Studies of the

Geology and Mineral Resources of the

Southern Antarctic Peninsula and

Eastern Ellsworth Land,

Antarctica

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1351

Work done in cooperation with 

the National Science Foundation

,«/*'
Studies of the

Geology and Mineral Resources of the

Southern Antarctic Peninsula and

Eastern Ellsworth Land,

Antarctica

PETER D. ROWLEY and WALTER R. VENNUM, Editors

A. Geology of the Southern Black Coast, Antarctic Peninsula

By PETER D. ROWLEY, KARL S. KELLOGG, WALTER R. VENNUM, RICHARD B. WAITT, and 

STEPHEN J. BOYER

B. Igneous Petrology of the Merrick Mountains, Eastern 

Ellsworth Land, Antarctica

By WALTER R. VENNUM and THOMAS S. LAUDON

C. Porphyry-type Copper Deposits and Potassium-Argon Ages 

of Plutonic Rocks of the Orville Coast and Eastern Ellsworth 

Land, Antarctica

By PETER D. ROWLEY, EDWARD FARRAR, PAUL E. CARRARA, WALTER R. VENNUM, and 

KARL S. KELLOGG

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1351

Work done in cooperation with 

the National Science Foundation

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1988
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging-in-Publication Data

Studies of the geology and mineral resources of the southern Antarctic Penninsula and eastern Ellsworth 

Land, Antarctica.

(U.S. Geological Survey professional paper ; 1351)

"Work done in cooperation with the National Science Foundation."

Contents: Geology of the southern Black Coast, Antarctic Peninsula/by Peter D. Rowley .. .[et al.] 

Igneous petrology of the Merrick Mountains, eastern Ellsworth Land, Antarctica/by Walter R. Vennum 

and Thomas S. Laudon Porphyry-type copper deposits and potassium-argon ages of plutonic rocks of 

the Orville Coast and eastern Ellsworth Land, Antarctica/by Peter D. Rowley. . .[et al.].

Supt. of Docs, no.: I 19.16:1351

1. Geology Antarctic regions Antarctic Peninsula. 2. Geology Antarctic regions Ellsworth 

Land. 3. Mines and mineral resources Antarctic regions Antarctic Peninsula. 4. Mines and 

mineral resources Antarctic Regions Ellsworth Land. I. Rowley, Peter D. II. Vennum, Walter 

R. III. National Science Foundation (U.S.) IV. Series: Geological Survey professional paper ; 1351. 

QE350.S78 1988 559.8'9 86-600024
CONTENTS

[Letters designate the chapters]

Page

(A) Geology of the southern Black Coast, Antarctic Peninsula, by Peter D. Rowley, Karl

S. Kellogg, Walter R. Vennum, Richard B. Waitt, and Stephen J. Boyer ..... 1

(B) Igneous petrology of the Merrick Mountains, eastern Ellsworth Land, Antarctica, by

Walter R. Vennum and Thomas S. Laudon .............................. 21

(C) Porphyry-type copper deposits and potassium-argon ages of plutonic rocks of the Orville Coast and eastern Ellsworth Land, Antarctica, by Peter D. Rowley, Edward 

Farrar, Paul E. Carrara, Walter R. Vennum, and Karl S. Kellogg ........... 35

Geology of the 

Southern Black Coast, 

Antarctic Peninsula

By PETER D. ROWLEY, KARL S. KELLOGG, WALTER R. VENNUM, 

RICHARD B. WAITT, and STEPHEN J. BOYER

STUDIES OF THE GEOLOGY AND MINERAL RESOURCES 

OF THE SOUTHERN ANTARCTIC PENINSULA AND 

EASTERN ELLSWORTH LAND, ANTARCTICA

US. GEOLOGICAL SURVEY PROFESSIONAL PAPER 135 1-A

Work done in cooperation with 

the National Science Foundation

Description of the bedrock geology of an area 

in the Andean belt of West Antarctica

UNITED STATES GOVERNMENT PRINTING OFFICE, W A S H I NGTON : 1988

CONTENTS

Page

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

Introduction ................................................................ 1

Acknowledgments ........................................................... 4

Latady Formation ........................................................... 4

Mount Poster Formation ..................................................... 5

Plutonic rocks .............................................................. 10

West Wegener Range batholith ............................................ 11

East Wegener Range batholith ............................................. 12

Werner batholith ..........................~ ............................. 13

Structural geology ........................................................... 15

Plate-tectonic setting ........................................................ 15

Altered and mineralized rocks ................................................. 16

References ................................................................. 17

ILLUSTRATIONS

Page

FIGURE 1. Reconnaissance geologic map of the southern Black Coast, Antarctica .... 2

2. Oblique aerial photograph of part of the southern Black Coast, Antarctica 3

3. Photograph showing typical outcrop of slate of the Latady Formation .... 5

4. Ternary plot of modal quartz, K-feldspar, and plagioclase in igneous rocks,

southern Black Coast, Antarctica ............................... 11

5. Photograph of two stoped-block masses within plutonic rock just inside the contact of the West Wegener Range batholith ....................... 12

6. Ternary plots of selected oxides and normative minerals from plutonic rocks

of the southern Black Coast and northern Lassiter Coast, Antarctica . 13

7. Photograph showing lighter-colored main-fades granite containing dark masses

of border-facies granodiorite .................................... 14

TABLES

TABLE 1. Modes of igneous rocks from the southern Black Coast, Antarctica ......

2. Chemical analyses and CIPW norms of fresh igneous rocks from the southern 

Black Coast, Antarctica .......................................

STUDIES OF THE GEOLOGY AND MINERAL RESOURCES OF THE SOUTHERN 

ANTARCTIC PENINSULA AND EASTERN ELLSWORTH LAND, ANTARCTICA

GEOLOGY OF THE SOUTHERN BLACK COAST, ANTARCTIC PENINSULA

By PETER D. ROWLEY', KARL S. KELLOGG1 , WALTER R. VENNUM2 , 

RICHARD B. WAITX,', and STEPHEN J. BOYERS

ABSTRACT

The southern Black Coast, in the southeastern Antarctic Peninsula, 

includes the Wegener Range, Carey Range, and northern Dana Mountains. The geology of the area is similar to that of the Lassiter Coast, 

Orville Coast, English Coast, and eastern Ellsworth Land, all of which 

lie farther south in the peninsula. All these areas are part of the Andean magmatic and deformational belt. Except for some late Paleozoic 

or Triassic sedimentary rocks in the English Coast, the oldest rocks 

in the southern Antarctic Peninsula are Middle and Upper Jurassic 

fine-grained volcaniclastic sedimentary rocks of the Latady Formation and interlayered silicic- to intermediate-composition rocks of the 

Mount Poster Formation. Siltstone, slate, and fine-grained sandstone 

dominate in the Latady Formation; ash-flow tuff, lava flows, and dikes 

dominate in the Mount Poster Formation. The Mount Poster Formation was deposited as a magmatic arc, southeast of which a shallow 

marine back-arc basin accumulated sediment that formed the Latady 

Formation. The magmatic arc, which now underlies the axis of the 

southern Antarctic Peninsula, resulted from southeastward subduction of the southern Pacific oceanic lithosphere beneath the Antarctic Peninsula

The Jurassic sedimentary and volcanic rocks were tightly folded 

along north- to north-northeast-trending axes as subduction continued. 

Late during deformation, in Early Cretaceous time, plutons and dikes 

were emplaced into the rocks of the Jurassic arc and back-arc basin. 

The intrusive rocks define either another magmatic arc that formed 

during continued subduction or a late phase of the Jurassic magmatic 

arc; any volcanic material that may have accompanied the Early 

Cretaceous intrusive activity, however, has not been identified in the 

southern Antarctic Peninsula. In the southern Black Coast area, exposed plutons consist of the west Wegener Range batholith, the east 

Wegener Range batholith, and the Werner batholith. Granite and 

granodiorite are the most abundant rock types in these plutons, but 

each pluton has a thin border facies of mafic rocks. The Jurassic 

sedimentary and volcanic wall rocks are contact metamorphosed over 

wider zones than farther south in the Antarctic Peninsula, where 

plutons are less abundant. Altered and mineralized plutonic rocks are 

widely scattered in the area but do not appear to be of economic value. 

Slightly mineralized, sheared phyllic-argillic zones, similar to those in 

the Lassiter Coast copper deposit to the south, occur in the western 

Carey Range.

U.S. Geological Survey.

Present address is Department of Geology, Sonoma State University, Rohnert Park, Calif. 

94928. 

3Present address is 7045 SW. 62nd Place, Portland, Oregon, 97219

INTRODUCTION

The southern Black Coast, which lies along the Weddell Sea on the eastern flank of the southern Antarctic 

Peninsula (figs. 1, 2), includes the Wegener Range, Carey 

Range, and northern Dana Mountains. The area was 

first visited and geologically mapped in reconnaissance 

during the 1972-73 austral summer by a U.S. Geological Survey field party that included the authors. The 

northern Lassiter Coast, to the south, also was mapped 

at this time (Rowley, 1973). The Antarctic Peninsula is 

part of the Andean magmatic and deformational belt 

of Early Jurassic to late Tertiary age, which extends 

from the Andes of South America southward through 

the Scotia arc and Antarctic Peninsula, and from there 

westward through Ellsworth Land, Marie Byrd Land, 

and the western rim of the Pacific Ocean (Craddock, 

1969, 1982; Herron and Tucholke, 1976; Craddock and 

Hollister, 1976; LeMasurier and Wade, 1976; LeMasurier 

and Rex, 1982; Cooper and others, 1982; Rowley, 1983).

The geology of the southern Black Coast (Rowley, 

1973; Kamenev, 1975; Rowley and Williams, 1982) is 

similar to that of the Lassiter Coast, Orville Coast, 

English Coast, and eastern Ellsworth Land, which lie 

successively farther south and west (Williams and 

others, 1972; Laudon and others, 1964, 1969; Laudon, 

1972; Rowley, 1978; Thomson and others, 1978; Rowley, 

Vennum, and others, 1983; Rowley and others, 1985). Except for some late Paleozoic or Triassic sedimentary 

rocks in the English Coast (Laudon and others, 1985), 

the oldest rocks of this overall region are Middle and 

Upper Jurassic volcaniclastic sedimentary rocks of 

the Latady Formation and intertonguing silicic- to 

intermediate-composition volcanic rocks of the Mount 

Poster Formation of the Antarctic Peninsula Volcanic 

Group. These rocks were tightly folded and later intruded by Lower Cretaceous plutons and dikes. The area! 

proportions of plutonic rocks progressively increases 

northward through the southern Antarctic Peninsula;

l
GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

30° W

EXPLANATION

CRETACEOUS BEARING OF FOLD AXIS 

Inclined

Horizontal

STRIKE AND DIP OF BEDDING 

STRIKE AND DIP OF AXIAL

Latady Formation

PLANE CLEAVAGE 

V85 OUTCROP LOCALITY g[|0

CONTACT Dotted where concealed 

under ice

West WegenerRange batholith

Werner, / 

batholith

-^ \ / \

63°W 62°W

20 KILOMETERS

FIGURE 1. Reconnaissance geologic map of the southern Black Coast, Antarctica. Large areas of rock outcrop are shown by patterns; unvisited outcrops are outlined but left blank. Dotted where concealed under ice. Contours in meters. Base map from British Antarctic 

Survey, by permission.
SOUTHERN BLACK COAST

FIGURE 2. U.S. Navy oblique aerial photograph (TMA 1745 16, F31) of part of the southern Black Coast, Antarctica. Two outcrop nunataks 

are shown, whose localities are marked in figure 1. View is eastward, toward the ice-covered Weddell Sea.

thus, Jurassic rocks are progressively less abundant and 

display more widespread contact-metamorphic effects 

northward. In the southern Antarctic Peninsula, rocks 

of the Mount Poster Formation are most abundant near 

the present axis of the peninsula, which probably was 

near the axis of a subduction-generated magmatic arc 

that formed no later than Middle(?) and Late Jurassic 

time and which has dominated the geologic setting since 

then (Rowley and Williams, 1982; Rowley, Vennum, and 

others, 1983). The Latady Formation represents deposition in a back-arc marine basin on the southeastern side 

of the contemporaneous magmatic arc (Suarez, 1976;

Rowley, 1978; Thomson and others, 1978; Rowley and 

Williams, 1982; Laudon and others, 1983; Rowley, Vennum, and others, 1983).

The central Black Coast, about 110 km north of the 

study area, is the only other part of the Black Coast that 

has been visited or geologically mapped. Singleton 

(1980a, b) mapped a so-called gneissic and schistose 

high-grade (amphibolite facies) metamorphic complex, 

overlain by a unit of fine-grained clastic sedimentary 

rocks and interbedded volcanic rocks (Mount Hill Formation) that he tentatively correlated with the Latady 

Formation. These rocks are overlain by sparse outcrops
GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

of tuff, lava flows, and clastic sedimentary rocks, all of 

which may be correlative with the Mount Poster Formation. All these rocks are intruded by Lower Cretaceous plutons and dikes. Hence, the main geologic 

difference between the central and southern Black 

Coasts is the presence in the north of a very tentative 

high-grade metamorphic complex; more probably, 

however, these metamorphic rocks represent contact 

phases of the Lower Cretaceous plutons (Meneilly, 1983, 

Pankhurst, 1983).

The only other nearby areas to the north that have 

been geologically mapped are the Seward Mountains 

near the axis of the Antarctic Peninsula 90 km westnorthwest of the Wegener Range, the Journal Peaks 

about 50 km west of the Wegener Range, and the 

Gutenko Mountains about 80 km northwest of the 

Wegener Range. The Seward Mountains are dominated 

by rocks of the Antarctic Peninsula Volcanic Group, 

which are intruded by probable Jurassic or Cretaceous 

plutons and, in turn, by an upper(?) Tertiary intrusive 

mass of olivine basalt (Singleton, 1980c). The Journal 

Peaks are underlain by rocks of the Antarctic Peninsula 

Volcanic Group (British Antarctic Survey, 1982). The 

Gutenko Mountains contain rocks of the possible highgrade metamorphic complex that are overlain by the 

Antarctic Peninsula Volcanic Group, all of which are intruded by plutons (British Antarctic Survey, 1982).

The British Antarctic Survey recently compiled a 

geologic map of the central Antarctic Peninsula as far 

south as latitude 73° South, including the southern 

Black Coast (British Antarctic Survey, 1982). We contributed the information for the southern Black Coast 

to this map; the present report gives the supporting 

data.

Outcrop numbers given in the text refer to rock 

mmataks or parts of nunataks that were studied. Each 

outcrop may have rock types of differing lithology or 

origin. When rocks were sampled they were assigned the 

same whole number as the outcrop; letters and even 

subscripts appended to the outcrop numbers refer to individual samples. Outcrops referred to here are shown 

in figure 1.

ACKNOWLEDGMENTS

We thank Exchange Scientist E. N. Kamenev of the 

Research Institute of the Geology of the Arctic, Leningrad, U.S.S.R., a member of the field party, for his 

geologic field observations. Charles Swithinbank, 

British Antarctic Survey, permitted use of the topographic base map for figure 1. We are grateful to Swithinbank and J. W Thomson of the British Antarctic

Survey for recently published and unpublished British 

Antarctic Survey data on the geology of nearby areas. 

Mapping and data reduction were financed by National 

Science Foundation grants AG-187 and DPP78-24217. 

Logistic support was provided by the U.S. Antarctic 

Research Program of the National Science Foundation 

and by U.S. Navy Operation Deep Freeze. We especially thank M. D. Turner for his assistance with funding 

and logistics. Isotopic age determinations by Edward 

Farrar, S. L. McBride, and A. H. Clark were a critical 

part of the geologic study. We appreciate advice in 

microscope techniques from M. A. Kuntz and assistance 

with petrography and lab work from A. M. Kaplan and 

D. M. Cheney. Technical reviews by D. L. Schmidt and 

P. E. Carrara greatly improved the report.

LATADY FORMATION

The oldest exposed rock unit in the southern Black 

Coast consists of black and gray, fine-grained marine 

volcaniclastic sedimentary rocks that were named the 

Latady Formation by Williams and others (1972). Where 

the rocks are less metamorphosed in the Lassiter Coast 

to the south, they locally are rich in Late Jurassic 

shallow-water temperate-marine invertebrate fossils (Imlay and Kauffman, in press). In the Orville Coast and 

eastern Ellsworth Land, most rocks of the Latady Formation also appear to be Late Jurassic (Stevens, 1967; 

Quilty, 1970, 1977, 1982, 1983; Thomson, 1980, 1983; 

Crame, 1981; Mutterlose, 1986), but in eastern Ellsworth 

Land and perhaps parts of the Orville Coast, faunas as 

old as Middle Jurassic also were found (Quilty, 1970, 

1972,1982,1983; Thomson, 1983; Stanek and Wormbs, 

1985). On the basis of poorly preserved fossil pelecypods, 

pollen, and spores from the northern Lassiter Coast, 

Kamenev and Orlenko (1982) suggested that parts of the 

Latady Formation may be Early or Late Cretaceous; 

Kauffman and Imlay (in press) and Thomson (1983) have 

disagreed with this interpretation. We consider the 

Latady Formation in the southern Black Coast to be 

Middle and Late Jurassic.

Metamorphism is too great in the southern Black 

Coast for fossils to be preserved. Because of the absense 

of fossils, Kamenev (1975) suggested that the rocks here 

belong not to the Latady Formation but to the Triassic 

(Thomson, 1975a, 1982; Edwards, 1982) Trinity Peninsula Formation ("Trinity Peninsula Series" of Adie, 1957; 

redefined by Thomson, 1982), which occurs in the northern Antarctic Peninsula. Rowley and Williams (1982) 

disagreed with this interpretation, and Kamenev and 

Orlenko (1982) later referred all sedimentary rocks to the 

Latady Formation.
SOUTHERN BLACK COAST

Contact metamorphism is minimal in the Orville 

Coast, and therefore evidence for environments of 

deposition of the Latady Formation is preserved. Here, 

depositional environments progress southeastward from 

(1) continental just east of a magmatic arc where the 

sedimentary rocks intertongue with the volcanic rocks 

of the Mount Poster Formation through (2) shallowmarine deltaic to (3) open-marine shallow water farthest 

southeast (Rowley, 1978; Thomson and others, 1978; 

Laudon and others, 1983; Rowley, Vennum, and others, 

1983). The clastic material of the Latady Formation was 

largely derived from contemporaneous volcanic rocks of 

the magmatic arc and was deposited rapidly.

The largest exposed area of Latady Formation in the 

southern Black Coast occurs in the western Wegener 

Range (fig. 1). The rocks here are medium-gray to black, 

moderately resistant, fine- to medium-bedded siltstone 

and slate (fig. 3) and subordinate medium-gray and tan, 

fine-grained sandstone. Similar rocks are exposed in 

small areas in the Carey Range. Slate and other rocks 

locally are coated with thin crusts of evaporation or oxidation products (Vennum, 1979,1980). A dark-gray porphyritic ash-flow(?) tuff in the Wegener Range (locality 

Ke80) and lava flows in the northern Carey Range (locality Ro315) are interbedded with the sedimentary rocks. 

The thickness of the exposed part of the Latady Formation in the southern Black Coast is uncertain because 

folding of monotonous beds repeats the section and 

because cleavage obscures bedding. The Latady Formation probably is thicker than several kilometers.

Contact metamorphism converted most sedimentary 

rocks in the field area to hornfels. Other evidence of 

penetrative deformation also locally accompanied 

metamorphism. Thus, original depositional structures 

and bedding have been obscured. In most places the 

metamorphic grade is albite-epidote hornfels, but within 

about 1 km of pluton contacts, andalusite crystals are 

as long as 3 cm and the metamorphic grade is hornblende hornfels. The metamorphic grades and the 

mineral assemblages are similar to those in the southern 

Lassiter Coast (Plummer, 1974) and central Black Coast 

(Singleton, 1980a). Unlike the areas farther south, 

however, all Jurassic rocks in the Black Coast are extensively affected by contact metamorphism (Rowley 

and Williams, 1982).

The widespread metamorphism in the southern Black 

Coast and northern Lassiter Coast led Kamenev (1975) 

and Kamenev and Orlenko (1982) to propose (1) that 

these areas exhibit zonal regional metamorphism on 

which contact metamorphism is superimposed and (2) 

that the zonal regional metamorphism is related to the 

folding, not to Early Cretaceous plutonism. We contend, 

on the contrary, that most metamorphic effects in the 

southern Black Coast are due to contact metamorphism

FIGUKE 3. Typical outcrop of slate of the Latady Formation. Outcrop 

Bo74, Wegener Range, Antarctica.

that is extensive because of the more abundant plutonic 

rocks, some of which may underlie the exposed Jurassic 

rocks. We agree, however, that a regional zeolite-grade 

or greenschist-grade metamorphism was imposed prior 

to Early Cretaceous plutonism on the Jurassic and older 

rocks of the southern Antarctic Peninsula and eastern 

Ellsworth Land during burial and (or) during development of folds and slaty cleavage. The effects of this 

metamorphism are best seen where plutonic rocks are 

sparse, in the southern Lassiter Coast, the Orville Coast, 

the English Coast, and eastern Ellsworth Land.

Dark-gray fine-grained micaceous schist is in contact 

with plutonic rocks at a small outcrop between the 

Wegener Range and the Carey Range (locality Ke79). 

The schist is considered to be a contact phase of the 

pluton, but it resembles descriptions of the possible 

high-grade metamorphic complex of Singleton (1980a) 

in the central Black Coast.

MOUNT POSTER FORMATION

Folded Jurassic volcanic rocks, previously called the 

"Upper Jurassic Volcanic Group" (Adie, 1972), occur 

throughout the Antarctic Peninsula. Thomson (1982) 

redefined them as the Antarctic Peninsula Volcanic 

Group; Thomson and Pankhurst (1983) suggested that 

they range in age from at least Early Jurassic to Tertiary.
GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

As used by Thomson, the group consists of numerous 

different types of volcanic rocks from widely scattered 

localities deposited in different environments of a 

magmatic arc. No regional study has described these 

different facies or their significance to the plate-tectonic 

development of the arc they define. To encourage 

regional facies studies, formation-rank stratigraphic 

names within the Antarctic Peninsula Volcanic Group 

are needed in local areas containing volanic rocks of 

the same general rock type and stratigraphic setting. 

Those rocks of the group in the southern Antarctic 

Peninsula consist of several subaerial calc-alkaline 

volcanic fields that interfinger with the Latady Formation. Accordingly, Rowley, Schmidt, and Williams 

(1982) defined these rocks as the Mount Poster Formation after a mountain in the western Lassiter Coast that 

contains a well-exposed volcanic section, summarized 

by Williams and others (1972). All rocks of the Antarctic Peninsula Volcanic Group in the southern Antarctic Peninsula appear to belong to the Mount Poster 

Formation.

The rocks of the Mount Poster Formation occupy 

axial parts of the southern Antarctic Peninsula. They 

have been mapped at Mount Poster in the western 

Lassiter Coast (Williams and others, 1972), in the 

northwestern Orville Coast (Rowley, Vennum, and 

others, 1983), in the northern part of eastern Ellsworth 

Land (Laudon and others, 1969; Laudon, 1972; Rowley, 

1978), in the western part of the central Black Coast 

(Singleton, 1980a, c), in the Gutenko Mountains (British 

Antarctic Survey, 1982), and in the western part of the 

southern Black Coast. The volcanic fields that comprise 

the formation thin to the east or southeast, away from 

the axis, where they intertongue with the Latady 

Formation, and farther east they pinch out in the 

Latady Formation. The mutual intertonguing indicates 

that the rocks of the Mount Poster Formation must be 

of the same age (Late Jurassic and in some places also 

Middle Jurassic) as the Latady Formation. At Mount 

Poster (Williams and others, 1972) and in the central 

Black Coast (Singleton, 1980a), however, the main 

volcanic mass apparently overlies the western 

featheredge of the Latady. The correlation of volcanic 

rocks in the English Coast with the Mount Poster 

Formation is less certain than in other parts of the 

southern Antarctic Peninsula because recent fieldwork

suggests that some sedimentary rocks here are older, 

perhaps late Paleozoic or Triassic (Laudon and others, 

1985; Rowley and others, 1985).

The Mount Poster Formation is well exposed in the 

Sverdrup Nunataks of the southern Black Coast, where 

the volcanic rocks are folded and steeply dipping. The 

sequence is at least 300 m thick and probably several 

times thicker than this amount; individual volcanic 

units are 1-20 m thick. The main volcanic rock type is 

a medium-greenish-gray to black, sparsely porphyritic, 

rhyolitic to dacitic, moderately welded to densely 

welded ash-flow tuff. Abundant lenticules of collapsed 

pumice, characteristic of ash-flow cooling units, have 

been erroneously interpreted to be mylonite zones or 

shear planes (Kamenev and Orlenko, 1982). Dark-green 

to black, dacitic to andesitic lava flows (and perhaps 

sills), generally containing amygdaloidal cavities flattened by folding, also are common. Tan to light-gray 

beds of airfall tuff or slightly welded ash-flow tuff are 

uncommon. Dark-greenish-gray andesitic dikes were intruded into and folded with the volcanic rocks. The 

volcanic rocks are interbedded with thin (perhaps 10 

percent by volume) Latady-type volcaniclastic finegrained sandstone, shale, and intraformational conglomerate. All rocks of the formation have undergone 

metamorphism of albite-epidote hornfels or greenschist 

facies.

In thin section (Ka311, Ka312-2, Ka312-4, Ke70b, 

V79a, V79e; table 1), ash-flow cooling units contain 5-20 

percent phenocrysts of plagioclase (mostly calcic 

oligoclase), subordinate biotite and sanidine, and minor 

"beta" quartz and Fe-Ti oxides4. The lava flows 

(Bo63a, V79f, Wa34, Wa35a; table 1) and dikes are 

generally aphanitic or contain sparse phenocrysts of 

pyroxene, subordinate hornblende and plagioclase, and 

minor biotite and Fe-Ti oxides. The aphanitic groundmass (Wa34; table 1) consists mostly of flow-foliated 

microlites of pyroxene, hornblende, and plagioclase, and 

minor biotite, Fe-Ti oxides, and sphene. Chemical 

analyses (table 2) show an ash-flow tuff (Ka311) to be 

rhyolitic and a lava flow (Bo63a) to be andesitic.

Opaque minerals, consisting of magnetite, ilmenite, pyrite, and related minerals, which 

contain iron and (or) titanium.
SOUTHERN BLACK COAST 7 

TABLE 1. Modes, in volume percent, of igneous rocks from the southern Black Coast, Antarctica

[Five hundred points counted in thin sections and stained rock slabs. Sample localities shown in figure 1. Tr., trace; n.d., not determined; ( ) leaders, not present; An determinations 

by Michel-Levy method using universal stage and either low-temperature or high-temperature curves of Slemmons (1962, table 3)]

Sample 

No.

Plagioclase K- Quartz

Volume 

percent

Anorthite feldspar contenf

Phenocrysts

Biotite Horn- Pyroxene Olivine Fe-Ti Sphene Apatite Chlorite Epidote Sericite 

blende oxides

Ground- Vesicles 

mass

Mount Poster Formation

Bo63a 

Ka311 

Ka312-2 

Ka312-4 

Ke70b 

V79a 

V79e 

V79f 

Wa34 

Wa35a

9.2 

2.0 

.4 

8.0 

13.0 

13.6

10.2

18-22 0.6 0.6 

26 .4 .4 

19-21 5.2 

17-31 .8 

18-26 1.0 .4 

19-26 .2 .2

n.d.

0.8 0.8 Tr. 0.4 Tr. 

2.6 .2 Tr. Tr. 

 .2 Tr. Tr. Tr. Tr. 

9.0 .8 Tr. Tr. Tr. 

8.6 .2 Tr. Tr. Tr. 

4.6 Tr. 1.0 Tr. Tr. 

1.2 16.4 36.2 .2 Tr. Tr. 

87.2 12.8 

90.0 

94.4 

94.2 

81.4 

76.8 

81.4 

74.6 25.4 

35.8 

83.0 17.0

Granite of west Wegener Range

Ro322a 

V85 

V86a

33.6 

30.4 

63.2

30-33 24.0 33.6 

26 37.4 26.6 

15-30 5.2 13.8

3.6 1.8 .6 .4 .2 

6.2 .4 .6 .8 

3.6 9.2 1.8 .2 Tr. Tr. Tr. 

 

Granite of east Wegener Range

Ro319a 

Ro319c 

V84b 

V84c

35.8 

36.6 

58.4 

60.2

20-21 10.0 22.6 

14-30 38.8 14.8 

37-46 .4 .2 

29-47 .4 4.4

11.2 11.2 .2 .2 Tr. .4 Tr. 

3.4 3.8 1.2 .4 Tr. 2.8 Tr. 

 40.2 .2 .2 Tr. Tr. 

Werner batholith from west Carey Range and north Dana Mountains

Bo68a 

Ro275a 

Ro312b 

Ro313a 

V80c 

Wa38b

55.4 

42.6 

41.0 

63.8 

38.0 

62.0

25-36 13.8 24.6 

24-34 18.8 31.0 

31-38 24.0 20.4 

25-30 5.2 20.8 

28-41 4.4 6.0 

25-50 12.8 8.2

2.8 2.0 .8 Tr. Tr. Tr. Tr. 

5.4 .6 1.0 .4 Tr. .6 Tr. 

10.6 4.2 1.0 .4 Tr. .4 Tr. 

1.8 .8 Tr. Tr. 5.8 .4 

2.0 41.0 2.6 .4 .2 6.4 1.4 Tr. 

4.4 11.0 1.4 .4 .2 .2 Tr.

 

Werner(?) batholith from east Carey Range

V83 40.0 26-34 17.4 28.6 9.0 2.6 .2 .2 Tr. 2.0 Tr. Tr. 

Cretaceous dike

Ka317 

Ro315d 

V89b

34.0 

22.0 

31.6

U-34 5.0 

15-32 .8 

27-36 2.2 5.2

6.0 5.8 1.2 Tr. Tr. 

 11.8 .6 Tr. Tr. .8 Tr. Tr. 

1.0 .6 1.4 .4 Tr. 3.2 .8 

52.2 

62.2 

57.4

Tertlary(?) dike
TABLE 2. Chemical analyses and CIPW norms of fresh igneous rocks from the southern Black Coast, Antarctica

[Sample locations shown in figure 1. Symbols for rock units given in table 1. Rapid rock chemical analyses by Hezekiah Smith. Semiquantitative spectrographic analy

Harris. Less than lower limit of detection: Ag, As, Au, B, Bi, Cd, Cs, Cr, Ge, Hf, Hg, In, Ir, Li, Lu, Nd, Os, Pd, Pt, Rb, Re, Rh, Ru, Sb, Sm, Ta, Tb, Tl, Tm, V, and 

than limit of detection, ( ) leaders, not present]

Granite of

Rock unit Mount Poster

Formation

Sample No. Bo63a Ka311

west Wegener

Range

Ro322a V86a Ro319a

Chemical analyses

Si02

A1 2 03

Fe 2 03

FeO

MgO

CaO

Na 2 0

K20

H2 0 (total)

Ti02

P 2 05

MnO

C02

Total

53.00

13.70

4.20

10.40

3.60

9.20

3.30

.60

.91

1.50

.31

.18

.12

101.02

71.30

12.10

1.90

3.20

.77

1.80

2.70

4.10

.63

.70

.25

.03

.04

99.52

68.90

15.40

1.90

1.50

.83

3.60

3.50

3.70

.38

.29

.21

.04

.05

100.30

60.10

18.50

3.10

3.20

1.50

7.50

3.60

1.40

.40

.59

.36

.13

.02

100.40

60.10

15.40

2.30

4.10

3.70

7.00

3.00

2.60

.75

.60

.46

.10

.01

100.12

Granite of

east Wegener

Range

Ro319c

(weight

68.00

15.40

2.00

1.40

.80

4.20

3.60

3.20

.77

.51

.26

.05

.03

100.22

Semiquantitative spectrographic

Ba

Be

Ce

Co

Cr

Cu

Dy

Eu

Ga

Gd

Ho

109

1

L

29

15

81

6

L

6

4

L

770

2

75

6

8

8

9

1

5

4

L

654

1

35

3

4

2

4

L

8

L

2

345

L

73

10

2

6

5

1

8

L

L

442

2

62

14

135

67

L

1

9

L

L

481

2

55

3

6

11

6

1

6

4

L

V84b

percent)

45.90

20.30

3.50

7.60

4.10

13.10

2.80

.43

1.00

1.20

.72

.21

.05

100.91

analyses

72

L

L

11

L

19

L

1

7

L

L

V84c

53.40

18.60

2.30

6.80

3.30

8.90

3.50

.94

.86

.62

.48

.19

.02

99.91

(ppm)

178

L

85

14

2

16

L

1

8

3

L

Werner batholith

W. Carey Range and E. Car

N. Dana Mtns.

Bo68a

69.20

15.90

1.40

1.40

.68

3.80

3.50

3.50

.41

.26

.19

.03

.03

100.30

1030

L

55

3

8

L

5

1

11

L

2

Ro275a

68.50

16.20

1.70

1.20

.41

3.60

3.90

3.10

.41

.18

.18

.01

.03

99.42

549

2

48

3

10

37

L

1

11

L

L

V

69

16

1

1

4

3

3

100

453

2

38

2

3

3

4

L

8

L

L
SOUTHERN BLACK COAST

 i ro ~H

ro -^ -^
10 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

PLUTONIC ROCKS

Calc-alkaline plutonic rocks are the most abundant 

rock type in the Antarctic Peninsula. Most of these plutonic rocks post-date the volcanic rocks now assigned 

to the Antarctic Peninsula Volcanic Group, and they 

were named the "Andean intrusive suite" (Adie, 1955). 

Isotopic age dating has subsequently shown that the 

plutonic rocks occupy several magmatic pulses within 

a broad time range (Rex, 1976; Pankhurst, 1982). Many 

of these dated plutons have Late Cretaceous and early 

Tertiary isotopic ages, as Adie (1955) suggested they 

would. But the rest range in isotopic age from Late 

TYiassic to late Tertiary (Rex, 1976; Pankhurst, 1982) 

and locally may be even as old as late Paleozoic 

(Smellie, 1981). Despite their diverse ages, however, all 

plutons are one-mica upper crustal (Hamilton, 1981) 

rocks that appear to be chemically similar to each other 

and to rocks of the Antarctic Peninsula Volcanic Group 

(Adie, 1964; Saunders and others, 1980,1982); all rocks 

probably reflect a similar long-lived subduction 

geometry.

Because of the wide range of ages of these plutonic 

rocks, the present use of "Andean" has become confused. 

Some workers have restricted it to only a latest 

Cretaceous to early Tertiary period of plutonism. Others 

have coined the name 'Andean orogeny" for deformation and plutonism along the Pacific margin of West Antarctica of either this same age or a broader time span, 

and they have contrasted this "orogeny" with the Gondwanide "orogeny" of Late THassic to Early Jurassic age. 

But in West Antarctica, the Pacific margin is characterized primarily by long-lived subduction-related igneous activity. Deformation in the belt is generally local 

and of diverse ages. The belt thus did not form in one 

or more "orogenies" of the classical sense. Thus, Rowley, 

Vennum, and others (1983) and Rowley (1983) suggested 

that "Andean" be retained as a general term for the 

Pacific-margin belt of subduction-related structures and 

calc-alkaline igneous rocks of Early Jurassic to late Tertiary age. Gondwanide and pre-Gondwanide structures 

and rocks in Pacific-margin parts of West Antarctica 

may also be the products of Andean-type subduction.

As isotopic ages become more abundant, recognition 

and definition of specific intrusive suites within the 

broad Andean belt will focus attention on differences 

in local genesis of various parts of the Antarctic Peninsula. The plutons in the Black Coast, Lassiter Coast, 

Orville Coast, and eastern Ellsworth Land occupy the 

same tectonic setting along the eastern side of the 

southern Antarctic Peninsula, and they appear to have 

a restricted age range of about 130-95 m.y. (million 

years). Following usage proposed by the North American 

Commission on Stratigraphic Nomenclature (Henderson

and others, 1980) as applied in the Sierra Nevada (Stern 

and others, 1981), Rowley, Vennum, and others (1983) 

proposed the name Lassiter Coast Intrusive Suite of 

Early Cretaceous age for all plutons in the southern Antarctic Peninsula known to be of this age. The plutons 

are best exposed and dated in the Lassiter Coast 

(Williams and others, 1972; Rowley and Williams, 1974, 

1982; Farrar and others, 1982).

In the southern Antarctic Peninsula, plutonism probably accompanied the volcanism that resulted in the 

volcanic rocks of Mount Poster. Such an older intrusive 

suite has been recognized in more northern parts of the 

Antarctic Peninsula (Rex, 1976; Pankhurst, 1982), but 

we have not yet identified any exposed plutons of this 

age in the southern Antarctic Peninsula. Because the 

volcanic rocks of Mount Poster thicken toward the present axis of the southern Antarctic Peninsula, it is likely that the first plutons of this age to be recognized in 

the southern Antarctic Peninsula will be found near the 

axis.

About 70 stocks and batholiths have been mapped in 

the southern Antarctic Peninsula and eastern Ellsworth 

Land, where they intrude folded rocks of the Latady and 

Mount Poster Formations. Compositions range from 

gabbro to granite, with the most abundant rock type being granodiorite (IUGS classification; see fig. 4). Isotopic 

dating indicates that the most silicic plutons are generally the youngest (Farrar and others, 1982). Most plutons 

contain sharp, chilled intrusive contacts and apophyses 

extending into wall rocks; they were emplaced by both 

forcible and passive means. Stoped wall-rock blocks 

locally occur along the intrusive contacts, and mafic inclusions are locally abundant within the plutonic rocks. 

Most plutons are zoned concentrically by composition: 

thin mafic margins grade abruptly into or are intruded 

by the main mass of silicic rock. Most plutons and, locally, adjacent country rocks are cut by late-stage pegmatite and aplite bodies, which are in turn cut by mafic 

dikes of various compositions and textures. Hydrothermal alteration and copper mineralization took place 

locally during the terminal stages of magma 

emplacement.

Plutons in the southern Antarctic Peninsula that have 

been isotopically dated (Halpern, 1967; Mehnert and 

others, 1975; Farrar and Rowley, 1980; Farrar and others, 

1982) have K-Ar and Rb-Sr ages of 123-98 m.y Early 

Cretaceous (ages corrected according to new constants 

of Steiger and Jager, 1977). Several plutons in the central Black Coast have K-Ar ages of from 127 to 107 m.y. 

(Pankhurst, 1980; ages corrected according to Steiger 

and Jager, 1977). Sample Bo68a from the Werner 

batholith in the western Carey Range has a K-Ar age 

of 103.1 m.y. (Farrar and others, 1982; age corrected according to Steiger and Jager, 1977).
SOUTHERN BLACK COAST 11

Silicic to mafic, mostly porphyritic dikes, containing 

the same minerals as the plutonic rocks, commonly cut 

the plutonic rocks. The isotopic dates of two dikes suggest that dike emplacement immediately followed 

plutonism Thus, a Rb-Sr age of 101 m.y. for a dike in 

the Behrendt Mountains of eastern Ellsworth Land is 

similar to ages of 101 and 100 m.y. for two nearby 

plutons (Halpern, 1967). A dike in the Copper Nunataks 

of the Lassiter Coast has a KAr age of 98.0 m.y, identical (within analytical uncertainty) to the pluton that 

it cuts (Farrar and others, 1982). All plutons and dikes 

that have been paleomagnetically analyzed have normal 

polarity, which suggests emplacement during the same 

Early Cretaceous Epoch of mostly normal polarity (van 

Hinte, 1976; Kellogg and Reynolds, 1978; Kellogg, 1980).

Three plutons are exposed in the southern Black 

Coast (fig. 1). One in the western Wegener Range is here 

named the west Wegener Range batholith, and another 

in the eastern and central Wegener Range is named the 

east Wegener Range batholith. The northern part of the 

Werner batholith, named by Vennum (1978) for exposures in the Werner Mountains of the northern 

Lassiter Coast, occurs in the northern Dana Mountains 

and western Carey Range. Plutonic rocks in the eastern 

Carey Range also probably belong to this pluton. The 

Werner batholith and probably the other two undated 

plutons belong to the Lassiter Coast Intrusive Suite.

WEST WEGENER RANGE BATHOLITH

The west Wegener Range batholith (fig. 1) extends 

about 19 km in long dimension (north-south). The main 

part of the pluton consists of pink to light-gray granite 

(fig. 4), but a locally foliated, chilled border facies, 

generally less than several hundred meters wide, of 

medium- to light-gray tonalite and granodiorite occurs 

along most contacts. Stoped blocks of metamorphosed 

Latady Formation, some at least 10 m long, occur along 

the southeastern contact (Wa47; fig. 5). At outcrop V86, 

foliated granite and pegmatite containing blocks of 

border-facies rock suggest slightly younger movement 

of the silicic main part of the pluton along this part of 

the contact. The granite is medium grained (1-5 mm) 

to very coarse grained (more than 3 cm), and commonly 

porphyritic; poikilitic phenocrysts of K-feldspar are as 

long as 4 cm. The border-facies rocks are fine grained 

(less than 1 mm) or medium grained. Mafic inclusions, 

as long as 20 cm, are sparse (rarely more than one inclusion per square meter of rock outcrop) in the pluton; 

locally, however, clusters of inclusions are present. 

Pegmatite, aplite, and mafic dikes (thin section V89b; 

table 1) are exposed in many outcrops. Probably nearly 

all dikes were emplaced shortly after the main period

Quartz

10 35 

K-feldspar 

(including albite)

90 

Plagioclase

Monzodiorite/ v Diorite, gabbro 

monzogabbro

EXPLANATION

Cretaceous

 Granite of west Wegener Range 

D Granite of east Wegener Range

 Werner batholith 

o Werner(?) batholith

FIGURE 4. A, Ternary plot of modal quartz, K-feldspar, and 

plagioclase in igneous rocks, southern Black Coast, Antarctica 

Calculated from data in table 1. B, Igneous classification used, 

from International Union of Geological Sciences (Streckeisen, 

1976).

of plutonism during Early Cretaceous time. One possible exception to this conclusion is a dike at outcrop 

Ro321 (table 1) that approaches basalt in composition, 

a distinctive chemistry that suggests that it correlates 

with Tertiary basalt dikes and volcanic rocks scattered 

about West Antarctica.
12 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

Sloped blocK?

FIGURE 5. Two stoped-block masses (topographically lower areas, on 

one of which the man is standing) within plutonic rock just inside 

the contact of the west Wegener Range batholith. Outcrop Wa47, 

Wegener Range, Antarctica

In thin section (table 1), both the main silicic part 

(Ro322a, V85) and the mafic border facies (V86a) of the 

west Wegener Range batholith have hypidiomorphicgranular textures. As is typical for other plutons in the 

Antarctic Peninsula, plagioclase in the west Wegener 

Range batholith is normally zoned; most crystals are 

calcic oligoclase to sodic andesine, but rims may be as 

sodic as sodic oligoclase. K-feldspar lacks grid twinning 

and is poikilitic petrographic features that are typical 

of plutonic rocks in the southern Antarctic Peninsula. 

Sphene is a common accessory mineral here and in many 

other plutonic rocks of the southern Antarctic 

Peninsula.

Chemical analyses and CIPW norms (table 2) show 

that the west Wegener Range batholith and other 

plutons in the southern Black Coast are similar to other 

Mesozoic and Cenozoic plutons in the southern Antarctic Peninsula (Laudon and others, 1969; Williams and 

others, 1972; Laudon, 1972, 1982; Rowley and others, 

1977; Vennum, 1978; Rowley and Williams, 1982) and 

in the northern Antarctic Peninsula (Adie, 1955; 

Saunders and others, 1980,1982). Major-element oxide 

trends for plutons in the southern Black Coast (table 

2), as elsewhere in the peninsula, define typical differentiated calc-alkaline magma bodies: with progressively

higher SiO2 in the rocks, CaO, MgO, and total iron oxides are progressively lower; whereas, K2O, and in some 

cases Na2O, are progressively higher. Alumina values 

are variable but generally are progressively lower with 

progressively higher silica Cobalt exceeds nickel in most 

rocks of the southern Black Coast (table 1), as in rocks 

elsewhere in the peninsula (Adie, 1955; Vennum, 1978; 

Laudon, 1982; Vennum and Laudon, 1983). Ternary plots 

of selected oxides and normative minerals (fig. 6) show 

some differences between trends for the west Wegener 

Range batholith (table 2), the east Wegener Range 

batholith (table 2), and northern and central Werner 

batholith (table 2; Vennum, 1978; unpub. data, 1981). 

Trace elements show systematic variations in plutons 

of the southern Black Coast. Rocks containing higher 

SiO2 contain lower values of TiO2, Co, Cu, Mn, Sc, Sr, 

V, and Zn, but higher values of Ba and Pb. The alkalilime index of the plutons in the southern Black Coast 

is 63, somewhat higher than the average (61) for all 

plutons in the Lassiter Coast and southern Black Coast 

(Rowley and Williams, 1982).

EAST WEGENER RANGE BATHOLITH

The east Wegener Range batholith is at least 24 km 

in long dimension. The main part of the pluton is composed of pink and light-gray, coarse to very coarse 

grained granite, but near the contact this facies grades 

abruptly into a thin, light- to dark-gray and pink, fineto medium-grained, locally foliated, chilled border facies 

of granodiorite, tonalite, and diorite. Both facies are 

locally porphyritic; in the main facies, poikilitic phenocrysts of K-feldspar attain lengths of 5 cm. As shown 

at outcrop Ro319 (fig. 7), the more silicic main part of 

the pluton (thin section Ro319c; table 1) locally intrudes 

and incorporates masses of the more mafic border facies 

(thin section Ro319a; table 1). Thus, at least in places, 

the mafic border facies is somewhat older than the main 

facies. Mafic inclusions as large as 15 cm are sparse in 

the pluton, but pegmatitic, aplitic, and mafic dikes are 

common.

A few thin sections (table 1; fig. 5), mostly of the 

border-facies rocks (Ro319a, V84b, V84c), suggest that 

the east Wegener Range batholith is petrologically 

similar to the west Wegener Range batholith. The most 

common minerals are (1) normally zoned plagioclase and 

(2) porphyritic to poikilitic K-feldspar that lacks grid 

twinning and is locally perthitic. The texture is 

hypidiomorphic-granular. In the silicic part, plagioclase 

is calcic oligoclase; in the border facies it ranges from 

calcic oligoclase to calcic andesine. As in other plutons 

in the southern Black Coast, plagioclase rims may have 

about 10 percent less anorthite than cores.
SOUTHERN BLACK COAST 13

Trend line for 

Werner batholith

Trend line for granite 

of west Wegener Rang

/ xTrend line for granite 

'S of east Wegener Range

\ \

35 65 90 Na2O 

Ab + An

CaO

B

F=Fe2O3+FeO+MnO

Alk=Na2O+K2O M=MgO C=CaO-(3P2O5+CO2) F=FeO+MnO+MgO+2Fe2O3-TiO2

D

FIGURE 6. Ternary plots of selected oxides and normative minerals from plutonic rocks of the southern Black Coast and northern Lassiter 

Coast, Antarctica. Data are from table 2, Vennum (1978, table 4), and unpublished analyses. Explanation of rock units is the same as 

that of figure 4. A, Normative quartz, orthoclase, and plagioclase (weight percent). Boundaries are from igneous classification defined 

in figure 4B. B, Na2O-K2O-CaO (weight percent), C, A-F-M (weight percent), D, A-C-F (weight percent).

The rocks of the east Wegener Range batholith are 

chemically similar to those of the west Wegener Range 

batholith (table 2; fig. 6). Rocks that are progressively 

higher in SiO2 are progressively lower in TiO2, Cu, 

Mn, Sr, V, Zn, and perhaps Co, but they are progressively higher in Ba, Pb, Y, and perhaps Zr. The alkalilime index of the east Wegener Range batholith is 

about 64.

WERNER BATHOLITH

The Werner batholith is the largest known pluton in 

the southern Antarctic Peninsula; it is exposed over a 

north-south length of more than 140 km (Vennum, 1978; 

Rowley and Williams, 1982). At the northern end of the 

batholith in the western Carey Range and northern 

Dana Mountains, it is at least 24 km wide (east-west),
14 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

FIGURE 7. Lighter colored main-fades granite containing dark 

masses of border-fades granodiorite. Outcrop Ro319, Wegener Range, 

Antarctica Compass for scale.

and it is 40 km wide if the plutonic rocks in the eastern 

Carey Range are included. Field relations and K-Ar ages 

(Farrar and others, 1982) indicate that the batholith is 

composite: it contains a mafic border facies dated at 

about 115 m.y. and a main silicic part dated as young 

as 100 m.y. The 103 m.y. age of the previously mentioned 

sample (Bo68a) from the western Carey Range is one of 

several samples dated from the main silicic part. The 

central part of the batholith, south of the mapped area 

of figure 1, contains extensive roof pendants and shows 

evidence of plutonic assimilation (Vennum, 1978; Vennum and Meyer, 1979).

In the western Carey Range and northern Dana Mountains, the batholith consists of a main part of light-gray 

and pink, medium- to coarse-grained granodiorite and 

subordinate tonalite and granite. This main part grades 

into a thin (generally less than 100 m), chilled border 

facies of light- to dark-gray, fine- to medium-grained 

tonalite and diorite (fig. 4). Near the northern contact 

(V80), pendants as long as 100 m of fine- to mediumgrained diorite (thin section V80c; table 1) occur within 

granodiorite. The contacts between the older diorite 

blocks and the younger granodiorite are sharp to gradational. Similar features occur in the central Werner 

batholith (Vennum, 1978); in both places the relations 

indicate forcible intrusion of the main facies rocks into 

partly consolidated, slightly older border-facies rocks.

Small mafic inclusions are abundant at outcrop V80, but 

elsewhere they are sparse and smaller than 20 cm. 

Pegmatite and aplite bodies and slightly younger mafic 

dikes (thin section Ka317) occur in many places.

The plutonic rocks in the eastern Carey Range are 

lithologically similar to those in the western Carey 

Range and northern Dana Mountains. In the eastern 

Carey Range, they consist of light-gray and pink, 

medium- to coarse-grained granodiorite and near the 

contacts of the pluton a thin border facies of light- to 

medium-gray, fine- to medium-grained tonalite and 

diorite. Mafic inclusions, as long as 30 cm, are uncommon. Pegmatite, aplite, and mafic dikes (thin section 

Ro315d) are common.

Thin sections (table 1) of rocks from the main silicic 

part (Bo68a, Ro275a, Ro312b, Ro313a, Wa38b; table 1) 

and from a small block of mafic border-facies rock (V80c) 

from the northern Dana Mountains and western Carey 

Range reveal a hypidiomorphic-granular texture consisting in large part of normally zoned plagioclase and poikilitic K-feldspar. Plagioclase compositions range from 

calcic oligoclase to sodic andesine; rims of zoned crystals 

are as sodic as calcic oligoclase. K-feldspar in some rocks 

(Ro275a, Ro312b, V83; table 1) is locally grid twinned, 

the only known occurrence of this petrographic feature 

in the southern Antarctic Peninsula. Grid-twinned Kfeldspar also occurs in the largest pluton in the central 

Black Coast, a granodiorite (Singleton, 1980a).

The rocks of the northern (table 2) and central (Vennum, 1978; P. D. Rowley, unpub. data, 1981) Werner 

batholith are petrologically and chemically similar to the 

plutons in the Wegener Range, but trend lines on ternary plots are somewhat different (fig. 6). Rocks from 

the northern part of the Werner batholith containing 

progressively greater SiO2 are progressively lower in 

TiO2, Co, Cu, Mn, Ni, Sc, V, and Zn but are progressively higher in Ba and Pb. Vennum (1978) noted similar relations for the central Werner batholith. The alkali-lime 

index of the northern and central Werner batholith is 

about 66, somewhat lower than the value of 69 for the 

central Werner batholith alone (Vennum, 1978) but well 

above the average (61) for plutons in the Lassiter Coast 

(Rowley and Williams, 1982).

One thin section (V83; table 1) examined from plutonic 

rocks in the eastern Carey Range is like those in the 

western Carey Range and northern Dana Mountains except for an absense of grid twinning in K-feldspar 

crystals. Chemical analyses (table 2) of rocks from the 

eastern Carey Range, western Carey Range, and northern Dana Mountains are similar, which further suggests 

that the plutonic rocks in the eastern Carey Range 

belong to the Werner batholith. These rocks also are 

chemically similar to those from the central Werner 

batholith (Vennum, 1978, table 4).
SOUTHERN BLACK COAST 15

STRUCTURAL GEOLOGY

The Latady Formation and Mount Poster Formation 

were tightly folded along north- to north-northeasttrending axes prior to plutonism of the Lassiter Coast 

Intrusive Suite. Folds range from open to isoclinal, but 

most are asymmetrical or overturned. Wavelengths of 

folds range from less than a centimeter to about a 

kilometer; most are betweeen 100 and 300 m. Welldeveloped axial-plane cleavage formed during folding. 

Cleavage and axial planes of most folds dip westnorthwest. Fold axes are horizontal to gently plunging. 

Some fold axes plunge steeply within 0.5 km of intrusive 

contacts where regional folds have been refolded during 

forcible intrusion of plutons.

Thrust faults, strike-slip faults, and high-angle dipslip faults, such as occur in the Orville Coast and eastern 

Ellsworth Land (Kellogg, 1979), were not recognized in 

the southern Black Coast. They may be present in the 

Black Coast, but if so, they are covered by ice or are 

obscured by the greater metamorphism and the poorer 

exposures.

PLATE-TECTONIC SETTING

The rocks now exposed in the southern Black Coast 

were deposited and deformed during almost continuous 

southeastward subduction of the southern Pacific plate 

under the area of the present Antarctic Peninsula 

(Dalziel and Elliot, 1973; Herron and Tucholke, 1976; 

Craddock and Hollister, 1976; Rowley and Williams, 

1982; Rowley, Vennum, and others, 1983; Rowley, 1983). 

The subduction probably varied in speed, geometry, and 

perhaps direction so that different rocks and structures 

were produced at different times (for example, Cross and 

Pilger, 1982). Discussion of the essential details of the 

plate-tectonic setting of the Antarctic Peninsula and 

Scotia arc was given first by I. W. D. Dalziel and D. H. 

Elliot in their 1973 publication and in subsequent papers 

with coworkers. Suarez (1976) and Smellie (1981) borrowed from their ideas and published useful summaries 

of magmatic arcs in the Antarctic Peninsula of, respectively, Middle Jurassic to Early Cretaceous age and preEarly Jurassic age.

Information on rocks that underlie those of the Black 

Coast is sketchy and is based on sparse exposures in 

the central Black Coast (Singleton, 1980a) and farther 

north. From these exposures, it appears possible that 

a middle-crustal, high-grade, schist-and-gneiss complex 

underlies the Latady Formation. The complex may 

represent pre-Jurassic continental lithosphere, or it may 

represent the root zone of a deeply eroded pre-Jurassic 

magmatic arc (Dalziel, 1975; Smellie and Clarkson, 1975;

de Wit, 1977; Smellie, 1981; Dalziel and others, 1981; 

Dalziel, 1982). Sedimentary rocks of the Trinity Peninsula Formation and related units, apparently all of mostly Triassic age (Thomson, 1975a, b, 1982; Edwards, 

1982), have been attributed to an outer-arc basin adjacent to a magmatic arc (Barker and others, 1976) that 

was either roughly axial to (Dalziel and others, 1981), 

or on the eastern flank of (Smellie, 1981), what is now 

the Antarctic Peninsula. The arc resulted from subduction of the Pacific lithosphere under the area of the present Antarctic Peninsula. On the basis of sparse 

information (Barker and others, 1976; Smellie, 1981) on 

the petrologic maturity of the igneous rocks (that is, how 

evolved they are; Hamilton, 1981) of the magmatic arc, 

the arc may have formed on continental lithosphere. The 

arc was deformed during the Late Triassic to Early 

Jurassic Gondwanide deformation, which coincided with 

a minor intrusive suite of calc-alkaline plutons (Rex, 

1976); on the basis of 87Sr/86Sr ratios and petrologic 

maturity of the rocks (Pankhurst, 1982), we conclude 

that continental lithosphere was present at least by this 

time in the Antarctic Peninsula area.

The tectonic setting of the oldest exposed rocks in the 

Black Coast is that of a Middle and Upper Jurassic 

continental-margin magmatic arc (Hamilton, 1981), 

whose axis was near or west of the topographic axis of 

the southern Antarctic Peninsula (Suarez, 1976). The 

Mount Poster Formation was extruded during calcalkaline igneous activity above the subduction zone; corresponding plutons, however, have not been identified. 

The petrologic maturity, including the silicic nature of 

many of the volcanic rocks, of the arc indicates that continental lithosphere underlay the arc. The eastern 

shoreline of the arc trended parallel to the long axis of 

the present peninsula and through its eastern flank. A 

back-arc marine basin formed east of the arc, on the 

craton side, during subduction. The Latady Formation 

was deposited in large part in this basin but in part also 

on the eastern flank of the arc, where continental 

sedimentary rocks intertongue with mostly subaerially deposited volcanic rocks.

The Jurassic rocks were folded during continuing east 

to southeastward subduction. North-northwest-dipping 

axial planes and cleavage (that is, structures showing 

east-southeast vergence) indicate that the rocks yielded 

toward the east-southeast. East-southeast thrusting accompanied folding in the Orville Coast (Kellogg, 1979; 

Rowley, Vennum, and others, 1983), but the rocks in the 

Black Coast are too poorly exposed to prove thrusting. 

This episode of crustal shortening of Late Jurassic to 

Early Cretaceous age may be due to east-southeastward 

gravitational spreading in response either to isostatic 

uplift caused by crustal thickening during subduction 

or to uplift and shouldering aside by emplacement of
16 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

the underlying batholith that was the source of the 

Mount Poster Formation. Alternatively, the crustal 

shortening may be due to collision of the present area 

of the southern Antarctic Peninsula and eastern 

Ellsworth Land with the craton of West Gondwanaland, 

or it may be due to either an increase in motion of the 

converging plates or a decrease in the angle of the subduction zone.

Development of the Middle and Upper Jurassic 

magmatic arc mostly preceded the start of the opening 

of the South Atlantic Ocean in Early Cretaceous time 

(Sclater and others, 1977). The continent was faulted 

near the western edge of the continent of Gondwanaland, thereby leaving a sliver of continental 

lithosphere that now deeply underlies the Antarctic 

Peninsula. At about this time, activity along the arc or 

a separate younger overlapping magmatic arc developed 

on continental lithosphere during Early Cretaceous 

plutonism of the Lassiter Coast Intrusive Suite. This 

magmatic pulse apparently occurred between 130 and 

95 m.y. ago according to the available isotopic ages. Calcalkaline plutons are the sole evidence for this Lower 

Cretaceous magmatic arc, for no corresponding volcanic 

ejecta have been identified in the southern Antarctic 

Peninsula. The trend of the axis of the Cretaceous arc, 

as for the older arc, appears to follow the trend of the 

present Antarctic Peninsula, but the location of the axis 

in the Black Coast area is uncertain because east-west 

differences in volume of plutonic rocks have not been 

identified. Either the arc was broader than the Jurassic 

arc or the axis of the Lower Cretaceous arc was farther 

east, because Cretaceous plutons occur well east of 

known concentrations of the Jurassic Mount Poster Formation. In the Orville Coast (Rowley, Vennum, and 

others, 1983), most plutons occur on the southeastern 

flank of the peninsula, southeast of the main part of the 

Mount Poster Formation but inland from the coastline 

itself, so here the margins of the magmatic arc can be 

inferred; the axis here seems to be east of the apparent 

axis of the Jurassic arc.

Subduction of Pacific oceanic lithosphere beneath 

West Antarctica ceased in Late Cretaceous time in 

Marie Byrd Land and western Ellsworth Land 

(LeMasurier and Wade, 1976; LeMasurier and Rex, 1982) 

and in Tertiary time in the northern and central Antarctic Peninsula (Herron and Tucholke, 1976). A new tectonic regime involving extensional block faulting and 

alkalic volcanism began no later than early Tertiary time 

in Marie Byrd Land and western Ellsworth Land 

(LeMasurier and Wade, 1976; LeMasurier and Rex, 

1982). A small volume of 6-m.y.-old lava flows and breccia of alkalic basalt (basanite) in eastern Ellsworth Land 

(Laudon and others, 1969; Laudon, 1972; chap. B, this 

volume) and the English Coast (O'Neill and Thomson,

1985) reflects a late stage of this regime. Fault-block 

topography also extended as far east as eastern 

Ellsworth Land, as indicated here by seismic-reflection 

and gravity data (Behrendt, 1964) that reveal rough subice topography, including valleys nearly 2,000 m below 

sea level (Laudon, 1982). A small intrusive mass of 

oh"vine basalt in the Seward Mountains (Singleton, 

1980c) and the dike at outcrop Ro321 within the west 

Wegener Range batholith are the only evidence that the 

extensional regime may have exerted an influence in the 

Black Coast area.

ALTERED AND MINERALIZED ROCKS

Small parts of plutonic rocks and dike rocks have been 

hydrothermally altered and mineralized in the southern 

Black Coast. Analytical data and a summary of 

localities containing metallic minerals are given by 

Rowley and others (1977); some localities are shown by 

the British Antarctic Survey (1982). No occurrences in 

the southern Black Coast appear to contain metal concentrations of economic significance.

Most altered or mineralized rocks are in the Carey 

Range, where at several places we found sheared phyllicargillic zones similar to those of the Lassiter Coast copper deposit (Rowley and others, 1977) of the Copper 

Nunataks. Similar zones and associated evidence of lowgrade copper mineralization also occur in stocks in the 

SkyHi Nunataks and Merrick Mountains of eastern 

Ellsworth Land (Rowley, 1978,1979; Rowley and Pride, 

1982; chap. C, this volume; Rowley, Williams, and Pride, 

1983; Rowley, Ford, and others, 1983). All these mineralized sites are interpreted to be the roots of porphyrytype mineral deposits. In the Lassiter Coast copper 

deposit, hydrothermally altered phyllic and argillic rocks 

occur in subvertical, closely spaced, subparallel, linear 

sheared zones, each of which is less than 20 m wide. The 

intensely altered rocks are softer than adjacent propylitic grade rocks and thus weather into trenches that 

are locally filled with snow and ice. The shear zones in 

the southern Black Coast are similar to those in the 

Lassiter Coast copper deposit, but they are less than 

5 m wide and underlie smaller areas (generally less than 

30 m wide). The shear zones of the Lassiter Coast copper deposit strike west-northwest to north-northwest, 

the extension direction that persisted during and since 

folding (folds axes trend northeast). The shear zones in 

the Carey Range trend west to west-northwest, the extension direction in that area, where folds trend almost 

north. Sparsely mineralized rocks of the Lassiter Coast 

copper deposit generally are in altered rocks adjacent 

to the shear zone rather than within the zones. In the 

Carey Range, the shear zones and their adjacent altered
SOUTHERN BLACK COAST 17

rocks are barren of megascopic metallic minerals other 

than pyrite and, locally, chalcopyrite, both of which are 

mostly oxidized. Semiquantitative spectroscopic 

analyses of altered rocks of the Lassiter Coast copper 

deposit (Rowley and others, 1977) show only low to 

moderate (40-100 ppm (parts per million)) metal contents, as do those at localities Bo68 (Pb), Bo71 (Cu, Zn), 

Ka316 (Cu, Zn), Ro313 (Cu, Pb, Zn), and Wa37 (Cu) in 

the southern Black Coast (Rowley and others, 1977). 

The only other types of hydrothermally altered and 

sparsely mineralized rocks in the southern Black Coast 

are at plutonic contacts. In the northern Carey Range 

(locality Ro315), quartz veins contain pyrite, chalcopyrite, and oxidized sulfides; Semiquantitative spectroscopic analyses of two of the veins revealed copper 

contents of 70-100 ppm, molybdenum contents of as 

much as 300 ppm, and zinc contents of as much as 

70 ppm. Rocks at the contact of the east Wegener Range 

batholith (locality Ke80) are locally altered and stained 

by oxidized iron sulfide.

REFERENCES CITED

Adie, R. J., 1955, The petrology of Graham Land II. The Andean 

granite-gabbro intrusive suite: Falkland Islands Dependencies 

Survey Scientific Report, No. 12, 39 p.

___1957, The petrology of Graham Land III. Metamorphic rocks 

of the Trinity Peninsula Series: Falkland Islands Dependencies 

Survey Scientific Report, No. 20, 26 p.

___1964, The geochemistry of Graham Land, in R. J. Adie, ed., Antarctic Geology: Amsterdam, North-Holland Publishing Company, 

p. 541-547.

___1972, Evolution of volcanism in the Antarctic Peninsula, in R.

J. Adie, ed., Antarctic Geology and Geophysics: Oslo, Universitetsforlaget, p. 137-141.

Barker, P. F, Dalziel, I. W. D., and others, 1976, Evolution of the 

southwestern Atlantic Ocean basin Results of leg 36, Deep Sea 

Drilling Project: Initial Reports of the Deep Sea Drilling Project, 

Volume 36, Washington, U.S. Government Printing Office, 

p. 993-1014.

Behrendt, J. G, 1964, Antarctic Peninsula Traverse geophysical results 

relating to glaciological and geological studies: University of 

Wisconsin Polar Research Center, Research Report Series 64-1, 

112 p.

British Antarctic Survey, 1982, British Antarctic Territory geologic 

map, northern Palmer Land: British Antarctic Survey, Series BAS 

500G, Sheet 5.

Cooper, R. A., Landis, C. A., LeMasurier, W E., and Speden, I. G., 1982, 

Geologic history and regional patterns in New Zealand and West 

Antarctica Their paleotectonic and paleogeographic significance, 

in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of Wisconsin Press, p. 43-53.

Craddock, Campbell, 1969, Map of Gondwanaland, in V. C. Bushnell, 

and Campbell Craddock, eds., Antarctic Map Folio Series: New 

York, America Geographical Society, Folio 12, pi. 23.

___1982, Antarctica and Gondwanaland (Review paper), in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of 

Wisconsin Press, p. 3-13.

Craddock, Campbell, and Hollister, C. D., 1976, Geologic evolution of 

the southeast Pacific basin, in C. D. Hollister, Campbell Craddock, 

and others, Initial Reports of the Deep Sea Drilling Project: 

Washington, D.C., U.S. Government Printing Office, v. 35, 

p. 723-743.

Crame, J. A., 1981, Preliminary bivalve zonation of the Latady 

Formation: Antarctic Journal of the United States, v. 16, 

p. 8-10.

Cross, T. A., and Pilger, R. H., Jr., 1982, Controls of subduction 

geometry, location of magmatic arcs, and tectonics of arc and backarc regions: Geological Society of America Bulletin, v. 93, 

p. 545-562.

Dalziel, I. W. D., 1975, The Scotia arc tectonics project, 1969-1975: 

Antarctic Journal of the United States, v. 10, p. 70-81.

___1982, The Early (pre-Middle Jurassic) history of the Scotia arc 

region A review and progress report (Review paper), in Campbell 

Craddock, ed., Antarctic Geoscience: Madison, University of 

Wisconsin Press, p. 111-126.

Dalziel, I. W. D., and Elliot, D. H., 1973, The Scotia arc and Antarctic 

margin, in A. E. M Nairn, and F. G. Stehli, eds., The Ocean Basins 

and Margins, Vol. 1, The South Atlantic: New York, Plenum Press, 

p. 171-246.

Dalziel, I. W. D., Elliot, D. H., Jones, D. L., Thomson, J. W, Thomson, 

M. R. A., Wells, N. A., and Zinsmeister, W. J., 1981, The geological 

significance of some Triassic microfossils from the South Orkney 

Islands, Scotia Ridge: Geological Magazine, v. 118, p. 15-25.

de Wit, M. J., 1977, The evolution of the Scotia arc as a key to the 

reconstruction of southwestern Gondwanaland: Tfectonophysics, 

v. 37, p. 53-81.

Edwards, C. W, 1982, Further paleontologic evidence of Triassic 

sedimentation in West Antarctica, in Campbell Craddock, ed., 

Antarctic Geoscience: Madison, University of Wisconsin Press, 

p. 325-330.

Farrar, Edward, and Rowley, P. D., 1980, Potassium-argon ages of Upper Cretaceous plutonic rocks of Orville Coast and eastern 

Ellsworth Land: Antarctic Journal of the United States, v. 15, 

p. 26-28.

Farrar, Edward, McBride, S. L., and Rowley, P. D., 1982, Ages and tectonic implications of Andean plutonism in the southern Antarctic Peninsula, in Campbell Craddock, ed., Antarctic Geoscience: 

Madison, University of Wisconsin Press, p. 349-356.

Halpern, Martin, 1967, Rubidium-strontium age measurements of 

plutonic igneous rocks in eastern Ellsworth Land and northern 

Antarctic Peninsula, Antarctica: Journal of Geophysical Research, 

v. 72, p. 5133-5142.

Hamilton, Warren, 1981, Crustal evolution by arc magmatism: 

Royal Society of London Philosophical Transactions, v. A301, 

p. 279-291.

Henderson, J. B., Caldwell, W. G. E., and Harrison, J. E., 1980, North 

American Commission on Stratigraphic Nomenclature, Report 

8 Amendment of Code concerning terminology for igneous and 

high-grade metamorphic rocks: Geological Society of America 

Bulletin, v. 91, p. 374-376.

Herron, E. M., and Tucholke, B. E., 1976, Sea-floor magnetic patterns 

and basement structure in the southeastern Pacific, in C. D. 

Hollister, Campbell Craddock, and others, Initial Reports of the 

Deep Sea Drilling Project: Washington, D.C., U.S. Government 

Printing Office, v. 35, p. 263-278.

Kamenev, E. N., 1975, Skladchatiyeh osadochniyeh i intruzivniyeh 

obrazovaniya Berega Lassitera i Berega Bleka (Antarkticheskii 

Polvostrova) [Folded sedimentary and intrusive formations of the 

Lassiter Coast and the Black Coast (Antarctic Peninsula)]: 17th 

Soviet Antarctic Expedition, Winter Research, 1971-1973, v. 65, 

p. 215-222.
18 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

Kamenev, E. N., and Orlenko, E. M., 1982, Metamorphism of sedimentary formations on the Lassiter Coast, in Campbell Craddock, ed., 

Antarctic Geoscience: Madison, University of Wisconsin Press, 

p. 357-361.

Kauffman, E. G., and Imlay, R. W., in press, Dominant Jurassic 

mollusca from the Lassiter Coast, southern Antarctic Peninsula: 

U.S. Geological Survey Professional Paper.

Kellogg, K. S., 1979, Structural geology of Orville Coast and eastern 

Ellsworth Land: Antarctic Journal of the United States, v. 14, 

p. 19-21.

___1980, Paleomagnetic evidence for oroclinal bending of the 

southern Antarctic Peninsula: Geological Society of America 

Bulletin, pt. I, v. 91, p. 414-420.

Kellogg, K. S., and Reynolds, R. L., 1978, Paleomagnetic results from 

the Lassiter Coast, Antarctica, and a test for oroclinal bending 

of the Antarctic Peninsula: Journal of Geophysical Research, v. 

83, p. 2293-2299.

Laudon, T. S., 1972, Stratigraphy of eastern Ellsworth Land, in R. J. 

Adie, ed., Antarctic Geology and Geophysics: Oslo, Universitetsforlaget, p. 215-223.

___1982, Geochemistry of Mesozoic and Cenozoic igneous rocks, 

eastern Ellsworth Land, in Campbell Craddock, ed., Antarctic 

Geoscience: Madison, University of Wisconsin Press, p. 775-785.

Laudon, T. S., Behrendt, J. C., and Christensen, N. J., 1964, Petrology 

of rocks collected on the Antarctic Peninsula traverse: Journal of 

Sedimentary Petrology, v. 34, p. 360-364.

Laudon, T. S., Lackey, L. L., Quilty, P. G., and Otway, P. M., 1969, 

Geology of eastern Ellsworth Land, in V. C. Bushnell, and Campbell Craddock, ed., Geologic Maps of Antarctica, Antarctic Map 

Folio Series: New York, American Geographical Society, Folio 12, 

pi. III.

Laudon, T. S., Lidke, D. J., Delevoryas, Theodore, and Gee, C. T, 1985, 

Sedimentary rocks of the English Coast, eastern Ellsworth Land, 

Antarctica: Antarctic Journal of the United States, v. 20, no. 5, 

p. 38^0.

Laudon, T. S., Thomson, M. R. A., Williams, P. L., Milliken, K. L., 

Rowley, P. D., and Boyles, J. M., 1983, The Jurassic Latady Formation, southern Antarctic Peninsula, in R. L. Oliver, P. R. James, 

and J. B. Jago, eds., Antarctic Earth Science: Canberra, Australian 

Academy of Science, p. 308-314.

LeMasurier, W. E., and Rex., D. G, 1982, Volcanic record of Cenozoic 

glacial history in Marie Byrd Land and western Ellsworth LandRevised chronology and evaluation of tectonic factors, in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of 

Wisconsin Press, p. 725-734.

LeMasurier, W. E., and Wade, F. A., 1976, Volcanic history in Marie 

Byrd Land-Implications with regard to southern hemisphere tectonic reconstructions, in Oscar Gonzales-Ferran, ed., Proceedings 

of the Symposium on Andean and Antarctic Volcanology Problems: Rome, International Association of Volcanology and 

Chemistry of the Earth's Interior, p. 398-424.

Mehnert, H. H., Rowley, P. D, and Schmidt, D. L., 1975, K-Ar ages 

of plutonic rocks in the Lassiter Coast area, Antarctica: U.S. 

Geological Survey Journal of Research, v. 3, p. 233-236.

Meneilly A. W., 1983, Deformation of granitic plutons in eastern Palmer 

Land: British Antarctic Survey Bulletin, no. 61, p. 75-79.

Mutterlose, J., 1986, Upper Jurassic belemnites from the Orville Coast, 

western Antarctica, and their palaeobiogeographical significance: 

British Antarctic Survey Bulletin, No. 7Q, p. 1-22.

O'Neill, J. M., and Thomson, J. W., 1985, Tertiary mafic volcanic and 

volcaniclastic rocks of the English Coast, Antarctica: Antarctic 

Journal of the United States, v. 20, no. 5, p. 36-38.

Pankhurst, R. J., 1980, Appendix, radiometric dating, in D. G. 

Singleton, The geology of the central Black Coast, Palmer 

Land: British Antarctic Survey Scientific Reports, No. 102, 

p. 49-50.

___1982, Rb-Sr geochronology of Graham Land, Antarctica: 

Geological Society of London, Journal, p. 701-711.

___1983, Rb-Sr constraints on the ages of basement rocks of the

Antarctic Peninsula, in R. L. Oliver, P. R. James, and J. B. Jago, 

eds., Antarctic Earth Science: Canberra, Australian Academy of 

Science, p. 367-371.

Plummer, C. C., 1974, Contact metamorphism of the Latady Formation, southern Lassiter Coast, Antarctic Peninsula: Antarctic Journal of the United States, v. 9, p. 82-83.

Quilty, P. G., 1970, Jurassic ammonites from Ellsworth Land, Antarctica: Journal of Paleontology, v. 44, p. 110-116.

___1972, Middle Jurassic brachiopods from Ellsworth Land, Antarctica: New Zealand Journal of Geology and Geophysics, v. 15, 

p. 140-147.

___1977, Late Jurassic bivalves from Ellsworth Land, 

Antarctica Their systematics and paleogeographic implications: 

New Zealand Journal of Geology and Geophysics, v. 20, p. 

1033-1080.

___1982, Tectonic and other implications of Middle-Upper Jurassic 

rocks and marine faunas from Ellsworth Land, Antarctica, in 

Campbell Craddock, ed., Antarctic Geoscience: Madison, University of Wisconsin Press, p. 669-678.

___1983, Bajocian bivalves from Ellsworth Land, Antarctica:

New Zealand Journal of Geology and Geophysics, v. 26,

p. 395-418. 

Rex, D. C., 1976, Geochronology in relation to the stratigraphy of the

Antarctic Peninsula: British Antarctic Survey Bulletin, No. 43,

p. 49-58. 

Rowley, P. D., 1973, Geologic observations of the northern Lassiter

Coast and southern Black Coast: Antarctic Journal of the United

States, v. 8, p. 154-155. 

___1978, Geologic studies in Orville Coast and eastern Ellsworth

Land, Antarctic Peninsula: Antarctic Journal of the United States,

v. 13, p. 7-9.

___1979, Geologic studies in Orville Coast and eastern Ellsworth Land: Antarctic Journal of the United States, v. 14,

p. 21-22. 

_1983, Developments in Antarctic geology during the past half

century, in S. J. Boardman, ed., Revolution in the Earth 

Sciences Advances in the Past Half Century: Dubuque, Iowa, 

Kendall/Hunt Publishing Company, p. 112-135.

Rowley, P. D., Ford, A. B., Williams, P. L., and Pride, D. E., 1983, 

Metallogenic provinces of Antarctica, in R. L. Oliver, P. R. James, 

and J. B. Jago, eds., Antarctic Earth Science: Canberra, Australian 

Academy of Science, p. 414-419.

Rowley, P. D., Kellogg, K. S., and Vennum, W. R., 1985, Geologic 

studies in the English Coast, eastern Ellsworth Land, Antarctica: 

Antarctic Journal of the United States, v. 20, no. 5, p. 34-^36.

Rowley, P. D., and Pride, D. E., 1982, Metallic mineral resources of 

the Antarctic Peninsula (Review paper), ire Campbell Craddock, 

ed., Antarctic Geoscience: Madison, University of Wisconsin 

Press, p. 859-870.
SOUTHERN BLACK COAST 19

Rowley, P. D., Schmidt, D. L., and Williams, P. L., 1982, Mount Poster 

Formation, southern Antarctic Peninsula and eastern Ellsworth Land: Antarctic Journal of the United States, v. 17, 

p. 38-39.

Rowley, P. D., Vennum, W R., Kellogg, K. S., Laudon, T. S., Carrara, 

P. E., Boyles, J. M., and Thomson, M. R. A., 1983, Geology and 

plate tectonic setting of the Orville Coast and eastern Ellsworth 

Land, Antarctica, in R. L. Oliver, P. R. James, and J. B. Jago, eds., 

Antarctic Earth Science: Canberra, Australian Academy of 

Science, p. 245-250.

Rowley, P. D., and Williams, P. L., 1974, Plutonic rocks of the Lassiter Coast: Antarctic Journal of the United States, v. 9, 

p. 225-226.

___1982, Geology of the northern Lassiter Coast and southern 

Black Coast, Antarctic Peninsula, in Campbell Craddock, ed., 

Antarctic Geoscience: Madison, University of Wisconsin Press, 

p. 339-348.

Rowley, P. D., Williams, P. L., and Pride, D. E., 1983, Mineral occurrences of Antarctica, in J. C. Behrendt, ed., Petroleum and Mineral 

Resources of Antarctica: U.S. Geological Survey Circular 909, 

p. 25-49.

Rowley, P. D., Williams, P. L., and Schmidt, D. L., 1977, Geology of 

an Upper Cretaceous copper deposit in the Andean province, 

Lassiter Coast, Antarctic Peninsula: U.S. Geological Survey Professional Paper 984, 36 p.

Saunders, A. D, Tarney, John, and Weaver, S. D., 1980, Transverse 

geochemical variations across the Antarctic PeninsulaImplications for the genesis of calc-alkaline magmas: Earth and 

Planetary Science Letters, v. 46, p. 344-360.

Saunders, A. D., Weaver, S. D., and Tarney, John, 1982, The pattern 

of Antarctic Peninsula plutonism, in Campbell Craddock, ed., 

Antarctic Geoscience: Madison, University of Wisconsin Press, 

p. 305-314.

Sclater, J. G., Hellinger, Steven, and Tapscott, Christopher, 1977, The 

paleobathymetry of the Atlantic Ocean from the Jurassic to the 

present: Journal of Geology, v. 85, p. 509-552.

Singleton, D. G., 1980a, The geology of the central Black Coast, Palmer 

Land: British Antarctic Survey Scientific Reports, No. 102, 

50 p.

___1980b, Physiography and glacial geomorphology of the central 

Black Coast, Palmer Land: British Antarctic Survey Bulletin, No. 

49, p. 21-32.

___1980c, Geology of the Seward Mountains, western Palmer Land:

British Antarctic Survey Bulletin, No. 49, p. 81-89. 

Slemmons, D. B., 1962, Determination of volcanic and plutonic

plagioclases using a three- or four-axis universal stage: Geological

Society of America Special Paper 69, 64 p. 

Smellie, J. L., 1981, A complete arc-trench system recognized in Gondwana sequences of the Antarctic Peninsula region: Geological

Magazine, v. 118, p. 139-159. 

Smellie, J. L., and Clarkson, P. D., 1975, Evidence for pre-Jurassic subduction in western Antarctica: Nature, v. 258, p. 701-702. 

Stanek, K.-R, and Wormbs, Jutta, 1985, Jurassic ammonites from the

Orville Coast, Antarctic Peninsula: Zeitschrift fuer Geologische

Wissenschaften, v. 13, p. 369-372. 

Steiger, R. H., and Jager, E., 1977, Subcommission on geochronology 

Convention on the use of decay constants in geo-[sic] and

cosmochronology: Earth and Planetary Science Letters, v. 12,

p. 1-33.

Stern, T. W., Bateman, P. C., Morgan, B. A., Newell, M. F., and Peck, 

D. L., 1981, Isotopic U-Pb ages of zircon from the granitoids of 

the central Sierra Nevada, California: U.S. Geological Survey Professional Paper 1185, 17 p.

Stevens, G. R., 1967, Upper Jurassic fossils from Ellsworth Land, 

West Antarctica, and notes on Upper Jurassic biogeography of 

the South Pacific region: New Zealand Journal of Geology and 

Geophysics, v. 10, p. 345-393.

Streckeisen, Albert, 1976, To each plutonic rock its proper name: Earth 

Science Reviews, v. 12, p. 1-33.

Suarez, Manuel, 1976, Plate-tectonic model for southern Antarctic 

Peninsula and its relation to southern Andes: Geology, v. 4, 

p.211-214.

Thomson, M. R. A., 1975a, First marine Triassic fauna from the 

Antarctic Peninsula: Nature, v. 257, p. 577-578.

_____1975b, New palaeontological and lithological observations on 

the Legoupil Formation, north-west Antarctic Peninsula: British 

Antarctic Survey Bulletin, No. 41-42, p. 169-185.

___1980, Late Jurassic ammonite faunas from the Latady Formation, Orville Coast: Antarctic Journal of the United States, v. 15, 

p. 28-30.

___1982, Mesozoic paleogeography of West Antarctica, in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of 

Wisconsin Press, p. 331-337.

___1983, Late Jurassic ammonites from the Orville Coast, Antarctica, in R. L. Oliver, P. R. James, and J. B. Jago, eds., Antarctic 

Earth Science: Canberra, Australian Academy of Science, 

p. 315-319.

Thomson, M. R. A., Laudon, T. S., and Boyles, J. M., 1978, Statigraphical studies in Orville Coast and eastern Ellsworth Land: 

Antarctic Journal of the United States, v. 13, p. 9-10.

Thomson, M. R. A., and Pankhurst, R. J., 1983, Age of postGondwanian calc-alkaline volcanism in the Antarctic Peninsula 

region, in R. L. Oliver, P. R. James, and J. B. Jago, eds., Antarctic Earth Science: Canberra, Australian Academy of Science, 

p. 328-333.

van Hinte, J. E., 1976, A Cretaceous time scale: American Association of Petroleum Geologists Bulletin, v. 60, p. 498-516.

Vennum,* W. R., 1978, Igneous and metamorphic petrology of the 

southwestern Dana Mountains, Lassiter Coast, Antarctic Peninsula: U.S. Geological Survey Journal of Research, v. 6, 

p. 95-106.

___1979, Evaporite encrustations and yellow and green surficial 

salts from Orville Coast and eastern Ellsworth Land: Antarctic 

Journal of the United States, v. 14, p. 22-24. 

_1980, Evaporite encrustations and sulphide oxidation products

from the southern Antarctic Peninsula: New Zealand Journal of 

Geology and Geophysics, v. 23, p. 499-505.

Vennum, W. R., and Meyer, C. E., 1979, Plutonic garnets from the 

Werner batholith, Lassiter Coast, Antarctic Peninsula: American 

Mineralogist, v. 64, p. 268-273.

Williams, P. L., Schmidt, D. L., Plummer, C. C., and Brown, L. E., 

1972, Geology of the Lassiter Coast area, Antarctic Peninsula 

Preliminary report, in R. J. Adie, ed., Antarctic Geology and 

Geophysics: Oslo, Universitetsforlaget, p. 143-148.

Igneous Petrology of the 

Merrick Mountains, Eastern 

Ellsworth Land, Antarctica

By WALTER R. VENNUM and THOMAS S. LAUDON

STUDIES OF THE GEOLOGY AND MINERAL RESOURCES 

OF THE SOUTHERN ANTARCTIC PENINSULA 

AND EASTERN ELLSWORTH LAND, ANTARCTIC^

U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1 3 5 1-B

Work done in cooperation with 

the National Science Foundation

Petrology of Lower Cretaceous 

plutonic rocks and related dikes 

as well as Tertiary basanite 

lava flows

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1988

CONTENTS

Abstract ...............................

Introduction ............................

Acknowledgments .......................

Geologic setting .........................

Jurassic sedimentary and volcanic rocks .

Plutonic rocks .......................

Ultramafic, mafic, and intermediate dikes

Rhyodacite porphyry dikes ............

Miocene(?) basanite ..................

Geochemistry ...........................

References cited .........................

Page

21

21

23

23

24

25

27

30

30

31

33

ILLUSTRATIONS

Page

FIGURE 1. Map of West Antarctica showing location of Merrick Mountains .......... 22

2. Photograph showing physiographic setting of the Merrick Mountains ...... 23

3. Geologic map of the Merrick Mountains ............................... 25

4. Ternary plot of modal quartz, alkali feldspar, and plagioclase from chemically 

analyzed samples of plutonic rocks and one dike rock from the Merrick Mountains ......................................................... 26

5. Quaternary plot of normative quartz, orthoclase, plagioclase, and felspathoids 

from chemically analyzed samples of dikes and lava flows from the Merrick 

Mountains ..................................................... 27

6. Harker silica-variation diagram for analyzed samples of igneous rocks from the

Merrick Mountains ............................................. 32

7. Ternary plot of total alkalies and magnesium, iron, and manganese expressed

as oxides in igneous rocks of the Merrick Mountains ................. 33

8. Ternary plot of sodium, calcium, and potassium expressed as oxides in igneous

rocks of the Merrick Mountains .................................. 33

TABLE

TABLE 1. Chemical and modal data of igneous rocks from the Merrick Mountains

Page 

28

STUDIES OF THE GEOLOGY AND MINERAL RESOURCES OF THE SOUTHERN 

ANTARCTIC PENINSULA AND EASTERN ELLSWORTH LAND, ANTARCTICA

IGNEOUS PETROLOGY OF THE MERRICK MOUNTAINS, 

EASTERN ELLSWORTH LAND, ANTARCTICA

By WALTER R. VENNUM' and THOMAS S. LAUDON2

ABSTRACT

A Lower Cretaceous composite stock of mafic to felsic composition, 

at least 10 km in largest exposed diameter, crops out in the Merrick 

Mountains of West Antarctica. This pluton, here named the Merrick 

Mountains stock and belonging to the Lassiter Coast Intrusive Suite, 

intrudes a folded Middle to Upper Jurassic sequence of clastic marine 

sedimentary rocks known as the Latady Formation and interbedded 

lava flows of intermediate to felsic composition. The pluton consists 

of two facies: (1) an older mafic quartz diorite that forms a thin 

(100-200-m-wide) border facies of the stock; and (2) a younger felsic 

quartz diorite that comprises the bulk of the stock and intrudes the 

older quartz diorite. The younger felsic quartz diorite appears to grade 

inward into quartz monzodiorite and locally into granodiorite. Dikes 

of diverse composition, ranging from olivine-rich wehrlite to rhyodacite 

porphyry, were emplaced after both the older and younger plutonic 

events. Quartz veins and numerous aplite, alaskite, and pegmatite dikes 

of uncertain age intrude both facies of the stock. Igneous activity recurred in Miocene(?) time when a basanite lava flow and associated 

hyaloclastite were deposited in the southwestern Merrick Mountains. 

These volcanic rocks appear to represent a subglacial eruption.

INTRODUCTION

The Merrick Mountains were discovered in 1935 by 

Lincoln Ellsworth and Herbert Kenyon during the first 

Antarctic transcontinental flight (Ellsworth, 1936). 

Trimetrogon aerial photographs of the range were taken 

in 1947 by the Ronne Antarctic Research Expedition 

(Ronne, 1949) and in 1965 and 1966 by the U.S. Navy. 

The Ellsworth Land oversnow traverse (Antarctic Peninsula Traverse) passed just north and southeast of the 

Merrick Mountains during the 1961-62 austral summer. 

Although brief stops were made to collect bedrock 

samples at nine nearby nunataks, the Merrick Mountains were not entered at this time (Behrendt and Parks, 

1962). Geological mapping of the Merricks and several 

other adjacent ranges and nunataks (figs. 1, 2) was 

conducted in November and December of 1965 by a

Present address is Department of Geology, Sonoma State University, Rohnert Park, Calif. 

94928.

Present address is Department of Geology, University of Wisconsin-Oshkosh, Oshkosh, 

Wis. 54901.

University of Wisconsin field party led by the junior 

author (Laudon and others, 1969; Laudon, 1972). At this 

time the pluton described in this report, the Merrick 

Mountains stock, was discovered and mapped. During 

the 1977-78 field season, a U.S. Geological Survey field 

party completed reconnaissance geological mapping of 

the Merrick Mountains (Rowley, 1978; Thomson and 

others, 1978).

Numerous geologists have reported hybrid plutonic 

rocks (summary in Vennum, 1978) and low grade 

sulphide mineralized rocks (Rowley and Pride, 1982) in 

more northerly portions of the Antarctic Peninsula. 

Therefore, reports of hybrid plutonic rocks and abundant 

occurrences of copper efflorescences and copper and iron 

sulphides in the Merrick Mountains (Laudon and others, 

1969) aroused our interest in this range. Consequently, 

several days in late January 1978, were devoted to detailed mapping in the Merrick Mountains. The composite nature of the stock proved to be noteworthy for 

the southern Antarctic Peninsula, and the mineralized 

rocks were found to be similar to, although lower in grade 

than, the noneconomic porphyry-type copper deposit 

which crops out in the Copper Nunataks (fig. 1) of the 

Lassiter Coast (Rowley and others, 1975, 1977). This 

report summarizes field data on the igneous petrology 

of the Merrick Mountains resulting from approximately 35 man-days of work and draws heavily on the field 

notes and reports of the 11 men privileged to have 

worked in this small, remote, yet highly interesting 

range of mountains just 1,500 km from the South Pole. 

The metallic minerals of the Merrick Mountains stock 

are discussed in chapter C (this report).

Outcrop numbers given in the text refer to rock 

nunataks or parts of nunataks that were studied. Each 

outcrop may have rock types of differing lithology or 

origin. When rocks were sampled they were assigned the 

same whole number as the outcrop; letters and even 

subscripts appended to the outcrop number refer to individual samples.

21
22 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

70°S

FIGURE 1. West Antarctica showing location of the Merrick Mountains. Modified from Rowley, Williams, and Pride (1983), using the 

suggestions of Swithinbank and others (1976). Hachures indicate edge of shelf ice.
MERRICK MOUNTAINS, EASTERN ELLSWORTH LAND 23

FIGURE 2. Physiographic setting of the Merrick Mountains. U.S. Navy high altitude oblique aerial photograph TMA 1645 135 F33. View

looking south from 7600 m, February 1965.

ACKNOWLEDGMENTS

We thank the other members of the 1965-66 field party (L. L. Lackey, P. G. Quilty, P. M. Otway, and P. J. 

Wasilewski) and the 1977-78 field party (J. M. Boyles, 

P. E. Carrara, K. S. Kellogg, P. D. Rowley, and M. R. A. 

Thomson) for their help with the fieldwork and for the 

use of their field notes and reports. P. D. Rowley did 

some of the modal analyses. This study was financed 

by National Science Foundation grants DPP76-12557 

and DPP78-24214. Logistical support was provided by 

the U.S. Antarctic Research Program of the National

Science Foundation and by U.S. Navy squadron VXE-6. 

A previous version of this report was reviewed by P. D. 

Rowley and J. M. O'Neill; these reviews greatly improved 

the manuscript.

GEOLOGIC SETTING

The oldest exposed rock unit in the Merrick Mountains, as in most other parts of the southern Antarctic 

Peninsula, is a thick sequence of Middle to Upper 

Jurassic clastic marine sediments named the Latady
24 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

Formation after exposures in the northern Latady 

Mountains of the southern Lassiter Coast (Williams and 

others, 1972). The formation is composed of black to 

gray slate, siltstone, subordinate sandstone that contains abundant volcaniclastic detritus, and minor lenses 

of coal, conglomerate, and limestone. Plant and invertebrate fossils are locally abundant. Most of the clastic 

material appears to have been deposited in a temperate 

nearshore enviroment. Structural complexity, metamorphism, and lack of continuous exposures and of mappable 

key beds negate the possibility of accurately estimating 

a total thickness; the sequence does, however, appear to 

be several thousand meters thick (Rowley, 1978; Thomson and others, 1978; Rowley and Williams, 1982).

Silicic calc-alkaline ash-flow tuff, andesitic to dacitic 

lava flows, and minor amounts of airfall tuff intertongue 

with and may in part overlie the Latady Formation. On 

the basis of age and lithology, these volcanic rocks are 

correlated with the Middle and Upper Jurassic Mount 

Poster Formation, named for exposures at Mount 

Poster, in the western Lassiter Coast (Rowley, Schmidt, 

and Williams, 1982). The Mount Poster Formation is 

part of the Antarctic Peninsula Volcanic Group (Thomson, 1982), which is exposed throughout the Antarctic 

Peninsula; the Mount Poster Formation is the only formation of the Antarctic Peninsula Volcanic Group in this 

area.

The Latady and Mount Poster Formations were folded 

about west-northwest-to east-northeast-trending axes 

that roughly parallel the trend of the Antarctic Peninsula. Lower Cretaceous stocks, batholiths, and associated mafic to intermediate dikes (Farrar and others,

1982) intruded these rocks. The stratigraphic unit to 

which all known plutons in the southern Antarctic 

Peninsula belong is termed (Rowley, Vennum, and others,

1983) the Lassiter Coast Intrusive Suite of Early 

Cretaceous (130-95 m.y. (million years)) age. The plutonic 

rocks range in composition from gabbro to granite; 

granite, granodiorite, and tonalite are the most common 

rock types. Field relations, petrography, and chemical 

analyses (Laudon and others, 1969; Laudon, 1972,1982; 

Rowley and Williams, 1974, 1982) indicate that the 

plutonic rocks are similar to Mesozoic and Cenozoic calcalkaline intrusive rocks exposed extensively throughout 

the Antarctic Peninsula and the Chilean and Patagonian 

Andes (Adie, 1955).

Contact metamorphic aureoles extend 1-2 km outward from intrusive contacts and attain a hornblendehornfels facies (Plummer, 1974). Scattered, local, 

porphyry-type copper and molybdenum mineralization, 

which are related to shear zones, was a late stage product of the igneous activity (Rowley and others, 1975, 

1977; Rowley and Pride, 1982). A Miocene(?) olivinebasanite lava flow and associated hyaloclastite crop out

at a single small nunatak in the southwestern Merrick 

Mountains; these rocks are lithologically similar to rocks 

of probable Tertiary age in the English Coast of northeastern Ells worth Land (O'Neill and Thomson, 1985).

JURASSIC SEDIMENTARY AND VOLCANIC ROCKS

The Latady Formation crops out in the Merrick 

Mountains and is also exposed at several scattered 

nunataks both north and south of the main mass of the 

Merrick Mountains (fig. 3). The rocks consist of darkgray to black carbonaceous slate and siltstone interbedded with fine- to medium-grained tan to gray sandstone. Axial-plane cleavage is locally strongly developed 

in the finer grained rocks, and the sandstone is 

laminated, bioturbated, and locally crossbedded in many 

places. An extensive fossil collection from Eaton 

Nunatak includes abundant tube worms (Rotularia sp.) 

and bivalves (mainly Inoceramus sp.), but the assemblage also contains belemnites, plant fragments, and 

rarely, some ammonites. Fossils collected from other 

Latady Formation outcrops in the Orville Coast and 

eastern Ellsworth Land are Middle and Late Jurassic 

in age (Quilty, 1970,1972; Thomson, 1980; Crame, 1981). 

Dark-gray plagioclase-porphyritic lava flows of intermediate to felsic composition are interbedded with 

Latady Formation at all nearby outcrops except in the 

Eaton Nunataks. These volcanic rocks correlate with the 

Mount Poster Formation of the Antarctic Peninsula 

Volcanic Group, and they comprise about 5 percent of 

the exposed section.

Contact-metamorphic effects produced in the Latady 

Formation by intrusion of the Merrick Mountains stock 

are similar to those described by Vennum (1978) and 

Plummer (1974) from contact aureoles in the northern 

and southern Lassiter Coasts, respectively. Most of the 

contact metamorphic rocks in the Merrick Mountains 

area are fine-grained subarkosic sandstone (Dott, 1964). 

In thin section these rocks are seen to contain various 

amounts of plagioclase (mainly oligoclase) and 

argillaceous material, minor amounts of slightly perthitic potassium feldspar, and sparse, opaque grains and 

subrounded zircons. Quartz makes up at least 80 percent of all samples examined.

Quartz in most places shows signs of recrystallization, 

and feldspar, especially plagioclase, is generally partly 

sericitized. The most commonly developed metamorphic 

groundmass minerals are sericite, pale-green, very weakly birefringent chlorite, red-brown biotite, and graphite 

dust. Porphyroblasts are not evident in any of the hand 

samples and are relatively small and uncommon in thin 

section. Numerous minute reddish-brown biotite grains 

locally occur in clots of 0.3-0.4 mm diameter. Andalusite
MERRICK MOUNTAINS, EASTERN ELLSWORTH LAND 25

72° 15' W 72° 00' W

5 KILOMETERS

J

EXPLANATION

Basanite 

Quartz diorite-granodiorite 

Mafic quartz diorite 

Latady Formation

\ TERTIARY

Y CRETACEOUS

JURASSIC

x'5/0 SUMMIT OF MOUNTAIN PEAK-Showing 

approximate elevation in meters

By56f SAMPLE LOCATION 

 CONTACT Dotted where concealed under ice

FIGURE 3. Geologic map of the Merrick Mountains. Geology by J. M. 

Boyles, P. E. Carrara, K. S. Kellogg, L. L. Lackey, T. S. Laudon, P. M. 

Otway, P. G. Quilty, P. D. Rowley, M. R. A. Thomson, and W. R. Vennum Outlines show nunataks and mountains that are surrounded 

by snow and ica

is present both as anhedral to subhedral granules and 

as euhedral prismatic porphyroblasts 0.5 mm long. 

Minor cordierite locally occurs as spongy indistinct porphyroblasts 0.3-0.4 mm long and is crowded with 

sericite inclusions. Garnet, metamorphic hornblende, 

and tourmaline which are present in other contact 

aureoles developed in the Latady Formation throughout 

the southern Antarctic Peninsula are not present in 

metamorphic rocks of the Merrick Mountains. Although

rare parallel lenses and streaks of graphite and sericite 

are present, the metamorphic minerals in most samples 

do not show preferred orientation, which indicates that 

their growth took place under static conditions. Retrograde effects include the development of epidote along 

biotite cleavage planes, thin rims of sericite on the 

euhedral andalusite porphyroblasts, and thin rims of 

hematite on magnetite. Contact metamorphism in the 

Merrick Mountains corresponds to Turner's (1968) 

hornblende-hornfels facies.

PLUTONIC ROCKS

The northern and northeastern two-thirds of the Merrick Mountains are underlain by a composite, concentrically-zoned!?) stock that is largely quartz diorite in 

composition, but which also includes quartz monzodiorite and, locally, granodiorite (fig. 3). Magnetometer 

surveys indicate that the snow-covered central portion 

of the Merrick Mountains is also underlain by plutonic 

rock (Laudon, 1982). The composite pluton, containing 

numerous lithologies, is here named the Merrick Mountains stock; it belongs to the Lassiter Coast Intrusive 

Suite. The pluton is best exposed at Mount Matheson, 

especially along a north-south ridge of almost continuous outcrop (fig. 3, outcrops Ro500, Ro501) extending from both flanks to the summit of the mountain. 

Here, the composite nature of the stock is best 

demonstrated, for much of the outcrop shows complex 

intrusive relations between a darker older plutonic facies 

and a lighter-colored younger plutonic facies. The northern part of the ridge is underlain mostly by the lighter 

plutonic facies; whereas, the southern part is underlain 

mostly by the darker plutonic facies. The major intrusive contact between the two is at the summit of 

Mount Matheson.

The older plutonic event of the Merrick Mountains 

stock formed a mafic border facies of irregular width (fig. 

3). The main rock type is dark-gray to black, mediumgrained (1-5 mm) quartz diorite (color index of 40-45). 

The border facies extends around the pluton margin 

from the southern slope of Mount Matheson clockwise 

to the northern slope of Mount Boyer. No outcrops of 

dark quartz diorite were seen along the southern and 

southeastern one-third of the intrusive contact with the 

Latady Formation (fig. 3). Outcrops in this area, however, are strongly frost shattered, and it is possible that 

dark quartz diorite is hidden beneath extensive talus 

accumulations of younger plutonic rocks.

Wherever exposed, the dark quartz diorite is intruded 

by light- to medium-gray, medium-grained quartz diorite 

(color index of 20-25) of the younger plutonic event, 

which makes up the bulk of the stock. Wherever the
26 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

mafic border fades and the main interior fades of the 

stock are observed in contact with each other, irregular 

pods, veinlets, and dikes of light quartz diorite are intimately intermixed with dark quartz diorite. This zone 

of hybrid or mixed rock is as much as several hundred 

meters wide. Agmatitic contact breccia composed of 

angular inclusions of dark quartz diorite in light quartz 

diorite occur at Mount Matheson and at Mount Becker. 

Although outcrops are limited, the light quartz diorite 

appears to grade inward into quartz monzodiorite and 

locally into granodiorite. It is possible that the interior, 

snow-covered portions of the pluton are more felsic than 

the exposed rocks. Concentrically zoned plutons with 

mafic border facies similar to the Merrick Mountains 

stock have been reported at numerous other localities 

in the southern Antarctic Peninsula (Rowley and others, 

1976, 1977; Vennum, 1978; Farrar and others, 1982; 

Rowley and Williams, 1982). Quartz veins and numerous 

aplite, alaskite, and pegmatite dikes intrude both the 

light and dark quartz diorite facies of the stock and were 

accompanied by shearing (crackling), hydrothermal 

alteration, and porphyry-type copper mineralization that 

are best exposed at Mount Matheson. Although the 

quartz veins and aplite, alaskite, and pegmatite dikes 

cut both facies of the pluton, field mapping rarely conclusively indicates whether any of these rocks were 

emplaced before the younger plutonic event. The 

mineralized rock is of noneconomic grade (chap. C, this 

report) and bears many similarities to that described by 

Rowley and others (1975,1977) in the Copper Nunataks 

area of the Lassiter Coast.

Chemical and semiquantitative spectrographic 

analyses, CIPW norms, and modes of analyzed samples 

are listed in table 1. Modes of analyzed samples are also 

plotted in a ternary diagram (fig. 4), using the International Union of Geological Sciences (IUGS) classification of Streckeisen (1976). Sample locations are marked 

in figure 3. A biotite whole-rock Rb-Sr isochron obtained 

from biotite "diorite" collected at Mount Berger yielded 

a radiometric age of 107 my. (Halpern, 1967; age corrected for new decay constants of Steiger and Jager, 

1977), which is the age of the dark quartz diorite of the 

older plutonic event of the Merrick Mountains stock. 

The age is generally similar to the ages of other plutons 

dated in the southern Antarctic Peninsula and eastern 

Ellsworth Land. All these plutons have been assigned 

to the Lassiter Coast Intrusive Suite (Rowley, Vennum, 

and others, 1983).

In thin sections from the Merrick Mountains stock, 

plagioclase occurs in conspicuously zoned subhedral to 

euhedral tablets. Individual crystals in the dark quartz 

diorite range in composition from calcic labradorite to 

sodic andesine, those in the light quartz diorite and 

quartz monzodiorite range from sodic labradorite or

calcic andesine to calcic oligoclase, and those in the 

granodiorite range from calcic andesine to sodic 

oligoclase.

Clinopyroxene (2Va =55°, zhc=41° 5 =0.025) is the 

most abundant mafic mineral in the dark quartz diorite 

and is present in lesser amounts in the light quartz 

diorite and quartz monzodiorite. In some places 

clinopyroxene forms poikilitic crystals that enclose 

plagioclase and, locally, biotite. Trace amounts of olivine, 

rimmed with hypersthene and clinopyroxene, occur in 

dark quartz dioritic rocks from the southern tip of 

Mount Matheson and from Mount Berger.

Euhedral and subhedral prisms of twinned hornblende 

(2Va =70°, e/\c=16°, 6 =0.020, z and y = olive brown, 

x = very pale yellow to colorless, z = y>x) occur in both 

the light and dark quartz diorite, but the prisms of hornblende are much more abundant in the more felsic rocks. 

In the dark quartz diorite this mineral is largely secondary after clinopyroxene, but in the more felsic rocks it 

is pyrogenetic in origin. The hornblende locally occurs 

as large (5-7 mm long) platelike crystals that 

poikolitically enclose groundmass grains. Biotite (2Va 

=10°, z=y=red brown, jc=straw yellow, z=y>x) is 

generally less abundant than hornblende, although the 

ratio of the amounts of these two minerals is variable.

Quartz

/ V

Alkali 10\ 

Feldspar

/ / Quartz 

' Syenite

Syenite

"^Alkali 

Feldspar 

syenite

/ Quartz 

/ Monzonite

/ Monzonite

\ By56f >66-JM Dio;jt- 

\ Ro^01g\66-157

35 65 

Quartz Monzodiorite 

or 

Quartz Monzogabbro

\ ~

\ 90 

\ Diorite or 

\ Gabbro 

Monzodior 

Monzogat

\bb-l t>a

Plagioclase

te or 

>bro

FIGURE 4. Ternary plot of modal quartz, alkali feldspar, and 

plagioclase from chemically analyzed samples of plutonic rocks and 

one dike rock from the Merrick Mountains. Classification is from 

Streckeisen (1976). Calculated from data in table 1.
MERRICK MOUNTAINS, EASTERN ELLSWORTH LAND 27

All mafic minerals tend to occur in clots, rather than 

distributed in a homogeneous fashion throughout the 

rock. Where present, quartz and potassium feldspar are 

generally interstitial. In the more felsic samples, 

however, potassium feldspar locally occurs as indistinct, 

slightly perthitic, poikilitic phenocrysts that have a 

maximum length of 10-15 mm. Accessory minerals in 

approximate order of abundance include opaques, 

apatite, sphene, and zircon.

ULTRAMAFIC, MAFIC, 

AND INTERMEDIATE DIKES

Virtually every outcrop of plutonic and sedimentary 

rock in the Merrick Mountains is cut by members of a 

mineralogically diverse series of dikes that are largely 

mafic in composition. The majority of these dikes appear to have been emplaced after the younger plutonic 

event; however, some were intruded after the older 

plutonic event, but prior to the intrusion of the light 

quartz diorite (younger event). For example, on the 

eastern ridge of Mount Boyer, a mafic dike that cuts 

Latady Formation is truncated by light-colored quartz 

diorite (Laudon, 1982).

Individual dikes are from a few centimeters to greater 

than 10 meters wide; some can be traced along strike 

for several hundred meters. Dikes of similar composition 

are associated with Lower Cretaceous plutonic rocks 

throughout the southern Antarctic Peninsula (Williams 

and others, 1972; Rowley and Williams, 1974, 1982; 

Laudon and others, 1969; Laudon, 1972; Rowley and 

others, 1977; Vennum, 1978). Farrar and others (1982) 

concluded that plutonism in the southern Antarctic 

Peninsula, including emplacement of most or all of the 

mafic dikes, occurred during a relatively short period 

of Early Cretaceous time. On the basis of field relations 

and chemistry of the dikes, we feel that this conclusion 

can be extended to eastern Ellsworth Land. Chemical 

and semiquantitative analyses and CIPW norms of 

analyzed samples are listed in table 1 and the normative 

mineralogy is plotted in figure 5.

Many of the dikes are porphyritic, but some are also 

equigranular and (or) aphanitic. Common phenocryst 

assemblages include clinopyroxene-plagioclase, 

hornblende-plagioclase, and plagioclase. Some of the 

hornblende-plagioclase porphyritic dikes contain scattered phenocrysts of biotite and partly resorbed "beta" 

quartz. Clinopyroxene and hornblende phenocrysts are 

mutally exclusive; none of the dikes are lamprophyres 

in the sense of containing only mafic phenocrysts.

Both clinopyroxene (2Va = 55°, eAc=42°, 6 =0.030) 

and plagioclase phenocrysts in the clinopyroxeneQ= Quartz

Dacite

20 . V177k 

66-79 

Andesite or 

Basalt .

V1 78fN 

66-77 65 Ro501h

Alk'Ji Basalt or 

Alkali Andesite 10

Foid-bearing 

alkalic Trachyte

A=Alkali Feldspar

(Normative 

Orthoclase)

P= Plagioclase

'(Normative Albite+ 

Normative Anorthite) 

60

F=Normative Feldspathoids

FIGURE 5. Quaternary plot of normative quartz, orthoclase, plagioclase, and feldspathoids from chemically analyzed samples of dikes 

and lava flows from the Merrick Mountains. Classification is from 

Streckeisen (1979). Calculated from data in table 1.

plagioclase porphyritic dikes are strongly zoned, with 

the plagioclase ranging in composition from calcic 

labradorite to calcic andesine. Plagioclase phenocrysts 

are commonly partly sericitized, and the clinopyroxene 

phenocrysts are usually altered to epidote on their 

margins. Groundmass minerals in these dikes include 

plagioclase, clinopyroxene, opaques, apatite, sphene, 

minor hornblende (e=pale olive green, y=pale red brown, 

^c=colorless to very pale yellow; z>y>x], and scarce 

quartz.

Both hornblende (2Va =70° eAc=21° 6 =0.024; same 

pleochroic and absorption scheme as mentioned 

previously) and plagioclase phenocrysts in the 

hornblende-plagioclase porphyritic dikes are strongly 

zoned, with the plagioclase ranging in composition from 

sodic labradorite to sodic andesine. The plagioclase 

phenocrysts are usually partly altered to sericite±
28 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

"* to "w 

§ "a

 S* o

<D to T)

^ >< 5

~" 5) &

X *

i N -o 2 °° * 

2- 2

ra c

T3 O o

§ 1 ^

° 2 5

 -3 O

§ s J

w * o

_ o> c

 S t- -

_ 1 .C 

T3 CO m

 S -C -9 "I3.

S § a J

3 » £ I

| «S 1

jg " CO «

E "S <i *°

0) J3 <D .-y

>§! J co" J

ft) .2 £ £ 

"^ i £ 1 K

fc .5 S -"-> _-

*+X >-* "53 - ~ C T3 ^ 

co X a * H

 «J -0 o -

fc. t- O> § a"

CO > - j EH

3 c " -

o "0 o ^- c § i T c w

C *. 3 | .a

 2> JS SJ .

**"" C 0 ® (3

* *«-» 4_r

 S 5 * ° CL< -S ° § 'S "

a o w S Cu

fS - -o "a '3

0 S § g a"

S > «1 1

*"tt **^ ° ^ ^

C lO H 5 **H"

*2 W -rt ^-1

**S - -tj

Q g£ If Q *

*NA § ^ ^

1 o s z" «3

»< * s ^

O a" £~ 3 O

J; I 2 | S

y be * PQ

pa S >> ^ P3

s "^ "S <-

1 § !.<

^ 0 § <*

I! 41

"3 § &> 1 

1 a 2

| -° |^

J3 C .^ 0

0 S i '-3

 3 J-S 3

O 'f! "ti (D

 o °- S f

 ^ 2 o-'o

^^

0)

^

SCO

cC

pq

OJ

 H

Q

tn

1*

.^

c 

o

3 -H

<f

O

VD

w

w

CO

O

VD

W

W

^

r%.

>

I

VD

CO

1

VD

VD

0

O

od

 H 

COr^.

>

S

m

PQ

O

O

m

S,

^

2

S

CO

,

1

S

1^o

a

>

i

VD

M 

O

i

,_4Q. 

S o

tfl Z 

en

ercent

a

 u

M

HI

S

C

CO

HI

><

C

rt

a

o

a)

6

<fi-H<j-c^coco<i'<j' <f<fcTiin

vo ico<r i-ncMin mcMr~.-H

<fLncMr^.coco<fcMOOcocMooo

 iro i<fr~.invOvo p^vom<fLn

COCO<fCO^HCM^CO <fO^H^H^D

rCMCOOOO^CM<fOO ^n IOOOCM

r~ ICO^OCM^COOVDCO <fO<f

 

COl-..COCMCMincOCM-(000000

oooocMr^.<fmo incM<fco

CO^CM^OCMO-COCMOOCOOOOO

^-HOOocM^o^vor- vor-r^

or^-oir^mo' < 'CMOOOOOO

*»O LO tOCOCMCMCO r^. « « > ( « «

O^OCMO'vOOCsl-HOOCM-HOOO

<t -H -H -H

cJSSSSSSSSS SSS

^^(.g^^l^^J^^QQQQQQ

-HCOLn^HO-HCMCMOO CMOO

comocsi^HCMcoin^HOooooo

^ i

ScOCMCoSCTlSSoO S22

OOCOCMCMmcMCM' tOOOOOO

incocTir^.cocMcor^.oo < < co <f

^HOOCO<fcOC^r^cOC^O ^O^H^H

CT.^OCOCOCMincMCMOOOOOOO

c^<f^nr^.r^.in^HCM ^OCOCM^H

<rr~co<rcor~.cocMoo 10000

in i

or^-coc^cMcTir^.co o<fcMco

<fOCMr^-CM^H^O^H COCOCO^H

co{T.comcoooco^-<oo^-

in -H

( oooo

OLncoin^ocr.<fo comcoco

COCOVD^COCMCOCO r~- CO CO 1

cococomcococo 

m F <

100 10000

cvi_i_ir>.in<fvocMcooo ^ovo<f

coco^^^c^coo-.oooooo

SS5KSSI32 °522

.-HCO-,^in^CM-,OOCMOOOO

S322SSSSSE5S S 5 2

rjcom.oinc^cMCM^oo-1000

o

X

CO CO r-t

O 

CMOO 

CMCMOOO 

o 

CMOOO4JOOO 

+icccMm CM

<f

CO

o^

o

o

o

o

%

in

o

o

~*

CO

f;

o

o

S,

CO

CO

CT.

<^

5

0^

CO

CM

0^

CO

o^

0V

c^r^>

o

o

^H

CO

o

o

"*

m

S

CM

O 

O

S

£

r-1

a

4-1

0

H

c

o

H

a) 

a

CO

a

c ,-f

,

a)

>^

rt

c

rt

o

 H

a

M

o

4-1 

O

a) 

a

CO

HI

-H

CC

4-1

 H

C

«!

S

tr

-H

QJ

cn

I I I 1 I I I I I I I

I I 1 I I I I t I I I

I I I I I I I I I 1 I

1 I I I I I I 1 I I 1

OinESOOESESESESOO

O 'H CO CO CM O

O O

_r

i i i i i i i i i i i i i i i i i i i i i i

ooooin2;i2o!2oo

OCOCMin < CM COO

co i r1 1 1 1 1 1 1 1 1 1 t 1 1 1 1 1 1 1 1 1 1 1

in

O co r^ T-* co co O

O 'H CO ^H O

o ~-< r^. CM -H CM o

o r~-

oor~-ooi2i-Jr~-!2oo

o CM o CM co o 

o i r~-

i I 1 1 1 I I 1 I 1 I 

I I I I I I i 1 I 1 I

I I I I I I I 1 I 1 I

1 I I I I I I I I I I

I I I I I I I I I I I

I I I I I I I I I I I

OOOOmi2iZiO!2OO

OCMCMO^ < mO

co < m

1 I I I I I 1 I 1 I 1 1 I I I 1 1 1 I 1 I 1

o CM in co ~-< co o 

m ^H o

-H"

COOS-1 ^CCOr^'Hr^ OM
V 

Y 

Yb 

Zr

200 

30 

3 

50

300 

30 

3 

30

CIPW Norms, in

Quartz

Corundum

Orthoclase

Albite

Anorthite

Nepheline

Wollastonite

Enstatite

Ferrosilite

Forsterite

Fayalite

Magnetite

Ilmenite

Apatite

Total -

Plagioclase

K-feldspar

Quar t z

Pyroxene

Amphibole

Biotite

Apatite

Zircon

Sphene

Opaques

Chlorite

Epidote

Groundmass

0

0

12.30

22.69

32.62

0

5.70

3.75

1.62

6.17

2.94

7.40

2.39

1.11

- 98.69

46.1

0

3.2

18.7

5.2

19.0

0.1

0.1

0

4.8

1.8

1.0

0

1.82

0

6.78

20.94

35.38

0

5.29

13.37

10.05

0

0

2.04

1.27

0.38

97.32

58.8

0

5.6

18.0

5.4

2.4

0

0

0

0.1

9.6

0.1

0

6.79

0

3.67

26.81

34.30

0

4.43

11.36

4.08

0

0

5.83

1.26

0.38

98.91

62.0

1.3

8.1

4.1

19.1

0.3

0

0

0.1

3.9

1.0

0.1

0

5.56

0

7.62

28.03

32.34

0

2.64

8.30

6.16

0

0

5.22

1.60

0.78

98.25

65.4

2.1

7.4

4.7

5.4

10.9

0

0

0

3.7

0.3

0.1

0

4.51

0

6.62

30.81

31.97

0

2.62

7.96

6.77

0

0

4.65

1.58

0.75

98.24

66.4

0

5.5

3.3

9.8

11.0

0

0

0

3.1

0.9

0

0

6.25

0

13.55

26.77

26.61

0

4.20

9.23

5.27

0

0

4.60

1.52

0.33

98.33

53.5

5.5

12.2

0.6

13.0

11.4

0

0

0

1.8

0

2.0

0

200 

30 

3 

50

150 

30 

3 

70

30 

30 

3

100

150 

15 

1.5 

30

200 

15

___ O ___

30

150 

30 

3 

100

weight percent

15.02

0

17.09

23.71

25.30

0

1.30

7.23

2.85

0

0

4.95

1.17

0.43

99.05

Modes , in

47.9

7.0

16.2

0.9

20.1

1.9

0.1

0

0.1

5.6

0.1

0.1

0

18.32

0

15.39

22.80

26.55

0

1.03

6.84

1.96

0

0

4.68

1.03

0.31

98.94

volume

51.4

11.1

15.5

0

15.7

1.7

0.1

0.1

0

4.4

0

0

0

21.91

1.14

31.29

27.36

10.04

0

0

2.49

3.14

0

0

0.81

0.55

0.21

98.94

percent

53.0

15.3

18.1

0

9.7

2.1

0

0

0

1.8

0

0

0

0

0

12.07

15.31

22.20

0

9.74

5.30

6.70

8.69

12.11

3.99

1.65

0.38

98.14

0

0

0

7.4

0

26.0

0

0

0

0

0

0

66.6

0 3.94 11.31

0 0 0.74

10.79 7.51 15.87

15.88 16.10 29.03

29.23 36.09 20.50

1.73 0 0

8.37 5.44 0

4.33 12.77 6.12

3.83 10.78 8.99

8.89 0 0

8.66 0 0

3.02 3.31 2.88

2.13 1.45 0.79

0.45 0.40 0.33

97.31 97.79 96.56

34.4

0

0

9.0

0

0

0

0

0.8

1.0

2.8

0

52.0

13.32 

0.02 

14.82 

30.81 

25.20 

0 

0 

6.05 

0.76 

0 

0 

5.57 

1.41 

0.71 

98.67 

62.6

11.0

10.0

3.2

0

8.6

0

0

0

2.2

2.4

0

0
30 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

carbonate, and the hornblende phenocrysts are altered 

along their margins to chlorite and epidote. Groundmass 

minerals in the hornblende-plagioclase porphyritic dikes 

and in the plagioclase porphyritic dikes include plagioclase, hornblende, red-brown biotite, opaques, quartz, 

apatite, and sphene.

The most unusual mineral assemblage occurs in a dike 

located on the northern ridge of Mount Becker; phenocrysts of hypersthene (locally rimmed with clinopyroxene), chloritized biotite, labradorite, and sparse anhedral 

poikolitic potassium feldspar are set in a groundmass 

of plagioclase, opaques, sphene, clinopyroxene, quartz, 

and scarce hornblende. Two olivine-rich wehrlite dikes 

that approach dunite in composition crop out on the 

northern and southern ridges of Mount Berger. Olivine 

occurs both as separate grains and as inclusions in 

poikilitic clinopyroxene grains. The clinopyroxene is 

relatively fresh, but olivine in the northern dike is altered 

to serpentine and magnetite. The southern dike is richer 

in olivine, most of which is totally serpentinized.

All dikes in the Merrick Mountains have undergone 

at least light to moderate hydrothermal alteration. A 

dike on Mount Matheson has been subjected to 

potassium hydrothermal alteration, so that all biotite 

reported in the mode (table 1, sample Ro501h) is finegrained hydrothermal biotite. (See chap. C, this report.) 

In addition to the altered phenocrysts mentioned 

previously, the groundmass of these rocks contains 

variable amounts of secondary chlorite, epidote, sericite, 

carbonate, hematite, and leucoxene.

RHYODACITE PORPHYRY DIKES

Cream-colored rhyodacite porphyry dikes, as wide as 

10 m, crop out at several localities (By56, C58, Ro500, 

VI78) on and near Mount Boyer and Mount Matheson. 

Much of this rock occurs as frost-shattered rubble; its 

contacts, although apparently sharp and chilled, are not 

well exposed. On Mount Matheson the dikes intrude the 

Merrick Mountains stock and apparently crosscut mafic 

dikes; their age relative to the quartz veins and aplite, 

alaskite, and pegmatite dikes that cut the Merrick 

Mountains stock is not known. Some bodies that are 

lithologically similar and thus perhaps correlative occur in sedimentary rocks of the Latady Formation at 

Eaton Nunatak, at locality L58 about 4 km west of 

Eaton Nunatak, and at the southern end of locality 

VI78. Some of these bodies are dikes or small irregularly 

shaped hypabyssal intrusions, but others appear to be 

sills.

The rhyodacite contains as much as 15 percent 

phenocrysts that attain a maximum size of 4 mm and 

are set in an aphanitic groundmass. Approximately 75 

percent of the phenocrysts are "beta" quartz, most of

which show strong resorption in which embayments are 

filled with groundmass material. Many quartz 

phenocrysts are also fractured or cracked. The remaining phenocrysts or glomerocrysts are oligoclase accompanied by minor potassium feldspar and by much 

smaller and less numerous microphenocrysts of 

muscovite and pyrite. Plagioclase is generally very 

strongly sausseritized; potassium feldspar, however, is 

much less altered. Pale-green to colorless chlorite and 

radial aggregates of clinozoisite are common pseudomorphs after muscovite microphenocrysts. The groundmass of most of these dikes is massive mosaic-textured 

quartz containing minor amounts of plagioclase, pyrite, 

and apatite, and variable amounts of sericite. The 

groundmass quartz most likely represents devitrified 

glass. Miarolitic cavities are locally abundant in a dike 

from the southern slope of Mount Boyer. X-ray and optical examination of tabular to blocky crystals projecting into these cavities indicate that the crystals are 

sericitized (2Ml polymorph) plagioclasa A single chemical analysis and its CIPW norm are listed in table 1.

MIOCENE(?) BASANITE

Miocene(?) nepheline-normative olivine-porphyritic 

basanite (an alkalic basalt) and basanitic breccia are the 

only rock types that crop out on a small (100 m long), 

low (30 m high) nunatak approximately 2.1 km southsouthwest of Mount Matheson. Halpern (1971) obtained 

a K-Ar whole rock date of 6 m.y. from this rock; the true 

age of this rock, however, is considered tentative because 

Halpern did not publish analytical data for the age. 

Although most of the outcrop consists of frost-shattered 

rubble, interpretation of the small amount of rock that 

is in place suggests that a single subaerial lava flow 

stratigraphically overlies a more voluminous basanitic 

breccia and suggests that the exposed section is no more 

than 10-12 m thick.

The breccia consists of subrounded to subangular 

clasts (as much as 5 cm long) of black highly vesicular 

aphanitic to olivine-porphyritic basanite set in a brown 

slightly palagonitized matrix of ash to lapilli-sized 

fragments of basanitic glass. The overlying flow has a 

highly vesicular to scoriaceous surface and is lithologically identical to the breccia clasts.

Petrographically, the flow consists of fresh olivine 

microphenocrysts (maximum size 0.75 mm, average size 

0.3-0.5 mm), which show only slight resorption, set in 

a pilotaxitic groundmass of plagioclase laths, granular 

opaque minerals, pale-brown glass, and minor olivina 

Universal-stage measurement of 2V angles indicate a 

composition of Fo85 for the olivine (Deer and others, 

1966). If the plagioclase laths are assumed to be 

elongated on the a crystallographic axis, then extinction
MERRICK MOUNTAINS, EASTERN ELLSWORTH LAND 31

angles measured parallel to elongation yield a maximum 

anorthite composition of An55 (Burri and others, 1967). 

The breccia matrix is vitrophyric and highly vesicular. 

Olivine microphenocrysts (0.1-0.5 mm) and randomly 

oriented plagioclase microlites, many of which are 

twinned on the Carlsbad law, are set in a dark-reddishblack, almost opaque, glassy groundmass. Plagioclase 

laths have the same composition as in the flow, but the 

olivine is higher in magnesium (Fo95). Around the 

margins of vesicles, the glass can be seen to be crowded 

with a myriad of minute opaque granules and prismatic 

crystallites. Some of the prismatic crystallites are 

apatite, but others have a 30-40° extinction angle and 

might be clinopyroxene. A few of the vesicles are lined 

with pale-yellow palagonite and (or) filled with an 

unidentified zeolite (slow elongation; parallel extinction; 

RI estimated at 1.50, 6=0.007). The single chemical 

analysis and accompanying normative mineralogy (table 

1; fig. 5) indicate that the analyzed sample is a basanite 

(Yoder and Tilley, 1962) that is very similar in composition to Miocene and Pliocene "basalt" from both the 

Hudson Mountains in western Ellsworth Land, 800 km 

west of the Merrick Mountains (Laudon, 1982), and from 

Marie Byrd Land (LeMasurier and Rex, 1982). The 

basanite is lithologically similar to hyaloclastite and 

basaltic lava flows recently discovered in the English 

Coast (fig. 1), 250 km northwest of the Merrick Mountains (O'Neill and Thomson, 1985).

LeMasurier and Rex (1982) presented convincing 

arguments that rocks of similar chemistry, age, and field 

relations (vitric clasts with lenses of holocrystalline lava) 

that are widespread throughout Marie Byrd Land and 

western Ellsworth Land are hyaloclastites that formed 

by eruption beneath a continental ice sheet. In spite of 

the vast distance separating these two areas, we suggest 

that based on a similar geologic setting the Merrick 

Mountains basanite is also a subglacial hyaloclastite.

GEOCHEMISTRY

Major element-oxide analyses, trace-element abundances, CIPW norms, and modes of nine plutonic rocks, 

six dikes, and the basanite lava flow are presented in 

table 1. Of the samples of plutonic rocks, two represent 

the older plutonic event (Ro500g, V178i). Samples V177a 

and 66-123, collected from the same area (fig. 3), probably represent the younger plutonic event. Compositions 

of rocks of both events locally appear to be chemically 

similar. Of the samples of dikes, sample Ro501h is from 

a dike related to, and cutting, plutonic rocks of the older 

plutonic event. Sample EE603 is from a rhyodacite porphyry dika The locations of analyzed samples are shown 

in figure 3.

Examination of a Harker silica-variation diagram (fig. 

6) reveals a calc-alkaline differentiation trend similar to 

that found in igneous rocks throughout the northern 

(Adie, 1955,1964) and southern (Laudon, 1982; Rowley 

and Williams, 1974, 1982) Antarctic Peninsula: as SiO2 

increases, MgO and total iron oxides decrease, while 

K2O and total alkalies increase; A12O3 and CaO, however, initially increase before beginning a slow decrease 

with increasing silica; sodium also increases slightly 

before becoming essentially constant, which is a relatively common feature in calc-alkaline rocks containing 

55-75 percent SiO2 .

The more mafic dikes of the Merrick Mountains are 

richer in MgO and total iron oxides and lower in A12O3 

than plutonic rocks with comparable SiO2 percentages. 

Otherwise, there are no appreciable chemical differences 

between the dikes and the plutonic rocks. Although 

corundum-normative igneous rocks are relatively uncommon in the Andean belt (Vennum, 1978), the Merrick Mountains rocks become corundum-normative at 

approximately 58.5 percent SiO2 . Laudon (1982) also 

reported a strong tendency for corundum-normative 

rocks to evolve with increasing differentiation throughout most of eastern Ellsworth Land. Cawthorn and 

Brown (1976) have shown that a crystallization trend 

from diopside-normative to corundum-normative rocks 

in differentiated calc-alkaline series can result from the 

fractional crystallization of hornblende from a diopsidenormative magma. One of the dikes (66-77) is also 

nepheline-normative, a rare but not a unique chemical 

feature in igneous rocks from the southern Antarctic 

Peninsula (Laudon, 1982).

When the analyses of table 1 are plotted on an alkalimagnesium-iron±manganese ternary diagram (fig. 7), 

they show the typical calc-alkaline trend (Nockolds and 

Alien, 1953) of late-stage alkali enrichment. If the 

analyses of the rhyodacite porphyry dike (EE603) and 

one of the granodiorites (V178i) are ignored, however, the 

overall intermediate composition of the Merrick Mountains rocks is emphasized by only a moderate increase 

in alkali elements with differentiation. The alkali-lime 

(Peacock) index of the Merrick Mountains stock is approximately 58 (fig. 6), close to that (59) for intrusive 

rocks of eastern Ellsworth Land (Laudon, 1982) and 

comparable to that (61) for intrusive rocks of the 

Lassiter Coast (Rowley and Williams, 1974). Relative 

abundance of CaO, K2O, and Na2O are shown in a 

ternary diagram (fig. 8), which also indicates a typical 

calc-alkaline trend. If the rhyodacite porphyry and 

granodiorite analyses are again ignored, the analyzed 

samples form a relatively small cluster near the CaO corner of the diagram and show only a moderate increase 

in K2O with increasing differentiation.

Ytterbium is the only trace or minor element whose
32 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

MJ o co o

LLJ CC CDCC

18 r 

I 13

12

18

15

i i i i

10

J___L

10

+ 

O (81 

2

i i i i I ii i ill

i i

5 

45

FIGURE 6. Harker silica-variation diagram for analyzed samples of igneous rocks from the Merrick Mountains.
MERRICK MOUNTAINS, EASTERN ELLSWORTH LAND 33

Fe2O3+FeO+MnO

EXPLANATION

 Plutonic rocks

X Mafic dikes

o Basanite

O Rhyodaclte porphyry dike

Na2 0+K2 0 MgO

FIGURE 7. Ternary plot of total alkalies and magnesium, iron, and 

manganese expressed as oxides in igneous rocks of the Merrick 

Mountains.

KoO

EXPLANATION

 Plutonic rocks

X Mafic dikes

o Basanite

D Rhyodacite porphyry dike

Na2O CaO

FIGURE 8. Ternary plot of sodium, calcium, and potassium expressed 

as oxides in igneous rocks of the Merrick Mountains.

concentration remains relatively constant. Cobalt, chromium, nickel, and manganese oxide all steadily decrease 

as SiO2 increases. These elements are all concentrated 

in mafic silicates and (or) oxides, and their decrease is 

obviously related to the corresponding decrease in these 

minerals with increasing differentiation. Copper also 

generally decreases with increasing SiO2 , although two 

of the analyzed samples are almost devoid of this element. Titania, however, remains relatively constant and 

does not begin to noticeably decrease in abundance until the more felsic end of the suite has evolved. Cobalt 

in excess of nickel, as in the Merrick Mountains rocks, 

is unusual in most calc-alkaline suites; Adie (1955) and 

Vennum (1978) have, however, previously noted this 

feature in plutonic rocks of the Antarctic Peninsula. 

Scandium, vanadium, and P2O5 increase to maximum 

concentrations at about 54 percent SiO2 , then slowly 

decrease in more felsic samples. The behavior of 

vanadium and P2O5 is believed attributable to fractional crystallization of opaque minerals and apatite, 

respectively. Molybdenum and lead were detected in 

only the most felsic samples analyzed.

REFERENCES CITED

Adie, R. J., 1955, The petrology of Graham Land; II, The Andean 

granite-gabbro intrusive suite: Falkland Islands Dependencies 

Survey Science Report 12, 39 p.

___1964, The geochemistry of Graham Land, in R. J. Adie, ed., Antarctic Geology: Amsterdam, North Holland Publishing Company, 

p. 541-547.

Behrendt, J. C., and Parks, P. E., 1962, Antarctic Peninsula Traverse: 

Science, v. 137, p. 601-602.

Burri, Conrad, Parker, R. L., and Wenk, Eduard, 1967, Die optische 

orientierung der plagioklase: Basel, Birkhauser Verlag, 334 p.

Cawthorn, R. G., and Brown, P. A., 1976, A model for the formation 

and crystallization of corundum-normative calc-alkaline magmas 

through amphibole fractionation: Journal of Geology, v. 84, 

p. 467-476.

Crame, J. A., 1981, Preliminary bivalve zonation of the Latady Formation: Antarctic Journal of the United States, v. 16, p. 8-10.

Deer, W. A., Howie, R. A., and Zussman, J., 1966, An Introduction 

to the Rock-Forming Minerals: New York, John Wiley and Sons, 

Inc., 528 p.

Dott, R. H., Jr., 1964, Wacke, graywacke and matrix What approach 

to immature sandstone classification?: Journal of Sedimentary 

Petrology, v. 34, p. 625-632.

Ellsworth, Lincoln, 1936, My flight across Antactica: National 

Geographic Magazine, v. 70, p. 1-35.

Farrar, Edward, McBride, S. L., and Rowley, P. D, 1982, Ages and tectonic implications of Andean plutonism in the southern Antarctic Peninsula, in Campbell Craddock, ed., Antarctic Geoscience: 

Madison, University of Wisconsin Press, p. 349-356.

Halpern, Martin, 1967, Rubidium-strontium isotopic age measurements of plutonic igneous rocks in eastern Ellsworth Land and 

northern Antarctic Peninsula: Journal of Geophysical Research, 

v. 72, p. 5133-5142.
34 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

___1971, Evidence for Gondwanaland from a review of West Antarctic radiometric ages, in L. C. Quam, ed., Research in Antarctica: 

Washington D.C., American Association for the Advancement of 

Science, p. 717-730.

Laudon, T. S., 1972, Stratigraphy of eastern Ellsworth Land, in R. J. 

Adie, ed., Antarctic Geology and Geophysics: Oslo, Universitetsforlaget, p. 215-223.

___1982, Geochemistry of Mesozoic and Cenozoic igneous rocks, 

eastern Ellsworth Land, in Campbell Craddock ed., Antarctic Geoscience: Madison, University of Wisconsin Press, p. 775-785.

Laudon, T. S., Lackey, L. L., Quilty, P. D., and Otway, P. M., 1969, Geology of eastern Ellsworth Land, in V. C. Bushnell and Campbell 

Craddock, eds., Geologic maps of Antarctica: New York, American 

Geographical Society, Antarctic Map Folio Series 12, plate 3.

LeMasurier, W A., and Rex, D. C., 1982, Volcanic record of Cenozoic 

glacial history in Marie Byrd Land and western Ellsworth LandRevised chronology and evaluation of tectonic factors, in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of 

Wisconsin Press, p. 725-734.

Nockolds, S. R., and Alien, R. A., 1953, The geochemistry of some igneous rock series, 1: Geochimica et Cosmochimica Acta, v. 4, 

p. 105-142.

O'Neill, J. M., and Thomson, J. W, 1985, Tertiary mafic volcanic and 

volcaniclastic rocks of the English Coast, Antarctica: Antarctic 

Journal of the United States, v. 20, no. 5, (in press).

Plummer, C. C., 1974, Contact metamorphism of the Latady Formation, southern Lassiter Coast, Antarctic Peninsula: Antarctic Journal of the United States, v. 9, p. 82-83.

Quilty, P. G., 1970, Jurassic ammonites from Ellsworth Land, Antarctica: Journal of Paleontology, v. 44, p. 110-116.

___1972, Middle Jurassic brachiopods from Ellsworth Land, 

Antarctica: New Zealand Journal of Geology and Geophysics, v. 

15, p. 140-147.

Ronne, Finn, 1949, Antarctic Conquest, the story of the Ronne Expedition 1946-1948: New York, G. P. Putnam and Sons, 299 p.

Rowley, P. D., 1978, Geologic studies in Orville Coast and eastern 

Ellsworth Land, Antarctic Peninsula: Antarctic Journal of the 

United States, v. 13, p. 7-9.

Rowley, P. D., Farrar, Edward, and McBride, S. L., 1976, Preliminary 

interpretation of potassium-argon ages of plutons in the northern 

Lassiter Coast and southern Black Coast, Antarctica: Antarctic 

Journal of the United States, v. 11, p. 257-258.

Rowley, P. D, and Pride, D. E., 1982, Metallic mineral resources of the 

Antarctic Peninsula, in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of Wisconsin Press, p. 859-870.

Rowley, P. D, Schmidt, D. L., and Williams, P. L., 1982, Mount Poster 

Formation, southern Antarctic Peninsula and eastern Ellsworth 

Land: Antarctic Journal of the United States, v. 17, p. 38-39.

Rowley, P. D., Vennum, W. R., Kellogg, K. S., Laudon, T. S., Carrara, 

P. E., Boyles, J. M., and Thomson, M. R. A., 1983, Geology and 

plate tectonic setting of the Orville coast and eastern Ellsworth 

Land, Antactica, in R. L. Oliver, P. R. James, and J. B. Jago, eds., 

Antarctic Earth Science: Canberra, Australian Academy of 

Science, p. 245-250.

Rowley, P. D., and Williams, P. L., 1974, Plutonic rocks of the Lassiter 

Coast: Antarctic Journal of the United States, v. 9, p. 225-226.

___1982, Geology of the northern Lassiter Coast and southern 

Black Coast, Antarctic Peninsula, in Campbell Craddock, ed., 

Antarctic Geoscience: Madison, University of Wisconsin Press, 

p. 339-348.

Rowley, P. D, Williams, P. L., and Pride, D. E., 1983, Mineral occurrences of Antarctica, in J. C. Behrendt, ed., Petroleum and Mineral 

Resources of Antarctica: U.S. Geological Survey Circular 909, 

p. 25-49.

Rowley, P. D, Williams, P. L., and Schmidt, D. L., 1977, Geology of 

an Upper Cretaceous copper deposit in the Andean province, 

Lassiter Coast, Antarctic Peninsula: U.S. Geological Survey Professional Paper 984, 36 p.

Rowley, P. D, Williams, P. L., Schmidt, D. L., Reynolds, R. L., Ford, 

A. B., Clark, A. H., Farrar, Edward, and McBride, S. L., 1975, Copper mineralization along the Lassiter Coast of the Antarctic Peninsula: Economic Geology, v. 70, p. 982-987.

Shapiro, Leonard, and Brannock, W. W, 1962, Rapid analysis of silicate, 

carbonate, and phosphate rocks: U.S. Geological Survey Bulletin 

1144-A, 56 p.

Streckeisen, Albert, 1976, Tb each plutonic rock its proper name: EarthScience Review, v. 12, p. 1-33.

Streckeisen, A. L., 1979, Classification and nomenclature of volcanic 

rocks, lamprophyres, carbonatites and melilitic rocks Recommendations and suggestions of the IUGS subcommission on the 

systematics of igneous rocks: Geology, v. 7, p. 331-335.

Steiger, R. H., and Jager, E., 1977, Subcommission on geochronology 

Convention on the use of decay constants in geo-[sic] and cosmochronology: Earth and Planetary Science Letters, v. 36, p. 359-362.

Swithinbank, Charles, Doake, Christopher, Wager, Andrew, and Crabtree, Richard, 1976, Major change in the map of Antarctica: Polar 

Record, v. 18, p. 295-308.

Thomson, M. R. A., 1980, Late Jurassic ammonite faunas from the 

Latady Formation, Orville Coast: Antarctic Journal of the United 

States, v. 15, p. 28-30.

___1982, Mesozoic paleogeography of western Antarctica, in Campbell Craddock, ed., Antarctic Geoscience: Madison, University of 

Wisconsin Press, p. 331-337.

Thomson, M. R. A., Laudon, T. S., and Boyles, J. M., 1978, Stratigraphical studies in Orville Coast and eastern Ellsworth Land: 

Antarctic Journal of the United States, v. 13, p. 9-10.

Turner, F. J., 1968, Metamorphic Petrology Mineralogical and Field 

Aspects: New York, McGraw-Hill, 403 p.

Vennum, W. R., 1978, Igneous and metamorphic petrology of the 

southwestern Dana Mountains, Lassiter Coast, Antarctic Peninsula: U.S. Geological Survey Journal of Research, v. 6, p. 95-106.

Williams, P. L., Schmidt, D. L., Plummer, C. C., and Brown, L. E., 1972, 

Geology of the Lassiter Coast area, Antarctic Peninsula A 

preliminary report, in R. J. Adie, ed., Antarctic Geology and 

Geophysics: Olso, Universitetsforlaget, p. 143-148.

Yoder, H. S., and Tilley, C. E., 1962, Origin of basalt magma; an experimental study of natural and synthetic rock systems: Journal 

of Petrology, v. 3, p. 342-353.
Porphyry-type Copper Deposits 

and Potassium-Argon Ages of 

Plutonic Rocks of the 

Orville Coast and 

Eastern Ellsworth Land, 

Antarctica

By PETER D. ROWLEY, EDWARD FARRAR, PAUL E. CARRARA, 

WALTER R. VENNUM, and KARL S. KELLOGG

STUDIES OF THE GEOLOGY AND MINERAL RESOURCES 

OF THE SOUTHERN ANTARCTIC PENINSULA AND 

EASTERN ELLSWORTH LAND, ANTARCTICA

U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 135 1-C

Work done in cooperation with 

the National Science Foundation

Description of two newly discovered Andean mineral deposits, 

which have affinities to the porphyry copper class 

but have no economic potential

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1988

CONTENTS

Page

Abstract ................................................................... 35

Introduction ................................................................ 35

Acknowledgments ........................................................... 36

Potassium-argon ages of plutonic rocks ......................................... 37

Sky-Hi Nunataks copper deposit ............................................... 39

Merrick Mountains copper deposit ............................................. 44

Discussion ................................................................. 46

Conclusions ................................................................ 48

References ................................................................. 48

ILLUSTRATIONS

Page

FIGURE 1. Map of the Orville Coast and eastern Ellsworth Land, Antarctica ........ 36

2. Geologic map of the Sky-Hi Nunataks ............................... 39

3. Ternary plots of selected modal and normative minerals from dated igneous

units, Orville Coast and eastern Ellsworth Land, Antarctica ......... 40

4. Geologic map of the Merrick Mountains ............................. 45

TABLES

Page

TABLE 1. Potassium-argon ages of plutons in the Orville Coast and eastern Ellsworth

Land, Antarctica .............................................. 37

2. Modal analyses and locations of dated samples, Orville Coast and eastern

Ellsworth Land, Antarctica ..................................... 38

3. Modal analyses of fresh igneous rocks from the the Sky-Hi Nunataks copper

deposit, Antarctica ............................................ 40

4. Chemical data of selected fresh rocks from the Sky-Hi Nunataks copper deposit,

Antarctica ................................................... 41

5. Semiquantitative spectrographic analyses of fresh, altered, and mineralized rocks

from the Sky-Hi Nunataks and Merrick Mountains, Antarctica ...... 42

STUDIES OF THE GEOLOGY AND MINERAL RESOURCES OF THE SOUTHERN 

ANTARCTIC PENINSULA AND EASTERN ELLSWORTH LAND, ANTARCTICA

PORPHYRY-TYPE COPPER DEPOSITS AND POTASSIUM-ARGON AGES

OF PLUTONIC ROCKS OF THE ORVILLE COAST

AND EASTERN ELLSWORTH LAND, ANTARCTICA

By PETER D. ROWLEY', EDWARD FARRAR2 , PAUL E. CARRARA', 

WALTER R. VENNUMS , and KARL S. KELLOGG'

ABSTRACT

Two weakly mineralized and hydrothepmally altered, Lower 

Cretaceous hypidiomorphic-granular (granitoid) plutons occur in the 

Orville Coast and eastern Ellsworth Land, Antarctica. The first, the 

Sky-Hi stock, and its crosscutting dacite porphyry dikes contain 

disseminated pyrite, magnetite, chalcopyrite, and related secondary 

minerals, and the same minerals are concentrated in associated quartz 

veins; average metal additions, however, probably do not exceed 200 

ppm (parts per million) copper and 50 ppm zinc. Most plutonic rocks 

are propylitically altered and are transected by abundant sheared zones 

that consist of phyllic and subordinate argillic and sparse potassic 

rocks. The second pluton, the Merrick Mountains stock, partly consists of a mafic quartz diorite containing related crosscutting mafic 

dikes. These intrusive rocks were transected by numerous randomly 

oriented shear planes and then intruded by a concentrically zoned 

quartz diorite and granodiorite and related crosscutting rhyodacite porphyry dikes. Added metallic minerals are like those in the Sky-Hi stock; 

average metal additions probably do not exceed 100 ppm copper. Large 

areas of the stock are propylitically altered, and parts are potassically altered; some rocks are transected by sparse sheared zones altered 

to phyllic and subordinate argillic rocks.

The Sky-Hi and Merrick Mountains copper deposits resemble the 

Lassiter Coast copper deposit, located 150 km northeast of the Orville Coast. All three deposits appear to represent deeply eroded 

noneconomic "plutonic" porphyry copper deposits. Isotopic ages show 

that these plutons and most of the other plutons in the southern Antarctic Peninsula and eastern Ellsworth Land belong to the Lassiter 

Coast Intrusive Suite, dated at 130-95 million years. Copper mineralization may be a local characteristic of upper parts of plutons of this 

suite. The plutons of the suite that are most likely to contain copper 

deposits are in more axial parts of the Antarctic Peninsula, where erosion has not cut down to as great a depth as it has in coastal areas.

U.S. Geological Survey.

Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6 

Canada. 

Department of Geology, Sonoma State University, Rohnert Park, Calif. 94928.

INTRODUCTION

The Orville Coast and parts of eastern Ellsworth Land 

of Antarctica were mapped geologically in reconnaissance during the 1977-78 field season. The area is underlain by Middle and Upper Jurassic sedimentary rocks 

of the Latady Formation that intertongue with calcalkaline volcanic rocks of the Mount Poster Formation, 

all of which were folded and then intruded by Lower 

Cretaceous calc-alkaline hypidiomorphic-granular 

(granitoid) plutons (Rowley, Vennum, and others, 1983). 

During the field studies, two of these plutons, one in the 

Sky-Hi Nunataks and the other in the Merrick Mountains (fig. 1), were found to be hydrothermally altered 

and weakly mineralized. These plutons were given 

greater attention during the fieldwork and subsequent 

laboratory studies, and they were dated by K-Ar 

(potassium-argon) techniques. Preliminary results of the 

studies were discussed by Rowley, Farrar, and others 

(1982, 1983).

The geology and the alteration-mineralization 

assemblages and patterns in the two plutons in the field 

area are nearly identical to those of the Lassiter Coast 

copper deposit (Rowley and others, 1975; Rowley and 

others, 1977) located in the Copper Nunataks about 

150 km northeast of the Orville Coast (fig. 1). The 

Lassiter Coast copper deposit formed during two pulses 

of Early Cretaceous plutonism (Farrar and others, 1982). 

The older pulse involved emplacement of hypidiomorphic-granular granodiorite followed by intrusion of 

mafic dikes and then by "crackling" (that is, facturing 

along numerous criss-crossing shear planes of small

35
36 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

74° W 72° W 70° W 68° W

EASTERN

ELLSWORTH

LAND

Area of 

figure 2

Ke193d

40 60 KILOMETERS

I_____|

FIGURE 1. Orville Coast and eastern Ellsworth Land, Antarctica, 

showing major rock exposures (stippled) and sample number and 

locality (dots) of rocks whose ages are reported in table 1. Also shows 

locations of areas of figures 2 and 4. On the insert index map that 

shows the area of figure 1, location of the Lassiter Coast copper 

deposit is shown by a mine symbol, and edges of ice shelves are shown 

by hachured lines. See Rowley, Vennum, and others (1983, fig. 2) for 

the geologic map of the area

displacement) and pyritization along randomly oriented 

shear planes. The younger pulse involved emplacement 

of hypidiomorphic-granular granite followed by intrusion 

of dacite porphyry dikes and then by shearing and 

related phyllic-argillic alteration and porphyry copper 

mineralization. Dikes, sheared zones, and extension 

joints in both plutons of the Lassiter Coast deposit 

strike northwest, parallel to extension joints in the 

folded Latady Formation, which strikes northeast. 

Pyrite, chalcopyrite, magnetite, molybdenite, and related 

minerals were introduced by hydrothermal solutions during the mineralization; average metal additions (that is, 

additions in content of metallic elements to the rocks) 

in the most mineralized nunatak, however, do not appear 

to average more than 200 ppm (parts per million) copper, 100 ppm lead, and 50 ppm molybdenum. The effects 

of potassic alteration were only recently recognized in 

thin section by the presence of scattered fine-grained

subhedral aggregates of hydrothermal biotite replacing 

primary hornblende. The potassic alteration as well as 

apparently attendant propylitic alteration occurred during two periods: (1) when relatively coarse-grained 

hydrothermal brown and light-brown biotite and 

associated minor rutile formed after intrusion of the 

granodiorite pluton and its mafic dikes and perhaps 

prior to "crackling;" and (2) when sparse fine-grained 

hydrothermal brown and light-brown biotite and 

associated minor rutile formed after intrusion of the 

younger porphyry dikes and perhaps prior to phyllicargillic alteration. The Lassiter Coast deposit and the 

two deposits discovered during the 1977-78 field season 

are of too low grade to be economic, even if they were 

located in a climate favorable for development.

K-Ar ages were determined for the pluton in the SkyHi Nunataks and for barren plutonic rocks elsewhere in 

the Orville Coast and eastern Ellsworth Land in order 

to determine regional relationships of plutonic rocks. 

The K-Ar analyses were done by Edward Farrar from 

samples collected during the 1977-78 season; the 

analyses were reported in preliminary form by Farrar 

and Rowley (1980). This present report gives the final 

analytical data (table 1) for the K-Ar ages, and describes 

the Sky-Hi and Merrick Mountains copper deposits.

Outcrop numbers given in the text refer to rock 

nunataks or parts of nunataks that were studied. Each 

outcrop may have rock types of differing lithology or 

origin. When rocks were sampled they were assigned the 

same whole number as the outcrop; letters and even 

subscripts appended to the outcrop number refer to different samples.

ACKNOWLEDGMENTS

J. M. Boyles, T. S. Laudon, and M. R. A. Thomson, 

as members of the 1977-78 field party, greatly contributed to the geologic mapping and study of the SkyHi Nunataks and Merrick Mountains. We are deeply 

grateful to them for their help in field and other aspects 

of the study. Conversations with D. P. Cox were extremely valuable in clarifying concepts about porphyry 

deposits. M. D. Turner played a key role in logistical matters that allowed field and laboratory studies to be dona 

Logistical support by other members of the U.S. Antarctic Research Program of the National Science Foundation, and by U.S. Navy Operation Deep Freeze is also 

acknowledged. Many samples used in this study were 

recovered by divers of the U.S. Navy after some rock 

boxes were dropped overboard during offloading cargo 

ships in California; without the help of these divers, as 

well as of M. D. Turner, C.H. Nordhill, and Sam Feola,
ORVILLE COAST AND EASTERN ELLSWORTH LAND 

TABLE 1. Potassium-argon ages of plutons in the Orville Coast and eastern Ellsworth Land, Antarctica

[Locations and rock types given in table 2. Constants used: X = 0.581 X 10 1 . \, = 4.962 X KT^yT1 , 40K = 0.01167 atomic

37

Sample 

No.

C2

Ke193d

Ro44ld

Ro498j

Vl48a

Mineral 

analyzed

Biotite

Biotite

Hornblende

Biotite

Hornblende

Hornblende

Biotite

Hornblende

Hornblende

Hornblende

Hornblende

Biotite

Potassium 

(weight 

percent)

5.145

5.145

0.584

6.530

0.643

0.643

6.789

0.459

0.459

0.957

0.957

6.400

Ar (radiogenic)

cm3 NTP/g 

x10~5

21 .27

22.85

2.548

27.29

2.835

2.895

29.59

2.222

2.273

4.321

4.010

29.80

Percent 

total

82.7

81.4

60.1

85.9

82.6

82.0

90.2

70.3

71 .0

89.1

87.3

90.0

'Age +_ 2a 

(Ma)

103.4_+1 .5

1 1 0 . 8jM . 5

108.9jM .6

104.5^1.5

110.0+_1 .6

1 1 2 . 3 +_1 . 6

108.8_+1 .6

1 20 . 5jM . 7

123.U1 .8

1 1 2 . 6+_ 1 . 6

104.711 .5

1 1 6 . 0 +_1 . 6

1 a= Standard deviation,

the study could not have been completed. K-Ar analyses 

were performed by Edward Farrar in the laboratory of 

the Institute of Nuclear Science, Department of Scientific and Industrial Research, Lower Hutt, New Zealand; 

he thanks C. J. Adams and J. E. Gabites for use of the 

laboratory and for many types of assistance during the 

work. We appreciate the aid of D. L. Schmidt, C. H. Thorman, and D. P. Cox for technical reviews of the report; 

of C. G. Cunningham for assistance with microscope 

work on fluid inclusions; and of A. M. Kaplan for 

petrographic studies of some plutonic rocks. K-Ar 

studies were supported by a grant to Farrar from the 

National Science and Engineering Research Council of 

Canada; the rest of the field and laboratory work was 

supported by National Science Foundation grants 

DPP76-12557, DPP78-24214, and DPP80-07388 to the 

Geological Survey.

POTASSIUM-ARGON AGES 

OF PLUTONIC ROCKS

Plutonic rocks of gabbro to granite composition are 

widespread in the southern Antarctic Peninsula and 

eastern Ellsworth Land. All plutons that have been 

dated range from 130 to 95 m.y. (million years), Early 

Cretaceous (Halpern, 1967; Mehnert and others, 1975; 

Pankhurst, 1980; Farrar and others, 1982). The products 

of this single broad period of calc-alkaline plutonism 

were named the Lassiter Coast Intrusive Suite by 

Rowley, Vennum, and others (1983).

Fresh plutonic rocks underlying both the Lassiter 

Coast and Merrick Mountains copper deposits previously have been isotopically dated. The K-Ar ages of igneous rocks of the Lassiter Coast copper deposit are 108 

m.y. for the granodiorite pluton, and 97 m.y. for both the
38 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

granite that cuts the granodiorite and the dacite porphyry dike that cuts the granite (Farrar and others, 

1982; corrected for new constants, Steiger and Jager, 

1977). The older of two plutonic bodies that make up 

the Merrick Mountains stock yielded a Rb-Sr isochron, 

from rocks at Mount Berger, of 107 m.y. (Halpern, 1967; 

corrected for new constants, Steiger and Jager, 1977). 

Plutonic rocks from the Orville Coast and eastern 

Ellsworth Land that have been dated also belong to the 

Lassiter Coast Intrusive Suite. The geology of the dated 

plutons was summarized by Farrar and Rowley (1980). 

Sample locations are shown in figure 1. Petrographic information and location descriptions of dated rocks are 

given in table 2; rock names are from Streckeisen (1976). 

Of the five dated plutons, the Sky-Hi stock (sample 

Ro498j) is 122 m.y based on the average of two concordant ages on hornblende splits. Younger porphyritic 

dikes, altered rocks, and mineralized rocks probably 

formed during late phases of this plutonism. Mineralization in the Sky-Hi stock thus is older than that of the 

Lassiter Coast and Merrick Mountains copper deposits.

The next oldest pluton in the field area is the Haggerty 

Peak pluton, which is exposed over a 5 km by 3 km area 

in the southeastern Sweeney Mountains. Only its eastern 

contact is exposed; at the outcrop the rock is a fine- to 

medium-grained monzodiorite and quartz monzodiorite. 

The pluton appears to be compositionally zoned with a 

more silicic interior, for it grades in a short distance 

westward through medium-grained (crystals of 15 mm 

long) granodiorite into medium-grained granite and 

granodiorite. Sample V148a has an age of about 114 m.y. 

based on the average of two concordant ages on hornblende and biotite (table 1). We do not know the reason 

for an age of 105 my. on hornblende, which we reject.

The Witte pluton occurs over an area of about 1 km 

in diameter in the Witte Nunataks, but only its southeastern contact is exposed. Most of the rock is mediumgrained granodiorite, but at the contact it consists of 

fine- to medium-grained diorite and quartz diorite. Sample Ro441d has an age of about 110 m.y. based on the 

average of three concordant ages on hornblende and 

biotite (table 1).

TABLE 2. Modal analyses and locations of dated samples, Orville Coast and eastern Ellsworth Land, Antarctica

[Modal analyses given in volume percent; 500 points counted on thin sections and stained rock slabs. All rocks contain poikilitic K-feldspar crystals that 

lack grid twinning and plagioclase crystals that are mostly zoned. Chlorite replaces biotite in all rocks. Locations from British Antarctic Survey 1:500,000 

map of Orville Coast (Sheet SS17-20/SE), TV., trace]

Sample No.- C2 Ke193d Ro44ld Ro498j Vl48a

Plagioclase -

K-feldspar -

Quartz -

Biotite -

Hornblende -

Chlorite -

Fe-Ti Oxides -

Sphene -

Ap at i t e -

Z ircon -

Epidote -

 33.6

 33.6

 18.2

 8.0

 6.0

--- 0.6

 Tr.

 Tr.

 Tr.

 0

 0

42.8

12.8

31 .2

9.2

3.0

0.6

0.4

Tr.

Tr.

0

0

50.3

12.2

23.7

3.4

9.2

0.2

0.8

Tr.

Tr.

0

0

50.6

19.5

17.3

1 .4

7.0

1 .8

2.2

Tr.

Tr.

Tr.

Tr.

39.4

25.0

23.2

4.8

6.2

0.4

1 .0

Tr.

Tr.

0

0

SAMPLE DESCRIPTION AND LOCALITY

C2. Medium-grained hypidiomorphic-granular granite of the Mount Smart

pluton. Sample from south flank of Mount Smart, lat 75° 17' S., long

70° 14' W., southwest Sweeney Mountains. 

Ke193d. Medium-grained hypidiomorphic-granular granodiorite of the Stanton

batholith. Sample from the Stanton Hills, west of the Behrendt Mountains,

19 km N. 74° W. from Mount Chandler, lat 75° 14' S., long 73° 13' W. 

Ro44ld. Medium-grained hypidiomorphic-granular granodiorite of the Witte pluton.

Sample from lat 75° 28' S., long 69° 22' W., north Witte Nunataks. 

Ro498j. Medium-grained hypidiomorphic-granular quartz monzodiorite of the

Sky-Hi stock. Sample from lat 74° 55' S., long 71° 19' W., southeast

Sky-Hi Nunataks. 

Vl48a. Medium-grained hypidiomorphic-granular granite from the Haggerty Peak

pluton. Sample from south flank of Haggerty Peak, lat 75° 18' S.,

long 68° 12' W., southeast Sweeney Mountains.
ORVILLE COAST AND EASTERN ELLSWORTH LAND

The Stanton batholith is exposed in the Stanton 

Hills4, about 10 km west of the Behrendt Mountains, 

where it underlies an area about 12 km (north-south) by 

7 km (east-west) in size; the western contact of the pluton 

is not exposed. In most places the pluton consists of 

medium- to coarse-grained granodiorite, but at its contact it consists generally of somewhat more mafic 

granodiorite or quartz diorite. Sample Kel93d has an 

age of 109-105 m.y. based on somewhat discordant ages 

on hornblende and biotite, respectively, from a sample 

collected from a slightly more mafic margin of the compositionally zoned body (table 1). The margin of the 

pluton probably crystallized before the interior of the 

body, and the biotite age may represent resetting of the 

"atomic clock" during the continued crystallization of 

the interior or during younger crystallization of biotite 

due to lower temperature retention; the older age for the 

pluton is preferable.

The Mount Smart pluton is exposed over a 3 km by 

2 km area in the southwestern Sweeney Mountains. Only 

its western contact is exposed; at the exposure the rock 

is a medium- to coarse-grained diorite and quartz diorite, 

but most of the body east of the contact appears to consist of medium- to coarse-grained granite. Sample C2 has 

an age of 111-103 m.y. based on two discordant ages on 

biotite from the same sample (table 1). The discordance 

probably is due to inhomogeneity in the biotite split 

(Farrar and Rowley, 1980).

SKY-HI NUNATAKS COPPER DEPOSIT

The study of the Sky-Hi Nunataks began during the 

1961-62 Antarctic Peninsula Traverse, when one nunatak was visited and later briefly described (Laudon and 

others, 1964). The rest of the nunataks were first mapped 

during the 1977-78 field season (Rowley, 1978; Rowley, 

Vennum, and others, 1983). They consist mostly of folded 

volcanic rocks of the Mount Poster Formation, into 

which plutonic rocks were emplaced (fig. 2). Intertongued sandstone and siltstone of the Latady Formation, locally containing marine fossils, underlie several 

small outcrops in the southwestern part of the nunataks. 

In this area, the main rock type of the Mount Poster 

Formation is a resistant, thick, dark-green, generally 

massive rhyodacite that in most places contains abundant large phenocrysts of feldspar and "beta" quartz. 

This rock type is widespread in eastern Ellsworth Land 

(Laudon, 1972) and the Orville Coast and seems to be one 

or more ash-flow tuff sheets (Rowley, Vennum, and others, 

1983). The strike of the stratified rocks in the Sky-Hi 

Nunataks appears to be northwest or west-northwest.

The Sky-Hi copper occurrence, discovered by Carrara 

and Kellogg during the 1977-78 season, has been

Name proposed in 1985 to the U.S. Board on Geographic Names.

71° 30' W

39

71° 00' W

10 KILOMETERS

EXPLANATION

Plutonic rock } CRETACEOUS

Mount Poster Formation

JURASSIC

Latady Formation

STRIKE AND DIP OF BEDS 

AXIAL PLANE CLEAVAGE

FIGURE 2. Geologic map of the Sky-Hi Nunataks, showing numbered 

outcrops referred to in the text. The area in the lower right corner 

is expanded (dashed lines) to show details of the Ski-Hi porphyry copper deposit. Geology by J. M. Boyles, P. E. Carrara, K. S. Kellogg, 

T. S. Laudon, P. D. Rowley, M. R. A. Thomson, and W. R. Vennum

mentioned in previous reports (Rowley, 1978, 1979; 

Rowley and Pride, 1982; Rowley, Williams, and Pride, 

1983, in press; Rowley, Ford, and others, 1983). This 

deposit is exposed along a narrow, partly snow-covered 

ridge, about 1.5 km long and with relief of about 15 m, 

in the southeastern part of the Sky-Hi Nunataks. This 

ridge is underlain by plutonic rocks, defined here the SkyHi stock, that belong to the Lassiter Coast Intrusive 

Suite. No intrusive contact with the older volcanic rocks 

is exposed. Modal analyses and chemical analyses of fresh 

igneous rocks from the ridge are given in tables 3 and 

4, and figure 3, and semiquantitative spectrographic analyses of fresh, altered, and mineralized rocks are given in 

table 5.

Rocks that are hydrothermally altered to propylitic 

facies make up most of the narrow, snow-covered ridge; 

the rocks are cut by numerous sheared phyllic-argillic 

zones and have been mineralized by iron and copper 

sulfides and oxides. The sheared phyllic-argillic zones are 

as wide as 15 m, but generally are less than 3 m, and are
40 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

TABLE 3. Modal analyses of fresh igneous rocks from the Sky-Hi Nunataks copper deposit, Antarctica

[Modal analyses given in volume percent; 500 points counted on thin sections and stained rock slabs. Modal analysis of sample Ro498j given in table 2, Tr., trace]

Sample No. 

Plagioclase 

Hornblende 

Chlor i te 

Fe-Ti oxides 

t\^jd u j. u c

Epidote 

Pyrite 

Granodiorite pluton

Ro498b

55.8 

15.0 

15.8 

1.6 

10.1

0.4 

0.8 

Tr. 

0.2 

0

0 

0 

0 

0

Ro498d2

53.9 

10.9 

23.0 

2.6 

2.2

6.4 

1 .2 

Tr. 

Tr. 

0

0 

Tr. 

Tr. 

0

Ro498m

48.0 

18.2 

20.7 

0.8 

10.2

0.8 

1 .2 

Tr. 

Tr. 

Tr.

0 

0 

0 

0

Mafic dike

Kel84c

0 

0 

0 

0 

0

0 

0 

0 

0 

0

0 

0 

0 

100.0

Porphyritic dacite dike

C55c

15.8 

0.2 

0.6 

0 

7.4

Tr. 

0.4 

Tr. 

Tr. 

0

0 

0.2 

Tr. 

75.4

Kel84a

13.0 

0 

0 

0 

16.4

Tr. 

1.2 

0.8 

Tr. 

0

0.6 

0.2 

0.4 

67.4

Ro498g

9.2 

0 

1.5 

0 

12.2

Tr. 

0.6 

Tr. 

Tr. 

Tr.

0 

0.2 

Tr. 

76.2

Ro498h

9.0 

0 

0.4 

0 

9.6

0.2 

0.4 

Tr. 

Tr. 

0

0 

0.8 

Tr. 

79.6

Quartz

10

K-feldspar 

(including albite)

Plagioclase Or

Quartz -~y~7 

syenite //

Syenite/ M/lonzonite/ / 

Monzodiorite/ 

monzogabbro

 v \xQuartz diorite, 

v \ "\quartz gabbro 

\ -V- Diorite. gabbro 

"Quartz monzodiorite. 

quartz monzogabbro

B

EXPLANATION

MOUNT SMART PLUTON 

STANTON BATHOLITH 

WITTE PLUTON 

SKY-HI STOCK 

MAFIC DIKE, SKY-HI 

PORPHYRITIC DACITE

DIKE, SKY-HI 

HAGGERTY PEAK PLUTON

FIGURE 3. Ternary plots of selected modal and normative minerals 

from dated igneous units, Orville Coast and eastern Ellsworth Land, 

Antarctica. Calculated from data in tables 2, 3, and 4, and from unpublished data of P. D. Rowley. Boundaries shown in A and B follow 

igneous classification of International Union of Geological Sciences 

(Streckeisen, 1976) which is shown in C. A, Modal quartz, K-feldspar, 

and plagioclase in fresh igneous rocks. Mafic dike of the Sky-Hi stock 

not plotted. B, Normative quartz (Q), orthoclase (Or), and plagioclase 

(Ab+An) in fresh igneous rocks.

distributed about every 10-20 m or less along the ridge. 

The zones are identical to zones in the Lassiter Coast 

copper deposit (Rowley and others, 1977). Most strike 

north-northeast, perpendicular to the regional strike of 

the folded rocks (west-northwest) and parallel to extension joints in both plutonic rocks and folded Jurassic 

rocks. They contain sparse to locally abundant fault 

planes generally less than a centimeter wide and along 

which the rock is broken and sheared by relative movement. In most other places in the sheared phyllic-argillic 

zones, however, the rock is not foliated or does not show 

any evidence of faulting. The sheared phyllic-argillic zones 

are recognized by their alteration, consisting mostly of 

tan to brown crumbly phyllically and subordinate argillically altered rock that weathers to form shallow rounded 

erosional trenches as deep as 0.5 m. The altered rock in 

the erosional trenches grades within several centimeters 

into almost ubiquitous propylitically altered rock. Two 

alteration events seem to have taken place in the sheared 

phyllic-argillic zones. The older event was potassic alteration, which may have the same age as the propylitically 

altered rock that is widespread outside the zones. The 

younger event was the phyllic-argillic alteration that characterizes most zones; it locally chlorltized and sericitized 

the crystals of presumed potassic hydrothermal biotite. 

Mineralized quartz veins, generally less than 1 cm 

wide, occur sparsely (rarely more than one vein every 

5 or 10 m of rock outcrop) and randomly distributed 

along the ridge. The veins generally strike northnortheast and do not appear to have envelopes of 

altered rocks. Where quartz veins occur within sheared
ORVILLE COAST AND EASTERN ELLSWORTH LAND

TABLE 4. Chemical data of selected fresh rocks from the Sky-Hi Nunataks copper deposit,

Antarctica

[Sample localities shown in figures 2 and 4. Kg, granodiorite pluton; Kd, mafic dike; Kp, porphyritic dacite dike; ( ) leaders, 

not present. Analyses of samples Eo498j and Kel84c by D. Hopping and J. Eiviello; analysis of sample Eo498g by S. 

Kramer. Semiquantitative spectrographic analyses of these samples given in table 5]

41

Rock unit 

Sample no. 

Si02

A1 2 03

Fe2°3

FeO

MgO

CaO

Na 2 0

K2 0

H2 0-

H2 0+

Ti02

P2°5

MnO

Total

Q

C

Or

Ab

An

Wo

En

Fs

Mt

11

Ap

Total

Kg

DrtA QQ -i K.O'+yoj

Chemical

63.33

16.41

2.66

2.25

1.94

5.48

2.85

2.58

.07

.80

.47

.17

.10

99.11

CIPW Norms

22.686

15.384

24.335

24.585

.721

4.875

1.356

3.892

.901

.406

99.142

TT J

K.d

Kel84c

analyses (weight percent)

50.55

18.32

4.16

6.00

4.85

6.47

3.22

1.07

.23

3.69

.95

.09

.07

99.67

(weight percent)

4.102

.318

6.344

27.337

31.614

12.119

6.163

6.052

1.810

.214

96.073

Kp

Ro498g

54.23

18.10

4.05

3.93

4.20

8.15

2.87

2.21

.11

.94

.66

.19

.17

99.81

6.482

13.084

24.331

30.035

3.854

10.480

3.103

5.883

1.256

.451

98.960
42 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

TABLE 5. Semiguantitative spectragraphic analyses of fresh, altered, and mineralized rocks from the Sky-Hi Nunataks

[Analyses listed by rock units, arranged in the order they are discussed in the text. Sample 

localities shown in figures 2 and 4. FA, fresh to propylitically altered aplite of younger 

pluton; FG, fresh to propylitically altered granodiorite; FM, fresh to propylitically altered 

mafic dike; FO, fresh to propylically altered older mafic pluton; FP, fresh to propylitically altered porphyry dike; FY, fresh to propylitically altered younger silicic pluton; PF, 

peripheral fresh or slightly mineralized rock; PS, peripheral sheared phyllic-argillic zone;

Rock 

unit

SPA

SPA

SPA

SPA

SPA

SPA

SPA

SPA

SPA

S

S

S

S

FM

FG

FG

FP

FP

PF

PS

PS

PV

PV

PV

PV

SPA

SPA

S

S

S

FO

FO

FO

FY

FY

FY

FY

FY

FA

Sample 

No.

Si Al Fe Mg

Kel84b G 10 3 .5

Kel84d G 10 2 .7

Ro498e G 10 31

Ro498e 2 23 7.9 3.5 1.3

Ro498f G 10 3 .7

Ro498f 2 20 6.5 3.4 .9

Ro498i 29 7.6 4.1 1.0

Ro4981 28 7.9 3.9 .6

Ro498n G 10 2 1

Ro498c 29 7.5 3.4 1.0

Ro498d G 10 3 .7

Ro498d 2 23 8.8 5.2 .7

Ro498o G 10 2 .7

Kel84c G G 10 3

Ro498j G G 5 1

Ro498m G 10 3 1

Ro498g 24 7.9 6.2 2.4

Ro498h 22 8.6 6.3 2.3

V173g 33 7.1 4.1 .8

C57c >34 1.3 .8 .1

C57d >34 6.1 2.7 .3

By52a G 5 10 1

L55a G 7 2 .5

L55b G 7 5 .7

V173f >34 1.3 1.9 .2

Ro500c G 7 7 2

Ro500k G 5 3 1.5

By56d G .5 3 .07

V177c G 10 5 2

V178h G .5 G .02

Ro500h 10 3 G 2

Ro501g G 10 7 2

Ro501h G 7 7 3

By56f G G 7 1.5

RoSOOa G G 7 1.5

V177a G G 10 1.5

V178i G 10 3 .3

V178f G 10 7 2

V177k G 10 7 1.5

Weight percent

Ca Na K Ti Ag

Sky-Hi

5 2 1.5 .2 N

3 23 .2 N

5 33 .31

3.7 .9 3 .15 <.l

7 53 .15 N

3.4 3.3 1.6 .13 .3

2.1 2.8 2.1 .13 .6

5.0 2.8 1.3 .13 <.l

3 35 .3 N

3.2 2.8 1.8 .17 <.l

2 5 2 .2 1.5

2.9 >7 1.5 .15 4

2 23 .2 N

7 5 1.5 3 N

7 3 3 3 N

5 33 .3 N

3.9 1.6 1.8 4 <.l

6.7 3.9 1.5 .21 <.l

1.8 2.1 3.9 .35 <.l

.03 .01 .3 .04 7.4

.26 .4 5.2 .19 38

5 .5 .7 .3 10

3 .75 .2 N

1 .52 .25

.6 .1 .1 .04 24

Me r rick

7 32 .IN

1.5 11 .2 N

.01 N N .01 50

3 .73 .3 1.5

.05 N .7 .07 1.5

3 .5 .7 1.5 1

7 33 .5 N

7 23 .2 N

5 33 .3 N

5 33 .5 N

7 3 .7 .3 N

1.5 55 .15 N

7 2 1.5 .3 N

5 33 .3 N

PV, peripheral vein; S, silicified area or quartz vein; SPA, sheared phyllic-argillic zone. 

Analysis of sample Eo498g by L. Mei; of C57c, C57d, Eo498c, Ro498d2, Ro498e2, Ro498f2, 

Ro498h, Ro498i, Ro4981, V173f, and V173g by J. L. Harris; and of the rest by J. C. 

Hamilton. Value of Ce for V173g: 110 ppm; value of Gd for V173g: 21 ppm; value of Li 

for C57a: 97 ppm; value of Li for C57d: 130 ppm; value of Sn for By52a: 15 ppm; value 

of Sn for Ro498f: 5 ppm. For all other samples, As, Au, Cd, Ce, Ge, Hf, In, Li, Pd, Pt,

Parts per million

B Ba Be Bi Co Cr Cu Ga La Mn

Nunataks

N

N

20

27

L

22

<5

<5

N

7

N

6

N

N

N

N

<10

<7

<5

<5

6

N

N

L

<5

300

500

200

410

150

140

270

370

1,000

520

300

290

500

700

500

1,000

360

270

870

70

680

70

1,000

200

50

1.5

N

1.5

2

N

1

1

<1

N

1

N

<1

N

N

1.5

N

1

<1

2

1

1

1.5

N

1.5

<1

N

N

N

<10

N

<10

<10

<10

N

<10

N

<10

N

N

N

N

<15

<10

<10

<10

26

30

N

10

24

N

N

10

12

15

9

11

7

10

11

7

14

7

50

15

15

18

24

9

<1

6

30

L

20

6

3

3

5

3

5

2

4

13

5

4

3

4

3

10

7

3

9

10

33

2

43

15

15

15

2

30

50

150

68

150

100

530

210

100

270

700

800

150

200

50

300

23

90

44

46

440

7,000

15

3,000

2,600

15

20

20

15

20

13

22

17

15

16

15

16

15

30

15

15

17

23

16

3

12

15

15

15

3

L

L

N

19

L

19

17

19

N

19

N

<10

N

N

N

N

29

17

48

<10

39

70

L

L

<10

2,000

500

1,000

1,700

1,500

2,500

1,700

1,100

500

640

500

1,000

300

700

700

500

2,200

1,900

650

120

1,500

2,000

700

700

330

Mountains

N

100

N

30

N

N

N

N

N

N

N

N

N

N

200

150

150

150

20

150

500

100

1,000

1,000

300

700

300

1,000

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

700

N

50

N

N

N

N

N

N

N

N

N

20

15

100

30

L

70

20

30

15

20

20

7

30

15

7

3

L

10

L

3

7

70

7

7

20

L

20

N

70

50

500

10,000

3,000

1,500

150

2

70

100

100

7

150

30

15

15

N

15

-

~

30

15

20

20

15

15

15

30

N

N

N

N

N

N

N

N

N

N

N

N

N

N

1,500

1,000

70

2,000

300

1,000

1,000

1,000

700

700

700

300

700

700
ORVILLE COAST AND EASTERN ELLSWORTH LAND 43

Merrick Mountains, Antarctica

Re, Sb, Sn, Sr, la, Te, Th, Tl, U, and W were not detected or were at limit of detection. For 

the samples analyzed by Mei and Harris, Dy, Er, Eu, Gd, Ho, Ir, Lu, Nd, Os, Pr, Ru, Sm,

Tb, and Th were less than the limit of detection. G, greater than 10 percent; N, not detected

or at limit of detection; L, detected but below limit of detection; leaders ( ), not looked 

for; <, less than: >. more thanl

Parts per mill

Mo

3

7

N

a

N

<1

10

°

3

<!

N

<1

30

N

N

5

<2

<l

<!

110

<1

N

30

10

<1

Nb

N

N

N

5

N

6

4

4

N

9

N

5

N

N

N

N

8

6

11

<3

6

N

10

10

<3

Ni

N

N

5

5

5

4

6

4

5

5

5

6

5

20

7

5

17

12

12

<2

21

15

10

15

<2

Pb

Skv-Hi

15

10

30

12

20

32

12

14

N

13

30

81

N

N

N

N

<7

16

16

70

1,900

200

30

150

500

Sc Sr

Nunataks Co

7 1

10 1

15

9

15

8

8

9

15

10

10

8

7

30

15 1

15 1

24

20

19

2

9

15

15

15

2

Merrick Moun

N

N

N

N

N

N

N

N

N

N

N

30

N

N

N

N

N

N

N

N

10

N

10

L

N

N

N

N

7

5

L

7

L

20

7

30

7

7

10

N

20

N

10

50

200

200

300

10

N

N

N

N

N

15

N

N

15

15

L

30

7

30

30 1

30

20

30

50

7

30

20 1

,000

,000

500

280

500

450

470

830

700

640

500

320

500

500

,000

,000

840

750

210

45

140

200

150

100

97

ion

V

ntin

70

100

100

80

70

64

76

100

100

92

70

49

70

300

150

100

230

160

74

45

51

50

50

50

13

Y

ued

30

30

30

9

30

11

9

9

30

13

20

6

15

15

20

30

20

9

37

6

16

70

30

70

12

Yb

3

3

3

2

3

2

1

1

3

2

3

1

1.5

2

3

3

3

2

5

1

2

7

3

5

1

Zn

700

N

N

84

N

55

69

33

N

25

N

110

N

N

N

N

48

60

35

16

280

700

N

1,500

71

Zr

150

150

150

53

70

59

37

71

70

98

70

58

70

50

70

100

62

48

230

45

84

150

150

150

82

tains Continued

200

150

N

200

N

150

,000

500

700

700

500

500

700

,000

100

70

7

150

70

500

200

150

150

200

300

30

200

150

20

15

N

30

N

30

30

15

30

30

30

30

15

30

3

1.5

N

3

3

1.5

3

3

3

3

3

3

N

N

N

300

700

500

N

N

N

N

N

N

N

N

70

100

N

50

20

30

50

30

70

50

30

100

30

100

phyllic-argillic zones, they are younger than the shearing in the phyllic-argillic zones; their age with respect to

the alteration, however, could not be determined. Small

irregularly shaped masses of silicified rock locally occur

in or adjacent to the sheared phyllic-argillic zones.

Oxidation of the primary sulfide minerals leaves the

rocks locally stained by yellow and orange secondary iron

minerals and green secondary copper minerals; the yellow

and orange stains look like limonite or hematite in hand

specimen, and the green stains look like malachite. X-ray

studies, however, indicate that here and in other parts of

West Antarctica, these all are complex minerals typical of

very dry climates (Vennum, 1980; Vennum and Nishi,

1981). The yellow and orange minerals are iron sulphates,

mainly minerals of the jarosite group, with or without

gypsum. The green minerals are copper sulfates and copper chlorides.

The best exposures of the Sky-Hi stock are on the northern part of the narrow ridge. The rock is a resistant homogeneous light- to medium-gray, medium-grained (1-5 mm)

hypidiomorphic-granular granodiorite. It contains subhedral plagioclase, subordinate K-feldspar, quartz, and

hornblende, minor biotite and Fe-Ti oxides5 , and traces

of sphene, apatite, and zircon (tables 2, 3). Both quartz

and K-feldspar crystals are poikilitic. Most plagioclase

crystals are zoned. Chlorite is common in fresh to propylitically altered rocks, where it replaces biotite; leucoxene replaces sparse sphene in some rocks. Fine-grained

diorite inclusions as long as 5 cm and sparse aplite dikes

rarely wider than 5 cm are scattered through the granodiorite. The rocks are cut by subvertical shear joints that

strike northwest and subvertical extension joints that

generally strike north-northeast; the latter are coated

with epidote and chlorite.

Two resistant light- to medium-greenish-gray dikes of

dacite porphyry cut the plutonic rocks. One on the northeastern end of the ridge is about 0.5 m wide and strikes

north-northeast (sample Ro498g; tables 3, 4); the other

crops out as a small exposure at the southwestern end of

the ridge where the thickness and strike are indeterminate. Both may represent porphyry intrusions typically

associated with porphyry-type mineralization, as in the

Lassiter Coast copper deposit. The dike rock consists of

sparse to moderately abundant phenocrysts of hornblende

and plagioclase, and minor "beta" quartz and Fe-Ti oxides

in an aphanitic groundmass of plagioclase, K-feldspar,

quartz, hornblende, and Fe-Ti oxides (table 3). Both dikes

are locally altered and mineralized. A third dike consists

of aphanitic, somewhat more mafic rock (sample Kel84c;

tables 3, 4), is as much as 6 m wide, and strikes northwest.

Pyrite is disseminated throughout the intrusive rocks

of the ridge. Pyrite, as well as magnetite and chalcopyrite

5Opaque minerals, consisting of magnetite, ilmenite, pyrite, and related minerals, which contain iron and (or) titanium.
44 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

in many places, also occurs in quartz veins. Despite the 

presence of primary and secondary metallic minerals in 

the Sky-Hi stock, average metal additions to the intrusive 

rocks are low. Semiquantitative spectrographic analyses 

(table 5) show only small additions in copper and, in 

places, zinc, lead, molybdenum, and silver whether the 

samples were collected from sheared phyUic-argUlic zones 

(9 samples: 30-530 ppm Cu, 15-700 ppm Zn, 7-30 ppm 

Pb, 1-10 ppm Mo, 0.1-1 ppm Ag), silicified areas and 

quartz veins (4 samples: 150-800 ppm Cu, 15-110 ppm 

Zn, 7-80 ppm Pb, 1-30 ppm Mo, 0.1-4 ppm Ag), fresh 

to propylitically altered granodiorite or mafic dikes (3 

samples: 50-300 ppm Cu, 1-5 ppm Mo, 15-50 ppm Co), 

or fresh to propylitically altered porphyry dikes (2 samples: 20-90 ppm Cu, 50-60 ppm Zn, 7-16 ppm Pb). On 

the basis of these analyses from outcrops C55, Kel84, 

and Ro498 on the ridge, it is doubtful that the average 

metal additions to the rocks of the ridge exceed 200 ppm 

Cu and 50 ppm Zn.

Higher metal additions occur in peripheral hydrothermal quartz veins that cut volcanic country rocks elsewhere in the Sky-Hi Nunataks. These veins are most 

abundant in nunataks close to, and northwest of, the SkyHi stock (table 5). At outcrop C57 (Mount Carrara6), 

abundant north-northeast-striking sheared phyllic-argillic 

zones as much as 3 m wide and locally overlapping northnortheast-striking quartz veins contain pyrite and magnetite. One sample from a sheared phyllic-argillic zone at 

this outcrop has moderate amounts of molybdenum (110 

ppm) and silver (7 ppm), and low amounts of lead (70 

ppm) and copper (50 ppm); whereas, another sample from 

another nearby zone has moderate amounts of silver (40 

ppm), lead (1,900 ppm), zinc (260 ppm), and copper (440 

ppm). At outcrop L55 (Mount Carrara), north-northeaststriking locally brecciated quartz veins and mineralized 

sheared phyllic-argillic zones as much as 7 m wide contain 

pyrite, secondary iron minerals, and secondary copper 

minerals. In one of these zones, moderate concentrations 

of copper (3,000 ppm), zinc (1,500 ppm), lead (150 ppm), 

and silver (5 ppm) occur in a rock containing magnetite, 

chalcocite(?), and secondary copper minerals. In a quartz 

vein containing secondary copper minerals in another 

sheared phyllic-argillic zone at this outcrop, low values 

of molybdenum (10 ppm) and lead (30 ppm) were noted.

At outcrop VI73 farther west, a 1-m-wide, west-northwest-striking sheared phyllic-argillic zone contains secondary copper minerals. A nearby float sample of a quartz 

vein containing magnetite, pyrite, chalcopyrite, and secondary copper minerals contains moderate values of copper (2,600 ppm), lead (500 ppm), and silver (24 ppm), and 

low values of zinc (70 ppm). A bedrock sample of porphyritic rhyodacite containing pyrite cubes, from elsewhere

Name proposed in 1985 to the U.S. Board on Geographic Names.

on the nunatak, however, is essentially barren of added 

base and precious metals. Two other sheared zones, one 

striking east and the other north, are as wide as 7 m but 

have no visible metallic minerals and were not sampled. 

Still farther northwest (By5 2), east-striking copperstained quartz veins in porphyritic rhyodacite have 

moderate concentrations of copper (7,000 ppm), zinc 

(700 ppm), lead (200 ppm), and silver (10 ppm). Other 

quartz veins at this outcrop, not analyzed, strike northnortheast but have no recognizable metallic minerals. 

North of the Sky-Hi stock, at outcrops Kel85 and Ro497, 

quartz veins in porphyritic rhyodacite are barren, and at 

Kel86, a locally silicified sheared phyllic-argillic zone, 0.5 

m wide and striking north-northwest, contains oxidation 

products of iron oxides and sulfides.

Microscopic study shows that most rock in the sheared 

phyllic-argillic zones is of the phyllic alteration facies. In 

other words, the rocks have been almost totally sericitized. Hornblende and biotite have been converted to sericite and subordinate chlorite and pyrite. Quartz generally 

is the only remaining primary mineral, and locally it grew 

during alteration. Most primary Fe-Ti oxide minerals have 

been altered to pyrite. Pyrite also was introduced along 

joints in or near phyllic-argillic zones. Sheared and 

foliated recrystallized rock is seen in some thin sections 

from the zones; in most places this sheared rock is of 

argillic facies. Most argillically altered rock occurs, however, at the edges of phyllic-argillic zones. In argillically 

altered rock, plagioclase is generally converted to montmorillonite and kaolinite, K-feldspar is partly converted 

to sericite, hornblende, and biotite are partly converted 

to chlorite and subordinate epidote, and Fe-Ti oxides are 

partly converted to pyrite and leucoxena

Microscopic study shows that the propylitically altered 

rocks contain small amounts of the same alteration products as argillically altered rocks. Epidote and chlorite are 

especially noticeable in rocks of this alteration facies. 

Potassic alteration, which form the highest temperature 

facies of alteration in many porphyry mineral deposits, 

is weakly developed in the Sky-Hi Nunataks. It is recognized only by the presence, as seen in thin section, of very 

fine grained subhedral sucrose aggregates of hydrothermal light-brown biotite, perhaps locally associated with 

tiny masses of rutile, replacing primary hornblenda

MERRICK MOUNTAINS COPPER DEPOSIT

The Merrick Mountains area was first mapped during 

the 1965-66 field season (Laudon and others, 1969; 

Laudon, 1972). It was mapped in greater detail during 

the 1977-78 season, at which time evidence of alteration 

and copper mineralization was recognized. The area is 

underlain mostly by the Merrick Mountains stock of the 

Lassiter Coast Intrusive Suite (fig. 4). Vennum and
ORVILLE COAST AND EASTERN ELLSWORTH LAND 45

75° 

00' 

S

72° 15' W 72° 00' W

75' 

07' - 

30" 

S

5 KILOMETERS

J

Mount ffi 

Matheson b|^\

EXPLANATION

-Tb Basanite

Quartz diorite-granodiorite

TERTIARY

CRETACEOUS

Mafic quartz diorite

Latady Formation - JURASSIC 

CONTACT Dotted where concealed by ice 

ANTICLINE Dotted where concealed 

SYNCLINE Dotted where concealed 

STRIKE AND DIP OF BEDS

FIGURE 4. Geologic map of the Merrick Mountains showing 

numbered outcrops referred to in the text.

Laudon (chap. B, this volume) discuss the petrology and 

chemistry of the stock; table 5 presents semiquantitative spectrographic analyses of fresh, altered, and 

mineralized rocks of the stock. The stock was emplaced 

into folded sedimentary rocks of the Latady Formation

that strike west-northwest. The Latady Formation, 

which locally contains marine invertebrate fossils, is interbedded with lava flows and is intruded by sill-like 

masses. A Miocene!?) hyaloclastite basanite (that is, an 

alkaline basalt) lava flow underlies a small nunatak in 

the southwestern part of the range.

The Merrick Mountains stock was named by Vennum 

and Laudon (chap. B, this volume) for plutonic rock exposures in the central part of the range. As in many 

other places in the southern Antarctic Peninsula, including the Lassiter Coast copper deposit, the pluton 

is composite. It consists of an older semiconcentric outer 

body of black mafic quartz diorite intruded by a younger, gray, concentrically zoned quartz diorite to granodiorite body in which the most silicic rocks are near the 

center. Both plutonic bodies are hypidiomorphic-granular in texture and contain mafic inclusions. The younger body, and perhaps also the older body, are intruded 

by aplite and pegmatite dikes. Dark mafic dikes were 

emplaced at the close of both periods of plutonism; most 

strike northwest. Tan rhyodacite porphyry dikes, as wide 

as 10 m and mostly striking northerly, were emplaced 

after the mafic dikes of the younger plutonic body 

(chap. B, this volume). The porphyry dikes contain 

sparse to moderately abundant phenocrysts of "beta" 

quartz and subordinate plagioclase and K-feldspar in a 

fine-grained silicic groundmass (chap. B, this volume). 

Joints appear to be randomly oriented in the Merrick 

Mountains stock.

On the summit and southern flank of Mount Matheson (outcrop Ro501), the older mafic plutonic body is 

"crackled" by numerous (locally as abundant as one 

shear plane about every 10 cm) randomly oriented, black 

or gray, narrow (generally less than 2 cm wide) shear 

planes of minor displacement. Shearing appears to 

predate the younger plutonic body. No metallic minerals were found associated with the shear planes, in contrast to lithologically similar black and gray shear 

fractures containing pyrite in the Lassiter Coast copper deposit.

Magnetite, pyrite, and chalcopyrite, as well as secondary iron and copper minerals, are scattered throughout 

both intrusive bodies in both disseminated form and in 

widely scattered quartz veins (table 5). The wall rock 

surrounding the quartz veins apparently is not highly 

altered. Small amounts of copper and lead were noted 

in sheared phyllic-argillic zones (2 samples: 50-70 ppm 

Cu, 10-50 ppm Pb) from the southern flank of Mount 

Matheson (outcrop Ro501). Moderate to high amounts 

of copper, lead, silver, zinc, bismuth, and cobalt occur 

in quartz veins containing chalcopyrite from outcrops 

By56 and VI78 and in quartz veins containing secondary copper minerals from outcrop V177 (3 samples: 

500-10,000 ppm Cu, 200-300 ppm Pb, 2-50 ppm Ag,
46 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

15-700 ppm Zn, 10-700 ppm Bi, and 1-100 ppm Co). 

Low to moderate amounts of copper, zinc, cobalt, and 

chromium were noted in fresh to propylitically altered 

rocks of the older mafic body from outcrops RoSOO and 

Ro501 (3 samples: 2-1,500 ppm Cu, 15-500 ppm Zn, 

20-70 ppm Co, 3-70 ppm Cr). Low amounts of copper 

or molybdenum occur in fresh to propylitically altered 

rocks of the younger plutonic body, including an aplite, 

at outcrops By56, Ro500, V177, and V178 (6 samples: 

7-150 ppm Cu, 1-30 ppm Mo). It is doubtful whether 

the average grade of metal values in the stock exceeds 

100 ppm copper.

Sheared phyllic-argillic zones, as wide as 20 m, occur 

scattered through rocks in the western and southern 

parts of the Merrick Mountains stock. On parts of the 

summit and northern flank of Mount Matheson, the 

zones are almost as abundant (one every 20 m or less 

of rock exposure) as they are in the Sky-Hi copper occurrence, but elsewhere they are not abundant. Mineralized 

and hydrothermally altered rocks also are most abundant in the Mount Matheson area. The sheared zones 

appear to postdate all plutonic rocks and all dikes. Most 

zones strike north to northeast, parallel to extension 

joints, and they consist largely of phyllically altered 

rock. They are similar in field and petrographic appearances to those in the Sky-Hi and Lassiter Coast copper deposits. Silicified areas in which fine grained to 

coarsely crystalline quartz replace plutonic rock are visible locally within the zones.

Potassic alteration resulted in very fine grained, brown 

and light-brown, hydrothermal biotite, locally associated 

with tiny masses of apparent rutile, replacing hornblende in crackled older mafic plutonic rocks and in 

some dikes (chap. B, this volume, table 1, sample 

Ro501h) on the southern flank of Mount Matheson. Propylitic alteration, perhaps related in age to the potassic 

alteration, affected most parts of the Merrick Mountains 

stock. In some places, the older mafic quartz diorite is 

argillically or phyllically altered even where sheared 

phyllic-argillic zones are absent. Similarly, rhyodacite 

porphyry dikes may be almost entirely altered to argillic, 

or less commonly, to phyllic facies even where adjacent 

plutonic rock is of propylitic facies.

DISCUSSION

The Lassiter Coast, Sky-Hi, and Merrick Mountains 

copper deposits contain the most significantly hydrothermally altered and mineralized rocks recognized in 

the southern Antarctic Peninsula and eastern Ellsworth 

Land. None of them, however, are economically important. K-Ar dating indicates that these mineral deposits 

span the age of the Lassiter Coast Intrusive Suite; thus,

copper mineralization probably developed in upper parts 

of many other plutons of this suite. In contrast to these 

three moderately mineralized plutons, however, most 

other plutons of the Lassiter Coast Intrusive Suite are 

fresh or contain only widely scattered sheared phyllicargillic zones and very small amounts of pyrite, 

magnetite, chalcopyrite, and molybdenite crystals or 

small clusters of crystals, as well as related secondary 

minerals (Rowley and others, 1977; Rowley and Pride, 

1982; Rowley, Ford, and others, 1983). These other mostly barren plutons may have been eroded to deeper structural levels than the three copper-bearing plutons, or 

they were never mineralized as much as the three copperbearing plutons.

The host rocks of the three copper deposits are hypidiomorphic-granular plutonic rocks ranging from a 

concentrically zoned body of mostly granite (Lassiter 

Coast deposit) through granodiorite (Sky-Hi deposit) to 

a concentrically zoned body of mostly quartz diorite 

(Merrick Mountains deposit). All plutons appear to be 

partly syntectonic, due perhaps to intrusion in a 

residual stress field. This conclusion is made because 

orientation of extension joints, porphyry dikes, and 

shear zones are more or less parallel to extension 

joints in the folded Jurassic wall rocks. The plutons 

of all three deposits are cut by silicic porphyry dikes 

emplaced during the latest stages of the intrusive activity that predates hydrothermal alteration and 

mineralization. These dikes may represent the igneous 

material from which hydrothermal solutions were derived that altered and mineralized the rocks, or the dikes 

may have provided the heat by which meteoric solutions 

altered and mineralized the rocks. The plutonic events 

that led to the main mineralization and alteration were 

preceded in the Copper Nunataks and Merrick Mountains by a plutonic event of more mafic material that 

terminated in dike intrusion and in breaking (crackling) 

the mafic rocks along closely spaced and randomly 

oriented fractures.

Alteration and mineralization patterns and metallic 

mineral contents are remarkably similar in all three 

deposits. Most mineralized rocks apparently occur in 

quartz veins and disseminations. The major added primary minerals are pyrite, magnetite, chalcopyrite, and 

molybdenite. The main metal additions were iron, copper, lead, molybdenum, zinc, and silver. Regional minor 

potassic alteration, indicated only by sparse development of hydrothermal biotite and possibly related 

regional propylitic alteration probably predated the 

development of sheared phyllic-argillic zones, which are 

oriented parallel to regional extension joints. These 

sheared zones are conspicuous features that are either 

widely scattered or densely distributed. Phyllically 

altered rock dominates in the zones; silicified rocks occur
ORVILLE COAST AND EASTERN ELLSWORTH LAND 47

in localized patches within the zones, as are to be expected in areas of sericitic alteration.

Altered and mineralized rocks of the Lassiter Coast, 

Sky-Hi, and Merrick Mountains deposits bear resemblances to the classical porphyry copper system (Lowell 

and Guilbert, 1970) in geologic setting, in primary disseminated or quartz-vein ore minerals, in principal metal 

additions, and in associated potassic, phyllic, argillic, and 

propylitic alteration facies. None of our three mineral 

deposits, however, appears to have the grade or area! extent of commercial porphyry ore deposits. Nor are fractures or quartz veins as closely spaced as in commercial 

ore bodies. Fluid inclusions in quartz grains from fresh 

and altered rocks of all plutonic bodies and porphyry 

dikes of the three mineral deposits do not contain 

evidence (cubic crystals) of the high salinity typical of 

porphyry copper deposits (for example, Nash, 1976); inclusions are small (generally less than 5 microns) and 

relatively sparse; they consist of either a vapor phase or 

a vapor plus liquid phase.

Whereas some of the differences between our three 

deposits and commercial porphyry deposits may be attributable to lack of exposures due to snow and ice covers, 

certain differences cannot be explained by such lack of 

exposures. One of the most significant of these differences 

is the fact that the host rocks of all three deposits are 

plutonic rocks of hypidiomorphic-granular texture not 

the shallow silicic plutons consisting of phenocrysts set 

in a fine-grained groundmass that normally are the hosts 

for, and provide the name to, porphyry copper deposits. 

Probably the three deposits formed at a deeper level than 

those normally associated with classical porphyry deposits. In fact, no trace of any volcanic cover that probably overlay plutons of the Lassiter Coast Intrusive Suite 

has been recognized in the southern Antarctic Peninsula 

and eastern Ellsworth Land. Furthermore, only the 

"crackle" net in the older, more mafic intrusive bodies 

of the Lassiter Coast and Merrick Mountains deposits 

resembles the fine-scale fracturing characteristic of 

classical porphyry deposits. Perhaps the older, more 

mafic bodies did not intrude to as shallow a level in the 

crust as did the younger, more silicic bodies; if so, the 

present level of erosion has exposed features in the upper part of the more mafic bodies and features in the 

lower parts of the younger silicic ones.

The roots of porphyry ore deposits have not been well 

studied, although Lowell and Guilbert (1970) and Sillitoe 

(1973) have presented models that suggest that as one 

passes downward through the porphyritic cupola into its 

related hypidiomorphic-granular stock, the most likely 

alteration grade is potassic and propylitic, quartz veins 

become more important relative to disseminated sulfides, 

magnetite becomes more abundant than pyrite, and shatter nets are less likely. Below porphyry deposits, rocks

are probably hypidiomorphic-granular, unaltered, and unmineralized (Sillitoe, 1973), as in most exposed barren 

plutons. Cox and others (1981) were the first to describe 

a possible root zone, in which quartz grains in the hypidiomorphic-granular plutonic rocks contain fluid inclusions 

typical of porphyry deposits, but the rocks are low in copper. Hydrothermal biotite is absent in hypidiomorphic-granular plutonic rocks, indicating that the potassic 

alteration zone dies out at depth (Cox and others, 1981).

Another way to look at porphyry-type deposits that 

formed at greater depths in hypidiomorphic-granular 

plutonic host rocks is the "plutonic porphyry" model of 

Sutherland Brown (1969, 1976) and Sutherland Brown 

and others (1971). Several such deposits occur in the 

Canadian cordillera, as in the Highland Valley, Brenda, 

Gibraltar, and Endako areas (Field and others, 1974; 

Drummond and others, 1976; Kimura and others, 1976; 

McMillan, 1976; Nielsen, 1976; Soregaroli and Whitford, 

1976; Sutherland Brown, 1976). Others occur at Butte, 

Montana (Miller, 1973; Brimhall, 1979); Glacier Peak, 

Washington (Grant, 1969); Papua New Guinea (Grant and 

Nielsen, 1975); the Philippines (Bryner, 1969), and other 

areas (Nielsen, 1976). With the "plutonic porphyry" 

model, ore deposits commonly occur in concentrically 

zoned plutons that have undergone complex multiple intrusive activity. Younger dikes or small bodies of silicic 

porphyry commonly are genetically linked with the mineralization and alteration. The mineral deposits commonly are controlled by faults, fractures, or porphyry dikes. 

Pyritic areas are generally sparsely mineralized. In the 

plutonic porphyry model, mineralization and alteration 

lack the obvious concentric patterns of high-level classical 

porphyry deposits; instead, they are largely confined to 

a regular parallel or conjugate vein set. Alteration, especially of potassic grade, tends to be weakly developed in 

plutonic porphyry deposits; potassic alteration may be 

represented almost entirely by the introduction of hydrothermal biotite. Phyllic alteration may be confined to fracture zones or veins. Most of these characteristics are 

similar to those of the three deposits in the southern 

Antarctic Peninsula.

In Antarctica, minor copper deposits have been recognized within Mesozoic and Cenozoic hypidiomorphicgranular plutonic rocks on Livingston Island, Anvers 

Island, Adelaide Island, and the Argentine Islands, all 

off the western coast of the northern Antarctic Peninsula (Rowley and Pride, 1982; Rowley, Williams, and 

Pride, 1983, in press; Rowley, Ford, and others, 1983). All 

these may be of the plutonic porphyry type. Of these, the 

one on Anvers Island includes "dike-like bodies of 

recrystallised mylonite" affected by high-grade alteration 

(Hooper, 1962) that resemble the sheared phyllic-argillic 

zones we mapped. Of the deposits, a mineralized but 

noneconomic deposit in the Argentine Islands has been
48 GEOLOGY, MINERAL RESOURCES, SOUTHERN ANTARCTIC PENINSULA, EASTERN ELLSWORTH LAND

described in greatest detail (Hawkes and Littlefair, 

1981); its northern part contains quartz-magnetite veins 

and sparse quartz-molybdenite-chalcopyrite and quartzpyrite veinlets as well as potassically and propylitically altered rocks in plutonic rocks of 57-56 m.y. and 

within Upper Jurassic or Lower Cretaceous volcanic 

rocks intruded by the plutonic rocks. Hawkes and Littlefair (1981) considered the deposit to represent the root 

zone of a porphyry copper system. An adjacent area of 

propylitic-altered volcanic wall rocks contains linear 

sheared phyllic zones like the sheared phyllic-argillic 

zones we describe previously. Hawkes and Littlefair 

(1981) have suggested that the area of propylitic alteration and sheared phyllic zones is an upper peripheral 

part of the deposit that has been dropped down along 

a fault. On the basis of the geologic similarity of the 

Argentine Islands with the three deposits in the southern Antarctic Peninsula, it seems equally possible that 

this area of propylitic- and phyllic-altered rocks underwent no displacement or could even have been upthrown.

CONCLUSIONS

Ericksen (1976), Rowley and Pride (1982), and Rowley, 

Ford, and others (1983) have noted that the southern 

Andes of South America and the Antarctic Peninsula 

are nowhere near as rich in metal deposits as the northern and central Andes. Rowley and Pride (1982) suggested that the break between the metal-rich and 

metal-poor parts occurs where the Chile Ridge is subducted beneath southern Chile, at about 45 ° S. lat. The 

difference in mineralization may be related to different 

subduction histories north and south of the Chile Ridge 

during Cenozoic and perhaps also late Mesozoic time. 

Compared to the oceanic plate north of the Chile Ridge, 

the oceanic plate to the south experienced a complex 

subduction history (Herron and lucholke, 1976) and may 

have been warmer, thinner, softer, lighter, and younger 

(Forsyth, 1975; DeLong and Fox, 1977; Rowley, 1983). 

Relative to the northern and central Andes, plutons in 

the Antarctic Peninsula including the three we discuss 

in this report may have been less rich in metals or 

availability of meteoric water, may have had less favorable heat-volatiles-pressure conditions, may have been 

emplaced at different crustal levels, may have been 

generally older, or may have been more deeply eroded 

following emplacement.

The Lassiter Coast, Sky-Hi, and Merrick Mountains 

copper deposits resemble deeply eroded porphyry (that 

is, plutonic porphyry) deposits. We cannot answer with 

certainty whether the mineral occurrences we have 

mapped get richer at depth or whether they pass into 

unaltered and unmineralized plutonic rock. We suspect

the latter, however, because the host plutons are among 

the most westerly of all plutons mapped in the area. In 

other words, the plutons are close to the topographic 

axis of the Antarctic Peninsula and are not as deeply 

eroded as those exposed farther east, at lower altitudes 

closer to the coast. The lower altitude, eastern plutons 

are generally fresh. Plutonic rocks that are exposed even 

closer to the topographic axis than those described here 

are even more likely to contain mineralized and altered 

rocks, for they may not be as deeply eroded.

REFERENCES

Brimhall, G. H., Jr., 1979, Lithologic determination of mass transfer 

mechanisms of multiple-stage porphyry copper mineralization at 

Butte, Montana Vein formation by hypogene leaching and environment of potassium-silicate protore: Economic Geology, v. 74, 

p. 556-589.

Bryner, Leonid, 1969, Ore deposits of the Philippines An introduction to their geology: Economic Geology, v. 64, p. 644-666.

Cox, D. P., Czamanske, G. K., and Bain, J. H. C., 1981, Mineral-rich 

fluid inclusions in the root zone of a porphyry copper deposit, Ajo, 

Arizona (abs.): Geological Society of America, Abstracts with Programs, 1981, v. 13, no. 7, p. 433.

DeLong, S. E., and Fox, P. J., 1977, Geological consequences of ridge 

subduction, in Manik Talwani, and W. C. Pitman, III, eds., Island 

arcs, deep sea trenches, and back-arc basins, Maurice Ewing 

Series, v. 1: Washington, D.C., American Geophysical Union, 

p. 221-228.

Drummond, A. D., Sutherland Brown, A., Young, R. J., and Tennant, 

S. J., 1976, Gibraltar Regional metamorphism, mineralization, 

hydrothermal alteration and structural development, in A. 

Sutherland Brown, ed., Porphyry deposits of the Canadian Cordillera: The Canadian Institute of Mining and Metallurgy, Special 

Volume 15, p. 195-205.

Ericksen, G. E., 1976, Metallogenic provinces of southeastern Pacific 

region, in M. T. Halbouty, J. C. Maher, and H. K Lian, eds., CircumPacific energy and mineral resources: American Association of 

Petroleum Geologists, Memoir 25, p. 527-538.

Farrar, Edward, and Rowley, P. D., 1980, Potassium-argon ages of 

Upper Cretaceous plutonic rocks of Orville Coast and eastern Ellsworth Land: Antarctic Journal of the United States, v. 15, 

p. 26-28.

Farrar, Edward, McBride, S. L., and Rowley, P. D., 1982, Ages and tectonic implications of Andean plutonism in the southern Antarctic Peninsula, in Campbell Craddock, ed., Antarctic Geoscience: 

Madison, University of Wisconsin Press, p. 349-356.

Field, C. W, Jones, M. B., and Bruce, W. R., 1974, Porphyry coppermolybdenum deposits of the Pacific Northwest: Mining Engineering Society, American Institute of Mining Engineers, Transactions, 

v. 256, p. 9-22.

Forsyth, D. W, 1975, Fault plane solutions and tectonics of the South 

Atlantic and Scotia Sea: Journal of Geophysical Research, v. 80, 

p. 1429-1443.

Grant, A. R., 1969, Chemical and physical controls for base metal 

deposition in the Cascade Range of Washington: Washington Division of Mines and Geology Bulletin, no. 58, 107 p.

Grant, J. N., and Nielsen, R. L., 1975, Geology and geochronology of 

the Yandera porphyry copper deposit, Papua New Guinea: Economic Geology, v. 70, p. 1157-1174.
ORVILLE COAST AND EASTERN ELLSWORTH LAND 49

Halpern, Martin, 1967, Rubidium-strontium age measurements of 

plutonic igneous rocks in eastern Ellsworth Land and northern 

Antarctic Peninsula, Antarctica: Journal of Geophysical Research, 

v. 72, p. 5133-5142.

Hawkes, D. D., and Littlefair, M. J., 1981, An occurrence of molybdenum, copper, and iron mineralization in the Argentine Islands, 

West Antarctica: Economic Geology, v. 76, p. 898-904.

Herron, E. M., and Tucholke, B. E., 1976, Sea-floor magnetic patterns 

and basement structures in the southeastern Pacific, in C. D. 

Hollister, Campbell Craddock, and others, Initial reports of the 

Deep Sea Drilling Project: Washington, D.C., U.S. Government 

Printing Office, v. 35, p. 263-278.

Hooper, P. R., 1962, The petrology of Anvers Island and adjacent 

islands: Falkland Islands Dependencies Survey Scientific Reports, 

No. 34, 69 p.

Kimura, E. T., Bysouth, G. D., and Drummond, A. D., 1976, Endako, 

in A. Sutherland Brown, ed., Porphyry Deposits of the Canadian 

Cordillera: The Canadian Institute of Mining and Metallurgy, 

Special Volume 15, p. 444-454.

Laudon, T. S., 1972, Stratigraphy of eastern Ellsworth Land, in R. 

J. Adie, ed., Antarctic Geology and Geophysics: Oslo, Universitetsforlaget, p. 215-223.

Laudon, T. S., Behrendt, J. C., and Christensen, N. J., 1964, Petrology 

of rocks collected on the Antarctic Peninsula Traverse: Journal 

of Sedimentary Petrology, v. 34, p. 360-364.

Laudon, T. S., Lackey, L. L., Quilty, P. G., and Otway, P. M., 1969, 

Geology of eastern Ellsworth Land, in V. C. Bushnell, and Campbell Craddock, eds., Antarctic Map Folio Series: New York, 

American Geographical Society, Folio 12, pi. 3.

Lowell, J. D., and Guilbert, J. M., 1970, Lateral and vertical alterationmineralization zoning in porphyry ore deposits: Economic 

Geology, v. 65, p. 373-408.

McMillan, W. J., 1976, Geology and genesis of the Highland Valley 

ore deposits and the Guichon Creek batholith, in A. Sutherland 

Brown, ed., Porphyry deposits of the Canadian Cordillera: The 

Canadian Institute of Mining and Metallurgy, Special Volume 

15, p. 85-104.

Mehnert, H. H., Rowley, P. D., and Schmidt, D. L., 1975, K-Ar ages 

of plutonic rocks in the Lassiter Coast area, Antarctica: U.S. 

Geological Survey Journal of Research, v. 3, p. 233-236.

Miller, R. N., ed., 1973, Guidebook for the Butte field meeting of the 

Society of Economic Geologists: Society of Economic Geologists, 

sections A to Q.

Nash, J. T., 1976, Fluid-inclusion petrology Data from porphyry copper deposits and applications to exploration: U.S. Geological 

Survey Professional Paper 907-D, 16 p.

Nielson, R. L., 1976, Recent developments in the study of porphyry 

copper geology A review, in A. Sutherland Brown, ed., Porphyry 

deposits of the Canadian Cordillera: The Canadian Institute of 

Mining and Metallurgy, Special Volume 15, p. 487-500.

Pankhurst, R. J., 1980, Appendix, radiometric dating, in D. G. 

Singleton, The geology of the central Black Coast, Palmer Land: 

British Antarctic Survey Scientific Reports, No. 102, p. 49-50.

Rowley, P. D., 1978, Geologic studies in Orville Coast and eastern 

Ellsworth Land, Antarctic Peninsula: Antarctic Journal of the 

United States, v. 13, p. 7-9.

___1979, Geologic studies in Orville Coast and eastern Ellsworth 

Land: Antarctic Journal of the United States, v. 14, p. 21-22. 

_1983, Developments in Antarctic geology during the past half

century, in S. J. Boardman, ed., Revolution in the Earth 

Sciences Advances in the Past Half century: Dubuque, Iowa, 

Kendal/Hunt Publishing Company, p. 112-135. 

Rowley, P. D., Farrar, Edward, Carrara, P. E., Vennum, W. R., and 

Kellogg, K. S., 1982, Metallic mineral resources and K-Ar ages

of plutonic rocks of the Orville Coast and eastern Ellsworth Land, 

Antarctica [abs.]: Volume of Abstracts, Fourth International Symposium on Antarctic Earth Sciences, Adelaide University, South 

Australia, p. 144. 

_1983, Porphyry-type copper deposits and K-Ar ages of plutonic

rocks of the Orville Coast and eastern Ellsworth Land, Antarctica [abs.], in R. L. Oliver, P. R. James, and J. B. Jago, eds., Antarctic Earth Science: Canberra, Australian Academy of Sciences, 

p. 437.

Rowley, P. D., Ford, A. B., Williams, P. L., and Pride, D. E., 1983, 

Metallogenic provinces of Antarctica, in R. L. Oliver, P. R. James, 

and J. B. Jago, eds., Antarctic Earth Science: Canberra, 

Australian Academy of Science, p. 414-419.

Rowley, P. D., and Pride, D. E., 1982, Metallic mineral resources of 

the Antarctic Peninsula (Review paper), in Campbell Craddock, 

ed., Antarctic Geoscience: Madison, University of Wisconsin 

Press, p. 859-870.

Rowley, P. D., Vennum, W. R., Kellogg, K. S., Laudon, T. S., Carrara, P. E., Boyles, J. M., and Thomson, M. R. A., 1983, Geology 

and plate tectonic setting of the Orville Coast and eastern 

Ellsworth Land, Antarctica, in R. L. Oliver, P. R. James, and J. 

B. Jago, eds., Antarctic Earth Science: Canberra, Australian 

Academy of Science, p. 245-250.

Rowley, P. D., Williams, P. L., and Pride, D. E., 1983, Mineral occurrences of Antarctica, in J. C. Behrendt, ed., Petroleum and Mineral 

Resources of Antarctica: U.S. Geological Survey Circular 909, 

p. 25-49.

___(in press), Metallic and nonmetallic mineral resources of Antarctica, in R. J. Tingey, ed., Geology of Antarctica: London, Oxford University Press.

Rowley, P. D., Williams, P. L., and Schmidt, D. L., 1977, Geology of 

an Upper Cretaceous copper deposit in the Andean province, 

Lassiter Coast, Antarctic Peninsula: U.S. Geological Survey Professional Paper 984, 36 p.

Rowley, P. D., Williams, P. L., Schmidt, D. L., Reynolds, R. L., Ford, 

A. B., Clark, A. H., Farrar, Edward, and McBride, S. L., 1975, 

Copper mineralization along the Lassiter Coast of the Antarctic 

Peninsula: Economic Geology, v. 70, p. 982-987.

Sillitoe, R. H., 1973, The tops and bottoms of porphyry copper 

deposits: Economic Geology, v. 68, p. 799-815.

Soregaroli, A. E., and Whitford, D. F., 1976, Brenda, in A. Sutherland 

Brown, ed., Porphyry deposits of the Canadian Cordillera: The 

Canadian Institute of Mining and Metallurgy, Special Volume 

15, p. 186-194.

Steiger, R. H., and Jager, E., 1977, Subcommission on 

geochronology Convention on the use of decay constants in geo- 

[sic] and cosmochronology: Earth and Planetary Science Letters, 

v. 36, p. 359-362.

Streckeisen, Albert, 1976, To each plutonic rock its proper name: 

Earth-Science Reviews, v. 12, p. 1-33.

Sutherland Brown, A., 1969, Mineralization in British Columbia and 

the copper and molybdenum deposits: Canadian Institute of Mining and Metallurgy, Transactions, v. 72, p. 1-15.

___1976, Morphology and classification, in A. Sutherland Brown, 

ed., Porphyry deposits of the Canadian Cordillera: The Canadian 

Institute of Mining and Metallurgy, Special Volume 15, p. 44-51.

Sutherland Brown, A., Cathro, R. J., Panteleyev, A., and Ney, C. S., 

1971, Metallogeny of the Canadian Cordillera: Canadian Mining 

and Metallurgy, Bulletin, v. 64, no. 709, p. 37-61.

Vennum, W. R., 1980, Evaporite encrustations and sulphide oxidation products from the southern Antarctic Peninsula: New Zealand 

Journal of Geology and Geophysics, v. 23, p. 499-505.

Vennum, W. R., and Nishi, J. M., 1981, New Antarctic mineral occurrences: Antarctic Journal of the United States, v. 16, p. 14-15.

U.S. GOVERNMENT PRINTING OFFICE: 1988 573-047/66,050 REGION NO. 8