The Alaska Mineral Resource 

Assessment Program: Background 

Information to Accompany Folio of 

Geologic and Mineral Resource Maps 

of the Circle Quadrangle, Alaska 

The Alaska Mineral Resource 

Assessment Program: Background 

Information to Accompany Folio of 

Geologic and Mineral Resource Maps 

of the Circle Quadrangle, Alaska 

By H.l. Foster, W.O. Menzie, J.W. Cady, S.l. Simpson, 

J.N. Aleinikoff, F.H. Wilson, and R.B. Tripp 

U.S. GEOLOGICAL SURVEY CIRCULAR 986 

1987 
Department of the Interior 

DONALD PAUL HODEL, Secretary 

U.S. Geological Survey 

Dallas L. Peck, Director 

Library of Congress Cataloging-in-Publication Data 

The Alaska Mineral Resources Assessment Program: Background Information 

to Accompany Folio of Geologic and Mineral Resource Maps of the Circle 

Quadrangle, Alaska. 

U.S. Geological Survey Circular 986 

Bibliography: p. 14-22. 

Supt. of Docs. No.: I 19.4/2:986 

1. Geology-Alaska-Circle region. 2. Mines and mineral resources-AlaskaCircle region. 3. Alaska Mineral Resource Assessment Program. I. Foster, 

Helen Laura, 1919- . II. Series: U.S. Geological Survey 986 

QE84.C6A43 1987 557.98 86-600377 

Free on application to the Books and Open-File Reports Section, 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 
CONTENTS 

Page 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Purpose and scope . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Geography and access. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Mineral production and exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Geologic investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Previous investigations............................................... 4 

Present study........................................ . . . . . . . . . . . . . . . 5 

Isotopic age data from the Circle quadrangle............................ 5 

Status of land in the Circle quadrangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Description of component maps and related reports of the Circle 

quadrangle folio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Geology (OFR-83-170-A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Mineral resources (OFR-83-170-B)..................................... 9 

Aeromagnetic and gravity maps and their interpretation 

(OFR-83-170-C and 83-170-D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Interpretation of Landsat imagery (OFR-83-170-E)....................... 12 

Geochemistry and selected mineralogy (OFR-83-170-F, G, H) . . . . . . . . . . • . . 14 

References............................................................. 14 

ILLUSTRATIONS 

Page 

Figure 1. Index map of Alaska showing location of Circle 

quadrangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . 3 

2. Map of Circle quadrangle showing adjacent quadrangles, 

physiographic provinces, and major streams and 

geographic features........................................... 4 

3. Map showing location of areas of Circle quadrangle used in 

describing the geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

4. Concordia plot of U-Pb data from zircons from augen 

gneiss, Circle quadrangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . 8 

5. Concordia plot of U-Pb data of detrital zircons 

from Circle quadrangle . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . 8 

6. Map showing distribution of major government-held tracts 

in Circle quadrangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

7. Graph showing distribution of tonnage of greisen 

tin deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

8. Graph showing distribution of tin grade of greisen deposits............ 11 

9. Computer-enhanced Landsat image showing Circle quadrangle......... 13 

TABLES 

Table 1. Component maps of the Circle mineral resource assessment . . . . • . . . . . • 2 

2. Uranium-lead isotopic data from zircons, Circle quadrangle, 

Alaska....................................................... 6 

III 

The Alaska Mineral Resource Assessment Program: 

Background Information to Accompany Folio of 

Geologic and Mineral Resource Maps of the 

Circle Quadrangle, Alaska 

By H.l. Foster, W.O. Menzie, J.W. Cady, S.l. Simpson, 

J.N. Aleinikoff, F.H. Wilson, and R.B. Tripp 

ABSTRACT 

The geology, geochemistry, geophysics, and 

Landsat imagery of the Circle quadrangle were. 

investigated by an interdisciplinary research team 

for the purpose of assessing the mineral potential of 

the area. The quadrangle covers approximately 

15,765 km 2 in east-central Alaska; most of it is 

included in the mountainous Yukon-Tanana Upland 

physiographic division, but the northernmost part is 

in the low-lying Yukon Flats section. The Circle 

mining district, in the east-central part of the 

quadrangle, has been a major producing area of 

placer gold since its discovery in 1893. 

For descriptive purposes, the Circle 

quadrangle is divided into three areas: the 

northwest Circle quadrangle, the area north of the 

Tintina fault zone, and the area south of the Tintina 

fault zone. The Tintina fault zone extends 

northwesterly through the northern part of the 

quadrangle. The northwest Circle quadrangle 

contains mostly folded and faulted, slightly 

metamorphosed sedimentary rocks that are intruded 

by Tertiary granitic plutons. In the northern part of 

the area north of the Tintina fault zone (Little 

Crazy Mountains and northern east Crazy 

Mountains), the rocks consist primarily of the 

gabbro and basalt of the Circle Volcanics and minor 

associated chert, graywacke, and limestone. 

Elsewhere in this area (south of the Circle Volcanics 

and in the western Crazy Mountains), the rocks are 

mostly slightly metamorphosed Paleozoic 

sedimentary rocks that have been folded and 

faulted. Rocks in the largest part of the 

quadrangle, the area south of the Tintina fault zone, 

consist largely of pelitic rocks that are regionally 

metamorphosed to greenschist and amphibolite 

facies. Felsic plutons, mostly Tertiary in age, occur 

throughout the area. The metamorphic rocks are 

separated from sedimentary rocks on the northwest 

by thrust faulting. 

The aeromagnetic and gravity data show clear 

differences between the areas north and south of 

the Tintina fault zone. The metamorphic terrane to 

the south has low overall gravity and local gravity 

lows over exposed granitic plutons. It is 

hypothesized that magnetic chlorite schist infolded 

with nonmagnetic quartzite and schist account for 

east-northeast-trending magnetic highs that 

1 

approximately parallel the regional strike of the 

most prominent foliation in the metamorphic 

rocks. North of the Tintina fault zone, the Circle 

Volcanics are characterized by high gravity and 

east-west-trending magnetic highs. The Tintina 

fault zone has an intense magnetic high near the 

western margin of the Circle quadrangle overlying 

the magnetic granodiorite of the Victoria Mountain 

pluton. A magnetic high near Circle Hot Springs is 

less intense, but broader, and could reflect a buried 

magnetic pluton similar to that of the Victoria 

Mountain pluton. 

Computer-enhanced Landsat images of the 

Circle quadrangle show trends and patterns of 

concentrations of linear features. Features 

trending northeast-southwest predominate 

throughout the quadrangle; northwest-southeasttrending linear features are found mostly south of 

the Tintina fault zone. High concentrations of 

linear features were not found to correspond to 

areas of known mineralization in any consistent or 

significant way that could presently be used in 

locating areas of mineralization. 

Geochemical and mineralogical studies of 

stream sediment and heavy-mineral concentrates 

from the Circle quadrangle identify areas of 

anomalous concentrations of metallic elements, 

including gold, silver, tin, tungsten, lead, antimony, 

zinc, thorium, uranium, and beryllium. The data 

delineate areas of known mineral occurrences and 

areas that may contain undiscovered mineral 

resources. 

To date, placer gold has been the only 

significant metallic mineral resource from the 

Circle quadrangle, but the general geologic setting, 

especially the presence of post-orogenic plutons, is 

similar to that of regions that contain tin greisen 

deposits, tungsten skarn deposits, lode gold deposits 

in metasedimentary rocks, and uranium vein 

deposits. Six areas or tracts were identified in 

which such deposits might occur, and two more 

tracts were delineated as possible for the 

occurrence of shale-hosted lead-zinc deposits. The 

discovery of two diamonds in the gravels of Crooked 

Creek point to the slight possibility of finding 

placer or lode diamond deposits. 

Although most of the past and present gold 

mining has taken place in four areas in the 

quadrangle, a sedimentary basin near the town of 
Central was identified as possibly containing buried 

placer gold deposits or sedimentary uranium 

deposits. 

INTRODUCTION 

Purpose and Scope 

This circular, together with a separately 

available folio of open-file maps of the Circle 

quadrangle, is one of a series of U.S. Geological 

Survey reports intended to provide information for 

formulating a sound long-range national mineral 

policy to aid in Federal, State, and local land-use 

planning; to provide significant data for mineral 

explorations; and to increase geologic understanding 

of the area. The work was carried out under the 

Alaska Mineral Resource Assessment Program 

(AMRAP), authorized by Congress to begin on ,July 

1, 1974. 

The Circle quadrangle mineral resource 

assessment consists of this circular, geologic, 

geophysical, and geochemical maps, interpretation 

of Landsat imagery, and an analysis of the mineral 

endowment (table 1). Most of the field and 

laboratory studies were carried on from 1978 

through 1982 by an interdisciplinary team of 

scientists; some additional work and related 

projects have continued and are continuing through 

the time of this writing (1986). 

Geography and Access 

The Circle quadrangle covers approximately 

15,765 km2 in east-central Alaska (fig. 1) between 

lat 65° and 66° N. and long 144° and 147° W. Most 

of it is included in the mountainous physiographic 

division termed the Yukon-Tanana Upland 

(Wahrhaftig, 1965); the northernmost part is in a 

low-lying area known as the Yukon Flats section 

(fig. 2). The Yukon River flows along the 

northeastern edge of the quadrangle. Large streams 

that drain northward into the Yukon include Birch 

Creek and Preacher Creek. In the southern part of 

the quadrangle, the Chena and Chatanika Rivers 

drain southwestward, their waters reaching the 

Yukon via the Tanana River. The Salcha River 

heads in the southeastern part of the quadrangle and 

its water also reaches the Yukon River via the 

Tanana River. 

The Yukon-Tanana Upland is a maturely 

dissected mountainous terrain, unglacia ted except 

for a few of the highest areas, which supported 

small alpine glaciers during part of the 

Pleistocene. Altitudes range from around 500 m to 

a little more than 1,800 m, and relief of more than 

300 m is common in many places. Much of the area 

is in alpine tundra; forest covers regions below 

1.000 m in altitude, especially in most of the large 

river valleys and on lower slopes of valley walls. 

The Yukon Flats section is underlain by thick 

TABLE 1.--Component maps of the Circle mineral resource assessment 

U.S. Geological Survey Open-File Report Subject 

83-170-A (Foster and others, 1983) ........... Preliminary geology 

83-170-B (Menzie and others, 1983) ........... Mineral resources 

83-170-C (Cady and Weber, 1983) .............. Aeromagnetic map and interpretation 

of aeromagnetic and gravity data. 

83-170-D (Cady and Barnes, 1983) .............. Gravity map 

83-170-E (Simpson, 1984) ...................... Landsat imagery 

83-170-F (Tripp and Crim, 1986) ............... Mineralogical maps showing distribution of selected minerals in the 

minus-30-mesh, nonmagnetic heavymineral fraction of stream sediment 

83-170-G (Tripp, Hoffman, and Risoli, 1986) ... Geochemical maps showing distribution of selected elements in the 

minus-30-mesh, nonmagnetic heavymineral fraction of stream sediment 

83-170-H (Tripp, O'Leary, and Hoffman, 1986) .. Geochemical maps showing distribution of selected minerals in minus80-mesh stream sediment. 

2 
PACIFIC OCEAN 

0 100 200 300 400 500 KILOMETERS l______j____l_____L__j 

FIGURE 1.--lndex map of Alaska showing location 

of Circle quadrangle (hachured area). 

unconsolidated deposits, primarily alluvium of 

several ages and windblown deposits of loess and 

sand. Most of the Yukon Flats is heavily forested. 

In the early 1900's, access to the region was 

by boat on the Yukon River to the town of Circle. 

Now, the all-weather Steese Highway connects 

Circle with Fairbanks and provides access to many 

short roads and trails leading into the principal 

placer gold mining areas. Some of these mining 

roads are maintained by the State of Alaska; 

however, neither they nor the Steese Highway are 

open during the winter months. Another highway 

extends from Fairbanks to Chena Hot Springs and is 

kept open all year. Good landing strips are 

maintained at Chena Hot Springs, Circle Hot 

Springs, Central. and Circle. 

The only towns in the quadrangle are Circle, 

at the northern end of the Steese Highway. and 

Central. about 45 km to the southwest. There are 

two hot-spring resorts, Chena Hot Springs in the 

southern part of the quadrangle and Circle Hot 

Springs near Central. 

Mineral Production and Exploration 

Mineral production from the Circle 

quadrangle, excluding sand and gravel, is limited to 

gold and possibly a little silver and tin as byproducts 

from gold placer mining. Gold was discovered in 

the Circle quadrangle in 1893; placer mining began 

in the summer of 1894 and has continued to the 

present. No lodes have been mined. Bundtzen and 

others (1984) estimated that at least 850,000 oz of 

placer gold has been recovered from the quadrangle. 

The major production of gold from the Circle 

quadrangle has been from the Circle ~ining district, 

an area of approximately 750 km in the east3 

central part of the quadrangle; however, the amount 

of gold produced from the Circle mining district is 

unknown. Barker (1979) estimated that 277,650 oz 

of gold and 52,270 oz of byproduct silver had been 

recovered from the district through 19 70, and a 

considerable amount of gold has been produced 

since that time. The district has been, and still is, 

one of Alaska's major gold-producing areas. Other 

gold-producing areas in the Circle quadrangle 

include Nome Creek, tributaries to the Chatanika 

River, and the Chena River and some of its 

tributaries, although the amount of production of 

these areas combined is much less than that of the 

Circle mining district. Most of the quadrangle has 

been intensively prospected for gold. 

Cassiterite is abundant in the heavy 

concentrates of many placer mines, but no 

significant effort has been made to recover it. 

Scheelite also occurs in many concentrates, and 

considerable exploration for tungsten deposits, 

including drilling, has gone on recently in the 

southeastern part of the quadrangle. Prospecting 

for uranium has been carried on at various times: 

bedrock from road cuts and concentrates of stream 

gravels were checked in 1946 (Wedow, Killeen, and 

others, 1954); in 1949 and 1952, Geological Survey 

parties did brief reconnaissance investigations for 

radioactive deposits (Wedow, White, and others, 

1954; Nelson and others, 1954); and in 1977, the U.S. 

Bureau of Mines carried out a limited sampling 

program (Barker and Clautice, 1977). 

Although considerable exploration has taken 

place intermittently for many years in the Circle 

quadrangle, lode mineral deposits favorable for 

development under present economic conditions 

have not been found, but the potential for locating 

one or more economic deposits exists (Menzie and 

others, 1983). The University of Alaska and State 

and Federal agencies have made studies that 

included the geothermal potential of the Circle 

quadrangle and particularly of the Chena Hot 

Springs area (Miller and others, 1975; Turner and 

others, 1980; and Geophysical Institute, 1980). 

Commercial deposits of oil, gas, and coal are not 

known in the Circle quadrangle, and the geology is 

not favorable for locating significant deposits in the 

future. 

Acknowledgments 

Many scientists have participated in and 

contributed to geologic mapping in the Circle 

quadrangle and to Circle AMRAP. William E. 

Davies and Daniel B. Krinsley mapped large parts of 

the quadrangle in the summers of 1960-1963 under a 

U.S. Geological Survey military geology program. 

Much assistance was rendered by local Alaskans, 

particularly at Central, Circle, Circle Hot Springs, 

and Chena Hot Springs. Competent commercial 

helicopter crews were essential in carrying out the 

geologic mapping, geochemical sampling, and 
147° 

FORT YUKON 

c 

~ z 

Ci) 

8 

Lime Peak 

(Rocky Mountain) 

6 

Mount Prindle 

6 

>-

w 

...J 

a: 

c( 

J: 

0 

.!!-~ \ 0 10 20 KILOMETERS 

~~ ~--~--~ 

v~/ .. & / 

• Chena Hot Springs ~· 

6~------~~-----------------i----L_ ____________________ _L ______ ~-=~~~~----------+--------- ~~'O 

~<Q~ 

~~ BIG DELTA 

FIGURE 2.--Circle quadrangle showing adjacent quadrangles, physiographic divisions, and major streams 

and geographic features. Heavy line indicates approximate boundary between Yukon Flats section and 

Yukon-Tanana Upland. 

geophysical observations. Able assistance in the 

field was given by Grant W. Cushing, Diana J. 

Nelson, Steven T. Luthy, Anna Burack Wilson, and 

others. 

GEOLOGIC INVESTIGATIONS 

Previous Investigations 

The earliest geologic notes on the Circle 

quadrangle were by R.G. McConnell, who in 1888 

described the rocks along the Yukon River en route 

from Fort Yukon upriver into the Yukon Territory 

(McConnell, 1890). In 1889 I.C. Russell examined 

surficial features along the Yukon River (Russell. 

1890). Spurr (1898), from his work in 1896, first 

introduced the term Birch Creek series for most of 

4 

the metamorphic rocks of the area, and later 

Prindle (1913) and Mertie (1937) continued to use 

the name as Birch Creek Schist. 

Collier (1903) gathered stratigraphic data 

along the Yukon River in 1902, but the first 

systematic geologic work was by Prindle, beginning 

in 1903 and continuing intermittently to 1911 

(Mertie, 1937). In 1906, Brooks and Kindle studied 

the section along the Yukon River as far 

downstream as Circle (Brooks and Kindle, 1908). 

Mertie continued the work of Prindle and spent 

considerable time in the Circle quadrangle, 

particularly in the mining districts. Mertie's (1937) 

comprehensive report on the Yukon-Tanana region 

has formed a foundation for all future work in the 

Circle quadrangle and adjacent parts of the YukonTanana region. 

Numerous short special investigations, such as 
a reconnaissance for radioactive deposits in 1949 

(Wedow, White, and others, 1954) and a 

reconnaissance for uranium and thorium in 1952 

(Nelson and others, 1954), have involved the Circle 

quadrangle. Several theses have been done on small 

parts of the quadrangle by graduate students at the 

University of Alaska. The U.S. Bureau of Mines has 

carried on short investigations of selected 

commodities such as uranium and tin. 

In 1960, Davies and Krinsley began geologic 

mapping in the eastern Circle quadrangle for the 

U.S. Geological Survey, but their work was not 

completed. 

Prospecting and exploration by mining 

companies has continued intermittently throughout 

the Circle quadrangle from the 1890's to the 

present. Although gold has been the commodity of 

primary interest, other metals such as silver, tin, 

tungsten, antimony, and molybdenum are also 

sought. Uranium continues to be of interest, and 

the hot springs may get further consideration as 

geothermal areas. 

Present Study 

Reconnaissance geologic mapping under 

AMRAP began with a short field season in 1978 and 

continued in 1979, 1980, and 1981. Geochemical 

sampling was mostly done in 1979 and 1980, and 

most of the geophysical work in the field was in 

1979 with a minor amount of work in 1981 and 

1982. An area in the Crazy Mountains was 

geochemically resampled in 198 3, and in 1984 

additional geochemical samples were obtained in 

the Lime Peak area. A number of short reports 

were published in the U.S. Geological Survey 

Accomplishments Circulars from 1979 to 1984. 

Most samples for potassium-argon age 

determinations were collected in 1979, and a few 

other samples were collected throughout the course 

of the fieldwork. Several samples for uranium-lead 

dating were also collected and processed. 

The aeromagnetic map of the Circle 

quadrangle used for aeromagnetic interpretation in 

this study was compiled from a survey flown in 1973 

by Geometries, Inc., and released by the U.S. 

Geological Survey in 1974. 

Isotopic Age Data from the 

Circle Quadrangle 

A total of 35 potassium-argon ages were 

determined on 15 igneous and 11 metamorphic rocks 

from the Circle and adjacent quadrangles as part of 

this AMRAP project. Analytical data for these ages 

have been reported in an open-file report (Dubois 

and others, 1986) and some of their significance 

discussed by Wilson and others (1984 and 1985). 

Ages on biotite, muscovite, and hornblende 

from 13 granitic intrusions ranged from 77.6±2.0 Ma 

5 

(million years) to 56.65±0.95 Ma. Most granitic 

rocks had ages ranging between 66 and 56 Ma; 

however, a very small body of tourmaline granite 

and two other granitic bodies had ages between 77.6 

and 72 Ma. All three of the older intrusions are in 

the southeastern part of the Circle quadrangle and 

yield ages only slightly younger than the 

metamorphic rocks they intrude. Ages of these 

metamorphic rocks appear to be reset by Late 

Cretaceous through early Tertiary plutonism and 

thermal events associated with the youngest 

plutons. 

Seventeen biotite, muscovite and amphibole 

ages from 11 metamorphic rocks ranged from 178.0 

to 63.4 Ma; some are partially reset to different 

degrees by Late Cretaceous through early Tertiary 

plutonism and thermal events. Discordant ages 

ranging from 63.4±1.5 Ma to 78.1±3.0 Ma on biotite 

and 71.0±2.0 Ma to 92.0±5.0 Ma on muscovite from 

four augen gneiss samples from several localities in 

the southeastern part of the Circle quadrangle are 

considerably younger than ages on augen gneiss 

from the Big Delta quadrangle to the south (Wilson 

and others, 1985), where ages range from 113 to 

106.5 Ma. Augen gneiss from the Circle quadrangle 

was apparently strongly affected by nearby Tertiary 

plutonic events, whereas Tertiary pluton ism is not 

known in or near the augen gneiss of the Big Delta 

quadrangle. Metamorphic and possibly Cretaceous 

igneous rocks in the southeastern part of the Circle 

quadrangle show significant thermal resetting that 

can be related to proximity to large Late 

Cretaceous and early Tertiary granitic plutons. 

Zircons from four samples collected in the 

Circle quadrangle were dated by the U-Pb method. 

The rocks from which the zircons were obtained 

include an augen gneiss, a quartzite, and two grits 

(table 2). The augen gneiss and quartzite are from 

the area south of the Tintina fault zone; one of the 

grits is from the northwest Circle quadrangle, and 

the other is from north of the Tintina fault zone in 

the east Crazy Mountains area (fig. 3). A concordia 

plot of the U-Pb data from zircons from the augen 

gneiss (sample 78AFr 150) forms a scatter pattern 

(fig. 4), which suggests that the zircons contain 

inheritance of radiogenic lead and may have also 

undergone at least one period of lead loss. A 

similar pattern occurs in data from augen gneisses 

in the adjacent Big Delta quadrangle (Aleinikoff and 

others, 1986). However. the augen gneiss from the 

Circle quadrangle has somewhat younger U-Pb ages 

(ranging from 254 to 301 Ma). 

Because routine analyses of zircons did not 

yield an age for the protolith of the augen gneiss, an 

alternative method was attempted. Aleinikoff 

(1983) showed that the mineral in which zircons are 

included has an effect on its relative retentivity of 

Pb. In this case, zircons were separated from a 

mixture of quartz and potassium-feldspar and also 

from biotite. From these populations, the zircons 

were sized into different fractions and analyzed 

individually. The three fine-grained fractions 
TABLE 2.--Uranium-lead isotopic data from zircons, Circle quadrangle, Alaska 

[--, not determined] 

Sample Concentration Atomic percent Ages (Ma) 

and (Epm) 

fraction u Th Pb 204Pb 206Pb 207Pb 208Pb 206Pb 207Pb 207pb 208Pb 

238u 235u 206Pb 232rh 

78AFr 150 (augen gneiss) 

(+150)NM 1 '759 113 78.5 0.068 85.84 5.680 8.415 277 290 395 901 

(-325 2,099 111 90.6 .015 89.00 4.960 6.023 281 288 342 987 

(+150)biot 1 '975 289 86.1 .035 87.21 5.254 7.497 277 289 386 413 

(-150+200)biot 1 '929 167 87.8 .020 87.95 5.033 6.997 292 301 368 731 

(-325)biot 2,160 138 88.0 .018 88.52 5.004 6.459 264 274 358 831 

(+150)q-K 1 ,423 297 65.3 .137 82.08 6.492 11 .29 268 283 404 303 

(-150+200)q-K 1 ,618 226 70.2 .069 85.45 5.623 8.853 268 279 370 435 

(-325)q-K 2,450 143 95.6 .023 88.82 5.058 6.097 254 263 343 793 

80AFr 255 (quartzite) 

(+150)pink * 227 72.3 .042 74.53 10.19 15.23 1 '558 1 '797 2,086 

80AFr 370 (grit from northwest Circle quadrangle) 

(+150)LT 159 38.2 .017 77.36 

80AFr 253 (grit north of Tintina fault zone) 

(+150)red * * 210 77.2 .054 72.64 

(+150)gray 1 ,501 131. .233 70.94 

* From Aleinikoff, Foster, and others (1984). 

(minus 325 mesh) from biotite, quartz+potassiumfeldspar, ~nd U!e bulk group have the 

youngest 20 Pb/20 Pb ages of any of the analyzed 

fractions (table 2), suggesting that little or no 

inheritance occurred in the smallest zircons. A 

similar relationship was noted by Aleinikoff and 

Nokleberg (1985) in zircons from terranes north of 

the Denali fault in the Mount Hayes quadrangle. 

The zircons from the fine (minus 325 mesh) 

bulk and fine quartz+potassium-feldspar fractions 

suggest an age of about 340 Ma for the H7trus~<fi'6 of 

the protolith of the augen gneiss. The 2 Pb/ Pb 

age of zircons from the fine biotite fraction is 

slightly older at 358 Ma. This maybe related to the 

order of crystallization of the rock-forming 

minerals in the protolith. Earlier formed zircons 

(which probably would contain relatively more 

inheritance than later zircons) would be included 

within early crystallizing phases such as biotite. 

Later zircons. included within quartz and feldspar. 

would have less inheritance. Thus, the smallest. 

latest zircons should contain the least inheritance 

and possibly record the true age of intrusion of the 

protolith of the augen gneiss. The maximum age of 

the protolith of the gneiss, based on this date alone, 

appears to be about 340 Ma. This age is in excellent 

agreement with age determinations for augen 

gneisses in the Big Delta quadrangle. dated at 341±3 

Ma (Aleinikoff and others, 1986). 

Four fractions from three metasedimentary 

rocks were analyzed to provide the beginning of a 

data base to aid in determining the age of the 

provenance(s) for the sediments. As shown by 

6 

8.105 14.52 1 ,254 1 '441 1 '656 

10.71 16.59 1, 723 1 '949 2,198 

11 .33 17.49 437 748 1 ,888 

Aleinikoff, Foster, and others (1984), detrital 

zircons from a quartzite in the area south of the 

Tintina fault zone (sample 80AFr 255) and a grit 

from north of the Tintina fault in the east Crazy 

Mountains (~1>1fple H,OAFr 253) have Early 

Proterozoic Pb/20 Pb ages and plot on a 

concordia diagram with other detrital zircons from 

the Mount Hayes quadrangle (fig. 5), indicating a 

provenance age of about 2.2 Ga (billion years). This 

age is also obtained by plotting similar data from 

the augen gneisses of the Big Delta quadrangle, 

which suggests that the Mississippian granitoid 

protoliths were derived from or included Early 

Proterozoic material. Thus, at least some of the 

sedimentary material of the area south of the 

Tintina fault zone appears to have been derived 

originally from Early Proterozoic sources. 

A detrital zircon fraction from a grit in the 

northwest Circle quadrangle (sample 80AFr 370) has 

somewhat different U-Pb systematics. The gray, 

medium-grained grit contains abundant glassy 

quartz grains and brown-weathering specks that 

may have been feldsparz, j!nd ~ locally cut by 

carbonate veinlets. The 0 Pb/2 6Pb age from the 

sample is 1,656 Ma; this data point does not plot on 

the previously established chord between about 2.2 

Ga and 346 Ma. These 1.66-Ga zircons appear to 

have been derived from a different source than 

other detrital zircons analyzed from the Circle and 

Big Delta quadrangles. The provenance is also Early 

Proterozoic in ·age, but apparently somewhat 

younger than the provenance(s) of the other detrital 

zircons. 
STATUS OF LAND IN THE 

CIRCLE QUADRANGLE 

Most of the Circle quadrangle consists of 

Federal lands administered by several different 

agencies. A small amount of land, principally 

around the towns of Circle and Central and the 

resort areas of Chena Hot Springs and Circle Hot 

Springs, is patented land. Areas in the mining 

districts are held largely in claims by individuals 

and small companies. Some areas, mostly in the 

vicinity of Circle and some near Central, are Native 

lands. The State of Alaska and North Star Borough 

control some areas, particularly in the southern part 

of the quadrangle. 

The largest areas of Federal lands are 

administered by the Bureau of Land Management, 

and others are under the National Park Service or 

Bureau of Fish and Wildlife Management. 

Regulations concerning mining and exploration are 

different in the various tracts. Very little land is 

open for new mining and exploration. Figure 6 

shows the approximate distribution of major 

government-held tracts in the Circle quadrangle as 

of 1985. 

DESCRIPTION OF COMPONENT MAPS AND 

RELATED REPORTS 

OF THE CIRCLE QUADRANGLE FOLIO 

Geology {OFR-83-170-A) 

The Circle quadrangle is located near the 

margin, possibly a fragmented margin, of the North 

AREA NORTH OF TINTINA FAULT ZONE 

Little Crazy Mountains 

l/fvf. • 80AFr 253 

lfv~ ~' .............. East Crazy Mountains 

-..... r,q lJ ""'-. ........... l../~0 ' 

...................... ~l'vs '-......... ........... ....... ....... ........... ......... ........... 

' • 80AFr 255 

AREA SOUTH OF TINTINA FAULT ZONE 

River 

10 15 20 25 KILOMETERS 

FIGURE 3.--Areas of the Circle quadrangle used in describing the geology, and sample locations (dots) 

used for uranium-lead age determinations (table 2). Faults are shown as heavy lines; sawteeth are on 

upper plate of thrust faults. 

7 
American era ton and occupies a critical position for 

the. interpretation of the geologic history of the 

Yukon-Tanana Upland. Because of large areas 

covered by vegetation and the lack of detailed 

geologic investigations, many of the complexities of 

this area remain to be worked out. 

The Tintina fault zone trends northwesterly 

through the northeastern and central part of the 

quadrangle, and two boundary faults have been 

postulated, the Preacher fault on the north and the 

Hot Springs fault on the south. The zone is not 

clearly defined in either the northwestern or 

southeastern parts of the quadrangle. To the 

northwest, it may be buried; there is no clear field 

evidence for such a northwesterly trend, although 

gravity data suggest an ancient northwestsoutheast-trending lineament (J.W. Cady, oral 

commun., 1984). The fault zone may bend 

southwestward, connecting with faults in the 

Livengood quadrangle, or it may lose its identity as 

a zone of strike-slip movement, the stresses instead 

resulting in faults with large thrust components. 

The Circle quadrangle comprises several 

different geologic components. Therefore, for 

description the geologic map is divided in to three 

major areas: the northwest Circle quadrangle, the 

area north of the Tintina fault zone, and the area 

south of the Tintina fault zone (fig. 3). 

The northwest Circle quadrangle consists 

mostly of slightly metamorphosed, folded, and 

faulted sedimentary rocks that include chert, slate, 

argillite, sandstone, grit, graywacke, conglomerate, 

limestone, dolomite, and tuff of dominantly 

:::J 

~ 0.048 

N 

.0 ' 

a. 

~ 0.044 

N 

0.040 

FIGURE 4.--Concordia plot of U-Pb data from 

zircons from augen gneiss (sample 78AFr 150, 

table 2), Circle quadrangle. Circles represent 

three fine-grained fractions (minus 325 mesh) of 

zircons included in quartz-potassium feldspar (qK), biotite (biot) and the bulk group (not labeled) 

of the augen gneiss. Diamonds represent all of 

the larger fractions of zircons analyzed from the 

augen gneiss. Note that the reference chord goes 

through two fine fractions and slightly above a 

third fine fraction. 

8 

Paleozoic age, but some rocks are Mesozoic in 

age. Lime Peak (Rocky Mountain) and Victoria 

Mountain are Tertiary granitic intrusions. Mafic 

rocks occur as dikes, sills, and small intrusions. 

Small ultra mafic and greenstone bodies are believed 

to have fault contacts. The area includes the 

Beaver, White Mountains, Kandik River, and 

Livengood terranes of Churkin and others (1982) 

(the Wickersham, White Mountains, and Livengood 

terranes, and deformed upper Mesozoic flysch of 

Jones and others, 1981). Lithologic units and major 

faults mapped in the Livengood quadrangle to the 

west (Chapman and others. 1971) have been 

extended into the Circle quadrangle, but locally 

there are problems in identifying contacts due to 

poor exposure and lack of detailed mapping in both 

quadrangles. 

The area north of the Tintina fault zone is 

composed of two very different groups of rocks. On 

the north, including the Little Crazy Mountains and 

probably extending beneath the Yukon Flats, are 

gabbros and basalts with some chert, graywacke, 

and limestone, which are mostly included in the 

Circle Volcanics and compose the Circle terrane of 

Churkin and others (1982) (the Innoko terrane of 

Jones and others, 1981). These rocks have an age 

range from Mississippian to Triassic based on 

radiolarians (Foster and others, 1983). Most of the 

rocks in the Crazy Mountains and the Preacher 

block, which compose the Crazy Mountains terrane 

of Churkin and others (1982) (Wickersham terrane of 

Jones and others, 1981) are slightly metamorphose<;! 

sandstone, grit, argillite, conglomerate, chert, and 

limestone. Locally they include or are cut by sills, 

dikes, and small rna fie intrusive masses. The rocks 

are folded and faulted. In general, rocks in the 

Crazy Mountains area are considered to be mostly 

of Paleozoic age and include Devonian limestones. 

The trace fossil Oldhamia, which indicates rocks of 

::l 

(I) 

(T) 

0. 32 

N 0.24 

.0 ' 

a. 

(0 

0 

N 0.16 

0.08 

FIGURE 5.--Concordia plot of U-Pb data of detrital 

zircons identified by sample number (table 2) 

from the Circle quadrangle with previously 

established reference chord (Aleinikoff, Foster, 

and others, 1984). 
probable Cambrian or possibly Late Proterozoic 

age, is a rarely found fossil. In the Tintina fault 

zone, Tertiary(?) conglomerate and sandstone crop 

out locally and are commonly overlain by 

Quaternary loess and alluvial deposits. 

The largest part of the quadrangle, the area 

south of the Tintina fault zone. contains regionally 

metamorphosed pelitic rocks intruded by Late 

Cretaceous and early Tertiary granitic plutons. 

Some orthogneisses, including augen gneiss, also 

occur. This is the Yukon crystalline terrane of 

Churkin and others (1982) (the Yukon-Tanana 

terrane of Jones and others, 1981). Rocks range 

from very slightly to highly metamorphosed (mid to 

upper amphibolite facies). Contact metamorphism, 

locally superimposed on regional metamorphism, has 

resulted in some hornfelsing and local seritization 

and chloritization. Contacts between rocks of 

different metamorphic grade are both sharp, 

indicating faults, and gradational, indicating gradual 

change in metamorphic conditions. Some faulting 

occurred before metamorphism, complicating the 

interpretation of many contacts. A thrust fault 

separates this metamorphic terrane from the 

slightly metamorphosed rocks to the northwest. 

Several very small exposures of eclogite are present 

in the southwestern part of the quadrangle; the 

eclogite is similar to that found in the Livengood 

quadrangle east of Fairbanks. 

EXPLANATION 

[SJ ~~::se National Conservation 

bd ~~~:e~W~~t:~:sa National 

CJ ~~:~;;~eharley Rivers National 

[]] ~~~~~r~!ats National Wildlife 

~ National Wild and Scenic Rivers System 

> Pinnell Mountain Trail 

,- ', -' (Bureau of Land Management) 

- r;t~~= ~:v:ra~:~leation Area 

0 Military Reservation 

FIGURE B.--Distribution of major government-held 

tracts in the Circle quadrangle (from U.S. 

Department of Interior Planning Group, 1980, and 

Bureau of Land Management, 1978). 

9 

The age of the protoliths is uncertain, as no 

fossils have been found. On the basis of very scarce 

fossils elsewhere in the Yukon-Tanana region and 

possible stratigraphic relations, they are believed to 

be at least partly Paleozoic but may also include 

Precambrian protoliths. Information from the study 

of zircons indicates that at least some of the 

sediment in many protoliths contains some zircon 

derived from Proterozoic rocks. The time of 

regional metamorphism is also unknown. Data from 

adjacent quadrangles suggest that it was probably 

during the Mesozoic, but Paleozoic metamorphism 

may have affected at least part of the quadrangle. 

No clear petrographic evidence for more than one 

regional metamorphism has been found in most of 

the rocks, but the area of eclogitic rocks may have 

a more complex metamorphic history. A few small 

serpentinized ultramafic masses are scattered 

throughout the metamorphic terrane; all are 

believed to have fault contacts. 

The metamorphic rocks are intruded by 

Cretaceous and Tertiary granitic plutons that range 

in age from 77 .6±2 Ma to 56.65±0.95 Ma. Small 

shallow felsic intrusions also occur in the central 

part of the quadrangle. Most mineral occurrences 

are largely associated directly or indirectly with the 

felsic intrusions. The metamorphic rocks are 

structurally complex, and much more detailed work 

is required to understand the structural relations 

within the quadrangle and within the Yukon 

crystalline terrane. At least three sets of folds can 

be recognized, two with axes trending northeastsouthwest and one with a northwest-southeasttrending axis. One or more of these folding events 

is probably related to thrusting, which occurred at 

least two different times in the metamorphic 

terrane south of the Tintina fault zone. A complex, 

but different history of folding and thrusting 

typifies the area north of the Tintina fault zone. 

High-angle northeast-southwest-trending faults 

postdate metamorphism, plutonism, folding, and 

thrusting. 

Mineral Resources 

(OFR-83-170-B) 

The mineral resources report, which consists 

of a map, explanatory text, and appendices, assesses 

the metalliferous mineral resources of the Circle 

quadrangle and discusses selected nonmetallic 

resources. The assessment is based upon the 

general methodology of Singer (1975). Tracts 

(areas) that are geologically permissive for the 

occurrence of various types of mineral deposits 

were delineated, descriptive and grade/tonnage 

models of the deposit types were constructed from 

data in the literature, and numbers of deposits that 

may occur within delineated tracts were 

estimated. Types of resources that did not lend 

themselves to representation by deposit models or 

to delineation of tracts are discussed separately in 

the text. 
The Circle quadrangle has been an area of 

gold placer mining since the 1890's; the amount of 

placer mining increased significantly from 1977 to 

1982, the period of fieldwork for the report. The 

general geologic setting of the Circle quadrangle, 

especially the presence of post-orogenic plutons 

intruded into regionally metamorphosed rocks. is 

similar to regions that contain tin-bearing greisen 

deposits, tungsten-bearing skarn deposits, lode 

deposits of gold in metasedimentary rocks, and vein 

deposits of uranium associated with peraluminous 

granites, though no such deposits are known to exist 

in the quadrangle. This report identified six tracts 

that may contain deposits of these types: four 

tracts, considered permissive for tin-bearing greisen 

deposits, were estimated to contain at least one 

deposit at a 50 percent probability level and at least 

three deposits at a 10 percent probability level, and 

two tracts considered permissive for tungsten skarn 

deposits were estimated to contain at least one 

deposit at a 50 percent probability level and at least 

two deposits at a 10 percent probability level. Two 

other tracts, which contain rocks with anomalous 

amounts of lead and zinc, were delineated as 

permissive for shale-hosted lead-zinc deposits. The 

rocks in these tracts are similar to Paleozoic 

sedimentary rocks in Canada that host such 

deposits; however, the anomalous values may 

merely represent elevated background values, as is 

common in these kinds of rocks. 

Most of the past and present gold placer 

mining in the quadrangle has taken place in four 

areas (Menzie and others, 1983). A fifth area, the 

sedimentary basin near the town of Central, was 

identified that may contain buried placer deposits 

and possibly sedimentary uranium deposits. Lastly, 

the quadrangle contains sources of crushed stone 

and sand and gravel for local use. 

Studies and events since publication of the 

mineral resource assessment in 1983 permit several 

additions and modifications to that report. First, 

two diamonds, 0.3 carat and 1.4 carat, were 

discovered in gravels of Crooked Creek in the 

Circle mining district. Although no source for the 

diamonds has been identified (Forbes, 1985), the 

possibility exists that the quadrangle could contain 

placer or lode diamond deposits. Second, new 

grade/tonnage models are available for tin deposits 

(Menzie and others, 1985), and the model that is 

most appropriate for the de linea ted tracts in the 

Circle quadrangle is the tin greisen model (figs. 7 

and 8). This model should supersede the 

vein/greisen grade/tonnage model in Open-File 

Report 83-170-B. Third, subsequent sampling 

confirmed the presence of rare-earth minerals, 

stibnite, scheelite, and cassiterite in stream 

concentrates in the eastern part of the Crazy 

Mountains (R.B. Tripp, oral commun., 1984). 

Additional field studies recognized small granitic 

dikes that cut the rna fie igneous rocks on the west 

side of the sampled area (T.E.C. Keith, oral 

commun., 1984). Therefore an additional area (the 

10 

eastern Crazy Mountains) is recognized as being 

permissive for the occurrence of tin deposits, 

tungsten skarns, and lode gold deposits. Finally, 

studies in 1983-1984 by the U.S. Bureau of Mines 

(Burton and others, 1984) and the U.S. Geological 

Survey in the Lime Peak area (tract I) confirm and 

further document the geologic characteristics of 

this area, as reported in Open-File Report 83-170-B, 

but do not change the resource estimates. 

Aeromagnetic and Gravity Maps and Their 

Interpretation (OFR-83-170-C and 83-170-D) 

Aeromagnetic and gravity data and their 

interpretation are contained in two separate openfile reports of the Circle AMRAP folio. The 

aeromagnetic survey of the Circle quadrangle was 

flown and the map compiled in 1973 by Geometries, 

Inc. and released by the U.S. Geological Survey in 

1974. With the aeromagnetic map in the report 

(OFH.-83-270-C) is an aeromagnetic interpretation 

map with a geologic base and a smaller reproduction 

of a spectrally colored aeromagnetic map overlaid 

with the complete Bouguer gravity anomaly 

contours. Some of the data upon which the 

complete Bouguer gravity map (OFR-83-170-D) was 

compiled were collected prior to the Circle AlVIRAP 

project by several different workers, and the 

remainder were obtained during the AM RAP 

fieldwork. 

The aeromagnetic map of the Circle 

quadrangle reflects the distribution of magnetic 

minerals in the upper few kilometers of the crust. 

0.9 

0.8 

~ 0.7 

ii5 

0 

fu 0.6 0 

~ 0.5 z 

0 

i= 

~ 0.4 D.. 

0 

g: 0.3 

0.2 

0.1 

0.87 

0.0 '--------'-------'--------'------'----'-------'--'--_____L_I------'-------'~-----' 

0.0004 0.0063 0.1 1.6 25 

METRIC TONS (IN MILLIONS) 

FIGURE 7 .--Distribution of tonnage of greisen tin 

deposits. n, number of data points. 

400 
Major discontinuities in the pattern of magnetic 

anomalies commonly coincide with boundaries 

between major tectonostratigraphic terranes. 

At the local scale, elongate magnetic 

anomalies indicate that lithologic units have greater 

continuity along strike than can readily be observed 

by the geologist in the field. Aeromagnetic 

interpretations were used to make hypotheses and 

to plan geologic traverses. Magnetic marker units, 

traced from aeromagnetic maps and checked in the 

field, are a useful geologic mapping tool. 

The quadrangle can be subdivided into three 

geophysical terranes on the basis of aeromagnetic 

and gravity data. The metamorphic terrane south 

of the Tintina fault zone has low overall gravity and 

local gravity lows over exposed and inferred granite 

plutons. These unmetamorphosed, nonmagnetic 

granites, which commonly occur in the cores of 

anticlines and are elongate parallel to the strike of 

foliation, are expressed as magnetic lows. They 

belong to the ilmenite series of Ishihara (1981) and 

are probably S-type granite according to the 

classification of Chappell and White (1974). 

Magnetic chloritic schist and minor serpentinite, 

infolded with nonmagnetic quartzite and schist, is 

associated with east-northeast-trending magnetic 

highs that approximately parallel the regional strike 

of the most prominent foliation (foliation D1, 

Cushing and Foster, 1982). Too few magnetic rocks 

of this type were found in outcrop to easily explain 

the observed magnetic anomalies, therefore, it was 

hypothesized in the report that the magnetic 

chloritic schist is an easily eroded unit commonly 

hidden by a resistent carapace of quartzite. 

0.9 ~ - - - __:=" - - - -

0.8 

~ 0.7 

I 0 

ii.i I \ 0 0 

fu 0.6 0 I LL. 

0 I 0.5 z 

0 I ~ 0.4 I 0 

ll.. 

0 I a: 

ll.. 0.3 I 

I 

0.2 I 

I 

0.1 I 

0.17 0.30 

0.0 

0.032 0.1 0.32 1.0 3.2 

TIN GRADE (IN PERCENT) 

FIGURE B.--Distribution of tin grade of greisen 

deposits. n, number of data points. 

10 

11 

Furthermore, magnetite may have been destroyed 

by oxidation due to weathering near the surface. 

North of the Tintina fault zone is an oceanic 

terrane characterized by high gravity. Elongate 

east-west-trending magnetic highs are postulated to 

be caused by allochthons of gabbro and peridotite, 

probably thrust south from the Yukon Flats. Good 

exposures of these oceanic rocks are found in the 

Crazy Mountains and along the Yukon River south 

of Six Mile Bluff near the town of Circle. Layered 

gabbro and peridotite occur in laccolith-like plutons 

that exhibit chilled contacts with quartz- and 

carbonate-rich marine sedimentary rocks and 

chert. Further north, in the Little Crazy Mountains 

and Yukon Flats, ovoid and irregular magnetic highs 

are interpreted to indicate buried volcanic 

centers. A broad, 30-mgal gravity high centered 

over the Little Crazy Mountains has no associated 

broad magnetic high, thus buried, nonmagnetic 

duni te or gabbro are possible explanations for the 

gravity anomaly. 

The Tintina fault zone is 10 to 13 km wide and 

marked by several magnetic highs. An intense 

magnetic high in the fault zone near the western 

boundary of the Circle quadrangle overlies magnetic 

granodiorite of the Victoria Mountain pluton. The 

Victoria Mountain pluton is a magnetic series 

granitoid according to the classification of Ishihara 

(1981) and probably is an !-type granitoid according 

to the classification of Chappell and White (1974). 

A pronounced contact-metamorphic aureole 

suggests that it was intruded hot into comparatively 

cool rocks in the upper crust. A magnetic high near 

Circle Hot Springs is less intense, but much broader 

than the Victoria Mountain magnetic high. 

Magnetic modeling showed that the high could 

reflect a source with the same magnetic 

susceptibility as the Victoria Mountain pluton, but 

buried at least 4 km deeper. The absence of a 

gravity high indicates that the pluton must be a low 

density rock such as a granodiorite, not a gabbro or 

peridotite. A narrow gravity low indicates that the 

inferred pluton is overlain by a narrow sedimentary 

basin coincident with Medicine Lake. In the report 

it was speculated that the pluton has stoped country 

rock and caused the local subsidence that has 

diverted many drainages into Medicine Lake. 

Several magnetic anomalies have possible 

implications for mineral exploration. The magnetic 

map suggests the presence of zonation within or 

contact aureoles around parts of the Lime Peak 

pluton. Some geochemical anomalies may be 

correlated with details of the magnetic anomaly. 

For example, one magnetic high appears to be 

correlated with an area of anomalous fluorine, 

another with one of anomalous lanthanum. A 

detailed aeromagnetic map might help to delineate 

mineral zonation within the pluton and surrounding 

rocks. Broad magnetic lows indicate that felsic 

hypabyssal rocks northeast of Mount Prindle are 

underlain by a large, nonmagnetic granitic pluton. 

Arcuate patterns of subdued magnetic highs and 
lows near the center of the Circle quadrangle, 

correlated with zonation in stream-sediment 

mineral concentrate data, indicate a buried pluton 

with possible economic importance. The continuity 

of magnetic lows over known and inferred plutons 

between the headwaters of the streams of the 

Circle placer gold mining district and Mount Prindle 

to the west suggests a common type of origin for 

gold placers in the western and central parts of the 

Circle quadrangle. A curious ring-shaped magnetic 

high in the western part of the Tintina fault zone 

surrounds a body of felsic tuff associated with a 

magnetic low. Barite, zinc, and nickel anomalies 

may be associated with a mineralized caldera, 

metamorphic aureole, or ring dike--all 

manifestations of a shallow pluton. Stream 

sediments anomalous in antimony, zinc, and thorium 

occur in the oceanic terrane in the northeastern 

part of the quadrangle. There is no magnetic 

evidence for a local felsic pluton, the expected 

source of the anomalies, although hydrothermally 

altered felsic dikes have been found cutting mafic 

volcanic rocks of the oceanic terrane. 

Interpretation of Landsat Imagery 

(OFR-83-170-E) 

In 1981, Le Compte presented two preliminary 

maps of numerous lineaments and circular and 

arcuate features observed on Landsat imagery of 

the Circle quadrangle. The lineament map was 

prepared following a method employed by Raines 

(1978). Later, a remote sensing study (OFR-83-170-

E), using computer-enhanced Landsat images (fig. 9) 

of the Circle quadrangle, was undertaken to identify 

geomorphic characteristics of the region as well as 

to determine trends and patterns of concentrations 

of linear features (Simpson, 1984). The 

multispectral scanner (MSS) data for Landsat scene 

2944-20083 (August 23, 1977) was processed by 

REMAPP remote sensing array processing 

procedures (Townsend and Sawatzky, 1976) to 

prepare enhanced images with optimal contrast for 

image interpretation. Bands 4, 5, and 7 were 

processed for black-and-white positive film 

transparencies and edge-enhanced images (Knepper, 

1982), and for a color-infrared composite of blue, 

green, and red, respectively, at a scale of 

1:800,000. All these images were used for 

geomorphic interpretation and for mapping linear 

features. 

From Landsat imagery, the Circle quadrangle 

south of the Tintina fault zone can be divided into 

two geomorphic domains on the basis of differences 

in surface characteristics. Domain A is a roughly 

rectangular, northeast-southwest-trending area of 

relatively low relief and simple, widely spaced 

drainages, except where igneous rocks are 

exposed. Domain B, which bounds two sides of 

domain A, is more intricately dissected and shows 

abrupt changes in slope and relatively high relief. 

The northwestern part of geomorphic domain A 

12 

includes the Beaver terrane, a tectonostratigraphic 

terrane mapped by Churkin and others (1982). The 

southeastern boundary of domain A lies entirely 

within the adjoining Yukon crystalline terrane. 

Analysis suggests that the southeastern part of 

domain A may be a subdivision of the Yukon 

crystalline terrane. 

Domain B appears to be divisible into several 

areas with somewhat different geomorphic 

characteristics by east-northeast-trending curved 

lines apparent on Landsat images. The curved lines 

possibly separate different geomorphic regions 

along segments of boundaries of subterranes mapped 

by Churkin and others (1982). On Landsat images, 

prominent north-south-trending lineaments together 

with the curved lines form a large-scale regional 

pattern that is transected by mapped northnortheast-trending high-angle faults (Foster and 

others, 1983). The lineaments indicate possible 

lithologic variations or structural boundaries. As 

used in this report, the term lineament, adapted 

from O'Leary and others (1976), describes a linear 

alignment of geomorphic features that forms a 

regional break in the terrain and is transverse to the 

structural grain of the region. 

A map of linear features was made in order to 

study trends and patterns of concentrations of 

linear features, using standard photogeologic 

methods on a transparent overlay that was 

transferred from image to image. Linear features 

were drawn on straight-appearing topographic 

features, such as stream valleys, slope breaks, and 

cliffs; for consistency a straight valley was mapped 

rather than the adjacent parallel straight ridge. 

Short aligned features were not connected by long 

interpretative lines. 

The final digitized map was analyzed by a 

statistical strike-frequency procedure to determine 

important azimuthal trends in the linear features 

data (Sawatzky and Raines, 1981). The number, or 

frequency, of linear features trending in each of 180 

1-degree classes was determined, and the 

frequencies were compared to the mean frequency 

of the 180 classes. The farther the frequency 

deviates from the mean, the higher its significance 

value. The strike-frequency histogram was 

examined for azimuthal intervals with frequencies 

above the 90 percent significance value. Generally, 

northeast -southwest -trending features pre do min ate 

in the Circle quadrangle, although north-south, 

east-west, and two northwest-southeast intervals 

also have frequencies well above the mean. 

Maps of spatial concentrations of linear 

features show that northeast-southwest-trending 

linear features predominate throughout the 

quadrangle, and that most northwest-southeasttrending linear features are found south of the 

Tintina fault zone. A major trend interval of N. 

64°-72° E. corresponds to the average strike of 

foliations in metamorphic rocks (measured on the 

geologic map; Foster and others, 1983) and to the 

average strike of magnetic anomalies (measured on 
FIGURE 9.--Computer-enhanced Landsat image of band 7 for scene 2944-20083 showing Circle 

quadrangle and names of some streams. Processed in the Geophysics Image Processing Laboratory, 

U.S. Geological Survey, Denver, Colorado. 

the aeromagnetic map; Cady and Weber, 1983) 

reflecting compositional variations; this 

correspondence suggests that most linear features 

in the southern part of the quadrangle probably are 

related to lithologic variations brought about by 

folding and foliation of metamorphic rocks. A 

second important trend interval, N. 14°-35° E., may 

be related to thrusting south of the Tintina fault 

zone, as high concentrations of linear features 

within this interval are found in areas of mapped 

thrust faults. Linear features trending N. 14°-35° 

13 

E. also occur in moderate to high concentrations 

near the plutons of Victoria Mountain, Lime Peak 

(Rocky Mountain), Circle Hot Springs, and the 

pluton between Lime Peak and Mount Prindle. The 

contour map of all linear features shows low 

concentrations in most areas of igneous intrusions. 

High concentrations of linear features do not 

correspond to areas of known mineralization in any 

consistent or significant way that would allow 

concentration patterns to be easily used as an aid in 

locating areas of mineralization. 
The conclusions of this remote sensing study 

are based on interpretation of Landsat images and 

information from published reports and have not 

been field checked; however, they are consistent 

with complementary studies of the Circle AMRAP 

project. The results of this study indicate that 

there are several possibly important areas where 

further detailed studies are warranted to check the 

relationship between geology, mineral occurrences, 

and interpretation of Landsat images. 

Geochemistry and Selected Mineralogy 

(OFR-83-170-F, G, H) 

Geochemical and mineralogical studies of 

stream sediment and heavy-mineral concentrates 

were made in the Circle quadrangle to identify 

areas of anomalous concentrations of metallic 

elements. The data delineate areas of known 

mineral occurrences and other areas that may 

contain undiscovered mineral resources. 

During the summers of 1979 and 1980, 

sediment samples were collected at 874 sites in 

streams whose drainage areas range from 

approximately 4 to 13 km 2. The minus-80-mesh 

fraction of these samples was analyzed for 31 

elements by a semiquantitative em 1Ss1on 

spectrographic method (Grimes and Marranzino, 

1968), for gold by atomic absorption (Ward and 

others, 1969), and for uranium by a fluorometric 

method (Centanni and others, 1956). Heavy-mineral 

concentrates of stream sediment were taken from 

860 of the stream sites. The nonmagnetic fraction 

of these samples was also analyzed for 31 elements 

by the spectrographic method and scanned under the 

binocular microscope to identify ore-related 

minerals. The spectrographic and geochemical 

results are available in an open-file report (O'Leary 

and others, 1986). 

In the Circle quadrangle, heavy-mineral 

concentrates have proved to be an excellent 

reconnaissance tool. Some areas of known mineral 

occurrences are well defined by the distribution of 

anomalous amounts of metals in the heavy-mineral 

concentrates of stream sediment. Gold, arsenic, 

antimony, lead, tin, and tungsten anomalies were 

found in nonmagnetic heavy-mineral concentrates 

collected from streams that drain Cretaceous or 

Tertiary granite and the Precambrian or Paleozoic 

quartzitic schist sequence in the Circle mining 

district. Spectrographic analysis of the heavymineral fraction of bulk samples from zones of 

mineralized quartzite and schist indicates 

anomalous amounts of gold, copper, antimony, lead, 

tungsten, bismuth, and zinc. Galena from pods and 

stringers in the mineralized zone contains 

anomalous amounts of tin, bismuth, antimony, 

silver, cadmium, and copper (Tripp and others, 

1982). At least some of the anomalous tin found in 

heavy-mineral concentrates is derived from small 

altered zones within the Circle Hot Springs pluton 

14 

and from altered felsic dikes that cut both the 

granite and country rock. 

Anomalous values of tin, tungsten, thorium, 

uranium, lanthanum, and beryllium form clusters 

around granite plutons near Lime Peak, Mount 

Prindle, between Lime Peak and Mount Prindle, and 

25 km east of Mount Prindle. In the Lime Peak 

area, sources of the anomalous tin are areas of 

altered sheared granite. 

Anomalous amounts of barium, silver, and zinc 

are found in stream sediment and in heavy-mineral 

concentrates from the south-central part of the 

Circle quadrangle. The metals are apparently 

derived from highly carbonaceous Paleozoic 

quartzite, meta-argillite, phyllite, calcareous 

phyllite, and marble that could contain shale-hosted 

lead-zinc deposits. Several gold and silver 

anomalies are also found within this area. 

The distribution of specific elements and 

minerals observed in the heavy-mineral 

concentrates and in stream sediment indicates 

potential for lode occurrences of the noble and base 

metals as well as tin, tungsten, beryllium, uranium, 

and thorium. 

REFERENCES 

The asterisks (*) denote references cited in this 

report. Plus signs (+) indicate uncited references 

that mainly or entirely pertain to the Circle 

quadrangle or are especially significant for regional 

relations of the Circle quadrangle. Unmarked 

references are uncited general, regional, or topical 

in scope but contain material relevant to the Circle 

quadrangle. 

Alaska Division of Geological and Geophysical 

Surveys, 1983, Mining claims location maps: 

Continuing series of map sets by 1:250,000 

quadrangles. 

*Aleinikoff, J.N., 1983, U-Th-Pb systematics of 

zircon inclusions in rock-forming minerals: A 

study of armoring against isotopic loss using 

the Sherman Granite of Colorado-Wyoming, 

USA: Contributions to Mineralogy and 

Petrology, v. 83, p. 259-269. 

+Aleinikoff, J.N., Dusel-Bacon, Cynthia, and Foster, 

H.L., 1981, Geochronologic studies in the 

Yukon-Tanana Upland, east-central Alaska, in 

Albert, N.R.D., and Hudson, Travis, eds., The 

United States Geological Survey in Alaska: 

Accomplishments during 1979: U.S. 

Geological Survey Circular 823-B, p. B34-B37. 

+ 1984, Uranium-lead isotopic ages of zircon 

--from sillimanite gneiss and implications for 

Paleozoic metamorphism, Big Delta 

quadrangle, east-central Alaska, in Coonrad, 

W.L., and Elliott, R.L., eds., The United 

States Geological Survey in Alaska: 

Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 45-48. 
* __ 1986, Geochronology of augen gneiss and 

related rocks, Yukon-Tanana terrane, eastcentral Alaska: Geological Society of 

America Bulletin, v. 97, p. 626-637. 

Aleinikoff, J.N., Dusel-Bacon, Cynthia, Foster, 

H.L., and Futa Kiyoto, 1981, Proterozoic 

zircon from augen gneiss, Yukon-Tanana 

Upland, east-central Alaska: Geology, v. 9, 

no. 10, p. 469-473. 

*Aleinikoff, J.N., Foster, H.L., Nokleberg, W.J., and 

Dusel-Bacon, Cynthia, 1984, Isotopic evidence 

from detrital zircons for Early Proterozoic 

crustal material, east-central Alaska, in 

Coonrad, W.L., and Elliott, R.L., eds., The 

United States Geological Survey in Alaska: 

Accomplishments during 1981: U.S Geological 

Survey Circular 868, p. 43-45. 

*Aleinikoff, J.N., and Nokleberg, W.J., 1985, Age of 

Devonian igneous-arc terranes in the northern 

Mt. Hayes quadrangle, eastern Alaska Range, 

in Bartsch-Winkler, Susan, ed., The United 

States Geological Survey in Alaska: 

Accomplishments during 1984: U.S. 

Geological Survey Circular 96 7, p. 44-49. 

Arcane, S.A., and Delaney, A.J., 1984, Radar 

investigations above the trans-Alaska pipeline 

near Fairbanks: Hanover, N.H., Cold Regions 

Research and Engineering Laboratory CRREL 

Report 84-27, 15 p. 

Armbrustmacher, T.J., 1984, Rare-earth/thorium 

deposits associated with a complex of syenitic 

rocks near Mount Prindle, east-central Alaska 

(abs.): Geological Society of America, 

Cordilleran Section, Abstracts with Programs, 

v. 16, no. 5, p. 266. 

Barker, J.C., 1978, Mineral deposits of the YukonTanana Uplands: A summary report: U.S. 

Bureau of Mines Open-File Report 88-78, 33 p. 

* __ 1979, A trace element study of the Circle 

mining district, Alaska: U.S. Bureau of Mines 

Open-File Report 57-79, 39 p. 

+ __ 1984, Concentrations of cobalt and other 

metals in the western Crazy Mountains, 

interior Alaska: U.S. Bureau of Mines OpenFile Report 213-84, 44 p. 

*Barker, J.C., and Clautice, K.H., 1977, Anomalous 

uranium concentrations in artesian springs and 

stream sediments in the Mount Prindle area, 

Alaska: U.S. Bureau of Mines Open-File 

Report 130-77, 19 p. 

Barnes, D.F., 1977, Bouguer gravity map of 

Alaska: U.S. Geological Survey Geophysical 

Investigations Map GP-913, 1 sheet, scale 

1:250,000. 

Bates, R.G., and Wedow, Helmuth, Jr., 1953, 

Preliminary summary review of thoriumbearing mineral occurrences in Alaska: U.S. 

Geological Survey Circular 202, 13 p. 

Berg, H. C., and Cobb, E. H., 1967, Metalliferous lode 

deposits of Alaska: U.S Geological Survey 

Bulletin 1246, 254 p. 

+Biggar, N.E., and Forbes, R.B., 1980, Geology, 

15 

geochemistry, and ground survey of the Chena 

Hot Springs area, Alaska, in A geological and 

geophysical study of the Chena Hot Springs 

geothermal area, Alaska: Preliminary report, 

a geothermal resource investigation by the 

Geophysical Institute, University of Alaska, p. 

3-18. 

+Bishop, Sam, 1984, Sharp eyes made surprise 

diamond discovery: Fairbanks Daily NewsMiner, December 11, 1984, p. 3. 

Brabb, E.E., and Churkin, Michael, Jr., 1969, 

Geologic map of the Charley River 

quadrangle, east-central Alaska: U.S. 

Geological Survey Miscellaneous Geologic 

Investigations Map I-573. 

Brabb, E.E., and Hamachi, B.R., 1977, Chemical 

composition of Precambrian, Paleozoic, 

Mesozoic and Tertiary rocks from east-central 

Alaska: U.S. Geological Survey Open-File 

Report 77-631, 165 p. 

Brook, C.A., Mariner, R.H., Mabey, D.R., Swanson, 

G.R., Guffanti, M., and Muffler, L.J.P., 1979, 

Assessment of geothermal resources of the 

United St ates--197 8: U.S. Geological Survey 

Circular 790, p. 18-85. 

Brooks, A. H., 1904, Placer mining in Alaska in 

1903: U.S. Geological Survey Bulletin 225, p. 

43-59. 

1905, Placer mining in Alaska in 1904: U.S. 

---Geological Survey Bulletin 259, p. 18-31. 

+ 1907, The Circle Precinct, Alaska: U.S. 

--Geological Survey Bulletin 314, p. 187-204. 

1907, The mining industry in 1906: U.S. 

---Geological Survey Bulletin 314, p. 19-39. 

___ 1908, The mining industry in 1907: U.S. 

Geological Survey Bulletin 345, p. 30-53. 

___ 1909, The mining industry in 1908: U.S. 

Geological Survey Bulletin 379, p. 21-62. 

___ 1910, The mining industry in 1909: U.S. 

Geological Survey Bulletin 442, p. 20-46. 

1911, Geologic features of Alaskan 

---metalliferous lodes: U.S. Geological Survey 

Bulletin 480, p. 43-93. 

1914, The Alaskan mining industry in 1913: 

---U.S. Geological Survey Bulletin 592, p. 45-74. 

1915, The Alaskan mining industry in 1914: 

---U.S. Geological Survey Bulletin 622, p. 15-68. 

1916, The Alaskan mining industry in 1915: 

---U.S. Geological Survey Bulletin 642, p. 16-71. 

1918, The Alaskan mining industry in 1916: 

---U.S. Geological Survey Bulletin 662, p. 11-62. 

1923, The Alaskan mining industry in 1921: 

---U.S. Geological Survey Bulletin 739, p. 1-44. 

1925, Alaska's mineral resources and 

---production, 1923: U.S. Geological Survey 

Bulletin 773, p. 3-52. 

Brooks, A.H., and Capps, S.R., 1924, The Alaskan 

mining industry in 1922: U.S. Geological 

Survey Bulletin 7 55, p. 3-49. 

*Brooks, A.H., and Kindle, E.M., 1908, Paleozoic 

and associated rocks of the upper Yukon, 

Alaska: Geological Society of America 
Bulletin, v. 19, p. 255-314. 

Brooks, A.H., and Martin, G.C., 1921, The Alaskan 

mining industry in 1919: U.S. Geological 

Survey Bulletin 714, p. 59-95. 

Brosgl, W.P., Brabb, E.E., and King, E.R., 1970, 

Geologic interpretation of reconnaissance 

aeromagnetic survey of northeastern Alaska: 

U.S. Geological Survey Bulletin 1271-F, 14 p. 

Brown, E.J., Luong, H.U., and Forshang, J.M., 1982, 

Gold-mine drainage in subarctic streams: 

Arctic, v. 35, no. 3, p. 419. 

Bundtzen, T.K., 1982, Bedrock geology of the 

Fairbanks Mining District, western sector: 

Alaska Division of Geological and Geophysical 

Surveys Open-File Report 155. 

*Bundtzen, T.K., Eakins, G.R., Clough, J.G., Lueck, 

L.L., Green, C.B., Robinson, M.S., and 

Coleman, D.A., 1984, Alaska's mineral 

industry, 1983: Alaska Division of Geological 

and Geophysical Surveys Special Report 33, 56 

P· 

Bundtzen, T.K., Eakins, G.R., and Conwell, C.N., 

198 2, Review of Alaska's mineral resources: 

Juneau, Alaska, Department of Commerce and 

Economic Development, Office of Mineral 

Development, v. 1, 4 pls. 

+Burack, A.C., 1983, Geology along the Pinnell 

Mountain trail, Circle quadrangle, Alaska: 

Durham, N.H., University of New Hampshire, 

M.S. thesis, 98 p. 

+Burack, A.C., Laird, Jo, Foster, H.L., and Cushing, 

G.W., 1984, Metamorphic petrology of the 

Table Mountain area, Circle quadrangle, 

Alaska, in Coonrad, W .L., and Elliott, R.L., 

eds., TheUnited States Geological Survey in 

Alaska: Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 54-57. 

+Burand, W.M., 1965, A geochemical investigation 

between Chatanika and Circle Hot Springs, 

Alaska: Alaska Division of Mines and Minerals 

Geochemical Report 5, 11 p. 

___ 1968, Geochemical investigations of selected 

areas in the Yukon-Tanana region of Alaska, 

1965 and 1966: Alaska Division of Mines and 

Minerals Geochemical Report 13, 51 p. 

*Bureau of Land Management, 1978, Steese 

National Conservation areas, Sheet 1, Circle, 

Alaska: U.S. Geological Survey, scale 

1:250,000. 

*Burton, P.J., Warner, J.D., and Barker, J.C., 1985, 

Reconnaissance investigation of tin 

occurrences at Rocky Mountain (Lime Peak), 

east-central Alaska: U.S. Bureau of Mines 

Open-File Report 85.:.31, 44 p. 

*Cady, J.W., and Barnes, D.F., 1983, Complete 

Bouguer gravity map of Circle quadrangle, 

Alaska: U.S. Geological Survey Open-File 

Report 83-170-D, scale 1:250,000. 

*Cady, J.W., and Weber, F.R., 1983, Aeromagnetic 

map and interpretation of magnetic and 

gravity data, Circle quadrangle, Alaska: U.S. 

Geological Survey Open-File Report 83-170-C, 

16 

31 p. 

*Centanni, F.A., Ross, A.M., and De Sesa, M.A., 

1956, Fluorometric determination of 

uranium: Analytical Chemistry, v. 28, p. 

1651. 

Chapin, Theodore, 1914, Placer mmmg in the 

Yukon-Tanana region: U.S. Geological Survey 

Bulletin 592, p. 357-362. 

Chapman, R.M., Trexler, J.H., Jr., Churkin, 

Michael, Jr., and Weber, F.R., 1985, New 

concepts of the Mesozoic flysch belt in eastcentral Alaska, in Bartsch-Winkler, Susan, and 

Reed, K.M., eds., The United States 

Geological Survey in Alaska: 

Accomplishments during 1983: U.S. 

Geological Survey Circular 945, p. 29-32. 

Chapman, R.M., Weber, F.R., Churkin, Michael, Jr., 

and Carter, Claire, 1980, The Livengood Dome 

Chert, a new Ordovician formation in central 

Alaska, and its relevance to displacement on 

the Tintina fault: U.S. Geological Survey 

Professional Paper 1126-F, p. F1-Fl3. 

*Chapman, R.M., Weber, F.R., and Taber, Bond, 

1971, Preliminary geologic map of the 

Livengood quadrangle, Alaska: U.S. 

Geological Survey Open-File Report 71-66, 2 

sheets. 

*Chappell, B.W., and White, A.J.R., 1974, Two 

contrasting granite types: Pacific Geology, 

no. 8, p. 173-174. 

Churkin, Michael, Jr., and Brabb, E.E., 1965, 

Occurrence and stratigraphic significance of 

Oldhamia, a Cambrian trace fossil, in eastcentral Alaska: U.S. Geological Survey 

Professional Paper 525-D, p. D120-D124. 

*Churkin, Michael, Jr., Foster, H.L., Chapman, 

R.M., and Weber, F.R., 1982, Terranes and 

suture zones in east-central Alaska: Journal 

of Geophysical Research, v. 87, no. B5, p. 

3718-3730. 

Cobb, E.H., 1970, Uranium, thorium, and rare earth 

elements in Alaska: U.S. Geological Survey 

Mineral Investigations Resource Map MR-56, 

scale 1:250,000. 

___ 1972, Metallic mineral resource map of the 

Circle quadrangle, Alaska: U.S. Geologia! 

Survey Miscellaneous Field Studies Map MF3 91, scale 1 :250,000. 

___ 1973, Placer deposits of Alaska: U.S. 

Geologia! Survey Bulletin 1374, 213 p. 

+ 1976, Summary of references to mineral 

--occurrences in the Circle quadrangle, 

Alaska: U.S. Geological Survey Open-File 

Report 76-633, 66 p. 

+ __ 1981, Placer gold occurrences in Alaska: U.S. 

Geological Survey Open-File Report 81-13 26, 

34 p., 1 sheet, scale 1:250,000. 

1982, Lode gold and silver occurrences in 

---Alaska: U.S. Geological Survey Open-File 

Report 82-0406, 32 p., 1 sheet, scale 

1:250,000. 

___ 1983, Occurrences of zinc minerals in 
Alaska: U.S. Geological Survey Open-File 

Report 83-199, 18 p., 1 sheet, scale 

1:2,500,000. 

___ 1984a, Map showing occurrences of lode gold 

and silver in Alaska: U.S. Geological Survey 

Mineral Investigations Resource Map MR-84, 

16 p., 1 sheet, scale 1:250,000. 

___ 1984b, Map showing occurrences of placer 

gold in Alaska: U.S. Geological Survey 

Mineral Investigations Resource Map MR-83, 

18 p., 1 sheet, scale 1:250,000. 

*Collier, A.D., 1903, The coal resources of the 

Yukon, Alaska: U.S. Geological Survey 

Bulletin 218, 71 p. 

Cruz, E.L., and Cobb, E.H., 1984, Map showing 

occurrences of mercury minerals in Alaska: 

U.S. Geological Survey Mineral Investigations 

Resource Map M R -8 7, scale 1 :250,000 

(supersedes MR-54). 

Csejtey, B~la, Jr., Mullen, M. W., and Foster, H.L., 

1983, Tectonostratigraphic terranes versus 

facies changes in the central Alaska range 

(abs.): Geological Society of America, 

Cordilleran Section, Abstracts with Programs, 

v. 15, no. 5, p. 428. 

*Cushing, G. W., and Foster, H.L., 1982, Recumbent 

folding in the northeastern Yukon-Tanana 

Upland, Alaska (abs.): Geological Society of 

America, Cordilleran Section, Abstracts with 

Programs, v. 14, no. 4, p. 158. 

+ __ 1984, Structural observations in the Circle 

quadrangle, Yukon-Tanana Upland, Alaska, in 

Coonrad, W .L., and Elliott, R.L., eds., The 

United States Geological Survey in Alaska: 

Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 64-65. 

Cushing, G. W ., Foster, H.L., Harrison, T.M., and 

Laird, J o, 1984, Possible Mesozoic accretion 

in the eastern Yukon-Tanana Upland (abs.): 

Geological Society of America, 97th Annual 

Meeting, Abstracts with Programs, v. 16, no. 

6, p. 481. 

+Cushing, G. W., Foster, H.L., Laird, Jo, and Burack, 

A.C., 1982, Description and preliminary 

interpretation of folds and faults in a small 

area in the Circle B-4 and B-5 quadrangles, 

Alaska, in Coonrad, W.L., ed., The United 

States Geological Survey in Alaska: 

Accomplishments during 1980: U.S. 

Geological Survey Circular 844, p. 56-58. 

Dadisman, S. V., 1980, Radiometric ages of rocks in 

south-central Alaska and western Yukon 

Territory: U.S. Geological Survey Open-File 

Report 80-183, 79 p. 

+Davies, W.E., 1972, The Tintina Trench and its 

reflection in the structure of the Circle area, 

Yukon-Tanana Upland: International 

Geological Congress, 24th, Montreal, Sec. 3 

(Tectonics), p. 211-216. 

Douglas, R.J.W., 1970, Geology and economic 

minerals of Canada: Geological Survey of 

Canada, Economic Geology Report No. 1, 838 

17 

P· 

Dover, J .H., 1985a, Dispersion of Tintina fault 

displacement in interior Alaska {abs.): 

Geological Society of America, Cordilleran 

Section, Abstracts with Programs, v. 17, no. 6, 

p. 352. 

1985b, Possible oroclinal bend in northern 

---Cordilleran fold and thrust belt, east-central 

Alaska (abs.): Geological Society of America, 

Cordilleran Section, Abstracts with Programs, 

v. 17, no. 6, p. 352. 

Dubois, G.D., Wilson, F.H., and Shew, Norah, 1986, 

Map and tables showing potassium-argon age 

determinations and selected major-element 

chemical analyses from the Circle quadrangle, 

Alaska: U.S. Geological Survey Open-File 

Report 86-392. 

Dusel-Bacon, Cynthia, 1984, Trace-element 

evidence for the tectonic affinities of some 

amphibolites from the Yukon-Tanana Upland, 

east-central Alaska, in Coonrad, W.L., and 

Elliott, R.L., eds., -The United States 

Geological Survey in Alaska: 

Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 50-54. 

___ 1985, Metamorphic facies map shows timing 

and grade of regional metamorphism in Alaska 

(abs.): Geological Society of America, 

Cordilleran Section, Abstracts with Programs, 

v. 17, no. 6, p. 352. 

Dusel-Bacon, Cynthia, and Aleinikoff, J.N., 1985, 

Petrology and significance of augen gneiss 

from a belt of Mississippian granitoids in the 

Yukon-Tanana terrane, east-central Alaska: 

Geological Society of America Bulletin, v. 96, 

no. 4, p. 411-425. 

Dusel-Bacon, Cynthia, Aleinikoff, J.N., Mortensen, 

J.K., and Foster, H.L., 1984, A belt of Middle 

Paleozoic augen gneiss batholiths with 

evidence for an early Proterozoic component 

in the crust beneath the Yukon-Tanana 

terrane {abs.): Geological Association of 

Canada, Abstracts with Programs, v. 8, p. 

A19. 

Eakins, G.R., 1981, Exploration in Alaska in 1980 

below record level, but hopes for 1981: 

Western Miner, v. 54, no. 2, p. 73-77. 

Eakins, G.R., Bundtzen, T.K., Lueck, L.L., Green, 

C.B., Gallagher, J.L., and Robinson, M.S., 

1985, Alaska's mineral industry, 1984: Alaska 

Division of Geological and Geophysical 

Surveys Special Report 38, 57 p. 

Eakins, G.R., Bundtzen, T.K., Robinson, M.S., 

Clough, J.C., Green, C.B., Clautice, K.H., and 

Albanese, M.A., 1983, Alaska's mineral 

industry, 1982: Alaska Division of Geological 

and Geophysical Surveys Special Report 31, 63 

P· 

Eakins, G.R., and Daniels, C.L., 1980, Survey of 

mineral activity in Alaska--1977: Alaska 

Division of Geological and Geophysical 

Surveys Open-File Report 122, 32 p. 
Eberlein, G.D., Chapman, R.M., Foster, H.L., and 

Gassaway, J.S., 1977, Map and table 

describing known metalliferous and selected 

nonmetalliferous mineral deposits in central 

Alaska: U.S. Geological Survey Open-File 

Report 77-168-D, p. 18-25. 

Eberlein, G.D., and Menzie4 W.D., 1978, Maps and 

tables describing areas of metalliferous 

mineral resource potential of central Alaska: 

U.S. Geological Survey Open-File Report 78-

1-D, 3 2 p., 2 maps. 

+Ellsworth, C.E., 1910, Placer mining in the 

Fairbanks and Circle districts: U.S. 

Geological Survey Bulletin 520, p. 240-245. 

___ 1910, Placer mining in the Yukon-Tanana 

region: U.S. Geological Survey Bulletin 442, 

p. 230-245. 

Ellsworth, C.E., and Davenport, R.W., 1913, Placer 

mining in the Yukon-Tanana region: U.S. 

Geological Survey Bulletin 542, p. 203-222. 

___ 1915, Surface water supply of the YukonTanana region, Alaska: U.S. Geological 

Survey Water Supply Paper 342, 343 p. 

Ellsworth, C.E., and Parker, G.L., 1911, Placer 

mining in the Yukon-Tanana region: U.S. 

Geological Survey Bulletin 480, p. 153-172. 

*Forbes, R.B., 1985, Prospecting for diamonds in 

Alaska: Alaska Mines and Geology, v. 34, no. 

2, p. 7. 

Foster, H.L., Brabb, E.E., Weber, F.R., and Forbes, 

R.B., 1970, Regional geology of Yukon-Tanana 

Upland, Alaska (abs.): American Association 

of Petroleum Geologists Memoir 19, p. 388-

395. 

+Foster, H.L. Cushing, G.W., Weber, F.R., Jones, 

D.L., Murchey, Benita, and Blome, C.D., 1984, 

Late Paleozoic and early Mesozoic 

radiolarians in the Circle quadrangle, eastcentral Alaska, in Coonrad, W.L., and Elliott, 

R.L., eds., The- United States Geological 

Survey in Alaska: Accomplishments during 

1981: U.S. Geological Survey Circular 868, p. 

62-64. 

*Foster, H.L., Laird, Jo, Keith, T.E.C., Cushing, 

G.W ., and Menzie, W.D., 1983, Preliminary 

geologic map of the Circle quadrangle, 

Alaska: U.S. Geological Survey Open-File 

Report 83-170-A, 3 2 p., 1 sheet, scale 

1:250,000. 

+Foster, H.L., O'Leary, R.M., McDougal, C.M., and 

Menzie, W.D., 1984, Analyses of rock samples 

from the Circle quadrangle, Alaska: U.S. 

Geological Survey Open-File Report 84-479, 

126 p., 1 sheet, scale 1:250,000. 

+Foster, H.L., Weber, F.R., and Dutro, J.T., Jr., 

1984, Some Paleozoic limestones of the Crazy 

Mountains and vicinity, Circle quadrangle, 

east-central Alaska, in Coonrad, W.L., and 

Elliott, R.L., eds., -The United States 

Geological Survey in Alaska: 

Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 60-62. 

18 

+Foster, H.L., Weber, F.R., and Keith, T.E.C., 1979, 

Metamorphic rock units of the southern Circle 

quadrangle, east-central Alaska, in Johnson, 

K.M., and Williams, J.R., eds., United States 

Geological Survey in Alaska: 

Accomplishments during 1978: U.S. 

Geological Survey Circular 804-B, p. B54-B55. 

Freeman, V.L., 1963, Examination of uranium 

prospects, 1956, in Contributions to economic 

geology of Alaska: U.S. Geologia! Survey 

Bulletin 1155, p. 29-33. 

Gedney, L., Shapiro, L., Van Wormer, D., and 

Weber, F.R., 1972, Correlation of epicenters 

with mapped faults, east-central Alaska, 

1968-1971: U.S. Geological Survey Open-File 

Report 72-128, 7 p. 

*Geophysical Institute, University of Alaska, 1980, 

A geological and geophysical study of the 

Chena Hot Springs geothermal area, Alaska, in 

Wescott, E., and Turner, D., eds., Preliminary 

report: Geophysical Institute, University of 

Alaska, 55 p. 

Gibson, D.E., Kingler, S.L., and Choate, Glenda, 

1982, Cultural resource surveys of Steese 

Highway from Central to Circle, Alaska, in 

Stern, R.O., Cultural resource surveys, 1981: 

Anchorage, Alaska Division of Parks 

Miscellaneous Publications, History and 

Archeology Series, no. 31, p.194-213. 

*Grimes, D.J., and Maranzino, A.P., 1968, Directcurrent arc and alternating-current spark 

emission spectrographic field methods for the 

semiquantitative analysis of geologic 

materials: U.S. Geological Survey Circular 

591, 6 p. 

Hamilton, Warren, 1984, Review of Circum-Pacific 

Plutonic Terranes, Roddick, J.A., ed.: 

Episode, v. 7, no. 2, p. 48. 

Hess, F.L., 1912, Tin resources of Alaska: U.S. 

Geological Survey Bulletin 520, p. 89-92. 

Hofmann, H.J., and Cecile, M.P., 1981, Occurrence 

of Oldhamia and other trace fossils in lower 

Cambrian(?) argillites, Niddery Lake map 

area, Selwyn Mountains, Yukon Territory, in 

Current research, Part A: Geological Survey 

of Canada Paper 81-1A, p. 281-290. 

Holdsworth, B.K., and Jones, D.L., 1980, A 

provisional radiolaria biostratigraphy, Late 

Devonian through Late Permian: U.S. 

Geological Survey Open-File Report 80-876, 

32 p. 

+Holm, Bjarne, 1973, Bedrock geology and 

mineralization of the Mount Prindle area, 

Yukon-Tanana Upland, Alaska: Fairbanks, 

University of Alaska, M.S. thesis, 55 p. 

*Ishihara, Shunso, 1981, The granitoid series and 

mineralization: Economic Geology, 75th 

Anniversary Volume, 1981, p. 458-484. 

Joesting, H.R., 1938, Circle district: Alaska 

Division of Geological and Geophysical 

Surveys, Territorial Department of Mines 

Document, Miscellaneous Report 50-1. 
___ 194Z, Strategic mineral occurrences in 

interior Alaska: Alaska Department of Mines 

Pamphlet 1, 46 p. 

___ 1943, Supplement to Pamphlet No. 1 

Strategic mineral occurrences in interior 

Alaska: Alaska Department of Mines 

Pamphlet Z, Z8 p. 

+Johnson, B.L., 1910, Occurrence of wolframite and 

cassiterite in the gold placers of Deadwood 

Creek, Birch Creek district: U.S. Geological 

Survey Bulletin 44Z, p. Z46-ZSO. 

*Jones, D.L., Silberling, N.J., Berg, H.C., and 

Plafker, George, 1981, Map showing 

tectonostratigraphic terranes of Alaska, 

columnar sections, and summary description 

of terranes: U.S. Geological Survey Open-File 

Report 81-79Z, 19 p. 

Jones, D.L., Silberling, N.J., Coney, P.J., and 

Plafker, George, 1984, Lithotectonic terrane 

map of Alaska (West of 141st meridian), Part 

A, in Silberling, N.J., and Jones, D.L., eds., 

Lithotectonic terrane maps of the North 

American Cordillera: U.S. Geological Survey 

Open-File Report 84-5Z3, p. A1-A1Z. 

+Jones, G.M., Menzie, W.D., and Foster, H.L., 1985, 

Statistical discrimination between potential 

tin- and uranium-bearing areas in east-central 

Alaska on the basis of stream-sediment traceelement geochemistry, in Bartsch-Winkler, 

Susan, and Reed, K.M.;-eds., The United 

States Geological Survey in Alaska: 

Accomplishments during 1983: U.S. 

Geological Survey Circular 945, p. 40-46. 

+Keith, T.E.C., Barnes, Ivan, and Foster, H.L., 1981, 

Laumontite occurrence in the Circle A-1 

quadrangle, Alaska, in Albert, N.R.D., and 

Hudson, Travis, eds-:-; The United States 

Geological Survey in Alaska: Accomplishments during 1979: U.S. Geological Survey 

Circular 8Z3-B, p. BZ8-BZ9. 

+Keith, T.E.C., and Foster, H.L., 1979, Big Windy 

Creek hot springs, Circle A-1 quadrangle, 

Alaska, in Johnson, K.M., and Williams, J.R., 

eds., TheUnited States Geological Survey in 

Alaska: Accomplishments during 1978: U.S. 

Geological Survey Circular 804-B, p. B55-B57. 

+Keith, T.E.C., Presser, T.S., and Foster, H.L., 

1980, New chemical and isotope data for the 

hot springs along Big Windy Creek, in 

Albert, N.R.D., and Hudson, Travis, eds., 

The United States Geological Survey in 

Alaska: Accomplishments during 1979: U.S. 

Geological Survey Circular 8Z3-B, p. BZ5-BZ8. 

Killeen, P.L., and Mertie, J.B., Jr., 1951, Antimony 

ore in the Fairbanks district, Alaska: U.S. 

Geological Survey Open-File Report 4Z, 43 p. 

*Knepper, D.H., Jr., 198Z, Lineaments derived from 

analysis of linear features mapped from 

Landsat images of the Four Corners region of 

the southwestern United States: U.S. 

Geological Survey Open-File Report 8Z-849, 

79 p. 

19 

+Koivula, J .L, and Misiorowiski, Elise, eds., 1985, 

Diamond found in Alaska: Gems and 

Gemology, Summer 1985. 

Koschmann, A.H., and Bergendahl, M.H., 1968, 

Principal gold producing districts of the 

United States: U.S. Geological Survey 

Professional Paper 610, Z83 p. 

+Kowalik, W.S., 198Z, The use of Landsat data in 

exploration for limonitic outcrops in the 

Circle quadrangle, Alaska: U.S. Geological 

Survey Open-File Report 8Z-5Z9, 13 p. 

+Laird, Jo, Biggs, D.L., and Foster, H.L., 1984, A 

terrane boundary of the southeastern Circle 

quadrangle, Alaska (abs.): Eos, Transactions 

American Geophysical Union, v. 65, no. 15, p. 

Z91. 

+Laird, J o, and Foster, H.L., 1984, Description and 

interpretation of a mylonitic foliated 

quartzite unit and feldspathic quartz wacke 

(grit) unit in the Circle quadrangle, Alaska, in 

Reed, K.M., and Bartsch-Winkler, S., eds., The 

United States Geological Survey in Alaska: 

Accomplishments during 198Z: U.S. 

Geological Survey Circular 939, p. Z9-33. 

+Laird, Jo, Foster, H.L., and Weber, F.R., 1984, 

Amphibole eclogite in Circle quadrangle, 

Yukon-Tanana Upland, Alaska, in Coonrad, 

W.L., and Elliott, R.L., eds., The United 

States Geological Survey in Alaska: 

Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 57-:-60. 

*Le Compte, J.R., 1981, Landsat features maps of 

the Circle quadrangle, Alaska: U.S. 

Geological Survey Open-File Report 81-78Z, Z 

sheets, scale 1 :ZSO,OOO. 

*McConnell, R.G., 1890, Report on exploration in 

the Yukon and Mackenzie basins, Northwest 

Territory: Canada Geological Survey Annual 

Report, new series, v. 74, p. 13D-14D. 

Malone, Kevin, 1965, Mercury in Alaska, in U.S. 

Bureau of Mines, Mercury potential of the 

United States: U.S. Bureau of Mines 

Information Circular 8ZSZ, p. 31-59. 

Martin, G.C., 1919, The Alaskan mining industry in 

1917: U.S. Geological Survey Bulletin 69Z, p. 

11-4Z. 

19ZO, The Alaskan mining industry in 1918: 

---U.S. Geological Survey Bulletin 71Z, p. 11-SZ. 

Matzko, J.J., and Freeman, V.L., 1963, Summary of 

reconnaissance for uranium in Alaska, 1955, in 

Contributions to economic geology of 

Alaska: U.S. Geological Survey Bulletin 1155, 

p. 33-49. 

*Menzie, W.D., Foster, H.L., Tripp, R.B., and 

Yeend, W.E., 1983, Mineral resource 

assessment of the Circle quadrangle, Alaska: 

U.S. Geological Survey Open-File Report 83-

170-B, 57 p. 

+Menzie, W.D., Reed, B.L., and Keith, T.E.C., 1986, 

Lime Peak tin occurrences, in BartschWinkler, Susan, and Reed, K.M., eds., Geologic 

studies in Alaska by the U.S. Geological 
Survey during 1985: U.S. Geological Survey 

Circular 97 8. 

Menzie, W.D., Reed, B.L., and Singer, D.A., 1985, 

Models of grades and tonnages of some lode 

tin deposits, in Report on the International 

Symposium onthe Geology of Tin Deposits: 

Chinese Academy of Geological Sciences and 

the ESCAP Regional Mineral Resources 

Development Centre, p. 48. 

+Mertie, J.B., Jr., 193 2, Mining in the Circle 

district: U.S. Geological Survey Bulletin 824, 

p. 155-172. 

* ___ 1937, The Yukon-Tanana region, Alaska: 

U.S. Geological Survey Bulletin 872, 276 p. 

+ ___ 1938, Gold placers of the Fortymile, Eagle, 

and Circle districts, Alaska: U.S. Geological 

Survey Bulletin 897-C, p. 133-261. 

Metz, P.A., and Robinson, M.S., 1980, Investigation 

of mercury-antimony-tungsten metal 

provinces of Alaska II, in Report for Mining 

and Mineral Resources-Research Institute; 

Office of Surface Mining: U.S. Department of 

Interior, p. 159-190. 

*Miller, T.P., Barnes, Ivan, and Patton, W. W., Jr., 

197 5, Geologic setting and chemical 

characteristics of hot springs in west-central 

Alaska: U.S. Geological Survey Journal of 

Research, v. 3, no. 2, p. 149-162. 

Moffit, F.H., 1927, Mineral industry of Alaska in 

1925: U.S. Geological Survey Bulletin 792, p. 

1-39. 

Mullins, W.J., McQuat, J.F., and Rogus, R.K., 1984, 

The Alaska asbestos project, Part 1, project 

review: Industrial Minerals, no. 199, p. 141. 

*Nelson, A.E., West, W.S., and Matzko, J.J., 1954, 

Reconnaissance for radioactive deposits in 

eastern Alaska, 1952: U.S. Geological Survey 

Circular 348, 21 p. 

*O'Leary, D.W., Friedman, J.D., and Pohn, H.A., 

197 6, Lineaments, linear, lineation: Some 

proposed new standards for old terms: 

Geological Society of America Bulletin, v. 87, 

p. 1463-1469. 

*O'Leary, R.M., Hoffman, J.D., Risoli, D.A., and 

Tripp, R.B., 1986, Analytical results of 

stream-sediment and non-magnetic heavymineral concentrate samples from the Circle 

quadrangle, Alaska: U.S. Geological Survey 

Open-File Report 86-204, 124 p. 

Oliver, W.A., Jr., Merriam, C. W., and Churkin, 

Michael, Jr., 197 5, Ordovician, Silurian, and 

Devonian corals of Alaska: U.S. Geologia! 

Survey Professional Paper 823-B, p. 13-44, 25 

pls. 

Overstreet, W.C., 1967, The geologic occurrence of 

monazite: U.S. Geological Survey 

, ,Professional Paper 530, 327 p. 

Fewe, T.L., 197 5, Quaternary geology of Alaska: 

U.S. Geological Survey Professional Paper 

835, 139 p •• 

+Prindle, L.M., 1905, The gold placers of the 

Fortymile, Birch Creek, and Fairbanks 

zo 

regions, Alaska: U.S. Geological Survey 

Bulletin 251, 89 p. 

1906, Yukon placer fields: U.S. Geological 

---Survey Bulletin 284, p. 109-127. 

+ 1906, The Yukon-Tanana region, Alaska: 

--Description of Circle quadrangle: U.S. 

Geological Survey Bulletin 295, 27 p. 

1908, The Fairbanks and Rampart quadrangles, 

---Yukon-Tanana region, Alaska, with a section 

on the Rampart placers, by F. L. Hess, and a 

paper on the water supply of the Fairbanks 

region, by C. C. Convert: U.S. Geological 

Survey Bulletin 337, 102 p. 

1910, Sketch of the geology of the 

---northeastern part of the Fairbanks 

quadrangle: U.S. Geological Survey Bulletin 

442, p. 203-209. 

* 1913, A geologic reconnaissance of the 

---Circle quadrangle, Alaska: U.S. Geological 

Survey Bulletin 538, 82 p. 

Prindle, L.M., and Katz, F.J., 1913, Geology of the 

Fairbanks district, in Prindle, L. M., ed., A 

geologic reconnaiss~ce of the Fairbanks 

quadrangle, Alaska: U.S. Geological Survey 

Bulletin 525, p. 59-152. 

Purington, C. W., 1905, Methods and costs of gravel 

and placer mining in Alaska: U.S. Geological 

Survey Bulletin 263, 273 p. 

*Raines, G.L., 1978, Porphyry copper exploration 

model for northern Sonora, Mexico: U.S. 

Geological Survey Journal of Research, v. 6, 

no. 1, p. 51-58. 

Roddick, J.A., 1967, Tintina Trench: Journal of 

Geology, v. 7 5, no. 1, p. 23-33. 

*Russell, LC., 1890, Notes on the surface geology of 

Alaska: Geological Society of America 

Bulletin, v. 1, p. 99-156. 

Saunders, R.H., 1967, Mineral occurrences in the 

Yukon-Tanana region: Alaska Division of 

Geological and Geophysical Surveys Special 

Report 2, 60 p., 1 sheet, scale 1:36,000. 

*Sawatzky, D.L., and Raines, G.L., 1981, Geologic 

uses of linear feature maps from small-scale 

imagery: International Conference on 

Basement Tectonics, 3d, Proceedings, p. 91-

100. 

*Simpson, S.L., 1984, Geomorphic domains and 

linear features on Landsat images, Circle 

quadrangle, Alaska: U.S. Geological Survey 

Open-File Report 83-170-E, 36 p., 2 sheets, 

scales 1:1,000,000 and 1:250,000. 

*Singer, D. A., 197 5, Mineral resource models and 

the Alaskan Mineral Resource Assessment 

Program, in Vogely, W. A., ed., Mineral 

materials modeling: Baltimore, Resources for 

the Future, p. 370-382. 

Smith, P.S., 1917, The mining industry in the 

Territory of Alaska during the calendar year 

1915: U.S. Bureau of Mines Bulletin 142, 66 p. 

1917, The mining industry in the Territory of 

---Alaska during the calendar year 1916: U.S. 

Bureau of Mines Bulletin 153, 89 p. 
___ 1926, Mineral industry of Alaska in 1924: U.S. 

Geological Survey Bulletin 783, p. 1-30. 

___ 1929, Mineral industry of Alaska in 1926: U.S. 

Geological Survey Bulletin 797, p. 1-50. 

___ 1930, Mineral industry of Alaska in 1927: U.S. 

Geological Survey Bulletin 810, p. 1-64. 

___ 1930, Mineral industry of Alaska in 1928: U.S. 

Geological Survey Bulletin 813, p. 1-72. 

___ 1932, Mineral industry of Alaska in 1929: U.S. 

Geological Survey Bulletin 824, p. 1-81. 

___ 1933, Mineral industry of Alaska in 1930: U.S. 

Geological Survey Bulletin 836, p. 1-83. 

___ 1933, Mineral industry of Alaska in 1931: U.S. 

Geological Survey Bulletin 844-A,. 117 p. 

___ 1934, Mineral industry of Alaska in 1932: U.S. 

Geological Survey Bulletin 857-A, 76 p. 

___ 1934, Mineral industry of Alaska in 1933: U.S. 

Geological Survey Bulletin 864-A, 81 p. 

___ 1936, Mineral industry of Alaska in 1934: 

U.S. Geological Survey Bulletin 868-A, 91 p. 

___ 1937, Mineral industry of Alaska in 1935: U.S. 

Geological Survey Bulletin 880-A, 95 p •• 

___ 1938, Mineral industry of Alaska in 1936: U.S. 

Geological Survey Bulletin 897-A, 107 p. 

___ 1939, Mineral industry of Alaska in 1937: U.S. 

Geological Survey Bulletin 910-A, 113 p. 

___ 1939, Mineral industry of Alaska in 1938: U.S. 

Geological Survey Bulletin 917-A, 113 p. 

___ 1941, Mineral industry of Alaska in 1939: U.S. 

Geological Survey Bulletin 926-A, 106 p. 

___ 1942, Mineral industry of Alaska in 1940: U.S. 

Geological Survey Bulletin 933-A, 102 p. 

Southworth, D.D., 1984, Geologic and geochemical 

investigation of the "Nail" allochthon, eastcentral Alaska: U.S. Bureau of Mines OpenFile Report 17 6-84, 26 p. 

*Spurr, J.E., 1898, Geology of the Yukon gold 

district, Alaska: U.S. Geological Survey 18th 

Annual Report, pt. 3, p. 87-392. 

Streckeisen, A.L., 1973, Plutonic rocks, 

classification and nomenclature recommended 

by the LU.G.S. Subcommission in the 

Systematics of Igneous Rocks: Geotimes, v. 

18, no. 10, p. 26-30. 

Tempelman-Kluit, D.J., 1976, The Yukon crystalline 

terrane: Enigma in the Canadian Cordillera: 

Geological Society of America Bulletin, v. 87, 

p. 1343-1357. 

___ 1979, Transported cataclasite, ophiolite and 

granodiorite in Yukon: evidence of arccontinent collision: Geological Survey of 

Canada Paper 79-14, 27 p. 

Thorne, R.L., Muir, N.M., Erickson, A.W., Thomas, 

B.I., Heide, H.E., and Wright, W.S., 1948, 

Tungsten deposits in Alaska: U.S. Bureau of 

Mines Report Investigations 4174, 22 p. 

*Townsend, T.E., and Sawatzky, D.L., 1976, 

Programmer's guide for REMAPP remote 

sending array processing procedures: National 

Technical Information Service, PB-256 693, 44 

P• 

*Tripp, R.B., and Crim, W.D., 1986, Mineralogical 

2.1 

maps showing the distribution of selected 

minerals for the minus-30-mesh, nonmagnetic 

heavy-mineral fraction of stream sediment, 

Circle quadrangle, Alaska: U.S. Geological 

Survey Open-File Report 83-170-F, scale 

1:250,000 •• 

*Tripp, R.B., Detra, D.E, and Nishi, J.M., 1982, 

Mineralized zones in bedrock near Miller 

Creek, Circle quadrangle, in Coonrad, W.L., 

ed., The United States Geological Survey in 

Alaska: Accomplishments during 1980: U.S. 

Geological Survey Circular 844, p. 62. 

*Tripp, R.B., Hoffman, J.D., and Risoli, D.A., 1986, 

Geochemical maps showing the distribution of 

selected elements in the minus-30-mesh 

nonmagnetic heavy-mineral fraction of stream 

sediment, Circle quadrangle, Alaska: U.S. 

Geological Survey Open-File Report 83-170-G, 

scale 1:250,000. 

*Tripp, R.B., O'Leary, R.M., and Hoffman, J.D., 

1986, Geochemical maps showing the 

distribution of selected elements in minus-80-

mesh stream sediment: U.S. Geological 

Survey Open-File Report 83-170-H, scale 

1:250,000. 

*Turner, D.L., Forbes, R.B., Albanese, Mary, 

Macbeth, Joyce, Lockhart, A.B., and Seed, 

S.M., 1980, Geothermal energy resources of 

Alaska: Geophysical Institute, University of 

Alaska, Report UAG R-279. 

*U.S. Department of Interior Planning Group, 1980, 

Steese National Conservation areas, Alaska: 

U.S. Geological Survey, scale 1:250,000. 

*W ahrhaftig, Clyde, 196 5, Physiographic divisions of 

Alaska: U.S. Geological Survey Professional 

Paper 482, 52 P•• 

*Ward, F.N., Nakagawa, H.M., Harms, T.F., and Van 

Sickle, G.H., 1969, Atomic absorption methods 

of analysis useful in geochemical 

exploration: U.S. Geological Survey Bulletin 

289, 45 p. 

Weber, F.R., 1983, Glacial geology of the YukonTanana Upland--a progress report, in Thorson, 

R.M., and Hamilton, T.D., eds., Glaciation in 

Alaska: University of Alaska Occasional 

Paper No. 2, p. 96-100. 

+Weber, F.R., and Foster, H.L., 1982, Tertiary(?) 

conglomerate and Quaternary faulting in the 

Circle quadrangle, Alaska, in Coonrad, W.L., 

ed., The United States Geological Survey in 

Alaska: Accomplishments during 1980: U.S. 

Geological Survey Circular 844, p. 58-60. 

+Weber, F.R., and Hamilton, T.D., 1984, Glacial 

geology of Mount Prindle area, Yukon-Tanana 

Upland, Alaska, in Short notes on Alaskan 

geology 1982-83: U.S. Geological Survey 

Professional Paper 86, p. 42-48 

Wedow, Helmuth, Jr., and others, 1953, Preliminary 

summary of reconnaissance for uranium and 

thorium in Alaska, 1952: U.S. Geological 

Survey Circular 24&, 15 p. 

*Wedow, Helmuth, Jr., Killeen, P.L., and others, 
1954, Reconnaissance for radioactive deposits 

in eastern interior Alaska, 1946: U.S. 

Geological Survey Circular 331, 36 p. 

Wedow, Helmuth, Jr., White, M.G., and Moxham, 

R.M., 1952, Interim report on an appraisal of 

the uranium possibilities of Alaska: U.S. 

Geological Survey Open-File Report 51, 123 p. 

*Wedow, Helmuth, Jr., White, M.G., and others, 

1954, Reconnaissance for radioactive deposits 

in east-central Alaska, 1949: U.S. Geological 

Survey Circular 335, 22 p. 

+White, M.G., and Tolbert, G.E., 1952, Radioactive 

granite in the Miller House-Circle Hot Springs 

area, east-central Alaska: U.S. Geological 

Survey Trace Elements Investigations Report 

194, 10 p. 

Williams, J.R., 1962, Geologic reconnaissance of the 

Yukon Flats district, Alaska: U.S. Geologia! 

Survey Bulletin 1111-H, p. 289-331. 

+Wilson, F.H., and Shew, Nora, 1981, Maps and 

tables showing preliminary results of 

potassium-argon age studies in the Circle 

quadrangle, Alaska, with a compilation of 

previous dating work: U.S. Geological Survey 

zz 

Open-File Report 81-889. 

Wilson, F.H., Smith, J.G., and Shew, Nora, 1985, 

Review of radiometric data from the Yukon 

Crystalline Terrane, Alaska and Yukon 

Territory: Canadian Journal of Earth 

Sciences, v. 22, no. 4, p. 525-537. 

*Wilson, F.H., Weber, F.R., and Angeloni, Linda, 

1984, Late Cretaceous thermal overprint and 

metamorphism, southeast Circle quadrangle, 

Alaska (abs.): Geological Society of America, 

Cordilleran Section, Abstracts with Programs, 

v. 16, no. 5, p. 340. 

+Yeend, W.E., 1982, Placers and placer mining, 

Circle District, in Coonrad, W.L., ed., The 

United States Ge(;logical Survey in Alaska: 

Accomplishments during 1980: U.S. 

Geological Survey Circular 844, p. 64. 

+ 1984, Gold in Tertiary(?) rocks, Circle 

---quadrangle, Alaska, in Coonrad, W .L., and 

Elliott, R.L., eds., The United States 

Geological Survey in Alaska: 

Accomplishments during 1981: U.S. 

Geological Survey Circular 868, p. 65-66. 

GPO 785-048/48021