Mineral Resources of Glacier Bay National Monument, Alaska

By E. M. MAcKEVETT, JR., DAVID A. BREW, C. C. HAWLEY, LYMAN C. HUFF, and JAMES G. SMITH

GEOLOGICAL SURVEY PROFESSIONAL PAPER 632

A reconnaissance study of the mineral deposits

~and - their geologic setting and a geochemical sampling program in one of our wildest, most beautiful, and most remote national monuments

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971 UNITED STATES DEPARTMENT OF THE INTERIOR

FRED J. RUSSELL, Acting Secretary

GEOLOGICAL SURVEY

William T. Pecora, Director

Library of Congress catalog-card No. 77--609011

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS

Page Page Abstract and summary ...... 1 Mineral deposits-Continued Mineral deposits ...... Metallic commodities-Continued Previously known deposits ...... Base and miscellaneous metals-Continued Nunatak molybdenum prospect ...... Arsenic ...... Brady Glacier prospect ...... Bismuth ...... Fairweather Range ...... Cadmium ...... Alaska Chief prospect ...... Copper...... Placer deposits near Lituya Bay ...... Distribution ...... Margerie prospect ...... Types of deposits ...... Reid Inlet gold area and Sandy Cove pros- Descriptions of deposits ...... pect ...... Mount Young area ...... Other previously known deposits ...... East of Casement Glacier ...... Deposits discovered during 1966 ...... North shore of Adams Inlet ...... Geochemical anomalies ...... North of White Glacier ...... Favorable areas ...... North of York Creek ...... Introduction ...... Minnesota Ridge ...... Geographic setting ...... Gable Mountain ...... Previous investigations ...... South of Rendu Glacier ...... Present investigation ...... West shore of Tarr Inlet ...... Acknowledgments ...... Margerie prospect ...... Regional geology ...... Curtis Hills ...... Stratigraphy ...... North Marble Island ...... Intrusive rocks ...... South Marble Island ...... Structure ...... Willoughby Island ...... Geochemical studies ...... Francis Island ...... Methods of analysis ...... Alaska Chief prospect ...... Sampling and sample preparation ...... East side of Dundas Bay ...... Anomalous and background values ...... Bruce Hills ...... Total heavy metals ...... West of mouth of Rendu Inlet .... Copper ...... South of Tidal Inlet ...... Lead ...... Blue Mouse Cove ...... Molybdenum ...... Southwest Gilbert Island and Chromium ...... nearby unnamed island ...... Nickel ...... West of Shag Cove ...... Other elements ...... West arm of Dundas Bay ...... Unaltered rocks ...... West of mouth of Tarr Inlet .... Causes of anomalous values ...... West of Tarr Inlet ...... Results of geochemical studies ...... North of Johns Hopkins Inlet .... Total heavy metals ...... South of Johns Hopkins Inlet .... Copper ...... East of Lamplugh Glacier...... Lead ...... Southwest of Lamplugh Glacier .. Molybdenum ...... East of Reid Glacier ...... Chromium and nickel ...... East of Hoonah Glacier ...... -...... Other elements ...... Fairweather Range ...... Areal descriptions ...... Southeast arm of Lituya Bay ...... Western Dundas Bay area ...... Other deposits that contain Eastern Dundas Bay area ...... copper ...... Miller Peak-Sandy Cove area ...... Lead ...... Mount Merriam area ...... Radioactive elements ...... Reid Inlet gold area ...... Tin ...... Mineral deposits ...... Zinc ...... Locality list keyed to maps and tables ...... Distribution and types of deposits .... Metallic commodities ...... Descriptions of deposits ...... Base and miscellaneous metals ...... Nunatak on Casement Glacier .... Antimony ...... Mount Brack ...... CONTENTS

Page Mineral deposits-Continued Mineral deposits-Continued Metallic commodities-Continued Metallic commodities-Continued Base and miscellaneous metals-Continued Iron and ferroalloy metals-Continued Zinc-Continued Iron-Continued Descriptions of Descriptions of deposits-Continued deposits-Continued Southwest of Red Mountain .... 55 West of Blackthorn Peak ...... Southwest of Alaska Chief pros- East of Brady Glacier ...... pect ...... 55 Fairweather Range ...... Hugh Miller Inlet ...... 55 Placer deposits ...... Mount Cooper 55 Chromium ...... Northwest shore of Johns Hop- Cobalt ...... kins Inlet ...... 55 Manganese ...... Other deposits that contain zinc .. 55 Molybdenum...... Precious metals ...... 56 Dlstrlbutlon ...... Gold ...... 56 Types of deposits ...... Distribution and occurrence ...... 56 Descriptions of deposits ...... Lode deposits ...... 56 Casement Glacier ...... Reid Inlet gold area ...... 56 Van Horn Ridge ...... Terry Richtmeyer prospect .... 56 West side of Tarr Inlet ...... LeRoy mine ...... 56 Nunatak prospect ...... Rainbow mine ...... 59 Geology ...... Sentinel mine ...... 60 Ore deposits ...... Monarch mines ...... 60 Geochemical studies ...... Incas mine ...... 62 Entrance of Adams Inlet ...... Sunrise prospect ...... 62 Wachusett Inlet ...... Hopalong and Whirlaway Triangle Island ...... claims ...... 63 Geikie Inlet ...... Galena prospect ...... 63 Lower Brady Glacier ...... Highland Chief prospect ...... 63 Ridge west of Rendu Inlet ...... Rambler prospect ...... 64 Other molybdenum deposits .. Other lode deposits in the Nickel ...... Reid Inlet area ...... 64 Descriptions of deposits ...... South of Lituya Bay ...... 64 Brady Glacier prospect, by H . R. Sandy Cove prospect ...... 64 Cornwall ...... West of McBride Glacier ...... 66 Geology ...... East of lower Brady Glacier ...... 67 Ore deposits ...... West of Dundas Bay ...... 67 Possibilities of commercial Russell Island ...... 67 . . ore deposits ...... Other lode deposits ...... 67 Tltanmm...... Placer deposits ...... 67 Dlstrlbutlon ...... South of Wood Lake ...... 67 Descriptions of deposits ...... Dundas River ...... 67 Fairweather Range ...... Outwash of Brady Glacier ...... 67 Placer deposits near Lituya Bay .. Oregon King Consolidated ...... 67 Tungsten ...... Lituya Bay ...... 68 Vanadium ...... Other placer deposits ...... 68 Geologic influences on localization of metalli- Platinum ...... 69 ferous deposits ...... Silver ...... 69 Nonmetallic commodities ...... Rendu Inlet prospect ...... 69 Petroleum and coal, by George Plafker ...... Iron and ferroalloy metals ...... 69 Petroleum ...... Iron ...... 69 Stratigraphy ...... Descriptions of deposits ...... 70 Structure ...... East of Dundas Bay ...... 70 Potential ...... West of Rendu Inlet ...... 70 Coal ...... Queen Inlet ...... 70 References cited ...... CONTENTS ILLUSTRATIONS

[Plates are in pocket1 Map showing bedrock lithology and locations of known metalliferous mineral deposits, Glacier Bay National Monument. Map showing total heavy-metals concentration in stream-sediment samples. Maps showing metal concentrations in stream-sediment samples: 3. Copper. 4. Lead. 5. Molybdenum. 6. Chromium. 7. Nickel. Map showing anomalous values of arsenic, beryllium, bismuth, cadmium, silver, strontium, tin, tungsten, and zinc in stream-sediment samples. Geologic sketch map showing sample locations at the LeRoy mine, Glacier Bay, Alaska. Geologic sketch map, magnetic profiles, and generalized geologic section, Queen Inlet magnetite locality, Glacier Bay National Monument, Alaska. Geologic map of the Nunatak molybdenum prospect. Map of the Nunatak molybdenum prospect showing sample locations, extent of known mineralization, and bathymetry of adjacent parts of Muir Inlet. Page Map of Glacier Bay National Monument, Alaska, showing selected mineral deposits, geochemical anomalies, and outlines of some areas favorable for mineral deposits ...... Index map showing Glacier Bay National Monument, Alaska, and geologic provinces within the monument Geochemical sampling maps: 3. Western Dundas Bay area ...... -....----... ..~~..~~~.~~~~~.....------.....--.--..------....----....------4. Eastern Dundas Bay area 5. Miller Peak-Sandy Cove area ...... --...... -...... -...... --...... --...... ------

6. Mount Merriam area ...... -...-.-...... -...... L...... -.....------.----..----.-.---..------.--.------7. Reid Inlet gold area ...... ~...... ~...... ~...~...... --...-.....~~.~-~~~~~~...... ~~~~--~-....~~~~~~~~~~~~------Geologic sketch maps showing sample locations: 8. Francis Island prospect ...... -...... -.-.-----..-...-...-...... ---...-....------.--...... -...... --.- 9. Alaska Chief prospect 10. Bruce Hills copper-molybdenum deposit 11. Rainbow adit ...... -....-...... -.--...... -..--...... ----.--..-----...... --.....----.-..--.-....--.--.....-...... -.-----....-- 12. Monarch No. 1 mine ...... --..-...... ----..-.....-...--...... -...... -.-..--..------.-...... --...-..------.------.. 13. Monarch No. 2 mine ..-.....-...... ---....-...... ---...... -...... --...... --..-....------.--..-...... -.....------....-..------...----..-.------14. Incas mine .-.----.-.--~~...... ~...... ~..~...... ~~.~...... ~~~...... ~.....~~~~~..~~~~.~...... ~~~.~...... ~~...... ~~.~~~~~~~.~~..~....~~.....~. 15. Sandy Cove prospect ...... -...... --..--...... -.-..-.....--..-.-----.....--....----...-.---....--.---.-...... -.-...... -.-----.-..-..----..------Geochemical map of Sandy Cove gold-copper prospect ...... Map showing magnetometer traverses west of Rendu Inlet ...... ------.-....-..--..-.-...... --...... -... Generalized geologic map of Brady Glacier nunataks showing nickel-copper sulfide lodes Geologic sketch map and structure section of Tertiary rocks in the Lituya district Tentative correlation of stratigraphic sections exposed in the Lituya district ......

TABLES

Page Average precipitation and average temperature for Cape Spencer and Gustavus ...... -...... ---.----.....------.8 Detection limits for some elements determined by the six-step and direct-reader spectrographic methods 12 Semiquantitative spectrographic analyses of representative unaltered rocks ...... --.....----.--...... ----...... ------.14 Total heavy-metalsand semiquantitative spectrographic analyses of stream-sediment samples: 4. Western Dundas Bay area 5. Eastern Dundas Bay area ...... 6. Miller Peak-Sandy Cove area ...... 7. Mount Merriam area 8. Reid Inlet gold area ...... CONTENTS

Page Semiquantitative spectrographic analyses and gold analyses of mineral deposits in the Glacier Bay National Monument ....-...... -...... --...... -.-....-...... --..-...----...... -...... ------..--...-...... -...--.--.-....--..-.....------.-.. Comparison of analytical results on soil samples from the Bruce Hills copper-molybdenum deposit Semiquantitative spectrographic analyses and gold analyses of samples from the Reid Inlet gold area ..-.---. Assay data on the LeRoy mine ...... -...... --...... --...... -.---...... -...------...... Semiquantitative spectrographic analyses and colorimetric analyses for molybdenum of samples from the Nunatak molybdenum prospect ...... Comparison of older and younger soils at the Nunatak molybdenum prospect in terms of molybdenum and

copper content ~ ...... Semiquantitative spectrographic analyses of rocks and ore from the Brady Glacier nickel-copper prospect .... MINERAL RESOURCES OF GLACIER RAY NATIONAL MONUMENT, ALASKA

By E. M. MACKEVETT,JR., DAVIDA. BREW,C. C. HAWLEY,LYMAN C. HUFF,and JAMESG. SMITH

ABSTRACT AND SUMMARY are limiting factors in most cases. Probably none of these The U.S. Geological Survey investigation of the mineral- newly found deposits will prove to be of major importance, resource potential of Glacier Bay National Monument was but they cannot be eliminated from consideration without made during the summer of 1966 at the request of the Na- exploration. tional Park Service for its use in planning future develop- The investigations were thorough enough to conclude that ment of the monument. The most important results of field most, if not all, sizable mineral deposits exposed in the tests and laboratory analyses are herein summarized. Back- Glacial Bay National Monument east of the Fairweather ground on the geography, geology, and study methods used is Range have been found. Some of the geochemical anomalies given in the "Introduction." detected in stream-sediment samples from this same part of The chief metallic commodities of potential economic im- the monument may indicate the existence of concealed minor portance are coqper, molybdenum, nickel, gold, silver, tita- deposits. In the Fairweather Range itself, most of the nium, and iron. A few other metals might constitute byprod- planned fieldwork was prevented by bad weather, and only ucts or form deposits in some favorable areas that are as yet small parts of its eastern margin were examined; therefore, unexplored or concealed. The belt of Tertiary sedimentary our appraisal of the deposits of the range is severely limited rocks that borders the Gulf of Alaska and probably occurs by lack of data. offshore is a possible host for petroleum, but the potential is low. The economic potential for nonmetallic deposits known MINERAL DEPOSITS in the monument, such as coal, limestone, and dolomite, is PREVIOUSLY KNOWN DEPOSITS minimal because of their low grade, impurities, cheaper availability elsewhere, and other limiting factors. Deposits at the Nunatak molybdenum prospect (fig. 1, The deposits considered to have the best economic potential loc. 1) consist of abundant, closely spaced molydenite (MoS2)- include eight that were previously known and seven that were bearing quartz veins, minor molybdenite disseminated in horn- found during our investigations. The previously known de- fels, and a mineralized fault zone. The deposits have been posits are the Nunatak molybdenum prospect; the Brady described by Twenhofel (1946), and they were sampled and Glacier nickel-copper prospect; titanium, iron, and copper explored with two diamond-drill holes by the U.S. Bureau of deposits associated with the layered mafic intrusive rocks of Mines (Sanford and others, 1949). Mining companies have the Fairweather Range; the Alaska Chief copper prospect; conducted limited exploration at the prospect. The deposits gold- and ilmenite-bearing beach placers north and south of are mainly in hornfels, but locally, they occur in an intrusive Lituya Bay; the Margerie copper prospect; and gold lodes in igneous body mapped as quartz monzonite porphyry, which is the Reid Inlet area and at the Sandy Cove prospect (fig. 1). exposed over a small area, and in a silicified zone near the The most attractive deposits found during our investigations edge of the igneous body. Pyrite (FeSz), pyrrhotite (FehS), include a copper-molybdenum deposit in the Bruce Hills; chalocopyrite (CuFeSz), and traces of silver are associated veins and altered zones north of White Glacier; base-metal with the molybdenite in parts of the deposit. lodes near Mount Brack; and copper deposits south of Rendu Satisfactory estimates of the grade of the deposits will Glacier, near Gable Mountain, east of Dundas Bay, and west require bulk sampling, and adequate estimates of the reserves of Tarr Inlet (fig. 1). are contingent upon determining the extent of the deposits. The previously known deposits are described in the order of Our reserve estimate for the closely spaced molybdenite- their probable economic potential. The Nunatak molybdenum bearing vein network, or stockwork, above sea level near Muir prospect and the Brady Glacier nickel-copper prospect are Inlet is 2,247,000 tons of material averaging 0.067 percent those most likely to be developed in the near future. The de- MoSz and 0.016 percent copper. Our estimate for the remain- posits of potential significance that we found cannot be der of the stockworks and the fault zone deposit is 129,530,250 ranked without additional data, and, at this stage, are con- tons of material averaging 0.026 percent MoSz and 0.018 per- sidered to. have about the same potential. They are all partly cent copper. The grades are based on assays of chip samples or largely covered by snow, ice, or surficial deposits, and sat- collected during our investigations. In addition, about isfactory appraisals of their configurations and grades re- 18,000,000 tons of material similar to that in the second cate- quire physical exploration. These newly found deposits are of gory above are inferred to underlie the steep cliffs near the interest because of their inferred sizes, their grades, and the southern end of the stockworks. Reserves that are compara- possibility that concealed parts of some deposit may be larger ble in tonnage and grade to those above sea level probably and richer than is apparent from surface examination. These also occur below sea level. deposits would be regarded as exploration possibilities by Twenhofel (1946, p. 17, 18) estimated that the whole stock- most mining companies, but remoteness and difficult access work contained 8,500,000 tons of material averaging 0.125 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

KEY TO LOCALITIES SHOWN ON MAP

1. The Nunatak Muir Inlet 11. White Glacier 2. Brady Glacier 12. South of Rendu Glacier 3. Alaska Chief 13. Gable Mountain 4. Margerie Glacier 14. Altered zone east of Dundas Bay 5. Reid Inlet 15. West of Tarr Inlet 6. Sandy Cove A. Main arm of Dundas Bay 7. Lituya Bay placers B. West shore of Tarr Inlet 8. Mount Crillon gabbro C. Mount Merriam 9. Bruce Hills D. Miller Peak-Sandy Cove 10. Mount Brack E. Upper Berg Creek FIGUREl.-Map of Glacier Bay National Monument, Alaska, showing selected mineral deposits, geochemical anomalies, and outlines of some areas favorable for mineral deposits. 0, previously known deposits with economic potential; X, deposits of possible economic interest found by USGS investigations; .,geochemical anomalies. percent MoSz and 91,600,000 tons of material averaging 0.080 tween 400 feet above sea level and 300 feet below sea level. percent MoS? and that the fault-zone deposit contained These cores are reported to indicate grades of MoSa similar to 640.000 tons of material averaging 0.169 percent MoS2. Twen- those in our and ~~~~h~f~lv~samples. hofel's grade estimates are based mainly on channel samples and may be more representative than ours; none of his The Nunatak molybdenum prospect contains a large re- samples were analyzed for copper. serve of low-grade molybdenum ore, and if the current trends Three diamond-drill holes drilled by the American Explora- in price and demand for molybdenum continue, it may be tion & Mining Co. in 1966 explored parts of the deposits be- minable in the near future. ABSTRACT AND SUMMARY 3

BRADYGLACIER PROSPECT sulfide deposits rich in nickel and copper and possibly small The Brady Glacier nickel-copper deposits are exposed on amounts of platinum. two small nunataks in Brady Glacier (fig. 1, loc. 2). The The little-explored and prospected layered intrusive rocks prospect is covered by patented claims held by the Newmont of the Fairweather Range are potentially important because Mining Co. Published descriptions of the deposits are based they contain known resources and are favorable hosts for a on meager information (Berg and others, 1964, p. 115; Corn- variety of mineral deposits. However, they occur largely in wall, 1966, p. 37). The deposits are localized near the base remote and rugged terrain where prospecting, exploration, of layered gabbro and in adjacent periodotite that forms part and mining are difficult and costly. of the layered mafic and ultramafic igneous rock complex known as the Crillon-LaPerouse stock. They consist of pyrrhotite (F~I-~S),pentlandite ( (Fe,Ni) 9S8), and chalcopyrite The Alaska Chief copper prospect (fig. 1, loc. 3) consists (CuFeSz) that form disseminations, veinlets, and lenticular of patented claims on a massive sulfide deposit in tactite, masses as much as 35 feet long and 5 feet in diameter). The hornfels, and marble near a granitic mass. Workings at the prospect has been explored by 46 diamond-drill holes, many prospect consist of a cleared and scraped area about 150 feet of which were drilled through several hundred feet of ice long and 55 feet wide and an adit 40 feet long. The deposit is in the nearby glacier. exposed throughout the cleared area and less extensively in the adit. The lateral extent of the deposit could not be ascer- The nunataks have not been systematically sampled, but tained because its surface exposures are surrounded by examination of their rocks indicate that disseminated sulfides densely vegetated steep hillsides that lack outcrops. Little is are present nearly everywhere. The amounts are small, and the overall average grade would probably be less than 0.5 known of its subsurface configuration. The deposit consists of pyrite (FeSz) pyrrhotite (Fel-*S), chalcopyrite (CuFeSz), percent each nickel and copper. Several of the sulfide masses , bornite (CusFeS4), and sphalerite (ZnS), and their oxidized in the nunataks have been sampled, and the assays shows 2-3 derivatives. Chip samples from the cleared area contained percent nickel, 1-1.4 percent copper, and 0.25 percent cobalt. about 1 percent copper, as much as 4.377 ounces of silver per Individual massive sulfide lenses are small; however, five such ton, and lesser amounts of gold and zinc. Drilling or similar bodies on the nunataks have lengths ranging from 15 to 35 exploration will be required to determine the reserves of the feet and average widths of about 6 feet. The vertical extents deposits. The prospect has been briefly described by Reed of the lenses are probably comparable to these dimensions. (1938, p. 72,73) and by the Wrights (1937, p. 221, 222). Diamond drilling thus far has shown that low-grade nickel- copper mineralization is widespread in the gabbro-peridotite PLACERDEPOSITS NEAR LITUYA BAY complex, but more drilling is needed to establish continuity of Placer deposits that contain gold and other heavy minerals the higher grade zones. By analogy with known commercial are distributed irregularly along the beaches for about 20 deposits of a similar nature elsewhere, it is possible that, as miles northwest of Lituya Bay and 15 miles southeast of the the basal contact of the layered complex is approached at bay (fig. 1, loc. 7). There may be similar placers just offshore greater depth, higher grades of nickel and copper mineraliza- beneath the Gulf of Alaska. The deposits consist of concen- tion will be encountered. The information available to us is trations of heavy minerals in modern bare beach sands and in inadequate for making any reserve estimates, but the results older beach sands whose surfaces are covered by vegetation. of exploration may be considered sufficiently favorable to They have been worked intermittently since the early 1890's. encourage mining the deposits. Between 1894 and 1917 they produced gold valued at about $75,000 (Mertie, 1933, p. 135). Their production since 1917 has been minor. A little platinum has been recovered from the The layered mafic and ultramafic rocks of the Fairweather deposits. The placer deposits also contain concentrations of Range include 'the Crillon-LaPerouse and the Astrolabe- ilmenite and, to a lesser extent, of magnetite. The deposits DeLangle stocks of Rossman (1963a) and an inferred intru- have been investigated by Rossman (1957) and by Thomas sive mass near Mount Fairweather (fig. 1). These rocks have and Berryhill (1962, p. 37-40); both of these investigations been little explored and prospected. Descriptions of them and stressed their ilmenite content. They could be worked under brief accounts of their mineral deposits (fig. 1, loc. 8) are in favorable economic conditions for gold, and they also consti- Rossman (1963a) and in Kennedy and Walton (1946, p. tute a potential resource of titanium, and possibly iron. 67-72). Some layers in the layered complexes are known to contain MARGERIEPROSPECT large amounts of ilmenite in low-grade concentrations and The Margerie copper prospect (fig. 1, loc. 4) is in granitic lesser amounts of titaniferous magnetite. These and similarly rock and hornfels. Its deposits consist of pyrrhotite (Fel-=S)- mineralized layers that undoubtedly occur elsewhere in the chalcopyrite (CuFeSa) lenses, copper-bearing altered zones complexes are a potential resource of titanium and iron. Minor about 6 feet thick, and thin quartz veins. All the deposits amounts of vanadium are associated with the ilmenite and examined appear to be too small or too lean to be exploitable; magnetite and constitute a remotely possible byproduct. Pods but the prospect has been little explored, and indications of and lenses of massive sulfides, chiefly pyrrhotite (Fel-=S) mineralization are widespread in the general vicinity. The with subordinate chalcopyrite (CuFeSz), have been reported deposits were discovered in 1960, but they have not been from some of the layers and contact zones of the complexes. described in the geologic literature.

By analogy with other layered mafic and ultramafic intru- REID INLETGOLD AREA AND SANDYCOVE PROSPECT sive masses, the poorly exposed and apparently largely con- The gold lodes of the Reid Inlet gold area (fig. 1, loc. 5) cealed ultramafic rocks of the lower part of the complexes are and the Sandy Cove prospect (fig. 1, loc. 6) occur in narrow possible hosts for chromite and platinum deposits. The pe- nonpersistent quartz veins and in the contiguous altered wall- ripheral and lower zones of the complexes may also contain rock. They are probably too small and too sporadically dis- MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

tributed to be minable now, but they probably would be GEOCHEMICAL ANOMALIES amenable to small-scale mining during more favorable eco- The geochemical sampling program disclosed numerous nomic conditions. areas with anomalous contents of metals. Five areas that The total value of gold production from mines in the Reid contain significant anomalies were detected by examination Inlet area was about $250,000 (Rossman, 1959, p. 39). The of stream sediments, but most of the anomalies were revealed geology and ore deposits of the Reid Inlet area have been by analyzing mineralized rock samples. The geochemical sam- described by Rossman (1959). The Sandy Cove prospect was pling also provided information about "background" concen-

described by Reed (1938, p. 65-68). tration of elements in geologically-. different terranes. Al- though some of the anomalous areas were revisited and OTHERPREVIOUSLY KNOWN DEPOSITS resampled in detail, none have been thoroughly evaluated; Several other mineral deposits, such as those on Willough- almost all, the five significant anomalies in particular, deserve by, Francis, and Marble Islands (Reed, 1938, p. 69-72), west further sampling and search for the causes of the anomal- of Rendu Inlet and on the southern part of Gilbert Island ously high metal contents. The data now available do not (Rossman, 1963b, p. K48-KSO), have been reported in the establish whether specific anomalies are derived from con- monument. All of these probably have low potentials for cealed mineral deposits with economic potential or from mineral production. areas of widespread, but, nevertheless, insignificant mineral- DEPOSITS DISCOVERED DURING 1966 ization. Comparison of the geochemical mais with the min- Several localities that contain mineral deposits of potential eral-deposit maps shows that not all known mineral deposits significance were discovered during the 1966 fieldwork (fig. have geochemical anomalies detectible by methods used in 1). No ranking is implied by the sequence of the descriptions this study; the various factors causing this problem are dis- that follow. Most of these deposits are poorly exposed and cussed in the main part of this report. The discrepancy does require additional work for their satisfactory evaluation. Our not lessen the importance of the anomalies that were mapped. brief examinations and limited sample data indicate that they A significant geochemical anomaly (fig. 1, loc. A) with as warrant exploration. much as 150 pprn (parts per million) tungsten and 30 pprn The Bruce Hills deposits (fig. 1, loc. 9) are in and near a tin occurs in stream sediments derived from light-colored fault zone that cuts granitic rocks. They consist of stockworks granitic rocks and adjacent metamorphic rocks near the main of quartz veins, disseminations, and fracture coatings, and arm of Dundas Bay. These stream-sediment samples were col- contain pyrite (FeSs), chacopyrite (CuFeSs), pyrrhotite lected late in the fieldwork, and there was no opportunity to ( F~I-~S),molybdenite (Moss), and malachite (CuzCo3(0H)z). resample the streams in the area. Geologically, the area is The deposits near Mount Brack (fig. 1, loc. 10) occupy veins favorable for tungsten and tin deposits. and altered zones in metamorphic rocks. They consist of Another unevaluated significant anomaly is on the west sphalerite (ZnS), galena (PbS), and probably a sulfosalt, and shore of Tarr Inlet (fig. 1, loc. B) not far south of a copper contain minor amounts of silver. deposit. This anomaly contains 700 pprn copper, 200 pprn lead, Deposits north of White Glacier (fig. 1, loc. 11) are localized 500 pprn tin, 1,000 pprn zinc, and anomalous amounts of other in small altered zones that cut limestone and marble and in metals also. The anomaly is within a north-trending belt of large altered zones that cut mafic volcanic rocks. The altered mixed granitic and undifferentiated metamorphic rocks. The zones in the limestone and marble contain chalcopyrite belt contains many small mineral deposits as well as the Reid (CuFeSz), particularly near intersections with dikes that cub Inlet gold area and appears favorable for base-metal the zones, and some altered zones in the volcanic rocks carry deposits. as much as 2 percent zinc. Anomalously high total heavy-metal, molybdenum, and A large mineralized altered zone is exposed in steep cliffs strontium contents characterize an anomaly in stream sedi- south of Rendu Glacier (fig. 1, loc. 12) near the contact ments derived from a complex geologic terrane near Mount between light-gray granitic rocks and metamorphic rocks. A Merriam (fig. 1, loc. C) Large iron-stained zones in hornfels sample of float from this zone contained 0.2 percent copper. and marble adjacent to intrusive granitic bodies there may be Mineralized joint coatings of unknown extent occur in the source of the anomalous elements. In as much as these coarse-grained dioritic rocks at Gable Mountain (fig. 1, zones have not been sampled and the stream sediments have loc. 13). The copper minerals in the joints are malachite not been resampled in detail, the anomaly is unevaluated; it (CusCOs(0H)r) and chrysocolla (CnSiOa . 2H20). A compos- is considered significant, however. ite grab sample from the deposit contained 0.1 percent copper Sediments from several streams in the vicinity of Sandy and minor quantities of silver and molybdenum. Cove and Miller Peak (fig. 1, loc. D) have anomalous total Low-grade copper deposits occur in a large altered zone heavy-metal, molybdenum, and strontium contents. These east of Dundas Bay (fig. 1, loc. 14). The altered zone, which is stream sediments have been resampled and the anomaly in quartz-rich metamorphic rock that locally is bounded by verified, but the source of the high metal content is not volcanic rocks, is as much as 300 feet wide and at least 1 mile known. Granitic bodies intrude marble in this area, and there long. Samples from the altered zone contained as much as 0.2 may be either widespread low-grade mineralization or hidden percent copper and traces of silver, molybdenum, and lead. mineral deposits associated with the granitic rock-marble Disseminated sulfides and quartz veinlets that carry copper contacts. minerals occur in siliceous lenses within light-colored granitic Anomalously high chromium and copper values occur in the rocks west of Tarr Inlet (fig. 1, loc. 15). A sample representa- sediments of upper Berg Creek (fig. 1, loc. E) near the monu- tive of the lenses yielded 0.1 percent copper. ment boundary. This anomaly has not been resampled or Numerous other deposits, including a few that probably evaluated, but the geology of the drainage area suggests that have potential equal to those described here, were found the metals may be derived from a volcanic terrane. The con- during our investigations. tiguous area outside the monument has not been examined. INTRODUCTION 5

FAVORABLE AREAS the monument and is probably the most likely area in which Specific areas in the Glacial Bay National Monument can be to find hidden molybdenum-copper deposits. selected as being more favorable for mineral deposits than A potentially favorable area (fig. 1, near loc. E) is included others from consideration of the distribution and characteris- in the eastern end of the area just described. Granitic intru- tics of known mineral deposits, the results of geochemical sive rocks, metamorphic rocks somewhat similar to those sampling, and the geology. There is no certainty that these near Muir Inlet, and a generally higher background content areas contain significant hidden mineral deposits, but they are of metals in stream sediments all suggest that the area on liklier to than other areas. both sides of the boundary in the northeastern part of the The contact zones between granitic intrusive bodies and monument may contain undiscovered mineral deposits of un- marble and other metamorphic rocks constitute favorable known size and significance. areas for several types of mineral deposits. Such contact Glacier Bay National Monument contains a few mineral zones are abundant in the monument east of the Fairweather deposits that are likely to be minable in the near future; some Range. Spatial and probably genetic relations exist between that may be minable in the more distant future, but which many of the known mineral deposits and granitic masses. In are not well enough known to be evaluated; some that prob- some places, such as the Alaska Chief copper prospect and ably would be minable with economic or technologic changes; the Queen and Rendu Inlet iron deposits, the indications of and many that are insignificant. The economic potential for genetic relationships are strong. petroleum, coal, and nonmetallic commodities in the monu- Another association between mineral deposits and granitic ment is low. rocks may be exemplified by the light-colored unfoliated granitic rocks that occupy a northwest-trending belt from INTRODUCTION Dundas Bay (fig. 1, near loc. A) to beyond Johns Hopkins Inlet (pl. 1). With the possible exception of the Reid Inlet The U.S. National Park Service, in November gold deposits, which are rather distant, only a few mineral 1965, requested that the U.S. Geological Survey deposits are known to be associated with this belt. However, study the mineral resources and mineral-resource po- many metallic elements are generally concentrated during the tential of Glacier Bay National Monument, Alaska. late evolutionary stages of similar granitic rocks, and such The purpose was to provide factual information for rocks are associated with deposits of tin, molybdenum, tungsten, beryllium, gold, and other metals. the use of the National Park Service in planning the The layered gabbro and ultramafic rock complexes of the future development of the monument for the public. Fairweather Range and their border zones (fig. 1, locs. 2, 8) A Geological Survey field party investigated the are favorable hosts for nickel, copper, iron, titanium, plati- mineral deposits of the monument and their regional num, and perhaps vanadium deposits of various types. These geologic setting during the summer of 1966. Three complexes are probably more likely to contain significant undiscovered mineral deposits than any other favorable area concurrent methods of study were used. The most in the monument. However, exploration and development important method consisted of detailed field exami- problems caused by the extremely rugged terrain and severe nation and a sampling of previously known deposits weather would be great. The beach and possible submarine and of new deposits found during the course of the placers on the Pacific Ocean shore west of the Fairweather overall investigation. The second involved extensive Range (fig. 1, near loc. 7) contain iron- and titanium-bearing heavy minerals derived from the gabbro and ultramafic rock collection and geochemical analysis of stream-sedi- complexes as well as some gold and platinum. This area prob- ment samples from all major drainages. About 2,700 ably contains very large low-grade placer deposits. stream-sediment and mineralized rock samples were A favorable belt of mixed rocks, including granitic intru- analyzed. The third method was reconnaissance geo- sions and many kinds of metamorphic rocks, extends from the logic mapping, which delineated the major rock units Brady Glacier northward past Reid and Johns Hopkins Inlets forming the host rocks of the mineral deposits, de- and along the west side of Tarr Inlet (fig. 1, south of loc. 5 north to 4). This belt contains many large iron-stained zones termined the bedrock compositions of the geochemi- and many known mineral deposits, including those in the Reid cally sampled drainage basins, and revealed new min- Inlet gold area and the Margerie prospect. The marble and eral deposits and areas favorable for deposits. metamorphosed volcanic units are favorable hosts for de- The investigation successfully covered almost all posits and are cut by at least two types of granitic intrusions. In the Muir Inlet area and in areas to the east and west of the monument, with only the high part of the Fair- the inlet is a structural zone with east to west trends (fig. 1, weather Range (fig. 2) and the Pacific coastal strip near locs. 1 and 9), rather than the north-northwest to southwest of that range left unvisited. Eighty-eight min- southeast trends which typify the monument as a whole. The eral deposits, both newly found and previously cause of these aberrant trends is not known, but the east- west zone is congruent with an area characterized by dikes known, are described in this report. Of this number, and plugs of porphyritic intrusive bodies whose compositions 16 deposits considered to be of greater economic in- are similar to many of the granitic rocks in the monument. terest than the rest are described in detail. Many In places, as at the Nunatak molybdenum prospect, the coun- insignificant mineral deposits were visited and Sam- try rock has been shattered by these shallow-depth intrusions. This area of congruent east-west trends and porphyritic in- pled; their locations are given in this report, al- trusions contains most of the molybdenum deposits known in though they are not described. MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

FIGURE2.-Index map showing Glacier Bay National Monument, Alaska, and geologic provinces within the monument. The geochemical sampling and analysis defined ca (fig. 2). Scenically and glaciologically, it is one of several significant geochemical anomalies, including ;he most spectacular parts of Alaska. The magnifi- some in areas known to contain mineral deposits. :ent Fairweather Range culminates in Mount Fair- Most of the amomalies have not been evaluated com- weather (15,300 ft) and forms an awe-inspiring de- pletely, although some were resampled in detail. lride between the Gulf of Alaska, only 12-15 miles The reconnaissance geologic mapping developed west of the range crest, and the deep fiords of Gla- the regional framework of the mineral deposits and :ier Bay proper, as close as 8 miles east of the crest. the background information essential to the inter- l'he rapid recession of the glaciers in Glacier Bay pretation of the geochemical data. The mapping also las not only provided an unparalled opportunity to contributed greatly to the knowledge of the regional study recessional glacial phenomena but has also ex- geology of this northern part of southeastern posed older glacial deposits and related features that Alaska. Are evidence for a complex sequence of relatively The geochemical sampling program relied heavily young glacial events. on rapid analyses of the samples. All stream-sediment The monument is located some 100 miles west- samples were dried and sieved to -80 mesh shortly northwest of Juneau, Alaska, (fig. 2) and is acces- after collection, and the total heavy-metals content sible only by water or air. Small boats can reach (copper, lead, and zinc) was determined on a split by Glacier Bay from the Inside Passage waters by way conventional field tests (Huff, 1951; see "Methods of Icy Strait. Reaching the Pacific coastal part of of analysis"). The samples were then airmailed to the monument involves an exposed and often rough the Geological Survey laboratories, where spectro- run through Icy Strait and around Cape Spencer into graphic analysis for 30 elements was made. Results the open ocean. Boating within Glacier Bay itself is were airmailed back to the field, usually arriving less difficult and conditions are generally good dur- within 2-3 weeks from the time the sample was col- ing the summer months, although strong tides and lected. Mineralized rock samples were in some cases sudden winds can abruptly change conditions. Char- screened by the total-heavy-metals test in the field ter float-equipped aircraft from Juneau and Haines before being sent to the laboratory for spectro- reach the Bay in about an hour and can land in most graphic analysis or assay. Samples were analyzed fiords, except where icebergs are numerous. Ski- spectrographically by Nancy M. Conklin, J. C. Hamil- wheel aircraft have landed on several of the large ton, R. G. Havens, Harriet G. Neiman, and A. L. glaciers. Alaska Airlines maintains regular daily air Sutton, Jr. service to the permanent community at Bartlett D. A. Brew wrote the introductory material and Cove (monument headquarters) during June, July, regional geologic summary and prepared the lithol- and August and to Gustavus (just outside the monu- ogy for the combined lithologic-mineral deposit loca- ment) all year. tion map. E. M. MacKevett, Jr., wrote all but one of The monument has an area of about 3,900 square the descriptions of the mineral deposits, incorporat- miles, excluding the water areas outside Glacier Bay ing geochemical material prepared by L. C. Huff. proper. Of this area, 530 square miles (or about 14 MacKevett was assisted by J. G. Smith in organizing percent) consists of the 50-mile-long Glacier Bay and data, by R. J. Wehr with laboratory studies, and by its various arms and inlets. About 830 square miles Susan R. Bartsch with drafting. H. R. Cornwall (or 21 percent) is covered by glaciers. Much of the wrote the description of the Brady Glacier deposit. remaining 2,550 square miles is covered by snow all George Plafker is responsible for the summary of but 3 or 4 months of the year. petroleum prospects in the Gulf of Alaska Tertiary province. C. C. Hawley prepared the maps showing The land areas in the monument are all mountain- the results of geochemical sampling and the discus- ous, except for a few broad plains underlain by gla- sions of geochemical anaomalies. Hawley and Huff cial outwash in the southern and east-central parts. wrote the section discussing the geochemical sam- Four general types of mountains are found, reflect- pling program. MacKevett and Brew wrote the "Ab- ing differences in total relief, glacial history, and stract and summary." vegetation development. Toward the north-northwest, the lower, rounded summits and, thickly for- GEOGRAPHIC SETTING ested steep slopes, typical of the Chilkat Range and Glacier Bay National Moument, Alaska, is an area the southern parts of the monument, give way to of rugged glacier-clad mountains and steep-sided slightly higher, bare, serrated peaks and ridges that fiords within the St. Elias Mountains physiographic border steeply narrow steep-gradient valleys. Still province in the northwestern part of southeast Alas- farther north, coalescing valley glaciers and ice- 8 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASU fields convert similar peaks and ridges to nunataks. least precipitation, that the fall and early winter In the highest parts of the monument, the precipi- months have the most, and that the temperatures, tous peaks of the Fairweather Range have impressive are, in general, mild in both summer and winter. ice-fluted flanks that descend to heavily crevassed valley glaciers below. TABLE1.-Average precipitation and average temperature fo~ The glaciers in the monument range from small Cape Spencer (1937-66) and Gustavus (1940-66) hanging types common on most peaks to ones of [Data from U.S. Weather Bureau. 1937-661 Precipitation Temwrature great expanse, such as the Brady Glacier Icefield, (inches) (degrees Fahrenheit) Cape Cape 240 square miles in area; but most are valley glaciers Month Spencer Gustnvus Spencer Gustavua -- -- 1-3 miles wide, which head in cirques or icefields at January ...... 8.14 4.44 32.05 25.90 an altitude of 4,000-6,000 feet and descend almost to February ...... 6.04 3.13 33.39 28.80 tidewater. The glaciers are, in general, quite cre- March ...... 6.31 2.89 35.29 32.39 April ....-.-...-...5.47 2.32 40.12 39.41 vassed and are easily traversed only in early sum- May ...... -.-.--.-6.60 2.86 45.12 46.17 mer. The Brady Glacier and Takhinsha Mountain June ...... 5.17 2.59 47.36 52.24 July ...... 7.55 4.04 50.31 55.48 Icefields are snow covered in their higher parts dur- August ...... 9.46 4.42 52.55 54.77 ing most summers and are therefore more easily September ..... 14.33 6.95 48.97 49.75 October ...... 16.70 9.31 44.20 42.26 traversed. November -....-13.28 6.19 37.65 33.38 December ...... 10.12 5.01 33.68 28.23 At present, the ice in the glaciers may be as much Annual as 1,000-1,500 feet thick in some of the deeper valley average 1 110.64 54.30 42.20 40.75 glaciers and as much as 1,000 feet thick on the Through 1966. broader and higher icefields. Adjacent to nunataks and valley walls the ice thickness increases rapidly, PREVIOUS INVESTIGATIONS but the bedrock surface may be very irregular lo- Glacier Bay has attracted many geologists and cally. Except for some stagnant ice at low altitude, glaciologists during the past 90 years, mainly be- all the glaciers in the monument are active, and there cause of the rapid recession of the glaciers. Few of are signs that some are growing. the earliest explorers and scientists came with eco- The fiords of Glacier Bay are steep sided and nomic interests in mind, but by 1892 some prospec- deep, local depths being greater than 1,000 feet. tors were in the area (Rossman, 1963b). In 1906, Shallower areas are found only near the broad ex- F. E. Wright and C. W. Wright (1937) studied the panses of outwash deposits in the southern part of Johns Hopkins Inlet area and other parts of the the monument and over the small deltas associated monument; in 1919, J. B. Mertie visited the area. with tidewater glaciers and the larger streams. Buddington (Buddington and Chapin, 1929) visited Most of the streams in Glacier Bay National Mon- the monument in 1924. Somewhat later, several other ument are small, have steep gradients, and drain Geological Survey geologists (Reed, 1938; Twenho- areas of only a few square miles. In the southern part fel and others, 1949; Kennedy and Walton, 1946) of the monument, however, several short, but vigor- visited specific mineral deposits then of interest or ous, rivers drain relatively large areas. These rivers, under development. Economic interest in the monu- most of their tributaries, and many of the other ment was lessened by prohibition of prospecting streams are swift and difficult to cross on foot. Al- from 1924 to 1936. most all streams, regardless of size, were found to In 1942, Twenhofel (1946) studied the Muir Inlet carry active stream sediment suitable for geochemi- Nunatak molybdenum deposit in detail, and the U.S. cal analysis. Bureau of Mines sampled the deposit (Sanford and The climate of the monument is generally mari- others, 1949). In 1949, D. L. Rossman began geologic time in the southern and lower altitude parts. In- studies in the monument, which are summarized in creasing altitude in the Fairweather Range, the three reports (Rossman, 1959, 1963a, b). In 1950-51, presence of many glaciers, and the rain-shadow effect J. F. Seitz studied the geology around Geikie Inlet of the Fairweathers tend to make the northern part (Seitz, 1959). Don J. Miller studied the Gulf of of the monument less humid and more like interior Alaska Tertiary province for several years; his map- regions. No weather data are available for the ping within the monument was incorporated by northern or higher altitude parts, but data are avail- Rossman (1963a) after earlier open-filing (Miller, able for Cape Spencer and Gustavus (fig. 2). These 1961). Reconnaissance studies in the Juneau data, summarized in table 1, show that the months 1:250,000 quadrangle part of the monument were from February through July or August have the made during the period 1956-58 (Lathram and INTRODUCTION 9 others, 1959). A few mining companies, notably Fre- examine the outcrops and obtain stream-sediment mont and Moneta-Porcupine, prospected in the mon- samples. Ridges accessible by helicopter and suitable ument during the late 1950's and early 1960's. for walking were traversed by geologists and examined in detail. The rougher ridges were examined PRESENT INVESTIGATION aerially from the helicopter, and spot landings for The Geological Survey party that made the studies outcrop study were made wherever possible. Some reported herein was led by D. A. Brew and E. M. streams were traversed on foot to gather sediment MacKevett, Jr., with Brew overseeing the operations samples and bedrock information, but most were and reconnaissance geologic mapping, and Mac- sampled during helicopter spot landings. Kevett, the studies of mineral deposits and the mineral-resource evaluation. In addition to Brew and ACKNOWLEDGMENTS MacKevett, the party consisted of Arthur B. Ford, The cooperation of the U.S. National Park Service Charles C. Hawley, Lyman C. Huff, A. Thomas staff at Glacier Bay National Monument contributed Ovenshine, Arthur S. Radtke (until July 9), James greatly to the efficiency of the field operation. We G. Smith (after July 13), geologists, and Raymond J. should like to thank, in particular, Robert B. Howe, Wehr, physical science technician. Huff and Hawley Superintendent, Charles Janda, ranger, and Kenneth coordinated the geochemical studies throughout the Youmans. project. Henry C. Cornwall joined the project tempo- We also thank the Newmont Mining Co. and rarily early in August to study the Brady Glacier American Exploration & Mining Co. for their coop- deposit. eration in the appraisal of the Brady Glacier copper- The USGS R/V Don J. Miller, a 105-foot power nickel and the Muir Inlet Nunatak molybdenum de- barge manned by Robert D. Stacey, master; Allen posits, respectively. L. F. Parker of Mount Parker Z. Komedal, chief engineer; and John J. Muttart, Mining Co., visited the Survey geologists in the field cook-seaman, was used as base for the field opera- on one occasion, as did Lawrence Duff, a private tions. The project was supported by a helicopter operator, both aided in locating prospects in the Reid operated by National Helicopter Engineering Co., Inlet area. with Dan Ellis, pilot, and Howard Grannell, mechanic. REGIONAL GEOLOGY The party started fieldwork on May 24, 1966, and Knowledge of regional geology is important to had excellent weather during May, June, and July. this mineral resource appraisal in three ways: (1) Frequent storms in August and early September the study of the rocks and their distribution aids in hampered the studies, and the party left Glacier Bay interpreting the geochemical data; (2) knowledge of on September 5,1966. the geologic framework of the known deposits leads The field studies were affected to a certain ex- to geologic insights about particular environments tent by the amount of snow cover present. There- that need to be carefully evaluated in areas where no fore, the sequence in which the different parts of the deposits are yet known; and (3) projection of known monument were studied is significant. In late May rock units from mapped areas into unmapped areas the investigations covered shoreline and island ex- provides a basis for appraising the mineral potential posures along the west side of Glacier Bay from of the unmapped areas. Ripple Cove to Blue Mouse Cove; in June, the north- The emphasis in this report is on the gross lithic eastern and east-central parts of the monument; in and structural framework of the monument, and no July, the north-central, some of the northwestern, detailed stratigraphic information is presented. The and the southeastern parts; and in August, the lithologic map (pl. 1) shows the major rock types and south-central part, the west-central, and some of the indicates the general geologic associations of the northwestern areas. In general, the amount of snow 1 mineral deposits. diminished rapidly through June and early July and Glacier Bay National Monument consists of five slowly in July and August; in September the terrain distinct geologic provinces, each of which is char- above 4,000 feet was covered by new snow. acterized by specific structural and lithologic fea- The results of the field studies are also a function tures. The Coastal province lies west of the Fair- of the way the data were gathered. All shoreline ex- weather fault (fig. 2). The Fairweather province is posures within Glacier Bay and most of those along 1 east of the Fairweather fault and extends eastward Icy Strait were traversed by slow-moving outboard- to the Brady Glacier, The Geikie province extends powered skiff, and frequent stops were made to north-northwestward through the center of the mon- 10 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA ument; at its northern end, it merges with the east- Tertiary strata unconformably overlie the meta- west-trending Muir province. The Chilkat province morphosed Mesozoic strata in the Coastal province; occupies the southeastern part of the monument. The they consist of at least 12,000 feet of Miocene and features which characterize these provinces are dis- Pliocene sandstone, shale, and minor volcanic rocks cussed below. and conglomerate. The Tertiary strata probably extend offshore onto the continental shelf. STRATIGRAPHY The bedrock stratigraphic section in the Glacier INTRUSIVE ROCKS Bay National Monument ranges from Early Silurian Intrusive rocks of probable late Mesozoic and through late Tertiary in age, with significant gaps in perhaps Tertiary age dominate the Geikie and Muir the late Paleozoic, late Mesozoic, and early Tertiary. geologic provinces and occur in all the other prov- The section is not well understood because of scanty inces to a lesser extent. Some of the foliated granit- fossil record, apparent abrupt facies changes, wide- ic rocks discussed below may actually be spread metamorphism, and the disruption caused by metamorphic rather than intrusive, but they are intrusive bodies. closely associated with the intrusives. The distribu- The Paleozoic part of the section crops out tion of the different intrusive rocks is shown on through the east half of the monument and is par- plate 1, from which it is apparent that most of the ticularly well exposed in the Chilkat province (fig. known mineral deposits are spatially related to 2). A stratigraphic thickness of 20,000 to 30,000 feet intrusions. is estimated to be present. Detrital clastic rocks, Most of the intrusives in the monument are meso- mostly graywacke and argillite, of Silurian and pos- zonal foliated granitic rock bodies. Hornblende sibly Dmevonian age are dominant; some discontinu- quartz diorite, hornblende diorite, and biotite-horn- ous nonfossiliferous limestones are also present. To blende quartz diorite are most common, but some the north, these rocks appear to grade into a com- biotite-hornblende granodiorite also occurs in foli- parable section that contains significant amounts of ated bodies. In general, foliation is parallel to that in volcanic rocks. In the western and northwestern the adjacent metamorphosed country rocks, but local parts of the Chilkat province are exposures of thick divergences are present. This relation suggests that reef limestones whose correlation with the rest of these bodies were intruded before the end of the the section is uncertain. Carbonate and detrital clas- episode in which the country rocks were deformed. tic units of Middle Devonian age occur in the north- Most of the foliated granitic bodies contain, and are central and northwestern parts of this province, and locally bordered by, areas of hornblende quartz di- also in the Muir province. The relations between the orite gneiss, which commonly contains abundant in- known Devonian rocks and the known Silurian rocks clusions and is in some places very heterogeneous. are obscured by structural complexities and poor Most of the mesozonal to epizonal unfoliated fossil control. granitic rocks in the monument are in the Geikie The Paleozoic rocks throughout most of the Chil- province, but isolated bodies also occur in the Fair- kat province are not greatly metamorphosed, except weather, Muir, and Chilkat provinces. Because these adjacent to intrusions. In the Geikie and Muir granitic bodies all lack well-developed foliation, provinces, these same rocks locally are highly meta- their intrusion is considered to postdate deforma- morphosed, and it is difficult to correlate them with tion. Compositionally, the unfoliated granitic rocks their less metamorphosed equivalents. range from hornblende-biotite granodiorite to bi- Mesozoic strata are found in the Coastal and Fair- otite granite. These bodies generally are free of dis- weather provinces along north-northwest trends tinctive border zones, but they do contain large similar to trends in the Mesozoic rocks of nearby hornfels inclusions. The intrusion at Johns Hopkins Chichagof Island. They include three gross units of Inlet (fig. 2; pl. 1) is unusual in that it is associated unknown thickness: (1) a low-grade metamorphic with very extensive and spectacular border zones of unit derived from mixed detrital clastic rocks and such inclusions. volcanic rocks, found only west of the Fairweather fault; (2) a biotite schist unit; and (3) an amphibo- A variety of dike rocks, ranging from aplites to lite unit. The schist unit is derived from a gray- lamprophyres, with andesites and diabases the most wacke-shale sequence known to be of Jurassic and abundant, were mapped in the monument. They are Cretaceous age on Chichagof Island, and the am- particularly common in the western and northwest- phibolite may be equivalent to volcanic rocks of ern part of the Chilkat province and in the meta- probable Triassic age in that same area. morphic rocks in the Muir province. Many of the GEOCHEMICAL STUDIES 11 dikes probably are relatively young, and in many The Geikie province is characterized by parallel places have mineral deposits associated with them. north- and northwest-striking foliations in the coun- The majority of dikes strike east or northeast, and try rocks and in the numerous granitic bodies. The they tend to occur in subparallel swarms. distribution of country rock units implies complex A layered gabbro complex occupies a large part of folding, but the intervening intrusive masses make the Fairweather province, and at least two other exact analysis difficult. In the northwestern part of bodies of gabbro occur nearby. The gabbro in the the province, northwest strikes and steep westerly synclinal structure of the largest complex is more dips of contacts suggest that most of the rocks in than 30,000 feet thick. The regularly layered center the province may be stratigraphically below units of this mass is commonly bordered by a structurally mapped in the adjacent Fairweather province. Geikie complex zone of gabbro and ultramafic rocks that province also contains a prominent north-northwest- locally contains important sulfide deposits. Other striking zone of discontinuous faults. mineral deposits are known to occur within the The structures in the Muir province are very simi- layered portion. lar to those in the Geikie province, but contacts and foliations strike west to northwest and dip moder- STRUCTURE ately to steeply to the north. These attitudes in the Each geologic province in the Glacial Bay Nation- country rocks may be related to the configuration of al Monument has characteristic structural features, the major intrusive bodies, but they may also repre- and two provinces-Muir and Chilkat-have unusual sent preintrusion attitudes in part. In any case, the complications. Certain features, however, are com- abrupt change from northerly trends near Muir Inlet mon to the whole monument: (1) a dominant north to westerly trends only a few miles to the north sug- to northwest strike of all units and planar structures gest that one or more major structural disconti- within all units, (2) steep dips, and (3) repetition of nuities are involved. The distribution of map units in section by large-scale folds. The major faults in the some areas between intrusive masses suggests that monument also strike north to northwest, although large folds, overturned to the south, may be present. there are minor local divergences from this pattern. The same abrupt change in strike has been In the Coastal province the moderately to gently mapped in the northern part of the Chilkat province, dipping Tertiary strata form two northwest-trend- near Tidal Inlet. There, the situation is complicated ing synclines and one anticline, which have been dis- by an east-west fault zone and, farther to the east, placed vertically by northwest-striking faults. Struc- by an important high-angle reverse fault that brings tures in the underlying Mesozoic rocks are not well relatively simply folded Devonian strata over more known but probably are similar to those in the adja- highly folded Silurian(?) rocks. Outside the area of cent Fairweather province. these complications, the rocks in the Chilkat province The Fairweather fault, which separates the Coast- are characterized by northwest strikes, moderate to al and Fairweather provinces, is part of a high-angle steep northeast dips, and large amplitude folds over- fault system that extends for more than 280 miles turned to the southwest. from Yakutat Bay on the north to Chatham Strait and western Baranof Island on the south. The seg- GEOCHEMICAL STUDIES ment of the fault within Glacier Bay National Geochemical studies in Glacier Bay National Mon- Monument is near the central part of the system. ument consisted of the collection, analysis, and sub- The dominant fault movement is inferred to be ver- sequent interpretation of more than 2,700 samples tical, with the west side down; but both historic dis- including (1) 1,200 stream-sediment samples, (2) placement (Tocher and Miller, 1959) and inferred 1,000 altered or mineralized rock samples, (3) 500 older movements farther south (Loney and others, soil samples (4) 30 unaltered and unmineralized 1967) suggest that a right-lateral component is also background level samples, and a few (5) panned present. stream-concentrate samples, (6) water samples, and Steeply dipping north- and northwest-striking (7) glacial-moraine samples. The resulting basic foliation characterizes the Fairweather province, data and preliminary interpretations provide only a and the map units apparently are repeated by large skeletal framework, and we believe that further geo- folds. The emplacement of the large gabbro bodies chemical interpretation of these data is possible. In had little structural effect on the country rock, particular, the relations between bedrock lithic types except close to the contact. and metal content of locally derived stream sedi- 12 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA ments should be considered in detail. The following trographic and THM tests are semiquantitative; but, interpretations are preliminary and inconclusive. within limits of error, comparison of the THM and Stream-sediment samples provide the greatest spectrographic analyses permits assignment of some amount of available geochemical data on the com- anomalies to copper, lead, or zinc. For example, the position of the rocks and surficial deposits and on TIlM test is especi;dly sensitive to zinc, an element abnormal accumulations of metals, which might in- that has a poor spectrographic sensitivity (table 2). dicate the presence of undiscovered buried mineral Stream-sediment samples that have high values of deposits. The density of strearn-sediment samples TIIM and low spectrographic values of copper and varies greatly because large areas in the monument lead are therefore believed to have anomalous con- have glacial, rather than normal, stream drainage. In centrations of zinc. areas of normal drainage,- there is more than one sample per square mile ; in the glacier-covered areas, TABLE2.-Detection limits, in parts per million, fo~some elements determined by the six-step and direct-reader spec- the samples are much more widely spaced. trographic methods The results of the stream-sediment studies are 1 Spectrographic method Spectrographic method given in figures 3-7, on plates 2-8, and in tables Six-step Direct-reader 1 Six-step Direct-reader 4-8. The concentrations of total heavy metals, chromium, copper, lead, molybdenum, and nickel are shown on individual maps, and one map (131. 8) sum- marizes other elements, such as arsenic, beryllium, bismuth, cadmium, silver, strontium, tin, tungsten, and zinc, which mere detected in anomalous amounts. Complete analytical data are given for several promising areas on separate maps and in tables. The analytical data derived from other samples are incorporated in the sections on mine and prospect dmescriptions. The spectrographic method supplements the THM test because the latter does not detect elements METHODS OF ANALYSIS such as chromium, molybdenum, nickel, tin, and Most samples were analyzed twice, first by n tungsten. These and other elements are detected by field geochemical prospecting test for total heavy spectrographic analysis if they are present in con- metals (hereafter referred to as THM) and then centrations as high or higher than those given in ta- spectrograpl~icallyin the laboratory. The results of ble 2. The sensitivity for elements such as cobalt, the THM tests were available 1 or 2 days after Sam- copper, chromium, molybdenum, and nickel is low pie collection and were used to guide further Sam- enough to detect minor concentrations of these ele- pling. The results of the sl>ectrographic analysis ments, but the sensitivity for gold, tungsten, and zinc were available to the field party within 2-4 weeks. is high enough that these elements need to be mark- The THM field test was made in a portable labora- edly enriched to be detectable. tory aboard the R/V Don J. Miller. The test is of the Two slightly different spectrographic methods type described by Huff (1951) in which the sample were used, referred to in table 2 as the six-step and is digested by heating with acid, and the dissolved direct-reader methods. The six-step method is simi- metal content determined by dithizone. This type of lar to that described by Myers, Havens, and Dunton TIlM test extracts much more of the zinc, copper, (1961) in that the concentrations are measured visu- and lead contained in the sample than does the com- ally from photographic plates; it differs in that con- monly used cold citrate soluble THM test described centration are reported in thme six-step geometrical by Hawkes (1963). The more complete extraction is array, 1, 1.5, 2, 3, 5, 7,. . . , instead of the three-step of considerable importance at Glacier Bay because array, 1, 3, 7, . . . . The direct-reader method refers the oxidation of the rocks there varies widely, and to a direct-reading spectrograph in which the con- more of the metal may be tightly bound than in a centrations are measured automatically by photo- more temperate or thoroughly weathered region. It multiplier tubes. The two methods are comparable in should be emphasized that the THM test samples only sensitivity and accuracy for most of the elements the acid-soluble part of the contained zinc, copper sought (table 2). and lead. The spectrographic method, however, mea- In addition to routine THM and spectrographic sures virtually all the metal present. Both the spec- analyses, many miner;ilized rock samples were ana- GEOCHEMICAL STUDIES 13 lyzed for molybdenum and gold in the laboratory by COPPER sensitive chemical methods. Copper ranges from about 5 to about 700 pprn in stream-sediment samples from the monument. The SAMPLING AND SAMPLE PREPARATION median copper content is about 40 ppm, based on the Stream-sediment samples were collected from both set of 636 samples (pl. 3) analyzed by the six-step large and small streams. Most of the streams sam- method. About 95 percent of the samples contain less pled were flowing, but some samples were taken from than 100 ppm, and the samples that contained 100 the dry beds of intermittent streams. Clayey and pprn or more copper are considered markedly silty sand was collected; this material is generally anomalous. present in considerable abundance in the major LEAD streams, but may be very scarce in steep, small, or Lead was not detected by spectrographic analysis intermittent stream courses. However, some clayey in the majority of Glacier Bay stream-sediment sam- and silty sand may be found even in small streams in ples. The median value is therefore less than the pockets behind boulders. The samples were placed in spectrographic detectibilities (table 2), although it water-resistant paper bags, then dried at about may be approximately the detectibility of the direct- 100°F. After drying, the sample was sieved at -80 reader method (4 pprn). Based on 636 samples (pl. mesh and that fraction was analyzed-first by the 4) analyzed by the six-step method, about 85 percent field THM test, then spectrographically. of the samples contain less than 10 ppm; and 94 percent, less than 15 ppm. The values above 15 pprn are ANOMALOUS AND BACKGROUND VALUES considered markedly anomalous. Every region is characterized by a range of con- MOLYBDENUM tent values for each element; the average of these Molybdenum is not reported in the majority of values is the background value. In many cases the spectrographic analyses, but its median value may median value is taken as background. Most samples not be much less than the 3 ppm detectibility of the have about this concentration, but a few will have six-step method. In some areas many samples much higher or much lower concentrations and these showed values by the direct-reader method of 5-10 values are considered anomalous. High values are of ppm; these values are below the general detectibility special economic interest because they indicate meas of the method and therefore were not considered in of enrichment which may, in turn, be done to the the statistical analysis. They may, however, indicate presence of potential ore bodies. Most regions are un- areas of slightly anomalous molybdenum content derlain by many rock types, and because each rock and are given on the detailed maps (figs. 3-7). In a type has a characteristic element content, back- group of about 1,000 samples, molybdenum exceeded ground values are not constant. Therefore, any group 10 pprn in only 36 samples (pl. 5). All values above of anomalous values must be interpreted with con- 10 pprn are considered anomalous. sideration of such variations. CHROMIUM The results of this geochemical investigation are The chromium content of stream sediments in the reported (pls. 2-8) in ranges of concentration, each monument ranges from less than 5 pprn to about range being identified by a specific symbol. The 2,000 pprn (0.0005-0.2 percent). Based on a group of data shown on the maps suggest patterns of element 957 samples (pl. 6), the median concentration is distribution. about 60 pprn and about 90 percent of the samples contain less than 100 pprn chromium. About 98 per- TOTAL HEAVY METALS cent of the samples contain less than 200 pprn Analyzed stream-sediment samples from Glacier chromium. Samples containing 200 pprn or more Bay National Monument contain from 20 to 1,000 chromium are considered markedly anomalous. pprn zinc, copper, and lead extractable in hot acid. NICKEL The median THM concentration is about 25 ppm, Nickel ranges from about 3 to 700 pprn in stream based on results from a set of samples from 915 lo- sediments in Glacier Bay National Monument. Based calities (pl. 2), which include the average values on the 636 samples (pl. 7) analyzed by the six-step from some duplicate analyses. About 75 percent of method, the median value is about 15 pprn nickel. the samples contain less than 60 ppm; 90 percent, About 90 percent of the samples contain less than 30 less than 100 ppm; and 95 percent, less than 120 ppm. ppm, and about 95 percent, less than 40 pprn nickel. The samples with 120 pprn or more THM are consid- Values of 40 pprn or more are considered markedly ered markedly anomalous. anomalous. 14 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

OTHER ELEMENTS Any tin and tungsten values detected by the spec- Based On the 636 (pl. ') by the trograph were considered anomalous and are shown six-step method, the median cobalt concentration in on plate 8, along with any detected values of a group stream-sediment samples is between 10 and 15 ppm, and about percent of the samples contain less of rare elements including silver and arsenic. Values than 20 pprn cobalt. Cobalt is not shown on the of strontium greater than 1,000 pprn were consid- maps, as it generally tends to vary directly with ered anomalous and are also shown on plate 8; al- nickel. though strontium is not very common in ore

TABLE3.-Semiquantitative spectrographic analyses in parts per million of representative unaltered rocks [0, looked for, but not found; ..... not looked for]

Semiquantitative spectrographic analyses Lab. No. Field No. Ag B Ba Co Cr Cu Fe La Mn Mo Ni Pb Sc Sn Sr Ti V Y Zr A. Detrital sedimentary rocks

B. Limestone 1 Dl25437 Hx289 O...... 5 0 7 3 200 0 30 0 0 0 ...... 0 200 0 0 0 ...... 2 Dl25438 Hx524 O...... 150 0 5 7 100 0 15 0 0 0 ...... 0 100 0 0 0 ...... 3 Dl26163 Hx681 0...... 15 0 15 20 500 0 150 0 5 0 ...... 0 70 50 0 0 ...... 4 Dl261104 Hx682 0 ...... 100 3 30 20 1,000 0 200 0 15 0 ...... 0 500 50 0 0 ...... C. Mafic dikes and eills 0.. .. o.... o.... o.... o.... o.... 0.. .. o.... o.... 0.. .. 0.. .. o.... o.... o....

1 Also found 2 ppm Be, 10 ppm Nb. D. Diorite, quartz diorite, and quartz monzonite or granodiorite (field identification) o...... 500 o.... o...... 500 0.. . o...... 700 o.... O...... 500 0.. .. O...... 300 0.. . O...... 150 o.... o...... 200 0.. . O...... 700 o.... 0 ...... 1,000 0.. ..

1 Also found 3 ppm Be.

E. Granite or aplite -- - - - 1 'Dl25440 Fa312 O...... 300 0 5 7 7,000 0 700 0 0 10 ...... 0 20 150 0 10 ...... 2 'D125160W Hx603B O...... 200 0 5 5 10.000 0 200 0 0 15 ...... 0 20 50 0 15 ...... 3 Dl25154 Hx564 0 ...... 3.000 0 1 7 10,000 0 100 0 0 10 ...... 0 500 500 15 0 ...... 1 Also found 7 pprn Be. Tr, Li. 2 Also found 1 pprn Be, 10 pprn Nb. F. Hornblende, garnetiferous rock of diorite composition and associated rocks

Al. Pale-gray calcareous siltatone with ellipsoidal massen of limestone. C6. Mafic dike. Tidal Formation of Rossman (l963b). 7. . do .... Dark-gray slaty argillite, interlayered with Al. Dl. Biotite-hornblende granodiorite. Interlayed siltatone and calcareous siltatone. Tidal Formation of 2. Biotite-hornblende quartz diorite. Rossman 11963b). 3. Biotite-hornblende granodiorite or quartz monzonite. 4. Hornblede-biotite quartz diorite. Gray finely crystalline massive limestone, Willoughby Limestone Biotite-hornblende diorite or granodiorite. of Rossman ( 1963b). 6. Gray finely crystalline thin-bedded limestone. 6. Hornblende diorite. . . 7. Hornblende-biotite diorite or granodiorite. Dark-gray carbonaceous limestone. Black Cap Formation of Ross- 8. Biotite quartz monzonite. man (1963b). 9. Quartz monzonite or granodiorite. Limestone and argillite, interlayered, typical of Rendu Formation El. Leucogranite or quartz monwnite. of Rossman (1963b). 2. Leucogranite. Mafic dike. 3. Aplite. Mafic igneous rock, forms sill-like masses. F1. Hornblende-garnet "diorite." Mafic dike. Gneissic diorite, disseminated sulfides visible. .... do...... Hornblendite associated with 2. ... do ... Hornblende-garnet "diorite." GEOCHEMICAL STUDIES 15 minerals or in metal deposits, it is shown because it CAUSES OF ANOMALOUS VALUES may indicate alteration or strontium metasomatism. Anomalous concentrations of metallic elements occur in stream-sediment samples from various UNALTERED ROCKS parts of Glacier Bay National Monument; some of Rocks in Glacier Bay National Monument contain these indicate the presence of min- differing amounts of trace elements, depending On eralized rocks and are discussed in the following see- their origin, lithology, and major-element composition. a few places, similar anomalous concentration. samples be required to define tions indicate unusual amounts of metals contained exactly the tEKe-element geochemistry of the bed- in the country rocks or, directly or indirectly, the rock units, but spectrographic analyses (table 3) of effects of glaciation. 30 apparently unaltered and unmineralized Swarms of mafie dikes are the probable source of provide a basis for some generalizations. anomalous concentrations of metallic elements in Limes~ones probably have lower trace-element parts of the monument. Such dike swarms contents than any other rock type common in the make up as much as 40 percent of the bedrock in monument. The range in concentraion in four ana- some Some of the contain unusual lyzed samples is 0-3 PPm cobalt, 5-30 PPm chromi- amountsof elements such as chromium and nickel, 3-20 ppm copper, and ppm No lead and most are bordered by thin selvages of baked and or zinc was detected. Streams draining unaltered bleached rock with abundant thin carbonate veinlets. limestone terranes should, therefore, have a low con- Erosion of the dike and contact-zone rocks provides tent of these metals. Three analyzed samples of de- material relatively rich in metallic elements; hence, trital clastic sedimentary rocks contain as much as the presence of anomalous nickel and chromium in l5 ppm 70 ppm chromium9 looppm the stream sediments probably indicates the presence and 30 ppm nickel, indicating that streams dralnlng of dike swarms rather than ore deposits. unaltered detrital clastic rock terranes should carry Aggrading glacial streams accumulated metal con- these metals in considerable abundance. centrates that may or may not be indicative of bed- Of the igneous rocks in the monument, the diorite- rock mineralization upstream. Some glacial outwash granodiorite-quartz diorite suite was the most ade- stream sediments show small, but real, concentra- quately sampled and analyzed. The average (arith- tions of a suite of elements including iron, titanium, metic mean) concentration of selected elements is lanthanum, chromium, niobium, vanadium, yttrium, compared below with values for similar rocks re- and zirconium. These were caused by a ported by Turekian and Wedepohl (1961) : Ba co Cr cu Ni Sr lag effect; the fast-moving glacial streams selec- High calcium granitic rocks : tively carried off light minerals and left the heavy 1. Granodiorites and other minerals that contain this suite of elements. That the granite rocks of same suite of metals was found in panning concen- Glacier Bay 506 l2 l4 40 443 trates indicates the validity of the proposed 2. Average of Turekian and Wedepohl (1961) 420 7 22 30 15 440 mechanism. Based on only three samples, the leucocratic gran- RESULTS OF GEOCHEMICAL STUDIES itic rocks (which are mainly adamellites) have an The geochemical studies show both many local appreciably different trace-element suite, including concentrations of metals in stream sediments and trace amounts of lead. Semiquantitative analysis systematic geographic distributions for individual shows that one sample contains 7 ppm beryllium and elements. Some of the distribution patterns are re- a trace of lithium, elements characteristic of some lated to mineral deposits in the bedrock, some to leucocratic granites that have associated ore metal-rich country rocks, some to lag concentrates, deposits. More mafic rocks, such as hornblendite and gneiss- and others are not clearly related to any of these. ic garnetiferous diorite, generally contain higher The distribution of anomalous values shown in fig- concentrations of the elements cobalt, chromium, ures 3-7 and on plates 2-8 are discussed below with copper, and nickel. Mafic dikes, including lampro- reference to known geologic features. The interpre- phyres, locally contain very high concentrations of tations given are necessarily brief, and further these elements, particularly chromium and nickel. development of the detailed relations between The mafic dikes are locally abundant and probably stream-sediment metal contents and bedrock com- contribute important amounts of these metals to position of the drainage basins involved is possible stream sediments. I in some instances. 16 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

TOTAL HEAVY METALS Inlet area, however. A very metalliferous stream Anomalous T'HM values are widely scatkered at sediment (1,000 ppm) was found north of the area in Glacier Bay (pl. 2). Some of them cannot be as- Tarr Inlet. signed to any distinct mineralized zone and are Only a small number of stream-sediment samples interpreted to be the result of widely scattered, but weye obtained from the Muir province because individually small, centers of hydrothermal altera- drainage is predominantly glacial. The region seems tion and metallization. to have a low THM content. Inspection of the map shows that THM values are generally higher in the relatively unmetamorphosed COPPER and predominantly detrital pJastic Chilkat province The copper distribution pattern (pl. 3) resembles than in the predominantly metamorphic and granitic that of the THM distribution, particularly in the Geikie or Muir province (fig. 2). Within the Chilkat generally higher metal values of the Chilkat Prov- province there are noticeable concentrations of ince in comparison with the Muir and Geikie anomalous THM values near the head of ~~~~~~i~~ provinces. The pattern is not, however, identical with River, near Miller Peak and Sandy Cove, and north- THM; part of the difference is due to test method: west of Tidal ~~l~tnear ~~~~t ~~~~i~~. ~h~ areas the THM test is most sensitive for zinc and less sen- near Miller peak-Sandy Cove and Mount Merriam sitive for copper and lead; hence, high THM does are underlain by a variety of sedimentary rocks cut not necessarily indicate high copper. The diffwence by small stocks and are discussed under between THM and copper values is very noticeable at descriptions." the head of Excursion River and in the Miller Peak- Anomalously high samples near the head of Ex- Sandy Cove area- At both of these places, only part. cursion River are close to a prominent fault zone, of the THM anomalies is due to copper and an ap- which controls the north-northwest course of the preciable part is due to zinc, as is shown by com- river and are probably related to mineralization parison of the THM and the copper, zinc, and lead along the fault zone, such as that known at the head spectrographic In places, as in upwr- of Adams Inlet. Farther east, additional subparallel Berg Creek east of Adams Inlet, faults are suggested by prominent topographic barely discernible in THM are better shown in alinements. Some of the anomalous samples, par- titularly those in uppermost Berg Creek, show high NO copper anomalies were found in the Muir prov- copper and chromium contents also. ince, although it should again be noted that this Isolated anomalous values scattered through the area is extensively covered by glaciers and has few Chilkat province are probably related to additive metamorphism or related mineralization. The Geikie province contains several conspicuous Isolated anomalous THM values east, west, and copper anomalies, even though the background cop- south of snowD~~~ are related to an abundantly per content is lower here than thme Chilkat province. iron-stained contact zone with small magnetite The largest anomaly is east of Dundas Bay, where masses adjacent to a granodiorite stock. An isolated the content is as much as 300 ppm in streams anomalous THM value north of the ~~~~t~kmo- draining a large altered and mineralized area (pl. 1). lybdenum prospect probably reflects copper and zinc Near the head Bay, 'OWer and THM val- added during molybdenum mineralization. ~i~hues are high in a small creek draining across a gold THM values north and south of White Glacier prob- prospect (Rossman, 1963b, PI. '1. Most of the Reid ably result from the zinc and copper deposits Inlet gold area does not contain copper anomalies, 1, loc. 6) known in the area. but stream sediments collected east and west of the In the Geikie province, high THM values are con- central part of the area have anomalous copper centrated near D~~~~~ B~~,M~~~ of these values contents. An isolated stream-sediment sample on the are due to high copper contents, and they are dis- west side of Tarr Inlet 700 ppm copper. A cussed either with copper deposits or in the descrip- single near the end of the penin- tions of the geochemical results in the eastern and sula between Tarr and Rendu Inlets shows a value western Dundas Bay areas. The Reid Inlet gold area that is barely anomalous, but may be significant, as is not marked by any consp~cuous TH~anomaly, the sample locality is near a locally magnetite-bear- even though the gold deposits contain some sphale- ing batholithic contact zone. rite,which should contribute zinc to the streams. One LEAD anomalously high and several moderately high The distribution of lead resembles that of THM, values of THM (60-119 ppm) are found in the Reid but the correlation with the copper pattern is less GEOCHEMICAL STUDIES 17 marked. The data indicate broad areas of anomalous also the site of a copper anomaly, is underlain by lead concentration in the southern part of the Chil- mixed volcanic and detrital clastic rocks, and some kat province and in the northern and southern parts iron-stained zones crop out nearby. The chromium of the Geikie province (pl. 4). anomaly may persist downstream to Adams Inlet. Lead is somewhat enriched in two samples south Another chromium anomaly traceable downstream of Snow Dome, one of which was marked by an was detected along a tributary on the west side of anomalous THM value; these high values are prob- Queen Inlet in an area where limestone and limy ably derived from mineralization in a nearby contact sandstone are intruded by granitic rocks. zone. Lead also furnishes one of the few geochemical Two anomalous and several moderately high clues to the Reid Inlet gold area; anomalous chromium values near Mount Wright are apparently amounts of lead are present in drainages on the caused by a mafic dike swarm, and isolated values Lamplugh Glacier side of the area. Galena present in elsewhere may mark mafic dikes. Nickel is also the gold deposits probably explains the anomalous markedly enriched near Mount Wright. values. OTHER ELEMENTS A small lead and THM anomaly north of Marble Anomalous amounts of tin, tungsten, strontium, Mountain may be related to hydrothermally altered silver, and other metals are recorded on plate 8. limestone country rock. The highest lead value found Tungsten was found in only two samples at the head (200 ppm) is from the west shore of Tarr Inlet and of Dundas Bay, near exposures of leucocratic gran- coincides with anomalous values in THM, copper, itic rocks. High tin content was noted there and at and other metals. Slightly enriched values of lead several other places, the most significant being the (16-24 ppm) occur in drainages entering the south 500 pprn content of the highly anomalous stream side of Johns Hopkins Inlet and also east of the Tarr sediment sample in Tarr Inlet. Inlet about due east of the 200 pprn anomaly noted Silver was found in amounts ranging from 1 to 10 above. At both places the streams drain leucocratic pprn in samples from several scattered localities, in- granitic rocks, the only unmineralized rocks in the I cluding the Tarr Inlet sample and a sample found monument which contain spectrographically detect- south of Margerie Glacier. Strontil~mis markedly able lead (table 3). enriched in two areas, the Miller Peak-Sandy Cove MOLYBDENUM area and the Mount Merriam area. Both are also The largest area of anomalous molybdenum con- characterized by relatively high THM and molybde- tent is in the northernmost Chilkat province near num values. Mount Merriam. Other areas of possible significance AREAL DESCRIPTIONS are near Miller Peak and Sandy Cove and at the head of Dundas Bay, Because of the relatively poor sen- More detailed geochemical data are available for sitivity (10 pprn), the spectrographic analyses indi- some of the areas of the monument in which mineral cated only markedly anomalous values of molybde- deposits are known or in which one or more geo- num. As a result, no regional molybdenum back- chemical anomalies were detected. Areas for which ground was detected (pl. 5). more complete data exist are western Dundas Bay, Detailed soil sampling (pl. 12) disclosed anoma- eastern Dundas Bay, Miller Peak-Sandy Cove, Mount lous molybdenum values near the Nunatak molyb- Merriam, and Reid Inlet (figs. 3-7). denum deposit. The stream-sediment sampling WESTERN DUNDAS BAY AREA program did not detect the deposit, probably because Scattered anomalous values of THM, beryllium, of the recent glacial erosion which stripped off all copper, molybdenum tin, and tungsten occur in the enriched soil and because of the diluting effect of the western Dundas Bay area (fig. 3). Some of the high surrounding extensive outwash deposits. THM values are caused mainly by anomalously high CHROMIUM AND NICKEL copper concentrations, others by zinc. Chromium (pl. 6) and nickel (pl. 7) have a dis- Tungsten-tin-molybdenum anomalies occur in two tribution pattern that generally resembles the pat- streams entering the head of Dundas Bay (table 4 tern for copper (pl. 3). As is true of all the metallic and fig. 3, samples 12, 13) The tungsten content of elements discussed, chromium and copper are region- these samples is unusally high and molybdenum and ally most abundant in the Chilkat province. tin are also noticeably enriched. The headwaters of The largest chromium anomaly in the Chilkat the stream of sample 12 drain an area near the con- province is in upper Berg Creek. This area, which is tact of older granitic rocks and a leucocratic pluton, 18 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

FIGURE3.-Geochemical sampling map of the western Dundas Bay area. GEOCHEMICAL STUDIES 19

TABLE4.-Total heavy-metals and semiquantitative spectrographic analyses, in parts per million, of streamsediment samples, western Dundas Bay area

[THM, total heavy-metals (Cu+Pb+Zn) field test; 0, looked for, but not found; , not looked for1

Loo. Lab. No. Field No. THM Semiquantitative spectrographic analyses

Ag B Ba Co Cr Cu Fe La Mn Mo Ni Pb Sc Sn Sr Ti V Y Zr

o...... o...... o...... 10 ...... o...... o...... o...... 0...... 0...... o...... o...... o...... o...... 0...... o...... o...... o...... o...... o...... o...... o...... o...... o...... o...... o...... o...... o...... 15...... o...... 15...... o...... o...... o...... 15...... o...... 15...... o...... o...... o...... 15...... o..... o...... o...... o...... o...... o...... o...... o...... o...... 0...... o...... o...... o...... 0...... o...... o...... o...... o...... o...... o...... o...... o...... o...... o...... 0...... 0...... 0 0 16 27 0...... o...... o...... o...... o...... o...... 10...... o...... 30 ...... o...... o...... o...... o......

46 744 0~1616 50 O...... 300 15 50 50 50,000 0 1,000 5 15 10...... 0 200 5.000 200 20...... 47 743 0~1614 20 0...... 300 15 30 30 50,000 0 1,000 0 10 0...... 0 200 3,000 200 20......

o...... 0 1,000 3 10 10...... o...... 30 700 0 10 O...... o...... 01,000 0 5 0...... o...... 01,000 0 7 0...... o...... 01,000 0 7 0...... o...... 0 1,500 <5 10 O...... o...... 301,000 0 20 0...... o...... 30 2,000 0 20 0...... o...... 01,000 0 10 0...... o...... 0 1,000 0 10 0...... o...... 0 1.000 3 10 0...... o...... 0 1.000 3 10 10...... o...... 0 1,000 0 15 10 o...... 0 700 0 30 O...... o...... 0 1,000 5 15 10...... o..... o..... o...... o......

1 Also found 150 ppm W. 4 Also found 2 ppm Be. Alao found 70 ppm W. Lost. 'Abo found S ppm Be. 'Sample contaminated by waste from old cannery. 20 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

TABLE4.-Total heavy-metals and semiquantitative spectrographic analyses, in parts per million, of stream-sediment samples, western Dundas Bay area--Continued

Loo. Lab. No. Field No. THM Semiquantitative spectrographic analyses (fig.3) Dl25 66- Ag B Ba Co Cr Cu Fe La Mn Mo Ni Pb Sc Sn Sr Ti V Y Zr 71 513 Bd614 40 0...... 200 15 50 30 30 1,000 0 15 15...... 0 200 3,000 200 20 ...... 72 515 Bd617 40 0...... 300 15 30 50 %g 30 1,000 0 15 10...... 0 300 3,000 200 20...... 73 514 Bd616 40 0 ...... 200 15 50 50 50,000 01,000 0 15 0 ...... 0 3003,000 200 20 ...... 74 516 Bd618 30 0 ...... 150 30 30 50 70000 0 1,000 0 30 0 ...... 0 2003,000 200 20 ...... 75 517 Bd620 30 0 ...... 500 15 50 70 70:000 301,000 0 15 15 ...... 0 3003,000 200 20 ...... 76 518 Bd621 30 0...... 300 15 30 30 50,000 0 1.000 0 10 0...... 0 300 3,000 200 20 ...... 64A 341 Fd289 20 0...... 150 15 15 20 50,000 0 1,000 0 5 0...... 0 150 2,000 150 15 ......

Samples north of Taylor Bay

and it seems probable that the source of the anomaly The first, near the shore, contains both high THM is mineralization along or near the contact. and copper values and occurs in an altered zone. The The compositon of the leucocratic pluton itself is metal content of the zone ranges from 100 to 300 reflected in the beryllium and lead content of stream- ppm copper and as much as 30 pprn lead (table 5, sediment samples from areas underlain by the pluton 2-5). This occurrence is described more completely (table 4, samples 14, 15, 17, 18, 20). The beryllium under copper mineral deposits. The second anomaly, content of these samples is not high in terms of esti- about 3 miles farther east, contains high THM values mated crustal abundance, but because beryllium is (table 5, samples 8-10, and possibly 18). The most generally present in the monument in concentrations metal-rich sample (No. 8) was taken from a stream- of less than 1 ppm. the 2-3 pprn concentrations bed along the contact of an igneous pluton with represent enrichment. Similarly, the lead content of limestone country rock. Near sample 18 on Icy these samples is only 15 ppm, a level that is not Strait, limestone exposed along the beach contains markedly anomalous around Glacier Bay, but is lo- jasperoid masses as much as a foot across. This cally anomalous for the western Dundas, where lead THM anomaly is partly due to zinc, because the content is generally low. Except for the 120 pprn THM values in samples 8-10 are in excess of copper TBM value of nearby sample 12, the area with plus lead. anomalous tungsten does not have anomalous THM MILLER PEAK-SANDY COVE AREA content. The Miller Peak-Sandy Cove area is on the east Samples that show anomalous values of THM inside of Glacier Bay, north of the mouth of Beartrack terpreted to be due primarily to zinc or copper are River and south of Mount Wright (fig. 5). The area concentrated in a small area on the west side of Dun- contains the Sandy Cove gold-copper prospect, which das Bay, near samples 56, 59, 60 and 65 (table 4). , is just to the east of sample locations 41 and 41A. In The high THM values of samples 56 and 59 are prob- addition, there are several small areas of anomalous ably caused by zinc, as spectrographic determina- metal content, discussed geographically starting at tions show no lead and near background values of the northwest part of the mapped area. copper. One markedly anomalous sample (No. 68,200 Stream-sediment samples collected south of pprn THM) is related to an abandoned cannery, as Mount Wright, particularly samples 1-13 and 19, 22, also evidenced by 0.1 percent tin (not given in table and 23 (table 6), are generally characterized by 4) anomalous or relatively high values in THM copper, Anomalous THM and copper values are also found chromium, and nickel. The area is mainly underlain in an unnamed stream draining into the head of by fine-grained detrital sedimentary rocks, subor- Taylor Bay (fig. 3 and table 4, samples 77, 78) from dinate limestone, and amygdaloidal basalt or ande- an area of gneissic rocks. Rossman (1963b) re- site, which are all cut by numerous mafic dikes. Our ported a gold prospect in the drainage. interpretation is that the anomalous metal value are EASTERN DUNDAS BAY AREA probably derived from the dikes or small-scale vein A small area east of Dundas Bay and not far north mineralization in the baked and altered adjacent of Icy Strait contains two THM anomalies (fig. 14). country rock. GEOCHEMICAL STUDIES

/ EXPLANATION

PP; Stream-sediment sample convention For illustratino- avvrozimate.- concen- tratwn, 6n parts per milljon, of elements where THM stands for total heavy metals

Sample location and analysis Sample 17 contains, in parts per million, 40 total heavy metals, 15 chromium (Cr), 10 copper (cu), no molybdenum (Mo), 10 nickel ( Ni ) but no lead ( Pb)

Base from U.S. Geolog~calSurvey Mt. Fa~rweather1'250,000, 1961 0 2 MILES

CONTOUR INTERVAL 200 FEET DATUM IS MEAN SEA LEVEL

FIGURE4.--Geochemical sampling map of the eastern Dundas Bay area.

Streams farther east (table 6, samples 14, 15) of samples 28-38, where the anomalous or relatively drain a mixed sedimentary terrane which includes high values of THM and trace amounts of lead may limestone, and the THM values may largely repre- be derived from a mixed sedimentary terrane. sent zinc from mineralized carbonate rocks like those , A group of samples in a tributary stream east of known to exist near White Glacier (pl. 1). Similar the Beartrack River (particularly samples 56-59) mineralization may exist to the south and southeast show relatively high or anomalous values of THM 22 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

TABLE5.-Total heavy-metals and semiquantitative spectrographic analyses, in parts per million, of stream-sediment samples, eastern Dundas Bay area [THM. Total heavy-metals (Cuf Pb+Zn) field test; 0, looked for, but not found ; , not looked for]

Loc. Lab. No. Field No. THM Semiquantitative spectrographic analyses

and copper. The bedrock in the stream drainage is ment, but it is not well marked by geochemical pat- graywacke and argillite, and the origin of the THM terns. and copper values is unknown. The mixed greenstone and granite terrane west of Samples in the southwestern part of the area lo- Lamplugh GIacier has a distinct copper anomaly, and cally show anomalous values of THM, copper, molyb- several of the samples, notably 8, 9 and 16 (table denum, and strontium. These values are probably 8) east of Reid Inlet also contain anomalous amounts related to a pluton near Miller Peak. Samples 92 and of copper. Most of the area, however, seems charac- 99 show anomalous concentration of copper and terized by less than background amounts of copper. molybdenum, respectively. As the gold generally is accompanied by galena, lead MOUNT MERRIAM AREA might be expected to be abundant, but results show There are no mines or prospects in the geologically it to be only locally abundant (table 8, samples 14); complicated Mount Merriam area (fig 6; pl. I), but a greater sample density might have given a strong- there are many stream drainages containing anoma- er pattern. Since gold was found by panning in lous concentrations of THM and molybdenum and Ptarmigan Creek below the LeRoy mine and is visible in vein material elsewhere, the Reid inlet area some outcrops of unprospected mineralized rock. The seems to be an example of an area in which old- high THM values seem to be due to zinc, for neither fashioned panning is more satisfactory than geo- lead nor copper is abundant. The area is similar to chemical methods. the Sandy Cove-Miller Peak area in having numerous high strontium values, suggesting the possibility MINERAL DEPOSITS of either alteration or additive contact metamor- Deposits of gold, silver, molybdenum, iron, nickel, phism in the hornfelses and marbles around the titanium, copper, and other metals are known from granitic stocks. Glacier Bay National Monument. Some of these de- The highest concentrations of molybdenum are posits have been mined or explored on a small scale, found in a small part of the area east of Composite but many of them are virtually unexplored. T\vo of Island (table 7, samples 8, 13, 14, 20, 21). Some of the deposits, the Brady Glacier nickel-copper deposit these samples also have high THM values, which are and the Nunatak molybdenum deposit, have been not confined to this small area, however. Molybden- investigated in some detail. The term "mineral de- um is present in greater-than-detectable quantities posit" is used broadly in this report to include in all samples from the Mount Merriam area. anomalous concentrations of ore metals. The de- REID INLET GOLD AREA posits described range from small insignificant The Reid Inlet gold area (fig. 7; pl. 1; tables 8, 11, mineral occurrences to some deposits that apparently 12) contains the main gold deposits of the monu- are large or rich enough to warrant explora t'ion. GEOCHEMICAL STUDIES

I I I CONTOUR INTERVAL 200 FEET DATUM IS MEAN SEA LEVEL

FIGURE5.-Geochemical sampling map o&the Miller Peak-Sandy Cove area. MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

TABLE6.-Total heavy-metals and semiquantitative spectrographic analyses, in parts per million, of streamsediment samples, Miller Peak-Sandy Cove area [THM, Total heavy-metals (Cu+Pb+Zn) field test; 0, looked for, but not found;. . .., not looked for] Loc. Semiqurntitative spectrographic analyaw (fig.5) Lab. No. Field No. THM 66- Ag B Ba Co Cr Cu Fe La Mn Mo Ni Pb So Sn Sr Ti V Y Zr

1 Also found 1 ppm Be. GEOCHEMICAL STUDIES 25

TABLE6.-Total heavy-metals and semiquantitative spectrographic analyses, in parts per million, of stream-sediment samples, Miller Peak-Sandy Cove area-Continued

Loo. Semiquantitative spectrographic analyses (fig.5) Lab. No. Field No. THM 66- An B Ba Co Cr Cu Fe La Mn Mo Ni Pb So Sn Sr Ti V Y Zr

0...... 20 15...... o...... 15 0...... 7 o...... 8'."'6 10 o...... o...... 15 10...... 0 0 43 30 16 o...... 30 20 ...... o...... 15 15 0 o...... 15 O...... 0...... 15 O...... 0 0 15 10...... o...... 15 O...... 10 o...... 8.. ...b 17 9 23 o...... 15 20 ...... Bd531 o...... 30 20...... Hx475 o...... 15 10 ...... Bd538 10 o...... Fd98 8.....0 21 0 19 FdlOl 0 0 29 0 19 0 0 16 0 7 20 o...... 8,....6 34 8 17 0 0 32 13 20 0...... o...... 20 10 ...... o...... 15 O...... 0 0 29 12 15 0 0 22 13 20 0 0 24 10 13 10 24 15 23 0 0 23 6 14 0 0 23 12 17 o...... 20 o...... 0 0 25 11 17

1 Also found 1 ppm Be. 9 1.5 ppm Be.

LOCALITY LIST KEYED TO information on the nature and distribution of the MAPS AND TABLES mineral deposits in the monument and a basis for All the deposits are listed alphabetically on page delineating additional target areas favorable for ore 30, together with the numbers that key them to figure deposits. The study is not detailed enough to provide 1 and plate 1, the commodity they are described evaluations as to the economic feasibility of devel- under (listed as "Main commodity"), and references oping and mining a specific deposit, either currently to tables and other figures and plates. or in the future. Such evaluations would require Our field investigations stressed evaluation of de- more extensive investigation and physical explora- posits of metallic commodities and involved examin- tion, metallurgical and cost-analysis surveys, and ing (1) all known mines and prospects, (2) the many other studies necessary to establish the feasibility of deposits discovered during the current investigation, present or future mining. and (3) some of the mineralized areas found by geo- The examinations were limited by such factors as chemical sampling. The mines and prospects were time, difficult access, and the poor exposures of some sampled and, in most cases, mapped in detail. The of the deposits. Evaluating the mountainous 3,900- discoveries made during the current investigation square-mile Glacier Bay National Monument in only were sampled, and their apparent sizes and probable 3% months necessitated cursory examinations of grades were appraised. We tried to establish the geo- many deposits. Access was impeded by rough terrain logic setting of the geochemically anomalous areas. that required time-consuming climbs and descents The current reconnaissance investigation provides and by locally dense brush. Foul weather was an- hxoq3sjs!ps quaaaxd yqy~s!xqap y30.1 pur! sy30.1 ayq $0 Lusm .aZusx xazlyeaMrysj ayljo sqxsd ;tayl!y uo!~sz!ggo)aux)sod asraa!p Ilq JO 'uo!~r!)aZaa pus 'a3! ay!) U! ~XOMpa~r!1dma)uo3 ayl $0 y3nu.1 pa)uaaaxd 'MOUS hq paJn3sqo pus palaaoa h~qrr!dare sqsodap xayqsafi )uaurapu: pur! spnop MOI PUB 'a13s)sqo ray30

VBSVTV 'LN3MflNOW TVNOILVN AV€l 8313V13 80 S332TflOSXZI TV83NIW 9Z GEOCHEMICAL STUDIES 27

TABLE7.-Total heawg-metals and semiquantitative spectrographic analyses, in parts per million, of streamsediment samples, Mount Merviam area

[THM. Total heavy-metals (Cu+Pb+Zn) field test; 0, looked for, but not found ; . . . .. not looked for]

Loc. Semiquantitative spectrographic analysea (fig.6) Lab. No. Field No. THM An B Ba CO Cr CU Fe La Mn Mo Ni Pb Sc Sn Sr Ti V Y Zr

1 Also found I ppm Be. a Lpt. estimates of their size and extent. Despite these lim- Most of the known mineral deposits within the itations, the coverage for most of the monument is boundaries of the monument are described in this good, and we believe that most large or significant report. The exceptions are the ilmenite-rich deposits deposits that crop out east of the Fairweather Range that are widely distributed in the mafic layered in- were examined. The results of the geochemical sam- trusive~ of the Fairweather Range (Rossman, pling program provide a basis for evaluating the 1963a); these were not examined during the current sizable tracts of the monument where bedrock is investigations. Only a few ilmenite localities are discovered. However, significant undiscovered deposits cussed specifically because the limited geologic in- that might be found by extensive and thorough pros- formation concerning them indicates that they are pecting, using modern geophysical and geochemical similar. However, comparable ilmenite-rich deposits methods, may exist in the monument, particularly in are probably extensive and widespread throughout covered parts or in the Fairweather Range. Explora- the mafic layered intrusives. tion of some known deposits may reveal larger and The following part of this report consists of de- (or) richer ore bodies than those indicated by the scriptions of the known metal-bearing mineral surface examinations. deposits within the monument. These descriptions MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

Mt. Fa~rweather1 256,000, 1961 0 2 MILES CONTOUR- INTERVAL 200 FEET DATUM IS MEAN SEA LEVEL

EXPLANATION

Stream-sediment sample convention Sample location and analysis For illustrating approximate concen- Sample 11 contains, in parts per million, tratwn, in parts per million, of elements 30 total heavy metals, 60 chromium (Cr ) , where THM stands for total heavy 83 copper (Cu) ,5 molybdenum ( Mo ) ,2l metals nickel (N i ) but no lead ( Pb ), and anomalous elements such as 88 tin ( Sn). N D stands for not determined X Location of mine, prospect,or mineral deposit

FIGURE7.-Geochemical sampling map of the Reid Inlet gold area. MINERAL DEPOSITS 29 are based largely on field and analytical data ob- descriptions are referenced in descriptions of other tained during the current project, but they also in- lesser commodities in the deposit. clude pertinent information obtained from previous The most important known deposits in the Monu- investigations. The parts of this report describing ment are: the Nunatak molybdenum prospect (loc. nonmetallic commodities and petroleum are based 21), the Brady Glacier nickel-copper prospect (72), mainly on previous investigations. the Alaska Chief copper prospect (29), the Margerie It should be emphasized that all deposits examined copper prospect (19), the gold deposits of the Reid in detail are reported on here, and all field and ana- Inlet gold area and the Sandy Cove prospect (7), the lytical data obtained are given for each deposit. placer gold deposits on the beaches near Lituya Bay Many other occurrences of metallic minerals were (87, 88), and several iron and titanium deposits also noted, sampled, and analyzed, but they were associated with the layered intrusives of the Fair- deemed wholly insignificant because of limited grade weather Range. or size and are therefore not described. The locations BASE AND MISCELLANEOUS METALS of such samples also are shown on plate 1. We have Anomalous concentrations of the following base neither included nor excluded data arbitrarily. and miscellaneous metals were found in the monu- METALLIC COMMODITIES ment: Antimony, arsenic, bismuth, cadmium, copper, Metallic commodities in the monument include the lead, tin, and zinc. Except for copper and zinc, none following groups: Base and miscellaneous metals, of these elements appear to occur in significant precious metals, and iron and ferroalloy metals. quantities, although a few, notably lead, may be con- Locations of deposits that contain anomalous considered possible byproduct metals. Minor occur- centrations of one or more of the metallic commodi- rences of radioactive minerals have been reported ties are shown on plate 1. Numbers or letters in the from the monument, and these are also discussed text refer to the deposit locality number or letter briefly. shown on plate 1 next to the circles. Each circle on plate 1 indicates a discrete deposit or a group of de- ANTIMONY posits. Analyzed samples that contain only back- Antimony is a minor constitutent of several of the ground concentrations of ore metals are shown by copper deposits, the Rendu Inlet silver deposit (loc. solid dots or solid dots with a cross; their analyses 37), and the silver-lead-zinc deposits near Mount are not included in this report. Individual deposits Brack (12). Only two of our samples contained are described under the commodity that would most detectable antimony: one from the Mount Brack likely yield the major mineral values, and these deposits contained 7,000 ppm antimony (table 9, loc.

TABLE&-Total heavy-?netals and semiquantitative spectrographic analyses, in parts peT million of stream-sediment samples, Reid Inlet gold area [THM. Total heavy-metals (Cu+Pb+Zn) field test; 0. looked for, but not found : ..... not looked for]

LOC. Semiquantitative spectrographic anslysea (6a.7) Lab. No. Field No. THM Aa B Ba Co Cr Cu Fe La Mn Mo Ni Pb Sc Sn Sr Ti V Y Zr 30 O..... 300 20 O...... 225 110 O..... 750 40 0 0 900 30 0 0 GOO 20 0 0 300 20 0 0 230 40 O...... 150 100 0 0 140 20 0 0 470

160 o...... 200 40 0 0 270 40 O...... 300 20 0 0 390 20 0 0 740 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

Locality list of deposits, Glacier Bay National Monument

Table Table giving givlng No. on- Main analy- Detailed on- No. on- Main analy- Detailed on- Name of locality corn- tical Name of locality com- tical Fig. 1 P1. 1 modity data Figure Plate Fig. 1 PI. 1 rnodity data Figure Plate

Adams Inlet...... 5 Cu ...... LituyaBay ...... 7 87 AU ...... Entrance of...... 22 Mo ...... 88 Au ...... Alaska Chief...... 3 29 Cu 9 9...... Southeast arm of...... 8.1 Cu ...... Southwest of...... 30 Zn 9 ...... Southof ...... 85 Au ...... Blackthorn Peak, Margerie...... 4 10 Cu 9 ...... West of...... 51 Fe ...... McBride Glacier, Blue Mouse Cove...... 42 Cu 9 ...... westof ...... 10 Au 9 ...... Brady Glacier...... 2 72 Ni 15 18...... Minnesota Ridge...... 13 Cu 9 ...... East of...... 54 Fe 9...... Monarch Mines (Reid East of lower...... 55 Au 9...... Inlet)...... E Au 11 12, 13...... Lower...... 56 Mo ...... Mount Abdallah...... 16 Ni 9 ...... Outwash of...... 59 Au ...... Mount Brack...... 10 12 Zn 9 ...... Bruce Hills...... 9 34 Cu 9, 10 10...... Mount Cooper...... 66 Zn 9 ...... Casement Glacier...... 9 Mo ...... Mount Young, near...... 1 Cu 9 ...... East of...... 4 Cu 9 ...... Northwest of...... 2 Cu 9 ...... Nunatak on...... 3 Zn 9 .... North Marble Island...... 24 Cu ...... Charpentier Inlet...... 47 Mo 9...... Nunatak, The...... 1 21 Alo 13, 14...... 11, 12 Curtis Hills...... 23 Cu 9,...... Oregon King Dundas Bay, east of ...... 33 Fe ...... Consolidated...... 81 Au ...... East side of...... 14 31 Cu 9...... Queen Inlet...... 10 Fe g...... 10 DO...... 32 Cu 9, ...... Rainbow Mine (Reid West arm of...... 58 Cu 9...... Inlet)...... C Au 11 11...... West of...... 57 Au ...... Ramblcr Prospect Dundas River...... 53 Au ...... (Reid Inlet)...... L Au 11...... Fairweather Range...... 8 73 Fe ...... Red hlountain, 78 Cu ...... southn-est of...... 20 Zn 9...... 79 Ti ...... Reid Glacier, east of...... 60 Cu 9 ...... 80 Ti ...... Reid Inlet...... 5 A-L Au 11 11-11 9 82 Cu ...... Southeast of head of...... 71 hlo 9 ...... 83 Fe ...... South end 86 Cu ...... of ridge west of...... 70 hlo 0 ...... Francis Island...... 28 Cu 9 8...... Rendu Glacier, south Gable Mountain...... 13 14 Cu 9 ...... of ...... 12 15 Cu $1...... Galena Prospect Rendu Inlet...... 37 Ag 0 ...... (Reid Inlet)...... J Au 11...... Ridge west of...... 60 AIo ...... Geikie Inlet, west of ...... 50 Mo ...... West of...... 39 Fc 9 17 ...... North shore of...... 48 Mo 9 ...... West of Gilbert Island, mouth of...... 38 Cu 9 ...... Southwest end of...... 44 Cu 9...... Russell Island...... 61 Au 9 ...... Do ...... 45 Cu 9...... Sand Cove...... 6 7 Au 9 15, 16...... Northern...... 43 W 9, ...... Sentinel Mine Highland Chief (Reid Inlet...... D Au 11 ...... Prospect (Reid Shag Cove, \vest, of...... 4:) Cu 0 ...... Inlet)...... K Au ...... South AIarble Island...... 25 Cu I)...... Hoonah Glacier, east of...... 75 Cu 9...... Sunrise Prospect Do ...... 77 Cu 9...... (Reid Inlet)...... H Au 11...... Hopalong and Tarr Inlet, west of...... 15 63 Cu 9...... Whirlaaay claims West. of mouth of...... (i2 Cu !) ...... (Reid Inlet,)...... I Au 11...... m'c>st.shore of...... 18 (:u 9 ...... Hugh Miller Inlct...... 46 Zn 9 ...... \Yest side of...... 17 hIo 0...... Incas Mine, Rcid Tcrry Richtmryer Inlet...... G Au 11 11...... Prospect (Reid Johns Hopkins Inlet, Inlet,)...... A Au ...... north of...... 64 Cu 9...... Tidal Inlet, south of...... 11 Cu $1...... Northwest shore of...... 76 Zn 9...... Triangl~Island...... 36 110 ...... Johns Hopkins Inlet, Van Horn Ridge...... 11 110 9...... South of...... 65 Cu 9...... \Yacl~usettInlet, South shore of...... 74 Mo 9...... nrar head of...... 35 hlo !) ...... Lamplugh Glacier, IYhitc Glacier, east of...... F Cu 11...... north of...... 11 6 Cu !) ...... Southwest of...... 67 Cu 9...... 1Villoughby Island, West of head of...... 68 Ni 9...... northeast sidr of...... 26 Cu ...... 1,eroy Mine (Reid \Yost sitlr of...... 27 Cu ...... Inlet)...... I3 Au $1, 11...... !) Wood Lsk(,, south of...... 52 .4u ...... York Crrck, north of...... 8 Cu g...... METALLIC COMMODITIES 31

TABLE9.-Semiquantitative spectrographic analyses and gold analyses of mineral deposits in the Glacier Bay National Monument, Alaska [Spectrographic analyses by J. C. Hamilton, Harriet Neiman, and A. L. Sutton, Jr. Gold analyses by Claude Huffman. Jr., J. D. Mensik, 0. I. Parker, L. B. Riley, V. E. Shaw, J. A. Thomas, and J. E. Troxel. Au: A, analyzed by atomic ahsorption ; B, analyzed by fire assay atomic absorption method1

Results are reported in parts per million, which for the spectrographic Besides the elements shown in the table, the following elements were also analyses have been converted from percent to the nearest number in the sought in all of the analyses: Be, Hg, La, Li. Pd, Pt. Ta, and Ti. series 1. 0.7. 0.5. 0.3. 0.2. 0.15. and 0.1 .... which represent approximate Reported values for these, except Be, La, and Li, were always 0. midpoints df group'daG on 'a geometric scale. The assigned group for results will inelude more accurately determined values for about AI. Ca, Mg, Si, and Sr were looked for and found in several of the analyses, 30 percent of the test results. Gold and silver values in ounceQ per ton but as they were in analyses, their values are are shown in parentheses below their corresponding parts per milllon values. reported herein. Symbols used: M, major constituent-areater than 10 percent; 0, looked Locations of the deposits are shown on PI. 1; individual samples are for. but not detected : ..... not looked for : < . less than. described at the end of the table. Local- Sample Au ity 66A- A B Aa As Ba Bi Cd Co Cr Cu Fe Mn Mo Nb Ni Pb Sb Sn Ti V W Y Zn - - Juneau quadrangle 1 Bd-130B ...... 1 0 700 0 0 70 1,500 150 M 300 7 10 150 150 0 0 3,000 1,500 0 70 700 (0.029) Bd-130C ...... 10 0 3,000 0 0 7 500 150 30,000 150 15 10 150 150 0 02,000 700 0 100 1,500 (0.292)

Skagway quadrangle 9 No analyses

See footnotes at end of table. MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

TABLE9.Semiquantitative spectrographic analyses and gold analyses of mineral deposits in the Glacier Bay National Monument, Alaska-Continued

Local- Sample Au ity 66A- - A B Ag As Ba Bi Cd Co Cr Cu Fe Mn Mo Nb Ni Pb Sb Sn Ti V W Y Zn Skagway quadrangle-Continued 11Mk-145A ...... _ 0 0 500 0 0 10 20 2050,000300 0 0 3 20 0 03.000150 0 15 0 Mk-145B ...... 0 0 300 0 0 15 30 50 70,000 300 5 0 5 10 0 05,000 200 0 15 0 Mk-146 ...... 0 0 7 0 0 0 15 100 M 500 200 0 3 15 0 0 700 0 0 0 0 Mk-151 ...... 0 0 200 0 0 30 30 70 50,0001,000 5 0 15 0 0 03,000 300 0 30 0

Mount Fairweather ausdrannle

22 No analyses ...... ,

26, 2i So analyses ......

30 Hx-50413 i 0 150 10 0 3 15 70 15,0001,500 7 0 0 300 0 0 700 30 0 01.500 31 llk-4Vl 0 0 300 0 03010 500 MI5020 010 0 0 01,000100 0 0 0 blh-492 0 0 300 0 0 20 7 700 30,000 300 20 0 5 10 0 01,000 70 0 0 0 ALL-4'4 0 0 500 0 0 15 10 1,500 30,000 300 3 0 7 15 0 01,000 70 0 0 0 11x-545 1 0 500 0 0 10 20 1,000 50,000 500 0 0 20 30 0 03,000 200 0 15 0 (0 01'1) 11~-544 0 0 200 0 0 10 15 1,000 70.000 300 15 0 10 0 0 01,500 100 0 0 0 117-54411 0 0 150 0 0 30 10 2,000 70,000 300 20 0 10 0 0 01,000 200 0 10 0 31 I!\-54'- 0 0 150 0 0 10 7 1,000 50,000 700 300 0 10 0 0 01,500 700 0 0 0 33 11,~~~al$a(a

See footnotes at end of table METALLIC COMMODITIES

TABLE9.-Semiquantitative spectrographic analyses and gold analyses of mineral deposits l in the Glacier Bag National Monument. Alaska.. Continued

Local- Sample Au ity 66A- . A B Ag As Ba Bi Cd Co Cr Cu Fe Mn Mo Nb Ni Pb Sb Sn Ti V W Y Zn

Mount Fairweather auadranele-Continued

36 No analyses ...... 37Mk-542 ...... 0 01,000 0 0 3 3 715.000700 0 0 3 0 0 050 7 0 0 0 Mk-544 <0.05 ...... 0 0 200 0 0 3 2 20 50.0001,000 15 0 0 0 0 15 700 50 0 15 0 (<0.0015)

. . 50-53 No analyses ......

56 . 57 No analyses

56. GO Noanalyses ......

61 Ov-2041 23 29 1 0 50 0 0 0 12010.000300 0 0 050 0 015015 0 0 0 (0.670) (0.845) (0.029)

62 Fd-428B <0.05 ...... 0 0 70 0 0 100 0 2.000 M 200 0 0 15 0 0 01.500 70 0 0 0 (<0.0015)

See footnotes at end of table. METALLIC COMMODITIES

TABLE9.-Semiquantitative spectrographic analyses and gold analyses of mineral deposits' in the Glacier Bay National Monument, Alaska-Continued

Local- Sample Au ity 86A- - A B Ag As Ba Bi Cd Co Cr Cu Fe Mn Mo Nb Ni Pb Sb Sn Ti V W Y Zn Mount Fairweather quadrangle-Continued

72 4 ...... 73 No analyses ......

- -- 7&W No analyses ......

1 Excluding the Nunatak molybdenum prospect, the Brady Glacier nickel- Wold value from six-step spectrographic analyses. copper prospect, and the Reid Inlet gold area. ' Brady Glacier nickel-copper prospect, see table 15. a Nunatak molybdenum prospect, see table 13.

SAMPLE DATA FOR TABLE 9

Sample Locality Geologic setting 66A- Description of sample 1 Juneau D-5 quadrangle. 1.8 miles N. Iron-stained altered wnes as much as Bd-13OB Selected specimen of sulfides replacing meta- 6' E. of Mount Young. 10 ft thick and 100 ft long in metavolcanic rocks. volcanjc rocks, hornfels, and slate Bd-13OC Grab sample of altered hornfels and slate. that are cut by numerous mafic dikes.

2 Juneau D-5 quadrangle, 3.5 miles N. Bleached and altered zone 20 ft thick in Mk-270 20-ft-long chip sample at 6-in. intervals 27%' W. of Mount Young. granodiorite. 'Irregular-trending iron- across altered zone. stained zones cutting metavolcanic( ?) Mk-273 Grab sample representative of iron-stained rocks. zones.

3 Juneau D-6 quadrangle, nunatak in Quartz-ankerite-barite veins as much as Mk-309 Selected sample of veins. Casement Glacier 2.1 miles S. 9' 1 ft thick within 10-15 ft thick al- E. from northwest corner of quad- tered zone in thin-bedded hornfels. rangle. 4 Juneau D-6 quadrangle 5 miles S. Altered granitic rock. Composite grab sample. 21x0 E. from northwkt corner of Selected sample of most altered rock. quadrangle. - 6 Juneau D-6 quadrangle, north shpre Amygdaloidal basalt, weakly mineral- Mk-156 100-ft-long chip sample at 2-ft intervals. Adams Inlet near triangulation ized. Mk-167 44-ft-long chip sample at 2-ft intervals. station "Upper." Mk-169 100-ft-long chip sample at 2-ft intervals. Mk-160 Selected sample representative of zone 4 ft long. Mk-162 100-ft-long chip sample at 2-ft intervals. Mk-164 110-ft-long chip sample at 2-ft intervals. MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

Sample Locality Geologic setting 66A Description of sample 6 Juneau D-6 quadrangle north of Baritebearing altered zone 10 ft thick, 10-ft-long chip sample across altered zone at White Glacier betwee; 6 and 6 adjacent to dike that cuts limestone. 6-in. intervals. miles N. 30' E. from southwest 10-it thick iron-stained shear zone cut- Selected sample adjacent to north wall of corner of quarangle. ting limestone: some dikes nearby. rliko Altered zones between 1 ft and 200 ft ~elezdspecimens near dikes. thick cutting volcanic rocks. Selected sample of richestappearing part of shear zone. 6-ft-long chip sample at 6-in. intervals. 200-ft-long chip sample at l-ft intervals. 50-ft-long chip sample at l-ft intervals. 7 Sandy Cove prospect. Juneau C-6 Steep quartz veins as much as 1 ft thick Mk-224 10-ft-long chip sample across face; sample quadrangle, 2.26 miles S. 29' E. cutting quartz monzonite. Local wall- interval 6 in. from northwest corner of quad- rock alteration adjacent to veins. (See Mk-226 6-ft-lorn channel through- hkh-grade-- zone in rangle. fig. 15.) face. Mk-226 6-ft-long chip sample at 6-in. intervals. Mk-227 Selected sample representing entire width of a 4-in.-thick vein. 6-ft-long channel sample across back of portal. Selected sample of 4-in.-thick pyrite-quartz vein. 14-in.-long channel sample in face. Selected sulfide-rich ore from highgrade zone in face. Selected sample representative of &in. of vein. I-ft-long channel sample across vein. Selected sample representative of altered wallrock. 18-in. chip sample across altered wallrock at 2-in. intervals. Selected sample of sulfide-rich ore. Do.

8 Juneau C-6 quadrangle, north of Numerous pyrite-rich veins as much as Mk-431 Seleqted samples renresentative of pyrite-rich York Creek about 7.6 miles S. 6 in. thick cutting hornfels. velns. 221h0 E. from northwest corner of Iron-stained breccia zone cutting horn- Mk-434A 20-ft-long chip sample at l-ft intervals across quadrangle. fels. breccia zone. 9 Skagway A-3 quadrangle ; location Molybdenite-bearing float found on mor- doubtful. aine of Casement Glacier by Ohio State Univ. nlacioIogists in 1966. ------10 Skagway A-3 quadrangle, west of Sulfide-hearing ankeritic zones at facies Mk-411 Selected samples of richest-appearing sulfide- McBride Glacier 3.8 miles N. 65" change between phyllite and marble. bearing rock. W. of Coleman Peak. Mk-412 2-ft-long channel sample across ankeritic zone. Hx-251 11 Skaaway A-3 quadrangle. 2.7 miles Small prospect pits and trenches on Mk-146A Selected sample from shear zone. N. 38' E. from southwest corner iron-stained breccia and shear zones Mk-145B Selected sample from breccia zone. of quadrangle. between 1 and 12 ft thick. Country Mk-146 Iron-stained rock from shear zone, selected rock is granodiorite and hornfels. Mk-151 sample. Grab sample from iron-stained fault zone 12 ft thick. 12 Skagway A-4 quadrangle, approxi- Altered zones as much as 30 ft thick Mk-316 Sulfide-rich float, source probably nearby. mately between 0.9 and 1.3 miles enclosing discrete ankeritic veins as Bd-280 Grab sample from sulfide-rich vein, about 8 west of Mount Brack. much as 1 ft thick in limestone, silt- in. thick, that cuts a mafic dike. stone, shale, and graywacke: some Grab sample from pyritic vein about 1 in. mafic dikes.

thick 13 Skagway A4 quadrangle, on Minne- Copper- and iron-stained tonalite or Bd-l85B Float. sota Ridge near Glacier Pass. granodiorite. 14 Skagway A-5 quadrangle. Gable Joint coatings in dioritic rock through- Bd-466B Composite grab sample. Mountain north of Carroll Glacier. out a large area. 15 Near southwest corner of Skayway Iron-stained altered zone about 100 ft Bd-723 Float, probably representative of altered zone. A-6 quadrangle. thick near contact between hornfels and instrusive rock. 16 Near southwest corner of Skagway Lens of copper- and iron-stained horn- Bd-746 Grab sample from lens. A-5 quadrangle. fels about 10 ft long and 6 ft thick. 17 Skagway A-6 quadrangle. west of Altered and brecciated zones in grano- Selected specimen. Tarr Inlet south of Margerie Gla- diorite, generally between 2 and 12 Composite grab sample from an altered zone cter. ft thick. about 12 ft thick. Grab sample representative of a 2-ft-thick altered zone. 18 Skagway A-6 quadrangle. west of Altered hornfels with sulfides as much Composite grab sample. Tarr Inlet south of Margerie Gla- as 2 ft thick. cler. 19 Margerie prospect, Skayway A-6 Quartz veins as much as 2 ft thick, al- 1-ft-long channel sample of quartz vein. quadrangle, south of Margerie Gla- tered zones as much as 12 ft thick. no cier. in hornfels and granodiorite. Do. Chip sample at intervals of 4 in. across 6 ft of altered zone. Massive sulfide float. pyrrhotite rich. 20 Mount Fairweather D-1 quadrangle, Small pyrite-rich pods less than 6 ft Mk-222 Selected specimen from pyrite-rich pod. 3 miles S. 37' W. from northeast long and 1 ft thick in limestone. corner of quadrangle. MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

SAMPLE DATA FOR TABLE 9-Continued

Sample Locality Geologic setting 66A- Description of samde 21 Nunatak molybdenum prospect. Extensive stockworks of molybdenite- Analyses are shown in table 13. Mount Fairweather D-1 quadran- bearing quartz veins mainly in horn- gle 3.6 miles S. 77" W. from fels. norbeast corner of quadrangle.

22 Mount Fairweather D-1 quadrangle. Molybdenite coating fractures in meta- No analyses. north shore of Adams Inlet near morphic rocks (Smith, 1942, p. 178). entrance; locality not found.

23 Mount Fairweather Dl quadrangle. Iron-stained nones 1-2 ft thick contigu- MIS-186A Selected specimen of pyritized and, iron- between 3.6 and 6.6 miles S. 46' E. ous to maflc dikes that cut hornfels: stained hornfels. from northwest corner of quad- some thin quartz veins in altered Mk-187 Grab sample representative of iron-stained rangle. At north edge of Plateau zones. zones. Glacier. ~k-200 Selected sample representative of 6-in.-thick quartz vein.

24 Mount Fairweather C1 quadrangle. Sulfides disseminated in marble near No analyses. North Marble Island. about 6.8 porphyritic dikes and also in the dikes miles S. 38' W. from northeast (Reed, 1938. p. 69). Not found during corner of quadrangle. present investigation.

26 Mount Fairweather C-1 quadrangle. Sulfides disseminated in maRc dikes and Mk-86 Selected sample near lower contact of large south Marble Island about 7.4 miles in silicified limestone and marble near dike. S. 1254' W. from northeast cor- dikes. Mk-38 Selected sample a few inches below upper ner of quadrangle. contact of large dike. MkJ9 Selected sample of sulfide-bearing mafic dike. Mk-41 Do. 26 Mount Fairweather C-1 quadrangle, Sulfide replacement in limestone (Reed. No analyses. prospect on northeastern part of 1938, p. 70-72). Not found during cur- Willoughby Island about 8 miles N. rent investigations. 34' W. from southeast corner of quadrangle : location doubtful.

27 Mount Fairweather C-1 quadrangle, Sulfide replacement of intersecting lam- No analyses. prospect on west side of Willough- prophyre dikes that cut marble (Reed, by Island; location doubtful, prob- 1938. p. 70-72). Not found during cur- ably about 8 miles N. 38%' W. rent investigation. from southeast corner of quadrangle.

28 Mount Fairweather GI quadrangle, Sulfides and their oxidation products in Mk-17 Sulfide-bearing float. near southwest extremity of Fran- tactite near quartz diorite. (See fig. Hf-l83B Grab sample of copper-stained metamorphic cis Island. 8.) rock. Hf-183C Grab sample of sulfide-bearing contact rock. - 29 Mount Fairweather B-1 quadrangle. Sulfide-rich replacementa and dissemina- Mk-469 61-ft-long chip sample at 1-ft intervals. Alaska Chief prospect, 6.4 miles S. tions in metamorphic rocks near con- Mk-470 63-ft-long chip sample at 1 ft intervals. 42%' W. from northwest corner tact wih granodiorite ; well-developed Mk-471 6-ft-long chip sample, at 6-in. intervals, of quadrangle. gossan. (See fig. 9.) across back of adit near face. Mk-472 6-ft-long chip sample, at 3-in. intervals, across back of portal of adit. ~k-473 61-ft-long chip sample at 1-ft intervals. Mk-476 Grab sample from ore pile. Mk-174 Soil sample.

30 Mount Fairweather El quadrangle Shear zone in granodiorite or quartz Hxb04B Grab sample from shear zone. about 1 mile southwest of Alaska monzonite. Chief prospect.

31 Mount Fairweather B-1 quadrangle, Altered zone, more than 100 ft thick, Mk-481 Grab sample from altered zone. east side of mouth of Dundas River in metamorphic rocks. Mk-482 30-ft-long chip sample at 1-ft intervals. about 9 miles S. 11' E. from north- Mk-483 Selected sam~leof sulfide-rich rock. west corner of quadrangle. Hx-643 Selected sam~leof pyritic schist. Hx-644 40-ft-long chip sample at 2-ft intervals across best appearing part of altered zone. Hxd44B Selected sample of copper-stained rock from altered zone.

32 Mount Fairweather B-1 quadrangle. Copper-stained quartz veins in cataclas- Hx-648 Selected sample representative of quartz veins east shore of Dundas Bay about tic quartz diorite. and host rock. 8 miles N. 17' E. of soLthwest corner of quadrangle.

33 Mount Fairweatber El quadrangle, Iron deposlt shown on unpublished map No analyses. about 8.8 miles N. 41' E. from by Rosaman. Probably along contact southwest corner of quadrangle. between quartz diorite and marble. 34 Mount Faitweather D-2 quadrangle. Narrow veins and extensive altered Mk-86A Selected specimen of sulfide-rich float ; source in Bruce Hills 1.4 miles S. 30' W. zones in fractured granodiorite with probably nearby. from northeast corner of quad- minor hornfels. (See fig. 10.) Mk-86B Selected specimen of granodiorite with sul- rangle. fide-bearing veinlets. ~k-85~ Grab sample of gossan. Mk-86A Sulfide-bearing float. Mk-86B Selected sample of pyriterich vein. bfk-178 Grab sample representative of 4-ft-thick altered zone in granodiofite. Mk-179 Channel sam~leacross 6-m.thick quartz vein. Re66 6.ft chip sample at 6-in. intervals across altered zone. 36 Mount Fairweather D-2 quadrangle, Two molybdenite- and chalcopyrite- Bd-273D Se!ected sample of richest-appearing material on Wachusett Inlet 3.7 miles S. bearing quartz veins. 1-2 in. thick, in ~n vein. 20' W. from northeast corner of tonalite. auadranule. METALLIC COMMODITIES

Samole Loeation Geologic setting 66A-- Description of sample 36 Mount Fairweather 0-2 quadrangle, A few hundred pounds of molybdenite No analyses. on Triangle Island near north end were reportedly (Rossman, 1963b, p. of Queen Inlet. K49) mined from Triangle Island in one day. No molybdenite was found on the island during the present study. 37 Mount Fairweather D-2 quadrangle. Two patented claims on short adit $at MI442 Grab sample representative of vein. west of Rendu Inlet. is caved at portal; not found wlth ldk-544 Selected specimen from a 6-in.-thick auxiliary certainty. Probably represented by vein. a badly caved working on 6-in.-thick calc~te-rich vem. Dioritic dike in footwall. marble in hanging wall. 38 Mount Fairweather D-2 quadrangle, Irregular iron-stained altered zones, less Mk-558 Selected sample from altered zone. west of mouth of Rendu nlet. than 1 ft thick and about 20 ft long. Mk-659 Selected sample from pyrite-rich lens, about in marble. 2 in. thick, near footwall of altered zone. 39 Mount Fairweather D-2 quadrangle. Irregular masses of skarn near contact Mk-648 Selected sample representative of an altered on ridge west of Rendu Inlet. between diorite and marble; local py- zone. about 16 ft thick. rite-rich lenses and altered zones. Mk-649 Grab sample of skarn. (See Ag. 17.) Hx-626 Do. - - 40 Mount Fairweather D-2 quadrangle. Magnetic in skarn near felsic intrusive Mk-298A 18-ft-long chip sample at 6-in. intervals east of Queen Inlet, northeast of rocks. Some irregular pyrite-rich zones across skarn. Composite Island. mainly in nearby metamorphic rocks. Mk-298B Selected sample of magnetite and sulfides. (See PI. 10.) Mk-299 Do. Mk-803 Grab sample of skarn and sulfldea from 2-ft- thick skarn. Mk-306 Grab sample sulfide-bearing altered zone. Mk-321 Selected sakple of pyrite-rich vein 6 in. thick. Mk-323 Selected eample. pyrite-rich vein 4 in. thick. Mk-824 Grab sample representative of pyrite-rich pod 6 ft thick and 20 it lon~r. 41 Mount Fairweather D-2 quadrangle. Near contact between metamorphic Hx-260V Grab sample float of sulfide-bearing quartz 3.2 milea N. 11' W. from southeast rocks, chiefly marble, and altered vem. corner of quadrangle. hornblende diorite. 42 Mount Fairweather D-2 quadrangle. Mineralized shear zones as much as 12 Mk-48 Chip sample across the richest appearing 2 it southern part of Gilbert Island. ft thick and a few quartz-calcite veins of an altered zone at 3-in. intervals. north of Blue Mouse Cove. as much as 1% ft thick.

43 Mount Fairweather D-2 quadrangle, Sulfide-bearing tactite 1 ft thick in Hx-659A Grab sample representative of a 1-ft-thick sul- north of summit of Gilbert Island. marble 3 ft thick. fide-bearing tactite zone. 44 Mount Fairweather D-2 quadrangle, Fractured quartz diorite that is cut Mk-84A Selected sample of quartz veins with minor island south of southwest tip of by aplite and alaskite dikes and by sulfides. Gilbert Island. thin veins and clay seams. Mk-44B Grab sample of quartz veins with minor sulfides. 45 Mount Fairweather D-2 quadrangle, Bleached and fractured quartz diorite Mk-66 Selected specimen of a 6-in.-thick quartz vein. near southwest tip of Gilbert that contains sockworks of quartz MI-67 Selected specimen of ouartz vein (float). Island. veins and veinlets abundant clay Mk-68 Grab sample from aplite dike. seams. and a few apiite dikes. Altered Mk-69 100-ft-long chip sample taken at 4-ft inter- zone is several hundred feet long and vals. at least 60 ft thick. Mk-72, 52-ft-long chip sample taken at 4-ft intervals. 46 Mount Fairweather D-2 quadrangle, Three iron-stained pyritic quartz veins Bd-37B Selected sample of beat appearing vein mate- west of Hugh Miller Inlet near each 1- than half an inch thick, ii rial. southwest corner of quadrangle. hornblende diorite.

47 Mount Fairweather C-2 quadrangle. Flat-lying altered zone about 60 ft Mk-123 30-ft-long chip sample at 1-ft intervals over about 0.7 mile northeast from the thick in fine-grained diorite. best appearing part of altered wne. head of Charpentier Inlet.

48 Mount Fairweather C-2 quadrangle, Sulfide-bearing greenschist, apparently Hx-67 Selected sample. north shore. Geikie Inlet about 2 large. miles from entrance.

49 Mount Fairweather C2 quadrangle. Quartz-pyrite veins in sheared quartz- Hx-32A 3-ft-long closely spaced chip sample of zone west shore of Shag Cove near its ose zone. and quartz stringers. entrance. About 7.2 miles S. So W. Hx-32B Selected sample mica1 of pyritic pod about from northeast corner of quad- 3 ft long and 6 in thick. ran~rle. 50 Mount Fairweather C-2 quadrangle. Not found durin~present investigation, No analyses. at a rather high elevation south- Molybdenite associated with garnet in west of the head of Geikie Inlet; tactite (Smith, 1942, p. 178). location doubtful. 51 Mount Fairweather C-2 quadrangle, Magnetic anomaly noted by Seitz (1969, No analyses. west of Blackthorn Peak. p. 16). Not found during present ~n- vestigation. 52 Mount Fairweather C-2 quadrangle. Gold placer in glacially derived gravels No analyses. south of Wood Lake: loeation (Rossman, 1963b. D. KSO). doubtful. 53 Mount Fairweather B-2 quadrangle: Gold placer claims on upper Dundaa No analyses. location doubtful. River. - -- 54 Mount Fairweather B-2 quadrangle. Several lenses of magnetite-rich skarn Mk-46OA Selected sample of sknrn. east of Brady Glacier. south of as much as 10 ft thick and 30 ft Mk-46OB Grab sample of sknrn. Abyss Lake. long ; minor sulfides. MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

SAMPLE DATA FOR TABLE 9-Continued

- Sample Locality Geologic setting 66A- Description of sample 66 Mount Fairweather B-2 quadrangle, On faulted quartz veins as much as 8 pdJ~Lk-466 Composite grab sample from quartz veins. east of lower Brady Glacier. in. thick. Probably at or near locality described by Rossman (19634 p. K60).

66 Mount Fairweather B-2 quadrangle, Float from molyhdenite-bearing quartz No analyses. on lower Brady Glacier. veins reported by Smith (1942, p. 177) and by Buddington and Chapin (1929, p. 329, 330). 67 Mount Fairweather B-2 quadrangle, Gold-bearing quartz veins reported by No analyses. south of West Arm of Dundas Bay. Rossman (unpub. data) : not found during current investigation.

68 Mount Fairweather B-2 quadrangle, Copper-bearing hornblendite dikes cut- Hx-484A Grab sample of copper-bearing hornblendite. on island in West Arm of Dundas ting diorite. Bay. 69 Mount Fairweather B2 quadrangle. Placer-gold deposita reported by Ross- No analyses. outwash of Brady Glacier. man (1963b. p. KSO). 60 Mount Fairweather D-3 quadrangle. Molybdenite-bearing quartz veins, less No analyses. west of Rendu Inlet. than 2 in. thick. with minor chalcopyrite and pyrite.

61 Mount Fairweather D-3 quadrangle Two quartz-calcite veins, 3-6 in. thick. Ov-2041 Selected sample of quartz veins. on north side of Russel Island. within a 3-ft-thick altered zone cut ting granodiorite. 62 Mount Fairweather D-3 quadrangle. Several copper-hearing quartz-calcite Fd-428B Grab sample of veins. on west side of Tarr Inlet. veins aa much as 6 in. thick within a 6-ft-thick zone of hornblende diorite pegmatite. 63 Mount Fairweather D-3 quadrangle, Altered pale-green quartz monzonite Hx-391 Grab sample containing sulfides. west of Tarr Inlet. with local disseminated sulfides and sulfide-bearing veinlets.

64 Mount Fairweather D-3 quadrangle, Altered zones between 3 and 100 ft wide Mk-396 Grab sample from an altered zone about 100 north shore of Johns Hopkins Inlet in metamorphic. intrusive, and vol- ft wide. near west edge of quadrangle and canic rocks. Mk-399 8-ft-long chip sample at 6-in. intervals. extending into Mount Fairweather Mk-621 40-ft-long chip sample at l-ft intervals. D-4 auadrannle. Mk-622 Selected sam~leof -~vrite-rich - oart of altered zone. Mk-624 76-ft-long chip sample at 1-ft intervals. Mk-626 Chip sample at I-ft intervals across 10 ft of altered zone of Mk-624 nearest contact with granodiorite. Mk-627 10-ft-long chip sample at 6-in. intervals. Mk-628 Grab sample representative of richest appearing part of a 30-ft-wide alteration zone.

65 Mount Fairweather D-3 quadrangle, Altered granitic rocks with copper Fd-397 Composite grab sample. south of Johns Hopkins Inlet west stained fractures : altered zone is of Lamplugh Glacier. about 200 ft wide and extends several hundred feet along strike. 66 Mount Fairweather D-3 quadrangle. Hornfels containing disseminated py- Fd-382B Composite grab sample. west of Lamplugh Glacier. rite, appears to be part of extensive iron-stained area on southwest flank of Mount Cooper.

67 Mount Fairweather D-3 quadrangle. Copper-stained hornfels cut by a few Fd-433A Selected samples of a pyritic quartz vein. southwe~tof Lamplugh Glacier. quartz veins. Altered zone is more Fd-433B Selected sample of copper-stained hornfela. than a half mile long and a quarter of a mile wide. 68 Mount Fairweather D-3 quadrangle. Altered zone 60 ft thick at contact be- Ov-1903B Selected sample of best appearing material in west of the head of Lamplugh tween intrusive and metamorphic altered zone. Glacier. rocks. 69 Mount Fairweather D-3 quadrangle. Altered zones as much as 26 ft thick Mk-666 Grab sample representative of 10-ft-thick east of Reid Glacier. and a few narrow quartz veins in altered zone. strongly folded metamorphic rocks. Mk-667 Grab sample representative of a 16-ft-thick mainly marble. altered zone. Mk-668 Float from quartz vein.

70 Mount Fairweather D-3 quadrangle. Altered zones as much as 6 ft thick in Mk-366 5-ft-long chip sample at 4-in. intervals. near south end of ridge west of metamorphic rocks: a few quartz Mk-368 2-ft-long channel sample across a quartz Reid Glacier. veins between 6 in and 4 ft thick. vein. 71 Mount Fairweather C-3 quadrangle. Several widely spaced iron-stained alter- Mk-664 Crab sample representative of an 8-ft-thick east of Brady Galcier, south of the ation zones between 6 and 10 ft thick Fd-400A altered zone. head of Reid Inlet. within a schist and hornfels sequence. Selected sample of bet appearing mineralized part of alteration zone.

72 Brady Glacier nickel-copper prospect, Layered mafic and ultramafic intrusive on nunatak in Brady Glacier in rocks with disseminated and massive the southwestern part of Mount sulfides. (See fig. 18.) Fairweather G3 quadrangle. 73 Mount Fairweather B-3 quadrangle, Magnetite- and ilmenite-bearing lay- on Astrolabe Peninsula. ered mafic intrusive rocks, widespread but mainly throughout a stratigraphic interval of about 1,000 ft (Rossman. 1963a. p. F44) METALLIC COMMODITIES

Sample Locality Geologic setting 66A- Description of sample - 74 Mount Fairweather D-4 quadrangle, Oxidized pyrite-bearing igneous complex Mk-666 Composite grab sample. on south shore of Johns Hopkins about a quarter of a mile wide. Inlet west of Lamplugh Glacier. 76 Mount Fairweather D-4 quadrangle, Pyritic hornfels between 4 and 6 ft Fd-402 Composite grab sample. south shore of Johns Hopkins Inlet thick. east of Hoonah Glacier. 76 Mount Fairweather D-4 quadrangle, Hornfels with disseminated sulfides Mk-631 Representative grab sample. northwest shore of Johns Hopkins throughout an extensive zone. Inlet. 77 Mount Fairweather D-4 quadrangle, Large altered zone (several hundred Bd-702A Composite grab sample of sulfide-bearing south of Johns Hopkins Inlet, east feet thick) in hornfels near intrusive hornfels. of Hoonah Glacier. contact. Bd-702C Composite grab sample of hornfels with gray sulfides. ------78 Mount Fairweather C-4 quadrangle, Copper-stained amphibolite (Rossman, both east and west of North Cril- unpub. notes). Ion Glacier. 79 Mount Fairweather C-4 and ques- Layered mafic intrusive rocks in contact tionahly C-6 quadrangle, north- with schist (Rossman, 1963a. P. F42, west edge of Crillon-LaPerouse F43; Kennedy and Walton, 1946, p. stock adjacent to North Crillon 67-72). Glacier. 80 Mount Fairweather C-4 and C-6 Layered mafic intrusive rocks near con- quadrangles, near contact of Cril- tact with metamorphic rocks (Ross- Ion-LaPerouse stock adjacent to man, 1963a. p. F42-F43; Kennedy South Crillon Glacier. and Walton, 1946, P. 71). 81 Mount Fairweather B-4 and G4 36 placer claims north of Laperouse quadrangles ; location doubtful, Or- Glacier (Alaska Div. Mines and Min- egon King claims. erals, written commun.) 82 Mount Fairweather B-4 quadrangle. Large cop~er-stained zone in gneias about 3 miles northwest of Mount near intrusive contact (Rossman. un- Marchainville. pub. notes). - 83 Mount Fairweather B-4 quadrangle. Iron-stained zones in layered mafic about 2% miles north of Mount intrusive rocks near contact with Marchainville. metamorphic rocks (Rossman, unpub.

84 Mount Fairweather C-6 quadrangle, Sulfides replacing dike (Kennedy and southwest shore of southeast arm Walton, 1946, p. 71). of Lituya Bay. 86 Mount Fairweather C-6 quadrangle, Hydrothermally altered zones with mi- southeast of Lituya Bay. nor gold values (Rossman, 1969, p. 67. 68). ------86 Mount Fairweather C-6 quadrangle, copper-bearing float in moraine (Ken- moraine on North Crillon Glacier. nedy and Walton, 1946, p. 71). 87 Mount Fairweather C-6 quadrangle. Beach placers (Rossman, 1963a. p. F46- south of mouth of Lituya Bay. F46; Rossman. 1957; Martin. 1933,

88 Mount Fairweather C-6 quadrangle. Beach placers (Rossman. 1963a. P. F46- north of mouth of Lituya Bay. F47; Rossman, 1957: Martin. 1933. p. 133-136). 12, sample Bd-280), probably as a constituent of a Mines and Minerals contained several percent anti- lead-bearing sulfosalt; the other, from the Francis mony. None of our samples from that general Island copper deposit (loc. 28, sample Hf-183B), vicinity contained antimony. contained 200 ppm antimony. ARSENIC Tetrahedrite has been reported from the prospect Arsenic was detected in samples from many local- on the west side of Willoughby Island (loc. 27) ities in the monument. It is particularly abundant in (Reed, 1938, p. 72), from the Rendu Inlet silver the Reid Inlet gold area (pl. 1) as a constituent of prospect (37) (A. F. Buddington, unpub. data, 1924) arsenopyrite that is associated with the gold lodes. (Rossman, 1963b, p. K48, K49), and from Blue Arsenic was also found in the Mount Brack argentif- Mouse Cove on the south shore of Gilbert Island erous base-metals deposits ( loc. 12), the Margerie (42) (Rossman, 1963b, p. K50). Buddington (1924, copper prospect (19), on the west side of Tarr Inlet unpub. notes) also reported jamesonite from the (17), and at a locality west of McBride Glacier (10). prospect on the west side of Willoughby Island and Most of the accessible Reid Inlet gold deposits noted that an ore sample from there contained 25 contain arsenic, which occurs commonly or entirely percent antimony. L. F. Parker (oral commun., 1966) in arsenopyrite. The arsenic content of samples from states that one of his samples from the north side of the LeRoy mine (table 11, loc. B) is as much as 20,- Johns Hopkins Inlet near locality 64 that was as- 000 ppm. Samples from the Rainbow mine (C) con- sayed by the State (then Territorial) Division of tained as much as 1,500 ppm arsenic, and those from 40 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA the Monarch mines (E) the Incas mine (G), and the CADMIUM Rambler prospect (L) , respectively, contained maxi- Cadmium was detected from four localities in the ma of 7,000, 20,000, and 50,000 ppm arsenic. Minor monument (tables 9, 11): the Mount Brack argentif- amounts of arsenopyrite are reported from the gold erous base-metal deposits (loc. 12), sulfide lenses quartz veins of the Sunrise prospect east of Reid southwest of Red Mountain (20), the LeRoy mine Inlet (Reed, 1938, p. 64). An unidentified arsenic ' (B), and the copper-zinc deposits north of White mineral was collected from a narrow vein on the Glacier (6). The most cadmium found, 1,000 ppm, eastern shore of Reid Inlet (Rossman, 1959, p. 57). was in a sample from the LeRoy mine. Cadmium Arsenopyrite is also a probable accessory mineral in proxies for zinc geochemically, and all the cadmium- the unsampled and inaccessible gold lodes near Reid bearing samples contained larger amounts of zinc Inlet, whose geologic settings are similar to those of than of cadmium. Probably most of the cadmium is nearby arsenic-bearing deposits., a minor constituent of sphalerite, but possibly some Two samples from the Mount Brack deposits of it forms the cadmium sulfide greenockite. (table 9, loc. 12) contained 7,000 and 30,000 ppm COPPER arsenic, respectively. These samples represent com- DISTRIBUTION plex silver-bearing base-metal deposits, but the min- Copper minerals are widespread and locally abun- eral host for the arsenic was not determined. A dant throughout the monument (pl. 1). Among the sample from a quartz vein at the Margerie copper previously known deposits whose major commodity prospect (19) carried more than 10 percent arsenic. is copper are those on the west side of Tarr Inlet Another sample from the same vein contained 50,000 (loc. 18), at the Margerie prospect (19), on Wil- ppm arsenic, and a sample from a nearby altered loughby Island (26, 27), on Francis Island (28), at zone revealed 2,000 ppm arsenic. Arsenic at the Mar- the Alaska Chief prospect (29), and at several local- gerie prospect is incorporated in arsenopyrite. An ities in the Fairweather Range (78, 80, 82). In addi- altered zone on the west side of Tarr Inlet (17) tion, copper constitutes a potential byproduct at the south of the Margerie Glacier contained 5,000 ppm Brady Glacier nickel-copper deposit (72), the Nuna- arsenic. Arsenic in quantities of 7,000 and 15,000 tak molybdenum prospect (21), the Sandy Cove gold-copper prospect (7), and the Rendu Inlet silver ppm was detected from a deposit localized at a facies prospect (37). change between marble and phyllite west of McBride Most of the discoveries resulting from our inves- Glacier (10). tigations contain anomalous concentrations of cop- Lollingite, an iron diarsenide, was questionably per. The most significant of these are north of White identified from the prospect on the northeast side of Glacier (pl. 1, loc. 6), near Gable Mountain (14), Willoughby Island (table 9, loc. 26) (Reed, 1938, p. south of Rendu Glacier (15), near Dundas Bay (31), 70, 71). Minor amounts of arsenic are reported in in the Bruce Hills (34), west of Shag Cove (49), and spectrographic analyses of the tactite that crops out west of Tarr Inlet (62,63). south of Mount Merriam in the Mount Fairweather TYPES OF DEPOSITS D-2 quadrangle (Rossman, 1963b, p. K41). The copper lodes occur in diverse types of deposits Many of the arsenic-bearing deposits are associ- in several different geologic environments; they inated with gold and silver, and, as often is the case, clude (1) altered zones, mainly mineralized fault the arsenic minerals may serve as useful indicators zones, (2) massive sulfide bodies, (3) veins, (4) in prospecting for those precious metals. fracture coatings, (5) local disseminations, (6) contact-metamorphic deposits, and (7) low-grade BISMUTH copper-bearing amygdaloid. A clear distinction of Small amounts of bismuth were detected in sam- type is impossible for many deposits because of in- ples from 12 localities (pl. 1; tables 9, 11). The high- tergradation of types. Typical examples of these est bismuth contents shown by the analyses were 500 types are described below. pprn from the Sandy Cove gold-copper prospect (loc. Deposits in altered fault zones are best exempli- 7), 300 ppm from the Margerie copper prospect (19), fied by those east of Dundas Bay (pl. 1, loc. 31). The 200 ppm from the Alaska Chief copper prospect massive sulfide deposits are diverse and include re- (29), and 150 ppm from the Francis Island copper placements in metamorphic rocks as at the Alaska prospect (28). No bismuth-bearing minerals were Chief prospect (29), the nickel-copper lenses in identified, but bismuth is probably a minor constitu- gabbro at the Brady Glacier prospect, and the ent of some of the sulfides or sulfosalts. cupriferous pyrrhotite-rich lenses(?) at the Mar- METALLIC COMMODITIES ' 41 gerie prospect (19). The copper-bearing veins are analytical results were from a sample consisting of widely distributed but are generally narrow. They sulfides, chiefly pyrite, replacing metavolcanic rocks are predominantly quartz veins, but some contain and from a sample of altered hornfels and slate moderate quantities of calcite. The gold-bearing (table 9, loc. 1). These samples contained as much as veins at the Sandy Cove prospect (7) carry good 1,500 ppm zinc and slightly anomalous amounts of copper values, and many other veins in the monu- silver, chromium, copper, molybdenum, and lead. The ment are enriched in copper. Stockworks of closely deposits consist of short quartz veins that commonly spaced veins and veinlets in bleached and altered are less than 6 inches thick and numerous altered metamorphic and intrusive rocks at the Nunatak zones, commonly about 2 feet thick, which were molybdenum prospect (21) form deposits that are traceable for only a few tens of feet because of con- similar to some porphyry copper deposits. Similar tiguous ice and snow. A few altered zones are as stockworks form parts of the Bruce Hills deposit (34) and parts of the deposits at and near the much as 10 feet thick and are exposed for about 100 southwestern end of Gilbert Island (44, 45). Copper feet. The altered zones transect metavolcanic rocks, minerals coat fractures at the deposit at Gable schist, hornfels, slate, and marble; a few zones are Mountain (14) and at a few other deposits. Dissem- localized along the margins of mafic dikes that cut inated copper minerals were noted in granodiorite in the metamorphic rocks. The altered zones consist of the Bruce Hills (34), in siliceous lenses west of Tarr hydrous iron sesquioxides, carbonate minerals, and Inlet (63), in hornblendite dikes near Dundas Bay quartz; subordinate pyrite, traces of chalcopyrite, (58), and in hornfels at a few localities near Johns probably a secondary zinc mineral, barite, and clay Hopkins Inlet (75, 76). Copper minerals are sub- minerals are also present. ordinant constituents of some of the skarns, as at The quartz veins are best developed in the schist. the Queen Inlet magnetite deposit (40) and the de- They also occur in the other metamorphic rocks, posit south of Abyss Lake (54). A very lean copper along the margins of dikes, and as ladder veins with- deposit is localized in the amygdaloid on the north in the dikes. Commonly, the veins contain minor shore of Adams Inlet (5). amounts of pyrite and, rarely, traces of chalcopyrite. In general, the deposits range in size from isolated Assays of samples from three of the quartz veins all veins and lenses only a few inches thick, through sul- showed less than 0.0015 ounce per ton gold. fide bodies a few tens of feet in minimum dimension, Several iron-stained ankeritic altered zones be- to extensive networks of veins and mineralized zones tween 5 and 30 feet thick cut granitic rocks near lo- that are several hundred feet wide. The deposits are cality 2, about 3.5 miles northwest of Mount Young in many different geologic settings, but most of them (pl. 1). Samples from these zones contained slightly are in or near intrusive rocks. anomalous amounts of copper and molybdenum Chalcopyrite is the predominant copper mineral in (table 9, loc. 2) and less than 0.0015 ounce per ton almost all the deposits. Bornite or tetrahedrite is the gold. Copper minerals have been reported near chief ore mineral in a few of the deposits and sub- Mount Young and in samples taken a few miles west ordinate associates of chalcopyrite in several others. of Mount Young (Lathram and others, 1959, their Secondary copper minerals, chiefly azurite, mala- Nos. 18, 20). The deposits near Mount Young which chite, and chrysocolla, are sparsely distributed in a were examined are too lean to be of economic im- few of the lodes. portance, but the abundant weak mineralization and concealment of much of the bedrock by snow and ice DESCRIPTIONS OF DEPOSITS might warrant additional prospecting during a rel- MOUNTYOUNG AREA atively snow-free summer or prospecting by geo- Several small base-metal and silver deposits occur physical methods. near Mount Young (pl. 1, loc. 1). Only two of our samples from these deposits showed anomalous EAST OF CASEMENTGLACIER amounts of metals, and in these the minor zinc and Several altered zones cut the granitic rocks near silver values outweigh those of copper. However, the the southeast edge of casement Glacier (pl. 1, loc. 4). deposits are discussed under copper because some of These zones are 5-30 feet thick and probably are them contain chalcopyrite and because copper min- mineralized fault zones. They are best developed erals have been reported nearby. near contacts between the granitic rocks and horn- The deposits are in a geologically complex area fels. The zones contain scattered pyrite and an array characterized by a variety of metamorphic rocks, of oxidized gangue minerals. Analyses of represen- small granitic plutons, and mafic dikes. The highest tative samples of these altered zones shows only 42 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA slightly anomalous amounts of copper and molyb- zones are near mafic dikes and a small granitic cu- denum (table 9, loc. 4). pola that cuts the limestone. The altered zones in the Many conspicuous altered zones as much as 50 feet limestone are less than 10 feet thick and generally thick occur near Snow Dome, about 5 miles north- not traceable for more than 100 feet. Those in the east of locality 4 (pl. 1). They are mainly localized volcanic rocks are less numerous but larger and near contacts between granitic rocks and hornfels. range in thickness from 2 to 200 feet; some of them Samples collected from these zones were virtually can be traced for long distances. barren of ore metals. The altered zones in the limestone contain abundant ankeritic carbonates and barite and lesser NORTH SHOREOF ADAMSINLET amounts of quartz, chlorite, pyrite, and copper min- Weakly mineralized amygdaloidal lavas are ex- erals. Parallel sets of quartz veins between 1 and 4 posed for about 500 feet along the north shore of inches thick transect some of the zones. Several Adams Inlet (pl. 1 loc. 5). A few steeply dipping zones are parallel to mafic dikes, and a few are cut mafic dikes cut the lavas. The lavas are flows of by mafic dikes. The sulfide mineralization com- amygdaloidal and vesicular altered basalt as much as monly is strongest near the borders of the dikes. 15 feet thick. They are prophyritic with plagioclase Thin pyritic lenses occur on bedding surfaces in the (labradorite) phenocrysts in a highly altered very limestone contiguous to the altered zones. Analyses fine grained groundmass that probably orignally of samples from altered zones that cut the limestone was intergranular or intersertal. Phenocrysts con- are shown in table 9 (loc. 6 Nos. 66AMk-253 stitute about a third of the rock and are as much as through 256B). These zones locally carry significant 6 mm long, but typically about 3 mm long. The amounts of copper and minor amounts of silver, altered groundmass is composed of epidote, actino- zinc, and cadmium. Their gold content is negligible. lite, and lesser amounts of calcite, dolomite, and The altered zones in the volcanic rocks are con- chlorite. Minor amounts of pyrite are scattered spicuously iron stained. A few locally contain abun- throughout the lavas. dant pyrite. A 6-foot-long chip sample representative All the lavas are weakly mineralized by sulfides, of one of these zones carried 20,000 ppm zinc (table most of which are localized along fractures and gen- 9, loc. 4 No.66AMk-257). The host mineral for the erally are most abundant near the dikes. The sul- zinc was not identified. Gold values in samples from fides, which probably formed during the low-grade these zones were negligible. metamorphism of the lavas, consist of pyrite and The deposits north of White Glacier appear to be trace amounts of chalcopyrite and pyrrhotite( ?). locally rich enough and large enough to warrant pros- Extensive sampling showed that the lavas are very pecting. A few altered zones south of White Gla- low in metal content (table 9, loc. 5). All the samples cier south of locality 8 were examined, but samples contained slightly anomalous amounts of copper; one from them yielded negative results. sample contained 300 ppm cobalt. Most samples contained trace amounts of molybdenum; one contained NORTHOF YORKCREEK silver and tin. About 15 widely spaced pyrite-rich veins and al- The mafic dikes are also altered basalts, but they tered zones containing pods of pyrite cut the hornfels are more intensely altered than the lavas. They are country rock north of York Creek (pl. 1, loc 8). A porphyritic and consist of medium-grained plagio- sample representative of the hornfels consists mainly clase phenocrysts in a highly altered, very fine of quartz and tremolite and moderate amounts of grained groundmass. The phenocrysts are probably plagioclase and minor biotite. Both the veins and the oligoclase, and their cores are generally more altered altered zones commonly strike betweeen N. 10" than their rims. The goundmass is predominantly E. and N. 40" E. and dip steeply. They both epidote and actinolite, but it contains small amounts consist mainly of quartz and smaller quantities of of calcite, chlorite, and leucoxene. Pyrite and subor- pyrite, pyrrhotite, and dolomite. Most of the veins dinate ilmenite and magnetite are scattered through- are about 6 inches thick. A sample representative of out the dikes. one vein (table 9, loc. 8) contained 1,500 ppm copper and small amounts of cobalt and nickel. Some of the NORTH OF WHITEGI.ACIER altered zones are brecciated, and some attain widths Many mineralized zones are exposed north and of about 50 feet. A chip sample across one of the al- northeast of a northward protruding lobe of White tered zones (table 9, loc. 8) carried 15 ppm of molyb- Glacier (pl. 1, loc. 6). These zones cut both limestone denum. The deposits north of York Creek are too and the structurally overlying volcanic rocks. Some small or too lean to justify exploration. METALLIC COMMODITIES 43

MINNESOTARIDGE cality is probably at or near two lode claims for cop- Copper minerals were found on Minnesota Ridge in per that are held by the Kenney Presbyterian Home, a small outcrop within an extensive snowfield (pl. but no workings or claim markers were found in the 1, loc. 13). The outcrop is composed of coarse-grained vicinity. Claims on copper lodes were reportedly biotite-hornblende granodiorite or quartz diorite that staked in the general area before 1906 (Wright and is cut by a 3-foot-thick porphyritic andesite dike. Wright, 1937, p. 221). A stream-sediment sample col- The deposit consists of pyrite, chalcopyrite, and sec- lected a few hundred feet south of locality 18 (see pl. ondary copper or iron minerals that were probably 8) contained 700 pprn copper, 0.29 ounce per ton (10 deposited as open-space fillings along narrow joints ppm) silver, 10 pprn molybdenum, 10 pprn bismuth, with subordinate replacement of the adjacent wall- 50 pprn cadmium, 30 pprn arsenic, 200 pprn lead, 500 rock. A sample of the richest appearing mineralized pprn tin, and 1,000 pprn zinc. The mineralized zones material contained 700 pprn copper (table 9, loc. 13). are fairly widespread, and further exploration might The size of the deposit is conjectural because of the be worthwhile. snow cover, but the deposit is too low in grade to MAROERIEPROSPECT encourage exploration. The Margerie prospect is in steep and rugged ter- GABLEMOUNTAIN rain south of Margerie Glacier at altitudes between Outcrops of coarse-grained dioritic rocks, probably 1,500 and 2,000 feet (pl. 1, loc. 19). The prospect is quartz diorite, are exposed irregularly in a largely on several claims located in 1960 for the Moneta Por- snow-covered area near Gable Mountain north of cupine Co. The deposits are in light-colored gran- Carrol Glacier (pl. 1, loc. 14). The deposits consist of odiorite and nearby high-rank metamorphic rocks, joint coatings of unknown extent. The chief copper chiefly hornfelses. They consist of quartz veins, minerals are malachite and chrysocolla. A composite mineralized shear zones, and pyrrhotite-rich massive grab sample from the deposits contained 1,000 pprn sulfide bodies. The quartz veins, which are as much copper and small amounts of silver and molybdenum as 2 feet thick, commonly strike northeast and dip (table 9, loc. 14). Remoteness, difficult access, and gently south. Their chief sulfide minerals are snow cover will inhibit the prospecting of these arsenopyrite and chalcopyrite. Samples from the deposits. quartz veins carry as much as 2,000 pprn copper, SOUTHOF RENDUGLACIER more than 10 percent arsenic, minor amounts of bis- A mineralized altered zone is exposed at altitudes muth, cobalt, and tungsten, traces of molybdenum, near 4,000 feet in the cliffs south of Rendu Glacier and as much as 0.145 ounce per ton (5 ppm) gold (pl. 1, loc. 15). The zone cannot be reached without a (table 9, loc. 19). difficult rock climb, and, consequently, it was not ex- The altered zones strike about N. 30" W. and dip amined closely. In aerial reconnaissance the altered steeply to the southwest. They are about 6 feet thick zone appears to be in mixed rocks near the contact and strongly sheared. Many of the nearby joints are with a light-gray granitic pluton. It is exposed over coated with the alteration products and probably a surface about 50 by 200 feet. The margins of the contain minor quantities or ore minerals. The altered zone are partly concealed, and its actual dimensions zones are profusely iron stained, and their constitu- may be much larger. A sample of float from the ent minerals were not identifiable megascopically. altered zone carried 2,000 pprn copper (table 9, loc. Samples from the altered zones contained as much 15). A thorough examination of the deposit, includ- as 700 pprn copper and 2,000 pprn arsenic and ing detailed sampling, is probably warranted despite slightly anomalous amounts of barium (table 9, loc. the deposit's inhospitable setting and remoteness. 19).

WEST SHOREOF TARRINLET The massive sulfides were not found in place, but Copper lodes occur on the west side of Tarr Inlet judging from float, they probably occur in the steep about a mile south of Margerie Glacier (pl. 1, loc. cliffs south of the prospect. The float is predomi- 18). The deposits are fairly extensive and consist of nantly pyrrhotite associated with minor chalcopy- alteration zones between 1 and 8 feet thick and local rite, quartz, and an unidentified tungsten mineral. A disseminated sulfides in hornfels. Chalcopyrite is the sample of the massive sulfide contained 3,000 pprn predominant copper mineral; it generally is asso- copper and 3,000 pprn tungsten, the highest tungsten ciated with more abundant pyrite. A sample in- value of any of our samples (table 9, loc. 19). dicative of one of the best mineralized outcrops The examination of the prospect was brief because contained 1,500 pprn copper and minor amounts of of inclement weather. The prospect and its environs bismuth, tungsten, and tin (table 9, loc. 18). This lo- warrant a more thorough examination. 44 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

CURTISHILLS labradorite is slightly normally zoned. Both augite Several small mineral deposits were found in the and pigeonite are present. Pyroxene rims are altered recently deglaciated terrain west of the Curtis Hills to green hornblende, which constitutes about 10 per- (pl. 1, loc. 23). Hornfels is the predominant rock in cent of the rock. Magnetite is a minor primary ac- the area; it is cut by a few steep mafic dikes and cessory mineral, and a little sericite is an alteration locally mantled by glacial drift and snow. The horn- product of the plagioclase. fels is composed largely of tremolite and lesser The mineral deposits are associated with the amounts of plagioclase, calcite, and quartz. largest dikes and consist of disseminated pyrite The deposits consist of narrow quartz veins, com- within the dikes and pyrite-rich impregnations in the monly less than 6 inches thick, and of altered zones, silicified wallrock near borders of the dikes. A few generally less than 2 feet thick. Many of the quartz barren calcite veins cut some of the dikes. Samples veins are joint fillings. Pyrite is the only sulfide from the deposits were all low grade and contained only slightly anomalous amounts of copper and mineral recognized in both the veins and the altered nickel (table 9, loc. 25). Reed (1938, p. 69) states zones. that the sulfide mineralization on South Marble Some of the deposits contain minor amounts of Island is similar to that on North Marble Island but copper and chromium (table 9, loc. 23). Although the appears to be less intense. area is almost virgin because of its recent denuda- tion, the deposits in it appear to be too small and too WILLOUCHBYISLAND lean to encourage prospecting. Willoughby Island is underlain by massive light- gray limestone that has been locally converted to NORTHMARBLE ISLAND marble and is cut by many mafic dikes and a few North Marble Island (pl. 1, loc, 24) consists of felsic dikes. Glacial drift mantles some of the north- massive white marble cut by a few mafic dikes. Most eastern part of the island. Both the mafic and felsic of the marble is fairly pure and consists of a mosaic dikes are very fine grained. The mafic dikes are 2-30 of calcite crystals from 2-5 mm long. Some of the feet thick and retain relict pilotaxitic textures, but marble is dolomitic. The only sulfide mineral noted their original glassy groundmasses have been devit- is pyrite that occurs disseminated in some of the rified. They consist of labradorite microphenocrysts dikes and in the silicified zones adjacent to the dikes. and andesine microlites associated with an array of Reed (1938, 11. 69) reports sulfide bodies as much very fine grained minerals including chlorite, po- as 195 feet thick and 15 feet long in the marble near tassium-feldspar ( ?), cristobalite ( ?), opaque dust, some of the dikes and small deposits locally along and calcite. Their primary mafic minerals have been the dikes and in joints within the dikes. He states obliterated. Reed (1938, p. 72) reports that one of that the sulfide deposits contain pyrite, pyrrhotite, the mafic dikes from a prospect on the west side of chalcopyrite, and covellite. Buddington (unpub. data, the island consists mainly of andesine with consider- 1924) reported a claim staked for nickel on North able chlorite, quartz, pyroxene, and magnetite, and a Marble Island. Rossman (196313, p. K51) mentions a little calcite. The felsic dikes consist chiefly of quartz mass of sphalerite and magnetite which occurs in the and plagioclase. limestone (marble) on North Marble Island. Minor amounts of oxidized, hydrothermally al- SOUTHMARBLE ISLASI) tered material occu y thin breccia zones contiguous South Marble Island (111. 1, loc. 25) is composed of to some of the ma dikes and in the limestone and medium-grained white marble cut by numerous mafic marble. dikes. The marble is fairly pure and consists almost Two prospects e reportedly on Willoughby Is- entirely of an interlocking network of calcite crys- land (Reed, 1938, . 70), but despite an intensive tals. The dikes are more numerous and thicker than search, neither wa found. One of the reported pros- those on North Marble Island. Most of them strike pects is on the no-theast side of the island at an north~vestand dip northeast at moderate angles. The altitude of about 7501 feet (pl. 1, loc. 26); the other is largest dike is about 50 feet thick and is character- on the west side of the island at an altitude of about ized by very fine grained chilled basaltic borders and 450 feet (pl. 1, loc. 27). The northeastern part of the medium-grained gabbroic interiors. A thin section island is covered with dense brush, and the western from the core of the largest dike reveals the rock to part is rugged and in places covered with slide be equigranular with an average crystal size of debris. about 2 mm. The thin section consists of about 55 According to Reed (1938, p. 70, 71), the prospect percent labradorite and 30 percent pyroxene; the on the northeastern part of the island (pl. 1, loc. 26) METALLIC COMMODITIES 45 is apparently a sulfide replacement of limestone; (fig. 8). A contact-metamorphic aureole consisting that is, the deposit consists of massive pyrite with of tactite and hornfels as much as 5 feet thick has subordinate chalcopyrite and lijllingite ( ?) , exposed formed in the marble adjacent to the intrusive. The over an area 15 by 5 feet and for a height of 15 feet. tactite consists largely of garnet and pyroxene, the One end of the deposit was covered with talus (Reed, hornfels, of tremolite and chlorite. 1938, p. 70, fig. 5). At least three other similar de- A brecciated, sheared, and silicified fault zone sep- posits have been reported from the northeastern arates the quartz diorite and the tactite at the site part of the island. of the deposit (fig. 8). The fault zone is as much as The prospect (loc. 27) on the west side of the is- 10 feet wide, but because of cover, it can be traced land is ambiguously reported to be both about 2 on the surface for only about 50 feet. The ore min- miles and about 1-l/q, miles south of the northwest erals are irregularly distributed along the fault zone tip of the island (Reed, 1938, p. 70, 71). The prospect and comprise chalcopyrite, bornite, malachite, sphal- is in marble near two intersecting lamprophyre erite ( ?) , tetrahedrite ( ?) , and chalcocite ( ?) ; all are (mafic) dikes (Reed, 1938, p. 71, fig. 6). The ore associated with pyrite, secondary iron minerals, and forms irregular pods or kidneys along intersections pyrolusite( ?) . of the dikes and thin veins along the dike contacts or Samples from the fault zone contained as much as along joints in the marble. It consists of chalcopy- 7,000 ppm copper, 1,000 ppm zinc, 200 ppm antimony, rite, pyrite, tetrahedrite, and an unidentified sulfide 150 ppm bismuth, and 1.46 ounces per ton (50 ppm) mineral. Reed (1938, p. 72) states that prospecting silver (table 9, loc. 28). Buddington (unpub. data, downward along the dike intersections might be 1924) visited the prospect and reported that a small justified. Buddington (unpub. data, 1924) reports pocket of bornite with gold and silver values was that a sample probably from this deposit assayed 25 found in the garnet-rich contact rock and that a percent lead, 25 percent antimony, 1.74 ounces per quartz diorite dike was locally impregnated with ton gold, and 42 ounces per ton silver. It is not pyrite and pyrrhotite. known whether this sample represents selected high- A semiquantitative spectrographic analyses of an grade specimens or is representative of the vein azonal soil sample collected during our initial exami- material. Buddington (unpub. data, 1924) also re- nation of Francis Island contained abnormal amounts ports jamesonite from an unspecified locality on the of copper, zinc, silver, and nickel and instigated the west side of Willoughby Island. subsequent geochemical survey. Results of the sur- FRANCISISLAND vey are shown in figure 8. THM tests of soil sam- A copper-zinc-silver deposit is near the contact of ples collected during the survey (fig. 8) indicate that quartz diorite and the predominantly marble country the ore mineralization is localized along the fault rock near the southwestern shore of Francis -Island zone near the probable site of the prospect. Prospect- (pl. 1, loc. 28; fig. 8) near a prospect described by ing the shear zone might be warranted, but indica- Buddington (unpub. data, 1924) that is now con- tions are that the deposit in small. cealed by landslide debris. Outcrops are good in the nearshore cliffs but are sparse toward the interior of ALASKACHIEF PROSPECT the island because of dense vegetation. The Alaska Chief prospect is at an altitude of The quartz diorite is a coarse- to medium-grained 1,150 feet in the mountains northwest of the mouth rock that is hypidiomorphic granular in texture. It of Glacier Bay (pl. 1, loc. 29). The prospect was consists largely of plagioclase with calcic andesine staked before 1906 and patented in 1924. It is on a cores and calcic oligoclase exteriors. Reddish-brown densely vegetated steep hillside and formerly was biotite and green hornblende are characteristic ac- accessible by a 2-mile-long trail from the beach, cessory minerals, and quartz is a minor interstitial now badly overgrown and in disrepair. The prospect phase. Magnetite is a minor accessory mineral. consists of a cleared and scraped area of about 150 by Pyrite is sparsely distributed in some of the quartz 55 feet in maximum dimensions and a short south- diorite, and in places is altered to hematite. Narrow trending adit (fig. 9). Sulfide-rich bedrock has re- seams of tremolite are irregularly distributed in tarded reestablishment of vegetation in the cleared some of the marble, and its presence, together with area. The Wrights (1937, p. 221, 222) report that a the coarseness of the marble, indicates that a pluton tunnel (adit) 130 feet long was driven from a point probably underlies the island at shallow depths. 60 feet beneath the surface workings, but neither the The quartz diorite intrudes the marble, and its writers nor Reed (1938, p. 37), who examined the irregular salients cut the marble in a few places property in the 1930's, was able to find the tunnel. 46 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

FIGURE8.-Geologic sketch map of Francis Island prospect, showing geochemical sample locations.

The prospect is in calcareous contact rocks east of and dip steeply to the southwest. The metamorphic a granodiorite pluton that is associated with subor- rocks are chiefly hornfels with subordinate tactite dinate diorite. The intrusive contact and the'bedding and marble. The hornfels consists mainly of plagio- in the metamorphic rocks strike about N. 30" W. clase, quartz, amphibole, garnet, and chlorite. The METALLIC COMMODITIES 47 tactite contains a similar mineral assemblage, but its ments of the metamorphic rocks. The Wrights (1937, predominant constituent is a grossularite-rich gar- p. 221, 222) state that some of the mineralization net. Reed (1938, p. 72) states that the contact rock consists of calcite veinlets along bedding planes and consists mostly of zoisite and epidote but includes that the peripheral parts of the intrusive are locally chlorite and calcite, and that the marble carries con- mineralized. Reed (1938, p. 73) notes that minerali- siderable quantities of chlorite, orthoclase, and zation less intense than that manifested in the quartz. The Wrights (1937, p. 221) also report cal- cleared area extends over a wide area. Efforts to as- careous argillite in the vicinity of the deposits. certain the extent of the deposit were unsuccessful The deposit is exposed over the entire extent because of the dense vegetation. The deposit's sur- of the cleared area and intermittently in the adit face exposures locally consist of a gossan. Sul- (4g. 9). It consists of massive sulfide replace- fide' minerals in the deposit are pyrite, pyrrhotite,

Portal of di .,;

...... EXPLANATION ...... :...... ------...... : ., ;,::..;. :::.:::: ...... :.;: ... Contact, approximately located Area covered chiefly by vegetation ULLUULLU 0M 40 FEET

Rim of cut, locally coincides CONTOUR INTERVAL 10 FEET with contact DATUM IS APPROXIMATE MEAN SEA LEVEL

Metamorphic rocks, chiefly hornfels 66AMk-473 N Location of chip sample (Sample data are given in table 9) t Cleared area underlain by gossan Location of grab sample and massive sulfides (Sample data are given in table 9)

FIGURE9.-Geologic sketch map showing sample locations at the Alaska Chief prospect. 48 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA chalcopyrite, sphalerite(?), and bornite. Oxidized EAST SIDE OF DUNDASBAY parts of the deposit contain malachite and little Two copper-bearing deposits were found on the azurite along with abundant secondary iron and east side of Dundas Bay (pl. 1, locs. 31, 32). One de- manganese minerals. The gangue is predominantly posit (31) occupies an extensive altered zone in calcite with lesser amounts of quartz. quartz semischist that has sharp contacts with adja- Chip samples from the cleared area contained as cent metabasalt. The altered zone is between 100 and much as 15,000 ppm copper, 700 ppm zinc, 0.232 300 feet wide and is traceable for at least 1 mile. It ounce per ton (8ppm) gold, 4.377 ounces per ton strikes approximately N. 20" E. and dips steeply, (150 ppm) silver, and minor to trace amounts of and contains sporadically distributed pods of sul- nickel, molybdenum, bismuth, and cobalt. A grab fides within abundant secondary iron minerals and sample from the ore pile contained more than 10 per- also a few quartz veins- The sulfides are mainly cent copper, 1,000 pprn zinc, 2.917 ounces per ton pyrite and minor chalcopyrite. Malachite stains a (100 ppm) silver and minor anomalous concentram small part of the zone. Semiquantitative spectro- tions of cobalt, molybdenum, nickel, and bismuth. A graphic analyses of samples from the deposit con- soil sample collected below the cleared area contain as much as 2,000 PPm copper and traces of tained 15,000 pprn copper, 1,500 pprn zinc, 1.46 silver, molybdenum, and lead (table 9, loc. 31). The ounces per ton (50 ppm) gold, 1.46 ounces per ton apparent size of the deposit makes it an exploration (50 ppm) silver, 300 ppm cobalt, 300 ppm bismuth, target even though its grade is somewhat low- The and 500 ppm nickel (see table 9, loc. 29; fig. 9.) Wrights (1937, p. 222) state that a number of min- Reserve estimates at the prospect are contingent ing claims were located east of Dundas Bay for upon estimates of the deposit's size and configura- copper, lead, zinc, and gold. tion, neither of which is known. The deposit is ex- The other deposit (32) is in cataclastic biotite- posed throughout the cleared area, which is about quartz diorite that has flaser structure. It consists of 150 feet long and 30 feet in average width. Assuming copper-bearing quartz veins between 1 and 2 inches that the deposit extends to 50 feet beneath the sur- thick which have formed along foliation planes. The face, which is a third of its exposed length, the extent of the deposit could not be determined be- deposit holds 225,000 cubic feet of indicated reserves cause of poor exposures. A sample of the quartz (150 by 30 by 50). About 8 cubic feet of the sulfide- veins contains 1,000 pprn copper and 300 pprn molyb- rich rock would weigh a ton, and therefore the indi- denum (table 9, loc. 32), but the average copper and molybdenum contents of the deposit are much cated reserve is 28,125 tons. The grade of this smaller, because the high values are in the quartz reserve as inferred by the surface sampling is veins, which are 1foot or more apart. slightly better than 1 percent copper. If the deposit extends to a depth of 100 feet below the surface, an BRUCEHILLS additional reserve of 28,125 tons could be inferred. The Bruce Hills deposit is in the central part of the Additional inferred reserves of known tonnage Bruce Hills north of Plateau Glacier (pl. 1, loc. 34). and grade exist beyond the lateral limits of the The deposit is in granodiorite near a steep fault zone cleared area and beneath the 100-foot subjacent that strikes N. 30" E. (fig. 10). Many of the rocks projection of the cleared area. near the fault zone are shattered and brecciated, and Negative factors to be considered in the reserve several subsidiary faults diverge from the fault zone and grade estimates are that the sample taken from (fig- 10). the adit (table 9, loc. 29, sample No. 66AMk-471) The part the that was examined Occu- was lean and that the surface samples consisted pies a that trends the of gossan, which might be richer than the crest of the Bruce Hills. Rocks underlain by the fault unoxidized ore. zone are intensely shattered, heavily iron stained, and probably mineralized, but they have not been Adequate reserve and grade estimates require tested by sampling. The granodiorite contains a few additional exploration and more thorough sampling. small roof pendants of hornfels and is cut by several The deposit justifies exploration on the basis of its andesite dikes that strike about N. 70 ' E. and dip indicated grade and the possibility that it is large. to the southeast. Surficial deposits comprising gla- An exploration program consisting of diamond drill- cial till and talus partly cover the bedrock (fig. 10). ing and geophysical and geochemical methods to lo- The heavily iron-stained mineralized rocks are cate targets in the concealed areas probably is mostly altered granodiorite containing numerous sul- warranted. fide-bearing thin quartz veins, disseminated sulfides, and mineralized fracture coatings. The ore the deposit to the southwest was precluded by cover, minerals are associated with pyrite and (or) pyrrho- including snow and ice. A few small outcrops along tite and include chalcoyprite, molybdenite, malachite, the crest of the hills northeast of the area shown in and minor amounts of molybdite, sphalerite, and figure 10 contain chalcopyrite and molybdenite and galena. Other minerals in the deposits include mont- probably represent a continuation of the deposit. morillonite, chlorite, hematite, and goethite. Samples Probably the molybdenite occurrence in the north- from the deposit carried as much as 3,000 ppm cop- central part of the Bruce Hills reported by Rossman per and 1,000 ppm molybdenum (table 9, loc. 34). (1963b, p. K49, K50) is a part of the deposit. The summit regions and north slopes of the Bruce Forty-four azonal soil samples were collected at Hills were largely snow covered at the time of the 50-foot intervals along several traverses at and near examinations, and the extent of the deposit to the the deposit. Some of the samples were analyzed by northeast could not be determined. Likewise, tracing the citratesoluble cold THM test at the sample site,

* *L >" r~~7 T">C v ,L p ',LV' 6 J~APL.

"--.,.,:.-" =+=;"= JqLrx; <.,::; J 2 ' L., r " - EXPLANATION

Talus and glacial till, mapped separately

u .ndesite dike, showing dip

, :v-&7lL " 14 Granodiorite

\ Hornfels

Disseminated sulfides

Contact, dashed where approximate, dotted where concealed

iVumber above line is sample number; number below line is total heavy-metal content (in parts per million). Tail on circle indicates slope qf land surface. Semi- quantitative spectrographic analyses are piven in table 9

100 150 FEET I11III I I Geology by L. C. Huff, A. S. Radtke, and APPROXIMATE SCALE R. J. Wehr, July 1966

FIGURE10.-Geologic sketch map of Bruce Hills copper-molybdenum deposit, showing geochemical sample locations. 50 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

and subsequently, all the samples were analyzed for thick, and contain scattered sulfides, chiefly pyrite, THM by our usual test. and abundant secondary iron minerals. A sample In order to check the analytical results, 24 of the from one of the altered zones contained 1,500 pprn samples were also analyzed by semiquantitative copper, 1,000 pprn nickel, and 700 pprn cobalt (table spectrographic methods. These analyses show that 9, loc. 38). copper and molybdenum are the only ore metals pres- SOUTHOF TIDALINLET ent in abnormal amounts. From a comparison of Several thin quartz veins occur in marble near the the analytical results (table lo), the THM methods contact with hornblende diorite on the eastern shore is judged to be a satisfactory exploration guide for of Glacier Bay south of Tidal Inlet (pl. 1, loc. 41). this geologic situation. The marble is white and massive, and near the contact it contains small amounts of wollastonite and TABLE10.-Comparison of analytical results on soil samples garnet. Sulfide minerals in the veins include pyrite, from the Bruce Hills Copper-molybdenum deposit chalcopyrite, and pyrrhotite(?). A sample repre- [Total heavy-metals test by L. C. Huff and R J. Wehr . analytical methods described under "Geochemical studies." ~&niquanti&tive spectrographic sentative of the veins carried 1,000 pprn copper, 300 analyses by R. C. Havens and Nancy Conklinl pprn nickel, and 300 pprn cobalt (table 9, loc. 41).

Semiquantitative BLUEMOUSE COVE spectrographic analyses Total heavy-met& teat (parts per million) Three mineralized areas were examined on the Sample southeastern part of Gilbert Island north of Blue Cold Hqt Copper Molybdenum (uarta 8erdon) Mouse Cove (pl. 1, loc. 42). The country rock is a complex assemblage of quartz diorite and younger granodiorite that has been cut by aplite and andesitic dikes. The first area, which is northwest of the easternmost tip of the island, is in a shear zone, 12 36 ...... 1 100 37 ...... 1 40 feet wide, adjacent to an andesitic dike. The shear 38 ...... 1 100 zone consists of abundant quartz and dolomite and 39 ...... 2 160 less abundant muscovite, secondary iron oxides, and an unidentified zinc mineral. The only anomalous sample from this zone (table 9, loc. 42) contained 700 pprn zinc and a trace of silver. The other areas are on the south shore of Gilbert Island north of Blue Mouse Cove. They contain several nearly parallel calcite veins and a quartz- calcite vein. The veins strike about N. 80" W. and dip between 75" NE. and vertical. The calcite veins are as much as 6 inches thick, and the quartz-calcite vein is a maximum of lY2 feet thick. The veins contain minor amounts of pyrite and secondary iron minerals. None of the samples from the veins contained anomalous amounts of ore metals, and their Figure 18 shows that the highest THM content, analyses are not given. The quartz-calcite vein is 600 ppm, was detected in a soil developed on talus probably the same vein that Rossman (1963b, p. about 20 feet west of a large dike. Many of the soil K50) reports to contain tetrahedrite, pyrite, and samples collected in this vicinity have a THM con- some gold and silver. None of the three areas ap- tent between 160 and 200 ppm. pears to be attractive for exploration. Because of cover and limited access, little is SOUTHWESTGILBERT ISLAND AND NEARBYUNNAJIED ISLAND known concerning its overall size and grade, but the Copper-molybdenum deposits are sparsely distrib- results of our examination suggiest that the deposit uted in the southwestern part of Gilbert Island (pl. is worth exploring. 1, loc. 45) and on the nearby small island to the WESTOF MOUTHOF RENDUINLET south (44). The deposits have about the same poten- Several small altered zones crop out in bleached tial for molybdenum as they do for copper. They marble west of the mouth of Rendu Inlet (pl. 1, loc. consist of stockworks of numerous quartz veinlets in 38). The altered zones strike northwestward and dip bleached and altered biotite-hornblende quartz dio- steeply. They are as much as 20 feet long and 1 foot rite that is cut by alaskite dikes with minor aplitic METALLIC COMMODITIES 51 phases. The quartz diorite is medium grained and pprn zinc, 200 pprn cobalt, and a trace of silver (table has a hypidiomorphic granular texture. It consists of 9, loc. 49, sample 66AHx-32B). The chances of find- about 45 percent plagioclase (andesine), 30 percent ing minable quantities of ore in the altered zone are blue-green hornblende, lesser amounts of quartz remote. and red-brown biotite, and traces of zircon, sphene, WEST ARMOF DUNDASBAY apatite, epidote, and clinozoisite. The alaskite is A small island in the southern part of the west strongly altered. It contains mainly plagioclase and arm of Dundas Bay is composed of gneissic dioritic quartz in near-equal amounts and about 15 percent rocks cut by several hornblendite dikes as much as potassium-feldspar. Some of the plagioclase is 10 feet thick (pl. 1, loc. 58). The dioritic rocks are albite. Other minerals form less than 10 percent of locally garnetiferous. Some of the hornblendite dikes the rock and include chlorite, muscovite, biotite, and contain disseminations and impregnations of sulfide epidote. minerals, chiefly chalcopyrite. A sample of high- Numerous east-striking near-vertical faults with grade material from one of the dikes carried 10,000 displacements of only a few inches transect the vein- pprn copper (table 9, loc. 58). The dikes might be lets and their host rock. Most of these faults contain worthy of additional prospecting, but the chances of gouge seams an inch or so thick. The veinlets gen- finding minable deposits in them are poor. erally are less than 3 inches thick. They commonly strike between N. 20" W. and N. 40" W. and dip WEST OF MOUTHOF TARRINLET northeastward at moderate angles. Minor amounts A zone of pegmatitic hornblende diorite about 8 of chalcopyrite and molybdenite are localized near feet thick, cuts the predominant heterogeneous horn- the borders of some of the veinlets. The bleached and blende diorite west of the mouth of Tarr Inlet (pl. 1, altered zones are exposed in seacliffs as much as 60 loc. 62). In addition to the pegmatitic diorite, the feet high. The northernmost mineralized zone is ex- zone contains quartz-calcite veins about 10 inches posed for about half a mile along the face of the sea- thick and a few thin aplite dikes. Besides abundant cliffs and the southernmost zone for about one-sixth quartz and calcite, the veins carry chalcopyrite, py- mile. These deposits probably include the few molyb- rite, epidote, and chlorite. Fractures in the veins are denite-bearing veins near the western shore of Gil- coated irregularly with secondary copper minerals, bert Island that were cited by Rossman (1963b, chiefly chrysocolla. A sample of the veins contained p. K49). 2,000 pprn copper (table 9, loc. 62). A selected specimen representative of the highest WEST OF TARRINLET grade material from the northernmost altered zone The leucocratic granitic rocks west of the medial contained 7,000 pprn copper, 2,000 pprn molybdenum, part of Tarr Inlet (pl. 1, loc. 63) locally are altered and 0.292 ounce per ton silver (table 9, loc. 45). and contain pale-pink to green siliceous lenses. The More representative and more extensive samples lenses carry abundant disseminated sulfides and from the stockworks of both altered zones were of sulfide-bearing veinlets. The sulfide minerals are much lower grade (table 9, locs. 44, 45). Despite the pyrite and subordinate chalcopyrite. A grab sample large size of the deposits, they probably are too low from one of the lenses contained 1,000 pprn copper, in grade to encourage exploration. 300 pprn zinc, and a trace of silver (table 9, Ioc. 63).

WEST OF SHAGCOVE A sheared and altered zone about 65 feet wide Several altered and mineralized zones are exposed occurs in quartzose rocks on the west side of Shag in the steep cliffs along the north shore of Johns Cove south of Geikie Inlet (pl. 1, loc. 49). The zone Hopkins Inlet (pl. 1, loc. 64). They are distributed strikes N. 50" E. and dips 75" NW. It contains intermittently from near the point opposite Lam- numerous thin quartz veins and several sulfide-rich plugh Glacier westward for about 4 miles. Because pods that have the same general trend as the major of their number, proximity, and similarity, they are structure. The quartz veins contain pyrite. A chip represented by a single symbol on plate 1. The al- sample representative of part of the altered zone tered zones near the eastern part of Johns Hopkins with abundant quartz veins yielded low values (table Inlet occur chiefly in septa of metamorphic rocks, 9, loc. 49, sample 66AHx-32A). The largest visible mainly marble, within a predominantly dioritic ter- sulfide pod is about 3 feet long and l/z foot thick. It rane. Those near the western part are in greenstone, consists of pyrrhotite and subordinate amounts of phyllite, or granodiorite, generally near intrusive pyrite, chalcopyrite, azurite, and cuprite(?). A sam- contacts. A few of the altered zones are near mafic ple from this pod contained 3,000 pprn copper, 700 dikes. 52 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

The altered zones range in width from a few feet adjacent wallrock contained only minor anomalous to several hundred feet and are exposed for lengths amounts of copper and molybdenum (table 9,67). as much as 1,000 feet. They consist of assemblages EAST OF REID GLACIER of quartz, calcite and ankeritic carbonates, plagioclase (including albite) amphibole, muscovite, Two altered zones, each about 10 feet thick, crop chlorite, barite, epidote, and secondary iron miner- out east of the divide between Reid and Scidmore als. The zones locally contain lenses of sulfides and Glaciers at altitudes near 4,000 feet (pl. 1, loc. 69). are cut by quartz and calcite veins. The sulfides are The altered zones trend irregularly and cut fractured pyrite and very small amounts of chalcopyrite. The metamorphic rocks, mainly marble. A few quartz content of ore metals in the altered zones is low. The veins between 1 and 2 feet thick also transect the highest values that were obtained in any of our sev- metamorphic rocks. The altered zones are conspicuously stained by reddish-brown secondary iron mineral chip samples from the zones were 1,000 ppm erals, but they lack visible ore minerals. Samples copper and traces of molybdenum and silver (table 9, loc. 64). The altered zones were examined by Reed from the altered zones carried negligible amounts of copper and molybdenum (table 9, loc. 69, samples during the 1930's (Reed, 1938, p. 58,59). L. F. Parker (oral commun., 1966) reports that a sample from one 66AMk-566, 567). The quartz veins contain small of the altered zones contained several percent quantities of sulfide minerals. A sample from a quartz vein yielded 1,000 ppm copper (loc. 69, sample antimony. Although some of the altered zones are large, all 66AMk-568). of them appear to be too low grade to encourage exploration. Two mineralized areas crop out east of Hoonah Glacier near the southeast shore of Johns Hopkins Inlet. The first of these, about three-quarters of a A large altered zone has formed in the granitic mile northeast of Hoonah Glacier (pl. 1, loc. 75), rocks south of John Hopkins Inlet west of the Lam- consists of disseminated pyrite in hornfels and ap- plough Glacier (pl. 1, loc. 65). The altered zone is pears to be extensive. The hornfels locally is faulted irregular in outline. It is as much as 100 feet wide and brecciated. A sample from this deposit contained and exposed for several hundred feet along its strike insignificant amounts of copper and molybdenum in the cliffs south of Johns Hopkins Inlet. The zone (table 9, loc. 75). is cut by a few granitic dikes. Surfaces of the altered The second area is contiguous to Hoonah Glacier granitic rocks are coated by malachite, chrysocolla, (pl. 1, loc. 77). It consists of a large altered zone and secondary iron minerals. A grab sample from several hundred feet thick that has formed in meta- the altered zone contained 1,500 ppm copper and 30 morphic rocks near their contact with granodiorite. ppm molybdenum (table 9, loc. 65). The altered zone contains abundant pyrite dissemi- EAST OF LAMPI.UGHGLACIER nations and impregnations, mainly in biotite horn- A few sulfide-rich lenses are in hornblende diorite fels, and is conspicuously iron stained. Only a small that crops out on the ridge east of Lamplugh Glacier part of it was examined. Samples from the zone in the Reid Inlet gold area (pl. 1, loc. F). The horn- yielded minor amounts of copper and molybdenum blende diorite contains abundant mafic inclusions (table 9, loc. 77). Although the analyses indicated and is cut by several aplite dikes. The lenses are as low contents of ore metals, a more thorough exami- much as 10 feet long and 1 foot in diameter. They nation might find richer parts in the altered zone. consist almost entirely of pyrite. Semiquantitative FAIRWEATHERRANGE spectrographic analyses of a sample from the Copper minerals have been reported from many largest lens disclosed 1,000 ppm copper and traces localities in the Fairweather Range. Most of the of nickel, cobalt, and chromium (table 11, loc. F). known occurrences are in the southern part of the range near or in rocks of the Crillon-LaPerouse Pyrite-bearing quartz veins as much as 10 inches layered gabbro stock. Rossman and members of his thick cut hornfels west of the upper part of Lam- 1952 field party (unpub. data) mention copper- plugh Glacier (pl. 1, loc. 67). The veins strike about stained outcrops on both sides of North Crillon N. 22" W. and dip nearly vertical. Wallrock contig- Glacier (pl. 1, loc. 78), from about 3 miles northwest uous to the veins is heavily iron stained and sparsely of Mount Marchainville (82) and from a few other copper stained. Samples from the veins and the localities in the range. METALLIC COMMODITIES 53

A 5-foot-thick layer of gabbro that is exposed for large scale. Chalcopyrite and bornite are associated several thousand feet along the south wall of the with gold-bearing quartz veins at the Sandy Cove valley occupied by North Crillon Glacier (pl. 1, loc. prospect (7). Samples from this prospect contained 80) contains between 2 and 3 percent pyrrhotite and as much as 5 percent copper (table 9, loc. 7). Argien- chalcopyrite (Kennedy and Walton, 1946, p. 71). tiferous tetrahedrite is the chief ore mineral at the Kennedy and Walton ( p. 71) also report that many Rendu Inlet silver prospect (pl. 1, loc. 37) (A. F. apparently similarly mineralized bands, including Buddington, unpub. data, 1924; Rossman, 1963b, some much greater in thickness, crop out in the p. K48, K49). nearby cliffs. They also report (p. 71) that specimens Chalcopyrite and subordinate secondary copper collected by R. G. Goldthwait from the north wall of minerals are minor constituents of many other de- the South Crillon Glacier contained between 5 and 6 posits in the monument, notably those of the Reid percent sulfide minerals, principally pyrrhotite and Inlet gold area (pl. l), near the head of Wachusetts chalcopyrite. These specimens were from near the Inlet (pl. 1, loc. 35), and the skarns east of Queen contact between the gabbro stock and schist. Many Inlet (40), south of Abyss Lake (54), and west of fragments of amphibole-quartz schist that are con- Rendu Inlet (39). A reported copper occurrence at stituents of a moraine on North Crillon Glacier near Beartrack Cove on the east side of Glacier Bay altitudes of 2,000 feet are stained with copper (Wright and Wright, 1937, p. 221) was not found carbonates (pl. 1, loc. 86) (Kennedy and Walton, during our investigations. The Wrights (1937, p. 1946, p. 71). 221) also report finding large masses of pyrrhotite The copper deposits in the Fairweather Range are with some copper (chalcopyrite?) in moraine de- in very rugged terrain, and they have not been ex- posits near Adams Inlet. They also mention (p. 221) amined in detail. Samples are not available from any copper claims on the mountain between Queen and of them, and little is known about their size and Tidal Inlets. tenor. Probably the deposits merit additional pros- LEAD pecting, but their remoteness and difficult access are The mineral deposits of the monument generally serious impediments to any contemplated prospect- are low in lead and none of the known de- ing or mining. posits could be worked for lead. Only two of the de- SOUTHEASTARM OF LITUYABAY posits, one reported from the west side of Willough- A gabbroic dike that cuts granitic rocks on the by Island (pl. 1, loc. 27) and the other near Mount southwestern shore of the southeast arm of Lituya Brack (12), contain lead in possible byproduct quan- Bay (pl. 1, loc. 84) contains irregular veinlets and tities. Buddington (unpub. data, 1924) reports jame- blebs of pyrrhotite (Kennedy and Walton, 1946, p. sonite from an undisclosed locality on the west side 71). Small amounts of chalcopyrite, which Kennedy of Willoughby Island. One sample, presumably from and Walton (p. 71) estimate to constitute less than this locality and presumably of selected high-grade 1 percent of the rock, are associated with the ore, contained 25 percent lead (A. F. Buddington, pyrrhotite. unpub. data, 1924). A sample from the Mount Brack argentiferous base-metal deposits, described under OTHERDEPOSITS THAT CONTAINCOPPER "Zinc," contained 7,000 ppm lead (table 9, loc. 12). In addition to those deposits that contain copper Two other deposits whose principal commodity is as their principal potentially economic commodity, zinc-the deposit of Red Mountain (pl. several other deposits in the monument are copper and table 9, 20) and a deposit about a mile baring. Among these are deposits at the Brady Gla- of the Alaska Chief prospect (30)40n- tier nickel-copper prospect (pl.1,loc. 72), the Nuns- tain minor amounts of A few of the copper de- tak molybdenum prospect (21), the Sandy Cove gold posits contain trace to minor amounts of lead. prospect (7), and the Rendu Inlet silver prospect Galena is a minor constituent of some gold-bearing (37). quartz veins in the Reid Inlet gold area, notably Chalcopyrite is an important constituent of the those at the hRoy mine (pl. 1, loc. B). A sample pyrrh~tite-richlenses, disseminations, and impreg- from the LeRoy mine carried 1,500 ppm lead (table nations at the Brady Glacier nickel-copper prospect 11, loc. B). However, the Reid Inlet gold deposits are (pl. 1, and table 15, loc. 72). It is a minor constituent too small to permit recovering their base metals at of the sizable lodes at the Nunatak molybdenum a profit. Samples from the Sandy Cove gold prospect prospect (pl. 1, loc. 2), and probably copper would contained minor to trace amounts of lead (table 9, be recovered from it if the deposits were mined on a loc. 7). 54 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

RADIOACTIVE ELEMENTS "Iron"; and in a few lodes in the Reid Inlet gold No uranium or thorium minerals were found area. during our investigations, although radioactive min- The zinc deposits are diverse in type, having erals were looked for during the field examinations, formed in several geologic settings. They consist of and all samples were routinely checked with a Geiger veins, altered zones, disseminations, and local sulfide- counter. Rossman (1963b, p. K52) states that some rich replacements in a variety of host rocks. Sphal- of the altered zones near Sandy Cove contain be- erite is the main zinc mineral in most of the deposits, tween 0.001 and 0.003 percent U30e. Seitz (1959, p. but some deposits contain fine-grained encrustations 116) reports that he checked the area that he of secondary zinc minerals. The best zinc deposits in mapped near Geikie Inlet for anomalous radioac- the monument seem to be near Mount Brack (pl. 1, tivity, and that the results were negative. No favor- loc. 12) and in an altered zone north of White Gla- able indications of uranium or thorium minerals cier (6) (described under "Copper") that carries 2 were noted during the examinations. Possibly un- percent zinc. detected deposits of these elements are in some of the leucocratic granitic rocks or in the altered zones. DESCRIPTIONS OF DEPOSITS NUNATAKON CASEMENTGLACIER TIN An iron-stained altered zone is exposed on a small No tin minerals were found, and no significant recently denuded nunatak on Casement Glacier (pl. anomalous concentrations of tin were detected in the 1, loc. 3). The nunatak consists of thin-bedded lime- rock and ore samples that were analyzed. The largest stone, argillite, and hornfels. The altered zone is amount of tin that was found in these samples was about 30 feet thick and contains several quartz- 30 pprn in a sample from the Queen Inlet magnetite ankerite-barite veins that are less than 1 foot thick. deposit (pl. 1 and table 9, loc. 40). Smaller amounts The veins and the altered zone strike N. 58" W. and of tin were detected in samples from several other dip vertically. Pyrite is the only visible sulfide min- localities (table 9). eral in either the veins or the altered zone. The de- A tin and tungsten anomaly in stream sediments posit is low in grade, and its only anomalous ore- was revealed by geochemical sampling near the metal concentration consisted of 300 pprn zinc (table north end of Dundas Bay. Samples from this area 9, loc. 3). contained 30 pprn tin and as much as 150 pprn tung- MOUNTBRACK sten (table 4, locs. 12, 13). The provenance of the The deposits near Mount Brack (pl. 1, loc. 12) con- streams that yielded the anomalous samples consists sist of veins and altered zones in graywacke, lime- partly of leucocratic granitic rocks, which are con- stone, hornfels, siltstone, and mafic dikes. The veins sidered favorable for tin deposits, and prospecting and altered zones strike north, and most of them dip the area seems justified. east. Six veins were exposed at the time of our ex- Two stream-sediment samples collected in the amination; others are probably concealed beneath northern part of the monument also contained the snow, which is widespread and perennial over anomalous amounts of tin. A sample collected on the much of the area. The veins are generally between 6 west side of Tarr Inlet a few hundred feet south of and 8 inches thick. They consist chiefly of quartz and locality 18 (pl. 1) contained 500 pprn tin, the largest calcite with, locally, abundant ankeritic carbonates, amount of tin detected during the investigation, in sulfides, and sulfosalts ( ?). Samples from the veins addition to anomalous amounts of other metals. The yielded higher values in zinc and most other ore second anomalous sample, from west of Lamplugh metals than those from the altered zones. The vein Glacier terminus, contained 33 pprn tin, but only samples (table 9, loc. 12, samples 66AMk-315, ordinary concentrations of copper, lead, and molyb- 66ABd-280) contained as much as 15,000 pprn zinc, denum. 0.875 ounce per ton (30 ppm) silver, 7,000 pprn lead, ZINC 30,000 pprn arsenic, 7,000 pym antimony, and 0.087 DISTRIRUTION AND TYPES OF IIEPOSITS ounce per ton (3 ppm) gold. The presence of sulfo- Although zinc is fairly widespread in the mineral salts is inferred from the arsenic and antimony con- deposits of the monument, most of the deposits in tent of the samples. which it is the principal commodity are in the east- Altered zones as much as 30 feet thick are fairly ern part. Seven zinc deposits discovered during the numerous near Mount Brack. They are composed investigation are described below. Zinc also occurs in principally of heavily iron-stained ankeritic carbon- seven deposits described under "Copper"; in the ates, chlorite, quartz, and calcite and minor p1;lgio- Queen Inlet magnetite deposit, described under clase and muscovite. Some of them enclose quartz- METALLIC COMMODITIES 55 carbonate veinlets. Samples from the altered zones 15,000 pprn barium (table 9, loc. 66). The dominant were lean; their maximum zinc content was 700 ppm. minerals in the altered zones are quartz, plagioclase, Indications of mineralization are widespread, and actinolite, and barite. the general area probably merits prospecting. A large altered zone north of the ones examined was not sampled because of difficult access, but its composition is probably similar to the zone that was Small pyrite-rich pods and impregnations occur in sampled. the Black Cap limestone, of Middle Devonian age, near a granodiorite cupola about 2v2 miles southwest of Red Mountain (pl. 1, loc. 20). The largest NORTHWESTSHORE OF JOHNSHOPKINS INLET pod is about 10 feet long and 1 foot in diameter. It Iron-stained hornfels crops out for several hundred consists largely of pyrite and subordinate calcite and feet along the northwest shore of Johns Hopkins encrustations of a secondary zinc mineral, probably Inlet and probably extends for many hundreds of hydrozincite or smithsonite. A sample from the feet to the northwest (pl. 1, Ioc. 76). The hornfels largest pod contained 7,000 pprn zinc, 500 pprn lead, contains abundant finely disseminated pyrite, but 70 pprn cadmium, and a trace of silver. The deposits apparently it lacks significant amounts of ore min- are too small to be of economic significance. erals. A sample of the hornfels carried 300 pprn zinc and traces of lead and molybdenum (table 9, loc. 76). An altered shear zone that cuts granitic rocks about a mile southwest of the Alaska Chief prospect contains minor zinc values (pl. 1, loc. 30). The al- Zinc is a constituent of several deposits whose tered zone is about 3 feet wide. Its attitude is N. major commodity is copper, gold, or iron, described 30" W., 80" SW. The granitic host rock at the de- elsewhere in this report. The zinc-bearing deposits posit is granodiorite or quartz monzonite. A sample that are described under "Copper" include those from the altered zone contained 1,500 pprn zinc, 300 near Mount Young (pl. 1, loc. 1), north of White Gla- pprn lead, and traces of molybdenum, bismuth, and cier (6), at the Margerie prospect (19), on Francis silver (table 9, loc. 30). The deposit probably is too Island (28), at the Alaska Chief prospect (29), near lean to encourage exploration. Blue Mouse Cove (42), and on the west side of Tarr Inlet (63). Sphalerite occurs in the gold-quartz veins HUGHMILLER INLET at the LeRoy and Rainbow mines in the Reid Inlet Three thin pyrite-rich veins cut biotite-hornblende gold area (B, C). Minor amounts of zinc are asso- quartz diorite on the west side of Hugh Miller Inlet ciated with pyrite in contact-metamorphic rocks at west of Gilbert Island (pl. 1, loc. 46). The veins the Queen Inlet magnetite deposit (40). strike between N. 40" W. and N. 55" W. and dip northeastward. A steep northwest-striking shear Samples from the Mount Young deposits contained zone cuts the quartz diorite near the veins. The veins as much as 1,500 pprn zinc (table 9, loc. 1). A sample are heavily iron stained and consist of abundant representative of a 6-foot-wide altered zone north of pyrite and its alteration products and probably White Glacier contained 20,000 pprn zinc (6). Quartz quartz, barite, and carbonate minerals. A sample veins at the Margerie prospect carry traces of zinc from the veins yielded 1,500 pprn zinc, 70 pprn bis- (19). A selected sample from the Francis Island de- muth, and a trace of molybdenum (table 9, loc. 46). posit yielded 1,000 pprn zinc (28). Chip, samples from Possibly the veins represent a fringe zone of the pre- the Alaska Chief prospect contained as much as 700 viously described extensive low-grade copper-molyb- pprn zinc, and a grab sample from the ore pile con- denum deposits that are exposed on nearby parts of tained 1,000 pprn zinc (29). A sample from an altered Gilbert Island (45). The veins probably are too small zone near Blue Mouse Cove yielded 700 pprn zinc and too lean to warrant exploration. (42). Zinc is a minor constituent of siliceous lenses west of Tarr Inlet which contain disseminated sul- MOUNTCOOPER fides (63). Samples from the LeRoy mine contained as Altered zones occur in iron-stained pyritic hornfels much as 15,000 pprn zinc (table 11, loc. B), and a near a peak locally referred to as Mount Cooper, west sample from the Rainbow mine carried 2,000 pprn of Lamplugh Glacier (pl., loc. 66). They are best zinc (C). Samples from the Queen Inlet magnetite developed near fine-grained porphyritic dikes that deposit have a very low zinc content table 9, loc. 40). cut the hornfels. A sample from one of the zones Conceivably, zinc constitutes a potential byproduct in contained 300 pprn zinc, traces of molybdenum, and a few of these deposits. 56 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

PRECIOUS METALS area. Almost all the Reid Inlet deposits occupy thin Gold is the only precious metal that has been nonpersistent quartz veins, the rest are sporadically found in significant amounts within the monument. distributed in narrow altered zones contiguous to the Silver is a constituent of several deposits, and small quartz veins. Iron stains on the veins and on altered amounts of platium have been reported from a few rock near the veins permits them to be readily iden- of the placers. tified at a distance. None of the deposits appear to GOLD be amenable to large-scale mining. DISTRIBUTION AND OCCURRENCE Terry Richtmeyer prospect Both lode and placer deposits of gold are wide- A gold claim about 1,200 feet south of Glacier Bay spread in the monument. The lode deposits are and 2 miles west of Ptarmigan Creek is reportedly mainly in the Reid Inlet gold area, but a few are held by Terry Richtmeyer (Alaska Div. Mines and known from elsewhere in the monument, notably at Minerals, written commun., 1966) (pl. 1, loc. A). We the Sandy Cove prospect (loc. 7). The best known of were unable to find the claim. It probably is on the placer deposits are on the beaches north and quartz veins in granitic rocks near their contact with south of Lituya Bay (87,88). (See pl. 1) hornfels. The lode deposits commonly occupy narrow non- LeRoy mine persistent quartz veins in granitic or metamorphic The LeRoy mine, the largest mine in the Reid Inlet rocks. A few of them are sporadically distributed in gold area, is a little less than 1 mile south of Glacier thin altered zones adjacent to the quartz veins. Minor Bay, at altitudes between 950 and 1,000 feet (pl. 1, amounts of gold occur in some of the larger altered loc. B). The mineralized veins at the mine were dis- zones in the monument, and gold constitutes the covered in 1938 by A. L. Parker and L. F. Parker main commodity of economic interest in a few of the (Rossman, 1959, p. 38). The mine workings consist altered zones. Gold is a minor constituent of a deposit of four southwest-trending adits with subsidiary that is localized along a facies change between mar- raises and stopes and minor surface workings (pl. ble and phyllite west of McBride Glacier (pl. l, loc. 9). The longest adit explores the LeRoy vein for 10). It is also a subordinate metal in some of the base about 240 feet. metal deposits, as at the Alaska Chief prospect. The The gold is in thin nonpersistent quartz veins and placer deposits comprise beach sands, outwash grav- less extensively in narrow altered zones adjacent to els, river and stream sediments, and a few residual the veins. The veins transect northwest-striking placers. metamorphic rocks that dip steeply and form a LODE D1:POSITS screen between granitic masses. The metamorphic REID INLET GOTI) AI~FA rocks consists of schist, slate, hornfels, and argillite The Reid Inlet gold area includes the ridge south and are differentiated into three units on plate 9. of Glacier Bay which is bordered by Reid and Petrographic studies of thin sections reveal that Lamplugh Glaciers and by Reid Inlet (pl. 1). It also many of the rocks mapped as schist are schist- includes small parts of the terrain east of Reid Inlet ose granodiorite that has been intensely sheared. and west of Lamplugh Glacier (131.1). The area con- With few exceptions the veins strike about N. 30" tains most of the gold lodes in the monument and E. and dip between 50" and 80" NW. About 15 also one small copper deposit. Gold has been produced veins are exposed on the property. Most of them are at six properties that are designated as mines; there only 1 or 2 inches thick, but one of them, the LeRoy also are six prospects for gold in the area. The total vein (pl. 9) attains a thickness of about 3 feet. The value of the gold produced from the mines is about veins are characterized by pinching and swelling and $250,000. The Reid Inlet gold area has been examined by a lack of continuity that appears an intrinsic fea- by several geologists and mining engineers and is the ture compounded by faulting. The LeRoy vein, which subject of a detailed report by Rossman (1959). Our has yielded the most production, apparently termi- studies were facilitated by the results of the earlier nates southwestward near its contact with argillite investigations, and in most instances, Rossman's (which Rossman (1959) considered to be a fine- maps have been used as bases for our sample local- grained mafic dike). The vein has been stoped ities and geologic data. , throughout much of its extent both above and below The Reid Inlet area is underlain chiefly by gran- the adit level. Some of the veins are strongly frac- odiorite and quartz diorite and by a few northwest- tured and brecciated. Gold is distributed irregularly striking screens and septa of metamorphic rocks. in the veins and uncommonly in the contiguous al- Fine-grained mafic dikes are locally abundant in the tered zones that generally are a few inches thick. METALLIC COMMODIT1E.S 57

TABLE11.4emiquantitative spectrographic analyses and gold analyses of samples from the Reid Inlet gold area [Spectrographic analyses by J. C. Hamilton Harriet Neiman, and A. L. Sutton. Jr. Gold analyses by Claude Huffman, Jr., J. D. Mensik. 0. M. Parker V. E. Shaw, J. A. Thomas, and J. E. ~roxel.'Au: A, analyzed by atomic-absorption cyanide method; B, analyzed by fire assay atomic-absorption methodj Results are reported in parts per million, which for the spectrographic Symbols used; M, major constituent-greater than 10 percent; 0, looked for. analvses have been converted from ~ercentto the nearest number in the but not detected; . . . ., not looked for; <, less than. seriG 1 0.7if 0.5 g;oup* 0.3 dais0.2 0.150on andgeometric 6.1 . . .scale. . which The represent assigned approximate group for The following elements were looked for, but not found: Be. Bi. Rs. La. Li. Pd, Pt, Sb. Sn. Ta, T1. W. six-step results will include more accurately determined values for about 80 percent of the test results. Gold and silver values. in troy ounces per Locations of the deposits nre shown on pl. 1; individual samples are tan, are shown in parentheses below their corresponding parts per million described at the end the values.

Sample Au 66A- Ae A1 As Ba Ca Cd Co Cr Cu Fe Mg Mn Mo Nb Ni Pb Si Ti V Y Zn A B

Locality A [Location: Mount Fairweather D-3 quadrangle. 1,200 ft south of Glacier Bay, 2 miles west of Ptarmigan Creek. Geologic setting : 1 claim :uppub. data from Alaskr Div. Mines and minerals1

Locality B [Location: LeRoy mine, Mount Fairweather D-3 quadrangle between Lamplugh Glacier and Reid Inlet. Geologic setting: Gold in quartz veins and contiguous altered zones within metamorphic rocks. Sample localities are shown on p1. 91

Locality C [Locption: Rainbow mine, Mount Fairweather D-3 quadrangle, west of Reid Inlet about 15 ft above mean high tide. Geologic setting: Intermittent quartz veins in an altered fault zone. Sample localities are shown in fig. 111

- Locality D [Location: Sentinel mine. Mount Fairweather D-3 quadrangle, west of Reid Inlet. Geologic setting: Altered fault zone in granodioritel

-- Locality E [Location: Monarch No. 1 and No. 2 mines. Mount Fairweather D-3 quadrangle, west of Reid Inlet. Geologic setting: Quartz veins and adjoining altered wallrock in granitic rocks. Sample localities are shown in figs. 12 and 131 Mk-337 0 70.000 0 200 30,000 0 10 10 30 50.000 30,0001,000 0 10 15 0 M3,000 150 10 58 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

TABLE11.-Semiquantitative spectrographic analyses and gold analyses of samples from the Reid Inlet gold area--Continued

- -- Sample Au 66A- An Al As Ba Ca Cd Co Cr Cu Fe ME Mn Mo Nb Ni Pb Si Ti V Y Zn A B

Locality F [Location: Mount Fairweather D-3 quadrangle, west of Reid Inlet. Geologic setting: Pyrite-rich pods of < 10 ft long and 1 ft thick in hornblende-rich dioritel

- Locality G [Location: Incas Mine. Mount Fairweather D--3 quadrangle, west of Reid Inlet. Geologic setting: Quartz veins intermittently distributed in an altered zone within granodiorite. Sample localities are shown in fig. 141 Mk-350 0 70,000 2,000 700 1.500 0 5 15 7 20,000 3,000 700 0 10 3 10 M1,500 30 15 0 0.4 0.4 (0.012) (0.012) Mk-351 0 70,W 1,000 700 2.000 0 0 1.5 5 20,000 3,000 500 0 10 0 15 M1,500 20 15 0 1 ,7 (0.029) (0.020) Mk-352 0 30,000 20,0002,000 30.000 0 5 100 7 20,000 3,0001,500 0 0 15 0 M1,500 30 0 0 1 1 (0.029) (0.029)

Localitv H [Location : Sunrise prospect. Mount Fairweather D-3 quadrangle, east of Reid Inlet. Geologic setting: Quartz veins cutting marble; some lamprophyre dikes in vicinity1

Locality I [Location: Hopalong-Whirlaway prospect. Mount Fairweather D-3 quadrangle, east of Reid Inlet. Geologic setting : Quartz veins in granitic rock1 Mk-571 0 7,000 0 15 M 0 0 3 30 10,000 2,000 700 0 0 0 0 M 200 30 0 0<0.05 ...... (<0.0015)

Locality J [Location: Galena prospect, Mount Fairweather D-3 quadrangle, at an altitude of about 500 ft west of Reid Inlet. Geologic setting: Quartz vein] Noanalyses ......

Locality K [Location: Highland Chief prospect, Mount Fairweather D-3 quadrangle, at altitude between 2.500 and 2.800 ft west of Reid Inlet. Geologic setting: Quartz veins in metamorphic rocks] Noanalyses ......

Locality L [Location: Rambler prospect, Mount Fairweather D-3 quadrangle, east, of Lamplugh Glacier. Geologic setting: Quartz veins in granitic rocks and uncommonly In metamorphic rocks]

DESCRIPTION OF SAMPLE Locality A : No analyses. Locality E---Continued Locality B : Monarch No. 1, channel sample 16 in. lonn. 66AMk-326 Chip sample 18 in. long at 2-in. intervals across quartz vein Monarch No. 1, channel sample 24 in. long. with minor horses. Monarch No. 1, channel sample 14 in. long. Selected sample of entire width of 4-in.-wide quartz vein. Monarch No. 1, channel sample 12 in. long. Selected sample representative of 3-in.-wide quartz vein. Monarch No. 2. channel sam~le6 in. lonn. Channel sample across 6-in.-thick quartz vein. Channel sample across 8-in.-thick quartz vein. do Channel sample across 5-ln.-thick quartz vein at surface. Monarch No. 2. channel sample 8 in. long. Channel sample across 3-in.-thick quartz vein and 12-in.- thick adjacent altered zone. Grab sample of pyrite-rich pod. Channel sample 15-in. long across quartz vein with subordinate altered wallrock. Locality G : Channel sample 8 in. long across quartz vein. Mk-350 Channel sample 10 in. long. Channel sample 12 in. long across quartz vein and altered Mk-351 Channel sample 18 in. long. Mk-352. Chip sample 4 ft long, at 4-in. intervals. ...~ll"n"L."'...a".n. Selected sample representative of 1-in.-thick quartz vein Locality H : and 1-in.-thick altered wallrock. Mk-572 Selected sample representative of a 4-in.- thick quartz vein. Locality C : Locality I : Mk-387 Grab sample from small ore pile near face. Mk-571 Grab sample representative of veins. Mk-388 Channel sample 1 ft long. Locality J : No analyses. Mk-389 Grab sample from quartz vein. Mk-390 Channel sample 1 ft long. Locality K : No analyses. Pruspect concealed by snow during 1966. Mk-391 Locality L : Mk-392 Sj-5 Crab sample of sheared and altered granodiorite from con- Locality D : tact with quartz vein (Sj-6). .Mk-393 Channel sample. 1 ft long, near easternmost outcrop of Selected sample of 1-in. massive white unstained quartz vein. altered zone. Selected sample from sulfide-bearine quartz vein. Locality E : do Mk-337 Monarch No. 1. 29-in.-lonn channel sample. Grab sample from qua1 tz velns 1-4 in. thick. Mk-339 Monarch No. 1. 10-in.-long channel sample across altered Grab sample from qua1 tz vein 2 in. thick. zone. do METALLIC COMMODITIES 59

The veins consist mainly of quartz and minor pling and analyses would aid in exploration for gold amounts of feldspars, calcite, and clay minerals. The lodes in the Reid Inlet area. The original prospectors sulfide minerals arsenopyrite, pyrite, galena, sphal- in the area relied heavily on panning to trace the erite, and chalcopyrite are minor constituents of gold-bearing veins. Where the veins are exposed, most of the veins. Subordinate amounts of silver panning works well; but throughout much of the are associated with the gold. The veins have been area the veins are covered by soil and galacial de- extensively sampled, and the locations and gold val- posits. Most of the veins contain more sulfide miner- ues in samples that were collected during the 1966 als, including galena, than gold. Rather than analyze investigations and during a previous examination by the samples for gold, it was decided to determine the Territorial Department of Mines are shown on their THM content, which would reveal any abnor- plate 9. Additional analytical and descriptive data mal amounts of lead. germane to these samples are shown in tables 11 and Eighteen azonal soil samples were collected at 50- foot intervals along two horizontal traverses near altitudes of the lower and upper portals (pl. 9). In TABLE12.-Assay data on the Leroy mine [From the Alaaka Div. Mines and Minerals (formerly Territorial addition, 13 samples were collected from near the Dept. Mines and Mineralogy) 1 caved stope above the LeRoy adit. All the samples Loc. Width Au Ag (PI. 9) (inches) (ounces per ton) were collected within 250 feet of known gold-bearing Surface samples veins and 11 were collected within 50 feet of known veins. 54-7 ...... 4 0.02 Nil 54-8 ...... 6 2.12 0.80 Analyses of the samples showed that none of them 54-9 ...... 6 10.34 7.40 contained significant amounts of lead or more than 54-10 ...... 6 1.37 Trace 54-11 ...... 16 .50 Trace ' 40 pprn total heavy metals. From these results it was Underground samples concluded that the small amounts of lead in the ore

54-12 ...... 12 Trace could not be detected in soil diluted with glacial 54-13 ...... 3 Nil detritus, and that the soil-sampling methods used 54-28 ...... 28 Trace 54-29 ...... 36 Trace are not satisfactory for the Reid Inlet area. 54-30...... 4 Trace 54-31 ...... 6 Nil Rainbow mine 54-32...... 1 Trace 54-33 ...... 12 Trace The Rainbow mine is west of the mouth of Reid 54-34 ...... 22 Trace Inlet (pl. 1, loc. C). The mine workings explore an al- 54-35 ...... 24 Trace Nil tered fault zone about l foot thick that contains vein Nil quartz. The fault zone, which is traceable on the sur- Nil Nil face for about half a mile southwestward from sea level to altitudes slightly more than 1,000 feet, 6 ...... iii .26 Trace 7 ...... 2.90 .66 strikes about N. 30" E. and dips between vertical g4 ...... r22 .16 Nil and 70" SE. The workings consist of a southwest- 9 ...... 18 .70 1.80 trending adit about 180 feet long, a short crosscut, 10 ...... (5) .26 Trace stopes above the adit level, and a small pit near the 1 Selected aample. 9 Fines. southwesternmost outcrops of the zone (fig. 11). 8 8 in. of drill core. 6 Location not known. The portal of the adit is in sea cliffs about 15 feet * Grab sample. above high-tide level. The fault zone cuts granodiorite and small masses of alaskite. A shattered and 12. The richest sample represents a 6-inch-thick vein brecciated quartz-calcite vein a few inches thick that is exposed at the surface and assayed 10.34 occupies the fault zone. The vein contains gold and ounces per ton gold and 7.40 ounces per ton silver an assemblage of sulfide minerals similar to those at (pl. 9; table 12). Samples representative of the the LeRoy mine. The altered zone, which is marked LeRoy mine lodes contained as much as 0.0045 ounce by abundant secondary iron minerals and gouge, also per ton (15 ppm) silver, 70,000 pprn arsenic, 1,000 contains widely scattered gold. pprn cadmium, 70 pprn copper, 1,500 pprn lead, Analytical results of samples from the Rainbow 15,000 pprn zinc, and 0.699 ounce per ton (24 ppm) mine are shown in table 11, loc. C). The highest gold gold (table 11, loc. B). About $100,000 in gold has value found in any of our samples from the monu- been produced from the mine. ment, 10.211 ounces per ton gold, was detected in one The LeRoy mine and vicinity were studied by geo- of the samples from the mine. Besides gold, samples chemical methods to determine whether soil sam- from the Rainbow mine carried as much as 2.043 60 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA ounces per ton silver, 1,500 ppm arsenic, 500 ppm mine is localized along a northwest-striking steep lead, and 2,000 ppm zinc. altered zone that cuts granodiorite. The altered zone The Rainbow mine probably is the second largest is about a foot thick and consists of intensely altered gold producer in the Reid Inlet area, but its produc- and comminuted granodiorite that contains sparse tion data are unavailable. The mine was worked dur- impregnations of sulfides, abundant secondary iron ing 1945 and shortly thereafter, and its ore was minerals. and erratically distributed gold. Several transported by barge and truck to the mill at the other altered zones that are similar in attitude and LeRoy mine. character to the one at the mine are exposed on the The Rainbow mine is similar geochemically to the hillside northeast of the property. A sample from one LeRoy mine, and the soil conditions are comparable. of these (table 11, loc. D) yielded negligible gold val- The Rainbow mine was sampled for the same pur- ues. The mine has yielded a small undisclosed pro- pose as the LeRoy mine-that is, to find out if anal- duction of gold. It was worked by shallow surficial ysis of the soil for lead could help trace the veins workings that are now obscured by overburden and where they are covered by soil and glacial material. vegetation. Most of the 12 soil samples that were collected Monarch mines were from the hillside 10-50 feet below an outcrop of The Monarch mines are on the steep hillside west the vein, where detection of an anomaly seemed most of Reid Inlet (pl. 1, loc. E). The Monarch No. 1 mine likely. None of these samples contained more than 40 is at an altitude of about 1,875 feet, and the Monarch ppm THM. These results support the conclusions No. 2 mine, at an altitude of about 1,500 feet. Both of made for the LeRoy mine-namely, that the amount the mines were worked from adits, and both probably of lead in the soils is too small to be useful in tracing produced minor amounts of gold. the veins. The adit at the Monarch No. 1 mine extends for Sentinel mine about 210 feet southward from its portal (fig. 12). The Sentinel mine is west of the mouth of Reid In- A small overstope was excavated about 70 feet from let at altitudes near 900 feet (pl. 1, loc. D). Ore at the the portal. The adit explores an altered zone between

Altitude of portal approximately EXPLANATION 5 feet above mean hlgh tide

in 1-foot-th~ck altered zone Granodiorite with minor alaskite 66A~k-392(.01) L +..$.+ Inclined Vertical Quartz vein Occupies alte7ed zone % to 1% feet thick Altered zone approximately 1 foot thick; scattered quartz and much gouge

Inclined workings; chevrons point downward

Foot of raise

Sample location Gold content (in ounces per N tun) is shown in paren-

0 40 FEET lI1II

Mapped by E. M. MacKevett, Jr., and J. G. Smbth; July 12, 1966 FIGURE11.-Geologic sketch map showing sample locations at the Rainbow adit. METALLIC COMMODITIES 61

1 and 5 feet thick within granodiorite. The zone rite, pyrite, galena, and gold. Calcite and clay min- strikes northward and dips steeply to the west. It erals constitute the lesser gangue minerals. Samples contains quartz veins and lenses a few inches thick from the mine showed low values in gold and other and abundant gouge and breccia. The granodiorite ore metals (table 11, loc. E, samples 66AMk-337 wallrock is medium to coarse grained and hypidio- through 66AMk-343). morphic granular in texture. It contains about 65 Rossman (1959, p. 50) reports a few other gold- percent plagioclase, 15 percent quartz, and 10 percent potassium feldspar. The rock is cut by micro- bearing veins near the Monarch No. 1vein. One vein, fractures and is altered, resulting in the obliteration a few hundred feet west of the Monarch No. 1 vein, of its primary mafic minerals and replacement of crops out over a length of about 100 feet and is as the original plagioclase by oligoclase. Its minor con- much as 10 inches thick. Some of the partly decom- stituents and alteration products consist of sphene, posed weathered material at the surface of the vein allanite, calcite, chlorite, epidote, and opaque min- has been mined. A small rich stringer vein about 5 erals. The veins and lenses, and less commonly the inches thick is exposed several hundred feet west of altered zones, contain sparsely distributed arsenopy- the south end of the Monarch No. 1vein.

Altitude of portal approximately 1,875 feet EXPLANATION

Granodiorite

Hydrother mally altered fault zone showing dip; contains veins and lenses of quartz

Quartz vein at surface

Sample location Gold content (inounces per 66AMk-341 (.Dl) ton) is shown in parentheses. Sample data are given in table 11

Position of fault zone at surface

0 40 FEET

DATUM- IS APPROXIMATE Geology modified from Rossman MEAN HIGH TLDE (1959, fig. 7)- FIGURE12.-Geologic sketch map showing sample locations at the Monarch No. 1 mine. 62 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

Workings at the Monarch No. 2 mine consist of a ine), 20 percent quartz, 10 percent potassium feld- westward-trending crosscut adit about 120 feet long spar, and 10 percent alteration products, chiefly epi- and two short drifts (fig. 13). The workings are in dote and chlorite. Much of the granodiorite has been granodiorite that is cut by a few quartz veins and by deformed cataclastically. The quartz lenses contain northward-striking mafic dikes and faults. The minor amounts of calcite and sulfides, chiefly arseno- granodiorite at the Monarch No. 2 mine is less al- pyrite, and sporadically distributed gold. The altered tered, but slightly more deformed, than its counter- zone consists of hydrothermally altered granodiorite part at the Monarch No. 1 mine. The quartz veins and traces of gold and sulfides. Our samples from strike northward and dip nearly vertical. They are the mine revealed only minor amounts of gold and between 2 and 8 inches thick and are bordered by ore metals (table 11, loc. G). thin gougey selvages. The veins contain sparsely dis- Rossman (1959, p. 48) states that several other tributed calcite, sulfides, and minor amounts of gold veins and altered zones crop out in the vicinity of (table 11, loc. E., samples 66AMk-344 through the mine. He also believes that the mine has not been 66AMk-348). A few other small quartz veins are explored sufficiently for evaluation of its economic near the Monarch No. 2 property (Rossman, 1959, possibilities. The small production from the prop- p. 51). erty was probably mainly from surficial workings.

Incas mine Sunrise prospect The Incas mine is west of Reid Inlet at an altitude The Sunrise prospect includes several shallow pits of about 1,000 feet (pl. 1, loc. G). The Incas and trenches on the hillside east of Reid Inlet at alti- lode, one of the first discoveries in the Reid Inlet tudes near 800 feet (pl. 1, loc. H). Rocks at the pros- area, was staked by Joseph Ibach in 1924 (Rossman, pect are marble and hornfels that strike northward 1959, p. 46). The mine consists of about 200 feet of and dip steeply. Subordinate fine-grained diorite or underground workings (fig. 14) and several quartz diorite is also present. Several northeast- trenches that are now badly caved and sloughed. The striking lamprophyre dikes, as much as 30 feet deposits are localized in quartz lenses in an altered thick, cut the other rocks. The gold occurs princi- fault zone within granodiorite. The fault zone strikes pally in several subparallel narrow quartz-calcite northward and dips steeply. It is between 1and 3 feet veins whose attitudes are similar to those of the thick and is traceable intermittently on the surface metamorphic rocks. The veins are between 2 and 12 for about 1,000 feet. The granodiorite is medium inches thick and are discontinuous. Generally, their grained and hypidiomorphic granular in texture. It outcrop lengths are between 20 and 40 feet. Pyrite is contains about 60 percent plagioclase (sodic andes- the only metallic mineral noted in any of the veins. EXPLANATION

Mafic dike

. . , 1,500 feet K Geoloev modified from Rossman -I.80-_ > (1959, fig. 8) Fault, approximately located, showing dip

Quartz vein betwean 2 and 6 inches 0, 40 FEET thick, showing dip DATUM IS APPROXIMATE MEAN HIGH TIDE x 66AM k-348 (.02) Sample location Gold content (in ounces per ton) is shown in parentheses. Sample data are givem in table 11

FIGURE13.-Geologic sketch map showing sample locations at the Monarch No. 2 mine. METALLIC COMMODITIE8 63

Reed (1938, p. 64) reports that a 10-inch sample Galena prospect across one of the veins carried 0.08 ounce of gold per The Galena prospect is west of Reid Inlet at an ton and 0.20 ounce of silver per ton. A sample from altitude of about 500 feet (pl. 1, loc. J). Its workings the largest vein at the prospect carried negligible consisted of trenches that are now obscured by values (table 11, loc. H) . sloughing and overburden. The prospect was staked Thin altered zones are developed adjacent to some in 1936 or 1937. The rocks at the prospect are gran- of the lamprophyre dikes; these zones and nearby odiorite, subordinate schist, and a few lamprophyre parts of the dikes carry minor amounts of pyrrhotite, dikes. The prospect is on a vein between 4 and 18 pyrite, and arsenopyrite. Rossman (1959, p. 56) re- inches thick that was exposed over a length of about 60 feet (Twenhofel and others, 1949, p. 33). The vein ports minor amounts of scheelite from a quartz vein consists of banded and vuggy quartz with fairly near the Sunrise prospect. abundant pyrite, sphalerite, and galena. A sample Hopalong and Whirlaway claims representing a 12-inch width of the vein contained According to Rossman (1959, p. 56), two claims 0.16 ounce per ton gold, 0.30 ounce per ton silver, and 0.79 percent zinc (Reed, 1938, p. 63). were staked on the Whirlaway and Hopalong veins on the west side of the ridge east of Reid Inlet, at Highland Chief prospect altitudes near 1,350 feet (pl. 1, loc. I). The veins cut The Highland Chief prospect is at altitudes be- fine-grained diorite or quartz diorite. They strike tween 2,500 and 2,800 feet west of the head of Reid northward and dip vertical and are as much as 1foot Inlet (pl. 1, loc. K) . Extensive snowfields, which per- thick. The veins pinch and swell, and throughout sist throughout most summers, covered most of the most of their exposures are only a few inches thick. prospect area during our examination. The rocks They can be traced for about 60 feet along their that were exposed consist of amphibolite, schist, and strike. Besides quartz, the veins contain abundant marble, locally penetrated by granodiorite salients. calcite, minor muscovite, uncommon pyrite and arse- The metamorphic rocks form part of a northwest- nopyrite, and probably erratically distributed gold. trending screen and dip steeply. None of the reported Our samples from them were virtually barren (table quartz veins at the property were exposed. Accord- 11, loc. I). Rossman (1959, p. 56) states that a small ing to information quoted in Rossman (1959, p. 54), amount of gold was recovered by sluicing the weath- the main quartz vein at the prospect is as much as 6 ered surficial parts of the veins. feet thick and contains considerable free gold. Ross-

EXPLANATION

Granodiorite

-----+ z=---<2:; -= z - - .. -->-=- Hydrothermally altered fault wne containing quartz lenses L Altitude at portal is 9 approximately 1,000 feet

- L Sample location Gold content (in ounces per tom) is shown in parentheses: Sample data are Geology modifled from Rossman in table 11 (1959; fig. 6) given

1 911141150 FEET DATUM IS APPROXIMATE MEAN HIGH TIDE

FIGURE14.-Geologic sketch map showing sample locations at the Incas mine. 64 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA man (1959, p. 54) reports that other steep north- contain gold. These veins are little explored, but they west-striking quartz veins near the prospect contain probably are similar to the better known quartz gold. These are alleged to be as much as 2 feet thick veins in the area. and traceable for as much as 700 feet along strike. The prospect probably is one of the most promising SOUTHOF LITUYABAY in the Reid Inlet area, but its exploration and devel- Rossman (1959, p. 57, 58, and his fig. 9) reports opment have been curtailed by the near-perennial zones of hydrothermally altered rocks south of snow cover. Lituya Bay and west of Crillon Glacier (pl. 1, loc. 85). These zones are reddish yellow and are devel- Rambler prospect oped in Tertiary volcanic and sedimentary rocks. The Rambler prospect is on the steep hillside east They are readily susceptible to erosion, and their of Lamplugh Glacier (pl. 1, loc. L). It consists of a best outcrops are in streambanks, ravines, or gulleys. few small surficial pits on quartz veins, mainly with- Most of the zones are virtually barren, but some of in leucocratic granodiorite. The granodiorite con- them contain gold. Their highest analyzed gold contains a few small screens of metamorphic rocks and tent was 0.24 ounce per ton (Rossman, 1959, p. 58, is cut by a few northeast-striking steep mafic dikes. and his fig. 9). The zones are numerous and exten- The quartz veins commonly strike between N. 60" sive and have been scarcely prospected. Parts of E. and east and dip steeply. They are mainly only 1 them may carry gold of higher grade than indicated or 2 inches thick, but in places attain a thickness of 3 by Rossman's samples; they probably merit addi- feet. Most of the veins pinch and swell conspicu- tional prospecting. ously. Typically, the veins are exposed for less than 200 feet along their strikes and are bordered by nar- SANDYCOVE PROSPECT row altered zones. The veins consist of quartz, cal- The Sandy Cove prospect is northeast of Sandy cite, feldspars, barite, scattered sulfides (mainly Cove, an embayment of the eastern part of Glacier arsenopyrite, pyrite, and galena), and traces of gold. Bay, at altitudes near 110 feet (pl. 1, loc. 7). The All our samples from the veins yielded low gold val- prospect consists of three claims that probably were ues (table 11, loc. L). High-grade samples rich in staked during the 1930's. It was explored by a north- gold reportedly have been collected at the prospect eastward-trending adit about 110 feet long and by a (Rossman, 1959, p. 55; Lawrence Duff, oral com- few surficial workings. The prospect is on a south- mun., 1966). facing hillside that is partly covered by vegetation and soil. The ore deposits are localized in a series of Other lode deposits in the Reid Inlet area northward-striking steep quartz veins and in the Several other gold-bearing lodes have been re- contiguous altered wallrock (fig. 15). Surface expo- ported from the Reid Inlet area, but they were not sures of the veins and the altered zones are strongly examined during our investigations. These include oxidized and colored reddish brown by widely dis- the A. F. Parker prospect and a few unexplored persed hydrous iron oxides. Most of the veins are in quartz veins. monzonite or quartz monzonite that forms small The A. F. Parker prospect is about two-thirds of a masses in marble country rock. Reed (1938, p. 66) mile northwest of the LeRoy mine at an altitude of considered the intrusive rock at the prospect to be 850 feet. The prospect was staked in 1938 and was monzonite; our petrographic studies indicate it is a worked by a 20-foot-long adit; it had a production of quartz monzonite. The rock is medium-grained 7 or 8 tons of ore (Twenhofel and others, 1949, p. hypidiomorphic granular and consists mainly of pla- 33, 34). The prospect explores irregular quartz vein- gioclase that is zoned from sodic andesine to calcic lets that are localized in a fault zone cutting grano- oligoclase. It contains about 25 percent potassium- diorite. The veinlets are between and 1 inch thick feldspar and 10-15 percent each quartz and green within a gouge zone about 10 inches thick. The fault hornblende. Minor accessory minerals and alteration zone strikes N. 70" E. and dips 86" SE. At the face products in the rock include sphene, apatite, allanite, of the adit, the fault zone is truncated by a fault that epidote, chlorite, muscovite, calcite, pyrite, and mag- strikes N. 66" E. and dips 64" NW. (Twenhofel netite. The quartz monzonite and monzonite are and others, 1949, p. 34). The quartz veinlets contain 1oc:llly silicified near the altered zones and quartz galena, pyrite, and a little free gold. veins. Rossman (1959, 11. 55, 56) reports a few other The quartz veins range in thickness from 1 to 12 quartz veins in the Reid Inlet area that probably inches, and the altered zones are as much as 10 feet METALLIC COMMODITIES

.. ."1 EXPLANATION

Monzonite and quartz monzonite Locally dlicified near altered zone

Altered zone, showing dip Contains gold- and sulfide-bearing quartz veins and lenses; scattered sulfides, clay minerals, chlorite, and secondary iron minerals

Location of chip or channel sample

,$@;$Lapped by E. M. MacKevett, Jrand A. S. Radtke, June 24, 1966 Location of grab or selected sample " Gold content (in ounces per ton) is Altitude at portal shown in parentheses. Sample data approximately 110 feet are given in table 9

0 40 FEET IIIII DATUM IS APPROXlMATE MEAN SEA LEVEL

FIGURE15.-Geologic sketch map showing sample locations at the Sandy Cove prospect. thick. Most of the quartz veins are lenticular and ton silver. Rossman (1963b, p. K52) detected be- discontinuous; some of them are in an en echelon tween 0.001 and 0.003 percent U308 in samples from pattern. In addition to quartz, their gangue minerals some of the altered zones near Sandy Cove. include ankeritic carbonates and probably barite. Soil samples were collected at the Sandy Cove Sulfide minerals which locally make up the bulk of prospect in an effort to trace the vein that is exposed the veins consist of pyrite, chalcopyrite, and bornite. near the portal of the adit. A soil sample from just In places the sulfide minerals have been oxidized to west of the adit contained 220 pprn THM, whereas malachite, chrysocolla, and diverse hydrous iron one from just east of the adit contained only 20 pprn minerals. Gold is distributed erratically in the veins. (fig. 16). Samples collected across the trend of the The altered zones carry minor amounts of gold and vein both to the northwest and to the southeast con- sulfides. tained only background concentrations of heavy Samples from the prospect contained as much as metals. 0.96 ounce per ton (33 ppm) gold, 50,000 pprn copper, Glacial till from the hillside above the prospect 1.46 ounces per ton (50 ppm) silver, 50 pprn molyb- dilutes the residual soil and interferes with the ap- denum, 500 pprn bismuth, and 150 pprn lead (table 9, plication of geochemical techniques. Despite this loc. 7). The richest samples were from near the face dilution, the soil samples collected close to, or just of the adit (fig. 15). The other veins and altered downhill from, mineralized areas seem to be geo- zones appear to be leaner in ore minerals than the ' chemically anomalous. The lack of anomalous sam- ones exposed in the adit. Reed (1938, p. 68) reports ples across the trend of the vein is interpreted as gold and silver assay results for 39 samples that indicating that the veins pinches out near the sur- were cut in the adit. These samples contained as I face both northwest and southeast of the adit. A much as 0.51 ounce per ton gold and 2.4 ounces per sample collected downhill from the dump contained ton silver. Their average content was 0.11 ounce per 480 pprn THM; this sample is believed to be contam- ton gold and 0.6 ounce per ton silver, and their medi- inated by ore metals from the dump, however, and an content was 0.04 ounce per ton gold and 0.3 ounce not to have any significance in prospecting. per ton silver. Reed (1938, p. 68) also reports that 4 The sampling and mapping disclosed several other tons of selected ore from near the portal of the adit veins northwest of the adit; they appear to form an contained 0.37 ounce per ton gold and 0.15 ounce per 1 en echelon pattern that trends northwestward. Soil MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

p 120 1 EXPLANATION

P *O Soil-sample site showing total heavy -metal content (in parts per million). Tail on circle indicates slope of land surface

+?I I=- Quartz veins

*L 7 Rock Portal of adit

0- 50 FEET

P 20 Geology by L. C. Huff and R. J. Wehr, July 1966 FIGURE16.-Geochemical map of Sandy Cove gold-copper prospect. sampling near these veins yielded geochemical anom- amenable to a small-scale mining operation under alies. Rock sample 66AHf-280B, which had a copper more favorable conditions. Copper is a possible by- content of 1,000 ppm (table 9, loc. 7), was collected product in the ore. Further exploration of the pros- near a soil sample that contained 240 ppm THM. A pect should attempt to find richer and larger lodes, soil sample collected near a vein west of sample possibly near intersections with crosscutting struc- 66AHf-280B contained 320 ppm THM. Geochemical tures. The Wrights (1937, p. 221) noted old claims studies indicate that several veins merit further near Sandy Cove that were allegedly staked on exploration. pyrrhotite-rich lodes that contain some copper and The Sandy Cove desposits do not appear to be nickel. large enough or rich enough to encourage mining WEST OF MCBRIDEGLACIER under current conditions. Possibly, they would be Gold is a minor constituent of altered zones west METALLIC COMMODITIES 67 of the middle part of McBride Glacier (pl. 1, loc. 10). some of the copper lodes (table 9). The Wrights The altered zones are near an irregular, interfin- (1937, p. 221) refer to gold occurrences in the schist gered contact that marks a facies change between belt south of Adams Inlet which were unsuccessfully marble and phyllite. Small irregular masses of limy explored during the early days. They also (p. 222) silicate rocks are near the contact. About 10 separate mention some old, and presumably abandoned, gold altered zones are present. They are less than 2 feet claims in the hills between the east and west arms of thick and less than 100 feet long and are virtually Dundas Bay. Buddington (unpub. data, 1924) notes conformable with the bedding, which strikes about that a claim was staked for gold at Dundas Bay, but N. 85" E. and dips 25" NW. The altered zones are no specific information concerning this claim is prevaded by intense iron staining derived from the available. Buddington (unpub. data, 1924) further alteration of their ankeritic carbonates and sulfide reports that specimens that contained free gold were minerals. They also contain arsenopyrite and traces found in the moraines of Johns Hopkins and Brady of gold. Samples from the zones carried as much as Glaciers.

15,000 ppm arsenic, 500 ppm copper, and 0.087 ounce PLACER DEPOSITS per ton gold (table 9, loc. 10). Gold placer deposits are fairly widespread in the EAST OF LOWERBRADY GLACIER Glacier Bay National Monument, but the only signif- Several small gold-bearing quartz veins crop out icant producers are the beach placers north and in the mountains west of Dundas Bay nearly east of south of Lituya Bay (pl. 1, locs. 87, 88). The placers the terminous of Brady Glacier (pl. 1, loc. 55). The include beach sands, stream deposits, old alluvial veins are in mafic gneiss and diorite. They com- terrace and bench placers, glacial outwash, and monly are only a few inches thick and are exposed minor residual placers that are associated with some for short distances along their strikes. The veins lodes in the Reid Inlet area. No significant gold presumably contain small amounts of gold, but no placer deposits were discovered during our investi- gold is visible in the hand specimens. A sample from gations. Descriptions of the known placer deposits in one of the veins yielded negligible amounts of gold the monument follow. and other ore metals (table 9, loc. 55). The area has SOUTHOF WOODLAKE not been prospected thoroughly, and it may contain Rossman (196313, p. K50) reports that placer gold undiscovered gold-bearing veins of interest. has been mined from glacially derived gravels south

WEST OF DUNDASBAY of Wood Lake in the upper part of the Dundas River Rossman (unpub. data) mentions a lode gold oc- drainage basin (pl. 1, loc. 52). The exact location of currence on the north shore of the peninsula between these deposits could not be ascertained. The general Dundas Bay and its west arnl (pl. 1, loc. 5). The region has been deglaciated fairly recently, and deposit was not found during the 1966 fieldwork. It probably its streams contain local auriferous placers. probably consists of small gold-bearing quartz veins DUNDASRIVER in dioritic rocks. According to records of the Alaska Division of RUSSELLISLAND Mines and Minerals, nine gold placer claims on the Two thin gold-bearing quartz veins occur in an Dundas River are held by the Jimmie Martin estate. altered zone near the northeastern tip of Russell Little is known about the claims, but they are in the Island (pl. 1, loc. 61), which is about 3 feet thick vicinity of locality 53 as plotted on plate 1. and transects biotite-hornblende granodiorite. The OUTWASHOF BRADYGLACIER veins and the altered zone strike N. 17" E. and dip According to information cited in Rossman (1963b, vertically. The veins are between 2 and 5 inches p. K50, K51), placer mining of the outwash in front thick. Neither the veins nor the altered zone can be of Brady Glacier (pl. 1, loc. 59) was carried on for traced for more than about 25 feet on the surface some time during the early part of the century. The because of cover. Besides quartz, the veins contain gold in these deposits is very fine grained, floury, and fairly abundant calcite and minor pyrite. A sample difficult to recover. Probably attempts to mine it of the veins carried 0.844 ounce per ton gold and were of short duration and yielded only small traces of silver and lead (table 9, loc. 61). amounts of gold. OTHERLODE DEPOSITS OREGONKING CONSOLIDATED Gold is a minor constituent of many of the de- Thirty-six placer claims, mainly on the beaches, posits described elsewhere in this report, particularly west of La Perouse Glacier (pl. 1, loc. 81), are held 68 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA by the Oregon King Consolidated organization bare beaches contain concentrations ot heavy mm- (Alaska Div. Mines and Minerals, written commun., erals that form deposits as much as several hundred 1966). The deposits have been explored intermit- feet wide and a few miles long. The vertical range of tently during recent years and probably include a the heavy sand concentrations in the bare beaches is few stream and terrace deposits as well as the beach not known. Most cutbanks show layers of heavy min- placers. eral to depths of about 6 feet. The tree-covered beaches also contain concentrations of heavy min- LITUYABAY erals on their upper surfaces, but little is known of The most extensive and best gold placer deposits the extent and depth of these deposits. The main in the monument are in the beach sands near Lituya heavy minerals of all the beach sands, in general Bay (pl. 1, locs. 87, 88). Auriferous sands are dis- order of decreasing abundance, are garnet, pyrox- tributed irregularly along the beaches for about 20 ene, ilmenite, amphibole, magnetite, staurolite, epi- miles northwest of Lituya Bay and for about 15 miles dote, rutile, sphene, and zircon. The light fractions of southeast of the bay. They have been worked inter- the dark sands include quartz, feldspar, mica, cal- mittently for many years. Mertie (1933, p. 133) cite, and small rock fragments. Rossman was con- states that mining by Americans near Lituya Bay cerned mainly with the economic potential of the commenced in 1894. The heyday of the mining was ilmenite in the sands. The heavy mineral sands near in 1896, when between 150 and 200 men were Lituya Bay were also investigated by the U.S. Bu- engaged in working the placer deposits. Between reau of Mines, mainly with emphasis on their iron 1894 and 1917, the placers produced gold worth and titanium content (Thomas and Berryhill, 1962, about $75,000 (Mertie, 1933, p. 135). A small amount p. 37-39). of platinum was recovered also. Production since Mertie (1933, p. 135) reports that attempts to 1917 has been small. mine some of the bench and terrace deposits were The minable placers are formed largely by the largely unsuccessful. The Wrights (1937, g. 223) reworking of older gold-bearing deposits, particu- note that the counteraction of waves and stream larly of poorly consolidated terrace, bluff, and bench currents near the mouth of a stream about 4 miles deposits near the seashore. This process is acceler- northwest of Lituya Bay is effective in concentrating ated by large waves generated during storms, and heavy minerals. the most favorable periods for mining are shortly The beach deposits near Lituya Bay are a poten- after storms. Most of the gold in the deposits has tial source of additional gold production and minor been recycled and reconcentrated during several amounts of platinum and possibly ilmenite. They stages and has been transported by glacial processes. could be worked on a small scale under favorable eco- Consequently, it is extremely fine grained, floury, nomic conditions, or possibly some of them could be and difficult to recover. The deposits were worked by worked on a large scale by dredging. Little is known fairly primitive methods, including Long Toms and concerning the possibility of offshore placer deposits sluice boxes, and undoubtedly a sizable amount of the near Lituya Bay, although the presence of such de- gold was not recovered. posits is conceivable. The pay streaks generally are less than a few feet thick. They are in black sands that are rich in garnet OTHERPI ACER DEPOSITS and contain ilmenite, magnetite, and other heavy Small amounts of gold have been recovered by minerals that were concentrated by washing and mining the residual and weathered material that gravity settling. The sparse platinum in the placers, overlies some of the gold lodes in the Reid Inlet area. like the gold, is very fine grained. Surficial parts of many of these lodes are for the Rossman (1957) examined the beach deposits dur- most part residual placers. Gold is sparsely distrib- ing 1952, and the descriptions given here are sum- uted in colluvium and in stream placers in the Reid marized from his report. The beach deposits overlie Inlet area but probably in quantities too small to be bedrock, glacial outwash, and moraines. All of them, exploited. except the modern bare beaches, are partly covered Many of the streams throughout the monument by alluvial fans, glacial out\vash, or swamp deposits. undoubtedly contain small concentrations of placer The beach deposits include modern bare ocean gold, but the likelihood of significant gold produc- beaches, tree-covered modern beaches, and older tion from them is small. The extensive glacial out- tree-covered modern beaches, and older tree-covered wash and other fluvioglacial deposits in the monu- beaches. The beaches that lack vegetation are be- ment likewise probably contain widely dispersed tween 800 and 2,700 feet wide. Upper parts of all the gold. Attempts to find concentrations of gold in METALLIC COMMODITIES 69 these deposits were unsuccessful, and it is unlikely the placers, particularly the recycled and glacially that they contain minable placers. derived ones, inhibits recovering substantial amounts of silver from them. PLATINUM Platinum is a rare constituent of some of the RENDU INLET PROSPECT beach placers near Lituya Bay, especially those The Rendu Inlet silver prospect, found at an alti- south of the bay (Mertie, 1933, p. 134), but no lode tude of 30 feet on the west side of Rendu Inlet about sources of platinum are known in the monument. By 3 miles northwest of the mouth of the inlet (pl. 1, analogy with known platinum deposits, such as those loc. 37), has been known for many years. According in the Bushveld Complex and at Sierra Leone in to Buddington (unpub. data, 1924), it consists of two Africa, or in the Stillwater Complex in Montana, the claims that were patented about 1892. Its workings platinum probably is a minor constituent of the consist of a short westward-trending adit that is mafic and ultramafic layered complex that forms caved at the portal. Recent slide material that covers the Crillon-LaPerouse and the Astrolabe-DeLangle most of the outcrops precluded a satisfactory exam- stocks in the Fairweather Range. The platinum ination of the prospect. The deposits are mainly in would most likely be associated with certain ilmen- an ankeritic carbonate-quartz vein about 6 inches ite-rich layers within these rocks or with some of thick and in continguous altered wallrock a few feet their sulfide deposits. Platinum and several other thick. The vein and altered zone both strike N. 85" metals, should be prospected for in the little-explored E. and dip 65" SE. White bleached marble forms layered mafic and ultramafic rocks because these the hanging wall of the deposit, and the footwall is rocks are assuredly the source of the placer a dioritic dike that is about 20 feet thick and in- platinum. trudes marble. A 4-inch-thick quartz-calcite vein occupies a steep northwest-striking fault that offsets SILVER the northeast-striking vein by a few inches. The only Silver is a subordinate metal in many of the gold indication of ore mineralization exposed at the time and base-metal deposits in the monument; in only of our examination was locally intense iron staining. one prospect, near Rendu Inlet, is silver a major Samples from the prospect were low in grade and commodity. The known silver minerals in the monu- lacked silver (table 9, loc. 37). Buddington (unpub. ment are minor constituents of veins, altered zones, data, 1924) states that argentiferous tetrahedrite and replacement bodies. They include argentiferous occurs on the claims. Rossman (1963b, p. K48, K49) tetrahedrite, jamesonite, and native silver. Besides found a specimen that contained tetrahedrite and the Rendu Inlet prospect (pl. 1, loc. 37), silver has wire silver along fractures in quartz. It is concluded been reported from the Reid Inlet gold lodes, the that these ore minerals are sporadically distributed Sandy Cove gold prospect, a prospect in the north- in the veins. Several similar-appearing veins and western part of Willoughby Island, a locality near altered zones are along the west side of Rendu Inlet Blue Mouse Cove on Gilbert Island, and the Nunatak near the prospect. Samples from these zones were molybdenum prospect. The richest silver values in barren, but possibly diligent prospecting would de- our samples are 4.377 ounces per ton (150 ppm) from tect small amounts of silver and copper minerals in the Alaska Chief prospect, 2.043 ounces per ton (70 them. ppm) from the Rainbow mine in the Reid Inlet area, 1.46 ounces per ton (50 ppm) from the Sandy Cove IRON AND FERROALLOY METALS prospect, 1.46 ounces per ton (50 ppm) from Francis The iron and ferroalloy metals discussed here Island, 0.875 ounce per ton (30 ppm) from the base- include iron, chromium, cobalt, manganese, molyb- metal lodes near Mount Brack, and 0.583 ounce per denum, nickel, titanium, tungsten, and vandium. De- ton (20 ppm) from the copper deposits north of posits described include the two that have the best White Glacier (tables 9, 11). Rossman (1963b, p. potential for mining in the near future, the Brady K49) states that a quartz-rich sample from a gulley Glacier nickel-copper deposit and the Nunatak mo- northeast of the Nunatak molybdenum prospect car- lybdenum deposit, and a few others that merit ried 7.07 ounces of silver to the ton, but our sam- exploration. ples from the Nunatak molybdenum prospect (table 1 I RON 13) carried only trace amounts of silver. Several iron deposits are within the monument, Small amounts of silver are associated with gold in but none of them appear to be large enough or rich most of the gold placer deposits in the monument. enough to be mined currently. The deposits include The high degree of mineral comminution in many of several magnetite-rich skarns, concentrations of 70 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA magnetite and ilmenite in the layered mafic rocks of fairly high magnetic background, but the anomalous the Fairweather Range, beach placers that contain magnetic values that were detected in it are attrib- magnetite and ilmenite, and an alleged hematite de- uted to pods of magnetite-rich skarn or tactite or posit of uncertain genesis and type. Although they possibly to local magnetite-rich segregations. Except are locally rich, all the known skarn deposits seem- for iron, samples of the skarn and tactite lacked ingly contain insufficient amounts of magnetite to be significant amounts of ore metals (table 9, loc. 39). exploited. The layered mafic rocks of the Fairweather QUEENISLET Range and the placer deposits northwest and southwest of Lituya Bay constitute a low-grade resource Masses of tactite that locally contain sufficient of iron as well as a titanium resource. magnetite to be termed "skarn" crop out in sea cliffs along the east shore of Queen Inlet east of DESCRIPTIONS OF DEPOSITS Composite Island (pl 1, loc. 40). The tactite bodies EAST OF DUNDASBAY are as much as 20 feet thick and intervene between Rossman (unpub. data) mentions an iron deposit alaskite and coarse white marble (pl. 10). Porphyrit- at an indefinite location east of Dundas Bay and ic felsic volcanic rocks are associated with some of north of Icy Strait (pl. 1, loc. 33). Little is known the alaskite. In addition to magnetite, the tactite about the deposit, but on the basis of the local geol- contains abundant garnet, quartz, calcite, horn- ogy, it probably is in skarn near the contact between blende, pyroxene, chlorite, and sporadically distrib- granodiorite and limestone. A magnetic disturbance uted veins and pods of sulfide minerals, chiefly reported from the north side of Lemesurier Passage pyrite. Some of the veins are rich in albite. A few near locality 33 (U.S. Coast and Geod. Survey steeply dipping mafic dikes as much as 15 feet thick Chart 8202, 13th ed., 1965) probably is all attribut- cut the other rocks. Several steep faults, apparently able to a magnetite-rich skarn deposit. with minor offsets, are exposed in the sea cliffs. Buddington (unpub. data, 1924) reports claims for The alaskite is a hypidiomorphic-granular me- hematite at an altitude of 1,700 feet in the mountains dium-grained rock that is slightly altered. A light- between ~undasBay and the next cove to the east. gray color prevails, but some of the feldspars are No additional information is available on these altered to milky white masses. The alaskite contains claims, which were probably abandoned many years 50-65 percent oligoclase, 20-30 percent quartz, mi- ago. nor potassium-feldspar, and subordinate amounts of magnetite and alteration products, including calcite, WEST OF RENDUINLET epidote, actinolite, and chlorite. Some of the alaskite Magnetite-rich skarn deposits are distributed is cut by veinlets and minute fractures. irregularly in the southern part of the peninsula The porphyritic volcanic rocks are yellowish west of Rendu Inlet (pl. 1, loc. 39). The deposits are white. They contain abundant phenocrysts of plagio- in small pods of tactite or skarn near the contact clase (sodic andesine) and quartz in a microcrystal- between quartz diorite and marble or within the line groundmass composed largely of plagioclase quartz diorite (fig. 17). The deposits appear to be microlites, quartz, and albite (?). Minute crystals of small, but much of the nearby bedrock is covered by pyrite and magnetite are widely dispersed through- surficial deposits, and the size and distribution of the out the rock. Calcite veinlets transect some of the magnetite deposits cannot be estimated accurately. volcanic rocks. The skarn and tactite consist of garnet that is rich The coarse white marble consists predominantly of in grossularite, associated with calcite, quartz, chlo- calcite. The mafic dikes are dark-gray to black al- rite, epidote, and with concentrations of magnetite. tered porphyritic andesites. They contain about 70 The marble is massive, coarse grained, and calcite percent plagioclase (andesine) , which forms pheno- rich. The quartz diorite is medium coarse grained crysts between l and 2 mm long and is also the and contains abundant hornblende. A few mafic dominant mineral in the groundmass. Other miner- dikes as much as 6 feet thick cut the other rocks; als in the rock are chlorite, actinolite, magnetite, some of them contain small pyrite-rich blebs and and pyrite. pods near their contacts. A magnetometer traverse along the beach contig- Two magnetometer traverses were made across uous to the sea cliffs revealed magnetic anomalies the marble-quartz diorite contact and for several greater than 1,000 gammas along projections of the hundred feet into the quartz diorite terrane (fig. 17). tactite bodies (pl. 10). These revealed local magnetic anomalies as high as The hillsides east and northeast of the sea cliffs 5,500 gammas (fig. 17). The quartz diorite has a are largely covered by glacial deposits. Outcrops on METALLIC COMMODITIES

EXPLANATION

u Moraine and alluvium

Magnetometer traverse and geology by E. M. MacKevett, Jr., and J. G. Smith, Jr., 1966

FIGURE17.-Magnetometer traverses west of Rendu Inlet. 72 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

these hillsides consist mainly of felsic siliceous rocks south of Abyss Lake (pl. 1, loc. 54). The deposits are that were mapped as alaskite but which also include at an altitude of about 1,350 feet. They consist of some siliceous porphyritic volcanic rocks. The alas- several steep lenses of magnetite-rich skarn that kite and the volcanic rocks are cut by steep mafic strike northwestward. The lenses comprise abundant dikes that contain sparsely distributed pods and thin magnetite and garnet, subordinate quartz and calc- veins of sulfides, chiefly pyrite. The petrography of silicate minerals, and minor pyrite and chalcopyrite, these rocks is analogous to their counterparts that and are bordered by marble and small masses of are exposed in the sea cliffs. A magnetometer survey leucocratic granodiorite. They are as large as 30 feet along a traverse extending southwestward from an long and 10 feet thick. altitude of 1,740 feet to near the beach was made to Semiquantitative spectrographic analyses showed trace the magnetite deposits inland and to find con- that samples of the skarn contained major amounts cealed deposits (pl. 10). This survey revealed anom- of iron and 1,000 pprn copper (table 9, loc. 54). alous magnetism to 1,300 gammas in some areas Magnetometer readings of as much as 5,000 gammas that are covered by glacial drift; this probably in- were obtained on some of the skarn outcrops. Al- dicates concealed magnetite-rich lodes similar to though some of the skarn bodies are rich enough to those exposed in the sea cliffs. constitute iron ore, they are too small to be exploited. Semiquantitative spectrographic analyses of the Development of the deposits is contingent upon the skarns showed major amounts (>I0 percent) of unlikely possibility of discovering concealed skarn iron, as much as 300 pprn copper, 300 pprn cobalt, 30 bodies that contain large tonnages of magnetite. pprn tin, and traces of molybdenum and nickel (table FAIRWEATHERRANGE 9, loc. 40, samples 66AMk-298A, -298B, -299, -303). Similar analyses of pyrite-rich pods, veins, and al- The layered mafic and ultramafic rocks of the Fairweather Range contain a large low-grade iron re- tered zones contained abundant iron and as much as source and appreciable amounts of other metals, 300 pprn copper, 70 pprn cobalt, 30 pprn tin, and notably titanium. These rocks form the Crillon- traces of molybdenum and lead (loc. 40, samples LaPerouse and the Astrolabe-DeLangle stocks of 66AMk-305, -321, -323, -324). Analyses of an 18- Rossman (1963a) and probably a similar, but unex- foot-long chip sample taken across the richest ap- plored, mass near Mount Fairweather. Four localities pearing magnetite deposit in the sea cliffs revealed where the layered rocks are known to contain con- 23.4 percent total Fe as FezOs, 38.5 percent SiOz, 7.0 centrations of iron minerals are shown on plate 1 percent Alz03, 0.11 percent P205, 1.54 percent S, 0.36 (locs. 73, 79, 80, 83). Undoubtedly, many other local- percent TiOe, and 30 pprn As.' ities in the Fairweather Range contain similar de- The known iron deposits east of Queen Inlet are posits, but the range has been only cursorily pros- too small and too lean to warrant economic interest, pected, chiefly because of its formidable terrain and but intensive prospecting might lead to the discovery difficult access. of larger and richer deposits near the known ones. The iron deposits in the Astrolabe-DeLangle stock

WEST OF BLACKTHORNPEAK are represented in a general way by locality 73 on Seitz (1959, p. 117) reports a magnetic anomaly plate 1. Rossman (1963a, p. F44, F45) reports that near the divide of Geikie Glacier west of Blackthorn some layers in the stock contain concentrations of Peak (pl. 1, loc. 51). The anomaly was detected from ilmenite and that other layers contain as much as 20 an airplaine from an altitude of about 2,500 feet percent titanium-bearing magnetite. At most places above the ground. Outcrops are poor in the vicinity the contact zones of the stock also contain titanium- of the ;tnomaly because of extensive ice and snow. bearing magnetite. Most of the layers that carry much magnetite or ilmenite crop over a "strati- Probably the anomaly indicates a magnetite-rich graphic" thickness of about 1,000 feet near the top skarn deposit, but confirmation of the nature of the of the mountain that forms Astrolabe Penisula. The del~ositand its size and grade would require drilling iron- and titanium-rich layers are at an altitude of or other physical exploration. 1,100-2,000 feet and appear to persist through the

I EAST OF BRADI.GI.A~:IBR mountain. Rossman (1963a, p. F45, table 8) gives the Ptli~gnetitedeposits were found in the hills east of magnetite and ilmenite contents of some rocks from the Astrolabe-DeLangle stock. the lower part of Brady Glacier about 3%. miles Several iron-stained layers that are signaled by 1 FerOa determined by atomic absorption by W. D. Goss. SiOs. Al.03, and Ti02 determined colorimetrically by G. T. Burrow. PsO;, determined volu- bright red outcrops have been reported from the metrically by L. F. Rader. S determined by induction furnace by Dorothy Kouba. As determined colorimetrically by E. J. Fennelly. Crillon-LitPerouse stock (Rossman, 1963a, p. F42, METALLIC COMMODITIES 73

F43) (Kennedy and Walton, 1946, p. 71). A few of detected in almost all our analyzed samples from the these are represented on plate 1 (locs. 79, 80, 83). monument, and anomalous amounts of cobalt were Most of these layers contain fairly abundant ilmenite detected in a few of them (tables 9, 11, 13, 15). The and subordinate pyrrhotite and chalcopyrite. The anomalous concentrations of cobalt are as much as layers have not been prospected thoroughly, and 2,000 pprn in massive sulfides from the Brady Gla- probably some of them and some of the other layers cier prospect (table 15, pl. 1, loc. 72); 700 pprn in in the stock also contain concentrations of magnetite. samples west of the mouth of Rendu Inlet (table 9, The presence of layered mafic intrusive rocks near loc. 38); 300 pprn north of Adams Inlet (5), the Mount Fairweather is indicated by float on the mo- Queen Inlet magnetite locality (40), and the Alaska raines of the Fairweather Glacier. Presumably, the Chief prospect (29) ; and 200 pprn from Shag Cove magnetite and ilmenite content of these unexplored (49). rocks is similar to that of the Crillon-LaPerouse and MANGANESE the Astrolabe-DeLangle stocks. . Manganese is widely associated with most of the PLACERDEPOSITS mineral deposits, but no potentially exploitable man- The beach placers north and south of Lituya Bay ganese deposits are known from the monument, and which were described under "Gold" contain concen- the likelihood of discovering such deposits is remote. trations of these heavy minerals in the monument Manganese-stained oxidized zones are conspicuous in are between 2 and 13 miles south of Lituya Bay outcrops of several deposits, particularly the base- (Rossman, 1963a, p. F46). Rossman's samples (1957, metal replacement lodes and altered zones. Samples table 1) from the beach placers contained as much as from several of the deposits contained between 2,000 10 percent magnetite and 21 percent ilmenite, but and 7,000 pprn manganese (table 9). The most not- their average content of these minerals was con- able of these are from Francis Island (loc. 28, No. siderably less. The probability of iron being recov- HF-183C) and the Alaska Chief prospect (29, No. ered from these deposits is remote. hk474).

CHROMIUM MOLYBDENUM No chromium lodes are known to occur in the DISTRIBUTION monument, but chromite float has been reported on Many mineral deposits that contain molybdenum glaciers in the Fairweather Range (Goldthwait, in are known in the monument. They include one im- Kennedy and Walton, 1946, p. 71, 72). The largely portant prospect, the Nunatak prospect (pl. 1, loc. unexposed ultramafic rocks that are inferred to 21); a few deposits, such as those in the Bruce Hills form the lower parts of the layered intrusive com- (34) and near the southwestern part of Gilbert Is- plexes of the Fairweather Range are potential hosts land (44, 45), that contain molybdenum and copper for chromite deposits. Trace amounts of chromium of near-equal potential; several small molybdenite were found in almost all our samples from the monu- deposits; and some deposits whose analyzed samples ment, and anomalous quantities of chromium were revealed trace to minor amounts of molybdenum. found in a few of the samples (tables 9, 11, 13, 15). Molybdenum is widely distributed throughout The largest amounts of chromium detected in the much of the eastern and northeastern parts of the samples were 1,500 pprn from new Mount Young monument where widespread, but generally small, (table 9, loc. I), 1,000 pprn from peridotite at the molybdenum content characterizes many of the met- Brady Glacier prospect (table 15, No. CSN-I), and alliferous deposits. The molybdenum deposits are 700 pprn from the Curtis Hills. (table 9, loc. 23). particularly abundant in parts of the Mount Fair- weather D-1 and D-2 quadrangles (pl. 1). COBALT Cobalt is a potential byproduct of the nickel-cop- TYPES OF DEPOSITS per deposits at the Brady Glacier prospect, but no The molybdenum deposits are commonly localized discrete cobalt minerals have been identified in the in metamorphic rocks near granitic masses or within deposits. Samples representative of the richest ore at the granitic rocks themselves. They form stock- the prospect contained an average of 0.25 percent co- works, disseminations, veins, mineralized fault zones balt. Cobalt probably is a minor constituent of simi- and fracture coatings, and at some places are lar sulfide deposits that may be associated with the parts of contact-metamorphic zones, dikes, or amyg- layered mafic and ultramafic complexes of the Fair- daloidal lavas. The largest known molybdenum de- weather Range. Minor amounts of cobalt were posits in the monument consist of swarms of closely 74 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA spaced veins and veinlets that are termed "stock- posits were explored with three diamond-drill holes works." Except for minor amounts of molybdite in by the American Exploration & Mining Co. Our field the Bruce Hills copper-molybdenum deposit (pl. 1, examination consisted of checking Twenhofel's geo- loc. 34), molybdenite is the only molybdenum miner- logic map and collecting numerous chip samples, soil al in the deposits. samples, and a few pertinent rock and mineral specimens. DESCRIPTIONS OF DEPOSITS CASEMENTGLACIER Deposits at the prospect consist of stockworks of Molybdenite-bearing float was found on lateral molybdenite-bearing quartz veins, uncommon dis- moraines fairly high on Casement Glacier (pl. 1, seminated molybdenite, and a mineralized fault zone. IOC. 9) by members of the Ohio State University They are mainly in hornfels, but locally they occur in field party sponsored by the Institute of Polar quartz monzonite porphyry and in silicified zones Studies (Colin Bull, written commun., 1965). The near the edge of the porphyry (pl. 11). float reportedly also contained some copper carbon- Geology-, ates. The following descriptions of the rocks at the VAN HORNRIDGE Nunatak prospect are largely from Twenhofel's re- Numerous claims for molybdenum are on Van port (1946). The oldest rocks are dark-blue thin- Horn Ridge east of the head of Muir Inlet (pl. 1, loc. bedded limestone and subordinate shale that crop 11). A few of the claims have been explored by shal- out in the southwestern part of "The Nunatak" (pl. low pits and trenches. The deposits are in iron- 11). These rocks are conformably overlain by a thick stained altered zones, both in steeply-dipping north- sequence of hornfels, which Twenhofel (1946, p. 12) striking hornfels and in granodiorite. Most of the differentiated into three units (pl. 11). The hornfels altered zones are along faults. Typically, they are a consists chiefly of orthoclase and clinozoisite with few feet wide and do not persist along strike. The some diopside, garnet, quartz, and oligoclase. The altered zones are weakly mineralized. Samples from lower hornfels unit-is characteristically thin bedded them contained as much as 200 ppm molybdenum and contains a few limy beds. The middle unit is also and traces of lead (table 9, loc. 11). thin bedded and contains many beds that are rich in clinozoisite. The upper hornfels unit is thick bedded. WEST SIDEOF TARRINLET Small discordant masses of quartz monzonite por- Many iron-stained altered and brecciated zones phyry cut the hornfelses (pl. 11). Numerous post- are exposed in the cliffs west of Tarr Inlet south of metallization andesitic dikes cut the hornfels, lime- Margerie Glacier (pl. 1, loc. 17). These zones are stone, and quartz monzonite porphyry. Surficial between 1 and 5 feet thick and cut granodiorite or, deposits, chiefly of glacial origin, cover parts of less commonly, hornfels. A few of them are near the "The Nunatak." Outcrops of the quartz monzonite edges of felsic dikes. The altered zones are lean in porphyry are locally bordered by siliceous zones as ore metals. Samples from them contained as much as much as 15feet thick. 100 ppm molybdenum, 5,000 ppm arsenic, and 1,000 ppm barium (table 9, loc. 17). The rock mapped as quartz monzonite porphyry by Twenhofel (1946) consists of ~henocrystsof NUNATAKPROSPECT oligoclase and less abundant hornblende, biotite, and The largest known molybdenum deposits in the quartz in a microcrystalline groundmass that con- monument are at the Nunatak prospect east of Muir tains potassium feldspar, quartz, and plagioclase. Inlet (pl. 1, loc. 21). The deposits are mainly in the The phenocrysts commonly are euhedral and 3-4 mm northern part of "The Nunatak," an isolated knob long. Accessory minerals in the rock are magnetite about 1,100 feet high which is surrounded by water and sphene. The alteration products include actinolite and periglacial debris. Before regression of the near- and epidote. Numerous quartz-rich veinlets cut the by glaciers, "The Nunatak" was surrounded by ice rock. Samples of the porphyry \irllich were studied and was a true nunatak. The deposits were located in petrographically contained less potassium-feldspar 1941 (Twenhofel, 1946, p. 12), and since then, they than a normal quartz monzonite; this fact, along have been explored intermittently. They were inves- with the characteristic microcrystalline groundmass, tigated and described by a Geological Survey field indicates that the rock sl~ould be classified as party under the direction of W. S. Twenhofel (1946) rhyodacite porphyry. However, the term "quartz and by the U.S. Bureau of Mines (Sanford and monzonite porphyry" is retained here for consis- others, 1949). During the summer of 1966, the de- tency with previous usage. METALLIC COMMODITIES 75

The andesitic dikes are predominantly hornblende molybdenite, generally as selvages or thin films andesite porphyry and some dacite porphyry. They along their borders, but, unusually, as scattered dis- are altered porphyritic rocks with pilotaxitic ground- seminations within the quartz. Molybdenite also masses. They contain between 50 and 60 percent forms rare thin films along some joint surfaces near plagioclase (sodic andesine) , the dominant mineral the stockworks. Diamond-drill cores reveal quartz- in both their phenocrysts and groundmasses. Horn- free molybdenite along fractures in some of the blende, both a phenocryst and groundmass mineral, hornfels and as very fine disseminations in some of forms between 10 and 15 percent of the rock. the quartz monzonite porphyry. Other primary minerals that are minor constituents Besides quartz and molybdenite, the veins contain of the andesitic rocks include biotite, pigeonite, minor to trace amounts of pyrite pyrrhotite, chal- magnetite, and apatite. The secondary minerals in- copyrite, tetrahedrite, bornite, enargite, alunite, clude actinolite, chlorite, epidote, and calcite. potassium feldspar, epidote, albite, malachite, and The dominant structural grain at "The Nunatak" chlorite. The copper minerals occur mainly near the is shown by north-striking beds that dip eastward margins of the stockworks, and their distribution (pl. 11). In the western part of "The Nunatak," the indicates a crude lateral zoning of the deposits. Thin beds are folded into an open anticline. Bedding is altered zones that border some of the veins contain obscure near the rock mapped as quartz monzonite phlogopite, montmorillonite, calcite, and feldspars. porphyry. Several steep faults, apparently with Rossman (196313, p. K49) reports that a grab sam- minor offsets, are exposed at the prospect (pl. 11). ple of mineralized quartz-rich rock that was col- These faults commonly strike north or northeast. lected from a gulley on the northeast side of "The The myriad fractures that developed in the quartz Nunatak" contained 0.04 ounce gold per ton and 7.07 monzonite porphyry and the hornfels before the inounces silver per ton. Silver was detected in only two trusion of the andesitic dikes were mineralized to of our samples (table 13). Minor amounts of both form the stockworks of quartz-molybdenite veins. gold and silver were found in some of the cores from the American Exploration & Mining Co. diamond- Ore deposits drill holes (Robert Garwood, oral commun., 1966). The ore deposits consist of stockworks of closely The fault deposits are largely confined to the steep spaced quartz veins and veinlets that contain almost north-striking fault that extends northward from all the known molybdenum reserves, mineralized the lake north of Nunatak Cove (pl. ll), but they fault zones, and less common fracture coatings and are also weakly developed in some of the lesser disseminations. The stockworks are widely distrib- faults at the prospect. They differ from the stock- uted throughout the northern part of "The Nuna- works mainly by containing molybdenite deposited tak," extending from near the summit westward and along fractures within fault zones. northwestward to Muir Inlet (pls. 11, 12). They con- Stockwork deposits are inherently difficult to sam- sist of myriad closely spaced quartz veinlets less ple, and a reliable grade estimate for the Nunatak than 1 inch thick, and thin quartz veins that are as deposits would require extensive bulk sampling. much as 18 inches thick but commonly are less than Adequate estimates of the reserves are contingent 6 inches thick. The stockworks are mainly developed upon determining the configuration of the deposits. in the hornfels, but they have formed in the quartz Indications that the deposits extend to considerable monzonite porphyry also, particularly in its par- depths are: (1) they are exposed throughout a large tially silicified peripheral zones. The stockworks are vertical range; (2) the richest exposures of ore are best exposed in the cliffs contiguous to the shoreline in sea cliffs that border Muir Inlet; (3) a company of Muir Inlet throughout a lateral extent of about diamond-drill hole was mainly in mineralized rock to 800 feet (pls. 11,12). There they consist of hundreds its bottom, about 300 feet below sea level; and (4) of quartz veins and veinlets that strike N. 70" W. to a Bureau of Mines diamond-drill hole penetrated west and dip nearly vertical. The veins and veinlets uniformly mineralized rock continuously to its bot- are cut by many steep northeast-striking fractures tom 158 feet below sea level. that are occupied by clayey gouge as much as 2 Twenholfel's reserve estimates (1946, p. 17, 18) inches thick and less common barren quartz and are based on the results of drilling and sampling by calcite. In places the transecting fractures offset the the U.S. Bureau of Mines during 1942 and on his veins a few inches. Poorly developed near-horizontal geologic mapping. The Bureau of Mines program fractures also cut some of the quartz veins and vein- consisted of drilling two diamond-drill holes totaling lets. Many of the quartz veins and veinlets contain 285 feet and collecting and analyzing a total of 249 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT. ALASKA

TABLE13.-Semiquantitative spectrographic analyses and colorimetric analyses for molybdenum of samples from the Nunatak molyodenum prospect

[Spectrographic analyses by Harriet Neiman . Molybdenum determined colorimetrieally by G . T . Burrow and E. J . Fennelly]

Results are reported in parts per million. which for the Spectrogra~hiC Symbols used: 0. looked for. but not detected ; <. less than analyses have been converted from percent to the nearest number in the . series 1. 0.1. 0.5. 0.3. 0.2. 0.1. ....which represent mid- The following elements were looked for. but not found: AS. AU . Be. 1 ~d . points of group data on a geometric scale. The assigned group for six-step Li. Nh. Pd . Pt. Sb. W*Zn . results will include more accurately determined values for about 30 percent Sample locations and descriptions are shown on pl . 12 . of the test results .

Sample GGA Mo (colormetric)

100 ...... 101 ...... 102.4 .... 102B ..... 103 ...... 104 ...... 105 ...... IOG ...... 107 ...... 108 ...... 101) ......

' 2 ppm Re detected in sample 66AMk-102A . METALLIC COMMODITIES 77 chip, drill-core, and channel samples. Sixteen sam- denum mineralization beyond areas known to con- ples were from the fault zone and 233 from the tain molybdenite. The soil samples were collected stockwork (Sanford and others, 1949). The average from a traverse along the crest of "The Nunatak" molybdenum content of 177 samples from the part and along other traverses in the medial and lower of the stockwork mapped as containing conspicuous parts of "The Nunatak" (pl. 12). Water samples molybdenite was 0.075 percent (Twenhofel, 1946, p. were collected from two glacial lakes on the west 17). Fifty-six samples that were collected from parts side of "The Nunatak." For comparison, four water of the stockwork mapped as containing inconspicu- samples were collected from creeks in the Glacier ous molybdenite contained an average of 0.048 per- Bay area far from known molybdenum mineraliza- cent molybdenum (Twenhofel, 1946, p. 17). The tion. samples from the fault zone contained an average of Soils from outside the mineralized area are typi- 0.12 percent molybdenum (Twenhofel, 1946, p. 17). cally azonal, are rich in bedrock fragments, and A summary of Twenhofel's reserve and grade contain less than 5 ppm molybdenum and less than estimates (1946, p. 17, 18) follow^.^ His grade esti- 30 ppm copper. During the ridge-crest traverse, mates were based partly on channel samples. many anomalous samples that contained between 10 Estimated and 29 ppm molybdenum were collected south of the grade area shown as mineralized on the geologic map (pls. Surface area Projected depth Estimated (percent (square feet) (feet) tms I MoSz) 11, 12) and from sites where close examinations of Fault deposit . . 18,000 300 540,000 0.169 the rocks revealed no molybdenite. Some of the mo- Stockworks . . . . 2,170,000 500 8,500,000 .I25 91,500,000 .080 lybdenum may have been transported by glaciers from north of "The Nunatak"; however, it is 1 Based on the assumption that 10 cu ft of ore weighs 1 ton. 2 Estimated from surface mapping to contain conspicuous rnolybdenite. believed that much of this molybdenum is of local 8 Estimated from surface mapping to contain inconspicuous rnolybdenite. derivation. Both molybdenum and copper are present Our investigations included collecting 58 chip in abnormal amounts in azonal soils near the south- samples from the stockworks, 3 chip samples from ern end of the crest of "The Nunatak," where min- the fault zone, and 98 soil samples (pl. 12). The chip erals containing these metals have not been identi- samples were between 20 and 120 feet in length, the fied in the nearby bedrock. sample interval, 1/2 to 5 feet. All the chip samples Samples collected along the east base of "The were analyzed colorimetrically for molybdenum and Nunatak," except those near the extreme northern by semiquantitative spectrographic methods. Our tip, have only background molybdenum and copper samples are inadequate for satisfactory grade esti- contents (lmess than 5 ppm and 30 ppm, respectively). mates, but they furnish information on the distribu- On the west side of "The Nunatak," however, most tion of molybdenum, copper, and other elements in of the samples contain anomalous values. The high- the rocks and soils at the prospect. est metal content in this group (910 ppm molybde- Three diamond-drill holes drilled by the American num, 270 ppm copper) occurs in sample 64 (pl. 12). Exploration & Mining Co. and associates during The samples indicate that the soils with high molyb- 1966 explored the lower part of the stockworks to a denum and copper content extend irregularly south- depth of 313 feet below sea level. The locations of ward beyond the area mapped and are mineralized the drill holes are shown on plate 11, but other data as far south as the eastcern tip of the Iarger lake from the drilling are considered restricted informa- (pls. 11, 12). These high values confirm the southern tion by the company and could not be released at the extension of the geochemical anomaly and also the time this report was prepared. In general, the results presence of copper in the southern part of the of the drilling corroborate the size and grade of the anomaly, which was indicated by the ridge-crest stockworks as indicated by the surface exposures. The Nunatak molybdenum prospect contains a sampling. large reserve of low-grade material, and if the cur- Several types of azonal soils are present and available for sampling along the base of "The Nuna- rent trends in price and demand for molybdenum continue, it may be minable in the future. tak." Of these, the oldest is slightly weathered glacial till composed of gray mud and rounded glacial Geochemical studies erratics. After deglaciation, a series of alluvial talus Ninety-eight soil samples and six water samples cones formed, composed in part of glacial materials were collected at the Nunntak prospect to determine and in p:irt of sand and angular pebbles of the local whether geochemical methods could trace the molyb- rock. Where talus cones of several different ages are

9 Twenhofel's samplea were not analyzed for copper, a possible byproduct. recognizable, the younger ones contain the most 78 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA local rock. The relative ages of the cones can be residues contain 700 pprn molybdenum, which is high identified from their physiographic relations, as the by comparison with the soil samples. These analyses older ones are being dissected and the younger ones show that molybdenum is fairly soluble in the sur- are still being formed. ficial envionment. Even though the places in the For comparison, samples of two different kinds of area where waters could be sampled are limited, the soil were taken at several sample sites. The results possible use of water analyses in prospecting appears in table 14 show that large differences exist in the to deserve more study here. Because plants are likely to absorb molybdenum from the ground water, study TABLE1PComparison of older and younger soils at the of the molybdenum content of the local plants seems Nunatak wwlybdenum prospect in terns of molybdenum and desirable. copper content ENTRANCEOF ADAMS INLET [Analytical methods described under "Geochemical studies." Semiquantita- tive-spectrographic anqlyses by R. G. Havens and Nancy Conkiin. See Buddington and Chapin (1929, p. 330) report PI. 12 for semple locat~onsl that molybdenite occurs in fractures in metamorphic Metal Content rocks on the north side of, and near the entrance to, Sample (parts per million) site Description Molybdenum Copper Adams Inlet (pl. 1, loc. 22). This occurrence was not 66AHF found, although the general area was examined in G Glacial till ...... 6 28 some detail. Possibly it is the same locality as the 40-. T Talus composed of local rock 10 46 copper-bearing amygdaloid contains trace amounts G Glacial till ...... 0 29 of molybdenum that crops out about 1Y2 miles from 41 the entrance to the inlet (5). T Talus composed of local rock 13 62 G Outwash sand ...... 7 31 45 A molybdenite-bearing quartz vein crops out in T Talus overlying outwash ...... 320 290 recently deglaciated rocks near the head of Wachu- G Glacial till ...... 6 30 sett Inlet (pl. 1, loc. 35). It strikes N. 34" E. and 51 T Talus; some molybdenite dips 85" SE. The vein is between 1 and 12 inches visible ...... 10 160 thick and is exposed for about 75 feet along its Older talus ...... 0 60 strike. The vein cuts quartz diorite, which has been 55 intruded by andesitic and pegmatitic dikes and con- B Younger talus; some molybdenite visible ...... 20 100 tains quartz, pyrite, molybdenite, chalcopyrite, and secondary iron minerals. A sample from the richest G Older talus ...... 0 100 61 part of the vein carried 7,000 pprn molybdenum, T Younger talus; mostly 15,000 pprn copper, 700 pprn zinc, and 0.0045 ounce local rock ...... 5 230 per ton (15 ppm) silver (table 9, loc. 35). The de- B Older talus ...... 5 31 64 posit is too small to be exploited; but it is rich Younger talus, 50 percent enough to encourage exploration for similar, but ' local rock ...... 910 270 larger, deposits in the vicinity, particularly since the nearby terrain was recently exposed and is vir- molybdenum and copper contents of these closely tually unprospected. related soils and that the younger soil at a given site TRIANGLEISLAND commonly contains much more of these metals than Rossman (1963b, p. K49) reports that a few hun- the associated older soil. dred pounds of molybdenite, which constituted the All soil samples from the Nunatak area composed entire deposit, was mined in one day from Triangle entirely of glacial till have a low metal content. Island, in the northern part of Queen Inlet (pl. 1, loc. Samples collected along the two traverses that ex- 36). Examination of the island, which is a seagull tend westward (pl. 12), except sample 61, are com- rookery, failed to reveal any molybdenite or signs of posed entirely of till, and all have low metal contents. workings. The island is composed of fine-grained Sample 61, which contains 230 pprn copper, is the granodiorite that is cut by a few east-striking aplitic only sample from these traverses composed in part dikes that commonly dip north at about 50". of local bedrock. The two samples of lake water from the Nunatak GEIKIEINLET area were dried to a residue and analyzed spectro- Buddington and Chapin (1929, p. 329,330) report graphically. One sample contains a remarkably high specimens of molybdenite float from near Geikie In- concentration of molybdenum, 7,000 ppm. The other let. Reed (in Smith, 1942, p. 178) reports claims on METALLIC COMMODITIES 79 molybdenite-bearing tactite at a rather high altitude (loc. 47), on the north shore of Geikie Inlet (48), on near the head of Geikie Inlet, probably near locality the south end of the ridge west of Reid Inlet (70), 50 on plate 1. A brief examination failed to disclose southeast of the head of Reid Inlet (71), on the south any molybdenite or signs of workings in the general shore of Johns Hopkins Inlet west of Lamplugh Gla- vicinity. Buddington (unpub. data, 1924) reports cier (74), and about a quarter of a mile northwest of that molybdenite ore was obtained from near Geikie the Sandy Cove prospect. (See pl. 1and table 9.) Inlet in 1918. NICKEL LOWERBRADY GLACIER Nickel occurs in trace to moderate amounts in Float specimzns of molybdenite-bearing quartz many of the sulfide deposits in the monument, and veins have been reported from Brady Glacier (pl. 1, it is the principal commodity in the major deposits at loc. 56). (See A. F. Buddington, unpub. data, 1924; the Brady Glacier nickel-copper prospect. Most of the Buddington and Chapin, 1929, p. 329, 330; Smith, samples that contained nickel are from deposits de- 1942, p. 177.) No specific information is available on scribed under "Copper." The highest nickel contents the locations of the float specimens, and we were un- in these samples were 1,000 ppm from a pyrite-rich able to find similar ones. The Brady Glacier mo- lens west of the mouth of Rendu Inlet (loc. 38) and raines contain diverse rocks that were derived from 500 ppm from soil at the Alaska Chief prospect (29). a large and geologically complex area. Among these Many other deposits described under "Copper" con- rocks are felsic-granitic types that are favorable tained between 100 and 300 ppm nickel. These in- hosts for some molybdenum deposits. clude the deposits near Mount Young (I), north of White Glacier (6), north of York Creek (8), in RIDGEWEST OF RENDUINLET the Curtis Hills (23), on the shore south of Tidal In- A swarm of thin quartz veins and subordinant thin let (41), on South Marble Island (25), and on Francis quartz-rich pegmatite dikes cut granitic rocks on the Island (28). Minor amounts of nickel were detected ridge west of Re~lduInkt (PI. 1,loc. 60) ;they OCCUPY in samples from two deposits that lack notable con- a zone about 25 feet wide. The veins and dikes have centrations of other metals : a deposit north of Mount diverse attitudes, but they generally strike north- Abdallah (16) that consists of iron-stained hornfels eastward' The veins commonl~ ward and and a deposit west of the head of Lamplugh Glacier are spaced several feet apart and are between l/z and (68) in altered zones that cut hornfels. (See pl. 1 and inches commonly less than inch thick. The table 9.) Probably some of the unsampled pyrrhotite- veins and quartz-rich parts of some of the dikes con- rich lenses and veins that have been reported from tain scattered sulfide minerals, including molyb- the Fairweather Range are nickeliferous (Kennedy denite, chalcopyrite, pyrite, and pyrrhotite. The and Walton, 1946, p. 71). deposits appear to be too small and too dispersed to The most favorable hosts for undiscovered nickel justify exploration. deposits are layered mafic and ultramafic complexes OTHER MOLYBDENUMDEPOSITS of the Fairweather Range, particularly their lower Molybdenum is a constituent of many other de- horizons and contact zones. Both of these environ- posits in the monument, particularly some of those ments are regarded as geologically favorable sites that are noteworthy for their copper contents. for nickel-copper sulfide lodes, such as those at the Molybdenum occurs in significant amounts in cop- Rrady Glacier prospect. per deposits in the Bruce Hills (loc. 34) and near the

southwestern part of Gilbert Island (44, 45). It DESCRIPTIONS OF DEPOSITS occurs in lesser amounts in deposits east of Dundas BRADYGLACIER PROSPECT Bay (32) and southwest of Lamplugh Glacier (67) and in minor to trace amounts in many other de- By H. R. CORNWAU posits that are indicated on plate 1 and in tables 9 Massive and disseminated nickel-copper sulfides and 11. were discovered in 1958 by the Fremont Mining Co. Molybdenum was detected in trace to minor in three nunataks near the west edge of Brady Gla- amounts in several samples that are not particularly cier in Mount Fairweather C-3 quadrangle (pl. 1, noteworthy for their contents of other metals. These loc. 72). The sulfides occur at the southeast margin samples represent deposits best regarded as occur- of a large lopolithic instrusion of gabbro and perido- rences with no economic potential, and they do not tite described by Rossman (1963a). The intrusion, merit individual descriptions. Included among them called the Crillon-LaPerouse stock by Rossman, is 17 are occurrences east of the head of Charpentier Inlet miles long and 8 miles wide and consists mainly of 80 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA layered gabbro. The nickel-copper deposits occur with greenstone and graywacke units on Chichagof near the base of the gabbroic intrusive in a zone I Island southeast of Brady Glacier. In the area of the where ultramafic rocks (peridotite) predominate. Brady Glacier nickel-copper deposits, the mafic com- The following descriptions of the geology and ore de- plex has intruded garnetiferous biotite schist. The posits include some material that was graciously minerals in this schist are quartz, plagioclase, ortho- supplied by the Newmont Exploration Co. clase, and biotite with sparse prophyroblastic pink garnets. Geology According to Rossman (1963a), the Crillon-La- This mafic complex is intruded into amphibole and Perouse gabbroic intrusive has an exposed thickness biotite schist that Rossman tentatively correlates of about 32,000 feet. The layers range in thickness

Mapped by Newmont Exploration,Ltd., and published with their permission 100u 0 100 200 FEET

EXPLANATION e Aplite dike Massive sulfides

Contact Peridotite with lenses and dikes of gabbro and diorite Fault LO Strike and dip of layering I OCSN-4 Gabbro, partly layered Location of sample FIGURE18.-Generalized geologic map of Brady Glacier nunataks showing nickel-copper sulfide lodes. METALLIC COMMODITIES 81 from less than one inch to tens of feet, which is due minerals. Forsterite (olivine) occurs in 0.1-3.0 mm to differences in grain size and proportions of the grains and is partly to completely altered to tremo- principal minerals, plagioclase, pyroxene, and oli- lite and serpentine group minerals. A little epidote vine; the layers dip toward the interior of the com- is present and small amounts of pyrrhotite, pentland- plex at angles of 70" or less. ite, and chalcopyrite are disseminated through the In the nickel-copper-bearing nunataks on Brady rock. Glacier, the structures are much more complex and Dikes as much as 5 feet or more wide of fine- stratiform relations are less apparent. This is due in grained gabbro, diorite, and aplite are very common part to later intrusions and in part to post-crystal- and tend to cross the layering of the peridotite and lization faulting near the margin of the intrusive. gabbro. The diorite is similar to the fine-grained The general relations of the rocks exposed in 1966 gabbro but has more sodic plagioclase (An*40). The are shown in figure 18. Two of the three nunataks aplite has plagioclase phenocrysts (Am) as much described by geologists of Newmont Exploration, as 2.5 mm long in a groundmass with grains less than Ltd. (written commun., 1961), were exposed in 1966 0.3 mm of euhedral biotite and anhedral plagioclase -the High Nunatak and the Small Nunatak. In these and quartz. exposures periodotite overlies fine- to medium- grained gabbro, in part layered, and the units dip Ore deposits 20"-50" southeast toward the margin of the in- ~h~ sulfides pyrrhotite (Fel,), pentlandite trusive. These rocks are intruded by dikes and ir- ((Fe,Ni)&), and chalcopyrite CuFeSn) occur in the regular bodies of gabbro, diorite, aplite, and Pas- host rocks described above as disseminated grains, sibly peridotite. A prominent shear zone strikes veinlets, and lenticular masses as much as 35 feet northeast parallel to the axis of the Small Nunatak, long and 5 feet in diameter. Most of the masses of and smaller faults run parallel to this shear zone in solid sulfide are, however, much smaller. Large sul- both nunataks. Several minor faults strike nearly flde masses were mainly observed only near the north- north-south across the High Nunatak. The faults dip east end of the Small Nunat&. The sulfide veinlets moderately to steeply east and southeast. are commonly less than 1 mrn thick and occur along Peridotite is the predominant host rock for the fractures and fissures. Small lenticular masses also Brady Glacier deposits. The periodotite most Corn- occur along the more prominent fissures and faults. monly consists of a mixture of forsterite (olivine) he grains and small patches of sulfides are scattered and enstatite (orthopyroxene); augite (ClinoPVo- through most of the host rock and occur in all types, xene) has been found in some specimens. Dunite con- except the aplite. The disseminated sulfides appear sisting entirely of olivine is present but not abun- to be abundant in altered peridotite and gabbro dant. The olivine crystals in the peridotite are Individual sulfide grains are commonly rounded, 0.2-3.0 mm in diameter, and commonly less than 2 mm in diameter. ~oikiliticall~enclosed by pyroxene. In most of the The relative order of abundance of the sulfides is peridotite, the pyroxene and, to a lesser extent, the pyrrhotite, pentlandite, chalcopyrite. Pyrrhotite 'livine have k3een partly to com~letel~altered to grains commonly have smaller peripheral grains of tremolite (amphibole), serpentine and minor epi- pentlandite and chalcopyrite. pentlandite also occurs dote. The peridotite contains small amounts of its lenticular blebs, 0.01-0.04 mm in diameter, in the chrome picotite (green spinel) and pyrrhotite (Fe pyrrhotite with nearly parallel orientation. ~h~~~ l-xS) 9 pentlandite ( (FE,Ni)~S8)9 and blebs probably formed by exsolution from the pyr- (CuFeSn). It also contains lenses or schlieren, as rhotite during cooling of the rock. Chalcopyrite is much as foot of 'Oarse gabbro and gabbro more erratically distributed than the other sulfides, pegmatite, elongate Parallel to layering where dis- and textural relations suggest that it may have cernible. formed slightly later. Near the surface in the nuna- Fine- to coarse-grained olivine gabbro is also a com- taks and upper pa* of diamond-drill holes the pent- mon host rock for the nickel-copper sulfide deposits. landite has been partly altered by weathering to Plagioclase (Anrs-ao) is commonly fresh in cr~stals violarite (NizFeS4) and polydymite (NisS4). ranging from 0.1 to 2.5 mm. Augite is interstitial to the plagioclase in grains less than 0.5 mm. Some Possibilities of commercial ore deposits orthopyroxene is present; locally, it is more abun- The Fremont Mining Co. staked claims covering dant than augite. The pyroxene is moderately to the Brady Glacier nickel-copper deposits in 1958, and completely altered to tremolite and serpentine group in 1958-59 sampled the nunataks and drilled 32 82 MINERAL RESOURCE,S OF GLACIER BAY NATIONAL MONUMENT, ALASKA diamond-drill holes (written commun., 1959). In eralization of somewhat higher grade than in the 1960-61, Newmont Exploration, Ltd. (written area described above. One hole intersected sulfide commun., 1961), under an agreement with Fremont, mineralization for more than 100 feet with 1 percent drilled 14 more holes and did more mapping and nickel and 0.4 percent copper; another intersected sampling of the nunataks. more than 100 feet averaging 0.7 percent nickel and Disseminated sulfides are widely distributed 0.4 percent copper. The area surrounding the nuna- throughout the nunataks. The amounts are small, taks appears to offer the greatest promise for com- however, and the overall average grade of the nuna- 1 mercial ore bodies, but more exploration is needed taks would probably be less than 0.5 percent each of for a reliable evaluation. nickel and copper. Several of the sulfide masses in TITANIUM the nunataks have been sampled and assays run 2-3 percent nickel, 1-1.4 percent copper, and 0.25 per- DISTRIBUTION Important amounts of titanium are in ilmenite- cent cobalt. Results of semiquantitative spectro- rich rocks of the layered mafic sequences of the graphic analyses of Survey ore and rock samples Fairweather Range and, to lesser extents, in ilmen- from the prospect are given in table 15. Individual ite-bearing beach placers north and south of Lituya massive sulfide lenses are small; five such bodies on Bay (locs. 87, 88). Titanium was detected in quan- the nunataks, however, have lengths ranging from tities of 10,000 ppm in samples from three other 15 to 35 feet and average widths of about 6 feet, and deposits examined during our investigations: Curtis the extent in depth is probably comparable to these Hills (23), South Marble Island (25), and east of dimensions. Charpentier Inlet (47). It was also found in amounts Diamond drilling thus far has shown that low- of 2,000-7,000 ppm in many other deposits. (See pl. grade nickel-copper mineralization is widespread in 1 and table 9.) These titanium values reflect host the gabbro-peridotite complex, but more drilling is rocks that intrinsically have moderate titanium con- needed to establish continuity of the higher grade tents but are too lean to be of economic significance. zones. A large area about 1,000 feet in diameter beneath the glacier 1,000 feet southwest of the nuna- DESCRIPTIONS OF DEPOSITS taks appears to contain 0.3-0.6 percent nickel and FAIRWEATHERRANGE 02-0.4 percent copper in gabbro and peridotite; the The ilmenite-rich gabbros of the layered intrusive depth of mineralization has not been determined. By complexes of the Fairweather Range constitute a analogy with known commercial deposits of a simi- large resource of low-grade titanium ore. The ilmen- lar nature elsewhere, it is very possible that, as the ite deposits have not been studied in detail, and the basal contact of the ultramafic complex is ap- limited information available is from Rossman proached with greater depth, higher grades of (1963a, p. F42-F45) and from Kennedy and Walton nickel and copper mineralization will be found. (1946, p. 71). The layered intrusive masses of the Several diamond-drill holes were drilled 200-700 Fairweather Range are the Crillon-LaPerouse and feet south of the nunataks and these revealed min- the Astrolabe-DeLangle stocks of Rossman (1963a)

TABLE15.-Semiquantitative spectrographic analyses of rocks and ore from the Brady Glacier nickebcopper prospect [Spectrographic analyses by A. L. Sutton. Jr.1 Results are reported in parts per million, which have been converted from Symbols used: M, major constituent-dontent greater than 100,000 ppm; percent to the nearest number in the series 100. 70, 60, 30, 20, 16, 10, 0, looked for, but not detected: <. leas than. . . . . which represent approximate midpoints of group data on a gee- In addition to the elements shown in the table, the following elements were metric scale. The assigned group for six-step results will include more also in all of the analyses: Au Ag As. Be. Bi. Cd. Hn La. accurately determined values for about 30 percent of the test results. Li. Nb. Pb, Pd. Pt. Sb. Sn. Ta. TI. w', 2n.' Reported values for 'these were always 0. Sample locations shown in fig. 18. F~eldNo. A1 Bs Ca Co Cr Cu Fe Mg Mn Mo NI Si Sr Ti V Y CHN-1 20,000 10 10,000 150 200 2,000 M M 1,000 <5 3,000 M 30 500 150 0 2 30,000 10 10,000 150 150 200 M M 1,000 <5 300 M 50 150 100 0 4 70,000 100 70,000 30 100 700 50,000 M1,000 0 300 M 1501,500 200 10 4A M 500 30,000 15 20 50 20,000 10,000 300 0 200 M 200 1,500 70 10 6. 70,000 100 50,000 30 300 70 70,000 M 1,000 0 200 M 200 500 200 30 CSN-1 30,000 15 10,000 70 1,000 1,500 M M 1,000 <5 1,500 M 20 70 150 O 4 200 0 0 2,000 500 20,000 M 200 150 70 15,000 1,500 0 20 50 0 4A 70 0 0 2,000 700 20,000 M 30 100 20 15,000 100 0 0 50 0 CHN-1 Selected sample of periodite with sulfides. CHN-6 Selected sample of diabase. 2 ...... do ....-...... CSN-1 Selected sample of periodotite. 4 Selected sample of gahbrb 4 Grab sample of massive sulfid-. 4A Selected sample of aplite. 4A ...... do...... METALLIC COMMODITIES 83 and an inferred and undefined stock near Mount and other metals. More accurate evaluations of their Fairweather. These masses have crude troughlike economic potential require detailed exploration and that are shown by northwest-trending sampling. Such investigations would be inhibited by axes and inward-dipping layers. In the Crillon- the remote and rugged terrain of the Fairweather LaPerouse stock, the largest of the layered masses, Range and would be costly and time consuming. the layered sequence has a maximum exposed thick- PLACERDEPOSITS NEAR LITUYA BAY ness of 32,000 feet and Consists largely of gabbr0. The beach placers north and south of Lituya Bay The ilmenite-rich layers represent magmatic de- (PI. 1, 10~s.87, 88) have been investigated by Mertie posits in which ilmenite was concentrated mainly by (1933, p. 117-135), Rossman (1g57), and Thomas gravity settling. Four of the ilmenite deposits are and Berryhill (1962, p. 37-39). The latter two in- shown on plate 1 (lots. 739 79-80), and similar de- vestigations stressed the ilmenite content of the posits undoubtedly Occur elsewhere in the little- placers. Detailed descriptions of the placers are in explored range. the section of this report describing gold placer de- Rossman (1963a~P- F42) rep0rts that the posits. The placer deposits have yielded a small pro- area of the Crillon-LaPerouse duction of gold, and they and their probable offshore southeast of Mount Lookout, probably contains be- extensions are potential sources for gold, titanium, tween 10 and 25 percent ilmenite through a distance and possibly other metals. The largest known placer of several hundred feet, but that the lateral extent of of heavy minerals in the monument the ilmenite-rich zone could not be determined be- are along the beaches between and 13 miles south cause of extremely rough terrain. R~ssmannoted Lituya Bay. The upper parts of all the bare similar zones in the valley walls beaches and most of the tree-covered beaches north Crillon Glacier. Layers of gabbro northwest of and south of Lituya Bay contain between 5 and 40 North Crillon Glacier contain between 7 and 10 per- percent heavy minerals. someof the deposits are cent ilmenite, and similar concentrations of ilmenite large, extending for more than 51 miles along the are near the southernmost exposures of the Crillon- beaches with widths of several hundred feet. LaPerouse stock (Rossman, 1963% p- F42)- Rossman R~ssman'~samples (1957, p. 6, table 1) from the also found a few layers that contain small concen- beach deposits between Palma B~~ and D~~ Bay in- trations of ilmenite and sulfide minerals elsewhere in dicate that these deposits contain percent the Crillon-LaPerouse stock- ~0Mman(166% p. ilmenite and as much as 10 percent magnetite. The F43, F44) shows tables indicating the ilmenite con- T~O~content of the ilmenite from these samples tents of samples from the Crillon-LaPerOuse ranges from 46.80 percent to 52.38 percent (Ross- and semiquantitative spectrographic analyses of ,,,, 1957, p. 8, table 2). heavy-mineral concentrates from the stock. The U.S. Bureau of Mines investigations of the layers the AstrO1abe-DeLangle stock 'On- placers north and south of Lituya Bay consisted of tain concentrations of ilmenite, and others contain sampling 26 auger holes and collecting 11 shovel as much as 20 percent titanium-bearing magnetite samples (Thomas and Berryhill, 1962, p. 37-39, table (Rossman, 1963a, p. F44). Most of the layers that 21, fig. 12). The magnetic fractions of these samples contain much ilmenite or magnetite crop out through contained 0.1-16.5 pounds of iron per cubic yard ; a "stratigraphic" thickness of about 1,000 feet, high the nonmagnetic fractions, 0.3-89.5 pounds of *iOz in the mountains that form Astrolabe Peninsula. ser cubic The mineralized layers appear to be continuous throughout the mountains. Rossman (1963a, p. F45, TUNGSTEN Deposits that contain tungsten in potentially min- table 8) shows the content of ilmenite- and titanium- able quantities are not known in the monument. The bearing magnetite from rocks of the Astrolabe- one previously reported tungsten occurrence consists DeLangle stock. of minor amounts of scheelite in a gold-quartz vein Kennedy and Walton (1946, p. 71) report that an east of Reid Inlet (Rossman, 1959, p. 56). Tungsten intrusive layer about 5 feet thick which crops out for was detected in samples from only two of the de- several thousand feet along the south wall of the posits that we examined. This is attributable in part valley of North Crillon Glacier contains as much as to the low sensitivity for tungsten in the semi- 60 percent ilmenite. quantitative spectrographic analysis, but it is mainly On the basis of present knowledge, the layered because of the scarcity of tungsten. gabbros of the Fairweather Range are a potentially A sample of pyrrhotite-rich massive sulfide float important resource of titanium and possibly iron from the Margerie copper prospect contained 3,000 84 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA pprn tungsten and a sample from a quartz vein at GEOLQCIC INFLUENCES ON LOCALIZATION OF the prospect, 150 pprn (pl. 1 and table 9, loc. 19). A METALLIFEROUS DEPOSITS sample representative of a 1-foot-thick sulfide-bear- Almost all the known deposits in the Glacial Bay ing tactite that has replaced marble in the northern National Monument can be related, at least spatially, part of Gilbert Island contained 150 pprn (pl. 1 and to magmatic sources. The relationships range from table 9, loc. 43). strictly magmatic deposits, such as the titanium and Samples of sediments from streams entering the iron deposits in the layered gabbros of the Fair- northern part of Dundas Bay contained as much as weather Range, through many deposits associated 150 pprn tungsten and 30 pprn tin, indicating a geo- with granitic plutons and dikes that are inferred to chemical anomaly (table 4). Tracing the anomalous be late-stage magmatic derivatives, to a few de- metals to their source might lead to the discovery of posits with only tenuous magmatic affiliations far a tungsten deposit of interest. from exposures of igneous rocks. Tactite bodies and, to a lesser extent, gold-quartz Correlations and affinities of specific rocks and veins are generally favorable hosts for scheelite de- geologic settings with specific types of mineral deposits; the fact that many deposits of these types posits are well documented in the geologic literature. were examined and sampled with negative results In the monument, such affinities are exemplified by presages little support for successful tungsten ex- the ilmenite and magnetite deposits in the layered ploration in the monument. Wolframite and other gabbro; the probability of chromite and platinum tungsten minerals are elsewhere associated with deposits in ultramafic rocks of the layered intrusive leucocratic granitic rocks similar to some rocks that complexes; nickel-copper deposits in the lower and are fairly abundant in the monument. With the pos- peripheral parts of the layered intrusives; mag- sible exception of the geochemical anomaly north of netite-rich skarn deposits and base metal deposits in Dundas Bay, no evidence linking tungsten minerali- marble near contacts with intrusive rocks; and mo- zation to these rocks was found during our investiga- lybdenite deposits in or near epizonal intrusive rocks. Many of the gold lodes may be inferentially tions. related to felsic granitic rocks. VANADIUM Structural and tectonic factors have been impor- Vanadium was detected in minor amounts in tant in localizing some of the deposits. Disruptive samples from many deposits in the monument. The intrusions shattered the wallrock at the Nunatak highest concentration of vanadium found was 1,500 molybdenum deposit and probably at a few other pprn in a sample of sulfides replacing metavolcanic molybdenum deposits, creating myriad fractures rocks near Mount Young (pl. 1 and table 9, loc. 1). that were sites for subsequent mineralization. An Vanadium was detected in quantities between 500 east-trending structural zone in the east-central part of the monument may have influenced the formation and 700 pprn in a few samples and in lesser amounts of the nearby molybdenum deposits. This zone con- in many samples (tables 9,11,15). tains many porphyritic plutons, and some of them The ilmenite and the titanium-bearing magnetite are associated with molybdenum deposits. in layered mafic intrusive rocks of the Fairweather Carbonate rocks near intrusive masses are favor- Range contain subordinate amounts of vanadium, able sites for a variety of ore deposits, and such and vanadium would possibly be a byproduct from associations are known from many places in the mining deposits of these minerals. Rossman (1963a, monument. Besides the carbonate rocks, hornfels p. F44, table 7) indicates that the vanadium content and other rocks near intrusive bodies are potential of heavy mineral concentrates of nine samples from hosts for metals derived from the magmas. The the Crillon-LaPerouse stock was less than 1 percent. northwest-trending mixed rocks and hornfels that By analogy with known deposits, the search for extend from west of Lamplugh Glacier to near the vanadium in the monument should focus on pros- northern boundary of the monument contain num- pecting for concentrations of vanadium-bearing erous altered zones. ilmenite and magnetite in the layered intrusive complexes of the Fairweather Range. The Bushveld com- NONMETALLIC COMMODITIES plex of Africa, which has some similarities with the Deposits of several nonmetallic commodities are layered intrusions of the Fairweather Range, con- known in the monument, but their economic poten- tains the largest known reserves of vanadiferous tial is minimal because of their low grade, small iron ore in the world. size, impurities, poor access, and cheaper availability NONMETALLIC COMMODITIES 85 from other sources. Limestone and marble are dis- The descriptions of the structure and stratigraphy of tributed widely throughout the central and eastern the Tertiary sequence in the Lituya district are based part of the monument, particularly on islands in the mainly on detailed mapping by Miller and others southern part of Glacier Bay and on the nearby (Miller, 1953, 1961) and on unpublished U.S. Geolog- mainland. The most extensive limestone and marble ical Survey field data obtained by the author during deposits are on Willoughby, Drake, Francis, and a stratigraphic reconnaissance of part of the area Marble Islands and on the mainland south of Sandy in 1963. Cove and near Marble Mountain (pl. 1). Although STRATIGRAPHY many of these deposits are large and are accessible Bedded rocks of Tertiary age in the Lituya district to tidewater, our limited examinations indicate that include marine and nonmarine clastic and volcanic most of them are contaminated with silicate or units totaling at least 12,000 feet which unconform- dolomitic phases or other impurities and that they ably overlie the Mesozoic basement. The sequence are also cut locally by numerous dikes and veins. has been subdivided into three formations: the Most of the dolomite bodies appear to be too small Cenotaph Volcanics and Topsy formation, both of to be of interest. A possible exception is the dolomite postearly Oligocene ( ?) to premiddle Miocene age, that is exposed at a rather remote location on the and the Yakataga Formation of middle Miocene to ridge west of Geikie and Hugh Miller Glaciers (pl. 1; early Pleistocene age (Plafker, 1967). Relations be- Seitz, 1959, p. 115, 116), but little is known concern- tween the Topsy Formation and Cenotaph Volcanics ing the composition and relative purity of this mass. are obscure; the two units are believed to be at least Minor amounts of several other nonmetallic com- partly equivalent in age, for the predominantly or modities are known from the monument. Barium is wholly nonmarine beds of the Cenotaph Volcanics associated with many of the lode deposits (table 9) appear to grade into, and interfinger with, the but in amounts too small and grades too lean to be marine Topsy Formation. Both formations are dis- significant. A small amount of celestite (strontium conformably overlain by the Yakataga Forma- sulfate) has been found in the monument (Seitz, tion. Generalized stratigraphic sections and tentative 1959, p. 115), but the deposits are too small to be correlations of the Tertiary sequence are shown in important. Sand and gravel are available at a few figure 20. places in the monument, but their utilization is negated by the lack of nearby markets and by the The Topsy Formation ranges in thickness from about 1,200 feet at the type section along upper widespread occurrence of similar and better deposits closer to potential markets. Topsy Creek to at least 4,400 feet at Icy Point. It consists of about 75 percent hard calcareous or con- cretionary siltstone, and 25 percent fine- to medium- PETROLEUM AND COAL grained gray or greenish-gray argillaceous and carbonaceous sandstone. Deposition in a marine environment in premiddle Miocene, probably Oligocene, PETROLEUM time is indicated by a sparse molluscan fauna. Within Glacier Bay National Monument poten- At Lituya Bay the Cenotaph Volcanics consist of tially petroliferous rocks of Tertiary age underlie a at least 850 feet of green, red, and purple volcanic coastal lowland-and-foothills belt less than 4 miles breccia and tuff overlain by 400 feet of interbedded wide and about 40 miles long southwest of the Fair- green and red tuffaceous siltstone, green glauco- weather fault (fig. 19). Tertiary rocks are also pre- nitic sandstone, and glauconitic pebble-cobble con- sumed to occur over much, if not all, of the adjacent glomerate. Andesitic lava flows are present in the offshore area within the monument. The Tertiary basal part of the formation south of Lituya Bay, and rocks are underlain by regionally metamorphosed lenses and discontinuous beds of low-rank coal occur and complexly deformed Mesozoic(?) sedimentary locally within the uppermost part of the formation. and volcanic rocks that represent effective "base- The Cenotaph Volcanics were probably deposited ment" for traps petroleum in this area. under predominantly nonmarine and nearshore con- The part of Glacier Bay National Monument de- ditions during a period of intermittent volcanic scribed herein lies within the Lituya district of the activity. Gulf of Alaska Tertiary province. The Gulf of Alas- The Yakataga Formation is the youngest and most ka Tertiary province has been studied by Don J. widely distributed Tertiary formation; it is as much Miller, who published many reports on the area and as 8,400 feet thick. This formation comprises a lower summarized its geology (Miller and others, 1959). unit, ranging in thickness from 600 to at least 2,400 86 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

0 10,000 FEET

HORIZONTAL- AND VERTICAL SCALE EQUAL I I I Geology after M~ller(1961) and Plafker (1967) PETROLEUM AND COAL 87 EXPLANATION feet, consisting mainly of interbedded siltstone and sandstone containing calcareous lenses or concre- tions and sparse isolated pebbles, and an overlying Unconsolidated surficial upper unit consisting of at least 6,000 feet of sandy deposits mudstone, siltstone, sandstone, and minor conglom- UNCONFORMlTY I ", erate interbedded with abundant conglomeratic sandy mudstone (marine tillite) which characteristically contains unsorted ice-transported clasts of diverse lithologies. Depositon in a cold-water shallow-marine environment is indicated by an abundant - molluscan fauna. - zI- STRUCTURE W C The narrow belt of Tertiary rocks south of Lituya Tt ,Topsy Formation Bay is folded into a shallow syncline and a highly Tc, Cenotaph Volcanics -- asymmetric faulted anticline (fig. 19, section Ic' A-A'). These folds pass to the southeast into a sea- UNCONFORMlTY WII: n ward-facing homocline which is nearly vertical or slightly overturned. The south limb of the anticline is believed to be cut by an unexposed thrust or re- Volcanic rocks Crystalline J ; verse fault that strikes parallel to the coast. Upper complex 2 0 Tertiary rocks in the two small outliers near Fair- -- - -. - - - V) W weather Glacier form a broad northwest-trending Contact E Dashed where approximate; syncline unconformably overlying the pre-Tertiary dotted where concealed 1 volcanic rocks. POTENTIAL ----..--U A- Fault The petroleum potential of the Tertiary sequence Dashed where approximate; dotted where within Glacier Bay National Monument is poor with- inferred. U, upthrown side. Arrows indicate relative sense of horizontal in the area of outcrop on land. There are no oil or displacement gas seeps such as those which occur abundantly throughout the coastal part of the western part of -.A.A.-A.A ...... the Gulf of Alaska Tertiary province. Deformation Thrust or reverse fault Dotted where irlferred or concealed. of the older siltstones and a low organic content in Sawteeth are on upper plate the less deformed younger siltstones limits the source-rock potential. However, the reported occurrence of an oily film and petroliferous odor in sand- ~nticline ~yicline Dashed where approximate stone at one locality near the top of the Cenotaph Volcanics (Miller and others, 1959, p. 44) suggests 50-80 1_ the possibility that at least some hydrocarbons may Average strike and dip of beds have been generated in the lower part of the section. P A critical factor for petroleum accumulation is the Average strike and dip of beds, top availability of adequate reservoir beds. Sandstones in unknown all units except the uppermost part of the Yakataga Formation are commonly argillaceous and probably have low permeability and porosity. Some of the Vertical beds, top unknown stratigraphically highest sandstones in the Yakataga 75 -d- Fermation are good potential reservoirs, but they Strike and dip of overturned beds are stratigraphically several thousand feet above the 0- possible source rocks and are separated from them Location of measured sections, shown by one or more disconformities or unconformities. in fire 20 The anticline (fig. 19, section A-A') is a marginal prospect as a structural trap because (1) it probably FIGURE19.-Geologic sketch map and structupe section of Tertiary rocks in the Lituya does not have structural closure; (2) potential res- district. ervoir sands in the upper parts of the Cenotaph and MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

EXPLANATION FEET 2000 - @ ...... LA PEROUSE GLACIER ...... 0 - (Higher beds not exposed) Covered section Sandstone 1000 - 0 @ - - - Sandy mudstone Siltstone - - 0 - 0 VERTICAL SCALE 0.

Conglomeratic sandy Calcareous sandstone and mudstone thin beds of'limestone 0ees*. Conglomerate Breccia

For locations of stratigraphic sections, see figure 19

0 Yakataga Formation FAIRWEATHER GLACIER (Higher beds not exposed) Upper Miocene(?)

rocks Cenotaph Volcanics

FIGURE20.-Tentative correlation of stratigraphic sections exposed in the Lituya district.

Topsy Formations are breached by erosion; and (3) the Fairweather fault. On the other hand, potential the structure is cut by an axial fault and is probably reservoir rocks are likely to become scarcer with in- complicated by faulting at depth. creasing distance from shore, and drilling depths to ' The offshore petroleum possibilities within the objective horizons in the Cenotaph Volcanics and monument cannot yet be adequately evaluated, but Topsy Formations could rapidly become excessive. there is no reason to believe that they will differ sig- nificantly from those landward. Structures may be COAL more favorable, and the source-rock potential of the Reported occurrences of coal in the Glacier Bay sequence may increase in a seaward direction away National Monument are limited to the sequence of from the zone of intense deformation associated with bedded sedimentary and volcanic rocks of Tertiary REFERENCES CITED 89 age exposed in the Lituya district and to a single Lathram, E. H., Loney, R. A., Condon, W. H., and Berg, H. C., specimen of float material of unknown origin found 1959, Progress map of the geology of the Juneau quad- near the terminus of the Casement Glacier (E. H. rangle, Alaska: U.S. Geol. Survey Map 1-303, scale 1:250,000 ; supersedes 1-276. Lathram, oral commun., 1966). Loney, R. A., Brew, D. A., and Lanphere, M. A., 1967, Post- In the Lituya district, coal occurs as thin stringers Paleozoic radiometric ages and their relevance to fault and beds less than 8 inches thick in conglomerates of movements, northern southeastern Alaska: Geol. Soc. the Cenotaph Formation at both the type section on America Bull., v. 778, no. p. 511-526. Cenotaph Island and in the valley of Coal Creek just Mertie, J. B., Jr., 1933, Notes on the geography and geology south of Lituya Bay. Thin beds of carbonaceous silt- of Lituya Bay: U.S. Geol. Survey Bull. 836, p. 117-135. stone and silty coal as much as 3 inches thick are also Miller, D. J., 1953, Preliminary geologic map of Tertiary rocks interbedded with sandstone and siltstone of the in the southeastern part of the Lituya district, Alaska, Topsy Formation at Clay Point. and correlated columnar sections of Tertiary rocks in the The one available analysis of the coal, which was Lituya district, Alaska: U.S. Geol. Survey open-file re- made on a grab sample collected by Don J. Miller, port. from Coal Creek, indicates that it has a high ash con- Miller, D. J. 1961, Geology of the Lituya district, Gulf of tent and is probably of subbituminous rank: Alaska Territory province, Alaska: U.S. Geol. Survey open-file report. Proximate analysis of coal from the Cenotaph Formation, Miller, D. J., Payne, T. G., and Gryc, George, 1959, Geology of Coal Creek possible petroleum provinces in Alaska, with an anno- [U.S. Bureau of Mines. lab. No. F-476431 tated bibliography by E. H. Cobb: U.S. Geol. Survey Bull. 1094, 131 p. As received Moisture free Myers, A. T., Havens, R. G., and Dunton, P. J., 1961, A spec- Moisture ...... 2.4 trochemical method for the semiquantitative analyses of Volatile matter ...... 34.6 35.5 rocks, minerals, and ores: U.S. Geol. Survey Bull. 1084-1, Fixed carbon ...... 34.0 34.8 p. 207-229. Ash ...... -29.0 -29.7 100.0 100.0 Plafker, George, 1967, Geologic map of the Gulf of Alaska Sulfur ...... 5 .5 Tertiary province, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-484, scale 1:500,000. (1 in. equals about 8 miles.) The coal in the Lituya district has little or no com- Reed, J. C., 1938, Some mineral deposits of Glacier Bay and vicinity, Alaska: Econ. Geology, v. 33, no. 1, p. 52-80. mercial potential because of its low rank and its I occurrence as thin discontinuous beds and stringers. Rossman, D. L., 1957, Ilmenite-bearing beach sands near Lituya Bay, Alaska: U.S. Geol. Survey open-file rept. 149, 10 p. REFERENCES CITED 1959, Geology and ore deposits in the Reid Inlet area, Berg, H. C., Eberlein, G. D., and MacKevett, E. M., Jr., 1964, Glacier Bay, Alaska: U.S. Geol. Survey Bull. 1058-B, Metallic mineral resources, in Mineral and water re- p. 33-59. sources of Alaska: U.S. 88th Cong., 2d sess., Senate 1963a, Geology and petrology of two stocks of lay- Comm. Interior and Insular Affairs, Comm. Print, p. ered gabbro in the Fairweather Range, Alaska: U.S. 95-125; U.S. Geol. Survey in coop. with Alaska Dept. Nat. Geol. Survey Bull. 1121-F, F1-F50. Resources. 1963b, Geology of the eastern part of the Mount Buddington, A. F., and Chapin, Theodore, 1929, Geology and Fairweather quadrangle, Glacier Bay, Alaska: U.S. Geol. mineral deposits of southeastern Alaska: U.S. Geol. Sur- Survey Bull. 1121-K, K1-K67. vey Bull. 800, 398 p. Sanford, R. S., Apell, G. A., and Rutledge, F. A., 1949, In- Cornwall, H. R., 1966, Nickel deposits of North America: U.S. vestigations of Muir Inlet .or Nunatak molybdenum Geol. Survey Bull. 1223, 62 p. deposits, Glacier Bay, southeastern Alaska: U.S. Bur. Hawkes, H. E., 1963, Dithizone field tests: Econ. Geology, v. Mines Rept. Inv. 4421, 6 p. 58, p. 579-586. Seitz, J. F., 1959, Geology of the Geikie Inlet area, Glacier Huff, L. C., 1951, A sensitive field test for detecting heavy Bay, Alaska: U.S. Geol. Survey Bull. 1058-C, p. 61-120. metals in soil or sediment: Econ. Geology, v. 46, no. 5, p. 524-540. Smith, P. S., 1942, Occurrences of molybdenum minerals in Alaska: U.S. Geol. Survey Bull. 9264, p. 161-210. Kennedy, G. C., and Walton, M. S., Jr., 1946, Geology and associated mineral deposits of some ultrabasic rocks in Thomas, B. I., and ~erryhill,R. V., 1962, Reconnaissance southeastern Alaska: U.S. Geol. Survey Bull. 947-D, p. studies of Alaskan beach sands, eastern Gulf of Alaska: 65-84. U.S. Bur. Mines Rept. Inv. 5986, 40 p. 90 MINERAL RESOURCES OF GLACIER BAY NATIONAL MONUMENT, ALASKA

Tocher, Don, and Miller, D. J., 1959, Field observations on ef- Twenhofel, W. S., Reed, J. C., and Gates, G. O., 1949, Some fects of Alaska earthquake of 10 July, 1958: Science, v. mineral investigations in southeastern Alaska: U.S. Geol. 129, no. 3346, p. 394-395. Survey Bull. 963-A, 43 p. Turekian, K. K., and Wedepohl, K. H., 1961, Distribution of U.S. Weather Bureau, 1937-66, Climatological data: U.S. the elements in some major units of the earth's crust: Dept. Commerce, Environmental Sci. Service Adm., v. Geol. Soc. America Bull., v. 72, no, 2, p. 175-192. 23-52. Twenhofel, W. S., 1946, Molybdenite deposits of the Nunatak Wright, F. E., and Wright, C. W., 1937, The Glacier Bay Na- area, Muir Inlet, Glacier Bay, in Twenhofel, W. S., Rob- tional Monument in southeastern Alaska, its glaciers and inson, G. D., and Gault, H. R., Molybdenite investigations geology: U.S. Geol. Survey open-file report, 224 p. in southeastern Alaska: U.S. Geol. Survey Bull. 947-B, p. 7-38.

*U.S GOVERNMENT PRINTING OFFICE: 1971 0-399-330