origin of the copper deposits of the ducktown type in the southern appalachian region

215 Pages·2011·51.22 MB·English

UNITED STATES DEPARTMENT OF THE INTERIOR
Harold L. Ickes, Secretary
GEOLOGICAL SURVEY
W. C. Mendcnhall, Director
Professional Paper 179
ORIGIN OF THE COPPER DEPOSITS OF THE
DUCKTOWN TYPE IN THE SOUTHERN
APPALACHIAN REGION
BY
CLARENCE S. ROSS
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1935
For sale by the Superintendent of Documents, Washington, D.C. - - Price'45 cents (paper cover)

CONTENTS
Page (cid:9)Page
Abstract. . _____.__-___________-___-___._____..___. 1 Genetic history of the copper-bearing veins of the south
Introduction ____---__-_--____-___-___-___-____-__- 2 ern Appalachian region Continued.
Scope and object of report. _____________________ 2 High-temperature silicate stage._________________ 27
Acknowledgments -_.____-_______--_____._______ 2 Pyroxenes. ..-.________---_____-------__-__ 27
Bibliography __________________________________ 3 Epidote group-_____-----_-_-------_------- 28
Methods of study. ____--__--__-_-_-_--_____-______- 7 Gahnite__-_.__.._.____..._....___ 28
Field work_ _ __________________________________ 7 Amphiboles. __-_..__.___-_-_-___-______---- 28
Laboratory studies. ____________________________ 8 Biotite-__________..-____-___--___-___ 29
Criteria for the determination of mineral sequence. 8 Garnet. ____.____....________.___ 30
Enclosure of one mineral in another________- 9 Barite.___....___________________ 31
Preservation of antecedent mineral and rock Accessory minerals-__________-__---_--_-_-_ 31
structures _______________________________ 10 Secondary hydrotherrnal minerals_-____--___--_-_ 31
Relation of vein minerals to rock structure. .__ 10 Chlorite. __-__--____...-______._..... 31
Filling of open spaces.. _____________________ 11 Talc... -__-- ___ -----'- -- 32
Unreplaced angular fragments. _ _____________ 11 Carbonate stage.__.____________-_______-__---_ 33
Physical properties _ _ _____________________ 11 Origin of carbonates._-________-__------------ 34
Euhedral form _____________________________ 12 Stratigraphic position of ore bodies...._____-_ 35
Shear planes the site for replacement. ________ 12 Structural relations_____________--__-__-_-_ 35
Zoning of minerals___----_------___-------- 12 Replacement of schist and gneiss by sulphides. 36
Suites of minerals of unlike origin.... ________ 13 Vein calcite and its relation to quartz._______ 36
Hounding, embayment, and isolated crystal Replacement of plagioclase by calcite.._______ 37
remnants _______________________________ 13 Hydrotherrnal vein minerals cut by calcite vein-
Conclusions _______________________________ 14 lets_.--.-_..-.--___---__-__-.__.--_ 37
Examples of mineral relations ___________________ 14 Character of the carbonates_--__--_----_--__ 38
Location and geomorphic relations.. _____-__--.-_- 17 Calcite in other ore deposits of the region-.__ 38
General geology of the southern Appalachian region.... 18 Conclusions. _________________________ 38
Archean rocks. _ _______________________________ 18 Postcalcite silicates._______________________ 38
Carolina gneiss ____________________________ 18 Sulphides. _ -_.______.___-_______--.__..__ 39
Roan gneiss. ______________________________ 20 Postsulphide minerals. _____________________ 40
Granites. __----___---.-._ -___-___-_,.-____- 20 Cavity coatings. _______________________ 40
Cranberry granite. _ .______-.__-__-_____ 20 Magnetite. __________________________ 40
Cambrian rocks -..._-______.-_---_-______._..__ 20 Supergene minerals..-._____________________ 40
Hiwassee slate --___--______--___-_-_______- 20 General outline of genetic history _____________ 40
Great Smoky conglomerate ----___-____-____- 21 Factors controlling deposition of vein minerals._._ 42
N antahala slate. . __________________________ 21 Mineral replacement.__________.:--_________ .42
Tusquitee quartzite. ____---_-__-___--.__._. 21 Faulting and fracturing._____________________ 43
Carboniferous intrusive rocks________ ____________ 21 Pressure of solutions.______________________ 44
Granite. __________--_______-____----_____- 21 Chemistry and physics of vein formation..._________ 44
Pseudodiorite __ _----_--------___-_______ 21 Physical differences between magmas and hydro-
Character. .__ _________________________ 21 thermal solutions.________-__-_----__-___ 45
Origin ________________________________ 21 Source of heat energy in vein-forming materials. 45
Relation to regional metamorphism______ 22 Magmas. _ ________________________________ 46
Pegmatites _ _____________________________ 22 Hydrothermal solutions.___________________ 46
Relation to regional metamorphism. ___.._ 22 Vapors ---_.___--__-.___-__-___-_-_----___ 47
Age of pegmatites as shown by the lead- Physical condition of magmatic emanations. _...-_ 48
uranium ratio -__-_________-_-.____..- 22 Development of pressure in a magma residuum.___ 49
General structure of the Appalachian province.... 22 Concentration of alkalies in the magma residuum. _ 49
Types of structure. ______-_-____.______..___ 22 Volatile constituents of magmas_________________ 50
22 Source and character of vein-forming materials._______ 50
Faults. . __________________________________ 23 Dissolved solid constituents_____-_-_,__--__---__ 51
Metamorphism ____________________________ 23 Aplite-pegmatite stage__-___-___---_-._____ 51
Earth movements. ___ ______________________ 23 Quartz stage_-_----____-________-_---.__-_ 51
Geologic age of the ore bodies. __________________ 23 High-temperature ferromagnesian stage... _ _ _ _ 51
Genetic history of the copper-bearing veins of the south Carbonate stage.__________________________ 54
ern Appalachian region.. _____________________ 24 Sulphide stage..__-_________--__---______._ 55
Country rocks. _ _______________________________ 24 Postsulphide stage.._____________._ ________ 57
Aplite-pegmatite stage. _ _----------- .---.____ 24 Volatile constituents.__________________________ 57
Quartz stage. __----__.---_-__._-___.._________ 26 . Aplite-pegmatite stage..._----------._-_-_. 57
IV CONTENTS
Pag« (cid:9)Page
Source and character of vein-forming materials Con. Local descriptions Continued.
Volatile constitutents Continued. Gossan Lead of Virginia Continued.
Quartz stage. ___.-__--__--_ _______________ 58 Paragenesis of the Gossan Lead ore bodies..._. 84
High-temperature ferromagnesian stage _______ 58 Peachbottom vein, North Carolina..--___________ 85
Carbonate stage. ______------_--___-_______ 59 Elk Knob vein, North Carolina________.._..____-__ 87
Sulphide stage--__----__--------_-_-_-_____ 59 Otto vein, North Carolina.__-_-____--.-__.__--. 87
Postsulphide stage. _ _______________________ 60 Cullowhee vein, North Carolina.._._______-_.___. 89
Summary of character of vein-forming solutions ... 60 Wayhutta vein, North Carolina.. ________________ 90
Mineralogy. ______________________________________ 62 Savannah vein, North Carolina.___-_____..____-- 91
Plagioclase__ . ____:._____---_-_-_-_-____________ 62 Fontana vein, North Carolina.__-_..--_--________ 92
Pyroxenes. . ___--___-__---_----_-___-_--_______ 63 Copper deposits of the Ducktowu district, Tennessee 94
Epidote group.----.--.--- --------__-__-___-___ 63 History of mining development._____________ 94
Garnets __._______ ______-___-_-_-______________ 63 Location and topography.___________________ 95
Gahnite. _______._--___--_--------_-_-.__-____ 64 General geology.___________________ ______ 96
Amphiboles ___________--_-_--_--__________-.__ 64 Mines of the Ducktown district.._____ 1 ____.._ 96
65 Burra Burra_.---_________________._.._. 96
66 London..________-______-__-----__-___ 97
Carbonates- ___________--__--__-_-_-_--______- 66 East Tennessee._________.._-___.___-___ 97
Local descriptions.._______--------------_-_-___-_-_- 67 Ocoee._______________________________ 97
Copper vein at Ore Knob, N.C______. ___________ 67 Isabella and Eureka.__.______...________ 97
Location __________-_-_J_-_________________ 67 Mary.._____________________________ 97
History of the mine- _ ____-_________'________ 68 Other mines_-__-_---..___....---_-____-__ 97
Results of previous work_______________ ____ 68 Vein paragenesis______________..____________ 97
General geology and geomorphology _________ 70 Feldspar-quartz stage __________________ 98
Vein paragenesis_____--__--__-__-__________ 70 Stage of high-temperature ferromagnesian
Gossan __'l ____________________________ 70 minerals.___________________________ 98
Supergene sulphides_______ ____________:. 70 Secondary minerals.___________________ 99
Hypogene vein mirierals____._--______._____ 70 Calcite stage_____._-_-_-__--_--_...._-_- 99
General relations. ____ _ _______________ 70 Postcalcite silicate stage___-_-_______-_- 100
Wall rock____--_---_--_---___-_ _______ 71 Sulphide stage-_-_-___--__-__--__------ 100
Aplite-pegmatite stage. ________________ 71 Character of Ducktown ores_____.___________ 100
Vein-quartz stage______________________ 72 Alabama pyrrhotite deposits____________________ 101
Stage of high-temperature ferromagnesian Sulphide-bearing zones in gneiss, North Carolina_'._ 102
minerals ____________________________ , Sulphides on Bryson-Franklin road--_-__-_-_- 102
Stage of vein carbonates- _______________ Sulphides near Bryson____________________ 103
Stage of postcalcite silicates _____________ Nickel-bearing pyrrhotite vein in Floyd County, Va._ 103
Sulphide stage_---_---___--_-__-___-___ Location and topography.__________________ 103
Stage of late thermal minerals___________ Geologic relations......... ___-________--- 103
Secondary mmerals__-__________________ Rocks associated with the veins._._-______--- 103
Mineral relations. _____________________ Sulphides- ________________._-_--_____--_ 104
Gossan Lead of Virginia, _______________________ Copperfield or Ely mine, Vermont.______________ 105
Location and topography____-_-_-___-_-____ Location and occurrence of deposits. _________ 105
History _ _________________________________ Studies of the ores______________________._. 105
Geology. __:_-_-_-_------ ----------------- Paragenesis of the pyrrhotite vein.___________ 105
Monarat mines_-_______-_--__-_---________ Ore deposits not of the Ducktown type.__________ 106
Location _._____._____-___-_-_-___..-___ Virgilina, Virginia-North Carolina.-__-__-_--- 106
Ore bodies. __-_ _ ---____._-___._-_.__ Arsenic veins, Craigford, Ala__-____0_-__-___- 107
Aplite and pegmatite stage ______________ Iron mine, Cranberry, N.C.--___-___________ 107
Quartz stage___-_----____.._-_--__-____ Location..___________-___-____-____--- 108
High-temperature ferromagnesian stage __ Orebody_______.____.______ 108
Secondary minerals___-___-________-____ Paragenesis-__________________________ 109
Carbonate stage. _______-_-_---_-__-___ Sudbury, Ontario... _______--__--_______ 112
Stage of postcarbonate silicates. ._ _______ Replacement of silicate minerals in other
Stage of sulphides __ -_---__.___-____._ regions.____________________________ 114
Cranberry mines. ________-_-_____--__---_-_ Fen area, Norway..._--____-_---_--.__- 114
Betty Baker mine...-----------------..---- Timiskaming district, Ontario___________ 114
Grayson County sulphide zone. _____________ Index...._____________________.____.. 163
ILLUSTRATIONS
PLATE 1. Relations between quartz and feldspar._______________________________________________________________ 118
2. Specimens from Cullowhee, N.C., showing relations between quartz and plagioclase---__---.._-__-_--___--_- 119
. 3; Specimens from Ore Knob, N.C., showing fracturing in quartz and albite_._____--_--__-___.______-__---_-- 120
4. Replacement of pegmatite and aplite by ferromagnesian minerals._____.___-___-____--__--_-------__-._--- 121
(cid:9)Page
PLATE 5. Replacement of pegmatiter-_-_-----------___----_-_---____--_--_--_-----_-------_-----_--_:.--------- 122
6. Specimens from Savannah, N.C., showing replacement of muscovite. -_-_-_____-_-_-___-_-___-_-__-____.__ 123
7. Replacement of plagioclase by biotite.________________________________________________________________ 124
8. A, Plagioclase from Fontana, N.C., inclosed in replacing chlorite; B, Sheared quartz with veinlets of sulphides
from Ore Knob, N.C.; C, Actinolite with replacing zoisite from Mary mine,Ducktown,Tenn.; D, Amphibole from
Isabella mine, Ducktown, Tenn., with cores of actinolite and rims of hornblende_--_---__-___-_--___------ 125
9. Replacement of quartz schist by silicates.----.._________________________________________________________ 126
10. Habit of different types of amphiboles.___-___--_--___-_-___-----__-_._____---________________________ 127
11. Relation of amphiboles to biotite, chlorite, and talc.____________________________________________________ 128
12. Relations of actinolite from Monarat, Gossan Lead, Va___.__.__________________________________________ 129
13. Relations of talc to biotite and chlorite__---_-----__-_-___---_----_--_.__--____-..._____-____________ 130
14. Pleochroic halos around zircon crystals.__.__________.__________________________________________________ 131
15. Replacement of quartz and albite by calcite, Ore Knob, N.C----______-_____-___----__-__________________ 132
16. Replacement of plagioclase and quartz by carbonates.__-______----_-_____-__---_-_-_______._______-____ 133
17. Replacement of vein quartz by calcite-_______________________________________________________________ 134
18. Replacement of quartz by calcite_.____________-_-___.________________________________________________ 135
19. Replacement of quartz and plagioclase by calcite-___--______________-_________._____________.__________ 136
20. Replacement of quartz by calcite________________________ ___________________________________________ 137
21. Replacement of quartz by calcite--___________-_-_--_-_-_-______--_________---________________________ 138
22. Replacement of quartz by calcite and ankerite._-----_________-_-_.__-_---_-_---_-_____.._.______________ 139
23. Replacement of plagioclase and quartz by ankerite and calcite, Copperfield, Vt.,___________________________ 140
24. Replacement of ferromagnesian minerals and quartz by carbonates.______________________________________ 141
25. Replacement of vein minerals by calcite-__.-__-------_.-_-__-_-_---_______.__________--_________._____. 142
26. Replacement by calcite._____________________________________________________________________________ 143
27. Relations between quartz and carbonates...___________________________________________________________ 144
28. Replacement of high-temperature vein minerals by calcite._____-___-_-_________-________________________ 145
29. Relations of barite and calcite to quartz and plagioclase at Peachbottom, N.C.._-_-_______-________________ 146
30. Carbonate and sulphide veinlets in older minerals.___------___----_--_---___--__-___________.__________ 147
31. Relations of carbonates._____-_--_--___-______-___-__-___-__---__-_-__________-____-________________ 148
32. Replacement of calcite by sulphides.____-____---_-_-_____-_----_-----_____-.._____-__________________ 149
33. Relations of sulphides to gangue minerals..____----_-_-----___-----_-_-____---..--_-_-______-___________ 150
34. Character of sulphides.__--__------_-_______-__-_-__-__________________ ___________________.L_________ 151
35. Replacement of schist by sulphides..-.--- .____-_---___-___-__-_--___-___-___-___________________.__._ 152
36. Relations of ore minerals to gangue..----___-__-----_----__--_-_--_--_-_-__-----_______________________ 153
37. Relations of sulphides in specimens from Fontana, N.C.._______________________________________________ 154
38. Relations of magnetite to sulphides in the Isabella mine, Ducktown, Tenn.________________________________ 155
39. Relations of sulphides from Burra Burra mine, Ducktown, Tenn_________________________________________ 156
40. Relations of chalcocite and other sulphides at Fontana, N.C....__--------_____---__-_____-.______________ 157
41. Relations of sulphides..-__..--__-----__-_--_----_-_____---_--_--_--_-____--_----_______.____________ 158
42. Relations of ohalcocite to other ore minerals, Betty Baker mine, Gossan Lead, Va...._-_____________________ 159
43. Relations of sulphides at Betty Baker mine, Gossan Lead, Va..__________________________________________ 160
44. A, B, Violarite replacing pentlandite from Floyd County nickel mine, Va.; C, Sulphide veinlets cutting igneous '
rock, Floyd Count}' nickel mine, Va.; D, Pyrrhotite and chalcopyrite showing subgraphic intergrowth, Betty
Baker mine, Va._________________________________________________________________________________ 161
FIGURE 1. Outline map showing the distribution of ore bodies described in this paper and related ore bodies._--__.______ 17
2. Geologic section of rocks of pre-Cambrian and Cambrian age associated with the ore deposits of the southern
Appalachian region._____-_-__-________-__-_-__-_______-__--_---_-___._-_---______________________ 19
3. Distribution of oxides in the different vein-forming stages.--___ -____-__-_-_-___--__--.______-___________ 40
4. Map showing the mines of southwestern Virginia and northwestern North Carolina.___-__-_.______.___.____ 68
5. Vertical section through a quartz vein in the James River gold belt, Virginia.-._-_-----_-_________________ 93
INSERT
Page
Mineral sequence at Ore Knob, N. C.__________________________________________________________________________ 76
ORIGIN OF THE COPPER DEPOSITS OF THE DUCKTOWN TYPE IN THE
SOUTHERN APPALACHIAN REGION
By CLARENCE S. Ross
ABSTRACT one deposit siderite, drusy quartz, and hisingerite were-
deposited in open cavities and are later than all other minerals,
A group of copper-bearing pyrrhotite veins of the Ducktown
and in a vein in the Ducktown district magnetite followed
type extends from southwestern Virginia to eastern Ala
sulphides.
bama. Similar deposits occur near Ely, Vt, and continue into
It is concluded that the carbonates, including the calcite at
Quebec, and other types of ore bodies that are genetically
Ducktown, do not represent partly replaced limestone lenses
related to these are widely distributed in the southern Appala
but are hydrothermally deposited vein material. Veins that
chian region.
contain the same type of ores and the same type of calcite
The pyrrhotite veins here described are in the Blue Ridge
occur in rocks of widely differing geologic age and even in
and Great Smoky Mountain region, where they cut highly
metamorphosed igneous rocks. Most of the veins follow
folded and metamorphosed rocks of different kinds and ages.
the structure of the country rock approximately, but many
Some veins are in the Carolina gneiss, an early pre-Cambrian
depart from strict conformity in important details. The Ore
rock that is composed of profoundly metamorphosed igneous
Knob vein, which contains abundant calcite that is identical
and sedimentary materials; some are in the Roan gneiss, a
with that at Ducktown, cuts sharply across the structure of
later highly metamorphosed gabbroic intrusive, also of early
the schist. The formation of veins of the Ducktown type has
pre-Cambrian age; others are in the Great Smoky conglom
not been dependent upon the presence of calcite, for all veins
erate, a metamorphosed sedimentary rock which has been
have been formed in part and some entirely by direct replace
assigned to the early Cambrian but which may be pre-Cam
ment of schist, metamorphosed gabbro, and pegmatite. Car
brian ; and one cuts a pegmatic mass that is believed to have
bonates are not older than vein minerals but have replaced
been intruded during the Appalachian revolution at the end of
schists, feldspar, quartz, and ferromagnesian minerals. Cal
the Carboniferous period.
cite fills veins in aplite at Ore Knob, and shear planes in quartz
Most of the veins of the Ducktown type follow the strike
at Ducktown. Carbonates are also abundant in a wide variety
of the country rock, but a few cut across it. Some of them
of mineral deposits in the southern Appalachian region, and
can be traced for long distances for example, the mineral
many of these are in plutonic or volcanic rocks where lime
ized zone known as the Gossan Lead of Virginia can be
stone lenses are precluded. It is therefore evident that the
traced for about 17 miles. All the deposits are character
carbonates in veins of the Ducktown type in the southern Ap
ized by abundant pyrrhotite, with small but variable pro
palachian region have been deposited by hydrothermal solu
portions of chalcopyrite and sphalerite and a very little
tions and have had a genetic history similar to that of the
galena; pyrite may be abundant or almost absent. The most
other vein minerals.
conspicuous gangue minerals are amphiboles, but quartz, cal-
The different vein-forming stages seem to have been initiated
cite, biotite, and in some mines plagioclase are abundant.
by movements within the vein that produced faulting, shearing,
Less abundant gangue minerals are garnets, epidote or zoisite,
and brecciation. This allowed the introduction of hot active
pyroxenes, spinels, talc, and chlorite.
solutions, which deposited the material held in solution and
The veins have been formed by a series of distinct genetic gradually sealed the channels of ingress. A renewal of move
stages, and each stage is characterized by a distinct group of ments that permitted a new surge of solutions was the cause
minerals. The minerals of each succeeding stage have re of each successive stage of vein formation.
placed those of preceding stages, and this relation gives the Several types of ore deposits other than the pyrrhotite veins
clue to relative age. The stages have not affected all the have been studied, and the veins of the Ducktown type are
veins equally, and in some veins a stage may be partly or compared with these and with ore deposits described by others.
wholly unrepresented. This comparison indicates that many of the genetic stages
The veins were no doubt derived from some differentiating that have been recognized in the copper-bearing .pyrrhotite
magma, but no parent igneous rock has been identified in veins are present in a wide variety of ore bodies in the south
the region. The first recognizable event in vein formation ern Appalachian region.
was the intrusion of a feldspathic magma that crystallized into The geologic age of the copper-bearing veins of the southern
an aplitic rock or less commonly into a pegmatite. This was Appalachian region is not exactly determinable, but it-is evi
followed by the introduction of vein quartz, and that by a dent that they were formed at less than profound depths
stage which is characterized by a large group of ferro and after the major orogenic movements that produced the
magnesian materials. In most of the veins this was succeeded schistosity of the rocks of the region. These movements are
by a carbonate stage in which calcite was the dominant believed to have marked the Appalachian revolution, at the
mineral, but dolomite is present in one deposit, and ankerite end of- the Paleozoic era. The ores are younger than some
has replaced calcite in another. A small group of silicates of the pegmatites of the region, and other pegmatites of the
followed and replaced carbonates, and sulphides followed and same type and believed to be of the same age are shown by
replaced carbonates, quartz, feldspars, ferromagnesian min their radioactive minerals to be of very late Paleozoic age. It
erals, and schist. The introduction of sulphides was the last therefore seems probable that the copper veins are at least as
vein-forming episode in most of the veins, but in at least late as the end of the Paleozoic.
1
COPPER DEPOSITS OF DUCKTOWN TYPE IN SOUTHERN APPALACHIAN REGION
The physicochemical laws that appear to have controlled the most forgotten by geologists contributed to the min
development of the copper-bearing pyrrhotite veins are re eral production of the day. In the early fifties of
viewed, and their genetic history is traced in the light of
the past century the Gossan Lead of southwestern
these laws.
Virginia was a notable source of black copper ores,
The feldspar of aplite and pegmatite and the quartz of quartz
veins represent material that was expelled from the parent and in the seventies and eighties Ore Knob, in north
magma when these materials had become concentrated through western North Carolina, produced copper from the
the early crystallization of ferromagnesian minerals and calcic primary ores after the exhaustion of the secondary
feldspars.
ores that led to its development. The success of these
The materials that formed the ferromagnesian minerals were
mines inspired much interest in copper mining in the
restored to the silica-alkali-rich residuum, being derived from
earlier crystallized pyrogenic minerals by a process of replace region. Copper veins at many localities were pros
ment, re-solution, or base exchange. The calcium, magnesium, pected, and at some of these smelters were built and
and ferrous iron of the carbonates probably had a similar briefly operated.
source.
The copper-bearing pyrrhotite veins of the south
Sulphides probably segregated "as an immiscible sulphide
ern Appalachian region all occur in a province that
fraction but remained dispersed in interspaces between the
crystals of the partly solidified silica fraction of the parent has had a similar geologic history throughout.; they
magma. Here they were in immediate contact with the vola contain almost identical ores and gangue minerals;
tile substances which had become concentrated through the they have been formed by similar geologic processes;
crystallization- of-anhydrous minerals. They were dissolved
and the sequence of genetic events has been nearly the
by--these' concentrated volatile substances and transported to
same. Therefore any theory of genesis that applies
the vein, where they were redeposited. '
- The character, the concentration, and the various reactions to one of these deposits must apply to all. Other ore
of. the volatile substances that formed the solvents and trans deposits of the region besides the copper veins show
porting agents for the vein materials are little understood. a closely related geologic history, and although this
They have left a very imperfect geologic record, and experi
paper is primarily a study of the copper deposits of
mental data are largely lacking. Ore deposits will not be
the Ducktown type, these genetically related veins
properly understood until the phase relations of vein minerals
and various solvents have been determined. will be briefly compared with those of the Ducktown
type.
INTRODUCTION ACKNOWLEDGMENTS
SCOPE AND OBJECT OF REPORT
The writer wishes to acknowledge the help and
This paper on the copper-bearing pyrrhotite de courteous treatment that has been given by the offi
posits of the Ducktown type and allied bodies in the cials of the mines visited and the men operating these
southern Appalachian region of the United States has mines. At the same time this study has been in
been prepared with two main objects in view. The progress W. T. Schaller has been engaged in a study
first has been the study of an interesting group of ore oi: the origin of pegmatites. Many of the processes
deposits, with the purpose of reconstructing the ge he has recognized play a part in the development of
netic history of the veins. This study has revealed ore veins, and the earlier stages in vein formation in
a connected and nearly continuous series of events, veins of the Ducktown type have been found to be
which extends from the intrusion of a- hypabyssal identical with the later stages in the development of
magma to the feeble reactions of the latest hydrother- pegmatites. Thus the work of Mr. Schaller and the
mal emanations that are believed to have been derived advice he has given have been a very great help in
from a parent magma. This genetic history includes the study of ore veins. M. N. Short, of the United
the later magma and the hydrothermal stages of min States Geological Survey, has cooperated in the
eral formation, which together constitute the later studies of the sulphides and has prepared many of
parts of the story of magmatic differentiation that the photomicrographs which show the relations of
is, we have here a group of intermediate processes that sulphides. The late Dr. Thomas L. Watson, State
appear to be transitional between those giving rise to geologist of Virginia, had long been interested in the
typical igneous rocks and those that commonly result Gossan Lead of Virginia and related deposits and at
in ore deposits. The second and possibly not the less the time of his death was planning to make a study
important object of this paper has been an attempt to of these deposits. The writer had several delightful
make the maximum use of petrologic methods in con conferences with Dr. Watson, in which specimens
nection with field studies in the investigation of an from Ore Knob, N.C., were compared with those
ore deposit and to test the power of these methods to from the Gossan Lead. The genesis of these veins
help solve the problems of vein genesis. was discussed, and Dr. Watson in general concurred
The mines of Ducktown, Tenn., and Fontana, N.C., in the writer's conclusions about paragenesis. In the
are the only important copper producers in the eastern preparation of the final sections of this paper on the
United States at present, but in times past other mines physicochemical processes of vein formation the
of the southern Appalachian region that are now al v/riter has received very valuable assistance from
BIBLIOGRAPHY
N. L. Bowen, George Tunell, and George W. Morey, rocks, with especial emphasis on the effects of sinking
of the Geophysical Laboratory, and from members of . crystals. The phase relations controlling assimilation of
rocks of various types are considered. The effects of vola
the United States Geological Survey.
tile substances on differentiation and the mode of develop
ment of extreme rock types are considered.
BIBLIOGRAPHY
The Fen area of Telemark, Norway: Am. Jour. Sci.,
Alien, E. T., Chemical aspects of volcanism, with a collection 5th ser., vol. 8, pp. 1-11, 1924. The carbonate rocks of the
of analyses of volcanic gases: Franklin Inst. Jour., vol. 193, Fen area, Norway: Idem, vol. 12, pp. 499-502, 1926. A
pp. 20-80, 1922. Water is shown to be the most important detailed study of the relations and genesis of calcite, dolo
of volcanic gases. The chemical relations are considered, mite, and siderite in an igneous rock. Concludes that they
and a compiled table of gas analyses is given. are secondary.
and Zies, E. G., A chemical study of the fuinaroles of The melting phenomena of the plagioclase feldspars:
the Katmal region: Nat. Geog. Soc. Contributed Tech. Am. Jour. Sci., 4th ser., vol. 35, pp. 577-596, 1913. A study
Papers, Katmai series, no. 2, pp. 77-155, 1923. A report of the phase relations between the various members of the
on the methods of collecting and analyzing volcanic gases; plagioclase series and the melts from which they crystallize.
the temperatures of these gases; their character and The later, stages of the evolution of igneous rocks:
amount. Jour. Geology, vol. 23, Suppl. to no. S, 1915. The crystal
Anstecl, D. T., On the copper lodes of Ducktown in eastern settling control of the differentiation of igneous rocks is
Tennessee: Geol. Soc. London Quart. Jour., vol. 13, pp. 245- discussed in detail.
254, 1S57. A description of mines in operation in 1855. The behavior of inclusions in igneous magmas: Jour.
Includes a sketch of part of the district and two cross Geology, vol. 30, Suppl. to no. 6, pp. 513-570, 1922. A study
sections. Contains valuable observations on the distribution of the relations that control the reactions between magmas
of the secondary ores. Notes a relation between the rich and various types of rock included in them.
ores and the present topography. Plats quartz veins not The reaction principle in petrogenesis: Jour. Geology,
visible today. Gives analyses of the rich ore and concludes vol. 30, pp. 177-198, 1922. A study of the part played in
that it is a mixture of iron and copper sulphides, with some the development of an igneous rock by reactions between
copper oxide. Ansted holds the opinion that the iron oxide early products of crystallization and the residual magma.
and black copper ore are later than the pyrrhotite but Crystallization-differentiation in silicate liquids: Am.
states that "the present veins could never by any possi Jour. Sci., 4th ser., vol. 39, pp. 175-191, 1915. Experiments
bility decompose into the present gossan and beds of ore." on crystal sinking and crystal floating in melts are de
Bastin, E. S., Large pyrrhotite bodies in Maine: Eug. and scribed, and the effect of such floating or sinking on the
Miu. Jour., vol. 104, pp. 758-759, 1917. differentiation of igneous rocks is discussed.
Graton, L. C., Lindgren, Waldemar, Newhouse, W. H., Geologic thermonietry, in Laboratory investigation of
Schwartz, G. M., and Short, M. N., Criteria of age relations ores, pp. 172-179, New York, McGraw-Hill Book Co., 1928.
of minerals, with especial reference to polished sections .of The various methods of determining the temperature of for
ores: Econ. Geology, vol. 26, pp. 561-610, 1931. mation of minerals and rocks are considered in detail, and
Bayley, W. S., A magnetite marble ore at Lansiug, N.C.: the different criteria are evaluated.
Elisha Mitchell Sci. Soc. Jour., vol. 37, pp. 138-152, 1922. Boyd, C. R., The utilization of the iron and copper sulphides
Describes, the occurrence of magnetite in association with of Virginia, North Carolina, and Tennessee. Am. Inst. Min.
marble and the probable mode of origin. Eng. Trans., vol. 14, pp. 81-84, 1885. Discusses in a general
The magnetite ores of North .Carolina and Tennessee: way the distribution of these ores at Ore Knob, Ashe County,
U.S. Geol. .Survey Bull. .735, pp. 209-270, 1922. A descrip N.C., and suggests possible methods for handling them.
tion of the magnetite deposits and a discussion of their The mineral wealth of southwestern Virginia: Ain.
origin. Inst. Miu. Eng. Trans., vol. 5, pp. 81-92, 1876; vol. 8, pp.
Magnetic iron ores of east Tennessee and western 338-344, 1880. Describes the mineral resources of Ashe,
North Carolina: North Carolina Geol. and Econ. Survey Alleghany, and Watauga Counties, N.C., including the Ore
Bull. 32, 1923. Describes the various types of iron ore and Knob and Elk Knob copper mines.
the mines of western North Carolina and east Tennessee, Mineral resources of Ashe and Alleghany Counties,
with n detailed description of the ores of the Cranberry N.C.: Resources of Southwest Virginia, 3d eel., pp. 311-320,
area and their petrology. Discusses briefly the origin of New York, John Wiley & Sons, 1881. Describes the physical
these ores. features of these counties and outlines rock formation, copper
The magnetitic ores of North Carolina their origin: veins, and magnetic ore veins. Describes Ore Knob, Elk
Econ. Geology, vol. 16, pp. 142-152, 1921. A detailed descrip Knob, and Peachbottom mines.
tion of the magnetite ores of North Carolina, with especial Brush, G. J., Am. Jour. Sci., 2d ser., vol. 28, p. 129, 1859. Dis
reference to those of the Cranberry area. Concludes that cusses the mineralogy of the Ducktown ores and concludes
the ores were brought in with .the pegmatite-forming ma that " ducktownite", so called by Shepjird, is not a species
terial, and that limestone lenses did not play a part in but is probably a mixture of pyrite and copper glance.
their formation. States chemical analyses to support this view. Regards
Becker, G. F., Gold fields of the southern Appalachians: U.S. " lepiclochlore " as a mixture of chlorite and mica.
Geol. Survey 16th Ann. Kept.,, pt. 3, pp. 251-331, 1895. Gives Butler, B. S., Some relations between oxygen minerals and
the history of gold mining in the South, outlines the gen sulphur minerals in ore deposits: Econ. Geology, vol. 22, pp.
eral geology of the region, and describes numbers of mines. 233-245, 1927. A study of some of the chemical problems
A list of mines and their gangue minerals is given. A involved in the formation of primary ores and especially
bibliography of gold mining in the region is given. the factors that control the state of oxidization.
Bowen, N. L., The evolution of igneous rocks, Princeton Uni and Burbank, W. S., Relation of electrode potentials of
versity Press, 1928. A presentation of the author's theories some elements to the formation of hypogene mineral de
of the factors controlling the differentiation of igneous posits : Am. liist. Min. and Met. Eng. Tech. Pub. 166, 1929.
G3S33 34 2
COPPER DEPOSITS OF DTJCKTOWN TYPE IN SOUTHERN APPALACHIAN REGION
A study of the relation of the order of formation of min sonian Inst. Ann. Rept, 1913, pp. 275-3051, 1914. Discusses
erals to their electric potential and the state of their oxi the part in volcanic activity played by water and other
dation. gases.
Clark, J. D., and Menaul, P. L., The role of colloidal migration Daly, R. A., The geology of Pigeon Point, Minn.: Am. Jour.
in ore deposits: Econ. Geology, vol. 11, pp. 37^1, 1916. Sci., 4th ser., vol. 43, pp. 423-448, 1917. Contains a dis
Describes experiments which indicate that sulphides may cussion of the origin of the red rock associated with the
be transported in colloidal solution, with an excess of hydro Duluth gabbro.
gen sulphide. On the escape of this gas they will be de Dresser, .J. A., On the copper-bearing volcanic rocks in the
posited. eastern townships of the Province of Quebec: Canadian
Clarke, F. W., and Washington, H. S:, The composition of the Min. Inst. Jour., vol. 5, pp. 81-86, 1902; A new area of
earth's crust: U.S. Geol. Survey Prof. Paper 127, 1924. copper-bearing rocks in the eastern townships of the Prov
. Conclusions from compiled analyses as to the distribution ince of Quebec: Idem, vol. 7, pp. 397-400, 1904. A very
of the various elements in the average rock of the earth's brief description of the occurrence of copper in eastern
crust, followed by figures for the composition of the rocks Quebec.
of the different regions of the world. Egleston, T., Investigations on the Ore Knob copper processes:
Coleman, A. P., The nickel industry, with special reference to Am. Inst. Min. Eng. Trans., vol. 10, pp. 25-26, 1881. A very
the Sudbury region: Canada Mines Branch 22d Ann. Kept, good description of the Ore Knob mine and its geologic
pt. 1, 1913. An outline description of the nickel mines of the relations. Gives a discussion of the secondary ores and
world, with a detailed description of the Sudbury region clearly recognizes the process of enrichment.
and the individual mines. The mining and smelting methods
Emmons, W. H., and Laney, F. B., Preliminary report on the
are also described.
mineral deposits of Ducktown, Tenn.: U.S. Geol. Survey
Cooke, H. C., Character and origin of the ore deposits Argo
Bull. 470, pp. 151-172, 1911. A brief summary of the
naut gold mine, Gauthier Township, Timiskaming District,
geology of the Ducktown district.
Ontario: Canada Geol. Survey Summary Kept., 1923, pt. Cl,
Geology and ore deposits of the Ducktown min
1924. A study of an interesting ore deposit, in which the
ing district, Tenn.: U.S. Geol. Survey Prof. Paper 139, 1926.
paragenesis of the ore and gangue minerals have been
A detailed study of the geology of the Ducktown district.
worked out with unusual detail.
Gives- descriptions of the various mines and the structural
Currey, R. O., A sketch of the geology of Tennessee, with Saf-
relations of the ore deposits. Concludes that the ore bodies
ford's geological map: Southern Jour. Med. and Phys. Scl.,
are the result of replacement of limestone lenses.
vol. 4, pp. 193-208, 257-272, 321-336, 385-^00, 1856; vol. 5,
Fenner, C. N., The Katmai magmatic province: Jour. Geology,
pp. 1-16, 77-83, 160-168, 246-262, 308-327, 1857; reprinted,
vol. 34, no. 7, pt. 2, pp. 673-772, 1926. A detailed descrip
x, 128 pp., Knoxville, 1857.
tion of the province, with petrographic description of the
History of the discovery and the progress of the min
rocks. Considers various methods of magma differentia
ing of copper at Ducktown, in A sketch of the geology of
tion, with especial emphasis on the effects of gases.
Tennessee, pp. 70-84, Knoxville, 1857.
Foreman, Fred, Hydrothennal experiments on solubility,
A geological visit to the Floyd-Carroll-Grayson County
hydrolysis, and oxidation of sulphides: Econ. Geology, vol.
plateau of the Blue Ridge, Virginia, Knoxville, Tenn., Beck-
24, pp. 811-837, 1929. Describes experiments which show
ell, Haws & Co., 1859. Reprinted in The Virginias, vol. 1,
that the solubility of pyrite, pyrrhotite, and chalcopyrite is
pp. 62-64, 70-71, 74-77, '80-81, 95, 1880. Describes the
extremely small. The presence of sodium carbonate and
region of the Gossan lead and the individual mines, and
sulphide appreciably increase the solubility, but the pres
gives observations on the occurrence of the different kinds
ence of hydrogen sulphide does not.
of ores. Also a brief description of the Peachbottom mine.
Freeman, Horace, The genesis of sulphide ores: Eng. and Min.
and Proctor, C. A., Copper district of Tennessee, Georgia,
Jour.-Press, vol. 120, pp. 973-975, 1925. Describes experi
North Carolina, and Virginia its history, geography, geol
ogy, and mining interests: Southern Jour. Med. and Phys. ments that lead to the conclusion that double sulphides of
Sci., vol. 3, pp. 38-44, Knoxville, 1855. Contains informa the metallic elements and of alkalies have a low fusion
tion relating to the Ducktown district, much of which had point and may play a part in the deposition of the sulphide
been previously published by Safford. ores.
Day, A. L., Some causes of volcanic activity: Franklin Inst. Genth, F. A., Contributions to geology: Am. Jour. Sci., 2d
Ann. Address, pp. 3-24, Philadelphia, 1924. (See also Pos ser., vol. 33, p. 194, 1862. Gives several analyses of Duck-
sible causes of the volcanic activity at Lassen Peak: Frank town ores, presumably galena, partly replaced by chalcocite
lin Inst. Jour., vol. 194, pp. 569-582, 1922.) A study of and argentite.
volcanic activity, based partly on Lassen Peak and partly The minerals of North Carolina: U.S. Geol. Survey
on experiments, leads to the conclusion that the water and Bull. 74, p. 23, 1891. A compilation of the known minerals
other gases that are in solution in a magma are concen of North Carolina with brief descriptions and analyses of
trated during crystallization. Great pressure may be de many specimens.
veloped if the cooling magma is under a cover, and the Gillson, J. L., Origin of the Vermont talc deposits, with a dis
explosive escape of these gases may explain many features cussion of the formation of talc in general. Econ. Geology,
of volcanic eruptions. vol. 22, pp. 246-287, 1927. A detailed study of the origin
and Alien, E. T., The volcanic activity and hot springs of talc in Vermont. Considers the minerals from which
of Lassen Peak: Carnegie Inst. Washington Pub. 360, pp. talc is derived and the mineral changes undergone.
1-186, 1925. Describes the volcanic activity at Lassen Peak, Goldschmidt, V.M., The distribution of the chemical elements:
the chemical and physical relations, the hot springs of the Nature [England], vol. 124, pp. 15-17, 1929. Considers the
region, and the part the water and gases play in volcanic distribution of the elements in the earth's crust, and con
activity. cludes that there is a sulphide shell between the silicate and
and Shepherd, E. S., Water and volcanic activity: iron shells. This is probably the source of the sulphide ore
Geol. Soc. America Bull., vol. 24, pp. 573-606, 1913; Smith- deposits.
BIBLIOGRAPHY
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mines' by Waldemar Lindgren: U.S. Geol. Survey Bull. 293, chalcocite zone, and of the low-grade pyrrhotite ores, and
1006. Describes the general geology and the rocks of the notes on the occurrence and genesis of the minerals of the
Kings Mountain area in North and South 'Carolina, also ores of each class.
the individual tin mines and prospects. In the section on Kerr, W. C., and Hanna, G. B., Ores of North Carolina:
the Dahlonega region the minerals and origin are briefly Geology of North Carolina, vol. 2, ch. 2, 1888. Gives a brief
described. description of the Ore Knob, Savannah, Wayhutta, Cul-
U.S. Geol. Survey Mineral Resources, 1906, p. 403, 1907. lowhee and other mines in the western part of the State.
Describes briefly the mining operations and mineral pro Lacroix,. A., Etude mine'ralogique des produits silicates de
duction of Ducktown for 1906, with notes on the geology Irruption clu Ve"suve (avril 1906) : du Mus. hist. nat. Nouv.
of the region. archives, 4th ser., vol. 9, fasc. 1, 1907. A very careful study
Holmes, Arthur, Ore-lead and rock-lead and the origin of of the inclusions of various types of foreign rock in the lavas
certain ore deposits: Nature [England], vol. 124, pp. 477- of Vesuvius, and the alteration developed by the action of
478, 1929. A consideration of the atomic weights of lead the lava and its contained gases.
from various sources leads to the conclusion that ore lead LaForge, Laurence, and Phaleri, W. C., U.S. Geol. Survey Geol.
does not have a radioactive source, and hence ore lead and Atlas, Ellijay folio (no. 187), 1913. The area described and
probably other metals cannot be derived from igneous rocks mapped includes a portion of the Ducktown district. The
but 'must come from a sulphide shell of the earth's crust. rocks and types of geologic structure are similar. The text
and Lawson, R.W., Factors involved in the calculation includes extensive discussions of the areal geology and struc
of the ages of radioactive minerals: Am. Jour. Sci., 5th ture, geomorphology, geologic history, and mineral resources
ser., vol. 13, pp. 327-344, 1927. Discusses the criteria for of a region contiguous to the Ducktown district. This folio
determining the .age of rocks by radioactive disintegration and the Nantahala folio by Arthur Keith give the results
and gives a list of rocks whose age has been determined. of most extensive studies of the stratigraphy, geomorphology,
Gives atomic weight corrections for the uraninite of North and areal and structural geology of the southern Appala
Carolina and gives the corrected age as 239 million years, chians.
and the geological age as late Paleozoic, probably late Laney, F. B., Preliminary report of geological survey of the
Carboniferous. Eagle Creek and a portion of the Hazel Creek watersheds
Hulin, 0. D., Metallization from basic magmas: California (manuscript), North Carolina Geol. Survey, 1906. A com
Univ. Dept. Geol. Sci. Bull., vol. 18, no. 9, pp. 233-274, 1929. mercial report on the area.
Discusses reasons for believing that ore deposits are com The Gold Hill mining district of North Carolina: North
monly derived from two distinct magmas, one " basic " and Carolina Geol. and Econ. Survey Bull. 21, 1910. A careful
one " acid." The minerals that may be expected from each description of the district and its mines and ores.
are listed. The geology and ore deposits of the Virgilina district
Hunt, T. S., The Ore Knob copper mine and some related of Virginia and North Carolina: Virginia Geol. Survey
deposits: Am. Inst. Min. Bng. Trang., vol. 2, p. 123, 1874. Bull. 14, 1917; North Carolina Geol. Survey Bull. 26, 1917.
Contains a brief but highly suggestive paper on the origin A description of the geology of the district, with a careful
of the Ducktown ores and the changes due to weathering. study of the genetic history. The relations of the sulphide
The lodes are regarded as fissure veins, not lenticular are described in detail.
masses. Notes that pyrrhotite will react with copper Lewis, J. V., Copper deposits of New Jersey: Econ. Geology,
sulphate, precipitating copper sulphide. vol. 2, pp. 242-257, 1907. Describes the copper deposits
On the copper deposits of the Blue Ridge: Am. Jour. and their relations to intrusive rocks. Concludes that they
Sci., 3d ser., vol. 6, pp. 305-308, 1873. Contains valuable were formed by solutions of magmatic origin derived from
notes on the mineralogy of the Ducktown ore deposits and the underlying Palisades trap.
states that the black copper is a sulphide of secondary Lieber, 0. M., The copper veins of the South: Mining Mag.,
origin deposited by sulphate mine waters, some of which vol. 7, pp. 367, 1856. Discusses the occurrence and origin
carry as much as 0.1 percent of copper. of the copper deposits of the southern Appalachian region.
Jackson, C. T., Report on the copper mine of the North Lindgren, Waldemar, Metasomatic processes in fissure veins:
Carolina Copper Co.: Mining Mag., vol. 1, pp. 44-47, 1853. Am. Inst. Min. Eng. Trans., vol. 30, pp. 578-692, 1901. A
Describes briefly the mine, the course of the vein, and the study of the changes in rocks contiguous to ore-bearing fis
future of the mine. sures. A collection of data relating to the alteration of
Keith, Arthur, Outlines of Appalachian structure: Geol. Soc. rocks near fissures, and an effort to indicate the active
America Bull., vol. 34, pp. 309-338, 19J3. A detailed dis processes and classify veins accordingly.
cussion of Appalachian structure and its bearing on theories Locke, Augustus, The formation of certain ore bodies by
of mountain-making. mineralization stoping: Econ. Geology, vol. 21, pp. 431-458,
U.S. Geol. Survey* Gaol. Atlas, Cranberry folio (no. 90), 1926. Describes deposits that lead to the belief that the
1903; Asheville folio (no. 116), 1904; Greeneville folio ore bodies are developed where partial solution of the rocks
(no. 118), 1905; Mount Mitchell folio (no. 124), 1905; Nan- has caused a caving in (stoping) of the country rock.
tahala folio (no. 143), 1907; Roan Mountain folio (no. 151), McCallie, S. W., The Ducktown copper-mining district: Eng.
1907. and Min. Jour., vol. 74, pp. 439-441, 1902. Notes on the early
and Sterrett, D. B., Tin resources of the Kings Moun history of the district.
tain district, North Carolina and South Carolina: U.S. Geol. March, W. J., A, sketch of the mines and copper region of
Survey Bull. 660, pp. 123-146, 1918. Describes the general southwestern Virginia: Mining Mag., vol. 9, pp. 217-220,
geology of the region and the individual tin mines. 1857. Describes in some detail the rich secondary ores of
Kemp, J. F., The deposits of copper ores at Ducktown, Tenn.: the Gossan lead of Carroll County, Va. Black ores are
Am. Inst. Min. Eng. Trans., vol. 31, p. 244, 1902. An most abundant, but red oxide, silicate, carbonate, and na
exceedingly suggestive paper based on field examination tive copper are found. The better grades of ore ran 35