GEOLOGICAL SURVEY CIRCULAR 855 

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The Alaska Mineral Resource 

Assessment Program: 

Guide to Information about 

the Geology and Mineral 

Resources of the 

Ketchikan and 

Prince Rupert Quadrangles, 

Southeastern Alaska 

By Henry C. Berg 

GEOLOGICAL SURVEY CIRCULAR 855 

1982 
United States Department of the Interior 

JAMES G. WATT, Secretory 

Geological Survey 

Dallas L. Peck, Director 

Library of Congress Cataloging in Publication Data 

Berg, Henry Clay, 1929-

The Alaska Mineral Resource Assessment Program: Guide to 

information about the geology and mineral resources 

of the Ketchikan and Prince Rupert quadrangles, 

southeastern Alaska. 

(Geological Survey circular ; 855) 

Bibliography: p. 21-24 

Supt. of Docs. no.: I 19.4/2:855 

1. Mines and mineral resources--Alaska. 2. Geology--

Alaska. I. Title. II. Series: United States. 

Geological Survey. Circular 855. 

QE75.C5 no. 855 622s 

CTN24.A4J [557.98'2] 

Free on application to Branch of Distribution, U.S. Geological Survey 

604 South Pickett Street, Alexandria, VA 22304 

82-600083 

AACR2 
CONTENTS 

Page 

Abstract -------------------------------------------------------------------------------------------- 1 

Introduction -------------------------------------------------------------------------------------- 1 

Purpose and scope ------------------------------------------------------------------ 1 

Geography and access------------------------------------------------------------ 1 

Previous investigations---------------------------------------------------------- 2 

AMRAP and subsequent investigations -------------------------- 2 

Acknowledgments ------------------------------------------------------------------ 4 

Descriptions of component maps and reports of the 

Ketchikan and Prince Rupert quadrangles AMRAP 

folio and of subsequent related investigations ____________________ 5 

Geology -------------------------------------------------------------------------------------- 5 

Gravina-Annette-Mary-Duke Islands area ______________ 5 

Revillagigedo Island and the Cleveland Peninsula 7 

Portland peninsula---------------------------------------------------------- 8 

Potassium-argon age determinations, 

by James G. Smith------------------------------------------------------------ 10 

Tectonostratigraphic terranes and structural framework 

of the Ketchikan and Prince Rupert quadrangles ___ 11 

Annette subterrane ------------------------------------------------------ 13 

Gravina-N utzotin belt-------------------------------------------------- 13 Thku terrane ____________________________________________________________________ 13 

Tracy Arm terrane-------------------------------------------------------- 14 

Descriptions of component maps and reports of the Ketchikan 

and Prince Rupert quadrangles AMRAP folio 

and of subsequent related investigations-Continued 

Tectonostratigraphic terranes and structural 

framework of the Ketchikan and Prince Rupert 

quadrangles-Continued 

Stikine terrane -------------------------------------------------------------- 15 

Mines, prospects, and mineral occurrences ------------------ 15 

Metalliferous deposits -------------------------------------------------- 15 

Nonmetallic minerals -------------------------------------------------- 16 

Geochemistry------------------------------------------------------·------------------- 16 

Stream-sediment geochemical investigations ______ 16 

Geochemical data and interpretation---------------------- 17 

Rock geochemical investigations ------------------------------ 17 

Interpretation of Landsat imagery---------------------------------- 18 

Geophysics ------------------------------------------------------------------------------ 18 

Aeromagnetic interpretation ------------------------------------ 18 

Bouguer gravity maps and interpretation, 

by David F. Barnes ---------------------------------------------------------- 19 

Mineral-resource assessment -------------------------------------------- 20 

Mineral-deposit types, mineral-resource areas, 

and metallogenesis---------------------------------------------------- 21 

References cited ---------------------------------------------------------------------------- 21 

ILLUSTRATIONS 

Page 

FIGURES 1-6. Maps showing: 

1. Location of Ketchikan and Prince Rupert quadrangles, and area of this investigation -------------------------- 1 

2. Ketchikan and Prince Rupert quadrangles, showing areas described in selected geologic reports ____ 3 

3. Annette and Gravina Islands, showing distribution of the Puppets Formation and its correlatives, 

unnamed conformably overlying massive limestone unit, and localities of samples collected 

in 1979 containing Upper Triassic fossils------------------------------------------------------------------------------------------------------ 6 

4. Southwestern part of Portland peninsula, showing stratigraphic revisions based on geologic 

investigations completed since publication of Open-File Report 78-73-A -------------------------------------------- 9 

5. Tectonostratigraphic terranes and structural elements in Ketchikan and Prince Rupert 

quadrangles---------------------------------------------------------------------------------------------------------------------------------------------------------· 12 

6. Ketchikan-Prince Rupert study area, showing 17 areas favorable for occurrence of mineral 

resources and types of mineral deposits known or predicted in those areas ______________________________________ 20 

TABLES 

TABLE 1. Component maps and reports of the Ketchikan-Prince Rupert quadrangles mineral-resource assessment.. ______________ 4 

III 

The Alaska Mineral Resource Assessment Program: 

Guide to Information about the Geology and Mineral 

Resources of the Ketchikan and Prince Rupert 

Quadrangles, Southeastern Alaska 

By Henry C. Berg 

ABSTRACT 

The Ketchikan and Prince Rupert 1-degree by 2-degree 

quadrangles, which encompass about 16,000 km2 at the south 

tip of southeastern Alaska, have been investigated by integrated field and laboratory studies in the disciplines of geology, geochemistry, geophysics, and Landsat data interpretation to determine their mineral-resource potential. Mineral 

deposits in the study area have been mined or prospected 

intermittently since about 1900, and production of small tonnages of ores containiqg gold, silver, copper, lead, zinc, and 

tungsten has been recorded. Extensive exploration and development currently (1981) is underway at a molybdenum prospect about 65 km east of Ketchikan. Our mineral-resource 

assessment indicates that the area contains potentially significant amounts of those metallic commodities, as well as of 

molybdenum, iron, antimony, and barite. The results of these 

studies have been published in afolioofmapsaccompanied by 

descriptive texts, diagrams, tables, and pertinent references. 

The present report serves as a guide to these investigations, 

provides relevant background information, and integrates 

the component maps and reports. It also describes revisions to 

the geology based on studies completed since the folio was 

published and includes a list of specific and general references on the geology and mineral deposits of the study area. 

INTRODUCTION 

PURPOSE AND SCOPE 

This report and a separately published folio 

of maps and accompanying tables are part of a 

series of U.S. Geological Survey publications 

released to provide public information on the 

mineral resources and mineral-resource potential of Alaska. This work is part of the Alaska 

Mineral Resource Assessment Program (AMRAP) and is intended to provide information both 

for long-range national minerals policy and for 

decisions by State, Federal, commercial, environmental, and Native interests concerning the 

future use of Alaskan lands and resources. In 

addition, AMRAP aims to increase geologic 

know ledge of the State and to provide guidance 

for mineral exploration. 

Most basic data for the maps and tables in the 

1 

c 

Ketchikan-Prince Rupert folio were collected 

during 1975 and 1977, when an interdisciplinary 

team of earth scientists conducted the field and 

laboratory investigations necessary for a mineralresource appraisal. The folio and this report describe the results of their individual investigations and the results of integrating those investigations for the resource assessment. 

GEOGRAPHY AND ACCESS 

The Ketchikan-Prince Rupert study area 

(fig. 1) comprises all but a small part of the Alaskan parts of the Ketchikan and Prince Rupert 

1:250,000-scale 1-degree by 2-degree topographic 

100 200 KILOMETERS 

FIGURE 1.-Location of Ketchikan and Prince Rupert quadrangles, and area of this investigation (dot pattern). 
quadrangles. The area covers about 16,000 km2 at 

the south tip of the southeastern Alaska panhandle between lat 54 o 45' -56°00' N. and long 130°00'-

132°00' W.; it is bounded on the east and south by 

the United States-Canadian (British Columbia) 

border, and on the west by Clarence Strait. 

The study area, which lies mainly in the 

Pacific Coast Mountains physiographic province, 

is characterized by islands and peninsulas deeply 

dissected by a complex network of coasjtl and 

inland tidal waterways. The terrain ranges from 

heavily forested rolling uplands on the southwest 

to bare rugged mountains with active glaciers on 

the northeast. The average relief increases from 

about 1,000 m on the southwest to about 1,500 m 

on the northeast; the highest point within the 

study area is a 2,200-m-high nunatak that rises 

above perennial snowfields and glaciers near the 

northeast corner of the Ketchikan quadrangle. 

Landforms in the study area are dominated 

by such glacially sculpted features as fiords and 

broad U -shaped valleys walled by sheer cliffs 300 

m or more high. Most of the area was completely 

overridden by glacial ice that produced broad 

rounded ridge crests. In the northeast corner, 

however, the mountaintops locally stood above 

the highest level of the ice and include many 

sharp pinnacles and knife-edge ridges. 

The prevailing maritime climate is characterized by heavy precipitation, probably equivalent to more than 250 em of rainfall per year. 

Vegetation consists of dense, nearly impenetrable 

rain forest at low elevations and of brush, moss, 

and lichens at higher levels. 

Except for scattered loggingorminingcamps 

and a few isolated cabins, nearly all the permanent population of the study area is concentrated 

in and near Ketchikan, Alaska, and adjacent 

parts of Gravina Island (population, approx 

10,000 in 1970), in and near theN ative village of 

Metlakatla (population, approx 1,000 in 1970), 

and at Hyder (population, approx 50 in 1970). The 

only town in the study area that can be reached by 

highway from Canada and the United States is 

Hyder, which is linked by way of Stewart, British 

Columbia, to western Canada, Alaska, and the 

Pacific Northwest. Other than to Hyder, access to 

and throughout the study area is by boat or 

aircraft. 

2 

PREVIOUS INVESTIGATIONS 

Before starting the AM RAP systematic mineral appraisal of the Ketchikan and Prince Rupert 

quadrangles in 1975, the U.S. Geological Survey 

had conducted numerous reconnaissance and 

local investigations of the geology and mineral 

deposits in the study area, beginning around 1900 

(fig. 2). The most significant results of these 

investigations were presented in the reports by 

Brooks (1902), Wright and Wright (1908), Smith 

(1915), Chapin (1918), Buddington (1929), Robinson and 1\venhofel (1953), West and Benson (1955), 

Byers and Sainsbury (1956), Sainsbury (1957a, 

b), Berg (1972a, b, 1973), Smith (1973), Berg and 

others (1977a), and Smith (1977). In addition, 

information on the geology and mineral deposits 

in the study area is contained in the regional 

reports by Martin (1926), Buddington and Chapin 

(1929), Berg and Cobb (1967), and Berg and others (1972). 

AMRAP AND SUBSEQUENT INVESTIGATIONS 

AM RAP investigations in the Ketchikan and 

Prince Rupert quadrangles began in 1975, when 

an interdisciplinary team of earth scientists and 

technicians undertook systematic geologic mapping and geochemical, geophysical, Landsat, and 

mineral-deposit studies leading to a mineralresource assessment of the study area (table 1). 

These collateral field and laboratory studies were 

completed early in 1978, when the results were 

combined and integrated into the mineral assessment that culminated AM RAP in the study area. 

In addition, certain topical and regional geologic 

and mineral-resource investigations begun by 

team members and guest scientists during the 

AMRAP study have been completed, and the 

results published in several reports. These reports 

describe the tectonic and structural setting of the 

study area and neighboring parts of Alaska and 

Canada (Berg and others, 1977b, 1978d); the 

petrology and geologic setting of the porphyry 

molybdenum deposit at Quartz Hill (Elliott and 

others, 1976; Hudson and others, 1977, 1978, 

1979); metamorphosed lower(?) Paleozoic trondhjemite on the southern part of the Portland peninsula (Koch and others, 1977); and metallogenesis 
0 10 20 

Revi II ag ig edo 

Island 

1:11trq11 ce 

30 KILOMETERS 

---------------

/ PRINCE RUPERT 

/ 

f' 

FIGURE 2.-Ketchikan and Prince Rupert quadrangles, showing areas described in selected geologic reports (see table 1): 

1, Brooks (1902); 2, Smith (1915); 3, Chapin (1918); 4, Buddington (1929); 5, Berg (1972a); 6, Berg (1973); 7, Irvine (1974); 

8, Smith (1977); 9, Berg and others (1977a); 10, Koch and others (1977); 11, Elliott and others (1976) and Hudson and others 

(1977, 1978, 1979). H, Hyder; K, Ketchikan; M, Metlakatla. 

3 
TABLE I.-Component maps and reports of the Ketchikan and Prince Rupert quadrangles mineral-resource assessment 

U.S. G~ulogicol Sun·e!J Open-File Rep(llt Subject 

72-17 (Barnes, 1972)1 ............................................................................... . Bouguer gravity maps 

Aeromagnetic-contour map 

Geologic map 

77-359 (U.S. Geological Survey, 1977) .............................................. .. 78-73-A (Berg and others, 1978b) ...................................................... .. -B (Elliott and others, 1978) 

-C (Koch and others, 1978a) ...................................................... .. Mineral-deposit map and table 

Geochemical-anomaly map: Cu 

Geochemical-anomaly map: Pb 

Geochemical-anomaly map: Zn 

Geochemical-anomaly map: Mo 

Geochemical-anomaly map: Au, Ag 

Geochemical-anomaly map: Cr 

Geochemical-anomaly map: Co 

Geochemical-anomaly map: Ni 

-D (Koch and others, 1978c) ...................................................... .. -E (Koch and others. 1978h) ..................................................... .. -F (Koch and others, 1978f) ....................................................... . -G (Koch and others, 1978b) ...................................................... . -H (Koch and others, 1978d) ...................................................... .. -I (Koch and others, 1978e) ........................................................ .. -J (Koch and others, 1978g) ....................................................... . -K (Steele and Albert, 1978) ...................................................... .. Landsat interpretation map 

-L (Griscom, 1981) ......................................................................... . Aeromagnetic interpretation map 

-M (Berg and others, 1978a) ..................................................... .. Mineral-resource assessment map and tables 

-N (Smith and Diggles, 1981) ................................................... . Map and table of potassium-argon age determinations 

78-156-A (Koch and Elliott, 1978b) .................................................. .. Analyses of rock geochemical samples, Ketchikan 

quadrangle 

-B (Koch and Elliott, 1978a) .................................................. .. Analyses of rock and stream-sediment geochemical 

samples, Prince Rupert quadrangle 

-C (Koch and Elliott, 1978c) .................................................... .. Analyses of stream-sediment geochemical samples, 

Ketchikan quadrangle 

'Information from this report and from subsequent AMRAP-supported gravimetric studies were included in the resource assessment. 

in the accreted terranes of southeastern Alaska 

(Berg, 1979, 1981). 

ACKNOWLEDGMENTS 

Throughout this report I use the term "we" in 

describing the scientific investigations and results of the AMRAP resource appraisal of the 

Ketchikan and Prince Rupert quadrangles. "We" 

includes my fellow members of the interdisciplinary team of energetic and talented earth scientists who successfully completed this difficult and 

complex investigation well within its tight budget 

and schedule, and I thank these colleagues for 

their collaboration, dedication, and professionalism. I am especially grateful to J. G. Smith, R. L. 

Elliott, R. D. Koch, R. B. Carten, M. F. Diggles, C. 

D. Holloway, R. J. Miller, R. J. Rudser, and B. D. 

Wiggins for their contributions to the geologic 

mapping; to J. G. Smith for isotopically (K-Ar) 

dating scores of rocks from throughout the study 

area; toR. D. Koch for leading the geochemical 

program with singular dedication, skill, and 

energy; to Andrew Griscom and D. F. Barnes for 

their aeromagnetic and gravimetric geophysical 

interpretations; to W. C. Steele and N. R. D. 

4 

Albert for their pioneering Landsat data interpretation of the study area; and to W. D. Menzie 

and D. A. Singer for their advice and guidance on 

the culminating resource assessment. 

I also acknowledge the special skills and contributions of my U.S. Geological Survey colleagues D. L. Jones, whose biostratigraphic studies led to new tectonic interpretations of the 

study area and neighboring regions; T. L. Hudson, who led our investigations at the Quartz Hill 

molybdenum prospect; J. G. Arth and T. W. 

Stern, for uranium-lead geochronology and 

rubidium-strontium isotope studies of the plutonic rocks; J. J. Criscione for his rubidiumstrontium isotope studies of the metasedimentary 

rocks; and Fred Barker for rare-earth- and traceelement investigations of key volcanic units. 

Finally, I thank the crew of the U.S. Geological Survey research vessel DonJ. Miller II and G. 

A. ("Bud") Bodding, master of the charter vessel 

Mytime, for providing comfortable and efficient 

base camps for our field investigations; Kenneth 

C. Eichner, Barry Roberts, and Mike Salazar of 

Temsco Helicopters, Ketchikan, Alaska, for providing us with outstanding helicopter support; 

and Ed Todd and Dixie Jewett of Todd's Air 

Service, Ketchikan, for providing reliable fixed-
wing aircraft support, often under adverse 

weather conditions. 

DESCRIPTIONS OF COMPONENT MAPS AND 

REPORTS OF THE KETCHIKAN AND PRINCE 

RUPERT QUADRANGLES AMRAP FOLIO AND 

OF SUBSEQUENT RELATED INVESTIGATIONS 

The following sections of this report briefly 

describe the six interdisciplinary components of 

the AMRAP mineral-resource assessment of the 

Ketchikan and Prince Rupert quadrangles: (1) 

geology, (2) mineral-deposit site studies, (3) geochemistry, ( 4) geophysics, (5) earth-satellite 

(Landsat) data, and (6) resource analysis. The 

first five of these components were collateral field 

and laboratory research investigations that 

yielded extensive new data in several branches of 

earth science relating to mineral resources. The 

sixth component integrated these data into the 

culminating resource assessment, which identifies tracts of land favorable for the occurrence of 

specific types of mineral deposits and, where the 

data permit, predicts at different probabilities 

the number, size, and grade of those deposits. The 

following sections also summarize the results of 

our geologic and mineral-resource investigations 

in the study area since the AMRAP folio was 

published early in 1978. 

GEOLOGY 

(Open-File Report 78-73-A) 

The geologic map of the Ketchikan and Prince 

Rupert quadrangles resulting from this investigation (Berg and others, 1978b) describes the 

rocks between the United States-Canadian border 

and Clarence Strait (fig. 1). We did not map the 

small areas of rocks on the west side of the strait 

because they are part of a separate investigation 

by the U.S. Geological Survey. 

The rocks that we mapped include diverse 

rock types and range in age from Silurian or 

older to Quaternary. Our investigations show that 

they are most conveniently treated within three 

geographic areas, each under lain by a characteristic assemblage of rocks with distinctive lithologic, structural, or metamorphic features. 

5 

GRAVINA-ANNETTE-MARY-DUKE ISLANDS AREA 

The Gravina-Annette-Mary-Duke Islands 

area includes the islands bounded by Clarence 

Strait, Dixon Entrance, Tongass Narrows, and 

Revillagigedo Channel and makes up about a 

sixth of the study area. The area contains the most 

diverse rock types and the most complete suite of 

stratified rocks in the Ketchikan and Prince 

Rupert quadrangles; it also includes the least 

metamorphosed and least deformed pre-Tertiary 

rocks in the map area. The bedded rocks range in 

age from Silurian or older to Late Jurassic or 

Cretaceous; the mapped intrusive rocks range in 

age from Silurian or older to Cretaceous. Pluglike gabbro plutons on northeastern Gravina 

Island (too small to show on the map), previously 

assigned a probable Cretaceous age (Berg, 1973), 

instead probably correlate with presumed Oligocene or Miocene gabbro near Ketchikan. Especially distinctive units include a Silurian or older 

stock of leucocratic trondhjemite, an Upper Triassic sequence of rhyolite, basalt, and sedimentary rocks, and a Cretaceous zoned ultramafic 

intrusive complex that contains spectacular zones 

of rhythmically layered dunite and peridotite 

(Irvine, 1974). Mineral occurrences include 

barite- and base- and precious-metal-bearing 

volcanogenic sulfide deposits in the Upper Triassic rocks; veins carrying gold, silver, and other 

metals in Upper Jurassic or Cretaceous andesitic 

metatuff; and stratiform titaniferous magnetite 

deposits in the zoned ultramafic rocks. 

New age assignment of rocks on Annette and 

Grav,ina Isla,nds.-The age of the Puppets Formation and its unnamed correlatives, and of an 

unnamed conformably overlying massive limestone and dolomite unit on Annette and Gravina 

Islands (fig. 3), is here revised from middle 

Paleozoic (Berg, 1973) to Late Triassic. This new 

assignment is based on the discovery (H. C. Berg, 

unpub. data, 1979) of Late Triassic marine fossils 

within the limestone unit in two localities on 

eastern Annette Island (fig. 3). The fossils were 

identified by Anita G. Harris of the U.S. Geological Survey as follows (written commun., 1980): 

Field No. 79ABG091A: E. coast of Annette Island 

about 33.9 km SE. of Ketchikan. Small cove 

about 1. 6 km S. of K wain Bay in sec. 26, T. 78 

S., R. 93 E. (lat 55°04'50" N ., long 131 °21'20" 

W.). Moderately massive to slaty very fine 
GRAVINA 

ISLAND 

0 

EXPLANATION 

- ---- Contact-Dashed where uncertain; dotted where concealed 

- ---· Fault-Dashed where uncertain; dotted where concealed 

79 92 A Sample locality 

0 Ketchikan 

13F30' 

REVILLAGIGEDO 

ISLAND 

ANNETTE 

ISLAND 

79ABG092A 

0 

OL.._ ____ __J.. _____ ~lO KILOMETERS ~ 

6 

FIGURE 3.-Annette and Gravina Islands, showing distribution of Puppets Formation and its correlatives (dot pattern), 

unnamed conformably overlying massive limestone and dolomite unit (line pattern), an outcrop area where these units 

were not mapped separately (crosshatch pattern), and localities of samples collected in 1979 containing Upper 'friassic 

fossils. Geology modified from Berg (1972a, 1973) and Berg and others (1978b). 

6 
grained crystalline metacarbonate containing sparse corals. Metacarbonate overlies 

rhyolite metatuff; exposed thickness of carbonate, about 30m; 5.48 kg of metacarbonate 

was processed for conodonts (1.2 kg of plus20-mesh insoluble residue) and yielded: 

1 Epigondollela sp. 

This genus is restricted to the Late Triassic. 

Field No. 79ABG092A: East side of Annette 

Island about 29.4 km SE. of Ketchikan. 

Locality is a cave at outlet of lake at elev 

approx 70 m in sec. 16, T. 77 S., R. 92 E. (lat 

550°6'35" N., long 131 °23'55" W.). Massive to 

thin-bedded fine-grained dark-gray metacarbonate, locally containing sandy lenses and 

layers, some of which seem to consist of 

comminuted organic material. Carbonate is 

about 100m thick, overlies rhyolite metatuff, 

and probably correlates with limestone at 

field No. 79ABG 091A; 4.9 kg of metacarbonate was processed (330 g of plus-20-mesh 

insoluble residue) and yielded: 

1 Epigondollela sp. 

Age: Late Triassic. 

REVILLAGIGEDO ISLAND AND 

THE CLEVELAND PENINSULA 

The central third of the map area is underlain by diverse plutonic rocks and by multiply 

deformed and metamorphosed strata that include 

small outcrop areas of: (1) very sparsely fossiliferous Permian and Middle Triassic sedimentary 

and volcanic rocks; and (2) slate, graywacke, and 

augite (hornblende) porphyry that we tentatively 

correlate with Jurassic or Cretaceous sedimentary and volcanic rocks of the Gravina Island 

Formation. By far the most abundant strata are 

metamorphosed and deformed bedded rocks 

whose premetamorphic age is unknown, and 

which we have subdivided into map units on the 

basis of lithology. These undated units include: (1) 

dark-gray phyllite and metagraywacke and darkgray pyritic metapelite intercalated with subordinate rusty-weathering felsic and intermediate 

metatuff; (2) green basaltic pillow flows, breccia, 

and metatuff; (3) volumetrically minor but locally 

conspicuous metaconglomerate and marble; ( 4) 

paragneiss and amphibolite; and (5) a catchall 

unit of several metamorphic-rock types too 

limited in extent to show individually on the geologic map. We have assigned the undated units an 

7 

age of late Paleozoic or Mesozoic because this 

assignment brackets the age of the oldest (Permian) fossiliferous strata known in this area, and 

of the oldest (Late Jurassic) isotopically dated 

plutonic rocks that intrude it. The youngest rocks 

known are basalt and andesite lava flows, breccia, and tuff that mainly coincide with or postdate 

Quaternary glaciation but may in part be as old 

as late Tertiary (5.5 m.y.). Key pre-Tertiary bedded units include: light-gray locally dolomitic 

marble that locally contains crinoid disks, conodonts, and brachiopods of Permian age (N.J. Silber ling and B. R. Wardlaw, written commun., 

1980); dark-gray pyritic metapelite and subordinate rusty-weatheripg felsic or intermediate 

metatuff, and basaltic pillow flows and breccia 

that are intercalated with crinoidal marble; 

dark-gray carbonaceous (graphitic) and locally 

concretionary limestone, mudstone, and siltstone 

locally containing Middle Triassic fossils (N. J. 

Silberling and B. R. Wardlaw, written commun., 

1980); basaltic pillow flows, breccia, and tuff, and 

pelitic basalt-siltstone clast conglomerate that 

apparently are interbedded with Triassic strata; 

and metaconglomerate in the Carroll Inlet and 

Thorne Arm that contains conspicuous relict 

roundstones of quartz diorite or trondhjemite and 

quartzite(?) in a pelitic, tuffaceous, or calcareous 

matrix. Although we have not yet found fossils in 

the metaconglomerate, field relations suggest 

that at least some of it is gradational or intercalated with the crinoidal marble. 

The oldest radiometrically (K-Ar) dated pluton in this area is a 140-m.y.-old (Late Jurassic) 

granodiorite stock near Moth Bay. The largest 

pluton is a radiometrically dated mid-Cretaceous 

foliated quartz diorite batholith on northern 

Revillagigedo Island and the adjacent Cleveland 

Peninsula. Other radiometrically dated plutons 

include a swarm of varyingly metamorphosed 

and deformed stocks, diapirs(?), dikes, and sills of 

garnet-bearing and locally plagioclase porphyritic granodiorite that give Late Cretaceous 

potassium-argon (Smith and others, 1979) and 

uranium-lead (T. W. Stern, oral commun., 1979) 

ages; and a composite Oligocene or Miocene gabbro to granodiorite intrusive complex near Ketchikan. Other intrusive rocks, mainly of known or 

assumed Cretaceous or older age. include stocks 

or sheets of aplite or alaskite, pluglike metadiorite bodies, a zoned ultramafic complex at Alava 

Bay, and several other small ultramafic bodies. 
Regional structures in the pre-Tertiary strata 

include southwest-verging overturned to recumbent refolded isoclines cut by bedding-plane 

thrusts and blastomylonite zones, and by highangle faults that postdate the thrusts. The rocks 

are regionally metamorphosed progressively from 

greenschist facies on the southwest to amphibolite 

facies on the northeast; this metamorphism, radiometrically dated as Cretaceous or older, locally is 

overprinted by contact metamorphism as intense 

as hornblende-hornfels facies. "Feather schist" or 

"garbenschiefer," a metamorphic rock distinguished by locally conspicuous feathery crystal 

aggregates of actinolite in a matrix of garnetbearing silvery muscovitt schist, is widespread 

on central and southwestern Revillagigedo Island; 

its distinctive mineralogy and texture suggest 

polymetamorphism of a bedded unit significantly 

different in original composition from the adjoining strata. 

Mineral occurrences that have been productive or extensively explored include massive leadand zinc-sulfide veins, auriferous quartz veins, 

and a stibnite vein in the undated metapelite and 

metatuff unit; and stratiform titaniferous magnetite deposits in the zoned ultramafic complex at 

Alava Bay. 

PORTLAND PENINSULA 

The east half of the Ketchikan-Prince Rupert 

study area is a peninsula, bounded by the (east) 

Behm Canal, Revillagigedo Channel, and Portland Canal, that we informally call the "Portland 

peninsula" (fig. 2). The youngest consolidated 

rocks known on the Portland peninsula correlate 

with the Tertiary or Quaternary basalt and andesite described on Revillagigedo Island. Except 

for small outcrop areas of these volcanic rocks, 

the peninsula is underlain mainly by the Coast 

Plutonic Complex of Brew and Ford (1978, 1981), 

which is bordered on the west by a fringe of 

enigmatic metamorphosed bedded and plutonic 

rocks and on the northeast by probable lower 

Mesozoic rocks that underlie only a small area at 

the northeast corner of the map area. Figure 4 

shows revisions to the geology of the southern 

part of the Portland peninsula, based on investigations completed since the publication of OpenFile Report 78-73-A. 

The Coast Plutonic Complex is a heterogeneous group of massive and foliated plutonic rocks 

and amphibolite-facies regionally metamorphosed bedded rocks that form septa, screens, 

roof pendants, and xenoliths within or between 

the plutons. The premetamorphic age of the 

bedded rocks is unknown; we assign them a 

Paleozoic or Mesozoic age to bracket the ages (1) 

of possibly correlative Paleozoic or older isotopically dated nearly identical metamorphosed 

bedded rocks of the so-called Central Gneiss 

Complex (Hutchison, 1970) of the Coast Plutonic 

Complex in the neighboring part of British 

Columbia (Wanless and others, 1975; Armstrong 

and Runkle, 1979), and (2) of the oldest isotopically dated (Jurassic) plutons known to intrude 

them. 

According to our radiometric-age data, the 

plutons were emplaced during Late Jurassic, 

Eocene, and Oligocene or Miocene time (Smith 

and others, 1979). Their structure ranges from 

gneissic to massive, and their composition from 

gabbro to granite; the most abundant rock type is 

foliated granodiorite. Not shown on the map are 

myriads of Oligocene or younger lamprophyre 

(Smith, 1973; Hudson and others, 1979) and 

quartz porphyry (Hudson and others, 1979) dikes. 

The metamorphic age of the foliated plutonic and 

bedded rocks is Eocene or older (Smith and others, 1979). Structural trends, isograds, and lithologic units strike northwest to north-south. In the 

Ketchikan-Prince Rupert study area, the westernmost unit of the Coast Plutonic Complex is a 

north-south-trending set of elongate foliated 

quartz diorite or tonalite plutons that beyond the 

project area coalesce into a remarkably persistent sill which marks the southwest limit of the 

Coast Plutonic Complex throughout southeastern 

I Alaska (Brew and Morrell, 1979; Brew and Ford, 

1981). 

8 

Adjoining the Coast Plutonic Complex on the 

west is a wedge-shaped outcrop belt of greenschist- to amphibolite-facies regionally metamorphosed bedded and intrusive rocks. The east 

limit of this belt is the west contact of the Coast 

Plutonic Complex, and the west limit is a northwest-trending linear fault zone that has been 

mapped from Harry Bay to beyond Kah Shakes 

Cove (fig. 4). The premetamorphic age of the 

bedded and intrusive rocks is largely unknown; a 

discordant potassium-argon determination on one 
55°00' 

54°45' 

::---.'< 

Sfate'Js, .. ~ 

/ 

EXPLANATION 

B 

Ultramafic rocks 

B 

Undivi!led metamorphic and intrusive 

rocks 

Includes units MzPza, 

MzPzm, MzPzp, MzPzu, 

and TKp on Open-File 

Report 78-73-A 

G 

Metamorphosed 

trondhjemite 

B 

Undivided metamorphosed bedded 

rocks 

m, marble 

Contact 

Dotted where concealed 

Fault 

Dotted where concealed 

::2 

0 

N 

0 

(JJ 

....l 

< Q. 

"· ii 

(JJ 

3: 

0 

....l 

ALASKA ·-------- ----- - ---BRITiSH- C<MMBi~ - 0- 1 - 2 - 3- 4- 5 KILOMETERS . 

0 5 MILES 

FIGURE 4.-Southwestern part of Portland peninsula, showing revisions based on geologic investigations completed since 

publication of Open-File Report 78-73-A. Base from U.S. Geological Survey, scale 1:250,000; Ketchikan and Prince Rupert, 

1959. 

9 
pluton suggests that it was emplaced before or 

during Late Cretaceous time. Other potassiumargon age determinations suggest Cretaceous or 

Tertiary metamorphism for both the bedded and 

intrusive rocks. Very sparse objects, doubtfully 

identified as crinoid disks implying a late Paleozoic age (H. C. Berg and C. D. Holloway, unpub. 

data, 1976), occur in marble layers along Very 

Inlet, and most of the other strata are lithologically similar to the rocks on central and southwestern Revillagigedo Island, to which we assign 

a late Paleozoic or Mesozoic age. For these reasons, we also assign these rocks a late Paleozoic or 

Mesozoic age. 

The most widespread unit southwest of the 

Harry Bay-Kah Shakes Cove fault zone is a 

metamorphosed trondhjemite stock that we correlate, on the basis of similar lithology and texture, with the Silurian or older Annette pluton on 

Annette Island (Koch and others, 1977). If this 

correlation is correct, the strata intruded by this 

pluton must be Silurian or older. Following this 

assumption, we assign these rocks an age of 

early(?) Paleozoic. However, most of the metamorphosed bedded rocks southwest of the fault 

are lithologically indistinguishable from those 

northeast of it. This observation suggests that: (1) 

nearly identical rock types of different age crop 

out on both sides of the fault, or (2) there has been 

at least local tectonic transport and mixing of 

possible younger Paleozoic or Mesozoic metamorphosed bedded rocks from northeast of the 

fault with the presumed lower Paleozoic country 

rocks intruded by the trondhjemite, or (3) both 

these interpretations. In any case, intense deformation and metamorphism, as well as poor 

exposures, prevented us from mapping any outcrop areas of these possibly younger rocks southwest of the fault. 

About 30 km2 of the northeastern most corner 

of the Ketchikan-Prince Rupert study area is 

under lain by recrystallized Triassic or Jurassic 

volcanic, sedimentary, and plutonic rocks. These 

rocks, which were cataclastically deformed during Mesozoic or early Cenozoic time and then 

intruded and locally contact metamorphosed by 

Eocene plutons of the Coast Plutonic Complex, 

differ markedly in degree of deformation and 

metamorphism from the more intensely deformed 

and higher grade regionally metamorphosed 

rocks to the southwest in the Coast Plutonic 

Complex. We infer that the boundary between 

these two contrasting assemblages was a moderately northeast dipping thrust zone which subsequently was intruded and largely obliterated by 

the Eocene plutons (Berg and others, 1977a, p. 29). 

The currently (1981) most commercially 

attractive mineral deposit on the Portland peninsula is the large porphyry molybdenum lode in an 

Oligocene granite porphyry at Quartz Hill (11, 

fig. 2). Other mineral deposits that have recently 

been explored include another porphyry molybdenum occurrence just across the mouth of Burroughs Bay from the Portland peninsula; gold, 

silver, and base-metal veins and disseminated 

deposits in the Triassic or Jurassic volcanic and 

intrusive rocks near Hyder; massive base-metal 

sulfide deposits in the metamorphosed bedded 

rocks southwest of Smeaton Bay and near Humpback Lake; and copper-, zinc-, and silver-bearing 

sulfide veins and disseminations in paragneiss at 

Walker Cove. 

10 

POTASSIUM-ARGON AGE DETERMINATIONS 

(Open-File Report 78-73-N) 

By James G. Smith 

This map and accompanying tables (Smith 

and Diggles, 1981) list all known potassiumargon age determinations on rocks and minerals 

from the Ketchikan-Prince Rupert study area as 

of mid-1980. Altogether, more than 130 determinations have been made, of which about 50 were 

previously unpublished; about 80 of the determinations were reported previously, most without 

complete analytical data. Where possible, the 

unpublished analytical data and sample locations 

have been supplied. We especially thank M. A. 

Lanphere of the U.S. Geological Survey for furnishing analytical data for samples from Annette 

and Duke Islands. 

In 1976 the International Union of Geological 

Sciences' Subcommission on Geo- and Cosmochronology recommended adopting a new set of 

abundance and decay constants (Steiger and 

Jager, 1977). Since then, most laboratories have 

adopted the new constants. For our report, we 

recalculated all ages using the new constants; 

therefore, radiometric ages reported more than a 

few years ago may differ by a few percent from 

those given in Open-File Report 78-73-N. 

The potassium-argon age determinations in 

our report, as well as the uranium-lead age 
determinations on zircons by T. W. Stern (Smith 

and others, 1979), indicate at least three episodes 

of metamorphism and seven episodes of igneous 

intrusion in the study area, extending in time 

from the Silurian through the Miocene. Owing to 

these multiple episodes of metamorphism and 

igneous intrusion, most of the potassium-argon 

age determinations on mineral pairs are discordant and must be interpreted with caution. 

The oldest radiometrically dated rocks in the 

study area are from the Annette pluton (Berg, 

1972a), which has yielded a potassium-argon age 

of 424 m.y. on hornblende and a uranium-lead 

(zircon) age of 375 m.y. (J. G. Arth, written commun., 1978). Allowing for analytical uncertainty, 

this trondhjemite stock probably was emplaced 

during Silurian time. The difference in apparent 

radiometric ages is within the limits of analytical 

precision for the two methods and probably can 

be accounted for by locally moderate shearing 

and recrystallization of the pluton (J. G. Arth, 

written commun., 1978). 

Zoned ultramafic complexes yielding Cretaceous potassium-argon ages occur on and near 

Duke Island and at Alava Bay. These determinations mostly fall between 99.0 and 135 m.y. 

Apparent ages younger than 115 m.y. east of 

Revillagigedo Channel are discordant and, therefore, assumed to be partially reset. 

Before our radiometric-dating studies, all 

the plutonic rocks on Revillagigedo Island and 

the Portland peninsula, and in adjacent areas to 

the south in Canada, were considered to be part of 

a single poorly documented Late Triassic to Late 

Cretaceous orogeny (Buddington and Chapin, 

1929). Our studies show, instead, that plutonism 

occurred in several separate pulses, some more 

widespread and intense than others. The oldest 

dated pluton in this part of the study area is the 

Texas Creek Granodiorite, which was emplaced 

about 205 m.y. ago and consequently is assigned a 

Late Triassic or Early Jurassic age (Berg and 

others, 1977a). No other plutons are known on 

Revillagigedo Island or the Portland peninsula 

that are so old, although the subsequent intense 

metamorphic and plutonic events could have 

completely reset the radiometric clocks of older 

plutons to make them radiometrically indistinguishable from younger intrusive rocks. 

Jurassic (140 m.y. old) quartz diorite and 

granodiorite intrude migmatite and gneiss on the 

Portland peninsula and .lower grade metasedi11 

mentary and metavolcanic rocks on southern 

Revillagigedo Island. Heating by subsequent 

metamorphic-plutonic events was great enough 

to reset the potassium-argon clocks in these rocks, 

and only the uranium-lead clocks in zircons still 

record this event (Smith and others, 1979). 

DuringCretaceousorearliertime, the bedded 

rocks on northern Revillagigedo Island and on 

the neighboring Cleveland Peninsula were regionally metamorphosed. Then, about 90 m.y. ago, 

they were intruded by a batholith of quartz diorite and by numerous smaller plutons of garnetbearing and plagioclase porphyritic granodiorite, all of which are more or less foliated and 

recrystallized. Plutons of this age have not yet 

been identified east of the (east) Behm Canal and 

of the topographic low that marks its extension 

through Vixen Bay and N a kat Inlet. 

A suite of coalescing Eocene quartz monzonite to granodiorite batholiths intruded the eastern Portland peninsula about 52 to 42 m.y. ago. 

Plutons in this age range are nearly all confined 

to that part of the study area, although a few are 

recognized elsewhere on the Portland peninsula. 

However, no plutons of this suite have been recognized on Revillagigedo Island, the Cleveland 

Peninsula, or the Portland peninsula west of 

Vixen Bay and Nakat Inlet. 

'Emplacement of the Eocene plutons was 

accompanied by a resetting of potassium-argon 

clocks throughout the Coast Plutonic Complex 

that has been attributed to widespread heating of 

enigmatic origin (Smith and others, 1979) or to 

regional uplift and cooling (Hutchison, 1970). 

During Oligocene and Miocene time, 31 to 19 

m.y. ago, a suite of widely scattered and volumetrically small epizonal plutons was emplaced; this 

suite ranges in composition from gabbro and syenodiorite to granite porphyry. The molybdenum 

deposits at Quartz Hill and Burroughs Bay are 

associated with the granite plutons. 

TECTONOSTRATIGRAPHIC TERRANES AND 

STRUCTURAL FRAMEWORK OF THE KETCHIKAN AND 

PRINCE RUPERT QUADRANGLES 

Regional tectonic and biostratigraphic investigations completed since our preliminary geologic map was published in 1978 show that the 

pre-Cenozoic strata in the Ketchikan-Prince 

Rupert quadrangles area can be interpreted as 
constituting five fault-bounded assemblages, each 

characterized by its own distinctive stratigraphy 

and tectonic history (Berg and others, 1977b), 

1978d). Northeastward from Clarence Strait, 

these five tectonostratigraphic assemblages are 

known as the Annette subterrane (of the Alex-

\ _ AL;~S~\- _....,_ 

RI flSH COLUvlBlA 

\ 

0 10 20 30 KILOMETERS 

FIGURE 5.-Tectonostratigraphic terranes and structural elements in Ketchikan and Prince Rupert quadrangles. Base from 

National Atlas of the United States of America, 1970. 

12 
ander terrane), the Gravina-Nutzotin belt, the 

Taku terrane, the Tracy Arm terrane, and the 

Stikine terrane (fig. 5). 

ANNETTESUBTERRANE 

The Annette subterrane, typified by preJurassic strata on Annette and Gravina Islands, 

is a subdivision of the Alexander tectonostratigraphic terrane, which mainly lies west of 

Clarence Strait (Berg and others, 1978d). The 

subterrane is distinguished by a heterogeneous 

assemblage of pre-Silurian, Silurian, and Devonian intrusive, extrusive, clastic, and carbonate 

rocks on and near Annette Island, and by the 

absence of any known post-Middle Devonian 

Paleozoic strata. The youngest pre-Cenozoic stratigraphic unit assigned to the Annette subterrane 

is the Upper Triassic Chapin Peak Formation 

(Berg, 1973). 

CR 

AN 

TK 

TA 

ST 

• • 

A A 

EXPLANATION 

Tectonostratigraphic terrane-Queried where 

assumed 

Gravina-Nutzotin belt-Unpatterned, basement not exposed. Line pattern shows distribution of mapped (solid lines) and assumed (dashed lines) rocks of GravinaNutzotin belt overlying subjacent terranes. 

Extent of assumed rocks of GravinaNutzotin belt in Taku terrane is unknown 

Alexander terrane 

Craig subterrane 

Annette subterrane 

Taku terrane 

Tracy Arm terrane 

Stikine terrane 

Contact 

Mapped high-angle fault-May coincide in strike 

with reverse or thrust fault 

Inferred fault 

Thrust fault-Sawteeth on upper plate. May 

coincide in strike with high-angle fault 

Mapped thrust fault 

Inferred thrust fault 

--?-Undefined boundary of terrane; queried where 

continuation is uncertain or speculative 

13 

These rocks record several episodes of 

magmatic-arc and possibly rift related volcanism, sedimentation, and intrusion that began at 

least as long ago as early Paleozoic time. They also 

record a history of deformation and metamorphism that, depending on their age and location, 

range from penetrative multiple folding and 

polymetamorphism as intense as amphibolite 

and hornblende-hornfels facies, to relatively 

simple folding accompanied by slaty cleavage 

and only slight recrystallization. 

The Annette subterrane is separated from 

the Craig su bterrane of the Alexander terrane by 

the Clarence Strait fault, and from the Taku terrane by east-dipping mapped and inferred thrust 

faults and zones of blastomylonite. On Annette 

and Gravina Islands, its contact with the GravinaNutzotin belt is an unconformity locally cut by 

normal and reverse faults. 

GRAVINA-NUTZOTIN BELT 

The Gravina-Nutzotin belt comprises Late 

Jurassic or Early Cretaceous volcanic and sedimentary rocks, and presumed subvolcanic dioritic to ultramafic plutons. The assemblage is 

interpreted as the remnants of a collapsed late 

Mesozoic volcanic arc (Berg and others, 1972). 

The bedded rocks are regionally metamorphosed 

to prehnite-pumpellyite and greenschist facies, 

and are folded into southwest-verging locally 

refolded isoclines whose axial surfaces dip moderately northeast. On the southwest, the GravinaNutzotin belt is in faulted stratigraphic contact 

with the Annette subterrane. On the northeast, 

the extent and distribution of Gravina-Nutzotin 

belt rocks are not yet known. In places, the belt is 

separated from the Taku terrane by mapped and 

inferred northeast-dippingthrustfaults and zones 

of blastomylonite; in other places, the Taku terrane contains undated pelite and tuff that may in 

part correlate with Jurassic or Cretaceous strata 

in the Gravina-Nutzotin belt. 

TAKU TERRANE 

The Taku terrane contains very sparsely fossiliferous late Paleozoic and Middle or Late Trias-
sic volcanic and sedimentary rocks, as well as 

undated pelitic and tuffaceous rocks that in part 

may correlate with Jurassic or Cretaceous strata 

in the Gravina-Nutzotin belt. The stratigraphic 

key to the terrane is a thick sequence of late 

Paleozoic basaltic tuff and agglomerate that occurs in this terrane mainly north of the Ketchikan-Prince Rupert study area and that is not 

known in any of the other terranes. The stratigraphic base of the Taku terrane is not known; 

clasts of leucocratic quartz diorite or trondhjemite in metamorphosed roundstone conglomerate 

in Carroll Inlet and at Thorne Arm on Revillagigedo Island are lithologically similar to trondhjemite in the Silurian or older Annette pluton 

(Berg, 1972a), which may have been their source, 

but there is no stratigraphic evidence of pre-late 

Paleozoic crystalline basement beneath the presently mapped extent of the Taku terrane. Although we have not found fossils in the metaconglomerate unit, field relations suggest that at 

least some of it is intercalated with, or grades 

structurally downward into, crinoidal marble of 

late Paleozoic age (p. 12). If the premetamorphic 

age of the metaconglomerate also is late Paleozoic 

and the source of the clasts was the Annette 

pluton, then this unit may record structural juxtaposition (amalgamation) of the Annette (Alexander) and Taku terranes during late Paleozoic 

time. 

The Taku terrane is intruded by myriad 

probable Late Cretaceous dikes, sills, and stocks, 

mainly of distinctive plagioclase porphyritic and 

garnet-bearing granodiorite; by a batholith of 

Cretaceous quartz diorite; and by diverse other 

plutons, ranging in age from Late Jurassic to 

Oligocene or Miocene and in composition from 

quartz monzonite to peridotite. The terrane is 

characterized by Late Cretaceous or older northeastward-increasing regional metamorphism 

from greenschist to amphibolite facies, locally 

overprinted by contact metamorphism as intense 

as hornblende-hornfels facies. Regional structures include northeast-dipping thrust faults and 

zones of blastomylonite cut by younger highangle faults. The stratified rocks are complexly 

folded into southwest-verging overturned to 

recumbent locally refolded isoclines. Regionally 

the terrane may be a giant melange or megabreccia, consisting of dismembered blocks of relatively competent rocks surrounded by pelitic and 

tuffaceous phyllite and semischist. The terrane is 

14 

bounded on the southwest by northeast-dipping 

thrusts and blastomylonite zones. In the Ketchikan-Prince Rupert study area, the northeast 

boundary of the Taku terrane is a line connecting 

the west contacts of a northwest- to north-southtrending series of elongate stocks of foliated 

quartz diorite (tonalite). Beyond the limits of the 

study area, these stocks apparently coalesce into a 

persistent sill that marks the southwest boundary 

of the Coast Plutonic Complex (Brew and Ford, 

1981) and that probably was emplaced along a 

Mesozoic suture which corresponds to the contact 

between the Taku and Tracy Arm terranes (Berg 

and others, 1978d; Brew and Morrell, 1979). This 

boundary also is spatially related to the Coast 

Range megalineament (Brew and Ford, 1978), an 

enigmatic topographic, structural, and geophysical feature that locally coincides with the southwest edge of the Coast Plutonic Complex. 

TRACY ARM TERRANE 

The Tracy Arm terrane is a belt of high 

(sillimanite)-grade regionally metamorphosed 

bedded rocks that form roof pendants, screens, 

and xenoliths within the Coast Plutonic Complex. 

Correlative rocks in the neighboring parts of 

British Columbia are known as the Central Gneiss 

Complex (Hutchison, 1970). In and near the 

Ketchikan-Prince Rupert study area, this terrane consists of sequences of pelitic and semipelitic paragneiss and schist, minor marble and 

amphibolite, and very sparse ultramafic rocks. 

These rocks are much less abundant than the 

massive to gneissic plutons of the Coast Plutonic 

Complex. Radiometric dating of rocks in the 

study area yields Late Jurassic, Eocene, and 

Oligocene to Miocene emplacement ages for the 

plutons and an Eocene metamorphic age for the 

metapelite and amphibolite; however, the premetamorphic age of the stratified rocks in the Tracy 

Arm terrane is unknown. Radiometric dating of 

possibly correlative rocks in the Central Gneiss 

Complex near Prince Rupert in British Columbia 

suggests that at least some of these stratified 

rocks have a premetamorphic age of late Paleozoic (Armstrong and Runkle, 1979) and Precambrian or early Paleozoic (Wanless and others, 

1975). 

In the Ketchikan-Prince Rupert study area, 

the southwest limit of the Tracy Arm terrane and 

of the Coast Plutonic Complex that generally 
envelops it is the west contact of the series of 

elongate foliated quartz diorite (tonalite) plutons, 

discussed in the foregoing description of the Taku 

terrane. The northeast limit of the Tracy Arm 

terrane is inferred to be a northeast-dipping 

thrust zone that has been intruded and largely 

obliterated by Eocene plutons (Berg and others, 

1977a, p. 29). 

STIKINE TERRANE 

Rocks assigned to the Stikine terrane crop 

out only in a 30-km2 area in the northeast corner 

of the study area. The rocks consist of Late Triassic or Early Jurassic andesitic tuff and agglomerate, volcanic graywacke and argillite, and 

granodiorite that have been regionally metamorphosed to greenschist facies and then intruded 

and thermally metamorphosed by Eocene quartz 

monzonite and granodiorite. The Mesozoic rocks 

make up the south westernmost fringe of a late 

Paleozoic and younger assemblage of marine and 

nonmarine volcanic, intrusive, and sedimentary 

rocks that crop out almost entirely in British 

Columbia and the Yukon Territory (Monger, 

1977; Monger and Price, 1979). The Stikine terrane probably originated as a late Paleozoic volcanic arc; its key stratigraphic sequence (in British Columbia) is a thick pile of Lower and Middle 

Jurassic andesitic volcanic rocks that are unknown in any of the terranes to the west. In the 

Ketchikan-Prince Rupert study area, we interpret the southwest boundary of the Stikine terrane as a northeast-dipping thrust zone that has 

been mostly obliterated by the Eocene plutons. 

MINES, PROSPECTS, AND MINERAL OCCURRENCES 

(Open-File Report 78-73-B) 

The map and accompanying table (Elliott 

and others, 1978) briefly describe 174 metalliferous mines, prospects, and mineral (including barite) occurrences, as well as nine occurrences of 

nonmetallic minerals, publicly known in the 

Ketchikan-Prince Rupert study area when the 

report was published early in 1978. Since then, 

several private companies have conducted extensive mineral explorations in the area, but except 

for the porphyry molybdenum deposit at Quartz 

Hill (Randolph, 1979), results of these explorations have not been made public. 

Our own investigations consisted of examining as many of the known mineral deposits as 

possible to determine their age, origin, classification, geologic setting, and extent, and of collecting and analyzing representative samples of ore 

minerals and host rocks. We did not enter or 

remap any abandoned underground mine workings because all of them are caved, flooded, or 

otherwise inaccessible or hazardous. There are no 

active mines in the study area. 

Our report (Elliott and others, 1978) shows 

the locations of the known deposits plotted on a 

combined topographic and generalized geologic 

map, alphabetically lists the commodities contained in them, classifies them by form and 

extent of development, and briefly describes each 

with appropriate references. The geologic settings of the deposits and our interpretations of 

their age, origin, history, and resources were 

summarized in our report describing the mineral 

resources of the study area (Berg and others, 

1978a). 

METALLIFEROUS DEPOSITS 

Between about 1900 and the early 1950's, the 

study area was the hub of what were formerly 

known as the Ketchikan and Hyder mining districts (Brooks, 1902; Wright and Wright, 1908; 

Berg and Cobb, 1967), which comprised numerous active small lode mines that shipped ores containing gold, silver, copper, lead, zinc, and tungsten (Byers and Sainsbury, 1956; Cobb, 1972a, b). 

The gold and (byproduct) silver mines were 

mainly on Gravina Island, at Helm Bay on the 

Cleveland Peninsula, along Tongass Narrows and 

at the Thorne Arm on Revillagigedo Island, and 

near Hyder, where some of the lodes were worked 

mainly for silver. In addition to gold and silver, 

the mines on Gravina Island also shipped small 

amounts of copper ore, and those near Hyder 

shipped or stockpiled a few hundred tons of ore or 

concentrates containing tungsten, copper, lead, 

and zinc. Mines that produced small amounts of 

zinc concentrates containing subordinate copper 

and lead were worked at George Inlet and Moth 

Bay (Robinson and Twenhofel, 1953). 

In addition to the productive mines, several 

metalliferous deposits were more or less extensively explored by drilling or underground workings, but there is no record of any production 

from them (Berg and Cobb, 1967). These include 

15 
deposits prospected for gold and silver on Annette 

Island; for copper at Walker Cove and near Smeaton Bay and Humpback Lake; for gold, silver, 

tungsten, and molybdenum near Hyder; for titaniferous magnetite on and near Duke Island; and 

for antimony near Caamano Point on the Cleveland Peninsula. Extensive drilling and other 

exploration is currently (1980) underway by private interests at a prospect locally known as 

Quartz Hill, about 65 km east of Ketchikan, 

where about 1.5 billion t of low-grade molybdenum ore reportedly have been blocked out (Randolph, 1979; Juneau Empire, March 25, 1981). 

In addition to the mines and prospects, the 

study area contains hundreds of occurrences of 

metalliferous minerals that have at most been 

only cursorily prospected. Our report (Elliott and 

others, 1978) includes only occurrences that we 

could confirm from published reports, from U.S. 

Bureau of Mines claim maps (U.S. Bureau of 

Mines, 197 4, 1977), or by our own field studies. We 

did not include unconfirmed reports of metallic 

minerals, nor did we consider anomalous amounts 

of metals in our rock or mineral geochemical 

samples as mineral occurrences, unless subsequent followup revealed metalliferous minerals 

at the geochemical-anomaly site. 

Numerous such mineral occurrences containing traces to potentially significant amounts of 

gold, silver, copper, lead, zinc, and barite occur 

on Annette (Berg, 1972a; Hawley, 1975), Gravina, 

and southwestern Revillagigedo Islands; of gold, 

silver, copper, and molybdenum on the Portland 

peninsula; of gold, silver, tungsten, and molybdenum near Hyder; and traces of an unidentified 

radioactive mineral on southern Gravina Island 

(Williams, 1956). 

NONMETALLIC MINERALS 

Several occurrences of mica, feldspar, and 

garnet near the south tip of the Portland peninsula have been prospected for their value as 

industrial minerals, but none has proved to be of 

commercial size or grade (Sainsbury, 1957b). 

A small amount of short-fiber chrysotile(?) 

asbestos occurs at Yellow Hill, south of Metlakatla on Annette Island. 

16 

GEOCHEMISTRY 

{Open-File Reports 78-73-C through 78-73-J 

and 78-156-A through 78-156-C) 

We conducted systematic geochemical investigations in the Ketchikan-Prince Rupert study 

area to identify areas of anomalous concentrations of metallic elements. We collected and analyzed two relatively easily obtainable types of 

geochemical samples: stream sediment and rocks. 

Our reports describe the results of these geochemical investigations in three ways: (1) the 

sample-locality maps and accompanying tables 

list complete analytical data for all samples 

(Koch and Elliott, 1978a, b, c); (2) the analytical 

data on all U.S. Geological Survey geochemical 

samples collected for resource assessment in the 

study area also are available on magnetic computer tape (Koch and others, 1978i); and (3) a set 

of eight maps shows the distribution of streamsediment samples containing anomalous amounts 

of nine metals (Koch and others, 1978a, b, c, d, e, f, 

g, h). We selected these particular metals because 

the existing information on mineral deposits in 

the study area indicated that they would be useful 

as pathfinders either to additional mineral deposits or to geologic tracts with potential for mineral 

resources. 

Analyses were performed by the U.S. Geological Survey for many as 30 elements by sixstep semiquantitative emission spectrography 

(Grimes and Marranzino, 1968), and for gold, 

copper, lead, and zinc by atomic-absorption spectrophotometry (Ward and others, 1969). Samples 

collected in 1972 and 1973 were analyzed for mer~ 

cury by a flameless atomic-absorption mercuryvapor-detection technique (Vaughn and 

McCarthy, 1964). Some analyses were not performed on all samples. 

STREAM-SEDIMENT GEOCHEMICAL INVESTIGATIONS 

We collected most of the 2,602 stream-sediment samples used in our resource assessment 

during 1975 through 1977; this total also includes 

samples collected during other U.S. Geological 

Survey geologic mapping and mineral-resource 

investigations in the study area between 1968 and 

1977 (for example, Berg, 1972a, 1973; Elliott and 

others, 1976; Berg and others, 1977a; Smith, 
1977). The total includes only "normal" samples 

collected specifically for resource assessment and 

does not include certain samples collected for 

quality control, or for special studies of samplesite density and for geochemical tests of different 

sample-size fractions (A. L. Clark, unpub. data, 

1972-74). 

We followed standard procedures in collecting and preparing the stream-sediment samples. 

We generally collected samples from the finest 

sediment freest of organic material in the active 

stream channel. In a few places where this procedure was not possible, we sampled bank or terrace deposits adjacent to the channel. At sites 

between sea level and timberline, we were not 

always able to collect a sample completely free of 

organic material, and a few samples have low to 

high organic content. 

We obtained stream-sediment samples at 

shoreline sites above highest tide level wherever 

possible. Most of the study area is steep, and the 

sediment in the resulting swift streams is almost 

all detritus formed by mechanical, not chemical, 

weathering. Most stream-sediment samples are 

composed of material ranging in size from very 

fine sand to pebbles. Samples containing large 

amounts of silt- and clay-size material are rare 

and generally from areas of low elevation and 

gentle gradient. Samples were dried and sieved; 

the minus-80-mesh (minus 0.2 mm) fraction was 

pulverized, and a split analyzed. 

GEOCHEMICAL DATA AND INTERPRETATION 

Data from our stream-sediment geochemical 

program are presented in two reports (Koch and 

Elliott, 1978a, c), in which the sample locations 

are plotted on 1:125,000-scale topographic maps, 

accompanied by tables of all analytical values, 

statistical summaries, and brief discussions of 

analytical precision and of the bias and variability 

affecting interpretation. A second set of eight 

reports (Koch and others, 1978a, b, c, d, e, f, g, h) 

graphically presents data for selected elements to 

aid in mineral-resource assessment. These reports 

consist of 1:250,000-scale combined topographic 

and generalized geologic maps showing the distribution of gold, silver, copper, lead, zinc, 

molybdenum, chromium, cobalt, and nickel in 

stream-sediment samples in the study area. Because geochemical background levels vary for 

different rock types and different areas, and 

because of other variables inherent in geochemical sampling practice and conditions, each map 

(other than the one for gold and silver) suggests 

background, threshold, and anomalous levels for 

a particular element by grouping its analytical 

values into four ranges, each represented by a 

different symbol on the map. Although higher 

values may indicate a greater likelihood of bedrock mineralization in the relevant drainage 

basin, confidence levels are low for single-element 

"anomalies" and for high values that are not supported by neighboring values. Because only 2.2 

percent of the stream-sediment samples analyzed 

for silver and only 0.8 percent of those analyzed 

for gold yielded measurable values, all such samples and their values are plotted on the map showing the distribution of gold and silver. 

17 

ROCK GEOCHEMICAL INVESTIGATIONS 

To complement our regional reconnaissance 

of stream-sediment geochemistry, we collected 

representative grab samples of the main geologic 

units in most of the study area and analyzed them 

for the same metals as the stream-sediment samples. We also collected and analyzed grab samples 

of rocks containing visible metallic minerals 

(most commonly pyrite, magnetite, and hematite), 

and of hydrothermally altered rocks (mainly 

from bleached or iron-stained zones). The objectives of these investigations were: (1) to establish 

background levels of approximately two dozen 

"ore" and pathfinder metals in the main geologic 

units, as an aid in interpreting data from the 

stream-sediment samples collected from streams 

draining those units; (2) to determine whether 

parts of any rock units have intrinsic value as 

potentially economic mineral resources; (3) to 

detect potentially valuable metals not visible in 

hand specimens; and ( 4) to provide rough assays 

of samples containing visible metallic minerals. 

Whenever possible, we revisited sites from which 

we had collected rock geochemical samples containing very high values of potentially economic 

metals, to evaluate them as mineral occurrences 

(see section entitled "Mines, Prospects, and Mineral Occurrences"). 
We collected a total of 1, 708 samples, most 

(about 85 percent) of which were apparently 

barren background samples of rock units. This 

total comprises all normal rock geochemical 

samples collected during U.S. Geological Survey 

geologic mapping and mineral-resource investigations in the study area from 1968 through 1977. 

Rock geochemical data from these investigations 

are presented in two reports (Koch and Elliott, 

1978a, b) that plot the sample locations on 

1:125,000-scale topographic maps, accompanied 

by tables of all analytical values, sample descriptions, and statistical summaries; describe the 

sampling procedures, sample preparation, and 

methods of analysis; and briefly discuss analytical 

precision and the bias and variability affecting 

interpretation. Analytical data for rock and ore 

samples collected in the study area by U.S. 

Bureau of Mines engineers for mineral appraisal 

of the Granite Fiords Wilderness study area 

(Berg and others, 1977a) are presented in a 

separate similar report (Koch and others, 1976). 

INTERPRETATION OF LANDSAT IMAGERY 

(Open-File Report 78-73-K} 

To aid in the mineral-resource assessment of 

the Ketchikan and Prince Rupert quadrangles, 

we analyzed Landsat images of the study area for 

color anomalies, lineaments, circular and arcuate 

features, and regional fracture patterns that 

might be related to known mineral occurrences 

(Elliott and others, 1978) or to areas of mineral 

resource potential (Berg and others, 1978a). To 

complement this comparison of Landsat data 

with the distribution of known or potential mineral resources, we also correlated features identified on Landsat imagery with faults, contacts, 

foliation, and lithologic trends identified during 

geologic mapping (Berg and others, 1978b ), with 

trends or deflections of aeromagnetic contours 

(U.S. Geological Survey, 1977), with interpreted 

aeromagnetic anomalies (Griscom, 1981), and 

with rock geochemical anomalies (Koch and Elliott, 1978a, b). 

Our report (Steele and Albert, 1978) consists of 

two 1:250,000-scale combined topographic and 

generalized geologic maps overprinted with our 

interpreted Landsat data. One map highlights 

linear, arcuate, and circular features and ironoxide-colored areas, and is accompanied by his18 

tograms of trends, cumulative lengths, and relative intensities of lineaments. The other map 

relates the Landsat data to geology, geophysics, 

and rock geochemistry, and is accompanied by 

indexes of the Landsat imagery used in our analyses of the Ketchikan and Prince Rupert quadrangles. 

Preliminary results of our Landsat studies of 

the Ketchikan and Prince Rupert quadrangles 

and neighboring areas of southeastern Alaska 

indicate that intersections of east-northeasttrending (azimuth 059°-072°) and east-westtrending (azin1uth 083°-094°) lineaments coincide with sites of significant or potentially significant porphyry molybdenum deposits (Hudson 

and others, 1979; R. L. Elliott, oral commun., 

1980). The porphyry-molybdenum deposits in the 

study area occur in relatively small granite porphyry stocks and in quartz porphyry dikes of 

Oligocene or Miocene age (Hudson and others, 

1979). Mapped porphyry-molybdenum-bearing 

plutons that coincide with these intersections are 

exposed at Quartz Hill and Burroughs Bay in the 

Ketchikan quadrangle (Berg and others, 1978b; 

Elliott and others, 1978). Molybdenite-bearing 

quartz veins at Walker Cove in the central part of 

the Ketchikan quadrangle also coincide with one 

such intersection, although these deposits are not 

known to be associated with an Oligocene granitic body. Porphyry molybdenum deposits in 

Oligocene(?) felsic plutons also coincide with the 

intersections of similarly oriented Landsat lineaments at Groundhog Basin in the Petersburg 

quadrangle (Twenhofel and others, 1946; J. R. 

LeCompte and W. C. Steele, unpub. data, 1979; 

D. A. Brew, oral commun., 1980), immediately 

northwest of the Ketchikan quadrangle. 

The coincidence of molybdenum deposits with 

zones of intersecting Landsat lineaments in the 

Ketchikan and adjancent quadrangles (J. R. 

LeCompte and W. C. Steele, unpub. data, 1979) 

suggests a spatial relation that can be used for 

future molybdenum exploration in this region, 

even though their genetic relations remain 

uncertain. 

GEOPHYSICS 

AEROMAGNETIC INTERPRETATION 

(Open-File Reports 77-359 and 78-73-L) 

The 1:250,000-scale aeromagnetic-contour 
map used for our resource assessment of the 

Ketchikan-Prince Rupert study area was compiled from aeromagnetic surveys flown in 1972 

(U.S. Geological Survey, 1976; Berg and others, 

1977a) and 1976 (U.S. Geological Survey, 1979), 

and released as an Open-File Report (U.S. Geological Survey, 1977). This aeromagnetic-contour 

map was republished in Open-File Report 78-

73-L (Griscom, 1981, pl. 1). The magnetic-field 

variations on such maps as these provide units 

containing varying amounts of magnetic minerals, commonly magnetite. Therefore, aeromagnetic maps are a most useful adjunct to geologic 

mapping, as well as for mineral-resource assessment. 

An interpretive map (Griscom, 1981, pl. 2), 

drawn on a 1:250,000-scale combined topographic and generalized geologic base map, identifies 

various rock units in the Ketchikan-Prince Rupert 

study area that possess characteristic magnetic 

intensities, and enables the interpreter to extrapolate geologic information from known areas into 

covered or inaccessible regions. This interpretive 

map features prominent magnetic anomalies related to several zoned ultramafic plutons and to 

several volcanic and metamorphic units. It also 

shows several major magnetic boundaries 

marked by differences in the magnetic properties 

of the rocks on either side. The most conspicuous 

such boundaries coincide with mapped or inferred 

major faults that separate tectonostratigraphic 

terranes in the study area (fig. 5; Berg and others, 

1978d). These boundaries lie along the Clarence 

Strait fault, which separates the Craig and Annette subterranes of the Alexander terrane; along 

and near an inferred northwest-trending thrust 

zone that separates the Gravina-Nutzotin belt 

from the Taku terrane; and along the (east) Behm 

Canal, which coincides approximately with the 

contact between the Taku and Tracy Arm terranes. The magnetic boundary along the (east) 

Behm Canal is the most prominent feature on the 

magnetic map; it represents the west limit of 

exposed magnetic rocks of the Coast Plutonic 

Complex, which are much more strongly magnetic than rocks of the terrane to the west, and 

also coincides with a major north-south-trending 

lineament that has been traced the length of 

southeastern Alaska (Andrew Griscom, in Berg 

and others, 1977a, p. 33-34; Brew and Ford, 

1978). 

19 

BOUGUER GRAVITY MAPS AND INTERPRETATION 

By David F. Barnes 

A set of 16 Bouguer gravity maps at 1:250,000 

scale of southeastern Alaska (Barnes, 1972) includes maps of the Ketchikan and Prince Rupert 

quadrangles. Although these maps were. published before our AMRAP mineral-resource 

assessment of the study area, additional gravimetric studies were conducted under AMRAP, 

and the results of some of these studies were 

incorporated into the resource assessment. 

The Bouguer gravity maps of the Ketchikan 

and Prince Rupert quadrangles were compiled 

from more than 550 shoreline gravity measurements, supplemented by about 70 measurements 

established by floatplane and helicopter to the 

interior, as well as a few hundred kilometers of 

marine gravity traverses (Dehlinger and others, 

1966). The resulting maps show a regional decrease in Bouguer gravity from about +30 mGal 

in the southwest corner of the study area to less 

than -120 mGal in the northeast corner. The 

empirical relations of Woollard and Strange 

(1962) suggest that most of this decrease probably 

represents a regional increase in crustal thickness from less than 30 km at the coastal corner to 

more than 45 km near the United States-Canadian 

border. Thus the gravity maps in part reflect 

deeper features of the crust than do most of the 

other maps described in this report (table 1). 

However, some local variations in this regional decrease may be more closely correlated 

with the relatively shallow features depicted on 

the geologic (Berg and others, 1978b) and aeromagnetic (Griscom, 1981) maps. Most of the 

decrease occurs in two steep-gradient steps that 

approximately coincide with recognized geologic 

and aeromagnetic lineaments. One of these steps 

is evident along Clarence Strait and Revillagigedo 

Channel, which are also the approximate west 

and east boundaries, respectively, of the Annette 

subterrane of the Alexander terrane (fig. 5). The 

second steep gradient was measured across the 

(east) Behm Canal, which follows the Coast Range 

megalineament (Brew and Ford, 1978) and approximately concides with the boundary between 

the Taku and Tracy Arm terranes. Both of these 

features in part probably represent significant 

increases in crustal thickness as well as lithologic 

changes. 
Local anomalies associated with intrustions 

have greater economic importance. These local 

anomalies are best recognized where the gravity 

field flattens between these steep-gradient steps 

and thus are most evident in the broad zone of 

gentle gradient in the southwest corner of the 

study area. The largest of these anomalies is the 

30-mGal high associated with the ultramafic 

body on Duke Island, where the data suggest a 

complex field and the desirability of more detailed 

surveys. Smaller gravity highs are associated 

with other mafic bodies near Humpy Point about 

9 km northwest of Cape Fox, on the Percy Islands, 

and on the Cleveland Peninsula. More silicic 

intrusions are associated with gravity lows, as on 

Annette Island, George Inlet, Francis Cove, and 

Bell Island. The larger silicic intrusions, such as 

the Coast Plutonic Complex, also contribute to 

low gravity values, although their anomalies are 

difficult to distinguish from the regional changes 

associated with crustal thickening. The marine 

data suggest that other gravity lows may be 

caused by thick sequences of Holocene sediment 

underlying some of the fiords and passages. 

MINERAL-RESOURCE ASSESSMENT 

(Open-File Report 78-73- M) 

The map and accompanying tables (Berg and 

others, 1978a), which describe the metallicmineral potential of the Ketchikan-Prince Rupert 

study area, consist of a 1:250,000-scale combined 

topographic and generalized geologic map showing 16 areas 1 favorable for metal resoures in eight 

specific types of mineral deposits and the commodities likely to be contained in them. The map 

also shows the locations of mines, prospects, and 

mineral occurrences known in the study area, 

and lists the commodities in each locality. We 

determined the mineral-deposit types and identified the favorable areas mainly from the type and 

distribution of known deposits and from geologic, 

geochemical, and geophysical evidence that favors 

the occurrence of mineral deposits (fig. 6). 

The map is accompanied by a 48-page pamphlet that describes the favorable areas shown on 

the map, lists the criteria we used to select each 

area, and, where data permit, predicts at three 

confidence levels the number of undiscovered 

'A seventeenth area (at Yellow Hill on southwestern Annette Isl and) has been 

since Open-File Report 78-73-M was published. 

20 

deposits of the specific types and the mineral 

resources that they contain. The pamphlet also 

describes the method we used for our resource 

assessment and includes three tables that essentially constitute the assessment. One table lists 

the known and inferred types of deposits in each 

area; summarizes the available data on geology, 

geochemistry, and geophysics and on production, 

AlA >l'\.1\ 

• - .bfH;:'l-::ri Z )L JM J- o'----_,1 a _ _,__-' 

FIGURE 6.-Ketchikan-Prince Rupert study area, showing 

17 areas favorable for occurrence of mineral resources and 

types of mineral deposits known or predicted in those areas 

(letters in parentheses followed by chemical symbols of 

relevant commodities). (A), porphyry molybdenum deposits 

in Oligocene or Miocene plutons; (B), porphyry copper deposits in Triassic or Jurassic plutons; (C), stratabound massive and disseminated volcanogenic base- and preciousmetal deposits in diverse host rocks (see text); (D), stratiform titaniferous magnetite deposits in Cretaceous zoned 

ultramafic complexes; (E), disseminated lode-gold deposits 

in pyritic late Paleozoic or Mesozoic greenschist and phyllite; (F), copper-iron skarn deposits in Paleozoic or Mesozoic 

metacarbonate, and tungsten skarn deposits in Triassic or 

Jurassic plutonic and bedded rocks; (G), stibnite-bearing 

epithermal replacement veins in late Paleozoic or Mesozoic 

metacarbonate and phyllite; (H), auriferous and polymetallic quartz (-carbonate) veins in diverse host rocks. Chemical 

symbols: Ag, silver; Au, gold; Cu, copper; Mo, molybdenum; 

Pb, lead; W, tungsten, Zn, zinc, Fe, iron; Pt, platinum, Sb, 

antimony; Ba, barium; U, uranium. Base from National 

Atlas of the United States of America, 1970. 
resources, and the status of geologic knowledge; 

and provides the numerical resource estimates. 

The second table summarizes the criteria we used 

to define the areas of metalliferous mineralresource potential. The third table shows the statistical grade-and-tonnage models we used to 

estimate the resources contained in four of the 

eight types of mineral deposits in the study area. 

MINERAL-DEPOSIT TYPES, MINERAL-RESOURCE AREAS, 

AND METALLOGENESIS 

The eight types of mineral deposits that we 

have identified or inferred in the study area occur 

in 16 partly overlapping areas characterized by 

several rock units containing potentially valuable 

metallic-mineral resources. These units, in turn, 

impart metallogenic significance to their host 

tectonostratigraphic terranes (Berg and others, 

1978d), which then become the framework for 

interpreting regional metallogenesis, and for resource appraisal and mineral exploration (Berg, 

1979, 1981). The eight types of mineral deposits 

are: (1) porphyry molybdenum deposits in Oligocene and possible Miocene granite porphyry 

stocks and peripheral swarms of quartz porphyry 

dikes in the 1!-acy Arm and Taku terranes (two 

areas); (2) porphyry copper deposits in the 1!-iassic or Jurassic Texas Creek Granodiorite of the 

Stikine terrane (one area); (3) stratabound massive and disseminated volcanogenic base- and 

precious-metal deposits (eight areas): (a) in Paleozoic or Mesozoic paragneiss of the 1!-acy Arm 

terrane, (b) in late Paleozoic or Mesozoic metamorphosed sedimentary and volcanic rocks of the 

Taku terrane, (c) in Late Jurassic or Early Cretaceous metamorphosed andesitic volcanic and 

vocaniclastic rocks of the Gravina-Nutzotin belt, 

(d) with barite in Late 1!-iassic felsic metavolcanic rocks of the Jurassic or older Hazelton(?) 

Group of the Stikine terrane; ( 4) stratiform titaniferous iron deposits (with traces of platinumgroup metals) in Cretaceous zoned ultramafic 

complexes that intrude the Annette subterrane, 

the Taku terrane, and possibly the GravinaNutzotin belt (four areas); (5) disseminated lodegold deposits in pyrite- and arsenopyrite-bearing 

greenschist and phyllite of the Taku(?) terrane 

and the Gravina-Nutzotin belt (two areas); (6) 

copper- and iron-bearing skarn deposits in Paleozoic or Mesozoic metacarbonate near the contacts 

of Cretaceous or Tertiary granodiorite and quartz 

21 

diorite plutons in the 1!-acy Arm terrane, and 

tungsten skarn in the Hazelton(?) Group near the 

contacts of the Texas Creek Granodiorite and possibly of Eocene granodiorite and quartz monzonite plutons in the Stikine terrane; (7) a stibnitebearing epithermal replacement vein in late 

Paleozoic or Mesozoic metacarbonate and phyllite of the Taku(?) terrane (one area); and (8) 

auriferous and polymetallic quartz fissure veins, 

stockworks, and breccia that occur in diverse host 

rocks throughout all the tectonostratigraphic 

terranes. 

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gravity anomaly maps of southeastern Alaska showing 

station locations, anomaly values, and generalized 10-

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Report 72-17, scale 1:250,000, 16 sheets. 

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Fiords wilderness study area, U.S. Geological Survey 

Bulletin 1403, 151 p. 

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pre-Cenozoic tectonostratigraphic terranes of southeastern Alaska and adjacent areas: U.S. Geological Survey 

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Ketchikan quadrangle, Alaska: U. S. Survey Miscellaneous Field Studies Map MF-420, scale 1:250,000. 

_l972b, Metallic mineral resources map of the Prince 

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Hood, D. W., 1966, Free-airgravityanomaliesalongthe 

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Elliott, R. L., Berg, H. C., and Karl, Susan, 1978, Map and 

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Report 78-73-B, 18 p., scale 1:250,000. 

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field methods for the semiquantitative analysis of geologic 

materials: U.S. Geological Survey Circular 591, 6 p. 

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the Ketchikan, Prince Rupert, and northeastern Craig 

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

Report 78-73-L, scale 1:250,000, 2 sheets. 

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Contract EOOC14201199, 82 p. 

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1977: U.S. Geological Survey Circular 772-B, p. 

B83-B85. 

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the Quartz Hill molybdenite deposit, southeastern Alaska: 

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1805-1822. 

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America Memoir 138, 240 p. 

22 
Koch, R. D., and Elliott, R. L., 1978a, Map showing copper 

determined by atomic absorption in stream sediments, 

Ketchikan and Prince Rupert Quadrangles, Alaska: U.S. 

Geological Survey Open-File Report 78-73-C, scale 

1:250,000. 

__ 1978b, Map showing gold determined by atomic absorption and spectrographically determined silver in stream 

sediments, Ketchikan and Prince Rupert quadrangles, 

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

78-73-G, scale 1:250,000. 

__ 1978c, Map showing lead determined by atomic absorption in stream sediments, Ketchikan and Prince Rupert 

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

Report 78-73-D, scale 1:250,000. 

_1.978d, Map showing spectrographically determined 

chromium in stream sediments, Ketchikan and Prince 

Rupert quadrangles, Alaska: U.S. Geological Survey 

Open-File Report 78-73-H, scale 1:250,000. 

__ 1978e, Map showing spectrographically determined 

cobalt in stream sediments, Ketchikan and Prince Rupert 

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

Report 78-73-I, scale 1:250,000. 

__ 1978f, Map showing spectrographically determined 

molybdenum in stream sediments, Ketchikan and Prince 

Rupert quadrangles, Alaska: U.S. Geological Survey 

Open-File Report 78-73-F, scale 1:250,000. 

__ 1978g, Map showing spectrographically determined 

nickel in stream sediments, Ket('hikan and Prince Rupert 

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

Report 78-73-J, scale 1:250,000. 

__ 1978h, Map showing zinc determined by atomic absorption in stream sediments, Ketchikan and Prince Rupert 

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

Report 78-73-E, scale 1:250,000. 

Kock, R. D. Elliott, R. L., Smith, J. G., and Berg, H. C., 1977, 

Metamorphosed trondhjemite of the Alexander terrane 

in Coast Range plutonic complex, in Blean, K. M., ed., The 

United States Geological Survey in Alaska: Accomplishments during 1976: U.S. Geological Survey Circular 

751-B, p. B72-B74. 

Koch, R. D., Van Trump, George, Jr., and McDanal, S. K., 

1978i, Magnetic tape containing analytical data for rock 

and stream-sediment samples from Ketchikan and Prince 

Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Report NTIS PB-276-277 [computer tape 

available from U.S. Department of Commerce, National 

Thchnical Information Service, Springfield, VA 22161]. 

Martin, G. C., 1926, The Mesozoic stratigraphy of Alaska: 

U.S. Geological Survey Bulletin 776, 493 p. 

Monger, J. W. H., 1977, Upper Paleozoic rocks of the western 

Canadian Cordillera and their bearing on Cordilleran 

evolution: Canadian Journal of Earth Sciences, v. 14, no. 

8, p. 1832-1859. 

Monger, J. W. H., and Price, R. A., 1979, Geodynamic evolution of the Canadian Cordillera-progress and problems: 

Canadian Journal of Earth Sciences, v. 16, no. 3, pt. 2, 

p. 771-791. 

Motooka, J. M., and Grimes, D. J., 1976, Analytical precision 

of one-sixth order semiquantitative spectrographic analysis: U.S. Geological Survey Circular 738, 25 p. 

Randolph, C. L., 1979, The story of the U.S. Borax Quartz Hill 

23 

molybdenum project in southeastern Alaska (2d ed.): U.S. 

Borax and Chemical Corp. brochure, 11 p. 

Robinson, G. D., and Twenhofel, W. S., 1953, Some lead-zinc 

and zinc-copper deposits of the Ketchikan and Wales districts, Alaska: U.S. Geological Survey Bulletin 998-C, 

p. 59-84. 

Sainsbury, C. L., 1957a, A geochemical exploration for 

antimony in southeastern Alaska: U.S. Geological Survey 

Bulletin 1024-H, p. 163-178. 

__ l957b, Some pegmatite deposits in southeastern Alaska: 

U.S. Geological Survey Bulletin 1024-G, p. 141-161. 

Smith, J. G., 1973, A Thrtiary lamprophyre dike province in 

southeastern Alaska: Canadian Journal of Earth Sciences,v. 10,no.3,p.408-420. 

__ 1977, Geology of the Ketchikan D-1 and Bradfield Canal 

A-1 quadrangles, Alaska: U.S. Geological Survey Bulletin 1425, 49 p. 

Smith,J. G., andDiggles, M. F., 1981, Map and tables showing 

location and results of K/ Ar determinations in the Ketchikan and Prince Rupert quadrangles, Alaska: U. S. 

Geological Survey Open-File Report 78-73-N, scale 

1:250,000. 

Smith, J. G., Elliott, R. L., Berg, H. C., and Wiggins, B. D., 

1977, Map showing general geology and location of chemically and radiometrically analyzed samples in parts of 

the Ketchikan, Bradfield Canal, and Prince Rupert 

quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-825, scale 

1:250,000. 

Smith, J. G., Stern, T. W., and Arth, J. G., 1979, Isotopic ages 

indicate multiple episodes of plutonism and metamorphism in the Coast Mountains near Ketchikan, Alaska 

[abs.]: Geological Society of America Abstracts with Programs, v. 11, no. 7, p. 519. 

Smith, P. S., 1914, Lode mining in the Ketchikan region: U.S. 

Geological Survey Bulletin 592, p. 75-94. 

__ 1915, Notes on the geology of Gravina Island, Alaska, in 

Shorter contributions to general geology 1915: U.S. Geological Survey Professional Paper 95, p. 97-105. 

Steele, W. C., and Albert, N. R. D., 1978, Map showing interpretation of Landsat imagery of the Ketchikan and 

Prince Rupert quadrangles, Alaska: U.S. Geological 

Survey Open-File Report 78-73-K, scale 1:250,000, 2 

sheets. 

Steiger, R. H., and Jager, Emilie, compilers, 1977, Subcommission on geochronology: Convention on the use of decay 

constants in geo- and cosmochronology: Earth and Planetary Science Letters, v. 36, no. 3, p. 359-362. 

Taylor, H. P., Jr., and Noble, J. A., 1960, Origin of the ultramafic complexes in southeastern Alaska, in Oftedahl, 

Christoffer, and Hjelmquist, Sven, eds., Petrographic 

provinces, igenous and metamorphic rocks: International 

Geological Congress, 21st, Copenhagen, 1960, Report, pt. 

13, p. 175-187. 

Twenhofel, W. S., Robinson, G. D., and Gault, H. R., 1946, 

Molybdenite investigations in southeastern Alaska: U.S. 

Geological Survey Bulletin 947-B, p. 7-38. 

U.S. Bureau of Mines, 1974, Claim map, Prince Rupert: U.S. 

Bureau of Mines Map 122, scale 1:250,000. 

__ 1977, Claim map, Ketchikan: U.S. Bureau of Mines Map 

120, scale 1:250,000. 
U.S. Geological Survey, 1976, Aeromagnetic maps of Granite 

Fiords wilderness study area, Ketchikan and Bradfield 

Canal quadrangles, southeastern Alaska: U.S. Geological Survey Open-File Report 76-558, scale 1:63,360, 15 

sheets. 

__ 1977, Aeromagnetic map of Ketchikan, Prince Rupert, 

24 

and northeastern Craig quadrangles, Alaska: U.S. Geological Survey Open-File Report 77-359, scale 1:250,000. 

__ 1979, Aeromagnetic map of parts of Ketchikan, Prince 

Rupert, and Craig quadrangles, Alaska: U.S. Geological 

Survey Open-File Report 79-937, scale 1:63,360, 19 sheets. 

GPO 587-041/42