Reconnaissance for Radioactive Deposits in Eastern Interior Alaska, 1946

UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary

GEOLOGICAL SURVEY W. E. Wraths*, Direotor

GEOLOGICAL SmnY CIRCULAR 331

RECONNAISSANCE FOR RADIOACTIVE DEPOSITS IN EASTERN INTERIOR ALASKA, 1946

By Helmutb Wedow, Jr., P. L. Killeen, and othera

This report concerns work done on behalf of the U. 9. Atomic EnVkrgy Cornmiasion and ir publiehed with the permiasion of the Commission.

W~hington,D. C., 1964

Fmu on application to the Gmlogifal Survey, Washington 26, D. C.

CONTENTS

Page Page CHAPTER A . -Areas adjacent to highways in the CHAPTER A . -Area.$ adjacent to highways in the Tana.na and upper Copper River valleys. by Tanana and upper Copper River valleys-Con . Helmuth Wedow. Jr., and J . J . Matzko Areas investigated-Continued Abstract ...... 1 Alaska . H1ghwa.y belt-Continued Introduction...... 1 Radioactivity studies-Continued Measurement of ra.dioa.ctivity.:...... 2 Loca.lities northwest of Outcrop tests ...... 3 Tok Junction...... 13 Unconcentrated crushed samples ...... 3 Loca.lities southeasstof Concentrated samples...... 3 Tok Junction ...... 16 Areas investiga.ted...... 3 Highwa.y area between Slana. and Fairba.nks district ...... 3 Tok Junction ...... 16 Geology ...... 3 Geology...... 16 Ra.dioa.ctivity studies in the Ra.dioa.ctivity studies ...... 16 Pedro Dome area ...... 6 Donnelly Dome-Paxson area...... 18 Ra.dioactivity studies in the Geology ...... 18 Ester Dome a.rea...... 7 Radioactivity studies ...... 18 Steese Highway belt in upper Conclusion ...... 18 Chatanika valley...... 8 Literature cited ...... , .... 20 Geology ...... 8 CHAPTER B . -Gra.nt Creek a.rea., by Radioactivity studies ...... 8 P . L. Killeen and M . G . White Livengood area...... 8 Abstract ...... 33 Geology ...... 11 Introduction...... 33 Radioactivity studies; ...... 11 Purpose and scope of investigation ...... 33 Ha.rding Lake-Richardson area.. : ...... 11 Loca.tion of a.rea ...... 33 Geology ...... 11 Geology ...... 33 Radioactivity studi'es ...... 13 Radioactivity ...... 33 Alaska Highwa.y belt ...... 13 Locations of tests ...... 33 Geclogy ...... 13 Conclusion ...... 35 Radioa.ctivity studies...... 13 Literature cited ...... 36

ILLUSTRATIONS Page

Figure 1. Index map to areas investigated along the highways in the Tanana and upper Copper River valleys. Alaska ...... 2 Diagram showing relationship between the equivalent uranium content of unconcentrated crushed samples and outcrop gamma counts...... 4 Geologic sketch map of the Pedro Dome area, Fairbanks district ...... 5 Topographic sketch map of the Ester Dome area ...... 6 Geologic sketch map of the Steese Highway belt in the upper Chatanika valley ...... 9 Geologic sketch map of the Livengood area...... 10 Geologic sketch map of the Harding Lake-Richardson area, Richardson Highway ...... 12 Geologic sketch map of the Alaska Highway belt, upper Tanana valley ...... 14 Geologic sketch map of the highway area between Slana and Tok Junction ...... 17 Geologic sketch map'of the Domelly Dome-Paxson area, Richardson Highway ...... 19 Drainage map of the Grant Creek area, Yukon region ...... 34

TABLES Page

Table 1. Data on ra.dioactivity tests in areas adjacent to highways in the Tanam and upper Copper River valleys. Alaska ...... 21 2 . Data on placer concentra.tes from Gran: and Tozimoran Creeks ...... 35

RECONNAISSANCE FOR WIOACTIVE DEPOSITS IN EASTERN INTERIOR ALASKA, 1946 By Helmuth Wedow, Jr., P. L. Killeen, and other8

CHAPTER A. -AREAS ADJACENT TO HIGHWAYS IN THE TANANA AND UPPER COPPER RIVER VALLEYS

By Helmuth Wedow, Jr., a.nd J. J. Matzko

ABSTRACT contributes to the radioactivity of the concentrates. Its bedrock occurrence is doubtless a.lso as an A reconnaissance conducted in 1946 in areas a.ccessory mineral in the granitic rocks. adjacent to highways in the Tanana and upper Copper River valleys was the first time that field radioactivity tests were made in eastern interior INTRODUCTION Alaska. Before 1948 the scanning of the Alaskan placer-concentrate collection of the Geological The Tanana and upper Copper River valleys Survey for radioactivity had indicated that radio- in eastern interior Alaska (fig. 1) are on OPPO- active minerals occurred in a few localities in site sides of the Alaska Range. The Tanana the Fairbanks and Livengood areas. The objectives River, on the north side of the range, flows of the 1946 reconnaissance were to determine northwest into the Yukon River, and the Copper whether significantly radioactive lodes occurred in River, on the south side, flows south into the the vicinity of the placers from which the radio- Gulf of Alaska. The principal highways in Alaska active concentrates had been obtained and to con- either follow these two valleys or cross the duct a routine survey for radioactive deposits in acces- intervening uplands. These highways and subsidiary sible areas adjacent to highways in eastern interior roads are shown on figure 1. Alaska. The techniques used in the survey consisted of the direct testing of outcrops for radio- The initial scanning of an Alaskan placer- activity with a portable survey meter and the sample collection for radioactivity in the winter collection of rock samples and placer concentrates of 1944-45 indicated a few sites in the Fairbanks for equivalent uranium analysis in the laboratory. and Livengood areas where radioactive materials were present in stream deposits. Subsequent field Although the 1946 reconnaissance did not sampling by R. R. Coats in 1945, during a yield any further information on the source of the reconnaissance of the Yukon-Tanana placer region few concentrates of higher radioactivity that had (Fortymile, Circle, Fairbanks, and Livengood been obtained previously, a few new sites of districts), increased the number of samples avail- radioactivity were found. Data for all sites, re- able from these areas, but did not reveal any gardless of favorable or unfavorable results, are additional sites of significantly radioactive material. presented in order that future investigators may Lnforrnation on those samples which were available evaluate how thoroughly negative areas have been before the 1946 reconnaissance in the Tanana and determined. Lode deposits, consisting primarily upper Copper River valleys is summarized in an of quartz veins containing gold and metallic informal file report by P. L. Killeen on trace sulphides, contain only as much as 0.005 percent elements investigations in Alaska and is reproduced equivalent uranium. Graphitic schists and black below. shales contain a maximum of 0.004 percent equivalent uranium; other types of schist contain only as much as 0.003 percent equivalent uranium. Radioactivity of samples collected before 1w in the Tests of granitic and mafic igneous rocks indicate Tanana and upper Copper River valleys, Alaska maximums of 0.006 and 0.005 percent equivalent uranium respectively. Concentrates from placer deposits, locally contain as much as 0.006 percent equivalent uranium. The slight radioactivity of the igneous rocks appears to be due to traces of uranium and thorium in such accessory minerals as zircon and allanite. The slightly higher radioactivity of the placer samples at some localities is probably due In 1946, a reco,,~aissa.nce for ra.dioactive to the natural concentration of the radioactive deposits in areas accessible from the highways zircon and allanite. At a few localities, monazite in the Tanana and upper Copper River valleys has been found in the placers and probably also was undertaken because the accessibility permitted I Figure 1. -Index map to areas.investigated along the highways in the Tanana and upper Copper River valleys, Alaska. covering a large area in the course of the field MEASUREMENT OF RADIOACTIVITY season and because previous information on radioactivity in areas adjacent to highways in the The radioactivity of outcrops of bedrock and Tanana and upper Copper River valleys was gravel, and of unconcentrated samples of crushed bed- either sparse or absent. The reconnaissance rock was measured in the field with a portable survey party consisting of Helrnuth Wedow, Jr., and meter designed by the Geological Survey for the meas- John J. Matzko, geologists, and Fred Freitag, urement of gamma-ray intensity. Tests on sam- camphand, was in the field from June through ples were made at base camps where readings were September 1946. not influenced by any radiation from large areas of outcrop of the material sampled. Most of the rock material were made with heavy liquids (bromoform, ,samples were later crushed to minus 4-mesh in a jaw sp gr 2.8; methylene iodide, sp gr 3.3). The crusher at the Fairbanks laboratory of the Geological unconcentrated crushed samples were crushed Survey. Subsequently, heavy-mineral separates of further to rninus 20-mesh and also separated with crushed rock samp16s, of panned concentrates of heavy liquids. The percent equivalent uranium crushed rock sam~les,and of panned concentrates in the resultant heavy fractions was then determined of gravels and wea'thered disintebrated rock materials by beta-gamma count with laboratory instruments. were prepared and tested for radioactivity by beta count on a laboratory scaler in Washington. Table 1, at the end of this report, gives the location and description AREAS INVESTIGATED of each test station, the radioactivity determinations made at the stations or on samples obtained therefrom, Fa.irbanks district and the concentrati~nratio of the ultimate concentrate for which the radioactivity was measured. The radio- The Fairbanks district, herein divided into activity throughout is expressed in terms of percent the Pedro Dome area (figs. 1 and 3) and the equivalent uranium. Ester Dome area (figs. 1 and 4), includes about 300 square miles of territory adjacent to the city of Fairbanks. Outcrop tests The Pedro Dome area, from 5 to 25 miles Outcrops of bedrock and gravel were tested northeast from Fairbanks, roughly includes the for radioactivity by pla.cing the probe on the sur- watersheds of the streams draining the area surface of the material and mea.suring the gamma rounding Pedro Dome and Gilmore Dome. The count for 5-minute interva.ls. Background readings, main streams are: Cleary, Little Eldorado, Dome, with the probe several feet above the surface of and Vault Creeks, north-flowing tributaries of the the ground, were taken severa.1 times a day as Chatanika River; Goldstream Creek and its west- a check. The results of the gamma count at each flowing tributary, Big Eldorado Creek; and outcrop, as shown in table 1, is expressed in Fairbanks, Fish, and Smallwood Creeks, tributaries terms of percent equivalent uranium by interpolating of the Little Chena River. In 1946 mining camps from the diagram shown in figure 2. were located in most of the major valleys, and many of the smaller streams had been mined In the construction of such a diagram (fig. 2) previously. The Steese Highway, crossing the the average background counting rate of the in- area in a general northeasterly direction, has its strument that was used was determined by averag- origin at Fairbanks and leaves the area shown ing the averages of groups of four consecutive. in figure 3 via the valley of Cleary Creek. The ba.ckgrounds. The fina.1 a.verage background wa.s Elliott Highway, or Livengood road, diverges from then plotted on the diagram a.s:0.001 percent the Steese Highway at Fox. Many secondary roads equivalent uranium. The equivalent- uranium values and trails lead from the main highways to sites of a number of crushed samples were then plotted of past and present mining operations. against the gamma co~lnts obta.ined a.t the outcrops from which the samples were taken. The diagonal The Ester Dome area, 10 to 15 miles west line, showing the proba.ble relationship between from Fairbanks, is drained by tributaries of the equivalent-uranium value and the outcrop gam- Goldstream Creek on the northwest and by tribu- ma count, wa.s then dra.wn by inspection from the taries of Cripple Creek on the southeast. In point where the average background was assumed 1946 the area was accessible by a graded gravel to represent*O. 001 percent equivalent uranium. road from Fairbanks, and by many secondary Deviation of points from the diagonal is attributed roads a,nd trails that bracch out to lode and placer either to sampling errors or to the random nature mining operations. A small settlement, Berry, P. O., of gamma radiation over short periods of time. located on Ester Creek, is the center of the dredging operations of the Fairbanks Exploration Department, U. S. Smelting, Refining, and Mining Unconcentrated crushed samples Co., in the Ester Dome area.

To determine the equivalent-uranium content of the crushed rock samples, 5-minute readings Geology of background, sample, a radioactive standard, sample, a.nd ba.ckground were made in that se- The general geology of the Fairbanks district quence. is relatively well known a.s a result of studies of its gold-bearing placers a.nd lodes (Prifidle, 1905, 1908, 1910a, 1913; Ellsworth, 1910; Bill, Concentrated samples 1933; Mertie, 1937; and Capps, 1940).

To increase the proportion of heavy minerals The Birch Creek schist of pre-Cambrian to be tested for radioactivity at any one station, age is the bedrock underlying the larger part of concentrates were made by panning unconsolidated the district. The schist is predominantly of materials such as stream gravel and slope wash, sedimentary origin and has a considerable range and disintegrated rock from mine dumps and of composition. The chief types, however, are weathered outcrops. Later, to obtain a standard quartz-mica and quartzite schist. Minor amounts type of concentration, separations of minus 20-mesh of augen gnei'ss and crystalline limestone are Gamma count per minute on outcrop

Figure 2. -Diagram showing relationshipbetween the equivalent uranium content of unconcentrated crushed samples and outcrop gamma. counts. Gsoloqy maditled fmm U.S. Oeolaqlool Surny aullatln 849-8; minor unconsolidatrd depo$It$ excluded 6 Miles

I I Base from us ~colcqlcolSurvey Alosko Map 40 Field work by Helmuth Wedow, Jr, and J J Matzko, June-July 1946

Figure 3. -Geologic sketch map of the Pedro Dome area, Fairba.nks district, Alaska. also present. Igneous rocks of two main types dikes, are numerous but scattered. All the igneous intrude the Birch Creek schist. One is a quartz rocks are presumably Mesozoic in age. Known diorite, well exposed on Pedro Dome; the other lode deposits in the Gilmore Dome watershed is coarse.-grained porphyritic granite underlying are mainly gold-quartz, bismuth, and tungsten a large area south and southwest of Gilmore veins and replacement bodies, all for the most Dome (fig. 3). In the vicinity of Fster Dome part closely associated with the large intrusive only a few small bodies of porphyritic granitic mass of granite near Gilmore Dome. Extensive rocks have been reported. Minor types of igneous muclf and gold-bearing gravel deposits cover rocks, represented primarily by altered granitic most of the valley bottoms and lower hill slopes. 5 EXPLANATION OE mz0 Outcmp test Uncancentratdd sample ma Outcrop hrst and ~(mcentratad sample Outcrop tesf and unconcentrated smplt

Numbers indlcate stations prefixed 'ED" in table I of text I 0 5 Milrr IIIIII I I I I i I Bone from U. 3. Olologbai Survay AIolka Mop 40 FIald M by Holmuth Wadow, Jr., ond J. a mma~,~une-~u~y 1046

r'igure 4. -Topographic sketch map of the Ester Dome area, Fa.irbanks district, Alaska.

Barren windrows of dredge tailings are now con- Radioactivity studies in the Pedro Dome area spicuous as a result of placer mining in the valley bottoms of Goldstream, Gilmore, Pedro, Fish, Previous equivalent uranium determinations Fairbanks, Cleary, and Ester Creeks. Slope on placer concentrates, obtained chiefly from gold- wash and a heavy moss-cover make natural rock mining operations, showed that some radioactive exposures on the hills a rarity, except locally material occurs in the Pedro Dome area. Seven of at the crests, where weathering has sculptured the concentrate samples had more than 0.01 percent the bedrock into odd castellated shapes. equivalent uranium. The creeks from which these more radioactive concentrates were obtained, and the Zircon, some of which is probably uranium- or determinations of equivalent uranium in the concen- thorium-bearing, is the only mineral as yet identified trates, are given below. in the concentrates of the Pedro Dome area, to which radioactivity can be ascribed. Thus, in most samples, Alaskan Percent equivalent the presence of radioactive zircon could account for Concentrate Creek uranium the small increases in equivalent-uranium content file no. A1 W when the heavy minerals are concentrated. It appears likely, however, that some other ra.dioactive mineral 355 Fish Creek------30.100 0.016 yeum pup------or minerals also occur in the samples containing more 628 .M8 .a than 0.01 percent equivalent uranium. 109 Gibre Creek------.013 Om 965 First Chance Creek------.029 --- 648c ~eattlepup------=.096 .024 The concentrate from Fish Creek (sample 355) 163 Clemy Creek------.013 .018 consists of few small nuggets obtained from a placer 9@ Bpecific locality unlmown- .014 --- operation about 24 miles northeast of Gilmore Dome. Although the original radioactivity determination made 'Detcminarions made about January 1945. in 1945 indicated 0.1 percent equivalent uranium, a 'Redetermined in April 1947. second test in 1947 showed only 0.016 percent equiv- alndicates sample conuidcred too mdl for accurate dctemination. alent uranium. A qualitative spectrographic examination of one of the nuggets shows that the ma:or elements are The first four streams in the above tabula.tion are bismuth and silicon with the bismuth preponderant. parts of the watershed that surrounds Gilmore Dome. The nuggets, therefore, are probably mostly native Cleary Creek and Seattle Pup are part of the watershed bismuth with some eulytite or argicolite possibly that surrounds Pedro Dome (fig. 3). present. The gold, listed among the minor elements in the examination, occurs as fine flakes and wires. The recent testing in the Pedro Dome area indi- Uranium and thorium are listed among those elements cated no appreciable amount of radioactivity except looked for but not found. One bismuth lode occurs in for two samples as follows: the Fish Creek watershed above the location of this concentrate. The lode is in a biotite granite on the (1) Sample 1398: spur along the east side of Monte Cristo Creek. Location: Station HI 107, near head of (Chapin, 1914, p. 330-331, ) This lode was not investi- Rex Creek. Nature of sample: Heavier-than-brwno- gated in the brief reconnaissance of the lodes in the form fraction of paned concentrate Pedro Dome area, nor were concentrates taken down- from 50 pounds of gravel. stream from it. Equivalent uranium content: 0.066 percent. Ccrmpesative data: Outcrop test, Radioactivity studies in the Ester Dome area 0,001 percent equivalent uranim.

(2) Sample 1538L: Five placer concentrates from the Ester Dome Location: Station PD 41, along west area that had been tested for radioactivity before side of the Steese Highway in the the 1946 field season ranged from e0.001 to 0.002 per- valley of Twin Creek about 6 miles cent equivalent uranium. Although such values are northeast of Fox. extremely low, the coverage represented by only five Nature of sample: Heavier-than-brrmno- samples was so scant that it seemed desirable to test form fraction of crushed vein materhl at least a few of the known lodes and collect a few on dung of abandoned ~cheelitemine. additional placer concentrates from the area. The Equivalent uranium content: 0.013 percent. locations of thetests are shown on figure 4, and the Comparative data: Outcrop test, results are included in table 1. 0.m percent equivalent uranium; unconcentrated crushed sample, Structural conditions have limited the best me- 0.W percent equivalent uranium. tallic mineralization of the area to the southeast flank of Ester Dome, and, therefore, placer and lode mining The radioactivity data of the remaining tests in activities have been restricted to this flank (Hill, 1933). the Pedro Dome area may be summarized as follows: Consequently, tests for radioactivity were similarly localized. (1) htcrop teat6 (n5 stations): Maximum equivalent-uranium content: Many of the mines and prospects in the Ester 0.003 percent. Dome area have long since been abandoned, and Average equivalent-uranium content: a.dits ha.ve colla.psed and are overgrown. Of 0.001 percent. necessity, therefore, the testing of lodes was (2) Unconcentrated crushed rock samples restricted to ore materia.1~scattered through the (4 samples): mine dumps. All the lmown lodes are of the Maximum equivalent-uranium content: gold-quartz va.riety, and ca.rry, in addition to free 0.003 percent. . gold, varying a.mounts of primary sulphides. Average equivalent-uranium content: 0.002 percent. Arsenopyrite and stibnite form the bulk of these sulphides, but minor amounts of boulangerite, jameson- (3) Concentrated samples (35 samples) : ite, and covellite have been reported (Hill, 1033, Maximum equivalent-uranium content : p. 120- 152). Weathered-pa.rts of the veins examined 0.006 percent. are much stained with oxides of iron, manganese, Average equivalent-uranium content: 0.0025 percent. antimony, and arsenic. The radioactivity of materials tested in this Nome Creek has more than 0.01 percent equiv- area ranged from e0.001 to 0.007 percent equivalent a.lent uranium, and in this the equivalent-Uranium uranium. The maximum value was obtained in the content is 0.026 percent. heavier-than-bromoform fraction of a concentrate panned from 50 pounds of gravel from St. Patrick The investigations in 1946 were restricted Creek (station ED 7, sample 1424). As in the to tests of bedrock cropping out in road cuts and Pedro Dome area, the slightly higher equivalent- to tests of concentrates of gravels from streams uranium values in the concentrates as compared in the immediate vicinity of the highway and sec- to the outcrop test may be attributed to the pro- ondary roads. The locations of the sites tested portional increase in radioactive zircon resultant are shown on figure 5, and the results are in- from concentration. cluded in table 1.

Several varieties of schist and granitic rocks Steese Highway belt in upper Chata,nika valley were tested. The data of these tests are summarized below. The portion of the Steese Highway midway between Fairba.nks and Circle lies mainly in the upper or headwater part of the Chatanika valley, but extends north and east to the headwater portions of Beaver, Birch, and Preacher Creeks (figs. 1 a.nd 5). As considered in this report and shown on figure 5 the belt adjacent to the highwa.y is about 60 miles long and 16 miles wide, and has a,n area of about 800 square miles. The topography generally consists , of long even-topped , ridges with long, broad, Xatera.1 spurs separating wide, sha,llow valleys, The Steese Highway enters the valley of the Chata,nika, River at the mouth of Clea.ry Creek a.nd follows the valley northeastwa.rd. At the head of McMa,nus Creek the highwa,y crosses the divide into the valley of Twelvemile Creek of the Birch Creek watershed. Short roads lead from the highway to the site of dredging operations on Nome Creek, and to other, sma,ller placer mines on Deep a.nd Sourdough 'A. Outcrop rents, Creeks. Most of the short trails that start from 'B. Tears of uneoncentmted crushed mck samples. %. Teats of tuomoform conecoma* tmm crushed rock amplea the highway are for access to the U. S. Smelting, Refining, and Mining Co. ditch. The upper Chatanika The relatively higher values of equivalent ura- valley ha,s few inhabitants. Those who live there nium in the granitic rocks (station UC 12, sample a.re employed ma.inly in prospeciing and mining, 153QL) is probably due to radioactive elements in or in ma.intaining the U. S. Smelting, Refining, zircon, which was identified in the concentrate. and Mining Co. ditch or the Steese Highway. A placer concentrate obtained from a dredge on Nome Creek was the only appreciably radio- Geology active placer material from the Chatanika area tested in 1946. Further concentration of the heavy The geology of the eastern or upper part minerals by separation in methylene iodide in- of the Chatanika valley is similar to that of the creased the radioactivity only to 0.012 percent Fairbanks district. The Birch Creek schist (see equivalent uranium. Minerals of interest in this previous discussion under Fairbanks district) is concentrate are rela.tively abundant topaz and again the major bedrock of the area. A large cassiterite, and sparse tourmaline and monazite. mass of ~ntrusivegranitic rock of Nlesozoic(7) This association suggests that tin-bearing veins age crops out in the north-central part of the may occur in the vicinity of the granite at the area in the headwater portions of Nome Creek, head of Nome Creek. and tributaries of Faith and Prcacher Creeks. Similar bodies of related igneous rock are preseni at the head of Sourdough Creek and in the divldc Livengood area. separating the Faith, Idaho, a~ldPreacher Creek - drainage areas. (Prindle, 1910, p. 203-209; The Livengood area (figs. 1 and 6), as 1913, pl. 8; 1913a, pl. 2.) considered in this report, consists of an area about 100 square miles. The town of Livengood, the only settlement in the area and the northern Radioactivity studies terminus of the Elijott Bighway, is 71 miles from Fox on the Steese Highway and 82 miles Before the present cxaminatlon of materials from Fairbanks. The Livengood area is part from the upper Chatanika valley area, only seven of the Yukon-Tanana upland and is characterized placer concentrates, three from Sourdough Creck by broad, even-topped ridges from which long, and fcur from Nome Creek, had beer1 tested for gently sloping spurs descend to the valley floors. radioactivity. Of the sever1 only a concentrate from 'The area is drained by Livengood Creek and the Geoioqy modified from U.S Geological Survey Bulletins 525, 538, 872, and 907i unconsolidated deposih excluded 40 Miles

L I Base modified from U. S. Geological Survey Field work by, Helmuth Wedow, Jr.,. Alaska Maps 27, 38, and 39 and J. J. Math, July 1946

Figure 5. -Geologic sketch map of the Steese Highway belt in the upper Chatanika valley, Alaska. I EXPLANATION

alluvium 013 Outcrop test 15 Concentrated somple 014 Outcrop test and concentrated sample Acidic (?) intruslves 0-16 Outcrop test and unconcentroted sample

Numbers indicate stations prefixed "L" in Chert and silicified table 1 of text limestone En Geology modified from U. S. Geological Survey Undifferentiated rock Bulletins 662-0, 872, and 907 )is Basic lavas 2 2 2 0 8 Miles IIIII I I I I

I Base from U S teologicol Survey F~eldwork by Helmuth Wedaw, Jr.,' Alaska Map 27 and J. J. Matzko, August 1946

Figure 6. -Geologic sketch map of the Livengood area, Alaska. Tolovana River of the Tanana drainage basin, found in the Livengood area are summa.rized and by tributaries of the South Fork of Hess below. Creek, which in turn is tributary to the Yttkon Percent equivalent River. Dredging operations of Livengood Placers, Material tested uranium Inc., on Livengood Creek and several large scale A' BZ C3 opencut, hydraulic -placer opera tions on tributaries of Livengood Creek and the Tolvana River are the Slulce concentrate: Station L 27, sample 1446 ------0.010 principal mining activities in the area. .oog

Panned concentrate: Geology Station L 19, sample 1454 --- - .004 The geology of the Livengood area has been Black shale: discussed in some detail elsewhere. (See Brooks, Station L 56a, sample 1553L 0.002 0.W .006 1910; Mertie, 1917; 1937; Overbeck, 1920; and Weathered @mite: Capps, 1940.) In general, the sedimentary rocks Station L sample 193L ,003 of the area have been mapped as two units: 3, .GO3 ,005 one, an undifferentiated, chiefly noncalcareous 'A. Outcrop teats. Dev0nia.n sequence, which lies to the south of 'B. Tests of unconcentrattd crushed rock aamplcs. Amy Dome; the other, a younger chert and "C. Teats of bromofom concenttates. silicified limestone sequence of Mississippian age, 'rest of methylent iodide concenuatt. which lies to the north of the dome (fig. 6). Mafic rocks of Paleozoic age, thought to be ex- trusive and intrusive, are closely associated with Mineralogical examination of the sluice con- both age groups of the consolidated sediments. centra.te listed a.bove indicates that the radioactivity Tertiary(?) granitoid rocks, predominantly felsic, is due to uranium- or thorium-bearing zircon, intrude the older rocks in the vicinity of Amy although a few grains of monazite also are present. Dome. Metamorphic effects and mineralization attributed to these later intrusives are clearly The Livengood area appears to hold little seen along the divide between Livengood Creek promise for significant ura.niIerous deposits, ex- and the Tolovana. River, and on the flanks of cept, possibly, for the source of the highly Amy Dome. radioactive mineral in the sample from Goodluck Creek. Radioactivity studies Harding Lake-Richa.rdson area Previous tests of 30 placer concentrates from the Livengood area indicated amounts of The Harding Lake-Richardson area (figs. 1and 7), radioa.ctivity of less than 0.01 percent equivalent about 50 miles southeast from Fairbanks, is on the ura.nium, except in a concentra.te from Goodluck northeast side of the Tanana River between the lower Creek which contains from 0.031 to 0.048 per- courses of the Salcha River and Shaw Creek. The Richardson Highway crosses the area roughly parallel cent equiva.lent ura.nium. Although a cursory to the course of the Tanana River. Small settlements examination of this concentrate before the begin- are located at Richardson, and at Birch and Harding , ning of the field sea.son of 1546 failed to reveal Lakes. The area shown in figure 7 is about 400 square a.ny ,minera.l to which the radioactivity could be miles, but only a small fraction of this is easily acces- a.scribed, more detailed study later indicated that sible from the highway. Placer gold was first mined the radioactivity is due to a black, pitchy-appearing, in this area in the early I£JOO1s,chiefly in the valleys ra.dioactive mineral with a condhoidal highly of Tenderfoot, Buckeye, and Banner Creeks, and in the fracture. headwater tributaries of Redmond Creek. Only one placer mine, located on claim 13 Below, on Tenderfoot Despite the apparently unpromising initial Creek, was being worked in 1946. information, some field work appeared warranted to complete coverage of the placers of the area in an attempt to obtain other radioactive concen- Geology trates, and for testing a few of the sedimentary and igneous rocks and the attendant lode deposits. Pre-Cambrian Birch Creek schist and granite The location of these concentrates and outcrop rocks of Mesozoic(?) age form the bedrock of the tests are shown on figure 6, and the results Harding Lake-Richardson area. The Birch Creek schist are included in table 1. in this area consists chiefly of micaceous and quartzitic schists, and intergradations between these two types. A concentrate donated by a, placer operator Minor rock types in the Birch Creek a.re graphitic on Ruth Creek (station L 27) was the only placer schist, crystalline limestone, and gneiss. Except for concentrate obtained in 1946 that contains a.s much the gneiss, the Birch Creek is considered to be derived as 0.01 percent equivalent uranium. Sedimenta.ry from sedimentary rocks. The gneiss is probably the land igneous rocks, for the most pa.rt, contain metamorphic equivalent of pre-Cambria.n intrusives. less than 0.001 percent equivalent uranium and Quartz veins, in part gold-bearing, are associated weathered granite 0.003 percent equivalent ura- with the schist. (Prindle, 1913, p. 35, 38, 52, 53, nium. Results of various radioactivity tests 140-142, pl. 8; Mertie, 1937, p. 47-59, 210-215, pl. 1; ma.de in 1946 on the most radioactive materials Capps, 1940, p. 134, 135, 145, 146, pl. 3.)

Radioa.ctivity studies Geology

Granitic rocks of Mesozoic(?) age and attendant The geology of the area crossed by the mineralization at outcrops of bedrock and in concen- Ala.ska Highwa.y (fig. 8) wa.s partly described and trates obtained from stream gravels eroded from the ma.pped by Mertie (1937). Moffit (1842), and intrusive masses and surrounding rocks were tested Van Alstine and Bla.ck. ' Some of this previous for radioactivity in the Harding Lake-Richardson area. work, however, was revised and extended in In addition concentrates were acquired from some of 1946 during the reconna.issa.nce for radioactive the streams formerly important as producers of gold, as deposits. this area was not previously represented in theAlaskan placer-concentrate file of the Geological Survey. Gra.nitic intrusives of Mesozoic(?) age con- stitute the bulk of the bedrock exposed in the The location of the outcrop tests and sites of highway belt. These intrusives a,pparently cut samples are shown on figure 7, and the data obtained pre-Cambrian or early Paleozoic schists and are included in table 1. A summary of the data on the gneisses which are similar to, and in pa.rt prob- most ra,dioactive materials found in the Barding Lake- ably the equivalent of, the pre-Cambrian Birch Richardson area is tabulated below. Creek schist of the Yukon-'Tanana upland. Percent equivalent Material. tested IliT,3%- Radioactivity studies

Granitic rock, weathered: The reconnaissance investigaiion of radio- StationRLa, aql.e1459L a,ctivity in the Alaska Highwa.~belt in 1946 was Granitic(?) dike, light-color- devoted chiefly to the granitic rocks of Mesozoic(?) ed, fine-grained, weathered: age,. For convenience in discussion the area is Station R ha, sample 1460L .005 .OM 0.060 .U0 divided into two parts: Station R 13, no sample .005 ------1. Localities northwest of Tok Junction Granitic dike, coarse-grained: (stations AH 1-AH 15, fig. 8 a.nd ta,ble 1). Station R 14a, sample 1556~Ill1 .W5 .~4,005 --- Graphitic schists: 2. Localities southea.st of Tok Junction Station R 25b, sample 1557L IiII.W2 ,001 ,005 --- (stations AH 1-AH 41, fig. 8 a.nd table 1). Stream ad 'bench gravels : .W1 ---- ,008 Btation R 23, sample 1464 --- Localities northwest of Tok Junction. -Data Station R 24, sample 1465 ------5.~0 Station R 2>, sample 1466 e.001 ------,009 on the most radioactive ma.teria.1~from localities northwest of Tok ~unct'ion a,re summarized ¶A. Tests at the outcrop. below. 'B. Tests of unCOncentrated crushed rock amples. 'C. Tcata of bromoform concentrates from crushed rock samples. *D. Tests of panned concensnlcs from 100-pound samples of uncon- Percent equivalent solidated material subsequently reconcenuatcd with bromoform. kterial tested uranium nMethylene iodide used for fin1 concenuation instead of bromoform. A1 BE The radioactivity of the granite may be due to the Granite, coarse-grained, presence of zircon and allanite(7) whichwere identified weathered: in a preliminary study of the concentrates. Scheelite is Station AH 15b, sample 1480~ 0.004 3~.~~8 also present. Minerals of interest in the radioactive con- centratefromBuckeye Creek (stationR 24, saniple no. 1465) Stream and bench grevels: Station AH la, sample 1469 are sheelite, tourmaline, rutile, zircon(?), titanite(?), .OM 3.014 Station AH 2, sample 1470 .OM 4.011 cassiterite(?), acd galena. This association uf minerals, Station AH 4, sample 1472 .OW 4,008 particularly that of tourmaline, cassiterite(?), andgalena, suggests the possibility for vein deposits in the drainage 'A. Tests at the outcrop. area upstream from the site of the concentrate. '8. Tests d concentrates panned from IOGpound samples of gravel. 'Final concentration made with methylcne iodide. 'Final concentration made with bromofotrn. Alaska Highway belt

The Alaska. Highway belt consists of a long na.rrow area, alcng the highway from Big Delta. to the interm- Preliminary study of the concentrates indica.les tional boundary. It is entirely within the drainage basin the presence of minor arr~ounts of zircon, a. of the Tanana. River. Ths highway is southwest of the mineral which may be radioactive because it ca.n river from Big Delta to a point a few miles east of contain uraniurn and thorium. All the gravels Tok Juriction; there it crosses the Ta.nana River a.nd listed in the above tabula.tion a.re from stred.ms follows successively the northea.st ba.nks of the Chisam dra.ining areas 'underlain by gra.nitic rocks. River and Scottie Creek to the boundary. The major settl.ements on the highway are BigDelta, rTa.na.cross, a.ndrI'okJunction; andN0rthwa.y is just southof the highwa.y nea.r the mouthof the NebesnaRiver (figs. 1 a.nd 8). 'van Alstine, R. E., and Black, R. F., 1944, Geology of the Alaska military highway from the intctnational boundary to Big Delta, Also, a, few sma.11 native villa.ges are scattered a.long Alaska. [unpublished rept., 1944. Manuscdpt and maps in the files the river banks. of the U. S. Geol. Survey Alaskan Geology ~ranch.1

Localities southeast of Tok Junction. -Data on Highwa.y area between Sla.na,a.nd Tok Junction the most radioactive materia.1~from 1oca.iities southeast of Tok Junction are summarized below. The highway area between Slana and Tok Junction (figs. 1 a.nd 9) lies across the divide between Percent equivalent the Copper River and Tanana River ba.sins. This new MBteslal tested road, a.bout 70 miles long and known informally as the "Tok cutoff, connects the Alaska Highway with the old Nabesna road by way of Mentasta. Pass (altitude Granite, coarse-grained, weathered : a.bout 2, 300 feet). It was originally constructed by Station AH 40, saanple 1490L the Army Engineers of the Alaska Depa.rtment, and and sample 1547~. more recently, has been' improved and maintained by Shtion AH 17a, sample 14811, the Ala.ska Roa,d Commission. This r0a.d has opened Station AB 37, sample 14@~ up much country formerly accessible only by pa.ck tra.in. Station AII 26, sample 1483~ The area is drained chiefly by the Tok River, a north- Station AH 36b, samples 14881 flowing tributary of the Tanana River, a.nd by the and 1546~. Slam River, a south-flowing tributa.ry of the Copper ~elsitic(7)dike, weathered : River. Station AH 31b, sample 16622 .OO3 , .003 ,010 --- i \ 'A. Tests st the outcrop. 'B. Tests of unconcenuated cmshcd rock samples. 'C. Tests of bromofotrn concentrates from.cmshed rock smmphs. *D. Testa of panned concen*atcs from 100-pound samples of uncon- The geology of the area between Slana and Tok solidated material subaequently rtconccntrntcd with methylene iodide. Junction has been described by Moffit (1938) in con: 'Bromoform wed for final concenuntion instead of methylane iodide junction with surveys in the Copper River basin. The bedrock of the Slana-Tok district is a part of the core Subsequently, samples 1481L and 14QOLin the above of the Alaska Range which here has a northwesterly tabulation were concentrated further by removing a trend. Moffit (1938, p. 1) states: magnetic fraction with a hand magnet. The equivalent- uranium content in the resultant nonma,gnetic fractions "The rocka of the district are prevailingly sedi- of these two samples was then determined to be 0.65 mentary but include tuff beds end Lava flows and many a.nd 0.89 percent, respectively. masses of intruded granitic rocks, most of which are diorite and related types rather Wan granite. Some of Preliminary mineralogical studies of the con- these rocks are highly metwmrphic. Others are greatly centrates from the granitic rocks show the pres- folded yet not notably altered. The structure is com- ence of zircon in all samples from the five plex and not clearly deratood. The rocka range in localities, usually in large amounts. Although it age from pre-Cambrian or eaxly Paleozoic to late Mesozoic. In places they are concealed by Recent wcon- is presumed that the concentration of the zircon solidated wuterlaid and glacial aeposits." is to a large extent responsible for the increased radioactivity of the concentrates, other Alaskan studies (Moxham and West, 1953, p. 7; White and The distribution and age of the different rock types Killeen, 1953, p. 3) have shown that the radio- are shown on the geologic sketch map of the area activity of pure zircon fractions of concentrates (fig. 9). from granitic rocks was found to range, only from 0. 1 to 0. 15 percent equivalent uranium. Hence, zircon alone probably cannot account for the total Radioactivity studies radioactivity in samples 1481L and 14BOL men- tioned above. Allanite, another mineral which Tests for radioactivity in the area along the Slana- may contain uranium and thorium, has been Tok highway were made principally on concentrates identified also in these two concentrates (samples from gravels in tributaries of theSlana and TokRivers. 1481L and 1490L) as well as in a third (sample The locations at which the concentrates were taken, 1483L). Although it is likely that the zircon and as well as the few other tests on a lode deposit, are allanite account for the bulk of the radioactivity shown on figure 9, The data are included in table 1. in the samples, traces of other, as yet unidenti- fied, highly radioactive minerals may also be The equivalent-uranium values for 20 concen- present. Other heavy minerals of interest identified trates from gravels in the Slana-Tok Jllnction highway in the concentrates from the granitic rocks are area range from ~0.001to 0.003 percent, and average epidote, tourmaline, and axinite( ?) . 0.001 percent. A silver prospect (Moffit, 1938, p. 46,471 on Silver Creek, a small tributary of Ahtell Creek The refractory nature of fhe chief radioactive near Slana, was also tested for radioactivity. The minerals in granitic rocks in the Alaska Highway belt mineralization consists of silver-bearing quartz veins indicates that these rocks should not be considered as in a fault zone. The country rock is chiefly medium- a possible commercial source of uranium or thorium. grained gray diorite and a dark basaltic-appearing If additional mineralogic study of the samples indicates rock that is probably igneous. The metallic minerals the presence of ra.dioacnve oxide minerals, the problem reported in the lode are sphalerite, pyrite, galena, and then arises as to whether such radioactive oxide min- tetrahedrite. The silver is probably associated chiefly erals occur as disseminated accessory minerals in with the tetrahedrite and galena. Tests on materials the granitic rocks or are limited to a particular facies from the Silver Creek lode indicate that the radioac- of the gra.nite, or occur in vein systems cutting the tivity is less than 0.001 percent equivalent uranium. granitic rocks. An unconcentrated crushed sample of the country rock Outcrop test

Concentrated sample

Outcrop test, unconcentrated sample, and concentrated sample

EXPLANATION

TO N4BESNA

rocks of various ages

Undifferentiated volconic rocks and basic intrusive rocks of vorious ages

Geology modified from U.S. Geological Survey Bulletin 904; minor unconsolidated deposits excluded

I I Base from U. 5. Geological Survey Field work by Helrnuth Wedow, Jr., and J.J. Alasko Map 48 Matzko, August-September 1946

Figure 9. -Geologic sketch map of the highway area between Slana and Tok Junction, Alaska. nea.r the lode (station TC lZc), however, shows on Ober Creek ranges from 0.003 to 0.011 percent and 0.005 percent equivalent uranium, but the bromoform a.verages about 0.006 percent. The radioactivity is appar- concentrate from this sample has only 0.001 percent ently due to the presence of small quantities of monazite equivalent uranium. in the concentrates. Tourmaline, zircon, fluorite, and epidote also occur in the Ober Creekconcentrates.

Donnelly Dome-Paxson area CONCLUSION The Donnelly Dome-Paxson area, as considered Some granitic rocks and placer concentrates in this report, is a, narrow strip along the Richardson tested in a.reas adjacent to highwa.ys in the Tanana and Highway about 70 miles in length between Donnelly upper Copper River valleys are moderately radioactive Dome on the north and Paxson on the south (figs. 1 and and thus may be of significance in the search for com- 10). It is drained by the Delta River and its tributaries mercial deposits of radioactive elements in these areas except at the most southerly end where it lies in the Bla.ck shale, carbonaceous or graphitic schist, and watershed of the Gulkana River, a tributary of the mineralized vein deposits tested in this reconnaissa.nce Copper River. In 1946, roadhouses were located at exhibited only traces of ra.dioa.ctive material. Rapids and Paxson. The most significant resultsfor the materia.1 tested are summarized below. Geology e of percent equivalent

The geology of the Donnelly Dome-Paxson area Type of material sad area has been described in reports of broader regional scope (Moffit, 1912, 1942). The northern part of the area is underlain by schists and gneisses of pre- Granitic rocka : Paleozoic or early Paleozoic age, which in part may Fairbank6 district----- C0.001-0.003 be equivalent to the pre-Cambrian Birch Creek schist Upper Chatenika valley of the Yukon-Tanana region to the north. The southern -e&-----"----"------.~l-.005 part of the area, although covered to a considerable Livengood wea------5.001- .005 H&rding Lake-Richardson degree by unconsolidated glacial and glacio-fluviatile ,006 deposits, is underlain by Carboniferous sedimentary we&------..."-- ,w- Maaka Highway belt---- .001- .005 rocks and lavas. Granitic rocks, considered to be Highway area between pre-Tertiary in age, intrude the schists in the north- Slaaa and Tok east corner of the area. Jurassic(?) intrusives of Jmction------.Go1 dioritic affinities are associated with the Carboniferous DOM~U~Dame-boa rocks'in the southern part of the area. In the vicinity &-a&-;-"-----"------of Donnelly Dome and Jarvis Creek, Tertiary coal- bearing sediments unconformably overlie portions of Mafic rocks : Fairbkaks district----- the metamorphic basement, and are covered with a Upper Cbataaika valley thin veneer of glacial debris. &Fea------Livengood area------Prospecting for placer gold in the Donnelly Dome- Harding Lake- Paxson area has been carried on intermittently since Richardson area------about 1900. The most promising streams are Jarvis, Alaska Highway belt---- Ober, and Macomber Creeks, although gravels of Highway esea between Slana and Tok several other streams also contain placer gold. Mining Junction------activity in 1946 was limited to prospecting of claims Donnelly Dome-Paxaon on Ober Creek by Charles DeWitt, and to operations by the Yukon Corporation on the east bank of the Delta River about a quarter of a mile downstream from the Mineralized veiae and mouth of Phelon Creek (fig. 10). vein mterials: Fairbatllrs district----- Upper Chatanika valley ma------m------Radioactivity studies Livengood area------Halding I&@- As only a few days remained toward the close of Richardson area------the 1946 field season for the investigation of the Alaska Highway belt---- Donnelly Dome-Paxson area, the work in that area Highway area between Slana and. Tok consisted only of panning concentrates from various J~tion------stream gravels. No concentrates had been available Donnelly Dane-Pexaon for study before the 1946 field season. The stations ma------"------at which the concentra.tes were obtained are plotted on figure 10, and the data are included in table 1. Schist, quurtaitic and micaceous varieties: The equivalent-uranium content of 12 bromoform Fairbauk~district----- Upper Chatanib valley concentrates (stations RH 1-12) from stream gravels wea------south of Donnelly (fig. 10) ranges from ~0.001to Livengood area------0.004 percent and averages about 0.002 percent. &ding Lake- The equivalent-uranium content of four concentrates Richardson area------(stationsRH 13-15) obtainedfrom prospecting operations Alaska Highway belt---- Diorltlc(?) intrusives

Arnygdaloidal lava

Metomorphosed sediments ond associated lntruslve rocks ,

Schists and gnelssas

Geology generalized from U. S. Geological Survey Bulletins 498 and 926-8, unconsolidated deposits excluded

Concentrated sample; number Indicates station prefixed "RH" in table I

Figure 10. -Geologic sketch ma.p of the Donnelly Dome-Paxson area, Richardson Highway, Alaska. 19 Capps, S. R., 1940, Geology of the Alaska Railroad region: U. S. Geol. Survey Bull. 907. Chapin, Theodore, 1914, Lode mining near Fairbanks [Alaska]: U. S. Geol Survey Bull. 592-J, p. 321-355. Ellsworth, C. E. , 1910, Placer mining in the Yukon- Tanana region [Alaska] : U. $. Geol. Survey Bull. 442-F, p. 230-245. Bill, J. M., 1933, Lode deposits of the Fairbanks district, Alaska: U. S. Geol. Survey Bull. 849-B, Donnelly Dome-Paxaon p. 29-163. Kidd, D. F., and Haycock, M. H., 1935, Mineralogy of the ores of Great Bear Lake: Geol. Soc. America Schlst, graphitic: Bull., v. 46, no. 6, p. 879-960. Faisbank6 district---- Mertie, J. B., Jr., 1917, The gold placers of the Upper Chtmika valley Tolovana district [Alaska] : U. S. Geol. Survey mea------Bull. 662-D, p. 221-277. Livengood area------&ding Lake- 1937, The Yukon-Tanana region, Alaska: U. S. Geol. Survey Bull. 872. Alaska Highway belt--- Moffit, F. H., 1912, Headwater regions of the Gulkana Highway area between and Susitna. Rivers, Alaska, with accounts of the slma and Tok Valdez Creek and Chistochina placer districts: U. S. Geol. Survey Bull. 498. Darnel& Dome-PBxson 1938, Geology of the Slam-Tok district, Alaska: U. S. Geol. Survey Bull. 904. Bhck shale: 1942, Geology of the Gerstle River district, Alaska: U. S. Geol. Survey Bull. 926-B, p. 107-160. Moxham, R. M.,and West, W. E., 1953, Radioactivity investigations in the Serpentine-Kougarok area, Seward Peninsula, Alaska, 1946: U. S. Geol. Survey Richardlaon area----- Alaska Highway belt--- Circ. 265. Highway area between Overbeck, R. M., 1920, Placer mining in the Tolovana Slana ana Tok district [Alaska] : U. S. Geol. Survey Bull. 712-F, Junction--..------p. 177-184. Donuelly Dome-Paxson Prindle, L. M.,1905, The gold placers of the Forty- area------mile, Birch Creek, and Fairbanks regions, Alaska: U. S. Geol. Survey Bull. 251. Stream and bench gravels, and slope wash: 1908, he Fairbanks and Rampart qmd- Fairbanks district---- rangle, Yukon-Tanana region, Alaska,: U. S. Geol. Upper Chutanilra, valley ~urvevBull. 337. Wea------1910, Sketch of the geology of the north- Livengod area------eastern part of the Fairbanks quadrangle [Alaska] Harding I&e- U. S. Geol. Survey Bull. 442-F, p. 203-209. 1910a., Auriferous quartz veins in the Highway area between Fairbanks district [Alaska] : U. S. Geol. Survey Slana and Tok Bull. 442-F. p. 210-229. Jmctioa------1913, A geologic reconnaissa.nce of the Donnelly Dome-Paxson Fairbanks quadrangle, Alaska, with a deta.iled de- scri~tionof the Fairbanks district., bv" L. M. Prindle and F. J. Katz, and an account of lode mining near -LITERATURE CITED Fairbanks, by P. S. Smith: U. S. Geol. Survey Bull. 525. Bastin, E. S., and Hill, J. M., 1917, Economic 1913a, A geologic reconnaissance of the geology of Gilpin County and adjacent parts of Clear Circle quadrangle, Alaska: U. S. Geol. Survey Creek and Boulder counties, Colora.do: U. S. Geol. Bull. 538. Survey Prof. Paper 94. White, M. G., and Killeen, P. L., 1953, Recon- Brooks, A. H., 1916, Preliminary report on the naissance for radioactive deposits in the lower Tolovana district [Alaska] : U. S. Geol. Survey Yukon-Kuskokwirn Highlands,region, Alaska, 1947: Bull. 642-G, p. 201-209. U. S. Geol. Survey Circ. 255. Table 1.-Data on radioactivity tests in areas adjacent to highways in the Tanana and upper Copper River valleys, Alaska [~bbre~iarionsin subheadings under 'Percent equiralem uranium" indicate the followirrg: OT, outcrop tea; UCS, m-e-ed crushed sample; BCG, bromofoan coocemrare frmn crushed sample; BC-PC, parmed concentrate horn 50- to 100-pmd samples of gravel or disimegrated rock material s&sequenrly ~coa-ted with hrmdm; dso iocIrdes stnice Eomearmtcs obtained horn placer-mine 0pZmtots.l

Sample Percent equivalent uranium Concen- Test file station tration Description and location no. OT UCS BC-CS BC-PC ratio

Pedro Dome area (fig. 3)

------Weathered quartz diorite; on road to summit of Pedro Dome. ------Weathered quartz diorite; 200 feet south of PD 1. ------Weathered quartz diorite; 300 feet south of PD 1. ------Weathered quartz diot-ite; 500 feet south of PD 1. ------Yeathewd quartz diorite; 700 feet south of PD 1. ------Weathered quartz diorite; 800 feet south of PD 1. 0.002 570:l Weathered quartz diorite; 900 feet south of PD 1. ------Weathered quartz diorite; 1,000 feet south of PD 1. ------Weathered quartz diorite; 1,100 feet south of PD 1. ------Weathered quartz diorite; 1,200 feet south of PD 1. ------Weathered quartz diorite; 1,300 feet south of PD 1. ------Quartz diorite talus; on road to swmit of Pedro Dome, 1,400 feet south of PD 1. --- 4: 1 Do. ------Do. ------Quartzitic schist; in stripped area about 0.6 mile northeast of Pedro Dome. ------Do. ------Weathered quartz vein; in series of old prospect pits about 1 mile northeast of Pedro Dome. ------Do. ------Weathered schist; same locality as PD 17. ------Weathered quartz vein; same locality as PD 17. ------Weathered quartzitic schist; sams locality as FD 15. ------Do. ------Weathered micaceous schist; same locality as PD 15. ------Weathered pl-qllite; same locality as PD 15. ------Weathered schist, same locality as PD 15. ------Do. ------Weathered schist, same locality as PD 17. ------Do. ------Do. ------Weathered quartz vein and schist; in old prospect pits west of road about 1.5 miles northeast of Pedro Dome. ------Do. --- 4:l Thin bed of graphitic schist; in stripped area along east side of road about 1.5 miles northeast of Pedro Dome. ------Do. ------Fractured quartz vein; same locality as PD 32.

I I See footnotes at the end of rhe table. Table 1.-Data on radioactivity tests in areas adjacent to highways in the Tanana and upper Copper River valleys, Alaska-Continued I I I I Tes Sample Concen- ti file Percent equivalent uranium station tration Description and location no. OT UCS BC-CS BC -PC ratio

Pedro Dome ~ma-Continued

------Graphitic schist; sanne locality as PD 32. ------Iron-stained quartz vein; Boyle1s prospect near junction of Fair- banks Creek road and Steese Highway. ------Do. ------Msintegrated rock on mine dump; same locality as PD 36. ------Weathered schist; in road cut on Steese Highway in Skoogy Gufch. ------Do. --- 3S:l Vein material on mine dump; Eagan scheelite mine on Twin Creek. ------Iron-stained Schist; in old prospect pit along Steese Highvay near mouth of Tuin Creek. ------Weathered quartz and schist on mine dump; at old prospect shaft on ridge betveen Fox Creek and Seattle Pup about 0 -85 mile east of road. ------Do. ------Do. ------Do. .00: 1,150:l Slop wash(?); in bull-dozer trench 0.6 mile east of station PD 43. ------Do. ------Weathered quartz vein and schist on mine dump; at old prospect shdt near station PD 46. ------Do. ------Slope wash; in trench about 300 feet east of station PD 46. ------Do. ------Weathered quartz vein and schist on mine dump; at old prospect shafts 0.7 mile east of station PD 43. .oOz 1,200: 1 Do. ------Do. ------Same as PD 53, but 0.3 mile farther east. .OO= 1,530:l Do. ------Same as PD 53, but 0 -45 mile farther east. ------Do. ' ------Do. ,001 n0:l Angular gravel from test pit; Seattle Pup. .WE 270: 1 Weathered rock on mine dump; at prospect shaft on divide between Seattle Pup and Moose Creek. --- 10:l Sulphi@-enriched limestone; at station PD 62. --- 2: 1 Do. .OO3 700:l Angular gravel from test pit; on south tributary of Last Chance Creek. ------Msintegrated rock on mine dump; on ridp;e between Engineer and Steele Creeks. ------Do. Do. Do. Do. 1 Diaintspated ~alron mine (Imp; on ridge between Engineer end Steele Creeks. Do. I Do. Slope brash from test pit; on ridge between Engineer and Steele Creeks. Do. Tungsten vein in drift; Gilmore Ikme. Bedrock In same drift; Gilmore Dome. Tungsten vein in second drift; Gilmore Dome. Tungsten vein 500 feet fmmouth of third drift; Gilmore Dome. Rock on dump of third drlft; Gilmore Dome. Maflc rock In dump of shaft at sunmit; Gilmore Dome. Tungsten vein in opencut near sat; Gilmore Dome. Do. Do. MaPic rock In dump of shaft at surmnlt; Gilmore Donre. Do. Tungsten veln in first drift; Gilmore Dame. Bedrock In f lrst drift; Gi1mol.e Dome. Tungsten vein in second drFft; Gilmore Dome. Bedrock in second drift; Gilmore Dome. Mafic rock in dump of shaft at summit; Gilmore Dome. Angular gravel from test pLt; north tributary of IsabePla Creek. Do. Stream gravel from test pits; Gilmore Creek. Do. Angular gravel P~omtest pit; north tributarg of Victoria Creek. Do. Do. Stream gravel (slope wash?) from several closely spaced gullies; Monte CrLsto Creek. Do. Stream gravel from test pit; east fork of Tom Creek. Stream gravel from &st pit; vest fork of Fish Creek. Stream gravel Prom test pit; Deadwood Creek. Angular @;cave1 from test pit; east headwater tributary of Engineer Creek. Angular gravel Pram test pit; west headwater tributary of Moose Creek. Angular gravel from test pit; middle fork of northwest tributary of Columbia Creek.. Angular gravel Prom test pit; Columbia Creek. Angular gravel from test pit; Engineer Creek. Stream gravel fmtest pit; Rex Creek. Angular gravel from test pit; middle fork of Steele Creek. Stream gravel; Willow Creek. Angular gravel in placer cut; Wolf Creek. Stream gravel; Chatham Creek. bornores at the end of the rable. 1. -'Data on radioactivitv tests in areas adjacent to hi&wam in the Tanana and umer Copper River valleys, Alaska-Continued

Sample Concen- Percent equivalent uranium Test file tration Description and location station no. OT UCS BC-CS BC-PC ratio Pedro Dame area-Continued

PD 112 1417 <0.001 ------(0 .001 120:1 Angular gravel; Bellows Creek. 113 1418 .001 ------.001 330: 1 Angular gravel; Solo Creek. 114 1419 .001 ------.001 540: 1 Angular gravel; south tributary of Fairbanks Creek. 115 1420 <. 001 ------c.001 1.770: 1 Angular gravel fram cut in stream bank; vest tributary of Fox C~ek. 116 14-21 ,001 ------005 1,510:l Angular gravel from test pit; Big Eldorado Creek. 117 , 1422 c.001 ------c. 001 830: f Angular gravel from test pit; northwest tributary of Big Eldorado Creek.

Ester Dome area (fig. 4) - - 19:l Massive quartz vein in drift; Michley mine on Sheep Creek. --- Shear zone in scbist; Mlchley mine on Sheep Creek. 48:1 Uneralized part of quartz vein; Michley mine on Sheep Creek. 390: 1 Stream gravel; Sheep Creek below Michleg mine. 28: 1 Rock material from mine dump; Bondholder mine. --- Rock mate~3.don mine dump; ~ohawk(?)mine. 400:l Stream gravel; St. Patrick Creek. 810: 1 Stream gravel from test pit; Ready ~ullionCreek. --- Rock material on mine dump; ~armer(?)mine at head of Ready Bullion Creek. --- Do. 19: 1 Do. 24: 1 Do. 1,080: 1 Rock material on mine dump; Clipper mine on Eva Creek. --- m. --- Rock material on mine dump; drift below Clipper mine on Eva Creek. --- Do. 1,100:l Stream gravel fmm test pit; ~ooseGulch. --- Do. 1,240: 1 Stream gravel From test pit; Eva Creek below Clipper mine. --- Mine dump; at prospect shaft on trail to sumlt of Ester be. --- Do. --- Weathered schist; trench near station ED 20. --- Do. --- Weathered antimony ore; trench near station ED 20. --- Mine dump; at inclined shaft about 0.2 mile southwest of s&t of Ester Donne. --- Do. --- Selected pieces of sulphide ore; sam location as station ED 25. --- (?) Vein material(?); Michley mine. I:: I:: --- / 8:1 Vein material(?); Eudson mine. --- / / --- 1) Vein material(?); SanfoH prospects. <..**PI 001 .mi 7: Vein material(?); Little Eva, mine. Steese Highway belt in upper Chatanita valley (fig. 5) (?I Stream gravel; McManus Creek about halfway between Montana and Idaho Crzeks. 100: 1 m. -- - Do. --- Do. --- Do. --- Stream gravel from prospect pit; Idaho Creek about 250 feet above highway bridge. --- no. go: 1 Do. --- Do. --- Stream gravel from prospect pit; Idaho Creek about 3,000 feet above highway bridge. 130: 1 DO. &7:1 Porphyritic biotite granite boulders and pebbles; same location as station UC 10. --- Schist boulders: same location as station UC 10. Stream gravel; Montana Creek about 25 feet above highway bridge. 120: 1 --- Stream gravel; Montana Creek about 0.5 mlle above himay bridge. 160: 1 Do, --- Stream gravel; North Fork of Twelvemile Creek (Circle district). --- Weathered igneous cobbles (granite?) ; North Fork of Twelvemile Greek (Circle district). --- Stream gravel; same location as station UC 19. 45: 1 Do. 90:l Stream gravel; Twelvemile Cree:< (Circle district) above mouth of North Fork. 110:l Bench gravel; Faith Creek, trench in northwest bank about 0.5 mile above mouth. --- Bench gravel; trench abqut 400 feet northeast of station UC 23. 280:1 Bench gravel; trench about 100 feet east of station UC 24. --- Do. --- %rich gravel; trench about 200 feet northeast of station UC 25. --- Stream gravel; Smith Creek about 0.25 mile above mouth. 380: r DO. --- Bench gravel; same location as station UC 28. 133: 1 Weathered gray-black micaceous schist (fault bmu@;e?) Steese High- way, Mile 70.2. --- Do. --- Do. --- Weathered quartz mica schist; Steese Highway, Mile 70.2. --- Do. --- Do. --- Stream gravel; Faith Creek about 5 miles above mouth.

See footnotes ar the end of rhe fable, Table 1,-Data on radioactivitv tests in areas adjacent to himam in the Tanana and upper Co~perRiver valleys. Mask%-Continued Sample Concen- Percent equivalent uranium Description and location OT 1 UCS 1 BC-CS 1 BC-PC I I I I I I I Steese Highway belt in upper Chatanita valley-Continued uc 38 ------0.001 (?) About 4 cubic foot sluice concentrates after removal of gold; Deep Creek; workings of Deep Creek Mining Co. 39 1440 0.001 ------.001 95: 1 Stream pavel; Cripple Creek about 50 feet above hlghway bridge. 40 1441 .001 ------.002 350: 1 Bench gravel; Flat Creek. 41 1442 .001 ------.002 190: 1 Stream gravel; Belle Creek about 100 feet above highway bridge. 42 l54Z ,003 0.004 C0.001 --- (?) Weathered graphitic schist; Steese Highway, Mile 64.3. 43 ---- c.001 ------Weathered gray schist; Steese IIIghuay, file 64.3. 44 ---- .001 ------Graphitic schist; Steese Highwar, Mile 64.3. 45 1443 ------.012 (?) Dredge concentrate; Deadwood Mining Co. mining operations on Name Creek.

Livengood area (Pig. 6)

L la 1555L 0.001 --- =O .001 --- 1.4: 1 Mineralized zone in altered limestone; prospect shaft on Money Knob. lb ---- < .001 ------Do. 2 ---- c .001 ------Iron-stdned chert; prospect shaft on Money Knob. 3a ---- .001 ------Altered shale; Livengood Ridge. 3b 1543L .003 0.005 -003 --- 1&': 1Weathered granite float; Livengood Ridge. 4 ---- .001 ------Black shale; Livengood Ridge. 5 ---- C. 001 ------Black siliceous rock; vest spur of Amy Dome. 6 ---- c.001 ------Skar zone in basic volcanic rocks; vest spur of Amy Dome. 7 ---- c. 001 ------Basic voloanic mks; uest spur of Amy Dome. 8 ---- e. 001 ------Coarse-grained diorite; Amy Dome. ga ---- e. 001 ------Diorite; Amy Dome. gb ---- <. 001 ------Weathered diorite; Amy Dome. 10 ---- .001 ------Black shale; Mvengood mad at Olive Creek. 11 1447 ------c.001 1,500:lStreamgravel; McCordCmeknearmouth. 12 1448 .001 ------c.001 1,300: 1 Bench gravel on bedroclr; low bench of Tolovana River downstream froan mouth of McCord Creek. u ---- .001 ------Fisslle black shale containing thin beds of gray sandstone; Livengood road just north of Tolovana River. 14 1449 e.001 ------c. 001 250:l Stream gravel fkm test pit; small unnamed tributary of Tolovana River on south side of' Amy Dwte, 2.1 miles east of Ester Creek. 15 1450 ------e.001 57O:l Stream gravel; Ester Creek near bridge over Livengood road. 16a 1553L .002 ,002 .006 --- 152: 1 Black shale; Livengood road near Clearg Creek. 16b ---- .oo1 ------Do. 16~ ---- .OO1 ------Conglomerate lens in black shale; Livengood road near Cleary Creek. 17a ---- ,001 ------Black shale; Livengmd mad about 1.2 miles east of Ester Creek. 1p ---- .DO1 ------Do. 18a 1452 ------.003 (?) Sluice concentrate; Parkerst claims on Olive Creek. 1811 1453 ------.OOl (?) Sluice concentrate after retorting; Parkersl claims on Olive Creek. 19 1454 ------.004 1,800:1 Stream gravel on bedrock; Jurichfs claim on Lillian Creek. 20 1455 ------<.OOl (?) Sluice concentrate; Mell's cut on Amy Creek. 21 1456 ------c. 001 8,790: 1 Bench(?) gravel; fran gravel pit on divide between Livengod and Hess Creeks. 22 1544L .001 c.001 .001 --- 17:l Weathered chert; south slope of Livengood Dome. 23 ---- <. 001 ------Do. Tba 1457A ------.002 (?) Gravel from drift dump pile; drift on Goodluck Creek. 24b lk57B ------.002 200:l Tdlings; drift on Goodluck Greek. 25a ---- c.001 ------Mineralized vein in altered limestone; north slope of Money Knob. 29, ---- c. 001 ------Do. 26 ---- e. 001 ------Rock material on mine dump; from drift on vein at same location as station L 25. 27 1446~ ------.OlO (?) Coarse Praction of sluice concentrate; Radakls cut on Ruth Creek. 1446~ ------*.009 (?) Fine fraction of sluice concentrate; Radakls cut on Ruth Creek. 28 1451 ------003 (?) Sluice concentrate; Benn Falls' workings on Wilbur Creek. Harding L&e-Richardson area (fig. 7)

R la 1459L 0.006 0.004 --- 0.009 1,910: 1 Weathered granite; south shore of Birch Lake on south side of Richardson Highway. lb ---- .004 ------Do. IC ---- -004 ------Fine-grained granitic dike; same location as station R la. 2a ---- ,004 ------Porphyritic granite; about 1 mile east of station R 1 on south side of Richardson Highway. 2b ---- .002 ------Mafic inclusion in granite; same location as station R 28. 2c ---- .004 ------Peeplatitic Wse of granite; same location as station R 2a. 2d ---- .005 ------Fine-grained phase of granite; same location as station R 2a.

N 3 ---- ,003 ------Weathered granite; about 500 feet east of station R 2 on north + side of Richardson Highwag. 4a ~GOAL .OO5 .002 0.060 --- 185:1 Fine-grained light-colored (granitic?) dike; same location as station R 3. 1460B~ ------.I10 (?) Do. 5a ---- .004 ------Same as station R 4a. 7a ---- .003 ------W. ---- ,004 ------Do, 98 ---- .004 ------Do. 5b ---- .OOj ------Weathered granite on northwest side of f ine-grained dike; same location as station R 3. ---- .003 ------Do. g, ---- .002 ------Do. 4c ---- .OO~ ------Weathered granite on southeast side of fine-grained dike; same location as station R 3. sc ---- .003 ------DO. 8~ ---- .002 ------Do. gc ---- .003 ------DO. 6 ---- -003 ------Mafic zone along side of dike; sane location as station R 3. 1Oa 1461 .001 ------.001 450: 1Bench(?) gravel of Tanana River; south side of Richardson Highway, Mile 309.4. 10b ---- <. 001 ------Do. lla ---- .003 ------Weathered porphyritic granite; south sfde of Richardson Highway, Mile 310.7. --- Do. --- IWio inclusion In grsniti; same location as station lla.

See fwmotes at the end of rhe table. Table 1. -Data on radioactivity tests in areas adjacent to highways in the Tanana and upper Copper River valleys, Alaska-Continued

Sample Goncen- Test file Percent equivalent uranium tration Description and location station OT I UCS ( x-CS I BC-PC ratio Harding Lake -Richardson area-Con tinued - 430:l Stream gravel; left bank of Salcha River about 30feet above highway bridge. --- Weathered granite; east shore of Birch Lake on north side of Richardson Highuay. --- m. --- Fine-grained light-colored (granitic?) dike; same location as station R Ua. --- Do. 65:1 Goarse-grained granitic dike; Richardson Highway, Mile 313.9. --- Do. --- Fine-grained border zone of panitic dike; same location as station R 14a. --- Quartz mica schist adjacent to granitic dike; saw location as station R 14a. --- Granitic dike; Richardson Highway, Mile 314.5. --- Yellow-stained zone in schist adjacent to fractured quartz vein; Richardson Highwag, Mile 314.7. --- Weathered igneous (granitic?) dike in schist; Richadson High- way, Mile 314.8. --- Fine-grained mafic dike in schlst; Richardson Highway, ~ile.314.85. --- Weathered granite; Richardson Highway, Mile 304.65. --- Iron-stained quartz vein in granite; Richardson Highway, Mile 304.65. --- Do. --- Altered limestone containing streaks of graphitic schist and a few thin quartz veins; Richardson Highway, Mile 302.65. --- Dark-colored dune sand; Richardson Righway, Mile 301 -75. 950: 1 Stream gravel; unnamed tributa~gof Tanana River at Mile 299.8, Richardson Highuay. &0:1 Bench gravel; Banner Creek about 100 feet above hiwag bridge. 1,590:l Gravel from old drift dump; near mouth of Buckeye Creek. 1,180: 1 Bench gravel on bedrwk; Tanana River at Mile 296.9, Richardson I ma^. 3:l Graphitic schist; same location as station R 25a. 590:l Gravel from old drift dumps; Tenderfoot Creek at Mile 293.7, Richardson Highway. 790:l Gravel ?ran bottom of 100 foot shaft; claim 13 at Mile 292.1, I Richardson Highway. Alaska Fiighway belt (fig. 8) 1469 0.002 Bench gravel; Berm Creek about 300 feet above highway bridge. AH la --- lb 1558~ Coarse-grained granite in bank of creek; same location as station AH la. AH lc ------Stream gravel; same location as station AH la. ld ------Bench gravel; same location as station AH la. 2 1470 790: 1 Stream gravel; Berry Creek about 0.25 mile above highway bridge. 3 1471 1,630: 1 Stream gravel; Sears Creek about 0.25 mile above highway bridge. 4 1472 1,010: 1 Stream gravel; Dry Creek about 250 feet above -way bridge. 5 i4n 670:1 Stream gravel; Uttle Gerstle River about 300 feet above Mghway bridge. 6 1474 560: 1 Glacial gravel; Alaska Highway, Mile 1,387, near mouth of Johnson River. 7 ------Granite; Alaska Highway, Mile 1,368.9. 8 155% 8:1 Granite; Alaska Highway, Mile 1,368.7. 9 1475 520:l Stream gravel; Chief Creek about 75 feet above hfghway bridge. 10a ------Granite, urnearnred; Alaska Highway, Mile 1,359.3. lob ------Granite, weathered; Alaska Highway, Mile 1,359.3. 11 1476 280: 1 Stream gravel; unnamed tributary of Tanana River at Mile 1,350, Alaska Highway. 12 1477 30: 1 Stream gravel; flood channel of unnamed tributarg of Tanana River at Mile l,B5, Alaska Highway. 400: 1 Stream gravel; main channel of same creek as at station AH 12, crosses Alaska Highway at Mile 1,344.6. 260: 1 Stream gravel; Yerrick Creek about 100 feet above highway bridge. --- Granite (slope wash?); in road-metal quarry about 0.5 mile east of intersection of old road with Alaska Highway near Mile 1,335. 180: 1 DO. --- Weathered gneiss; Alaska Highway, Mile 1,292.1. --- Crushed zone (gouge?) in weathered gneiss; Alaska Highway, Mile 1,292.1. 2,200: 1 Weathered granite; Alaska Highway, Mile 1,292.8. --- Do. --- Do. - -- Mafic (basalt?) dike in weathered granite; Alaska Highway, Mile 1,292.9. --- Wsathered &ic (basalt?) rock along fracture in weathered granite; Alaska Highway, Mile 1,293 .O. --- Yellow-brown rock in fracture zone in weathered granite; 25 feet west of location of station AH lga. 130: 1 Dark-colored wind-blown silt(?) , Alaska KiIi@;Irway, Mile 1,299.7. --- Weathered granite; Alaska Highway, Mile 1,304.0. --- Iron-stained fracture zone in weathered granite; Alaska Eighway, Mile 1,304.0. --- Cemented breccia zone in weathered granite; Alas& Eighway, Mile 1,304.2. 20:l Mafic dike in weathered granite; Alaska Klglway, Mile 1,304.4. --- Brown-black stained zone in weathered granite; Alaska Highway, Mile 1,308.5. --- Weathered granite; Alaska Highway, Mile 1,290.0. 236: 1 Light -colored f elsitic dike; Alaska Highway, Mile 1,290.0. --- Mafic dike; Alaska Hi&way, Mile 1,290.0. --- Weathered granite; Alaska.Highway, Mile 1,290.0. 2,700: 1 Weathered granite; Alaska Highway, Mile 1,286.9. --- Weathered fine-grainedgranite (dike?); Alaska HYghway, Mile 1,283.8. See foornores at the r:nd of the table.

6 1496 c.001 ------.001 170: 1 Pan gravel from test pit; unnamed tributary of Little Tok River about 1 mile belou Trail Creek, about 100 feet above highway bridge. 7 1497 ------.002 5w:l Pan gravel in cut bank of stream; unnamed tributary of Little Tok River about 4 miles below Trail Creek, above highway bridge. 8 1498 ------002 590:l Pan gravel in cut bank of stream; unnamed tributary of Little Tok River about 5.5 miles below Trail Creek, above M@way brldge. 9 1499 ------.OO~ 350: 1 Pan gravel In cut bank of stream; unnamed tributary of Tok River about 5.5 miles northeast of location of station TC 8.. 10 1500 ------e.001 23O:l Glaclto-f.luvial gravel; in road cut, Tok River valley, at mouth of Little Tok River. 11 1501 ------.003 670~1Stream gravel; unnamed tributary of Tok River about 5.5 miles below Little Tok River. 12a ---- .001 ------Weathered rock on mine dump; Silver Creek about 0.5 mile above tractor trail. 12b 1503 C.001 ------<. 001 140:l Angular gravel (slope wash?) on low bench; same location as station lT 12a. l2c 1$2L c. 001 .OO~ .001 --- 3:1 Weathered bedmcb; same location as station W 12a. 12d 1561~ .001 *. 001 <. 001 --- 19:l Sulphide-rich quartz vein; same location as station l!C 12a. 12e 1502 ------e.001 135:l Stream gravel; same locatfon as station TC l2a. 13 1504 ------<. 001 65: 1 Pan gravel from cut bank; first right limit tributary of "Indian Pass1' Creek. 14 1505 ------e.001 140: 1 Pan gravel; third left 1Mt tributary of "Indian pass1' Creek. 15 1506 ------e.001 8,5~:1 Pan gravel from test pit; first left limit tributarg of o "Indian Pass" Creek. w 16 ---- -001 ------Weamred diorite(?) ; Tok cutoff road near Mile 12. 17 1507 ------r.001 200: 1 Bench @;ravel on bedrock; second right limit tributary of Slana River above Porcupine Creek. la 1508 ------.001 (?) Sluice concentrate; upper workings on Grubstah Creek. 19 1552.A ------<.(I01 (?) Sluice concentrate; Bronnichefs workings on Slope Creek. 1552B ------c.001 (?) Coarse fraction of sluice concentrate; Bmnnichels worldngs on Slope Creek.

Donnellg Dome-Paxson ama (fig. 10)

RH 1 1509 ------=0.001 1X):l Glacio-fluvial gravel; Gulkana River about 1 mile below toe of glacier. 2 1510 ------<. 001 400: 1 Pan gravel; right lMt tributary of Phelan Creek about 4.5 miles above mouth of Phelan Cree&. 3 1511 ------.001 25O:l Pan gravel; ri&t 1Mt tributary of Phelan Creek about 3.5 miles above mouth of Phelan Creek. 4 1512 ------c. 001 350: 1 Pan gravel; right limit tributary of Phelan Creek about 2 miles above mouth of Phelan Creek. 5 15x5 ------c.001 300:l Bench gravel; Delta River about 0.25 mile below mouth of Phelan Creek, Yukon Corp. workings. 6 1514 ------,003 480:l Stream gravel; right limit tributarg of Delta River about 2.25 miles blow Castner Creek. 7 1515 ------003 500:l Stream gravel; right lMt trlbutarg of Delta River about 3.25 miles below Castner Creek. 8 1516 ------.002 310:l Stream gravel; right 1Mt tributary of Delta River about I [ I 1 1 i [ 4.25 miles below Castner Creek. See footnotes at the end of the table. Table 1.-Data on radimctivitg tests in areas adjacent to highways in the Tanana and upper Copper River valleys, Alaska-Continued I ~~~t Percent equivalent uranium Concen - tration Description and location station no. CYP UCS BC-CS BC-PC ratio Donnelly Dome -Faxson area-Continued

0.002 360~1Stream gravel; right limit tributary of Delta River about 6.25 miles below Castner Creek. .003 410: 1 Stream gravel; Darling Creek about 0.25 mile above highwaJ bridge. -004 480: 1 Pan gravel in cut bank; Gunnysack Creek about 0.25 mile above highway bridge. .003 (?) Stremgrave1;ClearCreekbelowfallsnearhi~uay. ,004 430: 1 Stream gravel; Ober Creek valley of DeWittt s workings. ,007 (?) Concentrates Prom drill-hole panninga; Ober Creek valley, DeElittls workings. .003 ( ?) Stream gravel on bedrclck; Ober Creek valley, old Miller cut near mouth of Mineral Creek. 2 .011 (?) Panned concentrates obtained from operator; Ober Creek valley, old cut about 30 feet above location of station RH 14.

'Methylme iodide used insttad of bmmofam tot conceomtioa 0 PMirms &mesh fxactioo tested instead of minus 20-mesb haction. to CHAPTER B. -GRANT1 CREEK AREA

By P. L. Killeen and M. G. White

ABSTRACT and Eakin (1913, 1916). Maddren's two reports contain short accounts of the geology of the area gathered In August 1946 field search failed to locate a during brief investigations of the placer-mining ac- reported occurrence of float from pitchblende veins in tivities in the area. Eakin's two reports were based the Grant Creek area north of the Yukon River about on geological reconnaissance investigations on a re- 30 miles west of Tanana in eastern interior Alaska. gional scale in which the Grant Creek area is included. The late Walter Fisher, placer-gold miner on Grant No deta,ils, however, of the areal distribution, age, Creek, reported the occurrence to the Geological and structural relations of the individual rock types in Survey. It is believed that fragments of black hematite the Grant Creek area are known. were mistaken for pitchblende. The Grant Creek area is pa.rt of a br0a.d zone of metamorphosed rocks that are well developed oa the INTRODUCTION north side of the Yukon valley between the Koyukuk River and the Yukon Flats. The rocks are thought to Purpose and scope of investigation be early Paleozoic in age. A complex of intensely folded and metamorphosed schist, limestone, quartzite, In the fall of 1945 the late Walter Fisher, Alaskan and greenstone occurs within the area. placer-gold miner, reported to R. M. Chapman of the Geological Survey at Fairbanks an occurrence of pitch- Pebbles with quartz stringers occur in the placer blende veinlets in hillside float along a tractor trail cuts on Grant Creek. The quartz stringers in the bed- near his placer-mining property on Grant Creek in the rock are probably the source of some of the placer Yukon valley. During the winter of 1945-46 no cor- gold. Some pebbles of a medium-grained pegmatite respondence was exchanged with Mr. Fisher on the are also present in the gravels. subject of the pitchblende because of the security reg- ulations in effect at that time. A monzonite mass mapped by Eakin (1913, p. 16) at the head of Golden Creek (fig. 11) was not found. In August 1946 a Geological Survey field party The rock at that locality consists of mica schist and went to Grant Creek to investigate the reported pitch- greenstone. A granitic intrusion of unknown areal blende. The party consisted of P. L. Killeen and extent was found at the head of Melozimoran Creek. M. G. White, geologists, and R. D. Hamilton, camphand. When the party arrived at Grant Creek, it was learned of Mr. Fisher's death earlier in the summer. The RADIOACTIVITY Fisher mine was closed, and none of the residents in the area had any information about the reported deposits. The principal objective of the investigation in Thus, no direct information was available as to the the Grant Creek area was the examination of an area location of the pitchblende, and a search was made of adjacent to a tractor trail along which the late Walter the area to determine whether the report had any Fisher had reported finding float frorrr a pitchblende- significance. bearing vein. When the search along this trail failed to reveal any deposits of radioactive materials, the investigation was extended to other trails and inter- Location of area vening areas. All possible materials representative of the bedrock in the area (outcrops, talus, and frag- Grant Creek enters the Yukon River from the ments selected from the soil mantle) were tested, 'north about 30 miles west from Tanana in central particularly at places where there were traces of Alaska. (fig. 11). The area is accessible from Tanana mineralization. Cnly a few concentrates of the heavy by boat. In a.ddition to Grant Creek the following other minerals in the stream gravels were collected for areas were examined during this investigation: the testing (table 2). The radioactivity tests in the Grant headwaters of Tozimoran Creek, a tributary of the Creek area were made with a portable survey meter Tozitna River which enters the Yukon River about designed by the Geological Survey. The background midway between Grant Creek and Tanana; and the for this meter in this area averaged 8 to 10 counts headwaters of Melozimoran Creek, a tributary of the per minute. Melozitna River which enters the Yukon River in the vicinity of Ruby about 100 miles west of Tanana. Locations of tests

GEOLOGY The main tractor trail in the Grant Creek area extends from the YukonRiver to Fisher's camp on upper The geology of the Grant Creek area was discussed Grant Creek, a distance of about 4 miles (fig. 11). briefly by Maddren (1909, p. 234-237; 1910, p. 80-83) The southern portion of this trail has been shifted Moran DomeH

3 Mllcs I I I

Dro~noge.trom topogrophlc mop by E Mundtne, 1941

Figure 11. -Dra.inage map of the Grant Creek area, Yukon region, Alaska. 34 Table 2.-Data on placer concentrates from Grant and Tozimorran creeks, Alaska I I I Equivalent *laskanuranium content Concentration Concentrate of concentrate ratio Location no* (prceat)

Grant Creek

733 0.005 (?) Fisher's placer cut, 1942. U60 .008 8,110: 1 Fisher' s placer cut, 1946. 1361 ,008 5,125: X Monday Creek, at footbridge about 60 feet above mouth, in Grant Creek valley. 1362 .005 1,790:l Monday Creek, at tractor-trail crossing just above edge of Grant Creek valley. U63 ,007 11,350:l Southern of two gulches on east side of Grant Creek, opposite Fisher's camp below Monday Creek. 445 - - - (?) Berton claim of the Tozi or Gold Hill district; probably from former prospects of Berton Anicish of Lynx Creek. 'Cozlmoran Creek Tozimoran Creek, between its tributaries, chicken and Ash creeks. Do. DO. Do. Do. Do. Do. Do. DO. Da. successively uphill as the lower route became boggy. area. In table 2 are listed the available data on samples Traces of the older, abandoned parts of the trail still from Tozimoran Creek. remain. A less distinct tractor trail runs via Lynx Creek and Windy Creek to some prospect pits. A third An attempt was made to examine the granitic in- and more prominent trail, cleared by ax and bulldozer trusion on Melozimoran Creek, but a heavy snowfall for a railroad survey, follows the north bank of the restricted the examination to a few tests with the Yukon River eastward from the mouth bf Grant Creek. portable survey meter. The radioactivity of the in- It was included in the investigation because many of trusion averaged 20 counts per minute as compared to Fisher's more recently staked claims were in that gen- an 8- to 10-count per minute average on the adjacent eral area. A few short old tractor trails were found metamorphic rocks. on the upper part of Grant Creek above Fidfier's mine; some lead to wood lots, others to drilling sites as far upstream as the mouth of Fox Gulch. Othen narrower CONCLUSION lines have been brushed out along many of the bound- aries of Fisher's claims. A prominent horse trail The investigations in the Grant Creek area extends from Fisher's camp to the head of Tozimoran disclosed no float rock corresponding to Fisher's Creek via Grant Dome. reported description of his pitchblende-bearing vein float material. The only material that appeared to All occurrences of bedrock albng the above trails fit his description was schist containing a few and in much of the intervening area were examined. narrow streaks of limonite, but this was found on Pieces of float were also tested, A portable survey the west side of Windy Creek near its headwaters meter was operated continuously over many parts of and a considerable distance from any tractor trail. the trails, and individual stations were selected arbi- It is improbable that this occurrence of limonite is trarily for taking 5-minute readings. No radioactive the float referred to by Fisher. Sufficient search material was indicated by these tests. was made of the hillsides to conclude that the pitchblende vein or veinlets as reported by Fisher A short time was spent investigating the area in probably do not exist. the vicinity of the headwaters of TozimoranCreek. At this locality galena veins occur on the south side of the Two fragments of a black platy mineral that were creek, and cassiterite is present in the gravels. The seen among the samples in Fisher's camp may have source of the cassiterite could not be located. No other been collected from hillside float rather than from evidence of important mineralization was found, and no his placer workings. If this is true, Fisher's "pitch- appreciable radioactivity was detected anywhere in the blende" is probably black hematite. LITERATURE CITED Maddren, A. G., lQO9, Placers of the Gold Hill district [~kska],in Brooks, A. H. , andothers, Mineral Eakin, H. M., 1913, A geologic reconnaissance of a resources of ~las,report on progress of investigation part of the Rampart quadrangle, Alaska: U. S. Geol. in 1908: U. S. Geol. Survey Bull. 379-13,p. 234-237. Survey Bull. 535. 1Qh0, The Innoko gold-placer district, 1916, The Yukon-Koyukuk region, Alaska: Alaska, with accounts of the central Kuskokwim ' U. S. Geol. Survey Bull. 632. Valley and the Ruby Creek and Gold Bill placers: U. S. Geol. Survey Bull. 410.