High-Alumina Hydrothermal Systems in 

Volcanic Rocks and their Significance to 

Mineral Prospecting in the Carolina 

Slate Belt 

U.S. GEOLOGICAL SURVEY BULLETIN 1562 

High-Alumina Hydrothermal Systems in 

Volcanic Rocks and their Significance to 

Mineral Prospecting in the Carolina 

Slate Belt 

B_v ROBERT G. SCHMIDT 

U.S. GEOLOGICAL SURVEY BULLETIN 1562 

Large alteration s_vstems in the slate belt have 

man r of the characteristics of high-alumina 

copper-, mol_vbdenum-, and gold-bearing deposits in other regions of the world 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1985 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Library of Congress Cataloging in Publication Data 

Schmidt, Robert Gordon 

High-alumina hydrothermal systems in volcanic rocks 

and their significance to mineral prospecting in the 

Carolina slate belt. 

(Geological Survey bulletin ; 1562) 

Bibliography: p. 53 

Supt, of Docs. no.: I. 19.3:1562 

1. Hydrothermal deposits-Middle Atlantic States. 2. 

Volcanic ash, tuff, etc.-Middle Atlantic States. 3. 

Prospecting-Middle Atlantic States. I. Title. II. 

Series. 

QE461.S35 1984 551.2'3 84-600129 

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Abstract 

Introduction ---------------------------------------------------------------------------------------------

Acknowledgments -------------------------------------------------------------------------------------

Metal deposits with associated zones of aluminous alterations in other regions ----

Examples in North America ------------------------------------------------------------------

Examples in South America ---------------------------------------------------------------

Large hydrothermal alteration zones and porphyry copper deposits of 

Kazakhstan --------------------------------------------------------------------------------

Examples in south Asia and Oceania ------------------------------------------------------

Hydrothermal clay deposits of Japan and Korea ----------------------------------------

General geology of the Carolina slate belt ---------------------------------------------------

Descriptions of selected high-alumina deposits in the Carolina slate belt 

The Brewer porphyry gold deposit ----------------------------------------------------------

General geology of the Pilot Mountain-Fox Mountain region (Ramseur 7 t' 

Quadrangle) ------------------------------------------------------------------------------

Pilot Mountain porphyry gold system ---------------------------------------------------

High-alumina deposits in Moore County ------------------------------------------------

Other deposits in North Carolina ----------------------------------------------------------

Origin and significance of the high-alumina alteration systems ------------------------

Summary --------------------------------------------------------------------------------------------

References cited ----------------------------------------------------------------------------------------

ILLUSTRATIONS 

Page 

1 

2 

9 

10 

10 

13 

15 

20 

22 

24 

28 

29 

36 

40 

49 

50 

51 

53 

53 

Page 

FIGURE 1. 

2. 

3. 

4. 

5. 

6. 

7. 

High-alumina alteration systems in the Carolina slate belt 3 

Porphyry copper deposits and other major hydrothermal 

alteration systems in central Kazakhstan, U.S.S.R. -------------- 16 

Schematic cross section of the North Kounrad alteration system 

and its copper ore body ----------------------------------------------------- 17 

Generalized geologic map of the Asheboro area, central North 

Carolina --------------------------------------------------------------------- 25 

Hydrothermal alteration at the Brewer mine, Chesterfield 

County, South Carolina ------------------------------------------- 32 

Hydrothermal alteration atPilot Mountain, Randolph County, 

North Carolina ---------------------------------------------------------- 42 

Soil sample analyses, Pilot Mountain area ---------------------------- 44 

III 
IV 

TABLE 1. 

2. 

CONTENTS 

TABLES 

Page 

Metals associated with selected pyrophyllite deposits -------------- 4 

Rapid rock analysis of topaz-rich hydrothermally altered rock 

from drill hole 8, 13.4-19.5 meters depth, Brewer mine area, 

South Carolina ------------------------------------------------------------ 35 

3. Analyses of hard rock with fresh pyrite from the Brewer mine 

area, South Carolina ---------------------------------------------- 36 

4. Semiquantitative spectrographic analyses of selected chip 

samples from U.S. Bureau of Mines drill holes, Brewer mine 

area, South Carolina ---------------------------------------------------- 37 

5. Analyses of 12 soil samples from unaltered felsic rock 

monadnocks, in ppm ------------------------------------------------------- 49 
HIGH-ALUMINA HYDROTHERMAL 

SYSTEMS IN VOLCANIC ROCKS AND 

THEIR SIGNIFICANCE TO 

MINERAL PROSPECTING IN THE 

CAROLINA SLATE BELT 

By RoBERT G. ScHMIDT 

ABSTRACT 

Large subvolcanic to solfataric hydrothermal systems characterized by an 

abundance of high-alumina minerals, very intense alteration by strong acids acting 

through large volumes of rock, and profound changes in bulk composition are found at 

many localities worldwide, and can be considered to form a separate sub-class of 

alteration system. The altered zones at many of the localities contain widespread 

disseminated pyrite, and may contain from traces to economically extractable 

quantities of gold, silver, copper, molybdenum, tin and other metals. Fluorine is 

commonly but not always more abundant than boron, and topaz is a widespread major 

mineral. Bismuth, arsenic, lead, and zinc are also present in many of the deposits. 

Characteristics of these systems are transitional to shallower solfataric and hot spring 

deposits, and with greater K-silicate alteration into classical subvolcanic porphyry 

copper deposits. 

One major area of high-alumina deposits is in the Southeastern United States. At 

least 40 large bodies of aluminous rock within volcanic rocks of the Carolina slate belt 

have been identified. Some bodies have many features of porphyry copper systems but 

others do not; the two types must have originated under somewhat different conditions 

of pressure and (or) temperature. Characterized by some or all of the minerals kaolinite, 

sericite, pyrophyllite, and rutile, and locally abundant disseminated sulfide, parts of 

some bodies are even more aluminous with abundant andalusite and topaz and traces of 

diaspore. These deposits are interpreted to be the result of intense hydrothermal 

alteration of predominantly andesitic eruptive rocks. Several are presently mined for 

andalusite and pyrophyllite. Although no metallic ores have been identified, copper, 

molybdenum, bismuth, arsenic, or tin are locally present in minor amounts. Gold has 

been mined at five aluminous deposits and may be associated with a few more. Two 

areas of former gold mines in large siliceous pyrophyllite-andalusite-topaz-bearing 

systems--the Brewer, in Chesterfield County, S.C., and Pilot Mountain, in Randolph 

County, N.C.--are tentatively classified as porphyry gold systems. Of 40 aluminous 

deposits, most occurring in North Carolina, at least 14 are topographically positive, and 

some have associated unique depleted floral suites and stunted trees. Aluminous 

deposits, especially kyanite deposits of the more metamorphosed Charlotte and Kings 

Mountain belts were not considered here. 
2 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Analogous deposits in other regions have economically minable metals associated 

with them and these call attention to the possible importance of the major systems in the 

Carolina slate belt. Other deposits that help us understand those in the slate belt 

include Mount Pleasant in New Brunswick, Canada, and scattered porphyry copper 

deposits in the North and South American Cordillera, and in southeast Asia. The 

Kounrad and certain other deposits in central Kazakhstan, U.S.S.R. are major porphyry 

copper systems where abundant andalusite and pyrophyllite closely associated with the 

ore zone have formed by hydrothermal action. Comparisons with Kazakh orebodies 

suggest that several Carolina deposits may be variations of true porphyry-type systems, 

that alteration mineral zonation is a potential tool to identify the part of a greater 

system represented by the surface exposures that we see, and that the systems deserve 

consideration for their copper and molybdenum potential. 

Many major problems concerning the relationships of the deposits to their 

enclosing rocks remain unresolved because the geologic history of the enclosing units is 

exceedingly complex and few features of the rocks have been mapped. Many of the 

deposits have granitic plutons nearby, but it is not clear whether a genetic relationship 

exists between them. A major objective of current studies in the area is the ordering of 

successive geologic events and the selecting of rock units for age dating in order to yield 

geologically significant values. More information on the ages and compositions of 

plutonic rocks may make it possible to assume that the volcanism took place on 

continental crust, that is, at a continental margin rather than on an island arc. Such 

new data are expected to help construct a probable model of a high- alumina alteration 

system in the Carolina slate belt and to select the best places for metal exploration. 

INTRODUCTION 

The Carolina slate belt, a thick sequence of metamorphic rocks 

derived from volcanic tuffs, flows, and tuffaceous sediments was 

probably formed in a volcanic arc environment in late Precambrian 

and early Paleozoic time. Extending about 650 km from Georgia to 

Virginia, some of these rocks are similiar to and might be related to 

the A val on zone rocks of Newfoundland. 

Within the Carolina slate belt, at least 40 large bodies of 

aluminous rock have been identified; part of them are shown on figure 

1. Characterized by some or all of the minerals kaolinite, sericite, 

andalusite, pyrophyllite, topaz, rutile, and diaspore, these deposits are 

interpreted to be the result of intense hydrothermal alteration of 

predominantly andesitic pyroclastic rocks by strongly reactive acidic 

fluids or gases acting at high temperatures and low pressures. While 

most or all of these deposits include abundant kaolinite, sericite, and 

pyrophyllite, and traces of rutile, about one-quarter of the deposits 

also have abundant andalusite and topaz, and minor diaspore, which I 

have designated a high-alumina assemblage. The latter tend to be 

enclosed by large envelopes of highly silicified rocks and to cut across 

stratigraphic layers. The subject of this report is this smaller group of 

crosscutting deposits generally containing andalusite and topaz and 

sometimes diaspore, in what is probably a high temperature mineral 

suite. The same group of deposits was designated "replacement 
INTRODUCTION 

3

r KENTUCKY 1

1 

f ,-./ 

~-------.r-' 

TENNESSEE 

NORTH CAROLINA 

\ 

~Belair belt 

Bradshaw mine 

and Mitchells Mt 

t ,:,EXPLANATION """ rn Carolina slate belt 

Adapted from 

3 

0 50 100 KILOMETERS H, Williams (1978) 

0 50 100 MILES 

FIGURE 1. High-alumina alteration systems in the Carolina slate belt. 

deposits" by Espenshade and Potter (1960), who differentiated them 

from the more abundant, lower temperature and perhaps stratabound 

deposits. A separation of the high-alumina bodies by mineral suite 

and structural form has not been attempted by most authors in 

describing the deposits. Although metallic ores have not been found 

in association with most of these aluminous deposits, gold is 

associated with some and may be inferred to be related to several 

more. Copper, molybdenum, and tin are locally present in minor 

amounts (table 1). The Brewer and Pilot Mountain deposits, where 

gold has been mined from large high-alumina alteration zones, are 

tentatively classified as porphyry gold systems (Schmidt, 1982). 

The deposits of pyrophyllite and andalusite, and the topaz that 

accompanies many of them, have been considered to have various 

origins by previous workers. Pardee and others (1937, p. 1064), after 

topaz was recognized as an important rock-forming mineral at the 

Brewer deposit, considered quartz, topaz, and pyrite to be the products 

of hydrothermal alteration of quartz-sericite schist by flourine-rich 
TABLE I.-Metals associated with selected pyrophyllite deposits 

Name of deposit County 

Brewer mine ----------------------------Chesterfield, S.C. 

Pilot mountain --------------------------Randolph, N.C. 

Fox Mt./Iron Mt.-------------------------Randolph, N.C. 

Standard Minerals -----------------------Moore, N.C. 

Glendron Pyrophyllite---------------------Moore, N.C. 

Staley mine -----------------------------Randolph, N.C. 

Snow Camp mine ------------------------Alamance, N.C. 

Hillsborough mine -----------------------Granville, N.C. 

Bowlings Mountain ----------------------Granville, N.C. 

White deposits --------------------------Granville, N.C. 

Daniels Mountain ------------------------Granville, N.C. 

Limonite from Gossan, Ore Hill, ------------Chatham, N.C. 

Mt. Vernon Springs 

Ammons (Comer-Aumen) mine -------------Montgomery, N.C. 

Average, 12 samples, unmineralized ---------Mostly Randolph, N.C. 

hilltop sites (see Table 3) 

State of development 

Former gold mine 

Undeveloped 

Undeveloped 

Operating pyrophyllite mine 

Operating pyrophyllite mine 

Former pyrophyllite mine 

Former pyrophyllite mine 

Operating pyrophyllite mine 

Small pyrophyllite production 

Undeveloped 

Undeveloped 

Former iron ore mines 

How disseminated sulfide is present 

Widespread disseminated pyrite, 5-15 percent 

Disseminated pyrite widespread, sparse molybdenite in Pine Hill mine dump 

Pyrite probably common before oxidation 

Present 

Abundantly disseminated in north wall of mine 

Only seen in blocks of waste rock 

Common in mine walls and floor 

Present in local masses 

Observed in waste rock 

Widespread in deposit 

Relict textures indicate sulfide common below zone of oxidation 

Lenses, pods (now all oxidized) 

Former pyrophyllite mine Disseminated in wall rock 

------------------------------Sparse dissemination in bedrock at part of sites 

~ 

:I: 

8 

:I: 

> t'"' 

c:: 

:.::: 

~ :I: 

~ 

t:l 

tzj 

~ 

~ t'"' 

~ 

~ 

~ C") 

> 

~ c 

~ 

~ ~ 

ttl 

tzj 

ti 
TABLE I.-Metals associated with selected pyrophyllite deposits-Continued 

Maximum analytical values, rocks (Cu, Mo, and Sn analyses by emmission specroscopy; Au Maximum analytical values, Numbers of samples 

Name of deposit Rock Soil or Saprolite 

Brewer mine------------------------- 44 >400 

Pilot mountain ----------------------- 3 60 

Fox Mt./Iron Mt.--------------------- 0 10 

Standard Minerals -------------------- 10 5 

Glendron Pyrophyllite----------------- 16 4 

Staley mine ------------------------- 1 0 

Snow Camp mine --------------------- 2 7 

Hillsborough mine -------------------- 1 1 

Bowlings Mountain ------------------- 0 4 

White deposits ----------------------- 0 1 

Daniels Mountain -------------------- 0 4 

Limonite from Gossan, Ore Hill, --------- 2 --------------

Mt. Vernon Springs 

Ammons (Comer-Aumen) mine ---------- 2 --------------

Average, 12 samples, unmineralized ------ 10 

hilltop sites (see Table 3) 

1

Sulfide-bearing rock from dump of old Pine Hill mine. 2 Analyses of three leached cap rocks. 

Cu Mo 

10,000 700 

I 2,200 '66 

----- 20 8 

1,100 500 

26 22 

25 1.8 

6.0 -----

-----

-----

----- ----- 200 51 

12 61 

----- -----

3

Analyses of limonite gossan from prospect pit; also contains 91 ppm Ph and 110 ppm Zn. 4 Average was calculated using 1 ppm for samples below level of detection. 

by atomic absorption) soil and saprolite 

Sn Au As Bi Ag c~ Mo Sn Au 

200 ----- 3,000 500 900 80 ----- .44 2 25 ----- '200 ----- .69 88 21 16 ----- ----- ----- ----- 94 <1. 4 

0.68 ----- ----- 10 4 ----- 0.24 

----- 0.04 ----- 30 10 0.04 

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

3.6 ----- ----- ----- 49 6.2 2.1 -----

4.6 ----- ----- ----- 6.6 < 1.0 3.1 

----- ----- ----- 8.6 2.8 7.0 -----

----- ----- 7.5 < 1.0 5.4 

----- ----- ----- 31 < 1.0 < 1.5 

----- 460 

6.5 ----- ----- ----- .16 

----- ----- ----- ----- ----- Ave. All Ave. 

11.7 1.0 • 2.1 

Mines and prospects 

nearby 

Au~ 

X 

X 

X ----- z X ----- >-3 X ~ tl 

c::: ----- 0 

>-3 

----- 0 ----- z 

CTI 
6 HIGH-ALUMINA HYDROTHERMAL SYSTEMS. CAROLINA SLATE BELT 

solutions. Broadhurst and Councill (1953, p. 10) considered the highalumina minerals to be products of mineralizing solutions associated 

with a shallow magma. Espenshade and Potter (1960, p. 25-27) 

believed that deposits of high-alumina minerals in the different 

geologic terranes of the Southeastern United States might have had 

different origins and that some of the andalusite-pyrophyllite 

deposits, which are most characteristically developed in the slate belt, 

might have formed in the deeper zones of extensive solfataric centers. 

Zen (1961) reasoned that, because of an excessive number of phases 

for the phase rule, the mineral assemblages present in the deposits 

required that the fugacity of H20 be internally defined by the 

assemblage. This would be inconsistent with a hydrothermal origin. 

He suggested instead that the deposits originated by metamorphism 

of aluminous saprolite bodies. Spence (1975) proposed that kaolinitic 

clays formed by hot springs and (or) fumarolic alteration of the 

volcanic rocks, and that the transformation to pyrophyllite (and 

presumably andalusite and diaspore as well) took place during 

regional metamorphism. Sykes and Moody (1978) showed H20 to be a 

variable or externally defined component and held that the andalusite 

formed as the result of metamorphism. They demonstrated from field 

and microscopic studies that there were not, in fact, an excessive 

number of phases for the phase rule (that is, kaolinite formed later 

and cut andalusite-bearing assemblages). They felt flourine was 

supplied by a hydrothermal event earlier than and distinct from the 

metamorphism, but gave no substantiating evidence. Worthington 

and others (1978) attributed the gold mineralization of the Brewer 

mine and presumably the accompanying pyrophyllite, andalusite, and 

topaz to alteration of volcanic rocks by a hot spring or fumarolic 

system. 

Allard and Carpenter have studied high-alumina alteration 

systems in the slate belt at Graves Mountain, Ga., and other sites, and 

at several more-metamorphosed deposits as well (Allard and 

Carpenter, 1981. 1982a. 1982b, 1983; Carpenter and Allard, 1980a, 

1980b). They have concluded that the hydrothermal systems have 

formed in submarine felsic volcanic piles by fumarolic action and that 

the quartz-rich high-alumina rocks and the quartz-sericite-pyrite 

rocks formed as separate parts of such systems. Though individual 

alteration types may cross- cut strata, the overall stratiform nature of 

the deposits was stressed (Carpenter and Allard, 1982, p. 20). The 

major high-alumina alteration minerals as well as certain alteration 

and metamorphic accessories such as hogbomite, sapphirine, 

tourmaline, dumortierite, lazulite, apatite, barite, rutile, nigerite, 

cassiterite, kornerupine, and gold were proposed as indictors that 

might be used to delineate prospective exploration areas (Allard and 
INTRODUCTION 7 

Carpenter, 1983). Parallels were drawn with deposits in other regions 

that have associated high-alumina minerals, such as Boliden, 

Sweden, and Kounrad, Kazakhstan, U.S.S.R. 

The results of this study also indicate that the large andalusitebearing high-alumina deposits in the Carolina slate belt had a 

subvolcanic hydrothermal origin. Deposits that we see probably 

represent a range in depths of formation, the shallower more 

fumarolic ones tend to be stratiform in shape, and the deeper ones 

cross-cutting and more pipe-like. It is the deeper systems which I 

have tried to study most extensively. Hydrothermal alteration 

accounts for both the high-alumina and associated high-Si02 rocks 

and for the specific mineral suites present; the widespread association 

of contemporaneous andalusite-topaz-quartz bodies enclosed in large 

highly silicic zones with later diaspore, pyrophyllite, and kaolinite 

cutting the andalusite are interpreted to have formed during a single 

high-temperature low-pressure event and its waning or collapse 

stages, without any significant changes wrought by later 

metamorphism. I believe these interpretations to be compatible with 

what has been established for the phase relations in the system Al20aSi02-H20 by Hemley and others (1980). 

The subvolcanic hydrothermal hypothesis proposed in this article 

is generally compatible with the ideas of origin proposed by Pardee 

and others (1937) and Espenshade and Potter (1960). It differs only 

slightly from the interpretation of Worthington and others (1978), 

mainly in the depth of formation in the volcanic system and the origin 

assumed for the siliceous rocks (those they have called sinters). 

Earlier workers have not generally emphasized the size and 

characteristics of the whole alteration system, nor the prevalence of 

high-alumina minerals such as topaz, andalusite, and diaspore, 

factors important in understanding the system. I believe that current 

studies by Carpenter and Allard deal primarily with shallower 

systems as indicated by the generally stratiform nature of the deposits 

they describe (Carpenter and Allard, 1982, p. 20); but my general 

conclusions regarding the hydrothermal process are very similar to 

theirs and the studies complement each other. The deposits I have 

examined lack evidence indicating a submarine origin, however. 

Like Espenshade and Potter (1960, p. 25-27), I believe that all of 

the slate-belt high-alumina deposits did not originate in the same 

manner. I have tentatively selected those with large envelopes of 

hydrothermally altered rock enclosing pods of high-alumina minerals 

as significant hydrothermal deposits with the most economic metallic 

mineral potential, and deserving of further study (Schmidt, 1982). 

It is the purpose of this article to explore the possibility that some 

of these deposits form a transition to a tvne of major porphyry copper-
8 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

molybdenum deposit that includes widespread silicification plus 

pyrophyllite or andalusite as a major alteration mineral intimately 

associated with hypogene sulfide ores. Comprehensive comparisons 

are neither possible nor intended at this time because adequate 

mineral assemblage data are available for only a few of the major 

foreign deposits, and studies comparing the various deposits of the 

Carolina slate belt are only beginning. Instead, my intention is to 

emphasize the possible significance of certain of the slate belt systems 

and to urge that they be given much more attention in mineral 

exploration. 

Studies made elsewhere that bear on the possible relationship of 

high-alumina alteration to porphyry-type systems include those of 

Hemley and others (1980), Knight (1977), Wallace (1979), and Sillitoe 

(1973). Hemley and others (1980) experimentally investigated and 

thermodynamically treated the chemistry of phase relations in the 

Al20a-Si02-H20 system and briefly discussed the implications to 

porphyry copper alteration-mineralization systems and to other 

systems as well. Similarity of the North Carolina pyrophyllite 

deposits to altered rock in certain parts of the greater Butte orebody 

was noted by the same authors (Hemley and others, 1980, p. 226). 

Knight (1977) conducted a number of thermochemical calculations in 

order to better interpret the alteration mineralogy above buried 

copper deposits; his results showed general consistency with 

published descriptions of deposits in other regions. Wallace (1979) 

developed a working model for the upper levels of porphyry copper 

systems to serve as an exploration guide to porphyry-type deposits not 

yet exposed by erosion. Sillitoe (1973) prepared an early synthesis of 

information obtained mostly from Andean examples to model the 

upper part of a porphyry system in a stratovolcano. Advanced argillic 

alteration, in places including andalusite and other high-alumina 

minerals, is definitely present in the upper part of some examples, as 

demonstrated by the detailed work of Gustafson and Hunt (1975) on 

the El Savador, Chile, deposit. 

Meyer and Hemley (1967, p. 170) pointed out that andalusitebearing alteration assemblages are high-temperature equivalents of 

what they termed advanced argillic. I have used the term highalumina alteration to distinguish assemblages with abundant topaz, 

andalusite, diaspore or corundum from advanced argillic alteration, 

containing mostly kaolinite or alunite; furthermore, many of the 

deposits discussed here contain only volumetrically minor amounts of 

true clay minerals. High-alumina alteration is typically accompanied 

by widespread highly silicified rocks for which I use the term quartz 

granofels. These siliceous rocks have been called secondary quartzites 

in Soviet literature, and altered rocks with over 90 percent quartz 
ACKNOWLEDGMENTS 9 

have been termed monoquartzites. I have not used the latter terms to 

avoid confusion with metasedimentary rocks. 

The more highly metamorphosed high-alumina deposits, 

especially the kyanite deposits of the Charlotte and Kings Mountain 

belts are geologically more complex and have not been considered at 

this time. 

Descriptions have been collected of deposits in other regions that 

may be analogous to the aluminous deposits in the Carolinas and can 

therefore help in understanding their origins. The Mount Pleasant 

deposit in New Brunswick is outstanding among these. Descriptions 

of hydrothermal andalusite-pyrophyllite clay deposits of Japan and,.. 

mineralogic data from active geothermal fields provide valuable 

information on the probable environment in which deposits like 

these formed. Several deposits of the porphyry-copper type are 

characterized by andalusite and pyrophyllite in zones of intense 

hydrothermal alteration; among them, the Kounrad and other 

deposits in Kazakhstan, U.S.S.R., the Tapadaa and Tombuililato 

copper districts, North Sulawesi, Indonesia, and the El Salvador 

deposit, Chile. The porphyry gold mineralization at Vunda, Fiji, has 

quartz-diaspore rock as one accompanying alteration phase 

(Lawrence, 1978, p. 26). 

This study grew out of a project conducted to evaluate favorable 

areas in the Eastern United States for the occurrence of porphyry-type 

copper deposits. The Mount Pleasant deposit, New Brunswick, 

Canada, was visited and the study of drill cores from the Brewer mine 

begun in 1973. Field examination of the Pilot Mountain area was first 

undertaken in 1978, with a brief field visit to the Brewer mine vicinity 

at the same time. Preliminary conclusions regarding the mineral 

potential of this area were presented at that time (Schmidt, 1979). 

Subsequently, information for preparation of this report was obtained 

from field examination of many aluminous deposits in North and 

South Carolina, together with the search of geologic literature for 

data on other localities. Geochemical sampling, especially soil 

sampling, was carried out at many places in North Carolina, and 

sample data obtained by other members of the U.S. Geological Survey 

were used in conjunction with my own. A detailed map of Pilot 

Mountain was prepared, and reconnaissance geologic mapping was 

carried out in the Ramseur and adjacent 7-112 minute quadrangles, 

North Carolina. 

ACKNOWLEDGMENTS 

The author is very grateful for the cooperation of Piedmont 

Minerals Co., Inc ; to Tom R. Kleeburg, consulting geologist working 
10 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

with them; and to Glendon Pyrophyllite Company for their help in 

making this study possible. My interpretations of the geology of the 

deposits have been greatly sharpened by many discussions with Tom 

Kleeburg; he has found some of my ideas less acceptable than others, 

as I expect certain readers will as well. Grayson Byrd, an owner of 

land in the western part of the Pilot Mountain alteration zone, has 

shown a continuing interest in this study and his kindness in showing 

us outcrops is appreciated. 

I have drawn heavily upon the results of detailed mapping and 

mineralogical studies by Terry L. Klein, U.S. Geological Survey, in 

the mines of Glendon Pyrophyllite Company and on parts of Pilot 

Mountain. Our many discussions have been most useful in shaping 

the concepts presented here. Special thanks are due to Dr. Shuichi 

lwao, Professor Emeritus, University of Tokyo, for calling my 

attention to the geologic significance of the Ashio copper-tin mine, 

Honshu, among the many high-alumina hydrothermal clay deposits of 

Japan, and to Henry Bell III for the loan of 29 thin sections of Brewer 

mine rocks. I wish especially to thank J. J. Hemley, T. L. Klein, and 

Henry Bell III for their reviews and suggestions for improvement of 

this paper. 

METAL DEPOSITS WITH ASSOCIATED ZONES 

OF ALUMINOUS ALTERATIONS IN OTHER REGIONS 

Alteration zones containing significant amounts of the aluminous 

minerals kaolinite and pyrophyllite, and particularly the highalumina minerals andalusite, diaspore, and corundum have been 

described from major porphyry copper deposits at several locations 

worldwide, including especially Kazakhstan in the U.S.S.R., and from 

one hydrothermal system described as a porphyry-gold deposit. Brief 

summaries of published descriptions of metal-bearing deposits with 

significant aluminous hydrothermal alteration follow. 

EXAMPLES IN NORTH AMERICA 

Few porphyry-type deposits of Western United States and Canada 

have much associated aluminous alteration other than kaolinite; of 

these Butte, Mont, and Island Copper, British Columbia, are the best 

known. The minerals that characterize aluminous alteration may 

have been overlooked at some porphyry deposits, and I may have 

failed to find references to the aluminous minerals in recent 

publications, but the occurrences north of Mexico must certainly be 

few. 
METAL DEPOSITS IN OTHER REGIONS 11 

The polymetallic deposit at Mount Pleasant, New Brunswick, is a 

major metal deposit that contains abundant aluminous alte·ration. 

High-alumina deposits without much associated sulfide ore minerals 

are present in Avalonian rocks of Newfoundland (Papezik and others, 

1978) and in Mesozoic volcanic rocks of Puerto Rico (Hildebrand, 

1961a, 1961b). 

Butte, Mont.--Widespread andalusite and corundum are present in 

the alteration envelopes surrounding pre-main-stage ore veins in the 

Butte district (Brimhall, 1977), and considerable pyrophyllite is 

known to be associated with sericite in the Berkeley pit in the same 

district (Guilbert and Zeihen, 1964). Assemblages recognized in 1964 

included pyrophyllite-topaz, sericite-topaz, sericite-zunyite, and 

topaz-zunyite. High-sulfur vein assemblages containing pyrite, 

covellite, digenite, and enargite are found only in the zone of 

pervasive sericitization, and are particularly associated with highalumina alteration minerals (Meyer and Hemley, 1967, p. 193). The 

control of H + activity in shifting equilibria toward high sulfur 

fugacity, as discussed by Meyer and Hemley, is thus illustrated at 

Butte and in many other examples of these deposits presented in this 

paper. 

Island Copper, British Columbia--The Island Copper deposit, 

British Columbia, formed in andesitic pyroclastic rocks in breccia 

zones along the sides of a large quartz-feldspar porphyry dike of 

granodiorite composition (Cargill and others, 1976). Plagioclase, 

mafic minerals, and matrix material have been extensively altered to 

pyrophyllite and lesser amounts of dumortierite in breccia zones 

above the dike and in zones that extend downward on the sides of the 

dike along the contacts. Copper concentrates from this deposit contain 

gold (7-10 ppm) and silver (35-40 ppm), and the molybdenum 

concentrates contain 1400 ppm rhenium, a relatively high rhenium 

content (Sutulov, 1970, p. 223). 

Kyuquot Sound, British Columbia--An alunite-pyrophyllite 

deposit containing sericite, kaolinite, and diaspore has been mined at 

Kyuquot Sound on Vancouver Island, about 50 km south of the Island 

Copper deposit. There, rocks in a thick series of interbedded 

amygdaloidal, porphyriic, and fragmental feldspathic andesites and 

dacites are altered to an aluminous mineral suite close to an intrusion 

of feldspathic quartz diorite (Clapp, 1915). Pyrite is disseminated 

through much of the altered rock, especially below the zone of 

oxidation, and minor amounts of copper, gold, and silver are present. 

Chalcopyrite is the only copper mineral described. The deposit is not 

the same locality as the Kyuquot porphyry-type Cu-Mo-W "showing" 

of Pilcher and McDougall (1975, table 2, map B). 
12 . HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Other Western North American examples--Aluminous alteration 

minerals are also associated with a major porphyry-type 

hydrothermal system at the Warren-Bisbee district, Arizona, where 

quartz porphyry of the Sacramento stock has altered to quartz and 

pyrophyllite with dickite, alunite, rutile, and zircon (Bryant and 

Metz, 1966, p. 196). 

Wallace (1979), building on the work of Gustafson and Hunt 

!1975) at El Salvador, various papers by Meyer and others at Butte, 

and Knight (1977), has proposed applying the presence of 

pyrophyllite-dominated advanced argillic alteration to indicate 

possible upper levels of porphyry-copper systems in the western Great 

Basin of Nevada. Knight (1977) had used certain mineral 

assemblages, especially alunite, pyrophyllite, and copper-arsenic 

sulfosalts, to suggest that alteration has taken place above a sulfurrich pluton. 

Mount Pleasant, New Brunswick--Porphyrylike deposits of 

tungsten, molybdenum, copper, tin, and bismuth are located in 

volcanic rocks of a caldera of Mississippian age at Mount Pleasant, 

New Brunswick (Ruitenberg, 1967; van de Poll, 1967). The aluminous 

minerals kaolinite, topaz, and dickite have been formed by intensive 

hydrothermal alteration related to volcanism (Petruck, 1964, p. 29); 

neither pyrophyllite nor andalusite has been described from these 

deposits. 

The geq_logy of the large and complex Mount Pleasant 

hydrothermal system has been described by McAllister and Lamarch 

(1972, p. 82-89) and Dagger (1972). Mineralization and intense 

alteration are related to two pluglike bodies that are interpreted to be 

erosional remnants of volcanoes. The plugs are highly altered felsite, 

tuff, and breccia; intruded rocks are mosty felsic ash-flow tuffs. Three 

overlapping zones of hydrothermal alteration are concentric about the 

plugs (Ruitenberg, 1967, 1972) within which the original felsic vent 

rock is mostly replaced by quartz and has not been a particularly 

favorable host for mineralization. 

Intense alteration has destroyed much of the primary rock 

texture, and locally it is difficult to interpret what the original rock 

may have been. Volcanics adjacent to the plugs have been more 

favorable hosts partly because they are more fractured and tend to 

form more vugs. Intense hydrothermal alteration of these rocks has 

resulted in some nearly complete replacement by quartz, but mostly 

the formation of a mixture of quartz, fine mica, flourite, topaz, and 

kaolinite. Less altered rocks are sercitized, silicified, and chloritized. 

A bright green "chlorite," shown to be a mixture of kaolinite and 

chlorite, is common with metallic mineralization. Chlorite extends 

beyond the other alteration products to form the outermost alteration 
METAL DEPOSITS IN OTHER REGIONS 13 

zone with a total mapped length of 2.6 km (Ruitenberg, 1967). 

Kaolinite and hydromica are common widespread products of 

hydrothermal alteration, either mixed or in separate form, and dickite 

has been found within kaolinized zones. Steeply plunging kaolinite 

pipes 2 to 7 min diameter have been described by Ruitenberg (1967, p. 

107)~ the pipes contain abundant large pale-green flourite crystals 

and large blocks of wall rock. 

Mineralization has taken place in individual veins, complex veins 

or narrow vein swarms, isolated pods, stockworks of numerous fine 

irregular veinlets, and disseminated patches; some breccia pipes are 

well mineralized. Feldspar porphyries are the best hosts for metallic 

minerals. Mineralized veins are associated with greisen zones of 

quartz, flourite, kaolinite, topaz, hematite, and chlorite. Most intense 

mineralization tends to be in breccia zones of dike or pipelike shape~ 

the origin of these breccias is in dispute. 

The principle ore minerals at Mount Pleasant are molybdenite, 

wolframite, native bismuth, bismuthinite, chalcopyrite, cassiterite, 

stannite, spalerite, and galena. Economic minerals in minor 

quantities include scheelite, chalcocite, tennantite, tetrahedrite, 

covellite, wittichenite, native gold, glaucodot, arsenobismite, and 

malachite; other significant associated minerals are pyrite, marcasite, 

pyrrhotite, arsenopyrite, flourite, topaz, zircon, rutile, quartz, sericite, 

kaolinite, chlorite, calcite, siderite, hematite, and goethite (Petruk, 

1964). 

Foxtrap deposit, Newfoundland--The Foxtrap pyrophyllite deposit, 

in the Avalon Peninsula of Newfoundland, is located in rhyolitic flows 

and pyroclastics of the Avalon zone, a sequence of volcanic rocks 

generally considered to be related to the Carolina slate belt. 

Pyrophyllite, muscovite, diaspore, barite, and rutile have formed 

along a shear or fracture zone close to the contact of an intrusive 

granitoid rock; it has been suggested that the alteration was produced 

by hydrothermal fluid related to the granitoid (Papezik and others, 

1978). 

EXAMPLES IN SOUTH AMERICA 

El Salvador, Chile--As much as 40 percent andalusite, 

pyrophyllite in significant amounts, and lesser amounts of diaspore 

and corundum have been described in parts of the porphyry copper 

deposit at El Salvador, Chile (Gustafson and Hunt, 1975). During the 

complex alteration and mineralization history of this large orebody, 

high-alumina and advanced argillic alteration minerals formed at two 

stages; the first in the upper part of the system overlapping the top of 

the main ore zone, and the last above the main ore occupying a space 

mostly in the present leached cap. 
14 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

According to the model proposed by Gustafson and Hunt (1975), 

andalusite and corundum were important constituents of alteration 

zones that formed after intrusion of the last major porphyry body (the 

L Porphyry) and are thus genetically related to the pyrite-bornite 

mineralizations that formed at the same stage; both formed in similar 

high-sulfur strongly hydrolytic environments. The deepest andalusite 

and corundum alteration occurs with the assemblage K-feldpar-Naplagioclase-anhydrite plus biotite or sericite. Gradationally upward, 

the high-alumina altered zone changes to the assemblage andalusitesericite-quartz and minor to trace amounts of pyrophyllite, diaspore, 

or alunite at the erosion surface. Outward at the surface, the 

assemblage grades to sericite-pyrite with local alunite and (or) 

pyrophyllite; at a greater distance, this is surrounded by propylitic 

alteration. Gold values in excess of 0.1 giT are restricted almost 

exclusively to a central chalcopyrite-bornite zone which is beneath 

and extends upward into the center of the high-alumina alteration 

(Gustafson and Hunt, 1975, p. 886 and fig. 28). The copper-gold 

mineralization is interpreted to have formed before the high-alumina 

alteration, however. 

The second high alumina alteration, being generally later than 

other alteration processes, overprinted the upper part of earlier 

alteration zones. It was restricted to a high level in the system but 

spread laterally beyond the ore and is now mostly within the leached 

capping (Gustafson and Hunt, 1975, p. 900 and fig. 28). The 

assemblages contain pyrophyllite and a variety of associated minerals 

such as diaspore, primary alunite, andalusite, sericite, and local 

corundum, but no kaolinite. This alteration is interpreted to be the 

product of a very late post-mineral hot spring stage, albeit formed as 

much as 600 m below the present erosion surface. 

Boron, present in tourmaline, is locally abundant in the El 

Salvador deposit, but I have found no reference to flourine-bearing 

minerals there. 

La Gran} a porphyry copper deposit, Peru--The recent discovery of 

this interesting deposit furnishes another important example of 

porphyry-type mineralization associated with a high-alumina 

hydrothermal alteration system in the American Cordillera 

(Schwartz, 1981, 1982). The copper-molybdenum deposit is situated in 

northern Peru in the Cordillera Occidental in an area of high relief, 

subtropical climate, and 800 mm of rainfall per year. Host rocks 

consist of quartzite and a clastic-calcareous sequence of Cretaceous 

age, and volcanic rocks of Tertiary age. A large intense alteration zone 

is associated with a feldspar-quartz porphyry intrusive. Less altered 

phases of the intrusive grade into biotite-granodiorite porphyry and 

hornblende-granodiorite porphyry. The central most altered area is a 
METAL DEPOSITS IN OTHER REGIONS 15 

large roughly circular sericite-clay zone about 3 km in diameter, 

within which there are 3 patches of"advanced argillic" alteration, 2 of 

which form a rough half-ring that is both surrounded' by and has 

within it alteration of the sericite-clay type (Schwarz, 1982, fig. 3). 

The "advanced argillic" zone is characterized by the mostly highalumina mineral assemblages andalusite-quartz, andalusitepyrophy llite-quartz, andal usi te-serici te-q uartz, diasporepyrophyllite-quartz, and sericite-pyrophyllite-quartz. The area of 

supergene ore with more than 0. 7 percent copper occupies much of the 

sericite- clay zone inside the half-ring of high-alumina alteration; the 

high-alumina rock itself is low in copper. 

Other South American examples--Both hypogene and supergene 

alunite have been identified at the Cerro Verde porphyry copper mine, 

Arequipa, Peru, and pyrophyllite is also an alteration mineral there 

(Cedillo and others, 1979). The zoning is similar to that in El 

Salvador, and kaolinite is common. Though tourmaline is the 

predominant boron mineral, especially in breccia pipes, dumortierite 

(an aluminum borosilicate) is also common at Cerro Verde. No 

flo urine minerals have been reported. 

LARGE HYDROTHERMAL ALTERATION ZONES AND 

PORPHYRY COPPER DEPOSITS OF KAZAKHSTAN 

The major porphyry copper province in central Kazakhstan, 

U.S.S.R, includes the most important group of deposits of Paleozoic 

age in the world. Most of the hydrothermally altered bodies have been 

formed in felsic and intermediate volcanic rocks including tuffs, tuffbreccias and tuff-agglomerate-breccias. Many ore deposits are 

associated with extensive high-alumina rocks, and there are also 

many additional zones of highly aluminous rocks without significant 

metallic ores in them. Evaluation of these zones in a large and 

generally remote regio·n has been carried out to varying degrees and 

on only a relatively few deposits (Nakovinik, 1968, p. 74). 

Nakovnik (1968, p. 85-86) suggested that the Kazakhstan deposits 

might be better understood by comparison with other areas, such as 

the well studied sulfur-iron sulfide, alunite, and diaspore-pyrophyllite 

deposits of Japan. The association of major porphyry copper deposits 

with andalusite-pyrophyllite-diaspore alteration zones, with both 

related to widespread felsic and intermediate volcanism, makes the 

geologic history of this region particularly important to interpreting 

the significance of the hydrothermal systems of the Carolina slate 

belt. 

Preliminary identification of the locations of zones of alteration 

has progressed far ahead of detailed evaluation and, whereas at least 
16 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

45° 

EXPLANATION 

x Deposit 

o Dzhezkazgan 

Base from Defense 

Mapping Agency, 1981 

70° 75° 

• Tselinograd 

o Bayan-Aul 

Semipalatinsk • 

~Semiz-Bugu 

• Karaganda 

Ol'ginskoe- J<arkaralinsk 

Akbiik o Kaynar 

\ 

oKaraaul 

Atasu Uspenski x Kalak-Tas I Koktenk~l ~ 0 

x Aktogay x South Bes-cheku 

A d '0 ~ X ga yr / Akchat u Kara-cheku 0 Barshatas 

Baanazar 0 Ba 

ory 1 

Zhanet x /1/ K~ Ken'kuduk 

Mointy o .);{ 0-Kaskyrkazgan 

Karatas IV ~lkhas~ Kounrad ~ Sayak 

Gul'shad~ r§'~ 

Sokurkoy/r ~ 

Saryshagon Q;<:tj 

2f v 

o Ushtobe 

Taldy Kurgan 

0 100 200 300 KILOMETERS 

0 100 200 MILES 

FIGURE 2. Porphyry copper deposits and other major hydrothermal alteration 

systems in central Kazakhstan, U.S.S.R. 

235 alteration zones were known in 1959, only 43 bodies had been 

explored in even preliminary ways (Nakovnik, 1968, p. 74). As many 

as 2,000 siliceous alteration zones were attributed to the region by 

Shcherba in 1965, but this high number includes a large number of 

"aposedimentary" bodies that are not properly included with the 

hydrothermal alteration zones--the "secondary quartzites" of Soviet 

literature (N akovnik, 1968, p. 7 4). It is not clear what these 

"aposedimentary" bodies are really like, which is most unfortunate 

because they might also have analogs among those pyrophyllite 

bodies of the Carolina slate belt that I interpret to be distal to or 

perhaps unrelated to porphyry systems. 

I have been able to obtain limited geologic information for 18 

copper, copper-molybdenum, and molybdenum porphyry deposits in 

central Kazakhstan. General locations for 12 of these, plus 5 

alteration systems perhaps lacking significant metals are shown on 

figure 2. Geologic information is easier to obtain than information on 

exploitation and exact locations. Several of the deposits are being 

exploited including the Kounrad, Sayak, and U spenski (this last may 

be the townsite and mill location for the Koktenkol' molybdenum-
b8 

D 

~ 

c=J 

E3 

[Z3 

g 

METAL DEPOSITS IN OTHER REGIONS 

0 1 KILOMETER 

'-----~--J (approximate) 

EXPLANATION 

Rhyolites 

Sericitic silicified rock (secondary quartzite) 

formed from rhyolite 

Zone of development of andalusite, corundum, 

diaspore, dickite and alunite 

Sericitic quartz-rich rock formed from granodiorite 

porphyry (zone of disseminated chalcopyrite) 

Zone of hydrothermal argillation 

Propylitized granodiorite porphyry 

Porphyritic granodiorite 

Limit of ore 

FIGURE 3. Schematic cross section of the North Kounrad alteration system 

and its copper orebody (after Nakovnik, 1958). Exaggerated vertical scale; 

no horizontal scale given on original. 

17 

bearing deposit)~ however, the status of most is unknown to me. Some 

are certainly too small or too low grade to be exploited but are 

metallogenically significant. It is hard to judge the completeness of 

descriptions of alteration minerals, but 6 of the 18 deposits are known 

to have high-alumina minerals, particularly andalusite, diaspore, 

pyrophyllite, corundum, dickite, alunite, and zunyite. 

Kounrad deposit--The Kounrad (Kounradski) copper-molybdenum 

porphyry deposit is the best known Kazakhstan deposit and also one 

that contains substantial amounts of high-alumina minerals. Copper 

and molybdenum mineralization and some high-alumina alteration 

are located within the top of an intrusive granodiorite porphyry stock 

which seems to have been dated at 280 m.y. Mineralization is not 

limited to the intrusive~ it extends a short distance into the adjacent 

hydrothermally altered rhyolites as well (fig. 3), but dies out rapidly 
18 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

away from the contact (Nakovnik, 1968, p. 164). Primary ore minerals 

are chalcopyrite, enargite, bornite, molybdenite, tennantite, 

tetrahedrite, and galena. Propylitic, quartz-sericitic, argillic, and 

high-alumina alteration zones have been described in relationship to 

the metallic mineralization (fig. 3). In the most-intensive highalumina zone in the rhyolites close to the contact with the 

granodiorite porphyries, andalusite locally comprises 50 to 80 percent 

of the rock, plus lesser corundum, topaz, barite, and alunite 

(Magak'yan, 1961, p. 334) as well as dumortierite (Nakovnik, 1968). 

Mineral assemblages described include andalusite-quartz-sericite, 

andal usi te-quartz, quartz-serici te-andal usi te-cord und urn, quartzsericite-andalusite-alunite, and andalusite-corundum-diaspore, all of 

which can also include minor rutile and major pyrite (Nakovnik, 1968, 

p. 157-159). It seems curious to me that pyrophyllite is not mentioned 

in these assemblages. Explosion breccias are exposed at many places 

in the Kounrad mine (Smirnov, 1977, p. 124). 

The exploitable copper orebody, 1,000 x 200 m on the exposed 

surface, is a thick blanket of secondary-enriched oxides and sulfides. 

The vertical zonation is well developed (Nakovnik, 1968, p. 164). The 

generalized thicknesses of the respective ore zones are as follows: 

oxidized zone, up to 60 m; mixed ores, up to 50 m; secondary sulfide 

enriched zone, up to 270 m, beneath which the primary sulfides extend 

to an undetermined depth as the deepest boreholes only reach 400 m. 

Leached cap rock is present in irregular pockets, some up to 30 m 

thick. Kaolinite, opal, limonite, malachite, and brochantite are the 

most widespread minerals in the oxidized zone. Jarosite, azurite, 

chalcanthite, cyanotrichite, chrysocolla, and copper-manganese pitch 

ore are oflimited distribution. 

This important copper-molybdenum (+gold?) deposit began 

production in 1940 and is still in operation. The total minable copper 

resource before mining began at the Kounrad deposit is reported to 

have been 10 million tons copper metal (Laznicka, 1976, p. B14). 

Other porphyry copper deposits and prospects in Kazakhstan--

Andalusite and dumortierite accompany the quartz and sericite of 

South Bes-cheku (Nakovnik, 1968, p. 75, 307), a porphyry copper 

deposit containing molybdenum. Kara-cheku, an alteration zone of 

about 5 km2 containing copper and lead and the alteration minerals, 

quartz, andalusite, dickite, and sericite, is not of the porphyry type 

(Nakovnik, 1968, p. 84), although the size and mineralogy seem 

appropriate. Sokurkoy is a large porphyry copper-molybdenum 

deposit near Lake Balkhash, southwest of the Kounrad mine. Quartz, 

alunite, dickite, sercite, andalusite, and zunyite are present in an 

alteration zone of 6.5 km2; there are four major breccia pipes within 

this zone (Nakovnik, 1968, p. 318; Puchkov and others, 1968, p. 68). 
METAL DEPOSITS IN OTHER REGIONS 19 

Karabas is another porphyry copper-molybdenum deposit about 

28 km northwest of Kounrad; high-alumina parts of the altered rocks 

there contain the mineral suites quartz-diaspore, quartz-sericitealunite, and zunyite (Puchkov and others, 1968, p. 68) formed by 

hydrothermal alteration of microgranite porphyry, granodiorite 

porphyry, granodiorite, and quartz diorite. 

Names of other copper-molybdenum porphyry deposits in central 

Kazakhstan are Aktogay, Borly, Kaskyrkazgan, Ken'kuduk, Karatas 

IV, Kaindy-cheku, Sayak, Tologai (Tulagai), and Zheke-zhuvan. In 

addition, the Ol'ginskoe-Akbiik deposit is reported to be copperbearing, and the Koktenkol' and Bainazar deposits are molybdenumbearing porphyry deposits (Laznicka, 1976). Some of these deposits 

may have high-alumina alteration as well. Locations of only some of 

these are shown on figure 2. 

Major high-alumina alteration zones--Of the 235 alteration zones 

in Kazakhstan tabulated by Nakovnik (1968), half were alunite 

bearing, and andalusite, dickite, diaspore, and corundum were 

present in 40 or more localities. Other minerals noted were 

dumortierite, barite, topaz, zunyite, tourmaline, lazulite, and 

augelite. Rather surprisingly, pyrophyllite was reported from a 

relatively small number of localities. The high-alumina minerals 

occur as nodules, pockets, pipes, veins, and lenses, the thickness of 

which is measured in tens of centimeters, less often in meters, and 

very rarely in tens of meters within the much more extensive highly 

siliceous "secondary quartzites," (Nakovnik, 1968, p. 83). 

Nakovnik (1968) considered that gold, silver, lead, mercury, and 

zinc were potential resources of the unevaluated hydrothermal 

alteration zones. Gold is of particular interest to us because of its 

possible genetic relationship to the aluminous alteration zones of the 

Carolina slate belt. Sutulov (1973, p. 161) has reported that the 

porphyry copper deposits of Kazakhstan produce a significant amount 

of gold, but information regarding individual deposits is not given. In 

his tabulation of 235 alteration zones, Nakovnik (1968) shows the 

Tologoi (Tulagai) deposit to contain Cu, Mo, Au, and Ph, with 

molybdenum the most important, and the Kaindy-cheku deposit to 

contain Cu, Mo, Sr, and Au, with copper the most important. Major 

alteration minerals noted at the Tologai deposit are quartz, sericite, 

and muscovite, and at the Kaindy-cheku, quartz, andalusite, sericite, 

and muscovite. I cound not obtain locations for these deposits, and 

they are not shown on figure 2. 

Four major high-alumina deposits with minor or no noted base 

metals, the Bol'shoy Semiz-Bugu, Malyy Semiz-Bugu, Zhanet, and 

Kalak-Tas, have also been described by Nakovnik (1968). All are 

associated with large zones of solfataric alteration in intermediate to 
20 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

felsic volcanic rocks. All have zones of silicification in the more highly 

altered parts, and all but the Malyy Semiz-Bugu deposits are probably 

enclosed in zones of sericitic alteration. Only the Zhanet deposit is 

discussed further here. 

The Zhanet dumortierite-corundum-andalusite deposit is 75 km 

northwest of the Kounrad copper-molybdenum mine (fig. 2). Highalumina alteration zones have formed in Upper Devonian and Lower 

Carboniferous felsic volcanic rocks including ashy tuffs, lavas, and 

pyroclastics, all dipping southwest at a low angle (N akovnik, 1968, p. 

168). The volcanic pile has been intruded by a variety of shallow and 

subvolcanic granitic stocks and felsic volcanic plutons that breached 

the surface. An important dumortierite-corundum-andalusite deposit 

is present as a narrow belt trending northwest for 2 km parallel to the 

strike of individual flows. Though not specifically stated, the ore is 

presumably present as a lens or layer roughly parallel to the 

stratification of the silicified volcanic rocks. Thus the deposit is a 

possible analog to certain lenticular stratiform orebodies in the 

Southeastern United States, though Nakovnik (1968, p. 171) seemed 

to consider the Zhanet deposit to be exceptional for Kazakhstan. 

The Zhanet altered rocks are mineralized mainly by sericite, 

andalusite, corundum, alunite, and dumortierite. Altered rocks 

locally consist of up to 70 percent hematite, which is present instead of 

the pyrite generally associated with deposits of this type. Diaspore, 

dickite(?), tourmaline, topaz, apatite, and perhaps some pyrite are also 

present. The corundum- rich zone is 50 to 60 m wide and 1 km long. 

Specific alteration zones above and below the ore may be present, but I 

could not work them out from the information available. N akovnik 

(1968, p. 178) concluded that the alteration took place during 

intensive circulation of hot acid waters adjacent to a volcanic vent. 

The examples of the Kazakhstan porphyry copper province are 

important in understanding the Carolina slate belt deposits. More 

than reminding us of the association of highly aluminous subvolcanic 

alteration with some exploitable hypogene copper and molybdenum 

deposits, these examples show that in this one region several copper 

and molybdenum porphyry deposits are intimately associated with 

just part of a much larger number of high-alumina alteration systems. 

EXAMPLES IN SOUTH ASIA AND OCEANIA 

North Sulawesi deposits--Widespread development of strong highalumina alteration is a distinctive characteristic of the Tapadaa and 

Tombuililato copper-gold districts, North Sulawesi, Indonesia 

(Lowder and Dow, 1978), and andalusite, pyrophyllite, diaspore, and 
METAL DEPOSITS IN OTHER REGIONS 21 

corundum are common in various mineral suites in the altered zones. 

At the Cabang Kiri prospect in the Tombuililato district, ore grade 

pyrite-bornite-chalcopyrite mineralization is associated with the 

assemblage quartz-diaspore-pyrophyllite; elsewhere in the same area 

high-alumina assemblages are not accompanied by ore-grade 

mineralization (Lowder and Dow, 1978, p. 638-639). It is important to 

note that the location of ore at the Cabang Kiri prospect is within the 

high-alumina alteration. 

V unda, Fiji, deposits--Sporadic gold mineralization in a 6 km 2 

hydrothermal alteration zone at Vunda, Fiji, has been described by 

Lawrence (1978). Alteration takes several forms and neither 

meaningful zonation nor correlation of alteration type with alteration 

intensity and strength of mineralization has been found. Pyritic, 

potassic, quartz-sericitic (phyllic), argillic, and propylitic alteration 

have been described by Lawrence (1978, p. 25-27), but three goldbearing alteration products are more important to this comparative 

study. These are quartz-sericite rock with traces of diaspore and 

gorceixite (a hydrous barium aluminum phosphate), quartz-sericitekaolinite rock, and quartz-diaspore rock. Lawrence (1978) interprets 

the Vunda deposit to be a weakly mineralized porphyry gold system 

probably related to the nearby Kingston porphyry copper deposit. 

Because the Vunda deposit is associated with shoshonite, Lawrence 

regards it as analagous to those porphyry deposits of British Columbia 

associated with alkali rocks. 

Tangse prospect, Sumatra, Indonesia--The Tangse coppermolybdenum prospect in Northern Sumatra is associated with a 

middle to late Miocene multiphase stock, consisting of various quartz 

diorite and dacite porphyries, that is intruded into a large composite 

middle-Eocene pluton of granitic to dioritic composition. As with the 

four porphyry occurrences in West Sumatra (Taylor and van Leeuwen, 

1980, p. 106-107), the intrusions and mineralization at the Tangse 

prospect are closely associated with the major northwest-trending 

Sumatran fault system. The deposit has been described by Taylor and 

van Leeuwen (1980) and Force and others (1981) and the material 

presented here is mostly condensed from the latter source. 

Hydrothermal alteration at Tangse is multistage and alteration 

types are telescoped. Early biotite alteration has affected almost all of 

the quartz diorite stock; late fracture controlled quartz-sericitic and 

high-alumina alteration characterized by andalusite have been 

superimposed on the early phase. The primary sulfide minerals pyrite, 

chalcopyrite, and molybdenite are present as disseminations and in 

veinlets. Chalcocite is generally present in a short interval directly 

below the oxidation zone. Lead and zinc are present as a well defined 

geochemical halo to the zone of copper and molybdenum 
22 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

mineralization. Gold is absent at Tangse, but substantial epithermal 

gold deposits are found along the fault zone further south in West 

Sumatra. 

HYDROTHERMAL CLAY DEPOSITS OF JAPAN AND KOREA 

High-alumina clays derived by hydrothermal alteration of 

volcanic rocks and some intrusive rocks are widespread in Japan and 

are also present in Korea. Deposits containing major pyrophyllite or 

andalusite, many of which are included in the type called Roseki 

clays, have features indicating that they formed close to the surface, 

yet have associated high-temperature minerals (Nakamura, 1954, p. 

35, lwao and Udagawa, 1969, p. 72, Kamitani, 1977, p. 50- 52). The 

largest hydrothermal clay deposits are in southwest Japan, where 

they are located in volcanic rocks of Cretaceous and early Tertiary 

age, but hydrothermal clays of Miocene through Quaternary age are 

also abundant, especially in central and northeast Japan (I wao and 

Udagawa, 1969, p. 71-72). Hydrothermal kaolin deposits are still 

being formed in active geothermal areas (Fujii, 1976, p. 7.) 

The high-alumina hydrothermal clays of Japan contain various 

combinations of the following minerals: alunite, andalusite, boehmite, 

chlorite, corundum, diaspore, dickite, dumortierite, halloysite, 

kaolinite, montmorillonite, pyrophyllite, sericite, sudoite (a 

dioctahedral aluminum-rich mineral of the chlorite group), topaz, and 

zunyite (lwao and Udagawa, 1969, p. 76-78). In addition, quartz is a 

common constitutent and may be abundant. Gypsum, pyrite, 

hematite, and native sulfur may be present. Very few anomalous 

values of Cu, Mo, Bi, W, and Sn have been reported, though it may 

that few analyses were made for the trace metals in the clays. 

The Ashio copper mine--The Ashio mine is located in Tochigi 

Prefecture, in central Japan north of Tokyo (36°38'N, 139°27'E). The 

mineralized zone is in an isolated mass of middle to upper Tertiary 

rhyolite that fills a funnel-shaped crater in Carboniferous and 

Permian sedimentary rocks (Nakamura, 1954, p. 36-38). Extensive 

hydrothermal alteration and polymetallic mineralization have taken 

place throughout much of this conical mass of rhyolite and to some 

extent in the surrounding Paleozoic rocks. The rhyolite funnel is 

elliptical in surface outline and 3.3 x 4.4 km (Kusanagi, 1955, p. 1). 

Rhyolitic lavas and pyroclastic rocks of Miocene age (S. I wao, 

1980, written commun.) fill a conical depression and rise to form the 

peak Bizendate, 1,272 m above sea level. A breccia of diverse clasts 

lining the inner slopes of the crater is interpreted to be a talus; the 

crater filling is rhyolitic lava, volcanic breccia, and tuff, changing 

upward to tuff breccia, lapilli tuff, and welded tuff, interpreted to be 
METAL DEPOSITS IN OTHER REGIONS 23 

the remnant of a stratovolcano, perhaps including a breccia pipe, 

(Kusanagi, 1955). 

Silicification, sericitization, and chloritization are major products 

of hydrothermal alteration associated with the metal-bearing veins. 

Most of the early high-alumina alteration has taken place in the 

breccia pipe, and Imai and others (1975, p. 667) report the minerals 

pyrophyllite, topaz, diaspore, corundum, zunyite, and andalusite; 

however, most of the ores appear unrelated to the early stage of 

alteration (Kusanagi, 1955, Nakamura, 1961). Pyrophyllite and topaz 

are present locally in the altered rhyolitic rocks of the high grade tin 

and copper ores (Nakamura, 1961, p. 108); these ores are interpreted 

to have formed early. The possible relationships of metallic ores to 

high-alumina alteration had not been fully studied at the time of 

Nakamura's article. 

Copper mineralization is present in an extensive stockwork of 

fissure veins that form a swarm about 2 km x 2 km in an area central 

in the crater, and extends downward 1 km. A few veins also extend 

outward into the surrounding Paleozoic rocks. Concentric mineral 

zones have been mapped by Nakamura (1954, fig. 1). A central Sn-WBi-Cu zone is present around the peak Bizendate; the grade of tin 

decreases abruptly downward. The intermediate zone contains Cu-AsZn, and the marginal zone is Zn-Pb-Cu-As. Gold, silver, and selenium 

are also present in the deposit. Flourine and phosphorus are indicated 

by the minerals fluorite, apatite and vivianite (Fukuchi, 1926, p. 10), 

and topaz is also present (lmai and others, 1975, p. 667). Flourine, by 

inference, must have been an important component of some alteration 

stage, but no evidence of boron enrichment has been noted. The 

breccia pipe, site of high-alumina alteration, is not central to the 

metal zones (Nakamura, 1954, fig. 1), but is located in Nakamura's 

zone III of marginal Zn-Pb-As-Cu mineralization. 

In addition to the vein swarm, massive replacement deposits and 

large disseminated orebodies also occur. Within the rhyolite these 

form crooked chimneys of sericitic and chloritic clay containing 

irregular masses of chalcopyrite (Fukuchi, 1926, p. 8-9). Bonanza 

deposits are also found as replacements in Paleozoic chert ("quartzite" 

of early authors) adjacent to the rhyolitic crater filling. 

Some of the mineral zonation at the Ashio mine is interpreted to 

be reversed due to inward collapse of the hydrothermal system (lmai 

and others, 1975, p. 667). 

Guryong prospect, southeastern Korea--Several porphyry-type 

copper and molybdenum prospects have been recognized north and 

west of Pusan in southeastern Korea (Sillitoe, 1980). One among 

these, near the Guryong vein-copper mine, is associated with an 

aluminous hydrothermal alteration zone. At Guryong, the zone of 
24 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

hydrothermal alteration is developed mainly in Upper Cretaceous 

andesitic volcanic rocks near an adamellite pluton. The core of the 

alteration zone, about 2 x 1.2 km, contains pyrophyllite and lesser 

amounts of diaspore, unidentified white clays, chalcedony, and pyrite; 

silicification is locally. dominant. Dumortierite was identified in one 

sample. Molybdenite, pyrite, and chalcopyrite are present in a 

stockwork of quartz veinlets that cut the aluminous altered rock 

beneath a thin leached capping. Pyrite and chalcopyrite are also 

present as exceptionally fine disseminations but disseminated 

molybdenite is rare. Sphalerite, galena, chalcopyrite, and pyrite were 

noted in a few late veinlets. At depth greater than 50 m, propylitic 

minerals and actinolite become more prevalent than aluminous 

minerals. 

GENERAL GEOLOGY OF THE CAROLINA SLATE BELT 

The main outcrop areas of rocks that are usually included in.the 

Carolina slate belt extend 650 km (400 mi.) from central"Georgia to 

southern Virginia in the Southeastern United States (fig. 1). Outlying 

localities and provisionally correlative areas can be included to make 

the belt even longer. The outcrop width is typically 40 to 80 km. More 

or less separated belts of similar rocks parallel the main slate belt to 

the northwest and southeast, such as the Belair belt on the GeorgiaSouth Carolina border and the eastern slate belt in north-central 

North Carolina. 

The slate belt in North Carolina has been mapped in detail in 

many local areas, and the rest has been completed on a reconnaissance 

scale. A recently completed map at approximately 1:125,000 covers six 

counties in north-central North Carolina, including the area around 

Asheboro (Carpenter, 1982). A preliminary geologic map at a scale of 

1:250,000 has been released for the Charlotte l

0

X2° quadrangle by 

Goldsmith and others (1982). Reconnaissance maps at a scale of 

1:250,000 have been prepared for the Raleigh 1 °X 2° quadrangle by" 

Wilson and others (1978) and for the Greensboro 1° X 2° quadrangle by 

J'Ones and Ferguson (1978, pl. 1a). For some of the State, the general 

lithologic map by Conley and Bain (1965) is still the most widely 

available. 

The volcanoclastic and epiclastic strata and a much lesser 

thickness of lava flows of the slate belt have been mapped in detail in 

the Denton, Albemarle, and Asheboro 15 min. quadrangles in central 

North Carolina, and in some adjacent areas (fig. 4). Stratigraphic and 

structural data have been recorded for this area (Conley, 1962; Seiders 

and Wright, 1977; Stromquist and Sundelius, 1969; Stromquist and 

others, 1971), although not all authors agree on major conclusions. 
GENERAL GEOLOGY, CAROLINA SLATE BELT 

ALBEMARLE 

§] 

~ 

[!EJ 

I mg I 

~ 0 

0 

X 

20 KILOMETERS 

10 

EXPLANATION 

15 MILES 

Area of volcanic and argillaceous rocks in which hard,flint-like 

rhyolitic flow rocks and associated felsic volcaniclastic strata are present 

Fine-grained, thinly laminat~d argillite and mudstone; locally 

includes sandstone, conglomerate, and felsic volcanic rock 

Andesitic to rhyolitic volcanic and volcaniclastic rocks; largely 

lapilli tuffs, crystal tuffs, and volcanic arenites 

Felsic and intermediate plutonic rocks; probably 

includes intrusives of two or more ages 

Metagabbro 

Felsic intrusive complex; massive to foliated 

Former gold mines and prospects 

Former pyrophyllite mine 

Pyrophyllite deposit 

FIGURE 4. Generalized geologic map of the Asheboro area, central North 

Carolina. Geology modified from Carpenter (1982). 

25 
26 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Part of the stratigraphic section here has been interpreted to be at 

least 25 km thick (Bell and others, 1980), and if this reconstruction is 

correct the total section could be even thicker, although there could 

also be undetected repetition. Black (1980, p. 271) has stressed that 

stratigraphic features can be expected to extend for only short 

distances in a volcanic arc environment of this type. Certainly little is 

known about the realiable extensions of facies and the distances over 

which reasonable stratigraphic correlations can be made. This is a 

major handicap in mineral resource studies as it is highly probable 

that several mineral commodities may be found here in environments 

that are essentially stratabound in distribution. 

The volcanosedimentary, epiclastic, and volcanic rocks of the 

Carolina slate belt are now generally believed to have originated in 

late Precambrian to Middle Cambrian continental margins or island 

volcanic arcs (Butler and Ragland, 1969; Glover 1973; and many other 

authors). Black (1980) calculated titanium-zirconium ratios in the 

manner of Kean and Strong (1975) and showed that the compositions 

of some of these rocks indeed best fit a model for volcanic arc areas, 

and that using several compositional criteria together, the rocks he 

studied definitely comprise a continental margin suite developed 

where the crust ranged upwards in thickness from 20 km. In contrast, 

Whitney and others (1978) concluded that the portion of the Carolina 

slate belt in the Lincolnton, Georgia-McCormick, South Carolina, 

area formed in a primative island arc where no thick continental crust 

is present, and may represent the earliest stage of island arc 

development found in the slate belt. They consider the formations in 

the upper part of the stratigraphic section in the Albemarle area, 

central North Carolina, to represent a later more calc-alkaline stage 

in arc development. With the limited geologic information now 

available, the position and dip direction of subduction zones associated 

with the original arc or arcs is highly problematic, but much discussed 

(Glover, 1976; Spence and Carpenter, 1976; Black and Fullargar, 

1976; and several others). 

Many persons now recognize that earlier interpretations of 

Carolina slate belt structure and stratigraphy have been too 

simplistic (Secor and others, 1983). It is generally known that 

different segments of the belt are characterized by widely divergent 

ages, structural styles, and metamorphic grades. The possibility that 

the belt is a complex assemblage of accreted terranes will certainly be 

considered in the near future, but truly reliable tests of 

interpretations of this sort are seriously limited by the dearth of 

detailed geologic mapping now available. 

Ages of705± 15 m.y. and 620 m.y. have been determined for rocks 

of the Carolina slate belt from Chapel Hill and Roxboro, N.C., 
GENERAL GEOLOGY, CAROLINA SLATE BELT 27 

respectively (Black, 1980). Rocks from the Albemarle area about 60 

km southwest of Asheboro have yielded ages in the 530 to 560 m.y. 

range (Black, 1980), and trilobites collected from relatively high in 

the stratigraphic section in the same general have been assigned an 

Early to Middle Cambrian age (St. Jean, 1973). Middle Cambrian 

trilobites from metamudstone in the Richtex Formation in the upper 

part of the slate belt section near Batesburg, S.C., 250 km southwest 

of Asheboro (Samson and others, 1982; Secor and others, 1983) have 

been described. 

Both radiometric and paleontologic ages in the Albemarle area 

relate to rock strata that are structurally high in the stratigraphic 

section; rocks that may be many kilometers lower in the section in this 

area are undated. Black (1979) concluded that slate belt rocks 

southwestward from Albemarle as far as the Georgia-South Carolina 

border are of the younger ages. 

Plutons have invaded the slate belt at many places; their ages 

have been shown to fall into two age brackets: 595 to 520 m.y. and 

about 300 m.y. (Fullagar and others 1973; Fullagar and Butler, 1979; 

and Speer and others, 1980). Thus, the older intrusions overlapped in 

time the deposition of many of the volcanic strata, and the possibility 

of a genetic relationship exists. 

Carolina slate belt strata range from gently folded and little 

deformed to very tightly folded and intensely sheared. In less well 

mapped areas, few top directions are know, but in many places the 

folding style can be surmised from the traces of resistant fold limbs 

that form hogback ridges many kilometers long. Abundant transverse 

faults and fractures are clearly expressed in drainage patterns. 

Regional metamorphism pervades the entire belt, the facies is mostly 

lower or middle greenschist. The gradation northwestward to gneisses 

of the Charlotte belt is essentially a metamorphic facies boundary 

(Secor and others, 1983). The time of deformation is bracketed by the 

ages of prekinematic plutons, about 560 m.y., and postkinematic 

plutons, about 400 and 300 m.y. (Kish and others, 1979), the main 

tectonic event having been "Taconic" (Kish and Fullagar, 1978). This 

places no limit on the number of orogenic events within the time 

bracketed1by these dates, however. As the absolute ages of slate belt 

rocks raqge from about 740 m.y. (Glover, 1973) to 500 m.y. (Butler, 

1979), it seems most unlikely that the slate belt strata were deposited 

in an unbroken continuum, and little is known about unconformities 

within the sequence, although one has been proposed in the Ramseur 

area (Harris, 1982). 

A volcanic belt, either at a continental margin or an island arc, is 

a highly favorable environment for the development of large vigorous 

hydrothermal systems and the formation of metal deposits of the 
28 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

porphyry-copper and porphyry-gold types. On the basis of volcanic and 

volcaniclastic rock suites, it should be possible to classify most areas 

in the Carolina slate belt as having formed near, at an intermediate 

distance, or far from volcanic sources. Assuming that porphyry 

alteration and mineralization systems form close to areas of eruption, 

the slate belt areas with coarse pyroclastic rocks and felsic flows 

should have formed closest to volcanic centers and, I think, be the 

most favorable prospecting areas. 

DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 

IN THE CAROLINA SLATE BELT 

Three deposits have been selected for further description because 

more geologic information regarding them is presently available. The 

Brewer mine in Chesterfield County, northeastern South Carolina, is 

presently inactive, has a long though intermittent history as a gold 

mine, and has many features of a porphyry-type deposit (fig. 1). The 

Pilot Mountain deposit in Randolph County, N.C., has been explored 

by Piedmont Minerals Co., Inc., as a potential pyrophylliteandalusite-sericite resource and has several substantial gold 

prospects or small abandoned mines at its margins (fig. 4). The mines 

operated by the Glendon Pyrophyllite Company in Moore County, 

N.C., are significant producers of pyrophyllite and other aluminous 

mineral products. They lack the widespread silification so strongly 

developed at the Brewer and Pilot Mountain deposits, which may 

indicate a different formative process. 

Each of these deposits is interpreted to be the site of major 

hydrothermal alteration of intermediate to felsic volcanic rocks. Each 

has significant amounts of iron sulfide associated with the altered 

rock and there are also various amounts of associated Cu, Mo, Sn, Au, 

and other metals. However, there is much difference in the total 

extent of alteration outside the orebodies and of general alteration 

style. The Brewer and Pilot Mountain alteration systems are mostly 

crosscutting in relationship to rock strata and structures while other 

deposits such as Hillsborough, and perhaps much of the Bowlings 

Mountain-Jones-White deposit group may be generally stratiform~ all 

of the deposits in Moore County seem generally stratiform, though 

cross- cutting features are present. These differences suggest that we 

may be dealing with very different types of hydrothermal systems, 

each yielding large bodies of high-alumina rock, but necessitating 

different interpretations for mineral exploration. 

Most of the high-alumina deposits of both types are present along 

two northeast-trending belts (fig. 1). The major belt extends for 170 

km from near Troy in Montgomery County, N.C., to near Oxford in 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 29 

Granville County, N.C. The Brewer mine near Jefferson in 

Chesterfield County, S.C., ma~elong in this belt as well, but is 

separated by a gaptf 100 km. Ot~r widely scattered monadnocks of 

high-alumina rock in the slate 'elt include Little Mountain and 

Boles Mountain, farther southwesl in South Carolina, and Graves 

Mountain, in Georgia (Espenshade and Potter, 1968). Several 

important pyrophyllite deposits are located in a lesser 20 km belt in 

Moore County, N.C., that trends a little more northeasterly than the 

major belt. The trend in Moore County seems to be approximately 

parallel to the strike of sedimentary layering but, lacking reliable 

stratigraphic markers, it is hard to know how stratabound the 

deposits actually are. It is very important to understand the structural 

or stratigraphic control that has caused these deposits to form mostly 

in narrow belts, but explanations are limited to speculations thus far. 

It is possible that the high-alumina deposits in both belts are 

subjected to certain lithologic controls. They seem to occur only in 

coarser pyroclastic materials such as lapilli tuffs and crystal tuffs or, 

as in Moore County, in pebbley volcaniclastic rocks and overlying fine 

sandstone and argillite. Near Asheboro, the deposits seem to be 

limited to areas of strongly deformed andesitic volcanic rocks. 

Elsewhere the stratigraphic section is less well known, but volcanic 

rocks of intermediate composition close to the Snow Camp and 

Glendon deposits are rather similar to rocks near Pilot Mountain. 

Volcanic and volcanosedimentary rocks north of Pilot Mountain were 

recently described by Harris (1982). 

Hydrothermal alteration at the Pilot Mountain deposit is believed 

to be related to a dacite porphyry stock and its dikelike apophyses. 

Subvolcanic dikes seem to have produced minor alteration effects in 

adjacent volcanic rocks at the Brewer mine but no specific source for 

major hydrothermal alteration effects has been identified there. The 

degree of hydrothermal alteration measured in terms of profound 

compositional change and near destruction of original volcanic 

textural features throughout surface areas measured in square 

kilometers at Pilot Mountain, the Brewer mine area, and several 

other deposits exceed that generally seen in porphyry copper systems. 

THE BREWER PORPHYRY GOLD DEPOSIT 

The alteration zone at this deposit is very large and has a 

polymetallic suite associated with it that seems characteristic of highflourine subvolcanic alteration at several known deposits in other 

regions. The mine produced gold intermittently from about 1828 until 

1939 or 1940; further evaluation of the deposit has been resumed 

(1980-84). Part of the following description has been modified from 

Schmidt (1978, p. E-24--E-25). 
30 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

The Brewer deposit is located near Jefferson in Chesterfield 

County, S.C. Gold mining was done first by placer in coastal plain 

sediments and saprolitic material, and later by openpit and 

underground methods in unweathered bedrock. The mining has been 

described by Leiber (1858, p. 63-68), Nitze and Wilkens (1896, p. 762-

767), and McCauley and Butler (1966, p. 36-40). 

The identification of topaz in the mine led to a drilling program by 

the U.S. Bureau of Mines in 1951-52 to determine the extent of the 

topaz reserve and the possibility of the use of the topaz for the 

production of calcium flouride with mullite as a coproduct. The results 

of this exploration program were described by Peyton and Lynch 

(1953). The cores of the 10 holes drilled on this program, retained by 

the U.S. Bureau of Mines, are the best source of information on the 

nature and extent of the rock alteration northwest of the old mine 

workings. The locations of part of the holes are shown in figure 5. 

General geology--The Brewer mine area is in felsic volcanic rocks 

of the Carolina slate belt close to and partly under the thin edge of the 

overlapping Coastal Plain strata. Minard (1971) and Nystrom (1972) 

divided the slate belt rocks present here into two units, one of 

volcaniclastic rocks, mainly felsic tuffs and flows but also some 

interbedded mafic units, and the second of gray and greenish gray 

thinly bedded argillite and slate. 

Geology of the Brewer alteration system--In the area close to the 

mine (fig. 5), the rocks that have been mapped by Minard (1971) as the 

volcaniclastic unit and by Nystrom (1972) as the felsic volcanic unit 

also include laminated argillite, as at point B-7 in the Tanyard Pit, as 

well as quartz-sercite schist and phyllite, sericitic argillite, 

porphyritic sulfide-bearing flow, various fragmental pyroclastic rocks, 

hard greenish-gray hornfelses, and three or more different kinds of 

probably hypabyssal porphyries. Country rock within the Brewer 

mine was described by Kinkel (written commun., 1968) as strongly 

silicified rhyolite, part of which is tectonic breccia, part pyroclastic 

breccia, and part tuff. Very recent work by Cherrywell and Butler 

(1984) provides additional data on the nature of this system. 

Over a large area near the old mines, including the areas explored 

by the U.S. Bureau of Mines core drilling, the rock has been so 

vigorously altered by hydrothermal action that in much of it the 

original rock textures have been destroyed. Although volcanic 

textures and bedding were noted in the mine, primary textures were 

widely destroyed there as well. Kinkel (written commun., 1968) 

described a variety of breccias in the dark gray chert like rocks in the 

walls of the mine, and breccias were common in three drill holes. Some 

of these had pyrite as the major cementing mineral. Some of the 

breccias may have been related to hydrothermal explosion events but 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 31 

data are now too scant to show this with certainty. The relative 

abundance of breccias in altered quartz rock was noted by Pardee and 

Park (1948, p. 107). Hypabyssal intrusive rocks have been recognized 

within the zone of strong hydrothermal alteration in the Tanyard pit, 

where a small dike of porphyritic rock penetrates laminated argillite 

in a thoroughly saprolitized exposure (point B-7, fig. 5). A zone of 

hematite-stained argillite saprolite about 5 m thick rims the porphyry 

intrusive, which is several meters thick. Xenoliths are common in the 

porphyry. The hematitic zone is interpreted to have been sulfidebearing before weathering. 

Scattered outcrops and float boulders along highway 110 about 1.5 

km west of the Brewer pit (fig. 5) include several porphyritic rocks 

that I believe to be other hypabyssal intrusive rocks (points B-13, B-14 

and B-16, fig. 5). Secondary hornblende has formed in argillaceous 

rocks at points B-16 through B-18, presumably by contact effects of 

the Pageland pluton about 0.5 km to the north. A dark gray 

porphyritic trachyte at point B-16 has been affected by this contact 

metamorphism, indicating that at least some of the hypabyssal rocks 

are older than the Pageland pluton. 

Two zones of hydrothermal alteration were first mapped by 

Nystrom (1972), an inner zone of quartz granofels, which he called 

"massive quartzite", and a surrounding zone of siliceous sericitepyrite schist that grades outward to unaltered laminated argillite and 

felsic volcanics (fig. 5). 

The quartz granofels is a fine-grained, dense, and compact quartz 

rock, very light to dark gray and bluish gray. The color is at least 

partly controlled by small amounts of included sericite or 

pyrophyllite, and disseminated pyrite, and local significant 

admixtures of topaz. Traces of relict breccia textures are widespread 

in the granofels; some rock preserves sedimentary or volcanic 

textures, but much of the rock retains the forms of neither clasts nor 

beds. Nystrom (1972, p. 16) emphasized the massiveness of this rock, 

"without bedding, cleavage, foliation, or any other planar or linear 

feature." Fresh rock contains from minor traces to over 15 volume 

percent sulfide, mainly pyrite. In the zone of oxidation this has been 

altered to iron oxide yielding a reddish or brown- stained quartz rock, 

or, where sulfide was most abundant, a gossan. 

In the quartz granofels adjoining the mined areas radial clusters 

of pyrophyllite as much as 5 em across are common, and smaller 

grains ofpyrophyllite and kyanite are present in the gold ore (Kinkel, 

written commun., 1968). Pyrophyllite, andalusite, and lesser kyanite 

were common minerals in the tunnel draining the Brewer pit, in a 

drift extending northward from that pit. and also in the U.S. Bureau 

of Mines drill cores. Some of the highly altered rock is more than 95 
32 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

qm 

Ia 

-------

tv 

tv 

0 

Cu" 3 

0 

fv 

Mo~~~ • 1 

(_Cp\ • 

" ", Cu,Mo t \.._~_) '.: \ 7~gossans @, As,Bi,Sn 0 1Vf' ~, , 'UI ... I 

A ·-G / --~// 

cp 

qsp 

Geology adapted from Pardee and 

Park (1948) and Nystrom (1972) 

2 KILOMETERS 

1 MILE 

FIGURE 5. Hydrothermal alteration at the Brewer mine, Chesterfield County, S.C. 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 33 

As-x 

7 __...-Cu 

~Mo 

so-@ 

-.......Sn 

1

0 __..--As 

"'-Bi 

EXPLANATION 1 

Alluvium-Includes sand, gravel, silt, clay, and mine tailings 

Coastal plain sediments 

Laminated argillite and slate-Fine-grained, greenish- and 

brownish-gray, probably tuffaceous 

Felsic volcanic rocks-Includes rhyolitic tuff, rhyolite porphyry, lapillite, hornblende plagioclase schist, and muscovite schist 

Quartz monzonite-Coarse-grained, pink and gray, porphyritic. Intrusive into rocks of Carolina slate belt 

Quartz granofels-Intensely silicified rock, quartz content 

commonly exceeds 80 percent; includes locally abundant 

andalusite, pyrophyllite and topaz. Areas of outcrop shown 

shaded 

Quartz-sericite-pyrite schist-Light-toned to white schist and 

phyllite, weathers white with patches of iron-oxide stain. 

Includes layers of quartz granofels south of the Brewer 

mine, shown shaded 

Contact-Dashed where gradational or inferred 

U.S. Bureau of Mines cored drill hole 

Field sample site and number 

Copper 100 ppm or more in soil sample 

Copper 100 ppm or more in gossan sample 

Arsenic 300 ppm in saprolite sample 

Copper 100 ppm or more in drill core 

Molybdenum 300 ppm or more in drill core 

Copper 10,000 ppm in drill core 

Tin 150 ppm or more in drill core 

Arsenic 3000 ppm in drill core 

Bismuth 500 ppm or more in drill core 

Hard rock gold mine, abandoned 

Placer gold mine, abandoned 

1

Analyses from A. R. Kinkle, Jr. (written communication, 

1967) and from samples of drill core collected by 

Henry Bell, Ill, 1973. 

FIGURE 5. Continued 
34 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

percent quartz and some contains as much as 80 percent andalusite. 

Rocks are commonly made up of only two or three hydrothermal 

alteration minerals; the assemblages most frequently noted are 

quartz-pyrophy llite, quartz-muscovite, and a 1 usi te-q uartzpyrophyllite, pyrophyllite-diaspore-kaolinite, and quartz-topaz. 

Pyrophyllite is commonly found forming a sheath around andalusite 

grains and isolating them from quartz. Rutile is a widespread trace 

mineral in the altered rock. There were minor amounts of several 

other minerals that I was not able to identify in a thin section. 

Topaz was identified in the altered volcanic rocks of the Brewer 

mine by Pardee and others (1937). These authors found the topaz to 

contain only 13.23 percent flourine and to have a correspondingly low 

specific gravity of 3.509. As in many other Carolina deposits, the 

topaz-rich material here is difficult to distinguish from dense siliceous 

quartz granofels rocks unless the high specific gravity is noted. The 

material was generally called flinty quartz or blue hornstone in the 

reports ofpre-1937 examinations, and the high area around the mine 

was called Blue Flint Hill (Leiber, 1858, p. 65). The topaz occurs as 

disseminated fine grains, as patches and streaks of aggregates, and as 

masses of microcrystalline grains. All these are made up of rounded 

individual grains only a few microns in diameter. Pardee and others 

(1937, p. 1062) reported that only a few grains had an euhedral form. I 

observed only rounded shapes. The composition of one sample of topazrich rock is given in table 2. 

A shell or band of siliceous sericite-pyrite schist completely 

surrounds the quartz granofels; Nystrom (1972) mapped this as a unit 

and called it sericite phyllite. Mostly moderately to strongly foliated, 

some phases of the schist retain faint to well-preserved textures of fine 

volcaniclastic sediments, tuffs, and coarse fragmental material. 

Traces to several percent of disseminated fine pyrite grains or small 

voids marking the former locations of sulfide grains are present in all 

of this rock. The extent to which siliceous sericite-pyrite schist may be 

present in the inner quartz granofels zone between outcrops of the 

weathering-resistant quartz-rich rocks is not clear, but none was 

penetrated by any of the U.S. Bureau of Mines drill holes. 

Primary gold ore, all within the area mapped as quartz granofels, 

consists of silicified topaz-pyrite altered rhyolite, in which local areas 

several centimeters across consist entirely of fine-grained granular 

pyrite (A. R. Kinkel, Jr., 1968, written commun.). Kinkel further 

stated in regard to mineralization in the Brewer pit and adjacent 

workings, "All of the pit walls were equally mineralized and to about 

the same degree as the few exposures in the bottom of the pits. Mining 

has certainly not reached the limits of the deposit in any of the pits, 

and there may be a considerable amount of unmined ore horizontally 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 35 

TABLE 2.-Rapid rock analysis of topaz-rich hydrothermally altered rock from drill hole 

8, 13.4 to 19.5 meters depth, Brewer mine area, South Carolina. 

[Lab no., W-180860; field no., B-8-44-64. Hole was drilled by U.S. Bureau of Mines, and the sample for analysis was kindly furnished by them. Analytical methods used are supplemented by atomic absorption; P. L. D. Elmore, 

analyst. Cu, Bi, Mo, and W were obtained by activation analysis; P. Aruscavage, E. Lillie, and L. Mei, analysts). 

Constituent Percent or parts per million 

Si02 ---------------- 76.0 

Al204 --------------- 16.0 

Fe203--------------- .43 

FeO---------------- .08 

MgO --------------- .02 

CaO---------------- .32 

Na20 --------------- .09 

K20---------------- .52 

H2o+ --------------- 1.2 

H2o- --------------- .oo 

Ti02 ---------------- .45 

P20s---------------- .09 

MnO --------------- .02 

C02 ---------------- <.05 

F ------------------ 4.0 

Cu ----------------- 63 ppm 

Bi ----------------- .41 ppm 

Mo ----------------- 23 ppm 

W ----------------- 4.2 ppm 

as well as in depth." He found gold in flakes several millimeters 

across, both in the granular pyrite and on joints. Kinkel was 

impressed with the copper content of considerable areas in the pits 

(table 3)~ enargite was the principal copper mineral he observed. 

Much of the gold mined at the Brewer during early years of 

· operation came from the placer working of overlying gravelly 

sediments of Cretaceous age and from supergene enriched deposits in 

saprolite (Nitze and Wilkins, 1896, p. 764). 

A diverse suite of metallic elements that tends to occur together at 

other subvolcanic hydrothermal ore deposits worldwide is found in the 

Brewer mine area. The presence of the metal suite Cu, Mo, Bi, W, Sn, 

As, and Au has been confirmed by recent chemical analyses, and the 

presence of Ag indicated (tables 3, 4). Minerals containing these 

metals were reported by various authors, mostly before 1895; these 

include chalcopyrite and enargite, (Lieber, 1856) covellite (Becker, 

1895, p. 295), and bismuth ochre (bismite) and native bismuth 

(Tuomey, 1848, p. 97). Cassiterite has been identified only in black 

sands associated with placer mining at the Brewer mine, but it was 

present "in some quantity" and crystals as large as 1 em. (one-half 
36 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

TABLE 3.-Analyses of hard rock with fresh pyrite from the Brewer mine area, South 

Carolina. 

[Traces of tin and bismuth were detected in a few samples. From A. R. Kinkle, Jr. (written commun., 1968~. All values in parts per million). 

Field no. Lab no. Au Cu As 

Brewer pit ---------SC JM 261 ABV 667 12.0 400 

Brewer pit ---------K 289 ABP 310 4.5 800 700 

Topaz pit ----------K 356 ABX 023 3.9 20 20 

Topaz pit ----------K 1458 ABX 972 0.56 500 200 

Hartman pit --------K 358 ABX 025 .64 < 10 20 

Hartman pit --------K 359 ABX 026 1.9 < 10 < 10 

Hartman pit --------K 361 ABX 028 .22 < 10 < 10 

inch) were collected (Clark and Chatard, 1884, p. 25). In addition, 

chalcanthite and rutile were listed by Peyton and Lynch (1953, p. 3). 

Sulfides make up an estimated 1 to 5 volume percent of all rock in 

the cores from 9 of the 10 U.S. Bureau of Mines drill holes. In two cores 

taken near the old Brewer pit, average sulfide content was close to 5 

volume percent. In one hole (No. I) the estimated sulfide content over 

an interval of33.2 m was 15 volume percent. 

Potassium-argon ages of muscovite-pyrophyllite rock at the 

Brewer pit were determined to be 430± 15 m.y. and 401 ± 14 m.y. (Bell 

and others, 1972). 

GENERAL GEOLOGY OF THE PILOT MOUNTAIN -FOX MOUNTAIN 

REGION (RAMSEUR 7i' QUADRANGLE) 

The area of figure 4 surrounding Pilot Mountain and Fox 

Mountain is underlain by a complex thick sequence of andesitic to 

felsic lapilli tuffs, interpreted to be a relatively older and more 

deformed part of the slate belt. I have not assigned these rocks to any 

formational unit, but a thesis by Harris (1982) proposes correlations 

with the Hyco and Aaron Formations of the Roxboro-Durham, N.C., 

area. West of Pilot Mountain, the strata of the Asheboro area have 

been divided into the Tillery Formation, largely thinly laminated 

siltstone and claystone, and the underlying Uwharrie Formation, 

chiefly felsic volcaniclastic rocks (Conley and Bain, 1965). Several 

small bodies of mafic-rich plutonic and porphyritic rocks (not shown 

on figure 4) crop out north and south of Pilot Mountain, and a felsic 

intrusive complex, the Parks Crossroads granodiorite of Tingle (1982), 

is present southeast and east of Ramseur. 

This larger area of plutonic rock southeast and east of Ramseur 

consists of several phases of two rock types, a mafic-rich foliated 
TABLE 4.-Semiquantitative spectrographic analyses of selected chip samples from U.S. Bureau of Mines drill holes, Brewer mine area, 

South Carolina 

[N=not detected at limit of detection; L=detected, but below limit of determination; G=greater than 1 percent. All values except TiO, in parts \>er million. In addition to values shown in table, all 

samples were analyzed for the following elements: Fe, all samples, 2-20 percent; B, Mg, all samples, detected but below limit of determinatiOns; Au, Cd, Zn, all samples, not detected at limit of detection; W, all samples "N" except hole 9, 24.4 meters, which is 70 ppm. Samples selected and analyses requested by Henry Bell; analyses by G. W. Day, U.S. Geological Survey, November 6, 1973] 

Hole Depth No. (meters) Ti (percent) Mn Ag As Ba Bi Co Cr Cu La Mo 

1 32.0 1 10 1 700 20 30 N N 50 N 50 

1 36.3 .7 15 N 200 100 500 N N 700 20 50 

1 58.2 .5 L .5 3,000 50 200 30 N 10,000 50 30 

1 78.9 .3 10 2 N 50 100 30 10 700 20 30 

7 45.1 .7 L 10 N 300 500 5 10 200 200 70 

9 24.4 G L N N 70 N 10 15 150 N 700 

Limit of 

Detection .002 .5 200 20 10 5 10 5 20 5 

--

Hole Depth I 

No. (meters) Nb Ni Pb Sb Sc Sn Sr v y Zr 

1 32.0 L 5 L 100 15 200 N 20 10 500 

1 36.3 N L 30 N 15 30 1,000 50 10 300 

1 58.2 N 20 100 200 10 150 100 30 10 300 

1 78.9 N 30 15 N 7 15 N 15 N 200 

7 45.1 N L 500 N 15 150 1,000 30 15 500 

9 24.4 30 5 30 N 30 70 N 150 30 1,000 

Limit of 

Detection 20 5 10 100 5 10 100 10 10 10 

0 

l::!lj 

~ 

e 

~ 0 

z 

rr; 

0 

I'!!J 

~ 

r; 

~ 

~ 0 

::z:: 

s 

::z:: 

> 

~ 

c:: 

~ > 

0 

~ 

"C 

0 

~ 

~ 

~ 

~ 
38 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

quartz-diorite and a potassic mafic-poor granitic porphyry. The 

relationship between the two has not been determined. 

The quartz-diorite contains 10 to 25 percent quartz, 50 to 65 

percent plagioclase, a trace of potassic feldspar and 10 to 40 percent 

mafic minerals. The latter are mixtures of relict shreds of chlorite, 

biotite, epidote, and amphibole; the texture suggests that foliated 

amphibole was the principal mineral at an earlier stage in the 

metamorphic history of the rock, and that biotite, epidote, and chlorite 

are products of the last greenschist-facies event. Thus the quartzdiorite may have undergone an earlier and higher grade period of 

metamorphism than other rocks of the area, including slate belt 

volcanic rocks from outcrops only a few meters distant. No certain 

aureole effects have been observed in slate belt rocks adjacent to this 

plutonic phase. The quartz diorite phase of this rock has been 

radiometrically dated by the Rb/Sr method as 566±46 m.y. (Tingle, 

1982). 

Quartz monzonitic and quartz dioritic rocks unmapped north of 

Pilot Mountain and others shown on figure 6 south of Pilot Mountain 

appear to be various phases of this same general type of plutonic rock. 

The second plutonic rock type, a fine-grained granitic porphyry, is 

found in an area of unknown size east of Ramseur. The rock is light 

gray with a salt and pepper appearance~ matrix grains are up to 0.5 

mm in greatest dimension, and relatively sparse plagioclase 

phenocrysts are about 5 mm long. The rock is quartz-rich, containing 

50 percent of that mineral, 35 percent potassic feldspar, and 15 

percent plagioclase. Sparse biotite was the predominant or only mafic 

mineral prior to metamorphism; its positions are now occupied by 

chlorite and epidote. Epidote is common as a metamorphic alteration 

product in many plagioclase grains. There are traces of fluorite 

present. Two-phase and gas-filled inclusions are common to abundant 

in quartz grains; cubic crystals presumed to be halite are present in a 

few inclusions. Minerals and textures in this rock do not seem to 

indicate more than one period of metamorphism, and it is tentatively 

interpreted to be younger than the nearby quartz diorite. It is not 

known if this granitic porphyry is unconformably overlain by the 

volcanic strata or if it is intrusive into them. I have not yet found 

places where a contact between the two plutonic rocks or between a 

plutonic rock and fresh slate belt rocks is exposed. 

The unnamed largely andesitic rocks near Ramseur, Pilot 

Mountain, and Fox Mountain consist of lapilli tuff, tuff breccia, and 

crystal tuff, with lesser flow rocks and locally extensive volcaniclastic 

materials. Their abundant chlorite and epidote suggest a more 

generally andesitic composition. The andesitic rocks also seem 

somewhat more deformed, but this may be a result of their greater 

mafic mineral content. Exposures of dominantly andesitic volcanic 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 39 

rock alternate with intervals of dacitic to rhyolitic volcanics in 

abundant outcrops in the bed of Deep River and along the abandoned 

railroad grade that runs close to the river from Cedar Falls to 

Ramseur. Many good outcrops, mostly andesitic, are also present in 

the bed of Richland Creek, and to a lesser extent along the smaller 

streams. Studies of bedrock at about 50 sites in the Ramseur 

quadrangle have suggested no simple subdivisions according to 

composition or texture, except that sandstone and mudstone seem to 

be more abundant close to the contact with the pluton east of 

Ramseur. The rocks between Cedar Falls and Ramseur have been 

divided into two major units and correlated with the Hyco and Aaron 

Formations of the Roxboro-Durham area by Harris (1982). 

Within the town of Ramseur, water-laid volcaniclastic arenite 

beds are common, though they are locally present farther west as well. 

These arenites and some silty argillites may comprise a stratigraphic 

thickness of several hundred meters in the easternmost 1,000 m of the 

formation. Close to the contact of the volcanic sequence with plutonic 

rocks, porphyritic rocks that I interpret to be dacite or latite flows are 

common. If the andesitic strata were deposited unconformably on the 

plutonic rocks, these flows and areni.te beds may form the lowermost 

strata in the andesitic sequence. 

The Uwharrie Formation in the Asheboro 15-min. quadrangle was 

mapped and described by Seiders (1981) as consisting of felsic 

volcaniclastic rock and lava and subordinate mafic volcanic rock. The 

predominant rock is thin to thick bedded light to dark gray and part 

pale green lapilli tuff, tuff, and tuff breccia; clasts in these volcanic 

rocks are very rarely as long as a meter; generally they do not exceed 2 

em and are angular to subrounded, or sometimes well rounded. Some 

clasts with poorly preserved lenticular textures may have been 

collapsed pumice. Local light to dark gray felsites are flow-layered 

and (or) spherulitic. Parts of the felsites have abundant phenocrysts of 

albite and quartz. Many felsite layers are closely associated with felsic 

arenite and volcaniclastic conglomerate. Strata of the Uwharrie 

Formation are considered to be of Cambrian and (or) Proterozoic Z age 

(Seiders, 1981). 

The volcanic rock strata are folded along northeast trending axes 

and near-vertical dips with strikes about N50° E characterize the 

bedding near Ramseur. The felsic volcanic bodies included within 

slate belt rocks west and south of Asheboro trend about N25° E. Many 

of these have shapes that suggest folds plunging both northeast and 

southwest, and fold axes plunging each of these directions have been 

identified in the field. 

Only one period of regional metamorphism can be distinguished 

for most slate belt rocks, but some of the quartz monzonite and quartz 

diorite southeast of Ramseur (fig. 4) may have been subjected to at 
40 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

least two periods of regional metamorphism, the first to amphibolite 

facies and the last to midgreenschist facies. Rocks of the andesitic 

volcanic sequence seem generally uniformly metamorphosed to the 

midgreenschist facies, with abundant chlorite and epidote. 

Penetrative deformation ranges from very strongly developed to 

moderate, but it is not certain whether this indicates different 

deformational histories or is a function of rock composition. Rocks 

mapped as Uwharrie Formation are also modified by metamorphism 

to the midgreenschist facies, with sparse fresh metamorphic biotite in 

the felsic volcanics and abundant biotite, epidote, and actinolite in 

nearby mafic strata. Pentrative deformation in the Uwharrie may be 

mostly moderately developed; some related porphyritic rocks with 

barely detectable foliation remain a puzzle. 

PILOT MOUNTAIN PORPHYRY GOLD SYSTEM 

Pilot Mountain is a prominent isolated monadnock 279 m above 

sea level, located 13 km southeast of Asheboro, N.C., in Randolph 

County (fig. 4). All of the monadnock is made up of hydrothermally 

altered rock and there are at least four groups of long-abandoned gold 

mines and prospects on the flanks of Pilot Mountain. A pyrophylliteandalusite body northwest of the crest has been evaluated for mining 

several times, the latest in 1978-83 by Piedmont Minerals Co., Inc. 

Additional concentrations of pyrophyllite and lesser amounts of 

andalusite scattered within quartz granofels and quartz-sericitepyrite schist extend westward from the mountain, altogether 

occupying an area 4.5 km long in an east-west direction and 2 km wide 

(fig. 6). All of the exposures of altered rock are presumed to be part of 

the same hydrothermal alteration system, but this is not proved. The 

system is also marked by a 4 km2 area of low-level but anomalous 

amounts of copper, molybdenum, and tin in soils (fig. 7, table 1). 

Geology of Pilot Mountain--The nature of most of the bedrock of 

Pilot Mountain prior to alteration is hard to determine because 

hydrothermal alteration has modified both composition and texture of 

the rocks. From sparse exposures of incompletely modified rocks 

around the edges of the zone of alteration and by projections of the 

trends of rock units present a few kilometers away, it is possible to 

conclude that most of the altered rock was formerly andesitic lapilli 

tuff plus smaller amounts of laminated argillite, volcanic-rich 

sediment, crystal tuff, and flows; but along the southeastern flank of 

Pilot Mountain the protolith was part of a subvolcanic(?) dacite 

porphyry body containing abundant rounded quartz grains up to 5 mm 

long. 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 41 

The area of hydrothermal alteration grades outward on the 

southwest, west, and north to metamorphosed andesitic and dacitic 

volcanic rock and laminated tuffaceous argillite, but the outcrops are 

sparse in these directions. Three different rock types bound the 

hydrothermal alteration on the southern and southeastern sides 

where the margin is more closely controlled. These include quartz 

monzonitic and dioritic plutonic rocks, gray felsic volcaniclastic rock, 

and subvolcanic dacite porphyry (fig. 6). 

The quartz monzonitic and dioritic rocks south of Pilot Mountain 

include a variety of generally foliated dark chloritic granitic rocks 

with both plutonic and porphyritic textures. Compositions also tend to 

differ considerably within each outcrop area as well as between areas. 

Textures range from faintly to distinctly porphyritic with largest 

feldspar grains ranging from 2 to 5 mm long. Quartz comprises 10 to 

30 percent in rounded grains or subhedral crystals. Some of the 

rounded grains are probably embayed and some of the porphyritic 

phases may include volcanic material. Plagioclase exceeds potassic 

feldspar by 3 to 4 times; the plagioclase is extensively altered to 

sericite and epidote. Biotite has been the principal or only mafic 

mineral and may have been as abundant as 30 percent of some phases 

but was much less common in others. It is now partly to entirely 

altered to chlorite and epidote. Most of the porphyritic rocks contain 

small pyrite cubes. Some small areas of porphyritic quartz monzonitic 

rock are included in the northern part of the area shown on figure 6 as 

gray felsic volcaniclastic rock. Part of the quartz monzonite there has 

been intensely altered to quartz and sericite and contains 15 to 20 

percent pyrite. At other localities the quartz monzonite and dacite 

lack effects of hydrothermal alteration, even when close to highly 

altered parts of the Pilot Mountain system, leading one to the 

conclusion that the contact may locally be a fault surface younger 

than the alteration. 

Gray felsic tuff and felsic arenite outcrops are common in a km2 

area southwest of Pilot Mountain and south of the zone of 

hydrothermal alteration (fig. 6). The outcrops include light to dark 

gray probably dacitic and rhyolitic rocks. Megacrysts of quartz and 

plagioclase are generally smaller than 2 mm and are not abundant. 

Isolated outcrops of similar rocks are found within the highly altered 

rocks, and these are interpreted to be unconformable younger strata 

infolded with the altered rocks. Tentatively, I interpret the outcrop 

area of gray felsic volcaniclastic rocks and felsite porphyry shown on 

figure 6 to be an extension along strike of the layered rocks of 

Needhams Mountain 10 km to the southwest, and thus a part of the 

Uwharrie Formation. I believe that this volcanic unit laps 
42 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Base from U S. Geolog1cal Survey, 

Ramseur, N.C. quadrangle. 1968 0 1 MILE 

f---------,------_j 

0 1 KILOMETER 

FIGURE 6. Hydrothermal alteration at Pilot Mountain, Randolph County, N.C. 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 43 

Geology by R G Schmidt 

and T L Klein. 1978-82 

Adapted from Milton and 

others. 1983 

r::::::1 

l.:____;_d 

EXPLANATION 

Gray felsic volcaniclastic rocks and felsic porphyry 

or crystal tuff-Light- to dark-gray felsic arenite 

and porphyritic dacite and rhyolite; megacrysts 

of quartz and plagioclase generally smaller than 

2 mm, not abundant. Unit probably unaffected 

by hydrothermal alteration. 

Andesitic and dacitic volcanic rocks-Largely lapilli 

tuffs and crystal tuffs or porphyritic flows, probably includes volcaniclastic units. Light- to darkgreenish-gray, chloritic. Probably a major protolith 

of hydrothermally alt~red rocks 

W Dacite porphyry- Generally light-gray; abundant 

quartz and plagioclase phenocrysts up to 5 mm 

across. Generally hydrothermally altered; contains 

pervasive disseminated pyrite 

Quartz monzonitic and dioritic plutonic rocks-Darkgreenish-gray; chlorite and epidote rich. Local 

porphyritic phases, some of which may include 

volcanic material. Generally foliated. No gradation 

to hydrothermally altered rocks recognized 

D Quartz granofels and quartz-sericite-pyrite schist 

with high-alumina pods- Moderately to intensely 

silicified rock; quartz content commonly over 80 

percent, especially on Pilot Mountain and Pine 

Hill. Generally contains sparse pyrophyllite and 

a few percent of disseminated sulfide. Encloses 

unknown amount of silicified argillite and quartzsericite-pyrite schist which does not commonly 

form outcrops. Includes pods containing abundant 

pyrophillite, andalusite, topaz, and pyrite. Textural 

features of protolith mostly obliterated except 

for quartz phenocrysts 

Quartz-sericite-pyrite schist-Includes small pods of 

quartz granofels and lenses of chloritic volcanic 

rocks. Pyrite content generally 2-10 percent. 

Gradational to unaltered andesitic and dacitic 

volcanic rocks 

Contact-Dashed where inferred 

~ Gold mines and prospects, abandoned 

FIGURE 6. Continued 
44 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

79°42'30" 

35°40' • 

Rt. 42 

/ 

/ 

35°40' !-/ 

? 

Rt. 42 

Molybdenum and tin 

• 

• 

• 

• 

? 7 I i 

• 

Copper 

• ? 

• • 

• 

• 

• 

• 

• 

79°40' 

EXPLANATION 

• Soil analysis site 

"" Mountain crest 

c;;::) Sn 5-16 ppm 

(f!Jjj) Mo 1Q-21 ppm 

0 2 KILOMETERS 

~----~~--~-~ 

FIGURE 7. Soil sample analyses, Pilot Mountain area. Adapted from 

Milton and others (1983). 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 45 

unconformably onto the altered rock southwest of Pilot and was 

deposited after alteration. 

Dacite porphyry is present in a 2 km2 area east and southeast of 

Pilot Mountain. This generally gray rock has abundant phenocrysts of 

quartz and plagioclase up to 5 mm across, but in some places the 

phenocrysts are less than 2 mm. Much or all of the porphyry, 

especially the coarse-phenocryst phase, has undergone strong 

hydrothermal alteration. Outcrops are generally poor and much 

weathered and do not permit easy interpretation of variations in 

texture, composition, and degree of hydrothermal alteration. In many 

weathered exposures and float blocks the abundant quartz 

phenocrysts are the only identifying feature. Southeast of Pilot 

Mountain the alteration is to quartz-sericite-pyrite rock with 

potassium feldspar in some samples. On the southeast slope of the 

mountain intense alteration has converted the porphyry to quartz 

granofels and only the phenocrysts remain to identify the protolith. 

Isolated occurrences of quartz granofels containing 3 to 5 mm relict 

quartz phenocrysts near the top and on the north slope of Pilot 

Mountain suggest the presence of dacite apophyses away from the 

main stock. 

Hydrothermal alteration--The hydrothermal alteration zone that 

includes Pilot Mountain is over 4.5 km long and as much as 2 km wide 

(fig. 6), and within this zone the composition and textures of much of 

the pre-existing rock have been profoundly changed. The rock with 

strongest alteration contains masses, lenses, and pods of highalumina minerals enclosed in quartz granofels and quartz-sericitepyrite schist. The enclosing rock in the eastern end of the zone, 

especially oh Pilot Mountain and Pine Hill, contains much quartz 

granofels, and most of the topaz recognized in the system is located 

there. Westward from Pilot Mountain quartz-sericite-pyrite schist 

encloses the pods and lenses of high-alumina minerals that 

characterize the innermost strongly altered zone, and quartz granofels 

is much less abundant. The high-alumina pods are made up of 

different proportions of pyrophyllite, andalusite, kaolinite, pyrite, 

chloritoid, and rutile; topaz is common at many locations on the west 

slope of Pilot Mountain and only a little has been identified west of 

there. Diaspore and lazulite were not observed although they occur in 

many similar deposits in the region. 

Quartz-sericite-pyrite schist without associated high-alumina 

pods has been mapped as a separate unit peripheral to the most 

strongly altered zone (fig. 6). The appearance of this unit contrasts 

sharply with the surrounding andesitic lapilli tuffs and greenstones. 

The schists appear considerably deformed and strongly 

hydrothermally altered. Pyrite is present mostly in disseminated 
46 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

grains a few of which are as large as 1 mm, but most of which are less 

than 0.5 mm and less commonly in small wispy stringers. The fine size 

makes abundance difficult to estimate, but the sulfide content in some 

phases may be as great as 30 percent. Near large masses of quartz 

granofels, the quartz-sericite-pyrite schist includes minor lenses or 

pods of the granofels, commonly pyrophyllite-bearing; near the 

gradational contact with surrounding andesitic volcanics, the quartzsericite-pyrite schist may contain small isolated pods of andesite or be 

quite intermixed with the less altered rock. 

Quartz-rich granofels with minor pyrophyllite and pervasive 

minor sulfide is the most prevalent type of altered rock throughout the 

eastern part of the zone of intense alteration and thus enclosing the 

high-alumina layers on the northwest slope of Pilot Mountain. It 

comprises most of the large outcrop area on the south slope of Pilot 

Mountain, especially on the low knob known as Pine Hill. 

Outcrops and large residual boulders on the crest and northwest 

slope for 100 m from the crest of Pilot Mountain include the following: 

(1) massive pyrophyllite rock made up of an intergrowth of radiating 

crystalline clusters up to 1 em in diameter, light gray to white, and 

with no other mineral in significant amount; (2) pyrophylliteandalusite-quartz rock in which the andalusite is present in rounded 

grains and knots, each commonly sheathed in a 0.5-2.0 mm layer of 

pyrophyllite, and set in a matrix of quartz and pyrophyllite; (3) topazquartz rock consisting of irregular nearly pure masses of each mineral 

a few millimeters to a few centimeters across; the quartz in mosaics of 

very fine grains up to 0.1 mm across, the topaz in mats of grainlets so 

fine as to be barely resolvable in a 0.3 mm thin section; and (4) quartzpyrophyllite-sulfide granofels in which the quartz generally comprises 

80 to 95 percent of the rock, and the spaces formerly occupied by 2 to 5 

percent sulfide are now voids partly filled by encrustations of 

hematite or goethite. Core drilling on the northwest slope of Pilot 

Mountain indicates the presence in the subsurface of several rock 

types not seen in outcrop, including laminated argillite, crystal and 

lapilli tuff, mafic flow rock and soft clay of unknown origin. 

There is little doubt that Pilot Mountain stands as an erosionresistant monadnock because of the highly aluminous and siliceous 

rocks present; still, the detailed physiography of the mountain and the 

outcrop patterns there tell us little about the sizes and shapes of the 

andalusite-pyrophyllite masses and of various other mineral facies of 

the quartz granofels. From the experience of mining other deposits 

with similar mineral suites but perhaps not identical formational 

history, masses rich in ore mineral species such as pyrophyllite are 

believed to form lenticular bodies several meters thick and tens of 

meters long. These lenses may be elongated in the general direction of 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 47 

the layers of volcanic rocks. In the mine at Hillsborough, N.C., the 

individual lenses seem to be arranged in a shingled or en echelon 

fashion rather than strictly parallel to the bedding strike. Elongate 

resistant outcrops of quartz granofels that are almost pure quartz are 

present on the low knob called Pine Hill on the south flank of Pilot 

Mountain. These outcrops trend about N .55°E. Elsewhere on Pilot 

Mountain low outcrops of quartz granofels, pyrophyllite-rich rock, or 

pyrophyllite-andalusite rock give little indication of the actual extent 

of these phases in the bedrock. 

Float material on the crest of the mountain includes pieces of 

quartz granofels with brecciated texture, but the origin of the breccia 

has not been determined. A type of rock common on the northwest 

slope of the mountain has 3 to 5 mm andalusite grains in a fine matrix 

distributed in a manner that resembles the texture of a porphyry. The 

porphyrylike texture may be only coincidence, but I believe that in a 

few of the rocks the andalusite grains have replaced the sites of former 

plagioclase phenocrysts. 

Metallic mineralization--In addition to widespread pyritization in 

the zones of hydrothermal alteration, anomalous amounts of copper, 

molybdenum, and tin are present in the overlying soils (fig. 7 and 

Milton and others, 1983). Gold was sought in several prospects within 

the alteration zones and three operations, the Pilot Mountain, 

Harney, and Pine Hill mines, may have yielded a profit, but there are 

no records of production. Nothing is known of the way the gold 

occurred. 

Pyrite is disseminated through much of the high-quartz and 

pyrophyllite-andalusite altered rock, and quartz-sericite-pyrite schist, 

but has been leached to such depths that it is not generally seen in 

outcrops and prospect trenches; however, surface rocks have abundant 

voids left by dissolution of the sulfide. Some voids contain linings of 

iron oxide or the surrounding rock is stained, but in others most of the 

iron oxide has been leached out as well. Fresh pyritic rock has been 

penetrated by exploration drilling on the northwest slope of the 

mountain, and is present in dump material at the old Pine Hill gold 

mine on the south flank and at old prospects on the north slope. 

Locally abundant small flakes of molybdenite were also found 

disseminated and in small veinlets in quartzose rock on the Pine Hill 

mine dump. Neither copper nor tin minerals were observed on the 

surface or in mine dumps. Very small patches stained by secondary 

copper minerals are present at many places in drill cores. 

Small but distinctly anomalous amounts of copper, molybdenum, 

and tin are present in soils on Pilot Mountain within the quartz 

granofels area known to have undergone strongest hydrothermal 

alteration, and anomalous copper is found in an adjacent area of 
48 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

sulfide-bearing quartz-sericite schist north of Pilot Mountain (fig. 7) 

also interpret~d to be altered. Soils of most of the anomalous area are 

believed to overlie rock that was formerly sulfide-bearing. The soils 

are residual and have been subjected to strong acid leaching by H2S04 

formed on oxidation of the widespread sulfide; organic acids produced 

by the decomposition of forest litter, largely oak leaves, provided 

leachants over long periods of time. Values for tin and molybdenum 

are highest near the area where andalusite and pyrophyllite are most 

developed and drop significantly away from the alteration area on 

Pilot Mountain; copper values decrease eastward and southward, but 

copper relationships to the north and west beyond the edge of the 

quartz-sericite-pyrite schist are not clear. Control soil samples were 

taken on other high rock ridges, some of them with small amounts of 

disseminated sulfide in the bedrock; analyses of copper, molybdenum, 

and tin from these control samples were very low (table 5). 

Hydrothermal alteration at Fox Mountain and Iron Mountain--Fox 

and Iron Mountains are two monadnocks separated by a low saddle, 8 

km east of Asheboro and 6 km northwest of the crest of Pilot Mountain 

(fig. 4). Surrounding rocks are believed to be andesitic lapilli tuffs but, 

as at Pilot Mountain, many of the rocks on these monadnocks are so 

altered that original characters are difficult to determine. 

Pyrophyllite is abundant near the crest of Fox Mountain, and 

especially down the southern flank; it is also present along the east 

side of the saddle and to some extent on the east slope of Iron 

Mountain, forming a zone elongate in a north-south direction about 1 

km long. Several long-abandoned mine workings and prospect pits on 

the east side of Iron Mountain appear to have been developed for gold 

or perhaps iron ore close to outcrops of pyrophyllite rock. The dump 

rock at the mines includes lapilli tuff, white quartz, gray metallic 

specularite, siliceous rock with 3 to 4 mm pyrite cubes, and pieces of 

limonitic gossan. Examination of what I believe to be a small ore pile 

suggests that mining was mostly in quartz veins in a zone of partial 

oxidation. A small prospect shaft on the southeast slope of Fox 

Mountain followed a weakly magnetic hematitic zone in siliceous 

coarse lapilli tuff or breccia. Breccia on the top of Fox Mountain 

consists of abundant small light gray fragments in a black matrix, and 

gray schistose rocks from the same area contain as much as 5 percent 

disseminated fine- grained pyrite. 

The Fox Mountain-Iron Mountain area has been tested using only 

ten soil samples. One sample from Iron Mountain contained an 

anomalous amount of copper (94 ppm) and three samples contained 3 

to 4 ppm of tin. All samples contained less than the detectable limit of 

molybdenum. Association of low levels of anomalous copper and tin, 

probably some gold ores, and extensive development of pyrophyllite 
DESCRIPTIONS OF SELECTED HIGH-ALUMINA DEPOSITS 49 

TABLE 5.-Analyses of 12 soil samples from unaltered felsic rock monadnocks 

[In ppm. Emission spectrographic analyses by J. L. Harris and Leung Mei. After Milton and others, 1983) 

Latitude Longitude Sample Monadnock north west No. Cu Mo Sn 

Shepherd Mt. ------------------35°45.11' 79°57.0' 27 9.4 <1.0 3.2 

35°45.25' 79°57.0' 28 24. <1.0 3.4 

35°45.32' 79°57.2' 30 7. <1.0 2.0 

35°45.05' 79°57.3' 33 17. <1.0 3.8 

35°45.27' 79°57.1' 68 6.2 <1.0 1.9 

35°45.06' 79°56.9' 69 3.9 <1.0 1.8 

Stackrock Mt. -----------------35°39.8' 79°48.3' 66 6.5 <1.0 1.6 

Caraway Mt. ------------------35°45.1' 79°53.4' 67 6.3 <1.0 1.6 

Buck Mt. ---------------------35°24.4' 79°59.9' 71 8. <1.0 <1.5 

"Pine M t." --------------------35 o 30.65' 79°29.5' 73 13. <1.0 <1.5 

35°30.58' 79°29.6' 74 26. <1.0 3.1 

Worth Mt. --------------------35°46.2' 79°46.9' 79 13. < 1.0 <1.5 

and disseminated sulfide suggests a hydrothermal system similar to 

that at Pilot Mountain, though smaller in scale. The hypothesis that 

the Fox Mountain-Iron Mountain alteration is part of a much larger 

Pilot Mountain system is a tentative working model that can only be 

tested by much more field work. 

HIGH-ALUMINA DEPOSITS IN MOORE COUNTY 

The Standard Mineral Company mines and Glendon Pyrophyllite 

Company mines of Moore County form a secondary linear trend 

separate from the major deposit trend (fig. 1). There is enough 

difference between the Brewer and Pilot Mountain systems in the 

northwestern major trend and the minor trend in Moore County to 

suggest origins under somewhat different physical conditions, but 

there are also features in common, such as the widespread association 

of gold and of minor amounts of copper and molybdenum (table 1). 

The deposits of Moore County are a lined along a trend generally 

corresponding to sedimentary strike for a distance of 20 km. In 

addition to major deposits and many prospects along this line, there 

are several small deposits and prospects a few kilometers to the south. 

High-alumina minerals are present in pod-shaped masses of 

pyrophyllite and kaolinite or sericite are locally abundant ,as well. 

Chloritoid and pyrite are abundant in the rocks adjacent to the ores; 

andalusite and diaspore are rare or absent. Major quartz veins are 

common within the ores, but silification of host rock, so important in 

certain deposits in the major trend, is minor or wholly lacking. The 
50 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

effects of hydrothermal alteration do not extend far beyond the ores 

and may be limited to an additional volume of rock little greater than 

the ores themselves. A little flourite is present but neither topaz nor 

tourmaline has been reported. 

In the part of the Moore County trend north of Glendon, 

unpublished detailed studies by T. L. Klein show that high-alumina 

deposits have formed close to the sedimentary transition from lapilli 

breccia and conglomeratic mudstone to an overlying fine-bedded 

tuffaceous argillite and lapillite. Both units have been altered to highalumina minerals and the alteration cuts across the bedding. There 

appear to be segments of volcanic rocks and sediments along strike 

between orebodies where little or no alteration has taken place. 

The volcaniclastic rocks have been affected by pervasive strong 

penetrative deformation, perhaps stronger here than in the Asheboro 

area. Many drag folds can be seen in the mines, and it is possible that 

folds are most intense in the zone favored by the ore deposits~ 

exposures are much poorer a way from the mines, however, and the 

regional distribution of drag folding is insufficiently known. 

Strike faulting and axial plane displacements on drag folds can be 

seen at several places in the mines. Faulting in several mines, 

interpreted as a single major strike fault, was held by Stuckey (1967, 

p. 29) to be an important control of hydrothermal solutions. Prominent 

quartz veins appear to occupy some of the fault planes and may well 

represent former solution channel ways. 

Many problems regarding ore controls and temporal relationships 

of ore-forming processes to deformational history remain, but the 

deposits in Moore County probably represent orebodies formed under 

different physical conditions from such deposits as the Brewer and 

Pilot Mountain. The Moore County deposits may represent lower 

temperature parts of similar systems and hence may have been more 

distant from the heat source. Lack of evidence that andalusite was 

ever abundant here and the absence of large silicified zones suggest a 

lower formational temperature, or less acid solutions in a weaker part· 

of a hydrothermal system. 

OTHER DEPOSITS IN NORTH CAROLINA 

Data on metal content of soils, veins, or associated sulfides have 

been obtained as part of this study, or earlier by Lesure (1981), for 10 

other pyrophyllite prospects and mines (fig. 1), and I have briefly 

visited at 15 more. All of these deposits are located in lapilli-bearing 

or tuffaceous volcanic strata and are known to have masses of rock 

containing disseminated sulfide associated with them in some way 

(table 1). Sulfide-bearing bedrock zones and associated soils were 
ORIGIN OF HIGH-ALUMINA ALTERATION SYSTEMS 51 

sampled for metal analysis. Two mine areas yielded soil and rock 

samples containing slightly anomalous amounts of copper and two 

areas had molybdenum analyses greater than background. 

ORIGIN AND SIGNIFICANCE OF THE HIGH-ALUMINA 

ALTERATION SYSTEMS 

Hydrothermal alteration has produced at least 40 large bodies of 

aluminous rock in andesitic to rhyolitic mostly pyroclastic volcanic 

rocks in the Carolina slate belt. Part of these include areas of silificied 

rock that may be as large as 4.5 km long and 2.5 km wide. Within the 

silicified bodies, pods and lenses of pyrophyllite have formed; these 

pods commonly include also andalusite, diaspore, topaz, and kaolinite. 

In some deposits the vicinity of some of the high-alumina 

mineralization is marked by anomalous amounts of copper, 

molybdenum, and tin in the residual soils. Gold has been mined from 

locations within the silicified zone of at least 5 of the deposits, but 

there are also many others from which no gold occurrences have been 

reported. In addition to the previously mentioned metals, arsenic and 

silver are present in anomalous amounts at several places within the 

Pilot Mountain alteration system, and arsenic, bismuth, and tungsten 

occur in small amounts at the Brewer deposit. 

Topaz is known to be present at many of the major deposits and 

may well be present though unreported at the rest. Tourmaline has 

been observed in patches in only one deposit, and being much easier to 

spot in the field, must be generally rare or absent. Thus, flourine is 

known to have been introduced by hydrothermal alteration in many of 

the systems while boron was probably not commonly present. 

Phosphorus-bearing minerals are widespread but are always very 

minor in amount. In rocks interpreted to have been hydrothermally 

altered, rutile as widespread very small grainlets is the most common 

titanium-bearing mineral recognized. 

The minerals present and the configurations of the Brewer and 

Pilot Mountain deposits suggest that these two systems formed under 

generally similar conditions of pressure, temperature, and solution 

chemistry. The widespread presence of andalusite and the absence of 

kyanite except for local concentrations at the Brewer deposit imply 

formation at relatively low pressures--less than 2 kilobars--and 

temperatures ranging 300 to 400°C. The temperature precludes 

deposition under atmospheric pressure and the deposits cannot be said 

to be spring-related in the sense of being almost at the surface, but low 

pressure required by the absence of kyanite in many deposits implies 

relatively shallow depth and a high geothermal gradient. For Graves 
52 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Mountain, Ga., and Willis Mountain, Va., Allard and Carpenter 

(1981) have described generally stratiform zones of high-alumina 

alteration, and by analogy to the Otake geothermal field of Japan, 

refer the origins of these deposits to shallower, more truly fumarolic 

systems. Less metamorphosed examples of such shallower systems in 

North Carolina may include the Moore County deposits, the 

Hillsborough deposit, and perhaps the more stratiform parts of the 

Bow lings Mountain-Jones-White deposit area as well. 

The capacity to alter large amounts of volcanic rock drastically, 

moving silica freely and leaching all other contituents except alumina 

from certain zones, required a strongly acid solution in large volumes. 

From the minerals present we can assume that flourine was probably 

an important constituent of the solution. 

Shallow but vigorous hydrothermal systems in volcanic rocks such 

as these in the slate belt are commonly associated with subvolcanic 

intrusive rocks as in the widely occurring subvolcanic types of 

porphyry copper deposits. Shallow intrusive bodies, mostly with 

porphyritic textures, are the heat engines that drive the hydrothermal 

circulation. In many porphyry copper deposits successive intrusive 

phases including both stock like masses and dike swarms have 

contributed to the total alteration history and the successive 

intrusives of these sequences tend to cut and cause alteration of the 

earlier bodies. Subvolcanic intrusives are interpreted to have been 

major altering agents in the Pilot Mountain deposit. Several 

porphyritic dikes have been noted within the Brewer system, but too 

little is known about them to specifically relate them to the major 

alteration. 

Examples of copper and molybdenum porphyry deposits associated 

with high- alumina alteration are scattered from Canada to Chile, and 

several porphyries with high-alumina alteration occur in east and 

southeast Asia, some having gold associated with them. However, the 

most important analog is the major Paleozoic porphyry copper 

province of central Kazakhstan in the Soviet Union. Of several 

hundred mapped highly-silicic alteration zones in felsic and 

intermediate volcanic rocks, many have strong high-alumina 

components. Several are larger than 30 km2, and many form 

monadnocks. In these relatively unmetamorphosed deposits, the 

minerals pyrophyllite, andalusite, diaspore, corundum, alunite, 

dickite, sericite, topaz, and abundant highly silicified rock are 

considered by Nakovnik (1968) and other workers to be hydrothermal 

in origin. Of 18 copper, copper-molybdenum and molybdenum 

porphyries there, at least 6 are related to high- alumina systems. The 

largest and best known, the Kounrad Mine, with 10 mil tons of copper 

metal, is a good example of a subvolcanic alteration system in volcanic 
REFERENCES CITED 53 

rocks with an alteration suite similar to certain of the Carolina 

deposits, but with copper and molybdenum in economic quantity. 

SUMMARY 

I believe it is reasonable to conclude that the large alteration 

systems in the Carolina slate belt with widespread quartzification and 

development of pyrophyllite, andalusite, and pervasive disseminated 

sulfides are variations of porphyry copper and (or) gold systems and, 

as a consequence, deserve careful consideration for their mineral 

resource potential. The pressure-temperature specific alteration 

suites indicate relatively shallow formation of the altered rocks now 

exposed. The Brewer deposit may represent a somewhat deeper level 

of erosion into the system; it also has the greatest amount of copper, 

molybdenum, and tin. Pilot Mountain and other large andalusitebearing deposits with large highly-silicified alteration envelopes are 

interpreted to be similar systems eroded to a slightly lesser depth than 

the Brewer. The Moore County deposits and perhaps other generally 

stratiform systems may be either considerably shallower, or the result 

of much smaller and weaker systems. 

REFERENCES CITED 

Allard, G. 0., and Carpenter, R. H.,1981, Alteration in the Otake geothermal field--A 

model for interpreting certain metamorphic assemblages in metamorphosed 

volcanic terranes (abs.), in Symposium on arc volcanism 0981: Tokyo, Japan, and 

Hakone-machi, Japan), D. Shimozuru and I. Yokoyama, eds.: Tokyo, Terra 

Scientific Publishing Co., p. 1-2. _ 

---1982a, The relationship between aluminosilicate assemblagesand sulfide 

mineralization in volcanic terranes (abs.): Geological Association of CanadaMineralogical Association of Canada, Program with abstracts, v. 7, p. 35. 

---1982b, Aluminosilicate assemblages: an exploration tool for metavolcanic 

terrains of the southeast: in Exploration for metallic resources in the Southeast, 

G. 0. Allard and R. H. Carpenter, conveners: University of Georgia Department of 

Geology and Center for Continuing Education, p. 19-22. 

---1983, Use of mineralogical anomalies in exploration for base and precious 

metals within metavolcanic terranes (abs.): Society of Mining EngineersAmerican Institute Mining and Metallurgical Engineers, 112th annual meeting 

technical program, p. 11. 

Becker, G. F., 1895, Gold fields of the southern Appalacians: U.S. Geological Survey, 

16th Annual Rept., pt. 3, p. 251-331. 

Bell, Henry, III, Marvin, R. F., and Mehnert, H. H., 1972, Potassium-argon ages from 

ages of hydrothermal alteration in South Carolina: U.S. Geological Survey 

Professional Paper800-D.,p. D117-D121. 

Bell, Henry, III, and Popenoe, P., 1976, Gravity studies in the Carolina slate belt near 

the Haile and Brewer mines, northcentral South Carolina: U.S. Geological Survey 

Journal of Research, v. 4, p. 667-682. 
54 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Bell, Henry, III, and Carpenter, R. H., and Feiss, P. G., 1980, Volcanogenic ore deposits 

ofthe Carolina slate belt: Excursions in southeastern geology, v. 1, R. W. Frey, 

(ed.): Falls Church, Virginia, American Geological Institute, p. 149-178. 

Black, W. W.,1980, Chemical characteristics ofmetavolcanics in the Carolina slate belt 

in the Caledonides in the U.S.A.: Proceedings ofi.G.C.P. project 27, Caledonide 

Orogen, 1979 meeting. Blacksburg, Virginia, Department of Geological Sciences, 

Virginia Polytechnic Institute and State University memoir 2, p. 271-278. 

Black, W. W., and Fullagar, P. D.,1976, Avalonian ages ofmetavolcanics and plutons of 

the Carolina slate belt near Chapel Hill, N.C. (abs): Geological Society America, 

abstracts with programs, v. 8, no 2, p.136. 

Brimhall, G. H., Jr., 1977, Early fracture-controlled disseminated mineralization at 

Butte, Montana: Economic Geology, V. 72, no.1, p. 37-59. 

Broadhurst, S.D., and Councill, R. J., 1953, A preliminary report on high-alumina 

minerals in the volcanic-slate series, North Carolina: North Carolina Department 

of Conservation and Development, Division of Mineral Resources Information 

Circular 10,22 p. 

Bryant, D. G., and Metz, H. E.,1966, Geology and ore deposits ofthe Warren mining 

district: in Geology of the porphyry copper deposits, Southwestern North America: 

Tucson, Arizona, University of Arizona Press, p. 189-204. 

Butler, J. R.,1979, The Carolina slate belt in North Carolina and northeastern South 

Carolina: a review: Geological Society of America abstracts with programs, v. 11, 

no. 4, p. 172-173. 

Butler, J. R., and Ragland, P. C., 1969, Petrology and chemistry of meta- igneous rocks 

in the Albemarle area, North Carolina slate belt: American Journal of Science, v. 

267. p. 700-726. 

Cargill, D. G., Lamb,J., Young, M. J., and Rugg, E. S., 1976, Island Copper, in Porphyry 

deposits of the Canadian Cordillera, A. Sutherland Brown, ed., Canadian Institute 

of Mining and Metallurgy, Special volume 15, p. 206-218. 

Carpenter, P. A., 111,1982, Geologic map of Region G, North Carolina: North Carolina 

Department of Natural Resources and Community Development, Geological 

Survey Section, Regional geology series 2 • 

Carpenter, R. H. and Allard, G. 0., 1980a, Volcanogenic mineralization near 

Lincolnton, Georgia, and McCormick, South Carolina, U.S.A. (abs.): Norges 

Geologiske Undersekelse, Bull. 57, p. 327. 

---1980b, Mineralization, alteration, and volcanism in the Lincolnton-McCormick 

district, Georgia and South Carolina (abs.): Geological Society of America, 

abstracts with programs, v.12, n. 7, p. 398-399. 

Cedillo, E., Munoz, C., and Yana, G., 1979, Procesos de alunitizacion en el yacimiento de 

Cerro Verde: Boletin Sociedad Geologica Peru, v. 62, pt. 3, p. 1-18. 

Cherrywell, C. H., and Butler, R. J., 1984, Geology of the Brewer gold mine, Chesterfield County, South Carolina (abs.): Geological Society of America abstracts with 

programs,v.16,n.6,p.469. 

Clarke, F. W., and Chatard, T. M.,1884, Mineralogical notes from the laboratory ofthe 

U.S. Geological Survey: American Journal Science, 3rd ser., v. 28, p. 20-25. 

Clapp, C. H.,1915, Alunite and pyrophyllite in Triassic and Jurassic volcanics at 

Kyuquot Sound, British Columbia: Ecomomic Geology, v.10, no.1, p. 70-88. 

Conley, J. F., 1962, Geology of the Albemarle quadrangle, North Carolina: North 

Carolina Department of Conservation and Development Bull. 75, 26 p. 

Conley, J. F., and Bain, G. L., 1965, Geology of the Carolina slate belt west of Deep 

River-Wadesboro Triassic basin, North Carolina: Southeastern Geology, v. 6, no. 

3,p.ll7-138. 
REFERENCES CITED 55 

Dagger, G. W.,1972, Genesis of the Mount Pleasant tungsten-molybdenum-bismuth 

deposit, New Brunswick, Canada: Institute of Mining and Metallurgy, 

Transactions, v. 81, p. B73-B102. 

Espenshade, G. H., and Potter, D. B., 1960, Kyanite, sillimanite, and andalusite 

deposits of the Southeastern States: U.S. Geological Survey Prof. Paper 336, 121 p. 

Force, E. R., Sirkirno Djaswadi, and van Leeuwen, Theo, 1981, Exploration for porphyry 

metal deposits based on rutile distribution: a test in Sumatra: Indonesia 

Directorate of Mineral Resources, Bulletin 1, n. 1, 13 p. 

Fujii, Noriyuki, 1976, General review on kaolin clay deposits in Japan, in the 7th 

gymposium on genesis of kaolin, Shimoda, S., ed: Tokyo, International Geological 

Correlation Programme,p.1-16. 

Fukuchi, Nobuyo, 1926, The Ashio copper mine: Guide-book Excursion C-1, Pan-Pacific 

Science Congress, 19 p • 

Fullagar, P. D., and Butler, J. R., 1979, 325 to 265 m.y .-old granitic plutons in .the 

Piedmont of the southeastern Appalacians: American Journal Science, v. 279, no. 

2, p.161-185. 

Fullagar, P. D., Ragland, P. C., and Butler, J. R., 1973, Geochemistry and geochronology of plutonic rocks in the southern Appalacian piedmont (abs.): Geological 

Society of America, abstracts with programs, v. 5, no. 2, p. 161- 162. 

Glover, Lynn, III, 1973, Age and origin ofthe volcanic Carolina "slate" belt of the 

Appalacian piedmont (abs.): Geological Society of America abstracts with 

programs,v.5,no.2,p.166-167. 

---1976, Tectonicsofthe piedmont of North Carolina and Virginia: review and 

speculation (abs.l: Geological Society of America abstracts with programs, v. 8, no. 

2,p.181. 

Goldsmith, Richard, Milton, D. J., and Horton, J. W.,Jr.,1982, Simplified preliminary 

geologic map of the Charlotte 1 °X2° quadrangle, North Carolina and South 

Carolina: U.S. Geological Survey Open-File Report OF 82-0056. 

Guilbert, J. M., and Zeihen, L. G., 1964, The mineralogy of the Butte district, Montana: 

Mimeographed text prepared for presentation to the Northwest Mining 

Association, Spokane, Washington, December 4, 1964, 12 p. 

Gustafson, L. B., and Hunt, J.P., 1975, The porphyry copper deposit at El Salvador, 

Chile: Economic Geology, v. 70,no.5, p.857-912. 

Harris, C. W., 1982, An unconformity in the Carolina slate belt of central North Carolina: new evidence for the areal extent: MS thesis, Virginia Polytechnic Institute 

and State University, Blacksburg, Va., 90 p. 

Hemley,J. J., Montoya, J. W., Marinenko,J. W., and Luce, R. W., 1980, Equilibria in 

the system Al20a-Si02-H20 and some general implications for 

alteration/mineralization processes: Economic Geology, v. 75, n. 2, p. 210- 228. 

Hildebrand, F. A.,1961a, Hydrothermally altered rocks in eastern Puerto Rico: U.S. 

Geological Survey Prof. Paper 424-B, p. B219-B221. 

---1961b, Andalusite-topaz greisen near Cagnas, East-Central Puerto Rico: U.S. 

Geological Survey Prof. Paper 424-B, p. B222-B224. 

Imai, Hideki, Min Sung Lee, Kohei I ida, Y oshinori Fujiki, and Sukune Takenouchi, 

1975, Geologic structure and mineralization of the xenothermal vein-type 

deposits in Japan: Economic Geology, v. 70, no. 4, p. 647-676. 

lwao, Shuichi, and Udagawa, Shiquekazu, 1969, Pyrophyllite and "Roseki" clays in The 

clays of Japan, edited by Editorial subcommittee for "The Clays of Japan," 

Organizing Committee, 1969 International Clay Conference: Geological Survey 

Japan, p. 71-87. 

Jones, P. L., and Ferguson, R. B., 1978, Preliminary basic data release, Greensboro 

l 0 X2° NTMS area, North Carolina and Virginia: Energy Research and 

Development Administration report 7 4-78. 
56 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Kamitani, Masaharu, 1977, Genesis of the andalusite-bearing Roseki ore deposits in 

the Abu district, Yamaguchi Prefecture, Japan: Bulletin Geological Survey Japan, 

v.28,n.4,p.201-271. 

Kean, B. F., and Strong, D. F., 1975, Geochemical evolution of an Ordovician island arc 

of the central Newfoundland Appalacians: American Journal of Science, v. 275, p. 

97-118. 

Kish, S. A., and Fullagar, P. D., 1978, The timing of Paleozoic metamorphism and 

deformation in the southern Appalacians: Geological Society of America, abstracts 

with programs, v.10, no. 7, p. 435 

Kish, S. A., Butler, J. R., and Fullagar, P. D., 1979, The timing of metamorphism and 

deformation in the central and eastern piedmont of North Carolina: Geological 

Society of America, abstracts with programs, v. 11, no. 4, p.184-185. 

Knight,J. E., 1977, A thermochemical study of alunite, enargite, luzonite, and 

tennantite deposits: Economic Geology, v. 72, no. 7, p.1321-1336. 

Kusanagi, Tadaaki,1955, On the geological structure and its relation to the mineralization in the rhyolitic complex of Ashio mine: Mining Geology, v. 5, n. 16, p. 77-

88. In Japanese with English abstract. 

Lawrence, L. J.,1978, Porphyry type gold mineralisation in shoshonite at Vunda, Fiji, 

Proceedings Australasian Institute of Mining and Metallurgy, no. 268, p. 21-31. 

Laznicka, P., 1976, Porphyry copper and molybdenum deposits of the U.S.S.R and their 

plate tectonic settings: Transactions Institute of Mining and Metallurgy, v. 85, 

February 1976,p. Bl4-B32. 

Lieber, 0. M., 1856, Report on the survey of South Carolina: 1st annual report, 

Columbia, S.C., 136 p. 

---1858, Report on the survey of South Carolina: 2nd annual report, Columbia, 

S.C., 145 p. 

Lesure, F. G., 1981, Maps showing reconnaissance geochemistry in north-western Moore 

County, North Carolina: U.S. Geological Survey Map MF -1301. 

Lowder, G. G., and Dow, J. A. S., 1978, Geology and exploration of porphyry copper 

deposits in north Sulawesi, Indonesia: Economic Geology, v. 73, no. 5, p. 628-644. 

Magak'yan, I. G., 1961, Rudnye mestorozhdeniya (promyshlennye tipy mestorozhdeniy 

metallicheskikh poleznykh iskopaemykh): Yerevan, Publishing house of the 

Academy of Sciences of the Armenian SSR, 548 p • 

McAllister, A. L., and Lamarche, R. Y., 1972, Mineral deposits of southern Quebec and 

New Brunswick: Guidebook Excursion A-58-C-58, 24th International Geological 

Congress, Montreal, 95 p • 

McCauley, C. K., and Butler, J. R., 1966, Gold resources of South Carolina: South 

Carolina Division Geology Bulletin 32, 78 p. 

Meyer, Charles, and Hemley, J. J ., 1967, Wall rock alteration, in Geochemistry of 

hydrothermal ore deposits, H. L. Barnes, ed.: New York, Holt, Rinehart and 

Winston, Inc., 670 p. 

Milton, N. M., Collins, William, Chang, Sheng-Huei, and Schmidt, R. G., 1983, Remote 

detection of metal anomalies on Pilot Mountain, Randolph County, North 

Carolina: Economic Geology, v. 78, n. 4, p. 605-617. 

Minard, J.P., 1971, Gold occurrences near Jefferson, South Carolina: U.S. Geological 

Survey Bull. 1334,20 p. 

Nakamura, T., 1954, Tin mineralization at the Ashio copper mine, Japan: Journal 

Institute Polytechnics, Osaka City University Ser. G., 2, p. 35-50. 

---1961, Mineralization and wall-rock alteration at the Ashio copper mine,J a pan: 

Journal Institute Polytechnics, Osaka City University, ser. G., v. 5, p. 53-127. 

Nakovnik, N. 1., 1936, Secondary quartzites and their ores: Transactions Central 

Geological and Prospecting Institute, no. 58, p. 1-50. 
REFERENCES CITED 57 

---1958,0 Korundovykh Mestorozhdeniyakh Sheshen'-Kara i Semiz-Bugu v 

Tsentral'nom Kazakhstane: Vestn. An KazSSR, n.12. 

---1968, Secondary quartzites of the U.S.S.R and mineral deposits related to 

them: Moscow, lzdatel'stvo "Nedra," 336 p. In Russian. 

Nitze, H. B. C., and Wilkens, H. A. J ., 1896, The present condition of gold mmmg in 

the southern Appalachian states: American Institute of Mining Engineering 

Transactions 25, p.661-796, 1016-1027. 

Nystrom, P. G., Jr., 1972, Geology ofthe Catarrh NW Quadrangle: Thesis submitted 

in partial fulfillment of the requirements for the Degree of Master of Science, 

Department of Geology, Univ. South Carolina, 49 p. 

Papezik, V. S., Keats, H. F., and Vahtra,J., 1978, Geology of the Foxtrap pyrophyllite 

deposit, Avalon Peninsula, Newfoundland: Canadian Mining and Metallurgical 

Bull. v. 71, no. 791, March 1978, p.152-160. 

Pardee, J. T., Glass, J. J ., and Stevens, R. E., 1937, Massive low flo urine topaz from 

the Brewer Mine, South Carolina: American Mineralogist, v. 22, p. 1058-1064. 

Petruk, William, 1964, Mineralogy of the Mount Pleasant tin deposit in New 

Brunswick: Canada Department of Mines and Technical Surveys, Mines Branch, 

Technical Bulletin TB 56, 37 p. 

Peyton, A. L., and Lynch, V. J., 1953, Investigation of the Brewer topaz deposit, 

Chesterfield County, South Carolina: U.S. Bureau of Mines Report of 

Investigations 4992, 19 p. 

Pilcher, S. H., and McDougall,J. J., 1976, Characteristics of some Canadian Cordilleran 

porphyry prospects in Porphyry deposits of the Canadian Cordillera, A. Sutherland 

Brown, ed., Canadian Institute of Mining and Metallurgy, Special volume 15, p. 

79-82. 

Puchkov, Ye. V., Alekseyeva, L. K., and Gulyayev, A. P., 1968, Eruptive breccias and 

connection between them and hydrothermal metamorphism and mineralization 

(northwestern Balkhash region): International Geology Review, v. 12, n. 1, 1970, 

p.65-73. 

Ruitenberg, A. A., 1967, Stratigraphy, structure and metallization, Piskahegan-Rolling 

Dam area: Leidse Geologische Mededelingen, v. 40, p. 79- 120. 

---1972, Metallization episodes related to tectonic evolution, Rolling Dam and 

Mescarene-Nerepis Belts, New Brunswick: Economic Geology, v. 67, No.4, p. 434-

444. 

Samson, S. L., Secor , D. T., Jr., Snoke, A. W., and Palmer, A. R., 1982, Geological 

implications of recently discovered Middle Cambrian trilobites in the Carolina 

slate belt: Geological Society of America Abstracts with programs, 1982, p. 607. 

Schmidt, R. G., 1978, The potential for porphyry copper-molybdenum deposits in the 

eastern United States: U.S. Geological Survey Professional Paper907-E, 31 p. 

Schmidt, R. G.,1982, High-alumina hydrothermal systems in volcanic rocks of the 

Carolina slate belt: Geological Society of America abstracts with programs, p. 81. 

Schwartz, M. 0., 1981, The geochemistry of the leached capping of the La Granja 

porphyry copper deposit, Peru: Journal Geochemical Exploration, v. 15, n. 1-3, p. 

93-113 (also published in Rose, A. W., and Gundlach, H. (eds.), Geochemical 

Exploration 1980, Association Exploration Geochemists, Special Paper n. 9, p. 93-

113). 

---1982, Geochemistry of the porphyry copper deposit at La Granja, Peru: 

GeologischeJahrbuch, v. 57, p. 3-35. 

Secor, D. T., Jr., Samson, S. L., Snoke, A. W., and Palmer, A. R., 1983, Confirmation of 

the Carolina slate belt as an exotic terrane: Science, v. 221, p. 649-651. 

Seiders, V. M ., 1981, Geologic map of the Asheboro, North Carolina, and adjacent areas: 

U.S. Geological Survey Miscellaneous Investigations Map I- 1314. 
58 HIGH-ALUMINA HYDROTHERMAL SYSTEMS, CAROLINA SLATE BELT 

Seiders, V. M., and Wright, J. E., 1977, Geology of the Carolina volcanic slate belt in the 

Asheboro, North Carolina, area: Field guides for Geological Society of America, 

Southeast Section meeting, Winston-Salem, North Carolina: Raleigh, North 

Carolina Department of Natural and Economic Resources, p.1-34. 

Sillitoe, R. H., 1973, The tops and bottoms of porphyry copper deposits: Economic 

Geology, v. 68, no. 6, p. 799-815. 

---1980, Evidence for porphyry-type mineralization in southern Korea: Mining 

Geology Special Issue, n. 8, p. 205-214. 

Smirnov, V. 1., (ed.), 1977, Ore deposits ofthe U.S.S.R, v. 2: London, Pitman Publishing 

Corporation, 424 p. 

Speer, J. A., Becker, S. W., and Farrar, S. S., 1980, Field relations and petrology of the 

post-metamorphic coarse grained granitoids and associated rocks of the southern 

Appalachian Piedmont in Wones, D. R., (ed.), Proceedings the Caledonides in the 

U.S.A.; Memoir 2: Virginia Polytechniclnstitute and State University,p.137-148. 

Spence, W. H., 1975, A model for the origin ofthe pyrophyllite deposits in the Carolina 

slate belt: Geological Society of America, abstracts with programs, p. 536-537. 

Spence, W. H., and Carpenter, P. A., Ill, 1976, Metallogenic zonation and a model for 

the development of the piedmont of eastern North Carolina <abs.>: Geological 

Society of America, abstracts with programs, v. 8, no. 2, p. 273-274. 

St.Jean,J.,1973,A new Cambrian trilobitefrom thePiedmont ofNorth Carolina: 

American Journal of Science 273A, p.196-216. 

Stromquist, A. A., and Sundelius, H. W., 1969, Stratigraphy of the Albemarle Group of 

the Carolina slate belt in central North Carolina: U.S. Geological Bulletin 1274-B, 

22p. 

Stromquist, A. A., Choquette, P. W., and Sundelius, H. W., 1971, Geologic map of the 

Denton quadrangle, central North Carolina: U.S. Geological Survey, Geological 

Quadrangle Map GQ-872. 

Stuckey,J. L., 1967, Pyrophyllite deposits in North Carolina: North Carolina Division 

of Mineral Resources Bulletin 80,38 p. 

Sutulov,Alexander, 1973, Mineral resources and the economy of the U.S.S.R: New 

York, Engineering and Mining Journal, 192 p. 

Sykes, M. L., and Moody,J. B., 1978, Pyrophyllite and metamorphism in the Carolina 

slate belt: American Mineralogist, v. 63, p. 96-108. 

Taylor, Dennis, and van Leeuwen, Theo, 1980, Porphyry-type deposits in Southeast 

Asia: Mining Geology Special Issue n. 8, p. 95-116. 

Tingle, T. N., 1982, Geology and geochronology of the Parks Crossroads Granodiorite, 

near Siler City, central North Carolina piedmont: Southeastern Geology, v. 23, n. 

2,p.117-122. 

Tuomey, Michael, 1848, Report on the geology of South Carolina: Columbia, S. (j., A. S. 

Johnson, 293 p. 

Van de Poll, H. W., 1967, Carboniferous volcanic and sedimentary rocks ofthe ~ount 

Pleasant area, New Brunswick: New Brunswick Department of Nat'4ral 

Resources, Mineral Resources Branch, Report of Investigation no. 9, 24 p. 

Wallace, A. B., 1979, Possible signatures ofburied porphyry-copper deposits in middle 

to late Tertiary volcanic rocks ofwestern Nevada: in Papers on mineral deposits of 

western North America, International Association on Genesis of Ore Deposits, 

Fifth Quadrennial Symposium Proceedings Vol. II, J. R. Ridge, ed.: Nevada 

Bureau of Mines and Geology Report 33, p. 69-76. 

Whitney, J. A., Paris, T. A., Carpenter, R. H., and Hartley, M. E., III, 1978, Volcanic 

evolution of the southern slate belt of Georgia and South Carolina: a primitive 

oceanic island arc: Journal Geology, v. 86, p.173-192. 
REFERENCES CITED 59 

Williams, Harold, 1978, Tectonic lithofacies map of the Appalacian orogen: St. John's 

Newfoundland, Memorial University of Newfoundland. 

Wilson, W. F., Carpenter, P. A., III, Burt, E. R., McDaniel, R. 0., Coffey,J. C., and 

McKensie, B. J ., 1978, Geology of the Raleigh 1 °X 2° quadrangle, North Carolina: 

Aiken, S.C., E. I. duPont de Nemours and Company, GJBX-51, 122 p. 

Worthington,J. E., Kiff,J. E., Jones, E. M., and Chapman, P. E., 1978, Applications 

of the hot springs or fumarolic model in prospecting for lode gold deposits: 

Society of Mining Engineering of AI ME, Pre print no. 78-1-358, 11 p. 

Zen, E-an, 1961, Mineralogy and petrology of the system A120a-Si02-H20 in some 

pyrophyllite deposits ofNorth Carolin!l: American Mineralogist, v. 46, p. 52-66. 

*U.S. GOVERNMENT PRINTING OFFICE: 1985-461-431:20003 


'