U.S. Department of the Interior

U.S. Geological Survey

Recent U.S. Geological Survey Studies in the Tintina Gold 

Province, Alaska, United States, and Yukon, Canada—

Results of a 5-Year Project

Scientific Investigations Report 2007–5289
Cover. View of a portion of the Black Mountain tectonic zone (ridge in background) looking northeast across the Tibbs Creek drainage within 

the Yukon-Tanana Upland. This zone, the subject of chapter D of this report, is the locus of almost all of the mineralized base and precious 

metal veins in the Big Delta B–1 quadrangle. The zone is characterized by complex faulting, shearing, intrusions, and zones of gold and 

antimony mineralization (photograph by Larry P. Gough).

Kuskokwim Mountains

Tanana-Kuskokwim Lowlands

KALTAG-TINTINA FAULT

FAREWELL-DENALI FAULT

Anchorage

Whitehorse

Fairbanks

Mayo

Dawson Yukon-Tanana Upland

Alaska

Yukon

CANADA

UNITED STATES

Northwest

Territories

British

Columbia

T I N T I N A G O L D P R O V I N C E

60°

65°

70°

160° 150° 140°

Yukon

River

Lowlands

Landsat-based shaded-relief map of the Tintina Gold Province in Alaska and Yukon (courtesy of Craig J.R. Hart, University of Western 0 100 200 300 400 500 KILOMETERS

Australia, Crawley).
Recent U.S. Geological Survey Studies in 

the Tintina Gold Province, Alaska, United 

States, and Yukon, Canada—Results of a 

5-Year Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Series 2007–5289

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. 

Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Gough, L.P., and Day, W.C., eds., 2010, Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, 

United States, and Yukon, Canada—Results of a 5-Year Project: U.S. Geological Survey Scientific Investigations 

Report 2007–5289, 148 p.
iii

Tintina Gold Province Project — Editors' 

Preface and Overview

By Larry P. Gough and Warren C. Day

This report presents summary papers of work conducted between 2002 and 2007 under 

a 5-year project effort funded by the U.S. Geological Survey Mineral Resources Program, 

formerly entitled "Tintina Metallogenic Province: Integrated Studies on Geologic Framework, 

Mineral Resources, and Environmental Signatures." As the project progressed, the informal 

title changed from "Tintina Metallogenic Province" project to "Tintina Gold Province" project, 

the latter being more closely aligned with the terminology used by the mineral industry. As 

Goldfarb and others explain in the first chapter of this report, the Tintina Gold Province (TGP) 

is a convenient term used by the mineral exploration community for a "region of very varied 

geology, gold deposit types, and resource potential." 

The TGP encompasses roughly 150,000 square kilometers (km2

), bounded by the KaltagTintina fault system on the north and the Farewell-Denali fault system on the south. It extends 

westward in a broad arc, some 200 km wide, from northernmost British Columbia, through the 

Yukon, through southeastern and central Alaska, to southwestern Alaska (fig. 1; Goldfarb and 

others, 2000; Smith, 2000). The climate is subarctic and, in Alaska, includes major physiographic delineations and ecoregions such as the Yukon-Tanana Upland, Tanana-Kuskokwim 

Lowlands, Yukon River Lowlands, and the Kuskokwim Mountains (Nowacki and others, 2002). 

Although the TGP is historically important for some of the very first placer and lode gold 

discoveries in northern North America, it has recently seen resurgence in mineral exploration, 

development, and mining activity. This resurgence is due to both new discoveries (for example, 

Pogo and Donlin Creek) and to the application of modern extraction methods to previously 

known, but economically restrictive, low-grade, bulk-tonnage gold resources (for example, Fort 

Knox, Clear Creek, and Scheelite Dome; see Chapter A by Goldfarb and others in this volume). 

In addition, the TGP hosts numerous other mineral deposit types, possessing both high and low 

sulfide content, which are currently not in development.

Until the recent increase in exploration activity at the huge Pebble porphyry copper-gold 

deposit near Iliamna Lake in 2001, by far most of the exploration dollars spent over the past 

decade, in Alaska and the Yukon for the identification of new gold resources, have been in the 

TGP. Chapters A and C of this report present new research that improves our understanding 

of the regional tectonic and hydrologic processes that localized these low-grade, high-tonnage 

gold resources. Chapter B describes the tectonic setting and metallogenesis of volcanogenic 

massive sulfide deposits in the Bonnifield mining district south of Fairbanks and provides the 

geologic framework for Chapters E and J. 

The TGP covers a vast region with very limited road or navigable river access. Thus, 

remote sensing techniques are critical for characterizing the geologic framework for the 

region. Geophysical studies, such as aeromagnetic surveys employed to help define the Black 

Mountain tectonic zone described in Chapter D, are often the only technique available to 

rapidly detect major tectonic features at the regional scale. Chapter E presents the results of 

satellite-borne remote sensing techniques using the Advanced Spaceborne Thermal Emission 

and Reflection Radiometer (ASTER) sensor mapping of hydrothermal alteration patterns 

associated with volcanogenic massive sulfide and porphyry deposits in the Bonnifield mining 

district. The technique detected some of the known mineral deposits in the region, as well as 

mineralogically similar targets that may represent potential undiscovered deposits. The research 

presented demonstrates that the ASTER technique is an extremely powerful tool for remotely 

characterizing the bedrock mineralogy, and hence, rock type, in areas with minimal to no vegetation cover within the TGP.
iv

In addition, geochemical, hydrogeochemical, and biogeochemical signatures are presented 

for both regional, unmineralized areas, and more localized deposit-specific areas throughout 

the TGP. Sampled media include soils, sediments, surface water, ground water, and vegetation. These signatures are interpreted in the context of bedrock mineralogy and geochemistry, weathering, and soil-forming processes, as well as bioavailability considerations. The 

information obtained assists in understanding the transport and mobility of trace elements—

some of which are important in an environmental context. The environmental signature studies 

were designed to incorporate the expertise and research capabilities of several disciplines. All 

such studies rely on an understanding of the geologic and hydrogeologic framework of the 

region.

Chapter F demonstrates a creative approach using aufeis ("ice" fields localized in drain-

age basins) as an unconventional proxy for the location of faults along high-gradient alpine 

drainages. The concept is that aufeis is an accumulation of winter ice, up to several meters 

thick, along stream and river valleys in arctic and subarctic environments, and is preferentially 

associated with high-gradient streams. This aufeis formed as a result of discharge of ground 

water from beneath a permafrost layer within the stream channels. Recent bedrock geologic 

mapping of the Big Delta B–2 quadrangle indicates that the streams in which aufeis occurs are 

underlain by throughgoing, high-angle brittle faults, suggesting that the faults are hydraulically 

conductive to ground water flow. Minor or no aufeis accumulations were observed contem-

poraneously in other drainage valleys where no extensive fault structures have been mapped, 

implying that aufeis formation results from more than a topographic effect or discharge from 

bank storage. Thus, the presence of thick and extensive aufeis in high-gradient streams may be 

a useful aid to identifying geologic structures in arctic and subarctic climates.

Epigenetic gold deposits are the principal exploration targets within the TGP at this time. 

Characterizing the geochemical dispersion of pathfinder elements associated with mineralizing 

systems in the natural environment is a powerful exploration tool. Chapter G synthesizes the 

efforts to study the natural dispersion of the pathfinder elements arsenic (As) and antimony 

(Sb) associated with several epigenetic gold mineralizing systems in the TGP. Arsenic and 

antimony also have garnered attention from the scientific community and the general public 

due to their potential toxicity. Understanding the fundamental geochemical controls on the 

natural and anthropogenic distribution of arsenic and antimony in the environment is critical for 

both mineral exploration and human health communities. This study found that the mobility of 

arsenic and antimony is controlled primarily by the local reduction-oxidation reaction (redox) 

environment, with arsenic being less mobile in oxidized surface waters relative to antimony, 

and arsenic more mobile in reduced ground waters.

A broad approach to landscape geochemistry is presented in Chapter H, which investigates 

the geochemical linkage among stream waters, streambed sediments, soils, and vegetation 

with that of regional bedrock. This study provides important premining data for any future 

mineral development in the Goodpaster River watershed, which lies in the heart of the 

Yukon Tanana Upland of east-central Alaska. A more focused study is provided in Chapter 

I, which characterizes the geochemical signature of a volcanogenic massive sulfide (VMS) 

deposit in the Bonnifield district of central Alaska. The Red Mountain base-metal deposit is 

a rare, natural laboratory that allows study of an acid-generating, metal-leaching VMS min-

eral deposit exposed in an undisturbed environment. Dissolution of pyrite and associated 

secondary reactions under near-surface, oxidizing conditions are the primary causes for the 

acid generation and metal leaching of the rocks at Red Mountain. However, the acidic waters 

mix with surrounding alkaline waters that have interacted with carbonate veinlets, resulting in 

self-mitigation via dilution, neutralization, and attendant co-precipitation. This process limits 

downstream hydrogeochemical evidence of the deposit to within a few kilometers. Chapter J 

reports on the occurrence and biogeochemistry of unusual plant species, and of their supporting 

sediment and soils, in the area of the Red Mountain deposit. Field studies of these occurrences 

are important for understanding the habitat requirements of rare or unusual species and for a 

full appreciation of the ecology and biogeochemical diversity of mineralized areas. 
v

Finally, Chapter K is a bibliographic listing of all reports that have been published by 

USGS personnel since inception of the TGP project in 2002. As noted in the acknowledgments, 

many of the reports are the result of the work with colleagues from other government agencies 

as well as academia and industry. 

P A C I F I C O C E A N

A R C T I C O C E A N

British Columbia

Alaska

Yukon

Northwest Territories

CANADA

RUSSIA

UNITED STATES

UNITED STATES

Arctic

Circle

C

A

G

G

G E

B

D I, J F, H

F

G AREWELL-DENALI FAULT

KALTAG-TINTINA FAULT

Fairbanks

Dawson

Anchorage

EXPLANATION

Tintina Gold Province

Study area—Letters identify chapters in this report

Major geologic fault system

Major mineral deposit

G

0 100 200 300 400 500 600 KILOMETERS Base from U.S. Geological Survey

1:15,000,000, Albers equal-area projection

Standard parallels 55°N. and 65°N.

Central meridian 145°W.

160° 155° 150° 145° 140° 135° 130°

175° °07170° 165° 160° 155° 150° 145° 140° 135° 130° 125° 120° 115° °07

°071

60°

65°

55°

°511

°571

°561

55°

°521

60°

65°

°021

Figure 1. Study areas within the Tintina Gold Province of Alaska and Yukon covered by the 

individual chapters (letters) in this compilation (see table of contents).
vi

Acknowledgments 

We would especially like to thank the following list of key agencies, universities, and 

industries that provided valuable logistical and technical assistance during both the field work 

and data interpretation phases of this effort:

Alaska Department of Natural Resources Teck Cominco, Ltd.

Division of Geological and Geophysical TNR Resources, Ltd.

 Surveys University of Alaska, Anchorage

Division of Mining, Land and Water University of Alaska, Fairbanks

Division of Forestry University of Colorado, Boulder

Alaska Department of Environmental University of Western Australia

 Conservation U.S. Bureau of Land Management

Avalon Gold Corporation U.S. Department of Agriculture, Natural 

Calista Corporation Resources Conservation Service

Doyon, Ltd. U.S. Geological Survey, Mineral Resources 

Fairbanks Gold Mining, Inc. Program

Grayd Resource Corporation U.S. National Park Service

Geo-Watersheds Scientific Denali National Park and Preserve

NovaGold Resources, Inc. Yukon-Charley Rivers National Preserve

Pacific Alaska Resources Company Yukon Geological Survey

Pacific Rim Geological Consulting

References Cited 

Goldfarb, R.J., Hart, C.J.R., Miller, M.L., Miller, L.D., Farmer, G.L., and Groves, D.I., 2000, 

The Tintina gold belt: a global perspective, in Tucker, T.L., and Smith, M.T., eds., The 

Tintina gold belt—Concepts, exploration and discoveries: British Columbia and Yukon 

Chamber of Mines Special Volume 2, p. 5–34.

Nowacki, G.J., Spencer, Page, Fleming, Michael, Brock, Terry, and Jorgenson, Torre, 2002, 

Unified ecoregions of Alaska, 2001: U.S. Geological Survey Open-File Report 02–297, scale 

1:4,000,000.

Smith, M.T., 2000, The Tintina gold belt: an emerging gold district in Alaska and Yukon, in

Tucker, T.L., and Smith, M.T., eds., The Tintina gold belt—Concepts, exploration, and discoveries: British Columbia and Yukon Chamber of Mines Special Volume 2, p. 1–3.
vii

Contents

[Letters designate the chapters]

Tintina Gold Province Project — Editors’ Preface and Overview

By Larry P. Gough and Warren C. Day

GEOLOGIC FRAMEWORK AND MINERAL RESOURCE INVESTIGATIONS 

A. Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and 

Yukon

By Richard J. Goldfarb, Erin E. Marsh, Craig J.R. Hart, John L. Mair, Marti L. Miller, and 

Craig Johnson

B. Tectonic Setting and Metallogenesis of Volcanogenic Massive Sulfide Deposits in the 

Bonnifield Mining District, Northern Alaska Range

By Cynthia Dusel-Bacon, John N. Aleinikoff, Wayne R. Premo, Suzanne Paradis, and 

Ilana Lohr-Schmidt

C. Matching Magnetic Trends and Patterns Across the Tintina Fault, Alaska and Canada—

Evidence for Offset of About 490 Kilometers

By Richard W. Saltus

D. The Black Mountain Tectonic Zone—A Reactivated Northeast-Trending Crustal Shear 

Zone in the Yukon-Tanana Upland of East-Central Alaska

By J. Michael O'Neill, Warren C. Day, John N. Aleinikoff, and Richard W. Saltus

E. Mapping Known and Potential Mineral Occurrences and Host Rocks in the Bonnifield 

Mining District Using Minimal Cloud- and Snow-Cover ASTER Data

By Bernard E. Hubbard, Cynthia Dusel-Bacon, Lawrence C. Rowan, and Robert G. Eppinger

F. Aufeis Accumulations in Stream Bottoms in Arctic and Subarctic Environments as a 

Possible Indicator of Geologic Structure

By Richard B. Wanty, Bronwen Wang, Jim Vohden, Warren C. Day, and Larry P. Gough

ENVIRONMENTAL SIGNATURES AND LANDSCAPE GEOCHEMISTRY INVESTIGATIONS

G. Surface-Water, Ground-Water, and Sediment Geochemistry of Epizonal and Shear-Hosted 

Mineral Deposits in the Tintina Gold Province—Arsenic and Antimony Distribution and 

Mobility

By Seth H. Mueller, Richard J. Goldfarb, Philip L. Verplanck, Thomas P. Trainor, Richard F. 

Sanzolone, and Monique Adams

H. Landscape Geochemistry Near Mineralized Areas of Eastern Alaska

By Bronwen Wang, Larry P. Gough, Richard B. Wanty, James G. Crock, Gregory K. Lee, 

Warren C. Day, and Jim Vohden

I. Environmental Geochemical Study of Red Mountain, an Undisturbed Volcanogenic Massive 

Sulfide Deposit in the Bonnifield Mining District, Alaska Range, East-Central Alaska

By Robert G. Eppinger, Paul H. Briggs, Cynthia Dusel-Bacon, Stuart A. Giles, Larry P. Gough, 

Jane M. Hammarstrom, and Bernard E. Hubbard

J. The Biogeochemistry and Occurrence of Unusual Plant Species Inhabiting Acidic, MetalRich Water, Red Mountain, Bonnifield Mining District, Alaska Range

By Larry P. Gough, Robert G. Eppinger, and Paul H. Briggs

K. U.S. Geological Survey Reports on the Tintina Gold Province—Products of Recent Mineral 

Resources Program Studies

By Larry P. Gough
viii

Conversion Factors and Notes

Multiply By To obtain

Length

centimeter (cm)

millimeter (mm)

meter (m)

kilometer (km)

0.3937

0.03937

3.281

0.6214

inch (in.)

inch (in.)

foot (ft) 

mile (mi)

Area

square kilometer (km2

) 247.1 acre

Volume

liter (L)

cubic meter (m3

)

ounce, fluid (fl. oz)

33.82

35.31

0.02957

ounce, fluid (fl. oz)

cubic foot (ft3)

liter (L) 

Pressure

kilobar 1000 kilopascal (kPa) 

Flow rate

cubic meter per second (m3

/s)

liter per second (L/s)

35.31

15.85

cubic foot per second (ft3/s)

gallon per minute (gal/min) 

Mass

microgram (μg) 0.00000003527 ounce avoirdupois (oz)

milligram (mg) 0.00003527 ounce avoirdupois (oz)

gram (g)

megagram (Mg) = metric ton (t)

megagram (Mg) = metric ton (t)

0.03527

1.102

0.9842

ounce avoirdupois (oz)

ton, short (2,000 lb)

ton, long (2,240 lb)

Density

kilogram per cubic meter (kg/m3

) 0.06242 pound per cubic foot (lb/ft3) 

Ore grade

gram per metric ton (g/t)

ounce avoirdupois, per ton (oz/ton)

0.032

31.25

ounce avoirdupois, per ton (oz/ton)

gram per metric ton (g/t)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L), 

micrograms per liter (μg/L), or parts per million (ppm).

Concentrations of chemical constituents in soil are given in milligrams per kilogram (mg/kg).
Geology and Origin of Epigenetic Lode Gold 

Deposits, Tintina Gold Province, Alaska 

and Yukon

By Richard J. Goldfarb, Erin E. Marsh, Craig J.R. Hart, John L. Mair, 

Marti L. Miller, and Craig Johnson

Chapter A of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–A

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract........................................................................................................................................................A1

Introduction..................................................................................................................................................A1

Overview and History of the Tintina Gold Province ..............................................................................A1

Geology and Gold Deposits of Central Yukon.........................................................................................A4

Geology and Gold Deposits of East-Central Alaska..............................................................................A6

Geology and Gold Deposits of Southwestern Alaska...........................................................................A9

Geochemical Constraints on Gold Ore-Forming Fluids ......................................................................A11

Fluid-Inclusion Studies....................................................................................................................A11

Noble-Gas Studies...........................................................................................................................A11

Stable-Isotope Studies ...................................................................................................................A12

Genesis of Lode Gold Deposits...............................................................................................................A12

References Cited.......................................................................................................................................A15

Figures

A1. Map showing main gold districts of the Tintina Gold Province of interior Alaska 

and adjacent Yukon, Canada ...................................................................................................A2

A2. Photographs showing ore deposits in east-central Alask .................................................A3

A3. Map showing gold, sliver, and tungsten deposits of the Tombstone-Tungsten 

magmatic belt.............................................................................................................................A5

A4. Photographs showing examples of ore veins.......................................................................A6

A5. Map showing gold districts of the Tintina Gold Province in east-central Alaska 

and spatially associated reduced mid-Cretaceous igneous rocks...................................A7

A6. Map showing gold deposits of the Fairbanks district..........................................................A8

A7. Photograph showing small shear-hosted gold vein system at the Tolovana 

deposit, Fairbanks district........................................................................................................A9

A8. Map showing main lode gold resources in the western end of the Tintina Gold 

Province ....................................................................................................................................A10

A9. Photographs of the Donlin Creek deposit............................................................................A11

A10. Diagram showing intrusion-related gold systems in the Tintina Gold Province...........A12

A11. Diagram showing a genetic model for evolution of the Donlin Creek gold deposit .....A14

Tables

A1. Major lode gold resources of the Tintina Gold Province (updated from Hart and 

others, 2002)................................................................................................................................A4

A2. Fluid inclusion and stable isotope geochemistry of ore-bearing samples from 

deposits in the Tintina Gold Province...................................................................................A13

Geology and Origin of Epigenetic Lode Gold Deposits, 

Tintina Gold Province, Alaska and Yukon

By Richard J. Goldfarb,1 Erin E. Marsh,1 Craig J.R. Hart,2 John L. Mair,3 Marti L. Miller,1 and Craig Johnson1

1

U.S. Geological Survey.

2

Mineral Deposit Research Unit, The University of British Columbia.

3

Geoinformatics Exploration Inc., Australia.

Abstract

More than 50 million ounces of lode gold resources have 

been defined in the previous 15 years throughout accreted 

terranes of interior Alaska and in adjacent continental margin 

rocks of Yukon. The major deposits in this so-called Tintina 

Gold Province formed around 105 to 90 million years ago in 

east-central Alaska and Yukon, and around 70 million years 

ago in southwestern Alaska, late in the deformational history 

of their host rocks. All gold deposits studied to date formed 

from CO2-rich and 18O-rich crustal fluids, most commonly of 

low salinity. The older group of ores includes the low-grade 

intrusion-related gold systems at Fort Knox near Fairbanks 

and those in Yukon, with fluids exsolved from fractionating 

melts at depths of 3 to 9 kilometers and forming a zoned 

sequence of auriferous mineralization styles extending 

outward to the surrounding metasedimentary country rocks. 

The causative plutons are products of potassic mafic magmas generated in the subcontinental lithospheric mantle that 

interacted with overlying lower to middle crust to generate 

the more felsic ore-related intrusions. In addition, the older 

ores include spatially associated, high-grade, shear-zonerelated orogenic gold deposits formed at the same depths from 

upward-migrating metamorphic fluids; the Pogo deposit is 

a relatively deep-seated example of such. The younger gold 

ores, restricted to southwestern Alaska, formed in unmetamorphosed sedimentary rocks of the Kuskokwim basin 

within 1 to 2 kilometers of the surface. Most of these deposits 

formed via fluid exsolution from shallowly emplaced, highly 

evolved igneous complexes generated mainly as mantle melts. 

However, the giant Donlin Creek orogenic gold deposit is a 

product of either metamorphic devolatilization deep in the 

basin or of a gold-bearing fluid released from a flysch-melt 

igneous body. 

Introduction

During the previous 5 years, we have carried out 

geological and geochemical studies of the major lode gold 

deposits in interior Alaska and adjacent Yukon, Canada. This 

area, termed the Tintina Gold Province (TGP), is a region of 

important new mineral discoveries and exploration interest. 

Our investigations included detailed descriptions of mineralization styles, mineralogical assemblages, geochemical 

signatures, and geochronological relations. Igneous rocks that 

are spatially and temporally associated with the deposits were 

studied in regard to their genesis and possible relation to the 

gold-bearing hydrothermal systems. Detailed fluid-inclusion 

and stable-isotope ore-genesis work was carried out to place 

geochemical constraints on the ore-forming fluids. Local 

ore-deposit models for the gold deposit types within the TGP 

were constructed from the data collected during the research 

program.

Overview and History of the Tintina 

Gold Province

The TGP is an area of greater than 150,000 square 

kilometers (km2

) that includes much of interior Alaska and 

adjacent parts of central Yukon (fig. A1; Goldfarb and others, 2000; Smith, 2000; see figure 1 of Editors' Preface and 

Overview). In Alaska, this highly mineralized province 

includes the area between the regional-scale Kaltag-Tintina 

and Denali-Farewell fault systems. Where the province 

continues to the east in Yukon, it is located northeast of 

the Kaltag-Tintina fault system. This vast region is defined 

by more than 15 individual gold belts and districts, which 

traditionally were mainly mined for their placer resources. 

Recently, however, many of these belts and districts have 

begun to be recognized for their lode gold potential. 

This broad and arc-shaped region, which is about 2,000 

km in length and continues from Yukon to southwestern 

Alaska, was first referred to as the Tintina Gold Belt in 1997 

by many company geologists. It was mainly a promotional 

term for a region of highly varied geology, gold deposit types, 
A2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

citcrA

elcriC

egarohcnA

ADANAC

SETATS DETINU

AISSUR

SETATS DETINU

P A C I F I C O C E A N

A R C T I C O C E A N

0 100 200 300 400 500 600 KILOMETERS

160° 155° 150° 145° 140° 135° 130°

175° 70°170° 165° 160° 155° 150° 145° 140° 135° 130° 125° 120° 115° 70°

170°

60°

65°

55°

115°

175°

165°

55°

125°

60°

65°

120°

Base from U.S. Geological Survey

1:15,000,000, Albers equal-area projection

Standard parallels 55°N. and 65°N.

Central meridian 145°W.

FAREWELL-DENALI FAULT

KALTAG-TINTINA FAULT

FI

KT

CH

BO

RS

GP

FB

DR

RP

CL

40

60

KD TB

EG

TG

TY

HR

LT

Fairbanks

Dawson

Fort Knox-True North

Cleary Hill

Brewery Creek

Clear Creek

Scheelite Dome

Dublin Gulch

Vinasale

Nixon Fork

Golden Horn

Donlin Creek

Ryan Lode

Pogo

EXPLANATION

Tintina Gold Province

Kuskokwim basin

Mining or placer districts

Major geologic fault system

Major mineral deposit

British Columbia

Alaska

Yukon

Northwest Territories

Figure A1. Main gold districts of the Tintina Gold Province of 

interior Alaska and adjacent Yukon, Canada. The districts are all 

known for their historic placer gold production, but many areas, 

notably the Kuskokwim, Fairbanks, Goodpaster, and Tombstone 

regions, have seen high levels of exploration and concomitant 

discovery and development during the last 15 years. Mining or 

placer district names abbreviated as follows: 40, Fortymile; 60, 

Sixtymile; BO, Bonnifield; CH, Chulitna; CL, Circle; DR, Dawson 

Range; EG, Eagle; FB, Fairbanks; FI, Flat-Iditarod; GP, Goodpaster; 

HR, Hot Springs-Rampart; KD, Klondike; KT, Kantishna; LT, 

Livengood-Tolvana; RP, Ruby-Poorboy; RS, Richardson; TB, 

Tombstone; TG, Tungsten; TY, Tay River (after Hart and others, 

2002).
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A3

A B

Figure A2. A, Underground development of the high-grade, flat-lying gold orebodies at the Pogo deposit, Goodpaster district, began 

in 2006. B, The first large-scale lode gold development in the Tintina Gold Province was at the Fort Knox deposit near Fairbanks, where 

low-grade gold ore has been mined since 1996 by open pit methods.

and significant resource potential. Because it was really not a 

distinct belt and was composed of numerous mineral districts 

of differing ages and characteristics, Hart and others (2002) 

argued that it simply be viewed as a large gold province withi

the northern North American Cordillera and termed the region 

the TGP. Most significantly, the province includes the Clear 

Creek, Scheelite Dome, Dublin Gulch, and Brewery Creek 

deposits of central Yukon; the Fairbanks and Goodpaster 

gold districts of east-central Alaska; and the lodes of the 

Kuskokwim basin of southwestern Alaska.

Exploration in the eastern part of the TGP began near 

the turn of the 20th century. At about the time of the great 

Klondike (in Yukon) gold rush of 1898, placer gold fields 

were identified in the eastern part of the TGP, both to the east 

of the Klondike at Scheelite Dome, Dublin Gulch, and Clear 

Creek (1894-1901) and to the west in the Fairbanks district 

of Alaska (1901). Those in the Fairbanks district yielded 

more than 8 million ounces (Moz) of gold during the 1900s, 

with other significant (0.5-1.0 Moz of gold each) east-central 

Alaskan placer districts (fig. A1) including Circle, Fortymile, 

Eagle, Circle Hot Springs-Rampart and Livengood-Tolvana 

(Goldfarb and others, 1997). The Yukon placer fields in the 

TGP were all small; the largest is probably Clear Creek, and 

it has yielded only 130,000 oz of gold (Allen and others, 

1999). Historical lode production had been minor; through 

the mid-1990s, there was almost no lode gold production 

from Yukon (Hart and others, 2002) and only a few hundred 

thousand ounces of gold were mined from a few small, 

high-grade (10-30 grams per metic ton (g/t) gold) quartz 

vein systems near Fairbanks (McCoy and others, 1997). 

However, recent exploration and development of the highgrade Pogo deposit within the Goodpaster district (figs. A1, 

A2A; Smith and others, 1999), located about 150 km southeast

of Fairbanks, has led to the start of mining of a 5.6 Moz gold 

resource late in 2006. 

n 

Technological advances during the last decade and favorable existing infrastructure (Mueller and others, 2004) have 

allowed for the economically successful recovery of large 

volumes of gold ore for the first time in the eastern AlaskaYukon region from material with grades of less than 1 g/t of 

gold (table A1). In 1996, the Fort Knox deposit, located 20 

km northeast of Fairbanks, was put into production as a lowgrade, bulk-tonnage resource (fig. A2B). It has so far yielded 

more than 4.5 Moz of gold, and has at least 4.6 Moz of gold 

remaining (Bakke, 1995; Bakke and others, 2000; Kinross 

Gold Corporation, 2009). During the previous 10 years, the 

Scheelite Dome, Dublin Gulch, and Clear Creek properties 

have been continually evaluated for similar bulk-tonnage 

gold resources. The nearby Brewery Creek deposit was mined 

for almost 250,000 oz of gold between 1995 and 2002, from 

shallow oxidized ore zones where refractory gold had been 

naturally liberated into a form that could be heap leached (Hart 

and others, 2002). 

The first exploration recorded within the western part to 

the TGP was by Russian prospectors in the Kuskokwim basin 

in the early 1800s. They discovered the first among many 

small mercury- and antimony-bearing quartz vein systems that 

are located throughout southwestern Alaska (Bundtzen and 

Miller, 1997). Between 1901 and 1916, placer gold accumulations were discovered in many parts of southwestern Alaska, 

and the resulting districts in the westernmost part of the TGP 

yielded slightly more than 3 Moz of gold during the subsequent 100 years. A very small amount of gold was recovered 

from gold-bearing quartz veins at the Golden Horn deposit 

in the Flat-Iditarod district between 1922 and the mid-1980s 

(Bull, 1988). U.S. Geological Survey work in the mid-1980s 

indicated significant gold concentrations in many of the 

mercury and antimony deposits in the central Kuskokwim 

basin (Gray and others, 1990), and isotope and fluid-inclusion 

studies indicated that hydrothermal fluids responsible for 
A4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Table A1. Major lode gold resources of the Tintina Gold Province (updated from Hart and others, 2002). 

[Abbreviations: Moz, million

Deposit

Donlin Creek

 ounces; g/t, grams per metric ton]

Location

Kuskokwim basin

Endowment

(Moz)

31.7

Grade

(g/t)

2.91

Production

to date

(Moz)

none

Fort Knox Fairbanks district 9.2 0.93 4.6

Pogo Goodpaster district 5.6 18.9 1.2

Dublin Gulch Selwyn basin 1.96 0.916 none

Cleary Hill Fairbanks district 1.6 34.0 0.5

Shotgun Kuskokwim basin 1.1 0.93 none

Vinasale Kuskokwim basin 0.92 2.4 none

Brewery Creek Selwyn basin 0.85 1.44 0.27

True North Fairbanks district 0.79 1.69 0.44

formation of these mineral deposits were typical of those that 

form many lode gold deposits (Goldfarb and others, 1990). 

Since that work, significant gold resources at historic stibnite 

prospects have been delineated at Vinasale Mountain and 

particularly Donlin Creek (table A1), with the latter being one 

of the world’s largest gold deposits known to date.

Geology and Gold Deposits of Central 

Yukon

The Yukon part of the TGP (fig. A3) is underlain by 

Neoproterozoic to Early Carboniferous continental margin 

rocks of the Selwyn basin, a fault-controlled depression 

developed on the edge of the North American craton. Gold 

deposits are hosted by phyllite, psammite, calc-phyllite, 

conglomerate, and marble of the Neoproterozoic to Early 

Cambrian Hyland Group (Murphy and others, 1993). Middle 

Jurassic to Early Cretaceous folding, thrusting, and lower 

greenschist-facies metamorphism of these rocks reflects 

seaward accretion of terranes along the continental margin. A 750-km-long belt of mainly felsic intrusions, termed 

the Tombstone-Tungsten belt (TTB), was emplaced into 

these rocks around 96 to 90 million years ago (Ma) and 

approximately 8 to 10 million years (m.y.) subsequent to final 

deformation (Hart, Mair, and others, 2004).

The notably reduced igneous rocks (Thompson and 

Newberry, 2000; Hart, 2007) of the TTB can be divided into 

the informally named Mayo, Tungsten, and Tombstone suites 

(Hart, Mair, and others, 2004). Most of the gold deposits, 

including those at Scheelite Dome, Clear Creek, and Dublin 

Gulch, are associated with the subalkaline, metaluminous to 

slightly peraluminous monzogranites to quartz monzonites, 

with minor granodiorite, of the Mayo suite. Isotopic data indicate that these rocks of the Mayo suite, as is common in many 

postcollisional settings, represent a mixture between potassic 

magmas that were generated in the subcontinental lithospheric 

mantle (SCLM) and those formed in the overlying lower to 

middle crust (John L. Mair, Geoinformatics Exploration, Inc., 

unpub. data, 2008). Emplacement of the more felsic and fractionated, weakly peraluminous, monzogranites and granites of 

the Tungsten suite, mainly generated from melted continental 

crust, is associated with formation of world-class tungsten 

skarn deposits at the easternmost end of the TGP. The least 

reduced, metaluminous, predominantly syenites of the Tombstone suite, generated from enriched SCLM, are associated 

with more copper-rich gold occurrences and, in addition, with 

the gold ores that were mined at Brewery Creek.

The Clear Creek gold deposits consist of auriferous 

sheeted quartz veins (fig. A4A) that cut six stocks of the 

Mayo suite and, to a lesser degree, are hosted by the surrounding 3- to 5-km-wide zones of hornfels rocks (Marsh 

and others, 1999, 2003). The veins contain 1 to 2 percent 

pyrite and arsenopyrite, with lesser pyrrhotite, scheelite, and 

bismuthinite. The more gold-rich veins may contain greater 

than 1 percent arsenic, and 100 to 1,000 parts per million 

(ppm) of both tungsten and bismuth. Gold to silver ratios 

range from 1:1 to 5:1. Individual veins are generally 0.2 to 5 

centimeters (cm) wide and tens of meters long. Vein densities 

are 3 to 5 veins per meter. Narrow alteration envelopes of 

quartz, potassium feldspar, and biotite, with some sericite, 

pyrite, chalcopyrite, hematite, and calcite, surround the quartz 

veins. Tourmaline and albite are also present in some of the 

veins. Several small tungsten-tin and tungsten-gold skarns 

occur where the country rocks are more calcareous. Dates on 

the stocks by U-Pb techniques are around 91.5 Ma; 40Ar/39Ar 

ages from vein-related micas are around 90 Ma. 

The main part of the Dublin Gulch deposit is localized 

within the apical zone of a granodiorite stock of the Mayo 

suite (Maloof and others, 2001; Hart and others, 2002). The 

600×400-meter (m) area hosts steep, sheeted quartz-feldspar 

extensional veins (fig. A4B), each a few centimeters in width, 

containing gold, molybdenite, lead-bismuth-antimony sulfo-
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A5

Carcross

Haines

Junction

WHITEHORSE

Carmacks

Faro

Ross River

Watson Lake

Dawson

Mayo

ALASKA

UNITED STATES

CANADA

YUKON

NORTHWEST TERRITORIES

BRITISH COLUMBIA

Fortymile

Sixtymile

Klondike

Tay River

Tombstone-Tungsten belt

Dawson

Range

Dublin Gulch-Ray Gulch

(Ag)

Brewery Creek

Clear Creek-Bear Paw

Scheelite Dome

(Ag)

(W)

Mactung (W)

(W) (W)

0 100 KILOMETERS

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

EXPLANATION

Mid-Cretaceous plutonic rocks

Selwyn Plutonic Suite

Other plutonic rocks

Tectonic terranes

Selwyn basin

Mackenzie-Cassiar platform

Accreted terranes

Mineral district

Stike-slip fault—Arrows show relative movement

Thrust fault—Sawteeth on upper plate

Fault (unspecified)

Mineral deposit—Gold except as follows: Ag, silver; 

W, tungsten. Only deposits discussed in text are 

labled by name

60°

65°

140° 135° 130° 125°

Figure A3. Gold, sliver, and tungsten deposits of the Tombstone-Tungsten magmatic belt in Yukon define the easternmost part of the 

Tintina Gold Province.

salts, galena, and bismuthinite; alteration phases include albite, 

potassium feldspar, sericite, carbonate, and chlorite. The 

deposit is within a few kilometers of the Ray Gulch tungsten 

skarn deposit, and silver- and lead-bearing veins are in more 

distal locations. Both pluton emplacement and vein formation 

are around 94 to 93 Ma (Selby and others, 2003).

In contrast to the other Yukon deposits, the gold occurrences at Scheelite Dome are dominantly hosted by hornfels 

and are more diverse in style (Mair and others, 2000, 2006). 

Gold is common in reduced skarns, quartz-feldspar-carbonate 

veins, and as disseminations in areas of carbonate- and 

sericite-altered country rocks, mainly in a 10×3-km easttrending zone. The extensional veins are 0.5 to 3 cm wide, 

and have densities of about 10 veins per meter. In addition to 

gold, they contain arsenopyrite, pyrite, quartz, albite, ankerite, 

microcline, muscovite, and tourmaline. Consistent geo-
A6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

chemical anomalies for bismuth, tellurium, and tungsten also 

characterize the veins. Alteration selvedges on the walls of the 

veins include muscovite, carbonate, quartz, and sulfide mineral phases. Locally, gold and scheelite are present in sheeted 

veins in the monzogranite to quartz monzonite igneous rocks. 

40Ar/39Ar dates on gold-related hydrothermal biotite are within 

2 m.y. of the 94.59±0.90 Ma U-Pb crystallization age for the 

igneous rocks. Small silver-, antimony-, lead-, and (or) zincbearing quartz vein occurrences surround the Scheelite Dome 

gold-bearing occurrences.

A

B

C

Figure A4. A, Typical goldand scheelite-bearing, sheeted 

quartz±feldspar±muscovite 

veins cutting granite at Dublin 

Gulch occurrence in Yukon. 

B, Gold-bearing sheeted 

veins from Dublin Gulch 

with potassium-feldsparrich alteration envelope and 

low-sulfide, quartz-rich infill. 

C, Highly fractured and veined 

ore from Fort Knox showing 

dominant “sheeted” veins, and 

intersecting cross-veins. This 

is unlike typical stockworks in 

porphyry deposits. The larger 

central vein also contains 

alkalic feldspar. Note the 

limited alteration selvages 

adjacent to the veins.

Geology and Gold Deposits of EastCentral Alaska

The east-central Alaskan part of the TGP (fig. A5) is 

underlain by medium- to high-grade metamorphic rocks, 

which include those of the widespread Fairbanks-Chena 

assemblage (Dusel-Bacon and others, 2006). Neoproterozoic 

to middle Paleozoic protoliths for the metamorphic rocks are 

mainly clastic sedimentary rocks, with lesser carbonate and 

magmatic units (Foster and others, 1994). Regional metamorphism likely occurred in the Late Jurassic to Early Cretaceous. 

The country rocks have been widely intruded by Early 

Cretaceous felsic to intermediate batholiths, stocks, and dikes. 

Similar to those of Yukon, these igneous rocks are reduced, 

have low ferric-to-ferrous ratios (less than 1), and are of low 

magnetic susceptibility (Hart, Goldfarb and others, 2004). In 

the Fairbanks area, they occur as shallowly emplaced (less 

than 3 to 5 km), 94 to 90 Ma isolated domal bodies; in the 

Goodpaster district, they are more deeply emplaced (5 to 9 

km, Dillworth, 2003), widespread 113 to 102 Ma batholiths 

and 99 to 95 Ma smaller bodies (Day and others, 2007). 

In the Fairbanks district, the Fort Knox deposit is located 

in the apex of a variably porphyritic, monzogranite to granodiorite stock (fig. A2B; Bakke, 1995). The gold occurs in 

steeply dipping, commonly sheeted, quartz-potassium-feldspar 

veins and in planar quartz veins that occur along later gently 

to moderately dipping shear zones cutting the igneous rocks 

(fig. A4C). High fineness gold in the veins is commonly intergrown with native bismuth, bismuthinite, and tellurobismuth 

(McCoy and others, 1997). Total sulfide volumes are much 

less than 1 percent and include phases such as pyrite, pyrrhotite, arsenopyrite, scheelite, and molybdenite. Alteration 

phases include potassium feldspar, albite, biotite, sericite, 

and ankerite. An Re-Os date on hydrothermal molybdenite of 

92.4±1.2 Ma is identical to the crystallization age of the Fort 

Knox stock (Selby and others, 2002). Isotopic data from the 

ore-hosting stock at Fort Knox indicate an origin similar to 

Cenomanian magmas in Yukon, reflecting both mantle and 

crustal contributions (Haynes and others, 2005).

Numerous smaller gold deposits are also spread throughout the Fairbanks district (fig. A6; Goldfarb and others, 1997; 

McCoy and others, 1997; Bakke and others, 2000; Hart and 

others, 2002). The True North deposit (figs. A5, A6), originally prospected 100 years earlier as an antimony prospect, 

was mined for gold at a small scale, providing additional 

feed for the Fort Knox mill, from 2001 to 2005. This deposit, 

located about 20 km northwest of Fort Knox, comprises gold 

in quartz veinlets, disseminations, and breccia along a shallow thrust in carbonaceous felsic schist. The fine-grained gold 

is associated with pyrite, arsenopyrite, and stibnite. Igne-
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A7 YUKON CANADA UNITED STATES ALASKA

FAIRBANKS

Delta Junction

Eagle

Tok

TINTINA FAULT

DENALI FAULT

SHAW CREEK

FAULT

Fairbanks

Circle

Eagle

Goodpaster

Richardson

Fortymile

Bonnifield

0 50 100 KILOMETERS

Fort Knox

Pogo

True North

Ryan

Lode

Democrat

Liberty Bell

Table Mtn.

Blue Lead

Circle-Hot

Springs

intrusions

65°

148° 146° 144° 142°

64°

EXPLANATION

Intrusion

Mining district

Fault

Deposit

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

Figure A5. Gold districts (pattern) of the Tintina Gold Province in east-central Alaska and spatially associated reduced mid-Cretaceous 

igneous rocks (shaded) (from Hart and others 2002).
A8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

r atani a Rive k

Ch

kee Cr h Fis

eek

 Cr m

ea str ld o G

River an he C

EXPLANATION

Cretaceous felsic intrusions

Chatanika terrane—Slate, felsic schist, marble

Yukon-Tanana terrane—Schist, quartzite, amphibolite

Normal fault—Bar and ball on downthrown block

Strike-slip fault—Arrows show relative motion

Thrust fault—Sawteeth on upper plate

Summit

Gold occurrences

High-level

Vein or disseminated

Replacement

Skarn

Intrusion-hosted

Placer

Hi-Yu

Christina

Newsboy

True North

Tolovana Frederich Dolphin

Gil

Fort Knox

Stepovich

Grant

Ryan Lode

CLEARY HILL

AREA

PEDRO DOME

AREA 

GILMORE DOME

AREA

ESTER DOME

AREA

148°

65°

147°

0 10 KILOMETERS

Pacific Ocean

Location map UNITED ST

Northwest

Alaska

CANADA

Territories

A

Study area

TES

Yukon

British

Columbia

Figure A6. Gold deposits of the Fairbanks district (from Hart and others, 2002).

ous rocks are not recognized at the deposit. The Gil deposit, 

about 10 km east of Fort Knox, is a sheeted gold-bearing vein 

system in calc-silicates that likely formed above an as-yetunroofed pluton intruding schist; other small and subeconomic tungsten skarns also occur in the same area. Many 

shear-hosted gold-bearing quartz veins, typically dominated 

by arsenopyrite, occur throughout the district (fig. A7). The 

largest, the Ryan Lode, occurs along the sheared margin of 

a tonalite stock. The majority of the schist-hosted deposits 

(for example, Grant, Cleary Hill, Newsboy, Hi-Yu, Christina, 

Tolovana) are along steeply dipping, northeast- or northwesttrending fault zones and have characteristic quartz-sericiteankerite alteration haloes. 40Ar/39Ar dates on micas of 89 to 

88 Ma for Ryan Lode (McCoy and others, 1997) and 103 Ma 

for Hi-Yu (R.J. Goldfarb, unpub. data, 2007), as well as a 

preliminary Re-Os sulfide date of 92 Ma for Tolovana (R.J. 
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A9

Goldfarb, unpub. data, 2007), suggest that the schist-hosted 

deposits both overlap and predate Cretaceous magmatism in 

the district.

High-grade, low-angle, multiphase, shear-hosted veins 

(fig. A2A) cutting mainly gneiss units (Day and others, 2003) 

and averaging 7 m in thickness with an areal extent of as 

much as 1.4×0.7-km (Smith and others, 1999; Rhys and 

others, 2003) were discovered at Pogo in 1996. Sulfide phases, 

comprising about 3 percent of the veins, include arsenopyrite, 

pyrite, pyrrhotite, loellingite, chalcopyrite, molybdenite, and 

bismuth- and tellurium-bearing phases. Alteration phases 

include biotite, quartz, sericite, potassium feldspar, ferroan 

dolomite, and chlorite. Reduced granites and tonalities of the 

Goodpaster batholith, located a few kilometers north of Pogo 

and comprising mainly crustal melts (in contrast to those at 

Fort Knox and in Yukon), were intruded around 109 to 103 

Ma, during the final stages of regional metamorphism and 

deformation (Dilworth and others, 2007). Igneous activity thus 

overlaps with the 104.2 Ma mineralization age as determined 

by Re-Os analysis of ore-related molybdenite (Selby and 

others, 2002). Other small gold prospects in the Goodpaster 

area (Shawnee Peak, Prospect 4021), however, have Re-Os 

ages of around 95 Ma (Hart and others, 2002).

Figure A7. Small shear-hosted gold vein system at the Tolovana 

deposit, Fairbanks district.

Geology and Gold Deposits of 

Southwestern Alaska

The far western end of the TGP (fig. A8) is underlain 

by Late Cretaceous clastic rocks of the Kuskokwim Group 

(Decker and others, 1994; Miller and others, 2002). These 

approximately 95 to 77 Ma sandstones and shales filled a 

northeast-trending, strike-slip basin between a series of older 

amalgamated terranes. Regional deformation was initiated 

in the Late Cretaceous and exposed rocks show evidence 

of only the lowest grades of regional metamorphism. Widespread, mainly intermediate, calc-alkaline volcanic-plutonic 

complexes formed throughout the region between 76 and 63 

Ma. These metaluminous igneous rocks are a part of a very 

broad (550 km long), subduction-related arc formed from 

crustally contaminated mantle melts (Moll-Stalcup, 1994). 

A second set of intrusive rocks is manifest by approximately 

75 to 65 Ma felsic to intermediate, peraluminous, hypabyssal 

granite porphyry dikes and plugs that are most likely melted 

Kuskokwim Group rocks (Miller and Bundtzen, 1994). Both 

intrusive suites are spatially associated with gold resources 

(Bundtzen and Miller, 1997; Miller and others, 2007).

The giant Donlin Creek gold deposit (fig. A9) occurs as 

a series of prospects localized within an 8×3-km swarm of 

the hypabyssal granite porphyry dikes (Goldfarb and others, 

2004). Thin quartz veinlets, with lesser dolomite and ankerite, 

fill brittle extensional fractures within the igneous rocks. 

Fine-grained pyrite, arsenopyrite, and stibnite comprise 3 to 5 

percent of the mineralized rock; orpiment, realgar, cinnabar, 

native arsenic, and graphite are also present. Gold is almost 

exclusively a refractory phase in the arsenopyrite. In contrast 

to many of the gold resources elsewhere in the TGP, bismuth, 

tellurium, and tungsten do not occur in anomalously high 

concentrations in the Donlin Creek orebody. Sericitization, 

carbonatization, and sulfidation are common in the veinlet 

wallrocks. 40Ar/39Ar dating of hydrothermal micas suggests 

veining occurred within a few million years after intrusion 

of the 75 to 69 Ma dike host rocks. Isotopic data indicate 

the source magma for the dikes was mainly of crustal origin, 

probably sediments of the lower parts of the Kuskokwim basin 

that were subjected to a localized domain of elevated crustal 

heat flow. A few other gold occurrences in this part of the TGP, 

including that at Vinasale Mountain, appear to be localized in 

similar peraluminous dike systems. 

A series of gold occurrences in the Shotgun Hills are 

associated with weakly metaluminous to strongly peraluminous granite to granodiorite stocks and dikes, some of which 

are porphyritic and locally fractionated to quartz-feldspar 

porphyry dikes. The Shotgun gold deposit is situated near the 

apex of one such evolved quartz-feldspar porphyry phase. It 

occurs as 0.5- to 5-cm-wide stockworks of auriferous quartz 
A10 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

FAREWELL-DENALI FAULT

Nixon

Fork

Vinasale

Donlin Creek

Golden Horn

Chicken Mountain

Shotgun

IDITAROD-NIXON FORK FAULT

160° 156°

63°

61°

0 50 KILOMETERS

EXPLANATION

Early Tertiary to Late Cretaceous rocks

Volcanic-plutonic complexes

Granite porphyry complexes

Calc-alkaline plutonic rocks

Kuskokwim Group (Early Cretaceous)

Strike-slip fault—Arrows show relative 

movement

Gold deposit

Gold occurrences

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

Figure A8. Main lode gold 

resources in the western end 

of the Tintina Gold Province 

(after Bundtzen and Miller, 

1997; Hart and others, 2002).

veinlets (Rombach and Newberry, 2001). The veinlets contain 

less than 1 percent sulfides that are dominated by gold-bearing 

arsenopyrite commonly associated with pyrite, pyrrhotite, and 

chalcopyrite, and also loellingite and bismuth-, tellurium-, 

and tungsten-rich mineral phases. Gold grades tend to correlate with abundance of albite alteration. Tourmaline and 

quartz commonly cement brecciated porphyry and hornfels 

rocks. The igneous host rock is dated as 69±1 Ma (Rombach 

and Newberry, 2001). Isotopic data indicate that this igneous 

rock has a source in common with those of the other volcanicplutonic complexes throughout the Kuskokwim region, which 

is most likely evolved mafic to intermediate mantle melts 

(J.L. Mair, unpub. data, 2007). 

In addition to the Shotgun Hills, important gold resources 

are associated with other relatively evolved, metaluminous 

intrusive phases of the volcanic-plutonic complexes that are 

scattered elsewhere in this part of the TGP. These include 

auriferous quartz stockworks in monzonite at the Golden Horn 

deposit in Flat (Bull, 1988) and auriferous skarns at Nixon 

Fork (Newberry and others, 1997). Where the igneous rocks 

in these complexes are the most evolved (syenitic to monzonitic), silver-, bismuth-, and tin-rich veins appear to be more 

dominant than gold-bearing veins. 
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A11

A

B

Figure A9. A, Aerial photograph of the Donlin Creek deposit 

area that is centered on a seriees of topographic domes in the 

Kuskokwim Mountains region of southwestern Alaska. B, Most 

of the mineralization at the Donlin Creek gold deposit occurs in 

these narrow, vuggy quartz-carbonate veinlets within an igneous 

dike-sill complex. The igneous host rocks are mainly rhyodacitic in 

composition, and sometimes porphyritic, as shown here.

Geochemical Constraints on Gold 

Ore-Forming Fluids

Fluid-Inclusion Studies

Fluid-inclusion microthermometric studies of ore-bearing 

quartz have allowed for definition of the pressure, temperature, and chemical composition of the ore-forming solutions 

responsible for the main gold resources in the TGP (table A2). 

Those gold deposits hosted by and within the surrounding 

hornfels of the mid-Cretaceous plutons (Fort Knox, Dublin 

Gulch, Scheelite Dome, Clear Creek) typically developed 

from low to moderate salinity (≤12 weight percent NaCl 

equivalent), gas-rich (typically ≥15-20 mole percent CO2

) 

fluids at temperatures of 290°C to 380°C, and pressures of 1 

to 2 kilobars (kb) (or 3.5 to 7 km depth); the Dublin Gulch 

veins appear to have been slightly cooler, and the Scheelite 

Dome veins are likely slightly deeper in origin relative to 

the others. Available data indicate that other mid-Cretaceous 

gold deposits hosted by metamorphic rocks in the Fairbanks 

and Goodpaster districts have the same gas-rich, low to 

moderate salinity fluid type. Pogo and adjacent prospects in 

the Goodpaster district show indications of being the most 

deeply formed and hottest among the TGP gold ore systems. 

In contrast to the gold deposits in the eastern part of the TGP, 

the Late Cretaceous Donlin Creek and Shotgun deposits in 

southwestern Alaska formed within the upper 1 to 2 km of 

the crust; Shotgun is also characterized by an anomalously 

high-salinity hydrothermal fluid.

Laser-ablation inductively coupled plasma-mass 

spectrometry (ICP-MS) microanalysis was applied to fluid 

inclusions in ore-stage quartz to obtain quantitative estimates 

of any significant differences in the relative abundances of a 

variety of trace elements in the hydrothermal solutions of the 

various gold deposits of the TGP (Marsh and others, 2005). 

Single fluid inclusions from intrusion-hosted, gold-bearing 

quartz-feldspar veins at Fort Knox were analyzed simultaneously for many major, minor, and trace element relative 

concentrations. Element ratio measurements (all to Na) range 

from 0.01 to 0.06 for arsenic and 0.004 to 0.03 for antimony 

in Fort Knox intrusion-hosted quartz veins, but one extremely 

gold-rich quartz-feldspar vein had a ratio as high as 0.37 for 

arsenic. In addition, whereas most bismuth ratios were less 

than or equal to 0.01, one inclusion within the quartz-feldspar 

vein had a ratio of 0.67. Base metal ratios were consistently 

less than 0.01 for lead, and 0.01 to 0.05 for copper and zinc. 

Similar values characterized fluid inclusions from sheeted 

veins within the stocks at Scheelite Dome and Clear Creek, 

but inclusions from auriferous veins in adjacent hornfels at 

Scheelite Dome commonly showed arsenic, lead, and antimony ratios of greater than 1. Data from reconnaissance 

examination of several other significant gold deposits that are 

not hosted by the reduced approximately 90 Ma stocks were 

compared and contrasted with those data from the Fort Knox 

and Yukon deposits. Analysis of a few of the inclusions from 

the Pogo deposit showed no obvious distinction from those 

that typified the intrusion-hosted deposits. At Donlin Creek, 

inclusions from the main gold resource exhibited highly 

anomalous ratios of 4 to 15 for arsenic and 3 to 5 for iron, and 

elevated ratios of 0.1 to 0.3 for antimony, whereas those from 

the subeconomic Dome property at the northern margin of the 

Donlin Creek mineralized zone were 0.004 to 0.016, 0.026 

to 0.079, and 0.001 to 0.003, respectively. It is unclear as to 

whether the Donlin Creek ore fluids were indeed exceptionally 

anomalous or if perhaps significant dissolution of abundant 

fine-grained arsenic- and antimony-bearing sulfide phases 

within the quartz veinlets occurred. 

Noble-Gas Studies

Noble-gas isotopes were determined for samples of 

quartz vein material from gold deposits of the TGP. Helium-
A12 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

?

?

?

Intrusion-hosted Proximal Distal

Au-Bi-Te ± W, Mo, As Au-As ± W, Sn, Sb Au-As-Sb-Hg ± Ag, Pb, Zn

Au-W calc-alkalic

and Au-Cu alkalic

contact skarns Au-As

veins Sb±Au,

As veins

Sheeted veins, aplite Ag-Pb-Zn and pegmatite dikes veins Distal skarn

Tensional zones, veins,

and lamprophyres

Replacement and

disseminations

Structurally prepared Hornfels limit Roof zone thermal aureole hanging wall above pluton

Hydrothermal

breccia

EPIZONAL DEPOSITS

Donlin Creek

True North

Brewery Creek

INTRUSION-RELATED

DEPOSITS

Sheeted Veins 

Fort Knox

Dublin Gulch

Dolphin Skarns

Marn, Gil Low-angle faults Pogo Stepovich

Replacements/Breccias Ryan Lode

Scheelite Dome

Bear Paw

SHEAR-RELATED DEPOSITS

Hi-Yu, Tolovana

Christina, Longline

Figure A10. Intrusion-related gold systems in the Tintina Gold Province are characterized by a model that has differing deposit styles, 

metallogeny, and geochemistry surrounding a causative mid-Cretaceous igneous body. Other shear-related ore deposits, although 

spatially and temporally associated with mid-Cretecous plutons, are more like classic orogenic gold deposits. Shallowly formed epizonal 

deposits are more difficult to classify and remain controversial regarding their genesis. (After Hart and others, 2002.)

isotope ratios have R/Ra (where R is the measured 3He/4He 

ratio and Ra the atmospheric ratio) values that varied from 

less than 0.1 for Pogo to greater than 15 for Clear Creek. 

Preliminary helium data suggest that deposits in Yukon (Clear 

Creek, Scheelite Dome) have a definite mantle contribution, 

whereas ore-forming fluids in the TGP deposits sampled 

in Alaska (Fort Knox, Pogo, Donlin Creek) are dominated 

by helium with a crustal origin. The 40Ar/36Ar ratios from 

Donlin Creek are close to those for air (295.5) and indicate 

contamination by air-saturated ground waters in this relatively 

shallowly formed ore deposit. The other studied gold deposits 

in east-central Alaska and adjacent Yukon have typical ratios 

of approximately 500, suggesting a consistent gas source 

added from the crust or mantle (see Allegre and others, 1987).

Stable-Isotope Studies

Stable-isotope data are consistent with deep crustal 

sources for major ore-fluid components. Oxygen-isotope 

data (table A2) for ore-bearing quartz in all gold deposits 

typically are in the range of 12 to 19 parts per thousand (per 

mil), indicating a fluid of magmatic or metamorphic source, 

but with little, if any, contribution from meteoric sources. 

Nitrogen-isotope data from the Christina deposit in the Fairbanks district suggest that at least the ore fluids for the sedimentary rock-hosted gold-bearing vein deposits in this specific 

area are of metamorphic origin (Jia and others, 2003). Large 

variations in sulfur-isotope data (table A2) reflect variable 

crustal reservoirs for the sulfur that transports the gold ore 

in the hydrothermal solutions. Extremely negative values for 

sulfur isotopes for sulfide minerals at Donlin Creek, in the 

hornfels-hosted veins at Clear Creek, and at Scheelite Dome 

reflect the highly reduced nature of the sedimentary rocks that 

provide sulfur to the hydrothermal fluids. 

Genesis of Lode Gold Deposits

Geological, geochronological, and geochemical data 

suggest that both magmatic and metamorphic models can 

be applied to explaining the distribution of gold resources 

across the TGP (Goldfarb and others, 2005). Most of the 

small and widely distributed, approximately 105 to 90 Ma 

shear zone-related, gold-bearing quartz veins in the Fairbanks 

(fig. A7) and Goodpaster (fig. A2A) districts are best classified 

as orogenic gold deposits (for example, Groves and others, 

1998), which formed during a period of high crustal heat flow 

and rapid uplift associated with orogenic collapse. Veins show 

evidence of both brittle and ductile deformation, are most 

consistently anomalous in arsenic, antimony, and tungsten, 

and formed from a low-salinity, CO2

-rich ore fluid. The fluid 

and gold were likely liberated during devolatilization at depth 

during final stages of deformation and regional metamorphism, and subsequently formed veins at shallower levels in 

uplifting rocks of the eastern TGP. Pressure fluctuations during 

hydraulic fracturing and shear movements were the most probable cause for vein formation and gold deposition. Although 

controversial, many features of the large Pogo deposit also 

suggest that it is a relatively deeply formed orogenic gold 

deposit (Goldfarb and others, 2000, 2005).

A second genetic model of intrusion-centered mineralizing systems is most appropriate for other approximately 

90 Ma gold resources in the eastern TGP, including the Fort 

Knox deposit near Fairbanks and those in Yukon (Hart and 

others, 2002; Hart and Goldfarb, 2005; Hart, 2007). These 

so-called intrusion-related gold systems (IRGSs) are similar 

to the orogenic gold deposits in that both deposit types are 

spatially and temporally associated with igneous rocks, may 

overlap in tectonic setting, have similar gangue mineralogy, 

can overlap in trace-element signatures (Ag, Au, As, Bi, Sb, 
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A13

Table A2. Fluid inclusion and stable isotope geochemistry of ore-bearing samples from deposits in the Tintina Gold Province.[Abbreviations and symbols are as follows: n.d., no data; °C, degrees Celsius; ≤, less than or equal to; ≥, greater than or equal to]

Deposit xCO2±N2, CH4 (mole percent) Salinity (weight percent equivalent NaCl) Immiscible Pressure (kilobars) Temperature (°C)

δ18O quartz 

(per mil)

δ34S sulfide 

(per mil) Reference

Clear Creek 15 12 Yes 1.4–1.8 300–350 14.0–18.7 -12.7– -9.5, 

-2.9–+0.4

Marsh and others, 2003

Scheelite Dome 20–60 ≤4 No 2–3 290–380 14.1–19.0 -10.9– -7.1 Mair and other, 2006Dublin Gulch 2–33 1.4–9.8 No ≥1.1 ≥150– 271 n.d. n.d. Maloof and others, 2001Fort Knox 22 2–8 Some 1.25–1.5 330–370 12.0–13.5 -3.4 Goldfarb and others, 

1997; McCoy and others, 1997; Paul Jensen, Teck-Cominco, unpub. data, 2006

Ryan Lode 12 ≤8 Yes 0.5–0.75 270–330 11.7–15.0 0.5–3.7 McCoy and others, 1997Others—Fairbanks 

district

1–20 3–5 n.d. n.d. 275–375 n.d. 0.3–4.1; 

8.2–10.9

Metz, 1991; Goldfarb 

and others, 1997

Pogo Highly variable Highly variable Yes 1.7–2.0 308–570 13.4–15.2 -2.5–+5.5 Smith and others, 1999; 

Rombach and others, 2002; C. Rombach, unpub. data, 2005

Others—Goodpaster 

district

Significant amounts 2.5–7.5 Yes 1.4–2.4 225–390 n.d. n.d. Dilworth, 2003; R.J. 

Goldfarb, unpub. data, 2005

Donlin Creek 3–7 3–6 Rare 0.3–0.6 275–300 14.3–24.7 -16– -10 Goldfarb and others, 

2004

Shotgun Variable Moderate to high Yes 0.5 280–630 16.4–17.1 -5.9– -5.0 Romach and Newberry, 

2001
A14 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

35

70

105

0

DEPTH, IN KILOMETRES

Donlin Creek

deposit Heated

meteoric

water

Farewell and Yukon

Tanana terranes

Togiak

terrane

Kuskokwim

basin

Kuskokwim

basin

Qtz

SL Qn D

Lithospheric mantle

Asthenospheric mantle

Asthenospheric mantle Latest Cretaceous to early Tertiary

rocks of the Kula plate

Accreted

arcs

Accreted

arcs

Early

magmatic

Magmatic fluid

fluid

Metamorphic

devolatilization

Metamorphic

devolatilization

Location of

inset C

Location of

inset B

R S

C

A

B

D

EXPLANATION

Contaminated mantle melt

Kuskokwim flysch melt

Kuskokwim Group—Shales and graywackes

Volcanic-plutonic complexes

Donlin Creek deposit

Hornfels

Mineralized zone—SL, South Lewis; R, 

Rochilieu; Qn, Queen; S, Snow; Qtz, 

Quartz; D, Dome 

Figure A11. Genetic model for evolution of the Donlin Creek 

gold deposit. A, Small-scale, regional model showing location of 

inset B. Field of view is approximately 480 kilometers. B, Inset B, 

showing partial mantle melting above the subducting Kula plate 

leading to the emplacement of crustally contaminated intrusions 

and volcanic-plutonic complexes throughout the Kuskokwim 

basin. In a few locations (including at the site of the Donlin Creek 

deposit), small, almost pure flysch melts evolved. Shows location 

of inset C. C, Inset showing gold-transporting hydrothermal fluids 

released during devolatilization of flysch adjacent to the larger 

melts and (or) from the melts themselves. The fluids localized the 

gold ores in the already crystallized and structurally competent 

flysch melt dike-sill complex at Donlin Creek. (After Goldfarb and 

others, 2004.)
Geology and Origin of Epigenetic Lode Gold Deposits, Tintina Gold Province, Alaska and Yukon A15

Te, and (or) W), and have formed from fluids with very similar 

chemistries. In fact, the low salinity and high CO2 content 

of the IRGSs are very different from most other magmatic 

gold deposits and has led to much of the controversy regarding identification of IRGSs versus orogenic gold deposits 

(Groves and others, 2003). A key distinction is that an IRGS 

represents a zoned system centered around a causative pluton 

(fig. A10); a complete model would include (1) sheeted goldbismuth-tellurium-tungsten-bearing quartz veins in the cupola 

of the intrusion; (2) gold-rich tungsten or copper skarns in 

any adjacent calcareous rocks; (3) gold-arsenic±antimony 

tension-vein arrays, disseminations, and breccias within 2- to 

3-km-wide hornfels zones; and (4) distal low-temperature 

silver-lead-zinc veins (Hart and others, 2002). The IRGSs are 

also significantly lower in grade (less than 1 g/t gold) than 

orogenic gold deposits (greater than 1-2 g/t gold; commonly 

greater than 10 g/t gold). The zoned mineralization styles 

indicate an exsolved magmatic fluid that moved outward from 

the late-stage crystallizing magma. An abundance of aplites, 

pegmatites, vein dikes, miarolitic cavities, and unidirectional 

solidification textures in the igneous rocks is consistent with 

a fluid-rich melt and thus with a magmatic model. Potassic 

magmas released from the SCLM could have been the source 

of the gold that was further concentrated during magmatic 

evolution in the overlying crust (John L. Mair, Geoinformatics 

Exploration, Inc., unpub. data, 2008).

Two distinct ore deposit models also characterize the 

approximately 70 Ma gold deposits in the western TGP 

(Goldfarb and others, 2004). The gold-forming fluids at the 

giant Donlin Creek orogenic gold deposit may have been 

derived by broad-scale metamorphic devolatilization above 

rising mantle melts that were emplaced into the sediments 

at the base of the Kuskokwim basin. Alternatively, exsolution of fluids could have taken place from a magma that was 

dominated by a significant sedimentary rock melt component 

(fig. A11). Other gold occurrences in the Kuskokwim basin, 

best broadly classified as simply magmatic gold deposits (for example, Shotgun and Golden Horn), formed via 

fluid exsolution from fractionation of high-level intrusive 

systems dominated by a mafic to intermediate composition 

parent magma of lower crustal or lithospheric mantle origin. These gold deposits seem to be localized at the apices 

of the more fractionated porphyritic intrusive bodies in 

the region. The high degree of fractionation is important 

for preconcentration of metals and volatiles in these gold 

depositing magmatic-hydrothermal systems.

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G.L., and Szumigala, D.J., 1997, Skarn deposits of Alaska, 

in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of 

Alaska: Economic Geology Monograph 9, p. 355–395.
A18 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Rombach, C.S., and Newberry, R.J., 2001, Shotgun deposit—

Granite porphyry-hosted gold-arsenic mineralization in 

southwestern Alaska, USA: Mineralium Deposita, v. 36, 

no. 6, p. 607–621.

Rombach, C.S., Newberry, R.J., Goldfarb, R.J., and Smith, 

Moira, 2002, Geochronology and mineralization of the 

Liese zones, Pogo deposit, Alaska [abs.]: Geological 

Society of America Abstracts with Programs, v. 34, no. 6, p. 

114.

Rhys, David, DiMarchi Jack, Smith, Moira, Friesen, Robert, 

and Rombach, Cameron, 2003, Structural setting, style 

and timing of vein-hosted gold mineralization at the Pogo 

deposit, east-central Alaska: Mineralium Deposita, v. 38, 

no. 7, p. 863–875.

Selby, David, Creaser R.A., Hart, C.J.R., Rombach, C.S., 

Thompson, J.F.H., Smith, M.T., Bakke, A.A., and 

Goldfarb, R.J., 2002, Absolute timing of sulfide and gold 

mineralization; A comparison of Re-Os molybdenite and 

Ar-Ar mica methods from the Tintina gold belt, Alaska: 

Geology, v. 30, no. 9, p. 791–794.

Selby David, Creaser, R.A., Heaman, L.M., and Hart, C.J.R., 

2003, Re-Os and U-Pb geochronology of the Clear Creek, 

Dublin Gulch, and Mactung deposits, Tombstone gold belt, 

Yukon, Canada; Absolute timing relationships between 

plutonism and mineralization: Canadian Journal of Earth 

Scinces, v. 40, no. 12, p. 1839–1852.

Smith, Moira, 2000, The Tintina gold belt; An emerging gold 

district in Alaska and Yukon, in Tucker, T.L., and Smith, 

M.T., eds., The Tintina gold belt—Concepts, exploration 

and discoveries: British Columbia and Yukon Chamber of 

Mines, Special Volume 2, p. 1–3.

Smith, Moira, Thompson, J.F.H., Bressler, Jason, Layer, 

Paul, Mortensen, James, Abe, Ichiro, and Takaoka, 

Hidetoshi, 1999, Geology of the Liese zone, Pogo property, 

east-central Alaska: Society of Economic Geologists 

Newsletter, v. 38, no. 1, p. 12–21.

Thompson, J.F.H., and Newberry, R.J., 2000, Gold deposits 

related to reduced granitic intrusions, in Hagemann, S.G., 

and Brown, P.E., eds., Gold in 2000: Reviews in Economic 

Geology, v. 13, p. 377–400.
Tectonic Setting and Metallogenesis of 

Volcanogenic Massive Sulfide Deposits 

in the Bonnifield Mining District, Northern 

Alaska Range

By Cynthia Dusel-Bacon, John N. Aleinikoff, Wayne R. Premo, Suzanne Paradis, 

and Ilana Lohr-Schmidt

Chapter B of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–B

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract........................................................................................................................................................B1

Introduction..................................................................................................................................................B1

Regional Geology........................................................................................................................................B1

Deposits........................................................................................................................................................B2

Methods........................................................................................................................................................B2

Results .........................................................................................................................................................B4

Conclusions .................................................................................................................................................B5

Acknowledgments......................................................................................................................................B6

References Cited.........................................................................................................................................B7

Figures

B1. Generalized geologic map of the Wood River area, northeastern Healy 

quadrangle..................................................................................................................................B3

B2. Photograph of Red Mountain, looking west, showing quartz-sericite-pyrite 

alteration and north-dipping metarhyolite of the Mystic Creek Member ........................B4

B3. Photograph showing sampling of drill core from the Dry Creek VMS deposit, 

stored at the Ester core facility, Alaska.................................................................................B4

B4. Discrimination diagram showing Zr/TiO2 versus Nb/Y for metaigneous samples 

from the Wood River area ........................................................................................................B5

B5. Diagram showing Yb versus Ta contents for felsic metaigneous samples from 

the Wood River area..................................................................................................................B6

B6. Hafnium-thorium-tantalum diagram for mafic metavolcanic samples from the 

Wood River area ........................................................................................................................B6

Tectonic Setting and Metallogenesis of Volcanogenic 

Massive Sulfide Deposits in the Bonnifield Mining District, 

Northern Alaska Range

By Cynthia Dusel-Bacon,1 John N. Aleinikoff,1 Wayne R. Premo,1 Suzanne Paradis,2 and Ilana Lohr-Schmidt1

1

U.S. Geological Survey.

2

Geological Survey of Canada.

Abstract

This paper summarizes the results of field and laboratory investigations, including whole-rock geochemistry and 

radiogenic isotopes, of outcrop and drill core samples from 

volcanogenic massive sulfide (VMS) deposits and associated 

metaigneous rocks in the Wood River area of the Bonnifield 

mining district, northern Alaska Range (see fig. 1 of Editors’ 

Preface and Overview). U-Pb zircon igneous crystallization 

ages from felsic rocks indicate a prolonged period of Late 

Devonian to Early Mississippian (373±3 to 357±4 million 

years before present, or Ma) magmatism. This magmatism 

occurred in a basinal setting along the ancient Pacific margin 

of North America. The siliceous and carbonaceous compositions of metasedimentary rocks, Precambrian model ages 

based on U-Pb dating of zircon and neodymium ages, and 

for some units, radiogenic neodymium isotopic compositions and whole-rock trace-element ratios similar to those of 

continental crust are evidence for this setting. Red Mountain 

(also known as Dry Creek) and WTF, two of the largest 

VMS deposits, are hosted in peralkaline metarhyolite of the 

Mystic Creek Member of the Totatlanika Schist. The Mystic 

Creek Member is distinctive in having high concentrations of 

high-field-strength elements (HFSE) and rare-earth elements 

(REE), indicative of formation in a within-plate (extensional) 

setting. Mystic Creek metarhyolite is associated with alkalic, 

within-plate basalt of the Chute Creek Member; neodymium 

isotopic data indicate an enriched mantle component for both 

members of this bimodal (rhyolite-basalt) suite. Anderson 

Mountain, the other significant VMS deposit, is hosted by 

the Wood River assemblage. Metaigneous rocks in the Wood 

River assemblage span a wide compositional range, including 

andesitic rocks, which are characteristic of arc volcanism. Our 

data suggest that the Mystic Creek Member likely formed in 

an extensional, back-arc basin that was associated with an outboard continental-margin volcanic arc that included rocks of 

the Wood River assemblage. We suggest that elevated HFSE 

and REE trace-element contents of metavolcanic rocks, whose 

major-element composition may have been altered, are an 

important prospecting tool for rocks of VMS deposit potential 

in east-central Alaska. 

Introduction

Devonian to Mississippian magmatism was widespread 

along the ancient Pacific margin of North America. Many 

of the volcano-plutonic complexes and associated sedimentary rocks contain volcanogenic massive sulfide (VMS) or 

sedimentary exhalative massive sulfide (SEDEX) syngenetic 

base-metal (zinc-lead-copper) mineral deposits, including 

several deposits in east-central Alaska (Newberry and others, 

1997; Dusel-Bacon and others, 2006). (Syngenetic means 

that the deposit formed contemporaneously with the enclosing rocks.) The discovery in the mid-1990s of zinc-leadsilver massive sulfide deposits in the Finlayson Lake area 

of southeastern Yukon, Canada, prompted renewed interest 

in known and potential base-metal sulfide occurrences in 

similar rocks in Alaska. The potential for economic deposits provided the impetus for our investigations of the major 

known VMS deposits of the Bonnifield mining district and 

their host rocks. We summarize herein the results of our study 

to characterize the regional tectonic setting of the host rocks 

to the VMS deposits, the mineralogy and isotopic characteristics of the deposits, and the controls of mineralization in a 

submarine hydrothermal environment. The reader is referred 

to Dusel-Bacon and others (2004, 2005, 2006) for complete scientific referencing and more detailed results of our 

investigations. 

Regional Geology

Greenschist-facies metavolcanic and metasedimentary 

rocks in the Bonnifield district form range-parallel, east-
B2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

trending belts (Wahrhaftig, 1968; Gilbert and Bundtzen, 

1979). Protoliths (premetamorphic rock types) consist of 

varying amounts of predominantly felsic and mafic volcanic 

and shallow intrusive rocks that are interlayered with carbonaceous and siliciclastic sedimentary rocks indicating deposition 

in a submarine, basinal setting. U-Pb zircon ages from felsic 

rocks indicate a prolonged period of Late Devonian to Early 

Mississippian (373±3 to 357±4 Ma) magmatism (DuselBacon and others, 2004, 2005, 2006; C. Dusel-Bacon and J.N. 

Aleinikoff, unpub. data, 2007).

Quartz-rich schists and subordinate carbonaceous schist 

and marble of the informally named Healy schist form the core 

of a regional anticline (fig. B1). Carbonaceous metasedimentary rocks and minor conglomerate and rhyolite of the Keevy 

Peak Formation crop out north of, and stratigraphically above, 

the Healy schist (fig. B1). Bimodal — having both silica-poor 

(mafic) and silica-rich (felsic) compositions — metaigneous 

rocks, and carbonaceous and siliceous metasedimentary rocks 

of the Totatlanika Schist overlie the Keevy Peak Formation. 

Totatlanika Schist is subdivided into the following five 

members (Wahrhaftig 1968), from bottom to top: (1) Moose 

Creek (felsic and minor mafic schist); (2) California Creek 

(augen gneiss, grading to metarhyolite porphyry); (3) Chute 

Creek (metabasalt, which interfingers with both California 

Creek and Mystic Creek Members); (4) Mystic Creek (metarhyolite—mostly metamorphosed crystal tuff); and (5) Sheep 

Creek (quartzofeldspathic schist derived from near-source, 

reworked volcanic deposits; metasiltstone, metatuff, and 

marble). Carbonaceous phyllite, indistinguishable from that 

in the Keevy Peak Formation, is found within all members of 

the Totatlanika Schist. These rocks form a syncline, with the 

Sheep Creek Member occupying its core (fig. B1).

The Wood River assemblage comprises a package of 

metavolcanic and metasedimentary rocks on the south flank 

of the anticline cored by Healy schist (fig. B1). This assemblage has gross lithologic similarities to the metavolcanic and 

carbonaceous sedimentary assemblages in the Totatlanika 

Schist and was proposed by Gilbert and Bundtzen (1979) to be 

equivalent to it. One of the goals of our study was to evaluate 

this hypothesis, and our conclusions regarding this correlation 

are given below.

Deposits

Two of the largest VMS deposits in the Bonnifield 

district, the Red Mountain (Dry Creek) deposit and the WTF 

deposit, are located approximately 90 kilometers (km) south 

of Fairbanks in the northeastern part of the Wood River 

area (fig. B1). Both deposits are hosted by the Mystic Creek 

Member of the Totatlanika Schist and occur near the contact 

between phyllitic felsic metavolcanic and subordinate carbonaceous rocks of the Mystic Creek Member and the overlying, 

predominantly metasedimentary rocks of the Sheep Creek 

Member (Newberry and others, 1997; Smit, 1999). Drilling 

of one of the massive sulfide horizons just north of Red 

Mountain, named for its distinctive 1,800-meter (m)-thick 

zone of quartz-sericite-pyrite footwall alteration (fig. B2), 

identified an estimated resource of 3.2 million tons averaging 

4.4 percent zinc, 1.9 percent lead, 0.2 percent copper, 3.01 

ounces per ton (oz/t) silver, and 0.018 oz/t gold (Szumigala 

and Swainbank, 1998).

The WTF deposit (fig. B1) is located about 3 km 

northeast of Red Mountain. The structural and stratigraphic 

relationship between the WTF and Red Mountain deposits is 

disputed. Smit (1999) placed the shallowly dipping host rocks 

of the WTF deposit and the steeply north-dipping host rocks of 

the Red Mountain deposit on the northern and southern limbs, 

respectively, of an east-west-trending syncline (within the 

broader syncline cored by the Sheep Creek Member; fig. B1). 

Newberry and others (1997), on the other hand, placed the 

Red Mountain deposit in a separate and lower stratigraphic 

interval. As discussed below, our geochemical and U-Pb 

zircon sampling addressed these two possibilities. WTF has 

an estimated resource of 3.09 million tons averaging 6 percent 

zinc, 2.5 percent lead, 0.1 percent copper, 5.73 oz/t silver, and 

0.029 oz/t gold (Szumigala and Swainbank, 1998).

The Anderson Mountain VMS prospect, located 32 km 

southwest of the Mystic Creek deposits, is exposed on the 

south limb of the antiform cored by the Healy schist. This 

prospect occurs within felsic to mafic metavolcanic rocks and 

associated carbonaceous metasedimentary rocks of the Wood 

River assemblage (fig. B1).

Methods

We collected outcrop and drill core samples of sulfidebearing and unmineralized rocks from the Wood River area 

(figs. B1, B3) of the Bonnifield district. We utilized sensitive 

high-resolution ion microprobe (SHRIMP) U-Pb dating of 

zircon crystals separated from felsic igneous rocks to determine the crystallization ages of volcanic and plutonic units 

in the Wood River area (fig. B1). This dating technique 

has the advantage of being able to analyze minute (about 

30-micrometer-diameter) areas, allowing age determination 

and analysis of both inherited zircon cores (from incorporated 

crustal material) and magmatic rims of zircons. Whole-rock 

neodymium isotopic compositions helped us identify the relative abundance of mantle versus continental crust components 

in the parent magmas of the metaigneous rocks.

A major part of our study employed whole-rock traceelement geochemistry of metaigneous rocks to determine their 

origin and tectonic setting, particularly of those that are associated with the VMS deposits. Considerable care was taken to 

sample only the freshest, least altered material. Our conclusions are based on trace elements that have been shown to be 

immobile, except during high-temperature metamorphism or 

because of pronounced hydrothermal alteration, neither of 

which has affected the rocks of the Wood River area. Because 
Tectonic Setting and Metallogenesis of Volcanogenic Massive Sulfide Deposits in the Bonnifield Mining District B3

EXPLANATION

Alluvium (Quaternary)

Granite (Cretaceous)

Totatlanika Schist (Early Mississippian to Late Devonian)— Individual 

members are mapped separately and listed below from youngest to 

oldest. Ages of individual members are based on SHRIMP U-Pb 

zircon ages and limited fossil age control. With the exception of the 

California Creek Member that yielded two Late Devonian ages, U-Pb 

zircon ages for all other dated members span the Late Devonian-Early 

Mississippian boundary (360±2 Ma; Okulitch, 2002); therefore, all 

members are assigned the map unit symbol of MD

Sheep Creek Member—Epiclastic quartz-feldspar-sericite schist and 

tuffaceous slate 

Mystic Creek Member—Felsic metavolcanic schist

Chute Creek Member—Mafic metavolcanic schist 

California Creek Member—Quartz-potassium feldspar-sericite schist 

and augen gneiss

Moose Creek Member—Quartz-potassium-feldspar gneiss, felsic 

schist, and mafic schist

Wood River assemblage (Early Mississippian to Late Devonian)

Metasedimentary rock—Includes marble, quartzite, and 

calcarenite

Green metavolcanic schist and carbonaceous schist 

Rhyolite schist 

Keevy Peak Formation (Devonian)—Quartz-sericite schist, carbonaceous quartz schist, slate, and stretched-pebble conglomerate 

Healy schist (informal) (Devonian and older)—Quartz-sericite 

schist, quartzite, chlorite schist, marble, and metagabbro

Carbonaceous schist—Pattern superimposed on various units

Contact

Anticline

Syncline

Thrust fault—Sawteeth on upper plate

Fault—Unclassified

Location of sample and SHRIMP zircon age (in Ma)

Major volcanogenic massive sulfide (VMS) deposit

D<h

Dk

MDwr

MDws

MDwm

MDtm

MDtc

MDtcc

MDtmc

MDts

Kg

Qa

Dry Cr.

Wood

River

Kansas Creek

River

Mystic Creek

Chute Cr..

Sheep Cr.

Healy River

Little Delta

Virginia Creek

Qa

Qa

Qa

Qa

D<h

D<h

D<h

D<h

MDts

MDtmc

MDtcc

MDtmc

MDtc

MDtc

MDtc

MDtc

MDtm

MDtm

MDtm

MDtcc

MDtcc MDtcc

MDws

MDws

MDwm

MDwm

MDwr MDwr

Kg

Kg

Kg Kg

Kg

Dk

Dk

Dk Dk

 373±3

360±5

357±4

365±5 370±2

 362±3

 362±3

 362±2

 363±2

356±3

366±4

372±5

368±4

367±4

363±2

356±3

Red Mountain

WTF

Anderson Mountain

148°00'

64°00' 147°30'

63°45'

148°30' 147°10'

0 5 KILOMETERS

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

Figure B1. Generalized geologic map of the Wood River area, northeastern Healy quadrangle, showing the location of the three 

main volcanogenic massive sulfide targets and U-Pb zircon ages. Abbreviations are as follows: SHRIMP, sensitive high-resolution ion 

microprobe; Ma, millions of years. Geology modified from Wahrhaftig (1968) and Gilbert and Bundtzen (1979); SHRIMP U-Pb zircon 

crystallization ages from Dusel-Bacon and others (2004, 2005) and C. Dusel-Bacon and J.N. Aleinikoff (unpub. data, 2007).
B4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

of major-element mobility, especially of alkalis and silica, 

magma compositions are identified utilizing a Zr/TiO2 versus 

Nb/Y diagram (fig. B4).

Figure B2. View of Red Mountain, looking west, showing quartzsericite-pyrite alteration and north-dipping metarhyolite of the 

Mystic Creek Member. Cynthia Dusel-Bacon and Melanie Hopkins 

(U.S. Geological Survey (USGS)) in foreground. Photograph by 

Charlie Bacon (USGS).

Results 

U-Pb zircon crystallization ages indicate a prolonged 

period of felsic magmatism from 373±3 to 357±4 Ma 

(fig. B1). Ages determined on felsic samples from the various map units overlap one another. Crystallization ages from 

throughout the Mystic Creek Member of the Totatlanika Schist 

overlap within the range of 363±3 to 357±4 Ma. Metarhyolites 

hosting both the WTF and Anderson Mountain deposits 

include SHRIMP U-Pb zircon ages of about 363 Ma, but 

their whole-rock compositions, trace-element signatures, and 

neodymium isotope compositions differ, as discussed below. 

U-Pb analyses of zircon cores from Totatlanika Schist and 

Healy schist felsic rocks yield Archean and Proterozoic ages 

(ranging from 2,681±16 to 981±31 Ma; Dusel-Bacon and 

others, 2004).

Epsilon neodymium isotope values (εNdt

; time-corrected 

to 360 Ma) are relatively elevated for the Mystic Creek 

Member metarhyolites (-1.0, -1.5, -1.6) and Chute Creek 

metabasalts (+1.7 and +5.3), indicating an enriched mantle 

component for both members of the bimodal suite. In contrast, 

metarhyolite from the Wood River assemblage and the Healy 

schist have lower εNdt

 values (-4.5 and -13.5, respectively), 

reflecting a large continental crustal component. Proterozoic 

neodymium model ages of 1,030 to 2,010 Ma for metarhyolites (including samples from the Mystic Creek Member, 

Wood River assemblage, and Healy schist) and 570 to 910 

Ma for Chute Creek Member metabasalt are consistent with a 

continental margin setting.

Trace-element analyses indicate that the metarhyolites of 

the Mystic Creek Member and the metabasalts of the Chute 

Creek, Sheep Creek, and Mystic Creek Members have high 

concentrations of high-field-strength and rare-earth elements, 

and yttrium and gadolinium, relative to average continental 

crust (for the metarhyolites) and primitive mantle (for the 

metabasalts). High-field-strength elements (HFSE) are those 

elements with a high charge to ionic radius ratio and include 

Zr, Hf, Nb, Ta, and Ti; rare-earth elements (REE) include La, 

Ce, Nd, Sm, Eu, Gd, Yb, and Lu. Rare-earth elements, not 

surprisingly, also are anomalously high in surface and water 

samples collected in the vicinity of Red Mountain, which is 

underlain by Mystic Creek metarhyolite (Eppinger and others, 

this volume, chap. I). The Zr/TiO2

–Nb/Y diagram (fig. B4) 

reveals the distinctive, highly alkaline (“peralkaline”) composition of the Mystic Creek metarhyolites, which plot as 

comendites. In contrast, felsic rocks from the California and 

Moose Creek Members of the Totatlanika Schist have lower 

Nb/Y and Zr/TiO2 ratios and plot as rhyodacite and dacite. 

Metabasalt from the Mystic Creek, Sheep Creek, and Chute 

Creek Members of the Totatlanika Schist also have high Nb/Y 

ratios and plot as alkali basalt. Compositions of the Wood 

River assemblage metavolcanic rocks differ from those of 

the Totatlanika Schist in that the former do not have alkaline 

compositions (that is, they do not fall within the alkali basalt, 

trachyandesite, trachyte, or comendite-pantellerite fields), with 

the exception of one sample that plots as a trachyte, and their 

compositions span a broad range that includes intermediatecomposition andesite.

Figure B3. Sampling drill core from the Dry Creek VMS deposit, 

stored at the Ester core facility, Alaska. Geologists from left to 

right: Rainer Newberry (University of Alaska), Curt Freeman 

(Avalon Development Corp.), Cameron Rombach (U.S. Geological 

Survey (USGS)), and Melanie Hopkins (USGS). Photograph by 

Charlie Bacon (USGS).
Tectonic Setting and Metallogenesis of Volcanogenic Massive Sulfide Deposits in the Bonnifield Mining District B5

Information about the tectonic setting in which magmas 

were generated can be attained from discrimination diagrams 

that utilize the immobile trace elements. The tantalumytterbium diagram (fig. B5) shows such information for our 

felsic igneous rocks (SiO2 is 68–86 weight percent). The high 

tantalum and ytterbium contents of Mystic Creek peralkaline 

metarhyolites cause them to plot in the within-plate-granite 

field on the tantalum-ytterbium discrimination diagram 

(fig. B5). Within-plate rhyolites commonly are associated 

with rifting, an example being within-plate rhyolites from 

the Yellowstone Plateau volcanic field. Metarhyolites from 

the other members of the Totatlanika Schist and the Keevy 

Peak Formation plot in the field for volcanic-arc granites; 

however, the fact that their tantalum and ytterbium values are 

similar to the values for average upper continental crust (UCC, 

fig. B5) allows the possibility that the their chemical signatures could reflect involvement of continental crust during 

magma generation and ascent rather than being an indication 

of an arc (as opposed to a within-plate) setting. Wood River 

assemblage metarhyolites form a linear cluster that extends 

from the volcanic arc field into the transitional field between 

within-plate and anomalous ocean-ridge granites, in addition 

to having two samples that plot just inside the within-plate 

granite field.

The hafnium-thorium-tantalum diagram (fig. B6) 

shows the empirically determined magma types applicable 

to Bonnifield metabasalts (SiO2

 is 47–53 weight percent). 

Metabasalts from the Sheep Creek and Chute Creek Members 

of the Totatlanika Schist plot as ocean-island basalt (OIB), a 

magma type that is commonly associated with rifting and also 

is referred to as “within-plate basalt.” Metabasalts from the 

Wood River assemblage plot in the calc-alkalic arc basalt and 

the enriched mid-ocean-ridge fields.

0.01

0.001

0.01

0.1

1

Zr/TiO2

0.1 1 10

Nb/Y

Trachyte

Phonolite

Comendite,

pantellerite

Rhyolite

Rhyodacite, dacite

Subalkaline basalt

Andesite, basalt

Andesite

Alkali basalt

Basanite,

nephelinite

Trachyandesite

Sheep Creek Member

Mystic Creek Member

Chute Creek Member

California Creek Member

Moose Creek Member

Wood River assemblage

Keevy Peak Formation

Healy schist

EXPLANATION

Figure B4. Metaigneous samples from the Wood River area 

plotted on the Zr/ TiO2

 versus Nb/Y discrimination diagram of 

Winchester and Floyd (1977).

Conclusions 

A continental margin setting and original proximity to 

the North American craton for the Late Devonian and Early 

Mississippian VMS host rocks of the Bonnifield district 

is indicated by (1) the quartz-rich compositions of many 

metasedimentary rocks; (2) the presence of Archean and 

Proterozoic inherited zircon cores and detrital zircons; (3) 

radiogenic neodymium isotopic compositions for the Healy 

schist and, to a lesser degree, the Wood River assemblage; 

(4) Proterozoic neodymium model ages for the Totatlanika 

Schist, Healy schist, and Wood River assemblage; and (5) the 

similarity in trace-element ratios between some of the felsic 

metaigneous samples and average upper continental crust.

Evidence for an extensional setting for the submarine 

eruption of the Mystic Creek Member metarhyolite consists 

of (1) its peralkaline composition and inferred within-plate 

tectonic setting; (2) its association with Chute Creek Member 

basalt, which also has alkalic, within-plate trace-element 

characteristics; and (3) elevated εNdt values for Mystic Creek 

metarhyolite and Chute Creek metabasalts that indicate an 

enriched mantle component for both members of the bimodal 

suite. Dusel-Bacon and others (2004) speculated that the 

distinctly peralkaline, within-plate metarhyolites of the Mystic 

Creek Member may have been partial melts of underplated, 

deep crustal alkalic gabbros that also were the source of the 

alkalic, within-plate metabasite of the Chute Creek Member. 

Dark-gray shales interstratified with metarhyolite and massive 

sulfide horizons at WTF and Red Mountain show HFSE and 

light-REE enrichment similar to that in Mystic Creek metarhyolite, suggesting a significant peralkaline rhyolitic tuff 

component in the seafloor sediments that is consistent with 

their deposition in a synvolcanic, extensional basin. Similar 

U-Pb ages and geochemical characteristics for the WTF and 

Red Mountain deposits suggest that they occur in the same 

host-rock stratigraphic interval and support the syncline model 

of Smit (1999).

Mid-Paleozoic bimodal magmatic rocks, including mafic 

rocks that have within-plate geochemical characteristics, occur 

throughout much of the Yukon-Tanana Upland and northern 

Alaska Range. Dusel-Bacon and others (2004, 2006) proposed 

that this magmatism resulted from attenuation of the continen-
B6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

100

ARTS PER MILLION

Within-plate

granite 10

Syn-collisional Within-plate and anomalous

ocean ridge

granite

A LUM, IN P

1

ANT

Ocean ridge T

granite

Volcanic arc

granite

.1

.1 1 10 100

YTTERBIUM, IN PARTS PER MILLION

EXPLANATION

Sheep Creek Member

Mystic Creek Member

California Creek Member

Moose Creek Member

Wood River assemblage

Keevy Peak Formation

Healy schist

Upper continental crust

Figure B5. Felsic metaigneous samples from the Wood 

River area and the composition of average upper continental 

crust (values are those of McLennan, 2001) plotted on the 

tantalum-ytterbium (Ta-Yb) diagram of Pearce and others (1984).

tal margin behind an east-dipping subduction zone. Evidence 

suggesting that the Wood River assemblage originated as an 

arc developed within continental crust above this subduction 

zone includes (1) metaigneous rocks that span a wide range of 

compositions, including andesitic rocks that are characteristic 

of arc magmatism; (2) some basalts that have trace-element 

arc signatures; and (3) an εNdt

 value of -4.5 indicating a 

crustal component in the melt. This interpretation implies that 

the coeval Mystic Creek Member of the Totatlanika Schist 

formed an extensional (back-arc) basin that was associated 

with an outboard volcanic arc that included rocks of the Wood 

River assemblage (Dusel-Bacon and others, 2005).

Peralkaline metarhyolites of the Mystic Creek Member 

of the Totatlanika Schist that exhibit extreme within-plate 

geochemical characteristics host, or are associated with, the 

largest VMS deposits in the Bonnifield mining district. This 

association suggests that the presence of highly elevated 

HFSE and REE trace-element contents in metarhyolites, 

whose major-element compositions may have been altered, is 

an important prospecting tool for VMS deposits that formed in 

an extensional setting. Our trace-element data for Wood River 

assemblage metarhyolites that host the Anderson Mountain 

deposit further indicate that even slightly elevated HFSE and 

REE contents (for example, tantalum and ytterbium; fig. B5) 

can be prospective for VMS deposits formed in an arc setting.

v

v

Th Ta

Hf/3

Primitive arc tholeiites

Calc-alkalic

N-MORB

E-MORB

OIB (Rift)

Arc basalts

Sheep Creek Member

Chute Creek Member

Wood River assemblage

Upper continental crust

EXPLANATION

Figure B6. Mafic metavolcanic samples from the Wood River 

area plotted on the hafnium-thorium-tantalum (Hf-Th-Ta) diagram 

of Wood (1980). Abbreviations are as follows: E-MORB, enriched 

mid-ocean ridge basalt; N-MORB, normal mid-ocean ridge basalt; 

OIB, ocean-island basalt.

Acknowledgments

We are indebted to Tom Bundtzen for introducing the 

senior author to the geology of the Wood River area. We also 

thank Pacific Alaska Resources Company geologists Barry 

Hoffmann, Jo Drechsler, Rob McLeod, Gary Andersen, and 

Ted Erdman; and Grayd Resource Corporation Vice President 

Hans Smit for providing access to drill core and company 

reports for the Bonnifield VMS deposits. Rainer Newberry, 

Sam Dashevsky, and Sean Bemis helped with drill core sampling. Curt Freeman, Cameron Rombach, Melanie Hopkins, 

and Charlie Bacon assisted during fieldwork, as well as drill 

core sampling. We thank Joe Wooden for re-analyzing one of 

the U-Pb zircon samples. This paper benefited from reviews 

by Marti Miller and Dave John.
Tectonic Setting and Metallogenesis of Volcanogenic Massive Sulfide Deposits in the Bonnifield Mining District B7

References Cited

Dusel-Bacon, Cynthia, Hopkins, M.J., Mortensen, J.K., 

Dashevsky, S.S., Bressler, J.R., and Day, W.C., 2006, 

Paleozoic tectonic and metallogenic evolution of the 

pericratonic rocks of east-central Alaska and adjacent 

Yukon, in Colpron, Maurice, and Nelson, J.L., eds., 

Paleozoic evolution and metallogeny of pericratonic 

terranes at the ancient Pacific margin of North America, 

Canadian and Alaskan Cordillera: Geological Association 

of Canada, Special Paper 45, p. 25–74.

Dusel-Bacon, Cynthia, Premo, W.R., and Aleinikoff, J.N., 

2005, Geochemical and Nd isotopic evidence for an 

extending continental-margin arc/back arc setting for 

peralkaline rhyolite-hosted massive sulfide deposits of the 

Bonnifield district, east-central Alaska [abs.]: Geological 

Society of America Abstracts with Programs, v. 37, no. 7, 

p. 97.

Dusel-Bacon, Cynthia, Wooden, J.L., and Hopkins, M.J., 

2004, U-Pb zircon and geochemical evidence for bimodal 

mid-Paleozoic magmatism and syngenetic base-metal 

mineralization in the Yukon-Tanana terrane, Alaska: 

Geological Society of America Bulletin, v. 116, no. 7–8, 

p. 989–1015.

Eppinger, R.G., Briggs, P.H., Dusel-Bacon, Cynthia, Giles, 

S.A., Gough, L.P., Hammarstrom, J.M., and Hubbard, B.E., 

2007, Environmental geochemistry at Red Mountain, an 

unmined volcanogenic massive sulphide deposit in the 

Bonnifield district, Alaska Range, east-central Alaska: 

Geochemistry: Exploration, Environment, Analysis, v. 7, 

no. 3, p. 207–223.

Gilbert, W.G., and Bundtzen, T.K., 1979, Mid-Paleozoic 

tectonics, volcanism, and mineralization in north-central 

Alaska Range, in Sisson, Alexander, ed., The relationship of plate tectonics to Alaskan geology and resources, 

Proceedings, Alaska Geological Society Symposium 6, 

Anchorage, Alaska, April 4–6, 1977: Anchorage, Alaska, 

Alaska Geological Society, p. F1–F22.

McLennan, S.M., 2001, Relationships between the trace 

element composition of sedimentary rocks and upper continental crust: Geochemistry, Geophysics, Geosystems, v. 2, 

no. 4, 24 p., available only online at http://www.agu.org/

journals/gc/gc0104/2000GC000109. (Subscription may be 

required.) (doi: 10.1029/2000GC000109)

Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., 

Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive 

sulfide deposits of Alaska: Economic Geology Monograph 

9, p. 120–150.

Okulitch, A.V., 2002, Geological time chart, 2002: Geological 

Survey of Canada, Open File 3040, 1 sheet.

Pearce, J.A., Harris, N.B.W., and Tindle, A.G., 1984, 

Trace element discrimination diagrams for the tectonic 

interpretation of granitic rocks: Journal of Petrology, v. 25, 

no. 4, p. 956–983.

Smit, H., 1999, The Dry Creek VMS project, Bonnifield 

district, central Alaska, in Pathways ‘99, Extended Abstracts 

Volume: Vancouver, British Columbia, Canada, British 

Columbia and Yukon Chamber of Mines, p. 17–18.

Szumigala, D.J., and Swainbank, R.C., 1998, Alaska’s 

mineral industry 1998: Alaska Division of Geological and 

Geophysical Surveys Special Report 53, 71 p.

Wahrhaftig, Clyde, 1968, Schists of the central Alaska Range: 

U.S. Geological Survey Bulletin 1254–E, p. E1–E22.

Winchester, J.A., and Floyd, P.A., 1977, Geochemical 

discrimination of different magma series and their 

differentiation products using immoble elements: Chemical 

Geology, v. 20, no. 4, p. 325–343.

Wood, D.A., 1980, The application of a Th-Hf-Ta diagram 

to problems of tectonomagmatic classification and to 

establishing the nature of crustal contamination of basaltic 

lavas of the British Tertiary volcanic province: Earth and 

Planetary Science Letters, v. 50, no. 1, p. 11–30.

Matching Magnetic Trends and Patterns 

Across the Tintina Fault, Alaska and 

Canada—Evidence for Offset of About 490 

Kilometers

By Richard W. Saltus

Chapter C of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–C

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract ........................................................................................................................................................C1

Introduction..................................................................................................................................................C1

Methods........................................................................................................................................................C1

Results and Importance .............................................................................................................................C5

Discussion and Conclusions .....................................................................................................................C5

Acknowledgments ......................................................................................................................................C6

References Cited.........................................................................................................................................C6

Figures

 C1. Map showing regional geology with faults and features ...................................................C2

Matching Magnetic Trends and Patterns Across the 

Tintina Fault, Alaska and Canada—Evidence for Offset of 

About 490 Kilometers 

By Richard W. Saltus1

1

U.S. Geological Survey.

Abstract

Magnetic anomaly patterns on opposite sides of the 

mapped Tintina fault in eastern Alaska and western Canada 

show an apparent offset of about 490 kilometers (km), 

probably of Eocene age. This estimate is compared with 

previous geologically based estimates of 400 to 430 km and 

paleomagnetically based estimates of more than 1,100 km. 

The apparent geophysical alignments have geologic implications that deserve further study. 

Introduction

The Tintina fault zone in eastern Alaska and western 

Canada (fig. C1) is a major tectonic boundary between 

cratonic North America and pericratonic rocks of the 

Yukon-Tanana and related terranes (Roddick, 1967; Gabrielse, 

1985; Gabrielse and others, 2006). Numerous estimates have 

been made of the amount and timing of offset on this fault 

system (for example, Dover, 1994; Plafker and Berg, 1994; 

Gabrielse and others, 2006). Several of the latest estimates, 

based on matching of geologic elements across the fault, 

indicate probable offset of at least 400 kilometers (km), 

primarily during the Eocene (Dover, 1994; Gabrielse and 

others, 2006), although published displacement estimates 

based on paleomagnetic data have ranged as high as 1,100 to 

2,400 km (Beck and others, 1981; Irving and others, 1985; 

Umhoefer and others, 1989). 

Regional geophysical data, such as magnetic and gravity 

field maps, display patterns and trends that are representative 

of the composition of the crust (for example, Blakely, 1995). 

The amount of offset on crustal faults can be investigated by 

“cutting and sliding” the geophysical maps to evaluate pattern 

and trend alignment under various slip scenarios. In particular, 

the compiled aeromagnetic data portrayed on the Magnetic 

Anomaly Map of North America (North American Magnetic 

Anomaly Group, 2002) provide an excellent base map for this 

endeavor. 

Regional magnetic anomalies reflect the amount and 

distribution of magnetic minerals, most notably magnetite, in 

regions of the crust and upper mantle at temperatures below 

about 580°C. Magnetic anomaly wavelengths are generally 

related to the depth to magnetic sources and show a geometric 

amplification of shallow-source amplitudes over those of 

deeper sources (Blakely, 1995; Sleep and Fujita, 1997). Thus, 

magnetic anomaly sources can arise from geologic features 

of varying depths within the crust and varying ages. Also, 

the magnetic properties of different sides of the fault may 

be modified by chemical and (or) thermal alteration before, 

during, or after fault slippage. Thus, the matching of magnetic 

anomaly patterns is somewhat subjective but can contribute 

to the larger body of evidence regarding the likely amount of 

displacement across a fault.

Methods

Regional geophysical data, specifically residual maps of 

the Earth’s magnetic field, provide a complex proxy overview 

of crustal composition and structure as reflected in the 

occurrence of magnetic minerals, especially magnetite. Crustal 

magnetic field data are collected primarily from airborne 

platforms, usually by helicopter or fixed-wing aircraft. For the 

purpose of geological interpretation, the measured data are 

adjusted by the removal of a theoretical regional surface, the 

International Geomagnetic Reference Field (IGRF), which 

is created from ground-based observatory and satellite data 

(International Association of Geomagnetism and Aeronomy, 

1992; Blakely, 1995). The IGRF is a model of the deep-seated 

and slowly varying geodynamic sources of the Earth’s overall 

magnetic field. Once the IGRF is removed, residual magnetic field maps (frequently called “total field” maps) reflect 

anomalies (perturbations) in the regional field caused by 

magnetic material within the crust and upper mantle. The 

primary magnetic mineral, magnetite, has a Curie temperature 
C2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, U.S.A., and Yukon, Canada

of about 580°C, so magnetic sources have a thermal limit with 

depth that typically falls somewhere near the crust-mantle 

boundary, which is typically about 35 to 40 km deep. 

The analysis and interpretation of magnetic anomalies 

typically involve some form of inversion to deduce 

the individual magnetic sources from their composite 

representation in the total field. In a strictly mathematical 

sense, this is a non-unique problem, which means that some 

assumptions must be made to constrain the solution. For 

the purpose of fault reconstruction by pattern matching, it 

is not required that the magnetic anomalies be inverted or 

interpreted. However, if the conclusions from geophysical 

pattern matching are to be evaluated geologically, it is 

useful to explore the possible geological associations of the

geophysical features. 

Fairbanks

Eagle

Watson Lake

UNITED STATES

CANADA

Yukon

Alaska

Denali fault

Tintina fault

Kaltag fault

T

RS

BC

WM

A’

A

Big Salmon fault

Macmillan

Pass

Finlayson Lake

Delta

Bonnifield

Kantishna

Hills

Teuchet

Creek

0 50 100 200 300 400 KILOMETERS

Late Cretaceous plutons

Yukon-Tanana terrane

Paleozoic and Late Proterozoic off-shelf sedimentary rocks

Selected geologic lineaments—Strain zones and boundaries between 

groups of plutonic rocks

Major fault

Thrust fault—Sawteeth on upper plate. BC, Brush Creek; RS, Robert 

Service; T, Tombstone; WM, White Mountains

Mining district in Devonian to Mississippian rock

Blueschist or eclogite occurrence

EXPLANATION

144° 140° 136° 132° 128° 124°

64°

66° 66°

62°

60°

148°

Pacific Ocean

Alaska

Yukon

Northwest

Territories

British

Columbia

Location mapCANADA UNITED STATES

Study area

Figure C1. Regional geology with faults and features (adapted from Gabrielse and others (2006) and Dusel-Bacon and others (2006)). 

Markers A and A′ are measurement points for proposed fault restoration.
Matching Magnetic Trends and Patterns Across the Tintina Fault, Alaska and Canada C3

Fairbanks

Eagle

UNITED STATES

CANADA

Yukon

Alaska

Denali fault

Tintina fault

Kaltag fault

T

RS

BC

WM

A’

A

Big Salmon fault

Macmillan

Pass

Finlayson Lake

Delta

Bonnifield Kantishna

Hills

Teuchet

Creek

60°

61°

62°

63°

64°

65°

66°

67°

68°

150° 147° 144° 141° 138° 135° 132° 129° 126°

0 50 100 200 300 400 KILOMETERS

-280 -160 -110 -75 -50 -30 -5 10 25 40 65 95 130 210 415

Magnetic intensity (in nannoteslas)

Selected geologic lineament

Major fault

Thrust fault—Sawteeth on upper plate. BC, Brush 

Creek; RS, Robert Service; T, Tombstone; WM, 

White Mountains

Mining district in Devonian to Mississippian rock

Blueschist or eclogite occurrence

EXPLANATION

Pacific Ocean

Alaska

Yukon

Northwest

Territories

British

Columbia

Location mapCANADA UNITED STATES

Study area

Figure C2. A subset of the Magnetic Anomaly Map of North America (North American Magnetic Anomaly Group, 2002) with selected 

geology elements (see fig. C1). Markers A and A′ are reference points for proposed fault restoration.
C4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, U.S.A., and Yukon, Canada

Fairbanks

Eagle

UNITED STATES

CANADA

Yukon

Alaska

Denali fault

Tintina fault

Kaltag fault

T

RS

BC

WM

A’

A

Macmillan

Pass

Finlayson Lake

Delta

Bonnifield Kantishna

Hills

Teuchet

Creek

60°

61°

62°

63°

64°

65°

66°

67°

68°

150° 147° 144° 141° 138° 135° 132° 129° 126°

0 50 100 200 300 400 KILOMETERS

-280 -160 -110 -75 -50 -30 -5 10 25 40 65 95 130 210 415

Magnetic intensity (in nannoteslas)

Selected geologic lineament

Major fault

Thrust fault—Sawteeth on upper plate. BC, Brush Creek; RS, 

Robert Service; T, Tombstone; WM, White Mountains

Mining district in Devonian to Mississippian rock

Blueschist or eclogite occurrence

EXPLANATION

Pacific Ocean

Alaska

Yukon

Northwest

Territories

British

Columbia

Location mapCANADA UNITED STATES

Study area

Figure C3. Proposed palinspastic restoration based on matching of magnetic anomalies across the Tintina fault. This figure is made by 

cutting and shifting figure C2. A shift of about 490 km from west to east aligns markers A and A′ as shown.
Matching Magnetic Trends and Patterns Across the Tintina Fault, Alaska and Canada C5

This study involves a very simple visual approach to 

magnetic anomaly interpretation for this study. I selected a 

subset of the recently compiled Magnetic Anomaly Map of 

North America (North American Magnetic Anomaly Group, 

2002). The Magnetic Anomaly Map of North America 

was created by carefully merging hundreds of individual 

aeromagnetic surveys into a single grid with uniform effective 

survey height. This compilation minimizes any artifacts 

related to individual magnetic survey boundaries and allows 

one to concentrate on geologically significant anomalies and 

patterns. 

A visual image (fig. C2) of the selected grid subset was 

created using a histogram-stretched color scale adapted to 

the data ranges and statistics for the region. This coloring 

enhances subtle magnetic anomaly amplitude variations in 

the central part of the anomaly range. This is appropriate 

for identifying geologically significant variations that 

would otherwise be difficult to see if a linear color scale were 

used. 

The colored magnetic anomaly image was then cut along 

the regionally mapped trace of the Tintina fault (Gabrielse 

and others, 2006) and slid by variable amounts along the fault 

trace to examine pattern and trend correlations for different 

slip scenarios. This pattern matching was based only on the 

magnetic anomalies and was done independent of geology. 

Our preferred matching of magnetic anomalies across the fault 

(fig. C2) requires about 490 km of total shift along the Tintina 

fault. 

Results and Importance

What are the geologic implications of this hypothetical 

fault slip restoration on the Tintina fault system? Figure C3 

shows the geologic base map from figure C1 cut along the 

Tintina fault and subjected to a 490-km shift. This shift 

produces a number of interesting geological alignments. Here 

we point out several implications of the proposed reconstruction, from southeast to northwest. For the purpose of 

discussion, the restored alignment points A and A′, located 

about 50 km northwest of the restored position of the town 

of Eagle, are used as the zero position for specifying features 

along the restored Tintina fault. 

Perhaps the broadest scale geologic alignment is the 

matching of the separate strands of the Inconnu thrust fault 

(IT as shown by Gabrielse and others, 2006) at both ends 

of the orphaned Yukon-Tanana block that lies northeast of 

the Tintina fault. The southeastern edge of this block, near 

Watson Lake (about 400 km southeast of A-A′), ends up 

near the three-way intersection of the Inconnu fault, the Big 

Salmon fault, and the Tintina fault. The northwestern edge 

of the orphan Yukon-Tanana block connects at position A-A′ 

with the thrust fault (thought to represent a continuation of the 

Inconnu thrust fault; Gabrielse and others, 2006) that separates 

the Yukon-Tanana terrane from off-shelf Late Proterozoic and 

Paleozoic sedimentary rocks to the northwest. 

Another interesting alignment produced by this proposed 

restoration is the coincidence of eclogite and blueschist 

occurrences (as shown by Dusel-Bacon and others, 2006) 

near the restored position of the town of Eagle with those 

across the Tintina fault in the northwestern edge of the 

orphan Yukon-Tanana block. The restoration then puts these 

occurrences along the trend with two occurrences to the west 

near Fairbanks. 

Several major Devonian to Mississippian mineral 

districts fall within the study area (fig. C1; Dusel-Bacon and 

others, 2006) and their relative locations are affected by the 

proposed restoration. The Kantishna Hills, Bonnifield, and 

Delta districts contain syngenetic volcanogenic massive 

sulfide deposits (see chapters B, E, I, and J in this volume). 

The proposed restoration brings these districts closer to the 

Finlayson Lake massive sulfide district in southeastern Yukon 

(fig. C3). The Teuchet Creek stratiform sedimentary exhalative 

(SEDEX) mineral district aligns along the geologic trend with 

the Macmillan Pass SEDEX district after restoration (fig. C3). 

To the northwest of A-A′, several geologic trends are 

mapped on opposite sides of the Tintina fault. These include 

faults, strain zones, and Cretaceous plutonic belts (shown as 

dashed lines on figs. C1 and C3). The first set of matching 

features, as mentioned above, is the opposite strands of the 

Inconnu thrust fault that join up at A-A′. Proceeding to the 

northwest, two plutonic suite boundaries line up on opposite 

sides of the fault. Farther to the northwest, two strands of the 

strain zones line up approximately on opposite sides of the 

restored fault. Continuing northwest, the trends and zones on 

the Alaskan side appear to be increasingly compressed relative 

to the trends on the Canadian side. This is presumably the 

result of overall compression on the Alaskan side approaching the Kaltag fault and possibly of extension on the Canadian 

side. Up to 250 km of variation in relative offset due to 

compression and extension is suggested by the differential 

positions of the trends in the off-shelf sequence on opposite 

sides of the fault in this zone. 

Discussion and Conclusions

The preliminary observations in this short paper are 

intended to stimulate continued comparative geologic study 

across the Tintina fault in Alaska and adjacent Canada. 

Correlations between magnetic anomalies and patterns can 

provide useful hypotheses about apparent fault slip but do 

not indicate timing of slip unless the individual anomalies 

and patterns are interpreted to associate them with geologic 

features with known ages. The significance of the geophysical 

alignments needs to be tested through geologic studies. 

The most detailed analysis of the Eocene slip history of 

the Tintina fault to date is by Gabrielse and others (2006). 

They conclude that geologic evidence supports slip estimates 
C6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, U.S.A., and Yukon, Canada

between 400 and 430 km. This amount of slip lines up the 

Beaver Creek-White Mountains thrust system on the Alaskan 

side with the Tombstone-Robert Service thrust system on 

the Canadian side of the Tintina fault. Their conclusions also 

depend on alignment of the Tombstone and McQuestern 

plutons across the fault. 

The preferred restoration of between 400 and 430 km 

of fault slip (Gabrielse and others, 2006) results in a 60+ km 

mismatch of the two crossings of the Inconnu thrust fault from 

the Alaskan side to the Canadian side of the fault. Gabrielse 

and others (2006) interpret this as indication of extension 

on the Canadian side, presumably related to extensive Late 

Cretaceous magmatism in the region. This extension would 

have preceded the later Eocene movement of the Tintina fault 

yet used the trace of the Tintina as a bounding “transform” 

between zones of differential extension. 

An alternate hypothesis to explain the difference in spacing of geologic features across this portion of the fault is that 

compressional deformation took place on the Alaskan side 

relative to the Canadian side. The amount of shortening might 

logically be expected to increase to the northwest toward the 

bend in the Tintina fault near its intersection with the Kaltag 

fault. This interpretation seems consistent with the character of 

magnetic anomalies along this part of the fault, although that 

conclusion is somewhat subjective. 

The apparent slip estimates based on alignment of 

magnetic anomalies fall far short of published displacement 

estimates from paleomagnetic studies (for example, 1,900±700 

km by Marquis and Globerman, 1988; Johnston and others, 

1996; Wynne and others, 1998). I agree with Gabrielse and 

others (2006) that the burden for resolving this discrepancy 

appears to fall on the side of the paleomagnetic studies. 

In conclusion, comparison matching of magnetic features 

on both sides of the Tintina fault in east-central Alaska and 

northwestern Canada indicates a good match of several key 

anomalies and magnetic patterns if slip of about 490 km is 

restored on the fault. This hypothetical fault slip restoration makes pre-slip predictions of the relation of geologic 

elements on opposite sides of the fault. The apparent relative compression of various thrust belts on the Alaskan side 

relative to the Canadian side may be due to tectonic compression or lateral ramps on the Alaskan side, possibly related to 

the geometry of the southwest bend of the Tintina fault near its 

intersection with the Kaltag fault.

Acknowledgments

The author is grateful for excellent and constructive 

reviews by Sue Karl and Dwight Bradley of the 

U.S. Geological Survey. 

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The Black Mountain Tectonic Zone—A 

Reactivated Northeast-Trending Crustal 

Shear Zone in the Yukon-Tanana Upland of 

East-Central Alaska

By J. Michael O’Neill, Warren C. Day, John N. Aleinikoff, and Richard W. Saltus

Chapter D of 

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–D

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract........................................................................................................................................................D1

Introduction..................................................................................................................................................D1

Black Mountain Tectonic Zone.................................................................................................................D5

Last Chance-Goodpaster Fault System..........................................................................................D5

Tibbs Fault ...........................................................................................................................................D5

Brink Fault ...........................................................................................................................................D6

Serpentine Fault.................................................................................................................................D7

Porphyry Fault Zone...........................................................................................................................D7

Lineaments..........................................................................................................................................D7

Summary.......................................................................................................................................................D8

References Cited.........................................................................................................................................D8

Figures

D1. Simplified geologic map showing tectonic assemblage of the Yukon-Tanana 

tectonostratigraphic terrane of east-central Alaska...........................................................D2

D2. Simplified geologic map of the Big Delta B–1 and B–2 quadrangles, east-central 

Alaska, showing location of gold mines and prospects and the surficial 

expression of the Black Mountain tectonic zone.................................................................D3

D3. Regional aeromagnetic map of the Yukon-Tanana Upland of east-central Alaska 

showing location of the Black Mountain tectonic zone......................................................D4

D4. Structural geologic map of the Big Delta B–1 quadrangle showing major 

high-angle strike-slip and normal faults, thrust faults, and lineaments in the 

Black Mountain tectonic zone.................................................................................................D6

The Black Mountain Tectonic Zone—A Reactivated 

Northeast-Trending Crustal Shear Zone in the YukonTanana Upland of East-Central Alaska

By J. Michael O’Neill,1 Warren C. Day,1 John N. Aleinikoff,1 and Richard W. Saltus1

1

U.S. Geological Survey.

Abstract

The Black Mountain tectonic zone in the YukonTanana terrane of east-central Alaska is a belt of diverse 

northeast-trending geologic features that can been traced 

across Black Mountain in the southeast corner of the Big Delta 

1°×3° degree quadrangle. Geologic mapping in the larger 

scale B1 quadrangle of the Big Delta quadrangle, in which 

Black Mountain is the principal physiographic feature, has 

revealed a continuous zone of normal and left-lateral strikeslip high-angle faults and shear zones, some of which have 

late Tertiary to Quaternary displacement histories. The tectonic 

zone includes complexly intruded wall rocks and intermingled 

apophyses of the contiguous mid-Cretaceous Goodpaster and 

Mount Harper granodioritic plutons, mafic to intermediate 

composite dike swarms, precious metal mineralization, early 

Tertiary volcanic activity and Quaternary fault scarps. These 

structures define a zone as much as 6 to 13 kilometers (km) 

wide and more than 40 km long that can be traced diagonally across the B1 quadrangle into the adjacent Eagle 1°×3° 

quadrangle to the east. Recurrent activity along the tectonic 

zone, from at least mid-Cretaceous to Quaternary, suggests 

the presence of a buried, fundamental tectonic feature beneath 

the zone that has influenced the tectonic development of 

this part of the Yukon-Tanana terrane. The tectonic zone, 

centered on Black Mountain, lies directly above a profound 

northeast-trending aeromagnetic anomaly between the Denali 

and Tintina fault systems. The anomaly separates moderate 

to strongly magnetic terrane on the northwest from a huge, 

weakly magnetic terrane on the southeast. The tectonic zone is 

parallel to the similarly oriented left-lateral, strike-slip Shaw 

Creek fault zone 85 km to the west.

Introduction

The Black Mountain tectonic zone, recently recognized 

and mapped in the Big Delta B–1 quadrangle, east-central 

Alaska, lies within the Yukon-Tanana Upland (YTU) (fig. D1; 

see also fig. 1 of the Editors’ Preface and Overview). The YTU 

is restricted to the terrane between the Tintina and Denali 

dextral-slip fault zones and extends from central Alaska 

eastward into Yukon, Canada. The YTU is underlain mainly 

by complexly deformed greenschist to amphibolite-grade 

metamorphic rocks at least as old as Middle Devonian. The 

supracrustal metasedimentary and metavolcanic Paleozoic 

units were intruded during the Devonian by plutonic rocks 

of intermediate composition, which are now preserved as 

augen and biotite orthogneiss. After the tectonic assembly 

of the Paleozoic units during the regional early Mesozoic 

deformation, Jurassic, Cretaceous, and Tertiary plutonism 

flooded the area with mainly granodioritic batholiths 

(Dusel-Bacon and others, 2002).

 The YTU between Fairbanks and Tok is cut by four 

prominent northeast-trending lineaments (Wilson and others, 

1985). One such lineament is the Shaw Creek fault (fig. D1), 

a major left-lateral strike-slip fault that cuts across the Salcha 

River gneiss dome (Foster and others, 1979; Werdon and 

others, 2004). Two other lineaments to the east, the Sixtymile 

and Tok, are recognized by the alignment of physiographic 

features, mainly stream drainages and topographic highlands. 

The Mount Harper lineament, about 100 kilometers (km) east 

of the Shaw Creek fault and confined mainly to the Eagle 

1°×3° quadrangle, directly east of the map area (see fig. D2), 

consists of mapped segments of faults, stratigraphic breaks, 

and physiographic alignments (Foster, 1976). The Mount 

Harper lineament appears to separate domains that have 

characteristic geochronologic signatures; Jurassic plutons do 

not occur west of this lineament (Foster, 1976). 

The YTU between Fairbanks and Tok also is bisected by 

a major linear magnetic anomaly located between the Shaw 

Creek and Mount Harper lineaments (Saltus and Day, 2006). 

A steep, pronounced, northeast-trending magnetic gradient, 
D2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

|w

|w

|cf

|cf

|cf

|cf |cf

|cf

|o

|o

|o

|o |o

|o

|n

|n

|sc

|ss

|ss

|ss

|n

|n

|n

|n

|f

|f

|gf

M|s

M|s

J^g

J^g

J^g

Kg

Kg

Kg

Kg

Kg

Kg

Kg

Kg

TKis

TKis

TKis

TKis

TKis

Qs

Qs Qs

Qs

Qs

Qs

|ss

|ss

|sc

Tintina fault

Salcha River

Dome Black Mountain tectonic zone

Mount Harper lineament

Shaw Creek fault

Tok lineament

Sixtymile lineament

Area of

figure 2

0 50 KILOMETERS

Eagle

Fairbanks

Delta

Junction

Big Delta

Chicken

Tok

EXPLANATION

Surficial deposit (Quaternary)

Igneous and sedimentary rocks, undifferentiated (Tertiary to Cretaceous)

Parautochthonous sedimentary rocks (pre-Tertiary)

Granitoid (Cretaceous)

Granitoid (Early Jurassic to Late Triassic)

Oceanic and associated sedimentary rocks (Paleozoic)—|ss, Seventymile 

assemblage; |sc, Chatanika assemblage

Tectonites of the Yukon-Tanana Upland (Paleozoic)

Fortymile River assemblage—Oceanic, arc, and marginal-basin 

tectonites

Nisutlin assemblage—Marginal-basin strata

Orthogneiss assemblage—Continental-affinity paragneiss and 

peraluminous augen 340-Ma orthogneiss

Rocks of the Chena River and Fairbanks 

“subterranes”—Parautochthonous continental strata

Parautochthonous Wickersham assemblage (Paleozoic)

Highest

Lowest Structural level

Contact

Fault

Thrust fault—Sawteeth on upper plate

Trend of tectonic feature—Lineament or 

tectonic zone

Major road

143°

65°

64°

63°

147°

146°

145°

144°

142°

Area of figure

Pacific Ocean

Alaska

Yukon

Northwest

CANADA

Territories

UNITED STATES

British

Columbia

Location map

Figure D1. Simplified geologic map showing tectonic assemblage of the Yukon-Tanana tectonostratigraphic terrane of east-central 

Alaska. Shows approximate outline of map area (fig. D2), and location of major northeast-trending lineaments of Wilson and others 

(1985). Modified from Hansen and Dusel-Bacon (1998).
The Black Mountain Tectonic Zone—A Shear Zone in the Yukon-Tanana Upland of East-Central Alaska D3

Goodpaster

River

Central

Creek

Tibbs

Creek

Goodpaster

River

Boulder

Creek

Qa

Qc

Tr

Tg

Kg

Kg

Kg

Kg

Kg

Kg

Kg

Km

Km

Qc

Qc

Qa

Qc

Km

Km

Km

Kbm

Kbm

Kbm

Kb

Kb

Kdt

Kdt

Kdt

Ka

Ka

Ka

Ka

Ka

Ka

Kd

Kd

Kd

Kmg

Kmg Kmg

|o

|o

|o

|o

|o

|m

|m

|m

|m

|m |m

80

64

55 38

32

65

32

15

32

36

22

55

34

10

10 36

25

20

34

22

52

45

70

32

45 43

40

45

26

22

48

60

40

47

Pogo

Shawnee

Peak

Grizzly Bear

Gray Lead

Blue Lead

Brink

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Map location

0 5 10 15 KILOMETERS

20

22

55

EXPLANATION

Alluvium (Quaternary)

Colluvium (Quaternary)

Rhyolite (Paleocene)

Gravel (Paleocene)

Granite, undifferentiated (Late Cretaceous)

Rocks of the Mount Harper batholith (Late Cretaceous)

Rocks of the Black Mountain intrusion (Late Cretaceous)

Rocks of the Brink intrusion (Late Cretaceous)

Diorite and tonalite (Late Cretaceous)

Augen gneiss (Devonian)

Diorite gneiss (Paleozoic)

Mafic and ultramafic gneiss (Paleozoic)

Orthogneiss (Paleozoic)

Metasedimentary rock, undivided (Paleozoic)

Black Mountain tectonic zone—Shown by gray tint

Fault—Dashed where approximatly located, dotted 

where inferred. Arrows show sense of relative 

horizontal movment, where known

Thrust fault—Teeth on upper plate. Dashed where 

approximately located, dotted where inferred

Strike and dip of foliation

Trend and plunge of mineral lineation

Trend and plunge of minor fold

Gold deposit or occurence

145°00’ 144°30’

64°30’

64°15’

144°00’

Figure D2. Simplified geologic map of the Big Delta B–1 and B–2 quadrangles, east-central Alaska, showing location of gold mines and 

prospects and the surficial expression of the Black Mountain tectonic zone (shaded area).
D4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

370

240

175

135

105

85

70

60

50

45

40

30

20

20

15

10

5

0

-5

0

-15

-20

-30

-35

-40

-50

-60

-70

-80

-90

- 100

- 110

- 120

- 140

- 180

- 245 oteslas)nnan( Total field magnetic intensity 

Fairbanks

Eagle

Big Delta

Chicken Delta

Junction

Tok

Area of

figure 2

t

Tintina fault

ul

k fa

e

w Cre

ahS

Black Mountain tectonic zone

Mount Harper lineament

Sixtymile lineament

Tok lineament

146°

145°

147°

144°

143°

142°

65°

141°

64°

63°

EXPLANATION

Fault

Trend of tectonic feature—Lineament 

or tectonic zone

Major road

0 50 KILOMETERS Pacific Ocean

Area of figure

Location map

Northwest

Alaska Territories

Yukon

British

Columbia

UNITED STA

CANADA

TES

Figure D3. Regional aeromagnetic map of the Yukon-Tanana Upland of east-central Alaska showing location of the Black Mountain 

tectonic zone.

representing a 20-nanotesla (nT) step in mean magnetic anomaly values (as measured at a flight height of 300 meters, m) 

with higher values to the northwest, extends from the Denali 

fault to the Tintina fault and bisects the YTU (Saltus and Day, 

2006) (fig. D3). In addition to the difference in mean values, 

there are distinct differences in the statistical character of the 

magnetic field on each side of the gradient, indicating that it 

is a fundamental boundary between magnetic source domains. 

Preliminary modeling of the magnetic boundary suggests that 

it represents a steeply east-dipping zone between contrasting 

crustal blocks that extend throughout the middle and lower 

crust (Saltus and Day, 2006). A gravity gradient coincides 

with a portion of the magnetic gradient in the Big Delta 

B–1 quadrangle (Saltus and Day, 2006; fig. D3). This gravity gradient is the eastern boundary of a 30-milligal (mGal) 

residual gravity high that occupies much of the western and 
The Black Mountain Tectonic Zone—A Shear Zone in the Yukon-Tanana Upland of East-Central Alaska D5

central portions of the Big Delta B–1 quadrangle. The adjacent 

lower gravity values to the east correlate, at least in part, 

with mapped postmetamorphic granitic rocks. Preliminary 

modeling of the gravity boundary suggests it also dips to the 

east as inferred for the magnetic feature (Saltus and Day, 

2006). If a density contrast of 200 kilograms per cubic meter 

(kg/m3) is assumed between the granitic intrusion (lower 

density) and the adjacent metamorphic rocks, the preliminary 

models suggest that the density contrast persists to depths of at 

least 8 km. 

Geologic investigations in the Black Mountain area 

reveal a northeast-trending structural corridor, recognized 

as the Black Mountain tectonic zone by O’Neill and others 

(2005) (figs. D2 and D3), that coincides with the prominent 

magnetic and gravity anomalies described by Saltus and Day 

(2006). The tectonic zone and its associated faults and shear 

zones controlled the emplacement of Cretaceous (113–110 

million years before present, Ma) granitoids and related felsic 

dikes, sills, elongate plugs, and quartz vein systems that 

carry gold deposits and occurrences. This high-angle tectonic 

zone formed a conduit along which subsequent basaltic to 

dioritic (109 Ma) dikes and dike swarms were emplaced and 

controlled the location and emplacement of a sulfide-bearing 

subvolcanic quartz-feldspar porphyry stock (99–95 Ma), and 

controlled the development of a Paleocene (57 Ma) rhyolite 

flow-dome complex. Reactivation and deformation along the 

Black Mountain tectonic zone has offset perched Tertiary 

erosion surfaces, and most recently, cut Quaternary alluvial 

deposits, indicating that tectonic activity along the zone is 

long-lived, complex, and ongoing (Day and others, 2007). 

Black Mountain Tectonic Zone

Four distinct tectonic events are recorded in the bedrock of the Big Delta B–1 quadrangle that can be correlated 

to major regional magmatic-tectonic events that affected the 

YTU—Devonian (D1) arc-related plutonism, Jurassic to Early 

Cretaceous (D2) dynamothermal convergent tectonism, Early 

Cretaceous (D3) ductile-brittle deformation and plutonism, and 

Paleocene to present (D4) uplift and high-angle, northeast- and 

northwest-striking faulting related to strike-slip displacement 

on the Tintina-Denali fault systems. The third and fourth major 

tectonic events (D3 and D4) were concurrent with deformation 

observed in the 6.5- to 13-km-wide, northeast-trending Black 

Mountain tectonic zone. 

The tectonic zone in the Big Delta B–1 quadrangle 

consists of five major left-lateral strike-slip faults spaced 

1.6 to 4.8 km apart; they are, from west to east: the 

Last Chance-Goodpaster, Tibbs, Brink, and Serpentine faults, 

and the east-northeast-striking Porphyry fault zone (fig. D4). 

All faults strike northeast and have conspicuous left-stepping 

fault segments that accommodated extension along their 

traces. 

Last Chance-Goodpaster Fault System

The Last Chance fault system marks the western 

boundary of the tectonic zone (fig. D2). The fault follows the 

northeast-trending Last Chance Creek on the southwest to 

Tibbs Creek, where a splay of the fault, the Goodpaster fault 

segment, steps left and trends north, following the creek to 

its intersection with the Goodpaster River. The eastern extent 

of the Last Chance fault system trends northeast to the map 

boundary, whereas the main strand of the fault trends north 

from Tibbs Creek to the northeastern corner of the map area. 

The Last Chance fault is a strike-slip structure and shows 

more than 4.8 km of sinistral displacement. On the northeast, 

the fault is marked by wide zones of shearing, by thin vertical 

screens of strongly deformed Paleozoic strata, and by dioritic 

to felsic dikes and dike swarms emplaced about 108 Ma. The 

area between the Goodpaster segment of the fault and the Last 

Chance fault on the north is unique; it is a graben underlain 

mainly by a Paleocene rhyolite flow-dome complex and is 

restricted to this part of the map area. The rhyolitic rocks 

were later partly covered and concealed by locally derived 

boulder gravel deposits of mid-Tertiary age. The Last Chance 

fault bounds the main body of the Black Mountain intrusive 

complex, a mixed granitic to granodioritic plutonic system, 

109 to 107 Ma, confined to the core of the tectonic zone. No 

rocks related to the Black Mountain intrusive complex and no 

northeast-trending faults of significant size and magnitude are 

present northwest of this fault system (Day and others, 2003, 

2007). The Last Chance fault separates markedly different 

rock types in the north part of the map area where Tertiary 

volcanic rocks and their extrusive centers on the east are 

juxtaposed against the Cretaceous Goodpaster batholith. 

Tibbs Fault

The Tibbs fault is a complex structure within the tectonic 

zone. The Tibbs fault includes several interconnected splays 

along its central part characterized by a 1.6-km-wide zone 

of oblique-slip faulting and shearing. The Tibbs fault is 

subparallel to the Last Chance fault and, like the Last Chance 

fault, is a strike-slip structure; however, the Tibbs fault shows 

only about 1 km of left-lateral displacement. The Tibbs 

fault also includes left-stepping segments along its trace, 

the most profound and tectonically significant of which is 

in the south part of map area. Here the Tibbs fault is north 

trending and bounds the east margin of the Brink intrusion; 

this left-stepping segment of the fault accommodated a zone 

of extension during deformation and is interpreted to have 

provided a tectonic opening that influenced the localization 

and emplacement of the 113-Ma Brink granodiorite and its 

associated base- and precious-metal mineralization. On the 

northeast, the Tibbs and Last Chance faults are only about 

1 km apart and may converge northeast of the map area where 

coalescing shear zones, dioritic dike swarms, and tectonic 

screens of strongly deformed Paleozoic strata are abundant.
D6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

TIBBS

TIBBS

TIBBS

FAULT

FAULT

FAULT

FAULT

FAULT

FAULT

SERPENTINE FAULT

SERPENTINE

BRINK

PORPHYRY FAULT ZONE

GOODPASTER

LAST

CHANCE

FAULT

0 1 2 3 4 5 KILOMETERS

144°30' 144°20' 144°10' 144°00'

64°30'

64°20'

64°25'

64°15'

Black Mountain tectonic zone

High-angle strike-slip fault or normal 

fault—For strike-slip faults, arrows show 

sense of relative horizontal movement

Thrust fault—Sawteeth on upper plate

Lineament—Interpreted from aerial 

photographs

EXPLANATION

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Map location

Figure D4. Structural 

geologic map of the Big Delta 

B–1 quadrangle showing major 

high-angle strike-slip and 

normal faults, thrust faults, 

and lineaments in the Black 

Mountain tectonic zone.

Brink Fault

The Brink fault is subparallel to the Tibbs fault and 

also has a major left-stepping segment along its trace in the 

southern part of the map area. The fault is clearly a strike-slip 

structure where a 50-m-wide gouge zone crosses the central 

part of Black Mountain, and it marks the southeast boundary of the Black Mountain intrusive complex. On the west 

side of Black Mountain, the fault turns abruptly south into 

the valley of the headwaters of the South Fork of Goodpaster 

River; there the fault is a profound down-to-the-west normal 

fault that is parallel to the left-stepping segment of the Brink 

fault on the west. In the area between the north-trending 

Brink and Tibbs fault segments is a leucocratic phase of the 
The Black Mountain Tectonic Zone—A Shear Zone in the Yukon-Tanana Upland of East-Central Alaska D7

Mount Harper batholith whose intrusion appears to have been 

accommodated along a pull-apart extensional zone created 

between these two faults (figs. D2 and D4). In this area only, 

the about 111 Ma Mount Harper pluton is sill-like, overlain 

by a metamorphosed, flat-lying carapace of augen gneiss; 

the pluton and the overlying gneissic rocks are also cut by a 

young, northeast-trending swarm of predominantly down-tothe-west normal faults that includes numerous small pull-apart 

grabens. These extensional faults and their scarps indicate 

ongoing left-lateral displacement and concomitant extension 

along and between the Tibbs and Brink fault systems (fig. D2). 

On the north, the Brink fault merges with the Serpentine fault 

directly south of the Eisenmenger Fork.

Serpentine Fault

The Serpentine fault in the southern part of the map area 

is marked by the juxtaposition of Paleozoic metasedimentary rocks against Devonian augen gneiss and underlying 

Devonian orthogneiss along a wide zone of strongly sheared 

rocks. The fault projects into the broad valley of Boulder 

Creek, where it is covered by widespread accumulations of 

Quaternary deposits. It follows Boulder Creek northward to 

its confluence with the Eisenmenger Fork, where it branches: 

the main segment continues northeastward across sheared, 

altered, and displaced metasedimentary and igneous rocks in 

the northeastern corner of the map; the northwest-trending 

segment of the fault, marked by normal faults that offset 

Quaternary deposits, appears to be a left-stepping tectonic 

link between the Serpentine fault and the converging Tibbs 

and Last Chance faults. This left-stepping link and the normal 

faults that define it outline a down-dropped zone of extension that has resulted in a northwest-trending graben that 

controls the course of the Eisenmenger Fork. Normal faults 

along the south side of this graben displace both older and 

younger Quaternary alluvial fan deposits, indicating that 

deformation along this graben has occurred in the recent 

past. Young fault displacements farther northwest along 

the Fork suggest that the tectonic linkage of the Serpentine 

fault with the Last Chance fault may actually extend farther 

northwest and connect with the Goodpaster segment of the 

Last Chance fault. The tectonic linkage of the Serpentine fault 

with the three strike-slip faults to the northwest, all within the 

Black Mountain tectonic zone and all accommodated along 

left-stepping normal fault segments, implies that the faults are 

coeval, are a part of the same kinematic movement picture, 

and have been recurrently active since the mid-Cretaceous. 

The northernmost segment of the Serpentine fault has a 

more northerly trend and, like the Tibbs fault, may merge with 

the Last Chance and Tibbs faults northeast of the map area; 

the area is unique in that it is the most strongly sheared part of 

the Black Mountain tectonic zone and is characterized by thin, 

closely spaced vertical screens of metamorphic tectonites and 

sheared granodioritic plutonic rocks, all intruded by swarms of 

vertical dikes of all compositions.

Porphyry Fault Zone

The Porphyry fault zone is marked by a 1-km-wide zone 

of intense shearing, folding, and faulting, and associated dike 

swarms. The Porphyry fault zone is confined to rocks of the 

Mount Harper batholith; although there are no piercing points 

along the trace of the fault to indicate the magnitude of fault 

displacements, S-C mylonitic fabric (Lister and Snoke, 1984), 

and small-scale folds within the fault zone. These mesoscopic 

features are all consistent with dextral offset. The zone appears 

to have controlled the intrusion of a subvolcanic 99- to 95-Ma 

quartz-feldspar porphyry stock where it intersects and merges 

with the Serpentine fault at an acute angle along the south 

margin of the map area (fig. D3). This fault zone is marked by 

abundant normal faults and by swarms of subparallel granitic, 

aplitic, and pegmatitic dikes. This fault zone is also the locus 

of many sulfide-bearing dikes of quartz-feldspar porphyry and 

basaltic composition. 

Lineaments

Linear features of various origins, mostly fractures and 

faults and less commonly dike swarms and geologic contacts, 

were mapped from aerial photographs of the Big Delta B–1 

quadrangle. The major faults of the Black Mountain tectonic zone are visible on aerial photographs as are many 

of the mapped dike swarms; however, the vast majority of 

lineaments mapped from aerial photographs are fractures with 

no obvious offset. These fracture sets and other lineaments are 

ubiquitous and abundant across the quadrangle (fig. D4) (Day 

and others, 2007).

The northwest corner of the Big Delta B–1 quadrangle shows lineaments with a somewhat random pattern 

to preferred northwest-trending orientation. The fracture 

orientations appear to reflect the northwest-trending tectonic 

grain of small faults and dikes mapped in the adjacent Big 

Delta B–2 quadrangle (figs. D3 and D4) (Day and others, 

2003).

The Last Chance strike-slip fault and associated 

Goodpaster fault segment separate the fracture pattern 

in the northwest corner of the quadrangle from a zone of 

consistently northeast-oriented fractures and recognizable 

faults east of the fault. The abrupt change in fracture patterns 

from random to dominantly northeast-striking across the 

Last Chance-Goodpaster faults coincides with the northwest 

boundary of the Black Mountain tectonic zone.

Southeast of the Last Chance fault, the predominant 

fracture orientation is northeast and continues uninterrupted 

to the southeast to the Serpentine fault. The width of this zone 

of consistently oriented fracturing, as much as 13 km wide, is 

inferred to define the scale, breadth, and tectonic continuity 

of the Black Mountain tectonic zone. The fracture pattern 

cuts rocks of the Mount Harper batholith southeast of the 

Serpentine fault; however, east of this fault, especially east of 

the Boulder Creek in the east-central part of the quadrangle, 
D8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

the fracture patterns define intermixed, contiguous blocks 

or domains of randomly oriented fractures separated by 

northeast-trending zones of mixed fractures and faults. 

Summary

Geologic investigations in the Black Mountain area 

reveal a northeast-trending structural corridor, described 

herein as the Black Mountain tectonic zone, that consists 

of five major strike-slip faults, spaced 1.6 to 4.8 km apart 

(fig. D2). The tectonic zone and its associated faults, fractures, 

and shear zones controlled the emplacement of 110- to 95-Ma 

Cretaceous granitoids and related felsic dikes, plugs, and 

quartz vein systems; formed a conduit along which subsequent 

basaltic to dioritic dikes and dike swarms were emplaced; 

and controlled the location and emplacement of a 57-Ma 

Paleocene rhyolite flow-dome complex erupted during the 

Paleocene. Reactivation and deformation along the Black 

Mountain tectonic zone have offset perched Tertiary erosion 

surfaces, and most recently, cut Quaternary alluvial deposits, 

indicating that tectonic reactivation of the zone is long-lived, 

complex, and ongoing. The tectonic zone coincides with 

fundamental geophysical crustal anomalies, suggesting that it 

is related to deep-seated crustal discontinuities; the tectonic 

zone is also a magmatic conduit that has a long-lived intrusive 

history and has localized gold deposits associated with 

igneous activity.

References Cited

Day, W.C., Aleinikoff, J.N., Roberts, Paul, Smith, Moira, 

Gamble, B.M., Henning, M.W., Gough, L.P., and Morath, 

L.C., 2003, Geologic map of the Big Delta B–2 quadrangle, 

east-central Alaska: U.S. Geological Survey Geologic 

Investigations Series I–2788, 12 p., 1 sheet, scale 1:63,360. 

(Also available online at http://pubs.usgs.gov/imap/i-2788/.)

Day, W.C., O’Neill, J.M., Aleinikoff, J.N., and 

Green, G.N., 2007, Geologic map of the Big Delta B–1 

quadrangle, east-central Alaska: U.S. Geological Survey 

Scientific Investigations Map 2975, scale 1:63,360. (Also 

available online at http://pubs.usgs.gov/sim/2007/2975/.)

Dusel-Bacon, Cynthia, Lanphere, M.A., Sharp, W.D., Layer, 

P.W., and Hansen, V.L., 2002, Mesozoic thermal history and 

timing of structural events for the Yukon-Tanana Upland, 

east-central Alaska; 40Ar/39Ar data from metamorphic and 

plutonic rocks: Canadian Journal of Earth Sciences, v. 39, 

no. 6, p. 1013–1051.

Foster, H.L., comp., 1976, Geologic map of the Eagle 

quadrangle, Alaska: U.S. Geological Survey Miscellaneous 

Investigations Series I–922, 1 sheet, scale 1:250,000.

Foster, H.L., Albert, N.R.D., Griscom, Andrew, Hessin, T.D., 

Menzie, W.D., Turner, D.L., and Wilson, F.H., 1979, The 

Alaskan mineral resource assessment program; Background 

information to accompany folio of geologic and mineral 

resource maps of the Big Delta quadrangle, Alaska: U.S. 

Geological Survey Circular 783, 19 p. (Also available 

online at http://pubs.er.usgs.gov/usgspubs/cir/cir783.)

Hansen, V.L., and Dusel-Bacon, Cynthia, 1998, Structural and 

kinematic evolution of the Yukon-Tanana Upland tectonites, 

east-central Alaska—A record of late Paleozoic to Mesozoic 

crustal assembly: Geological Society of America Bulletin, 

v. 110, no. 2, p. 211–230.

Lister, G.S., and Snoke, A.W., 1984, S-C mylonites: Journal of 

Structural Geology, v. 6, no. 6, p. 617–638.

O’Neill, J.M., Day, W.C., Aleinikoff, J.N., and Saltus, R.W., 

2005, The Black Mountain tectonic zone—A long-lived 

lithospheric shear zone in the Yukon-Tanana Upland 

of east-central Alaska: Geological Society of America 

Abstracts with Program, v. 37, no. 7, p. 82. (Also available 

online at http://gsa.confex.com/gsa/2005AM/finalprogram/

abstract_96201.htm.)

Saltus, R.W., and Day, W.C., 2006, Gravity and 

aeromagnetic gradients within the Yukon-Tanana 

Upland, Black Mountain tectonic zone, Big Delta 

quadrangle, east-central Alaska: U.S. Geological Survey 

Open-File Report 2006–1391, poster, available only 

online at http://pubs.usgs.gov/of/2006/1391/. (Accessed 

March 9, 2009.)

Werdon, Melanie, Newberry, R.J., Athey, J.E., and Szumigala, D.J., 2004, Bedrock geologic map of the Salcha 

River-Pogo area, Big Delta quadrangle, Alaska: Alaska 

Division of Geological and Geophysical Surveys Report of 

Investigations 2004–1b, scale 1:63,360.

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

radiometric data from the Yukon crystalline terrane, Alaska 

and Yukon territory: Canadian Journal of Earth Sciences, 

v. 22, no. 4, p. 525–537.
Mapping Known and Potential Mineral 

Occurrences and Host Rocks in the 

Bonnifield Mining District Using Minimal 

Cloud- and Snow-Cover ASTER Data

By Bernard E. Hubbard, Cynthia Dusel-Bacon, Lawrence C. Rowan, and 

Robert G. Eppinger

Chapter E of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–E

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract ........................................................................................................................................................ E1

Introduction ................................................................................................................................................. E1

Geologic Setting ......................................................................................................................................... E1

Background, Methodology, and Relevance .......................................................................................... E3

Results ......................................................................................................................................................... E3

Host-Rock Mapping Using ASTER TIR Decorrelation Stretch Data .......................................... E3

Alteration Mineral Maps of Known and Undiscovered VMS and Porphyry Deposits ........... E3

Conclusions ................................................................................................................................................. E7

References Cited......................................................................................................................................... E7

Figures

 E1. Map showing locations of the Bonnifield mining district south of Fairbanks, 

Alaska .......................................................................................................................................... E2

 E2. ASTER thermal-infrared decorrelation stretch image (ASTER bands 13, 12 and 10, 

displayed as red, green, and blue, respectively) covering a portion of the Healy 

quadrangle .................................................................................................................................. E4

 E3. ASTER-derived mineral maps of portions of the 1:250,000-scale Healy quadrangle, 

Alaska .......................................................................................................................................... E5

 E4. Photograph and stratigraphic section of the well-exposed Red Mountain deposit 

and the unmapped and poorly exposed WTF deposit ......................................................... E6

Mapping Known and Potential Mineral Occurrences 

and Host Rocks in the Bonnifield Mining District Using 

Minimal Cloud- and Snow-Cover ASTER Data 

By Bernard E. Hubbard,1 Cynthia Dusel-Bacon,1 Lawrence C. Rowan,1 and Robert G. Eppinger1

1

U.S. Geological Survey.

Abstract

On July 8, 2003, the Advanced Spaceborne Thermal 

Emission and Reflection Radiometer (ASTER) sensor 

acquired satellite imagery of a 60-kilometer-wide swath 

covering a portion of the Bonnifield mining district within 

the southernmost part of the Tintina Gold Province, Alaska, 

under unusually favorable conditions of minimal cloud and 

snow cover. Although rocks from more than eight different 

lithotectonic terranes are exposed within the extended swath of 

data, we focus on volcanogenic massive sulfides (VMS) and 

porphyry deposits within the Yukon-Tanana terrane (YTT), 

the largest Mesozoic accretionary terrane exposed between the 

Denali fault system to the south of Fairbanks and the Tintina 

fault system to the north of Fairbanks. 

Comparison of thermal-infrared region (TIR) 

decorrelation stretch data to available geologic maps indicates 

that rocks from the YTT contain a wide range of rock types 

ranging in composition from mafic metavolcanic rocks to 

felsic rock types such as metarhyolites, pelitic schists, and 

quartzites. The nine-band ASTER visible-near-infrared 

region–short-wave infrared region (VNIR-SWIR) reflectance 

data and spectral matched-filter processing were used to map 

hydrothermal alteration patterns associated with VMS and 

porphyry deposit types. In particular, smectite, kaolinite, 

opaline silica, jarosite and (or) other ferric iron minerals 

defined narrow (less than 250-meter diameter) zonal patterns 

around Red Mountain and other potential VMS targets. Using 

ASTER we identified some of the known mineral deposits 

in the region, as well as mineralogically similar targets that 

may represent potential undiscovered deposits. Some known 

deposits were not identified and may have been obscured by 

vegetation or snow cover or were too small to be resolved.

Introduction 

On July 8, 2003, the Advanced Spaceborne 

Thermal Emission and Reflection Radiometer (ASTER) 

sensor aboard the TERRA satellite acquired a 60-kilometer 

(km)-wide orbital swath of data covering parts of the 

1:250,000-scale Healy quadrangle in east-central Alaska 

(fig. E1). The orbital swath of data continues on to include 

parts of the Talkeetna Mountains 1:250,000-scale quadrangle (see Hubbard and others, 2007) and areas to the 

south of Anchorage and the populated Matanuska Valley. 

Figure E1 illustrates the Healy and Bonnifield mining district 

portion of the ASTER data coverage used in this study, which 

was acquired under unusually low cloud- and snow-cover 

conditions (see also fig. 1 of Editors’ Preface and Overview).

Mineral resource exploration throughout much of the 

State has been hampered by the large geographic distances, 

lack of roads, and paucity of detailed geologic maps at 

1:63,360 scale or less. This leaves a large part of the State 

with possible undiscovered metallogenic resources. The 

purpose of this paper is to show the utility of ASTER for 

lithologic mapping of mineral deposit host rocks that define 

permissive tracts and for targeting hydrothermal alteration 

zones indicative of potential undiscovered occurrences.

Geologic Setting 

Several important volcanogenic massive sulfide 

(VMS) deposits are located within the Yukon-Tanana 

terrane (YTT), and their metallogenesis is discussed 

by Nokleberg and others (1994) and Newberry and others 

(1997). The Healy quadrangle (fig. E1) contains a variety 

of rocks ranging from mafic metavolcanic rocks to felsic 

metavolcanic rocks with a range of intermediate compositions (Csejtey and others, 1986, 1992, and references therein). 

Felsic metavolcanic and metavolcaniclastic rocks are 

important host rocks for Kuroko-type VMS deposits 

(Lydon, 1984; Cox and Singer, 1986–deposit model 
E2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Hines Creek strand

(Denali fault)

McKinley strand

(Denali fault)

Yukon-Tanana

terrane

Healy

McKinley

Park

Cantwell

Paxson

Richardson

Fairbanks

To Talkeetna

and Anchorage

To Kantishna

To Valdez

Alaska Highway

To Yukon

Delta Junction

64° 147° 64°

150°

150°

63° 63° 147°

0 45 KILOMETERS

EXPLANATION

Approximate boundary of Bonnifield mining district

Approximate boundary of Healy quadrangle 

Fault

Road

Pacific Ocean CANADA UNITED STATES

Healy

quadrangle

Alaska

Yukon

Northwest

Territories

British

Columbia

Location map

Figure E1. Map showing locations of the Bonnifield mining district south of Fairbanks, Alaska, and the 1:250,000-scale Healy 

quadrangle boundary. Also shown are the Hines Creek and McKinley strands of the Denali fault system and a false-color image (ASTER 

bands 6, 3 and 1, displayed as red, green, and blue respectively) showing the extent of minimal cloud- and snow-cover ASTER data for 

the area.
Mapping Known and Potential Mineral Occurrences and Host Rocks Using ASTER Data E3

28a). Mafic metavolcanic and metavolcaniclastic rocks 

typically host Besshi-type VMS deposits (Cox and Singer, 

1986–deposit model 24b), which are distinct from the Cyprustype VMS deposits associated with ophiolites (Cox and 

Singer, 1986–deposit model 24a). Several of the VMS deposits 

mapped using ASTER are associated with greenschist-facies 

metamorphic host rocks (Dusel-Bacon and others, 1993; 

Hubbard and others, 2007; Dusel-Bacon and others, this volume, chap. B). Differences in host rock composition and metamorphic grade lead to differences in the phyllosilicate mineral 

assemblages associated with VMS deposits, potentially 

providing a remote sensing basis for their discrimination. For 

instance, greenschist-grade metamorphic rocks show 

enhanced crystallinity of clay minerals, both associated with 

hydrothermal alteration, and within the groundmass (for 

example, McLeod and Stanton, 1984; McLeod, 1985, 1987; 

McLeod and others, 1987). Higher metamorphic grades, such 

as amphibolite facies, will destroy clay minerals, such as 

kaolinite, unless these clay minerals are replenished through 

supergene alteration processes.

Background, Methodology, and 

Relevance 

ASTER measures reflected radiation in the three 

wavelength bands between 0.520 and 0.860 micrometers 

(mm) (visible-near-infrared region, or VNIR) and in six 

bands from 1.00 to 2.43 mm (short-wave infrared region, or 

SWIR), with 15-m and 30-m spatial resolution, respectively 

(Fujisada, 1995). In addition, ASTER measures emitted 

thermal radiation in five bands in the 8.125- to 11.650-mm 

wavelength region (thermal-infrared region, or TIR) at 90-m 

resolution (Fujisada, 1995). Both standard calibrated ASTER 

data products (VNIR-SWIR reflectance, TIR emissivity, and 

TIR decorrelation stretch) and (or) their equivalents were 

used in this study (see Rowan and others, 2003; Rowan 

and Mars, 2003). Briefly, hydrothermal alteration minerals 

were mapped based on image spectral endmembers derived 

through principal component analysis (for example, Green 

and others, 1988; Boardman and others, 1995) of the nine 

ASTER VNIR-SWIR bands. These spectral endmembers (for 

example, Hubbard and others, 2007) were used as reference spectra in subsequent matched-filter image classification procedures (Harsanyi and Chang, 1994). The standard 

decorrelation stretch image product (fig. E2) shows ASTER 

TIR bands 10, 12, and 13 displayed as blue, green and red, 

respectively. Decorrelation stretch images are used to enhance 

the brightness variations between TIR bands related to 

compositional differences and emissivity, while suppressing 

correlated interchannel brightness values dominated by radiant 

temperature (Gillespie and others, 1986). Further processing 

details are discussed by Hubbard and others (2007).

Results 

Host-Rock Mapping Using ASTER TIR 

Decorrelation Stretch Data

Within YTT and rocks south of the Hines Creek 

strand of the Denali fault, linear enhancement of the TIR 

decorrelation stretch data shows a variety of lithologic 

compositions ranging from the mostly mafic, such as the 

labeled Chute Creek Member of the Totatlanika Schist (of 

Csejtey and others, 1992; blue shades, fig. E2), intermediate 

(mixed red-blue, or purple through magenta shades, fig. E2), 

and quartz-rich rocks such as granitic intrusions and 

prominent quartzite exposures (red shades, fig. E2). Several 

of these rock types are grouped together into formations 

at a scale of 1:250,000 (such as the Totatlanika Schist) but 

also are shown as distinct lithological members in the more 

detailed 1:63,360 geologic maps (for example, from oldest to 

youngest, the Moose Creek, California Creek, Chute Creek, 

Mystic Creek, and Sheep Creek Members of the Totatlanika 

Schist; Wahrhaftig, 1970a,b; Gilbert, 1977). In particular, the 

metarhyolite-dominated Mystic Creek Member hosts the Red 

Mountain and WTF VMS prospects (figs. E3, E4). Spectral 

analysis of sampled ground truth areas is discussed in greater 

detail by Hubbard and others (2007). 

Alteration Mineral Maps of Known and 

Undiscovered VMS and Porphyry Deposits

Figure E3 shows the resulting mineral maps generated 

using nine-band ASTER VNIR-SWIR data and spectral 

matched-filtering methods. Large areas of the upper two 

scenes of the ASTER mosaic (fig. E3A) were classified as 

containing zones of ferric-iron-rich minerals, chlorite and 

(or) epidote, and muscovite and (or) illite. Chlorite and (or) 

epidote are Fe,Mg-OH minerals that commonly occur in the 

predominantly greenschist and prehnite-pumpellyite facies 

of metamorphic rocks throughout the area. Muscovite and 

(or) illite can occur either as primary minerals in the 

groundmass of igneous and metamorphic rocks, within 

sericitic hydrothermal alteration zones, or as the weathering 

product of potassium-rich rocks.

Spectral analysis of fine-grained rock and soil samples 

collected at Red Mountain contain kaolinite, illite-muscovite, 

smectite, and goethite. These minerals were all mapped as 

distinct zoning patterns using ASTER data (fig. E3B, C). In 

addition, a variety of ferric-iron and aluminum oxy-hydroxide 

and sulfate mineral precipitates are found in and around 

the streams draining the mountain, reflecting natural acidrock drainage conditions within the pristine (unmined) Red 

Mountain VMS deposit (Eppinger and others, this volume, 

chap. I).

Alteration mineral zones were mapped at a more 

detailed scale for the Red Mountain deposit and the location 
E4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

of the WTF massive sulfide deposit (fig. E3B), the Anderson 

Mountain massive sulfide deposits (fig. E3C), and an area 

of possible alunite occurrence at Nenana Mountain in rocks 

mapped as Tertiary granites and Quaternary Nenana Glacier 

lateral moraines (fig. E3D). The Nenana Mountain and Nenana 

Glacier distribution could represent argillic and propylitic 

alteration zones of a porphyry copper deposit which can 

extend from 1 to 4 km (Lowell and Guilbert, 1970; Cox and 

Singer, 1986–deposit model 17). This distribution differs in 

scale and mineralogy from what is expected in hydrothermal 

alteration zones associated with VMS deposits such as Red 

Mountain, which generally extends for less than a few hundred 

meters (Lydon, 1984). The red, orange, and yellow colors 

(fig. E4A) and related mineralogy (fig. E3B) displayed by the 

Red Mountain deposit are due mostly to supergene alteration 

of pyrite and other massive sulfide layers (figs. E4B, C), and 

exposed silica exhalite and chert deposits (figs. E4B, C).

Nearly 200 potential VMS deposits were mapped by 

Hubbard and others (2007) in portions of the Healy and 

Talkeetna Mountains quadrangles covered by ASTER. Their 

identification was based on small-scale (about 100–200-m 

diameter) mineral zoning patterns between hydrous silica, 

jarosite, kaolinite, and smectite, which graded into background 

rocks dominated by ferric iron, chlorite, and sericite. Potential 

porphyry deposits such as at Nenana Mountain and the 

Nenana Glacier are defined by larger scale (greater than 1 km 

diameter) argillic and propylitic alteration zones.

64°

147°

0 20 KILOMETERS

Chute Creek Member (mafic

metavolcanic schist)

Clouds

Glacial snow and

ice (masked prior

to decorrelation

stretching)

Yukon-Tanana

terrane rocks 

Boundary of Healy

quadrangle

Hines Creek 

strand of the 

Denali fault

system

Quartzite, siliceous

schists and other

quartz-rich rocks at 

or above Hines 

Creek fault contact 

Pingston

terrane rocks 

McKinley

terrane rocks

Figure E2. ASTER thermal-infrared decorrelation stretch image 

(ASTER bands 13, 12 and 10, displayed as red, green, and blue, 

respectively) covering the portion of the Healy quadrangle shown 

in figure E1, including maximum exposure of rocks from the YukonTanana terrane. Snow and ice fields of glaciers south of the Denali 

fault have been masked prior to contrast stretching and appear 

as darkest shades to almost black. Vegetation appears mostly 

lighter green. Clouds and cloud shadows appear yellow. Red 

areas are exposed rocks that are more silicic in composition and 

blue areas depict rocks that are more mafic in composition. Colors 

in between (for example, purple, magenta, and cyan) represent 

mixtures of the aforementioned materials.
Mapping Known and Potential Mineral Occurrences and Host Rocks Using ASTER Data E5

Red Mountain Anderson

Mountain

Nenana

Mountain

Boundary of Healy quadrangle

B

C

D

B C

D

Location of unmapped WTF deposit

within the tundra vegetation

0 15 30 KILOMETERS

64° 147° 64°

150°

150° 63°

63°

147°

Nenana Glacier

lateral moraine

A

EXPLANATION 

(for parts A–D)

Ferric-iron minerals

Chlorite or epidote

Muscovite or illite

Alunite

Smectite clays

Kaolinite

Hydrous silica minerals

Limit of ASTER image swath

Figure E3. ASTER-derived images of portions of the 1:250,000-scale Healy quadrangle, Alaska, showing the distribution of host rocks 

and glacial sediments containing the three most abundant minerals. A, Overview map of a major portion of the Healy quadrangle 

showing locations of detailed hydrothermal alteration mineral zonation maps (B, C, and D). Shaded-relief base image was generated 

from U.S. Geological Survey digital elevation model dataset. B, Red Mountain and WTF massive sulfide deposits, with approximate 

northeastern (NE) and southwestern (SW) extents of profile shown in figure E4B. C, Anderson Mountain massive sulfide deposits. D, 

Area of possible alunite occurrence at Nenana Mountain in the McKinley terrane.
E6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

EXPLANATION

Sandstone with coal (Tertiary)

Totatlanika Schist (Mississippian?, as used 

by Csejtey and others, 1992)

Sheep Creek Member

Graywacke

Green shale

Calcareous shale

Gray to black shale

Mystic Creek Member

Rhyodacite lapilli tuff

Rhyolite tuff

Silica exhalatives and pyrite

Dacite tuff

Rhyodacite tuff

Chert (hydrous silica)

Massive sulfide horizon

B

Mtsg

Ts

Mtsgr

Mtsc

Mtss

Mtmc

Mtmt

Mtmd

Mtms

Mtmr

Mtml

Ts

Mtsg Mtgsr

Mtsc

Mtmt

Mtmc

Mtmd Mtms

Mtml

Mtmr Mtss

Mtmr

Mtmc

#

#

#

# #

#

#

#

#

#

#

# #

# #

DISTANCE, IN FEET

Red Mountain

VMS deposit

WTF

VMS deposit 

1,000

-1,000

2,000

3,000

4,000

5,000

SW NE

0

0

4,000 8,000 12,000

FEET

A

Red Mountain

Mystic Creek Member

of Totatlanika Schist

Figure E4. Photograph and 

stratigraphic section of the 

well-exposed Red Mountain 

deposit and the unmapped and 

poorly exposed WTF deposit. 

A, View of Red Mountain. B, 

Stratigraphic section showing 

geology, generalized and 

modified after Nokleberg and 

others (1994, fig. 6). Vertical 

scale is greatly exaggerated 

and topographic surface is 

generalized. Red Mountain is 

located in the higher and better 

exposed portion of the syncline 

structure. The southwestern 

and northeastern extents 

of the stratigraphic section 

correspond to the locations 

of Red Mountain and the 

WTF massive sulfide deposits 

mapped using ASTER as 

labeled on figure E3B. Note, 

however, that the minerals 

mapped at Red Mountain in 

figure E3B do not necessarily 

correspond to the individual 

stratigraphic units shown in 

the section.
Mapping Known and Potential Mineral Occurrences and Host Rocks Using ASTER Data E7

Conclusions 

We show in this study the utility of ASTER as an 

exploration tool for mapping potential occurrences of 

VMS and porphyry deposit types based on the deposit 

model characteristics such as host rock lithology and 

weathering characteristics, deposit size and scale, 

and hydrothermal alteration zonation patterns as described 

in Cox and Singer (1986). The results of this study show the 

utility of remote sensing, and in particular ASTER, for use in 

future mineral resource assessments. For example, such data 

are useful for the recognition of unknown deposits, definition 

of favorable or permissive tracts, and for providing basic rock 

composition data in geologically poorly known areas.

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E8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

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McLeod, R.L., Gabell, A.R., Green, A.A., and Gardavsky, 

V., 1987, Chlorite infrared spectral data as proximity 

indicators of volcanogenic massive sulphide mineralization, 

in Proceedings, Pacific Rim Congress 87, Gold Coast, 

Queensland, Australia, August 26–29, 1987: Parkville, 

Victoria, Australia, Australasian Institute of Mining and 

Metallurgy, p. 321–324.

Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., 

Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive 

sulfide deposits of Alaska: Economic Geology Monograph 

9, p. 120–150.

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major mineral deposits of Alaska, in Plafker, George 

and Berg, H.C., eds., The geology of Alaska, chapter 

G–1 of The geology of North America: Boulder, Colo., 

Geological Society of America, p. 855–903.

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Mapping hydrothermally altered rocks at Cuprite, Nevada, 

using the Advanced Spaceborne Thermal Emission and 

Reflection Radiometer (ASTER), a new satellite-imaging 

system: Economic Geology, v. 98, no. 5, p. 1019–027.

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Thermal Emission and Reflection Radiometer (ASTER) 

data: Remote Sensing of Environment, v. 84, no. 3, 

p. 350–366.

Wahrhaftig, Clyde, 1970a, Geologic map of the Healy D–2 

quadrangle, Alaska: U.S. Geological Survey Geologic 

Quadrangle Map GQ–804, scale 1:63,360.

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quadrangle, Alaska: U.S. Geological Survey Geologic 

Quadrangle Map GQ–805, scale 1:63,360.
Aufeis Accumulations in Stream Bottoms 

in Arctic and Subarctic Environments as a 

Possible Indicator of Geologic Structure

By Richard B. Wanty, Bronwen Wang, Jim Vohden, Warren C. Day, and 

Larry P. Gough

Chapter F of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–F

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract.........................................................................................................................................................F1

Introduction...................................................................................................................................................F1

Description of Study Area ..........................................................................................................................F2

Methods.........................................................................................................................................................F3

Results and Discussion...............................................................................................................................F4

Cholla Creek.........................................................................................................................................F4

Sonora Creek.......................................................................................................................................F5

Occidental Creek.................................................................................................................................F5

Relation Between Aufeis Locations and Fractures ......................................................................F6

A Conceptual Model for the Mechanism of Aufeis Formation in Alpine Catchments ............F6

Summary .......................................................................................................................................................F7

Acknowledgments.......................................................................................................................................F8

References Cited..........................................................................................................................................F8

Figures

F1. Map showing surface hydrologic features of the Big Delta B–2 quadrangle in

 east-central Alaska ...................................................................................................................F3

F2. Landsat 7 satellite image (path 68, row 15) of the Cholla and Sonora Creek area, 

Big Delta B–2 quadrangle, taken June 2, 2001 ......................................................................F4

F3. Landsate 7 satellite image (path 68, row 15) of the Occidental Creek area, Big 

Delta B–2 quadrangle, taken June 2, 2001 .............................................................................F5

F4. Photograph of thick (2–3 meters) aufeis at the upper site on Occidental Creek, 

taken in early June 2002 after approximately 1 meter of the ice had melted...................F6

F5. Landsat 7 satellite image (path 68, row 15) of the northern portion of the Big 

Delta B–2 quadrangle, taken June 2, 2001 .............................................................................F7

F6. Schematic cross section of a stream fed by discharging ground water that is 

carried by regionally extensive fractures...............................................................................F8

Aufeis Accumulations in Stream Bottoms in Arctic 

and Subarctic Environments as a Possible Indicator of 

Geologic Structure 

By Richand B. Wanty,1 Bronwen Wang,1 Jim Vohden,2 Warren C. Day,1 and Larry P. Gough1

1

U.S. Geological Survey.

2

Alaska Department of Natural Resources, Division of Mining, Land, and 

Water.

Abstract

Thick accumulations of ice, called “aufeis,” form during 

winter along stream and river valleys in arctic and subarctic 

regions. In high-gradient alpine streams, aufeis forms mostly 

as a result of ground-water discharge into the stream channel. 

The ice occludes this discharge, perturbing the steady-state 

condition, and causing an incremental rise in the local water 

table until discharge occurs higher on the stream bank above 

the previously formed ice. Successive freezing of onlapping 

ice layers can lead to aufeis accumulations several meters 

thick.

The location and extent of aufeis in high-gradient streams 

may be useful to relate local hydrology to geologic structure. 

In the Goodpaster River basin study area, mineral deposits 

are known to occur, the location of which may be structurally 

controlled. Therefore, a more thorough understanding of 

regional geologic structures may facilitate a more detailed 

understanding of the genesis of the mineral deposits.

Extensive aufeis was observed during visits to the 

Goodpaster River basin in east-central Alaska during 1999, 

2001, and 2002. Seeps from the sides of the valleys caused 

ice to build up, giving the ice surface a concave-upward 

shape perpendicular to the stream direction. This concavity is 

evidence for ground-water discharge along the length of the 

aufeis, as opposed to discharge from a single upstream point. 

During thaw, streamflow is commonly observed out of the 

normal channel, evidence that occlusion of the channel (and 

shallow sediments) by ice is a viable mechanism for causing 

the water table to rise.

The thickest (>3 meters) and most extensive aufeis 

(100’s of meters to kilometers along valleys) coincided with 

locations of laterally extensive (>5 kilometers) mapped 

high-angle brittle fault zones, suggesting that the fault zones 

are hydraulically conductive. Additional evidence of water 

flow is provided by observed changes in stream-water chemistry in reaches in which aufeis forms, despite a lack of 

surface tributaries. Minor or no aufeis was observed in many 

other drainage valleys where no laterally extensive structures 

have been mapped, implying that aufeis formation results from 

more than a topographic effect or discharge from bank storage. 

Thus, the presence of thick, laterally extensive aufeis in highgradient streams may be a useful aid to geologic structural 

mapping in arctic and subarctic climates. 

Introduction

In high-latitude ecoregions, where prolonged subfreezing 

temperatures exist for a significant part of the year, thick 

accumulations of ice, called aufeis or naled, may form in areas 

of ground-water discharge, or where ice dams form in flowing rivers. For example, in our study area northeast of Delta 

Junction, Alaska, the average monthly temperature is below 

0°C from October through April and the average January 

temperature is about -20°C (Weatherbase, 2007). Aufeis 

that forms as a result of ground-water discharge serves as an 

indicator of the location and extent of discharge. In areas with 

crystalline bedrock, ground-water flow is typically constrained 

by fractures. Aufeis that forms in such areas likely indicates 

locations of hydraulically conductive fractures. This paper 

demonstrates the coincidence of areas of aufeis formation in 

several alpine catchments with locations of regional-scale 

(from 1 kilometer (km) to 10’s of kilometers) fractures. In 

physiographic settings such as the study area described herein, 

aufeis may be helpful to understand locations of geologic 

structures as well as to qualitatively indicate the possible 

hydraulic conductivity of those fractures.

Aufeis in high-gradient catchments tends to reform 

in the same locations year after year (Dean, 1986; Lauriol 

and others, 1991; Hu and Pollard, 1997a), perhaps due to 

relatively invariant geologic, geomorphic, and hydrologic 

circumstances. In such catchments, where soil cover is 

thin, geologic properties that control ground-water flow 

(for example, fractures in crystalline bedrock) may be more 
F2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

important to aufeis formation than the hydrologic properties 

of unconsolidated material overlying bedrock. In this context, 

aufeis may also serve as a guide to the existence of potential 

ground-water resources (Harden and others, 1977).

A useful genetic classification of aufeis that was proposed 

by Carey (1973) includes spring aufeis, ground aufeis, and 

river aufeis. Spring aufeis forms as a result of ground-water 

discharge from beneath a permafrost layer (Hall and Roswell, 

1981; Yoshikawa and others, 2001) and is the primary focus 

of this study. Ground aufeis forms by discharge of shallow ground water from within the “active layer,” which is 

that portion of seasonally frozen ground between permafrost and the ground surface. River aufeis forms as a result 

of fluvial processes, often related to ice dams and commonly found in areas where the river gradient abruptly 

decreases (Hu and Pollard, 1997a). 

Hu and Pollard (1997a) describe the formation and 

buildup of aufeis using a three-stage model: freeze-up, 

obstruction, and overflow. Initial freeze-up is primarily 

responsible for aufeis location, while the latter two stages 

define the growth and abundance of individual icings. Hu 

and Pollard (1997b) developed a statistical model for aufeis 

growth during the overflow stage and found that ice thickness 

decreases away from the water source. In this study, relatively 

uniform ice thickness over distances of hundreds of meters to 

several kilometers implies numerous water sources or, more 

likely, a long continuous water source to the accumulating 

aufeis.

On an annual basis, aufeis serves as a reservoir for winter 

baseflow (Slaughter and Benson, 1986) that is released during 

late spring and early summer (Li and others, 1997). Aufeis 

formation during the winter quantitatively captures groundwater discharge, but because aufeis melts more slowly than 

regional snowpack, exceptionally thick (2 to 3 meters (m) 

or more) aufeis deposits may persist well into the summer 

months, continually releasing water to streams. Kane and 

Slaughter (1973) studied a watershed north of Fairbanks, 

Alaska, and found that the volume of water stored in the ice 

was only 4 percent of the total annual stream discharge but 

represented about 40 percent of the discharge for the winter 

months. They showed that if this ice melted within a 1-month 

period, there would be a significant increase in streamflow 

after snowmelt runoff was complete. Similarly, Osterkamp and 

others (1975) found significant (30–50 percent) reductions in 

streamflow just in the early stages of ice formation, implying 

temporary storage of the water as ice.

Previous studies have suggested links between aufeis 

formation and geologic properties of catchments. Lauriol 

and others (1991) noted that aufeis in the northern Yukon 

formed in spatial association with fault zones in carbonate 

bedrock. Hall and Roswell (1981) also noted a general spatial 

correlation between aufeis occurrences and locations of 

bedrock fracture zones, with greater density of aufeis in more 

heavily fractured areas. They proposed that the faults represent 

conduits along which ground water may flow between gaps in 

permafrost.

A baseline geochemical study was conducted in our study 

area (see fig. 1 of Editors’ Preface and Overview) from 1999 

to 2002, prior to new mining activity. New geologic mapping 

also was performed to complement concurrent sampling of 

surface water, soils, and plants, and to relate the chemical variations in the sampled media to surface or bedrock lithology. 

Because this study was conducted in a remote area, no 

possibility existed for sampling ground water other than by 

sampling springs in the area. During several visits to the area, 

thick aufeis accumulations were observed in some areas. 

These observations were used to investigate the spatial and 

causative relations between aufeis and local and regional 

hydrology. In contrast to earlier work, this study presents 

evidence for direct spatial correlations between streams that 

accumulate aufeis and specific fracture sets.

Description of Study Area

The study area is in the Goodpaster River drainage 

(fig. F1) about 70 km northeast of the town of Delta Junction, 

Alaska, and includes the entire Big Delta B–2 quadrangle 

(U.S. Geological Survey, 1958). Elevations range from 1,433 

m above sea level atop Shawnee Peak to just less than 400 m, 

where the Goodpaster River flows along the southwest edge 

of the quadrangle. Drainages from the Shawnee Peak massif 

and an unnamed highland that spans the southern half of the 

quadrangle are the source of many of the streams sampled 

during this study. 

Climate in the study area is characterized by long, cold 

winters, with an average of 223 days per year below 0°C. 

Average snowfall is about 1 m, with about 30 centimeters (cm) 

of rain between May and September (Weatherbase, 2007). 

The study area is located within the Intermontane Boreal 

Ecoregion (Nowacki and others, 2003), characterized by 

closed spruce hardwood forest over discontinuous permafrost. 

On south-facing slopes, where permafrost is less pervasive, 

the predominant forest species are white spruce, aspen, paper 

birch, and balsam poplar.

The geologic framework of the area is composed 

of Paleozoic to Tertiary crystalline rocks, with Devonian 

augen gneiss, Paleozoic biotite gneiss and paragneiss, and 

Cretaceous granitic plutonic rocks occupying most of the 

area of the quadrangle (Day and others, 2003). Through its 

complex geologic history, the Yukon-Tanana Upland, of 

which our study area is a part, has experienced a number 

of orientations of tectonic stresses, leading to metamorphism, 

foliation, and faulting of the rocks. Within the study area, the 

dominant direction of major fault zones is north-northwest 

in the northeastern part, northeast in the southern part, and 

northwest to east-northeast in the northwest part. Mapped 

structures have long strike lengths, in many cases in excess of 

5 km. 

The most important surface-water feature in the area 

is the Goodpaster River, which originates to the east of the 
Aufeis Accumulations in Stream Bottoms in Arctic and Subarctic Environments F3

Big Delta B–2 quadrangle and follows the northern and 

western edges of the quadrangle. Central Creek flows from 

east to west through the middle of the study area and represents another major drainage feature. The focus of our study 

has been the numerous smaller streams that empty into either 

the Goodpaster River or Central Creek. This paper describes 

results of geochemical sampling along Cholla, Sonora, and 

Occidental Creeks (fig. F1), all of which accumulate aufeis in 

the winter.

G o o d p a s t e r

R i v e r

O c c i d e n t a l C r e e k

C e n t r a l C r e e k

Liese Creek

S o n o r a C r e e k

Cholla Creek

Pogo gold

deposit

S h a w n e e

P e a k m a s s i f

U n n a m e d h i g h l a n d

0 1 2 3 KILOMETERS

144° 30’

64° 30’

64° 15’

145° 00’

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

Figure F1. Map showing 

surface hydrologic features of 

the Big Delta B–2 quadrangle 

in east-central Alaska. Green 

areas show approximate 

extent of aufeis observed in 

satellite images or by ground 

observations. The approximate 

location of the Pogo gold 

deposit also is shown.

Methods

Aufeis was located in stream valleys by a variety of 

means. In early July of 1999, remnant aufeis was observed in 

some stream bottoms. More aufeis was found by examining 

satellite images from early June 2001. In March of 2002, a 

low-altitude overflight of the area was made; then, in early 

June of 2002 fieldwork was conducted to examine aufeis 

locations in greater detail. Where aufeis has occluded stream 

channels, it commonly has led to the formation of braided 

immature channels in low-gradient sections of streams. It is 

therefore possible to infer the presence of aufeis on the basis 

of channel morphology.

An attempt was made to collect several water samples 

along each major stream drainage in the study area, including 

drainages with or without aufeis. Sampling was accomplished 

by walking the length of each stream to be sampled from 

the drainage divide to the confluence with the next higher 

order stream, usually Central Creek or the Goodpaster River. 

Along each stream length we sampled at the highest elevation 

of continuously flowing water and worked downstream, 

monitoring conductivity and temperature of the stream water 

along the way. If any change was observed, or if there were 

any tributaries, samples of the tributary and of the stream 

above and below the tributary were collected. Using this 

approach commonly resulted in collection of 2 to 10 samples 

per catchment.
F4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

At each sample site, field measurements were 

made for stream discharge, pH, conductivity, temperature, dissolved oxygen, and dissolved Fe2+. If feasible, 

discharge was measured with a pygmy flow meter 

(U.S. Geological Survey, 2007). The pH was measured using 

a combination glass electrode with automatic temperature 

compensation. Each morning, the pH electrode was calibrated with buffers of pH 4.0, 7.0, and 10.0. Calibration was 

checked at least once in the afternoon by measuring the pH 

of a buffer solution. The measured value of the buffer was 

always within ±0.05 pH units of the accepted value for the 

buffer. Conductivity was not calibrated and was therefore used 

only for relative measurements during sampling. Temperature was measured using a digital thermometer traceable to 

thermometric standards of the National Institute of Standards 

and Technology (NIST). Dissolved oxygen and Fe2+ were 

measured using CHEMetrics self-filling ampoules.

In addition to the field analyses, samples were collected 

and preserved for later laboratory analyses. Samples were 

filtered through a 0.45-micrometer (μm) Gelman Supor filter 

and collected into acid-washed high-density polyethylene 

bottles and acidified to pH of approximately 1 with ultrapure 

HNO3. These samples were analyzed for major and trace 

cations and rare earth elements using inductively coupled 

plasma–atomic emission spectroscopy (ICP–AES) and mass 

spectrometry (ICP–MS). A second sample was collected, 

which was filtered but not acidified, for anion analysis by ion 

chromatography. A raw sample was collected for alkalinity 

titration. The latter two samples were kept cool upon returning 

to the hotel each evening, whereupon they were refrigerated 

until analysis. Further details of the analytical methods can be 

found in Briggs (1996), Lamothe and others (1999), and Papp 

and others (1996).

Results and Discussion

This paper focuses on the Occidental, Cholla, and Sonora 

Creek catchments—all are high-gradient streams draining 

the flanks of the Shawnee Peak massif (fig. F1). Cholla and 

Sonora Creeks are located on south-facing slopes, where 

less permafrost is expected. Occidental Creek drains to the 

northwest on a north-facing slope, but the vegetation density 

is similar to the other two, suggesting an absence of permafrost, or incomplete permafrost in the shallow subsurface. In 

all three of these cases, the direct observation of aufeis extent 

is supported by stream-water chemical data and other measurements, including measurements of hydraulic head in the 

hyporheic zone at one of the sites.

Cholla Creek

Cholla Creek was sampled at two sites, numbered 44 

and 45 (fig. F2), in July 1999. The two sites are about 1 km 

apart, with an elevation change of about 90 m. At the time of 

44

45

Ch

olla

Creek

Sonora

Creek

upper

lower

0 1 2 KILOMETERS

64°22’

64°25’

144°50’ 144°45’

Figure F2. Landsat 7 satellite image (path 68, row 15) of the 

Cholla and Sonora Creek area, Big Delta B–2 quadrangle, taken 

June 2, 2001. Blue pixels are areas covered by ice or snow. Most 

of the blue area near the top of the image is snow, but some aufeis 

is visible along Sonora Creek just downstream from the lower site. 

Red dots are sample locations referenced in text.

sampling, remnant aufeis was still present in the drainage from 

the previous winter at elevations above site 44. No aufeis was 

observed in the stream between these two sites, but in a March 

2002 low-altitude overflight of the area, aufeis was observed 

between sites 44 and 45. Given the relatively small area of 

the Cholla Creek drainage, it is likely that smaller volumes of 

ice might form and that the 1999 sampling occurred after the 

aufeis melted from the Cholla Creek valley between the two 

sample sites.

Between the two sample sites, there were no surfacewater tributaries, but the measured stream discharge increased 

from 1.1 to 2.5 liters per second (L/s) between sites 44 and 

45. This observed increase in flow can be attributed only to 

ground-water discharge. Electrical conductivity of the stream 

water increased from 190 to 220 microsiemens per centimeter (μS/cm) between the two sites, which can be explained 

primarily by increases in calcium (34 to 42 milligrams per 

liter, mg/L), SO4

 (45 to 57 mg/L) and alkalinity (88 to 106 

mg/L as HCO3). Smaller increases were observed in concentrations of sodium, magnesium, and potassium. At both sites 

total dissolved iron was below detection (<0.02 mg/L).

On the basis of the observed changes in concentrations 

of dissolved constituents, the discharging ground water 
Aufeis Accumulations in Stream Bottoms in Arctic and Subarctic Environments F5

must have greater total dissolved solids, and in particular, 

significantly higher alkalinity and concentrations of calcium 

and SO4 than the stream water. The increases in calcium 

and alkalinity are expected, on the basis of the local aquifer material, a Paleozoic paragneiss that consists of biotite 

schist layers and quartzofeldspathic biotite schist layers. In 

an outcrop sample collected above site 44, fine-grained pyrite 

and possible marcasite were observed, suggesting that the 

incremental increase in SO4 may be at least in part derived 

from the oxidation of sulfide-bearing minerals in the shallow 

subsurface. 

Sonora Creek

Sonora Creek was sampled in July 1999 and early June 

2002 at the sites marked “upper” and “lower” on figure F2. 

The same sites were sampled each time. In 1999, no aufeis 

remained along this reach of Sonora Creek, but during the 

2002 sampling, aufeis covered the valley bottom continuously 

between the two sites, a distance of approximately 0.6 km. 

The vertical drop between the two sites is approximately 85 m.

The formation of aufeis in the Sonora Creek drainage 

is an indication of ground-water discharge throughout the 

winter. In July 1999, ground-water hydraulic potential in the 

shallow subsurface was measured using a device described 

by Wanty and Winter (U.S. Geological Survey, 2000). Several sites were tested, comparing the elevation of the water 

in the shallow subsurface (15 to 40 cm below the streambed) to that in the stream. In some cases, no head difference 

was observed, but in most cases, head differences between 

1 and 5 cm were observed, with the ground-water potential 

always above the stream surface. This result indicates the 

tendency for ground-water discharge in this reach of Sonora 

Creek. In 1999, the stream discharge increased from 0.003 

to 0.006 m3

/s between the upper and lower sites, with only 

one surface-water tributary between the sites. The discharge 

of that tributary was insufficient to make up the difference in 

discharge. At both times, the electrical conductivity (specific 

conductance, SpC) decreased slightly between the upper and 

lower sites, suggesting that discharging ground water had 

lower total dissolved solids. Chemical analyses indicated small 

but significant decreases in virtually all the major cations and 

anions. For example, in 1999, SpC decreased from 270 to 170 

μS/cm, and decreases were observed for calcium (41 to 27 

mg/L), magnesium (13 to 7 mg/L), sodium (3 to 2.5 mg/L), 

HCO3

 (140 to 80 mg/L), and SO4 (53 to 38 mg/L) between the 

upper and lower sites.

Occidental Creek

Occidental Creek drains the north side of the Shawnee 

Peak massif (fig. F3). Occidental Creek was sampled in July 

1999 and again in early June 2002 at the sites marked “upper” 

and “lower” on figure F3. The two sites are separated by a 

distance of approximately 1.6 km and an elevation drop of 

140 m. Aufeis was present at the upper site in July 1999, 

but in 2002, a thick (3 m or more) layer of aufeis extended 

continuously between the upper and lower sites. The satellite 

image in figure F3, taken June 2, 2001, shows the continuous 

aufeis in the Occidental Creek valley between the upper and 

lower sites.

In June 2002, the aufeis was beginning to melt but was 

still greater than 3 m thick at the upper site (fig. F4). Maximum thickness of the ice was probably about 1 m greater, 

based on observations of willows embedded in the ice that 

had their tops cut off at the same level, either by animals or 

by shearing of debris-laden water during the early stages 

of breakup. A notable feature of the aufeis at this location was its shape within the valley—viewed down the axis 

of the valley, the aufeis is concave upward and appears to 

climb up the valley walls. This morphology suggests that the 

source water for the aufeis came from spatially and temporally 

continuous discharge from the valley sides rather than from a 

point or series of points along the stream channel. A conceptual model for aufeis formation, used to explain this morphology in greater detail, is discussed later in this report.

The chemical changes observed in stream water in 

Occidental Creek between the upper and lower sites is similar 

to that in Cholla Creek in that discharging ground water is 

upper

lower

Shawnee Peak

Occidental Creek

0 0.5 1 KILOMETERS

64°25’

64°27’

64°29’

144°45’ 144°40’

Figure F3. Landsate 7 satellite image (path 68, row 15) of the 

Occidental Creek area, Big Delta B–2 quadrangle, taken June 

2, 2001. Blue pixels are areas covered by ice or snow. The blue 

areas along the southern part of the image are accumulated 

snow near the top of Shawnee Peak; nearly continuous aufeis is 

observed along Occidental Creek between the upper and lower 

sites. Red dots are sample sites discussed in text. Other sample 

sites along Occidental Creek are shown with yellow dots.
F6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Figure F4. 

Figure F4. Photograph of thick (2–3 meters) aufeis at the 

upper site on Occidental Creek, taken in early June 2002 after 

approximately 1 meter of the ice had melted. The flowing water 

that is visible at the bottom of the chasm is flowing on the ground, 

but in many areas, most of the streamflow was still over ice at the 

time our samples were collected.

likely to be a source of sulfate. Resolving the contributions 

of ground and surface water in Occidental Creek is complicated by the inputs of a surface-water tributary that has higher 

total dissolved solids and whose chemical contributions 

explain some of the changes observed between the upper and 

lower site. This tributary enters Occidental Creek from the 

southwest about midway between the upper and lower sites 

(fig. F3). Measured discharges were 0.03 m3/s at the upper 

site, 0.006 m3/s in the tributary, and 0.04 m3/s at the lower 

site. Variations in stream discharge, sodium, magnesium, and 

conductivity can be explained by a conservative mixing model 

with about 85 percent of the water from Occidental Creek and 

15 percent being added by the tributary. However, calcium is 

overestimated, and potassium, HCO3, and SO4 are underestimated by this mixing model, so we propose that discharging 

ground water has lower concentrations of calcium and greater 

concentrations of potassium, HCO3

, and SO4 as compared to 

the surface-water tributary. The significance of this result is 

discussed in the next subsection.

Relation Between Aufeis Locations and 

Fractures

Much of the data presented on the three catchments 

can be explained by ground-water discharge causing aufeis 

formation in winter. One aspect of this phenomenon that 

has not been discussed is the control of ground-water flow 

in the bedrock aquifers. During the field studies, aufeis was 

observed in some stream drainages but not in all stream 

drainages. A spatial relation between the locations of aufeis 

and major fracture systems as mapped by Day and others 

(2003) was apparent. This relation is shown in figure F5, using 

an expanded view of the satellite image base from which 

figures F2 and F3 were taken. This relation is true for many 

of the locations where aufeis was studied. For example, one 

of the most laterally extensive fracture zones in the study area 

defines the Occidental Creek valley. This valley had some 

of the most extensive aufeis in the study area, in terms of 

both lateral extent and thickness. Another area with laterally 

extensive fractures lies in the southern part of the study area, 

south of Central Creek (“A” in figure F5). Extensive aufeis 

was observed along this creek. Ground-water discharge that 

leads to the formation of this aufeis continues through the 

summer months and serves as a significant water source to 

the base flow of these streams. Evaluating regional baseline 

geochemistry, and determining the chemical contribution of 

ground water to the streams, should give a “window” to the 

ground-water chemistry and a greater understanding of the 

water-rock interactions that take place in the subsurface.

An important distinction needs to be made between the 

depths of ground-water sources feeding the streams in the 

study area. It is likely that all the streams in the area are fed 

by ground-water discharge, but many of the streams in the 

area do not form aufeis. This difference may be explained 

by considering the depth from which the discharging ground 

water originates. Streams that do not form aufeis may be fed 

by shallower ground water, from within the “active layer.” 

The active layer is that range of depth within the ground that 

undergoes seasonal freeze and thaw. In many areas, especially 

on north-facing slopes, the active layer sits atop permafrost. 

If ground water from the active layer is the primary source 

of stream water, then these streams would not be expected 

to form aufeis, as this water source freezes in winter. If the 

ground water discharging into the streams originates from 

a deeper source, such as flow within a laterally extensive 

fracture or fault system, there should be perennial flow, and 

thus aufeis formation in winter.

A Conceptual Model for the Mechanism of 

Aufeis Formation in Alpine Catchments

Streams aligned with hydraulically conductive fractures 

serve as discharge outlets for ground water. During summer 

months, ground-water discharge through the streambed is 

unimpeded (“A” in fig. F6). At the onset of winter, the streams 

freeze, occluding the channel and blocking the discharge of 

ground water. This blockage perturbs the steady state condition that was obtained over the summer months and leads to 

a small incremental rise in the potentiometric surface beneath 

the stream. As the water table rises above the level of ice 

in the stream, discharge resumes along the margins of the 

ice (“B” in fig. F6). Throughout the winter, the water table 

continually rises above the level of the previously formed ice, 

and discharge proceeds along the margins of the valley (“C” in 

fig. F6). By this mechanism, the sides of the valley represent a 

continuous locus of discharge; therefore, the highest elevation 

of the ice should be along the valley sides, as was observed. 

In the spring and summer as the ice melts, the potentiometric 
Aufeis Accumulations in Stream Bottoms in Arctic and Subarctic Environments F7

surface retreats to the position of “A” in figure F6, and a new 

annual cycle begins.

A

Occidental

Creek

Sonora Creek

C e n t r a l C r e e k

G o o d p a s t e r

R i v e r

S h a w n e e P e a k

C

m a s s i f

h

olla

Creek

0 1 2 3 KILOMETERS

144°50’ 144°40’ 144°30’

64°20’

64°25’

64°30’

Figure F5. Landsat 7 satellite image (path 68, row 15) of the northern portion of the Big Delta B–2 quadrangle, taken June 2, 2001. 

Yellow lines show major faults as mapped by Day and others (2003). Location A is an additional area of laterally extensive fractures 

with aufeis.

Summary 

Aufeis forms during the winter in high-gradient alpine 

streams in arctic and subarctic environments. There is a 

spatial correlation between streams that accumulate aufeis 

and regionally extensive fractures. Significant changes in 

stream-water chemistry were observed in stream reaches that 

accumulate aufeis. These changes can be explained on the 

basis of the chemistry of ground water in contact with local 

aquifer rocks.

The proposed conceptual model for aufeis formation 

begins with occlusion of normal ground-water discharge 

flowpaths as streams freeze solid at the beginning of winter. 

The ground-water level rises incrementally, and discharge 

proceeds throughout the winter by a succession of freezing of 

onlapping layers of ice followed by the next incremental rise 

in the water-table level.
F8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Soil zone

Bedrock

A

B

C

Fractures

Figure F6. Schematic cross section of a stream fed by 

discharging ground water that is carried by regionally extensive 

fractures. See text for explanation.

Acknowledgments

The authors thank the Mineral Resources Program of 

the U.S. Geological Survey and the Alaska State Department 

of Natural Resources, Division of Mining, Land and Water, 

for funding this project. Thanks to Byron Berger and Ron 

Rickman for constructive reviews of earlier versions of this 

manuscript.

References Cited

Briggs, P.H., 1996, Forty elements by inductively coupled 

plasma–atomic emission spectrometry, in Arbogast, B.F., 

ed., Analytical methods manual for the Mineral Resource 

Surveys Program: U.S. Geological Survey Open-File 

Report 96–525, p. 77–94. (Also available online at 

http://pubs.er.usgs.gov/usgspubs/ofr/ofr96525.)

Carey, K.L., 1973, Icings developed from surface water 

and ground water: U.S. Army Cold Regions Research 

and Engineering Laboratory, Cold Regions Science and 

Engineering Monograph III–D3, 65 p.

Day, W.C., Aleinikoff, J.N., Roberts, Paul, Smith, Moira, 

Gamble, B.M., Henning, M.W., Gough, L.P., and 

Morath, L.C., 2003, Geologic map of the Big Delta B–2 

quadrangle, east-central Alaska: U.S. Geological Survey 

Geological Investigations Series I–2788, 12 p., 1 sheet, 

scale 1:63,360. (Also available online at http://pubs.usgs.

gov/imap/i-2788/.) 

Dean, K.G., 1986, Regional distribution of stream icings in 

Alaska, in Cold Regions Hydrology Symposium, Fairbanks, 

Alaska: Bethesda, Md., American Water Resources 

Association, p. 339–344.

Hall, D.K., and Roswell, Charles, 1981, The origin of water 

feeding icings on the eastern north slope of Alaska: Polar 

Record, v. 20, no. 128, p. 433–438.

Harden, D.R., Barnes, P., and Reimnitz, E., 1977, Distribution 

and character of naleds in northeastern Alaska: Arctic, v. 30, 

no. 1, p. 28–39.

Hu, Xiaogang, and Pollard, W.H., 1997a, The hydrologic 

analysis and modeling of river icing growth, North Fork 

Pass, Yukon Territory, Canada: Permafrost and Periglacial 

Processes, v. 8, no. 3, p. 279–294.

Hu, Xiaogang, and Pollard, W.H., 1997b, Ground icing 

formation; Experimental and statistical analyses of the 

overflow process: Permafrost and Periglacial Processes, 

v. 8, no. 2, p. 217–235.

Kane, D.L., and Slaughter, C.W., 1973, Seasonal regime and 

hydrological significance of stream icings in central Alaska, 

in Role of Snow and Ice in Hydrology, Banff Symposium 

Proceedings: International Association of Hydrological 

Sciences Publication 107, v. 1, p. 528–540.

Lamothe, P.J., Meier, A.L., and Wilson, S.A., 1999, The 

determination of forty-four elements in aqueous samples 

by inductively coupled plasma–mass spectrometry: 

U.S. Geological Survey Open-File Report 99–151, 14 p. 

(Also available online at http://pubs.er.usgs.gov/usgspubs/

ofr/ofr99151.)

Lauriol, Bernard, Cinq Mars, Jacques, and Clark, I.D., 1991, 

Localisation, genese et fonte de quelques naleds du nord du 

Yukon (Canada): Permafrost and Periglacial Processes, v. 2, 

no. 3, p. 225–236.

Li, Shusun, Benson, C.S., Shapiro, L., and Dean, K., 1997, 

Aufeis in the Ivishak River, Alaska, mapped from satellite 

radar interferometry: Remote Sensing of Environment, 

v. 60, no. 2, p. 131–139.

Nowacki, G.J., Spencer, Page, Fleming, Michael, Brock, Terry, 

and Jorgenson, Torre, 2003, Unified ecoregions of 

Alaska, 2001: U.S. Geological Survey Open-File Report 

02–297, 1 sheet, scale 1:4,000,000. (Also available at 

http://pubs.er.usgs.gov/usgspubs/ofr/ofr2297.)

Osterkamp, T.E., Gilfilian, R.E., and Benson, C.S., 1975, 

Observations of stage, discharge, pH, and electrical 

conductivity during periods of ice formation in a small 

subarctic stream: Water Resources Research, v. 11, no. 2, 

p. 268–272.
Aufeis Accumulations in Stream Bottoms in Arctic and Subarctic Environments F9

Papp, Clara, Brandt, Elaine, and Aruscavage, Phillip, 1996, 

Carbonate carbon by coulometric titration, in Arbogast, 

B.F., ed., Analytical methods manual for the Mineral 

Resource Surveys Program: U.S. Geological Survey 

Open-File Report 96–525, p. 60–66. (Also available online 

at http://pubs.er.usgs.gov/usgspubs/ofr/ofr96525.)

Slaughter, C.W., and Benson, C.S., 1986, Seasonal snow and 

aufeis in Alaska’s taiga, in Proceedings of the Cold Regions 

Hydrology Symposium, Fairbanks, Alaska: Bethesda, Md., 

American Water Resources Association, p. 101–109.

U.S. Geological Survey, 1958, Big Delta (B–2), Alaska, 

topographic map: Washington, D.C., U.S. Geological 

Survey, scale 1:63,360. 

U.S. Geological Survey, 2000, A simple device for measuring 

differences in hydraulic head between surface water and 

shallow ground water: U.S. Geological Survey Fact Sheet 

077–00, 2 p. (Also available online at http://pubs.usgs.gov/

fs/fs-0077-00.)

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collection of water-quality data: U.S. Geological Survey 

Techniques of Water-Resources Investigations, Book 

9, available only online at http://water.usgs.gov/owq/

FieldManual/. (Accessed March 9, 2009.)

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LLC Web site at http://www.weatherbase.com/. (Accessed 

May 2, 2007.)

Yoshikawa, Kenji, Petrone, Kevin, Hinzman, L.D., and 

Bolton, W.R., 2001, Aufeis development and stream 

baseflow hydrology in the discontinuous permafrost 

region, Caribou Poker Creeks research watershed, 

interior Alaska [abs.], in 2001 American Water Resources 

Association Alaska Section Conference Proceedings, 

Fairbanks, Alaska, April 4–6, 2001: Anchorage, Alaska, 

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(Available only online at http://state.awra.org/alaska/

proceedings/2001abstracts/yoshikawa.html/.) (Accessed 

January 25, 2010.)

Surface-Water, Ground-Water, and 

Sediment Geochemistry of Epizonal and 

Shear-Hosted Mineral Deposits in the 

Tintina Gold Province—Arsenic and 

Antimony Distribution and Mobility

By Seth H. Mueller, Richard J. Goldfarb, Philip L. Verplanck, Thomas P. Trainor, 

Richard F. Sanzolone, and Monique Adams

Chapter G of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day 

Scientific Investigations Report 2007–5289–G

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract .......................................................................................................................................................G1

Introduction..................................................................................................................................................G1

Geology of Mineral Deposits.....................................................................................................................G2

Keno Hill...............................................................................................................................................G3

Brewery Creek....................................................................................................................................G3

Fairbanks District ...............................................................................................................................G3

Kantishna Hills ...................................................................................................................................G3

Donlin Creek........................................................................................................................................G4

Sample Collection and Methods ..............................................................................................................G4

Ground-Water Samples ....................................................................................................................G4

Surface-Water Samples ...................................................................................................................G4

Sediment Samples .............................................................................................................................G5

Results and Discussion ..............................................................................................................................G5

Water Geochemistry .........................................................................................................................G5

Sediment Geochemistry ...................................................................................................................G5

Arsenic and Antimony Distribution and Mobility ..........................................................................G5

Exploration ...................................................................................................................................................G7

Conclusions..................................................................................................................................................G7

Acknowledgments ......................................................................................................................................G8

References Cited.........................................................................................................................................G8

Figures

 G1. Landsat-based shaded relief map showing the outline of the Tintina Gold 

Province, major faults, mining districts, and sudy areas ....................................................G2

 G2. Photographs of geologists performing data collection at various locations ..................G5

 G3. Graphs showing arsenic and antimony concentrations .....................................................G6

Tables

 G1. Sampling locations, sample types, and number of samples collected for each 

location in this study. .................................................................................................................G4

Surface-Water, Ground-Water, and Sediment 

Geochemistry of Epizonal and Shear-Hosted Mineral 

Deposits in the Tintina Gold Province—Arsenic and 

Antimony Distribution and Mobility 

By Seth H. Mueller,1 Richard J. Goldfarb,1 Philip L. Verplanck,1 Thomas P. Trainor,2 Richard F. Sanzolone,1 and 

Monique Adams1

1

U.S. Geological Survey.

2

University of Alaska—Fairbanks.

Abstract 

Epigenetic mineral deposits in the Tintina Gold Province 

are generally characterized by high concentrations of arsenic 

and antimony in their mineral assemblage. A total of 347 samples (ground water, surface water, and stream sediment) were 

collected to investigate the distribution and mobility of arsenic 

and antimony in the environment near known mineral deposits. Samples were collected from east to west at Keno Hill and 

Brewery Creek, Yukon, Canada; and Cleary Hill, True North, 

Scrafford Mine, Fairbanks, Ryan Lode, Stampede Creek, 

Slate Creek, and Donlin Creek, all in Alaska. Surface- and 

ground-water samples are all slightly acidic to near-neutral 

in pH (5–8), have a wide range in specific conductance 

(surface water 17–2,980 microsiemens per centimeter and 

ground water 170–2,940 microsiemens per centimeter), and 

show elevated dissolved arsenic and antimony concentrations 

(arsenic in surface water is less than 1 to 380 micrograms per 

liter and in ground water is less than 1 micrograms per liter to 

1.5 milligrams per liter; antimony in surface water is less than 

2 to 660 micrograms per liter and in ground water is less than 

2 to 60 micrograms per liter). Stream sediments downstream 

from these deposits have high concentrations of arsenic and 

antimony (arsenic median is 1,670 parts per million, maximum is 10,000 parts per million; antimony median is 192 

parts per million, maximum is 7,200 parts per million). The 

mobility of arsenic and antimony is controlled by the local 

redox environment, with arsenic being less mobile in oxidized 

surface waters relative to antimony, and arsenic more mobile 

in reduced ground water. These factors suggest that both antimony and arsenic may be useful pathfinder elements in water 

and sediment for targeting similar style deposits elsewhere in 

the Tintina Gold Province. 

Introduction

In recent years, trace elements such as arsenic 

and antimony have garnered significant attention from 

the scientific community and the general public due to 

their toxicity and our initially limited, but rapidly growing 

understanding of their geochemical behavior in the natural 

environment (Welch and others, 2000; Filella and others, 

2002a,b; Smedley and Kinniburgh, 2002). Arsenic and 

antimony are strongly associated with both gold and base 

metals in epigenetic shear-zone-related mineral deposits within 

the Tintina Gold Province (TGP; Hart and others, 2002). We 

have carried out numerous investigations on the distribution, 

speciation, and mobility of arsenic and antimony in ground 

and surface waters as well as stream sediments in multiple 

environments (prior to, during, and after mining); and on their 

efficiency as pathfinder elements in exploration for similar, 

as of yet undiscovered gold deposits in the TGP. Studies of 

the speciation and mobility of trace metals, such as arsenic 

and antimony, are also critical to understanding the natural 

degradation of both mined and undisturbed mineral deposits 

and can provide empirical data necessary for the development 

of environmental geochemical models of epizonal shear- and 

shear zone-hosted mineral deposits.

Four primary areas within the TGP were studied. As 

shown in figure G1 (from east to west) our study included 

(1) Keno Hill and Brewery Creek in the Tombstone district of 

Yukon, Canada; (2) several deposits in the Fairbanks mining 

district, including Cleary Hill, True North, Scrafford, and Ryan 

Lode, as well as undeveloped shear- and fault-hosted zones of 

mineralization within the vicinity of the city of Fairbanks; (3) 

the Stampede and Slate Creek deposits in the Kantishna Hills 

mining district; and (4) the Donlin Creek gold deposit in the 

Kuskokwim district in southwestern Alaska.
G2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

KALTAG-TINTINA FAULT

FAREWELL-DENALI FAULT

Anchorage

Whitehorse

Fairbanks

Mayo

Dawson

Alaska

Yukon

CANADA

UNITED STATES

Northwest 

Territories

British

Columbia

T I N T I N A G O L D P R O V I N C E

KK

FB

KD TB KT

Donlin Creek

Slate Creek Stampede

Ryan Lode

Scrafford

Cleary Hill

True North

Brewery

Creek 

Keno Hill

0 100 200 300 400 500 KILOMETERS

60°

65°

70°

160° 150° 140°

Figure G1. Landsat-based shaded-relief map showing the outline of the Tintina Gold Province, major faults, mining districts 

(KK, Kuskokwim; KT, Kantishna; FB, Fairbanks; KD, Klondike; TB, Tombstone Gold Belt), and study areas.

Geology of Mineral Deposits

The TGP is an arcuate east-west-trending belt of rocks 

made up of multiple and diverse geologic terranes generally 

bounded on the north by the Kaltag-Tintina fault system and 

on the south by the Farewell-Denali fault system (fig. G1). 

Three dominant geotectonic regimes lie within the TGP. They 

are, from east to west, (1) Neoproterozoic to middle Paleozoic 

turbidites, basinal clastic rocks, and limestones of the Selwyn 

basin continental margin sequence (Gordey and Anderson, 

1993); (2) Neoproterozoic to Paleozoic polymetamorphosed 

metasedimentary and meta-igneous assemblages of the 

Yukon-Tanana Upland in east-central Alaska (Foster and others, 1994); and (3) Paleozoic to Mesozoic basement terranes 

overlapped by Cretaceous flysch sequences of the Kuskokwim 

basin (Decker and others, 1994).

The majority of the mineral deposits are shear zoneand (or) fault-hosted epizonal gold-bearing ores, typically 

containing as much as several volume percent arsenopyrite, 

pyrite, and (or) stibnite. The Keno Hill silver-lead-zinc deposit 

in the Tombstone district (fig. G1), although having a different metallogenic signature, was included for study because 

it is a similar style of epigenetic vein-type mineralization, 

and appears to have a spatial and temporal relationship with 

gold-bearing deposits in the eastern part of the TGP. Other 

gold deposits in the TGP with significantly lower sulfide 

volumes (for example, Fort Knox in Alaska and Scheelite 

Dome in Yukon), commonly termed intrusion-related gold 

systems (Hart and others, 2002), were not examined in these 

studies because arsenic and antimony mobility is less of a 

concern surrounding this deposit type. The following are brief 

summaries of the local geology of each study location from 

east to west across the TGP. For more detailed descriptions of 

the characteristics of these deposits, see Goldfarb and others 

(this volume, chap. A).
Surface-Water, Ground-Water, and Sediment Geochemistry of Epizonal and Shear-Hosted Mineral Deposits G3

Keno Hill

The Keno Hill silver-lead-zinc deposits are located 

270 kilometers (km) east of the Alaska-Yukon border, 

approximately 60 km northeast of the Brewery Creek deposit 

(fig. G1). This district is composed of about 70 subparallel 

veins (or vein systems) comprising a composite 6-km-wide 

by 30-km-long, east-west-trending mineralized zone. The 

vein deposits are hosted in the Carboniferous quartzite, 

carbonaceous phyllite, and calcareous quartzite of the 

informally named Keno Hill quartzite, and Middle to Late 

Devonian quartz-sericite-chlorite phyllite, carbonaceous 

phyllite, siliceous carbonaceous metasiltstone, and crystalline 

limestone of the Earn Group. These rocks are intruded by 

numerous granitic dikes and sills dated at about 90 million 

years before present (Ma) (Sinclair and Tessari, 1981; 

Franzen, 1986). Stibnite and arsenopyrite are associated with 

the silver-lead-zinc mineralization. Alteration and gangue 

minerals include quartz, calcite, and siderite. The majority 

of the historical mines in the Keno Hill district have been 

abandoned without reclamation. 

Brewery Creek

The Brewery Creek deposit is located 60 km east of 

Dawson in east-central Yukon, in the hanging wall of the 

Jurassic to Cretaceous Robert Service thrust fault (Diment, 

1996; Lindsay and others, 2000). The area is underlain by 

graptolitic shale, chert, mudstones, calcareous andesitic 

flows, tuffs and breccias, and siltstone of the Cambrian to 

Upper Devonian Road River Group, and argillite, silty shale, 

sandstone, graywacke, and limestone of the Earn Group 

(Diment and Craig, 1999; Lindsay and others, 2000). Granitic 

dikes and sills intrude these units and are the dominant ore 

host rocks. The deposit is characterized by an epizonal style 

of mineralization and is dated at 91 Ma (Lindsay and others, 

2000). The ore-bearing quartz veinlets and disseminated 

sulfide zones are continuous along strike for 12 km. The 

ore contains a few percent arsenopyrite and pyrite, with 

gold-enriched rims. Stibnite postdates the main phase of 

gold mineralization (Diment and Craig, 1999; Lindsay and 

others, 2000). The mineralogical characteristics result in a 

gold-arsenic-antimony signature. Strong carbonate alteration 

occurs along the mineralized zone. The deposit is presently 

being reclaimed. 

Fairbanks District

The deposits within the Fairbanks mining district 

included in this study are the Cleary Hill, True North, Scrafford, and Ryan Lode deposits. In addition, ground- and surface-water samples were collected throughout the city of Fairbanks, Alaska, area to determine the extent and environmental 

aspects of undeveloped fault- and shear-hosted disseminated 

sulfide zones concealed under Quaternary surficial materials. The mineral deposits of the Fairbanks mining district 

are hosted in a heterogeneous mixture of metasedimentary 

rocks that include quartz-muscovite schist, quartzite, chlorite 

quartzose schist, amphibolite schist, biotite schist, and marble 

of the Fairbanks Schist; slate, phyllite tuff, quartzite, calcareous schist, and marble of the Birch Hill sequence; and, in the 

case of True North, eclogite-bearing amphibolite and quartzite 

of the Chatinika terrane.

 The Cleary Summit area is located 30 km northeast of 

the city of Fairbanks and contains about 30 small, high-grade 

(about 10 grams/ton gold) historical lode mining operations, 

including the Hi-Yu, Chatham Creek, and McCarty deposits. 

The deposits of Cleary Hill are best described as shear-hosted 

orebodies, with veins occurring as open-space fractures dominated by massive white quartz with variable sulfide content 

(Metz, 1991; McCoy and others, 1997). Alteration minerals 

include quartz, sericite, calcite, and ankerite. 

The True North epizonal gold deposit is located 8 km 

north of the Cleary Hill mines. The ore zones are shallowly 

dipping and variably brecciated within the eclogitic rocks of 

the Chatinika terrane. Strong structural control is indicated by 

coincidence of ore zones with local thrust faults (Bakke and 

others, 2000). Gold occurs with fine-grained pyrite, arsenopyrite, and stibnite. In the developed oxidized zone, the pyrite 

and arsenopyrite have weathered to goethite and scorodite, 

respectively. Alteration minerals include quartz, manganese 

oxides, ankerite, mariposite, sericite, and graphite. The deposit 

is now abandoned and there is no reclamation.

The Scrafford deposit, located 18 km to the north of 

Fairbanks, was mined from 1915 to 1918 and was the second 

largest producing antimony mine in Alaska (Robinson and 

Bundtzen, 1982). Massive, fibrous stibnite occurs in blocks 

(about 3 m wide) within shear zones and in quartz stockwork 

veinlets (Robinson and Bundtzen, 1982). Minor arsenopyrite, 

gold, and galena are present within the lode. The shafts have 

since collapsed, leaving tailings piles and an open trench. 

The Ryan Lode deposit is 13 km west of Fairbanks. The 

ore zone consists of northeast-striking, subparallel shear zones 

along the margin of a 90 Ma granodiorite plug (McCoy and 

others, 1997). The ore is mixed oxide-sulfide and contains 

several percent arsenopyrite and stibnite. Alteration minerals 

include albite, sericite, ankerite, and calcite.

Kantishna Hills 

The Kantishna Hills mining district is located within the 

northwestern part of Denali National Park and Preserve. This 

district contains a number of gold- and antimony-bearing lode 

deposits, including Alaska’s largest past antimony producer, 

the Stampede mine, as well as occurrences along Slate Creek. 

The host rocks consist of Precambrian to Paleozoic chlorite 

and graphite schists, marble, and metavolcanic rocks of 

the Spruce Creek sequence and calcareous schist, marble, 

slate, phyllite, tuff, and quartzite of the Birch Creek schist 

(Bundtzen, 1981). The district is defined by a number of 
G4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

vein deposits that trend toward the northeast for greater than 

60 km, from Slate Creek in the southwest to Stampede in 

the northeast. Individual veins that make up the bulk of the 

orebodies in the area are structurally controlled along faults 

and range in width from 8 cm to greater than 9 m and range in 

length from 30 m to greater than 500 m. The orebodies at both 

Stampede and Slate Creek are composed predominately of 

massive stibnite. 

Donlin Creek

The Donlin Creek deposit is located 450 km northwest of 

Anchorage, in the Kuskokwim Mountains. The approximately 

70 Ma deposit consists of a hypabyssal dike-sill complex that 

intrudes the Kuskokwim Group sedimentary rocks (Miller and 

Bundtzen, 1994; Bundtzen and Miller, 1997). The gold occurs 

in north- to northeast-striking, steeply dipping quartz veins 

and veinlets with lesser dolomite that fill brittle extensional 

fractures in the rhyolite-rhyodacite porphyry dikes and sills. 

The gold is contained in arsenopyrite and rarely pyrite, and is 

refractory in nature (Szumigala and others, 2000). Late-stage 

stibnite, orpiment, realgar, cinnabar, and native arsenic are 

also present in small quantities (Goldfarb and others, 2004). 

Sericite and carbonate are common alteration minerals.

Sample Collection and Methods

A total of 196 surface-water samples, 65 ground-water 

samples, and 86 stream-sediment samples were collected 

from sites surrounding active mines, exploration targets, and 

unreclaimed and partially reclaimed sites, and areas in the 

vicinity of Fairbanks previously identified as having elevated 

ground-water arsenic concentrations (table G1, fig. G2). 

Detailed information regarding sample collection, analysis, 

quality assurance, and quality control can be found in Mueller 

(2002), Mueller and others (2002, 2003, 2004), and Verplanck 

and others (2003).

Ground-Water Samples

Three types of ground-water sites were sampled: individual domestic supply wells, ground-water 

monitoring wells, and drilling water-supply wells. In the case 

of domestic supply wells, a flow-through cell was connected 

to the plumbing system upstream of any household filtration or 

treatment systems. Water pH, specific electrical conductance, 

and temperature were monitored until all three readings 

stabilized, then a composite sample was collected in a 

sterilized 5-gallon bucket, from which a subset of samples was 

transferred into polypropylene bottles. The subset included 

the following samples: unfiltered-acidified (ultrapure nitric), 

filtered-acidified (0.45-micrometer (μm) disposable capsule 

filter and ultrapure nitric acid), filtered-unacidified (0.45-μm 

disposable capsule filter), and filtered-acidified (0.45-μm 

disposable capsule filter and ultrapure hydrochloric acid). All 

samples were refrigerated until analysis.

Surface-Water Samples

At surface-water sites (springs, seeps, and streams), pH, 

specific conductance, and temperature measurements were 

taken after the readings stabilized. Then, a representative 

sample was collected and a subset of samples transferred 

to polypropylene bottles and refrigerated until analysis (see 

above).

Table G1. Sampling locations, sample types, and number of samples collected for each location in this study.

Mining district Sample location

Number of samples

Surface water Ground water Stream

sediment

 Tombstone

 Fairbanks

 Kantishna

 Kuskokwim

Keno Hill

Brewery Creek

Fairbanks (city of)

Cleary Hill

True North

Scrafford Mine

Ryan Lode

Slate Creek

Stampede

Donlin Creek

14

13

27

9

6

6

22

18

81

1

40

2

10

132

4

2

14

7

7

6

22

3

18

12

Total 196 65 68

1

 Ground-water samples not associated with known mineralization.

2

 Monitoring wells.

3

 Analyses have not been completed on these samples as of this publication.

4

 Drilling supply wells. 
Surface-Water, Ground-Water, and Sediment Geochemistry of Epizonal and Shear-Hosted Mineral Deposits G5

A B

C D

Figure G2. Photographs of 

geologists performing data 

collection at various locations. 

A, Sampling the reclaimed 

area of Slate Creek, Kantishna 

Hills mining district, Denali 

National Park and Preserve. B, 

Sampling streams near Keno 

Hill, Yukon. C, Monitoring well 

sampling setup, Ryan Lode 

mine, Fairbanks, Alaska. D, 

Examining the Ryan Lode shear 

zone, Fairbanks, Alaska.

Sediment Samples

Bedload stream-sediment samples (less than 63-μm wet 

sieved onsite) were collected using a variation of the method 

described in Shelton and Capel (1994). This size fraction 

includes high surface area, reactive materials such as clays and 

iron and aluminum hydroxides that are likely associated with 

downstream transport of adsorbed or co-precipitated arsenic 

and antimony. Samples were split, with one portion air dried 

at room temperature for inductively coupled plasma–mass 

spectrometry (ICP-MS) analysis.

Results and Discussion

The information described herein is partially drawn and 

summarized from Mueller (2002), Mueller and others (2002, 

2003, 2004, 2005), and Verplanck and others (2003). 

Water Geochemistry

Generally, both ground and surface water can be 

classified as Ca-Mg-HC - dominated. Specific conductivity values show wide variation across the TGP (surface water 17–2,980 microsiemens per centimeter (μS/cm), 

ground water 170–2,940 μS/cm). Regardless of lithology, and 

absence or presence of permafrost, ground and surface waters 

associated with epizonal vein mineralization in the TGP have 

slightly acidic to slightly basic pH (5–8). Acid-rock drainage is 

generally not an issue with these types of deposits in the TGP 

because the metasedimentary host rocks are often calcareous; 

both gangue minerals and alteration products include calcite, 

ankerite, and dolomite, all of which contribute to a natural 

acid-neutralizing capacity within the vicinity of the deposits. 

Sediment Geochemistry

Elemental concentrations in stream sediments collected 

downstream from the gold deposits vary greatly. Arsenic, 

antimony, iron, and aluminum occur in relatively high 

concentrations (arsenic median=1670 ppm, maximum=10,000 

ppm; antimony median=192 ppm, maximum=7200 

ppm; iron median=5.9 percent, maximum=43 percent; 

aluminum median=8 percent, maximum=15 percent). Median 

concentrations for arsenic and antimony downstream from 

known lodes are at least an order of magnitude greater than in 

sediments from streams draining unmineralized areas.

Arsenic and Antimony Distribution and Mobility

Arsenic concentrations in surface-water samples from 

different deposits in the TGP range from below detection (less 

than 1 microgram per liter, μg/L) up to 380 μg/L (fig. G3A). 

The sampling locations with the highest surface-water arsenic 

concentrations were downstream from deposits at Slate Creek, 

undeveloped sulfidized shear zones in the Fairbanks area, 

Scrafford, Cleary Hill, and Brewery Creek. Surface-water 

antimony concentrations ranged from below detection (less 

than 2 μg/L) to 660 μg/L (fig. G3A). Antimony concentrations 

were significantly higher in streams draining the Slate 
G6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

W E

SURFACE WATER

DISSOLVED FRACTION,

IN MICROGRAMS PER LITER

GROUND WATER

DISSOLVED FRACTION,

IN MICROGRAMS PER LITER

STREAM SEDIMENT,

IN PARTS PER MILLION

700

100

200

300

400

500

600

1,400

200

400

600

800

1,000

1,200

10,000

2,000

4,000

6,000

8,000

A

B

C

0

0

0

Scrafford Mine

Cleary Summit

Brewery Creek

Keno Hill

Fairbanks

Keno Hill

Fairbanks Ryan Lode

Slate Creek Scrafford

Mine

Cleary

Hill

Brewery

Creek

Donlin Creek Slate Creek Stampede

Creek

True North

True North

Donlin

Creek

Donlin Creek

Arsenic

Antimony

Arsenic

Antimony

Arsenic

Antimony

Figure G3. Graphs showing arsenic and antimony concentrations. A, Dissolved (less than 0.45-micrometer (μm) 

fraction) arsenic and antimony concentrations in surface water from west to east across the Tintina Gold Province 

(TGP). B, Dissolved (less than 0.45-μm fraction) arsenic and antimony in ground water from west to east across 

the TGP. C, Arsenic and antimony concentrations in the less than 63 μm fraction of stream-sediment samples from 

west to east across the TGP. 
Surface-Water, Ground-Water, and Sediment Geochemistry of Epizonal and Shear-Hosted Mineral Deposits G7

Creek, Stampede Creek, and Scrafford deposits. Arsenic 

concentrations in stream sediments are relatively elevated 

in stream channels downstream from the Donlin Creek, 

Slate Creek and Scrafford deposits (fig. G3C). Antimony 

is significantly enriched in sediment samples near the Slate 

Creek and Scrafford deposits (fig. G3C). Proximity to the 

sulfide source has the greatest effect on the relative concentration of arsenic and antimony. Generally, areas with exposed 

ore and (or) tailings at or near the surface (for example, Slate 

Creek and Scrafford Mine) have higher surface and streamsediment concentrations of arsenic and antimony than do areas 

that have been revegetated naturally or by reclamation efforts 

(for example, Cleary Hill, Brewery Creek, and Keno Hill). 

The absolute concentrations of arsenic and antimony in 

sediments are relatively similar from a given mineral deposit 

area (fig. G3C). In contrast, corresponding surface-water 

samples contain significantly less arsenic than antimony 

(fig. G3A, C). Surface-water arsenic concentrations are not 

as high as surface-water antimony concentrations due to the 

fact that in these near-neutral-pH oxidizing environments, 

arsenic undergoes oxidation from the more mobile arsenite 

(As(III)) to arsenate (As(V)) and adsorbs effectively onto 

iron hydroxides (Smedley and Kinniburgh, 2002). In contrast, 

antimony, even as oxidized Sb(V), has an apparent lower 

affinity for adsorption to iron or aluminum hydroxides and, 

therefore, remains mobile in solution. Surface-water arsenic 

concentrations commonly decrease significantly (to below 

detection limits) within less than 1 km from the source, 

whereas antimony concentrations can remain significantly 

above detection limit for as far as 8 km from the source. 

Ground-water arsenic concentrations range from below 

detection (less than 1 μg/L) to 1.4 mg/L, with the highest 

concentrations being recorded in domestic water supply wells 

in the Fairbanks area (fig. G3B). Ground-water antimony 

concentrations are significantly lower than arsenic from all 

areas in the TGP, with concentrations ranging from below 

detection limit (less than 2 μg/L) to 60 μg/L. The highest concentrations of antimony in the Fairbanks area are in 

domestic supply wells and monitoring wells at the Ryan 

Lode deposit. The sources of the arsenic and antimony in the 

ground water are arsenopyrite and stibnite associated with 

subsurface shear- and fault-hosted sulfide zones. Both As(III) 

and As(V) are present in many of the ground-water samples. 

The presence of mixed arsenic species, along with the absence 

of acidic ground water, suggests that the source of arsenic in 

the ground waters is not the direct oxidation of arsenopyrite 

but rather the reductive dissolution of secondary oxide phases, 

such as arsenic adsorbed to iron hydroxides (see above 

discussion). 

Ground-water arsenic concentrations in the Fairbanks 

area have been observed to vary by orders of magnitude over 

short distances (less than 500 m). The distribution of elevated 

arsenic concentrations in ground water in the Fairbanks area 

suggests that developed mineral deposits are not a major 

source of the arsenic; rather, it appears that undeveloped 

fault- and shear-hosted disseminated sulfides may extend in a 

northeast-striking trend several kilometers away from known 

lode deposits and may be a major contributor to the anomalous 

arsenic.

Exploration

This study not only provides valuable information on 

the distribution and mobility of arsenic and antimony but 

also provides information that can be used in exploration 

for disseminated and shear-hosted mineralization styles 

of epigenetic gold deposits in the TGP. We have demonstrated that regardless of the state of development of a given 

deposit (historical, exploration target, current production), 

both arsenic and antimony are relatively enriched in 

stream sediments within and downstream from mineralized 

areas when compared to background stream-water and 

sediment samples. Antimony may be detectable in surface 

waters several kilometers downstream of a mineralized source, 

whereas arsenic in surface waters will increase closer to the 

mineralized source.

Conclusions

Arsenic and antimony are typically highly anomalous 

in the Cretaceous epizonal and shear-zone-related gold 

deposits within the TGP. The geochemistry of surface-water 

and stream-sediment samples suggests that arsenic mobility 

is restricted by oxidation and adsorption processes. Antimony appears to be more mobile, remaining in solution at 

elevated concentrations for several kilometers downstream 

from a known source. The exposure and proximity of the 

mineralization to the surface environment directly affects 

the concentrations in the stream sediments and waters. The 

concentration of arsenic in ground water, particularly in 

the Fairbanks, Alaska, area, reflects proximity to numerous 

sulfide-rich fault and shear zones. Arsenic concentrations in 

ground waters are also controlled by the reduction-oxidation 

reaction (redox) state of the ground water, with the more 

strongly reduced ground waters having higher arsenic concentrations. 

All of these aspects of arsenic and antimony 

geochemistry in the subsurface- and near-surface environment 

show that antimony and arsenic are useful pathfinder elements 

in exploration for epizonal and shear-related gold deposits 

within the TGP. Owing to the greater mobility of antimony, 

it could serve to more broadly target a mineralized zone, 

whereas arsenic could then conceivably be used to focus and 

target mineralized zones. 
G8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Acknowledgments

Vanessa Ritchie, Kunal Tanwar, Anastasia Ilgen, 

Dr. Rainer Newberry, Dr. Larry Hinzman (University of 

Alaska, Fairbanks), Dr. LeeAnn Munk (University of 

Alaska, Anchorage), Emily Youcha (Alaska Department of 

Environmental Conservation), Michael Lilly (GW Scientific), Marti Miller and Erin Marsh (U.S. Geological Survey), 

and Michelle Roller (formerly of Fairbanks Gold Mining, 

Inc.) provided assistance in planning and sample collection. Paul Briggs and Mike Anthony performed laboratory 

analyses. Additionally, we thank Fairbanks Gold Mining, Inc., 

NovaGold Resources, Inc., Avalon Gold Corp., Calista Corp., 

and Dr. Craig Hart and Mike Burke of the Yukon Geological 

Survey, and the National Park Service for property access and 

logistical support. We are grateful to the citizens of Fairbanks 

and Ester who volunteered their domestic wells for sampling.

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Surface-Water, Ground-Water, and Sediment Geochemistry of Epizonal and Shear-Hosted Mineral Deposits G9

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geologic map of the Iditarod quadrangle, Alaska, 

showing potassium-argon, major-oxide, trace-element, 

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water near Fairbanks, Alaska, with emphasis on arsenic 

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Briggs, P.H., McClesky, R.B., and Theodorakos, P.M., 

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the Donlin Creek gold deposit, southwestern Alaska: 

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and geology 2003: Whitehorse, Yukon, Canada, Yukon 

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Hart, C.J.R., and Newville, M., 2005, Antimony speciation 

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Scrafford antimony-gold lode deposit, Fairbanks mining 

district, Alaska: Alaska Division of Geological and 

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for analysis of trace elements and organic contaminants 

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an exploration tool in Keno Hill camp, Yukon Territory, 

Canada: Journal of Geochemical Exploration, v. 14, p. 1–24.

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source, behaviour and distribution of arsenic in natural 

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Geology and gold mineralization at the Donlin Creek 

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Geological and Geophysical Surveys Professional Report 

119, p. 91–115.

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Sanzolone, R.F., McClesky, R.B., Briggs, P.H., Roller, M., 

Adams, M., and Nordstrom, D.K., 2003, Chemical analyses 

of ground and surface waters, Ester Dome, central Alaska, 

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03–244, 40 p. (Also available online at http://pubs.usgs.gov/

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2000, Arsenic in groundwater of the United States; 

Occurrence and Geochemistry Groundwater, v. 38, no. 4, 

p. 589–604.

Landscape Geochemistry Near Mineralized 

Areas of Eastern Alaska

By Bronwen Wang, Larry P. Gough, Richard B. Wanty, James G. Crock, 

Gregory K. Lee, Warren C. Day, and Jim Vohden

Chapter H of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–H

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract........................................................................................................................................................H1

Introduction..................................................................................................................................................H1

Methods........................................................................................................................................................H3

Results and Discussion..............................................................................................................................H3

Aqueous Major-Ion Chemistry.........................................................................................................H3

Arsenic and Antimony in Soil and Selected Vegetation .............................................................H4

Summary.......................................................................................................................................................H6

References Cited.........................................................................................................................................H6

Figures

H1. Map showing site locations, simplified regional geology, and arsenic concentrations 

in bedrock and quartz veins, Pogo deposit region, eastern Alaska......................................... H2

H2. Map showing concentration and distribution of arsenic in stream water, Pogo deposit 

region, eastern Alaska..................................................................................................................... H5

H3. Shaded-relief maps showing the concentration and distribution of arsenic and gold 

in bed sediments, Pogo deposit region, eastern Alaska............................................................ H6

H4. Graph and diagram showing the major-ion characteristics of the water............................... H7

H5. Trilinear diagram showing the compositional range of the major ions for waters 

draining the intrusive and gneissic rocks, Pogo deposit region, eastern Alaska.................. H8

H6. Graphs showing arsenic and antimony concentrations of soil horizons, Pogo deposit 

region, eastern Alaska..................................................................................................................... H8

Tables

H1. Aqueous concentration ranges for selected regulated metals and corresponding 

State of Alaska Water Quality Criteria and Primary Drinking Water Standards............ H4

Landscape Geochemistry Near Mineralized Areas of 

Eastern Alaska

By Bronwen Wang,1 Larry P. Gough,1 Richard B. Wanty,1 James G. Crock,1 Gregory K. Lee,1 Warren C. Day,1

and Jim Vohden2

1

U.S. Geological Survey.

2

Alaska Department of Natural Resources, Division of Mining, Land, and 

Water.

Abstract

The Pogo lode gold deposit was discovered in eastern 

Alaska in the early 1990s and provided the opportunity 

to study elemental distribution and mobility in the natural 

environment prior to mine development. Studying 

mineralized systems prior to mining allows us to compare 

the natural biogeochemical signature in mineralized versus 

nonmineralized areas. The resultant data and interpretation 

also provide a baseline for evaluating what, if any, changes in 

elemental distribution result from development. This report 

investigates the chemistry of stream water, streambed sediment, and soil in the context of regional bedrock geology. The 

major-ion chemistry of the waters reflects a rock-dominated 

aqueous system, and the waters are classified as Ca2+ and 

Mg2+ - HC toCa2+ 2+

 and Mg - waters. Creeks draining 

the gneissic lithologies tend to be more sulfate dominated 

than those draining the intrusive units. Sulfate also dominated 

creeks draining mineralized areas; however, the underlying 

paragneiss unit could be contributing substantially to the 

sulfate concentration, and the sulfate concentration in these 

creeks may reflect a complex baltholith-paragneiss boundary rather than mineralization. Arsenic concentrations in 

bed sediments were elevated in mineralized areas relative 

to nonmineralized areas. Elevated concentrations of nickel, 

chromium, iron, manganese, and cobalt appear to reflect 

the presence of ultramafic rocks in the drainage. In general, aqueous metal concentrations were below the State of 

Alaska’s Aquatic Life Criteria and Drinking Water Standards, 

with the exception of arsenic in stream water, which ranged 

in concentration from less than 1 to 14 micrograms per liter 

(μg/L) and exceeded the drinking water standard at one site. 

The arsenic and antimony concentration in the A, B, and C 

soil horizons ranged from 3 to 410 milligrams per kilogram 

(mg/kg), 6.1 to 440 mg/kg, and 2 to 300 mg/kg, respectively, 

for arsenic and 0.4 to 24 mg/kg, 0.6 to 25 mg/kg, and 0.2 to 

16 mg/kg, respectively, for antimony. The arsenic and antimony concentrations in stream waters correlate well with the 

concentrations in soils. However, significantly less arsenic and 

antimony was extracted from C horizon soils in water leaching 

experiments, indicating that the arsenic and antimony in the 

C horizon is present in a less available form than in the A or 

B horizons. Arsenic and antimony uptake by grayleaf willow 

(Salix glauca L.) appears minimal, with arsenic concentrations ranging from less than 0.01 to 0.14 mg/kg and antimony 

concentrations ranging from less than 0.003 to 0.23 mg/kg 

in willow leaves. In general, the highest concentrations of 

both arsenic and antimony in water and soils were found 

near mineralized areas. Elevated arsenic concentrations were 

also found in bed sediments from mineralized areas. In these 

sample matrices, the presence of arsenic and (or) antimony 

was a good indicator of contact with mineralized rock units. 

Introduction

The Pogo vein gold deposit was discovered in the 

early 1990s (Smith and others, 1999). Because our work 

was implemented before the mine was developed, we were 

able to study elemental distribution and mobility in the 

natural, undisturbed environment. The Tintina Gold Province 

(TGP) study area is located in the subarctic boreal forest of 

east-central Alaska (fig. H1; see fig. 1 of the Editors’ Preface 

and Overview). The Pogo gold deposit, as well as other 

mineralized localities, is located within the study area. In 

1999, we had the opportunity to compare the effect of the 

Pogo deposit mineralization type and other area mineralization 

on the soil, sediment, and water geochemistry relative to nonmineralized areas prior to active mining. Studying mineralized 

systems prior to mine development allows us to investigate 

the natural hydrogeochemical and biogeochemical signatures 

in mineralized versus nonmineralized areas. The resultant data 

and interpretation also provide a baseline for evaluating what, 

if any, changes in elemental distribution result from mineral 

development. Our goals were (1) to define geochemical 
H2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Ddg

Ddg

Dag

Dag

Dag

Dag

Dag

Dag

Dag

Kgs

Kgs

Kgs

Kg

Kg

|um |um

Dog

Pzmg Kg

Tb Kg

Kg

Pzq

Kgru

Kdt

Kdt

Kgsp

Kgcd

Kgcd

Kg

Kg

Kg

Kgb

Kgb

Qac

Qac

Qac

Qac

Qac

Qac

Qac

Kgb

Kgb Dog

Dog

Dog

Dog

Dog

Dog Kgru

Kdt

Kdt

Approximate boundary of mineralized area

Approximate boundary of Pogo property

Location of rock sample and arsenic concentration

Arsenic in bedrock less than 2 milligrams per kilogram

Arsenic in bedrock more than 2 milligrams per kilogram

Arsenic in quartz vein more than 2 milligrams per kilogram

Arsenic in quartz vein less than 2 milligrams per kilogram

|mg

|mg

|mg

|um

|um

|q |q

|q

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|g

|g

|g

|g

|gn

Area of

mineralized

dikes

Shawnee Peak

Liese mineralized

zone

Mineralized area

6

29

57

California Creek B al rne Creek

Shawnee Creek

Sonora Creek

Central Creek

Oriental Creek

E wl ood Creek

Occidental Creek

Goodpaster River

Liese Creek

EXPLANATION

Alluvium and colluvium, undifferentiated (Quaternary)

Basalt (Tertiary)

Igneous rocks (Cretaceous)

Diorite and tonalite

Rocks of the Shawnee Peak intrusion

Granite of Swede Peak

Granite stock

Rocks of the Goodpaster batholith

Granitoid dike

Granitoid, undifferentiated

Metamorphic rocks (Devonian)

Augen gneiss

Diorite gneiss

Orthogneiss

Qac

Tb

Kdt

Kgsp

Kgs

Kg

Kgb

Kgcd

Kgru

Dag

Ddg

Dog

Metamorphic rocks (Paleozoic)

Mafic gneiss

Ultramafic gneiss

Quartzite

Paragneiss

Biotite gneiss

Biotite-sillimanite gneiss

|mg

|um

|q

|pg

|g

|gn

0 1 2 3 4 5 KILOMETERS

145° 144°45' 144°30'

64 30'

64 15'

°

°

Pacific Ocean

Alaska

Yukon

Northwest

Territories

British

Columbia

Location mapCANADA UNITED STATES

Study area

Figure H1. Site locations, simplified regional geology, and arsenic concentrations in bedrock and quartz veins, Pogo 

deposit region, eastern Alaska. 
Landscape Geochemistry Near Mineralized Areas of Eastern Alaska H3

signatures imparted to the aqueous, soil, and biogeochemical 

environments from geologic (mineralized and nonmineralized) 

substrates, and (2) to provide a predevelopment snapshot of 

the geochemical signatures in selected drainages.

The Yukon-Tanana Upland has a continental climate 

with cold winters and warm summers and low to moderate 

annual precipitation (Gough and others, 2005). The area is 

characterized by heavily vegetated mountain drainages with 

alpine tundra and rounded barren peaks at higher elevation. 

The small river drainages are densely vegetated with alder 

and willow, whereas the larger rivers, such as the Goodpaster 

River and Central Creek, have broad meandering channels with forested banks and numerous sandbars. Boreal 

forest vegetation of the region is composed of closed 

spruce-hardwood subarctic forest containing white and black 

spruce, paper birch, aspen, and balsam poplar. Alpine tundra 

of the region is composed of low shrubs (willow, birch, spirea, 

and high bush cranberry) and a ground cover of forbs, mosses, 

and lichens.

The area soils are classified primarily as Cryepts 

(Inceptisols) and Orthels (Gelisols) (Gough and others, 2005). 

Discontinuous permafrost is found throughout the region and 

was typically observed at 15 to 50 centimeters (cm) below the 

surface at the soil sample sites (Gough and others, 2005). Soils 

in the study area typically had distinguishable A, B, and C 

horizons. The A and B horizons were usually less than 10 cm 

thick. The A horizon was typically dark brown with abundant 

root penetration, while the B horizon was lighter and more 

reddish than the A horizon and had moderate root volume. The 

C horizon was about 20 cm below the surface and consists of 

fine to coarse sand with blocks of angular bedrock and few 

roots (Gough and others, 2005).

The regional geology is described in detail in Day and 

others (2003) and condensed here as figure H1. Paleozoic 

gneisses are the predominant lithologies, although the 

Goodpaster batholith occupies much of the north to 

northeastern region of the Big Delta B–2 quadrangle study 

area. Gold mineralization, such as that found on the Pogo 

deposit, is associated with various phases of the Cretaceous 

plutonic rocks, which intrude the gneissic units (Smith and 

others, 1999; Day and others, 2003). Mineralization is also 

associated with dikes found in the eastern edge of the study 

area (Day and others, 2003). 

Methods

Site selection, sampling, and analytical methods, as 

well as the complete analytical data for these samples, are 

given in detail in Gough and others (2005) and Wang and 

others (2006). Water and soil sites were selected on the basis 

of the regional geology and represent both mineralized and 

nonmineralized areas. Sites selected included (1) those that 

characterize the regional influence of the various lithologic 

units on the soil and water geochemistry and (2) downstream 

sequences designed to characterize the localized influence 

of mineralized areas, changes in lithology, or cross-cutting 

structural features. 

Results and Discussion

The elements Sb, As, Ba, Be, Cd, Cr, Cu, Pb, Hg, 

Ni, Se, Ag, Tl, and Zn are all those for which either Water 

Quality Criteria for Priority Toxic Pollutants and (or) 

Primary Drinking Water Standards are available (State of 

Alaska, 2003). Of these fourteen elements, Be, Cr, Se, Ag, 

and Tl were not detected in any of our samples, and Hg 

concentrations were not determined (Wang and others, 2006). 

The concentration ranges for Sb, As, Ba, Cd, Cu, Pb, Ni, and 

Zn and their relevant standards are given in table H1. Samples 

collected from one site exceeded the drinking water standard 

for As. The spatial distribution of As concentrations in water 

samples is shown in figure H2. Those samples with detectable 

As concentrations were typically found near mineralized areas. 

A similar pattern was found for Sb and, in general, detectable 

concentration of As and Sb were found only in samples 

adjacent to, or downstream from, mineralized areas (Wang and 

others, 2005). 

Bed sediments near mineralized areas also showed 

elevated As concentrations relative to nonmineralized areas. 

In bed sediments, Au and As correlated well, and the highest values of both were located along Liese and Occidental 

Creeks (fig. H3), Ni, Cr, Fe, Mn, and Co concentrations in bed 

sediment were also correlated. The greatest concentrations 

of these elements were located along Sonora Creek and may 

reflect the presence of ultramafic rock units in the area (Wang 

and others, 2005).

Aqueous Major-Ion Chemistry

On a plot of total dissolved solids versus the ratio of Na 

to Na plus Ca (Na/(Na+Ca)) in stream waters, the data points 

lie in the general region of rock-dominated systems as defined 

by Gibbs (1970) (fig. H4A), indicating that the composition of 

these samples is more rock dominated, as opposed to evaporation or precipitation dominated. The stream waters are classified primarily as Ca and Mg bicarbonate (Ca2+ and Mg2+ - 

HC ) to Ca and Mg sulfate (Ca2+ and Mg2+- ) (fig. H4B). 

Waters draining the gneissic and intrusive lithologies of the 

study area can be differentiated on the basis of their major-ion 

chemistry (Wang and others, 2005). Stream waters draining 

gneissic units are more dominated than those draining 

granitic units (fig. H5). Wang and others (2005) also found 

that the anionic composition of water in creeks draining the 

mineralized area was more dominated. However, they 

concluded that the underlying paragneiss unit in this region 

could be contributing substantially to the concentrations 

in these watersheds, and the increase in the concentration 
H4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

may reflect a complex batholith/paragneiss boundary rather 

than sulfide oxidation. 

Table H1. Aqueous concentration ranges for selected regulated metals and corresponding State of Alaska Water Quality Criteria and 

Primary Drinking Water Standards.

 [Abbreviations are as follows: mg/L, milligrams per liter; μg/L, micrograms per liter; mg/kg, milligrams per kilogram; –, not listed]

Element Concentration range 

(μg/L)

Aquatic life criteria for fresh waters Drinking water primary 

maximum contaminant 

level1

 (μg/L)

Acute Chronic 

(μg/L) (μg/L)

Sb

As

Ba

Cd

Cu

Pb

Ni

Zn

<0.1– 0.7

<1– 14

5.4 – 31.8

<0.02–0.04

<0.5– 2

< 0.09– 0.84

<0.45–3.3

<0.7–4.7

–

340

–

2.13*

14*

81.65*

469.16*

119.82

–

150

–

0.27*

9.33*

3.18*

52.16*

119.82

6

10

2,000

5

1,300*

–

–

–

1 Source: State of Alaska, Department of Environmental Conservation (2003).

*These aquatic life criteria (acute and chronic) are a function of the hardness of the water. Value given corresponds to a hardness of 100 mg/L calcium 

carbonate.

 **Human health criteria for noncarcinogens, for consumption of water plus aquatic organisms.

Arsenic and Antimony in Soil and Selected 

Vegetation 

The primary arsenic- and antimony-containing minerals 

in the mineralized areas are pyrite, loellingite, arsenopyrite, 

and other sulfide minerals (Smith and others, 1999). In 

soils, arsenic and antimony may be present in either residual 

primary mineral phases or in secondary weathering products 

formed during soil formation. The arsenic in the A, B, 

and C soil horizons ranged from 3 to 410 milligrams per 

kilogram (mg/kg), 6.1 to 440 mg/kg, and 2 to 300 mg/kg, 

respectively, whereas antimony concentrations in these 

horizons ranged from 0.4 to 24 mg/kg, 0.6 to 25 mg/kg, and 

0.2 to 16 mg/kg, respectively. The concentrations of arsenic 

and antimony among the soil horizons were highly correlated, 

and the concentrations of both typically increased in the order 

A < B < C horizon. Consequently, higher concentrations of 

arsenic and antimony in the A horizon were generally found in 

those soils with high concentrations in the B and C horizons 

(fig. H6). The greatest concentrations of both elements were 

generally found near mineralized areas (Wang and others, 

2007). The arsenic and antimony concentrations in stream 

waters collected near the soil sites correlate well with the 

total arsenic and antimony concentrations in the soils from 

all horizons (Wang and others, 2007); however, significantly 

less of the total arsenic and antimony in the C horizon was 

extractable in water leaching experiments compared to that 

extracted from the A and B horizon samples. The greater 

extractability of the arsenic and antimony in the A and B 

horizons indicates that a greater proportion in these horizons is present in more easily available forms. The lower 

extractability of the arsenic and antimony in the C horizon 

could arise if a greater proportion of the element is present 

in resistant primary mineral phases rather than on exchange 

surfaces (Wang and others, 2007). 

The arsenic and antimony data for the willow samples 

are highly censored, with nearly half of the samples falling 

below the detection limit. Arsenic concentrations in willow 

ranged from less than 0.01 to 0.14 mg/kg (dry weight) 

for leaves and less than 0.01 to 0.16 mg/kg for twigs. The 

concentration range of arsenic in willows is consistent with 

arsenic concentrations of plants grown in uncontaminated soil 

(Kabata-Pendias and Pendias, 2001) and may indicate minimal 

plant uptake even in the mineralized regions. Antimony 

concentrations in both the willow leaves and twigs ranged 

from less than 0.003 to 0.23 mg/kg and less than 0.002 to 0.05 

mg/kg, respectively. Arsenic and antimony concentrations in 

the leaves and twigs were correlated, but significantly more 

antimony is found in the leaves than in the twigs (Wang and 

others, 2007). Arsenic concentrations, however, did not differ 

between the twigs and leaves. Plant arsenic and antimony 

concentrations did not correlate with the A, B, and C soil 

horizon concentrations or the soil extractable concentrations. 

Lack of correlation between the plant concentrations and 

either the total or water-extractable soil concentrations also 

suggests the limited bioavailability of these elements within 

the system; however, the small number of data pairs coupled 

with the large amount of censored data made evaluation 

difficult.
Landscape Geochemistry Near Mineralized Areas of Eastern Alaska H5

Ddg

Ddg

Dag

Dag

Dag

Dag

Dag

Dag

Dag

Kgs

Kgs

Kgs

Kg

Kg

|um |um

Dog

|mg Kg

Kg Tb

Kg

Pzq

Kdt

Kgru

Kdt

Kdt

Kgsp

Kgcd

Kgcd

Kg

Kg

Kg

Kgb

Kgb

Qac

Qac

Qac

Qac

Qac

Qac

Kgb

Kgb Dog

Dog

Dog

Dog

Dog

Dog

Kgru

Kdt

|mg

|mg

|mg

|um

|um

|q |q

|q

|pg

|pg

|pg

gpg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|pg

|g

|g

|g

|g

|gn

Area of

mineralized

dikes

Shawnee

Peak

Liese

mineralized zone

Mineralized area

California Creek B al rne Creek

Shawnee Creek

Sonora Creek

Central Creek

Oriental Creek

E wl ood Creek

Occidental Creek

Goodpaster River

Liese Creek

7.2

2

2

2

2

3.7

14

4

8.6

2 2 2.7

4.4

7.7

6.9

2

3

4.2

3.4

2.1

2.5

EXPLANATION

Alluvium and colluvium, undifferentiated (Quaternary)

Basalt (Tertiary)

Igneous rocks (Cretaceous)

Diorite and tonalite

Rocks of the Shawnee Peak intrusion

Granite of Swede Peak

Granite stock

Rocks of the Goodpaster batholith

Granitoid dike

Granitoid, undifferentiated

Metamorphic rocks (Devonian)

Augen gneiss

Diorite gneiss

Orthogneiss

Qac

Tb

Kdt

Kgsp

Kgs

Kg

Kgb

Kgcd

Kgru

Dag

Ddg

Dog

2

Approximate boundary of mineralized area

Approximate boundary of Pogo property

Location of stream water sample and arsenic 

concentration

Arsenic in stream water less than 1 microgram per liter

Arsenic in stream water greater than 1 

microgram per liter—Numbers indicate 

values in micrograms per liter. Exceeds 

Alaska State Drinking Water Standards

Metamorphic rocks (Paleozoic)

Mafic gneiss

Ultramafic gneiss

Quartzite

Paragneiss

Biotite gneiss

Biotite-sillimanite gneiss

|mg

|um

|q

|pg

|g

|gn

0 1 2 3 4 5 KILOMETERS

145° 144°45' 144°30'

64 30'

64 15'

°

°

Pacific Ocean

Alaska

Yukon

Northwest

Territories

British

Columbia

Location mapCANADA UNITED STATES

Study area

Figure H2. Concentration and distribution of arsenic in stream water plotted on a simplified regional geology map, 

Pogo deposit region, eastern Alaska.
H6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Gold concentration

<0.027 ppm

0.028 to 0.056 ppm

0.057 to 0.084 ppm

0.085 to 0.113 ppm

0.114 to 0.142 ppm 

0.143 to 0.171 ppm

0.172 to 1.122 ppm

Arsenic concentration

<63 ppm

64 to 126 ppm

127 to 189 ppm

190 to 252 ppm

253 to 315 ppm 

A B

Central Creek

California Creek

Sonora Creek

Liese Creek

Occidental Creek

Shawnee

Peak

Elwood Cr.

Goodpasture

River

Central Creek

California Creek

Sonora Creek

Liese Creek

Occidental Creek

Shawnee

Peak

Elwood Cr.

Goodpasture

River

145° 144°45’ 144°30’ 64°30’

64°25’

64°20’

64°15’

145° 144°45’ 144°30’ 64°30’

64°25’

64°20’

64°15’

Figure H3. Shaded-relief maps showing the concentration and distribution of arsenic and gold in bed sediments, Pogo deposit region, 

eastern Alaska. A, Arsenic; B, Gold. ppm, parts per million.

Summary

In general, aqueous metal concentrations were below 

the Aquatic Life Criteria and Drinking Water Standards 

(State of Alaska, 2003); however, arsenic exceeded drinking water standards in one sample from a stream that 

drained a mineralized area. Both aqueous arsenic and 

antimony concentrations were greatest near mineralized 

areas, consistent with the oxidation of minerals, such as 

arsenopyrite, found in the region. The arsenic and antimony 

concentrations in stream waters correlated well with the total 

arsenic and antimony concentrations in the soils, but uptake 

by the vegetation examined appears minimal. Although the 

anionic composition of creeks draining the mineralized areas 

is also consistent with pyrite oxidation, the potential exists that 

the underlying paragneiss unit in this region is contributing 

substantially to the sulfate concentrations. Consequently, 

the presence of arsenic and (or) antimony in the water is the 

strongest indicator of a mineralizing influence in these waters. 

Bed sediments near mineralized areas also showed elevated 

arsenic concentrations relative to nonmineralized areas. Bed 

sediment arsenic concentrations were also highly correlated 

with gold concentrations, whereas nickel, chromium, iron, 

magnesium, and cobalt appear to reflect the presence of 

ultramafic rocks within the watershed.

References Cited

Day, W.C., Aleinikoff, J.N., Roberts, Paul, 

Smith, Moira, Gamble, B.M., Henning, M.W., 

Gough, L.P., and Morath, L.C., 2003, Geologic map 

of the Big Delta B–2 quadrangle, east-central Alaska: 

U.S. Geological Survey Geologic Investigations Series 

I–2788, 1 sheet, scale 1:63,360. (Also available online at 

http://pubs.usgs.gov/imap/i-2788/.)

Gibbs, R.J., 1970, Mechanisms controlling world water 

chemistry: Science, v. 170, no. 3962, p. 1088–1090.
Landscape Geochemistry Near Mineralized Areas of Eastern Alaska H7

Mg2+

SO4 0 1

Cl 0 - 1

HCO3 1 0

0 1

Ca2+ 1 0

Na+

 + K+ 1 0

Cl-

 + SO4 1 0

Ca2+ + Mg2+

1 0

2-

2-

-

B

1

10

100

1,000

10,000

0.00 0.50 1.00

Na/(Na+Ca)

Evaporation

dominance

Rock

dominance

Precipitation

dominance

ATOTAL DISSOLVED SOLIDS, IN MILLIGRAMS PER LITER

Figure H4. Graph and diagram showing the major-ion characteristics of the water. A, Graph showing total dissolved solids versus Na/

(Na+Ca) ratio. “Boomerang” envelope approximated from Gibbs (1970). B, Trilinear diagram showing the range of major-ion composition. 

Diamonds and squares are samples collected in 1999 and 2001, respectively.

Gough, L.P., Day, W.C., Crock J.G., Gamble, B.M., 

Henning, M.W., Ager, C.M., Meirer, A.L., Briggs, P.H., 

Brown, Z.A., and Adams, Monique, 2005, Regional 

geochemistry results from the analyses of rock, soil, and 

vegetation samples—Big Delta B–2 quadrangle, Alaska: 

U.S. Geological Survey Open-File Report 2005–1431, 

16 p., available only online at http://pubs.usgs.gov/

of/2005/1431/. (Accessed August 13, 2007.)

Kabata-Pendias A., and Pendias H., 2001, Trace elements in 

soils and plants: Boca Raton, Florida, CRC Press, 413 p.

Smith, Moira, Thompson, J.F.H., Bressler, Jason, Layer, Paul, 

Mortensen J.K., Abe, Ichiro, and Takaoka, Hidetoshi, 1999, 

Geology of the Liese zone, Pogo property, east-central 

Alaska: Society of Economic Geologists Newsletter, v. 38, 

p. 1, 12–21. 

State of Alaska, Department of Environmental Conservation, 

2003, Alaska water quality criteria manual for toxic and 

other deleterious organic and inorganic substances as 

amended through 15 May, 2003: Juneau, Alaska, State of 

Alaska Department of Environmental Conservation, 51 p. 

(Also available online at http://dec.state.ak.us/water/wqsar/

wqs/pdfs/70wqsmanual.pdf.) 

Wang, Bronwen, Gough, Larry, Wanty, Richard, Vohden, Jim, 

Crock, Jim, and Day, Warren, 2006, Water and sediment 

chemical data and data summary for samples collected 

in 1999 and 2001 in the Goodpaster River basin, Big 

Delta B–2 quadrangle, Alaska: U.S. Geological Survey 

Open-File Report 2006–1131, 18 p. (Also available online 

at http://pubs.usgs.gov/of/2006/1131/.)

Wang, B., Gough, L., Wanty R., Crock, J., Day, W., and 

Vohden, J., 2007, Landscape geochemistry near mineralized 

areas of eastern Alaska with a focus on As and Sb, in

Bullen, T.D., and Wang, Y., eds., Proceedings of the 12th 

International Symposium on Water-Rock Interaction: 

London, Taylor and Francis Group, p. 1513–1516.

Wang, Bronwen, Wanty, R.B., and Vohden, Jim, 2005, 

Geochemistry of surface-waters in mineralized and 

non-mineralized areas of the Yukon-Tanana Upland, in

Walton, Raymond, ed., Impacts of global climate change, 

Proceedings of the 2005 World Water and Environmental 

Resources Congress, Anchorage, Alaska, May 15–19, 

2005: Reston Va., American Society of Civil Engineers, 

p. 173–245.
H8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Figure H6. Graphs showing arsenic and antimony 

concentrations of soil horizons, Pogo deposit region, eastern 

Alaska. A, Arsenic, B, Antimony.

0 100 200 300 400 500

500

400

300

200

100

0

0 5 10 15 20

20

15

10

5

0

ARSENIC CONCENTRATION IN SOIL HORIZON A OR B,

IN MILLIGRAMS PER KILOGRAM

ARSENIC CONCENTRATION IN SOIL HORIZON B OR C,

IN MILLIGRAMS PER KILOGRAM

ANTIMONY CONCENTRATION IN SOIL HORIZON A OR B,

IN MILLIGRAMS PER KILOGRAM

ANTIMONY CONCENTRATION IN SOIL HORIZON B OR C,

IN MILLIGRAMS PER KILOGRAM

EXPLANATION

Comparison between soil horizons A and B

Comparison between soil horizons A and B

Comparison between soil horizons A and B

[for parts A and B]

A

B

Figure H5. Trilinear diagram showing the compositional range 

of the major ions for waters draining the intrusive and gneissic 

rocks, Pogo deposit region, eastern Alaska.

Range of waters draining instrusive rocks

Range of waters draining gneissic rocks

EXPLANATION

Mg2+

SO4 0 1

Cl 0 - 1

HCO3 1 0

0 1

Ca2+ 1 0

Na+

 + K+ 1 0

Cl-

 + SO4 1 0

Ca2+ + Mg2+ 1 0

2-

2-

-
Environmental Geochemical Study of Red 

Mountain—An Undisturbed Volcanogenic 

Massive Sulfide Deposit in the Bonnifield 

District, Alaska Range, East-Central Alaska

By Robert G. Eppinger, Paul H. Briggs, Cynthia Dusel-Bacon, Stuart A. Giles, 

Larry P. Gough, Jane M. Hammarstrom, and Bernard E. Hubbard

Chapter I of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project

Edited by Larry P. Gough and Warren C. Day 

Scientific Investigations Report 2007–5289–I

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract ........................................................................................................................................................ I1

Introduction .................................................................................................................................................. I1

Geology, Alteration, and Mineral Deposit Setting .................................................................................. I1

Methods......................................................................................................................................................... I2

Results and Discussion ............................................................................................................................... I2

Waters .............................................................................................................................................. I2

Sediments ........................................................................................................................................ I2

Precipitates ..................................................................................................................................... I4

REE in Water .................................................................................................................................... I4

Comparison With Mine Drainage Waters .................................................................................. I6

Comparison With Water Quality Standards ............................................................................... I6

Conclusions................................................................................................................................................... I7

Acknowledgments ....................................................................................................................................... I8

References Cited.......................................................................................................................................... I8

Figures

 I1. Generalized geologic map and sites for samples collected at the Red Mountain 

deposit, east-central Alaska ..................................................................................................... I3

 I2. Photographs showing precipitates in outcrop and alluvium at Red Mountain ................ I5

 I3. Graph showing cerium in Red Mountain filtered and acidified water compared 

to cerium from mine drainage and mineralized water from diverse deposit types 

from Argentina, Brazil, Canada, Spain, and the United States ........................................... I6

 I4. Ficklin diagram of pH versus the dissolved metals Cd + Co + Cu + Ni + Pb + Zn 

from filtered and acidified water samples .............................................................................. I7

Tables

 I1. Sulfide, hydroxysulfate, and unusual minerals identified in samples from Red 

Mountain detected by X-ray diffraction and scanning electron microscopy .................. I4

Environmental Geochemical Study of Red Mountain—An 

Undisturbed Volcanogenic Massive Sulfide Deposit in the 

Bonnifield District, Alaska Range, East-Central Alaska

By Robert G. Eppinger,1 Paul H. Briggs,1 Cynthia Dusel-Bacon,1 Stuart A. Giles,1 Larry P. Gough,1

Jane M. Hammarstrom,1

 and Bernard E. Hubbard1

1

U.S. Geological Survey.

Abstract 

The Red Mountain volcanogenic massive sulfide (VMS) 

deposit exhibits well-constrained examples of acid-generating, 

metal-leaching, metal-precipitation, and self-mitigation (via 

co-precipitation, dilution, and neutralization) processes that 

occur in an undisturbed natural setting, a rare occurrence in 

North America. The unmined pyrite-rich deposit displays 

a remarkable environmental footprint of natural acid 

generation, high metal concentrations, and exceedingly high 

rare-earth-element (REE) concentrations in surface waters. 

Dissolution of pyrite and associated secondary reactions under 

near-surface, oxidizing conditions are the primary causes for 

the acid generation and metal leaching. The deposit is hosted 

in Devonian to Mississippian felsic metavolcanic rocks of the 

Mystic Creek Member of the Totatlanika Schist.

Water samples with the lowest pH values, highest 

specific conductances, and highest major- and trace-element 

concentrations are from springs and streams within the 

quartz-sericite-pyrite alteration zone. Aluminum, As, Cd, Co, 

Cu, Fe, Mn, Ni, Pb, Y, and particularly Zn and the REEs are 

all found in high concentrations, ranging across four orders of 

magnitude. Waters collected upstream from the alteration zone 

have near-neutral pH values, lower specific conductances, 

lower metal concentrations, and measurable alkalinities. Water 

samples collected downstream of the alteration zone have 

pH values and metal concentrations intermediate between 

these two extremes. Stream sediments are anomalous in 

Zn, Pb, S, Fe, Cu, As, Co, Sb, and Cd relative to local and 

regional background abundances. Red Mountain Creek and its 

tributaries do not support, and probably never have supported, 

significant megascopic faunal aquatic life.

Introduction 

Environmental geochemical studies of a group of 

unmined volcanogenic massive sulfide (VMS) deposits in 

the Bonnifield mining district include a detailed study of the 

Red Mountain deposit, in the northern flank of the Alaska 

Range (see fig. 1 of Editors’ Preface and Overview). The 

Red Mountain deposit (also known as the Dry Creek deposit) 

displays a significant environmental footprint of natural 

acid generation, high metal concentrations, and remarkably 

high REE concentrations in surface waters. The deposit and 

its associated alteration halo are well exposed, allowing for 

sample collection above, within, and downstream of the 

mineralized rocks and surrounding alteration zone. Details on 

the physiography and biota at Red Mountain are presented by 

Gough and others (this volume, chap. J).

This study is important because it establishes a premining 

geochemical baseline of an exposed, unmined VMS deposit, 

a rare occurrence in North America. Data and interpretations from this study may be useful as natural analog data to 

previously developed VMS deposits in similar climatic settings where premining data do not exist.

Geology, Alteration, and Mineral 

Deposit Setting

The 26 known VMS prospects in the district occur 

within a greenschist-facies assemblage of metavolcanic and 

metasedimentary rocks of the Yukon-Tanana terrane. The 

volcanic rocks are Late Devonian to Early Mississippian 

(376–353 million years old, Ma) in age, compositionally 

bimodal, and were emplaced in an extensional setting, inferred 

to be the attenuating continental margin of ancestral North 

America (Dusel-Bacon and others, 2004, 2005; Dusel-Bacon 

and others, this volume, chap. B).

At Red Mountain, a 4-square-kilometer (km2

) 

quartz-sericite-pyrite alteration zone (QSPAZ) is characterized 
I2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

by prominent shades of red, maroon, orange, and yellow in 

outcrop and colluvium and by a general lack of vegetation. 

Although actively explored through 1998, the Red Mountain 

deposit has never been mined. Mineralized rocks lie within 

the Mystic Creek Member of the Totatlanika Schist (fig. I1; 

Newberry and others, 1997; Smit, 1999). 

Red Mountain is a pyrite-rich VMS deposit containing 

sphalerite, galena, chalcopyrite, and locally precious metals, 

as massive to semimassive sulfides. The deposit is tilted to the 

north, and subsequent erosion has exposed underlying quartz 

stockwork veins in pyrite-bearing altered footwall rocks and 

massive sulfide horizons in hanging wall rocks. Supergene 

oxidation of pyrite and ground-water flow are facilitated by 

the intensely fractured nature of the footwall and hanging wall 

rocks.

Methods

Bedload stream sediment, stream and spring water, or 

rock samples were collected at 36 sites in the vicinity of 

Red Mountain (fig. I1), under low-flow conditions during 

precipitation-free periods. Details on sample collection, 

analysis, quality assurance/quality control procedures used, 

and a listing of the analytical data are found in Giles and 

others (2007). Advanced Spaceborne Thermal Emission and 

Reflection Radiometer (ASTER) satellite data were used to 

identify the extent of altered bedrock at Red Mountain by indicating the distribution of ferric iron, illite-muscovite, kaolinite, 

smectite, and hydrous silica-jarosite (Eppinger and others, 

2007; Hubbard and others, this volume, chap. E). Secondary 

efflorescent salts and mineral precipitates that form in streambeds were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

At water sample sites, onsite measurements included pH, 

specific conductance, alkalinity, acidity, dissolved oxygen, 

water temperature, ferrous iron, turbidity, and a qualitative 

estimate of discharge. A representative water sample was 

collected at each site, filtered (0.45 micrometer, μm), and 

acidified with ultrapure nitric acid. Unacidified water samples 

were refrigerated prior to analysis. Samples were analyzed 

by inductively coupled plasma–atomic emission spectroscopy (ICP-AES), ICP-mass spectrometry (ICP-MS), and ion 

chromatography.

Bedload stream sediment samples were collected 

at 20 sites. Sieved samples were analyzed by ICP-AES, 

ICP-MS, and several element-specific methods. For the water 

and sediment samples, site duplicates, analytical duplicates, 

blanks, and reference standards comprised approximately 15 

percent of the samples analyzed.

Results and Discussion

The information described herein is summarized from 

Eppinger and others (2004, 2007).

Waters

Surface and spring water samples were collected from 

within (19 samples), upstream of (8 samples), and downstream 

of the QSPAZ (6 samples). With respect to major ions, the 

waters are largely dominated by sulfate and intermediate with 

respect to calcium and magnesium. High concentrations of 

aluminum, iron, and sulfate are found in water samples within 

and downstream of the QSPAZ.

Water pH values range from 2.4 to 7.8. Waters upstream 

of the QSPAZ are all near-neutral, while those within the 

QSPAZ generally have pH values below 3.5. Specific 

conductances upstream of the QSPAZ are lowest, ranging from 370 to 830 microsiemens per centimeter (μS/cm), 

rise significantly in waters within the QSPAZ (commonly 

above 2,500 μS/cm; maximum = 4,800 μS/cm), and fall to 

580 μS/cm upon mixing with surrounding streams. Below 

the QSPAZ, pH values remain low to the mouth of Red 

Mountain Creek (pH 4.2), about 2.5 kilometers (km) downstream, but pH quickly rises to 7.1 after mixing with the 

alkaline, glacial-silt-laden stream water of Dry Creek.

Trace elements in water that exhibit the widest variation, 

spanning four or more orders of magnitude, include Al, As, 

Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn, La, Ce, Pr, Nd, Sn, and Y. 

Extremely high concentrations are found for Zn (median 

13,000 micrograms per liter (μg/L), maximum=240,000 μg/L), 

Mn (median=4,200 μg/L, maximum=49,000 μg/L), and the 

summed REEs (median=3,200 μg/L, maximum=59,000 μg/L). 

In all cases, the highest trace-metal concentrations are found 

in springs and streams having low pH and high specific conductance, all within or downstream of the QSPAZ. Elements 

exhibit low concentrations above the QSPAZ, very high concentrations within and downstream of the QSPAZ, and rapid 

attenuation via co-precipitation, sorption, and dilution upon 

mixing with water from Dry Creek.

Sediments

Elemental abundances in stream sediments vary 

across one to two orders of magnitude. Zinc, Pb, 

S, and Fe are found in relatively high concentrations 

(Zn median=440 parts per million (ppm), maximum=2,300 

ppm; Pb median=71 ppm, maximum=410 ppm; S 

median=0.39 percent, maximum=1.2 percent; Fe median=4.8 

percent, maximum=30 percent), with median concentrations 

that are about an order of magnitude above those expected for 

average granitic or local Mystic Creek Member background 

rocks. Other elements found in high concentrations relative to 

these background rocks include As, Cd, Cu, Co, Mn, Mo, Sb, 
Environmental Geochemical Study of Red Mountain, Alaska Range, East-Central Alaska I3

Dry Creek

Foster Creek

Megans Draw

Red

Mountain Creek

Lago Creek

Red Mountain

Tu

Tu

Tu

Tu

Tu

Tu

Tu

Tu

Tu

Tb

Tb

Tc

Tc Tc

MDts

MDts

MDts

MDts

MDts

MDts

MDtm

MDtm

MDtm

MDtm

MDtm

MDtm

MDtmt

MDtmt

MDtmt

MDtmt

MDtmt

MDtmt

MDtmt

MDtc

MDtc

MDtc

MDtc

MDtc

MDtcc

MDtcc

MDtcc

MDtcc

MDtmc

MDtmc

Dk

Dk

Dk

MDtm

Sedimentary rocks, undifferentiated (Tertiary)

Basalt dike (Tertiary)

Coal-bearing rocks, undifferentiated (Tertiary)

Totatlanika Schist (Lower Mississippian to Upper Devonian)

Sheep Creek Member—Metasedimentary and metavolcanic rocks

Mystic Creek Member—Metavolcanic rocks and graphitic phyllites

Rhyolite dike(?) and (or) welded tuff

Chute Creek Member—Mafic metavolcanic rocks

California Creek Member—Felsic metaporphyry and augen gneiss

Moose Creek Member—Felsic to mafic metavolcanic rocks and schist

Keevy Peak Formation (Devonian)—Phyllite and quartzite

Contact

Fault

Syncline

Approximate extent of visible alteration

Sample location

EXPLANATION

0 1 KILOMETER

63°57’

63°54’

147°26’ 147°20'

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

Figure I1. Generalized geologic 

map and sites for samples 

collected at the Red Mountain 

deposit, east-central Alaska. 

Regional geology from Gilbert 

(1977). Topographic map of this 

general area is provided elsewhere 

in this report (Gough and others, 

this volume, chap. J). The feature 

names, Foster Creek, Lago Creek, 

and Megans Draw are all local 

names.
I4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Table I1. Sulfide, hydroxysulfate, and unusual minerals 

identified in samples from Red Mountain detected by X-ray 

diffraction and scanning electron microscopy. 

Mineral Formula

Sulfides

Chalcopyrite

Galena

Pyrite

Sphalerite

CuFeS2

PbS

FeS2

ZnS

Hydroxysulfates

Alunogen

Goslarite

Gypsum

Halotrichite

Hexahydrite

Hydronium jarosite

Jarosite

Kalinite

Melanterite

Natrojarosite

Pentahydrite

Pickeringite

Schwertmannite

Slavikite

A12(SO ) • 17H O 4 3 2

ZnSO • 7H O 4 2

CaSO • 2H O 4 2

Fe2+Al2(SO ) • 22H O 4 4 2

MgSO • 6H O 4 2

(H O)Fe (SO ) (OH) 3 3 4 2 6

KFe (SO ) (OH) 3 4 2 6

KAl(SO ) • 11H O 4 2 2

FeSO • 7H O 4 2

NaFe (SO ) (OH) 3 4 2 6

MgSO • 5H O 4 2

MgAl2(SO ) • 22H O 4 4 2

(Fe3+) O OH (SO ) 16 16 12 4 2

NaMg (Fe3+) (SO ) (OH) 2 5 4 7 6 • 33H O2

Oxyhydroxides

Ferrihydrite

Goethite

5Fe O • 9H O or Fe O 2 3 2 2 3

2.6H2O

α-Fe3+O(OH)

 • 2FeOOH • 

Carbonates/Halides/Oxifluorides

Bastnäsite(?)1

Häleniusite(?)1

(Ce,La)(CO )F3

(La,Ce)OF

1

Identification uncertain.

Se, Tl, and V. This suite generally agrees with the anomalous 

metals found in mineralized rock samples. Cerium and La 

concentrations in stream sediments have moderately elevated 

medians that are near those for local background rocks, likely 

a reflection of the intrinsically high REE concentrations found 

throughout peralkaline metarhyolites of the Mystic Creek 

Member (Dusel-Bacon and others, 2004).

Precipitates

Efflorescent salt precipitates are common in protected 

bedrock areas within the QSPAZ and downstream along 

the edges of the creeks (fig. I2A, B). Mineral precipitates 

identified by XRD and SEM include a variety of Fe-, Al-, 

Mg-, K-, and Na-hydroxysulfate and oxyhydroxide minerals 

(table I1). These minerals are all compositional endmembers 

of pseudo-stable secondary minerals and are products of 

oxidative pyrite dissolution and coincident acid rock drainage. 

The presence of these various efflorescent salts indicates 

mobility of the above elements in the weathering environment. 

Ferricrete (Fe-oxyhydroxide-cemented alluvium) up to several 

meters thick actively cements alluvium in creek beds within 

lower pH portions of the QSPAZ (fig. I2C). As stream pH 

rises downstream from the low-pH zones, milky white to tan, 

amorphous aluminum floc forms centimeter-thick gels in calm 

stretches to the mouth of Red Mountain Creek (fig. I2D).

REE in Water

The summed (∑) REE concentrations in water samples 

upstream of the QSPAZ range from 0.5 to 10 times the 

average background concentration in river waters worldwide 

listed in Martin and Whitfield (1983). Extreme concentrations 

of ∑ REEs are found in waters within and downstream of the 

QSPAZ, where all but four of the water samples have ∑ REE 

concentrations that are greater than 10,000 times background. 

Several spring samples within the QSPAZ have ∑ REE 

concentrations of greater than 100,000 times background.

Profiles for REEs in waters from the QSPAZ, normalized 

to the North American shale composite (NASC), indicate 

moderately light REE enrichment but are overall exceedingly 

high at 0.01 to 0.5 times NASC. Normally, REE profiles 

for natural waters are around 10-6 times NASC, and mine 

drainage profiles rarely exceed 10-3 times NASC. Preliminary SEM investigation of the source of the REEs in the 

felsic metavolcanic rocks reveals a micron-scale Ce-La-F-O 

accessory mineral that is tentatively identified as the carbonate 

mineral bastnäsite (table I1; fig. I2E). Accessory bastnäsite 

likely is being preferentially dissolved by acidic ground water, 

resulting in light REE enrichment in the spring and stream 

waters in the QSPAZ. The premise that accessory minerals in 

host rocks rather than mineralized horizons are the source of 

the REEs is supported by two facts: (1) the waters containing 

high REE concentrations are widespread throughout the 

alteration zone, not confined to mineralized horizons, and 

(2) sulfide-rich rock samples from the mineralized horizons do 

not contain Ce and La in concentrations above those of local 

background rocks.

A plot of pH versus cerium illustrates the high 

light-REE concentrations in Red Mountain waters in a 

global context (fig. I3). Presented for comparison are 

data from 300 waters representing mine drainage, natural 

mineralized areas, and active volcanic systems, all from 

various mineral deposit types including VMS, sedimentary exhalative (SEDEX), copper-molybdenum porphyry, 

polymetallic vein, replacement, and skarn deposits, and from 

the hyperacidic (pH <1) Copahue Volcano in Argentina. 

Cerium concentrations from waters within and downstream 

of the QSPAZ at Red Mountain are at the upper end of the 
Environmental Geochemical Study of Red Mountain, Alaska Range, East-Central Alaska I5

A

B

C D

E

Figure I2. Photographs showing precipitates in outcrop and 

alluvium at Red Mountain. A, Salts under protected outcrop 

overhang adjacent to Red Mountain Creek. Minerals identified 

by X-ray diffraction include the water-soluble, acid-generating 

hydroxysulfates halotrichite (Fe, Al), pickeringite (Mg, Al), kalinite 

(K, Al), hexahydrite (Mg), melanterite (Fe), and alunogen (Al). 

B, Bright orange-tan precipitate is dominantly the metastable 

Fe-hydroxysulfate schwertmannite. This metalliferous spring 

along Lago Creek (local name) has a pH of 2.4 and specific 

conductance of 3,000 microsiemens per centimeter (μS/cm). 

The black organism growing just above the waterline is the 

unusual liverwort Gymnocolea inflata, which thrives in the low-pH 

waters (Gough and others, this volume, chap. J). C, Ferricretecemented alluvium in Foster Creek (local name) where spring 

merges with stream. Spring pH is 3.4 and specific conductance 

is 2,900 μS/cm. D, Amorphous aluminum floc settled in calm part 

of Red Mountain Creek below alteration zone. Stream pH is 4.6 

and specific conductance is 1,200 μS/cm. Floc thickness locally 

reaches several centimeters. E, Scanning-electron microscopy 

photomicrograph of Ce-La-F-O accessory mineral (bastnäsite?) in 

polished thin section of Mystic Creek Member metarhyolite from 

the Red Mountain area.
I6 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Red Mountain waters—33 samples

Within alteration zone—19 samples

Downstream of alteration zone—6 samples

Upstream of alteration zone—8 samples

Other waters—300 samples from Argentina, Brazil, Canada, 

Spain, and the United States

Diverse mine drainage

Natural, mineralized

Copahue Volcano, Argentina

EXPLANATION

0.001

0.01

0.1

1

10

100

1,000

10,000

100,000

1 2 3 4 5 6 7 8 9 10

pH

CERIUM, IN MICROGRAMS PER LITER

Figure I3. Cerium (in 

micrograms per liter) in Red 

Mountain filtered and acidified 

water compared to cerium from 

mine drainage and mineralized 

water from diverse deposit 

types from Argentina, Brazil, 

Canada, Spain, and the United 

States. For data references, 

see Eppinger and others (2007).

cluster of samples at all pH levels and are among the highest 

concentrations found in the literature. Clearly the REE 

concentrations at Red Mountain are unique and exceedingly 

high. More work is needed to identify additional REE-bearing 

mineral phases at Red Mountain.

Comparison With Mine Drainage Waters

Spring and stream waters from Red Mountain are similar 

in composition to mine drainage waters found elsewhere 

in the United States, as illustrated in the Ficklin diagram 

(Plumlee and others, 1999) of pH versus the sum of the metals 

Cd+Co+Cu+Ni+Pb+Zn (fig. I4). The 125 mine drainage 

waters in the figure are from the above-listed mineral deposit 

types. Samples collected upstream of the QSPAZ plot in 

the near-neutral and low-metal-concentration field, whereas 

samples collected within and downstream of the QSPAZ 

plot in the acid to high-acid and high- to extreme-metal 

concentration fields. Many of the comparison mine drainage samples that plot in the same portion of the diagram are 

from Kuroko and SEDEX massive sulfide deposits (Plumlee 

and others, 1999), emphasizing that the composition of the 

natural spring and stream waters at Red Mountain mimic 

metalliferous acid mine drainage.

Comparison With Water Quality Standards

Water samples were compared to established potable 

water maximum contaminant level (MCL) standards listed 

by the Alaska Department of Environmental Conservation 

(2003a,b) and U.S. Environmental Protection Agency (2003). 

The median concentrations in Red Mountain waters exceed 

the established MCLs for , Al, Fe, Zn, Mn, Cd, Pb, 

total dissolved solids (TDS), and pH, indicating that most 

of the natural stream and spring waters are not potable. The 

water samples were also compared to freshwater quality 

standards for aquatic life listed by the Alaska Department of 

Environmental Conservation (2003a,b). Nearly all sampled 

streams and springs within and downstream of the QSPAZ 

exceed these standards for Al, Cd, Cu, Pb, and Zn and 

many exceed the standards for As, Fe, Ni, and Se. Element 

concentrations in stream sediment samples were compared to 
Environmental Geochemical Study of Red Mountain, Alaska Range, East-Central Alaska I7

Red Mountain waters—33 samples

Within alteration zone—19 samples

Downstream of alteration zone—6 samples

Upstream of alteration zone—8 samples

Diverse mine drainage waters—125 samples

EXPLANATION

1

pH

-1 0 1 2 3 4 5 6 7 8 9

0.0001

0.001

0.01

0.1

10

100

1,000

10,000

100,000

High acid, high metal

High acid, low metal

Acid, high metal

Ultra acid, extreme

metal

High acid, extreme

metal

Acid, extreme metal Near neutral, extreme metal

Near neutral, high metal

Acid, low metal Near neutral, low metal

Ultra acid, ultra

metal High acid, ultra metal

SUM Cd+Co+Cu+Ni+Pb+Zn, IN MILLIGRAMS PER LITER

Figure I4. Ficklin diagram 

of pH versus the dissolved 

metals Cd+Co+Cu+Ni+Pb+Zn 

(in milligrams per liter) from 

filtered and acidified water 

samples. Comparison mine 

drainage waters are from 

diverse mineral deposits in 

the United States (data from 

appendix of Plumlee and 

others, 1999).

guidelines for freshwater ecosystems (MacDonald and others, 

2000). The guidelines are exceeded for As, Cd, Cu, Ni, Pb, 

and Zn in most sediment samples, suggesting that the stream 

sediment is inhospitable to benthic organisms, using this 

standard.

Conclusions

The Red Mountain deposit is a well-constrained example 

of acid-generating, metal-leaching, metal-precipitation, and 

self-mitigation processes that occur in an undisturbed natural setting. Dissolution of pyrite and associated secondary 

reactions under near-surface, oxidizing conditions are the 

primary causes for the acid generation and metal leaching of 

the rocks at Red Mountain. However, the acidic waters mix 

with surrounding alkaline waters that have interacted with 

carbonate veinlets, resulting in self-mitigation (via dilution, 

neutralization, and attendant co-precipitation). This process 

limits downstream hydrogeochemical evidence of the deposit 

to within a few kilometers. Red Mountain Creek and its 

tributaries within the QSPAZ do not support, and probably 

never have supported, significant megascopic faunal aquatic 

life, except perhaps those organisms that have adapted to 

the extreme environment of low pH and very metalliferous 

conditions.

Water geochemistry varies widely, largely as a function of the local geologic setting. Samples with the lowest pH values, highest specific conductance, highest TDS 

concentrations, and highest major- and trace-element concentrations are all from springs and streams within the QSPAZ. 

Samples collected upstream of the QSPAZ have near-neutral 

pH values, lower specific conductance, lower metal concentrations, and measurable alkalinities. Water samples collected 

downstream of the QSPAZ have pH values and metal concentrations intermediate between these two extremes. As demonstrated here, an understanding of the local geologic setting 

is of first-order importance for environmental geochemical 

studies.

Some of the metals found enriched in waters within the 

QSPAZ, such as Fe, Zn, Pb, Cd, and Co, are directly related 

to dissolution of sulfides and associated secondary minerals. 

The high concentrations of REEs in these waters are a result 

of ground-water interaction with Mystic Creek Member felsic 

metavolcanic rocks that are intrinsically elevated in REEs due 

to their peralkaline composition. REE enrichment is considerably enhanced by the presence and selective dissolution of 

accessory REE minerals, such as bastnäsite, by dissociated 

sulfuric acid-rich ground water. High concentrations of Al, 
I8 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Mg, F -, K, Mn, and Si in the waters, and extensive mineral precipitates, ferricrete, and Fe and Al flocs in the lower 

reaches of the creeks are all indications of extensive supergene 

bedrock dissolution. The oxidation of pyrite and associated 

acid generation are enhanced by the dense fault and fracture 

network, the extensively exposed QSPAZ, and the relative 

abundance of shallow ground water. Any future exploration 

and exploitation of the Red Mountain VMS deposit needs 

to include a thorough recognition and understanding of the 

deposit’s great acid-generating and metal-liberating potential.

At the mouth of Red Mountain Creek, about 2.5 

km below the QSPAZ, stream water is acidic (pH is 4.2) 

and metalliferous. In contrast, Dry Creek, both upstream 

and just 0.3 km downstream of the confluence with Red 

Mountain Creek, is near neutral, alkaline, and relatively 

nonmetalliferous. The neutralization and reduction of metals 

are attributed to dilution by, and the acid-consuming capability 

of, Dry Creek, a relatively large, turbid, glacial flour-rich creek 

that drains rock types with high acid-neutralizing capacities. Red to orange iron-oxide staining on alluvium (with 

co-precipitated metals) is prominent along Red Mountain 

Creek within and downstream of the QSPAZ and continues 

down Dry Creek for about 1.5 km. Beyond this point, weaker 

hues of red and orange continue for another 0.5 km. The 

extreme hydrogeochemical and visual indications that characterize the Red Mountain VMS deposit appear to be largely 

self-mitigating within a few miles downstream of the deposit.

Acknowledgments

Thanks are given to the following U.S. Geological Survey employees: Melanie Hopkins and Cameron 

Rombach for help with sample collection; Monique Adams, 

Mike Anthony, Phil Hageman, Pete Theodorakos, and 

Ruth Wolf for laboratory analyses; Steve Sutley for X-ray 

diffraction; Phil Zelenak for drafting; and Robert Oscarson for 

SEM imaging and mineral identification. Ed and Megan Busby 

provided excellent food and lodging in a wilderness setting at 

Busby’s Camp. Pilot Arnie Johnson of Johnson Flying Service 

provided helicopter logistical support. Reviews by David Fey 

and Bill Langer significantly improved the manuscript.

References Cited

Alaska Department of Environmental Conservation, 

2003a, Water quality standards: Alaska Department of 

Environmental Conservation Report 18–AAC–70, 54 

p. (Also available online at http://www.dec.state.ak.us/

regulations/pdfs/70mas.pdf.)

Alaska Department of Environmental Conservation, 2003b, 

Alaska water quality criteria manual for toxic and other 

deleterious organic and inorganic substances: Alaska 

Department of Environmental Conservation, 51 p. (Also 

available online at http://www.dec.state.ak.us/water/wqsar/

wqs/pdfs/70wqsmanual.pdf.)

Dusel-Bacon, Cynthia, Premo, W.R., and Aleinikoff, J.N., 

2005, Geochemical and Nd isotopic evidence for an 

extending continental-margin arc/back arc setting for 

peralkaline rhyolite-hosted massive sulfide deposits of the 

Bonnifield district, east-central Alaska [abs.]: Geological 

Society of America, Abstracts with Program, v. 37, no. 7, 

p. 97.

Dusel-Bacon, Cynthia, Wooden, J.L., and Hopkins, M.J., 

2004, U-Pb zircon and geochemical evidence for bimodal 

mid-Paleozoic magmatism and syngenetic base-metal 

mineralization in the Yukon-Tanana terrane, Alaska: 

Geological Society of America Bulletin 116, p. 989–1015.

Eppinger, R.G., Briggs, P.H., and Dusel-Bacon, Cynthia, 

2004, Environmental geochemistry of an undisturbed 

volcanogenic massive sulfide deposit, Red Mountain, Bonnifield mining district, east-central Alaska, in

Wanty, R.B., and Seal, R.R., II, eds., Water-rock interaction, 

Proceedings of the Eleventh International Symposium 

on Water-Rock Interaction, Saratoga Springs, N.Y., 

June 27–July 2, 2004: London, Taylor and Francis Group 

Publishers, p. 1483–1487.

Eppinger, R.G., Briggs, P.H., Dusel-Bacon, Cynthia, 

Giles, S.A., Gough, L.P., Hammarstrom, J.M., and 

Hubbard, B.E., 2007, Environmental geochemistry at 

Red Mountain, an unmined volcanogenic massive sulphide 

deposit in the Bonnifield district, Alaska Range, east-central 

Alaska: Geochemistry: Exploration, Environment, Analysis, 

v. 7, no. 3, p. 207–223.

Gilbert, W.G., 1977, General geology of Healy D–1 and 

southern Fairbanks A–1 quadrangles and vicinity, Alaska: 

Alaska Division of Geological and Geophysical Surveys 

Open-File Report 105, 13 p., 2 sheets, scale 1:63,360.

Giles, S.A., Eppinger, R.G., Granitto, Matthew, Zelenak, P.P., 

Adams, M.G., Anthony, M.W., Briggs, P.H., Gough, 

L.P., Hageman, P.L., Hammarstrom, J.M., Horton, J.D., 

Sutley, S.J., Theodorakos, P.M., and Wolf, R.E., 2007, 

Geochemical data for stream-sediment, surface-water, 

rock, and vegetation samples from Red Mountain (Dry 

Creek), an unmined volcanogenic massive sulfide deposit 

in the Bonnifield district, Alaska Range, east-central 

Alaska: U.S. Geological Survey Data Series DS–204, 64 p., 

1 CD-ROM. (Also available online at http://pubs.usgs.gov/

ds/2006/204/.)
Environmental Geochemical Study of Red Mountain, Alaska Range, East-Central Alaska I9

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, 

Development and evaluation of consensus-based sediment 

quality guidelines for freshwater ecosystems: Archives of 

Environmental Contamination and Toxicology, v. 39, no. 1, 

p. 20–31.

Martin, J.M., and Whitfield, Michael, 1983, The significance 

of the river input of chemical elements to the ocean, in

Wong, C.S., Boyle, E.A., Bruland, K.W., Burton, J.D., and 

Goldberg, E.D., eds., Trace metals in sea water: New York, 

Plenum Press, p. 265–296.

Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., 

Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive sulfide deposits of Alaska, in Goldfarb, R.J., and 

Miller, L.D., eds., Mineral deposits of Alaska: Economic 

Geology Monograph 9, p. 120–150.

Plumlee, G.S., Smith, K.S., Montour, M.R., Ficklin, W.H., and 

Mosier, E.L., 1999, Geologic controls on the composition 

of natural waters and mine waters draining diverse 

mineral-deposit types, in Filipek, L.H., and Plumlee, G.S., 

eds., The environmental geochemistry of mineral deposits, 

part B, Case studies and research topics: Reviews in 

Economic Geology, v. 6B, p. 373–432.

Smit, Hans, 1999, The Dry Creek VMS project, Bonnifield 

district, central Alaska, in Pathways ‘99, Extended abstracts 

volume: Vancouver, British Columbia, Canada, British 

Columbia and Yukon Chamber of Mines, p. 17–18.

U.S. Environmental Protection Agency, 2003, National 

primary drinking water standards: U.S. Environmental 

Protection Agency Report EPA 816–F–03–016. (Also 

available online at http://www.epa.gov/safewater/mcl.html.) 

The Biogeochemistry and Occurrence 

of Unusual Plant Species Inhabiting 

Acidic, Metal-Rich Water, Red Mountain, 

Bonnifield District, Alaska Range

By Larry P. Gough, Robert G. Eppinger, and Paul H. Briggs

Chapter J of

Recent U.S. Geological Survey Studies in the Tintina Gold Province, 

Alaska, United States, and Yukon, Canada—Results of a 5-Year 

Project 

Edited by Larry P. Gough and Warren C. Day

Scientific Investigations Report 2007–5289–J

U.S. Department of the Interior

U.S. Geological Survey

iii

Contents

Abstract........................................................................................................................................................ J1

Introduction.................................................................................................................................................. J1

Geological and Ecological Setting........................................................................................................... J1

Methods........................................................................................................................................................ J2

Results and Discussion.............................................................................................................................. J3

Bryophyte Assemblage..................................................................................................................... J3

Bryophyte Substrate Geochemistry ............................................................................................... J4

Element Concentrations of Moss.................................................................................................... J4

Conclusions ................................................................................................................................................. J5

Acknowledgments...................................................................................................................................... J5

References Cited......................................................................................................................................... J5

Figures

J1. Photograph of U.S. Geological Survey scientist examining alteration zone rocks 

of Red Mountain......................................................................................................................... J1

J2. Map showing locations and identification numbers of sampling site locations 

within and near the Red Mountain volcanogenic massive sulfide deposit alteration 

zone.............................................................................................................................................. J2

J3. Photograph showing liverwort and moss species growing in areas influenced by 

acidic waters.............................................................................................................................. J3

Tables

J1. Comparison of the average concentration of selected elements in haircap 

mosses (Red Mountain VMS deposit) and in feather moss from a nonmineralized 

area in Alaska (Severson and others, 1990).......................................................................... J4

The Biogeochemistry and Occurrence of Unusual Plant 

Species Inhabiting Acidic, Metal-Rich Water, Red 

Mountain, Bonnifield District, Alaska Range 

By Larry P. Gough,1 Robert G. Eppinger,1 and Paul H. Briggs1

1

U.S. Geological Survey.

Abstract

This report presents results on the occurrence and 

biogeochemistry of unusual plant species, and of their 

supporting sediment, in an undisturbed volcanogenic 

massive sulfide deposit in the Tintina Gold Province (see 

fig. 1 of Editors’ Preface and Overview). The extraordinary 

plant assemblage found growing in the acidic metal-rich 

waters that drain the area is composed predominantly of 

bryophytes (liverworts and mosses). Ferricrete-cemented 

silty alluvial sediments within seeps and streams are covered 

with the liverwort Gymnocolea inflata, whereas the mosses 

Polytrichum commune and P. juniperinum inhabit the area 

adjacent to the water and within the splash zone. Both the 

liverwort-encrusted sediment and Polytrichum thalli have high 

concentrations of major- and trace-metal cations (for example, 

Al, As, Cu, Fe, Hg, La, Mn, Pb, and Zn). Soils in the area do 

not reflect the geochemical signature of the mineral deposit, 

and we suspect that they are most influenced by the chemistry 

of airborne dust (aeolian material) derived from outside the 

area. 

Introduction

In June 2004, we began investigating the occurrence, 

general ecology, and biogeochemistry of plants growing in 

association with acidic metal-rich water associated with the 

Red Mountain volcanogenic massive sulfide (VMS) deposit 

(Gough and others, 2006; Dusel-Bacon and others, this 

volume, chap. B; Eppinger and others, this volume, chap. I, 

Hubbard and others, this volume, chap. E). These unusual 

plant assemblages included liverworts and mosses (bryophytes) as well as forbs, grasses and shrubs, especially willow 

(Salix).

Many terrestrial and aquatic bryophytes are known 

to accumulate large amounts of metals through direct ion 

exchange at the leaf surface and have been used in both 

mineral exploration studies and as biomonitors of airborne 

metal deposition. Some bryophytes are found most commonly 

on substrates that are high in particular bioavailable metals 

(for example copper or lead) and may actually be restricted 

to this type of substrate (Shacklette, 1967; Shaw, 1987). Field 

studies of these occurrences are important for understanding 

the habitat requirements of rare or unusual species and for a 

full appreciation of the ecology of mineralized areas. 

Geological and Ecological Setting

The Bonnifield mining district, and the Red Mountain 

VMS deposit, are part of the Tintina Gold Province (TGP). 

Red Mountain (fig. J1) has been the target of past mineral 

exploration activity. A detailed discussion of the geology and 

mineral potential of the Bonnifield mining district is given 

Figure J1. U.S. Geological Survey scientist examining alteration 

zone rocks of Red Mountain. Photograph by R.G. Eppinger.
J2 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

by Eppinger and others (2004), Dusel-Bacon and others 

(this volume, chap. B); and Eppinger and others (this volume, chap. I). In brief, Red Mountain is a pyrite-rich VMS 

deposit containing sphalerite, galena, chalcopyrite, and, 

locally, precious metals as outcropping and concealed massive to semimassive sulfides. A primary quartz-sericite-pyrite 

alteration zone (QSPAZ) is extensive, and pyrite oxidation is 

prevalent (fig. J2; see also fig. I1 in Eppinger and others, this 

volume, chap. I). 

 Red Mountain lies on the north slope of the Alaska 

Range foothills. The altitude of most of the Red Mountain 

study area (800 meters (m) to 1,800 m) is above the tree limit, 

and alpine tundra shrubs, grasses, sedges, and forbs dominate 

the vegetation. Many of the steep slopes are covered with 

scree and rubble whose stability is decreased by the rapid 

physical and chemical weathering of the extensive sulfidic 

alteration zone. Both permanent and intermittent streams, 

seeps, and springs permeate the slopes and ravines. In the 

mineralized areas, the submerged and emergent aquatic 

vegetation is dominated by bryophytes. Forbs and shrubs such 

as Labrador tea, spirea, cassiope, crowberry, and blueberry 

dominate the drier areas between the seeps, where there is a 

layer of soil. Willow, grasses, and sedges are common in the 

riparian zone immediately within and beside the several permanent streams that drain both the mineralized and nonmineralized areas.

Location and identification number 

of sample sites 

EXPLANATION

04AK15

0 1 KILOMETERS

Foster Creek

Megans Draw

Lago Creek

04AK19

04AK18

04AK15 04AK16

04AK17

04AK25

04AK26

04AK23

04AK22

04AK21

04AK20

Approximate limit of

alteration zone

Red

Mountain

147°26’ 147°24’ 147°22’ 147°20’

63°56’

63°55’

Pacific Ocean

Alaska

Yukon

Northwest

Territories

CANADA

UNITED STATES

British

Columbia

Location map

Study area

Figure J2. Map showing 

locations and identification 

numbers of sampling site 

locations within and near the 

Red Mountain volcanogenic 

massive sulfide deposit 

alteration zone. Red Mountain, 

Lago Creek, Foster Creek, and 

Megans Draw are all local 

names. Base map from U.S. 

Geological Survey Healy D–1 

quadrangle, scale 1:63,360; 

contour interval 100 ft (30.48 m).

Methods

We did not attempt to sample and analyze individual 

liverwort thalli (plant body), as they are very small (commonly 
The Biogeochemistry and Occurrence of Unusual Plant Species, Red Mountain, Bonnifield District, Alaska Range J3

less than 1 millimeter, mm), compact, and grow in intimate 

association with the silty iron-rich sediments of the seeps and 

streams. We did, however, sample the composite iron- and 

organic-rich liverwort sediment substrate. 

Samples of the mosses Polytrichum commune and P. 

juniperinum, nearby soils, and diamondleaf willow (Salix 

pulchra) leaves were collected for chemical analysis. The 

soils are poorly developed Gelisols that are dominated by silty 

colluvium. All geochemical data for this report can be found in 

Giles and others (2007).

Results and Discussion

Bryophyte Assemblage

The reader is referred to Gough and others (2006) 

for complete scientific referencing and more detailed results 

of our investigations. Figure J3 shows a typical bryophyte 

association found in or near acidic seeps and springs in 

the QSPAZ (fig. J2). From a distance, the stream or seep 

bryophyte-inhabited areas appeared black because of the 

visual dominance of the liverwort Gymnocolea inflata. At Red 

Mountain the liverwort occurred both in very damp sites and 

in areas with flowing water. 

It is frequently observed that certain moss genera and 

a few liverworts are most common on, if not completely 

restricted to, substrates enriched with bioavailable heavy 

metals (Shaw, 1987). It is unclear, however, whether the 

bryophytes in this assemblage are simply acidophilic or 

actually require an abundance of a particular heavy metal 

such as copper. Also found in association with G. inflata, but 

much less common, was the moss Pohlia obtusifolia; we could 

find no mention in the literature of its association with acidic 

waters.

Of particular interest was the appearance of a mix of the 

haircap mosses Polytrichum commune and P. juniperinum

within the splash zone of the seeps and small streams (fig. 

J3). At Red Mountain the acidic, metal-rich waters are an 

pH meter

Moss (Polytrichum)

Liverwort (Gymnocolea)

0 10 cm

Acidic metal-rich water

Acidic metal-rich water

Figure J3. Liverwort and moss species growing in areas influenced by acidic waters. Gymnocolea inflata, Pohlia obtusifolia (not 

shown), and Polytrichum juniperinum mixed with P. commune. Photograph by R.G. Eppinger.
J4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

important component of the Polytrichum habitat. When ice 

free, the water is introduced both through capillary upward 

movement and aerial spray deposition. The moss grows in 

polsters (small mounds) that are 10 to 20 centimeters (cm) 

high (fig. J3) and occurs in luxuriant mixed populations 

when present near the seeps. We found no mention in the 

literature of Polytrichum being associated with highly acidic 

mineralized substrates or waters. 

Bryophyte Substrate Geochemistry

Eppinger and others (this volume, chap. I) characterize 

the waters within the quartz-sericite-pyrite alteration zone 

(QSPAZ) as sulfate dominant with high concentrations of Al, 

Cd, Co, Cu, Fe, Mn, Ni, Pb, Y, Zn, and the rare-earth elements; 

and to a lesser extent F- and Si. Upstream of the alteration 

zone they found that all streams had pH values of 6.5 or 

greater and conductivities from 370 to 830 microsiemens 

per centimeter (μS/cm), whereas within the QSPAZ, pH 

values below 3.5 (as low as 2.4) and conductivities above 

2,500 μS/cm (up to 3,400) were common. Within the portion 

of the QSPAZ where this bryophyte association was observed, 

the pH of the water in 2003 varied from 2.7 to 3.3 (with 

conductivities of 1,270 to 3,410 μS/cm) and in 2004 varied 

from 2.6 to 4.5 (with conductivities of 1,350 to 4,800 μS/cm).

The water within and immediately below the QSPAZ had 

extremely high concentrations of trace elements; for example, 

Zn (mean, 41,000 micrograms per liter (μg/L); median, 

13,000 μg/L), Mn (mean, 8,500 μg/L; median, 4,200 μg/L), 

and the rare-earth elements (mean, 6,100 μg/L, median 

3,200 μg/L). Other metals having high concentrations and 

associated high means include Al, Fe, Cd, and Cu, and to a 

lesser extent Co, Ni, and Pb. 

Compared to both the Red Mountain soils and surficial 

materials throughout Alaska, the Red Mountain iron-rich 

sediment samples showed notably higher concentrations of As, 

Cu, Fe, Hg, La, Pb, S, and Sb (Gough and others, 1988, 2006). 

Concentrations of other elements in sediment associated 

with VMS deposits (Co, Cr, Mn, Ni, and Zn) either differed 

little from amounts found in Red Mountain soils and Alaska 

surficial materials or contained somewhat less. This is due to 

the predominance of aeolian dust, from outside the area, that is 

incorporated into these soils (Gough and others, 2001, 2005).

Element Concentrations of Moss

Concentrations of elements in the dry material of 

a Polytrichum commune and P. juniperinum mix are 

reported in table J1. Also listed for comparison are data for 

another terrestrial moss, Hylocomium splendens, collected 

in an unmineralized area of the Kenai Peninsula of 

Alaska (Severson and others, 1990). Although these two 

species have different growth habits, both are often found 

together in high latitude alpine and subalpine areas. We do 

not know how similar their inorganic chemistries would be 

if collected contiguously, but the concentration of some of 

the major elements in these two populations is quite similar 

(Mg, K, and P). The trace element and metal cation levels in 

Polytrichum from Red Mountain are considerably higher than 

the levels in Hylocomium (As, Cu, Fe, Hg, Mn, Pb, Zn, and 

the rare-earth elements La, Ce, as well as Y). We assume that 

Table J1. Comparison of the average concentration of selected 

elements in haircap mosses (Red Mountain, volcanogenic 

massive sulfide deposit) and in feather moss from a 

nonmineralized area in Alaska (Severson and others, 1990). 

[Concentrations are in parts per million, dry weight basis, except as noted; 

n.d., not determined.]

Element

Haircap mosses1

mean

( n=4)

Feather moss2

geometric 

mean

 (n=21)

Ash yield3

Aluminum (Al)

Antimony (Sb)

Arsenic (As)

Barium (Ba)

Cadmium (Cd)

Calcium (Ca)

Cerium (Ce)

Chromium (Cr)

Cobalt (Co)

Copper (Cu)

Galium (Ga)

Iron (Fe)

Lanthanum (La)

Lead (Pb)

Magnesium (Mg)

Manganese (Mn)

Mercury (Hg)

Nickel (Ni)

Phosphorus (P)

Sodium (Na)

Selenium (Se)

Strontium (Sr)

Sulfur (S)

Titanium (Ti)

Vanadium (V)

Yttrium (Y)

Zinc (Zn)

7.5

7,870

0.4

2.3

93

2.2

2,200

210

2.4

2.1

290

2.6

6,170

75

120

1,590

130

0.25

2.9

920

320

0.26

8.6

n.d.4

120

6.2

20

570

7.5

3,740

n.d.

0.14

69

n.d.

6,830

1.3

3.4

1.1

4.6

0.9

1,740

1.2

2.1

1,620

450

0.09

2.0

1,200

1,320

0.06

44

720

170

5.3

0.94

34

1 Polytrichum commune and P. juniperinum mix

2 Hylocomium splendens

3

 percent 
The Biogeochemistry and Occurrence of Unusual Plant Species, Red Mountain, Bonnifield District, Alaska Range J5

this difference is the direct result of element uptake from the 

large dissolved metal load in the water that bathes the moss 

and of the bioavailable forms of these metals in the sediment. 

Conclusions 

The Red Mountain quartz-sericite-pyrite alteration zone 

(QSPAZ), and the VMS deposit that it is part of, are characterized as having acidic (as low as pH 2.4) metal-rich, high 

sulfate waters, active ferricrete formation in the silty alluvial 

sediments, and an abundance of primary (pyrite) and secondary (sulfate) acid-generating minerals. Areas such as Red 

Mountain are an important ecological niche because they 

support the presence of rare or unusual species. The seep, 

spring, and stream habitats contain an extraordinary bryophyte 

community dominated by the liverwort Gymnocolia inflata

in the areas with standing or flowing water and the mosses 

Polytrichum commune and P. juniperinum adjacent to, but 

elevated above, the water. Both the sediment upon which the 

liverwort grows and the Polytrichum thalli that receive acidic 

metal-laden spray have high concentrations of some major and 

trace metals, especially As, Cd, Cu, Fe, Hg, Pb, and Zn. We 

were unable to determine whether G. inflata requires an acidic 

environment or, alternatively, high concentrations of a specific 

dissolved metal, such as copper. The moss assemblage of P. 

commune and P. juniperinum that dominates the vegetation 

of the splash zone near the acidic metal-rich waters is truly 

unusual and we could find no report in the literature of similar 

observations.

The shallow Gelisol soils that are found throughout the 

QSPAZ alteration zone are, in general, similar in their major 

and trace element chemistry to soils found throughout Alaska 

due to the influx of airborne dust. 

Acknowledgments

Dr. JoAnn W. Flock, University of Colorado, and Dr. 

Won S. Hong, University of Great Falls, aided in the identification of the mosses and liverworts. Chemical analyses were 

preformed by Monique Adams, Zoe Ann Brown, and Cathy 

Ager. 

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U.S. Geological Survey Reports on the Tintina Gold Province K3

Hart, C.J.R., and Goldfarb, R.J., 2005, Distinguishing 

intrusion-related from orogenic gold systems, in Realising 

New Zealand’s mineral potential, Proceedings of the 

Australian Institute of Mining and Metallurgy, 2005 New 

Zealand Minerals Conference, Auckland, New Zealand, 

November 13–16, 2005: Wellington, New Zealand, Ministry 

of Economic Development Crown Minerals Group, 

p. 125–133. 

Hart, C.J.R., Goldfarb, R.J., Lewis, L.L., and Mair, J.L., 

2004, The northern Cordilleran mid-Cretaceous Plutonic 

province—Ilmenite/magnetite series granitoids and 

intrusion-related mineralization: Resource Geology, v. 54, 

no. 3, p. 253–280.

Hart, C.J.R., Mair, J.L., Goldfarb, R.J., and Groves, D.I., 

2004, Source and redox controls on metallogenic variations 

in intrusion-related ore systems, Tombstone-Tungsten belt, 

Yukon Territory, Canada, in Ishihara, Shunso, Stephens, 

W.E., Harley, S.L., Arima, Makoto, and Nakajima, Takashi, 

eds., Fifth Hutton Symposium on the Origin of Granites and Related Rocks, Proceedings, Toyohashi, Japan, 

September 2–6, 2003: Transactions of the Royal Society of 

Edinburgh, v. 95, parts 1–2, p. 339–356.

Hart, C.J.R., Mair, J.L., Groves, D.I., and Goldfarb, R.J., 

2003, The influence of source variations on redox state and 

metallogeny of a cross-orogen plutonic province, Yukon, 

Canada, in The origin of granites and related rocks, Hutton 

Symposium V: Geological Survey of Japan, Interim Report 

29, 42 p.

Hart, C.J.R., Villeneuve, M.E., Mair, J.L., Goldfarb, R.J., 

Selby, D., Creaser, R.A., and Wijns, C., 2004, The duration 

of magmatic-hydrothermal ore systems—Comparative U-Pb 

SHRIMP & TIMS, Re-Os and Ar-Ar geochronology of 

mineralizing plutons in Yukon and Alaska, in Muhling, T., 

and others, eds., SEG 2004—Predictive Mineral Discovery 

Under Cover, Extended abstracts: University of Western 

Australia Publication 33, p. 347–349.

Hubbard, B.E., Rowan, L.C., Dusel-Bacon, Cynthia, and Eppinger, R.G., 2007, Geologic mapping 

and mineral resource assessment of the Healy and 

Talkeetna Mountains quadrangles, Alaska using minimal 

cloud- and snow-cover ASTER data: U.S. Geological 

Survey Open-File Report 2007–1046, 18 p. (Also available 

online at http://pubs.usgs.gov/of/2007/1046/.)

Jia, Yiefei, Kerrich, Robert, and Goldfarb, R.J., 2003, 

Metamorphic origin of the ore-forming fluid for orogenic 

gold-bearing quartz vein systems in the North American 

Cordillera; Constraints from δ15N, δD, and δ18O: Economic 

Geology, v. 98, p. 109–123.

Macalady, D.L., Ritter, Kaylene, Redman, A.D., and 

Skold, Magnus, 2004, Comparative characteristics of 

natural organic matter in the Fortymile River, Alaska, in

Gough, L.P., ed., Selected geochemical and biogeochemical 

studies of the Fortymile River watershed, Alaska: U.S. 

Geological Survey Professional Paper 1685, p. 45–52. (Also 

available online at http:/pubs.er.usgs.gov/usgspubs/pp/

pp1685.) 

Mair, J.L., Goldfarb, R.J., Johnson, C.A., Hart, C.J.R., and 

Marsh, E.E., 2006, Geochemical constraints on the genesis 

of the Scheelite Dome intrusion-related gold deposit, 

Tombstone gold belt, Yukon, Canada: Economic Geology, 

v. 101, no. 3, p. 523–553.

Marsh, E.E., Goldfarb, R.J., Hart, C.J.R., and Johnson, C.A., 

2003, Geology and geochemistry of the Clear Creek 

intrusion-related gold occurrences, Tintina gold province, 

Yukon, Canada: Canadian Journal of Earth Sciences, v. 40, 

no. 5, p. 681–699.

Mortensen, J.K., Dusel-Bacon, Cynthia, Hunt, Julie, and 

Gabites, Janet, 2006, Lead isotopic constraints on the 

metallogeny of middle and late Paleozoic syngenetic 

base metal occurrences in the Yukon-Tanana and Slide 

Mountain/Seventymile terranes and adjacent portions of 

the North American miogeocline, in Colpron, Maurice, and 

Nelson, J.L., eds., Paleozoic evolution and metallogeny of 

pericratonic terranes at the ancient Pacific margin of North 

America, Canadian and Alaskan Cordillera: Geological 

Association of Canada Special Paper 45, p. 261–279.

Mueller, S.H., Goldfarb, R.J., Hart, C.J.R., Mair, J.L., 

Marsh, E.E., and Rombach, C.S., 2004, The Tintina gold 

province, Alaska and Yukon—New world-class gold 

resources and their sustainable development: Australasian 

Institute of Mining and Metallurgy, v. 5, p. 189–198.

Mueller, S.H., Goldfarb, R.J., Miller, M.L., Munk, L.A., 

Sanzolone, R.F., Lamothe, P.J., Adams, Monique, Briggs, 

P.H., McClesky, R.B., and Theodorakos, P.M., 2003, 

Surface and ground water geochemistry near the Donlin 

Creek gold deposit, southwestern Alaska: U.S. Geological 

Survey Open-File Report 03–492, 37 p. (Also available 

online at http://pubs.usgs.gov/of/ofr-03-492/.)

Mueller, S.H., Hart, C.J.R., Goldfarb, R.J., Munk, L.A., 

and Diment, R., 2004, Post-mining hydrogeochemical 

conditions, Brewery Creek gold deposit, central Yukon, 

in Emond, D.S., and Lewis, L.L., eds., Yukon exploration 

and geology 2003: Whitehorse, Yukon, Yukon Geological 

Survey, p. 271–280.
K4 Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada

Nelson, J.L., Colpron, Maurice, Piercey, S.J., 

Dusel-Bacon, Cynthia, Murphy, D.C., and Roots, C.F., 

2006, Paleozoic tectonic and metallogenetic evolution of 

pericratonic terranes in Yukon, northern British Columbia 

and eastern Alaska, in Colpron, Maurice, and Nelson, J.L., 

eds., Paleozoic evolution and metallogeny of pericratonic 

terranes at the ancient Pacific margin of North America, 

Canadian and Alaskan Cordillera: Geological Association of 

Canada Special Paper 45, p. 323–360.

Oliver, D.H., and Dusel-Bacon, Cynthia, 2003, Kinematic 

analysis from tectonites in the northern part of the Big 

Delta quadrangle, east-central Alaska, in Galloway, J.P., 

ed., Studies by the U.S. Geological Survey in Alaska, 2001: 

U.S. Geological Survey Professional Paper 1678, p. 61–70. 

(Also available online at http://pubs.er.usgs.gov/usgspubs/

pp/pp1678.)

Piercey, S.J., Nelson, J.L., Colpron, Maurice, Dusel-Bacon, 

Cynthia, Simard, R-L., and Roots, C.F., 2006, Paleozoic 

magmatism and crustal recycling along the ancient Pacific 

margin of North America, northern Cordillera, in Colpron, 

Maurice, and Nelson, J.L., eds., Paleozoic evolution and 

metallogeny of pericratonic terranes at the ancient Pacific 

margin of North America, Canadian and Alaskan Cordillera: 

Geological Association of Canada Special Paper 45, p. 

281–322.

Saltus, R.W., and Day, W.C., 2006, Gravity and 

aeromagnetic gradients within the Yukon-Tanana 

upland, Black Mountain tectonic zone, Big Delta 

quadrangle, east-central Alaska: U.S. Geological Survey 

Open-File Report 2006-1391, poster, available only 

online at http://pubs.usgs.gov/of/2006/1391/.) (Accessed 

August 13, 2007.)

Verplanck, P.L., Mueller S.H., Goldfarb, R.J., and 

Nordstrom, D.K., 2007, Elevated arsenic in ground water, 

Ester Dome (Alaska), in Cidu, R., and Frau, F., eds., Water 

in mining environments, Proceedings, International Mine 

Water Association Symposium, Cagliari, Italy, May 27–31, 

2007: Cagliari, Italy, University of Cagliari, p. 473–477.

Verplanck, P.L., Mueller, S.H., Goldfarb, R.J., 

Nordstrom, D.K., and Youcha, E.K., 2008, Geochemical 

controls of elevated arsenic concentrations in groundwater, 

Ester Dome, east-central Alaska: Chemical Geology, v. 255, 

no. 1–2, p. 160–172.

Verplanck, P.L., Mueller, S.H., Youcha, E.K., Goldfarb, R.J., 

Sanzolone, R.F., McCleskey, R.B., Briggs, P.H., Roller, M., 

Adams, Monique, and Nordstrom, D.K., 2003, Chemical 

analyses of ground and surface waters, Ester Dome, 

central Alaska, 2000-2001: U.S. Geological Survey OpenFile Report 2003–244, 40 p. (Also available online at 

http://pubs.usgs.gov/of/2003/ofr-03-244/.)

Wang, Bronwen, Gough, L.P., Wanty, R.B., Vohden, Jim, 

Crock, J.G., and Day, W.C., 2006, Water and sediment 

chemical data and data summary of samples collected 

in 1999 and 2001 in the Goodpaster River basin, Big 

Delta B-2 quadrangle, Alaska: U.S. Geological Survey 

Open-File Report 2006–1131, 18 p. (Also available online 

at http://pubs.usgs.gov/of/2006/1131/.)

Wang, Bronwen, Wanty, R.B., and Vohden, Jim, 2004, 

Geochemical processes and geologic framework influencing 

surface-water and sediment chemistry in the Fortymile 

River watershed, east-central Alaska, in Gough, L.P., ed., 

Selected geochemical and biogeochemical studies of the 

Fortymile River watershed, Alaska: U.S. Geological Survey 

Professional Paper 1685, p. 3–19. (Also available online at 

http://pubs.er.usgs.gov/usgspubs/pp/pp1685.)

Tintina Gold Province Research 

Funded by the U.S. Geological Survey’s 

Mineral Resources Program, External 

Research Program 

For further information, see this Web site: http://minerals.

usgs.gov/mrerp/index.html/.

Year 2005. Principal Investigator: G. Lang Farmer. 

Affiliation: University of Colorado, Boulder. Title: 

Petrogenesis of Cretaceous, gold-related plutons, eastern 

Tintina Gold Province (TGP), Alaska and Yukon–implications 

for ore genesis and resource distribution in the northern 

Cordillera.

Year 2006. Principal Investigator: Thomas Trainor. 

Affiliation: University of Alaska, Fairbanks. Title: Controls 

on antimony speciation and mobility in Legacy Mine tailings 

environments–a case study of mineral occurrences in the 

Tintina Gold Province, Alaska and Yukon.
Manuscript approved for publication December 27, 2007.

Prepared by the Reston and Raleigh Publishing Service Centers.

Edited by John M. Watson and Elizabeth D. Koozmin.

Graphics by Will R. Stettner.

Photocomposition by Cathy Y. Knutson.

For more information concerning the research in this report, contact 

the following

U.S. Geological Survey

Eastern Mineral Resources Science Center

12201 Sunrise Valley Drive, MS 954

Reston, VA 20192

703-648-6327

http://minerals.usgs.gov/east/index.html
Gough and Day, eds.—Tintina Gold Province, Alaska, United States, and Yukon, Canada—Scientific Investigations Report 2007–5289