were derived from a northerly source area. The sediments were introduced into a locally reducing environment in which pyrite and possibly other sulfide minerals were accumulating. Locally, the Kanayut Conglomerate does contain disseminated pyrite and galena and near the top. of the unit, black pyritic shales constitute the dominate rock type. Therefore, there may be some potential for black shale hosted base-metal sulfide accumulations in the upper part of the Kanayut Conglomerate. To the east in the Romanzof Mountains, the Kanayut Conglomerate may have some uranium potential. The core of the Romanzof Mountains is dominated by a Pre- cambrian(?) and lower Pa7eozoic sequence of shales, limestones and conglomerates that are intruded by Devonian(?) granitic intrusives (Sable, 1965). The granites are stanni ferous granites and contain a higher than background content of uranium and thorium (Donald Grybeck, U. S. Geological Survey, Personal Comunication, 1977), and could be a good source for uranium accumulations in the younger sedimentary rocks. The Kanayut Conglomerate near Atigun Pass, in the Pipe1 ine Corridor is very we1 1 indurated. The si1iceous cement- ation of the conglomerate has resulted in a tight rock .with low porosity and permeability. No anomalous uranium concentrations were found in these rocks and the potential for finding sedimentary uranium accumulations in the Kanayut Conglomerate near the Pipeline Corridor seems low. Unlike the rocks of the Kanayut Conglomerate, rocks of the overlying Kayak Shale are dominantly marine shales and limestones that were deposited in a marine stable-shelf environment. Both the shales and carbonaceous limestones of the Kayak unit contain disseminated pyrite, indicating that a reducing, sul f ide-producing environment was present 1ocal ly. Stream sediment samples collected by the U. S. Geological Survey in areas where the dominant rock unit is Kayak Shale, contain anomalous concentrations of copper, lead, zinc, barium and silver. One stream sediment sample from a stream in the Atigun ~a'lley,draining rocks of the Kayak Shale contains at least 500 ppm lead and another sample contained 110 ppm zinc. The potential for finding bedded 1ead-zinc deposits of stratabound or stratiform lead and zinc affinities seems high for the rocks of the Kayak Shale unit. Near the top of the Kayak Shale, the unit contains a large proportion of anastomozing quartz veins. Porter (1965) reported the presence of quartz veins, near Anaktuvak Pass, that contain chalcopyrite, borni te, azurite and malachite. The probability of finding other such mineralized veins near the top of the Kayak Shale unit seems high. Rocks of the Lisburne Group, although composed largely of bioclastic limestone, have good potential for base-metal sulfide and barite deposits. The Lisburne Group rocks in the eastern Brooks Range were deposited in part in a sabkha-type environment (Arm- strong, 1975). The accumulation of fine-grained sediments and 1irnestone in a restricted, stable-shelf, marine environment that impinges on some sort of deltaic complex in a semi-arid climate, where a high rate of evaporation is present, often results in the deposition of sabkha-1 i ke sequences of sediments. The movement of ground waters and ocean waters containing compl exed metal ions, through the sabkha interface, which usually contains a large amount of decaying organic material that produces a reducing environment, may result in the precipitation of sulfides in the sabkha. If the interpretation of sabkha-type environment of deposition for some of the rocks in the Lisburne Group is correct, the potential for finding base-metal sulfide deposits of the sabkha-type in the Lisburne Group is high. At Drenchwater Creek, in the Howard Pass quadrangle, west of the Pipeline Corridor (TlOS, R1E Kateel River Meridian) the U. S. Geological Survey has recognized volcanic rocks that are believed to be part of the Lisburne Group. The volcanics are mainly tuffs that may . be genetically associated with black shales and chert that are the host . of "significant" base-metal sulfide mineral ization. The U. S. Geo- 1ogical Survey be1 ieves that the base-metal sulfide mineral ization may be syngenetic and stratiform. Further work is needed to understand fully the genetic relationship between the volcanic rocks and the fine- grained sediments in the region. The massive sulfide occurrence at Drenchwater Creek indicates that the Li sburne Group contains volcanogenic massive sulfide deposits of stratiform or stratabound lead, zinc and barite affinities. West of Shainin Lake, the Lisburne Group contains a marked increase in the amount of black shale and chert. A thin, generally continuous zone of black chert and paper shale near the top of the Alapah Limestone contains phosphate concentrations as high as 35.8% P205 (Patton and Matzko, 1959). The phosphate-bearing horizon in the Alapah Limestone has been traced from the Kiruktagiak River, approximately 64 kilometers (40 mi 1es) northeast of Anaktuvak Pass, to' Shainin Lake, about 32 kilometers (20 miles) northeast of Anaktuvak Pass, a distance of about 80 kilometers (50 miles). The black chert and shale member is not recognized east of Shainin Lake, and no phosphate accumulations of significance have been found east of the Shainin Lake locality. At the Skimo Creek locality, about 24 kilometers (15 miles) northwest of Anaktuvak Pass, the entire black chert and shale horizon of the Alapah Limestone is exposed (Patton and Matzko, 1959). The phosphate-bearing zone is 11 meters (36 feet) thick and one zone 1 meter (40 inches) thick contains an average of 21% P 05. The phosphatic beds vary in thickness from 5 to 23 centimeters $2 to 9 inches) and contain up to 35.8% P205.. Trace amounts of vanadium, copper, barium, lead, manganese and uranium have been detected in samples from the black chert and shale members. Ifan eastern extension of the black chert and shale member can be found east of Shainin Lake, the potential for finding phosphate deposits near the Pipe1 ine Corridor seems high.. ~oweier,the Alapah Limestone in the Pipeline Corridor apparently contains only minor shale and chert and is composed predominantly of massive bioclastic 1 imestone. Rocks of the Si ksi kpuk Formation of Permian age a'nd rocks of the Echooka Formation of mid Permian and lower Triassic age have moderate to high potential for barite and base metal sulfide deposits of stratiform or stratabound lead, zinc and barite affinities. Detterman (1976) has for the first time recognized volcaniclastics in the Permian Echooka Formation of the northeastern Brooks Range. The presence of volcanic rocks indicates that there may be a high probability of finding volcanogenic base-metal sulfide deposits associated with the flows, breccias and tuffs. Stream sediment samples, highly anomalous in base metals and barium, collected by the U. S. Geological Survey along the north-flank of the Brooks Range indicate that the region contains a high background of metal concentrations and may contain base-metal and barite deposits of unknown size and distribution. Barium concentrations as high as 7,000 ppm; zinc concentrations as high as 300 ppm; lead concentrations as high as 70 ppm and vanadium concentrations as high as 200 ppm are not uncommon for stream sediment samples. Rocks of the Si ksi k- puk Formation in the Pipe1 ine Corridor contain thin to moderately- thick, discontinuous zones of barite and disseminated as well as con- cretionary forms of pyrite. The rocks are dominantly shale, siltstone and thin-bedded carbonaceous chert. The barite occurs in concordant layers that pinch and swell along strike. Layers as much as 0.3 meters (1 foot) thick are present in the Siksikpuk section in Atigun Canyon. No lead or zinc mineralization has been found in the area, however, stream sediment samples from the area contain anomalous concentrations of lead and zinc. The Atigun Canyon occurrence may or may not be of economic significance, however, the occurrence of bedded barite reinforces the probabil ity of finding stratiform and stratabound base metal and barite deposits in the Permo-Triassic of northern Alaska. The Shublik Formation contains phosphate concentrations west of the Pipeline Corridor, near Chandler Lake. Minor occurrences of phosphate are known in the Pipeline Corridor, and samples of shale col ? ected in Atigun Canyon contain phosphorous concentrations as high as 2%. The occurrence of phosphate-bearing siltstone and shale to the west indicates that the unit may contain phosphate deposits of unknown size and distribution. Pyrite is commonly found in rocks of the Shublik Formation and occurs as concretions and as rhombs and irregular masses of sol id pyrite. The overall mineral potential of these rocks seems high, and further work on the Shublik Formation is clearly needed. Rocks of the Shublik Formation in the Atigun Canyon contain higher than background radioactivity when tested with a hand-held scintil lometer. Readings on the order of 200 to 300 counts per second were detected. No deposits . of uranium are known in rocks of the Shubl i k Formation, however the unit may have some uranium potential. REFERENCES CITED

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Smith. North, and Berg. Richard, 1973, Encountering marsive ground ice duriq rood comtrvction in central Alosko, in Permohost;.North Punericon Contribution, kcond Inletnot. Coni.; PtincipK of construction in permafrost regions, p. 730-736: Notl. Acad. Sci., Woshington. D.C.

Stereos, A. E., and Milne. W. G.. 1974, A study of lairmic risk near pipeline carridors in northwestern Conado ond eortcrn AiosLo: Conadion kvr. Eorth Sci., r. II, n. I, p. 143-164.

Toilleur, I. L., ond %osge, W. P., 1970, Tectonic history of northern Alorko (with discussion), in Proceeding, of the gcologicol seminar on the thth Slope of AIosko: A~TAssoc. Petroleum Geologists Pacific Sec., Lor Angeier, p. EI-E20.

Taillcw, lrvin L., end &osge, Willim P., 1971. B

Wotcr Rerouccs Division, Alosko District, 1969, Hydrological obrerwtionr, Foirbonks to ?rudho+ byand other Arctic Slop. orcos, Moy 1969: U.S. Geol. Swwy open-file rep!.. 12 p.

Woto Resources Division, AIOILO District, 1969, Woter rerourccr of the Arctic Slop region, Alarko: U.S. Geol. Survey open-file rept., 31 p.

Wollson, J. R., ond others. 1962, Seismic 04gravity swveys of Novol Petrolem Rcrerre No. 4 ond adjoining oreos, Alasko: U.S. Geol. Survey Prof. Popr 3WA, p. 1-25.

Yochelson, E. L.. ond Dutro, J. 1.. Jr., 1960, Lote Paleozoic gast&opodr han mrthern Alosko: U.S. Gcol. Suvey Prof. Paper 334-D, p. 111-147. Sagavani rktok Quadrangle

Previous Investigations Geologic investigations in the region near the Sagavanirktok quadrangle began as early as 1901 when F. C. Schrader of the U. S. Geological Survey traversed the area between Bettles and Barrow. A1 though Schrader may not have actually been in the Sagavanirktok quadrangle, his observations of the various rock units west of the quadrangle served as a base for future explorationists. Work by Ernest De K. Leffingwell (7919) has proven to be one of the classic studies of geology in the northeastern Brooks Range. Leffingwell 's work centered in the area east of the Sagavanirktok quadrangle, near the Canning River. In 1940, the U. S. Geological Survey initiated a program to evaluate the oil and gas potent.ia1 in the Naval Petroleum Reserve f4. Several publications have been produced as a result of this work. Keller et a1 (1961) investigated the geology between the Sagavanirktok River and the Shaviovik River region. Keller out1 ined the regional geology and structure of the rocks in the area and also commented on the petroleum potential of the region. Recent work by Wood and Armstrong (1975) on the diagenesis and stratigraphy of the Lisburne Group has resulted in a better understanding of the depositional history and diagenesis of rocks in the Lisburne Group in the northeastern Brooks Range. Work by Detter- man (1976) in the Ivashak River area has resulted in the recognition of volcanic flows, tuffs and breccias in Permian rocks, probably be1 onging to the Ivashak Formation of the Sad1 erochi t Group. Work by the U. S. Geological Survey, as part of their Alaska Mineral Resource Assessment Program (AMRAP), has shown that the rocks in the northern foothills belt of the Brooks Range contain a high background of metal concentrations. Other work by the U. S. Geological Survey to the west has shown that the rocks of the Lisburne Group contain stratiform and stratabound mineral occurrences of lead, zinc and barite affinities. Work by the U. S. Bureau of Mines in the Porcupine Lake area to the southeast has shown that similar mineral ization may occur in other parts of the northeastern Brooks Range. In addition to the lead, zinc and barite mineralization, some fluorite concentrations are known. Detailed work by Reed (1968) in the Peter's Lake area has resulted in a good treatment of the bedrock geology of the area. Detailed geologic and geochemical investigations by Tourtelot and Tai 1leur (1971) have resulted in a better understanding of the nature, deposition history and diagenesis of rocks in the Shubl i k Formation. Armstrong and Mamet (1975) have studied in detail, eight carboniferous stratigraphic sections in northeastern A1 aska, and have described the biostrati- ,graphy of these rocks. Regional Geology and Petrology Rocks in the Sagavanirktok quadrangle are part of a thick sequence of marine and nonmarine cl astic sedimentary, submarine volcanic and marine carbonate rocks of Mississippian through Tertiary age. Basic to jntermediate volcanic flows, tuffs and breccias have been recognized (Detterman, 1976) in the Ivashak River area. The 01 dest rocks to crop out in the Sagavanirktok quadrangle consist of 1ight-to dark-gray 1imestone, dolomitic 1imestone, siliceous 1imestone, argill aceous 1imestone, chert, shale, shaly 1 imestone, and dolomite of the Lisburne Group of lower and upper Mis- sippian age. The Lisburne Group has been subdivided into three formations, the klachsmuth Limestone of. early Mississippian age, the Alapah Limestone of mid-to late Mississippian age, and the Wahoo Limes tone of Pennsylvanian age. The Wachsmuth Limestone has been subdivided into four members. The lowest member is composed of i nterbedded, dark-gray to 01 ive-gray, f ine-grained, shaly, argillaceous, nodular limestone and shale. The shaly limestone member is about 5 meters (18 feet) thick at the type locality, and probably represents sedimentation in a quiet water, open-marine environment during the early Mississippian. Conformably overlying the shaly limestone member of the Wachsmuth Limestone is a richly fossili- f erous sequence of medi urn-to dark-gray , medi um-to coarse-grai ned crinoidal limestone. The crinoidal limestone member is about 55 meters (180 feet) thick at the type locality near Shainin Lake and thins to the northeast. Conformably overlying the crinoidal limestone member is a thick sequence of light-gray to white, medium-to coarse-grained, sl ightly argi 1laceous, bioclastic, dolomi tic limestone. Theedolomitic section of the Wachsmuth Limestone is about 170 meters (564 feet) thick. at Shainin Lake. The dolomitic 1 imestone is locally interbedded with chert and mir~orshale. The chert is present throughout the section and appears to increase in abundance toward the top of the section. Chert constitutes as much as 40 to 50% of the section local 1y. The upper member of the Wachsmuth Limestone is composed of about 130 meters (429 feet) of thin- banded 1irnestone and chert. Minor dolomi tic 7 imestone inter- 1aminations occur throughout the section and some interbedded bioclastic limestone is also present. The total thickness of the Wachsmuth Limestone at the type locality is about 375 meters (1,230 feet). The unit appears to thicken to the west, near Anaktuvak Pass, where 410 meters (1,350 feet) of section is present (Porter, 1965). To the east near Peters Lake the entire Wachsmuth unit is not recognized (Reed, 1968). Conformably overlying the Wachsmuth Limestone is the A1 apah Limestone of mid and late Mississippian age. The Alapah Limestone has been subdivided into nine members and is represented by about 295 meters (970 feet) of section at its type locality near Shainin Lake. The Alapah unit thickens to the east and west and thins to the north along the north front of the Brooks Range. About 710 meters (2,325 feet) of Alapah Limestone is present near Anaktuvak Pass and about 595 meters (1,947 feet) of section, recognized as Alapah Limestone is present near Wahoo Lake. For ease in mapping, the nine members of the Alapah have been lumped into three units. The lowest four members of the Alapah'have been lumped by Porter (1965) into a unit consisting of a basal sequence of dark-gray, fine-grained, shaly 1imestone and minor black chert. The basal sequence is inturn over1 ain by a thick sequence of dark-gray, f i ne-grained, argi 11aceous, thin-bedded to massive, cherty, bioclastic 1imestone. Next, a sequence of 1ight-brown to gray, fine-to medium-grained, fossil i- ferous limestone is present. This sequence is overlain by a member composed of brownish-gray, fine-to medium-grained, bioclastic limestone. The middle lumped unit of the Alapah limestone is . composed of about 75 meters (250 feet) of non-resistant, dark-gray, calcareous shale and grayish-black chert. Minor interbeds of platy 1 imestone and phosphorite are also present. The upper lumped sequence of Alapah Limestone consists of interbedded 1jght-gray 1imestone and dark-gray , thin-bedded chert. Minor interbeds of thick- bedded, light-gray limestone are also present. The thick-bedded 1ayers contain a rich fossil assemblage including l ithostrotionella coral s and Gigantoproductus brachi pods Recent work by Amstrong (1975) has shown evidence of a great variety of environments of deposition during the time of Lisburne Group sedimentation. The environments of deposition represented by the Lisburne Group rocks incl ude open marine sedimentation, stabl e- shelf sedimentation, open-platform sedimentation, restricted platform sedimentation and intertidal and supratidal sedimentary environments. The intertidal and suptratidal environments of deposition are characterized by the deposition of irregularly laminated dolomite and dolomitic 1imy mudstone, anhydrite and pseudomorphs of calcite after anhydrite; Algal mats are common in the sediments of this zone. Armstrong (1975) feels that the intertidal and supratidal environments of deposition may represent deposition in a. sabkha-like environment. In northeastern Alaska, the Wahoo Limestone, of Pennsylvanian and 1owest Permian age conformably over1 i es the A1 apah Limestone, and has been recognized as the upper unit of the Lisburne Group. The Wahoo Limestone marks a regional transgression from stabl e-platform sedimentation, represented by the upper Alapah Limestone, to an open . platform-shoal environment of deposition. The Wahoo Limestone has been divided into two informal members. The lower member is characterized by the lack of dark-gray limestone and by the presence of medium-and 1ight-gray, coarse-grained, 1imestone and 1i thographic 1imestone (Reed, 1968). The upper member consists of coarse-grained, crinoidal limestone interbedded with shale and shaly limestone. Disconformably overlying the rocks of the Lisburne Group in northeastern Alaska are rocks of the Sadlerochit Group of Permian and early Triassic age. The Sadlerochit Group is composed of a variety of rock types including orthoquartzi te, chert, 1imestone, sandstone, siltstone and shale. Detterman (1976) has for the first time recognized volcanic rocks in Permian strata near the Ivashak River and to the south near Porcupine Lake. The Sadlerochit Group has been subdivided into two formations, the Echooka Formation of early and late Permian age and the Ivashak Formation of early Triassic age. The Echooka Formation has been further subdivided into two members; the Joe Creek Member and the Ikiakpaurak Member. The Joe Creek Member is composed of thin-bedded, calcareous si1 tstone and calcareous mudstone near its base. The siltstone and calcareous mudstone are poorly indurated and weather to a dusky yellow and yellow-brown color. Near the middle'of the Joe Creek Member, medium- to massive-bedded chert is the dominant rock type. The chert zone is in turn overlain by a sequence of irregularly-bedded clastic 1imestone. The Joe Creek Member contains an abundant fossil assemblage including brachiopods, bryozoans, corals, and less commonly trilobites and pelecypods. The trace fossil zoophycos is diagnostic of rocks in the Echooka Formation. Overlying the early Permian Joe Creek Member is the Ikiakpaurak Member of late Permian age. The contact between the Joe Creek Member and the Ikiakpaurak Member is conformable and . local ly gradational. The Ikiakpaurak Member consists mainly of dark, highly quartzose, sandstone and si1 tstone with interbeds of si1ty shale. The sandstones are mainly fine-to very-f ine grained quartz arenites. The quartz grains that make up the arenites are generally subrounded to subangular and are commonly cemented by silica although calcite cement is known. Glauconite is a common constituent of the quartz arenite and constitutes as much as 10% of the rock locally. Nhere the glauconite is a dominant constituent of the sandstone, the rock should be called a glauconitic quartz wacke (Detterman et al, 1975). The Echooka Formation is recognized as the lower formation of the Sadlerochit Group in the northeastern Brooks Range. However, the Echooka Formation-is not recognized west of the Sagavanirktok River and the Siksikpuk Formation of early Permian age is considered the lower formation of the Sadlerochi t Group. The Si ksi kpuk Formation consists of about 110 meters (354 feet) of variegated red and green, cherty, shale and siltstone, at the type locality on Skimo Creek, west of Chandler Lake. The Siksikpuk rocks weather to a characteristic red-yellow color and are often easily recognizable. Rocks of the Siksi kpuk Formation have been recognized along the north-flank of the Brooks Ra'nge from the Sagavanirktok River, on the east, to the Lisburne Peninsula, in northwest Alaska, a distance of over 640 kilometers (400 miles). The Si ksi kpuk Formation contains an abundant fossil assemblage including brachiopods, corals and some gastropods. Detterman (1976) has recognized volcanic rocks in the Permian rocks of northeastern Alaska. The volcanic rocks occur as flows, tuffs and tuff breccia near the Ivashak River and also near Porcupine Lake in the Arctic quadrangle. The volcanic rocks occur in a sequence of rusty-weathering si 1ty 1imestone and tuff that conformably over1 ie rocks of the Lisburne Group (~etterman,1976). The 1imestone contains brachiopods and corals that yield a Permian age. 181 Unconformably overlying the Echooka Formation is the Ivashak Formation of early Triassic age. The Ivashak Formation has been subdivided into three members and is considered the upper formation of the Sadlerochi t Group. The lowest member of the Ivashak Formation is the Kavik Member that consists of thin-bedded, silty shale and sil tstone, interlaminated with very-fine grained argillaceous sandstone. Rocks of the Kavi k Member contain Ophiceras commune Spath and Claraia stachei Bittner; two diagnostic cephalopods that mark ,. the base of the lower Triassic in northeastern Alaska. Conformably overlying rocks of the Kavi k Member are rocks of the Ledge Sandstone Member also of lower Triassic age. The Ledge Sandstone Member consists primarily of massively-bedded, quartz arenite. The quartz I - I arenite is generally a light-gray to dark red-brown, well bedded, I quartz arenite in beds ranging from 0.6 to 3 meters (2 to 10 feet) I I thick. Petrographically, the sandstone is composed of subrounded to well rounded grains of quartz that constitute as much as 60% of I - the rock. Chert is a dominant constituent and constitutes up to 40% 1 .I of the rock, while plagioclase feldspar, zircon, tourmal ine and pyrite are present as accessory minerals. Conformably overlying rocks of the Ledge Sandstone Member are rocks of the Fire Creek Siltstone Member.

-A The Fire Creek Siltstone Member, as its name imp1 ies is composed of thin bedded to massive, dark-gray to black, si1iceous siltstone.

I I Petrographically, the siltstone is composed of 40 to 80% well- rounded, quartz and chert grains set in a matrix of siliceous, sericitic clay. Secondary calcite constitutes as much as 15% of the rock locally. Pyrite is the most common accessory mineral, but usually does not exceed more than a few percent of the rock. Unconformably and locally conformably overlying the Sadlerochit Group in northern Alaska are rocks of the Shublik Formation of mid Triassic age. The Shubl ik Formation consists of a sequence of sil tstone, phosphatic sil tstone, and shale and has been subdivided into three members. The basal siltstone member is composed of about 20 meters (70 feet) of thin-bedded, phosphatic siltstone that contains l imestone concretions 1ocal ly. Petrographical ly, the si1 tstone is composed primari 1y of angular to subangul ar quartz grains 0.02 to 0.05 mil 1imeters (0.001 to 0.002 inches) in diameter. Secondary calcite is a common constituent in the rocks and is often the primary cementing agent and may be as much as 40% of the rock. Phosphate grains with quartz nuclei are common and minor plagioclase and sericite are also present. Conformably overlying the basal siltstone member is a sequence of rock composed of limestone and phosphatized coquinite layers. Detridal quartz is present in subrounded grains and locally constitute as much as 20% of the rock. The clay shale member at the top of the Shublik Formation is very soft and incompetent. A few silty, very fine-grained calcareous sandstone beds are also present. Conformably overlying the Shubl ik Formation in northeastern Alaska is a thin unit composed of very-fine grained, massively bedded, dark, sil iceous, quartz arenite known as the Karen Creek Sandstone. The Karen Creek Sandstone is of late Triassic age and 1ies between the Shubl i k Formation and the overlying Kingak Shale. The Karen Creek Sandstone has a restricted distribution and is exposed best between the Kavik and Aichili k Rivers, where it forms distinctive hogback ridges. The unit thins rapidly to the west and is not readily recognized west of the Kavik River. The Karen Creek Sandstone also thins to the north and changes character away from the north front of the Brooks Range. The rocks of the northern belt are generally more carbonate-rich and apparently ref1 ect a change in depositional environment to the north in the late Triassic (Detterman et al, 1975). Unconformably overlying rocks of the Shubli k Formation in north central Alaska and rocks of the Karen Creek Sandstone in northeastern Alaska is a thick sequence of sil tstone, shale, claystone and clay-ironstone known as the Kingak Shale Formation. The lowest part of the Kingak Shale unit is composed of about 181 meters (600 feet) of black, fissi le, paper shale. Large cannonball concretions are present near the center of the paper shale section. Overlying the paper shale section is a sequence between 91 to 300 meters (300 to 1,000 feet) of soft, dark-gray, clayshale and minor claystone. The upper part of the claystone sequence contains nodules of clay- ironstone and weathers to a characteristic brick-red color. Overlying the clay-shale section is a sequence of thin-bedded siltstone and silty shale. The siltstone is composed of 75 to 80% rounded quartz grains and up to 10% siderite. Accessory plagiocl ase, zircon and minor phosphate and glauconi te are a1 so present. The siltstone and silty shale sequence contains an abundant ammoni te and pelecypod assemblage that yield an early Jurassic age. Unconformably overlying rocks of Shubi i k Formation, Kingak Shale and 1vasha.k Member of the Sadlerochit Group in northern Alaska is a lower Cretaceous sequence of quartz arenite, clay shale and graywacke sandstone,--known as the 'Kongakut Formation. The contact between the Kongakut Formation and the underlying strata marks a najor early Cretaceous unconformity in northern Alaska (Detterman, 1975). The Kongakut Formation has been subdivided into one formal and three informal members. The lowest member of the Kongakut Formation is composed of 106 meters (350 feet) of clay shale. Conformably overlying the clay shale member is the Kemi k Sandstone Member, a sequence of very fine-grained, quartz arenite with minor amounts of g1auconi te, phosphate, serici te, and zircon. Overlying the Kemi k Sandstone Member is a pebble shale member that is 158 meters (520 feet) thick. The pebble shale member contains a section of about 53 meters (175 feet) of highly manganiferous beds of silty shale. The manganese beds are uniformly black with small pellets and thin beds of manganese carbonates (Detterman et al, 1975) .' Conformably overlying the pebble shale member is a thick sequence, 291 meters (960 feet) of section, composed of thin-bedded siltstone with minor interbeds of sandstone. The Okpikruak Formation, named by Gryc et a1 (1951, p. 159) is exposed along the Okpikruak River in the Chandler River area west of Anaktuvak Pass. The formation was extended to the eastern Brooks Range by Detterman (1961, p. 1951, who defined the base of the Okpi kruak Formation as the base of the fc.emik Sandstone Fienber of the Kongakuk Formation, therefore the two formations are at least in part equival ent correlatabl e units. Unconformably overlying rocks of the 0 kpi kruak Formtion and rocks of the Kongakut Formation is a fairly thick sequence of marine sandstone, siltstone, shaly limestone, clay shale and conglomerate of the Fortress Mountain Formation of lower Cretaceous age. The conglomerate and sandstones are typically graywacke-type sedimentary rocks that contain abundant clasts and fragments of black and green chert, feldspar and angular mafic igneous rock fragments, all set in a green mudstone matrix (Keller et al, 1961). At the type section, the Fortress Mountain Formation is about 3,000 meters (10,000 feet) thick, however, the type locality is probably the thickest section of Fortress Mountain Formation exposed on the north-f l an k of the Brooks Range, and exposures of 1,500 meters (5,000 feet) of section are common. The Torok Formation of lower Cretaceous age is be1 ieved to be the 1ateral equivalent of the Fortress Mountain Formation (Kell er et a1 , 1961 ). The Torok Formation is predominantly dark-gray and dark bluish-gray, fissile to platy, soft, silty shale and clay shale. Locally, lenticular bodies of sandstone, as much as 242 meters (800 feet) thick, occur in the shale sequence. The base of the Torok Formation is not exposed, however, 1,818 meters (6,000 feet) of section is present at the type locality. Keller et a? (1961) be1 ieve that a lateral facies change and major interf ingering between the two formations accounts for the lithologic differences between the Torok Formation and Fortress Mountain Formation. Unconforrzably overlying rocks of the Kongakut Formation, Torok Formation and Fortress Mountain Formations in the northern foothills . be1 t of the Brooks Range are rocks of the Nanushuk Group of early Cretaceous Age. The Nanushuk Group contains both marine and non- marine rocks and has been subdivided into two formations. The Tuktu Formati on is a marine sequence of interbedded, thin-bedded, fine- grained, greenis h-ye1 l ow, calcareous sandstone, dark si 1tstone and shale. The sandstone contains abundant sole markings, ~ainlyflute casts, skip and drag marks, and flame structures, a11 of which are suggestive of deep water turbidite deposition. The Tuktu Formation may be as thick as 515 meters (1,700 feet), but exposures of about 212 meters (700 feet) thick are common. Conformably overlying the Tu ktu Formation are rocks of the non-mari ne Chandler Fornation. The Chandler Formation is composed of 1,447 meters (4,775 feet) of cycl ica7 ly deposited polymictic conglomerate, sa1t and pepper sandstone, si listone and shal e. The sequence is entirely non-marine and contains abundant features of fluvial deposition including: cut and fi11 structures; crossbedding; channel deposits; and fine- grained, shaly siltstones containing abundant plant fragments. The shaly siltstones are interpreted as being overbank fluvial deposits and coal is a fairly common feature. The polymictic conglomerate consists mainly of clasts of black and gray chert and limestone. The clast are well rounded and average between 1 and 5 centimeters (0.5 and 2 inches) in diameter. The conglomerate beds tend to be lenticular and cut and fill structures are common. The sandstone

I i.. beds associated with the conglomerate are generally medium-to I -. I .:' coarse-grained, massively bedded, 1ithic sandstone. Petrographically, 12 the sandstone is composed of 40 to 70% lithic fragments, 10 to 15%quartz, 5 to 10% feldspar and minor accessory- minerals. Unconformably overlying the Kingak Shale and rocks of the Nanushuk Group in northern Alaska are rocks of the Colville Group of upper Cretaceous age. - The contact between the Colvil le Group and the underlying strata marks another major Cretaceous unconformity across northern Alaska. The Colville Group has been subdivided into two formations: the Seabee Formation and the Prince Creek Formation. The Seabee Formation has been further subdivided into the Shale Wall Member and the Ayiyak Member. The Shale Wall Member consists of dark, poorly consol idated, thin bedded, bentoni tic clay shale. The bentonite occurs primarily in beds 1.3 to 5 centimeters (0.5 to 2 inches) thick throughout the Shale Wall Member. Near the top of the Shale Wall Member, the rocks are dominantly fissile, paper shale i nterbedded with bentonite 1ayers genera1 ly 1ess then 1 centimeter (0.5 inches) thick. The upper part of the Shale Wall Member consists mainly of bedded, devitrified, welded tuff composed of about 90% glass. -The Ayiyak Member of the Seabee Formation is composed of a sequence of interbedded sandstone, shal e, and sil tstone. Minor interbeds of tuff are present near the top of the sequence. The overlying Prince Creek Formation includes a11 of the late Cretaceous nonmarine rocks above the Seabee Formation. The Prince Creek Formation consists of interbedded sandstone, conglomerate, si 1tstone, s ha1 e, coal and carbonaceous shale. The sandstone is primarily a subfelds- pathic lithic arenite, composed of 30 to 60% chert, quartzite, shale and phyll i te cl asts, 30 to 40% quartz, up to 8% feldspar and generally less 5% matrix composed of sericitic clay. The siltstone and shale constitute a major part of the Prince Creek Formation, and are carbonaceous locally. The Prince Creek Formation has been subdivided into the stratigraphical 1y lower, Tuluvak Tongue and the upper Kogosukrok Tongue. The sandstones of the Tuluvak Tongue are usually clean and porous and occur in beds 3 to 15 meters (10 to 50 feet) thick. The sandstones of the Kogosukruk Tongue occur mainly in thin beds and are generally dirty sandston~scontaining pebbles between 0.5 and 5 centimeters (0.25 and 2 inches) in diameter. Ths sandstones of the Kogosukruk Tongue also contains coal beds ranging up to 1 .25 meters (4 feet) thick, no coal beds are known from rocks of the Tuluvak Tongue (Detterman et a1 , 1975). ' The Schrader B1 uff Formation occurs across the 1ow foothills of the Brooks Range from the type locality on the lower Anaktuvak River to the Canning River in the northeastern part of the Brooks Range. The stratigraphic relationship between the Schrader Bluff Formation and the Prince Creek Formation is uncertain. The Schrader Bluff Formation has been subdivided into three members. The lowest member, the Rogers Creek Member, is composed of rusty-weathering bentoni tic clay shale with .thin interbeds of very fine grained sandstone and siltstone. The siltstone is micaceous and tuffaceous (Detterman et al, 1975). Overlying the Rogers Creek Member is the Barrow Tail Member, that consists mainly of fine-to coarse grained, thin-to massively-bedded, feldspathic wacke that is tuffaceous locally. Tuff and bentonite are common in the Barrow Tail Member, and are generally interbedded with sandstone and siltstone. The overlying Sentinel Hill Member is composed of light-gray to tan, thin- bedded, tuffaceous si 1tstone and si1 ty s ha1 e. Conformably(?) overlying the Kogosukruk Tongue of the Prince Creek Formation are Tertiary nonmarine and marine sedimentary rocks of the Sagavanirktok Formation. The Sagavanirktok Formation has been subdivided into three members. The lowest member, the Sagwon Member, is the coal -bearing sequence of the Tertiary in northerg Alaska. The coal in the Sagwon Member is 1ignite coal with carbonaceous shale partings. The coal is i nterbedded with dark-gray to brown, fissile, clay shale and siltstone. Massive, 1ithic, arenitic sandstone and conglomerate form the upper part of the Sagwon Member near Sagwon. The 1ithic arenite and conglomerate is composed of 60 to 70% clasts of chert and quartzite. The remainder of the clasts are chief 1y quartz, feldspar and carbonaceous materi a1 . The Sagwon Member is about 142 meters (470 feet) thick at the type locality and contains coal beds as much as 6 meters (20 feet) thick. conformably(?) overlying the Sagwon Member is a sequence of cycl ically-bedded clay shale and sil tstone known as the Frankf in Bluffs Member, that were apparently deposited in a subaerial environment. Interbedded with the varve-1 i ke sequences of clay-shal e and si 1tstone are 1ayers of massively bedded, pink, tan, orange and ye1 low, unconsol idated sand and gravel. Large-scale cross bedding of probable eol in origin are common in the sand and gravel intervals. Beds of volcanic ash are also present. Conformably overlying the Frank1 in Bluffs Member is the Nuwok Member that apparently reflects a return to nearshore marine deposition. The Nuwok Member is composed of a sequence of cross-bedded sandstone and pebble conglomerate that is overlain by a sequence of pebbly mudstone and silty 1imestone, be1 ieved to have been deposited in a lagoonal environment. The sandstone and conglomerate sequence has been interpreted as being the result of deposition in a barrier beach environment.

Structural Geology The structural geology of the rocks in the Sagavanirktok quadrangle is dominated by east and west plunging, asymmetric folds, normal faulting, high-angle reverse faulting, and thrust faulting. The northern foothi 11 s province of the east-central Brooks Range consists of several distinct structural zones that are sub-parall el to the Brooks Range mountain front. The southern-most structural be1 t is generally restricted to rocks of the Mississippian Lisburne Group. The rocks in this zone appear as a regular southerly dipping sequence of marine carbonates and shales that may be as much as 3,000 meters (10,000 feet) thick, and occupies a belt 16 kilometers (10 miles) wide locally. However, upon close examination of the Mississippian sequence, it has been shown that the entire sequence is structurally thickened by isocl inal folding and imbricate thrust faulting and perhaps the true stratigraphic thickness of Lisburne Group rocks does not exceed 910 meters (3,000 feet) (Patton and Tailleur, 1964). To the south, in the Philip Smith Mountains quad~angle,the imbricate thrust faulting appears to have been the result of shearing along the axial trace of north-vergent isocl i nal overturned folds. The axial plane shearing and subsequent imbricate stacking of thrust slices has resulted in the structural thickening of the rocks in the entire Lisburne Group. The northward directed overthrusting has juxaposed rocks of the Lisburne Group over rocks of the younger Siksikpuk Formation, Echooka Formation, and Shubl i k Formation. Rocks that are found within upper Paleozoic and Mesozoic sequence of the northern foothills province in the central Brooks Range, have complex structural relationships that are characterized by tightly compressed north-vergent isocl i nal overturned folds. The folded strata are commonly cut by south-dipping high-angle reverse faults and less commonly by normal Saul ts and transverse faults (Patton and Tai 11eur, 1964). The high-angle reverse faults have thrust slices of the underlying Paleozoic rocks over rocks of the Mesozoic sedimentary sequence. Cretaceous rocks of the northern foothi 11s province are folded into large-scale, east trending, open anticlines and. sync1 ines that general ly have steepened northern 1imbs. Local ly, rocks of the Fortress Mountain Formation are tightly compressed and isocl inal ly fo1 ded. This intense deformation is accompanied by high-angle faulting and some thrust faulting.

Mining Activity and Economic Geolog~ Remoteness of the Sagavanirktok quadrangle has limited the amount of mineral exploration within the quadrangle. A1 though no known mineral claims are present in the region, the overall mineral potential of the rocks seems high. Rocks of the Lisburne Group in the Sagavanirktok quadrangle are 1argely biocl astic 1imestone with minor shale and si1tstone. The carbonates, shale and siltstone were deposited in a variety of depositional environments ranging from open marine to carbonate reef and sabkha environments . Penecontemporaneous volcanic activity , is evf denced by fel sic-to intermediate-flows, tuffs and breecias in Lisburne Group rocks near Drenchwater Creek in the north-central Brooks Range (Nockleberg, 1978), and by basic flows in the Iktillik River area, west of Galbraith Lake. The felsic-to intermediate-volcanics are the hast of "significant" concentrations of galena, sphalerite and minor barite. The sulfides occur in tuff and in chert and dark shales adjacent to the tuff units. Nockleberg (1978) believes the mineralization at Drenchwater Creek, formed from volcanic exhalations, is stratiform, and may represent a piece or fragment of a larger dis- membered stratiform body. Although the occurrence of lead and zinc mineralization at Drenchwater Creek is more than 150 kilometers (100 miles) west of the Pipeline Corridor, the similarity and continuity of the rocks in the Lisburne Group across northern Alaska, strongly suggest that the Lisburne Group rocks near the Pipe1 ine Corridor may have moderate to high mineral potential and may indeed contain stratiform lead, zinc and barite mineral ization. Armstrong (1975) has shown that the rocks that constitute the Lisburne Group in the eastern Brooks Range were at least in part deposited in a sabkha-type environment. The deposition of fine-grained sediments and limestone in a restricted stable shelf marine environment that impinges on some sort of deltaic complex often results in the deposition of sabkha-li ke sediments, in an arid climate. The sabkha interface usually contains a large amount of organic material, mainly alga1 mats, that upon decay result in a reducing environment. The movement of ground waters and seawaters containing complexed metal ions through the sabkha may result in the precipitation of sulfide minerals at the reductive interface. If the interpretation of sabkha-type environments of deposition for some of the rocks in the Lisburne Group is correct, the potential for finding base-metal sulfide deposits of the sabkha-type in rocks of the Lisburne Group seems high. West of Shainin Lake, the Lisburne Group contains a marked phospathic shale component. The phosphatic zone occupies a thin, generally continuous zone of black shale and chert near the top of the Alapah Limestone, and contains phosphate concentrations as high as 35.8% P O5 (Patton and Matzko, 1959). The phosphate-bearing horizon in t 6 e Alapah Limestone has been traced for a distance of about 80 kilometers (50 miles) across northern Alaska. The black chert and shale member is not recognized east of Shainin Lake, and no phosphate accumulations of significance are known east of the Shainin Lake locality. On Skimo Creek, northwest of Anaktuvak Pass, the entire phosphate-bearing zone of the Alapah Limestone is exposed. The zone is about 10 meters (36 feet) thick and one section, 1 meter (40 inches) thick contains an average of 21% P205. Trace amounts of vanadium, copper, barium, lead, manganese and uranium have been detected in samples from the black shale and chert member. The potential for finding phosphate accumul ations in the A1 apah Limestone in the Pipe1 ine Corridor seems low, because the rocks of the Alapah Limestone in the Pipeline Corridor are composed mainly of bioclastic 1imestone and 1ittle if any shale and chert. However, if . an extension of the phosphate-bearing black shale and chert zone can be found east of Shainin Lake, there is good potential for finding other phosphate deposits. West of the Sagavanirktok River, rocks of the Siksikpuk For- mation have a moderate to high potential for barite and base metal sulfide deposits of stratiform lead, zinc and barite affinities. East of the Sagavanirktok River, the Echooka Formation of the Sadlerochit Group is equivalent to the Si ksi kpuk Formation, and Detterrnan (1976) has recognized volcanoclastic rocks in the Echooka Formation. The volcanic rocks occur as flows, tuffs and breccias and are intercalated with 1imestones that contain Permian fossi 1s. To the south near Porcupine Lake, volcanic rocks that may be part of the Sadlerochit Group contain fluorite, lead and zinc mineralization (U. S. Bureau of Mines, 1978). No lead or zinc mineral ization has been identified in the Ivashak River sequence. However, the favorable geology coup1 ed with highly anomalous stream sediment geochemistry in the area, indicate an area in which there exists a high potential for lead, zinc, barite and fluorite mineralization. The Shubl i k Formation contains phosphate concentrations and anomalous metal concentrations locally. No obviously economic phosphate deposits are known, near the Pipel ine Corridor, however, the occurrences of phosphate-bearing siltstone and shale near the base of the Shublik Formation indicate that the unit may contain phosphate deposits of unknown size and distribution. The phosphate occurs primarily as concretions and as oolites within the siltstone and shale sequence. Pyrite is the most common sulfide mineral found in the Shublik Formation. The pyrite occurs in concretions and as rhombs and irregular lenses of nearly sol id pyrite. Samples of siltstone and siderite collected by the U. S. Geological Survey contained chromium values as high as 1,500 ppm and vanadium concentrations as high as 3 percent. No sulfides other than pyrite were found in these rocks, however. Even though only minor phosphates and barite concentrations were found in rocks of the Shublik For- mation, in the Pipeline Corridor, the overall mineral potential of these rocks seems high. Further work on rocks of the Shubl i k Formation is clearly needed. The lower Cretaceous Kongakut Formation contains a zone of manganiferous shale. The paper shale member contains a section 53 meters (175 feet) thick, of black, thin-bedded, pebble shale. The pebble shale contains pel lets - and thin beds of manganese carbonates. Manganese concentrations as high as 5 percent were detected by the U. S. Geological Survey (Detterman et al, 1975). The presence of manganese concentrations in the pebble shale member of the Kangakut Formation is interesting and clearly needs further work. The Mesozoic rocks of the north slope province represent a wide range of depositional environments. The rocks may have some potential for sedimentary uranium deposits. Locally, the Mesozoic sediments south of Happy Valley Pipeline Camp contain a higher than background -- response when tested with a scintillometer. Readings as high as 180 counts per second were recorded near a fairly thick sequence of quartzose sandstone and dark-gray shale. No obvious uranium mineralization was found however.

I North of Happy Valley Pipeline Camp near Sagwon, the rocks of I the Sagwon Member of the Sagavanirktok Formation contain 1ignite and sub-bituminous coal seams as much as 6 meters (20 feet) thick. Several seams are exposed at the Sagwon bluffs locality and one 2 meter (6 foot) seam was sampled for analysis. , REFERENCES CITED

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Yochclron. E. L., ond Dulfo. J. 1.. Jr.. 1960, Lot. Poieoxoic pastrop& ftom ncrthrrn Alosl.o: U.S. Gcol. Survey Prof. Popet 3344, p. 111-147. APPENDIX A Rock and Stream Sediment Sample Trace Element Concentrations and Threshold Values . . TABLE 1

VALDEZ QUADRANGLE

Rock Sample Descriptions and Trace Element Concentrations

Sampl e Sampl e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90zC.L. 95%C.L. Elements 98xC.L.

Graywac ke Sr Graywacke ~ithquartz veining Cu Metagraywacke with 1 meter wide quartz vein Metagraywacke with quartz veining Graphitic slate Graywac ke Graywac ke Graywacke with quartz veining Bi,V . Graywacke and slate with pyrite ' Graywac ke Graywac ke Graywac ke Graywac ke Graywac ke Graywacke and slate with pyrite Graywacke with quartz veining Graywacke with quartz veining Cr,Ni ,Ta Graywacke Graywac ke Cu Graywac ke wit h quartz veining and pyrite Graywacke Graywacke with quartz veining Graywacke with quartz veining Graywacke with quartz veining Graywacke with quartz veining TABLE 1 VALDEZ QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations (continued)

Samp 1e Samp 1e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95%C.L . Elements 98%C.L.

Graywac ke Y Graywacke and mudstone Ca,Cr,Cu,Fe,Mn,Ni,Sc Graywac ke Sc, Y Z r Graywac ke Meta-argi 11 i te and graywacke Graywacke and argil 1 i te Graywac ke Slate and graywacke Graywac ke Graywac ke Graywacke and slate with pyrite Chlorite schist Graywac ke Graywac ke Graywacke Graywac ke Graywacke with quartz veining Graywac ke Graywac ke Meta-volcanic Greenstone with pyrite and (?)chalcopyrite Chert and volcanics with pyrite and (?)chalcopyrite TABLE 2 VALDEZ QUADRANGLE Stream Sediment. Sampl e Trace El emen t Concentrations

Sampl e Weakly Anomal ous Anomalous El ements Strongly Anomal ous Number Elements 90%C.L. 95%C.L. El ements 98%C.L. 196 TABLE 3

. NIRL Rock Samples, Chugach Terrane, 1976 (based on 47 samples) Values in PPM or Percent (as noted) Minimum or Thresh01 d Values to give indicated confidence level Level Weakly Anomalous Anomalous at Strongly Anomalous Element of at 90Xconf idence 95%confidence at 98Xconfidence Detection 1eve1 1eve1 1eve1 _, Ag 20 3 2 34 36 A1 12.16% 12.70% 13.16% As 8 00 800 801 801 Au 20 20 20 20 B 100 100 100 100 Ba 7 00 779 793 807 Be 10 10 10 10 B i 200 443 484 522 Ca 40 5.81% 6.65% 7.44% C d 4 00 400 400 400 C o 40 40 40 40 Cr 20 145 161 175 Cu 40 91 100 109 Fe 6.97% 7.53% 8.05% Ga 2 0 31 33 35 K 1.1% 4.59% 5.01% 5.40% La 2 00 200 200 200 L i 1 .O% 1 .O% 1 .O% 1 .O% Mg 3.11% 3.42% 3.71% M n 60 1420 1558 1686 Mo 10 26 29 3 1 11 3 1% 1.11% 1.13% 1.16% Nb 800 800 801 801 N i 20 8 5 94 102 P 800 ' 1045 1088 1128 P b 80 298 338 374 Pd 20 2 0 20 20 P t 20 20 2 0 20 Sb 500 51 9 523 526 Sc 10 33 37 41 Se 3 00 300 300 300 S i 10.0% 10.0% 10.0% Sn 60 71 74 76 Sr 10 125 135 144 Ta 3 00 366 381 396 T e 2 00 291 31 8 343 Ti 500 2843 3023 31 90 V 4 0 104 111 118 W 200 200 200 200 Y 70 122 129 136 Zn 10 51 8 609 693 Zr 2 0 71 78 84 TABLE 4 MIRL Stream Sediment Samples, Chugach Terrane, 1976 (based on 23 samples) Values in PPM or Percent (as noted) - Minimum or Threshold Values to give indicated confidence level Level Weakly Anomalous Anomalous at Strongly Anomalous Element of at 90%confi dence 95%confidence at 98%confi dence Detection 1eve1 1eve1 1eve1 TABLE 5 GULKANA QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations

Sample Samp 1e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L . 95%C.L . Elements 98%C.L.

A1 tered andesi te with epi dote Green basalt with epidote Dark green basalt with epidote Sheared greenstone with quartz veining Coarse-grained gabbro Greenstone with pyrite Biotite granite with pyrite Biotite granite with pyrite Gneissic granite with pyrite Gneissic biotite granite Gneissic biotite granite with epidote Gneissic granite with pyrite and c ha1 copyri te Granite and gneissic granite Greenstone with pyrite Greenstone with calcite veining Greenstone 1 TABLE 5 GULKANA QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations (conti nu&)

Sampl e Samp 1e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95%C.L. Elements 98%C.L.

76AMR394 Greenstone Ti 395 Greenstone with malachite and azurite 396 Greenstone with pyrite and' V Co,Cu,Sc ma1 achi te 397 Greenstone with pyrite and Co ,Sc Al,Co,Cu,Ga,La,Mo,Sc, quartz veining Se,Sn,Ti ,W,Zn,Zr,Au 762220 Greenstone with quartz veining, Cd,Cr,K,Mg,Ni,Sc, Cu,K,Mg,Ti,Y,Zn Ag,Co,Cu,La,Mg,Mn,Ni, pyrite and chalcopyrite Te, V Y TABLE 6 MIRL Rock Samples, Amphi theater Terrane, 7 976 (based on 85 samples) Values in PPM or Percent (as noted) - Minimum or Threshold Values to give indicated confidence level Level Weakly Anomalous Anomalous at Strongly Anoma1o.u~ Element of at 90%confi dence 95%confi dence at 98Zconf idence Detection 1eve1 1eve1 1eve1

Ag 20 33 35 37 A 1 12.37 13.61 14.29 As 800 800 800 800 Au 20 22 22 22 B 100 100 100 100 B a 700 1098 1174 1245 Be 10 10 10 10 B i 200 435 478 51 8 Ca 4 0 11.22% 12.71% 14.09% C d 400 400 400 400 Co 4 0 49 5I 52 C r 20 164 184 203 Cu 4 0 201 228 254 F e 12.19% 13.50% 14.73% Ga 20 26 27 28 K 1.1:; 8.46% 9.45% 10.37% La 200 237 244 251 L i 1.0% 1 .O% 1.0% 1 .O% Mg 7.21% 8.11% 8.95% Mn 60 2113 2334 2540 Mo 10 44 49 54 Na 1% 1.20% 1.26% 1.31% N b 800 800 800 800 N i 20 90 100 110 P 800 1015 1054 1090 P b 80 96 99 102 P d 20 23 24 2 5 TABLE 7 MT . HAYES QUADRANGLE Rock Sample Descriptions and Trace Element concentrations

Sampl e Sampl e WeaklyAnomalous Anomalous Elements StronglyAnomalous Number Description Elements 90%C.L. 95%C.L. Elements 98%C.L.

Iron-stained quartz muscovite schist Chlorite schist Ca ,Fe Quartz muscovite schist with pyrite Quartz muscovite schist and B i micaceous quartzite Quartz muscovite schist with quartz veining Quartz muscovite schist and ' micaceous quartzite with pyrite Quartz mica schist with quartz veining Quartz mica schist Altered granoblastic amphibolite Micaceous quartzite and quartz muscovite schist Quartz mica schist with pyrite and (?)arsenopyrite Sheared basalt with pyrite Graphitic schist and micaceous quartzite Iron-stained quartz mica schist and micaceous quartzi te Quartz muscovite schist Sheared gabbro(?) TABLE 7

MS. HAYES QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations (continued)

Sample Sampl e Weakly Anomal ous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95%C.L . Elements 98%C.L.

76AMR346 Quartz muscovite schist with Mo I I I calcite veining 1 348 Iron-stained quartz mica alb-ite schist 349 Quartz muscovite schist 350 Quartz muscovite schist 351 Amphiboli te with pyrite and Cu Mn ,Mo chalcopyrite 352 Quartz muscovite schist Mo 353 Chlorite schist 354 Quartz muscovite schist and Mo micaceous quartzite 356 Sheared basalt with calcite veining 357 Silicified, altered, igneous rock witti pyrite and chalcopyrite 358 Chlori tized diorite with pyrite 359 Gneissic quartzite with chalcopyrite 360 A1 tered intrusive rock 361 A1 tered felsite with pyrite 362 Diabase 363 Quartz monz~niteporphyry 364 A1 tered quartz monzonite porphyry with chalcopyrite 365 Prophl iti zed intrusive rock 366 Altered diabase with pyrite Bi 367 Lithic tuff with calcite veining TABLE 7

MT. HAYES QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations (continued)

Sample Sampl e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90zC.L. 95%C.L. Elements 98%C.L.

76AMR368 Propyl iti zed intrusive rock 369 Lithic tuff with calcite veining 370 A1 tered diorite with pyrite 371 Lithic tuff Cr,Mi 372 Hornblende diorite with quartz and calcite veining 373 Altered lithic tuff TABLE 8 MT. HAYES QUADRANGLE Stream Sediment Sample Trace El ement Concentrations

Sample . Weakly Anomalous Anomalous Elements Strongly Anomalous Number El emen ts 90%C. L. 95XC. L. Elements 98%C.L.. TABLE 9 MIRL Rock Samples, Birch Creek Terrane, 1976 (based on 155 samples) Values in PPM or Percent (as noted) Minimum or Threshold Values to give indicated confidence level Level Weakly Anomalous Anomalous at Stronqly Anomalous Element of at 96%confidence 95%confidence at 98%confidence Detection 1eve1 1eve1 1eve1 TABLE 10 MIRL Stream Sediment Samples, Birch Creek Terrane, 1976 (based on 31 samples) Values in PPM or Percent (as noted)

to give indicated confidence 1evel Level Weak1 Y Anomalous Anomalous at Strongly Anomalous Element of at 9$%conf i dence 95%confi dence at 98%confidence Detection 1eve1 1eve1 1eve1 TABLE 11 MIRL Rock Samples, Amphitheater Terrane, 1976 (based on 85 samples) Values in PPM or Percent (as noted) . Minimum or Threshold Values to give indicated confidence 1evel Level Weakly Anomalous Anomalous at Strongly Anomalous ~leme.nt of at 90%confi dence 95%confi dence at 98%confi dence Detection 1eve1 1eve1 1eve1

A g 20 33 35 37 . A1 12.87 13.61 14.29 As 800 800 800 800 AU 20 22 22 22 . B 100 100 100 . 100 B a 700 1098 11 74 1245 Be 10 10 10 10 B i 200 435 478 51 8 Ca 40 11.22% 12.71% 14.09% C d 400 400 400 400 Co 40 49 51 52 Cr 20 164 184 203 Cu 40 201 228 2 54 Fe 12.19% 13.50% 14.73% Ga 20 26 27 28 K 1.1% 8.46% 9.45% 10.37% La 200 237 244 251 L i 1.0% 1 .O% 1 .O% 1 .O% Mg 7.21% 8.11% 8.95% M n 60 2113 2334 2540 Mo 10 44 49 54 Na 1% 1.20% 1.26% 1.31% N b 800 800 800 800 N i 20 90 100 110 P 800 1015 1054 1090 Pb 80 9 6 99 102 P d 2 0 23 24 25 P t 20 26 28 29 Sb 500 506 507 508 Sc 10 58 64 70 Se 300 382 398 41 3 S i 10.0% 10.0% 10.0% Sn 60 6 5 67 68 Sr 10 173 198 221 Ta 300 41 7 448 477 Te 200 271 289 306 Ti 500 5285 5906 6484 V 4 0 234 260 285 W 200 237 244 251 Y 70 184 199 231 Zn 10 77 87 96 Z r 20 102 114 125 TABLE 12 BIG DELTA QUADRANGLE Rock Sample ~escri~ti0n.sand Trace Element Concentrations

Sample Samp 1e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95XC.L. Elements 98%C.L.

76AMR304 Quartz muscovite schist 306 Garnetiferous quartz, muscovite schist 307 Micaceous metasiltstone 308 Quartz biotite schist 309 Quartz muscovite schist 323 Quartz biotite schist 324 Cal cic amphi bol i te . TABLE 13 BIG DELTA .QUADRANGLE Stream Sediment Sample Trace El ement Concentrations

Sampl e Weakly Anornal ous Anomalous El ements Strongly Anomalous Number Elements 90%C.L. 95%C.L. Elements 98%C.L. TABLE 14 MIRL Rock Samples, Birch Creek Terrane, 1976 (based on 155 samples) Values in PPM or Percent (as noted) c to give indicated confidence level Level Weakly Anomalous Anomalous at Strongly Anomalous Element of at 90Xconf idence 95%confidence at 98%confidence Detection 1eve1 1eve1 I eve1

Ag 20 26 27 28 A1 11.58% 12.67% 13.69% As 800 855 867 877 A u 20 2 1 22 2 2 B 100 108 110 112 Ba 700 881 91 8 953 Be 10 10 10 10 B i 200 385 41 2 436 Ca 40 4.20% 4.95% 5.64% C d 400 400 401 401 C o 40 47 49 50 C r 20 141 159 176 C u 40 238 278 31 4 Fe 7.14% 7.94% 8.69% Ga 20 24 2 5 25 K 1 .l% 7.44% 8.31% 9.11% TABLE 15 MIRL Stream Sediment Samples, Birch Creek Terrane, 1976 (based on 31 samples) Values in PPM or Percent (as noted) Minimum or Thresh01 d. Values to give indicated confidence 1eve1 Level Weakly Anomalous Anomalous at Strongly Anomalous Element of at 90%confidence 95Zconfi dence at 98%confidence Detection 1eve1 1eve1 1eve1 Ag 20 23 24 25 . A 1 10.68% 11.28% 11.83% As 800 800 800 800 A u 20 20 ' 20 2 0 B 100 100 100 - 100 B a 700 700 700 701 Be 10 10 10 10 Bi 200 344 371 396 Ca 40 601 0 6642 7229 Cd 400 400 400 400 Co 4 0 40 40 40 Cr 20 87 9 5 102 Cu 40 40 40 40 F e 4.84% 5.15% 5.44% Ga 20 20 20 20 K 1 .l% 4.67% 5.16% 5.61% TABLE 16 FAIRBANKS QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations

Sample Samp 1e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95%C. L. Elements 98XC.L.

Garnetiferous quartz muscovite Z r schist Muscovite schist Quartz muscovite schist and Mg micaceous quartzite Porphyroblastic schist ? ? ? ? ? Quartz vein material Quartz vein material A1 tered rock ? A1tered rock Gouge ? . Granite ' Quartz monzonite ? ? ? ? ? ? TABLE 16

FAIRBANKS QUADRANGLE

Rock Sample Descriptions and Trace Element Concentrations (continued)

Sample Sampl e Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95%C.L . Elements 98%C.L.

- --- - ? ? ? ? ? Quartz muscovite schist Quartz mica schist Quartz mica schist Quartzite Quartz mica schist Quartzite and amphi bol ite Quartz mica schist Quartzite Quartz mica schist Quartz mica schist Quartzite TABLE - 17 MIRL Rock Samples, Birch Creek Terrane, 1976 (based on 155 samples) Values in PPM or Percent (as noted) Minimum or Threshold Va 1ues to give indicated confidence level Level Weakly Anomalous Anomalous at Strongly Anomalous Element of at 90%confi dence 95%confi dence at 98%confi dence Detection 1eve1 1eve1 1eve1 TABLE 18

LIVENGOODQUADRANGLE

Rock Sample Descriptions and Trace Element Concentrations

Sampl e Sample Weakly Anomalous Anomalous Elements Strongly Anomalous Nunlber Description Elements 90%C.L. 95%C. L . Elements 98%C.L.

Metagraywac ke Rhyol ite porphyry Quartz porphyry with epidote and Cu chlorite Quartz porphyry with epidote, S r chlorite and biotite Metas i1 tstone Siltstone with quartz veining Bi

and iron-staining . s Coarse-grai ned conglotnerate B i Meta-siltstone and meta-conglomerate Siltstone Siltstone Quartz monzonite porphyry with pyrite Si1 tstone Meta-sil tstone Meta-siltstone Siltstone Siltstone Siltstone Siltstone Si1 ts tone Siltstone with limonite staining is C 0 Y .r U a+' 0 Q L -Q.r 'a, 52 Y LI) V) 'F aaJ -a u aJ TABLE 18 LIVENGOOD QUADRANGLE Rock Sample Descriptions and Trace Element Ctincentrations (continued)

Sampl e Sample Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95XC.L. Elements 98%C.L.

------Black chert with quartz stringers Chert Chert Chert Chert Chert with limonite staining Vesicular basalt Chert Chert Chert Meta diorite(?) with galena(?) Diabase Sil tstone and sandstone Chert with limonite staining Chert Chert Chert Chert Chert Chert Chert with heavy 1 imonite staining Chert Chert Chert Amygdal oidal basalt Chert Chert TABLE 18

LIVENGOOD QUADRANGLE

Rock Sample Descriptions and .Trace Element Concentrations (continued)

Sampl e Sample Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95XC.L. Elements 98%C.L.

Chert Chert Interbedded chert and carbonaceous Mo si 1 ts tone Chert with manganese staining and Ca,Mn,Mo quartz veining Trachyte with calcite veining Mo Chloritized hornblende diorite Interbedded siltstone and sandstone Sandstone and shale Sandstone with calcite and quartz veining Trachyte V Si1 tstone Chloritized hornblende diorite with biotite Siltstonewithlimonitestaining Ca Chloritized diorite Siltstone with heavy iron staining a Chloritized diorite with pyrite Ca ,Mo ,Ti ,V Chloritized diorite C a Chert and siltstone Coarse sandstone with iron Ca,Mo,Ti staining Silicif ied siltstone with limonite staining Silicified sandstone Ca . TABLE 18 LI VENGOOD QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations (continued)

Samp 1 e Sampl e' Weakly Anomalous Anomalous Elements Strongly Anomalous Number Description Elements 90%C.L. 95%C. L. Elements 98%C.L.

Chloritized diorite Si 1tstone Bi ,V Chloritized diorite Silicified siltstone Silicified siltstone Silicified siltstone Silicified siltstone at contact with diorite sill (?) Chloritized diorite Siliceous siltstone Chert Hornblende diori te with P chalcopyrite and pyrite Chloritized granodiorite with pyrite Hornblende granodiori te with Mo pyrite, chalcopyrite,malachite Chl ori tized granodiori te Granodiori te with pyrite and Mo ,Y chalcopyrite Chlori tized diori te with pyrite Ca ,Mo Sil icified metasil tstone with pyrite Chloritized, biotite Ca diorite with pyrite Si 1 tstone ------~~L;;J&-iJ~~L3-L.LI*r--- C -... --

TABLE 18 ' LIVENGOOD QUADRANGLE Rock Sample ~escriptionsand Trace Element Concentrations (continued)

Sampl e Sample Weakly Anomalous Anomalous Elements Strongly Anomalous . Number Description El ements 90%C. L. 95%C. L. Elements 98gC.L.

76AMR112 Biotite diorite with pyrite Ca Ti ,V 113 Chert Bi , 114 Biotite diorite 115 Greenstone Mg Sc 116 Hornblende diorite Ga 117 Chert 118 Chert Chert Vo1 cani cs and argill i te Ca ,Mg K Lithic tuff Si 1ts tone P Y Argillite in contact with vol canics Sheared vol canics with calcite Y veining Volcanics and argillite Mo A1 tered vol cani cs - Mo Sandy siltstone Lithic tuff with calcite and C a quartz veining Si1 icified tuff with pyrite and Ca ,Mo ,Ti quartz vei nl ets Well -indurated sandstone Ca . . Diori te Ca ,Mo Basalt with' calcite veining Ca Greenstone with ca1 cite veining Ca ,Mo TABLE 18 LIVENGOOD QUADRANGLE Rock Sample Descriptions and Trace Element Concentrations (continued)

Sampl e Sampl e Weakly Anomalous Anomalous Elements . Strongly Anomalous Mumber Description Elements 90%C.L. 95%C.L. Elements 98%C.L.

76AMR134 Andesi te with calcite veining C a 135 Tuff 136 Lithic tuff with calcite veining 137 Argillite with manganese staining 138 Argillite with manganese staining Cd and quartz stringers 139 Tuff with limonite staining and

calcite stringers I 140 Lithic tuff with calcite and quartz stringers 141 Argillite 142 Shale with limonite staining 143 Argillite 144 Lithic tuff with calcite veinlets 145 Lithic tuff 146 Argillite 147 Tuff V 148 Lithic tuff with manganese staining 150 Greenstone with calcite stringers Ca 151 Lithic tuff with calcite stringers and manganese staining 152 Micaceous argill i te 153 Argi 11 i te with manganese staining