Studies by the U.S. Geological Survey in Alaska, 2005

U.S. Geological Survey Professional Paper 1732–C

Geochemical and Sulfur-Isotopic Signatures of 

Volcanogenic Massive Sulfide Deposits on Prince of 

Wales Island and Vicinity, Southeastern Alaska

By John F. Slack, Wayne C. Shanks III, Susan M. Karl, Pamela A. Gemery, 

Peter E. Bittenbender,1 and W. Ian Ridley

Abstract

Stratabound volcanogenic massive sulfide (VMS) 

deposits on Prince of Wales Island and vicinity, southeastern 

Alaska, occur in two volcanosedimentary sequences of Late 

Proterozoic through Cambrian and of Ordovician through 

Early Silurian age. This study presents geochemical data on 

sulfide-rich samples, in situ laser-ablation inductively coupled 

plasma mass spectrometry (LA–ICP–MS) of sulfide minerals, 

and sulfur-isotopic analyses of sulfides and sulfates (barite) 

for identifying and distinguishing between primary sea-floor 

signatures and later regional metamorphic overprints. These 

datasets are also used here in an attempt to discriminate the 

VMS deposits in the older Wales Group from those in the 

younger Moira Sound unit (new informal name). The Wales 

Group and its contained VMS deposits have been multiply 

deformed and metamorphosed from greenschist to amphibolite grade, whereas the Moira Sound unit and related VMS 

deposits are less deformed and generally less metamorphosed 

(lower to middle greenschist grade). Variations in the sulfide 

mineral assemblages and textures of the VMS deposits in 

both sequences reflect a combination of processes, including 

primary sea-floor mineralization and sub-sea-floor zone refining, followed by metamorphic recrystallization. Very coarse 

grained (>1 cm diam) sulfide minerals and abundant pyrrhotite 

are restricted to VMS deposits in a small area of the Wales 

Group, at Khayyam and Stumble-On, which record high-grade 

metamorphism of the sulfides.

Geochemical and sulfur-isotopic data distinguish the 

VMS deposits in the Wales Group from those in the Moira 

Sound unit. Although base- and precious-metal contents vary 

widely in sulfide-rich samples from both sequences, samples 

from the Moira Sound generally have proportionately higher 

Ag contents relative to base metals and Au. In situ LA–ICP–

MS analysis of trace elements in the sulfide minerals suggests 

that primary sea-floor hydrothermal signatures are preserved 

in some samples (for example, Mn, As, Sb, and Tl in pyrite 

from the Moira Sound unit), whereas in other samples the 

signatures are varyingly annealed, owing to metamorphic 

overprinting. A limited LA–ICP–MS database for sphalerite 

indicates that low-Fe sphalerite is preferentially associated 

with the most Au rich deposits, the Niblack and Nutkwa.

Sulfur-isotopic values for sulfide minerals in the VMS 

deposits in the Wales Group range from 5.9 to 17.4 permil (avg 

11.5±2.7 permil), about 5 to 6 permil higher than those in the 

Moira Sound unit, which range from –2.8 to 10.4 permil (avg 

6.1±4.0 permil). This difference in δ34Ssulfide values reflects a 

dominantly seawater sulfate source of the sulfides and is linked 

to the δ34S values of contemporaneous seawater sulfate, which 

were slightly higher during the Late Proterozoic through Cambrian than during the Ordovician through Early Silurian.

Introduction

Stratabound volcanogenic massive sulfide (VMS) deposits occur worldwide in metasedimentary and metavolcanic 

rocks of Archean through Tertiary age (for example, Barrie 

and Hannington, 1999; Franklin and others, 2005). These 

commercially important mineral deposits form by submarine 

hydrothermal processes on and beneath the sea floor, depositing Fe, Cu, Zn, and (or) Pb sulfide minerals that in places are 

accompanied by economic amounts of Ag, Au, Sn, and other 

metals. In southeastern Alaska, VMS deposits are recognized 

in three major lithostratigraphic belts of Late Proterozoic 

through Cambrian, Ordovician through Silurian, and Triassic 

age that extend discontinuously from northwest of Haines in 

the north to Prince of Wales Island in the south (Newberry and 

others, 1997b). The Triassic deposits, which currently are the 

most important economically, include the polymetallic Greens 

Creek Zn-Pb-Cu-Ag-Au massive sulfide ore body that presently is being mined on Admiralty Island, ~250 km northwest 

of Prince of Wales Island (Taylor, 1997; Newberry and Brew, 

1999; Taylor and others, 1999). 1

U.S. Bureau of Land Management.
 Studies by the U.S. Geological Survey in Alaska, 2005

In this study, we report geochemical and sulfur-isotopic 

analyses of samples of massive and semimassive sulfides from 

the two older groups of VMS deposits and occurrences on 

southern Prince of Wales Island and vicinity (fig. 1). These 

data are used here together with geologic and textural features 

to better characterize the metallogeny of the deposits and to 

provide an analytical framework for potentially discriminating 

the Late Proterozoic through Cambrian from the Ordovician 

through Silurian VMS deposits in the region.

Geologic and Metallogenic Setting

Prince of Wales and surrounding islands (fig. 1) are 

underlain by a wide variety of stratified and intrusive rocks of 

Late Proterozoic through Tertiary age (Gehrels and Saleeby, 

1987; Gehrels, 1990, 1992; see Karl and others, this volume) 

that constitute part of the regionally extensive Alexander 

terrane, which extends from eastern Alaska and southwestern Yukon Territory southward into southeastern Alaska 

and coastal British Columbia (for example, McClelland and 

others, 1992; Karl and others, 1999; Nokleberg and others, 

2001). On Prince of Wales Island and vicinity, the oldest unit 

is the Upper Proterozoic through Cambrian Wales Group, 

which comprises various deformed metavolcanic and lesser 

metasedimentary rocks, including greenstone and amphibolite, 

felsic schist and gneiss, graphitic phyllite, minor marble, and 

sparse metaconglomerate (see Karl and others, this volume). 

The Wales Group also hosts most of the VMS deposits in the 

study area. The age of the Wales Group is constrained mainly 

by a concordant U-Pb zircon age of 554±4 Ma for a crosscutting granitic (now orthogneiss) pluton on southern Dall Island 

(fig. 1; Gehrels, 1990). A maximum age for the Wales Group 

Intrusive rocks

Stratified rocks

Volcanogenic massive sulfides

Mesozoic plutons

Paleozoic plutons

Upper Proterozoic plutons

Silurian and younger strata, undivided

Cambrian through Upper Proterozoic Wales Group

Lower Silurian through Ordovician Moira Sound 

unit and correlatives

Silurian through Ordovician Descon Formation

55o30'

132o00'

Moira Sound unit (and correlative) deposit

Wales Group deposit

High-angle fault

Thrust fault

Faults

Craig

KY

CC

NKN

SC

DH

NB-7

MC NL

BHW

CCR

Wales Group occurrence

NBLO

LP

CB

Stratabound barite

Wales Group deposit

HZ

Moira Sound unit (and correlative) occurrence

KI

BI-1

BI-3

BI-2/4

BI-5

BI-6

DM

SO

Suemez

Island

DB

TB

Prince of

Wales

Prince

of

Wales

Island

Island

Sukkwan

Island

Noyes

Island Lulu

Island

Baker

Island

San

Fernando

Island

RL

KIN

LS

BHE

RTP

RTF EL

9/10

NB-8

NKM

EXPLANATION

ALASKA

Map Area

Barrier

Islands

Long

Island

Dall

Island

0 5 10 15 20 KILOMETERS

Datzkoo

Harbor

Big Harbor

LPP

Sound

Clarence Strait

Hetta

Inlet

x

Mount

Jumbo

McKenzie

Inlet

Moira

Nichols Bay

TrocaderoBay

Figure 1. Simplified geologic map of southern Prince of Wales Island and vicinity, showing locations of volcanogenic massive sulfide 

deposits and occurrences in study area. Geology from Karl and others (this volume). Deposits and occurrences: BHE, Big Harbor East; 

BHW, Big Harbor West; BI, Barrier Islands; CB, Corbin; CC, Copper City; CCR, Cable Creek roadcut; DB, Deer Bay; DH, Datzkoo Harbor; 

DM, Dama; EL, Eek Lake; HZ, Hozer; KI, Keete Inlet; KIN, Keete Inlet North; KY, Khayyam; LO, Lookout Mountain; LP, Lime Point (barite); 

LS, Lindsy/88; MC, Moira Copper; NB, Nichols Bay; NKM, Nutkwa Main; NKN, Nutkwa North; NL, Niblack; RL, Rock Lake; RTF, Ruby 

Tuesday (Fish Show; includes the Chomly deposit); RTP, Ruby Tuesday (Polymetal); SC, Security Cove; SO, Stumble-On; TB, Trocadero 

Bay. In the Niblack area, the Trio and Broadgauge deposits (not shown) are located between the Dama and Lindsy/88 deposits. 

Numbered suffixes for Barrier Islands (BI–1 through BI–6) and Nichols Bay (NB–7 through NB–10) deposits and occurrences (table 1) 

correspond to those used by Gehrels and others (1983). Note that thick limestone and dolostone of the Moira Sound unit on Dall and 

Long Islands are not distinguished from other rock types in this sequence.
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 

is estimated at 600 m.y. on the basis of U-Pb geochronology 

of igneous zircons from apparently coeval plutons and of 

detrital zircons from younger strata (see Karl and others, this 

volume). Rocks of the Wales Group, together with several 

enclosed plutons, were deformed and regionally metamorphosed twice, in the Early Ordovician and Early Devonian. 

Geochemical studies of mafic metavolcanic rocks in the 

Wales Group reveal mainly transitional to midocean-ridge 

basalt (MORB) magmatic signatures that suggest formation 

in an oceanic-arc terrane (Barrie and Kyle, 1988; see Karl and 

others, this volume). Lead-isotopic values for sulfide minerals in the VMS deposits in the Wales Group are relatively 

unradiogenic, consistent with a primitive-arc setting for these 

deposits and their volcanosedimentary host sequence (see 

Ayuso and others, this volume).

Younger stratified metavolcanic and metasedimentary 

rocks of the Moira Sound unit (new informal name), which 

are dated at Early Ordovician through Silurian (see Karl and 

others, this volume), are economically important because, like 

the Wales Group, they also contain VMS deposits and occurrences. The Moira Sound unit consists dominantly of siltstone, 

mudstone, graywacke turbidite, and carbonaceous argillite, 

alternating with thick sections of mafic, intermediate-composition, and silicic volcanic rocks and minor conglomerate 

and limestone. Graptolites and conodonts range in age from 

late Early Ordovician to Early Silurian. The oldest dated 

pluton that intrudes the Moira Sound unit is a 472±5-m.y.-old 

granodiorite on southern Prince of Wales Island (Gehrels and 

Saleeby, 1987), which probably was emplaced into the lower 

part of this sequence contemporaneously with deposition of 

the upper part of the Moira Sound unit; the youngest dated 

pluton that intrudes this unit, in Moira Sound, has a U-Pb zircon age of 427±4 m.y. (R. Friedman, written commun., 2004). 

Geochemical data for the mafic volcanic rocks indicate mainly 

calc-alkaline petrologic affinities that imply deposition in an 

island-arc setting (see Karl and others, this volume).

Most younger strata in the study area (fig. 1) are dominated by sedimentary rocks. The widespread Descon Formation, of Middle Ordovician through Silurian age, comprises 

volcaniclastic graywacke turbidite, siliceous shale, chert, and 

minor calc-alkaline to alkaline basalt and andesite but no rhyolite or dacite. Various other Silurian and Devonian sedimentary rocks also occur in the region. None of these sequences 

contains massive sulfide deposits. Unconformably overlying 

the Paleozoic strata are Tertiary sedimentary rocks, including 

coal, Tertiary through Quaternary basalt, and various alluvial, 

colluvial, and glacial deposits.

Three major tectonometamorphic events affected Prince 

of Wales Island and vicinity. The first event was in the Late 

Proterozoic, as documented by 554-m.y.-old orthogneiss on 

Dall Island that cuts a preexisting fabric in rocks of the Wales 

Group (Gehrels, 1990). The second event was in the Early 

Ordovician, after deposition of the Wales Group but before 

deposition of the Moira Sound unit. This event produced 

isoclinal to recumbent folds and a regional metamorphic grade 

ranging from lower greenschist to upper amphibolite facies 

(Gehrels and Saleeby, 1987; Gehrels, 1990). Peak conditions 

during this Ordovician metamorphism were temperatures of 

610–690oC and pressures of 8.4 to 10.1 kbars (Zumsteg and 

others, 2004). The third major event, which occurred in the 

Early Devonian as dated by Ar-Ar geochronology (see Karl 

and others, this volume), followed deposition of the Moira 

Sound unit and the Descon Formation, generating open folds, 

slaty cleavage, and greenschist-facies mineral assemblages. 

Peak metamorphic conditions during this event were a temperature of ~535oC and a pressure of 6.8 kbars (Zumsteg and 

others, 2004). Rocks of the Wales Group are generally recognizable by the presence of two periods of penetrative deformation (for example, F2 folds), in contrast to the single period of 

deformation that characterizes the Moira Sound unit (see Karl 

and others, this volume).

Plutonic rocks in the region are abundant and vary widely 

in age and petrology. Geologic and geochronologic data indicate ages of Late Proterozoic, Ordovician, Silurian, Devonian, 

Permian, Jurassic, and Cretaceous (Gehrels and Saleeby, 1987; 

see Karl and others, this volume) and compositions ranging from granite, through syenite, to gabbro and pyroxenite. 

Some of the Paleozoic and Mesozoic plutons are genetically 

related to economically important magmatic-hydrothermal ore 

deposits, including the Devonian Kasaan and the Cretaceous 

Jumbo-Copper Mountain Fe-Cu-Au skarns (Wright, 1915; 

Newberry and others, 1997a), the Devonian through Silurian 

Salt Chuck Cu-Au-Ag-Pd-Pt deposit (Watkinson and Melling, 

1992; Foley and others, 1997), and the Jurassic Bokan Mountain U–Th–rare-earth-element–Nb–Ta dike system (Thompson, 

1988; Foley and others, 1997). Small posttectonic base- and 

precious-metal veins are widespread in the region, some of 

which are spatially associated with the Paleozoic and Mesozoic 

plutons (Maas and others, 1995).

Faults are common throughout the study area (fig. 1; 

see Karl and others, this volume). Deformed thrust faults 

occur within the Wales Group and along its contacts with the 

younger Moira Sound unit; thrust faults also cut the Cretaceous pluton at Mount Jumbo (Herreid and others, 1978; see 

Karl and others, this volume). These relations indicate that 

thrusting occurred during Ordovician and Cretaceous and, 

possibly, other tectonic events. High-angle faults cut all major 

units, including many Late Proterozoic and Devonian plutons. Major regional strike-slip faults of Tertiary age on the 

east side of Prince of Wales Island (for example, in Clarence 

Strait) record transform faulting between the Pacific and North 

American Plates, after Jurassic through Cretaceous accretion 

of the Alexander terrane to the inboard terranes of southeastern Alaska and coastal British Columbia (Karl and others, 

1999; Nokleberg and others, 2001).

Analytical Methods

Whole-rock compositions of samples of massive and 

semimassive sulfide were obtained by XRAL Laboratories in 

Denver, Colo. Major and minor elements were analyzed by 
 Studies by the U.S. Geological Survey in Alaska, 2005

inductively coupled plasma atomic-emission spectrometry 

(ICP–AES) after acid digestion of powdered samples. Total 

S content was determined by Leco furnace methods, As, Sb, 

Hg, Se, Te, and Tl contents by atomic-absorption spectrometry, and Au content by fire assay. Analytical results are not 

reported for Nb, Ta, Cr, Ba, Sn, Th, Y, La, and Ce, which 

typically concentrate in resistate heavy minerals (for example, 

rutile, chromite, barite, cassiterite, monazite), because a flux 

was not used in the ICP–AES analyses to ensure their complete dissolution; similarly, data for Ti may not be meaningful 

(that is, are too low) and should be viewed with caution.

Trace-element contents in sulfide minerals were determined by laser-ablation inductively coupled plasma mass 

spectrometry (LA–ICP–MS) at the U.S. Geological Survey 

(USGS) laboratory in Denver, Colo. This technique has the 

advantage of providing in situ analyses at low concentrations 

and high precision (for example, Watling and others, 1995; 

Ridley and Lichte, 1998; Butler and Nesbitt, 1999; Axelsson 

and Rodushkin, 2001). Polished thin sections were used for 

the LA–ICP–MS analyses to allow integration of the geochemical results with information on textures and mineral 

assemblages. Analyses were obtained for counting times of 5 

minutes on 50-μm-diameter spots, according to the methods of 

Ridley and Lichte (1998), using a synthetic sulfide standard, 

as described by Wilson and others (2002). Data reduction 

was done offline with GeoPro software (CETAC Technologies, 2000). This software program was used to select spectra 

that were unaffected by analysis of small mineral inclusions 

(for example, chalcopyrite in sphalerite), thus providing more 

robust data on the phase-specific trace-element contents of 

the sulfide minerals. Total analytical precision by the LA–

ICP–MS method is estimated at 2 to 8 percent (Ridley, 2000; 

Norman and others, 2003).

Sulfur-bearing phases from mineralized samples were 

physically separated and analyzed for δ34S values, using an 

automated elemental analyzer interfaced to an isotope-ratio 

mass spectrometer (Giesemann and others, 1994), at the USGS 

laboratory in Denver, Colo. The δ34S values were calibrated 

to the Cañon Diablo troilite standard and are reported here in 

conventional permil notation; relative error is estimated at ±0.2 

permil. Disseminated sulfides in unmineralized host rocks 

were separated in bulk, using the CrCl2 dissolution method of 

Tuttle and others (1986), which extracts all sulfide minerals. 

Barite from the Big Harbor West deposit (BHW, fig. 1) that is 

intergrown with fine-grained sulfides was separated by using 

the NaCO3 method of Breit and others (1985) to permit analysis of barite only and not also admixed sulfides.

VMS Deposits

History and Production

VMS deposits and occurrences in the study area are 

restricted to Late Proterozoic through Cambrian rocks of the 

Wales Group and Silurian through Ordovician rocks of the 

Moira Sound unit (fig. 1; table 1). In this report, VMS deposits 

are distinguished from occurrences by evidence at the deposits of past mining development or mineral exploration (for 

example, trenching, core drilling). The largest known deposits 

are the Khayyam and nearby Stumble-On ore bodies in the 

Wales Group, at the head of McKenzie Inlet, which were 

mined from 1901 to 1907, producing 210,000 t of massive sulfide ore averaging 1.7 weight percent Cu, 9.6 ppm Ag, and 1.9 

ppm Au (Barrie, 1984; Barrie and Kyle, 1988). The Khayyam 

deposit (KY, fig. 1) has an additional estimated resource of 

78,700 t of massive sulfide averaging 2.9 weight percent Cu, 

0.8 weight percent Zn, 17 ppm Ag, and 1.3 ppm Au (Maas and 

others, 1995). The Copper City Mine (CC, fig. 1) produced 

77 t Cu, 146 kg Ag, and 10.6 kg Au between 1903 and 1905; 

the Corbin Mine (CB, fig. 1) produced smaller amounts of Cu 

(9.7 t) and Ag (12 kg) during 1906–13 (Bufvers, 1967). The 

Niblack deposit (NL, fig. 1), in the Moira Sound unit on the 

north side of Moira Sound, was mined from 1902 to 1908, 

producing 18,000 t of ore averaging 4.9 weight percent Cu, 34 

ppm Ag, and 2.3 ppm Au (Maas and others, 1995). Mineral 

exploration in the Niblack area from 1993 to 2006 has identified several more VMS deposits, including the Lookout Mountain deposit (LO, fig. 1), with an inferred resource of 2.52 Mt 

averaging 3.22 weight percent Zn, 1.70 weight percent Cu, 

36.4 g Ag/t, and 2.77 g Au/t. The nearby Dama (DM, fig. 1), 

Lindsy/88 (LS, fig. 1), and Trio/Broadgauge deposits contain 

significant amounts of Zn, Cu, Ag, and Au in some drill holes 

(Adamson and Gray, 1995; Niblack Mining Corp., 2006, URL 

http://www.niblackmining.com/). Other VMS deposits on 

Prince of Wales Island and vicinity were not mined or have 

only minor reported production (Barrie and Kyle, 1988; Maas 

and others, 1995), estimated at no more than 500 t. During the 

1990s, the Nutkwa deposits (NKM/NKN, fig. 1) were extensively explored and drilled, while the Big Harbor East and 

West, Copper City, Corbin, and Hozer deposits (BHE/BHW, 

CC, CB, and HZ, respectively, fig. 1) had only limited exploration and drilling.

Deposits in the Wales Group

The Khayyam and Stumble-On deposits (KY and SO, 

respectively, fig. 1) form elongate lenses of massive and semimassive sulfide, as much as 6 m thick and at least 170 m long, 

within amphibolite-facies metavolcanic and metasedimentary 

rocks of the Wales Group (Fosse, 1946; Barrie, 1984; Barrie 

and Kyle, 1988). Major host rocks at and near these deposits 

include mafic and felsic schist and gneiss, intermediate-composition schist, and siliceous schist. Lenses of amphibolite 

and large bodies of both foliated and unfoliated diorite occur 

in the area. Thin (<1 cm thick) beds of coticule (spessartine 

quartzite) are also present in some felsic schist and gneiss. 

Sulfide minerals are clearly recrystallized by postore regional 

metamorphism, typically forming a mixture of euhedral and 

granoblastic grains in which coarse-grained to very coarse 

grained (>1 cm diam) pyrite occurs within a matrix of chalco-
Table 1. Data for volcanogenic massive sulfide deposits and occurrences on southern Prince of Wales Island and vicinity, southeastern A

Deposit or occurrence Latitude Longitude Host Principal Opaque Major refe

(fig. 1) (oN.) (oW.) rocks metals minerals

Wales Group

Khayyam ---------------------------- 55.29861 132.38611 fels, amp, gab, cot Cu, Zn, Ag, Au py, cp, sl, po, asp, mt Barrie and Kyle Stumble-On ------------------------- 55.29583 132.37222 fels, amp, gab Cu, Zn, Ag, Au py, cp, sl, po, asp, mt Do.Rock Lake--------------------------- 55.30833 132.50000 fels, amp Cu, Zn, Au py, cp, sl, mt Barrie (1984).Big Harbor East -------------------- 55.37611 132.95361 fels, bas, sh Cu, Ag, Au py, cp Maas and otherBig Harbor West ------------------- 55.37556 132.96389 bas, fels, sh Cu, Zn, Ag, Au py, cp, sl Do.Ruby Tuesday (Polymetal) ------- 55.21667 132.32278 fels, bas, cht, mbl Zn, Pb, Cu, Ag py, sl, gl, cp Kucinski (1987Ruby Tuesday (Fish Show)------- 155.22167 132.33528 fels, bas, cht, mbl Zn, Pb, Cu, Ag py, sl, gl, cp Maas and otherCopper City ------------------------- 55.13417 132.60944 rhy, phy, bas, if, jas Cu, Zn, Ag, Au py, cp, sl, gl, mt Thurston (1994Eek Lake ---------------------------- 55.17042 132.67375 rhy, fels, bas Cu py, cp Casselman and Corbin ------------------------------- 55.23139 132.64861 fels, rhy, phy Cu, Zn, Ag, Au py, cp, sl Thurston (1994Keete Inlet -------------------------- 55.08111 132.48889 fels, rhy, bas, if Cu, Zn, Ag, Au py, cp, sl, bn, mt Maas and otherKeete Inlet North------------------- 55.10986 132.47561 fels, rhy, bas Cu, Zn, Ag, Au py, cp, sl Do.Nutkwa Main ----------------------- 55.07653 132.55128 rhy, fels, bas Zn, Cu, Pb, Ag py, sl, cp, gl Casselman and Nutkwa North ---------------------- 55.08681 132.54153 rhy, fels, bas Zn, Cu, Pb, Ag py, sl, cp, gl Do.Hozer -------------------------------- 55.04000 132.54250 fels, rhy, bas Zn, Cu py, sl, cp Maas and otherDeer Bay exhalite ------------------ 55.26917 132.66667 fels, bas, phy Cu, Zn, Ag, Au py, cp, sl Maas and otherCable Creek roadcut --------------- 55.35179 132.83060 fels, phy, bas Cu, Zn, Ag, Au py, sp, sl Do.Trocadero Bay exhalite------------ 55.35849 132.82680 fels None identified py Do.Security Cove (Dall Island)------- 54.75000 132.85694 fels, bas, mbl Zn, Pb, Ag, Ba py, sl, gl, cp Maas and other

Moira Sound unit and correlatives

Niblack ------------------------------ 55.06667 132.14639 rhy, bas, if, jas, cht Cu, Zn, Ag, Au py, cp, sl Peek (1975).Lookout Mountain ----------------- 55.05639 132.14139 rhy, bas Zn, Cu, Ag, Au py, sl, cp Niblack Mining Dama -------------------------------- 55.05389 132.12528 rhy, bas Zn, Cu, Ag, Au py, sl, cp Adamson and GLindsy/88 --------------------------- 55.06306 132.13833 rhy, bas Zn, Cu, Ag, Au py, sl, cp Do.Moira Copper----------------------- 55.07644 132.17987 rhy, bas Cu, Ag, Au py, cp, mt Wright and WriBarrier Islands No. 1--------------- 54.81222 132.44889 bas, rhy, bs Zn, Ba py, sl Gehrels and othBarrier Islands No. 2--------------- 54.80139 132.45464 rhy, bas Zn, Pb, Ag py, sl, gl Do.Barrier Islands No. 3--------------- 54.81000 132.49472 rhy, bas None identified py Do.Barrier Islands No. 4--------------- 54.79722 132.45056 rhy, bs, bas, dol None identified py Do.Barrier Islands No. 5--------------- 54.80389 132.39167 rhy, gab None identified py Do.Barrier Islands No. 6--------------- 54.79722 132.33833 bs, rhy None identified py Do.Nichols Bay No. 7 and 8 ---------- 54.70237 132.11715 rhy, bas None identified py Do.Nichols Bay No. 9 and 10--------- 254.73514 132.14154 grw, bs, rhy, grn Zn, Ag po, py, sl, mt Do.Datzkoo Harbor (Dall Island) ---- 54.74056 132.74944 fels, bas Zn, Ag, Ba py, sl Maas and other

1Includes the nearby Chomly deposit ~500 m to the west (Kucinski, 1988; Maas and others, 1995). 2These small deposits occur within the contact aureole of a Silurian(?) granite (see Karl and others, this volume).

[Numbered Barrier Islands occurrences correspond to locations in Gehrels and others (1983). Longitudes in parentheses are approximate. Host rocks, listed in decreasidance: amp, amphibolite; bas, basalt or metabasalt (including greenstone, andesite, and chlorite schist); bs, black shale and slate; cht, chert or metachert; cot, coticule; fels, felsic schist and gneiss (including quartz-sericite schist and volcaniclastic sedimentary rocks); gab, gabbro or metagabbro (including diorite and quartz diorite); grgraywacke; if, iron-formation; jas, jasper; mbl, marble; phy, phyllite; rhy, rhyolite or metarhyolite (including tuff, breccia, and conglomerate); sh, shale and slate (incluPrincipal metals are listed in decreasing order of concentration in production records or chemical analyses (Maas and others, 1995; this study). Opaque minerals, listed order of abundance: asp, arsenopyrite; bn, bornite; cp, chalcopyrite; gl, galena; mt, magnetite; po, pyrrhotite; py, pyrite; sl, sphalerite]
 Studies by the U.S. Geological Survey in Alaska, 2005

pyrite, pyrrhotite, and (or) sphalerite (figs. 2A, 2B, 3A). Some 

samples contain abundant granoblastic sphalerite, especially 

at the Stumble-On deposit (fig. 2C); pyrrhotite is common 

at both deposits. Among all the VMS deposits on Prince of 

Wales Island and vicinity, the Khayyam and Stumble-On 

deposits have the coarsest grained sulfide minerals.

Massive sulfides at the Corbin deposit (CB, fig. 1) occur 

within a deformed sequence of lower-greenschist-facies 

rhyolitic tuff and tuffaceous sedimentary rocks (Wright and 

Wright, 1908; Maas and others, 1995). A schist unit containing distinctive pink piemontite (Mn-epidote) is locally present in the footwall (Thurston, 1994; Hattie and others, 1996). 

The sulfide ore body is as much as 1 m thick and at least 75 

m long. Detailed surface and underground mapping reported 

by Thurston (1994) reveals complex structures within the 

massive sulfides, including isoclinal folds and shear zones. 

Massive granoblastic pyrite is widespread, accompanied by 

varying amounts of chalcopyrite and sphalerite that in places 

define a conspicuous mineralogic layering (fig. 3B).

VMS deposits in the Big Harbor area (fig. 1) occur in 

two main areas on the north side of Trocadero Bay (Chapin, 

1916; Twenhofel and others, 1949). The deposits are within 

a greenschist-facies sequence of tightly folded quartz-sericite 

schist, metabasaltic greenstone, and dacitic tuff that are spatially associated with an elongate body of feldspar porphyry 

(Terry and Gibson, 1998). The Big Harbor East deposit 

(BHE, fig. 1) consists mainly of siliceous pyritic sulfide, as 

much as 9 m thick, containing varying amounts of matrix 

chalcopyrite and minor sphalerite and sericite. About 750 m 

to the west, the Big Harbor West deposit (BHW, fig. 1) forms 

a nearly 1-m-thick stratiform lens of massive chalcopyrite 

and minor pyrite and sphalerite (fig. 3C) within greenstone 

and quartz-sericite schist. A thin stratiform unit about 150 m 

to the north, composed of Mn-calcite and spessartine garnet, 

minor quartz, barite, magnetite, and galena, and sparse 

sphalerite and chalcopyrite, probably represents an exhalative chemical sediment in the upper hanging-wall sequence 

(Terry and Gibson, 1998).

The small Keete Inlet deposit (KI, fig. 1) consists of 

massive siliceous pyritic sulfide with minor chalcopyrite, 

sphalerite, and rare bornite, hosted in metarhyolitic tuff and 

metabasaltic greenstone (Chapin, 1916; Maas and others, 

1991). Massive sulfide layers are as much as 0.6 m thick. 

Common textures show granoblastic pyrite within a matrix 

of fine-grained chalcopyrite and sphalerite (figs. 2D, 3D). 

A thin unit of magnetite iron-formation, which occurs in 

shoreline outcrops several hundred meters south of the 

deposit (see Karl and others, this volume), may be related 

to the sulfide mineralization. Metamorphic grade in the area 

is lower to middle greenschist facies. A similar but smaller 

VMS occurrence, here designated Keete Inlet North (KIN, 

fig. 1), is about 3.4 km north-northeast of the main deposit 

(Maas and others, 1991).

The Copper City (also known as Red Wing) deposit 

(CC, fig. 1) consists of a massive sulfide layer, as much as 2 

m thick and nearly 100 m long, within a sequence of mainly 

felsic metavolcanic and metasedimentary rocks (Wright and 

Wright, 1908; Herreid and others, 1978). Footwall strata 

are composed of sericite-altered metarhyolite and metadacite with thin interbeds of mafic metatuff; the hanging wall 

contains jasper, magnetite iron-formation, and ferruginous 

micaceous phyllite (Wright and Wright, 1908; Thurston, 

1994; Maas and others, 1995). Thurston (1994) and Forbes 

and others (1995) also reported a 0.3-m-thick pink layer in 

the hanging wall that contains abundant piemontite. Sulfide 

minerals consist mainly of pyrite and chalcopyrite, minor 

sphalerite, and rare galena (figs. 2E, 3E). As much as 6,700 

ppm Ba occurs in some sulfide-rich samples (Maas and 

others, 1995, table A–2), but whether this element resides 

in minor barite or in Ba-feldspar or mica is unknown. To 

the northwest, across Hetta Inlet, the Eek Lake occurrence 

(EL, fig. 1) is a small lens, less than 0.3 m thick, composed 

of pyrite and abundant chalcopyrite within altered felsic 

metavolcanic rocks (Casselman and Bohme, 1997).

The only true polymetallic VMS deposits on Prince 

of Wales Island and vicinity (fig. 1) are in the Ruby Tuesday area. Several VMS deposits have been identified here, 

including the Chomly, Fish Show, and Polymetal; the first 

two (RTF, fig. 1) are about 1.5 km west-northwest and 1 

km northwest, respectively, of the Polymetal deposit (RTP, 

fig. 1; Fowler, 1949; Kucinski, 1987; Maas and others, 

1995). The deposits occur at two or, possibly, three different 

stratigraphic levels, in a folded and faulted volcanosedimentary sequence with a lower-greenschist-facies metamorphic 

overprint. The Polymetal deposit is in locally fragmental 

felsic volcaniclastic schist, whereas the Chomly and Fish 

Show deposits are in siliceous graphitic argillite. Metabasaltic greenstone and marble also occur in parts of the Ruby 

Tuesday area (Kucinski, 1987). Massive sulfide from the 

Fish Show deposit is noteworthy in containing conspicuous 

volcanic clasts within a matrix of fine-grained sphalerite, 

galena, pyrite, and minor chalcopyrite (figs. 2F, 3F).

Two main areas of massive sulfide are known in the 

Nutkwa area (Nutkwa Main and North deposits; NKM/NKN, 

fig. 1), west of the Keete Inlet deposit (KI, fig. 1). The 

Nutkwa deposits occur in a sequence of lower-greenschistfacies, dacitic to rhyolitic volcanic rocks and volcaniclastic sedimentary rocks, together with varying amounts of 

metabasaltic greenstone (Hattie and others, 1996; Casselman and Bohme, 1997). Massive sulfides at both deposits 

are in stratiform layers, 0.3 to 1.5 m thick. On the basis of 

outcrop distribution and drill-hole intersections, the Nutkwa 

Main and North deposits have strike lengths of 430 and 

400 m, respectively, and are believed to represent the same 

stratigraphic horizon (Hattie and others, 1996). Pyrite and 

abundant fine-grained sphalerite are the dominant sulfides, 

together with minor chalcopyrite and sparse galena. A clastic 

texture is characteristic of the Nutkwa Main deposit, in 

which fragments of chlorite schist, sericite schist, and quartz 

occur within a pyrite- and sphalerite-rich matrix. The presence of as much as 1.8 weight percent Ba in drill cores at the 

Nutkwa North deposit (Hattie and others, 1996) suggests the 
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 

Figure 2. Representative sulfide-rich samples from volcanogenic massive sulfide deposits in study 

area (fig. 1). A, Very coarse grained porphyroblastic pyrite in a matrix of chalcopyrite, pyrrhotite (partially 

altered to marcasite), and minor sphalerite. Stumble-On Mine dump, sample JS–00–36A. B, Coarsegrained granoblastic pyrite within a matrix of fine-grained chalcopyrite and minor sphalerite. Khayyam 

Mine upper dump, sample JS–00–62A. C, Coarse-grained disseminated pyrite (minor) within a matrix of 

coarse-grained, granular sphalerite (abundant). Stumble-On Mine dump, sample JS–00–36C. D, Pyritic 

massive sulfide with minor interstitial sphalerite and trace chalcopyrite. Keete Inlet Mine dump, sample 

JS–00–53A. E, Massive chalcopyrite and sphalerite with minor pyrite. Copper City Mine dump, sample 

JS–00–55A. F, High-grade polymetallic massive sulfide with abundant sphalerite and galena, and minor 

chalcopyrite, and relict volcanic clasts (dark). Ruby Tuesday (Fish Show) Mine dump, sample RT–FS–MS. 

G, Layered pyrite, sphalerite, minor chalcopyrite, with local coarse-grained pyrite (right). Dama deposit, 

sample LO–53/624.2. H, Pyrite and sparse galena with sericite-rich rhyolite lapilli(?). Barrier Islands No. 2 

occurrence, sample BI–2–MS.
 Studies by the U.S. Geological Survey in Alaska, 2005

A B

C

G H

D

sl

sl

py

py

py

cp

py

py cp

cp

cp

py

sl

sl

po po

sl

sl gl

py

py

py

py

sl

cp

chl

qz

qz

qz

F

py

py

cp

cp

sl

mt

E

py

Figure 3. Photomicrographs (all in reflected light) of sulfide-rich samples from the study 

area (fig. 1). Minerals: chl, chlorite; cp, chalcopyrite; gl, galena; mt, magnetite; po, pyrrhotite; 

py, pyrite; qz, quartz; sl, sphalerite. A, Abundant pyrrhotite intergrown with chalcopyrite, 

sphalerite, and minor pyrite and quartz. Stumble-On Mine dump, sample JS–00–36D. B, 

Layers of sphalerite- and pyrite-rich massive sulfide. Corbin Mine dump, sample JS–00–56I. 

C, Chalcopyrite and coarse-grained pyrite within a matrix of foliated chlorite and quartz. Big 

Harbor West deposit, sample JS–00–31C. D, Coarse-grained pyrite within a matrix of finegrained chalcopyrite, quartz, and minor sphalerite. Keete Inlet Mine dump, sample JS–00–53A. 

E, Coarse-grained pyrite within a matrix of chalcopyrite and minor sphalerite and magnetite. 

Copper City Mine dump, sample JS–00–55C. F, Intergrowths of sphalerite and galena with 

minor pyrite. Ruby Tuesday (Fish Show) deposit, sample RT–FS–MS. G, Granular pyrite within a 

matrix of fine-grained sphalerite, chalcopyrite, and quartz. Dama deposit, sample LO–53/624.2. 

H, Fine-grained anhedral and coarse-grained euhedral pyrite in quartz. Barrier Islands No. 2 

occurrence, sample BI–2–MS.
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 

presence of barite, although this element could also reside in 

Ba-rich feldspar and (or) mica. The deposit contains zones 

of abundant Mn oxides, as much as 1 m thick (Hattie and 

others, 1996).

The small Hozer deposit (HZ, fig. 1) occurs south of the 

Nutkwa deposits on the south side of Keete Inlet. Host rocks 

are mainly felsic schist, quartz-rich metatuff, and greenstone 

breccia, all of which are metamorphosed to lower-greenschist-facies assemblages. Sulfides consist of disseminated 

pyrite, minor sphalerite, and sparse chalcopyrite, together 

with stringers and veinlets of pyrite; no massive sulfide is 

known from the area (Maas and others, 1991). This mineralized sequence may be part of the same stratigraphic section 

that contains the Nutkwa deposits to the north.

Four small stratiform sulfide occurrences in the Wales 

Group probably represent exhalative VMS deposits. Such 

exhalites are believed to form by chemical precipitation of 

sulfide and other minerals from hydrothermal plumes distal 

from high-temperature sea-floor vent sources (for example, 

Spry and others, 2000). The Deer Bay exhalite (DB, fig. 

1), on the west side of Hetta Inlet, consists of disseminated 

pyrite, minor chalcopyrite, and sparse sphalerite in a pyritic 

quartz-sericite-chlorite schist (Maas and others, 1995). To 

the northwest, the Cable Creek roadcut occurrence (CCR, 

fig. 1; Maas and others, 1995) contains disseminated to semimassive pyrite with minor sphalerite and chalcopyrite; barren 

pyritic schist to the east, termed the “Trocadero Bay exhalite,” is probably a lateral facies equivalent. A similar sulfide 

occurrence at Security Cove (SC, fig. 1), on the southwest 

side of Dall Island, consists of thin (<20 cm thick) layers of 

massive pyrite and locally abundant sphalerite and galena 

with sparse chalcopyrite; accessory barite is implied by the 

presence of as much as 2.3 weight percent Ba (Berg, 1984; 

Maas and others, 1995).

One stratabound barite deposit is known on the south 

end of the Lime Point peninsula (fig. 1). Although it lacks 

associated sulfide minerals, the Lime Point deposit (LP, fig. 

1) is important metallogenically because it occurs in the 

same metavolcanic and metasedimentary sequence that hosts 

the Copper City ore body 8 km to the north (CC, fig. 1; Maas 

and others, 1995). The Lime Point deposit differs, however, 

in being localized within a unit of calcite marble and minor 

interbedded talc schist. Barite there consists of massive, 

essentially pure bodies, 3 to 12 m thick and ~30 m long, that 

are discordant to bedding in the host marble (Elmendorf, 

1920; Fowler, 1948; Twenhofel and others, 1949). In outcrop 

and underground in the adit, the barite shows abundant 

evidence of an early, pretectonic replacement of the precursor limestone, including the presence of tightly folded barite 

lenses in marble. It is unknown, however, whether this barite 

formed mainly on the sea floor contemporaneously with carbonate sediment, as a broadly synsedimentary (early diagenetic) replacement of limestone, like some stratabound barite 

deposits elsewhere (for example, Ketner, 1975; Ahsan and 

Mallick, 1999; Kelley and others, 2004), or as a late diagenetic replacement deep in the subsurface.

Deposits in the Moira Sound Unit and 

Correlatives

Several VMS deposits are known in the Niblack anchorage area (fig. 1; table 1). Massive sulfides and local stringer 

sulfides there occur in a sequence composed dominantly of 

felsic metavolcanic and tuffaceous metasedimentary rocks 

that traditionally have been assigned to the Wales Group (for 

example, Peek, 1975; Gehrels and Berg, 1992; Maas and 

others, 1995). These assignments are supported by a U-Pb 

zircon age of 595±20 m.y. determined by Gehrels and others 

(1996) on a massive rhyolite at Lookout Mountain. This Late 

Proterozoic age is inconsistent, however, with various geologic 

data which suggest that the host rocks of these VMS deposits 

belong to the younger Moira Sound unit and not to the older 

Wales Group (see Karl and others, this volume).

The Niblack deposit (NL, fig. 1) consists of a series of 

irregular lenses of massive sulfide, as much as 9 m thick and 60 

m long, within a host sequence of tuffaceous metarhyolite and 

minor interbedded clastic sedimentary rocks (Brooks, 1902; 

Wright and Wright, 1908; Herreid, 1964; Peek, 1975). Footwall rocks stratigraphically below the mineralized sequence 

comprise metadacite and metabasaltic greenstone; hangingwall rocks above this sequence consist largely of metabasalt 

(Niblack Mining Corp., 2006, URL http://www.niblackmining.

com/). Regional metamorphic grade is lower greenschist facies. 

The massive sulfides consist of pyrite and chalcopyrite, generally minor sphalerite, and sparse galena. Disseminated and 

stringer sulfides also occur nearby, the stringers probably representing part of a footwall feeder zone to the massive sulfides 

stratigraphically above. Related hydrothermal sedimentary 

rocks present in the mine area include jasper, magnetite ironformation, metachert, and quartz-piemontite-spessartine (Peek, 

1975; Adamson and Gray, 1995).

Several other significant VMS deposits occur in the 

Niblack area, the largest of which is the Lookout Mountain 

deposit (LO, fig. 1), about 1,300 m south-southeast of the 

Niblack Mine (NL, fig. 1). Host rocks to this deposit consist of a deformed sequence of pyritic rhyolite metatuff that 

locally contains sulfide-rich clasts; a Mn-rich piemontite-spessartine-rhodonite layer occurs in the stratigraphic hanging 

wall (Adamson and Gray, 1995). Footwall rocks are mainly 

metabasaltic amygdaloidal greenstone that in places displays 

relict pillow structures. The massive sulfides on Lookout 

Mountain form three stacked lenses separated by zones of 

disseminated and stringer sulfides with an aggregate thickness 

of about 60 m; individual massive sulfides lenses are as much 

as 14 m thick (Green, 2006; Niblack Mining Corp., 2006, 

URL http://www.niblackmining.com/). Comparable thicknesses of mineralized rock have been intersected in drilling 

at the nearby Dama (DM, fig. 1), Lindsy/88 (LS, fig. 1), and 

Trio/Broadgauge deposits (Adamson and Gray, 1995). In all 

of these deposits, pyrite is the chief sulfide mineral, accompanied by varying amounts of sphalerite and chalcopyrite with 

appreciable gold in places. The sulfides form massive zones 

and seams within strongly sericite altered rhyolite tuff or, less 
10 Studies by the U.S. Geological Survey in Alaska, 2005

commonly, alternating layers composed dominantly of pyrite 

and sphalerite (fig. 2G). Some samples show relatively coarse 

grained pyrite with interstitial sphalerite and chalcopyrite 

(figs. 2G, 3G).

The Moira Copper deposit (MC, fig. 1), also known as the 

Wakefield group of claims (Wright and Wright, 1908; Maas and 

others, 1995), occurs about 2 km west-northwest of the Niblack 

Mine (NL, fig. 1). This small VMS deposit forms a lens of sulfides, as much as 3 m thick, within a sequence of metabasaltic 

greenstone and metarhyolitic rocks that also includes interbedded volcaniclastic sedimentary rocks. Similar to the deposits in 

the Niblack area, the Moira Copper deposit is hosted in weakly 

deformed rocks that have been regionally metamorphosed to 

lower greenschist facies. The sulfide body consists of semimassive pyrite and chalcopyrite with trace sphalerite.

Small VMS deposits and occurrences are known in 

several places along the southwest and south ends of Prince 

of Wales Island (fig. 1). Dominantly volcanic and lesser 

sedimentary host rocks in these areas are correlated with the 

Moira Sound unit by Karl and others (this volume). Occurrences on the Barrier Islands are mainly within rhyolitic tuff 

and siliceous black slate and are surrounded by a sequence 

composed dominantly of pillow basalt and pyroclastic breccia 

(Gehrels and others, 1983); rhyolite domes are present locally. 

Thin stratiform lenses of barren semimassive to massive pyrite 

are common, associated with lenses of sericite schist (fig. 2H). 

Textures of the pyrite are distinctive and differ from those 

in all other VMS deposits of the region, in which aggregates 

of fine-grained anhedral pyrite and rare framboidal pyrite 

are intergrown with coarse-grained euhedral pyrite (fig. 3H). 

Some sulfide-rich samples include sparse sphalerite and chalcopyrite and traces of galena. One pyritic lens in black slate at 

the Barrier Islands No. 1 deposit (BI–1, fig. 1) contains >5,000 

ppm Ba (Gehrels and others, 1983, table 1), probably in barite 

or Ba-rich mica.

VMS deposits and occurrences are also known in the 

Nichols Bay area (fig. 1), the largest of which, at the northeast 

end of the bay, is the Nichols Bay Shaft deposit (NB, fig. 1; 

Chapin, 1918; Gehrels and others, 1983; Maas and others, 

1995). Host rocks consist of interbedded slate, graywacke, and 

siliceous volcanic rocks, including chert. This deposit is within 

the contact aureole of a large granitic pluton of Devonian or 

Silurian age (Gehrels, 1992; see Karl and others, this volume). 

Sulfides form lenses and layers, several centimeters thick, 

composed of pyrite, pyrrhotite, minor sphalerite and magnetite, and sparse chalcopyrite; garnet porphyroblasts also occur 

in the massive sulfide. Other VMS occurrences in the Nichols 

Bay area are small and consist chiefly of pyrite with trace 

sphalerite (Gehrels and others, 1983; Maas and others, 1995).

A small VMS occurrence on the southeast side of Dall 

Island at Datzkoo Harbor (DH, fig. 1) consists of thin (<10 cm 

thick) lenses within quartz-sericite phyllite of probable felsic 

volcanic or volcaniclastic origin, associated with hornblende 

schist, talc schist, and felsic schist (Maas and others, 1995). 

Metamorphic grade is upper greenschist or, possibly, lower 

amphibolite facies. The sulfide lenses are composed almost 

wholly of coarse-grained pyrite with only sparse sphalerite 

and trace chalcopyrite. Accessory barite is suggested by the 

presence of 1.3 weight percent Ba in one sample analyzed by 

Maas and others (1995).

Bulk Geochemistry of Sulfide-Rich 

Samples

Sampling and Data Compilation

The limited number of samples collected during this 

study provides only a reconnaissance coverage of VMS 

deposits in the region. Although care was taken to obtain representative samples from mine dumps, adits, and drill cores, 

these samples do not necessarily reflect the true mineralogic 

and chemical variations in a given deposit, especially in mine 

dumps that were previously sampled—some extensively—by 

earlier workers. Moreover, before 1910 and the widespread 

use of froth-flotation technology for efficiently separating Zn 

from Cu and Pb in polymetallic ores, sphalerite commonly 

was not recovered; sphalerite also was a penalty in the ores 

during smelting. Thus, a disproportionate amount of this 

mineral may have been left on the mine dumps during early 

mining operations.

For compilation purposes here, geochemical data for base 

and precious metals acquired during this study are combined 

with those of Maas and others (1995, table A–2) and several 

exploration and mining company reports. The mining-company data were obtained in the 1980s and 1990s on a diverse 

suite of sulfide-rich samples from mine dumps, underground 

workings, and drill cores. Because of proprietary issues, these 

data are not individually cited here but, instead, are included 

with those of Maas and others (1995) and this study to permit 

calculation of more meaningful averages for Cu, Zn, Pb, Ag, 

and Au contents in the deposits under consideration.

Base and Precious Metals

Average base- and precious-metal contents in the major 

VMS deposits of the study area (fig. 1) are listed in table 2, 

and representative analyses of individual samples are listed in 

table 3 (Wales Group) and table 4 (Moira Sound unit). Overall, 

the sulfide-rich (>10 volume percent) samples contain proportionately much more Cu and Zn than Pb (fig. 4A). Elemental 

data in samples from the VMS deposits in the Wales Group 

deposits display a similar distribution to those from the 

Moira Sound unit, which are dominated by more Zn rich bulk 

compositions. We note, however, that this difference may be 

only an artifact of sampling density. The maximum average 

Pb content was measured in samples from the Ruby Tuesday 

(Fish Show) deposit (table 2). One relatively Pb rich sample 

from the Nutkwa North deposit (NKN, fig. 1), in the Wales 
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 11

Pb (wt pct) Zn (wt pct)

A Cu (wt pct)

Wales Group

VMS samples

Moira Sound unit

VMS samples

LO

NK

Cu+Pb+Zn (percent) Ag (ppm)

Au (ppm)

Auriferous

Base-metal

Wales Group

VMS samples

Moira Sound unit

 VMS samples

B

Lookout Mountain

Big Harbor West

Khayyam

Copper City

Corbin

Nutkwa area

Ruby Tuesday

Keete Inlet

EXPLANATION

Figure 4. Ternary plots of average whole-rock compositions of sulfiderich samples from significant volcanogenic massive sulfide (VMS) 

deposits in study area (fig. 1). Separate fields for samples from Wales 

Group deposits (stippled) and Moira Sound unit deposits (hachured) are 

compiled from data of Barrie (1984), Thurston (1994), Maas and others 

(1995), Terry and Gibson (1998), Abacus Mining and Exploration Corp. 

(2003, URL http://www.amemining.com/), and this study (tables 3, 4). A, Cu-PbZn ternary plot. LO, Lookout Mountain (including the Dama deposit); NK, 

Nutkwa area. Data for two samples of base-metal-poor massive pyrite 

from the Barrier Islands are omitted. B, (Cu+Pb+Zn)-Au-Ag ternary plot. 

Auriferous and base-metal fields for ancient VMS deposits (n=370) from 

Hannington and others (1999).
12  Studies by the U.S. Geological Survey in Alaska, 2005

Group, is compositionally distinct from the other samples (fig. 

4A), probably because of its very low base-metal contents.

Average proportions of base and precious metals in major 

VMS deposits of the study area (fig. 1), including the fields 

defined by individual samples from the VMS deposits in the 

Wales Group and Moira Sound unit, are plotted in figure 4B. 

In contrast to the pattern shown by base metals only (fig. 4A), 

figure 4B suggests that the samples from the Moira Sound unit 

are slightly Ag rich relative to those from the Wales Group. 

Sulfide-rich samples from the Wales Group generally contain 

proportionately more Cu+Pb+Zn and less Ag relative to those 

from the Moira Sound unit. We do not consider this difference 

to be an artifact of sampling density because the Ag-poor compositions of samples from the Wales Group are distinct from 

those of samples from the Moira Sound unit. Au proportions 

are broadly similar in both sample groups. We note, however, 

that the Au proportions in individual samples vary considerably, with the maximum values occurring in samples from the 

Copper City, Lookout Mountain, and Nutkwa deposits (table 

2), possibly reflecting isolated gold grains in single samples 

rather than a homogeneous distribution of Au.

Trace Metals

Bulk compositions of sulfide-rich rocks vary widely 

for many metals. Among the trace metals, Co content ranges 

from <10 to 398 ppm and broadly correlates with Ni content (<10–253 ppm); maximum contents of both Co and Ni 

occur mostly in samples from the Khayyam and Stumble-On 

deposits (fig. 5A). Samples containing more than 1 weight 

percent Cu show an overall positive correlation of Cu with Ag 

contents; maximum Ag contents were measured in samples 

from the Copper City and Niblack-Lookout Mountain deposits 

(fig. 5B). A positive correlation between Pb and Sb in some 

samples (fig. 5C) suggests the presence of one or more Pb-Sb 

sulfosalt minerals, such as boulangerite (Pb5Sb4S11) or bournonite (PbCuSbS3), particularly in galena-rich samples from the 

Ruby Tuesday (Fish Show) deposit. Somewhat high contents 

of Sb (max 77 ppm) and Ag (max 310 ppm) may reflect, 

respectively, Sb-rich pyrite in one sample from the Barrier 

Islands No. 2 deposit and minor tetrahedrite [(Cu,Fe,Ag)12(Sb,

As)4S13] in one sample from the Copper City deposit (fig. 5D). 

Overall, Zn and Hg contents show a positive correlation, with 

samples from the Khayyam and Stumble-On deposits yielding 

the maximum Hg content for a given Zn content (fig. 5E). Au 

and As contents are uncorrelated, even for Au-rich (4.4–9.3 

ppm) samples from the Copper City, Khayyam, Lookout 

Mountain, and Niblack deposits (fig. 5F).

Sulfide Mineral Chemistry

LA–ICP–MS analyses of different sulfide minerals 

show a range of nonessential-element contents that reflects 

both mineral inclusions and crystallographic substitutions 

(for example, Huston and others, 1995), where “nonessential 

elements” are defined as metals and nonmetals that are not 

required for the formation of a specific sulfide mineral, such as 

Cu and Pb in pyrite and Sb and Ag in galena. Mineral inclusions containing nonessential elements are easily observed 

microscopically in reflected light, although some are too small 

(<1 μm diam) to be visible even at 500× magnification. The 

Deposit Cu Pb Zn Ag Au n (fig. 1) (wt pct) (wt pct) (wt pct) (ppm) (ppm)

Khayyam ----------------- 29 4.86 <0.01 5.16 27.2 1.65

Big Harbor West -------- 12 11.7 0.04 1.07 56.9 0.85

Ruby Tuesday1 ---------- 5 0.52 4.44 16.4 25.6 0.11

Copper City -------------- 7 9.52 0.08 15.3 155 5.70

Corbin -------------------- 14 2.69 0.09 14.0 38.8 0.87

Keete Inlet --------------- 4 2.36 <0.01 4.13 8.8 0.29

Nutkwa2 ------------------ 25 1.29 0.42 18.1 47.7 2.33

Lookout Mountain3 ----- – – 1.70 40.03 3.22 36.4 2.77

Table 2. Average base- and precious-metal contents in sulfide-rich samples from major volcanogenic 

massive sulfide deposits on southern Prince of Wales Island, southeastern Alaska.

1

Includes both the Fish Show and Polymetal Lode deposits.

2

Includes both the Nutkwa Main and Nutkwa North deposits.

3

Inferred geologic resource from Niblack Mining Corp. (2006, URL http://www.niblackmining.com/).

4

Estimated from analyses of four U.S. Geological Survey samples.

[Data are compiled only for mineralized samples containing >3 weight percent Cu+Pb+Zn; data sources: Barrie (1984), 

Thurston (1994), Maas and others (1995), Terry and Gibson (1998), and this study]
Sample ------- 1 2 3 4 5 6 7 8 9 10 11 12 

Major elements

Al2O3 ---- 0.18 0.72 0.12 0.24 0.13 6.40 5.45 3.66 0.35 0.43 0.12 1.27 TiO2------ 0.01 0.04 0.01 0.01 0.01 0.03 0.03 0.13 0.01 0.01 0.1 0.01 Fe2O3 ---- 43.6 41.3 37.2 15.2 43.9 29.0 31.0 16.0 33.6 43.8 23.0 40.0 MnO ----- 0.006 0.012 0.002 0.029 0.005 0.137 0.284 0.019 0.063 0.016 0.023 0.556 MgO ----- 0.09 0.36 0.06 0.22 0.09 3.83 5.78 0.02 0.08 0.42 0.09 1.28 CaO------ 0.08 0.04 0.08 0.03 0.03 0.13 0.27 0.01 0.26 0.03 0.11 2.11 Na2O----- 0.01 0.01 0.01 0.01 0.01 0.04 0.01 0.25 0.01 0.01 0.01 0.01 K2O ------ 0.01 0.01 0.01 0.01 0.01 0.06 0.11 2.41 0.01 0.01 0.01 0.01 P2O5 ------ 0.03 0.03 0.01 0.02 0.02 0.09 0.17 0.01 0.16 0.03 0.02 0.04 S---------- 50.4 43.6 34.7 34.3 37.0 18.9 26.6 27.1 41.2 42.1 36.9 37.4 

Minor and trace elements

Li--------- 2 2 2 2 2 20 16 2 2 2 2 2 Sr--------- 2 2 2 2 2 5 3 7 15 2 109 130 Ga -------- 48 40 30 121 48 63 38 25 60 39 76 50 V --------- 74 86 27 67 85 96 19 16 24 34 15 158 Sc--------- 2 2 2 2 2 2 2 3 2 2 2 2 Co -------- 78 146 19 45 112 39 16 4 19 157 40 24 Ni--------- 14 16 11 4 42 8 7 14 15 15 7 12 Mo ------- 26 56 8 14 26 20 8 111 46 46 27 24 Cu -------- 13,910 63,850 342,000 386 18,950 45,160 233,700 700 69,780 107,800 588 13,830 3,Pb -------- 19 41 50 12 8 37 620 63,440 205 205 5,600 69 4,Zn -------- 30,530 113,100 19,140 566,700 124,100 490 2,840 248,300 251,200 2,420 426,100 71,340 297,Cd -------- 72 269 80 2,160 422 2 13 806 763 4 1,600 173 Bi--------- 50 50 50 50 50 50 50 50 50 50 95 50 Ag-------- 9 35 136 4 22 17 97 62 127 70 81 7 Au-------- 0.60 1.65 1.37 0.09 0.10 1.08 1.49 0.15 5.38 1.48 0.30 0.41 Sb -------- 0.60 0.60 0.60 0.70 0.60 2.00 1.00 56.2 10.8 11.0 3.80 0.60 As -------- 64.1 59.0 6.50 4.70 37.9 41.8 11.8 250 21.2 591 11.0 12.2 Se--------- 11.5 39.3 0.20 1.50 4.50 4.60 3.50 13.3 0.20 168 6.30 1.70 Te -------- 2.30 53.8 0.10 0.40 2.30 8.10 0.40 5.90 5.70 37.7 36.3 1.00 Hg-------- 0.38 1.14 0.40 8.71 1.94 0.14 0.56 8.46 15.9 1.2 31.3 1.17 Tl--------- 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 2.1 0.1 0.2 

Table 3. Representative whole-rock analyses of sulfide-rich samples from volcanogenic massive sulfide deposits in the Wales Group on southern Pvicinity, southeastern Alaska.

Samples:

1. JS–00–33H, upper Khayyam Mine dump; pyritic sulfide with minor matrix chalcopyrite and sphalerite.2. JS–00–62E, lower Khayyam Mine dump; pyritic sulfide with abundant matrix sphalerite and chalcopyrite.3. JS–00–62F, lower Khayyam Mine dump; massive fine-grained chalcopyrite with sparse sphalerite and quartz.4. JS–00–36C, Stumble-On Mine dump; sphalerite with minor pyrite.5. JS–00–36D, Stumble-On Mine dump; massive fine-grained pyrrhotite with sphalerite and minor pyrite.6. JS–00–29C, Big Harbor East Mine adit; semimassive pyritic sulfide in quartz-chlorite schist with abundant chalcopyrite.7. JS–00–31D, Big Harbor West Mine outcrop; semimassive chalcopyrite in chlorite schist with minor pyrite and sparse sphalerite.8. RT–FS–MS, Ruby Tuesday (Fish Show) Mine dump; semimassive sphalerite in felsic tuff with abundant galena and sparse chalcopyrite.9. JS–00–55C, Copper City Mine dump; massive fine-grained chalcopyrite with abundant pyrite and minor chalcopyrite and quartz.

10. JS–00–56D, Corbin Mine dump; massive fine-grained pyritic sulfide with abundant chalcopyrite and trace sphalerite.11. JS–00–56J, Corbin Mine dump; layered massive sphalerite and pyrite with sparse quartz and trace galena.12. JS–00–53D, Keete Inlet Mine dump; massive pyritic sulfide with minor chalcopyrite, sphalerite, quartz, magnetite, and carbonate.13. JS–00–39A, Nutkwa Mine dump; massive pyritic sulfide with abundant sphalerite, minor quartz, chlorite, and sericite, and sparse chalcopyrite and ga14. JS–00–42A, Trocadero Bay “exhalite” outcrop; coarse-grained pyritic sulfide with minor quartz, sericite, and chlorite and trace chalcopyrite and sphal15. JS–00–66, Deer Bay “exhalite” outcrop; quartz-sericite-chlorite schist with disseminated pyrite and sparse chalcopyrite.

granoblasticgranoblastic

granoblastic

[Major-element analyses in weight percent; minor- and trace-element analyses in parts per million. All analyses were performed at XRAL Laboratories in Denver, Colo., by indatomic-emission spectrometry, atomic-absorption spectrometry, and fire-assay methods. Total Fe as Fe2O3. Elements analyzed for but not measured above their lower limits of d(1 ppm), U (100 ppm)]
Sample ----- 1 2 3 4 5 6 7 8 9 10 11 12 

Major elements

Al2O3 ---- 0.48 4.77 4.79 0.23 0.29 2.11 5.88 1.87 3.53 5.87 1.33 14.3 TiO2------ 0.008 0.045 0.008 0.008 0.008 0.008 0.008 0.018 0.017 0.025 0.13 0.42 Fe2O3 ---- 44.3 26.9 39.9 46.2 40.3 34.0 39.5 43.5 40.5 35.6 47.8 30.3 MnO ----- 0.019 0.002 0.065 0.048 0.011 0.080 0.081 0.004 0.052 0.003 0.006 0.032 MgO ----- 0.35 0.26 3.56 0.29 0.24 1.28 4.91 0.14 2.29 0.11 0.64 0.99 CaO------ 0.04 0.02 0.27 1.10 0.20 1.99 0.04 0.03 0.01 0.01 0.14 0.22 Na2O----- 0.01 0.03 0.01 0.02 0.01 0.01 0.01 0.61 0.09 0.20 0.03 0.27 K2O ------ 0.01 1.64 0.01 0.01 0.01 0.01 0.01 0.25 0.13 1.63 0.19 4.06 P2O5 ------ 0.02 0.02 0.19 0.11 0.03 0.01 0.03 0.02 0.01 0.01 0.01 0.01 S---------- 41.9 23.8 34.5 18.1 45.5 32.1 33.7 44.2 29.9 26.4 37.5 23.0 

Minor and trace elements

Li--------- 2 2 7 2 2 2 8 2 12 2 9 10 Sr--------- 2 4 4 16 3 22 2 10 5 17 4 17 Ga -------- 40 24 41 124 65 37 40 40 6 13 4 13 V --------- 33 16 31 74 39 77 68 34 12 13 26 260 Sc--------- 2 2 2 2 2 4 3 2 2 6 2 37 Co -------- 26 12 29 19 23 19 26 23 55 22 55 28 1Ni--------- 24 6 12 13 10 8 15 13 3 3 253 47 Mo ------- 16 40 105 36 44 104 88 9 146 16 58 13 Cu -------- 31,540 16,200 42,530 31,990 57,010 290,700 17,130 4,310 1,100 11,310 45 71 Pb -------- 146 19 32 4220 29 35 20 423 12 10 25 1,230 Zn -------- 9,870 152 8,660 65,750 134,400 1,740 15,930 785 496 30 56 153 1Cd -------- 51 2 18 170 493 10 62 2 3 2 2 2 Bi--------- 50 50 51 50 50 50 50 50 50 50 50 50 Ag-------- 78 8 42 116 62 150 47 112 4 29 2 30 Au-------- 4.62 0.53 1.09 11.0 0.66 0.30 0.34 4.39 0.76 2.15 0.03 0.47 Sb -------- 5.80 0.80 1.00 1.80 0.60 0.60 0.60 0.90 0.60 0.80 23 77 As -------- 257 23.7 85.5 94.2 14.5 3.90 41.9 8.80 7.10 2.90 248 1,820 Se--------- 3.90 2.10 19.0 0.40 1.10 0.40 4.70 5.20 19.5 4.00 3.40 0.20 Te -------- 29.7 9.60 66.2 50.0 22.2 0.10 18.5 59.6 9.00 49.6 0.10 0.10 Hg-------- 2.81 0.07 1.12 9.11 4.39 0.26 0.53 0.14 0.40 0.84 0.07 1.53 Tl--------- 0.3 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.2 0.6 72 

Table 4. Representative whole-rock analyses of sulfide-rich samples from volcanogenic massive sulfide deposits in the Moira Sound unit on southeand vicinity, southeastern Alaska.

Samples:

1. JS–00–28A, lower Niblack Mine dump; weakly layered massive pyritic sulfide with minor chalcopyrite and sparse sphalerite.2. JS–00–28C, lower Niblack Mine dump; siliceous rocks with abundant disseminated pyrite, lesser chalcopyrite, and minor sericite.3. JS–00–28I, upper Niblack Mine dump; semimassive pyrite and chalcopyrite in quartz-bearing chlorite schist.4. 84AGK053C, upper Niblack Mine dump; massive magnetite iron-formation with abundant pyrite and chalcopyrite and angular clasts of jasper.5. LO–53/624.2, Dama Prospect drill core, Niblack area; layered pyrite, sphalerite, and minor chalcopyrite.6. LO–61/573.0, Dama Prospect drill core, Niblack area; massive fine-grained chalcopyrite with minor pyrite and sparse sphalerite.7. LO–61/577.5, Dama Prospect drill core, Niblack area; semimassive pyritic sulfide in chloritic tuff(?) with sparse chalcopyrite and sphalerite.8. LO–99/367, Lookout Mountain Prospect drill core, Niblack area; massive pyritic sulfide with minor quartz and sericite and trace chalcopyrite and sphalerite.9. MC–MS–2, Moira Copper Mine dump; semimassive pyritic sulfide with abundant quartz, minor chlorite, and trace chalcopyrite.

10. MC–MS2, Moira Copper Mine dump; semimassive pyritic sulfide with minor quartz, chlorite, and sericite and sparse chalcopyrite.11. BI1–MS, Barrier Islands Prospect No. 1; brecciated massive fine-grained pyrite with sparse quartz and chlorite.12. BI2–MS, Barrier Islands Prospect No. 2; semimassive pyritic sulfide with abundant sericite and sparse quartz.13. BI7–MS, Barrier Islands Prospect No. 7; semimassive pyritic sulfide with minor quartz and chlorite.14. BI9–MS–1, Nichols Bay Mine dump; massive fine-grained pyrrhotite (partially oxidized) with abundant disseminated Mn-rich garnet, minor pyrite, and sparse sphaler15. JS–00–57A, Datzkoo Harbor occurrence, southeastern Dall Island; massive pyritic sulfide with minor quartz and chlorite and trace sphalerite.

[Major-element analyses in weight percent; minor- and trace-element analyses in parts per million. All analyses were performed at XRAL Laboratories in Denver, Colo., by inductively couspectrometry, atomic-absorption spectrometry, and fire-assay methods. Total Fe as Fe2O3. Elements analyzed for but not measured above their lower limits of detection (in parentheses): Be 
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 15

1 10 100 1,000

1

10

100

1,000 Ni CONTENT, IN PPM

Co CONTENT, IN PPM

A

100 1,000 10,000 100,000 1,000,000

1

10

100

1,000 B

10 100 1,000 10,000 100,000

0.1

1

10

100

C

1 10 100 1,000

0.1

1

10

100

D

1 10 100 1,000 10,000

0.01

0.1

1

10

F

Niblack

Lookout Mountain

Moira Copper

Barrier Islands and Nichols Bay

Big Harbor West

Big Harbor East

Khayyam

Stumble-On

Copper City

Corbin

Nutkwa area

Ruby Tuesday

Keete Inlet

Hozer

Datzkoo Harbor

Cable Creek

Deer Bay

Trocadero Bay 

100 1,000 10,000 100,000 1,000,000

0.01

0.1

1

10

100

E

EXPLANATION Ag CONTENT, IN PPM

Cu CONTENT, IN PPM

Sb CONTENT, IN PPM

Pb CONTENT, IN PPM

Sb CONTENT, IN PPM

Ag CONTENT, IN PPM

Hg CONTENT, IN PPM

Zn CONTENT, IN PPM As CONTENT, IN PPM Au CONTENT, IN PPM

Figure 5. Binary plots of whole-rock compositions of sulfide-rich samples from study area (fig. 1). A, Co versus Ni contents. B, 

Cu versus Ag contents. C, Pb versus Sb contents. D, Ag versus Sb contents. E, Zn versus Hg contents. F, As versus Au contents. 

Lookout Mountain includes the Dama deposit.
16  Studies by the U.S. Geological Survey in Alaska, 2005

very high nonessential-element contents determined from some 

LA–ICP–MS spectra of apparently inclusion free spots probably record the presence of mineral inclusions on the surface 

of the sample that were too small to be easily visible, or were 

intersected by the laser beam during penetration as much as 10 

μm below the surface. In our study, very large spectral peaks for 

nonessential elements (for example, Bi in pyrite, Sn in chalcopyrite) were screened during data reduction of the LA–ICP–MS 

analyses, such that the high contents of these elements were 

excluded from the calculated compositions. In some samples, 

such as those from the Big Harbor and Copper City deposits, 

meaningful analyses of sphalerite were unobtainable, owing to 

myriad small inclusions of chalcopyrite and (or) pyrite.

Pyrite

High nonessential-element contents in pyrite are dominated by Cu, Zn, and Pb contents that correlate with inclusions of chalcopyrite, sphalerite, and galena, respectively. 

Absolute abundances of these elements are unknown but 

estimated to range from several thousand parts per million 

to as much as several weight percent. Excluding base metals 

and trace elements that are unlikely to substitute for Fe within 

the pyrite lattice, the largest LA–ICP–MS spectral peaks are 

dominated by Mo, which likely reflects inclusions of molybdenite, although possible stoichiometric substitution of Mo for 

Fe cannot be ruled out (see Huston and others, 1995). High 

Mo contents were measured in pyrite grains from the VMS 

deposits in both the Wales Group (Corbin, Keete Inlet, Nutkwa 

Main) and the Moira Sound unit (Copper City, Dama). Some 

pyrite grains from the Corbin deposit also have high Bi, As, 

and Sb contents in the same analytical spots, suggesting residence in one or more sulfosalt minerals. Very high Bi contents 

unaccompanied by high Cu, Zn, Pb, As, or Sb contents in 

several pyrite grains from the Lookout Mountain and Niblack 

deposits may reflect the presence of native bismuth, which 

occurs in massive sulfide deposits elsewhere (for example, 

Craig, 1980; Callaghan, 2001). The high Sn content in some 

pyrite samples from the Moira Copper deposit suggests a host 

in either cassiterite or stannite. Detailed microbeam studies 

involving scanning electron microscopy and electron-microprobe analysis will be required to identify the mineralogic 

residence of these high metal contents.

Analyses of inclusion-free spots in pyrite (n=170) indicate mostly low contents of such elements as Co, Ni, Mn, Tl, 

As, Sb, and Se (figs. 6A, 6B; tables 5, 6), any of which may 

replace Fe (Co, Ni, Mn, Tl) or S (As, Sb, Se) within the pyrite 

lattice by either stoichiometric or nonstoichiometric substitution (Huston and others, 1995). With few exceptions, maximum contents are 200 ppm As, 30 ppm Sb, 200 ppm Co, 150 

ppm Ni, 100 ppm Mn, 200 ppm Se, and 1 ppm Tl. As contents 

are relatively high in some pyrite samples from the Big Harbor 

East deposit (max 1,848 ppm) and the Ruby Tuesday (Fish 

Show) deposit (max 3,050 ppm), suggesting the presence of 

an Fe(As,S)2 solid solution, as discussed for pyrite samples 

from other VMS deposits by Huston and others (1995). Pyrite 

samples from the Khayyam and Stumble-On deposits are Co 

rich (max 1,436 and 2,057 ppm, respectively). Pyrite samples 

from the Barrier Islands deposits are distinctive in their 

extremely high contents of several trace elements, including 

maximum contents of 1.44 weight percent As, 283 ppm Sb, 

3,552 ppm Mn, and 274 ppm Tl (figs. 6A, 6B; table 6). Pyrite 

from the Barrier Islands No. 2 deposit has the highest contents 

of these elements among the three localities sampled. Overall, 

pyrite samples from the Barrier Islands VMS deposits are 

chemically unlike those from other VMS deposits in the study 

area (fig. 1), suggesting different conditions of formation or 

preservation. The very high As, Sb, Mn, and Tl contents in 

pyrite samples from the Barrier Islands deposits do not require 

separate mineralogic residence but, instead, probably reflect 

substitution by these elements within the pyrite lattice (see 

Huston and others, 1995).

Pyrrhotite

Six analyses of inclusion-free pyrrhotite in a sample of 

massive coarse-grained pyrrhotite-pyrite-chalcopyrite ore from 

the Stumble-On Mine generally indicate low contents (<30 

ppm) of a broad suite of trace elements (table 5), except for 

maximum contents of 86.6 ppm Ni and 1,147 ppm Se, which 

were measured in different analytical spots. Ni can substitute for Fe within the pyrrhotite lattice; however, it is unclear 

whether the high Se content reflects crystallographic substitution (that is, of Se for S) or the presence of a small Se-rich 

mineral inclusion.

Sphalerite

In hand specimens, sphalerite in the VMS deposits of 

the study area (fig. 1) varies widely in color, ranging from 

yellow at the Niblack area and Nutkwa deposits to black at 

the Khayyam and Stumble-On deposits. Sphalerite in all of 

these deposits is unzoned, as observed in polished and doubly 

polished thin sections. Some deposits (for example, Corbin, 

Khayyam, Ruby Tuesday) contain sphalerite with abundant 

small chalcopyrite inclusions. Galena inclusions are also 

common in sphalerite grains from the Corbin, Dama, Lookout 

Mountain, and Ruby Tuesday (Fish Show) deposits. During 

data reduction, large spectral peaks for Hg were identified in 

some sphalerite grains from the Khayyam deposit, and large 

peaks for In were measured in some sphalerite grains from the 

Dama and Nutkwa Main deposits, but because the size of these 

peaks implied contamination by inclusions (for example In in 

chalcopyrite), elemental contents were not determined.

Analyses of inclusion-free spots in sphalerite (n=35) 

show the presence of various trace elements (tables 7, 8) with 

generally dispersed patterns (figs. 6C–6F). These elements 

substitute for either Zn or S within the sphalerite lattice (for 

example, Huston and others, 1995). Overall, Fe contents range 

from 330 ppm in the Nutkwa Main deposit to 7.46 weight 

percent in the Khayyam deposit. Mn contents are relatively 
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 17

0.1 1 10 100 1,000 10,000

0.1

1

10

100

1,000 Sb CONTENT, IN PPM

Mn CONTENT, IN PPM

A

1 10 100 1,000 10,000 100,000

0.01

0.1

1

10

100

1,000 Tl CONTENT, IN PPM

As CONTENT, IN PPM

B

100 1,000 10,000 100,000

1

10

100

1,000 Mn CONTENT, IN PPM

Fe CONTENT, IN PPM

C

100 1,000 10,000 100,000

1

10

100

1,000 Cu CONTENT, IN PPM

D

100 1,000 10,000 100,000

1

10

100

1,000 Hg CONTENT, IN PPM

E

1 10 100 1,000

1

10

100

1,000 In CONTENT, IN PPM

Cu CONTENT, IN PPM

F

Niblack

Lookout Mountain

Moira Copper

Barrier Islands and Nichols Bay

Khayyam and Stumble-On

Copper City

Big Harbor West

Big Harbor East

Corbin

Nutkwa area

Ruby Tuesday

Keete Inlet

Pyrite Pyrite

Sphalerite Sphalerite

Sphalerite Sphalerite

EXPLANATION

Fe CONTENT, IN PPM

Fe CONTENT, IN PPM

Figure 6. Binary plots of laser-ablation inductively coupled plasma mass-spectrometric analyses of sulfide-rich samples 

from study area (fig. 1). A, Mn versus Sb contents in pyrite. B, As versus Tl contents in pyrite. C, Fe versus Mn contents 

in sphalerite. D, Fe versus Cu contents in sphalerite. E, Fe versus Hg contents in sphalerite. F, Cu versus In contents in 

sphalerite. Lookout Mountain includes the Dama deposit.
Sample ----- 1 2 3 4 5 6 7 8 9 10 11 12 1Mineral----- py py py py py py py py py py py py pMn ---------- 2.90 2.02 0.01 3,550 0.01 0.01 0.01 0.29 0.01 0.85 0.38 1.03 0.Cu ----------- 1.52 8.66 8.57 56.4 9.64 n.r. 4.01 2.90 0.01 n.r. n.r. 1.58 3.Pb ----------- 0.02 0.27 0.01 3.23 0.01 0.01 0.07 3.20 0.31 0.01 0.01 0.22 0.Zn ----------- 3.22 0.01 18.1 58.7 0.01 12.5 5.40 7.66 0.85 8.30 8.61 6.29 18.Sn ----------- 0.01 0.01 0.01 1.25 3.87 1.01 1.49 2.30 0.44 1.59 2.77 0.01 0.Co ----------- 1.25 152 8.34 62.1 698 3.46 2,060 104 9.37 0.96 37.7 96.5 1.Ni------------ 12.4 4,600 131 32.3 6.65 271 1.22 55.4 79.4 35.0 22.2 29.5 5.Mo ---------- 1.10 3.18 0.01 2.40 0.01 2.16 0.15 0.01 0.78 0.01 0.42 1.25 0.In ------------ 0.05 0.01 0.01 0.12 0.01 0.01 0.01 0.74 0.11 0.10 0.13 0.14 0.Cd ----------- 2.60 0.01 1.42 0.01 0.01 0.01 0.01 3.82 3.91 0.51 0.01 0.68 2.Bi------------ 0.01 0.01 0.02 0.01 0.01 0.01 0.01 0.15 0.01 0.01 0.01 0.01 0.Ag----------- 0.01 2.29 2.01 4.67 0.01 0.01 1.02 0.01 0.01 0.09 0.62 2.02 0.Sb ----------- 0.01 1.36 0.01 154 0.31 1.01 0.01 0.01 0.91 1.08 0.87 0.14 0.As ----------- 28.1 1.92 8.16 4,800 127 0.01 64.7 813 360 28.8 30.1 9.68 1.Se------------ 42.3 24.0 40.4 0.01 38.9 0.01 0.01 0.01 0.01 0.01 8.81 24.2 0.Te ----------- 0.01 0.01 1.50 0.01 5.47 6.89 0.01 0.01 0.01 0.58 1.89 0.62 1.Hg----------- 0.01 0.51 0.01 3.61 0.01 0.31 0.09 0.33 0.01 0.64 0.50 0.01 0.Tl------------ 0.01 0.29 0.10 212 0.44 0.01 0.01 0.46 0.01 0.01 0.01 0.01 0.

Samples:

1. JS–00–28A, lower Niblack Mine dump; pyrite with minor sphalerite and chalcopyrite.2. LO–99/290, Lookout Mountain Prospect drill core; pyrite with minor chalcopyrite and sphalerite in fine-grained rhyolite.3. MC–MS, Moira Copper Mine dump; pyrite and chalcopyrite.4. BI–2–MS, Barrier Islands occurrence No. 2 (Gehrels and others, 1983); pyrite with trace sphalerite.5, 6. JS–00–62E, upper Khayyam Mine dump; pyrite with sphalerite and chalcopyrite.7. JS–00–36C, Stumble-On Mine dump; pyrite porphyroblasts in massive granular sphalerite.8. JS–00–29C, Big Harbor East Mine adit; pyrite with abundant chalcopyrite.9. RT–FS–MS2, Ruby Tuesday (Fish Show) Mine dump; pyrite with sphalerite, galena, and minor chalcopyrite.

10. JS–00–55C, Copper City Mine dump; pyrite with abundant chalcopyrite, minor magnetite, and trace sphalerite.11. JS–00–56I, Corbin Mine dump; pyrite with abundant sphalerite.12. JS–00–53D, Keete Inlet Mine dump; pyrite with abundant chalcopyrite and minor sphalerite.13. JS–00–39A, Nutkwa Main Mine dump; pyrite with abundant sphalerite, minor chalcopyrite, and trace galena.14, 15. JS–00–36D, Stumble-On Mine dump; pyrrhotite with abundant pyrite and sphalerite and minor chalcopyrite.

Table 5. Representative minor- and trace-element analyses of pyrite and pyrrhotite in sulfide-rich samples from southern Prince of Wales Island and vi

[Laser-ablation inductively coupled plasma mass-spectrometric analyses at the USGS laboratory in Denver, Colo. N.r., not reported. Minerals: po, pyrrhotite; py, pyrite. All sampamounts of quartz, and some also contain a minor amount of sericite. Fe content not reported]
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 19

Wales Group deposits Moira Sound unit deposits Barrier Islands deposits ___________________________ _____________________________ ________________________________

n----------- 113 27 30

Mean S.d. Range Mean S.d. Range Mean S.d. Range

Mn -------- 1.53 7.75 0.0–72.0 0.44 0.76 0.0–2.90 445 864 0.0–3,552

Co--------- 203 366 0.0–2,057 21.6 31.8 0.0–152 46.0 77.8 0.0–315

Ni --------- 34.5 71.2 0.0–468 288 968 0.42–4,593 132 220 0.0–874

Cu--------- 5.72 7.68 0.0–47.5 7.77 7.97 0.58–31.1 28.5 44.7 0.0–191

In---------- 0.11 0.18 0.0–0.97 0.16 0.33 0.0–1.32 0.11 0.14 0.0–0.44

Zn--------- 11.2 29.3 0.0–290 8.99 12.6 0.0–55.1 34.6 76.5 0.0–380

Cd--------- 1.07 1.67 0.0–7.58 0.95 1.47 0.0–5.71 1.11 1.73 0.0–6.36

Pb --------- 0.18 0.36 0.0–3.20 0.18 0.22 0.0–0.84 1.24 1.81 0.0–8.41

Ag -------- 0.77 1.11 0.0–5.93 2.53 5.01 0.0–18.3 2.67 4.81 0.0–19.1

As--------- 124 382 0.0–3,050 20.8 44.1 0.0–204 1,979 3,679 0.0–14,412

Sb --------- 0.39 0.62 0.0–4.03 0.38 0.50 0.0–2.12 39.2 78.6 0.0–283

Bi --------- 0.02 0.05 0.0–0.32 0.06 0.12 0.0–0.54 0.02 0.02 0.0–0.10

Hg -------- 0.67 1.08 0.0–8.79 0.34 0.52 0.0–1.85 2.21 3.79 0.0–14.9

Tl --------- 0.08 0.14 0.0–0.69 0.09 0.14 0.0–0.65 46.4 94.5 0.0–275

Se --------- 48.0 143 0.0–1,134 34.1 50.7 0.0–204 45.8 66.0 0.0–224

Te --------- 1.20 2.98 0.0–27.3 0.48 0.65 0.0–2.38 0.68 1.37 0.0–7.23

Mo -------- 2.90 21.1 0.0–225 88.8 420 0.0–2,186 12.4 46.3 0.0–251

Sn --------- 0.73 0.94 0.0–4.79 0.42 0.62 0.0–2.23 0.96 1.29 0.0–6.30

Table 6. Average composition and ranges in composition of pyrite in sulfide-rich samples from southern Prince of Wales Island and 

vicinity, southeastern Alaska.

high (100–500 ppm) only in spots containing >1 weight percent Fe. An opposite trend is apparent for Cu, with maximum 

Cu contents (>100 ppm) measured in the most Fe poor (<0.2 

weight percent) spots. Results for Hg are clustered mainly 

by deposit, with minimum Hg contents (<10 ppm) measured 

in Fe-rich (>3 weight percent) spots in sphalerite samples 

from the Khayyam deposit but maximum Hg contents (>100 

ppm) measured in sphalerite samples from the Nutkwa Main 

and Corbin deposits. Significantly, the lowest Hg/Fe ratios in 

sphalerite were determined in samples from the Khayyam and 

Stumble-On deposits, which are the most highly metamorphosed, to upper amphibolite grade.

Chalcopyrite

Inclusions of native bismuth in chalcopyrite are inferred 

by the very high spectral peaks measured for Bi in some 

samples from the Moira Copper and Niblack deposits. These 

peaks lack associated As, Sb, Pb, or Ag peaks and so apparently do not reflect residence in a Bi-rich sulfosalt mineral. 

Native bismuth is considered the likely host, although microbeam techniques, such as scanning electron microscopy, would 

be required to confirm this hypothesis. Chalcopyrite from the 

Moira Copper deposit also has a very high Sn content but not 

a low Cu or S content, suggesting the presence of stannite or a 

similar Sn-rich sulfosalt mineral.

Analyses of inclusion-free spots in chalcopyrite (n=40) 

show relatively low contents (<100 ppm) of most of the trace 

elements analyzed (tables 7, 9). However, samples from the 

Khayyam deposit, in particular, are metal rich, including maximum contents of 252 ppm Ni, 437 ppm Zn, 2,400 ppm Se, and 

153 ppm Cd. High Zn contents also were measured in some 

chalcopyrite grains from other VMS deposits in the study 

area, with maximum contents of 625 ppm Zn in a sample 

from the Corbin deposit, 200 ppm As in a sample from the 

Dama deposit, 1,830 ppm Se in a sample from the Copper City 

deposit, and 213 ppm In in a sample from the Moira Copper 

deposit. The high Zn and Cd contents may reflect submicroscopic sphalerite inclusions, whereas the high Ni, Se, As, and 

In contents probably reflect substitution by these elements 

within the chalcopyrite lattice: Ni and In for Cu or Fe, and 

Se and As for S (see Huston and others, 1995; Axelsson and 

Rodushkin, 2001).

Galena

Galena is abundant only in the Ruby Tuesday deposit 

but also occurs in other deposits as small grains or inclusions 

in sulfides. Visible inclusions are generally absent in galena 

from VMS deposits of the study area (fig. 1). However, very 

high spectral peaks for some elements suggest the presence of 

submicroscopic inclusions in the galena. For example, galena 

from the Ruby Tuesday (Fish Show) deposit locally has high 

Sb and Ag contents that together imply residence in a sulfosalt mineral, such as tetrahedrite. One sample from the Dama 

deposit contained galena grains in sphalerite with high Ag 

[Minor- and trace-element analyses in parts per million by laser-ablation inductively coupled plasma mass spectrometry at the USGS laboratory in Denver, Colo. 

the Standard deviation (s.d.) is 1σ value. Grouping of deposits (see table 1) is based on stratigraphic, structural, and metamorphic parameters. Wales Group 

deposits comprise two samples each from the Khayyam, Ruby Tuesday (Fish Show), and Stumble-On deposits and one sample each from the Big Harbor East, 

Big Harbor West, Copper City, Corbin, Keete Inlet, Nutkwa Main, and Nutkwa North deposits]
Sample ----- 1 2 3 4 5 6 7 8 9 10 11 12 Mineral----- sl sl sl sl sl sl sl sl cp cp cp cp 

Fe------------ 2,990 4,620 2,280 59,100 32,100 9,830 17,800 1,540 N.r. N.r. N.r. N.r. Mn ---------- 10.1 38.4 53.2 113 117 127 66.6 11.6 0.50 0.01 6.73 0.01 Cu ----------- 86.8 125 15.7 N.r. 14.9 147 N.r. 368 N.r. N.r. N.r. N.r. Pb ----------- 6.27 1.68 0.37 0.01 0.01 7.56 0.01 11.6 0.44 0.01 0.01 0.67 Zn ----------- N.r. N.r. N.r. N.r. N.r. N.r. N.r. N.r. 81.3 0.01 119 133 Sn ----------- 3.49 14.9 4.10 6.93 2.23 10.8 0.01 46.5 0.01 10.3 1.55 2.44 Co ----------- 7.97 0.01 12.9 0.64 6.04 0.01 0.01 0.01 0.01 0.79 4.57 0.01 Ni------------ 0.01 17.6 0.74 0.01 0.01 0.01 0.01 7.23 0.017 17.0 1.64 0.01 Mo ---------- 0.01 0.01 0.44 33.9 1.08 28.3 42.9 22.1 80.8 3.45 0.01 0.01 In ------------ 140 143 24.4 12.2 4.85 0.01 33.8 102 64.6 213 2.56 18.1 5Cd ----------- 2,480 2,220 1,670 1,090 1,480 898 1,520 1,760 0.01 10.7 6.08 16.9 Bi------------ 3.73 0.65 0.01 0.01 0.01 0.66 0.01 0.26 0.01 0.23 0.12 0.18 Ag----------- 87.5 0.01 5.77 0.01 0.36 0.01 10.0 2.50 29.1 0.01 17.2 5.41 Sb ----------- 0.01 4.23 0.01 0.01 0.01 0.01 38.2 0.01 13.7 0.01 0.01 3.99 As ----------- 8.52 0.01 4.62 0.01 1.32 95.2 54.0 20.5 0.01 0.01 0.01 32.1 Se------------ 0.01 196 102 1,040 99.1 661 1,043 0.01 1,370 0.01 646 0.01 1,83Te ----------- 0.01 34.8 0.01 4.22 0.06 5.70 15.5 0.01 21.3 13.1 3.41 0.01 Hg----------- 24.9 35.7 29.5 16.8 3.46 14.7 229 241 0.01 0.01 5.33 3.75 Tl------------ 0.50 0.01 0.52 0.43 0.01 0.01 8.94 0.43 6.28 1.49 2.66 0.01 

Samples:

1, 2. LO–53/624.2, Dana Prospect drill core, Niblack area; sphalerite with pyrite and chalcopyrite.3. LO–99/290, Lookout Mountain Prospect drill core, Niblack area; sphalerite with pyrite and minor chalcopyrite.4. JS–00–62E, lower Khayyam Mine dump (tram terminal); sphalerite with pyrite and chalcopyrite.5. JS–00–36C, Stumble-On Mine dump; sphalerite with porphyroblastic pyrite.6. RT–FS–MS2, Ruby Tuesday (Fish Show) Mine dump; sphalerite with pyrite, galena, and minor chalcopyrite.7. JS–00–56I, Corbin Mine dump; sphalerite with abundant pyrite.8. JS–00–39A, Nutkwa Main Prospect dump; sphalerite with pyrite, minor chalcopyrite, and trace galena.9. LO–53/624.2, Dama Prospect drill core, Niblack area; chalcopyrite with pyrite and minor sphalerite.

10. MC–MS, Moira Copper Mine dump; chalcopyrite with pyrite and trace sphalerite.11. JS–00–62E, lower Khayyam Mine dump (tram terminal); chalcopyrite with pyrite and minor sphalerite.12. JS–00–31D, Big Harbor West Mine outcrop; chalcopyrite with pyrite and trace sphalerite.13. JS–00–55C, Copper City Mine dump; chalcopyrite with pyrite, minor magnetite, and trace sphalerite.14. JS–00–39A, Nutkwa Main Prospect dump; galena with pyrite and minor sphalerite and chalcopyrite.15. RT–FS–MS2, Ruby Tuesday (Fish Show) Mine dump; galena with sphalerite, pyrite, and minor chalcopyrite.

Table 7. Representative minor- and trace-element analyses of sphalerite, chalcopyrite, and galena in sulfide-rich samples from southern Prince vicinity, southeastern Alaska.

[Minor- and trace-element analyses in parts per million by laser-ablation inductively coupled plasma mass spectrometry at the USGS laboratory in Denver, Colo. N.r., not reportrite; gl, galena; sl, sphalerite. All samples contain minor to major amounts of quartz, and some also contain a minor amount of sericite]
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 21

Table 8. Average composition and ranges in composition of sphalerite in sulfide-rich samples from 

southern Prince of Wales Island and vicinity, southeastern Alaska.

Wales Group deposits Moira Sound unit deposits

______________________________ _________________________________

n -------- 28 7

Mean S.d. Range Mean S.d. Range

Fe---------- 2.43 2.03 0.03–7.46 0.30 0.12 0.21–0.49

Mn -------- 121 102 0.0–470 40.2 22.0 3.68–58.4

Co --------- 4.56 6.67 0.0–25.4 9.70 7.95 0.0–22.4

Ni---------- 8.44 25.4 0.0–121 6.85 5.37 0.74–17.7

Cu --------- 83.5 127 0.0–472 41.0 43.3 7.44–114

In ---------- 29.2 30.4 0.0–102 54.5 49.0 24.4–133

Cd --------- 1,465 336 898–2,354 1,928 344 1,616–2,556

Pb --------- 1.21 2.65 0.0–11.6 1.45 1.31 0.37–4.16

Ag --------- 12.7 19.9 0.0–74.3 17.7 14.3 4.00–44.2

As --------- 25.9 42.9 0.0–156 15.0 18.0 0.0–46.7

Sb --------- 3.43 8.28 0.0–38.2 0.65 1.44 0.0–3.87

Bi---------- 0.09 0.17 0.0–0.66 0.65 1.43 0.0–3.87

Hg --------- 71.5 80.3 0.0–241 29.2 9.96 15.6–44.2

Tl---------- 0.87 1.92 0.0–8.94 0.18 0.23 0.0–0.52

Se---------- 311 424 0.0–1,233 14.6 38.6 0.0–102

Te --------- 3.97 8.12 0.0–32.8 1.49 1.97 0.0–5.13

Mo -------- 15.4 30.5 0.0–134 5.68 14.3 0.0–38.1

Sn --------- 11.3 14.8 0.0–53.8 5.93 6.42 0.0–19.0

and Bi contents, consistent with the presence of other types of 

sulfosalt inclusion. One galena grain from the Ruby Tuesday 

(Fish Show) deposit also had a very high Sn content (estimated at >1 weight percent) without a concomitant decrease 

in S content, implying the presence of stannite or a similar 

Sn-rich sulfosalt mineral.

Limited data for inclusion-free spots in galena (n=7) 

show uniformly low contents (<20 ppm, table 7) of most of 

the trace elements analyzed, except in galena from the Nutkwa 

Main deposit, which has maximum contents of 164 ppm Sb, 

247 ppm Se, and 609 ppm Ag. High contents of these elements were also measured in galena from the Ruby Tuesday 

(Fish Show) deposit, with maximum contents of 97.3 ppm Sb, 

949 ppm Se, and 132 ppm Ag. These trace elements probably 

are hosted mainly within the galena lattice, although the high 

Ag content could reflect residence in one or more sulfosalt 

minerals (see Watling and others, 1995).

Sulfur Isotopes

Sulfur-isotopic analyses were performed to determine the 

sulfur sources of the VMS deposits of the study area (fig. 1) 

and to assess mineralizing processes. Sulfur-isotopic values 

of sulfides in the deposits (fig. 7; table 10) mainly range from 

−3 to 17 permil, excluding one very low value of −31.1 permil 

for semimassive pyrite from the Barrier Islands No. 1 deposit. 

The highest δ34Ssulfide values were measured in samples from 

the Big Harbor East and West deposits. Two groups of samples 

form isotopic outliers: one with δ34S values near 0 permil for 

sulfides in magnetite iron-formation from the Niblack deposit, 

and the other with a δ34S value of ~3 permil for semimassive 

pyrite from the Barrier Islands deposits. Massive pyrrhotite 

and pyrite in separate samples from the Nichols Bay deposit 

have δ34S values of −2.8 and −0.8 permil, respectively. Minor 

barite in a Mn-rich exhalite associated with the Big Harbor 

West deposit has a δ34S value of 30.6 permil; a similar δ34S 

value of 30.4 permil was measured on a pretectonic barite lens 

in limestone from the Lime Point deposit.

The δ34S values for sulfide minerals in the VMS deposits 

in the Moira Sound unit (fig. 8) range from −2.8 to 10.4 permil 

(avg 6.1±4.0 permil; n=22), overlapping some of those for 

sulfide minerals in the VMS deposits in the Wales Group, which 

range from 5.9 to 17.4 permil (avg 11.5±2.7 permil; n=67). In 

comparison, modern sea-floor hydrothermal systems with a 

significant sedimentary component in their footwall sequences 

have δ34Ssulfide values averaging −5 to 8 permil, with an overall 

range of 10 to 15 permil (Shanks, 2001). Sulfur-isotopic values 

for sulfides in Phanerozoic VMS deposits elsewhere show a 

comparable spread, with δ34Ssulfide values averaging 5 to 10 permil over a similar range (Ohmoto, 1986). Thus, the VMS depos-

[Minor- and trace-element analyses in parts per million by laser-ablation inductively coupled plasma mass spectrometry at 

the USGS laboratory in Denver, Colo. Standard deviation (s.d.) is 1σ value. Grouping of deposits (see table 1) is based on 

stratigraphic, structural, and metamorphic parameters. Wales Group deposits comprise one sample each from the Corbin, 

Khayyam, Nutkwa Main, Nutkwa North, Ruby Tuesday (Fish Show), and Stumble-On deposits; Moira Sound unit deposits comprise two samples from the Lookout Mountain Prospect]
22  Studies by the U.S. Geological Survey in Alaska, 2005

Wales Group deposits Moira Sound unit deposits ___________________________ __________________________

n ------- 30 10

Mean S.d. Range Mean S.d. Range

Zn------- 88.3 133 0.0–625 70.1 49.0 0.0–143

Mn------ 5.82 15.9 0.0–88.1 0.66 1.05 0.0–3.19

Co ------ 1.34 2.13 0.0–9.60 0.56 1.04 0.0–3.34

Ni------- 12.4 45.8 0.0–252 6.81 6.63 0.0–17.0

In ------- 21.3 21.2 0.0–84.6 42.8 63.3 6.46–213

Cd ------ 9.86 27.8 0.0–153 8.79 9.65 0.0–27.4

Pb------- 0.65 0.97 0.0–3.67 0.37 0.42 0.0–1.19

Ag ------ 14.9 18.2 0.0–94.5 9.23 12.9 0.0–30.0

As------- 10.7 19.2 0.0–76.1 46.8 73.3 0.0–200

Sb------- 2.11 3.09 0.0–10.1 3.30 4.64 0.0–13.7

Bi ------- 0.13 0.21 0.0–0.84 0.46 0.53 0.0–1.45

Hg ------ 2.16 3.30 0.0–11.5 1.28 1.34 0.0–3.36

Tl ------- 0.49 0.72 0.0–2.66 1.44 1.94 0.0–6.28

Se ------- 239 563 0.0–2,400 258 465 0.0–1,374

Te------- 2.61 4.82 0.0–21.0 8.17 8.57 0.0–21.3

Mo------ 3.36 4.79 0.0–15.5 13.3 25.1 0.0–80.8

Sn------- 16.9 17.8 0.0–68.3 4.48 5.44 0.0–16.3

Table 9. Average composition and ranges in composition of 

chalcopyrite in sulfide-rich samples from southern Prince of 

Wales Island and vicinity, southeastern Alaska.

its on Prince of Wales Island and vicinity (fig. 1) display fairly 

typical δ34S values for these types of massive sulfide deposit.

Wherever possible, individual sulfide minerals were 

separated and analyzed for their δ34S value to identify potential mineral-mineral fractionations that might be used for 

sulfur-isotope geothermometry and for calculating primary or 

metamorphic temperatures. In table 10, δ34S data for sulfide 

minerals are listed in the expected order of fractionation, from 

isotopically heaviest to lightest: pyrite>sphalerite~pyrrhotite>

chalcopyrite>galena. Analysis of these data indicates that most 

of the sulfide minerals lack significant fractionation, and so 

sulfur-isotope geothermometry would not be meaningful. The 

fractionations may be within analytical error because of hightemperature metamorphism. We conclude that the δ34S values 

for individual sulfide minerals in the VMS deposits partially to 

completely reequilibrated during metamorphism, but that the 

distinct ranges obtained for different samples reflect original, 

premetamorphic whole-rock values.

Sulfur-isotopic values of bulk sulfide in country rocks of 

the study area (fig. 1; table 11) were measured to determine 

whether the sulfur sources of the hydrothermal systems that 

formed the VMS deposits could be delineated. The wide variation in δ34S values (−10.2 to 19.7 permil) makes source fingerprinting difficult. These δ34S values show some differences 

that broadly correlate with host lithology (fig. 8) but not with 

host-rock age. In general, metavolcanic rocks contain sulfides 

with the highest δ34S values (1.1 to 19.7 permil), followed by 

carbonates (−3.7 to 11.3 permil) and siliciclastic metasedimentary rocks (−10.2 to 3.2 permil). Probably most of the siliciclastic rocks, many of which are graphitic, and some of the 

metacarbonate rocks were affected during diagenesis by bacterial sulfate reduction (BSR) that produced negative sulfur-isotopic values (for example, Machel, 2001). The large negative 

δ34S value (−31.1 permil) for pyrite from the Barrier Islands 

No. 1 deposit probably records extensive BSR, which likely 

produced the framboidal texture in some of this pyrite. In the 

metavolcanic rocks (fig. 8), however, no evidence exists for 

BSR or the introduction of isotopically light sulfur. Instead, 

the relatively high δ34Ssulfide values of these rocks, far above 

the typical range for primary sulfide in unaltered volcanic 

rocks (−1 to 3 permil; Shanks, 2001), probably reflect minor 

amounts of hydrothermally introduced seawater sulfate that 

was reduced to sulfide by thermochemical sulfate reduction 

(TSR). Most likely, these δ34S values represent samples from 

the low-temperature fringes of sea-floor hydrothermal systems 

that were only mildly affected by VMS-forming processes.

Additional insight can be gained by comparing the 

δ34Ssulfide values of the hydrothermal deposits with those of 

contemporaneous seawater sulfate (fig. 9). On the basis of 

the ages of the host rocks, ~500–600 m.y. for the Wales 

Group and 430–480 m.y. for the Moira Sound unit, and the 

temporal seawater sulfate curve established by analyzing 

marine evaporates (Claypool and others, 1980; Ross and 

others, 1995), we conclude that the higher δ34Ssulfide values 

obtained for the VMS deposits in the Wales Group reflect 

higher δ34Ssulfate values in contemporaneous seawater sulfate. 

Studies of modern sea-floor massive sulfide deposits (Shanks 

and others, 1995; Shanks, 2001), together with experimental 

(Shanks and others, 1981; Seyfried and Shanks, 2004) and 

theoretical (Janecky and Shanks, 1988) studies of sulfide 

formation, provide a general framework for understanding 

sea-floor hydrothermal mineralization. These studies have 

shown that sulfides in VMS deposits, which have long been 

known to contain volcanic and seawater sulfur components, 

form as follows. Seawater sulfate is mostly screened from the 

circulating hydrothermal system by precipitation of anhydrite 

and Mg hydroxysulfate at temperatures above 150oC, and the 

fraction of seawater sulfate that enters the high-temperature 

hydrothermal system is quantitatively reduced to sulfide. 

Simultaneously, the seawater-derived hydrothermal fluids 

leach and dissolve igneous sulfide from footwall rocks, 

which is mixed with the reduced seawater sulfate to produce 

δ34Ssulfide values intermediate between those of igneous rocks 

(~0 permil) and contemporaneous seawater sulfate. Although 

this process can cause a large variation in δ34Ssulfide value, in 

practice the systems tend to be self-regulating. Sulfate reduction is accomplished by iron-bearing minerals and the H2

they produce during hydrothermal reactions, and in modern 

systems that have been studied to date, ~10–40 percent of the 

sulfide derives from reduced seawater sulfate that is added to 

the mix without apparent sulfur-isotope fractionation.

The sulfur-isotopic data for VMS deposits of the study 

area (fig. 1) provide strong evidence for formation at or near 

the sea floor by processes much like those in modern subma-

[Minor- and trace-element analyses in parts per million by laser-ablation 

inductively coupled plasma mass spectrometry at the USGS laboratory in 

Denver, Colo. Standard deviation (s.d.) is 1σ value. Grouping of deposits (see 

table 1) is based on stratigraphic, structural, and metamorphic parameters. 

Wales Group deposits comprise one sample each from the Big Harbor East, 

Big Harbor West, Copper City, Corbin, Keete Inlet, Khayyam, Nutkwa Main, 

and Ruby Tuesday (Fish Show) deposits; Moira Sound unit deposits comprise 

three samples from the Lookout Mountain Prospect and one sample from the 

Moira Copper Prospect] 
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity 23

F

R

E

Q

U

E

N

C

Y

0 10 15

5

0

10

15

-5 20

20

5

In magnetite

iron-formation

-31.1

Pyrite

30.4

Barite

Wales Group

Big Harbor deposits

Ruby Tuesday

Nutkwa area deposits

Lime Point

Moira Sound unit

Niblack

Moira Copper

Barrier Islands

Lookout Mountain

Datzkoo Harbor

Nichols Bay

Khayyam and Stumble-On

Copper City

Keete Inlet

Corbin

Deer Bay exhalite

Trocadero Bay exhalite

Cable Creek roadcut

Hozer

30.6

Barite

S VALUE, IN PERMIL

EXPLANATION

Figure 7. Histogram of sulfur-isotopic values for sulfide mineral separates (pyrite, 

sphalerite, chalcopyrite, galena, pyrrhotite) from volcanogenic massive sulfide deposits 

in study area (fig. 1). Isotopically light pyrite sample is from the Barrier Islands No. 1 

occurrence; barite sample is from the Lime Point barite deposit. All values in permil 

relative to Cañon Diablo Troilite standard.

rine hydrothermal systems. The Wales Group deposits have 

somewhat higher δ34S values because they formed during a 

period when seawater sulfate had a δ34S value near 30 permil, whereas the Moira Sound unit deposits formed during a 

period when seawater sulfate had a δ34S value of ~25 permil. 

Major sulfur sources of the deposits were igneous sulfide and 

reduced seawater sulfate. The δ34S values of disseminated 

barite in a Mn-rich exhalite from the Big Harbor West deposit 

(30.6 permil) and in massive barite from the Lime Point 

deposit (30.4 permil), both of which are in rocks of the Wales 

Group, support these conclusions, possibly reflecting the sulfur-isotopic composition of contemporaneous seawater sulfate 

during Late Proterozoic through Cambrian time.

Discussion

Primary Textural and Geochemical Signatures

Whole-rock and mineral compositions of VMS deposits 

in deformed and metamorphosed sequences reflect various 

processes, including primary sea-floor mineralization, hydrothermal zone refining in the subsurface, and recrystallization 

and new-mineral growth during postore deformation and 

metamorphism (for example, Lydon, 1988; Hannington and 

others, 1995). In general, sea-floor mineralization in chimney 
24  Studies by the U.S. Geological Survey in Alaska, 2005

Table 10. Sulfur-isotopic analyses of sulfide minerals and barite in stratabound mineral deposits on southern Prince of Wales Island 

and vicinity, southeastern Alaska.

[Minerals: cp, chalcopyrite; po, pyrrhotite; py, pyrite; sl, sphalerite]

Sample Description δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

Mineral------------------------------------------------------------

-----

py sl po cp Bulk Barite

Moira Sound unit

Niblack deposit:

JS–00–28A Weakly layered pyritic massive sulfide with 

minor sphalerite and chalcopyrite.

– – – – – – – – 7.0 – –

JS–00–28C Siliceous rock with abundant disseminated 

fine–grained pyrite and minor chalcopyrite.

– – – – – – – – 10.4 – –

JS–00–28F Massive fine-grained magnetite and hematite with abundant seams of pyrite and 

chalcopyrite.

−0.5 – – – – 0.8 – – – –

JS–00–28G Complex mixture of fine-grained magnetite with carbonate, quartz, pyrite, and 

chalcopyrite.

– – – – – – – – 7.9 – –

JS–00–28I Semimassive sulfide (pyrite and subequal 

chalcopyrite) in chlorite schist with 

minor quartz and sphalerite. 

– – – – – – – – 9.9 – –

Moira Copper deposits:

MC–MS–1 Semimassive pyritic sulfide with abundant 

chalcopyrite and quartz and minor chlorite and sericite.

– – – – – – – – 8.8 – –

MC–MS–2 Semimassive pyrite with abundant quartz, 

minor chlorite and sericite, and sparse 

chalcopyrite.

9.6 – – – – – – – – – –

MC–MS–3 Semimassive pyrite with quartz, minor 

chlorite and sericite, and trace chalcopyrite and sphalerite.

9.0 – – – – – – 8.7 – –

Lookout Mountain and Dama deposits:

LO–53/624.2 Layered massive sulfide composed of pyrite, sphalerite, and minor chalcopyrite.– – – – – – – – 9.3 – –

LO-61/573.0 Massive sulfide composed of fine-grained 

chalcopyrite with minor pyrite and matrix quartz and chlorite.

– – – – – – 9.5 – – – –

LO–99/290 Fine-grained metarhyolite with disseminations and veinlets of chalcopyrite and 

pyrite, abundant fine-grained sericite, 

minor sphalerite, and trace galena. 

– – – – – – 7.5 – – – –

LO–99/367 Massive pyritic sulfide with matrix quartz 

and sericite and trace sphalerite and 

chalcopyrite.

8.5 – – – – – – – – – –

LO–99/378 Altered rhyolite metatuff with abundant 

disseminated pyrite and minor sphalerite 

and chalcopyrite.

– – – – – – 8.6 – – – –
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity  25

Table 10. Sulfur-isotopic analyses of sulfide minerals and barite in stratabound mineral deposits on southern Prince of Wales Island 

and vicinity, southeastern Alaska.­—Continued

Sample Description δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

Mineral----------------------------------------------------------------- py sl po cp Bulk Barite

LO–99/469 Coarse-grained rhyolite lithic metatuff with 

abundant matrix pyrite, sparse sphalerite, 

and trace chalcopyrite.

8.7 – – – – – – – – – –

Barrier Islands deposits:

JS–00–58 Sericite-altered rhyolite metatuff(?) with 

moderate disseminated pyrite and trace 

sphalerite.

3.4 – – – – – – – – – –

BI1–MS Brecciated fine-grained massive pyrite with 

quartz and sparse sericite, carbonate, and 

chlorite.

−31.1 – – – – – – – – – –

B12–MS Semimassive pyrite with abundant sericite, 

minor quartz, and trace sphalerite and 

galena.

2.8 – – – – – – – – – –

B17–MS Semimassive pyrite with quartz, chlorite, 

and minor sericite.

5.1 – – – – – – – – – –

Datzkoo Harbor occurrence:

JS–00–57A Semimassive pyritic sulfide with trace 

sphalerite in quartz-chlorite-sericite 

schist.

3.8 – – – – – – – – – –

Nichols Bay Mine:

B19–MS–1H Fine-grained massive pyrrhotite (partially 

oxidized) with abundant diopside(?), 

minor pyrite, garnet, sericite, and Mn 

carbonate, and sparse 

– – – – –2.8 – – – – – –

B19–MS2MS Fine-grained massive magnetite with minor 

pyrite and sparse sphalerite associated 

with abundant Mn carbonate and trace 

quartz.

 −0.8 – – – – – – – – – –

Wales Group

Big Harbor deposits:

JS–00–29C Semimassive pyritic sulfide in siliceous 

schist with abundant chalcopyrite and 

trace sphalerite.

16.3 – – – – 16.6 – – – –

JS–00–29E Quartz-sericite schist with abundant disseminated pyrite and sparse chalcopyrite.17.4 – – – – – – – – – –

JS–00–31B Chloritic schist with abundant disseminated chalcopyrite and pyrite and sparse 

sphalerite.

– – – – – – 16.4 – – – –

JS–00–31D Semimassive sulfide composed of chalcopyrite, minor pyrite, and sparse sphalerite in chlorite schist.– – – – – – 15.8 – – – –

JS–00–32A Siliceous exhalite composed of quartz, Mn 

carbonate, minor piemontite and barite, 

and trace sulfides.

– – – – – – – – – – 30.6
26  Studies by the U.S. Geological Survey in Alaska, 2005

Table 10. Sulfur-isotopic analyses of sulfide minerals and barite in stratabound mineral deposits on southern Prince of Wales Island 

and vicinity, southeastern Alaska.­—Continued

Sample Description δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

Mineral----------------------------------------------------------------- py sl po cp Bulk Barite

84AGKO39E Quartz vein with margins composed of 

massive chalcopyrite, minor pyrite, 

and trace sphalerite with some chloritic 

wallrock.

– – – – – – 16.5 – – – –

Ruby Tuesday deposit:

JS–00–49B Quartz-rich schist with quartz veins and 

minor disseminations of pyrite, sphalerite, and galena and trace chalcopyrite.

7.9 8.1 – – – – – – – –

RT–81–9/211 Altered rhyolite metatuff(?) with abundant 

disseminated pyrite (partially laminated), sparse sphalerite and chalcopyrite, 

and trace galena.

12.3 – – – – – – – – – –

RT–FS–MS Semimassive sphalerite with subequal 

pyrite and galena and trace chalcopyrite 

associated with quartz, feldspar, and 

sparse sericite.

9.5 7.3 – – – – – – – –

RT–FS–MS2 Semimassive sphalerite with subequal pyrite and galena, minor chalcopyrite with 

quartz and sparse sericite, and small 

volcanic rock fragments.

– – 6.2 – – 7.1 – – – –

Khayyam Mine (main workings):

JS–00–33B Sericite-chlorite with disseminations and 

veins of pyrite, minor chalcopyrite, and 

sparse sphalerite and magnetite.

10.9 – – – – – – – –

JS–00–33C Massive granular pyritic sulfide with 

abundant matrix chalcopyrite and minor 

sphalerite.

– – – – – – – – 12.4 – –

JS–00–33D Sericite-chlorite with quartz boudins, minor chalcopyrite, pyrite, and pyrrhotite, 

and sparse sphalerite.

– – – – 10.7 10.9 – – – –

JS–00–33E Feldspathic(?) rock with disseminated pyrite and pyrrhotite, minor chalcopyrite, 

and sparse sphalerite.

– – – – – – – – 11.0 – –

JS–00–33F Massive fine-grained pyrrhotite with minor 

coarse-grained pyrite and pyrite layers, 

and sparse chalcopyrite and sphalerite.

10.5 – – 10.4 – – – – – –

JS–00–33G Massive granular pyritic sulfide in a matrix 

of chalcopyrite, minor sphalerite, and 

quartz.

– – – – – – – – 12.1 – –

JS–00–33K Feldspathic(?) rock with abundant disseminated pyrite and pyrrhotite, and 

some disseminated magnetite, sparse 

chalcopyrite, and trace sphalerite.

– – – – – – 9.9 – – – –
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity  27

Table 10. Sulfur-isotopic analyses of sulfide minerals and barite in stratabound mineral deposits on southern Prince of Wales Island 

and vicinity, southeastern Alaska.—ContinuedKhayyam Mine (lower tram terminal):

JS–00–62A Massive granular pyritic sulfide with abundant 

matrix chalcopyrite and minor sphalerite

– – – – – – – – 13.0 – –

JS–00–62C Massive granular pyritic sulfide with abundant 

matrix sphalerite and minor chalcopyrite

12.9 11.3 – – 12.0 – – – –

JS–00–62E Massive granular pyritic sulfide with abundant 

matrix sphalerite and chalcopyrite.

12.4 11.5 – – 11.8 – – – –

JS–00–62F Massive fine-grained chalcopyrite with minor 

sphalerite and sparse quartz.

– – 12.1 – – 11.9 – – – –

Stumble-On Mine:

JS–00–36A Massive fine-grained pyrrhotite with abundant 

chalcopyrite and minor sphalerite.

12.2 12.0 12.3 11.8 – – – –

JS–00–36B Massive granular pyritic sulfide with minor 

chalcopyrite, interlayered with coarsegrained sphalerite and quartz with disseminated chalcopyrite.

12.9 13.3 – – 13.7 – – – –

JS–00–36C Massive granular sphalerite with minor matrix 

pyrite.

14.2 13.7 – – – – – – – –

JS–00–36D Massive fine-grained pyrrhotite with minor 

coarse-grained pyrite and minor matrix 

sphalerite and chalcopyrite.

– – 13.4 – – 13.4 – – – –

JS–00–36E Chlorite with abundant coarse-grained pyrite, 

minor pyrrhotite and sphalerite, and sparse 

chalcopyrite and magnetite.

13.8 – – – – – – – – – –

Copper City Mine:

JS–00–54C Fine-grained jasper with lenses of coarsegrained magnetite and minor quartz, sparse 

pyrite and chalcopyrite, and trace sphalerite.

10.3 – – – – – – – – – –

JS–00–55A Fine-grained massive chalcopyrite and sphalerite with minor pyrite and quartz.– – – – – – – – 12.8 – –

JS–00–55C Fine-grained pyritic massive sulfide with minor chalcopyrite and sphalerite and minor 

matrix quartz.

– – – – – – – – 12.7 – –

JS–00–55D Magnetite and chlorite interlayered with 

quartz, chalcopyrite, and sphalerite.

– – – – – – 8.4 – – – –

JS–00–55E Fine-grained massive pyritic sulfide with 

abundant chalcopyrite, minor sphalerite and 

quartz, and trace galena.

– – – – – – – – 12.8 – –

Sample Description δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

Mineral----------------------------------------------------------------- py sl po cp Bulk Barite

JS–00–35B Sericite-quartz with abundant disseminated 

pyrite and pyrrhotite, and minor chalcopyrite.

– – – – 13.6 14.7 – – – –
28  Studies by the U.S. Geological Survey in Alaska, 2005

JS

Corbin Mine:

JS–00–56C Pyritic massive sulfide with abundant matrix 

sericite and quartz, minor chalcopyrite, and 

trace sphalerite.

– – – – – – – – 8.0 – –

JS–00–56F Quartz-sericite with abundant disseminated 

pyrite and sparse chalcopyrite.

– – – – – – – – 8.6 – –

JS–00–56I Layered/laminated massive sulfide with subequal pyrite and sphalerite, minor quartz, 

sparse chalcopyrite, and trace galena.

6.4 5.9 – – – – – – – –

Nutkwa Prospects:

JS–00–37A Quartz-sericite-chlorite schist with abundant 

disseminated pyrite and trace sphalerite 

and galena.

9.1 – – – – – – – – – –

JS–00–37C Sericite-chlorite-quartz schist with abundant 

disseminated coarse-grained pyrite, minor 

sphalerite, and sparse chalcopyrite.

9.7 – – – – – – – – – –

JS–00–39A Semimassive pyritic sulfide with abundant 

sphalerite, sparse chalcopyrite and galena, 

and matrix quartz, sericite, and chlorite.

9.6 – – – – – – – – – –

JS–00–39C Semimassive sulfide with subequal finegrained pyrite and sphalerite; minor chalcopyrite and trace galena.– – – – – – – – 8.6 – –

Keete Inlet Mine:

JS–00–53A Pyritic massive sulfide with minor chalcopyrite.– – – – – – – – 12.2 – –

JS–00–53C Semimassive pyritic sulfide with matrix 

quartz and chlorite.

12.6 – – – – – – – – – –

JS–00–53D Pyritic massive sulfide with minor chalcopyrite, sphalerite, magnetite, quartz, and 

carbonate.

– – – – – – – – 11.4 – –

Hozer Prospect:

JS–00–51A Quartz-sericite schist with minor disseminated pyrite and trace chalcopyrite.7.6 – – – – – – – – – –

Trocadero Bay exhalite:

JS–00–42A Semimassive pyritic sulfide with matrix sericite, chlorite, and quartz.10.6 – – – – – – – – – –

JS–00–42C Quartz-sericite-chlorite schist with abundant 

disseminated pyrite.

9.4 – – – – – – – – – –

Deer Bay exhalite:

JS–00–66 Quartz-sericite schist with disseminated pyrite 

and sparse chalcopyrite.

9.5 – – – – – – – – – –

Cable Creek roadcut:

JS–00–65 Semimassive pyritic sulfide in quartz-sericite 

schist with trace chalcopyrite.

8.7 – – – – – – – – – –

Lime Point barite deposit:

JS–00–50B Massive barite (replacement of limestone). – – – – – – – – – – 30.4

Table 10. Sulfur-isotopic analyses of sulfide minerals and barite in stratabound mineral deposits on southern Prince of Wales Island 

and vicinity, southeastern Alaska.Sample Description δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

δ34S

value

(permil)

Mineral----------------------------------------------------------------- py sl po cp Bulk Barite
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity  29

Field No. Description

D34S

value

(permil)

Latitude

(oN)

Longitude

(oW)

Moira Sound unit

00SK220A Mafic volcanic agglomerate. 19.7 54.95694 132.16800

LO–99/512 Unaltered(?) fine-grained greenstone from the Lookout

Mountain Prospect, Niblack Mine area; probably

stratigraphic hanging wall.

7.5 55.05972 132.14167

LO–99/345 Altered quartz-feldspar porphyry from the Lookout

Mountain Prospect, Niblack Mine area; probably

stratigraphic footwall.

9.2 55.05972 132.14167

LO–53/630 Altered quartz-eye felsic tuff from the Dama Prospect,

Niblack Mine area; uncertain whether stratigraphic

hanging wall or footwall.

11.6 55.05972 132.14167

00SK217A Felsic volcanic breccia. 1.1 54.99745 132.11100

00SK225A imestone in carbonaceous phyllite. 9.7 54.98308 132.30200

00SK116A Metalimestone in carbonaceous phyllite. 3.7 55.33098 132.79700

00SK048A Calcareous wacke turbidite. 
1.4 54.96136 132.94700

00SK009D Graphitic semischist. 
9.6 54.73742 132.72900

00SK148C Carbonaceous phyllite. 3.2 54.74082 132.75600

00SK152A Graphitic phyllite. 3.2 55.24591 132.69300

Wales Group

JS–00–35C Garnet-bearing amphibolite from Khayyam deposit;

uncertain stratigraphic relations.

13.2 55.29861 132.38611

00SK011A Amphibolite (metaintrusive). 4.3 54.75697 132.72800

JS–00–34A Hornblende-bearing felsic gneiss from the Khayyam

deposit; uncertain stratigraphic relations.

9.8 55.29861 132.38611

JS–00–29A Altered massive rhyolite from wallrock (mine adit)

directly adjacent to the Big Harbor East deposit;

uncertain stratigraphic relations.

15.1 55.37611 132.95361

JS–00–30 Sulfidic rhyolite crystal tuff from outcrop ~75 m from

adit to the Big Harbor East deposit; uncertain

stratigraphic relations.

16.8 55.37611 132.95361

00SK168A Sericitic marble. 
3.7 55.14529 132.07700

00SK251A Pyritic black argillite. 
10.2 55.06988 132.10600

00SK327A Graphitic quartzite. 
7.3 55.34372 132.48342

00SK281A Graphitic semischist intercalated with felsic volcanic

semischist.


6.7 55.21383 132.26500

00SK321A Pyritic semischist-metavolcanic rock. 
8.0 55.37311 132.37300

meta

meta

meta

Metal

meta

meta

meta

Table 11. Sulfur-isotopic analyses of metavolcanic and metasedimentary rocks of southern Prince 

of Wales Island and vicinity, southeastern Alaska.

structures and exhalites produces fine-grained sulfide and 

gangue minerals because of relatively fast precipitation during 

rapid cooling of the hydrothermal fluids. After initial formation on the sea floor, however, chimneys and related sulfide 

mounds commonly undergo extensive zone refining in which 

circulating hydrothermal fluids dissolve some minerals, such as 

anhydrite, recrystallize others, including common sulfides, and 

precipitate new phases, such as pyrite and amorphous silica. 

Studies of both modern and ancient VMS deposits that have 

undergone minimal deformation and metamorphism indicate 

that hydrothermal zone refining can, in many places, form 

complex textures and coarse grains in sulfide minerals, including euhedral crystals of sphalerite and pyrite as much as several 

centimeters in diameter (for example, Eldridge and others, 

1983; Petersen and others, 2000; Slack and others, 2003). Primary textures are therefore difficult to identify with confidence 

in VMS deposits of the study area (fig. 1), except possibly in 

the Dama deposit, where conspicuous mineralogic layering 

of sulfides (fig. 2G) likely reflects alternating deposition of 

pyrite and sphalerite on the sea floor and not later metamorphic 

segregation, because this VMS deposit in the Moira Sound 

unit underwent only lower-greenschist-facies metamorphism. 

Similar layering locally in the Corbin deposit (fig. 3B) is also 

believed to be primary, although a metamorphic origin cannot 

be ruled out, given the greater deformational and amphibolitefacies overprint on this older Wales Group deposit.

Primary whole-rock and mineral compositions are 

believed to generally be preserved in the sulfide-rich samples. 
30 Studies by the U.S. Geological Survey in Alaska, 2005

Figure 8. Range of δ34S values for disseminated sulfide minerals separated from different rock 

types of the Wales Group and the Moira Sound unit.

-20

-10

0

10

20

30

Moira Sound unit

Early Silurian through Ordovician

Wales Group

Cambrian through Late Proterozoic

Wales Group sulfide deposits

6 to 17 permil

Igneous sulfides

Contemporaneous seawater sulfate

Moira Sound unit sulfide deposits

-3 to 10 permil

D34S VALUE, IN PERMIL

Figure 9. Summary of δ34S values for sulfide minerals in volcanogenic massive sulfide (VMS) 

deposits of the Moira Sound unit (yellow) and the Wales Group (orange). δ34S values for igneous 

sulfides (violet), δ34S values for metasedimentary and metavolcanic country rocks (undivided) of 

the Moira Sound unit and the Wales Group (diamonds) (see fig. 8), and ranges of δ34S values for 

contemporaneous seawater sulfate (blue) during the Ordovician through Early Silurian (Claypool 

and others, 1980) and the Late Proterozoic (Strauss, 1993; Ross and others, 1995; Hurtgen and others, 

2002) are shown for reference. Note that δ34S values for sulfide minerals from VMS deposits in the 

Moira Sound unit and for contemporaneous seawater sulfate are ~5 to 7 permil lower than those for 

sulfide minerals from VMS deposits in the Wales Group and for contemporaneous seawater sulfate.

Except in deposits that underwent pervasive metamorphic 

recrystallization and (or) a high fluid flux during metamorphism, or late faulting, bulk compositions should approximate 

those that existed during sea-floor and sub-sea-floor mineralization. The major-element contents in sulfide minerals are 

also interpreted as being mainly primary, except for such VMS 

deposits as the Khayyam and Stumble-On that were metamorphosed to amphibolite grade. In such sulfides as pyrite from 

the Barrier Islands No. 2 deposit (figs. 2H, 3H), very high Mn, 

As, Sb, Se, and Tl contents (tables 5, 6) likely reflect primary 

deposition at temperatures below ~250oC (see Huston and 

others, 1995; Houghton and others, 2004). The very low δ34S 

value (−31.1 permil) of pyrite from this deposit supports this 

interpretation because such values are generally limited to 

low-temperature BSR (for example, Machel, 2001). Fe contents in sphalerite are also believed to record early sea-floor 

-25

-20

-15

-10

-5

0

5

10

15

20

25

Mafic agglomerate

Greenstone

Felsic porphyry

Felsic tuff

Volcanic breccia

AmphiboliteAmphibolite

Felsic gneiss

Felsite

Felsic crystal tuff

LimestoneLimestone

Marble

Calc wacke

Black argillite

Calc wacke

Black argillite

Graphitic schist

Phyllite

Phyllite

Quartzite

Schist

Schist

Moira Sound unit

Wales Group

Volcanic rocks

Carbonates Siliciclastic rocks

EXPLANATION

D34S VALUE, IN PERMIL
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity  31

and (or) sub-sea-floor hydrothermal processes in deposits that 

have undergone limited metamorphic overprinting, such as the 

deposits in the Niblack area in the Moira Sound unit and in the 

Nutkwa area in the Wales Group. The Fe content in sphalerite 

from these two deposits varies widely within single thin sections, by as much as 72 and 129 relative percent, respectively. 

In contrast, the Fe content in sphalerite from the high-grademetamorphosed Khayyam and Stumble-On deposits varies by 

no more than 20 relative percent within single thin sections.

Additional support for the preservation of primary 

geochemical signatures comes from an apparent inverse 

correlation between Fe contents in sphalerite and average 

Au contents in the VMS deposits. Except for the Copper 

City deposit, for which reliable LA–ICP–MS analyses of 

sphalerite could not be obtained, owing to abundant inclusions of chalcopyrite and other sulfides, the two most Au 

rich deposits, at Lookout Mountain and Nutkwa (table 2), 

contain sphalerites with the lowest Fe contents (0.21–0.63 

and <0.16 weight percent Fe, respectively) measured in 

this study. The geologic resource for the Lookout Mountain 

deposit includes an average of 2.8 ppm Au (Niblack Mining 

Corp., 2006, URL http://www.niblackmining.com/); the average Au content in the Nutkwa Main and North deposits is 

estimated at 2.3 ppm (table 2). A database of VMS deposits 

throughout Alaska shows a similar trend, including for the 

Au-rich Greens Creek ore body on Admiralty Island (avg 5.8 

ppm Au; Taylor and others, 1999), in which the highest gold 

grades (≥3 ppm Au) occur in deposits that contain Fe-poor 

sphalerite (<2 mol percent FeS [<1 weight percent Fe]; Newberry and others, 1997b, fig. 25A). Because such Fe-poor 

sphalerite is generally pale in color (for example, yellow, 

light brown), it can generally be easily distinguished in hand 

specimen from dark-red-brown to black, Fe-rich sphalerite. 

Preferential occurrence of Fe-poor sphalerite in the gold-rich 

VMS deposits on Prince of Wales Island and elsewhere in 

Alaska is consistent with the data of Hannington and Scott 

(1989), who proposed that such features reflect mineralization at low temperatures (150–250oC) under high-sulfidation 

(aS2) conditions. Other aspects of this topic, including applications to mineral exploration, were discussed by Hannington and others (1999).

Effects of Metamorphic Recrystallization

Metamorphic processes have significantly affected most 

VMS deposits in the study area (fig. 1). The Wales Group 

deposits were overprinted by three tectonothermal events in 

the Late Proterozoic, Ordovician, and Early Devonian that in 

many samples produced new textures, mineral assemblages, 

mineral compositions, and sulfur-isotope distributions. VMS 

deposits in the Moira Sound unit were overprinted only by the 

Early Devonian metamorphic event and so show less deformation, recrystallization, and mineral-specific changes in chemical 

and sulfur-isotopic compositions. The wide variation in sulfide 

grain sizes in the Wales Group deposits (figs. 2, 3) reflects 

varying degrees of postore deformation and metamorphism, and 

the extent of fluid flow (flux) associated with these processes, 

together with the inferred effects of earlier zone refining on and 

beneath the sea floor. The greatest textural changes occurred 

at the Khayyam and Stumble-On deposits, where amphibolitefacies metamorphism produced very coarse grained, porphyroblastic pyrite (fig. 2A) and coarse-grained, granoblastic pyrite 

and sphalerite (figs. 2B, 2C). This metamorphism also formed 

abundant pyrrhotite (fig. 3A), which is absent from other VMS 

deposits in the study area except for the Nichols Bay No. 9 

and 10 deposits (table 1), which are within the contact aureole 

of a large granitic pluton. Pyrrhotite commonly forms during 

high-grade metamorphism of such deposits by the breakdown 

of pyrite during desulfurization processes (for example, Vokes, 

1969; Brooker and others, 1987). Uncommon sulfide-rich veins 

that cut massive sulfide and metamorphic fabrics in wallrocks 

at these and other Wales Group deposits probably reflect local 

remobilization of sulfide minerals by high fluid flow during 

the Ordovician metamorphic event (see Marshall and Gilligan, 

1993; Marshall and others, 2000). Distinguishing effects of the 

greenschist- to amphibolite-facies Late Proterozoic and Ordovician metamorphic events from those of the greenschist-facies 

Early Devonian metamorphic event is beyond the scope of this 

study. However, because the earlier events were characterized 

by higher temperatures and pressures (Zumsteg and others, 

2004), the Early Devonian metamorphism likely produced only 

minor recrystallization of sulfides and small-scale deformational 

features, except in areas within or adjacent to Devonian and 

younger faults or shear zones, which may have focused remobilization of the sulfides, including increased grain sizes (for 

example, Marignac and others, 2003). The absence of zoned 

sphalerite in all of the VMS deposits, assuming its original presence based on studies of essentially unmetamorphosed deposits 

elsewhere (Barton, 1970; Eldridge and others, 1983; Zaw and 

others, 1996; Slack and others, 2003), probably reflects chemical annealing during all three metamorphic events.

Metamorphic effects on whole-rock and mineral 

compositions of the sulfide-rich samples are believed to be 

generally minor. Except in the highly deformed and metamorphosed Khayyam and Stumble-On deposits, the scale of 

chemical equilibration reached in most of the VMS deposits 

during the various metamorphic events (combined effects) is 

estimated at <10 cm. This interpretation is based on widespread trace-element heterogeneity in the sulfide minerals 

(especially pyrite and sphalerite), as determined by in situ 

LA–ICP–MS analyses. In theory, if fractionation of trace elements among different sulfide minerals reached equilibrium 

conditions during metamorphism, these minerals would be 

mostly homogeneous (for example, Scott, 1983; Huston and 

others, 1995). However, because evidence for this equilibrium is generally not observed, metamorphic effects on the 

sulfide compositions were apparently limited spatially. Significant variations in Mn, As, Sb, and Tl contents in pyrite 

from the Barrier Islands deposits (fig. 6) probably reflects 

the fact that these are the least deformed and least metamorphosed VMS deposits in the study area.
32  Studies by the U.S. Geological Survey in Alaska, 2005

In contrast to the compositional heterogeneity of sulfide 

minerals from most of the VMS deposits, those at Khayyam 

and Stumble-On display a more nearly homogeneous traceelement distribution. This contrast is shown, for example, by 

the relatively uniform As, Sb, and Tl contents in pyrite and Co, 

As, Hg, and In contents in sphalerite within the same samples, 

and even within different samples from the same deposit. 

Such homogeneity suggests a redistribution of trace elements 

among the sulfide minerals due to different fractionation factors and higher pressure-temperature conditions than those that 

occurred during sea-floor and sub-sea-floor mineralization. 

Some trace elements, such as Hg, were probably lost to the 

metamorphic fluids, at least partly, during amphibolite-grade 

metamorphism of the Khayyam and Stumble-On deposits. 

This process is recorded by whole-rock data indicating that the 

Hg contents in sulfide-rich samples are about a tenth those in 

samples from other VMS deposits in the study area, measured 

at similar Zn contents (fig. 5E). Inclusion-free sphalerite 

grains from the Khayyam and Stumble-On deposits also have 

the lowest Hg/Fe ratios, on the basis of LA–ICP–MS data (fig. 

6E) that support this interpretation.

Discriminating VMS Deposits in the Wales 

Group and the Moira Sound Unit

Both geochemical and sulfur-isotopic data may be 

used to distinguish the VMS deposits in Late Proterozoic 

through Cambrian rocks of the Wales Group from those in 

Ordovician through Early Silurian rocks of the Moira Sound 

unit. A first-order discrimination may be made by using 

basic geologic information, together with immobile-element 

geochemical signatures of the metabasaltic host rocks. The 

stratigraphic settings of a few deposits, however, such as 

the Copper City and Ruby Tuesday (CC and RTF, respectively, fig. 1), are poorly constrained, and so other criteria 

are needed for accurate formational assignment. Within the 

VMS deposits, textures and mineral assemblages are not 

reliable guides except in such deposits as the Khayyam and 

Stumble-On (KY and SO, respectively, fig. 1), where highgrade Ordovician metamorphism produced coarse-grained 

porphyroblastic pyrite, granoblastic pyrite and sphalerite, 

and abundant pyrrhotite (figs. 2A–2C, 3A). These features 

are absent in the VMS deposits in the Moira Sound unit, 

owing to uniformly lower grade overprints during the Early 

Devonian metamorphic event (Zumsteg and others, 2004). 

However, because many other VMS deposits in the Wales 

Group have sulfide textures and sulfide assemblages similar 

to those in the Moira Sound unit, other criteria must be used 

to distinguish them. Geochemical data for sulfide-rich rocks 

can also provide valuable insight, such as the tendency for 

the VMS deposits in the Moira Sound unit to have proportionately higher Ag contents relative to base metals and Au, 

in comparison with those in the Wales Group (fig. 4B).

Sulfur-isotopic data for sulfide minerals in VMS 

deposits of the study area (fig. 1) can also be used to discriminate the VMS deposits in the Wales Group from those 

in the Moira Sound unit. Although minor overlap exists, 

δ34S values for sulfides in the Wales Group average ~5 

to 7 permil higher than for those in the Moira Sound unit 

(fig. 8). This difference in δ34Ssulfide values reflects seawater 

sulfate as the dominant sulfur source of the VMS deposits, 

and the related fact that the δ34S values of contemporaneous seawater sulfate during the Late Proterozoic through 

Cambrian were slightly higher than during the Ordovician 

through Early Silurian.

From a mineral-resource standpoint, base-metal grades 

vary widely among VMS deposits in both the Wales Group 

and Moira Sound unit. Overall, the VMS deposits in the 

Wales Group appear to have a lower potential for high silver 

grades than those in the Moira Sound unit, whereas the 

VMS deposits in both groups may have either high or low 

gold grades. On the basis of limited data, we suggest that 

future exploration in the study area (fig. 1) for preciousmetal-rich VMS deposits should focus on the Moira Sound 

unit, including the use of Fe-poor sphalerite as a guide to 

Au-rich VMS deposits. On Prince of Wales Island, such 

Fe-poor sphalerite is characteristically yellow or yellowish 

brown and is generally discernible in both hand specimens 

and drill cores. The Copper City and Nutkwa areas, which 

are underlain by the Wales Group, also have a potential for 

Au-rich VMS deposits (table 2).

Acknowledgments

We thank K.M. Maas of the U.S. Forest Service, 

Juneau, Alaska, for his assistance during fieldwork. Advice 

during planning of the study was provided by L.E. Burns of 

the Alaska Department of Geological and Geophysical Surveys, Fairbanks; D.J. Grybeck of Bellingham, Wash.; R.P. 

Harris of Sealaska Corp., Juneau; and D. Hedderly-Smith 

of Park City, Utah. C.T. Barrie of Ottawa, Ontario; M.J. 

Gray of Rubicon Minerals, Vancouver, British Columbia; 

and S.M. Weekes of Abacus Minerals, Vancouver, British 

Columbia, supplied information on specific deposits in the 

study area. The manuscript was improved by the detailed 

comments of R.R. Seal II, J.M. Hammarstrom, and R.G. 

Luedke of the USGS.
Geochemical and Sulfur-Isotopic Signatures of Volcanogenic Massive Sulfide Deposits on Prince of Wales Island and Vicinity  33

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