I nte,.p,ret8J tt of pia :ion 

Geochemieaf Data from the 

Uga~hik, B, i~tol a· 

Western tuk' 

Alaska 
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Interpretation of Exploration 

Geochemical Data from the 

Ugashik, Bristol Bay, and 

Western Karluk Quadrangles, 

Alaska 

By S. E. CHURCH, j. G. FRISKEN, and F. H. WILSON 

U.S. GEOlOGICAl SURVEY BUllETIN 1858 
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government. 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1989 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

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Box 25425 

Denver, CO 80225 

Library of Congress Cataloging-in-Publication Data 

Church, S. E. 

Interpretation of exploration geochemical data from the Ugashik, Bristol Bay, 

and Western Karluk Quadrangles, Alaska. 

(U.S. Geological Survey bulletin; 1858) 

Bibliography: p. 

Supt. of Docs. no.: I 19.3:1858 

1. Mines and mineral resources-Alaska-Alaska Peninsula. 2. Geochemical 

prospecting-Alaska-Alaska Peninsula. I. Frisken, James G. II. Wilson, 

Frederick H., 195Q-. Ill. Title. IV. Series. 

QE75.B9 no. 1858 557.3 s [553'.09798'4] 88-607953 

[TN25.A4] 
CONTENTS 

Abstract 1 

Introduction 1 

Geographic setting 1 

Regional geologic setting 2 

Mineral occurrences on the Alaska Peninsula 3 

Geology of the Ugashik-Karluk study area 3 

Exploration geochemistry 4 

Sample media and data collection 4 

Data presentation 7 

Factor analysis 10 

Methods 10 

Geologic significance of the factor solutions 13 

Drainage basin analysis 19 

Rex prospect 28 

Mike prospect 29 

Agripina Bay batholith 33 

Pyritic lode mineralization on the eastern end of David Island 33 

Pacific coastal areas from Portage Bay to Cape Kubugakli 36 

Area northeast of Becharof Lake and northwest of the Kejulik River 41 

Summary and comparison with areas of known mineralization 41 

References cited 43 

FIGURES 

1. Index map of the Alaska Peninsula showing location of the UgashikKarluk study area 2 

2. Simplified geologic map of the Ugashik, Bristol Bay, and western Karluk 

quadrangles 5 

3. Generalized stratigraphy of the Ugashik, Bristol Bay, and western Karluk 

quadrangles 6 

4. Boxplot of the geochemical data for stream-sediment samples, UgashikKarluk study area 10 

5-10. Maps of the Ugashik-Karluk study area showing: 

5. Correlation of stream-sediment factor 1 and heavymineral-concentrate factor 2 with mafic volcanic rocks and 

volcaniclastic sediments 14 

6. Correlation of stream-sediment factor 4 with Quaternary volcanic 

rocks and with the Tolstoi formation 15 

7. Correlation of stream-sediment factor 3 with mafic volcanic rocks 

and with areas of hydrothermal alteration associated with Tertiary 

igneous centers 16 

8. Correlation of stream-sediment factor 5 and heavymineral-concentrate factor 1 with conglomeratic sections of the 

Naknek Formation 17 

9. Correlation of stream-sediment factor 6 with the Shelikof and 

Naknek Formations 18 

10. Correlation of stream-sediment factor 2 with areas of hydrothermal 

alteration associated with Tertiary intrusive rocks 20 

Contents Ill 
11. Map showing five major areas of prominent geochemical anomalies in the 

Ugashik-Karluk study area: the Rex prospect, the area of widespread 

pyrite and inferred Oligocene to Pliocene intrusive activity, the Agripina 

Bay batholith, Portage Bay, and Cape Kubugakli 21 

12-15. Maps of the Ugashik-Karluk study area showing: 

12. Correlation of heavy-mineral-concentrate factor 5 with areas of hydrothermal alteration associated with Tertiary intrusive bodies 22 

13. Correlation of heavy-mineral-concentrate factor 3 with areas of 

hydrothermal alteration associated with Tertiary intrusive 

bodies 23 

14. Correlation of heavy-mineral-concentrate factor 6 with areas of 

hydrothermal alteration associated with Tertiary intrusive 

bodies 24 

15. Correlation of heavy-mineral-concentrate factor 4 with sedimentary 

rocks of the Tolstoi Formation and areas of altered volcanic rocks 

overlying the intrusive rocks in the southern part of the study 

area 25 

16. Map showing possible mineralized areas in the Ugashik-Karluk study area 

defined on the basis of geochemical data 26 

17-18. Drainage basin anomaly map (A) and generalized geologic map (B): 

17. Rex prospect 28 

18. Mike prospect 30 

19. Generalized geologic and geochemical map of the Mike prospect 32 

20-24. Drainage basin anomaly map (A) and generalized geologic map (B): 

20. Agripina Bay batholith 34 

21. Portage Bay area 36 

22. Cape Kubugakli 38 

23. Area along west side of Wide Bay 40 

24. Kejulik River area 42 

TABLES 

1. Comparison of geometric and arithmetic means for elements determined in 

stream sediments and in various nonmineralized intrusive, volcanic, and 

sedimentary rocks from the Ugashik, Bristol Bay, and western Karluk 

quadrangles 8 

2. Threshold values of elements by sample medium, Ugashik, Bristol Bay, and 

western Karluk quadrangles 11 

3. Factor loadings for the first six factors after varimax rotation of the streamsediment data, Ugashik, Bristol Bay, and western Karluk quadrangles 12 

4. Factor loadings for the first six factors calculated by means of an extremevariable, oblique solution for the nonmagnetic heavy-mineral-concentrate data, 

Ugashik, Bristol Bay, and western Karluk quadrangles 12 

5. Summary of geochemical suites and associated minerals found in mineralized 

areas in the Ugashik, Bristol Bay, and western Karluk quadrangles 27 

IV Contents 
Interpretation of Exploration Geochemical 

Data from the Ugashik, Bristol Bay, and 

Western Karluk Quadrangles, Alaska 

By S.E. Church, J.G. Frisken, and F. H. Wilson 

ABSTRACT 

Analysis of the geochemical data obtained from 

exploration geochemical studies of the Bristol Bay, Ugashik, 

and western Karluk quadrangles, Alaska, defines the general 

limits of several porphyry copper-molybdenum target areas, 

at least some of which were previously known. Widespread 

geochemical anomalies and hydrothermally altered rock are 

associated with an inferred Oligocene to Pliocene intrusive 

complex in the southern part of the Ugashik-Karluk study 

area. Two of these areas, one a porphyry coppermolybdenum system associated with a composite Oligocene 

intrusion (the Rex prospect), and the other a porphyry 

molybdenum system associated with Pliocene intrusive 

activity (the Mike prospect), are outlined by coppermolybdenum-tungsten anomalies, surrounded by drainage 

basins containing base- and precious-metal anomalies. Of 

the two areas, the Mike prospect appears to have the more 

favorable geochemical expression for mineralization. Aeromagnetic studies of this area suggest several buried plutons 

beneath these and adjacent geochemical anomalies. Suites 

of elements present suggest porphyry-type mineralization. 

Further examination of several of these areas may be 

warranted. 

Additional evidence of mineralization is associated with 

an area of possible hydrothermal alteration on Cape lgvak 

and may be associated with a pluton of Pliocene age. 

Miocene mineralization on Cape Kubugakli appears to be 

restricted to quartz veins within the outcrop pattern of 

intrusive rocks. The intrusive rocks appear, from the aeromagnetic anomaly, to extend offshore to the east. Cape 

Kubugakli has produced an estimated 5 kg (160 oz) of 

placer gold. 

Factor analysis of the stream-sediment data defines 

one general mineralization factor, whereas the data from the 

nonmagnetic heavy-mineral concentrates panned from 

stream sediments define several mineralization factors. Two 

of the factors defined by the stream sediments outline areas 

of hydrothermal alteration; a zone of propylitic alteration 

Manuscript approved for publication November 16, 1988 

associated with the early Tertiary volcanic and hypabyssal 

rocks is suggested by boron in the nonmagnetic heavymineral concentrates. 

INTRODUCTION 

The U.S. Geological Survey is required by the 

Alaska National Interest Lands Conservation Act 

(ANILCA, Public Law 96-487) to survey certain Federal 

lands to determine their mineral resources. As a part of 

the Alaska Mineral Resource Assessment Program 

(AMRAP), a multimedia, multidisciplinary study of the 

geology, geophysics, and geochemistry of the Ugashik, 

Bristol Bay, and western Karluk quadrangles (together 

referred to as the "Ugashik-Karluk study area" in this 

report) was undertaken during the summers of 

1979-1982. Two days of additional work were done in the 

summer of 1986. This report presents an interpretation 

of the semiquantitative geochemical data collected 

during the course of this investigation. We refer 

extensively to geochemical maps (Church and others, 

1988; Frisken, Church, and others, 1988; Wilson and 

O'Leary, 1986, 1987) and to mineralogical maps of the 

nonmagnetic heavy-mineral concentrates panned from 

stream sediments (Frisken, Church, and Willson, 1988). 

In addition, we have included results of evaluations of the 

Mike and Rex properties made by the exploration group 

at the Kennecott Corporation. 

Geographic Setting 

The Ugashik-Karluk study area is on the Alaska 

Peninsula (fig. 1) between lat 56° and 57° N. The 

northern boundary of the study area cuts across Becharof 

Lake and the southern boundary is just north of 

Aniakchak Crater. The eastern and western boundaries 

Introduction 
EXPLANATION 

• Quaternary volcanic center 

Quaternary volcanic rocks 

Quaternary alluvium 

Older rocks 

• •• • • • •·• •••• •• Boundary between physiographic provinces 

---• Bruin Bay fault (dotted where concealed) 

Unimak Island 

oundary of Ugashik-Karluk 

study area 

N 

/ 

Figure 1. Index map of the Alaska Peninsula showing location of the Ugashik-Karluk study area, Ugashik, Bristol Bay, 

and western Karluk quadrangles, Alaska. Physiographic provinces, major faults, Quaternary volcanoes, and major 

geographic features of the Alaska Peninsula are shown for reference. 

of the study area are the coast lines. Two physiographic 

provinces are present: the Nushagak-Bristol Bay Lowland, along the coast of Bristol Bay, and the Aleutian 

Range (Wahraftig, 1965). The Nushagak-Bristol Bay 

Lowland is characterized by broad coastal plains, low 

topographic relief, many bogs and small lakes, and slow, 

meandering streams. Few samples were collected in this 

province. In sharp contrast, the Aleutian Range is 

composed of Quaternary volcanic cones, flows, and 

stratovolcanoes that partly cover older sedimentary and 

igneous rocks. Elevations exceed 2,000 m (6,500 ft) at 

Mount Chiginagak. Streams in the Aleutian Range 

follow steep gradients down youthful valleys. Glaciers are 

present on some of the dormant volcanic peaks, where 

ice flows to elevations below 300m (1,000 ft) on the coast 

of Wide Bay. The Aleutian Range ends abruptly at the 

Pacific coast, but the rocks that form the Aleutian Range 

appear to extend offshore into Shelikof Strait (Burk, 

1965; Detterman and others, 1983; von Huene and 

others, 1985). The axis of the Aleutian Trench is about 

320 km (200 mi) to the southeast, off the Pacific coast of 

Kodiak Island (Jacob and others, 1977; von Huene and 

others, 1985). 

Regional Geologic Setting 

The Alaska Peninsula marks the transition zone 

between the volcanic island arc of the Aleutian Islands 

and the continental magmatic arc of southern Alaska. At 

the northern end of the Alaska Peninsula, what has been 

2 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
defined as the "Alaska Peninsula terrane" is structurally 

separated into the Iliamna and Chignik subterranes by 

the Bruin Bay fault, north of Becharof Lake (Wilson and 

others, 1985). This fault was intermittently active from 

Late Jurassic time to Middle Tertiary time (Detterman 

and others, 1987). South of Becharof Lake all exposed 

Mesozoic rocks belong to the Chignik subterrane. The 

southernmost exposure of the Iliamna subterrane is on 

one small island on the south side of Becharof Lake. 

The Nushagak-Bristol Bay Lowland is dominantly 

composed of unconsolidated Quaternary alluvium and 

glacial deposits; however, small areas of late Tertiary and 

Quaternary volcanic rocks are present (Detterman and 

others, 1983, 1987). Plutonic rocks of Jurassic to middle 

Tertiary age, which form the Alaska-Aleutian Range 

batholith, are exposed north of lat 57° N. (Reed and 

Lanphere, 1969, 1973). They are also known to occur in 

the subsurface to the south (Brockway and others, 1975). 

These rocks intrude a thick section of Mesozoic and 

Tertiary clastic sedimentary rocks recording fore-arc 

basin sedimentation. The Mesozoic sedimentary rocks 

were derived largely from the erosion of the Jurassic 

volcanic arc and batholith, and they include shale, siltstone, sandstone, and conglomerate deposited in a nonmarine and nearshore marine environment; some deepwater turbidite occurs in the Middle Jurassic (Callovian) 

Shelikof Formation (Allaway and others, 1984; Detterman and others, 1987). Some volcanic tuffs and 

agglomerate are preserved in the Lower Jurassic Talkeetna Formation (Detterman and others, 1987). 

Minor folding and uplift of the Mesozoic 

sedimentary rocks occurred prior to early Tertiary volcanism. Starting in the early Eocene, calc-alkaline volcanism commenced forming the Meshik arc (Wilson, 

1985). This early phase of volcanic and intrusive activity 

was followed by a second pulse beginning in the late 

Miocene forming the Aleutian volcanic arc (Burk, 1965; 

Wilson and Shew, 1988; Detterman and others, 1983, 

1987; Wilson, 1985). Most of the folding and faulting on 

the Alaska Peninsula commenced in Miocene time and 

continued through Quaternary time. For a regional 

summary of the stratigraphy of the Alaska Peninsula, the 

reader is referred to Wilson and others (1985). 

Mineral Occurrences on the 

Alaska Peninsula 

Known mineral occurrences on the Alaska 

Peninsula are dominated by porphyry-type coppermolybdenum sulfide systems. For the Chignik-Sutwik 

Island study area, immediately to the south, Wilson and 

Cox (1983) described porphyry mineralization associated 

with early Tertiary to Quaternary rocks of intermediate 

composition that intrude marine and nonmarine clastic 

rocks. Copper- and molybdenum-rich porphyry systems 

are characterized by drainage basins in which stream 

sediments are anomalous in copper and molybdenum, 

usually associated with tungsten, surrounded by drainage 

basins in which stream sediments are anomalous in lead, 

zinc, bismuth, arsenic, and precious metals. Drainagebasin anomalies show overlapping, zoned geochemical 

patterns. Rocks exposed in these basins typically show 

argillic, sericitic, or phyllic alteration associated with 

veins and disseminated molybdenite, chalcopyrite, and 

scheelite. Surrounding the exposures of intense 

alteration are zones of propylitically altered rock 

containing both disseminated and vein pyrite and lesser 

amounts of galena, sphalerite, arsenopyrite, precious 

metals, barite, and tourmaline. Minor gold is commonly 

associated with the porphyry systems, and some placer 

gold may be found in streams surrounding the centers of 

mineralization. Weathering and oxidation of exposed 

pyrite commonly produces characteristic yellow-brown 

and reddish color anomalies. Our observations indicate 

that similar geologic and geochemical features are 

associated with possible centers of mineralization in the 

Ugashik-Karluk study area. 

Acknowledgments.-We thank the Kennecott 

Corporation and Koniag Incorporated for permission to 

use their unpublished geologic mapping and geochemical 

data from the Mike and Rex prospects in this report. A.L. 

Miesch and R.R. Tidball reviewed portions of the 

manuscript and made valuable comments on the 

discussion of the statistical data. Their contributions to 

the manuscript are appreciated. 

GEOLOGY OF THE UGASHIK-KARLUK 

STUDY AREA 

Geologic mapping in the Ugashik-Karluk study 

area by Detterman and others (1983, 1987) forms the 

geologic base for the interpretations made in this bulletin 

(fig. 2). The description of the stratigraphy (fig. 3) has 

been simplified for the purpose of clarity. 

The oldest rocks exposed in the Ugashik-Karluk 

study area are Permian limestone (Hanson, 1957) that 

crops out on a small island offshore of Cape Kekurnoi on 

the Pacific coast. On shore are small outcrops of Triassic 

limestone, shale, and minor clastic and volcanic rock that 

were deposited in a shallow-water, quiet basin 

environment and that are now exposed along the Pacific 

coast at Puale Bay and to the north towards Alinchak 

Bay. 

The Alaska-Aleutian Range batholith includes 

rocks of Jurassic, Cretaceous, and early Tertiary age 

(Reed and Lanphere, 1969, 1973). The Jurassic plutonic 

rocks of the batholith were emplaced to form the core of 

the Alaska Peninsula; they are contemporaneous with 

Geology of the Ugashik-Karluk Study Area 3 
the Lower Jurassic Talkeetna Formation, which consists 

of volcanic rocks and tuffaceous sandstone, in part, and 

the Lower and Middle Jurassic Kialagvik Formation, 

which consists of shallow-water marine sandstone and 

shale. Later, the Middle Jurassic Shelikof Formation, 

composed of volcanically derived sandstone, 

conglomerate, siltstone, shale, and minor deep-water 

turbidite, was deposited. The Shelikof Formation is 

widely exposed along the Pacific coast of the study area, 

and the Kialagvik Formation is exposed at Wide Bay on 

the axis of the anticline centered in Wide Bay (Allaway 

and Miller, 1984). During Late Jurassic time, the Naknek 

Formation was deposited, derived from the erosion of the 

Alaska-Aleutian Range batholith, followed by nearly 

continuous deposition of the overlying thin-bedded feldspathic siltstone and sandstone. Detterman and others 

(1987) stated that in the study area the Lower 

Cretaceous part of the Staniukovich Formation has been 

removed by erosion and that the thin-bedded sandstone 

and shale that overlie the Naknek may be considered a 

member of the Naknek Formation. For simplicity, these 

two units will be referred to as the "Naknek Formation" 

in this report. The lower, conglomeratic part of the 

Naknek Formation was deposited in a nonmarine, fluvial 

environment, whereas the upper sandstone and shale, 

containing limestone concretions, represent a marine 

environment. Overlying these rocks is the Chignik 

Formation of Late Cretaceous age, which was deposited 

in a cyclical fluvial to nearshore marine sedimentary 

environment (Detterman, 1978). The Upper Cretaceous 

Hoodoo Formation, which interfingers with and overlies 

the Chignik Formation, is a turbidite indicating a deeper 

water environment. 

The Meshik arc formed during Eocene to early 

Miocene time (Wilson, 1985). It is best exposed on the 

northwest side of the Aleutian Range, in the southern 

part of the study area. Basaltic and andesitic calc-alkaline 

volcanic rocks of the Meshik Formation and the volcaniclastic, nonmarine sedimentary rocks of the upper 

part of the Tolstoi Formation constitute the Meshik arc 

in the study area. The Paleocene and Eocene Tolstoi 

Formation is a nonmarine clastic unit, whereas the 

Miocene Bear Lake Formation is primarily a nearshore 

marine deposit containing some nonmarine rocks. In the 

southern part of the study area, along the Pacific coast, 

the Mesozoic sedimentary rocks contain many hypabyssal dikes and sills too small to be shown at the 

1:250,000 scale of the published maps (Detterman and 

others, 1987). 

Further calc-alkaline magmatism during late Miocene to Quaternary time (Wilson and Shew, 1988) 

formed the bulk of the plutons throughout the area. 

Quaternary volcanism produced the volcanic peaks and 

stratovolcanoes that dominate the landscape. Most of the 

young volcanoes lie west of the axis of the Aleutian 

Range, where they form two northeast-trending 

segments, one in the southern Ugashik quadrangle and 

one near the south shore of Becharof Lake. Upper 

Miocene and Pliocene plutons intruded folded Mesozoic 

sedimentary rocks along the Pacific coastline. Aeromagnetic studies (Case and others, 1987) suggest that 

other plutons may be present in the subsurface. 

The overall geologic structure of the Alaska 

Peninsula north of Wide Bay is a gentle, broad arch, the 

axis of which parallels the Bruin Bay fault. Gentle 

anticlines and synclines are superimposed on this broad 

arch. South of Wide Bay, structures are much tighter and 

anticlines are aligned in a northeast-trending en echelon 

pattern. The folding and extensive intrusive activity has 

deformed rocks as young as Pliocene (Burk, 1965, p. 

137). Normal faulting, largely associated with folding, has 

caused numerous offsets in the older lithologic contacts. 

EXPLORATION GEOCHEMISTRY 

Sample Media and Data Collection 

Heavy-mineral-concentrate and stream-sediment 

samples were collected from active stream channels 

draining areas of 5-16 km2 (2-6 mi2

). During the 

reconnaissance geochemical sampling program, 586 

stream-sediment samples and 569 heavy-mineral-concentrate samples from stream sediments were 

collected. Both sample media were collected by wet 

sieving through a 10-mesh stainless steel screen. At each 

site, one 35-cm (14-in.) gold pan full of sediment was 

collected and about 0.5 kg (lib) of minus-2-mm material 

was retained as the stream-sediment sample. The 

remaining material was panned at the site to produce the 

heavy-mineral concentrate (Detra and others, 1981). 

The minus-2-mm stream-sediment samples were 

dried in an oven and then shipped to the laboratory, and 

there they were sieved through an 80-mesh screen. This 

fraction was ground between ceramic plates to minus150 mesh and retained for chemical analysis. The heavymineral concentrates from stream sediments were dried 

in an oven and then shipped to the laboratory, where they 

were sieved to minus-20 mesh. Following removal of the 

light-mineral,fraction by flotation in bromoform (specific 

gravity about 2.8), the heavy-mineral fraction was 

separated into three magnetic splits with a Frantz isodynamic magnetic separator. The most magnetic fraction 

(C1) contained magnetite and rock fragments including 

large amounts of magnetite. The second fraction (C2) 

was of intermediate magnetic susceptibility and consisted 

of rock fragments as well as most of the more magnetic 

mafic silicates. The nonmagnetic fraction ( C3) contained 

the high-specific-gravity rock-forming minerals such as 

4 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
~ "0 

0 

; 

= 0 

:::J 

C) 

CD 

0 

() 

J 

CD 

3 

;;· 

qo 

'< 

(11 

58° 

158° 

EXPLANATION 

r::::J Qal !:: :·:,J Qv 

Tbl 

Tm 

E:J Tt 

r::::J KJs 

r::::J J"RPs 

/"'V Contact 

:;::-:: Fault 

........... Thrust fault 

~ 

~ 

s 

\. 

·\ 

\; 

0 

Ti 

[ ::::::::] Tqd 

EI::]Tv 

C!J Jqd 

--4, 

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~ 

157° 

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;._-r ,, i) ~'7_~ ~-0 '~ ,,, __ ~ I 

._,.,o _.; -'1 / 

57 o 1 t · · ... ·r· ·· ....... · ·· ::- :. · · ·:; · . .:-·.: tJt·.,:s,~/ .-~::-..o:v~c.ff[ : i>~!f+ 

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SCALE 1:1 ,000,000 

0 5 10 15 MILES ,, II,, I I 

0 5 10 15 KILOMETERS IJI!J I I I 

+ 

155° 

Figure 2. Simplified geologic map of the Ugashik, Bristol Bay, and western Karluk quadrangles (Detterman and others, 1983, 1987). Geologic units: Qal, Quaternary 

alluvium; Qv, Quaternary volcanic rocks; Tbl, Tertiary sandstone, siltstone, and conglomerate of the Bear Lake Formation; Tm, Tertiary volcanic flows, breccia, and 

sediment of the Meshik Formation; Tt, Tertiary volcaniclastic sediment of the Tolstoi Formation; Tv, Tertiary (generally Miocene to Pliocene) andesite and basalt; Ti, 

Tertiary (Miocene to Oligocene) hypabyssal hornblende andesite and dacite; Tqd, Tertiary (generally Pliocene) hornblende quartz diorite and quartz monzonite; KJs, 

Cretaceous and Jurassic clastic sediment of the Hoodoo, Chignik, and Naknek Formations; J"RPs, Jurassic, Triassic, and Permian clastic sediment, limestone, and 

metamorphic rocks of the Shelikof, Kialagvik, and Talkeetna Formations; and Jqd, Jurassic granodiorite of the Alaska-Aleutian Range batholith exposed on a small 

island in Becharof Lake just west of the Bruin Bay fault. Faults dashed where approximately located; sawteeth on upper plate of thrust faults. 
AGE THICKNESS UNIT LITHOLOGY 

CORRELATION 

(meters) OF MAP UNITS 

>- Holocene and Surficial deposits and Volcanic rocks, sand, silt, a: 10-1700 Gal Qv ~ 1.6 Ma Pleistocene volcanic rocks, undivided and gravel z 

a: - - UJ 570-730 Sandstone, siltstone, clay, 

IIJj Pliocene Milky River Fm. Tmr 

5 .3 Ma subsurface and conglomerate 

?------? Tqd 

100-1030 Bear Lake Fm . Sandstone, siltstone, lig- Tv 

Miocene mainly u-r=-_ .- Tbl 23.7 Ma nite, and conglomerate 1--- subsurface 

>- Oligocene Volcanic flows, breccia - a: 36.5 Ma ~ 500-1675 Meshik Fm. tuff, and minor sedi- Tm Ti f= - - ~ ments a: 

UJ Eocene f- 57 .8 Ma 

500-1500 - Tolstoi Fm. Sandstone, siltstone, lig-

~=-~ Tt 

66.4 Ma Paleocene nite, and conglomerate 

0-30 Dark siltstone and shale Hoodoo Fm . 

\ ~ 0-100 Chignik Fm . 

~ 

Siltstone, sandstone, mudIt) stone, and shale (/) _J 

::::> 

0 

UJ - u 

~ 

fUJ 

a: 

u 97.5 Ma 

KJs 

> 

~ UJ 

144 Ma 

0-150 Staniukovich ~--F~'\., Thin Sandstone 

~ It) 

_J Sandstone, conglomerate, 1000- 2500 Naknek Fm . siltstone, and shale 

163 Ma I_ IL u 

Ui 800-1500 Shelikof Fm. Siltstone, shale, sand-

(/) Q) I [I~ stone, and conglomerate 

~ =c a: ~ Jqd ::::> 

....., ~ 

- Sandstone, siltstone, 187 Ma 425-850 Kialagvik Fm. shale, and mudstone 

._......---- t-'-

:?: 

n; 

UJ 

- i--1._. 

---- ............. Tuff, limestone, and 

208 Ma 425 Talkeetna Fm. sandstone 

JRPs 

~ 760 Unnamed rocks Limestone, conglomerate, u It) 

Ui _J and basalt 

(/) 230 Ma -- ---r----

~ I 

a: ~Q) 

f- ~=c 240 Ma 

UJ 

~~ 245 Ma 

z ~ It) 

~ _J 258 Ma 

~ 30 

........ ~...-

Unnamed ---rocks Limestone a: > n UJ 

a.. ~ - UJ "'' 

6 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
apatite, zircon, rutile, and sphene, as well as minerals that 

might indicate mineralization, such as epidote, 

tourmaline, fluorite, barite, scheelite, and the sulfide 

minerals. This least magnetic fraction of the heavymineral concentrate was then split if adequate sample 

was recovered. One portion was used for mineral 

identification ( 486 of 569 samples), and a second portion 

was ground for spectrographic analysis. For simplicity, 

the stream-sediment samples and the nonmagnetic 

heavy-mineral-concentrate samples from stream 

sediments are referred to as the "SS samples" and the 

"NMHMC samples," respectively, throughout the 

remainder of this bulletin. 

Stream -sediment, rock, and nonmagnetic heavymineral-concentrate samples were analyzed by a six-step, 

semiquantitative direct -current -arc emission spectrographic method (Grimes and Marranzino, 1968). In 

addition, atomic-absorption spectrophotometry was used 

to determine copper, lead, and zinc in the SS samples by 

means of a nitric acid partial digestion procedure (Ward 

and others, 1969). Gold in some of the rock samples was 

also determined by atomic absorption. Some of the silver 

values, especially those determined near the limit of 

detection by direct-current-arc emission spectrography, 

were not reproducible when checked by atomicabsorption methods; sample sites that are anomalous 

only in silver should be viewed with skepticism. The SS 

and NMHMC data were reported in Detra and others 

(1981 ). Rock samples were collected at many of the field 

stations during the geologic mapping. Geochemical 

results from the analysis of rock samples were reported in 

and summarized by Wilson and O'Leary (1986, 1987). 

Data Presentation 

Geologic mapping in the study area (Detterman 

and others, 1983, 1987) forms the geologic framework 

for geochemical interpretations. A simplified geologic 

map of the study area is shown as figure 2 and the 

stratigraphic column as figure 3; this base is used as an 

underlay for figures that are referenced in the 

Figure 3 (facing page). Generalized stratigraphy of the 

Ugashik, Bristol Bay, and western Karluk quadrangles, 

Alaska (Detterman and others, 1983, 1987). Igneous rocks 

shown in the far right-hand column are Qv, Holocene and 

Pleistocene basaltic andesite and basalt flows and volcaniclastic deposits including some air-flow tuff; Tv, Tertiary 

(generally Miocene to Pliocene) andesite and .basalt, locally 

propylitically altered; Ti, Tertiary (generally M1ocene to Oligocene) hypabyssal hornblende andesite and da?it~; Tqd, 

Tertiary (generally Pliocene) hornblende quartz d1onte and 

quartz monzonite; and Jqd, Middle Jurassic r:'e?ium- to 

coarse-grained, hypidiomorphic granular granod1onte of the 

Alaska-Aleutian Range batholith. 

interpretative discussions that follow. In table 1, we list 

statistical summaries of geochemical data from the 

analysis of stream-sediment samples as well as from 

nonmineralized intrusive, volcanic, and sedimentary 

rocks (Wilson and O'Leary, 1986, 1987). In figure 4, the 

elemental distributions of the stream-sediment data are 

shown by the boxplot method of Tukey (1977). The 

maximum value, 95th percentile, upper quartile, median, 

lower quartile, and minimum values are shown for the 

elements listed in table 1. Censored distributions, that is, 

those elements whose concentrations could not be 

determined in all samples because of a lack of 

·instrumental sensitivity or calibration, are not shown in 

their entirety in figure 4. 

Comparison of the geometric means for most 

elements for the three rock units shows no large geochemical variation among rock types; by inference, 

threshold values determined from the SS samples are 

therefore applicable to the entire Ugashik-Karluk study 

area because of the low variance among rock types. 

Direct comparison of stream-sediment and rock data is 

difficult because of the significant difference in the 

sampling media and because rock samples represent 

point-source information, whereas SS samples represent 

an integrated sample over the upstream basin and 

include possible contributions from glaciation. No effort 

was made to separate SS samples into classes on the basis 

of the dominant rock type in the drainage basin. 

Empirical comparison of the variations between the 

geometric means for the stream-sediment data and the 

plutonic rocks are the most pronounced. Higher median 

values for calcium, strontium, and barium in the plutonic 

rocks suggest a higher plagioclase content in the rock 

samples than found in the average stream-sediment 

composition. This tendency occurs in the volcanic rocks 

as well, but it is less pronounced. The median streamsediment values for iron, titanium, manganese, 

vanadium, and chromium are higher than those for the 

three rock groups sampled and suggest that the SS 

samples are enriched in heavy minerals, such as pyroxene 

(iron, chromium), amphibole (titanium, manganese), 

and (or) magnetite (iron, titanium, vanadium, chromium), relative to the rocks. The high-energy 

environment encountered in the mountainous terrain, 

where mechanical weathering processes are much more 

important than chemical weathering, favors a 

concentration of heavy minerals in the stream sediments. 

Factor analysis of the geochemical data from the 

stream sediments and the nonmagnetic heavy-mineral 

concentrates was used to define geochemical suites. In 

this report, we emphasize the places within the study area 

for which mineralization is suggested by clusters of 

anomalous geochemical values, hydrothermal alteration, 

and (or) sulfide mineralogy. Data from different media 

were compared to evaluate the spatial distribution of 

Exploration Geochemistry 7 
Table 1. Comparison of geometric and arithmetic means for elements determined in 

stream sediments and in various nonmineralized intrusive, volcanic, and sedimentary 

rocks 1 from the Ugashik, Bristol Bay, and western Karluk quadrangles, Alaska. 

[Dashes indicate no data] 

Element2 Detecti~n 

limit 

Geometric 

mean 

Geometric Arithmetic 

deviation4 mean 

Standard 

deviation 

Stream sediments 

Mg 

Ca 

Fe 

Ti 

B 

Be 

Sr 

Ba 

Sc 

La 

y 

Zr 

Mn 

y 

Cr 

Ni 

Co 

Cu 

Cu* 

Mo 

Ag 

Pb 

Pb* 

Zn* 

0.02 

0.05 

0.1 

0.005 

10 

1 

100 

20 

5 

20 

10 

20 

10 

10 

10 

5 

5 

5 

5 

5 

0.5 

10 

5 

5 

1.4 

1.3 

5.8 

0.58 

25 

1.0 

370 

470 

33 

25 

28 

120 

960 

320 

79 

30 

18 

42 

28 

9.8 

0.9 

13 

15 

60 

1.6 

1.7 

2.1 

1.8 

2.2 

1.1 

1.9 

1.5 

1.5 

1.4 

1.4 

1.7 

1.9 

2.0 

1.9 

1.8 

1.8 

2.0 

1.9 

2.0 

2.0 

1.7 

1.7 

1.6 

1.6 

1.5 

7.4 

0.66 

39 

1.0 

520 

510 

36 

28 

30 

150 

1200 

450 

100 

37 

22 

59 

37 

14 

1.3 

17 

18 

71 

0.91 

0.71 

4.9 

0.3 

60 

0.1 

840 

220 

16 

14 

11 

120 

780 

660 

99 

30 

20 

86 

54 

23 

1.9 

29 

19 

110 

Intrusive rocks 

Mg 

Ca 

Fe 

Ti 

B 

Be 

Sr 

Ba 

Sc 

La 

y 

Zr 

Mn 

y 

cr 

Ni 

Co 

Cu 

Cu* 

Mo 

Ag 

Pb 

Pb* 

Zn* 

0.02 

0.05 

0.1 

0.005 

10 

1 

100 

20 

5 

20 

10 

20 

10 

10 

10 

5 

5 

5 

5 

5 

0.5 

10 

5 

5 

1.5 

2.1 

4.1 

0.35 

26 

1.2 

530 

570 

29 

25 

29 

110 

820 

220 

45 

15 

17 

38 

32 

9.0 

17 

14 

32 

geochemical anomalies in different media in relation to 

geologic setting and geophysical data. The threshold used 

for determining anomalous concentrations for each 

element in each of the different media is given in table 2. 

2.1 

1.8 

1.6 

1.7 

2.5 

1.3 

1.6 

2.0 

1.9 

1.4 

1.7 

2.0 

1.8 

1.6 

2.6 

2.3 

2.0 

2.3 

2.2 

2.4 

1.7 

1.7 

2.0 

2.0 

2.4 

4.6 

0.39 

46 

1.2 

590 

700 

36 

27 

33 

140 

940 

240 

70 

21 

21 

51 

41 

15 

20 

15 

40 

1.6 

1.2 

2.0 

0.19 

70 

0.4 

330 

460 

21 

11 

16 

82 

440 

120 

75 

18 

15 

40 

28 

22 

18 

7.8 

30 

The threshold values were determined using both 

statistical methods (mean plus twice the standard 

deviation) and visual inspection of histograms (Church 

and others, 1988; Frisken, Church, and others, 1988). 

8 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
Table 1. Comparison of geometric and arithmetic means for elements determined in 

stream sediments and in various nonmineralized intrusive, volcanic, and sedimentary 

rocks 1 from the Ugashik, Bristol Bay, and western Karluk quadrangles, Alaska-Continued. 

Element2 Detecti~n Geometric Geometr1c Arithmetic Standard 

limit mean devfation4 mean deviation 

Volcanic rocks 

Mg 0.02 1.7 2.5 2.4 2.1 

Ca 0.05 1.9 2.3 2.4 1.6 

Fe 0.1 4.0 1.9 4.8 2.8 

Ti 0.005 0.38 2.1 0.47 0.25 

B 10 23 1.9 29 25 

Be 1 1.1 1.3 1.1 0.3 

Sr 100 600 1.9 720 420 

Ba 20 460 2.2 630 680 

Sc 5 27 1.9 32 19 

La 20 35 1.7 40 22 

y 10 25 1.7 28 15 

Zr 20 100 1.6 120 68 

Mn 10 680 2.0 830 530 

v 10 210 1.8 240 130 

Cr 10 73 3.1 130 160 

Ni 5 30 2.8 51 59 

Co 5 20 1.9 25 16 

Cu 5 32 2.5 47 40 

Cu* 5 27 2.4 38 35 

Mo 5 9.8 1.7 11 5.0 

Ag 0.5 0.8 2.3 1.3 2.0 

Pb 10 15 1.8 19 21 

Pb* 5 18 1.5 20 19 

Zn* 5 46 2.4 77 150 

Sedimentary rocks 

Mg 0.02 1.3 1.9 1.6 0.8 

Ca 0.05 1.1 2.0 1.7 1.8 

Fe 0.1 4.0 1.9 4.9 3.5 

Ti 0.005 0.36 1.8 0.43 0.24 

8 10 27 2.2 38 58 

Be 1 1.1 1.1 1.1 0.3 

Sr 100 370 1.9 450 280 

Ba 20 500 1.9 590 350 

Sc 5 26 1.7 30 16 

La 20 27 1.5 30 12 

y 10 26 1.7 30 16 

Zr 20 82 1.8 93 43 

Mn 10 660 2.0 830 690 

v 10 210 1.7 235 110 

Cr 10 63 2.2 85 72 

Ni 5 32 2.1 42 35 

Co 5 15 1.9 18 12 

Cu 5 36 2.3 50 49 

Cu* 5 33 2.1 42 31 

Mo 5 7.7 1.4 8.0 2.5 

Ag 0.5 0.65 1.4 0.68 1.2 

Pb 10 13 1.4 14 7.0 

Pb* 5 19 1.5 20 7.6 

Zn* 5 60 1.9 70 49 

1Rock data summarized from Wilson and O'Leary (1986, 1987). 

2cu*. Pb*. and Zn* determined by atomic-absorption methods; all others 

determined by direct-current-arc emission spectrography. 

3concentrations of Mg. ca. Fe. and Ti are in percent; all others in parts 

per million. 

4The geometric deviation is expressed as the log of the concentration of 

the element. 

Exploration Geochemistry 9 
10 ~------------~--------------------------------------------------------------~ Mn Sr V 

6102 

i= 

<{ 

a: 

fz 

w 

u 

z 

0 

u 

lL 

0 

c.::J 

~ 10 1 

1.0 

Fe 

Mg Ag 

Ca 

Ba 

Cr Cu 

B 

Co 

Mo 

La 

Be 

I 

Zn 

Zn* 

Zr 

Cu* 

Pb 

Pb* 

Sc 

y 

Nt 

EXPLANATION 

Greater than censored concentration 

Maximum 

95th percentile 

Upper quartile 

Median 

Lower quartile 

Minimum 

Less than censored concentration 

10- ~------------------------------------------------------------------------------

Figure 4. Boxplot of the geochemical data for stream-sediment samples, Ugashik-Karluk study area. Analyses by 

emission spectrography except where atomic absorption indicated by asterisk. Concentrations of iron, magnesium, 

calcium, and titanium are expressed in weight percent; all others expressed in parts per million. 

FACTOR ANALYSIS 

Methods 

Factor analysis is a mathematical technique that, 

according to Johnston (1980, p. 127-128), serves three 

objectives when evaluating multivariant data sets: 

1. To identify groups of inter-correlated variables, 

2. to reduce the number of variables being studied, and 

3. to rewrite the data set in an alternative form. 

When applied to geochemical data, factor analysis groups 

elements within a data set that behave similarly. When 

applied to a set of data in which each element has a high 

detection ratio (that is, where most of the values for each 

element in the data set are determinate), factor analysis 

reduces the variables to a smaller number of more easily 

represented factors. Factor analysis utilizes the 

correlation matrix to group variables, mathematically 

reducing a large number of variables to a few that show 

geochemically coherent behavior. The factors define the 

mathematical structure within the data set and may be 

interpretable in terms of geochemical processes or suites 

of lithologically related minerals. The reader is referred 

to Davis (1973, p. 473-536) or Johnston (1980, p. 

127-182) for further discussion of the factor analysis 

method. 

We used the R-mode factor analysis program 

available from the U.S. Geological Survey's STATPAC 

10 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
Table 2. Threshold values of elements by sample medium, Ugashik, Bristol Bay, and western Karluk quadrangles, Alaska. 

[Dashes indicate no data; < indicates concentration less than the stated value; MF maps in the Ugashik, Bristol Bay, and western Karluk 

quadrangle folio indicated to show from which sources the data have been taken] 

Stream sediment 

Element1 90th 

percentile 

95th 

percentile 

98th 

percentile 

Stream 

sed1ment2 

ananalous 

value 

{MF-1539-F) 

Panned 

concentrate2 

anomalous 

value 

(MF-1539-G) 

Rock2 

anomalous 

value 

(MF-1539-C) 

B 

Ba 

Nb 

N1 

Co 

Cu 

Cu* 

Mo 

w 

Sn 

81 

Au 

Au* 

Ag 

Ag* 

Pb 

Pb* 

Zn 

Zn* 

Cd 

As 

73 

760 

71 

36 

110 

55 

23 

25 

100 

110 

820 

99 

44 

170 

75 

5.7 

34 

36 

130 

220 

1100 

130 

66 

270 

120 

13 

0.8 

53 

55 

320 

210 

70 

70 

30 

100 

<5 

<0.5 

30 

100 

1000 

5000 

100 

200 

100 

200 

10 

<100 

50 

<20 

<20 

1.5 

100 

<500 

<100 

<500 

1000 

100 

100 

5 

0.1 

1.0 

0.7 

30 

30 

200 

100 

200 

1 Element concentrations all in ppm; Cu*. Au*. Ag*, Pb*, and Zn* determined by atomicabsorption methods; all others determined by direct-current-arc emission spectrography. 

2 Only those elements that were plotted on the MF maps were assigned threshold values. 

library (VanTrump and Miesch, 1977) for the analysis of 

the geochemical data from the SS and NMHMC samples. 

For the SS samples, a varimax solution was obtained 

from log-transformed data for 18 elements for which 

detection ratios (DR in table 3) were greater than 0.70; 

beryllium (detection ratio of 0.55) was also included in 

this solution. The program first determines the principal 

components from the correlation matrix. The number of 

factors (no more than a maximum of 10) was determined 

from the discontinuity criterion described by Rummel 

(1970, p. 364). There was a significant break in the 

eigenvalue curve between factor 6 (1.09) and factor 7 

(0.78). The six factors are rotated using Kaiser's 

orthogonal varimax criteria, and the factor loadings (SSP 

1--6) are given in table 3. Seventy-five percent of the total 

variance of the data is explained by the six factors. 

The elements lanthanum, molybdenum, silver, and 

arsenic have detection ratios of 0.28, 0.065, 0.043, and 

0.003, respectively, and therefore these elements were 

excluded from the factor analysis solution. Correlation 

analysis was performed for each of these elements, whose 

distributions were highly censored, to determine their 

possible geochemical associations. A subset of data for 

which each of the elements had unqualified values was 

extracted from the stream-sediment-sample data set. For 

example, in the case of lanthanum all the samples in the 

Factor Analysis 11 
Table 3. Factor loadings for the first six factors after varimax rotation of the stream-sediment data, Ugashik, Bristol 

Bay, and western Karluk quadrangles, Alaska. 

[The six stream-sediment factors (SSF 1-6) explain 75 percent of the 

total variance in the data set. Factor loadings less than 0.40 are 

indicated by the dashes unless the value was quite close, in which case 

it is enclosed in parentheses] 

Ele-1 SSF-1 SSF-2 SSF-3 SSF-4 SSF-5 SSF-6 Detecti2n 

ment ratio 

Mg 0.78 

Ca 0.62 (0.35} Fe 0.87 

T1 0.85 

8 0.47 

Be 

Sr 0.95 

Ba 0.41 

y 0.72 

Zr 0.91 

Sc 0.52 0.68 

Mn 0.86 

v 0.75 (0.38) Cr 0.48 0.64 

N1 0.78 

Co 0.82 

Cu 0.64 0.50 

Cu* 0.75 

Pb 0.79 

Pb* 0.89 

Zn* 0.85 

1Ele.ent concentrations determined by ato.tcabsorpt1on 11ethods indicated by asterisk. 

1.0 

1.0 

0.98 

0.73 

0.97 

0.55 

0.99 

1.0 

1.0 

0.99 

1.0 

0.99 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

0.76 

1.0 

1.0 

2

The elements La. Mo, Ag. and As have detection 

rat1os of 0.28. 0.065. 0.043, and 0.003, respectively: because they are highly censored. these elements were not 

included 1n the factor analysis solution. 

SS data set that had detectable values of lanthanum (that 

is, concentrations greater than or equal to the limit of 

detection for lanthanum (20 ppm)) were extracted into a 

separate data set. Meaningful values of r, the correlation 

coefficient, were chosen from the tables published by 

Fisher (1970, p. 211); the degrees of freedom were 2 

fewer than the number of samples and the 5 percent 

level-of-significance column was used. This same 

procedure was used for molybdenum, silver, and arsenic. 

The following geochemical associations are suggested for 

these elements: lanthanum correlates with magnesium, 

calcium, iron, manganese, vanadium, yttrium, and 

zirconium; molybdenum correlates with cobalt and 

copper; silver correlates with manganese, and with lead 

and zinc determined by atomic absorption; and arsenic 

does not show any significant correlation. These 

correlations suggest that lanthanum is a member of 

SSF-1, and that molybdenum and silver are members of 

SSF-2 (table 3). No statistically rigorous significance can 

be inferred from this treatment of the data. These 

elements, when included in the elemental suite for a 

given factor, are always enclosed in brackets, for 

example, SSF-1: iron, manganese, titanium, magnesium, 

vanadium, yttrium, calcium, scandium, [lanthanum]. 

A different kind of factor analysis solution was 

derived for the geochemical data from the NMHMC 

samples. The log-transformed data for 18 elements that 

had detection ratios (DR) greater than about 0.5 (table 

4) were used. Silver (DR of 0.28) and tin (DR of 0.38) 

were also included in the final solution. After derivation 

of the principal components, rather than use the varimax 

rotation, the first six principal-component vectors were 

rotated to oblique positions representing the six extreme 

variables. The extreme-variable solution showed the best 

relationship to the observed mineralogical suites found in 

the NMHMC samples (Frisken, Church, and Willson, 

1988). The factor loadings (PCP 1-6) are given in table 4. 

Seventy-nine percent of the variance in the data is 

explained. 

The elements zirconium, beryllium, zinc, arsenic, 

molybdenum, cadmium, tungsten, gold, and bismuth 

have detection ratios of 0.14, 0.035, 0.088, 0.069, 0.040, 

0.025, 0.025, 0.023, and 0.017, respectively. Because the 

distributions for these elements were highly censored, 

they were not included in the factor analysis solution. 

Correlation analysis of subsets of the NMHMC data was 

used to define geochemical associations for these 

Table 4. Factor loadings for the first six factors calculated 

by means of an extreme-variable, oblique solution for the 

nonmagnetic heavy-mineral-concentrate data, Ugashik, Bristol Bay, and western Karluk quadrangles, Alaska. 

[The six panned-concentrate factors (PCF 1-6) explain 79 percent of 

the total variance in the data set. Factor loadings having values less 

than 0.40 are indicated by the dashes] 

Ele- PCF-1 PCF-2 PCF-3 PCF-4 PCF-5 PCF-6 Detection 

.ent1 (Nb) (Mg) (Co) (Sr) (Ag) (B) ratiol 

Mg 1.00 

Ca 0.88 

Fe 1.00 

T1 0.91 

B 1.00 Sr 1.00 

Ba 0.59 0.62 

La 0.98 0.44 

y 0.68 

Nb 1.00 

Sc 0.93 

Mn 0.89 

v 0.68 0.75 

Cr 0.97 

N1 0.57 

Co 1.00 

Cu 0.73 

Sn 0.93 

Pb 0.87 0.43 

Ag 1.00 

1Element concentrations determined by atomicabsorption methods indicated by asterisk. 

1.0 

1.0 

0.99 

0.59 

0.95 

0.94 

0.86 

0.99 

1.0 

0.54 

0.97 

1.0 

1.0 

0.99 

0.92 

0.92 

0.75 

0.38 

0.54 

0.28 

2

The elements Zr, Be, Zn. As. Mo, Cd. w. Au, and B1 

have detection ratios of 0.14, 0.035, o.oaa. 0.069. 0.040, 

0.025, 0.025. 0.023, and 0.017, respectively; because 

these elements are highly censored. they were not included 

in the factor analysis solution. 

12 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
elements. A subset of data for which each of the elements 

had unqualified values was extracted from the NMHMC 

data set in the same manner as described above for the 

stream-sediment data. Meaningful values of r, the 

correlation coefficient, were chosen from the tables 

published by Fisher (1970, p. 211); the degrees of 

freedom were 2 fewer than the number of samples and 

the 5 percent level-of-significance column was used. The 

following geochemical associations are suggested for 

these elements: zirconium correlates with titanium, 

vanadium, yttrium, and [thorium]; beryllium correlates 

with no other element; zinc correlates with copper, 

molybdenum, and cadmium; arsenic correlates with gold; 

molybdenum correlates with iron, lead, and zinc; 

cadmium correlates with iron, silver, lead, and zinc; 

tungsten correlates with copper; gold correlates with 

silver, arsenic, and tin; and bismuth correlates with 

copper and zinc. This procedure suggests that zirconium 

is a member of PCF-1 and that the ore metals (zinc, 

arsenic, molybdenum, cadmium, tungsten, gold, and 

bismuth) are associated with the two mineralization 

factors PCF-3 and PCF-5 (table 4). No statistically 

rigorous significance can be inferred from these 

associations. These elements, when included in the 

elemental suite for a given factor, are always enclosed in 

brackets, for example, PCF- 1: niobium, lanthanum, tin, 

titanium, vanadium, yttrium, [zirconium], [thorium]. 

Geologic Significance of the 

Factor Solutions 

The factor sample-scores from the streamsediment data (SSF) appear to be generally related to 

rock compositions, wher_eas the sample-scores obtained 

from the NMHMC data (PCP) appear to be related to 

mineral suites. The map area defined in particular by 

panned concentrate factor 2 (PCF-2: magnesium, 

chromium, scandium, manganese, calcium, vanadium; 

point-plot data, fig. 5) and by factor 1 from the streamsediment data (SSF-1: iron, manganese, titanium, 

magnesium, vanadium, yttrium, calcium, scandium, [lanthanum]); contoured data, fig. 5) appears to coincide 

with the drainage areas where volcanic rocks crop out, 

especially with rocks of the Meshik Formation. The 

elements that make up these two factors occur at high 

concentrations in basaltic rocks such as those that are a 

component of the Meshik Formation (Detterman and 

others, 1987), and they also match the area of high 

contributions of nonmagnetic pyroxenes present in the 

NMHMC fraction (Frisken, Church, and Willson, 1988). 

Likewise, associations of nickel, chromium, copper 

(SSF-4, fig. 6) with mafic volcanic rocks presumably 

reflects the presence of amphibole or pyroxene. 

Stream-sediment factor 3 (SSF-3: cobalt, scandium, chromium, [molybdenum] ) is associated with areas 

underlain by Quaternary volcanic rocks (fig. 7) including 

Aniakchak Crater (lat 57° N. to 57°10' N. and long 

157°45' W. to 158°30' W.) in the Chignik quadrangle, the 

southeastern flank of Mount Peulik, Mount Chiginagak, 

and the area of Quaternary volcanic rocks northeast of 

Becharof Lake and northwest of the Kejulik River (lat 

57°55' N. to 58° N. and long 155°45' W. to 156° W.). The 

Quaternary volcanic rocks are also delineated by PCF-2 

(magnesium, chromium, scandium, manganese, calcium, 

vanadium; fig. 5); however, SSF-3 also delineates the 

area from north of Portage Bay to Puale Bay. This last 

area is underlain mainly by volcaniclastic sedimentary 

rocks of the Jurassic Shelikof Formation (R.L. Detterman, oral commun., 1987). Comparison with the 

mineralogical data (Frisken, Church, and Willson, 1988) 

from analysis of the NMHMC samples shows that all of 

these sites contain abundant detrital mafic minerals. 

Because most of the Mesozoic sedimentary rocks, which 

were derived from erosion of the Alaska-Aleutian Range 

batholith, contain 5-10 percent amphibole and (or) biotite, it is not surprising that PCF-2 also delineates the 

Mesozoic sedimentary rocks. Areas of hydrothermally 

altered rock in the Agripina Bay batholith and areas 

immediately adjacent to it on the west side of the 

batholith are also delineated by SSF-3. 

Stream-sediment factor 5 (SSF-5: zirconium) 

correlates spatially with PCF-1 (niobium, lanthanum, 

tin, titanium, yttrium, [zirconium]) and with abundant 

zircon in the corresponding nonmagnetic heavy-mineralconcentrate samples (Frisken, Church, and Willson, 

1988). The two factors SSF-5 and PCF-1 coincide with 

the outcrop pattern of the Naknek Formation (fig. 8). 

The distribution of zirconium in SSF-5 uniformly covers 

the outcrop area of the Naknek Formation, whereas 

PCF-1 reflects a more diverse suite of heavy minerals. 

Most of the tin geochemical anomalies are associated 

with the PCF-1 suite and appear to be derived from the 

Upper Jurassic Naknek and Upper Jurassic and Lower 

Cretaceous Staniukovich Formations. These rocks 

contain abundant granitic and metamorphic clasts 

derived from the deroofing of the Jurassic part of the 

Alaska-Aleutian Range batholith. 

Stream -sediment factor 6 (SSF-6: strontium, 

[calcium]; fig. 9) reflects the presence of carbonate. 

Along the Pacific coast, SSF-6 coincides with the area 

underlain by the Shelikof and Naknek Formations, which 

contain limestone concretions (Detterman and others, 

1983; Allaway and Miller, 1984). The two streamsediment factors SSF-5 and SSF-6 are mutually 

exclusive and are interpreted to reflect different marine 

depositional environments. The two factors SSF-5 and 

PCF-1 are interpreted to reflect a shallow marine, littoral environment of the Naknek Formation, whereas the 

presence of carbonate concretions (SSF-6) reflects a 

quieter, deeper water environment, perhaps rich in 

organic material. 

Factor Analysis 13 
.... 

.;a 

m 

>< 

"C 

0 

; 

.... 

(5" 

:::s 

C) 

CD 

0 

0 

:::r 

CD 

3 

[ 

~ 

c: 

co 

Q) 

t/1 

:::r 

F 

~ 

[ 

2. 

Ill 

Q) 

':( 

Q) 

:::s 

c. 

t/1 

~ .... 

CD 

3 

" ~ 

c 

~ 

0 

c 

Q) 

c. 

; 

:::s 

co 

(i" 

~t/1 

> i" 

t/1 

~ 

Q) 

58° 

158° 

EXPLANATION 

c:J Qal !:::·::::.:.:1 Qv 

r::J Tbl c::J Ti 

- Tm c::J Tqd 

<:$~~t Tt r:::J Tv 

c:J KJs 

~ J"RPs C!J Jqd 

/V Contact 

;:::-.:: Fault 

~ Thrust fault 

~ 

~ 

s 

\ 

"\ 

'v 

0 

~ 

\"' ~ 

157° 

57o~ t:D1?1~(:'.:;.;:!/t: Pf·(:.::~:::~~>>~<:~:~:J!f![f/BiJ;": ~-~~ 

156° 

~ \"' 

+ 

(; 

\\ 

(;\ 

0 

+ 

\"'~ 

(;\:.. 

SCALE 1:1 ,000,000 0 5 10 15 MILES I I I I,, I I 0 5 10 15 KILOMETERS 11111 I I I 

+ 

155° 

Figure 5. Map of the Ugashik-Karluk study area showing the correlation of stream-sediment factor 1 (SSF-1: iron, manganese, titanium, magnesium, vanadium, yttrium, 

calcium, scandium, [lanthanum]) and heavy-mineral-concentrate factor 2 (PCF-2: magnesium, chromium, scandium, manganese, calcium, vanadium) with mafic 

volcanic rocks (Qv and Tm) and volcaniclastic sediments (Tt). SSF-1 is shown as a contour plot of factor sample-scores (2.0 = 99th percentile, 1.5 = 92nd percentile, 

1.0 = 80th percentile), and PCF-2 is shown as a point plot of factor sample-scores (90th percentile shown as a filled square). See figure 2 for explanation of other geologic 

map symbols. 
58° 

158° 

EXPLANATION 

r:::::J Oal L:·: :·.J Ov 

r:::::J Tbl c::J Ti 

c:::::J T m c:J T qd 

c:J T t c:::::J Tv 

r:::::J KJs 

c:::::J J"RPs 

rY Contact 

~ Fault 

.......... Thrust fault 

~ 

<0 

·\ 

C;) 

\ 

v 

0 

[!] Jqd 

~ 

...1.. 

t" 

157 ° 

5701 F):::·\<(>::;.:.0_:::._: .. ~.:~ :: ::·:: ;>> df\ -1Y,:J%X ·t{§~-~4(~ \ ' 

+ 

Agripina Bay 

D David 

Island 

~ 

156 ° 

(; 

~t" 

+ 

\(; 

\« 

0 

+ 

~ 

~t" (; 

SCALE 1:1,000,000 

0 5 10 15 MILES ,,, I,, I I 

0 5 10 15 KILOMETERS IIIJII I I 

+ 

155° 

, Figure 6. Map of the Ugashik-Karluk study area showing the correlation of stream-sediment factor 4 (SSF-4: nickel, chromium, copper) with Quaternary volcanic rocks a (Qv) and with the Tolstoi Formation (Tt). SSF-4 is shown as a contour plot of factor sample-scores (2.0 = 97th percentile, 1.5 = 92nd percentile, 1.0 = 85th percentile, 

~ 0.5 = 70th percentile); hachured contours indicate lows. See figure 2 for explanation of other geologic map symbols. 

)> 

;::, 

• -< en 

;· 

.... 

U1 
.... 

Q) 

tr 

"0 

0 

! 

()" 

:::J 

C) 

~ 

0 

(') 

:r 

~ 

3 

;· 

=: 

~ 

c: 

co 

Ill 

(I) 

:r 

F 

~ ;· 

[ 

DJ 

Ill 

~ 

Ill 

:::J 

Q. 

(I) 

~ .. 

~ 

3 

~ c 

~ 

0 

c 

Ill 

Q. 

; 

:::J 

co 

i" 

~ 

> iii" 

(I) 

~ 

Ill 

58° 

57° 

158° 

EXPLANATION 

CJ Qal f:: ·:>·. :] Qv 

C) Tbl fiB Ti 

CJ Tm [JZJ Tqd 

CJ Tt c::::J Tv 

C]KJs 

CJ J"RPs C!J Jqd 

/V Contact 

;::-::: Fault 

......... Thrust fault 

~ 

s 

\ 

~ 

'\ 

'v 

0 

·;:~·:::~:·}::: Hornfels 

~ Altered rocks 

...t. 

~ 

~ 

157° 156° 

+ 

Becharo/ Lake 

G 

~~ 

+ 

\.G 

,~ 

0 

+ 

~~ 

G~ 

SCALE 1:1 ,000,000 

0 5 10 15 MILES ,, I I I I I I 

0 5 10 15 KILOMETERS lp !J I I I 

+ 

155,

0 

Figure 7. Map of the Ugashik-Karluk study area showing the correlation of stream-sediment factor 3 (SSF-3: cobalt, scandium, chromium, [molybdenum]) with mafic 

volcanic rocks (Qv) and with areas of hydrothermal alteration associated with Tertiary igneous centers (Ti and Tqd). SSF-3 is shown as a point plot of factor 

sample-scores (90th percentile shown as an open circle). See figure 2 for explanation of other geologic map symbols. 
58° 

158° 

EXPLANATION 

r::J Gal r::J Ov 

r::J Tbl c:::J Ti 

r::J Tm c:::J Tqd 

CJ Tt r::J Tv 

r::J KJs 

r::J J"RPs 

/"'"\./ Contact 

~ Fault 

......... Thrust fault 

~ 

s 

\ 

~ 

·'\ 

\; 

0 

C!J Jqd 

...1. 

t" ~ 

157° 

57 ° t-• I I II ' » "> - (eq=G\., '•""'?' IJ:::Ot:C'D )Yl \ l 

156° 

+ 

(; 

~ t" 

+ 

\(; 

\<: 

0 

+ 

t"~ 

(;~ 

SCALE 1:1,000,000 

0 5 10 15 MILES ,, I I I I I I 

0 5 10 15 KILOMETERS I Jill I I I 

+ 

155° 

"TI Figure 8. Map of the Ugashik-Karluk study area showing the correlation of stream-sediment factor 5 (SSF-5: zirconium) and heavy-mineral-concentrate factor 1 (PCF-1: a niobium, lanthanum, tin, titanium, yttrium, vanadium, [zirconium]) with conglomeratic sections of the Naknek Formation (KJs). PCF-1 is shown as a contour plot of factor 

~ sample-scores (2.0 = 99th percentile, 1.5 = 95th percentile, 1.0 = 85th percentile, 0.5 = 70th percentile), and SSF-5 is shown as a point plot of factor sample-scores 

~ (95th percentile shown as an open circle); hachured contours indicate lows. See figure 2 for explanation of other geologic map symbols. I» 

-< en 

0 

.... 

-...! 
... 

co 

rn 

>< 

"C 

0 

; 

... 

c;· 

:I 

C) 

CD 

0 

n 

:I" 

CD 

3 

0 

... 

g. 

c: 

(Q 

~ 

Cll 

:I" 

if 

~ ;· 

... 

2.. 

m 

~ 

~ 

~ 

:I 

c. 

== (I) 

Cll 

... 

CD 

3 

~ 

~ 

E" 

;Ill:" 

0 

c 

~ 

c. 

; 

:I 

(Q 

CD' 

~ 

> iii 

Cll 

;Jf(" 

~ 

158° 

58° EXPLANATION 

r:::J Oal c::::J Ov 

r:::J Tbl c::J Ti 

r:::J Tm c::J Tqd 

c::l Tt r:::J Tv 

c:::J KJs 

IM JliPs C!J Jqd 

/""\/ Contact 

:;:-:: Fault 

..,lt....,.,. Thrust fault 

.J., 

ov ~/ '\ 

co 

'\ 

~ 

~ 

57° 

157 ° 

« ~ 1!/0_q 'i) /f.,.r:J -?~~ O~ _, t:/)"l:.O"; ....... ~ - , 

+ 

Agripina Bay 

0 

David 

Island 

~ 

156° 

~ ~ 

+ 

(; 

,G 

,~ 

0 

+ 

~~ 

(;\:,. 

SCALE 1:1,000,000 

0 5 10 15 MILES I I I I,, I I 

0 5 10 15 KILOMETERS I !1 1J I I I 

+ 

155° 

Figure 9. Map of the Ugashik-Karluk study area showing the correlation of stream-sediment factor 6 (SSF-6: strontium, [calcium]) with the Shelikof and Naknek 

Formations (JRPs and KJs). SSF-6 is shown as a point plot of factor sample-scores (95th percentile shown as an open triangle). See figure 2 for explanation of other 

geologic map symbols. 
The remaining factors, from both SS and NMHMC 

samples, reflect either mineralization or hydrothermal 

alteration associated with it. SSF-2 (lead, zinc, copper, 

boron, barium, [silver]) defines base-metal anomalies 

associated with intrusive centers of Tertiary age (fig. 10), 

whereas factors PCF-3-PCF-6 identify particular suites 

of elements (table 4) associated with individual centers 

of mineralization. In figure 11, we distinguish five areas 

that are delineated by factor sample-scores where 

widespread, multi-element geochemical anomalies 

occur: 

A, Area surrounding the Rex prospect of Oligocene age (lat 57°10' N. to 57°20' N. and long 156°50' 

W. to 157°10' W.) 

B, Large area outlined by widespread pyrite in the 

NMHMC samples (lat 57° N. to 57°07' N. and long 157° 

W. to 157°30' W.), which also includes the Mike prospect 

C, Area of the outcrop pattern of the Pliocene 

quartz-diorite and granodiorite at Agripina Bay 

D, Area of the outcrop pattern of Pliocene granodiorite at Cape Igvak, southwest of Portage Bay 

E, Area of the outcrop pattern of the Miocene(?) 

granodiorite at Cape Kubugakli 

Mineralized rock associated with the Rex prospect 

is also shown by PCF-5 (silver, lead, [gold], [arsenic], 

[tin] ) in figure 12. The area surrounding the Mike 

prospect and the Oligocene altered rock near the Agripina Bay batholith are also delineated by this factor. The 

Portage Bay localities are indicated by several SS samples 

and the altered zone underlain by the granodiorite at 

Cape Kubugakli by three sample sites. Finally, possible 

sulfide mineralization may be indicated by PCF-5 in a 

broad area underlain by Naknek Formation and 

Quaternary volcanic rocks northwest of the Kejulik River 

near lat 57°50' N. to 58° N. and long 155°15' W. to 156° 

15' w. 

The geochemical assemblage from PCF-3 (cobalt, 

iron, copper, lead, nickel, barium, [zinc], [molybdenum], 

[cadmium], [tungsten], [bismuth]) outlines hydrothermally altered areas where pyrite is abundant and some 

chalcopyrite occurs (fig. 13) as shown by the NMHMC 

samples (Frisken, Church, and Willson, 1988). An area 

of abundant pyrite extends from the headwaters of 

Pumice Creek east to the head of Wide Bay. There is a 

strong spatial correlation with the Pliocene intrusive 

rocks (Wilson and Shew, 1988) associated with the Mike 

prospect, but the geochemical association of this factor 

with the Agripina Bay batholith, also of Pliocene age, and 

the Oligocene intrusive rocks (Wilson and Shew, 1988) at 

the Rex prospect is much less pronounced. 

Boron (PCF-6, fig. 14) shows a strong association 

with the areas of hydrothermal alteration.associated with 

dikes and sills of Oligocene age. Comparison with the 

mineralogical data (Frisken, Church, and Willson, 1988) 

shows that this factor may reflect the presence of 

tourmaline in the concentrates in areas where there is 

mineralized rock. Some tourmaline was also found in the 

area north and west of the Mike prospect and at the head 

of Wide Bay. This factor also reflects a zone of propylitic 

alteration ·overlying the Agripina Bay batholith (the 

Kilokak Creek area) as well as along its western margin. 

The geochemical association strontium, barium, 

and lanthanum (PCF--4) may reflect barite and pyrite in 

veins distal to mineralized rock at the Mike prospect and 

the Agripina Bay batholith. In addition, barite and pyrite, 

in some places associated with chalcopyrite, occurs in 

samples collected in the area of widespread pyrite 

exposed from the headwaters of Pumice Creek to Wide 

Bay (area B, fig. 15). There are two other occurrences 

northeast of the head of Portage Bay and at Puale Bay. In 

addition, the area along the northwest side of Wide Bay 

is outlined by this factor. The area is underlain by the 

Shelikof Formation, and the NMHMC samples from this 

area may include sedimentary barite; however, the 

minerals pyrite, chalcopyrite, and scheelite were found in 

NMHMC samples from some of these drainage basins. 

Some of the area north of Portage Bay is also outlined by 

PCF--4. 

DRAINAGE BASIN ANALYSIS 

Comparison of the geochemical data with the 

geologic map and the geophysical data defines ten areas 

that may have mineral endowment (fig. 16). Five of these 

areas were delineated by factor analysis. The Rex 

prospect (area 1, also defined as area A from the factor 

sample-scores) is associated with a composite Oligocene 

intrusive center. Much of the southern part of the study 

area (areas 2-5, which are coincident with area B) is 

strongly altered and contains numerous dikes and sills, 

probably of Oligocene to Pliocene age. Area 3 is defined 

by the factor sample-scores around the Mike prospect. 

Similar geochemical suites define anomalous areas that 

extend to the south into the Chignik and Sutwik Island 

quadrangles (Cox and others, 1981 ). Areas 6 and 7 

include all of the outcrop area of the Pliocene Agripina 

Bay batholith (areas C and D as defined by the factor 

sample-scores), and area 8 is associated with Miocene 

alteration at Cape Kubugakli (area E as defined by factor 

sample-scores). Area 9 encompasses the folded Mesozoic strata on the west side of Wide Bay, and area 10 

includes the Naknek Formation and the overlying 

Quaternary volcanic rocks north of the east end of 

Becharof Lake, northwest of the Kejulik River. Detailed 

summaries of the geochemical suites and ore-related 

minerals for each of the sites discussed below are given in 

table 5. 

Drainage Basin Analysis 19 
1\) 

0 

m 

>< 

'0 

0 

; 

.... 

()" 

:::s 

G') 

(II 

0 

n 

=r 

(II 

3 

0 

.... 

~ 

c: 

(Q 

I» 

en 

=r 

F 

~ u;· 

[ 

Ill 

I» 

~ 

I» 

:::s 

Q. 

~ (II 

en 

.... 

(II 

3 

" ~ 

c 

;Ill:" 

0 

c: 

I» 

0. 

; 

:::s 

(Q 

i" 

_en 

> i" 

en 

;Ill:" 

I» 

158° 

58° EXPLANATION 

CJoal CJov 

CJTbl IIITi 

C]Tm [ :>:<:>J T qd 

CJn c:::J Tv 

C]KJs 

CJ J"RPs C!J Jqd 

/'\/ Contact ·;:~·~::~:·~·::: Hornfels 

~ Altered rock 

:::::-::::: Fault 

......... Thrust fault 

...t, 

\>' ~ 

v 

0 

'\ 

'.? 

\ 

~ 

~ 

57° 

157° 156° 

+ 

(; 

« \>' 

+ 

\(; 

\'< 

0 

+ 

\>'~ 

(;~ 

SCALE 1:1 ,000,000 

0 5 10 15 MILES It! 1 rl I I 

0 5 10 15 KILOMETERS I!IJII I I 

+ 

155° 

Figure 10. Map of the Ugashik-Karluk study area showing the correlation of stream-sediment factor 2 (SSF-2: lead, zinc, copper, boron, barium, [silver]) with areas 

of hydrothermal alteration associated with Tertiary intrusive rocks (Ti and Tqd). SSF-2 is shown as a contour plot of factor sample-scores (3.0 = 98th percentile, 2.0 = 

95th percentile, 1.0 = 90th percentile). See figure 2 for explanation of other geologic map symbols. 
c 

; 

:;· 

Q) 

(Q 

Gl 

aJ 

Q) 

0 

:r 

~ 

:::s 

Q) 

-< 0 

u;· 

1\) 

.... 

158 ° 157 ° 156° 155° 

+ + + 

58 °1c-~:---~---,--___:::r---,----T----.,.----~ 

+ 

~ 

~ 

~ 

\ 

'\ 

v 

0 

57o I , I I" ' » > -- I I ...... ,-- 'Cb I h. 

Becharof Lake 

rv---

1 ~ Pt tage +ry __ .J 

G 

~\'-

+ 

\G 

\« 

OG 

+ 

~ 

~t' 

SCALE 1:1 ,000,000 

5 0 5 10 MILES ,,, I I I I I 

5 0 5 10 KILOMETERS 1 J1 Jll I 1 

+ 

Figure 11. Map showing five major areas of prominent geochemical anomalies in the Ugashik-Karluk study area (heavy dashed lines): the area of the Rex prospect 

(A), the area of widespread pyrite and inferred Oligocene to Pliocene intrusive activity (B), the Agripina Bay batholith (C), the Portage Bay area (D), and the Cape Kubugakli 

area (E). Major Quaternary volcanic centers are labeled and the Quaternary lava flows are shown by the thin black lines. 
N 

N 

~ 'tJ 

0 

.. 

a o· 

:;:, 

C') 

CD 

0 

n 

:r 

CD 

3 

;· 

... 

~ 

c: 

(Q 

I» 

en 

:r 

w~ 

~ 

en 

[ 

tD 

I» 

~ 

I» 

:;:, 

Q. 

:E 

(I) 

en 

co 

3 

;;,.;; 

~ 

c 

~ 

0 

c 

I» 

Q. 

; 

:;:, 

(Q 

CD' 

.!' 

::t> 

i' 

en 

~ 

I» 

158° 

58° EXPLANATION 

r:::::J Gal r:::::J Ov 

(::J Tbl .. Ti 

r:::::J Tm L:-:-:-:-:-:1 Tqd 

r:::::J Tt c::J Tv 

c::J KJs 

c::J J'RPs [!] Jqd 

r'v' Contact ·;:~·~~::·}::: Hornfels 

~ Altered rock 

:;:::-::: Fault 

........... Thrust fault 

...J., 

\" ~ 

v 

0 

'\ 

~ 

\ 

~ 

~ 

57° 

157° 156° 

+ 

(; 

~t' 

+ 

\(; 

\~ 

0 

+ 

t'~ 

(;XSCALE 1:1 ,000,000 

0 5 10 15 MILES ,, 'I I I I I 

0 5 10 15 KILOMETERS IIIJJI I I 

+ 

155° 

Figure 12. Map of the Ugashik-Karluk study area showing the correlation of heavy-mineral-concentrate factor 5 (PCF-5: silver, lead, [gold], [arsenic], [tin]) with areas 

of hydrothermal alteration associated with Tertiary intrusive bodies (fi and Tqd). PCF- 5 is shown as a point plot of factor sample-scores (95th percentile shown as a filled 

diamond; 90th percentile shown as a filled square). See figure 2 for explanation of other geologic map symbols. 
c 

; 

:r 

I» 

co 

CD 

CD 

I» 

0 

:; 

l> 

::s 

I» 

j 

Cii" 

N 

w 

58 ° 

158 ° 

EXPLANATION 

c:::J Q a I c:::J 0 v 

c::J Tbl i,lg Ti 

c:::J Tm [ ::::::::] Tqd 

c:::J Tt c:::J Tv 

c:::J KJs 

c:::J JliPs 

/"'V Contact 

:;::-:: Fault 

.,_.., Thrust fault 

<(> 

'::> 

\ 

~ 

·\ 

'v 

0 

L!J Jqd 

-[.~·~:::·:·::: Hornfels 

~ Altered rocks 

-4. 

\>' ~ 

57°1 ' I I'' ' br » -----.. ~ 

157 ° 156° 

+ 

G 

~\>' 

+ 

\G 

\~ 

OG 

+ 

~ 

\:.-'t" 

SCALE 1:1,000,000 

0 5 10 15 MILES I I 11 I I I I 

0 5 10 15 KILOMETERS IIJJJ I I I 

+ 

155° 

Figure 13. Map of the Ugashik-Karluk study area showing the correlation of heavy-mineral-concentrate factor 3 (PCF-3: cobalt, iron, copper, lead, nickel, barium, [zinc], 

[molybdenum], [cadmium], [tungsten], [bismuth]) with areas of hydrothermal alteration associated with Tertiary intrusive bodies (Ti and Tqd). PCF-3 is shown as a point 

plot of factor sample-scores (95th percentile shown as a filled diamond; 90th percentile shown as a filled square). See figure 2 for explanation of other geologic map 

symbols. 
I'IJ 

~ 

~ "C 

0 

! 

0 

:::1 

C) 

CD 

0 

() 

:r 

CD 

3 

~ 

~ 

c: 

cc 

01 

(I) 

:r 

F 

gJ 

;· 

.. 

2.. 

llJ 

01 

~ 

01 

:::1 

a. 

:= 

CD 

(I) 

.. 

CD 

3 

" ~ 

c 

~ 

0 

c 

01 

Q. 

; 

:::1 

cc 

CD' 

_U» 

~ 

i' 

(I) 

~ 

01 

158° 

58° EXPLANATION 

CJoal c::Jov 

C]Tbl .. Ti 

C]Tm t:ZJ .Tqd 

CJn c::J Tv 

CJ KJs 

CJ JliPs L!J Jqd 

/"V Contact ·;·:~·~::~:·:·:=: Hornfels 

~ Altered rock 

Fault 

........ Thrust fault 

.J.. 

\" 

~ 

'v 

0 

-\ 

s 

\ 

~ 

~ 

57° 

157° 156 ° 

+ 

(;\ 

~~ 

+ 

G ~\ 

0 

+ 

~~ 

(;~ 

SCALE 1:1,000,000 

0 5 10 15 MILES I I I 1 ,, I I 

0 5 10 15 KILOMETERS IIJJII I I 

+ 

155° 

Figure 14. Map of the Ugashik-Karluk study area showing the correlation of heavy-mineral-concentrate factor 6 (PCF-6: boron) with areas of hydrothermal alteration 

associated with Tertiary intrusive bodies (Ti and Tqd). PCF-6 is shown as a point plot of factor sample-scores (95th percentile shown as a filled diamond; 90th percentile 

shown as a filled square). See figure 2 for explanation of other geologic map symbols. 
c 

; 

5" 

I» 

ca 

(1) 

CD 

I» 

Cit 

:r 

l> 

::s 

I» 

-< Cit 

u;· 

!\) 

(II 

58° 

158° 

EXPLANATION 

c::J Gal c::J Qv 

c:::J Tbl .. Ti 

c::J Tm (:=J Tqd 

~ ~ Tt ~ r.:"='l Tv 

c::J KJs 

c::J JliPs L!J Jqd 

/"\/ Contact 

::::=-::: Fault 

~ Thrust fault 

\ 

~ 

~ 

'\ 

';:) 

v 

0 

·;·~·(:~:·}::: Hornfels 

~ Altered rock 

--l, 

~ 

~ 

57ol ' I 111 ~~ l 

157 ° 156 ° 

+ 

G 

~ ~ 

+ 

\G 

\~ 

0 

+ 

£"~ 

G\-

SCALE 1:1 ,000,000 

0 5 10 15 MILES I I I I,, I I 

0 5 10 15 KILOMETERS 1 1 1J J1 I I 

+ 

155° 

Figure 15. Map of the Ugashik-Karluk study area showing the correlation of heavy-mineral-concentrate factor 4 (PCF-4: strontium, barium, lanthanum) with sedimentary 

rocks of the Tolstoi Formation (Tt) and areas of altered volcanic rocks (Tv) overlying the intrusive rocks (Ti) in the southern part of the study area. PCF-4 is shown as a 

contour plot of factor sample-scores (2.0 = 98th percentile, 1.5 = 95th percentile, 1.0 = 90th percentile). See figure 2 for explanation of other geologic map symbols. 
1\) 

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Becharof Lake 

, DO..q 

/) ,.,:i'Z. ';J ~<>, - - (' 'J) 0. -1- ~ -

-~< I I 5-6 

,~~ I I t::JJ ' I --~i· I oi Mt. Kla lagvl --k { ~ ,x lo · )a, g -~ I :~: .... 'L ~ '<J 

)\ - _ ~ -~ t Ch;g.n ols ok~Agripi ~ Bay 

))_ 1 2 - 4 ~ I oov;d I 

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+tv 

Areas 2 - 6 exten d south . . mto Sutwik Island qua drangle 

156° 

G 

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155° 

8 11 

I CapeK I 

' Cape I Kubugakli 

I 

I 

SCALE 1:1 ,000,000 

5 0 5 10 MILES ,, I I I I I I 

5 0 5 10 KILOMETERS IIJ!JI I I 

+ 

Figure 16. Map showing possible mineralized areas in the Ugashik-Karluk study area. Outlined areas (heavy dashed lines) defined on the basis of geochemical data 

(table 5). Detailed maps of specific areas are shown in the following figures: area 1, figure 17; areas 2-4, figure 18; areas 5--6, figure 20; area 7, figure 21; area 8, figure 

22; area 9, figure 23; area 10, figure 24. Major Quaternary volcanic centers are labeled and the Quaternary lava flows are shown by the thin black lines. 
c 

; 

:; 

I» 

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CD 

m 

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0 

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-< 0 

i" 

N 

...... 

Table 5. Summary of geochemical suites and associated minerals found in mineralized areas in the Ugashik, Bristol Bay, and western Karluk quadrangles, Alaska. 

[Dashes indicate no data; MF maps in the Ugashik, Bristol Bay, and western Karluk quadrangles folio indicated to show from which sources the data have been taken] 

General area 

1. Rex prospect 

2. West of Painter 

Creek and east 

of Pumice Creek 

3. Mike prospect 

4. Mt. Ch1g1nagak- Chig1nagak Bay 

5. Mt. k1alagv1k to 

west of Agrip1na Bay batholith 

6. Agr1pina Bay batholith 

7. Portage Bay 

a. Cape kubugakl1 

9. West s1de of Wide Bay 

10. East of 8echarof 

lake and north of 

the Kejul1k River 

---

Anomalous concentrations 

of el~nts 1n streamsediments (MF-1539-F) 

Cu, Mo, Ag, Pb, Zn, Co, 

N1 

Cu, Ag, Pb, Zn, 8, Ni, 

Co 

Cu, Mo, Ag, Pb. Zn, B, 

H1, Co 

Cu, Mo, Ag, Pb, Zn, B, 

Co 

Cu, Mo, Pb, Ag, Zn, 8, 

Co 

Cu, Mo, Ag, Pb, Zn, 8, 

Co 

Mo, Ag, Pb, Zn, B, Co 

Mo 

Ag, Co 

Ag, Co 

Anomalous concentrations of 

elements 1n nonmagnetic, heavy- mineral panned-concentrate samples (MF-1539 -G) 

Cu, Mo, Ag, Pb, H1, Co, As, 

W, Au, 81, Ba 

Cu, Ag, Pb, Zn, 8, Hi, Co, As, 

81, Cd, Ba 

Cu, Mo, W, Ag, Pb, Zn, As, Cd, 

Ba, N1, Co, 8, Bi, Au 

Cu, Mo, Pb, Ag, Zn, 8, As, Co, 

Ba 

Cu, Mo, W, Pb, Ag, Zn, B, Co, 

As, 81, Ba 

Cu, Mo, Ag, Pb, Zn, 8, Co, As, 

Au, Cd, Sn, Ba 

Cu, Pb, Ag, Zn, B, Co, As, W, 

Cd, Sn, Bi 

Cu, 8, Au, Ag, W, Co 

Cu, Ag, Pb, N1, 8a 

Cu, Ag, Pb, Cd, 8a, Sn 

1

The following abbreviations have been used in the table and 1n figures 17, 18, 20-24: 

tourmaline; bar, barite; mly, molybdenite; gal, galena; cin, cinnabar; and sph, sphalerite. 

Minerals found in the 

nonmagnetic heavy- 111neral panned 

concentrates (MF-1539-H)l 

py, cpy, sch, gold 

py, cpy, sph, c1n, tour, 

bar 

py, cpy, mly, sph, gal, 

tour, bar, c1n, rutile 

py, tour, bar 

py, cpy, sch, gold, bar, 

tour 

py, cpy, gal, gold, cin, 

tour, bar 

py, cpy, gal, sph, sch, 

tour, rutile 

py, cpy, tour, sch 

py, sch, tour, bar 

cpy, py, bar 

Anomalous concentrations 

of elements 1n mineralized 

rock (MF-1539-C) 

Cu, Mo, Pb, Zn, Ba, Ag 

Cu, Ho, Pb, Zn, Ba, Au, Ag 

Cu, Pb, Zn 

Pb, Cu, Mo, Zn, Ba 

Cu, Mo, Pb, Zn, Ba, Au, As 

Cu, Mo, Pb, Ba, As, Ag 

Cu, Mo, Pb, Zn, Au, Ag 

Cu, Zn, Ag 

py, pyrite; cpy, chalcopyrite; sch, schee11te; tour, 
157° 00' 

57° 15' 

A 

Figure 17. Drainage basin anomaly map (A) and 

generalized geologic map (8) of the Rex prospect (area 1, 

table 5). The area containing more than 5 percent pyrite and 

(or) barite and sulfide minerals is outlined on A by the heavy, 

dashed contour. Drainage basins are shown by dotted lines; 

those containing anomalous concentrations of copper, 

molybdenum, and tungsten are shown by hachures on the 

drainage basin outlines. Sample sites are shown by the dots. 

Other elements having anomalous concentrations in 

individual drainage basins are also indicated on A; Tour, 

tourmaline identified in NMHMC samples. The geologic base 

map is simplified from Detterman and others (1987); uncolored areas are Quaternary alluvium; map unit symbols 

shown in explanation correspond to those used in figure 2. 

Topographic base is from U.S. Geological Survey, 1 :250,000; 

Ugashik, 1963; contour interval 200ft. 

Rex Prospect 

The Rex prospect (area 1) is associated with a 

composite Oligocene hypabyssal intrusion in the Chignik 

and Tolstoi Formations. The country rocks are hornfelsed, silicified, and propylitically altered sandstone and 

shale. The western side of the mountain has been 

intensely altered and andesitic dikes are pervasive; pyrite 

is common (Detra and others, 1982). The Rex prospect is 

located on a series of copper-molybdenum-tungsten 

anomalies defined by SS samples. The anomalous 

drainage basins are surrounded by drainage basins 

containing anomalous concentrations of lead, zinc, silver, 

gold, and bismuth as determined from both SS and 

NMHMC samples. Gold is common in the panned 

concentrates surrounding the prospect. The distributions 

of the geochemical anomalies are shown in figure 17. The 

geochemical anomalies from this area appear to define a 

porphyry copper-gold system. 

The Rex prospect was evaluated by the Kennecott 

Corporation (Bear Creek Mining Company) in 1977 

following a reconnaissance stream-sediment geochemical survey in 1975 (J. Hammitt, written commun., 

1986). The descriptive data given below were taken from 

B 

• 

0 

I I I •' 

0 

15JC 00' 

5 MILES 

I 

5 KILOMETERS 

EXPLANATION 

Oligocene quartz diorite, hypabyssal 

andesite and dacite (Ti) 

Tertiary Meshik Formation (Tm) 

Tertiary Tolstoi Formation (Tt) 

Cretaceous and Jurassic Hoodoo, 

Chignik, and Naknek Formations (KJs) 

Altered rock 

---Contact 

---Fault 

a company report and are published here with 

permission of Kennecott Corporation and Koniag, 

Incorporated. Their data outline an area of pronounced 

copper, molybdenum, lead, zinc, silver, and gold 

anomalies in the area as determined from both streamsediment and rock geochemistry. Copper anomalies are 

in the range of 500--1,000 ppm, and anomalous 

molybdenum concentrations (20--30 ppm) surround the 

core of the intrusion. Rock-chip samples from one small 

area in the NWV4 sec. 19 showed high values for both 

copper and molybdenum indicating a relatively uniform 

grade of mineralization. Elsewhere, sporadically high 

concentrations of copper were found, but mineralization 

did not appear to be of uniform grade. Concentrations of 

lead and zinc are sporadically high peripheral to the 

central copper and molybdenum anomaly, entirely 

consistent with our stream-sediment and NMHMC 

sampling. 

Chalcopyrite and molybdenite at the Rex prospect 

are confined almost exclusively to the zone of potassic 

alteration within the intrusive rocks. Sulfide content of 

this core area is in the range of 2-3 percent. Rock-chip 

geochemistry indicates a good correlation of gold with 

copper content (0.8 ppm Au at 1 percent Cu, or about 

28 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
0.8 giT (0.023 oz Auff) at 1 percent Cu). Chalcopyrite is 

present both as disseminated and stockwork ore, whereas 

molybdenite is locally present in the stockwork. Pyrite is 

the only other sulfide in the ore zone. The boundary of 

the core area, which covers about 2.5 km2(1 m?), is 

surrounded by a halo in the country rocks that contains 

5-10 percent pyrite. Weathering of hornfelsed and pyritized sediments and volcanic rocks produces a 

pronounced reddish-brown color anomaly. Zones of 

phyllic alteration are minor (NEYI sec. 24 and NWYI sec. 

19). The dominant alteration seen at the prospect is 

propylitic. Intrusive rocks near the top of the ridges 

contain disseminated chalcopyrite (500-1,000 ppm Cu). 

A zone of mineralized rock, associated with an area of 

secondary biotite alteration about 150m (500ft) in width 

and containing about 0.2 percent Cu, can be outlined on 

the basis of work carried out by the staff of the Kennecott 

Corporation. 

Mike Prospect 

The Mike prospect, a large color anomaly (area 3 ), 

as well as the adjacent anomalous areas to the west (area 

2) and east (area 4), are shown in figure 18. The Mike 

prospect is centered on a large copper-molybdenum 

anomaly defined by stream-sediment data. Surrounding 

drainage basins contain anomalous concentrations of 

copper, lead, zinc, silver, arsenic, cadmium, and bismuth 

that extend south into the Sutwik Island quadrangle (Cox 

and others, 1981). The area of the Mike prospect is a 

felsic dike and sill complex that intruded sandstone and 

siltstone of the Naknek Formation (Detra and others, 

1982). Pyrite is abundant in the NMHMC samples as 

well as are many sulfides, hydrothermal barite, and 

tourmaline. Geochronologic studies of this area (Wilson 

and Shew, 1988) indicate that the Mike prospect is 

associated with intrusive rocks of Pliocene age and that 

the hydrothermal alteration is also of Pliocene age. 

Intense sericitic and phyllic alteration surrounds a welldeveloped stockwork in the core area of the prospect. 

Field investigations at the Mike prospect were 

carried out by the exploration staff of the Kennecott 

Corporation (Bear Creek Mining Company) in 1977. 

The following summary is from their studies. Cretaceous 

and Jurassic sedimentary rocks over an 8-km2 (3-mi2) 

area were domed, hornfelsed, and altered by a late-stage 

composite hypabyssal rhyolitic stock and numerous sills 

(silica values ranged from 77.9 to 81.5 percent Si02). 

This central rhyolitic intrusion and the surrounding 

domed sedimentary rocks were then crosscut by a quartzeye porphyry dike system (73.9 percent Si02). This 

central rhyolitic stock is surrounded by numerous dacitic 

dikes to the north and west. Small stocks of quartz 

monzonite and quartz monzonite porphyry occur in the 

area of the central rhyolitic sill as well as to the northeast 

of the main rhyolite stock (fig. 19). 

The central rhyolitic stock is a mixture of silicified 

rhyolite and quartz monzonite. Silica flooding made it 

difficult to distinguish the intrusive rocks from the 

silicified sediments in the field. Small pebble dikes 

present in some parts of the system suggest that they 

were near the top of the intrusion. An area of intense 

quartz stockwork veining and silica flooding in the westcentral part of the rhyolitic stock shows intense sericitic 

alteration and overlaps the silica core. Potassium 

contents are low (2.4-3.7 percent K20). Sulfides, 

dominated by pyrite, reach 5-10 percent over a 2.5-km2 

(1-m?) area and grade outward to 1-2 percent over an 

8-km2 (3-m?) area. Average molybdenum contents of 

samples from the core area were about 130 ppm. 

Molybdenum occurs as fine-grained molybdenite along 

small quartz-filled fractures, but it also occurs locally in 

coarse quartz veins and veinlets. Lesser amounts of 

molybdenum occur sporadically in the hornfelsed 

sediments at the margin of the rhyolitic stock (see area 

outlined by the 40-ppm-Mo contour defined on the basis 

of rock-chip sampling). Copper contents of samples from 

the zone of molybdenum mineralization were generally 

low, in the range of 10-50 ppm. Chalcopyrite was absent. 

Lead, zinc, and silver anomalies are also low over this 

zone. Lead and zinc anomalies, as well as small amounts 

of sphalerite and galena, were observed in the hornfelsed 

sediments peripheral to the rhyolite stock west of the 

main zone of molybdenum mineralization. Tin and 

tungsten anomalies were also observed in rocks in the 

mineralized zone of the rhyolite stock. Fluorine values 

average 710 ppm, but range to as much as 2,100 ppm in 

the central zone of molybdenum mineralization. A strong 

correlation of molybdenum and fluorine exists in the 

zone of molybdenum mineralization. No fluorite was 

observed at the surface. Magnetite and hematite are both 

present in the veins. The abundance of pyrite and the low 

molybdenum contents of the quartz-eye porphyry dikes 

suggest that the molybdenum-mineralization event 

occurred prior to the intrusion of the dikes. 

Results of shallow drilling (fig. 19) by Bear Creek 

Mining Company in 1977 indicated weak molybdenite 

mineralization along the entire length of core 77-1. This 

drill hole penetrated 33 m (108 ft) of silicified rhyolite 

(76.5 percent Si02; 3.5 percent K20) averaging 1-2 

percent pyrite and 35 ppm Mo. Drill hole 77-2 

penetrated 6 m (19 ft) of rhyolite sill (76.5 percent 

Si02; 4.1 percent K20) averaging 3 percent pyrite and 18 

ppm Mo and 18 m (58 ft) of silicified sediments 

averaging 1-2 percent pyrite and 10 ppm Mo. Drill 

hole 77-3 penetrated 22 m (73 ft) of altered 

Drainage Basin Analysis 29 
w 

0 

C' 

'tJ 

0 

; 

.. 

0 

:::s 

C) 

CD 

0 

() 

:T 

CD 

3 

~ 

~ 

c: 

cc 

D) 

0 

:T 

l~ 

g:J 

~ llJ 

D) 

~ 

D) 

:::s 

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~ 0 

; 

3 

~ c 

~ 

0 

c 

D) 

Q. 

.. 

D) 

:::s 

cc 

i' 

~"' 

)> 

ii' 

"' ~ 

D) 

157° 30' 15rOO' 

57° 00 ' 

A 0 5 10 M ILES 

I I I I I I I I I I I I I 

0 5 10 Kl LOM ETERS 

Figure 18 (above and facing page). Drainage basin anomaly map (A) and generalized geologic map (B) of the area surrounding the Mike prospect (areas 2-4, table 

5).The area shown extends south into the Chignik-Sutwik Island study area (Cox and others, 1981). The area containing more than 5 percent pyrite and (or) barite and 

sulfide minerals is outlined on A by the heavy, dashed contour. Drainage basins are shown by dotted lines; those containing anomalous concentrations of copper, 

molybdenum, and tungsten are shown by hachures on the drainage basin outlines. Sample sites are shown by the dots. Other elements having anomalous 

concentrations in individual drainage basins are also indicated on A; if the element was anomalous in both the SS and the NMHMC media, the element symbol is 

underlined. Heavy minerals identified in the NMHMC samples are also indicated (Gin, cinnabar; Sch, scheelite; and Tour, tourmaline). The geologic base map is simplified 

from Detterman and others (1981, 1987); uncolored land areas are Quaternary alluvium; map unit symbols shown in explanation correspond to those used in figure 2. 

Topographic base is from U.S. Geological Survey, 1 :250,000; Ugashik, 1963; Sutwik Island, 1963; contour interval 200ft. 
c 

iil 

5' 

II) 

co 

C1) 

tD 

II) 

en 

:; 

)> 

::::s 

II) 

-< en 

;· 

~ 

57° 00' 

157° 30 ' 

B 

~ GTID 

Quaternary volcanic rocks (Qv) 

Pliocene to Oligocene basalt, andesite, 

and dacite (Tv) 

Tertiary quartz diorite (Tqd) 

157° 00 ' 

0 5 10 MILES 

I I I I I I I I I I I I I 

0 5 10 KI LOMETERS 

EXPLANATION D Cretaceous and Jurassic Hoodoo, Chignik, 

and Naknek Formations (KJs) 

Altered rock 

Tertiary intrusive rocks (Ti) 

Tertiary Meshik Formation (Tm) :-= Hornfels 

Tertiary Tolstoi Formation (Tt) 

.. ... Contact-Dashed where 

approximately located 

Thrust fault- Dashed 

where concealed; 

sawteeth on upper 

plate 
157° 13' 30" 

EXPLANATION 

~ Tbx Tqmp _r--'.1 Silica > 70 percent 

57° 

03 ' 

30" 

~Tqp Tr 

IT!I!J] Tqm DKJs ~Fault 

,.---/ Geologic contact 

__ Mo > 40 parts per mil_lion 

I 

500 

2500 

I 

I 

5000 FEET 

I 

1000 METERS 

Figure 19. Generalized geologic and geochemical map of the Mike prospect (fig. 18) showing the rhyolitic 

intrusion (Tr); the quartz monzonite porphyry (Tqmp); the quartz monzonite (Tqm); the late-stage quartz porphyry 

dikes (Tqp, dotted where approximately located); and the breccia pipe (Tbx) and associated zones of silica 

enrichment and molybdenum mineralization. The surrounding country rocks are Cretaceous and Jurassic 

sedimentary rocks (KJs); geologic map courtesy of Kennecott Corporation (published with permission). Sites of the 

drill holes are also indicated (77-1, 77-2, and 77-3). 

quartzitic siltstone averaging 1-3 percent pyrite and 125 

ppm Mo, the bottom 7 m (22ft) averaging 253 ppm Mo, 

where the hole was lost due to caving. Fluorite was 

observed in this core. 

A small quartz monzonite stock, about 2.5 km2 (1 

mi2), intruded the rhyolitic stock on the east side (fig. 19), 

and a second small quartz monzonite stock intruded 

sediments about 1.6 km (1 mi) east-northeast of the 

32 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
rhyolitic stock. A large breccia pipe (120 by 215 m, or 400 

by 700ft) also occurs near this second quartz monzonite 

body. Copper contents of these small stocks range from 

500 to 1,000 ppm; one sample from a copper skarn in 

sediments adjacent to a dacite dike contained 3,450 ppm 

Cu. Molybdenum concentrations of samples from the 

quartz monzonite stocks ranged between 10 and 20 ppm. 

One grab sample from the breccia pipe contained 160 

ppm Mo. Reconnaissance geological investigations 

summarized here suggest mineralization associated with 

a low-fluorine porphyry molybdenum system at the Mike 

prospect. 

Geochemical anomaly patterns indicated by SS and 

NMHMC samples from area 2 are similar to those 

associated with the quartz monzonite stocks in the area 

of the Mike prospect. These geochemical anomalies 

occur in an area of widespread sericitically altered rock 

probably underlain by intrusive rocks (table 5). Like the 

stream-sediment geochemical anomaly pattern 

associated with the Mike prospect, this anomaly can also 

be traced into the Sutwik Island quadrangle to the south. 

The geochemical anomaly is not as pronounced as that of 

the Mike prospect, but contains essentially the same suite 

of elements. An extensive area of hornfelsed country 

rock and a small area of hydrothermal alteration were 

mapped in area 2 (Detterman and others, 1983). The 

area may contain high-level base- and precious-metal 

vein systems overlying porphyry-type systems at depth. 

Area 4, east of the Mike prospect and south of 

Mount Chiginagak to Cape Kuyuyukak, is an area of 

scattered copper-molybdenum-lead-zinc-cobalt-silverarsenic anomalies determined on the basis of SS and 

NMHMC samples from drainage basins where the 

country rock contains numerous dikes and sills. This 

pattern of anomalies may have been partially obscured by 

the Quaternary volcanic activity associated with Mount 

Chiginagak. Extensive areas of hydrothermal alteration 

and hornfelsed rock were noted in the Naknek, Chignik, 

Hoodoo, and Tolstoi Formations during field mapping in 

area 4 (Detterman and others, 1983). The area may 

contain high-level base- and precious-metal vein systems 

overlying porphyry-type systems at depth. 

The SS and NMHMC samples from the Kialagvik 

Creek area draining the northeast side of Mount Kialagvik, area 5, contained anomalous concentrations of many 

elements (fig. 20). Stream sediments and panned 

concentrates from the drainage basins contained 

anomalous concentrations of copper, molybdenum, 

tungsten, lead, zinc, silver, arsenic, and bismuth. A small 

area of pyritic alteration was also mapped northwest of 

Mount Kialagvik and south of Goblet Creek (Detterman 

and others, 1983). Drainage basins in this area contain 

anomalous amounts of copper and zinc associated with 

tourmaline in the NMHMC samples; this set of 

anomalies may also be related to this episode of 

mineralization. 

Agripina Bay Batholith 

Geochemical anomalies determined from SS and 

NMHMC samples spatially associated with the Agripina 

Bay batholith of Pliocene age (area 6) are shown in figure 

20. Both the Tertiary volcanic rocks and the Upper 

Jurassic Naknek Formation along the borders of the 

Agripina Bay batholith are extensively altered near hypabyssal dikes and sills of Oligocene and younger age. 

Some extensively hornfelsed and hydrothermally altered 

volcanic and hypabyssal rocks overlying and intruded by 

the Pliocene Agripina Bay batholith give Oligocene ages. 

Hydrothermally altered rock and geochemical anomalies 

associated with the batholith may also reflect the Oligocene intrusive event. The factor analysis of the 

NMHMC samples discussed above (PCF-6, fig. 14) 

clearly shows a boron signature associated with the 

hypabyssal rocks to the west of the batholith, as well as 

with the older rocks intruded by the Agripina Bay 

batholith. Epidote was common in the heavy-mineral 

concentrates collected from drainage basins between 

Chiginagak Bay and Imuya Bay to the north. 

Furthermore, there were copper-molybdenum-tungstenlead-zinc-silver-arsenic-gold anomalies in the SS and 

NMHMC samples associated with cinnabar, hydrothermal barite, and tourmaline. These anomalies are 

particularly pronounced at Cape Kilokak (fig. 20), where 

small inliers of hornfelsed and altered Naknek, Chignik, 

Hoodoo, and Tolstoi Formations are completely 

surrounded by the Pliocene Agripina Bay batholith. The 

data suggest that base- and precious-metal vein 

mineralization largely affected the rocks surrounding the 

Agripina Bay batholith and may be older than the dated 

intrusive phases of the batholith. 

Pyritic Lode Mineralization on the 

Eastern End of David Island 

Case and others (1987) noted a magnetic low over 

David Island, and Wilson and O'Leary (1986, 1987) 

reported anomalous values for copper, lead, and 

molybdenum in samples from David Island. In the 

summer of 1986, we visited David Island to examine it for 

possible mineralized rock. We observed a large area at 

the eastern end of David Island where a massive pyritic 

lode, estimated to be 3-6m (10-20 ft) thick, is exposed at 

wave base on the south side of the small point at the 

Drainage Basin Analysis 33 
57° 

15 ' 

156° 30 ' 

0 21() Ashiiak I 

450 

·Lone Rock 

60 

~oltava I 

·~ ~vy I 

rovidence 

rtm 

102 

C) 150 

362 G) 

Figure 20 (above and facing page). Drainage basin 

anomaly map (A) and generalized geologic map (8) of the 

Agripina Bay batholith (areas 5-6, table 5). The area 

containing more than 5 percent pyrite and (or) barite and 

sulfide minerals is outlined on A by the heavy, dashed 

0 5 10 MILES 

I I I I I I I I 

0 5 10 KILOMETE RS 

contour. Drainage basins are shown by dotted lines; those 

containing anomalous concentrations of copper, 

molybdenum, and tungsten are shown by hachures on the 

drainage basin outlines. Sample sites are shown by the dots. 

Other elements having anomalous concentrations in 

34 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
57° 

15 ' 

57° 

00 ' 

362 

individual drainage basins are also indicated on A; if the 

element was anomalous in both the SS and the NMHMC 

media, the element symbol is underlined. Heavy minerals 

identified in the NMHMC samples are also indicated (Gin, 

cinnabar; Tour, tourmaline). The geologic base map is 

156° 30' 

~50 

60 

I . 

~ 

. P.rovi en~ 

150 

rtm 

102 

Ashiiak I 

EXPLANATION 

Quaternary volcanic rocks (Qv) 

Pliocene to Oligocene basalt, 

andesite, and dacite (Tv) 

Tertiary quartz diorite (Tqd) 

Tertiary intrusive rocks (Ti) 

Tertiary Tolstoi Formation (Tt) 

Cretaceous and Jurassic Hoodoo, 

Chignik, and Naknek 

Formations (KJs) D Jurassic sedimentary rocks (JliPs) 

~ Altered rocks 

~::;::;~~:~:x:;:·;· Hornfels 

---- Contact 

Fault- Dashed where concealed 

simplified from Detterman and others (1981, 1987); uncolored land areas are Quaternary alluvium; map unit symbols 

shown in explanation correspond to those used in figure 2. 

Topographic base is from U.S. Geological Survey, 1 :250,000; 

Ugashik, 1963; Sutwik Island, 1963; contour interval 200ft. 

Drainage Basin Analysis 35 
A 0 

I I I I 

0 

5 MILES 

I 

5 KILOMETERS 

eastern end and along the northeast shore of the main 

part of the island. Analyses of grab samples from these 

localities showed anomalous concentrations of arsenic, 

bismuth, and antimony. No anomalous concentrations of 

gold or silver were found. Hydrothermal alteration is 

widespread. No stream-sediment samples were taken on 

the island. 

Pacific Coastal Areas from Portage Bay 

to Cape Kubugakli 

Similar geochemical anomalies, although from 

seemingly somewhat smaller areas of mineralized rock 

associated with intrusive rocks west of Portage Bay from 

Mount Becharof south to Cape Igvak (area 7; fig. 21), 

Figure 21 (at left and facing page). Drainage 

basin anomaly map (A) and generalized 

geologic map (8) of the Portage Bay area 

(area 7, table 5). The area containing more 

than 5 percent pyrite and (or) barite and sulfide 

minerals is outlined on A by the heavy, dashed 

contour. Drainage basins are shown by dotted 

lines; those containing anomalous concentrations of copper, molybdenum, and 

tungsten are shown by hachures on the 

drainage basin outlines. Sample sites are 

shown by the dots. Other elements having 

anomalous concentrations in individual 

drainage basins are also indicated on A; if the 

element was anomalous in both the SS and the 

NMHMC media, the element symbol is 

underlined. Heavy minerals identified in the 

NMHMC samples are also indicated (Tour, 

tourmaline). The geologic base map is 

simplified from Detterman and others (1987); 

uncolored land areas are Quaternary alluvium; 

map unit symbols shown in explanation 

correspond to those used in figure 2. 

Topographic base is from U.S. Geological 

Survey, 1 :250,000; Ugashik, 1963; Karluk, 

1963; contour interval 200 ft. 

may also indicate porphyry and related mineralization 

(table 5). Numerous lode claims for iron have been filed 

in the Portage Bay area (Cobb, 1978) surrounding the 

Pliocene pluton near Cape Igvak. These claims were not 

examined in the field. The geochemical data show a 

higher proportion of tungsten and arsenic relative to 

other porphyry copper-molybdenum areas in the study 

area. The magnetic fraction (C2) of the heavy-mineral 

concentrates contained garnet and scheelite. Abundant 

rutile was also seen in one of the NMHMC samples from 

this area. Chemical digestion of the nonmagnetic fraction 

revealed that additional sulfides were separated into the 

magnetic fraction because they were coated with ironoxides. Some C2 samples contained as much as 200 ppm 

arsenic and 500 ppm zinc. Four samples contained 

36 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
5JO 30 ' 

B 0 

I I I I 

0 

5 MILES 

I 

5 KILO METERS 

small amounts of gold. The iron lode claims may be 

located on possible iron skarn deposits. 

In addition to the mineralization associated with 

the Pliocene intrusive body west of Portage Bay, 

numerous scattered silver, copper, and barium anomalies 

and several gold (silver, copper) lode and placer claims 

occur northeast and northwest of the Portage Bay area 

(MacKevett and Holloway, 1977; Cobb, 1978). Small 

dikes and sills are numerous in the folded Mesozoic 

strata. Pyrite in heavy-mineral concentrates from the 

Shelikof Formation occurs predominantly in botryoidal 

form and the associated cobalt concentrations are low, 

less than 70 ppm. Threshold values for cobalt were 

selected such that sedimentary pyrite does not affect the 

geochemical anomaly distribution pattern. 

156° 00 ' 

EXPLANATION 

Tertiary quartz diorite (Tqd) 

Tertiary intrusive rocks (Ti) 

Cretaceous and Jurassic Hoodoo, Chignik, and 

Naknek Formations (KJs) 

D Jurassic sedimentary rocks (JiPs) 

~ Altered rock 

:':!~:~:)::;::~::::;~ Hornfels 

---Contact 

---Fault 

6 + + Thrust fault 

A few of the SS samples showed evidence of 

mineralization at Cape Kubugakli (area 8; fig. 22). 

Between 1915 and 1923, small-scale placer mining at 

Cape Kubugakli produced an estimated 5 kg (160 oz) of 

gold derived from quartz stringers in felsic dikes (Cobb, 

1978). Stibnite, tetrahedrite, galena, molybdenite, and 

magnetite also occur at this locality. Both propylitic and 

sericitic alteration were observed in the area. The 

alteration assemblage at Cape Kubugakli has been dated 

as Miocene (Wilson and Shew, 1988). No analyses of the 

carbonate rocks intruded by this pluton were made, but 

the geologic environment is permissive for the formation 

of a carbonate-hosted gold deposit. 

Mineralization in the area northwest of Cape 

Kubugakli (fig. 22) and east of the Kejulik River is 

Drainage Basin Analysis 37 
A 5 

I 

10 Kl LOM ETERS 

lOMILES 

I 

Figure 22 (above and facing page). Drainage basin anomaly map (A) and generalized geologic map (B) of the 

Cape Kubugakli area (area 8, table 5). The area containing more than 5 percent pyrite and (or) barite and sulfide 

minerals is outlined on A by the heavy, dashed contour. Sample sites are shown by the dots. Drainage basins are 

shown by dotted lines; those containing anomalous concentrations of copper, molybdenum, and tungsten are 

shown by hachures on the drainage basin outlines. Other elements having anomalous concentrations in individual 

drainage basins are also indicated on A. The geologic base map is simplified from Detterman and others (1987); 

uncolored land areas are Quaternary alluvium; map unit symbols shown in explanation correspond to those used 

in figure 2. Topographic base is from U.S. Geological Survey, 1 :250,000; Karluk, 1963; contour interval 200ft. 

suggested by a few low-level silver and barium drainagebasin anomalies shown by the heavy-mineral concentrates. Some of these sites contain minor epidote, 

possibly reflecting propylitic alteration. Some of the 

geochemical anomalies may reflect hydrothermal vein 

activity associated with poorly exposed hydrothermal 

systems, but none of the anomalies occurs in areas of 

mapped altered rock or exposed intrusive rocks. 

The geochemical data for the area immediately 

northeast of Puale Bay define several drainage basins 

along Portage Creek where anomalous concentrations of 

silver, barium, and molybdenum were determined from 

NMHMC samples (fig. 22). A fluorescent mineral, 

perhaps pbwellite, may account for the molybdenum 

anomaly. The geochemical anomalies in the Portage 

Creek area may be related to the faulting mapped in this 

drainage basin by Detterman and others (1983). 

The area along the northwest side of Wide Bay 

(area 9; fig. 23) showed scattered anomalies of copper, 

silver, gold, lead, and barium as determined from 

the NMHMC samples and from observations of scheelite, tourmaline, and barite in the NMHMC samples. No 

38 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
155° 30 ' 

B 

/ 

~vjj 

0 

I I 

I I 

0 

I 

5 

5 

I 

10 Kl LOM ETERS 

EXPLANATION 

Quaternary volcanic rocks (Qv) 

Tertiary quartz diorite (Tqd) 

10 MILES 

I 

Cretaceous and Jurassic Hoodoo, Chignik, and 

Naknek Formations (KJs) 

Jurassic to Permian sedimentary and metamorphic rocks (JliPs) 

Altered rock 

---- Contact 

----Fault 

6 6 Thrust fault 

/ 

igneous rocks or areas of altered rock were shown on the 

1:250,000-scale map of this area, although numerous 

small dikes and sills cut both the Shelikof and Naknek 

Formations (R.L. Detterman, oral commun., 1987). 

Pyrite is abundant in most of the NMHMC samples, but 

is predominately botryoidal or stalactitic in form rather 

than crystalline or massive as found in areas 1-8. Cobalt 

values for NMHMC samples containing high 

percentages of sedimentary or botryoidal pyrite are 

about a factor of ten lower (20-70 ppm) than cobalt in 

Drainage Basin Analysis 39 
0 

', ,' 

0 5 

5 

I 

10 KILOMETERS 

lOMILES 

I 

40 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
EXPLANATION 

Tertiary intrusive rocks (Ti) 

Cretaceous and Jurassic Hoodoo, Chignik, and 

Naknek Formations (KJs) 

D Jurassic sedimentary rocks (J"RPs) 

::~·~::;::~::;::;:.;·) Hornfels 

---Contact 

---Fault 

Figure 23 (above and facing page). Drainage basin 

anomaly map (A) and generalized geologic map (8) of the 

west side of Wide Bay (area 9, table 5). The area containing 

more than 5 percent pyrite and (or) barite and sulfide 

minerals is outlined on A by the heavy, dashed contour. 

Sample sites are shown by the dots. Drainage basins are 

shown by dotted I ines; those containing anomalous 

concentrations of elements are indicated on A. Heavy 

minerals identified in the NMHMC samples are also indicated 

(Tour, tourmaline). The geologic base map is simplified from 

Detterman and others (1987); uncolored land areas are 

Quaternary alluvium; map unit symbols shown in explanation 

correspond to those used in figure 2. Topographic base is 

from U.S. Geological Survey, 1 :250,000; Karluk, 1963; 

contour interval 200 ft. 

NMHMC samples derived from hydrothermally altered 

areas (200--700 ppm). The botryoidal pyrite and perhaps 

the associated barite are probably syngenetic and do not 

reflect hydrothermal processes. The highly permeable 

sedimentary rocks and numerous small normal faults 

would, however, provide excellent conduits for hydrothermal fluids if intrusive rocks occur at depth (fig. 23). 

Southwest of Deer Mountain are several scattered 

copper anomalies determined from NMHMC samples 

associated with tourmaline. 

Area Northeast of Becharof Lake and 

Northwest of the Kejulik River 

Mineralized rock in area 10, north of the east end 

of Becharof Lake and northwest of the Kejulik River (fig. 

24), is characterized by anomalous copper, silver, lead, 

and barium determined from NMHMC samples. Chalcopyrite and barite were seen in one sample, and pyrite in 

both crystalline and botryoidal forms was the dominant 

sulfide in most samples. A small area of altered rock was 

mapped (Detterman and others, 1983), but no intrusive 

rocks are exposed. Botryoidal pyrite is dominant and the 

cobalt content of pyrite is apparently low. Dikes and sills 

are present in the Naknek Formation: the anomalies may 

represent high-level galena-chalcopyrite-barite veins 

over a buried intrusive body. Work in the Mount Katmai 

study area immediately north of the Ugashik-Karluk 

study area indicates a copper-gold porphyry system may 

be associated with the Kejulik volcanic field (S.E. 

Church, unpub. data, 1986). 

SUMMARY AND COMPARISON WITH 

AREAS OF KNOWN MINERALIZATION 

Mineralization on the Alaska Peninsula, 

particularly sulfide mineralization associated with 

porphyry-type systems, has been previously recognized. 

Hollister (1978, p. 72-73) summarized the geologic data 

for eight porphyry copper sulfide systems from the 

Alaska Peninsula, south of Lake Iliamna, that had been 

described in the published literature. Work in the 

Chignik-Sutwik Island AMRAP study area immediately 

to the south also delineated several porphyry-type 

systems (Cox and others, 1981). Both factor analysis and 

drainage-basin analysis of the stream sediment and nonmagnetic, heavy-mineral-concentrate geochemical data 

delineate several areas of possible sulfide mineralization 

associated with Tertiary intrusive activity in the UgashikKarluk study area. Geochemical anomalies and geologic 

features of these deposits are very similar to those 

described for the Chignik and Sutwik Island quadrangles. 

Detailed studies of the copper-molybdenum mineralization at Bee Creek, in the Chignik quadrangle about 

120 km (75 mi) southwest of the Rex prospect, showed 

that the Bee Creek sulfide system is associated with a 

Pliocene calc-alkaline porphyry system. Drilling at the 

Bee Creek prospect indicated that deposition of chalcopyrite and associated sulfides in the arkosic Naknek 

Formation were deposited by saline hydrothermal fluids 

that were driven out from the intrusion into the 

surrounding sedimentary rocks (Wilson and Cox, 1983). 

At the Rex prospect, in the Ugashik-Karluk study 

area, a porphyry copper-gold system of Oligocene age 

(area 1 ), shows concentrically zoned alteration patterns 

and is defined by a zoned geochemical pattern in the 

drainage-basin anomalies. An aeromagnetic low within 

the target area defined by the geochemical data is 

interpreted as an indication of hydrothermal alteration 

(Case and others, 1987). Hydrothermal veins containing 

base metals surrounding the central core of mineralized 

rock are also common. The presence of gold in the 

NMHMC samples in the area north and west of the Rex 

prospect indicates a gold halo around the sulfide system. 

This model is typical of our field observations in the areas 

surrounding sulfide mineralization and is typical of 

copper porphyry-type systems in volcanic arcs (Cox and 

Singer, 1986, p. 110--119). The geochemical anomalies 

defined in table 5 for areas 1-6 are characteristic of those 

associated with copper porphyry mineralization. 

Geochemical anomalies similar to the Rex 

prospect were noted for drainage basins near the plutons 

Summary and Comparison with Areas of Known Mineralization 41 
57° 

52' 

30" 

57° 

52 ' 

30" 

A 

B 

156° 00 ' 

0 

0 

I I 

I I 

5 

5 

I 

10 KILOMETERS 

10 MILES 

I 

42 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
~ w 

EXPLANATION 

Quaternary volcanic rocks (Qv) 

Cretaceous and Jurassic Hoodoo, Chignik, and 

Naknek Formations (KJs) 

Jurassic sedimentary rocks (J"RPs) 

---Contact 

---Fault 

6 A Thrust fault 

Figure 24 (above and facing page). Drainage basin 

anomaly map (A) and generalized geologic map (8) of the 

Kejulik River area (area 10, table 5). The area containing 

more than 5 percent pyrite and (or) barite and sulfide 

minerals is outlined on A by the heavy, dashed contour. 

Sample sites are shown by the dots. Drainage basins are 

shown by the dotted lines; those containing anomalous 

concentrations of elements are indicated on A. The geologic 

base map is simplified from Detterman and others (1987); 

uncolored land areas are Quaternary alluvium; map unit 

symbols shown in explanation correspond to those used in 

figure 2. Topographic base is from U.S. Geological Survey, 

1 :250,000; Ugashik, 1963; contour interval 200 ft. 

on Cape Igvak (area 7) and Cape Kubugakli (area 8). 

Small geochemical anomalies were found in the Kejulik 

volcanic field on the north side of the study area, east of 

Becharof Lake (area 10). Work in the Mount Katmai 

study area (S.E. Church, unpub. data, 1986) indicates a 

possible copper-gold porphyry system beneath one of the 

major intrusive centers in the Kejulik volcanic field. 

The most probable areas for the discovery of either 

porphyry or hydrothermal vein-type mineralization are in 

the southern part of the Ugashik quadrangle (areas 2-6) 

in the extensively altered Tertiary volcanic rocks of the 

Meshik arc (Detterman and others, 1983). Drainagebasin geochemical anomalies in areas 2-6 continue into 

the northern Chignik-Sutwik Island study area 

immediately to the south (Cox and others, 1981). Case 

and others (1987) indicated that the volcanic rocks in 

areas 2-6 may be underlain by several buried plutons, 

and the mapping by Detterman and others (1983) 

indicates extensive alteration and areas of hornfelsed 

rock. The geochemical data identify numerous drainage 

basins characterized by copper-molybdenum-tungsten 

anomalies, the surrounding drainage basins characterized by base- and precious-metal anomalies. These 

base-metal anomalies are probably indicative of the 

hydrothermal vein systems that surround large coppermolybdenum porphyry systems. 

The Mike prospect (area 3) differs from other 

areas of sulfide mineralization within the study area. It 

shows widespread silica "flooding" and MoS2 

mineralization and represents a low-fluorine porphyry 

molybdenum system associated with a felsic porphyry 

stock. Areas of similar mineralization on the Alaska 

Peninsula are not known, but should be anticipated in a 

convergent volcanic-arc environment (Westra and Keith, 

1981; Cox and Singer, 1986, p. 120-122). The Mike 

prospect was investigated by Kennecott Corporation 

(Bear Creek Mining Company) in 1977; their work 

outlined an area of molybdenum mineralization having 

an average grade of 0.2 percent MoS2. 

REFERENCES CITED 

Allaway, W.H., and Miller, J.W., 1984, Newly recognized 

sedimentary environments in the Shelikof Formation, 

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. 34-37. 

Brockway, R.G ., Alexander, Bryan, Day, Paul, Lyle, W.N., 

Hiles, R.M., Jr., Decker, William, Polski, William, and 

Reed, B.L., 1975, Bristol Bay region, stratigraphic 

correlation section, southwest Alaska: Anchorage, 

Alaska, Alaska Geologic Society. 

Burk, C.A., 1965, Geology of the Alaska Peninsula-Island arc 

and Continental Margin, Geological Society of America 

Memoir 99, pts. 1-3, 250 p. 

Case, J.E., Detterman, R.L., Wilson, F.H., Chuchel, B.A., and 

Yount, M.E., 1987, Maps showing aeromagnetic survey 

and geologic interpretation of the Ugashik and part of 

the Karluk quadrangles, Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1539-D, 2 sheets, 

scale 1:250,000. 

Church, S.E., Frisken, J.G., Detra, D.E. and Willson, W.R., 

1988, Geochemical map showing the distribution of 

selected elements determined in stream sediments from 

the Ugashik, Bristol Bay, and western Karluk 

quadrangles, Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1539-F, scale 

1:250,000. 

Cobb, E.H., 1978, Summary of references to mineral 

occurrences (other than mineral fuels and construction 

materials) in the Mognak, Karluk, Kodiak, and Trinity 

Islands quadrangles, Alaska: U.S. Geological Survey 

Open-File Report 79-860, 47 p. 

Cox, D.P., Detra, D.E., and Detterman, R.L., 1981, Mineral 

resource maps of the Chignik and Sutwik Island 

quadrangles, Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1053-K, 2 sheets, 

scale 1:250,000. 

Cox, D.P., and Singer, D.A., editors, 1986, Mineral deposit 

models: U.S. Geological Survey Bulletin 1693, 379 p. 

Davis, J.C., 1973, Statistics and data analysis in geology: New 

York, John Wiley and Sons, 550 p. 

Detra, D.E., Detterman, R.E., Cox, D.P., Wilson, F.H., and 

Theodore, T.G., 1982, Reconnaissance geochemical 

studies in the Bristol Bay, Ugashik, and Karluk 

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

States Geological Survey in Alaska-Accomplishments 

during 1980: U.S. Geological Survey Circular 844, 

p. 87-88. 

References Cited 43 
Detra, D.E., Risoli, D.A., O'Leary, R.M., Hurrell, J.A., and 

Everman, W.E., 1981, Analytical data and statistical 

summary from the analyses of stream-sediment and 

heavy-mineral-concentrate samples collected in Bristol 

Bay, Ugashik, and Karluk quadrangles, Alaska: U.S. 

Geological Survey Open-File Report 81-963, 88 p. 

Detterman, R.L., 1978, Interpretation of depositional 

environments in the Chignik Formation, Alaska, in 

Johnson, K.M., ed., The United States Geological Survey 

in Alaska-Accomplishments during 1977: U.S. 

Geological Survey Circular 772-B, p. B62-B63. 

Detterman, R.L., Case, J.E., and Wilson, F.H., 1979, Paleozoic 

rocks on the Alaska Peninsula, in Johnson, K.M., and 

Williams, J.R., eds., The United States Geological Survey 

in Alaska-Accomplishments during 1978: U.S. 

Geological Survey Circular 804-B, p. B85-B86. 

Detterman, R.L., Case, J.E., Wilson, F.L., and Yount, M.E., 

1987, Geologic map ofthe Ugashik, Bristol Bay, and part 

of the Karluk quadrangles, Alaska: U.S. Geological 

Survey Miscellaneous Investigations Series Map I-1685, 

scale 1:250,000. 

Detterman, R.L., Case, J.E., Wilson, F.H., Yount, M.E., and 

Allaway, W.H., Jr., 1983, Generalized geologic map of 

the Ugashik, Bristol Bay, and part of the Karluk 

quadrangles, Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1539-A, scale 

1:250,000. 

Detterman, R.L., Miller, T.P., Yount, M.E., and Wilson, F.H., 

1981, Geologic map of the Chignik and Sutwik Island 

quadrangles, Alaska: U.S. Geological Survey 

Miscellaneous Investigations Series Map I-1292, scale 

1:250,000. 

Fisher, R.A., 1970, Statistical methods for research workers: 

New York, Hafner Press, 14th edition, 362 p. 

Frisken, J.G., Church, S.E., Detra, D.E., and Willson, W.R., 

1988, Geochemical map showing the distribution of 

selected elements determined in nonmagnetic heavymineral-concentrates from the Ugashik, Bristol Bay, and 

western Karluk quadrangles, Alaska: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-1539-G, 2 

sheets, scale 1:250,000. 

Frisken, J.G., Church, S.E., and Willson, W.R., 1988, 

Mineralogical map showing the distribution of selected 

ore-related minerals identified in the nonmagnetic 

heavy-mineral concentrates from the Ugashik, Bristol 

Bay, and western Karluk quadrangles, Alaska: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-1539-H, scale 1:250,000. 

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc 

and alternating-current spark emission spectrographic 

field methods for the semiquantitative analysis of 

geologic materials: U.S. Geological Survey Circular 591, 

6 p. 

Hanson, B.M., 1957, Middle Permian limestone on the Pacific 

side of Alaska Peninsula: American Association of 

Petroleum Geologists Bulletin, v. 41, p. 2376-2378. 

Hollister, V.F., 1978, Geology of the porphyry copper deposits 

of the Western Hemisphere: New York, American 

Institute of Mining Engineers, 219 p. 

Jacob, K.H., Nakamura, Kazuaki, and Davies, J.N., 1977, 

Trench-volcano gap along the Alaska-Aleutian ArcFacts, and speculations on the role of terrigenous 

sediments for subduction, in Talwani, Mark, and Pitman, 

W.C., III, eds., Island arcs, deep sea trenches, and 

back-arc basins: Washington, D.C., American Geophysical Union, p. 243-258. 

Johnston, R.J., 1980, Multivariant statistical analysis in 

geography: London, Lorgman, 280 p. 

MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing 

metalliferous mineral deposits in the western part of 

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

Report 77-169-F, 39 p., scale 1:1,000,000. 

Reed, B.L., and Lanphere, M.A., 1969, Age and chemistry of 

Mesozoic and Tertiary plutonic rocks in south-central 

Alaska: Geological Society of America Bulletin, v. 80, p. 

23-44. 

___ 1973, Alaska-Aleutian Range batholith-Geochronology, chemistry, and relation to circum-Pacific plutonism: 

Geological Society of America Bulletin, v. 84, p. 

2583-2610. 

Rummel, R.J., 1970, Applied factor analysis: Evanston, Ill., 

Northwestern University Press, 617 p. 

Tukey, J.W., 1977, Exploration data analysis: New York, 

Addison-Wesley, 250 p. 

VanTrump, George, Jr., and Miesch, A.L., 1977, The U.S. 

Geological Survey RASS-STATPAC system for 

management and statistical reduction of geochemical 

data: Computers and Geosciences, v. 3, p. 475-488. 

von Huene, Roland, Fisher, M.A., McClellan, P .H., Box, 

Stephen, and Ryan, Holly, 1985, Centennial Continent/ 

Ocean Transect A-2-North Pacific Ocean Basin to 

Kuskokwim Mountains: Boulder, Colo., Geological 

Society of America, scale 1:500,000. 

Wahraftig, Clyde, 1965, 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 1289, 45 p. 

Westra, Gehard, and Keith, S.B., 1981, Classification and 

genesis of stockwork molybdenum deposits: Economic 

Geology, v. 76, p. 844-873. 

Wilson, F.H., 1985, The Meshik arc-An Eocene to earliest 

Miocene magmatic arc on the Alaska Peninsula: Alaska 

Division of Geological and Geophysical Surveys 

Professional Report 88, 14 p. 

Wilson, F.H. and Cox, D.P., 1983, Geochronology, geochemistry, and tectonic environment of porphyry 

mineralization in the central Alaska Peninsula: U.S. 

Geological Survey Open-File Report 83-783, 24 p. 

Wilson, F.H., Detterman, R.L., and Case, J.E., 1985, The 

Alaska Peninsula terrane; a definition: U.S. Geological 

Survey Open-File Report 85-450, 17 p. 

Wilson, F.H., and O'Leary, R.M., 1986, Maps and tables 

showing data and analysis of semiquantative emission 

spectrometry and atomic-absorption spectrometry of 

44 Exploration Geochemistry, Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska 
rock samples, Ugashik and western Karluk quadrangles, 

Alaska: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1539-C, 2 sheets, scale 1:250,000. 

___ 1987, Tables showing analyses of semiquantitative 

spectrometry and atomic-absorption spectrophotometry 

of rock samples collected in the Ugashik, Bristol Bay, and 

western part of the Karluk quadrangles, Alaska: U.S. 

*U.S GPO: 1989 773-047/06010 

Geological Survey Open-File Report 87-419, 35 p. 

Wilson, F.H., and Shew, Nora, 1988, Map and tables showing 

geochronology and whole-rock geochemistry of selected 

samples from the Ugashik, Bristol Bay, and part of 

Karluk quadrangles, Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1539-E, 4 sheets, 

scale 1:250,000. 

References Cited 45 



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Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations. 

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; principal scale 

is 1:24,000 and regional studies are at 1:250,000 scale or smaller. 

Catalogs 

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Section, Federal Center, Box 25425, Denver, 

CO 80225. (See latest Price and Availability List) 

"Publkatlons of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche. 

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form. 

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only 

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet form only. 

Selected copies of a monthly catalog "New Publications of the U.S. 

Geological Survey" avail able free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092. 

Note.--Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications.