PYRITE PORPHYROBLAST PARAGENESIS at the CHEROKEE MINE, DUCKTOWN, TENNESSEE by Donald Duane Brooker

PYRITE PORPHYROBLAST PARAGENESIS AT THE CHEROKEE MINE, DUCKTOWN, TENNESSEE by Donald Duane Brooker

Thesis submitted to the Faculty of Virginia Polytechnic Institute and State University in partial fulfillment of the requirement of the degree of MASTER OF SCIENCE in Geology

APPROVED:

Jam'°15 R. Craig, ChliJrman /I!. Donald Rimstidt

W. ftandy Slater

September 18, 1984 Blacksburg, Virginia PYRITE PORPHYROBLAST PARAGENESIS AT THE CHEROKEE MINE,

DUCKTOWN, TENNESSEE

Donald Duane Brooker

(ABSTRACT)

Pyrite porphyroblasts up to 300 mm in size are common in the polym.etamorphosed, iron-rich, stratabound, massive sul-

fide ore at the Cherokee Mine, Ducktown, Tennessee. These porphyroblasts contain abundant inclusions of sphalerite,

calcite, and micas that are used to determine the paragenesis

of the porphyroblasts and the metamorphic history of the ore deposit. The ore mineralogy at the mine is: hexagonal pyr-

rhotite (60%), pyrite (30%), chalcopyrite (4%), sphalerite

(3 %), and magnetite (3 %) with minor galena, molybdenum,

tetrahedrite, bismuth, ilmenite, and rutile. The ore body is

interpreted to have been syngenetic and to have contained

both primary pyrrhoti te and primary pyrite: additional

pyrite may have formed as crusty accretions resulting from

oxidation of primary pyrrhotite shortly after deposition.

The early pyrites were later deformed and acted as seeds for

the formation of the larger porphyroblasts by Ostwald ripen-

ing, and by the annealing of small pyrite grains into larger

porphyroblasts, during isochemical metamorphism. Sphaler-

ite geobarometry indicates initial growth of the pyrite por-

phyroblasts began at 6.8± 0.8 kilobars and that many sphalerite grains underwent some degree of re-equilibration at a later stage. Fluid inclusions formed during retrograde metamorphism have salinities near 12 % NaCl with a vapor phase rich in C02 • Pyrrhotite-pyrite compositional profiles indicate at least partial re-equilibration of hexagonal pyrrhoti te down to about 270°C. At lower temperatures further compositional re-equilibration was probably prevented, because the coexisting pyrite was too refractory to release the sulfur needed for the hexagonal pyrrhotite to react to monoclinic pyrrhotite. ACKNOWLEDGEMENT I am extremely grateful for the guidance and support that my committee chairman, Dr. James R. Craig, has given me throughout this study. Special thanks goes to Dr. J. Donald Rimstidt for his assistance and ideas, and to Dr. Carol Simp- son and Randy Slater for their review and comments on this paper. I would like to thank the Tennessee Chemical Co. for allowing access to the Cherokee Mine and for allowing and Randy Slater to take me down into the mine. Technical assistance in photography was supplied by and made an invalu- able contribution of time and thoughts during electron microprobe analysis. Research money for this project was supplied by a Chev- ron grant-in-aide, and by a Virginia Mining and Mineral Research and Resource Institute grant. Special thanks go to for being there when I needed her.

iv TABLE OF CONTENTS

ABSTRACT. ii

ACKNOWLEDGEMENTS. iv

LIST OF FIGURES vii

LIST OF TABLES ix

INTRODUCTION . 1

GEOLOGIC SETTING. 3 Regional geology 3 Mine geology 8 ORE MINERALOGY 10 Pyrrhotite . 11 Pyrite 14 Chalcopyrite 20 Sphalerite . 21 Other sulfides 23 Oxides . 24 Ganque . 24

PYRITE PORPHYROBLASTS 25 Size and shape .. 25 Fracturing 28 Inclusion Patterns 29 Rotation effects 33

FLUID INCLUSIONS 35

SPHALERITE GEOBAROMETRY 37 PYRITE-PYRRHOTITE PHASE RELATIONSHIPS 68 DISCUSSION 77 Initial ore composition . 77 Nucleation and growth of pyrite 79 Growth of large porphryoblasts 84 Time of growth 88 SUMMARY AND CONCLUSION 89 REFERENCES 91

v APPENDICES 96 Modal analysis of the ore. 96 Sample localities. 100 Microprobe data 102

VITA 113

vi LIST OF FIGURES Fiqure page

1. Pyrite porphyroblast 2

2. Regional location map 4

3. Ducktown mining district 7

4. Cherokee mine geologic map 9 5. Kinked pyrrhotite grains 12 6. Recrystallized pyrrhotite 13 7a. Pyritic ore 15

7b. Pyrite grains in the pyritic ore 16 8. Porphyroblastic-pyrrhotitic ore 17

9. Remnant pyrite cores 19

10. Chalcopyrite vs. sphalerite 22

11. Elongated pyrite porphyroblasts 27

12. Fracturing in pyrite porphyroblast 30 13. Inclusion patterns in porphyroblast 31

14. Chlorite next to porphyroblast 34

15. Fluid inclusions 36

16. Sphalerite geobarometer 41

17. FeS content in sphalerites (undifferiated) 43

18. FeS content in sphalerites (outside pyrite) 44

19. FeS content in sphalerites (pyritic ore) 45

20. FeS content in sphalerites (porphyroblasts) 46

21. FeS content in sphalerites (porphyroblasts) 47

22. Sphalerite geobarometer 49

vii Figure page 23. Bleb-shaped sphalerite grains so 24. Sphalerite grains within fractures 53 25. Irregular-shaped sphalerite grains 54 26. Large, massive sphalerite grains 55 27. FeS content in sphalerite grains. 58 28. FeS content sphalerite grains in fractures 59 29. FeS content in irregular-shaped grains 60 30. FeS content in massive sphalerite grains 61 31. FeS content in rectangular sphalerite grains 62 32. FeS content in bleb-shaped sphalerite grains 63 33. FeS content in sphalerite vs. location 65 34. Phase diagram for the Fe-S system 69 35. FeS content in pyrrhotite near a 25 mm pyrite 71 36. FeS content in pyrrhotite near a 25 mm pyrite 72 37. FeS content in pyrrhotite near a 75 mm pyrite 73 38. FeS content in pyrrhotite near a 100 mm pyrite 74 39. FeS content in pyrrhotite 75 40. Small pyrite grains being annealed 82 41. Small porphyroblast enclosing other pyrite 83 42. Paragenesis of pyrite porphyroblasts 85

viii LIST OF TABLES Table page

1. Deformation Events 6

2. Fluid inclusion data 38

3. Summary of geobarometry at Ducktown 40 4. Summary of sphalerite geobarometry 56

ix INTRODUCTION

The development of euhedral pyrite porphyroblasts is a char-

acteristic and sometimes striking feature of metamorphosed,

stratabound deposits rich in iron sulfides. Al though the

shape and size of the porphyroblasts may be related in a gen-

eral manner to the grade of metamorphism (Mookherjee, 1976),

the crystals rarely grow larger than 10 to 20 millimeters.

However, in the massive pyrrhotite-pyrite ores at Ducktown,

Tennessee, the crystals range upward in size to 300 millime-

ters and are the largest ever reported (Fig. 1). Although

these porphyroblasts have been known for years, they have

received little study and only passing mention as petro-

graphic curiosities.

The present study of the ore mineralogy , with emphasis

upon the porphyroblasts and their petrologic significance,

examines the distribution and setting of the pyrite crystals

in the ore and their relationships to the composition of

matrix and deformational features of the ore zones. In addi-

tion, the nature and distribution of the numerous inclusions

that occur within the crystals was investigated, because the

inclusions may yield information on the growth mechanism and

on the conditions under which the growth occurred. Specific

attention was given to the sphaleri te, because of its poten-

tial use as a geobarometer. 2

Fig. 1. An 11.5 cm pyrite porphyroblast within pyrrhotite from the Cherokee Mine, Ducktown, Tenn. The porphyroblasts in this mine range up to 30 cm. GEOLOGIC SETTING

The Ducktown mining district is located within the Blue

Ridge Province of the Southern Appalachians in the extreme southeast corner of Tennessee (Fig. 2). The rocks in th,e area are Precambrian metagraywackes and schists belonging to the Great Smokey Group of the Ocoee Series which unconform- ably overlies Grenville age basement (Hatcher, 1978). The massive sulfide deposits at Ducktown occur in the lower sequence of the Great Smokey Group within the Copperhi 11 For- mation.

The metagraywackes of the Great Smokey Group are dominantly composed of sub-rounded to angular quartz, feldspars, muscovite, and bioti te. Accessory minerals include graphite, ilmenite, garnet, calcite, and sulfides. In the

Ducktown area the metagraywackes become intermixed with quartz-mica schists containing garnet or stauroli te. Hadley

(1970) interprets the metagraywackes and schists and their enclosed metaconglomerates, quartzi tes, and calc-silicate hornfels as being initially deposited by turbidity currents with the sediments being derived from a granitic source to

the northwest. Detailed descriptions of the stratigraphy

are given by Emmons and Laney ( 1926), Magee ( 1968), and Hol-

combe { 1973).

Metamorphism in the area increases from west to east

(Fig. 2) and reaches staurolite facies (Carpenter, 1970) in

3 I l / I \ / "'· .r- ./ I ... "'"'.' / itr'I'"'" .L - -.------·-· _,; .....I

Ducktown I .. I -· 64 •·r us - .. 35. ....r

H.C.

Ga •

."11111 H Explanation Sc1le

Cambrian-Ordovician Units fil!I Thrust Fault <"4 0 4 1111 les ;;;;a Ocoee Serles D lsograds .. Murphy Belt [Il] l 5 k i 1ometers

Fig. 2. Location map and qeneral geology of the Ducktown area. Metamorphic isograds increase from west to east. (After Magee, 1968; Carpenter, 1970) 5

the mine area. Isotopic ages within the mining district have been used to infer three periods of metamorphic events

(Magee, 1968; Dallmeyer, 1975). Initial regional metamorphism (M 1 ) occurred during the Taconic ( 480-420 m. y.) orogeny. Peak metamorphism (M 2 ) was obtained during the Acadian orogeny (430-360 m.y.) and reached staurolite facies.

Retrograde metamorphism (M 3 ) is attributed to the Alleghani- an (300-250 m.y.) orogeny (Holcombe, 1973). Nesbitt (1979) using various silicate geobarometers and geotherrnometers determined a maximum metamorphic temperature in the mining district at 540±50°C and a pressure of 6±1 kilobars; approximately the same pressure determined by Hutchison and Scott

(1980) using the sphalerite geobarometer.

Deformation increases from west to east. Holcombe

(1973) interpreted five phases of deformation at Ducktown: two ductile and three brittle. The types of deformation are

summarized in Table 1. The major folds in the mining district are the Burra anticlinorium and the Coletown synclino-

rium; both are interpreted as F 2 • The ore bodies at Ducktown

are located on the limbs of these major folds (Fig. 3) .

Because of the complex structures and polymetamorphism, the

ore bodies have not been correlated stratigraphically

(Magee, 1968). Currently, the ore bodies are thought to be

syngenetic in origin (Slater, 1982). Table l. Sull1llary of Structural Events at Ducktown

Event Type Cleavage Orientation Structures and Remarks

Fl Ductile Sl axial planar slaty cleavage N200E, 30-45° SE Tight to isoclinal folds in high grade defined by orientation of metamorphic areas; s1 cleavage usually the micas obliterated by s2

F2 Ductile Sz differentiated crenulation N3o0E, 7d'SE large scale folds.(Burra anticline and cleavage defined by the Coletown syncline) produced; s2 is the orientation of the micas d01111nant metamorphic fabric. °'

F3 Ductile- 53 Occasionally differentiated Na°E, 45°E Siil411 amplitude folds and kink-like Brittle crenulation cleavage folds; minor faulting; structures 110re localized than F2

F4 Brittle S4 Occasionally differentiated N60°W Small chevron folds and crenulations crenulation cleavage defined by orientation alone

F5 Brittle S5 Localized crenulation cleav- lWO sets of strike-slip faults: age t1Jo0 w, 70~NE-sinstral movement N90°E. 6D s- dextral movement

{After Magee, 1968; Holcombe, 1973; Addy and Ypma, 1977) 7

/ / 1'

----/ ' ' , I 'I,, I/\I~ I I~ I I /

/ ' ------/~ ~- /0 .l'~

.._o~//'/ / Calj.ow=/iiay~ ?

v ~ry /; I / • ',' v --/ ~ I , ;I '; -\'

y /' I /I / ,, ~ • ""':·~::::•• -~= Olk ti , (~ t:/ "°°'"'" -+ - • I( :>( ••co"" mo•- - "'" JI \~Ir '-----__--ft_ ::::,'.:.:." """' = ~ u s • ------o rooo '££ r

Fig. 3. Location map and general structures of the Ducktown mining district. (From Tenn. Chemical Co. map)

\. 8

Mine Geology

The Cherokee ore body, which is approximately 2000

meters in length and extends 800 meters below the surface, is

located on the northwest limb of the Burra anticlinorium

(Fig. 3) . Average thickness is 30 meters, but localized

folding has produced thicknesses of up to 50 meters (Magee,

1968). The deposit is conformable with the schistosity of

the surrounding rocks, striking N35°E and dipping between

45° to 65°SE. Small, tight to isoclinal folds appear to be

common throughout the ore (Slater, pers. com., 1984) along with minor shear zones. A northwest crossfaul t bisects the

ore creating a left lateral offset of 80 meters between sec-

tions (Magee, 1968).

The upper part of the hanging wall of the Cherokee mine

is composed of sericite-biotite schist. In the lower levels

of the mine, the serici te-bioti te schist grades into a chlor-

i te-garnet schist containing seriticized staurolite pseudo-

morphs. The upper part of the footwall contains

metagraywackes and graywacke schist (Fig. 4). In the lower

portion of the footwall, chlori te schist and serici te schist

occur. Amphiboli te uni ts possibly representing early intru-

sive sills occur in the immediate proximity of the mine (Sla-

ter, 1982). Wall rock alteration includes a decrease in iron

content in the bioti te and chlori te within a narrow zone of 6

to 8 meters from the ore body (Brown, 1961; Magee, 1968), and ?O ri . [XPLANAI ION

/ ~ _.... l n,. 1 te schist f •ult /-

Fig. 4. General geologic map of the 14th level of the Cherokae ore body. (from Tennessee Chemical Co. map prepared for Slater, 1982) 10

an increase in sericite and epidote as compared to the host rocks. A zoning pattern of chlori te schist footwall, copper enriched footwall mineralization, zinc enriched hanging wall mineralization, and sericite schist hanging wall alteration occurs at Ducktown (Slater, 1982). Lenses of chlori te schist, quartzite,· and talc outline fold limbs and hinges within the ore.

ORE MINERALOGY The ore can be classified into six major types; A) pyrrhoti tic ore, with more than 60 per cent pyrrhotite and no pyrite, B) porphyroblastic-pyrrhoti tic ore, composed of pyrite porphyroblasts and pyrrhotite, C) pyritic ore, composed primarily of small grains (1 to 3 mm) of pyrite, D) siliceous pyrrhoti tic ore with less than 60 per cent pyrrhoti te, E) veined ore with chalcopyrite and pyrrhotite within the quartzites and the wall rocks, and F) banded magnetite ore up to a meter thick. The ores vary from massive to moderately foliated with aligned micas defining a foliation which parallels that of the surrounding rocks. The pyrrhotite is also aligned with the regional schistosi ty, indicating that the entire deposit underwent regional metamorphism (Larsen, 1973). Other common metamorphic features include chalcopyri te pressure shadows and 120° dihedral grain boundaries tyPical of 11

recrystallization. A detailed description of the ore mineralogy is given below.

Pyrrhotite

Hexagonal pyrrhotite with an iron content ranging from

47.4 to 47.6 atomic weight percent is the dominant ore mineral in most of the ores of the Cherokee Mine. Electron microprobe analysis failed to detect elements (particularly

Ni, Co, As) other than Fe and S (detection limit 100 ppm).

The pyrrhotite grain size, which is generally larger in the pyri tic ore (type C} than in the porphyroblastic-pyrrhoti tic

(type B) ores, ranges from 0.03 to 1.0 millimeters and aver- ages 0. 35 millimeters.

Most pyrrhoti te grains in the ores di splay undulose extinction, deformation twins, kink bands (Fig. 5}, or pre- ferred crystallographic orientation (caused by slip) as a result of deformation that followed the peak of metamorphism. The pyrrhoti te grains in the pyri tic ore usually display only mild deformation as opposed to the pyrrhoti te grains in the pyrrhotitic and porphyroblastic-pyrrhotitic which ranges from moderately to

intensely deformed. Recrystallization to very fine-grained pyrrhotite occurs in zones associated with intense shearing

(Fig. 6). Pulverized pyrites are also frequently seen in

these shear zones. The common presence of grains that are 12

Fig. 5. Kinkbands within pyrrhoti te produce by a late stage deformation event. (Width of field= 1. 1 mm) 13

Fig. 6. Finely recrystallized pyrrhotite grains (white to dark grey) located within a shear zone with pulverized pyrite grains (light grey). (Width of field= 2. 0 mm) 14

elongated and then twinned in different directions, usually at 45° or 90° to each other, may indicate two different deformation events, or the activation of a second set of glide planes within the pyrrhotite (Clark and Kelly, 1973; Atkinson, 1975a). The close proxirni ty of highly stressed pyrrhotite near recrystallized grains demonstrates irregular recrystallization patterns.

Pyrite Pyrite, the second most abundant ore mineral in the deposit, ranges in grain size from a few microns up to 300 millimeters. These later crystals are the largest crystals ever reported; similar, but unstudy crystals have been noted in several other mines in the district (Slater, pers. corn. 1984}. The average size for the pyrite depends on the ore type. In the pyritic ore, the pyrites range from 0.01 to 5 millimeters with a mean size of 1.5 millimeters (Fig. 7a and 7b}, but within the porphyroblastic ores the crystals range from 1 to 300 millimeters across with an average size of approximately 10 millimeters (Fig. 8). Electron microprobe analysis (detection limit of 100 ppm) failed to reveal Ni,

Co, or As, and etching of the pyrite with HN0 2 , H2 0 2 and HCl did not produce any zoning or growth patterns of the types noted by Craig ( 1981) . The shape of the pyrite also depends on ore type. In the 15

0 1 2 3cm I I

Fig. 7a. Sample of pyritic ore. Average grain size is 1.5 mm and the grains are often rounded in shape. Gangue minerals are calcite and actinolite. 16

Fig. 7b. Rounded pyrite grains (white) surrounded by pyrrhotite (grey) within the pyritic ore. (Width of field=2.0 mm) l7

Fig. 8. Sample of the large porphyroblastic-pyrrhoti te ore. The average grain size is 25 mm. pyri tic ore the grains are more rounded and are considerably less fractured than are the porphyroblasts in porphyroblastic-pyrrhoti tic ore. Some of the pyrites in the pyri tic ore are completely rounded, but most grains possess at least one well developed face. Many of the grain boundaries are embayed by the surrounding pyrrhotite possibly indicating absorption of the pyrite by the pyrrhoti te {Fig. 7). Most of the pyrite grains within the pyritic ore that are smaller than 2 millimeters in diameter are inclusion-free, although some pyrites may contain one or two large inclusions. The number and the density of inclusions increases with grain size of the pyrite. Commonly, within the rounded pyrites. grains, and occasionally in the pyrite porphyroblasts, is the ,appearance of one or more rounded pyrite cores. These cores are evident because of a different polishing hardness than the host pyrite (Fig. 9). No differences in chemical composition was detected between the host pyrites and cores, therefore, the hardness difference between them may be related to dislocation densities (inferred by etch pi ts, Cox et al., 1981; Mcclay and Ellis, 1984), or other imperfections

in the crystal structure. The lack of etch pits within the pyrite cores along with the lack of inclusions and fracturing

in the cores suggest that they are remnants of earlier formed

pyrites that were incorporated in later forming crystals.

Porphyroblastic pyrites are euhedral to subhedral, but 19

Fig. 9. Rounded pyrite cores located within a pyrite grain in the pyri tic ore. These cores are commonly seen in the pyritic ore, but are also found in the larger pyrite porphyroblasts. These cores acted as nuclei for additional pyrite growth. Etching indicates the cores have a low etch pit density as compared with the surrounding pyrite. (Width of field =l.Omm) 20

intense fracturing, rounded corners, and pulverization of these crystals are common. The porphyroblasts contain more and larger inclusions than the pyrite grains in the pyritic ore. These inclusions display wide ranges of compositions depending on the mineralogy of the surrounding ore. Smaller euhedral pyrite crystals occur within the larger porphyroblasts. Pressure shadows of chalcopyrite, sphalerite, and chlori te occur around many of the porphyroblasts.

Chalcopyrite

Chalcopyri te is the most abundant base metal sulfide at the Cherokee mine and ranges from 1 to 10 modal percent of the ore, with an average of approximately 4 percent. The chalcopyri te appears to be more abundant nearer to the footwall

(Slater, 1982) . Point counting of samples from Cherokee indicates that the copper content is lower in the pyri tic ore than in the pyrrhotitic ore (Appendix 1). The porphyroblastic ore has the highest copper content, but this may be caused by a bias in the point counting based on the large size of the pyrites and the pressure shadows compared to the amount of pyrrhoti te in the sections examined.

The occurrence of the chalcopyrite differs in the ore types. Within the pyrrhotitic ore the chalcopyrite grains are either small (0.01 mm) blebs in the pyrrhotite, or they occur as pressure shadows, or within fractures in the gangue 2]

material. Within the porphyroblastic zones, the chalcopyrite occurs in large pressure shadows around the pyrites or within dilated fractures in the pyrites; only rarely does the chalcopyrite occur as blebs in the pyrrhotite. In the pyritic ore the chalcopyri te occurs as a fine-grained matrix material between pyrites.

After etching, the chalcopyri te in the pressure shadows appears to be fine-grained and annealed with only minor deformation twins. Chalcopyrite grains within the pyrrhotite are elongated in the direction of schistosity and commonly show deformation twins.

Sphalerite

Sphaleri te constitutes up to 4 percent of the ore

(Magee, 1968) and generally varies in abundance inversely with the abundance of copper (Fig. 10). Sphalerite is more evenly distributed within the pyrrhoti te than is the chalcopyri te, but is predominantly found in low pressure zones,

such as fractures in pyrite grains and pressure shadows

around silicates. The sphaleri te grains within the pyrrho-

ti te are often elongated in the direction of schistosi ty.

Sphaleri te inclusions in the pyrite are much larger and more abundant than are chalcopyri te inclusions. The FeS con-

tent ranges from 7. 5 to 15. 5 weight percent as discussed

below. The sphaleri te ranges from amber (low Fe content) to 22

C"" I I I• .I •• I I I I 16 . I I I •• .I

12 I I I I 10 .

+ • I I I I 6 . x I I I I ~ . I• x ,. )( I• I x z x ..,. )( 1; x t• )I 0 . .. + ... - ...... - ...... - .. --...... - .... - -·--..... -· ...... --...... --... --___ ...... - ·---- - .. ---·.. - ...... - ...... --.. + ...... --· o.o o.s 1.0 1.s 2.0 2.s i.o i.s -.o -.s s.o s.s 6.

SPH

NOT(: 6 08$ HIOO(ll

Fig. 10. Chalcopyrite vs. sphalerite content for the different ore types. (+ = porphyroblastic-pyrrhotitic ore; * = pyrrhotitic ore; x = pyritic ore) 23

deep red (high Fe content) in color and may contain inclu-

sions of chalcopyrite, galena, tetrahedrite, or pyrrhotite.

In doubly polished thin sections, the sphaleri te grains often show zoning with orange colored rims surrounding deep red .colored cores.

Other Sulfides

Galena occurs in only trace amounts in most of the samples, but may reach abundances of one percent in samples rich in chalcopyrite and sphalerite. Galena rarely occurs in the pyrrhotite, but is commonly observed with chalcopyrite and

sphalerite within fractures in pyrites, in pressure shadows with sphaleri te or chalcopyri te, and in small inclusions within pyrite porphyroblasts. When both sphaleri te and

chalcopyri te are present, the galena is more abundant in the

sphalerite.

Molybdenite occurs in several samples as single laths

or as small groups of twinned and kinked laths within the pyrite and pyrrhoti te. Tetrahedri te was found within a sam-

ple of pyritic ore as fine-grained inclusions within sphal-

eri te and chalcopyri te. Native bismuth occurs as small

inclusions in galena in a sample of pyritic ore. Other sul-

fide ore minerals that have been reported at Ducktown include

cubanite, stannite, and bornite. Traces of gold and silver

have been reported in assays but have never been observed as 24

discrete phases (Emmons and Laney, 1926; Magee, 1968).

Oxides

Magnetite, the only oxide common at the Cherokee Mine,

occurs disseminated throughout the pyrrhoti tic ore and in bands up to a meter in thickness. The magnetite commonly

contains inclusions of gangue minerals and pyrrhotite, but

rarely of chalcopyrite or sphalerite. The magnetite grains

average O. 5 millimeters and commonly show 120° dihedral

grain boundaries indicative of annealing. The disseminated

grains di splay boundaries embayed by pyrrhoti te.

Minor oxides that occur at Cherokee include rutile as

needles in quartz grains, manganese-rich i.lmeni te within

pyrite porphyroblasts, and goethite alteration adjacent to

fractures.

Gangue

The gangue minerals within the massive ores, in order of

decreasing abundance appear to be; calcite (and other carbo-

nates), quartz, chlori te, bioti te, actinoli te, and talc.

The micas commonly are fractured or bent. The quartz and

calcite are commonly completely annealed into medium grained

(0.5 millimeters) crystals. However, many of the calcite

grains do contain deformation twins and several quartz

grains show weak undulose extinction. 25

Some calcite, which fluoresces orange under shortwave

ultraviolet light, contains minor manganese, iron, and mag-

nesium. The calcite contains large solid inclusions of chal-

copyri te, sphalerite, pyrite, pyrrhotite, and galena, and

contains abundant fluid inclusions up to 80 microns across.

PYRITE PORPHYROBLASTS

Pyrite porphyroblasts were obtained from numerous drill

core samples and hand specimens representing many areas of

the mine (Appendix 2). There does not appear to be any definite distribution patterns of the porphyroblasts in the mine. The porphyroblasts occur in pockets that average 15

meters in length and 7 meters in width; however, correlation

between these pockets is not possible because of the deforma-

tion within the ore and the variations in the pyrites' char-

acteristics.

Size and Shape

The size of the pyrite porphyroblast ranges from 1 to

300 millimeters (average 8 millimeters), and generally var-

ies inversely with their abundance. The pyrite grains dis-

play variable degrees of crystal development and

deformation. Regardless of size, matrix, or abundance, most

pyrite grains display at least partial development of

external crystal forms. In the areas of greatest abundance, 26

many of the crystals are incomplete, because of considerable mutual interference during growth.

The pyrite porphyroblasts grow as euhedral crystals, because their surface free energy is much higher than that of the surrounding matrix (Stanton, 1964; Stanton and Gorman,

1968). Subhedral pyrites represent either deformed porphyroblasts that grew before tectonic activity, or corroded porphyroblasts that have suffered some resorption by the pyrrhotite matrix. Only a small percent of the pyrites are completely euhedral.

However, even in areas of moderate to low abundance many of the crystals are not truely cubes, but are elongated and have rectangular faces and cross-sections. Typically the degree of elongation approaches 20 percent (Fig. 11). Meas- urements of the orientation of the long axis of numerous pyrites reveal a slight tendency for alignment parallel to

schistosi ty. Randomly oriented rectangular objects when

placed under stress will tend to align themselves so that

their long axes are perpendicular to the maximum compressive

stress {Hobbs et al., 1976). Thus, the partial alignment of

the pyrites suggests they grew after the development of the

regional schistosity (F2 ), but before a third deformational

event (F 3 ). Small pyrite crystals observed on the surfaces

of large rectangular porphyroblasts (Fig. 11) were found, on

sectioning, to be partially embedded within the larger crys- 27

1 2 3cm L I I I

•

Fig. 11. Elongated pyrite porphyroblast containing a smaller porphyroblast within a pyrrhoti te matrix. Elongation may approach 20 %. 28

tal s. Many of the smaller pyrite porphyroblasts di splay rounding, that varies from a slight effect on the corners to nearly spherical shapes. The edges of the rounded pyrites are often very irregular and indented, and tails composed of pulverized pyrite are seen around the larger porphyroblasts.

Vokes ( 1969) has attributed the rounding of similar grains in massive pyrite-pyrrhotite ore in the Norwegian Caledonides to rolling of the pyrite during deformation.

Juve ( 1974) noted that the degree of development of the pyrite crystal face is dependent upon the adjacent matrix; a single phase matrix favors development of smooth faces whereas a two phase matrix results in the formation of poorly developed faces at the point of intersection. The pyrite porphyroblasts at Ducktown show well- and poorly developed faces with the same adjacent matrix. This may be attribut- able to the remobilization of minerals and new mineral growth around a pyrite during progressive stages of metamorphism.

Sphalerite and chalcopyrite at the pyrite surfaces created embayments that the pyrite grew around.

Fracturing

Many of the pyrite porphyroblasts display deformation features that may range from hairline fractures or abraded corners, to complete pulverization. The primary fracture plane is the (100) with secondary planes existing on the 29

(110) and (111) (Graf and Skinner, 1970; Atkinson, 1975b; Cox

et al., 1981). In zones of intense deformation, the frac-

tures are commonly filled with chalcopyrite, sphalerite,

galena, and pyrrhoti te. In some samples the pyrite cubes are

totally pulverized with chalcopyri te between fragments (Fig.

12). Very fine-grained twinned pyrrhotite, a typical tex-

ture in shear zones at this mine, is associated with the pulverized pyrites.

Inclusion patterns

The pyrite porphyroblasts contain numerous inclusions

as shown in figure 13. In general, the inclusion abundance

per unit volume increases with grain size. Also, there is

considerable variation in the mineralogy, shapes, and con-

figuration of the inclusions depending on the size and abun-

dance of the pyrite crystals. Three general types of

inclusion patterns are common in the pyrite: ( i) random,

(ii) circular, and (iii) parallel to regional schistosity.

Random patterns of blob-shaped sulfides and unoriented gan-

gue minerals are found in pyrite porphyroblasts that are less

than 7 millimeters and in the center of larger

porphyroblasts. The outer edges of many larger pyrites por-

phyroblasts commonly contain elongated inclusions of

fine-grained micas, calcite, and sulfides in crudely circu-

lar patterns so that the inclusions are parallel to the crys- 30

Fig. 12. Fractured pyrite grains (white). Fracturing is common in most pyrite grains, but is more intense within the porphyroblasts. The most common fracture plane is the (100) and then the (110). Chalcopyrite usually fills the fractures. (Width of field= 2. 0 mm)

\ 31

1 2 3cm 0 I. _j

Fig. 13. Cross-section of an elongated porphyroblast show- ing both inclusion and fracture patterns. The center of the porphyroblast contains random inclusions of calcite, quartz, and amphiboles. Usually the random pattern is surrounded by an area of large inclusions outlining an earlier phase of porphyroblast growth. At the rim of the porphyroblast is a inclusion pattern composed of micas parallel to the pyrite face. 32

tal faces and are curved at the corners (Fig. 13). Some of the larger pyrite cubes have nearly inclusion- free centers surrounded by several zones of inclusions separated by relatively inclusion free zones. Inclusion patterns in which the internal schistosity parallels the external schistosity are moderately common. Crumpling of micas at the interface of the pyrite in most of the samples indicates that these pyrites are younger than the schi stosi ty. The occurrence of micas half overgrown by the pyrite further suggest that the pyrites are post-tectonic to the deformational phase producing the regional schistosity. Spiral patterns representing rolling during the growth of the pyrites are not clearly evident.

The most common inclusion types in decreasing abundance are: micas, calcite, quartz, amphiboles, pyrrhotite, sphalerite, galena, and chalcopyrite. The abundance of a partic- ular mineral as an inclusion corresponds roughly to its abundance in the matrix at the time of the pyrite's growth.

However, sphalerite is more abundant as an inclusion than chalcopyrite, and galena is often seen only within pyrite grains, because of the difference in ability of the growing pyrite to incorporate different sulfides. Pyrrhotite, chalcopyrite, and galena occur as small elliptical shaped inclusions within the pyrite whereas the sphalerite is either elongated or in large masses. The gangue minerals occur as 33

indi victual grains or in large masses. Magnetite is a common inclusion in pyrites found in magnetite rich ores, but the amount of magnetite within the pyrite is considerably less than that in the surrounding matri.x. A similar situation occurs in calcite and mica-rich areas, where the number of inclusions is small in the pyrite compared to their abundance outside of the pyrite. This can be a result of two processes: the destruction of the micas and calcite during the pyrites' growth, or the shouldering aside of the non-sulfide inclusions during growth (Misch, 1971; Ferguson and Harvey,

1972).

Rotational Effects with the Matrix

Because many of the porphyroblasts are deformed and contain post-tectonic inclusion patterns, they must have grown after the schi stosi ty ( M2 ) developed. Adjacent to some of the larger porphyroblast crystal faces are chlorite surfaces that have lineations similar to slickensides striae, but are not associated with faulting. The chlori te surfaces also contain chalcopyrite grains that are elongated in the direction of the lineations. Three different sets of lineations occur on some surfaces implying that the pyrite was being moved as a response to stress. Microscopic examination of these interfaces show an intertwining network of chalcopyri te and chlorite (Fig. 14). The lineations imply that a 34

Fig. 14. Chlorite (grey) growing at the interface of the pyrrhotite and large pyrite porphyroblast. The chlorite is enclosed by chalcopyri te (white). (Width of field = 2. 0 mm)

\ 35

minor deformation occurred after the growth of the porphyroblasts.

FLUID INCLUSIONS

Microscopic examination of the calcite and quartz grains within the ·ore reveals numerous fluid inclusions.

Very little data has been collected on fluid inclusions in metamorphosed ores and rocks ( Roedder, 1984) , and no data has been reported from Ducktown. The ubiquitous presence of calcite throughout the ore and within the pyrite porphyroblasts allowed a study to be done to determine the feasibility of the fluid inclusions for yielding temperatures and fluid compositions during retrograde metamorphism.

Doubly-polished thin sections were prepared (see Craig and Vaughan, 1981) of clear calcite found within a 7 millimeter fracture running through a 30 millimeter pyrite porphyroblast, and of rutilated quartz adjacent to the large porphyroblast. A few primary inclusions were located, but most of the fluid inclusions within the calcite appear to lie along cleavage traces or healed fractures. These primary inclusion are as large as 80 microns with an average size of

30 microns; the secondary ones are commonly less than 15 microns. The fluid inclusions are composed of a liquid phase

and a vapor phase that is approximately 10 to 15 percent of the total volume of the inclusion (Fig. 15). The liquid 36

Fig. 15. Fluid inclusions within calcite. The average salinity for the inclusions is 12. 5 % NaCl and the vapor phase containing C0 2 (Width of field=O. 52 mm) 37

phase appears to be NaCl with an average salinity of 12.5 percent. The vapor phase is C02 and was determined by crush-

ing of the ca lei te grains within oi 1 and observing the expan-

sion of the vapor ( Roedder, 1984). Heating and freezing temperatures are given in Table 2. Heating was stopped at

342°C with the C02 bubble clearly visible.

The results of this study indicates that C02 was present during retrograde metamorphism. The presence of C0 2 in the fluid inclusions is probably responsible for the high temperature values obtained during heating. An additional study of the fluid inclusions is needed to determine their utility in helping interpret the history of the Ducktown

ores.

Sphalerite Geobarometry

The pyrite porphyroblasts of the Cherokee ores grew

within the pyrrhotite, which is the dominant phase of the

ores. Thus, the sphaleri te inclusions that were trapped

within the growing pyrite porphyroblasts were buffered by

both pyrrhotite and pyrite at the time of entrapment, and

have a potential value as geobarometers (Hutchison and

Scott, 1980). Because the larger pyrite cubes contain

several zones of sphalerite inclusions, it was anticipated

that the inclusions might preserve information regarding the

growth history of the porphyroblasts. 38

Table z. Fluid inclusion data

Freezing Temp. Heating Temp. Salinity Obser. Mineral (oC) ( oc) (wt. % NaCl) l calcite - 8.2 >201.5 12.0 2 calcite - 17.1 203.4 (burst) 20.3 3 calcite - 8.5 >220.2 12.3 4 calcite - 8.7 215.3 (burst) 12.6 5 calcite - 8.5 >222.2 12.3 6 calcite - 7.4 >342.5 11.0 7 calcite - 9.5 >250.0 13.7 8 quartz - 4.5 162.3 7.0

( > indicates heating was stopped at this temperature with the vapor bubble clearly visible; all temperatures are uncorrected for pressure) 39

The sphalerite geobarometer is based upon the equilibrium content of FeS in a sphaleri te grain (buffered by pyrite and hexagonal pyrrhotite) and is a function of the pressure, temperature, and activity of FeS (Barton and Toulmin, 1966;

Scott and Barnes, 1971; and Scott, 1973, 1976). Within the temperature range of 350°C to 600°C, the FeS content of the sphaleri te is thought to be temperature independent. At temperatures below 350°C, the relationship between FeS content, pressure, and temperature is poorly understood. Very slow cooling of sphalerite below 350°C, especially in the presence of chalcopyrite, commonly results in retrograde re-equilibration in which the FeS is expelled from the sphaleri te structure.

Previous studies at Ducktown have produced a wide range of results as summerized in Table 3. Ringler ( 1978) and Nes- bitt ( 1979) found a FeS content within the sphaleri te of 8 to

10 mole percent, indicative of a pressure of 10 to 12 kilobars (Fig. 16). In those studies only sphaleri tes in contact with pyrite within the pyrrhoti te matrix were analyzed. Nes- bitt attributes the high pre_ssures to non-equilibrium conditions and Ringler suggested that the high pressures were caused by lateral stresses, rather than low temperature re-equilibration. Hutchison and Scott (1980), using only sphaleri te grains encapsulated within the pyrites obtained a pressure of 5 kilobars, which is in reasonable agreement with Table 3. Su111nary of sphalerite geobarometry from Ducktown

R1nqt , ' f•SI 'r•nvre ..,.... l••I Aut-.Or Dl'OOltl flo. of Oh\...... ••• ... .. loc•tlOft of 1pU•erH• tr•'"' .... ,.., ...... f ltl•I c...... ,. 1.1 R.0 ll.l IJ.t IJ. I O..t>t• of "'' "'t to coauct ••• •Ith ...... ,.,,,

JS I.I R. ~ l).ft 11.0 ll.S O..t• •••, .., ..... lo ..., ••, ••• with lt0·~'1 .... ill ,.,,,, c.11-1 ll 9.S ll.S 10.0 10.9 I. I 10.I n..ut• of ,,, aut I• CMtlCt c.15 a CuS > O.l •le I; ~ Oerotff 1l 9.7 "·' 11.0 10.6 1.0 ••• with jlO•ltf•CH lloS bet- O.S , .. l.l •It 1; 0 Hutc1tht1M •M ,... _, 11 11.0 16.0 IJ.• a.t J.6 lllthl• ,, ...... ,...... " Scott (19'0) '·'

..., .. •t "'· ,...... , 11 ll.O 14.0 7.6 S.6 hohted wllhto c.IS • CuS > 0.1 .... s; I•• preu) toul to- Mo5 bet-• o.S aM 0.6 •It I; SI"' ire 1-4 wlllt ,.., feS ll.O ... o 1.6 S.6 Cores of 11,. spll trolos ...., .., .. lllt ..... •' the,••••••

9.0 ll.O 11.7 7.6 l•lertor of •Ith .,.1101 wltll ,.., ...,..1. en loelu11 ..1 9.0 t.S 11.1 10.1 wl I •Ith valns lo -llCl with other sulfides (po, C'1, •I

9.0 9.S 11.1 10.7 5jlll v1tos I• c.. uct with ''""' sulfl4t tratos; I• rroctures lrooktr Chtre>':H ,. 1.0 ll.S IJ.) 1.1 10.S o..u •••, .., • "'' '" ••... tlCl c.15 .. 0.1 .... l; ••• with po-Pf 60 t.S 14.S 11.t 10.9 s.o I.I 5jlll_.., trains within ...11 .. '·' 11.S "·' 11.S s.o ••• Spll 9rolo1 within '1 ,...... ,robhsll 41

700

600

0 2.5 5.0 7.5 10.0 kb ...., 500 ., "'L. .,"' "'c:

""'- .'.! 400 ...L. c:. "'e ...."'

300

200.

24 20 16 12 8 0

Mole i FeS in sphalerite Fig. 16. T-X projection of the sphalerite-pyrite- pyrrhotite solvus isobars. (Hutchison and Scott, 1980) 42

the pressure inferred by Nesbitt ( 1979) using silicate phase assemblages. Barton et al. ( 1984) used sphaleri te grains adjacent to various sulfides and outside of pyrite grains to show that the cores of the sphalerites are FeS enriched

( 12-14 mole %) whereas the rims are FeS poor (9 mole%). The cores are thought to represent the sphalerite that was pro- tected from retrograde metamorphism by the rims. Sphalerite grains that are fractured have FeS depleted cores, further indicating re-equilibration.

In the present study, the Fe, Cd, and Cu content of more than 500 sphaleri te grains was determined (Appendix 2) using a 9 channel ARL electron microprobe with sulfide standards.

Sphaleri te grains with chalcopyri te inclusions were avoided.

The data are broken into two groups with the first group used to determine metamorphic pressures at the formation of the different pyrites, and the second group used to determine growth patterns within the porphyroblasts.

Figures 17 through 21 represent the first data set. The data set is divided into four subgroups: ( i) sphaleri te inclusions outside the pyrites, but in contact with pyrite and pyrrhoti te; (ii) sphaleri te inclusions within the rounded pyrite grains; (iii) sphalerite inclusions in small porphyroblasts; and (iv) sphaleri te inclusions in porphyroblasts between 15 to 20 millimeters. The sphalerite grains outside of the pyrite (subgoup 1) occur in low pres- 43

FREQUENCY UR CHART

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Mole % FeS in sphalerites

Fig. 17. Frequency diagram of the FeS content in sphalerite qra ins disregarding the location of the sphalerite grain. 44

SYHl•I FREQUENCY BAR CHART

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!------~~=~------=~~~--~=~~--=~~~--~~~~--~~=~--~~~~--~~~~--~~~:!6.0 15.5 15.0 l~.s I'·' ls.5 ll.O IZ.5 IZ.0 11.S 11.0 10.S 10.0 9.5 i.O .,.s 1.0 __

Mole ~ FeS

Fig. 18. Frequency diagram of the FeS content in sphalerite grains located outside of the pyrite grains, but in contact with pyrite and pyrrhotite. 45

):T"I•+ FREQUENCY IAR CHART

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llole ,: feS

Fig. 19~ Frequency diagram of the FeS content in sphalerite grains encapsulated within rounded pyrite qrains within the pyritic ore zones 46

SY,.i•O FREQUENCY au CHART

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Mole % feS Fig. 20. Frequency diagram of the FeS content in sphalerite grains located within the small (10 mm) porphyroblasts. 47

SYMl•X FREQUENCY IAR CHART

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Hole ~ FeS

Fig. 21. Frequency diagram for the FeS content is spha 1erite grains within pyrite porphyroblasts that are between 15 and 20 ITITI in size. 48

sure areas creating difficulties in determining their metamorphic history. The sphalerite grains cluster between 9.0

to 10. 0 mol % FeS corresponding to a pressure between 10. 0 to

11. 6 ki lobars at temperatures above 350 °C. However, the FeS

content in the pyrrhotite, along with the sulfur isotope

fractionation (Mauger, 1972), gives a temperature of approx-

imately 280°C. At this temperature the FeS activity is

reduced causing a loss of FeS from the sphaleri te. Using the

isobars (figure 22) that Barton et al. (1984) postulated, a pressure of 5 kilobars is interpreted. The relatively few high FeS values are attributed to remnant cores that were

shielded from re-equilibration.

Because the rounded pyrite grains in the second sub-

group grew before or near peak metamorphic conditions, the

sphalerites entrapped within them should yield peak metamorphic pressures (similar to the silicates). The sphaler-

ite inclusions are elliptical in form and are virtually free

from chalcopyri te inclusions (Fig. 23). As indicated by fig-

ure 19, the FeS value is much greater than that of the first

subgroup. The mean FeS content in the pyrites is 11.9 mol % which correlates to a pressure of 7.8 kilobars (the range is

5 to 10 kb) . The lower FeS values appear to be the result of

sphalerite grains not completely enclosed by pyrites and

thus not shielded from retrograde metamorphism.

The final two subgroups represent inclusions within the 49

700

I 600 I I \

1. 0 2.5 s.o 7.5 10.0 kb u., soo .,...... "" \ "'c \ ...... ,:::i \ .,~ 400 c::...... E \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

16 lZ 8 4 0

Hole ~ FeS in Sphalerite Fig. 22. T-X projection of the sphalerite-pyrite- pyrrhotite solvus isobars extrpolated for re-equilibration of the sphalerite by Barton et al., 1984). 50

Fig. 23. Bleb-shaped sphalerite grains (grey) within pyrite (white). In both the pyri tic ore (rounded pyrite) and the pyrite porphyroblasts these sphal'eri te grains are usually free of chalcopyrite inclusions and are not intersected by fractures. Thus, they are the most reliable in giving the metamorphic pressure at the time of entrapment. (Width of field=2. 0 mm)

\ 51

porphyroblasts. Figure 20 represents the porphyroblasts that are less than 15 mm. in size. These pyrite cubes have a mean FeS content of 11. 6 mol % corresponding to a pressure of

8. 1 ki lobars. However, the distribution of points shows two populations, one at 12.8 mol % FeS (6.7 kbs.) and the other at

10.5 mol % FeS (9.6. kbs.). The 12.8 mol % is similar to the sphaleri tes in the rounded pyrites, but the 10. 5 mol % FeS is higher than the sphalerite that re-equilibrated at 280°C.

The porphyroblasts between 15 and 20 mm show a similar pattern to the smaller ones, but the pressure range and the lower distribution is towards a lower FeS content (Fig. 21).

To determine if these separate populations correspond to different sets of conditions during growth, a detailed

analysis was carried out on a single 40 x 42 x 50 millimeter pyrite porphyroblast. As with most large porphyroblasts, this specimen is highly fractured, contains several small pyrite crystals, and has inclusion-rich zones around an

inclusion free core. The small pyrite crystals are small and

inclusion-free, no larger than six millimeters, and are pre-

sent throughout the large porphyroblast. Often these cubes

are separated from the porphyroblast by a layer of silicates.

Adjoining the porphyroblast is a smaller pyrite cube measur-

ing 10 millimeters across.

The porphyroblast was cut into twelve 1. 5 to 2. 5 milli-

meter thick sections, perpendicular to the short axis. A 52

cartesian coordinate system with the origin in the center of the porphyroblast allowed the location of individual sphaleri te grains within the pyrite to be specified. If the pressure varied during entrapment of the sphaleri te grains, then variations in the FeS contents of the sphalerite might be found when plotted against the distance of the grain from the center of the pyrite.

Microscopic examination of the porphyroblast indicated several different types of sphalerite grains: (i) elongated grains within fractures (Fig. 24); (ii) irregular-shaped grains (Fig. 25); (iii) large massive grains up to one millimeter (Fig. 26); (iv) small rectangular-shaped grains; and

(v) elliptical blebs (Fig. 23) less than 0.1 millimeter.

Because earlier findings suggested that the FeS content of a sphaleri te grain is different depending on the type of sphaleri te grain, a reliability factor was assigned to each of the specific grain type analyzed (Table 4). The bases for the reliability estimates are: the location of the grain within the pyrite, the relationship of the sphalerite grain to surrounding sphalerite grains, and the sphalerite grain's shape. The sphalerite grains that were analyzed appear to occur in the inclusion enriched zones, or within fractures.

Microscopic examination of other pyrite porphyroblasts indicate that during growth the sphalerite grains were incorporated as elliptical-shaped blebs if they occurred in the 53

Fig. 24. Sphaleri te grain within a large fracture in a porphyroblast cross-cut by a small chalcopyrite vein. Chalco- pyrite inclusions are abundant. The sphalerite can easily re-equilibrate to lower temperatures, because it is not enclosed by the pyrite. (Width of field=l. 1 mm) 54

Fig. 25. Irregular-shaped sphalerite grains (grey) within a pyrite porphyroblast. This type of sphaleri te grain occurs in clusters, contain abundant chalcopyrite inclusions, and are intersected by fractures running to the outside of the pyrite. The irregular-shaped grains appear to have been entrapped under different conditions than the bleb-shaped sphaleri te grains. (Width of field= 2. 0 mm)

\ 55

Fig. 26. Large massive sphalerite grains (grey) within a porphryoblast. This type of sphaleri te grain contains abundant chalcopyrite inclusions as well as being intersected by fractures. (Width of field=2. 0 mm)

'\ Table 4. Sunmary of FeS content in different sphalerite grains

..,... (•I• I res> ,,.... ,. r .... Ct•I ,,,. ... of"'· lttll••ll1t1 DHcrlptlOft •I• ...... •t• .... latt.,NtH loo A )1 I (-r) U-ted 9r1ln1 .. to I • I• 1.5 11.D H.Z Splo ..-1111u Into fnctuNS .,,l"t 1..,.th c-11 f- lo hrte ••• 11.• • l•H defo-UOll perlM ...i ,._... fr1eture1 i cpy Inc lus tons '·' to low t-rltUN ,..• ....,11 lkttloo •t.und•nt lrrttUhr .Uped tr•las up to o:s 1.0 11,5 t.I 15,l I.I 11.5 5'll t••las tau "'"' tr.,...... 1t1o1a • acrou •It• •...,....t Cfl' lo• ,,.. ,.,. ••• Mt- " """' , .... •'.Ul clu• I""" fouad la •-• rte• I• ...... tllt '"""' ., "" ,..,,.,..... 1 .. t otlltr l.l'ffl of lac lus loo l•lc11); ·O\ C-17 IAltrHctH "1 MlrllM fr1cture1 97 Llrtt l'OUll4I 1htpe4 tri los up lO· 1.0 u.o 15.1 Sl•tl1r to t1'0 I, 11111' ...,.. ,,.,,... ta 0.1 M ICNll with .-...nt CPI ••• tllt -tor of t11t '1 c171UI fKff tM laclusl0111; ,_ I• taclu1I011 '·' "·' _...,_ .., tllt ,...,..,...,.. , rich •-• tad l•UnKtd "1 fractures

D n t.O 14.0 II.) 11.1 5.5 Splo trtlas tMt "'" tr-.1 ta old :"!! ~1'!."'i!":,:~.. ,~:~· ••• fr1CtuN1 or v.ia -•tff that ,..,. ..tthl• " ...... t .. , ... ,...,..,.,.... , trwtll ... 5 (-4) S..11 olltptlul '"'"" tr•I•• 1.0 14.5 II.I lJ,) 1.0 S..11 spll tr•la• tlott ...,.. ootr_.i .. to O.Z .. 1crou tsohtd .. , .., "" ,...1.. ,...,..,....,.. , •ltht• tllt " 57

middle of a crystal face, or as irregular shaped grains if squeezed into fractures or trapped at the corners of pyrite grains. Unlike the rounded pyrites and smaller porphyroblasts / the sphaleri te grains in the large porphyroblasts contain abundant chalcopyrite inclusions, especially within the irregular, elongated, and massive sphaleri te grains.

The data for the sphalerite grains were entered into a computer program in order to prepare for each section: histo- grams of FeS content, plots of FeS as a function of di stance, and to calculate means of FeS content. A comparison of the histogram each type of sphaleri te grain (Fig. 27 through 32) indicates that the elongated grains within fractures have the lowest mean FeS content: 9.25 mole% (Fig. 28). Because the pyrite is extremely fractured, it is likely that the sphalerite grains in the cracks have re-equilibrated with the surrounding ore during retrograde metamorphism. The irregularly shaped sphaleri te grains (type 2) and larger type 3 grains occur in clusters (Fig. 25) and appear to be grains that were trapped during the pyrites' growth. Because both of these grain types are intersected by small fractures and contain abundant chalcopyri te inclusions, their reliability is questionable. The most reliable grains should be the rectangular and bleb-shaped grains (type 4 and 5) that are found between fractures, lie along zones defining growth of the pyrite grains, and have only an occasional chalcopy- 58

FRE~UENCY IAR CHART

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Mole % feS Fig. 27. Frequency diagram of the FeS content in sphalerite grains within a 40 x 42 x 50 nm porphyroblast disregarding the type of sphalerite grain and location within the porphyroblast. 59

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Mole % FeS Fig. 28. Frequency diagram of the FeS content in sphlaerite grains located within fractures in the porphyroblast (type 1). Because of the chalcopyrite inclusions within the sphalerite qrains and possible exposure to re-equilibration, these sphalerites are considered the least reliable for metamorphic pressures during the porphyroblast growth. 60

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fig. 29. Frequency diagram of the FeS content in sphalerite grains that are irregular in shape, intersected by small fractures, and contain chalcopyrite inclusions within the large porphyroblast. The reliability factor is 2 01

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Fi~. 30. Frequency diagram of the FeS content in sphalerite grains that are large {up to 1 rrm), intersected by fractures, and contain abundant chalcopyrite inclusions. The reliability factor for these sphalerite grains is 3. 62

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Mole i FeS Fig. 31. Frequency diagram of the FeS content of the rectangular shaped sphalerite grains within pyrite porphyroblasts 63

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Mole 1 FeS

Fig. 3,. Frequency diagram of the FeS content of the bleb- shaped sphalerite grains within the large pyrite porphyroblast. These grains are. not intersected by fractures and are relatively chalcopyrite free. Their reliability factor is 5 64

rite inclusion. The mean FeS values for these grain types are 10.5 and 10.3 mole percent, respectively (Fig. 31, 32). As with the sphalerites within the rounded pyrites, the FeS content is bimodal. Plots of the sphalerites' FeS content versus distance from the center of 'the porphyroblast (either as individual grains or as means of a group of grains) do not show any sim- ple trends (fig. 33). Possible reasons for the lack of a correlation between the FeS content of the sphaleri te grains and their location in the pyrite include: ( i) intense fracturing throughout the pyrite that allowed re-equilibration of the sphalerite grains; (ii) the annealing of many small pyrite grains into a single large grain that initially grew under different sets of conditions; and (iii) the incorporation of sphalerite grains that were equilibrating at temperatures below 350° C into the pyrite porphyroblast. If fracturing has ·caused the sphaleri te grains to re-equilibrate, then most of the sphalerite grains in the porphyroblasts should have FeS contents below 9.5 mole percent (or still show a weak zoning from the interior outward, because the interior is less fractured). Because many of the FeS values are above 10 mole percent, fracturing alone cannot be fully responsible for the scatter of data. A second cause for the variation in FeS content is that the porphyroblasts are composed of smaller pyrite grains. Etching each section revealed rem- PLOT or Hs•o l[G(NO: A = I OBS, B = 2 OBS, CTG.

f [ s 11

16 . A A

15 A

14 A A A A A A A A A A A A A I) A A A A A I A A I A A AA A A A AA A l 8 A A A A A 12 + A A A A A A A A A A A A A A A A A A A A A A A A A V') 11 A A A A A A A QJ A A A A LL A A A AA A A A A A A Cl"< 10 A A A A AA AAA A AA A A A A A A A A A A AA A A A QJ I I A A A A A ,.,.. AB A A C AA BA A A A A 88 AB A A A A .-- I A A A A A A A A 8 A A BA 0 9 + A A c AA A A AA A A 8 A A A AA A AA A A A ::E: A A B A A A AB A A B A A A A A A B A A A A A A AA C D AA AA A A A BAA A AA A AA 8 A A A B A A A AA B 8 A A c A A A A A AA A A A I A A M I AA A A A A A I A I + A A A

6 +

5 + -·-M·----·------+------·------+------+------·------+·------+------+~------·------+------·------+·------·------+------0, 0 11.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 Distance cm Fig. 33. Plot of the FeS content in sphalerite grains versus distance from the center of a 40x42x50 r.un pyrite porphyroblast. 66

nant pyrite grains, rounded and less than a millimeter in

diameter, dispersed throughout the porphyroblast. These

rounded pyrite grains were most prominent in sections 4b and

4a that contained the anomalously high FeS values. Contour maps of FeS values of sphaleri te around the remnant cores and

pyrite grains for each section did not indicate any definite

zoning pattern. The remnant cores suggest that the pyrite

porphyroblast may have formed partly by the overgrowth of

several pyrite cubes. The fact that smal 1 pyrite cubes exist

throughout the pyrite may be related to the overgrowth during

the porphyroblast development, or they may have been pro-

tected from complete annealing by the surrounding silicates.

A third alternative is that the porphyroblast grew at period-

ic intervals, starting at a temperature above 350°C and end-

ing at a temperature below 300°C. The amount of chalcopyri te

within the sphaleri te grain would indicate that the sphaler-

i te grains were subject to different conditions than the

sphalerite in the rounded pyrite. However, fractures filled

with chalcopyrite within the pyrite crosscut several sphal-

erite grains suggesting that the sphalerites were incorpo-

rated in the pyrite before brittle deformation of the pyrite.

To determine if the sphaleri te was entrapped at lower temper-

atures, the FeS content was converted into approximate pres-

sure using Barton et al. (1984) isobars for the sphalerite

geobarometer. No clear relation exist, indicating the geoba- 67

rometer is incorrect or the sphalerite was not entrapped at low temperatures.

Conclusions

Sphaleri te grains within the pyrite porphyroblasts display a bimodal distribution of FeS content, whereas, sphalerite grains within the small rounded pyrite grains (pyritic ore) exhibit a broad but unimodal distribution range. The high FeS contents lie between 13. 5 and 12. 0 mole percent corresponding to a pressure range of 6.8±0.8 kilobars for both the porphyroblasts and rounded pyrite grains. This pressure is slightly higher than the pressure obtained by Nesbitt,

(1979), of 6.0±1.0 kilobars using silicate phase assemblages, but is reasonable for amphibolite-grade metamorphism. The lower FeS values lie between 10.0 to 8.5 mole percent and apparently represent sphaleri te grains that have undergone re-equilibration at temperatures below 350 °c.

Application of extrapolated isobars (from Barton et al.,

1984) below 350°C for the sphalerite geobarometer suggests a pressure of 5. 5±1. 0 ki lobars (as opposed to a pressure of

11.0 kb for Scott's geobarometer). The FeS values between the two ranges probably represent grains that underwent only partial re-equilibration. If the pressures were caused by a normal pressure gradient of 3 ki lobars per 10 kilometers, the maximum burial depth would have been 22 kilometers. This 68

figure is reasonably consistent with an estimated thickness of 17 kilometers for the overlying sediments prior to any folding and thrust faulting (calculated from stratigraphic thicknesses}. If the temperature gradient was 25 °c per kilo- meter, the temperature at a depth of 22 kilometers would have been 550°C which is in agreement with the 550±50°C determined by Nesbitt, ( 1979). Accordingly, the maximum pressure of

6.8±0.8 kilobars appears reasonable.

PYRITE-PYRRHOTITE PHASE RELATIONS

The ubiquitous presence and overwhelming dominance of pyrite and pyrrhotite in the Ducktown ores permits their characterization in terms of the Fe-S system. The frequent presence of minor amounts of primary magnetite further allows definition of assemblages in the Fe-S-0 system.

Phase relations for the Fe-S system have been investigated by numerous authors (Kullerud and Yoder, 1959; Arnold,

1962; Toulmin and Barton, 1964; Yund and Hall, 1970; Kissin,

1974; and Kissin and Scott, 1982). The central portion of the Fe-S system at temperatures above 254°C is dominated by pyrite and hexagonal (lC) pyrrhotite (Fig. 34). Below this temperature monoclinic (4C) pyrrhotite is stable and coex- ists in equilibrium with pyrite. The high temperature lC pyrrhotite field persists to temperatures as low as 100°C, below which it subdivides into several hexagonal polytypes. 69

92 go

IC Hexaqonal 'yrrhotite HC} Hexagona 1 Pyrrhot ite ~ with superstructures 4C Monoclinic pyrrhotite

500

400

u 0 lC IC + Pyrite QJ ~ :::J +,) RS ~ 300 QJ c. E QJ MC + Pyrite I- llA + P rite

~00 It If It I I I I I lC t NC I NC + 4C + Pyrite ,It, 4C 11 100 48.0 47 .0 46.0 45.0 Atomic % Fe Fig. 34. Phase diagram for the Fe-S system for the pyrite-pyrrhotite solvus. The arrows indicate the cooling path of the ore body. The final composition of the hexagonal pyrrhotite is 47.4 mole % Fe in the pyrrhotitic ore, and 47.7 mole % Fe adjacent to the pyrite. 70

36 25 nn pyrite cube

J 24 r--~ !: ... ~ 5 18 ...... "'u ...c.. "' 0 12

6 I I

47.B 47.7 47.6 47.5 47.4 AtOllliC l Fe Fig. 35. Fe content in pyrrhotite located an a traverse starting at the edge of a 25 mm pyrite porphyroblast and ending 36 ... mm away from the pyrite. The dri 11 holes for the samp 1es are 1.5 mm (vertical bars) and the error in measurement is 0.05 atomic % Fe (horizontal bars). 71

36 2S""' pyrite cube

30 1-,--

24 !

0 '--~~~--=~--~~--L~~--.:-.~~~~~--~~~~--...... 47.8 47. 7 47.6 47.S 47.4 Atomic i Fe Fig. 36. Fe content in pyrrhotite located on a traverse starting at the edge of a 25 "'" pyrite porphyroblast and ending 32 mm away from the pyrite. The drill holes used in sampling are 1.5 mm in diameter (vertical bars) and the error in measurement is a.as atomic % Fe. 72

75 11111 pyrite cube 36

! 24 ~ ~ ~ ~ ~ ~ 18 ~

~ uc 4 ~ ~ Q 12

0 "-~----~------~------~------47. 8 47.7 47.6 47.5 47.4 AtCllltC S Fe Fig. 37. Fe content in pyrrhotite located on a traverse starting at the edge of a 75 mn pyrite porphyroblast and ending 30 rrm away from the pyrite. The drill holes used in sampling are 1.5 1m1 in diameter (verticle bars) and the error in measurement is 0.05 atomic % Fe (horizontal bars). 73

100 Im\ pyrite cube

24 ! ~ ~

~ ~ ~ 18 ~ ~ w u c ~ ~ ~ Q 12

47.8 47.7 47,6 47.S 47,4 Atomic s Fe Fig. 38. Fe content in pyrrhotite located on a traverse starting at the edge of a 100 mm pyrite porphyroblast and ending 37mm. away from the pyrite. The drill holes used in sampling are 1.5 rrm in diameter (verticle bars) and the error in measurement is 0.05 atomic % Fa (horizontal bars). 74

+ pyrrhotitic ore • pyrrhotltlc ore • 250 11111 pyrite cube a 305 "11111 pyrite cube 30

24 ! !! ;: >. a. 18 ~ .....~ ...... ,..c: 12 0..

47 .8 47.7 47.6 47.5 47.4

Atomic % Fe Fig. 39. Fe content in pyrrhotite located within the pyrrhotitic ore and adjacent to the large pyrite porphyroblasts. 75

Re-equilibration of the pyrrhotite phase is generally rapid on cooling {Kissin and Scott; 1982), hence the formation of monoclinic pyrrhoti te in pyrite bearing ores would be expected on the basis of the bulk composition of the Ducktown ores in light of the presently accepted Fe-S relationship.

However, the iron sulfide ores of the Cherokee Mine consist completely of hexagonal pyrrhotite and pyrite. Apparently, only limited re-equilibration occurred on cooling from the metamorphic peak conditions of approximately 550°C and 7 to 8 kb. The composition of numerous pyrrhoti te samples was determined by measurement of the position of the ( 1012) reflection (commonly referred to as the d 102 ) by standard x-ray diffraction techniques (Vaughan and Craig, 1978) using silicon as an internal standard. Pyrrhoti tes were sampled by drilling holes, 1.5 to 2.0 millimeters in diameter and 3.0 millimeter deep, along traverses starting at a pyrite porphyroblast and moving outwards for approximately 35 millimeters. The results (Figures 35-39) demonstrate that the pyrrhotite is not homogeneous, but rather it has a compositional gradient from 47. 7 atomic percent Fe immediately adjacent to the pyrite to 47. 4 atomic percent Fe at distances more than 20 mm from the pyrite. The Fe content in the massive pyrrhotitic ore also is 47.4 atomic percent. This suggests that there has been limited, local re-equilibration of the pyrite and pyrrhotite during cooling. On the basis of 76

the position of the pyrrhotite solvus given by Kissin and

Scott, ( 1982), this represents re-equilibration down to a temperature of 270°C. The cooling curve tracks along the pyrite-hexagonal pyrrhoti te solvus. The explanation for the non-equilibrium assemblage of pyrite and hexagonal pyrrhoti te can be explained by the need for hexagonal pyrrhoti te to obtain sulfur to convert into monoclinic pyrrhotite. Upon cooling sulfur was lost from the hexagonal pyrrhotite and consumed by the growing pyrite porphyroblasts. At low temperatures, the diffusion rate for sulfur is so low that it is not available for the hexagonal pyrrhoti te to convert to monoclinic pyrrhotite.

The assemblage of pyrite, pyrrhoti te, and magnetite within the porphyroblast zones fixes the sulfur and oxygen fugaci ty for a given temperature. Bands of magnetite up to a meter thick suggests that the magnetite is primary, implying that the ore body remained buffered by the pyrite, pyrrhotite, and magnetite. Magnetite grains that overgrew micas parallel to the regional schistosity, further indicates a closed system with respect to the sulfur and oxygen fugaci ties. The occurrence of ruti le and ilmenite in the ore zone indicates minor fluctuations in the oxygen and sulfur fugacities that were associated with the pyrite-pyrrhotite-magnetite assemblage. \. '

DISCUSSION The genesis and post-depositional history of the Duck- town ores have been speculated upon by numerous workers (Ma- gee, 1968; Addy and Ypma, 1977; Slater, 1982), but little has been written regarding the mineralogical changes involving the iron sulfides. It is now possible, however, to consider the mineralogical and textural changes of the pyrrhoti te and pyrite on the basis of the general geologic picture, observed mineralogy, phase equilibria studies, crystal growth studies, and comprehensive summaries of metamorphic effects on ore.

Initial Composition of the Ore Pyrrhotite and pyrite account for 90 to 95 percent of the ore minerals with an overall pyrrhotite to pyrite ratio of approximately 65: 35. This abundance and ratio is typical of similar Appalachian-Caledonide metamorphosed, massive sulfide deposits (Gair and Slack, 1981). In the past, many authors have suggested that the pyrrhotite in these metamorphosed ores is a product of desulfidation of the pyrite, but several recent papers (Plimer and Finlow-Bates, 1978; Gair and Slack, 1981; Craig, 1983) have concluded that much or all of the pyrrhoti te is primary. Further evidence in support of a primary origin for pyrrhotite is that it is a major phase in some of the modern sea floor sulfide deposits

77 78

(Edmond and Von Damm, 1983; Haymon, 1983; Zierenberg and Schanks, 1983). If the pyrrhotite in the ore body had all formed as a result of pyrite breakdown, the pyrrhoti te present would be approximately equal to twice the amount of the pyrite which had been destroyed. Half of the pyrrhoti te would likely be di s·persed throughout the host rock adjacent to the ore body where the sulfur would have extracted iron from iron-rich silicates or carbonates. However, only minor pyrrhotite exists throughout the host rocks of the Ducktown deposits, and the margins of most ore zones are very sharp. The loss of this amount of sulfur from the ore bodies would result in an approximate 20 percent volume decrease in the. ore. There is no evidence for such a volume loss in the ore body, although it is possible that any shrinkage might not be recognizable after amphibolite grade metamorphism and polydeformation. Finally, considering the possible oxidation reactions that can cause sulfidation during metamorphism:

2FeS + 4Fe2 0 3 = FeS2 + 3Fe304 po hem py mt less than 4 percent of the pyrrhotite can be converted from pyrite. No one of these points is compelling, but taken together with Plimer and Finlow-Bates (1978) arguments, they 79

strongly support the view that the present bulk composition of the ore is probably similar to that at the time of original deposition. Therefore, the ore deposit is an isochemical system where the sulfur and oxygen fugaci ties were con- strained by the pyrite-pyrrhotite-magnetite assemblage during metamorphism.

Nucleation and Growth of Pyrite

The growth history of these crystals can be interpre- tated on the basis of inclusions, textural features, and experimental studies. The two steps involved in the formation of a pyrite porphyroblast are nucleation and growth.

Minor nucleation may have occurred during metamorphism as a result of changes in pyrrhoti te composition during cooling (heterogeneous nucleation), or by the oxidation of pyrrhotite. However, the number of pyrite grains, the discontinuous pyrite zones, and the presence of pyrite cores, suggests that the nucleation of the pyrite grains probably occurred shortly after deposition of pyrrhotite on the seafloor as a result of partial oxidation of pyrrhoti te:

2H + 2FeS + ~o = Fe + FeS2 + H20

Modern seafloor deposits possess very small euhedral pyrite grains as well as crustiform accretions. Many low to moder- BO

ately grade metamorphosed, dominantly iron-rich massive sulfide deposits in the Appalachian-Caledonide Orogen and else- where, contain similar zones or bands rich in small primary pyrite grains. Furthermore, the hematite and goethite commonly associated with submarine hydrothermal deposits, such as the black smokers, might react with surrounding pyrrhotite during diagenesis to produce small amounts of pyrite

(2po + 4hem = py + 3mt). It is likely that the pyrite grains grew during the initial stages of metamorphism by Ostwald ripening where larger grains grow at the expense of the surrounding grains to decrease the over al 1 surface energy of the system. The other primary growth mechanism in this isochemical system is by sulfidation utilizing the sulfur released from the hexagonal pyrrhoti te as it cools during re-equilibration to lower temperatures. However, this process can account for only 1 percent of the total pyrite in the deposit if the deposit is cooled from 550°C to 300°C:

FeS + S = FeS 2

(a change in pyrrhoti te composition of 46. 4 to 47. 4 mole percent Fe release 1 mole percent S). These considerations combined with the general observations that: (i) pyrite crystal size varies inversely with abundance; (ii) many pyrite crystals have smaller pyrite crystals within them; and (iii) the 81

small rounded pyrites have envelopes of larger porphyroblasts around them, suggests that the final growth stage of the small pyrite porphyroblasts was accomplished by remobilization of the sulfur from other pyrite grains to form overgrowths on favorably oriented grains or cores. Because these cores are inclusion free and contain low dislocation densities (inferred by etch pi ts similar to pi ts described by Cox et al., 1981; McClay and Ellis, 1984), they are interpreted to have formed before major deformation possibly at the partial destruction of earlier formed pyrite to enable the pyrrhoti te to readjust to higher temperatures (become more sulfur-rich).

Several of the porphyroblasts, approximately 10 to 20 millimeters in size, are composed of several smaller anhedral pyrite grains. Indi victual anhedral pyrite grains stand out within the porphyroblasts, because the sulfides and and gangue minerals outline the pyrites' grain boundaries, etching produces different dislocation directions in different pyrite grains, and pyrite overgrowths are present on the edges of the anhedral pyrite. Other porphyroblasts are bordered by irregular pyrite grains containing pyrite cores that have undergone partial annealing into a single grain (Fig. 40).

Most of the pyrite porphyroblasts are probably formed of smaller pyrite grains, but they have undergone complete

annealing (Fig. 41) . This model would explain the the inc on- 82

Fig. 40. Growth and interlocking of small pyrite grains (light grey) into a single pyrite grain. 120° dihedral boundaries are visible indicating annealing. Further annealing would cause the grain boundaries to disappear. The new pyrite grain is anhedral, but. will try to lower its grain boundary energy by becoming euhedral by additional growth. (Width of fie 1d=2 . 0 mm ) 83

Fig. 41. Euhedral pyrite porphyroblasts overgrown by a larger pyrite porphyroblast trying to reduce its surf ace energy. (Width of field=2. 0 mm) 84

sistent FeS content in the sphaleri tes along with the observed inclusion patterns of randomly oriented minerals in the center of the pyrite surrounded by oriented micas on the rims. Once several of the pyrite grains interlock and begin growing together, possibly by solid state diffusion, they will try to decrease their combined surface energy by becoming more euhedral. Figure 42, based upon the concept of P-T loops describes by Spear and Selverstone (1983), summarizes the complete paragenesis of the small porphyroblasts.

Growth of Large Porphyroblasts The occurrence of a zone containing porphyroblasts which are at least 25 times larger than the average porphyroblast size is anomalous and is likely related to a local change in the surrounding environment. In the zone containing the 300 millimeter porphyroblasts, there are very few of the rounded or small porphyroblasts less than 20 millimeters across, which are common in other zones. Similar to the the porphyroblast zones composed of smaller grains, this anomalous zone has its largest porphyroblasts at the outer rim. In contrast to the smaller porphyroblasts, the larger ones are more rectangular, contain small euhedral pyrite crystals, have a more euhedral appearance, contain more inclusions, have small and large mica grains on their outer rims, and have large amounts of chalcopyri te and chlori te at ~ S..11 porphyrobl••u gcow arovnd the Sitep }: l.kofoc-1 lon 1•c•~1luf"••· ..11,,c.i.ntinvou11o prrtu ll'ain• frott •l•P ) br Ostwald rlpi1ntna. acme• of pycHr aloflA w1•l• • l°•11'h•d and DurlDf, th1• 1rowth unortent.-d .lncludaaa ere rounde4 pyrlu· ar•ln• th•t •cl•d ••nuclei t"C&ppit

~ hv pyrite arovir:h occure Hound thm above lnurloclr.H ll'•in• to r•htc.• the fr.. •neray H the &Uia ltoundarlu. lvrla& thh arowth &•n.t.t.ae alnenh He tr.ppff lty Che 1rovlq -'1•• of th pyrite to pror:luc• the circular tnc:lualon paueraa.

!u:£...l.:. Mlnor 1rG1Wth oc::~s-• •• th. pyn·botlt• cool• Mck 4own the PJl'h•.. PJTrMtlte aolV\lA CX> atlid ulea.. • auUuir to r ...... utltbl'eU. c.n

!!.!JL.!.:. fl ... l re-ect..alllbncloa of the pynhottc• co .approdaately JaG°c to J00°c.

lli2....l!.. HydrocMrsul eaanaU.on of •Ynacnetic ~pyrlt• 4cposUed vlth p:-onhottco •• au~ ------(!) •tllh1ctt·r cryu-111. h•bratd•, •nd accretlOftt..

zoo 400 600

TEMPEAAIUllE, o C

Fiq. 42. Paragenetic diagram for the formation of the pyrite porphyroblasts at the Cherokee Mine, Ducktown, Tennessee. P-T loop is simplified after Spear and Selverstone,(1983). 86

their interfaces. The sphalerite inclusions study suggests that all the pyrite began growing under approximately the same conditions. Thus, time is not a major factor in the increasing the size. Because the assemblage pyrrhotite-pyrite-magnetite occurs in this zone as well as most other porphyroblast zones, sulfur and oxygen fugaci ties did not influence growth significantly. Furthermore, the limited extent of the zones in which the large porphyroblasts occur indicates that higher temperature was not responsible for the greater size. Two factores that may have enhanced pyrite porphyroblast growth are: (i) change in the deformational conditions; or (ii) the presence of a fluid interface between the pyrite and pyrrhotite. The deformation of the pyrite in this zone is less than that of most other porphyroblast zones as evidenced by the more euhedral nature of the porphyroblasts. The porphyroblasts are, however, highly fractured (commonly containing calcite), frequently display interfaces that are chlori te coated and have smeared chalcopyri te and oriented sets of grooves. The entrapment of large inclusions towards the center of the grains along with relatively inclusion free centers with remnant pyrite cores suggests that the center of these porphyroblasts grew from the annealing of several smaller pyrite grains. During a later deformation event these pyrite grains may have been located in a low pressure zone in a fold that promoted diffusion of 87

either iron out or sulfur into the area. Several workers

(Stephansson, 1974; Stephansson et al., 1974) have demon- strated that mineral composition and crystal size vary within folds as a function of changing pressure gradients.

Pyrrhotite-pyrite assemblages may also be controlled by the location within a structure (Kubler and Lindqvist, 1979).

Furthermore, Berglund and Ekstrom (1974) suggested that the

FeS contents of sphaleri te grains may change as a function of the stress field around a boudin and that recrystallized pyrite grains are larger in the gaps between the boudins (low pressure zone). Little is known on the diffusion rate of sulfur at temperatures of 550°C, but during folding it appears that the sulfur moves to low pressure zones causing a more rapid growth of pyrite in this area. Folding may also bring adjacent pyrite grains into contact producing crushed and interlocked grains. If pressure gradients existed on different faces of the pyrite porphyroblasts, then either the iron or the sulfur may have moved to areas of lower pressure and produce elongation (Hobbs et al., 1976). Pressure solution within pyrite can also occur (McClay and Ellis,

1984). Another alternative, the creation of a fluid interface, where new sheet silicates nucleated on the pyrite's crystal face, could be evidenced by the occurrence of very small micas on the outer edges of the pyrite, and the presence of large amounts of chlorite around the larger porphy- 88

roblasts. A fluid interface could have resulted the loss of fluids from the calcite. The growth of iron bearing chlor- i tes could result in iron depletion and thus leave a sulfur enriched zone where the pyrite could grow. This would explain the perfect parallel orientation of the small micas to the pyrite's crystal face. The inclusion patterns and

abundant pyrite cores within the larger porphyroblasts indicate they underwent the same process as the smaller porphy-

roblasts, possibly at an increased rate.

Time of Growth

The sphalerite grains encapsulated within the pyrite

grains indicate that major pyrite grain growth began at a minimal pressure of 6 kilobars. Other indications of the

conditions of the pyrite grain growth are the presence of

large inclusions of amphiboles and micas representing min-

eral growth at high metamorphic temperatures (M 2 )., and the

occurrence of recrystallized quartz and calcite indicating

annealing after deformation ( F 2 ). The absence of spiral

inclusions in the pyrite, but the presence of penetrating

micas and internal inclusions paralleling the schistosi ty of

the ore suggest at least some post-tectonic growth. Major

fracturing and rounding of most porphyroblasts, the presence

of chalcopyrite within the fractures, and deformed pyrrho-

tite grains throughout the ore body suggest that the pyrite 8-9

porphyroblasts finished growth before a third deformation

(ductile-brittle) period. Finally, the occurrence of completely pulverized pyrite porphyroblasts indicating local shear zones may either be related to F 3 or another deformation event.

SUMMARY AND CONCLUSIONS

The study of the pyrite porphyroblasts at the Cherokee mine, Ducktown, Tennessee, permits the following conclusions to be drawn:

1. Most of the pyrrhoti te in this deposit formed during initial deposition onto the sea floor. The pyrite and magnetite formed approximately at the same time as the pyrrhoti te either by oxidation of the pyrrhotite or by increased H2 S activity. The ore body behaved as an isochemical system after burial and through metamorphism, buffered by the pyrrhoti te-pyri te-magneti te assemblage.

2. The pyri tic cores found within many of the pyrite grains and porphyroblasts represent remnant pyrite grains formed during initial diagenesis or metamorphism of the deposit.

These cores then acted as nuclei for further pyrite growth.

3. The pyrite porphyroblasts are composed of several smaller 9-0

pyrite grains that formed into a single large grain by

annealing, diffusion of sulfur to areas of lower pressure to minimize surface free energy, and by consuming sulfur

expelled by the pyrrhotite during the pyrrhotite

re-equilibration.

4. Sphaleri te geobarometry indicates the pyrite grains

began their growth at 6.8 ± 0.8 kilobars of pressure with an

approximate temperature of 550°C. Only small bleb-shaped

sphaleri te grains that are not intersected by fractures

within pyrite should be used to determine metamorphic pres-

sures. Most other sphalerite grains shows signs of

re-equilibration.

5. The pyrite porphyroblasts and surrounding hexagonal pyr-

rhoti te are not in total equilibrium as seen by zoning of

pyrrhoti te cornposi tions around the porphyroblasts. The pyr-

rhoti te farthest from the pyrite has a composition of 47.4

mole percent FeS whereas the pyrrhoti te adjacent to the

pyrite has a composition of 47. 7 mole percent FeS. The

retention of sulfur within the pyrite lattice at a

re-equilibration temperature of 300°C, as calculated from

the pyrrhotite composition, prevented the hexagonal pyrrho-

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Vokes, F. M., 1969, A review of metamorphism of sulphides deposits: Earth Sci. Rev., v. 5, p. 99-143. Yund, R. A., and Hall, H. T., 1970, Hexagonal and monoclinic pyrrhotite: Econ. Geol., v. 64, p. 420-423. Zierenberg, R. A., and Schanks, W. C. III, 1983, Mineralogy and geochemistry of the epigenetic features in metalliferous sediments, Atlantis II Deep, Red Sea: Econ. Geol., v. 78, p. 57-72. .. APPENDIX 1

Ore Mineralogy

The following data set was obtained by point counting both polished surfaces and doubly-polished thin sections.

Approximately 1000 points were selected on the polished surfaces and small thin sections, and 2000 points for the larger thin sections (4 cm x 7 cm). The symbols used in the data table represents the following:

+ samples taken from the porphyroblastic ore

x samples from the pyri tic ore * samples from the pyrrhoti tic ore

The column titled base represents chalcopyrite + sphalerite

± galena. Correlation graphs of chalcopyrite vs. ore type, sphaleri te vs. ore type, and chalcopyri te vs. sphaleri te are presented after the data.

96 .97

OIS SN PO PY CPY MT 5PH GANO SYMI FES JASE 1 S737-U 53.5 15.1 4.20 o.o 0.30 27.0 + 61.6 4.50 2 5517-24 45.9 23.2 2.70 0.1 2.20 26.6 + 69.1 4.90 3 5X 29.6 54.3 1.40 0.0 3.40 11.6 x 13.9 4.IO 4 51512-15 33.9 41.9 7.10 5.9 0.20 10.4 + 75.1 1.00 5 5511-27 34.4 21.9 3.50 9.5 o.oo 23.9 + U.3 3.50 6 5129-U 20.3 62.9 3.00 o.o 3.30 10.7 x 13.2 6.30 7 510.-25-3 5.6 52.5 6.00 0.0 0.70 35.6 x 51.1 6.70 I 5514-1 30.1 30.4 l.10 0.6 3.10 33.6 x 61.2 4.90 9 5604-27 39.l 25.1 1.20 o.o o.ao 27.0 + 64.2 9.00 10 $607-2 46.9 20.0 5.40 2.7 1.40 24.5 + 66.9 6.H 11 5736-17 24.6 39.5 17.70 0.0 a.so 11.2 + 64.1 11.20 12 5137-1 56.5 4.1 3.10 o.o 0.01 36.1 + 61.3 3.11 u 5965-62 51.6 17.1 1.20 o.o o.oo 29.1 + 69.4 1.20 14 5610-17 57.1 20.7 1.60 6.5 o.oo 14.0 + 71.5 l.60 15 "607-13 3.3 51.9 11.30 o.o 5.50 21.0 x 62.2 16.IO 16 "611-1 50.4 23.5 1.90 6.1 o.oo 17.1 + 73.9 1.90 17 M741-6 32.4 57 .1 1.00 o.o o.oo 10.6 + 19.5 1.00 11 M960-35 42.1 37.6 2.10 4.9 0.00 13.3 + 79.7 2.10 19 M737-U2 52.4 5.2 11.90 4.5 0.00 19.l + 57.6 11.90 20 M957-13 19.1 36.7 6.20 23.3 0.10 U.2 + 56.5 7.00 21 M712-3 62.9 1.4 0.90 0.0 0.10 27.3 + 71.3 1.70 22 "605-21 49.4 21.6 0.60 0.0 o.oo 21.1 + 71.0 0.60 23 Ml29-3 45.2 37.7 2.60 0.0 0.20 15.3 + 12.9 2.ao 24 Hl21-37 21.5 66.3 2.40 o.o 0.10 9.0 x 11.1 3.20 25 "423-14 65.1 u.1 3.40 5.7 o.oo 12.1 + 71.9 3.40 26 MISl-24 55.9 21.5 2.70 o.o 0.00 13.2 + 14.4 2.70 27 5423-14 73.4 o.o 3.00 1.0 0.50 15.2 73.4 3.50 21 5514-5 74.4 o.o 3.30 5.5 0.10 17.1 • 74.4 4.00 29 5737-11 66.1 0.0 3.00 0.1 o.oo 29.7 • 66.1 .s.oo 30 5752-6 41.1 0.0 4.10 0.0 o.5o 47.0 • 41.1 5.30 31 5161-34 71.3 0.0 5.60 o.o 2.60 20.2 • 71.3 1.20 32 5965-51 39.4 o.o 0.10 44.9 0.10 15.2 • 39.4 0.90 33 51502-31 13.9 55.5 1.00 0.0 3. 00 26.6 •x 69.4 4.00 34 Mll-6 7.7 41.2 3.60 0.0 0.10 47.9 x 41.9 3.70 35 CI02-6 23.9 42.1 0.65 O.D 1.20 32 • .S x 66.0 1.15 36 Cl54-11 11.9 41.7 0.40 0.0 3.90 21.1 x 67.6 4.30 37 Cl64-32 26.2 54.3 o.ao 0.0 2.90 15.1 x ao.5 3.70 ~ Cl69-14 17 .6 62.1 0.40 o.o 2.10 11.0 x 79.7 2.50 39 Sl0-4 36.9 39.6 3.70 o.o 2.50 17.6 + 76.5 6.20 40 514-6 30.5 39.3 6.90 0.0 1.70 21.9 + 69.1 1.60 41 MlO 76.1 0.0 3.40 0.0 1.20 11.9 76.1 4.60 - 42 Ml4-6 72.7 0.0 3.50 o.o 0.70 23.0 • 72.7 4.20 'I.OT Of ,.,..,,... ._._ IS VAi.UC 01 SYM9 N I I I I '° +

10 + I I I I 10 + x x )( 60 + I• x 12 I )( x I x $0 + x

x • x 40 • I+ • I I I lO + )( I+ I I+ I 20 ++ I+ • I I+ I 10 + I I+ I+ I 0 +• -·--- ...... --·-.... --...... ----...... ------+-- .. ------·-...... _... --·--...... ---·--·--.. ---...... --· .. ··--...... --... -...... -·-... -----...... o.o 0.5 1.0 1. 5 2.0 l.O 3. 5 4. 5 5.0 5. 5 6.0 SPH NOTE: 4 oes HIOO(N 99

l'\.OT or PY"CPY ._ II YALU[ Of IYM PY

90 + I I I I 80 + I I I I 70 + I I x I I x x 60 + I 2 I( x I I( ~ + I )( I I I x x + 40 + •I + + • I I • I JO )( •I I • • + I + I • 20 + •I + I I • I • 10 + I I I + I 0 . -·----·---··----·----·----·----··---·----·----·----·----·----·----·----·----·----·----·----·----·----·----·-··-·----·0 2 6 a 9 10 11 12 1J IS 16 17 18 19 zo 21 CPY "' llOTE: 1 Olll HtDO(ll 100

APPENDIX 2

Sample localities

The following table gives a partial listing of the sample

localities. The first number of the sample represents the drill hole in the mine, and the second number represents the footage in the drill hole. Additional information can be obtained from Tennessee Chemical Co. 101

Drill hole Section level sub level

143 1 N 10 159 1 N 10 423 8 s 10 5 574 9 s 10 1 575 9 s 10 1 579 11 s 10 1 581 12 s 10 1 582 13 s 10 1 583 13 s 10 1 584 14 s 10 l 605 16 s 10 4 607 15 s 10 4 608 15 s 10 4 609 9 s 10 4 610 9 s 10 4 611 9 s 10 4 612 9 s 10 4 724 20 s 734 20 s 10 1 735 18 s 10 1 736 19 s 10 1 737 20 s 10 6 748 15 s 10 6 754 22 N 10 2 782 20 s 10 4 802 19 N 10 3 828 2 s 14 2 829 l s 14 2 832 3 s 14 3 835 2 s 14 1 858 0 N 12 2 957 16 s 14 2 960 12 s 14 2 962 15 s 14 2 965 13 s 14 2 1502 23 N 1512 33 N 10 1515 22 N 14 10-25 open pit 10-26 5 s 14 1 102

APPENDIX 3

Sphalerite Geobarometer

The Zn, Fe, Cd, Cu, and S contents of the sphalerite grains were determined on the Virginia Tech, 9-channel, ARL electron microprobe. All values in this appendix are reported in atomic percent. The standards were natural chalcopyri te for copper and iron, synthetic CdS for cadmium, and synthetic ZnS for zinc and sulfur. Operating voltage was 15 or 20 kv and the filament current was 20 or 40 nanoamps. The data were reduced by Bense-Albe reduction method. Counting time was 20 seconds for both background and peak. For the first set of sphaleri te composition the following symbols

( symb) were used:

* sphaleri te in contact with pyrite and pyrrhoti te

+ sphaleri te within small rounded pyrite

o sphaleri te within small ( < 15 mm) porphyroblasts X sphaleri te in porphyroblasts between 15 and 20 mm l 03

OBS SN FE ZN cu FES TYPE SYMB 1 Ml69-16- 4.5 46.0 0.10 9.0 PO * 2 M2A 5.0 45.6 0.01 10.0 PY + 3 M3A 5.5 44.7 0.03 11. 0 PY + 4 M3A 5.6 44.8 0.06 11. 2 PY + 5 M3B 6.5 44.4 0.02 13.0 PY + 6 M3C 5.2 45.8 0.02 10.4 PO * 7 M5A 5.0 45.9 0.01 10.0 PO 4 M5B 5.5 45.5 0.02 11. 0 PY +* 9 M6A 6.1 45.4 0.00 12.2 PY + 10 M7A 6.1 45.4 0.02 12.2 PY + 11 M7B 5.3 46.0 0.00 10.6 PY + 12 M8A 6.5 45.2 0.01 13.0 PY + 13 M8B 6.8 45.4 0.03 13.6 PY + 14 M724-147 6.2 45.4 0.01 12.4 POR 0 15 M3A 6.5 45.6 0.00 13.0 POR 0 16 M4A 6.2 45.8 0.01 13.2 POR 0 17 M5A 6.9 45.5 0.00 13.8 POR 0 18 M7A 5.8 45.6 0.01 11.ii POR 0 19 M8A 6.5 46.l 0.00 13.0 POR 0 20 M9A 6.4 46.1 0.01 12.8 POR 0 21 M2DT-1A 6.3 44.5 0.04 12.6 POR 0 22 M2A 5.8 44.5 0.04 11.6 POR 0 23 M3A 5.2 44.9 0.03 10.4 CR * 24 M4A 6.3 43.8 0.05 12.6 POR 0 25 MSA 5.7 44.8 0.03 11.4 CR 26 M829-13- 6.1 43.9 0.00 12.2 PY +* 27 M2A 5.9 44.4 0.01 11.8 PY + 28 M3A 6.6 44.1 0.00 12.6 PY + 29 M829-15- 4.8 45.8 0.00 9.8 PY + 30 M828-3-l 4.6 45.4 0.01 9.2 PO 31 MlB 7.1 44.0 0.01 14.2 PY +* 32 MlC 4.8 45.6 0.04 9.6 PO 33 M2A 5.5 44.7 0.00 11. 0. PY +* 34 M3A 5.8 45.2 0.00 11.6 PY + 35 M3B 5.3 45.2 0.60 10.6 CR 36 M4A 5.0 45.2 0.01 10.0 PO * 37 M4B 6.8 44.2 0.00 13.6 PY +* 38 M4C 4.7 45.4 0.01 _9. 4 PO * 39 M5A 5.9 44.9 0.01 11. 8 PY + 40 M5B 5.3 44.6 0.03 10.6 PY + 41 Ml43-S3- 5.6 45.l 0.00 11. 2 POR 0 42 M2A 4.1 46.6 0.00 8.2 CR 43 M3A 6.5 43.7 0.01 13.0 POR *0 44 M4A 4.9 45.4 0.01 9.8 POR 0 45 M609-14- 5.0 45.8 0.01 10.0 PO 46 M3A 6.9 43.9 0.01 13.8 POR *0 47 M4A 4.5 46.0 0 .15 9.0 PO 48 M605-21- 6.4 44.2 0.04 12.8 POR 0* 49 M4A 6.2 43.9 0.04 12.4 POR 0 50 M7A 6.6 42.9 0.01 13.?. POR 0 51 M8A 6.2 43.6 0.03 12.4 POR 0 52 M8B 7.3 43.2 0.04 14.6 POR 0 53 M9A 6.2 43.9 0.02 12.4 POR 0 54 MlOA 6.3 44.l 0.03 12.6 POR 0 55 51512-15 6.6 44.0 0.00 13.2 POR 0 56 S2A 6.0 44.7 0.03 12.0 PY + 104

OBS SN FE ZN cu FES TYPE SYMB 57 S3A 6.3 43.8 0.02 12.6 PY + 58 S4A 6.4 44.2 0.01 12.8 PY + 59 SSA 6.2 44.4 0.02 12.4 PY + 60 S6A 6.5 44.0 0.01 13.0 PY + 61 S6B 5.1 45.7 0.01 10.2 PY + 62 5607-2-1 5.5 45.0 0.06 11. 0 POR 0 63 52A 5.0 45.9 0.01 10.0 CR lE 64 S3A 5.0 46.3 0.00 10.0 POR 0 65 S4A 5.2 46.1 0.01 10.4 POR 0 66 SSA 5.0 45.0 0.01 10.0 POR 0 67 S5B 4.4 45.9 0.01 8.8 PO 68 51512-84 5.3 45.5 0.30 10.6 POR *0 69 S2A 3.9 46.3 0.02 7.8 PO 70 S2B 5.5 45.8 0.02 11. 0 POR *0 71 S3A 7.0 42.6 2.88 14.0 POR 0 72 S3B 5.4 45.2 0.80 10.8 POR 0 73 54A 5.0 46.0 0.22 10.0 POR 0 74 Sl515-1A 5.8 44.5 0.00 11.6 PY + 7S S2A 6.1 44.7 0.01 12.2 PY + 76 S3A 6.1 43.8 0.01 12.2 PY + 77 S4A S.6 45.1 0.00 11.2 POR 0 78 S8A 7.3 43.3 0.00 14.6 PY + 79 S609-23- 4.9 45.3 0.01 9.8 POR 0 80 S2A 5.0 46.1 0.04 10.0 POR 0 81 S3A 5.3 44.9 0.00 10.6 POR 0 82 S4A 6.2 44.3 0.01 12.4 POR 0 83 SSA 6.4 44.2 0.01 12.8 POR 0 84 S5B 4.9 45.9 0.03 9.8 POR 0 85 S6A S.2 45.8 0.03 10.4 POR 0 86 S6B 4.7 4S.8 0.04 9.4 PO 87 S86S-12- 5.8 45.8 0.00 11.6 POR *0 88 S2A 5.4 45.l 0.02 10.8 POR 0 89 S3A 5.4 45.3 0.30 10.8 POR 0 90 S4A S.5 45.0 0.02 11. 0 POR 0 91 5587-2-1 4.5 47.1 0.00 9.0 PO 92 SlB 5.5 46.3 0.03 11. 0 PY +* 93 S2A 6.3 44.3 0.00 12.6 POR 0 94 S3A 5.9 44.2 0.02 11.8 POR 0 95 S4A 6.6 43.8 0.01 12.2 POR 0 96 SSA 4.8 46.6 0.01 9.6 PY + 97 S5B 5.6 46.4 0.04 11.2 PO 98 S6A 5.0 46.2 0.20 10.0 POR *0 99 Sl.99-0- 7. 0 42.8 0 .60 14.0 POR 0 100 S2A 6.6 43.5 0. 70 13.2 POR 0 101 S3A 5.9 44.3 0.07 11.8 POR 0 102 S4A 5.0 4S.7 0.02 10.0 POR 0 103 S4B 5.0 45.9 0.60 10.0 POR 0 104 SSA 5.0 44.9 0.04 10.0 POR 0 105 56A 4.7 46.4 0.40 9.4 POR 0 106 S7A 5.0 45.3 0.12 10.0 POR 0 107 S8A 6.4 43.4 o.os 12.8 POR 0 108 S9A 5.5 44.0 0.54 11. 0 POR 0 109 SlOA 6.4 44.l 0.04 12.8 POR 0 110 SllA 5.0 4S.1 0.04 10.0 POR 0 lll SUB 6.2 43.9 0.17 12.4 POR 0 112 Sl2A 6.7 44.0 0. 70 13.4 POR 0 105

OBS SN FE ZN cu FES TYPE SYMB 113 Sl3A 6.3 44.2 0.04 12.6 POR 0 114 Sl4A 6.4 43.3 0.54 12.8 POR 0 115 SlSA 4.2 45.5 0.05 8.4 POR 0 116 Sl6A 5.4 44.6 0.06 10.8 POR 0 117 S17A 5.6 44.3 0 .64 11.2 POR 0 118 Sl7B 6.6 43.9 0.10 13.2 POR 0 119 Sl8A 6.5 43.0 1.12 13.0 POR 0 120 Sl8B s.o 45.6 0.05 10.0 POR 0 121 Sl9A 5 .1 45.4 0.05 10.1 POR 0 122 S20A 5.0 45.1 0.06 10.0 POR 0 123 Sl8-5A 4.9 45.7 0.00 9.8 POR 0 124 S6A 4.3 46 .0 0 .13 8.6 POR 0 125 S7A 5.0 45.0 0.05 10.0 POR 0 126 SSA 5.7 44.8 0.00 11.4 POR 0 127 S9A 5.1 44.6 0.00 10.2 POR 0 128 SlOA 4.9 45.4 0.09 9.8 POR 0 129 S14A 4.7 46. 0 0.04 9.4 POR 0 130 Sl5A 4.6 45.1 0.10 9.2 POR 0 131 Sl6A 5.1 45.2 0.00 10.2 POR 0 132 Sl6B 5.5 44.5 0.36 11. 0 POR 0 133 S17A 5.3 45.7 0.33 10.6 POR 0 134 S19A 6.8 43.8 0.10 13.6 POR 0 135 Sl98 5.8 44.4 0.00 11. 6 POR 0 136 S20A 5.4 45.2 0.00 10.8 POR 0 137 S23A 5.8 44.4 0.00 11.6 POR 0 138 S24A 6.3 44.3 0.00 12.6 POR 0 139 S25A 5.4 45.3 0. 70 10.8 POR 0 140 S27A 4.9 45.9 0.06 9.8 POR 0 141 S28A 5.5 45.0 0.00 11. 0 POR 0 142 S29A 4.8 45.4 0.01 9.6 POR 0 143 S30A 4.7 45.9 0.01 9.4 POR 0 144 M607-10- 4.4 45.9 0.13 8.8 PO 3E 145 MlB 4.5 46. 4 a.so 9.0 PO 3E 146 MlC 4.5 47.3 0.40 9.0 PO 147 M2 5.1 44.8 1.10 10.l PO 3E* 148 M5A 4.9 46.0 0.00 9.8 PO 149 M4A 6.4 44.3 0.03 12.4 PY +* 150 M4B 6.2 44.6 0.02 12.4 PY + 151 M4C 5.3 46.2 0.00 10.6 PO 152 M588-10- 5.7 46.3 0.00 11. 4 PY +* 153 M3A 5.4 45.3 0.00 10.8 PY + 154 M3B 5.2 45.6 0.00 10.4 PY + 155 M4A 4.5 47.0 0.00 9.0 PO 3E 156 M4B 4.5 45.7 0.00 9.0 PO 3E 157 M5A 4.2 45.7 0.00 8.4 PO 158 M5B 4.8 46.1 0.00 9.6 PO 3E* 159 1502-383 5.8 45.4 0.04 11. 6 PY + 160 SlOA 6.8 43.7 0.20 13.6 PY + 161 SlOB 6.6 43.8 0.40 13.2 PY + 162 SIOC 5.0 45.9 0.00 10.0 PY + 163 Sll 4.5 45.9 0 .12 9.0 PO 3E 164 SllB 5.8 43.9 0 .65 11.6 PY + 165 $12 5.7 45.2 0.43 11. 4 PY + 166 S12B 6.5 43.6 0.12 13. 0 PY + 167 513 4.7 45.7 0.05 9.4 PY + 168 SUB 6.4 44.l 0 .12 12.8 PY + 106

OBS SN FE ZN cu FES TYPE SYMB 169 Sl3C 5.4 44.7 0.04 10.8 PY + 170 ' Sl4 6.8 43.S 0.21 13.6 PY + 171 SlS 6.2 44.4 1.03 12.4 PO )E 172 Sl6 s.o 45.7 0.29 10.0 PO )E 173 Sl7 S.l 45.6 0.07 10.2 PO )E 174 Sl8 6.2 43.8 1.60 12.4 PO )E 175 Sl9 6.4 43.8 0.40 12.8 PY + 176 Sl 5.1 45.3 0.12 10.2 PY + 177 SlB 6.2 44.S 0.21 12.4 PY + 178 S2 6.0 44.3 0.19 12.0 PY + 179 S3 6.8 43.3 0.05 13.6 PY + 180 S4 5.2 45.7 0.16 10.4 PY + 181 SS 6.1 43.7 0.03 13.4 PY + 182 SSB 6.4 43.0 o.so 12.4 PY + 183 S6 4.9 45.7 0.20 10.0 PO )E 184 S7 6.2 43.9 0.04 12.4 PY + 185 S7B s.s 44.4 0 _,J8 11. 0 PY + 186 Sl0-25-3 S.3 44.S 0.03 10.6 POR x 187 Sl4B s.o 44.6 0.02 10.0 POR x 188 Sl4C 5.1 44.8 0.00 10.2 POR x 189 Sl3 4.1 46.5 0.00 8.2 POR x 190 Sl3B S.9 44.1 0.00 11.8 POR x 191 Sl2 6.S 44.0 0.00 13.0 POR x 192 SU 4.7 45.4 0.01 9.4 POR x 193 SlO 4.8 45.0 0.0! 9.6 POR x 194 S9 4.8 44.9 0.01 9.6 POR x 195 S8 6.1 43.9 0.09 13.4 POR x 196 S7 S.2 44.6 0.01 10.4 POR x 197 S7B 6.1 44.2 0.00 12.2 POR x 198 S6 4.7 45.1 0.00 9.4 POR )E 199 SS 6.6 43.5 0.02 13.2 POR x 200 S3 6.1 43.0 o.oe 13.4 POR x 201 S3B 6.8 43.3 0.02 13.0 .6 POR 202 Sl 4.6 45.3 0.02 9.2 POR x 203 Sl8 6.0 44.1 0.00 12.0 POR x 204 Sl7 6.4 43.4 0.03 12.8 POR x 205 Sl6 5.1 44.8 -o. 02 10.2 POR x 206 Sl5 5.4 46.1 0.00 10.8 POR x 107

The second set of data were derived from the sections cut from a single large porphyroblast ( 40 x 42 x 50). The following list of symbols are used in this data set:

R: reliability of the sphalerite grain to represent peak metamorphic condition (5 is most reliable).

Symb: each symbol represent a different section cut from the large porphyroblast and can be determined by the x value.

x,y,z: coordinates measured from the center of the pyrite (mm).

d: distance of the sphalerite grain from center of pyrite (mm).

Following the data table is a correlation graph demonstrat- ing the relationship between FeS content and Cu content in

sphalerite grains. 108

OBS SM FE ZN cu FES SY"ll x y z R D l DT4A-l 3.7 46.2 o.oo 7.4 0 1.15 z.o 2.0 2 3.05321 2 SU 3.4 46 .1 0.01 6.1 0 1.15 z.o z.o 2 3.05321 3 S2A 4.3 45.6 0.10 9.0 0 1.15 1.5 1.6 2 2.47639 4 S4A 4.7 45.6 0.01 9.4 0 1.15 1.1 0.3 l 1.61941 s SSA 6.2 43.4 0.03 13.8 0 1.15 1.3 1.5 4 2.29401 6 S4B. 6.9 43.7 0.00 13.a 0 l.15 l. l 0.3 5 1.61941 7 S6A 4.a 44.7 0.02 9.6 0 1.15 1.3 1.5 2 2.29401 a S7A 4.7 45.7 0.00 9.4 0 1.15 1.5 1.9 2 2.61002° 9 S711 4.5 45.4 0.06 9.0 0 1.15 1.5 l.9 2 2.61002 10 S7C 6.9 43.5 o.oa 13.9 0 1.15 l.S 1.9 s 2.68002 11 S9A 3.4 46.0 o.oo 6.a 0 l.15 0.0 1.7 3 2.05244 12 SlOA 4.S 45.a 0.03 9.0 0 l. lS 1.0 1.9 3 2.43567 13 SllA 4.9 44.7 0.00 9.a 0 1.15 1.2 1.5 2 2.23a&6 14 Sllll s.o 4S.1 0.30 10.0 0 1.15 1.2 l.S 5 2.23816 15 SllC 4.a 45.1 0.00 9.6 0 1.15 1.2 l.S 2 2.23886 16 Sl2A 4.2 45.6 0.00 8.4 0 l.lS 1.5 1.0 l 2.13134 17 Sl211 4.a 45.6 0.00 9.6 0 1.15 1.5 1.0 l 2.13834 - u Sl2C 4.a 45.6 0.00 9.6 0 1.15 1.5 l. 0 2 2.1313tt 19 Sl3A tt.3 45.1 0.00 a.6 0 1.15 1.6 0.4 5 2.01060 20 Sl4A 3.6 46.3 o.oo 7.2 0 1.15 1.5 0.3 2 1.91377 21 Sl5A 4.4 45.2 0.00 a.a 0 1.15 1.6 0.3 3 1. 99311 22 Sl6A 4.2 46.tt 0.03 8.4 0 1.15 1.4 1.2 2 2.17313 23 SlaA tt. 2 45.6 0.00 a.4 0 1.15 0.3 1. 7 2 2.07425 24 Sl9A 4.1 45.3 0.21 a.2 0 1.15 1.0 1.5 2 2.13134 25 SZOA 6.0 43.9 0.16 12.0 0 1.15 0.4 1.0 2 1.57560 26 S21A 4.7 45.l 0.01 9.4 0 1.15 0.2 l. 0 z 1.53704 27 S23A 4.5 45.3 0.00 9.0 0 l.15 0.4 0.6 3 1. 35739 21 S2311 6.4 43.6 0.00 12.a 0 1.15 0.4 0.6 5 1.35739. 29 S24A 5.6 44.0 0.00 11.2 0 1.15 0.6 0.6 2 1.42916 30 S25A 4.7 46 .0 0.00 9.4 0 l.15 0.1 0.4 4 1.22161 31 S26A 6.3 43.a 0.40 12.6 0 1.15 0.5 0.5 4 1. 35000 32 S26B 6.0 43.a 0.00 12.0 0 1.15 0.5 0.5 4 1.35000 33 S27A 5.S 41't.5 0.01 11.0 0 1.15 0.3 1.3 2 l.76139 31't S2SA 4.4 45.2 o.oo a.a 0 l.lS 0.0 1.2 3 1.66201 35 S29A 4.7 44.9 0.02 9.4 0 1.15 0.5 l.O 1.60390 36 S2911 7.2 43.3 0.00 14.l 0 1.lS o..s 1. 0 5 1.60390 37 S30A 4.3 l't5.3 0.01 a.6 0 1. lS 0.6 0.5 1 1.39014 33 S31A 6.5 43.6 0.00 13.0 0 l. lS a.5 0.5 5 l.3SOOO 39 DTZA-1 4.1 4S.9 o.aa a.2 x 0.50 1.7 1.9 s 2.59301 40 S2A 4.4 46.l 0.00 a.a x 0.50 1.4 1.9 3 2.41247 41 S3A 4.2 45.6 0.03 a.o x 0.50 1.2 0.9 3 l .Sall4 42 S4A 4.a 44.7 o.oo 9.6 x 0.50 0.7 1.1 2 1.39642 43 SSA 6.6 '13.0 0.01 13.2 x 0.50 0.4 o.a 5 1. 02470 44 S511 5.S 44.3 o.oo 11. 0 x 0.50 0.4 o.a 5 1.02470 45 S5C 4.6 46 .o 0.00 9.2 x 0.50 0.4 o.a 5 1.02470 46 S7A 5.0 4S.3 0.39 10.0 x 0.50 0.5 1.1 s l. 30767 47 SIA 5.9 44.4 0.00 11.a x a.so 0.3 0.6 2 0.33666 41 SIB 4.4 4S.7 0.03 a.a x 0.50 0.3 0.6 s o.a3666 49 sac 4.7 li5.3 0.03 9.4 x 0.50 0.3 0.6 3 o.a3666 50 S9A 4.6 45.9 0.00 9.2 x 0.50 0.2 0.3 1 0.61644 Sl S911 S.2 45.l 0.01 10.4 x 0.50 0.2 0.3 5 0.61644 52 SlOA 4.2 45.a o.oo a.4 x o.so 0.4 o.o s 0.64031 53 SllA s.o 44.7 0.00 10.0 x 0.50 0.6 o.o 2 0.71102 54 SllB 6.1 43.3 0.03 12.3 x 0.50 0.6 o.o 2 0. 73102 S5 SllC S.9 44.3 0.00 11. 9 x o.so 0.6 o.o 5 0. 73102 56 Sl2A 4.2 45.Z 0.00 a.4 x a.so 0.7 0.3 2 0.91101't 109

DIS SH FE ZN cu FES SYMI x y z R D 57 S13A 4.4 45.40 0.01 a.a x 0.50 0.9 0.3 2 1.07231 ~I Sl4A 5.a 43.90 0.02 11.6 x 0.50 0.9 0.9 4 1.36741 59 SlSA 4.4 45.90 0.01 a.a x 0.50 0.2 1.0 1 1.13.571 60 Sl6A 4.1 44.90 0.00 9.7 x a.so 0.1 1.9 2 1.96723 61 Sl61 6.3 43.40 0.00 12.6 x 0 • .50 0.1 1.9 5 1.96723 62 S17A 5.5 4.5.30 0.00 11.0 x 0 . .50 0.1 2.3 .5 2.3.5514 63 Sl71 4.0 46.00 0.40 a.o x 0 . .50 0.1 2.3 2 2.3.5514 64 SllA 3.1 4.5.70 0.00 7.6 x 0.50 0.6 1.1 2 1.96214 6.5 Sl9A 4.0 4.5 • .50 0.00 a.o x 0.50 0.7 1.6 1 1.11659 S20A 3.9 45.99 o.oo 7.1 x 0 • .50 0.9 2.0 2 2.Z4944 67 SZlA 4.7 45.40 0.07 9.4 x 0 • .50 1.4 2.0 1 Z.49199 "61 SZll 3.7 45.60 0.04 7.4 x 0 • .50 1.4 2.0 1 Z.49199 69 SZZA 4.4 46.40 o.oo a.a x 0.50 1.4 1 • .5 1 Z.11117 70 S23A 5.6 44.60 o.oo 11.1 x 0.50 1.6 1.Z 5 Z.061.55 71 S231 4.~ 4.5.70 o.zo 1.1 x 0 • .50 1.6 1.z , Z.06155 7Z SZ4A 4.0 46.00 0.01 a.a x 0 • .50 1.6 0.7 , 1.116.59 73 SZ.5A 6.6 43.60 0.00 13.Z x 0 • .50 1.6 0.6 .5 1.7104.5 74 S26A 3.1 46.30 o.oo 7 • .5 x 0 • .50 1.6 o.o z 1.67631 7.5 szn 4.3 46.40 0.00 1.6 x 0 • .50 1.6 o.o 2 1.67631 76 SZ7A 4 • .5 45.40 a.oz 9.0 x 0.50 1.5 0.5 z 1.6.5131 77 S21A 4.4 46.20 0.00 a.a x 0 . .50 1..5 a.a z l.77ZOO 71 S30A 4.2 4.5.IO a.oz 1.4 x 0 • .50 1.4 2.0 1 Z.49199 79 DTll-1 3.3 46.60 o.oo 6.6 [ 1.7.5 o.s Z.3 3 ,.90.560 ao Sll 4.0 46. 00 0.0.5 a.a [ 1.75 0.3 z.s 3 2.90560 11 SZA 4.6 45.90 o.oo 9.1 [ 1.75 1.1 1.9 z 2.10751 12 S3A 4.4 4.5.60 a.oz a.a t 1.75 o.a 1.1 z Z.Z164Z 14 S4A 3.1 46.40 a.oz 7.6 [ 1.75 1.0 a.a z 2.16152 15 S7A 5.2 44.00 0.09 10.3 [ 1.75 1.1 1.0 z 2.70231 SIA 4.4 46.00 0.04 a.a [ 1.75 1.6 0.6 z Z.44591 17 S9A 4.6 45.10 0.00 9.Z [ 1.75 1.z 0.5 s z.11002 "aa SlOA 4.0 46 • .50 0.00 a.a [ 1. 7.5 l.Z 0.1 s Z.1Z4Z6 19 SllA 5.9 43 . .50 a.oz ll.1 [ 1.7.5 1.1 0.2 5 Z • .5114S 90 SUB 4 • .5 45.10 0.06 9.0 [ 1.7.5 1.1 0.2 3 Z • .51143 91 SlZA 4.2 46.30 o.oo 1.4 [ 1.75 1.a 0.7 1 Z.606Z4 92 Sl3A 4 . .5 4.5.10 0.09 1.9 [ 1.7.5 1.1 1.0 .5 Z.70231 93 Sl3B 4.2 46.00 0.01 1.4 [ 1.7.5 1.1 1.0 1 2.70Z31 94 Sl4A. 4.5 46.20 0.04 9.0 [ 1.75 1.1 1.5 5 2.9Z447 95 SlSA 4.2 46.40 0.00 1.4 [ 1.75 1.5 1.1 3 2.9Z447 96 Sl.5B 5.0 46 .oo 0.02 10.0 [ 1.75 1 • .5 1.1 3 Z.9Z447 97 Sl6A 4.3 46.20 o.oa 1.6 [ 1. 75 1.0 1.1 1 z. 70Z31 91 Sl7A 4 • .5 46.20 0.03 9.0 [ 1. 7.5 0 • .5 1.1 1 2 • .5.5979 99 SllA 4.3 45.60 0.01 1.6 [ 1. 75 0.1 1.7 .. 2 2.4411Z 100 Sl9A 4.9 44.40 0.09 9.1 c 1.75 0.1 1.0 2 Z.01104 101 S20A 4.4 43.IO 0.19 a.a c 1.7.5 0.1 0 • .5 z l.IZZ77 102 S21A 4.7 44.IO o.oo 9.4 [ 1.75 0.1 0 • .5 2 1.IZZ77 103 szu 4.0 45 • .50 0.01 a.o [ 1.7.5 0.1 0.5 z l.IZZ77 104 S22A 4.6 45.00 0.04 9.Z [ 1.75 0.6 a.a 1 Z.01556 10.5 DT3A-S 4.5 45.60 0.04 9.0 ] a.so 0.5 1.1 4 l.Z4499 106 S3B 5.6 44.00 0.17 11.Z ] 0.30 0.5 1.1 z 1.24499 107 S4A 4.1 46.00 0.06 a.z ] 0.30 0.3 1.0 2 l.OUZI lOI SSA 4.6 45.40 0.50 9.2 ] 0.30 0.0 1.1 1 1.14011 109 S6A 5.2 44.90 0.17 10.4 ] 0.30 o.z 1.4 2 1.44561 110 S7A 4.9 45 .10 0.00 9.1 ] a.so o.z 1.1 1 1.15751 111 SIA 4.0 46.00 0.00 a.o ] 0.30 0.4 1.4 1 1.41661 llZ SU 4.9 411.40 0.17 9.1 l a.so 0.4 1.if 3 1.41661 113 S9A 5.5 43.00 0 • .51 11.0 J 0.30 0.6 0.6 1 0.90000 110

oas SH FE ZH cu FES SYMI x y z R D 114 S91 s.z 45.3 0.04 10.4 l 0.30 0.6 0.6 5 0.90000 115 SlOA 5.9 43.6 O.Z4 11.a J 0.30 l. 0 1.3 1.66733 116 SllA 4.7 44.5 0.1' 9.4 ] 0.30 1.5 0.5 2 1. 60935 117 Sl2A 4.a 45.2 0.22 9.6 ] 0.30 1.1 0.3 z l.17&91 111 Sl3A 4.5 45.5 0.16 9.4 ] 0.30 1.2 0.3 z 1.27279 119 Sl4A 4.9 45.3 0.01 9.a ] 0.30 1.0 0.3 1 1. Oa6ZI lZO SlSA 4.4 44.a 0.00 a.a ] 0.30 l.5 0.3 3 1.55'85 121 SlSll 4.a 44.7 0.19 9.6 J 0.30 1.5 0.3 3 l .55U5 122 Sl6A If. 3 45.7 o.oo a.6 J 0.30 1.7 0.5 5 1. 79722 123 SUll 7.3 42.1 o.2a 14.6 J 0.30 1.7 0.5 5 1.79722 124 Sl7A 5.9 43.4 O.Sl 11.a J 0.30 1.7 o.a 5 1. 90263 125 Sl7B s.a lf4.4 0.13 11.6 J 0.30 l. 7 o.a 5 1. 90263 126 SlSA 6.5 43.3 o.oa 13.0 l 0.30 1.a 1.1 4 2.13075 127 Sl9A 6.6 43.4 0.00 13.2 ] 0.30 1.9 1.4 2 2.379Ga 22a Sl98 4.3 45.5 o.oa a.6 l 0.30 1.9 1.4 3 2.3790I 129 S20A 4.4 46.1 0.00 a.a ] 0.30 l.4 l.l 3 l.9~3ql 130 S21A 4.2 45.4 0.00 a.4 ] 0.30 1.0 0.9 l l.3}340 131 S22A 5.1 44.9 0.03 10.l J 0.30 1.2 l.5 3 1.94422 132 S2111 5.0 45.6 0.03 10.0 l 0.30 1.0 0.9 3 l. 37a40 133 S23A 4.3 45.4 0.10 a.6 J 0.30 0.4 1.5 3 l.5all4 134 S24A 4.6 45.5 0.00 9.2 l 0.30 0.7 1.2 2 1.42127 135 S25A 6.5 43.4 0.00 13.0 l 0.30 0.4 1.4 5 l.4&661 136 S25B 4.6 lf5.l 0.09 9.2 J 0.30 0.4 l.4 2 l .lfS661 137 S26A 4.a 45.3 0.00 9.6 l 0.30 0. If 1.9 3 1. 96469 13& S27A 4.6 lfS.l 0.00 9.1 l 0.30 0.7 I.a 2 l.9544a 139 S2SA 4. 3 45.7 0.00 S.6 J 0.30 0.9 1.9 5 2.12368 140 S29A 4.5 44.3 0.06 9.2 J 0.30 1.2 2.0 2 2. 35160 141 S30A 4.6 45.1 0.00 9.2 J 0.30 1. 7 2.1 2 2.11at.6 142 SllA 5.0 44.S o.oo 10.0 J 0.30 1. 7 2.2 2 2.79643 143 DT3-2 4.5 45.9 o.oo 9.0 0.65 0.2 2.0 3 2.11246 144 S3A 6.1 43.7 o.oo 12.2 • 0.65 0.7 2.0 4 2.21642 145 S311 3.9 46.4 0.00 7.7 • 0.65 0.7 2.0 1 2.21642 146 S4A 4.4 45.4 o.oo a.a • 0.65 0.7 1.4 2 1.694&5 147 SSA 6.3 43.S 0.00 12.6 •$ 0.65 1.1 1. 0 5 1.62250 148 S6A 4.3 45.6 o.oa S.6 0.65 1.1 0.3 2 1.31244 149 S7A 5.a 44.l 0.65 11.6 • 0 .65 1.9 0.1 5 2.01060 150 SSA 4.4 45.S 0.00 a.a •$ 0.65 1.2 0.3 3 1. 397 !·~ 151 S9A 5.0 45.6 0.00 10.0 0. 65 1.3 1.1 2 1.82277 152 SlOA 5.4 44.3 0.00 10.a • 0.65 0.5 0.7 1.07819 153 SlOB 4.S 45.0 o.oo a.a • 0.65 0.5 0.7 4 1.07&19 154 SllA 4.2 '+5.9 0.03 a.4 • 0.65 0.5 1.4 2 1.62250 155 SUB 4.4 45.S 0.00 a.a • 0.65 0.5 1.4 4 1.62250 156 S12A 3.9 46.4 0.00 7.a • 0.65 0.9 1. 7 3 z_.03039 157 SllA 3.7 46. 0 0.00 7.S • 0 .65 1.1 l. 7 3 2.12662 158 Sl38 4.2 46.3 0.13 S.4 •$ 0 .65 l. l 1.7 4 2.12662 159 Sl4A 4.0 46.6 0.00 a.o $ 0 .65 1.2 2.1 2 2.50450 160 Sl5A 5.0 44.a o.oo 10.0 $ 0.65 0.1 0.5 2 0.&2614 161 S158 5.4 44.2 0.06 lo.a $ 0 .65 0.1 0.5 0.112614 162 Sl6A 4.1 45.7 0.00 S.2 $ 0 .65 0.7 0.6 3 i.12ao5 163 Sl7A 6.5 43.9 0.00 12.9 $ 0.65 0.9 0.4 5 l.la004 164 SlSA 4.7 45.7 0.04 9.4 $ 0 .65 0.9 1.5 2 l.a6615 165 SlSB 4.4 46. 0 0.11 a.a $ 0 .65 0.9 1.5 2 l.a6615 166 DT2-1 4.3 45.9 0.00 a.6 x 0.10 0.6 1.6 2 1.71172 167 Sl8 4.1 46.3 0.00 a.2 x 0.10 0.6 1.6 2 1.71172 16& S2A 6.3 '+4.4 0.00 12.6 x 0.10 0 . .s 1. 0 2 1.04&81 169 S2B 4.a 45.6 0.03 9.5 x 0.10 0.3 l. 0 2 1.04881 111 112

OBS SN FE ZN cu FES SYHB x y z R D 226 SlOA 4.4 45.5 o.oo a.a a 1.10 1.6 1.4 2 2.39374 227 SllA 4.0 45.5 0.23 a.o a 1.10 l.li l.li 2 2.26495 zza Sl2A 4.3 45.3 0.02 a.5 a 1.10 1.2 l.& 3 2.li2693 229 Sl3A 4.9 45.0 o.oo 9.a a 1.10 o.a 2.2 4 2.5a650 230 Sl3B 5.0 45.6 0.12 10.0 a 1.10 a.a 2.2 3 2.5a650 231 S14A 5.0 45.0 0.00 10.0 a 1.10 1.0 1.1 2 l.&4932 232 Sl5A 4.2 45.6 0.04 1.4 a 1.10 0.9 0.1 5 1.63095 233 Sl6A 4.3 45.3 0.02 a.6 a 1.10 0.7 0.9 3 l.Sa430 234 Sl7A 4.2 45.1 0.03 &.4 a 1.10 0.5 1.1 1 1.63401 235 SUA 4.7 44.a o.oa 9.4 a 1.10 0.4 0.9 2 l.4764a 236 Sl9A 5.3 44.a 0.00 10.6 a 1.10 0.2 0.7 5 1.31909 237 Sl9B 5.4 44. l 0.01 lo.a a 1.10 0.2 0.7 2 1.31909 23& S19C 4.6 45.2 0.01 9.2 a 1.10 0.2 0.7 1.31909 239 S20A 4.1 45.a 0.01 a.z a 1.10 0.1 0.4 3 1.17473 240 SZOI 4.5 45.a o.oa 9.0 a 1.10 0.1 0.4 5 1.17473 241 SZlA 4.7 45.4 0.00 9.4 a 1.10 0.4 0.5 l 1.27279 242 S22A 6.4 44.D 0.12 lz.a a 1.10 0.4 0.9 4 l.4764a 243 S23A 6.1 43.a 0.17 12.2 a 1.10 0.2 0.9 5 1.43527 244 S23B 5.1 44.S 0.02 10.2 a 1.10 0.2 0.9 l 1.43527 245 S24A 5.3 44.4 o.oa 10.6 a 1.10 0.0 0.9 2 1.42127 246 S25A 4.7 44.6 0.06 9.4 a 1.10 0.4 0.9 3 1.4764& 247 S26A 4.7 44.9 0.00 9.4 a 1.10 0.4 0.9 3 1. 47648 24a S27A 6.1 44.0 0.05 12.2 a l.10 o.a 0.9 s 1.63095 249 SZSA S.7 44.3 0.00 11. 4 a 1.10 0.9 0.9 3 1.64226 250 S29A 4.2 45.7 0.03 a.4 a 1.10 0.7 1.2 3 1.77200 251 S29B 4.7 45.0 0.06 9.4 a l.10 0.7 1.2 2 1. 77200 252 S30A 5.0 44.4 o.oa 10.0 a 1.10 o.a 1.3 l .Ul49 253 S30B 6.3 43.0 a.oz 12.6 a 1.10 o.a 1.2 5 1.513a4 254 DT4B-l 4.4 45.0 0.02 a.a t 1.45 0.9 z.o 3 2.62916 255 SlB 4.5 45.1 0.01 9.0 t 1.45 1.9 2.0 2 3.11649 256 S2A ".1 45.9 0.00 a.z I 1.45 1.2 1.1 2 2.60432 257 s2a 4.4 45.9 0.00 a.9 I 1.45 1.2 l.& 2 2.60432 25& S3A 5.0 44.6 0.00 10.0 1.45 l.2 1. 0 2 2.13131 259 S4A 4.4 44.9 0.01 a.a • 1. 45 0.4 0.7 3 1.65907 260 SSA 4.2 45.6 0.01 1.4 • 1.45 0.4 0.5 3 l.Sa509 261 S6A 4.2 45.3 0.00 8.4 • 1.45 0.7 D.2 5 1.62250 262 S7A 4.5 45.1 0.02 9.0 • 1.45 0.2 1.1 5 l.a.309& 263 S7B 4.4 45.5 0.01 a.a ' 1.45 0.2 1.1 5 l .a.309& 264 SaA 5.7 4.3.9 0.02 11. 4 •t 1.45 0.2 1.1 5 l.a309a 265 S9A 4.5 45.0 0.10 9.0 I 1.45 0.5 1.1 5 l .U746 266 SlOA 4.5 45.1 0.03 9.D t 1.45 o.a 1.0 2 1.93455 267 SllA 4.7 45.2 0.00 9.4 I 1.45 1.1 1.1 2 2.12662 264 SllB 4.a 45.2 0.00 9.6 I 1.45 1.1 1.1 2 Z.12662 269 Sl2A 7.0 4.3.4 0.00 14.0 t 1.45 1.9 o.a 5 2.52042 270 Sl3A 6.2 43.6 0.00 12.4 1. 45 1.5 1.2 4 2.40676 271 Sl.38 6.1 43.0 o.oo lZ.Z • 1.45 1.5 1.2 z 2.40676 272 Sl4A 5.6 44.0 0.94 11.2 •t 1.45 1.4 1.3 5 2 . .39544 Z72 Sl4B 4.9 44.7 o.oo 9.8 t l.45 1.3 1.4 2 2.39844 27.3 S16A 5.6 43.7 1. 31 11.2 1.45 0.0 z.o 3 2.47032 274 S17A 4.1 45.7 0.00 8.2 •I 1.45 o.o 1. 7 l 2.23439 275 Sl8A 5.1 44.l 0.13 11.6 1.45 0.3 1.6 2 2.1&002 276 Sl8B 5.0 44.9 0.00 10.0 •t 1.45 0.3 1.6 2 2.UOOZ 277 Sl9A 4.7 45.0 o.oo 9.3 1.45 0.7 1. 7 2.34147 278 S20A 4.0 45.0 0.01 a.o l. 45 1.2 2.0 2 Z.74636 279 S2011 4.7 44.9 0.00 9.4 •' l. 45 1.2 z.o 2 2.74636 280 S22A 6.0 44.2 0.00 12.0 •t 1.45 1.5 1.0 5 2.31355

OBS SN FE ZN cu FES SYMll )( y z R D 281 S22B 4.9 45.5 0 9.8 1.45 l. 5 1. 0 s 2. 31355 2a2 S23A 4.1 44.7 0 8.2 • l. 45 1.5 0.7 l 2.20057 2a3 S24A 3.a 45.7 0 7.6 • l. 45 1.5 0.1 3 2.0&166 214 SZ6A 6.5 4.3 . .3 0 13.0 • 1.45 o.a 0.6 4 1.76139 285 S27A 4.• 45.1 0 9.6 • l. 45 0 . .3 l. 7 5 2.25444 za6 S27B 5.9 43.5 0 11. 8 • 1. 45 0.3 1. 7 2 2.25444 287 S21A 4.2 45.9 0 &.4 • 1.45 2.1 0.3 3 2.56953 za8 S30A 4.0 45.4 0 a.o •I 1.45 2.1 o.s 3 2.60048 The vita has been removed from the scanned document