PENDALA - EXPERIMENTAL DEFORMATION OF SULFIDE...

PENDALA - EXPERIMENTAL DEFORMATION OF SULFIDE ORES.

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1

EXPERIMENTAL DEFORMATION OF

SULFIDE ORES

by

Penda1a Krishnamurthy

A thesis submitted to the Facu1ty of Graduate Studies and Research in partial fu1fi1ment of the requirements for the degree of Master of Science.

Department of Geo1ogica1 Sciences, McGi11 University, Montreal.

March 1967 •

. 0 Penda1a Krishnamurthy 1968

ABSTRACT

The deformation behaviour of chalcocite, galena, chalcopyrite,

pyrrhotite, sphalerite and pyrite were studied in a closed system subjected

to pressures and elevated temperatures.

Chalcocite was found to flow at 300°C. under a confining

pressure of 15,500 p.s.i.

Galena flowed plastically with translation gliding at around

40004under confining pressures up to 13,000 p.s.i.

Chalcopyrite readily flowed above 475°C. and below 650°C.

under confining pressures of 10,000 to 25,000 p.s.i. The mobility of

chalcopyrite was increasingly retarded as a result of loss of sul fur between

650°C. and SOOoC. under a constant confining pressure of 10,000 p.s.i.

Chalcopyrite recrystallized at and above 500°, 540°, and 562°C. under

confining pressures of 25,000, 20, 000, and 10, 000 p. s. i. respectively.

"Domains", developed during quenching from temperatures above 562°C., are

interpreted as evidence of a phase change from isometric to tetragonal at that

temperature.

The results on pyrrhotite single crystals, sphalerite and

pyrite substantiated earlier findings.

CONTENTS

INTRODUCTION

COLD SEAL BOMB EXPERIMENTS

Apparatus and general conditions

Results:

A. Deformation experiments on polycrystalline

chalcopyrite.

l

Page 1

2

2

15

15

B. Heating experiments on polycrystalline chalcopyrite. 30

C. Cold seal bomb and heating experiments on single

crystal chalcopyrite. 36

D. Exp1anations for the decrease in the amount of

intrusion with increase in tempe rature under a

confining pressure of 10,000 p.s.i. 42

E. Hardness tests. 44

EXPERIMENTS USING "TRI-AXIAL COMPRESSION" EQUIPMENT 50

Apparatus and general conditions 50

Resu1ts 55

DISCUSSION OF RESULTS 99

CONCLUSIONS 105

APPLICATION TO GEOLOGY 108

FURTHER WORK 110

ACKNOWLEDGEMENTS 111

BIBLIOGRAPHY 113

~PPENDIX 118

Previous experimenta1 work on the deformation of sulfides. 118

Polymorphism in chalcopyrite. 123

Number

1

II

Figure

4

5

43

Tables

Cold Seal Bomb and Heating Experiments

TriRAxial Compression Experiments

Graphs

II

A Plot of the amount of intrusion against temperature.

A plot of the amount of intrusion against confining

pressure.

A plot of mean Vickers Hardness number against

Page

3

56

16

17

temperature for a confining pressure of 25,000 p.s.i. 46

44 A plot of mean Vickers Hardenss number against


45A A plot of the amount of intrusion against temperature

for a confining pressure of 10,000 p.s.i. 47

45B A plot of mean Vickers Hardness number against


1

2

3

6

7

8

Photographs and Diagrams

Cold Seal Bomb apparatus in operating position.

A mullite tube between two samples. Sea1ed gold capsule.

Opened gold capsule after deformation.

Grain boundaries and mechanical twinning in original

polycrysta11ine chalcopyrite.

P-13. Fracturing in chalcopyrite before intruding into

the mullite tube.

P-l. Intrusion of chalcopyrite as a coherent masse

Il

11

13

19

19

19

III

Figure Page

9 P-13. Grain boundaries and mechanical twinning in

chalcopyrite. 20

10 P.l.a. Recrystallization and mechanical twinning in

chalcopyrite in the unintruded part. 20

11 P-l. Recrystallization and mechanical twinning in

chalcopyrite. 21

12 P-2. Recrystallization and increase in grain size in

chalcopyrite. 21

13 P .. 7. Mechanical twinning and grain boundaries in

chalcopyrite. 22

14 P-6.a. Recrystallization and mechanical twinning in

chalcopyri te. 22

15 P-12. a. Recrystallization and increase in grain size

in chalcopyrite. 23

16 P .. 16. Mechanical twinning and grain boundaries in

chalcopyri te. 23

17 P-15. Recrystallization and increase in grain size in

chalcopyrite. 24

18 P-10. a. Recrystallization and increase in grain size

in chalcopyrite. 24

19 2-24. Recrystallization and increase in grain size

in the intruded part in chalcopyrite. 25

20 P-24. Recrystallization and increase in grain size

in the unintruded part in chalcopyrite. 25

2l. P-32.a. Recrystallizatiol1 and increase in grain

size in chalcopyrite. 26

Figure

22

23

24

25

26

P-l. Intergrowths of cubanite and chalcopyrite.

P-ll. Reaction rim (cubanite-chalcopyrite inter-

growths) around a pyrrhotite grain.

P-17. Intergrowths of cubanite and chalcopyrite.

P-15. Domains in chalcopyrite.


27A and B.X-ray diffraction photographs obtained from Guinier

camera for chalcopyrite at different temperatures.

28

29

30

31

32

33

34

35

36

37

P-2. Domain patterns in chalcopyrite.


P-33. Domains in a chalcopyrite grain.

P .. 2·S.a. Domains in chalcopyrite.

P .. 31.b. Domains in chalcopyrite.

P-5. Fracturing in pyrite.

P-6.b. Shear fracturing in pyrite.

P .. 19. Intergrowths of cubanite and chalcopyrite.

P .. 18. n~mains in chalcopyrite.

P-IO. Domains and twinning in chalcopyrite.

38A and B.X-ray diffraction photographs obtained from Guinier

camera for polycrystalline chalcopyrite, and single

crystal chalcopyrite.

39

40

41

P-22. Recrystallization and mechanica1 twinning in

single crystal chalcopyrite.

P-20. Recrystallization and increase in grain size

in single crystal chalcopyrite.

P-20. Domains in single crystal chalcopyrite.

IV

Page

26

28

28

29

29

31

32

32

33

33

34

34

35

35

~7

37

38

40

40

41

Figure

42 P-2l. Domains in single crystal chalcopyrite.

v

Page

41

46 Tri-Axial Compression apparatus in the operating conditio~ 51

47 Bomb-fittings (Tri-Axial Compression apparatus). 51

48 Assembled bomb (Tri-Axial Compresa~~n apparatus). 52

49 Bomb-fittings with deformed specimen (Tri-Axial

50

51

52

53

54

55

56

57

58

59

60

Compression apparatus).

K-13. Undeformed specimen (sketch).

K-13. Deformed specimen.

K-13. Fracturing in galena.

~13. Streakingout of pyrite between two galena bands.



K-15. Streakingout of pyrite between two galena bands.



K-17. Curving of triangular pits in galena.

K-17. Contortion of triangular pits in galena along a

fracture zone.

61 K-17. Fracturing and granulation in galena in contact

with pyrite.

62 K-17. Streakingout of pyrite grains between two galena

63

64

65

66

bands.





52

59

59

59

61

61

61

62

62

62

64

64

65

65

66

66

66

68

VI

Figure Page

67 K-12. A fracture in galena. 68

68 K-12. Chalcocite appears to intrude galena. 69

69 K-14. Undefonned specimen (sketch). 69

70 K-14. Defonned specimen. 69

71 K-14. Pinch and swell structure. 71

72 K-14. Fractures in galena 71


74 K-16. Defonned specimen. 72

75 K-16. Flow texture in galena. 72

76 K-16. Undulating boundary between galena and

chalcopyrite-bornite masse 74


78 K-18. Deformed specimen. 74

79 K-18. Undulations in pyrrhotite in contact with galena. 76

80 K-18. Undulations in pyrrhotite in contact with galena. 76

81 K-18. Chalcopyrite in troilite, parallel to pyrrhotite

basal parting. 77

82 K-8. Undeformed specimen (sketch). 77




86 K-9. Curving of triangular pits in galena. 79

87 K-9. Pyrrhotite grains drawn along the direction of flow

of lead and chalcocite. 80

88 K-lO. Undefonned specimen (sketch). 80

89 K-ll. Undeformed specimen (sketch). 83

Figure

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

VII

Page

K-ll. Deformed specimen. 83

K-ll. Pyrrhotite grains carried along the direction of

flow of galena. 83

K-19. Undèformed specimen (sketch). 85

K-19. Deformed specimen. 85

K-19. Fracturing and granulation in pyrrhotite. 85

K-19. Curving of pyrrhotite basal partings. 86

K-19. Undulating boundary between pyrrhotite and pyrite. 86

K-5. Undeformed specimen (sketch). 88

K-5. Grain boundaries~) in chalcocite. 88

K-l. Undeformed specimen (sketch). 90

K-l. Shear fracture, with granulation in the shear zone. 90



K-2. Deformed specimen. 91


K-4. Brecciation in chalcopyrite. 92


K-6. Bornite lamellae in chalcopyrite. 94

108 K-6. Bornite lamellae andtroilite stringers inchalcopyrite. 95

109 K-7. Undeformed specimen (sketch). 95

VIII

Abbreviations

Galena Gn

Chalcocite Cc

Chalcopyrite Cp

Pyrrhotite Po

Magnetite M

Pyrite Py

Lead Pb

INTRODUCTION

This thesis is based on experimenta1 work undertaken in an effort

to provide more precise information about the behaviour of su1fides when

subjected ta stress and e1evated temperatures, such as have affected many

rocks du ring metamorphism. Many controversies about the origin and histories

of ore deposits cou1d, it wou1d appear, be 'reso1ved if more facts were

avai1ab1e about the behaviour of su1fides individua11y and in mineraI

assemblages under different environmenta1 conditions. Outstanding e~p1es

of such controversies are those re1ating to the Ramme1sberg 1ead-zinc-copper

deposits (Llndgren and Irving, 1911; Newhouse and Flaherty, 1930; Ramdohr,

1953), the Broken Hill, New South Wa1es, lead-zinc deposits (Gustafson et al.,

1950; Ramdohr, 1953; King and Thomson, 1953; Gustafson, 1954), and the ,

Bathurst, New Brunswick 1ead-zinc-copper deposits (Lea and Rancourt, 1958;

Stanton, 1959, 1960; Dechow, 1960; Ka11iokoski, 1965).

The su1fides ga1ena, chalcopyrite, pyrrhotite and pyrite were

chosen for study because of their common occurrence.

Before the experimenta1 work was started, the literature was

searched for ear1ier work a10ng the same 1ines. The published information

is summarized in the appendix.

The present study is the continuation of the "closed system

differential pressure experiments" performed by Sotes (1959), Davies

(1964-65), and Roberts (1965) under the direction of J. E. Gill.

COLD SEAL BOMB EXPERIMENTS

These experiments were undertaken to supplement preliminary

investigations of the behaviour of chalcopyrite by ~ Davies (unpublished).

They are numbered·P-l to P-34 and are arranged according to the

characteristics of the chalcopyrite used and the conditions under which the

experiments were performed. The physical conditions under which the

experiments were carried out are given in table l. The results of the

experiments are described collectively.


The experiments were performed in cold seal bombs heated in an

electric furnace. The cold seal type pressure bomb was described in detail

by OJa (1959, pp. 10-24). The method employed was devised by R. Davies and

has been described in detail by him (Davies, 1965a, pp. 101-103). Figure 1

shows j,the apparatus in operating condition. The essential features of the

technique are mentioned below.

2

An impervious single bore mullite tube (MacDane»was packed between

two cylindrical samples and placed in a gold tube. This was then sealed with

a carbon arc. Figure 2 shows a mullite tube between two sample pieces, and a

sealed gold capsule. The gold tube has a 0.15 inch internaI diameter, a

0.010 inch wallthickness and was cut to a length of one inch. The mullite

tube has an internaI diameter of 1.6 mm. It was ground on a rotating lap to

a length of a little over 5.5 mm. Small pieces of ore were ground on a

rotating lap to a cylindrical shape, in length a little over 2.5 mm., to fit

tightly into the gold tube. The gold tubewas not evacuated before sealing

because of the difficulties involved in sealing.

To insure that the gold capsule was completely sealed, the capsule

was tested in the bomb under low confining pressure (less than the pressure

e e

TABLE l,

Cold Seal Bomb and Heating Experiments

Exp.No. Confining Tempera" Amount of Intrusion MM. Mean Vickers Standard Observations pressure. ture. oC. End l End II Average Hardness Number Deviation and Remarks p.s.i.

Cold Seal Bomb Experiments: Polycrystalline chalcopyrite.

p .. l3 25,100 477 0.43 0.24 0.335 205.6 4.87 Mechanica1 twinning present.

P ... 3 25,800 502 0.57 0.54 0.55 212.2 7.04 Recrysta11ization in the intruded part and a minor portion outside the ~u11ite tube.

P .. 14 25,000 526 1.345 1.315 1.33 209.7 6.41 Recrysta11ization in the intruded part and a major portion outside the mullite tube.

P .. 26 25,000 540 2.06 2.00 2.03 218.7 13.14 Recrysta11ization with a few mechanica1 twins in one corner of the sample.

P .. 1 25,400 555 1.70 1.58 1.64 206.7 5.44 Recrysta11ization ':vith a few mechanical twins in one corner of the sample. Less intrusion th an predicted. Cause undeterminab1e.

P-1.a 25,000 550 2.30 2.88 2.59 246.7 8.44 Same as in P-26.

P-2 25,000 603 Complete intrusion 2.933 252.4 3.73 Recrysta11ization and increase in grain / size. Domains present.

P .. 7 20,000 500 0.075 0.18 0.127 207.5 4.50 Mechanica1 twinning.

P-ll 20,000 527 0.54 0.30 0.42 204.6 5.31 Mechanica1 twinning.

w

e e

TABLE l continued

Exp.No. Confining Tempera" Amount of Intrusion MM. Mean Vickers Standard Observations pressure. ture oC. End l End II Average Hardness Number Deviation and Remarks p.s.i.

Cold Seal Bomb Experiments: Polycrysta1line chalcopyrite.

P-27 20,000 540 1.06 0.62 0.84 Recrysta11ization in the intruded part and a major portion outside the mu11ite tube.

P-6.a 20,000 550 2.48 2.32 2.40 219.3 13.86 Recrysta1lization in the intruded part and a major portion outside the mul1ite tube. Samp1es are oblique with respect to the mul1ite tube. Go1d tube intruded into the mu11ite tube.

P-6. b 20,000 552 0 3.164 215.5 6.45 Recrysta11ization in the intruded part and a major portion outside the mu11ite tube. One end, pyrite, not intruded. Chalcopyrite intruded twice the amount with pyrite at one end when chalcopy-rite was present at both ends.

P-6. bb 20,000 550 0 1.48 Recrysta1lization in the intruded part and a major portion outside the mu11ite tube. (Repeat of P-6.b. One end, single crystal pyrite, not intruded.

P .. 6.c 20,100 550 1.52 1.20 1.36 214.8 7.98 Recrysta11ization in the intruded part and a major portion outside the mu11ite tube. 20% impurities.

P-6.d 20,200 550 1.70 1.56 1.63 Recrysta11ization in the intruded part and a major portion outside the mullite tube. 10% impurities.

.po.

Exp. No.

e

Confining Tempe rapressure. ture oC. p.s.i.

TABLE l continued

Amount of Intrusion MM. Mean Vickers Standard End l End II Average Hardness Number Deviation


P ... 12.a

P .. 5

p .. 4

P .. 16

P .. 9

P-17

P-17. a

P-15

20,000

20,000

20,000

10,000

10,000

10,000

10,000

10,000

1 576

602

650

525

550

562

562 /

575 ,/

2.80 2.36 2.58 248.0 5.22

Complete Intrusion 2.86 229.5 9.50

Complete Intrusion 2.69 243.5 7.73

0.045 0.045 0.045 210.6 5.64

o o o 211.6 10.10

0.15 0.12 0.l35 2l0.5 5.02

0.36 0.12 0.24 235.9 7.58

1.64 1.50 1.57 248.5 5.96

Observations and Remarks

e

Recrystallization and increase in grain size. Domains present. At one end, sample oblique, gold tube penetrated the mullite tube, and intruded more.

Recrystallization and increase in grain size. Domains of same size as in P-12.a.

Recrystallization and increase in grain size. Twins are present. Domains of smaller size than in P-5.

Mechanical twinning.

Mechanical twinning.

Recrystallization in the intruded part and a minor portion outside the mullite tube. 30% pyrite at one end.

Recrystallization in the :lntruded part and a major portion outside the mullite tube. 20% impurities at one end.

/Recrystallization and increase in grain size. Domains present. More intrusion. Cause not known.

VI

- e

TABLE l continued

Exp. No. Confining Tempe ra- Amount of Intrusion MM. Mean Vickers Standard Observations pressure. ture oC. End l End II Average Hardness -Number Deviation and Remarks p. s. i.

Co1d Sea1 Bomb ExperilIlents =-_ Po1ycrys ta11.ine ~ha1c:cœyri te.

P-8.a 10,000 603 1.28 1.04 1.16 236.2 8.39 Recrysta11ization and increase in grain size. Twins are present. Domains of same size as in P-15.

P-29 10,000 626 1.48 1.48 1.48 244.1 6.82 Recrysta11ization and increase in grain size. Domains of sma11er size than in P-8. a. 20% impurities. Samp1e at one end oblique to the mul1ite tube.

P-34 10,200 640 2.34 1.18 1.76 250.8 6.71 Recrysta11ization and increase in grain size. Twins are present. Domains of same size as in P-29. More intruded end is great1y oblique to the mu11ite tube and contains 20% impurities.

P-34.a 10,000 640 1.82 1.27 1.545 243.5 2.66 Recrysta11ization and increase in grain size. Domains of same size as in PN34.

P-lO 10,000 650 2.00 2.36 2.18 245.3 8.97 Recrysta11ization and increase in grain size. Domains of same size as in P-34.a.

P-lO.a 10,000 650 1.91 1.17 1.54 245.73 5.24 Recrysta11ization and increase in grain size. Domains of same size as in P-10. More intruded end is oblique to the mullite tube.

P-lO. b. 10,000 650 1.67 1.57 1.62 245.40 9.19 Recrysta11ization and increase in grain size. Domains of same size as in P-10.a.

0\

e e

TABLE l continued

Exp.No. Confining Tempe ra- Amount of Intrusion ~ Mean Vickers Standard Observations pressure. ture oC. En'd l End II Average Hardness Number Deviation and Remarks p.s.i.

Co1d Sea1 Bomb Experiments: Po1ycrysta11ine chalcopyrite.

P-lO. c 10,200 650 1.30 1.12 1.21 247.10 8.20 Recrysta11ization and increase in grain size. Domains of same size as in P-10.b. Less intruded end has 30% pyrite. More intruded end has 15% pyrite and magnetite.

P-lO. d 10,000 650 0.97 0.82 0.90 243.50 4.15 Recrysta11ization and increase in grain size. Domains of same size as in P-IO.c.

P-33 10,200 660 1.54 1.33 1.44 250.60 5.40 Recrystal1ization and increase in grain size. Domains of sma11er size than in P.lO.d. More intruded end has 20% pyrite.

P-24 10,000 675 1.41 1.47 1.44 226.30 7.90 Recrysta11ization and increase in grain size. Domains present.

P-25 10,000 700 1.10 1.00 1.05 229.50 6.90 Recrysta11ization and increase in grain size. Domains of sma11er size than in P-33.

P-25.a 10,000 700 1.10 0.98 1.04 Recrysta11ization and increase in grain size. Domains of same size as in P-25.

P .. 30 10,000 725 1.33 0.98 1.15 231.00 8.20 Recrystal1ization and increase in grain size. Domains of same size as in P-25.a.

P-28 10,000 750 1.40 0.53 0.965 243.00 6.38 Recrysta11ization and increase in grain size. Domains of same size as in P-30.

'"

e

TABLE 1 continued

Exp. No. Confining Tempera- Amount of Intrusion ~ Mean Vickers pressure. ture oC. End 1 End II Average Hardness Number p. s. i.


P-32 10,000 775 0.74 0.53 0.64 254.83

P-32.a 10,000 776 1.10 0.83 0.96 256.10

P-3l.a 10,000 800 0.96 0.70 0.83

P-3l.b 10,000 800 1.00 0.86 0.93 267.00

Heating Experiments: Polycrystallinechalcopyrite.

P-19 525

P-18 600


P-23 25,000 575

P-6 20,000 550

204.9

248.4

Standard Deviation·

6.77

10.10

7.8.5

5.04

6.65

e


Recrystallization and increase in grain size. Domains of same size as in PN28.

Recrystallization and increase in grain size. Domains of same size as in P-32.

Recrystallization and increase in grain size. Domains of same size as in P-32.a. Annealing time is 3~ hours.

Recrystallization and increase in grain size. Domains of same size as in P-3l.a.

Domains present and are of comparable size as in P-2. Sul fur dioxide was given off. Sul fur deposited on the silica tube wall.

Leak in gold capsule.


ex>

Exp. No.

e

Confining Tempe rapressure. ture oC. p.s.i.

TABLE l continued

Amount of Intrusion MM. End l End II Average

Mean Vickers Hardness Number


P-12 20,100 578

P-8 10,000 600

P .. 28.x 10,600 755 1.21 0.83 1.02 261.33

P .. 3l 10,000 800

Cold Seal Bomb Experiments: Single crystal chalcopyrite.

P .. 22 20,100 550 1.56 1.50 1.53 207.9

P .. 20 20,000 602 2.90 2.50 2.70 232.2

Heating Experiment: Single crystal chalcopyrite:

P-21 600 ...... 232.0

Standard Deviation

8.15

5.73

10.10

6.20




e

Sample used previously and withdrawn when pressure 1eaked. Again spoiled under uncontrolled conditions.


Recrystallization in the intruded part and a minor portion outside the mul1ite tube. Minor pyrite impurities.

Recrystallization and increase iri grain size. /Domains present and are of greater size than in P-2. Minor pyrite impurities.

li Domains are of same size as in P .. 20. Minor pyrite impurities.

\0

ct e

TABLE 1 continued

~ - -- - ---- --- -- - - - - - - ---- -- ------Note:

1) Annea1ing time is 2~ hours in a11 experiments.

2) Average is the arithmetic mean of the amount of intrusion at the two ends of the mu11ite tube.

3) Where significant quantities of pyrrhotite, pyrite, magnetite, and gangue are present the modal percentages

are stated. A11 samp1eshave minor impurities 5

4) The po1ycrysta11ine chalcopyrite sample was from Noranda Mines. Five, single crystals of chalcopyrite were

from French Creek Mines, Chester County, Pennsylvania.

~

1-' o

Fig. 1. Co1d Sea1 Bomb apparatus in operating positipn.

"tI

QI ......

~ CIl

QI ......

~ CIl

...... o 00

Fig. 2. A mu11ite tube between twa samp1es. Sea1ed gold capsule.

11

~-UVU.L ining

( )

Fig. 1. Cold Seal Bomb apparatus in operating positipn.

'0

Qi ..-1

~ CIl

CIl

..-1 o 0.0

Qi '0..-1 Qi ;::l

..-1 Ul CIl Q.. Qi CIl

CIl CJ

Fig. 2. A mullite tube between twa samples. Sealed gold capsule.

_..:....:..l~_.

11

ining

Seal

12

to be used in theexperiment) at room temperature for a few minutes; it was

then removed from the bomb and examined for 1eaks. The capsule was rep1aced

in the bomb and a confining pressure, 1ess than the required pressure, was

app1ied. The pressure circuit was tested for 1eaks. The temperature of the

bomb was raised to the required tempe rature of the experiment and the -

pressure was simu1taneous1y adjusted to the required pressure. An "on - off"

type temperature contro1ler was used to regu1ate the temperature. A Leeds-

Northrup potentiometer was used to measure the temperatures accurately to

within 20C. The maximum and minimum temperatures were noted in each rune

The greatest 'temperature drop was 100 below the maximum temperature.

The confining pressure was maintained within SOO p.s.i. of its

maximum throughout each experiment. After reaching the required temperature,

each samp1e was annealed for 2~ hours. The bomb was quenched in water. The

capsule was mounted in Quickmount (Fisher Co.) and then opened by grinding

on a rotating 1ap using fine grinding powders. The maximum distance of

intrusion on each end was measured under a ref1ecting microscope with an

ocular sca1e, calibrated with a micrometer. The specimen was then carefu1ly

poli shed and examined under the microscope. Figure 3 shows an opened sample.

The minerals were a1so identified from X-ray diffraction patterns

obtained from a Guinier focussing camera using COk radiation. The Guinier 0{

camera enab1ed the examination of smal1 amounts of the samp1e: it was used

to check smal1 impurîties in the chalcopyrite, and to check for the high

tempe rature po1ymorph of chalcopyrite.

Davies (196Sa) fu11y discussed the pressure gradient fram the

outside confining pressure to the pressure of trapped gas (air) inside the

mul1ite tube at the advancing end of the samp1e. He ca1cu1ated the pressure

of enc10sed air to be 88 p.s.i. at a temperature of 62SoC. before intrùsion.

·13

al ,..0 ::1 .j.J al

,..0 al ::1

al .j.J .j.J

.-1 .~

~ .-1 "tl .-1 .-1

tI) ~ 8

Fig. 3. Opened gold capsule after deformation.

o

o

14

The resistance of the pressure of the trapped gases increases as the sample

intrudes and becomes equal to the outside confining pressure at a certain

reduced volume limit.

Sulfur vapour pressure from the sulfide samples (dissociation

pressures) should be taken into consideration. Merwin and Lombard (1937,

p. 222) determined the dissociation pressures in terms of mm. of mercury for

certain copper and iron sulfides. The dissociation pressures for

chalcopyrite and pyrite are given below in terms of p.s.i.:

CHALCOPYRITE PYRITE

Temperature Oc Pressure (p.s.i.) Temperature Oc Pressure (p.s.i.)

627 12 682 10

597 3 670 6.5

575 1.2 655 3.7

560 0.5 635 1.4

625 0.75

610 0.24

590 0.08

The total pressure of a mixture of gases, according to Dalton's law

of partial pressures, is the sum of the partial pressures of each gas, where

the partial pressure of a component gas is the pressure exerted by that gas

if it alone occupied the container. The total pressure (P) of two gases

present in a container will be the air pressure plus the sulfur pressure (as

above). In the experiments below 650oC. it was less than 100 p.s.i.

14

The resistance of the pressure of the trapped gases inèreases as the sample

intrudes and becomes equal to theoutside confining pressure at a certain

reduced volume limit.

Sulfur vapour pressure from the sulfide samples (dissociation

pressures) should be taken into consideration. Merwin and Lombard (1937,

p. 222) determined the dissociation pressures in terms of mm. of mercury for

certain copper and iron sulfides. The dissociation pressures for

chalcopyrite and pyrite are given below in terms of p.s.i.:

CHALCOPYRITE

Temperature Oc Pressure (p.s.i.)

627 12

597 3

575 1.2

560 0.5

Temperature

682

670

655

635

625

610

590

Oc

PYRITE

Pressure (p.s.i.)

10

6.5

3.7

1.4

0.75

0.24

0.08

The total pressure of a mixture of gases, according to Dalton's law

of partial pressures, is the sum of the partial pressures of each gas, where

the partial pressure of a component gas is the pressure exerted by that gas

if it alone occupied the container. The total pressure (P) of two gases

present in a container will be the air pressure plus the sul fur pressure (as

above). In the experiments below 650oC. it was less th an 100 p.s.i.

Results

A, Deformation experiments on polycrystalline chalcopyrite:

In the experiments with tri-axial compression, chalcopyrite was

intensely fractured in the tempe rature ~ange from 250 to 350Gt:as shawn

in pp.89-98. Experiments were then made to find the limits under which

15

chalcopyrite flows readily in a solid state. These runs were made in a cold

seal type pressure bomb under differential pressures and elevated

temperatures. The essential principle in these experiments is that a sample

was forced to intrude into an open space. The method was described earlier

in detail (pp.2-l4), The experiments were performed at temperatures

ranging from 4750 to 800oC. and under confining pressures of 10,000,

20,000 and 25,000 p.s.i. Irregularities in the amount of intrusion between

the two ends was mainly due to impurities in the sample, and the loose fit

of the sample in the gold tube. The amount of intrusion in each run was

plotted against tempe rature and three curves were obtained for differential

pressures of 10,000, 20,000 and 25,000 p.s.i. (Fig.4). Also the amount

of intrusion was plotted against differential pressure, and curves were

obtained for temperatures of 5250 and 550oC. (Fig.5). AlI the curves

indicate that for a given amount of intrusion the temperature required may

be lowered with an increase of differential pressure and~ versa.

o Figure 4 indicates that the chalcopyrite flows readily above 475 C. and

below 6500 C. under confining pressures of 10,000 to 25,000 p.s.i.

In the following experiments, chalcopyrite contained pyrrhotite,

pyrite, magnetite and gangue as impurities (Fig.6).

In experiments with temperature at 477 oC. under a confining

pressure of 25,000 p.s.i., and with temperature at 500oC. under confining

pressures of 25,000 and 20,000 p.s.i., fracturing occurred similar to that

3.0

2.5

~ s:: o 2.0

-ri ltJ ::s J.I ~ \:

-ri

~ o QI 1.5 u t:: cu ~ ltJ

-ri o

1.0

0.5

o

-

g -ri ~ cu N

-ri .-1 .-f . cu ~ ltJ ~ J.I u QI ~

1 1

1

1 1 1 1

8 1 ,

(:j' 1 1 .... :.1

1 W 1 Qj

Ji.... 01 r 81 1 0 1

';j 1 CV! ll.'1\: 1

8' ·~;....,)\I 01 ~~

, 1

tQI ~. 1'71 , cvI -ri ~I

~ 1 ~ ÉI ~I

1

8 1 1 1 1

1

~ 1 ~I

1 1 1

El

QI co \: cu \: .c o u

-ri ~ QI cu ltJ

1/ 1

N cu -rI.e .-Ip-. .-1 cu ~ ltJ ~ /' / J.I U

JI 11 . 1

/ 1

8:/ El ...... / /1

1

" /

El /

'"

500 0

/

"....... (;) _~_.......... 1

1 1 1

. .1

iJ Q,,1

8/ 0, ~I 1

1 1

A El

~ El

Ci)

o e

,..c:>-o .... " if 0 'a.... ......

/ "

e > .......

Figure'~ is a plot of the amount of intrusion against temperature. The plotted curves indicate the amount of intrusion of the polycrystalline chalcopyrite into a mullite tube of 1.6 mm. internal diameter at various temperatures under confining pressures of 10,000, 20,000, and 25,000 p.s.i. in a closed system for 2 1/2 hours; and the relative degree of mobility of polycrystalline chalcopyrite.

A indicates amount of intrusion under 25,000 p.s.i.

El indicates amount of intrusion under 20,000 p.s.i.

~ indicates amount of intrusion for single crystals under 20,000 p.s.i.

o indicates amount of intrusion under 10,000 p. s. i.

/ " 1 ...... ,

1 <:) G, l "

? '0, 0

'-.

1 <:)

<:)

Temperature Oc

" , ............ ,

<:)

o <:)

', . ' ...

...... 0\

600° 7ar? 8000

3.0

2.5

2.0 ~

0.5

/ o

/

1 /

1

/

/ 1

1 /

vI 01

~Ol fI)/ 1

1

1

G 1 /

1 1

10 1

/

/ Pi.

///

/ /

////

------.--.'

1 ;'

1

1 1

1 1

1 1

1

/ /

/ ,1 ,

/ 1

1

Li

oVI !fJ1 .,1'

/ 1

/

1

1 /

1 1

/

Confining pressure p.s.i.

Figure ) is a plot of the amount of intrusion against confining pressure. The plotted curves indicate the amount of intrusion of the polycrystalline chalcopyrite into a mullite tube of 1.6 mm. internal diameter under various confinin g pressures at temperatures of 5250 and 5500 C in a closed system for 2 1/2 hours; and the relative degree of mobility of polycrystalline chalcopyrite.

~ _ indicates 525°C curve

o - indicates 5500 C curve

17

e.

(

18

observed in tri-axial compression experiments. The chalcopyrite was

beginning to intrude as a pellet broken from tbe parent mass (Fig.7). Above

5000 C. it intruded as a coherent mass (Fig.8).

Grain boundaries were brought out in chalcopyrite on etching with

.-- .-...

Under a confining pressure of 25,000 p.s.i., mechanical twinning

was observed at 477oC. (Fig.9); recrystallization took place at 5000 C. in

both the intruded part and a major portion outside the mullite tube (Figs.

10, 11); recrystallization and increase in grain size was observed at 6000

C.

(Fig.12), but the increase in grain size may occur between 5500 and 6000 C.


was observed at 5270 C. and below (Fig.13); recrystallization occurred at

5400 C. in both the intruded part and a major portion outside the mullite tube

(Fig.14); recrystallization and increase in grain size occurred at 5750 C.

(Fig. 15).


was present at 5500 C. and below (Fig.16); recrystallization occurred at

5620 C. in both the intruded part and a minor portion outside the mullite

tube; recrystallization and increase in graiïi. size occurred at 575OC. (Figs. C

17, 18, 19, 20, 21).

Grains produced by recrystallization and increase in grain size are

randomly oriented and varied in shape. Twins were observed in some grains.

On etching with acidic K2Cr207' no grain boundaries were brought

out in chalcopyrite in the experiments below 5750 C. (Fig.22). However,

pyrrhotite grains were revealed with reaction halos around them (Fig.23).

The chalcopyrite reacted with the pyrrhotite grains fonning intergrowths with

two types of lamellae (Fig.22). One type of lamellae had a brownish green

19

Fig. 6. Grain boundaries ,and mechanica1 twinning in original po1ycrysta11ine

chalcopyrite. Grains with high relief are pyrite and magnetite.

Etched with 1:1 H202 and NH40H. Plain ref1ected 1ight (X 40).

Fig. 8

Fig. 7

Fig. 7. P-13 (477 oC., 25,100 p.s.i.). Fracturing in chalcopyrite before

intruding ÏLlto the mu11i te tube. The fractures appear to be shear

fractures. Tbe intruding part appears to have broken as a pellet

fram the original masse ~tched with K2Cr207. Plain ref1ected

light (X 33).

Fig. 8. P-1 (555 0 C., 25,400 p.s.i.). Chalcopyrite intruded into the mu11ite

tube as 'a coherent mass without showing fractures. Etched with

K2Cr207• Plain reflec~ed 1ight (X 33).

(

Fig. 6.

19

Grain boundaries and mechanical twinning in original polycrystalline

chalcopyrite. Grains with high relief are pyrite and magnetite.

Etched with 1:1 H20 2 and NH40H. plain reflected light (X 40).

Fig. 8

Fig. 7

Fig. 7. P-13 (477°C., 2S,100 p.s.i.). Fracturing in chalcopyrite before

intruding into the mullite tube. The fractures appear to be shear

fractures. The intruding part appears to have broken as a pellet

from the original massa Etched with K2Cr207. Plain reflected

light (X 33).

Fig. 8. PMl (SSSoC., 25,400 p.s.i.). Chalcopyrite iùtruded into the mullite

tube as a coherent mass \vithout shO\ving fractures. Etched with

- ,

Fig. 9. P-13 (477°C., 25,100 p.s.i.). Figure shows grain bounda~ies in

cha1capyrite. Mechanica1 twinnin.g is present on the 1eft side.

20

Creamy white grains are pyrrhotite. Etched with 1:1 H202 and NH40H.

Plain ref1ected 1ight (X 40).

Fig. 10. P-1.a (550°C., 25,000 p.s.i.). Unintruded part. Chalcopyrite is

recrysta11ized towards mu11ite tube (right side). The chalcopyrite

shows comp1ex mechanica1 twinning away from the mu11ite tube (1eft 1

side). Pyrite (high relief, white) and magnetite (dark gray) grains

are unaffected. Etched with 1:1 H202 and NH40H. Plain ref1ected

light (X 40).

Fig. 9. P-13 (477°C., 25,100 p.s.i.). Figure shows grain boundaries in

chalcopyrite. Mechanical twinni Ig is present on the 1eft side.

20

Creamy white grains are pyrrhotite. Etched with 1:1 H202 and NH40H.

Plain reflected light (X 40) •

.,.. ... . -'.' #.

~ .... ~ ~ . .. '~' .. .... A

,:~, .. ~ • ,rl. ~ .

..; .... ~ ..... '

. ",~ ."& il

Fig. 10. P-l.a (550°C., 25,000 p.s.i.). Unintruded part. Chalcopyrite is

recrystallized towards mullite tube (right side). The chalcopyrite

shows complex mechanical twinning away from the mullite tube (left ,

side). Pyrite (high relief, white) and magnetite (dark gray) grains

are unaffected. Etched with 1:1 H202 and NH40H. Plain reflected

light (X 40).

21

Fig. 11. p-1 (5550

C, 25,400 p.s.i.). Intruded and unintruded parts.

Chalcopyrite is recrysta11ized in the intruded part and a minor

porti0n0utside the mu11ite tube. Mechanica1 twins are present

aw~~ ·from the mu11ite tube. Etched with 1:1 H202 and NH40H. Plain

ref1ected light . (X 40).

Fig. 12. P-2 (603()C., 25,000 p.s.i.). Intruded part. Recrystallization and

and increase in grain size in chalcopyrite. Domains are present in

some grains. Black areas are either pyrrhotite or pà1ishing pits.

Etched ~ith 1:1 H202 and NH40H. Plain ref1eèted 1ight (X 40).

~ ~

21

Fig. 11. P-l (555°C, 25,400 p.s.i.). Intruded and unintruded parts.

Chalcopyrite is recrystallized in the intruded part and a minor

portion outside the mullite tube. Mechanical twins are present

aw~y ·from the mullite tube. Etched with 1:1 H202 and NH40H. Plain

reflected light(X 40).

Fig. 12. P-2 (603 0 C., 25,000 p.s.i.). Intruded part. Recrystallization and

and increase in grain size in chalcopyrite. Domains are present in

some grains. Black areas are either pyrrhotite or pàlishing pits.

Etched with 1:1 H202 and NH40H. Plain reflected light (X 40).

22

Fig. 13. P-7 (500°C., 20,000 p.s.i.). Mechanical twinning in chalcopyrite.

Pyrite (high relief, white) and magnetite (high relief, dark gray)

are present. Etched with 1:1 H202 and NH40H. Plain reflected

light (X 40).

1 f " ,''1 'fT· ~ •

• 1. 1 ~ ... Co .: ,.~

Fig. 14. P-6.a (550°C., .20,000 p.s.i.). Chalcopyrite recrystallized in the

intruded part and a minor portion outside the mullite tube.

Chalcopyrite shows mechanical twinning away from the mullite tube.

Gold (white) intruded into the mullite tube. High relief white

grains are pyrite. Etc~~d with 1:1 H202 and NH40H. Plain

reflected light (X 40).

(

22

Fig. 13. P-7 (500°C., 20,000 p.s.i.). Mechanica1 twinning in chalcopyrite.

Pyrite (high relief, white) and magnetite (high relief, dark gray)

are present. Etched with 1:1 H202 and NH40H. Plain ref1ected

light (X 4û).

Fig. 14. P-6.a (550°C., 20,000 p.s.i.). Chalcopyrite recrysta1lized in the

intruded part and a minor portion outside the mullite tube.

Chalcopyrite shows mechanical twinning away fram the mul1ite tube.

Gold (white) intruded into the mu1lite tube. High relief white

grains are pyrite. Etched with 1:1 H202 ~nd NH40H. Plain


23

Fig. 15. P-12.a (576°C., 20,000 p.s.i.). lntruded and unintruded parts.

Recrystallization and increase in grain size in chalcopyrite. Some

grains show domains. High relief white grains are pyrite. Black

areas are either pyrrhotite or polishing pits. Etched with

1:1 H202 and NH40H. Plain ref1ected light (~ 40).

Fig. 16. P-16 (525°C., 10,000 p.s.i.). Grain boundaries and mechanical

twinning in chalcopyrite. High relief white grains are pyrite.

High relief dark gray grains are magnetite. Etched with

1:1 H202 and NH40H. Plain reflected light (X 40).

23

Fig. 15. P-12.a (576°C., 20,000 p.s.i.). Intruded and unintruded parts.

Recrystallization and increase in grain size in chalcopyrite. Some

grains show domains. High relief white grains are pyrite. Black


1:1 H202 and NH40H. Plain ref1ected light (~ 40).

Fig. 16. P-16 (525°C., 10,000 p.s.i.). Grain boundaries and mechanical

twinning in chalcopyrite. High relief white grains are pyrite.

High relief dark gray gra~ns are magnetite. Etched with


: .~ Û ) .. "~'),...V'l Fig. 17. P-15 (5750 C., 10,000 'p.s.i.). Recrystallization and increase in

grain size in chalcopyrite. Seme grains show demains. One twin

is present on the right side bottem. Black areas are either

pyrrhotite or polishing pits. Etched with 1:1 H202 and NH40H.

Plain reflected light (X 40).

24

Fig. 18. P-10.a (6500 C., 10,000 p.s.i.). Recrystallization and increase in

grain size in chalcopyrit~. A few twins are present. Black areas

are either pyrrhotite or polishing pits. Etched with'l:l H202 and

NH40H. Plain reflected light (X 40).

(::'-~'. -;-) ...

" . Fig. 17. P-15 (575°C., 10,000 p.s.i.). Recrysta11ization and increase in

grain size in chalcopyrite. Sorne grains show domains. One twin

is present on the right side bottom. Black areas are either

pyrrhotite or po1ishing pits. Etched with 1:1 H202 and NH40H.

Plain ref1ected light (X 40).

24

Fig. 18. P-10.a (650°C., 10,000 p.s.i.). Recrysta11ization and increase in

grain size in chalcopyrite. A few twins are present. Black areas

are either pyrrhotite or po1ishing pits. Etched with-1:1 H202 and

NH40H. Plain ref1ected light (X 40).

25

Fig. 19. P-24 (675°C., 10,000 p.s.i.). Intruded part. Recrysta11ization

ànd increase in grain size in chalcopyrite. Black areas are either

pyrrhotite or po1ishing pits. A few twins are present. Etched with

1:1 H202 and NH40H. Plain ref1ected 1ight (X 40).

Fig. 20. P-24 (675°C., 10,000 p.s.i.). Unintruded part (continuation of

Fig. 19). Recrysta11ization and increase in grain size in

chalcopyrite. A few twins are present. High relief white grains

are pyrite. High relief dark gray grains are magnetïte. Black

areas a.re either pyrrhotite or polishing pit's. Etched with

1:1 H202 and NH40H. Plain ref1ected 1ight (X 40).

25

Fig. 19. P~24 (675°C., 10,000 p.s.i.). Intruded part. Recrystallization

and increase in grain size in chalcopyrite. Black areas are either

pyrrhotite or polishing pits. A few twins are present. Etched wil~


Fig. 20. P-24 (675°C., 10,000 p.s.i.). Unintruded part (continuation of

Fig. 19). Recrystallization and increase in grain size in

chalcopyrite. A few twins are present. High relief white grains

are pyrite. High relief dark gray grains are magnetlte. Black


1:1 H202 and NH40H. Plain reflected light eX 40).

Fig. 21. P-32.a (776oC., 10,000 p.s.i.). lntruded and unintruded parts.

Recrystallization and increase in grain size in chalcopyrite. A

few twins are present. Black areas are either pyrrhotite or

polishing pits. Etched with 1:1 H20

2 and NH

40H. Plain reflected

1l.ght (X 40).

r~ . ~

.

~~~~""., ,': . ..

, '" lÎl ' • .". 1

~, . ~

.\ ,.',' . .,.=-,',

26

Fig. 22. P-l (555 0 C., 25,400 p,s.i.). Pyrrhotite (black) grains surrounded

by reaction rims. The r~action rim (intergrowths of cubanite and

chalcopyrite) has sharp boundary with chalcopyrite. The inter

growths of chalcopyrite and cubanite define the chalcopyrite grain

boundaries. The intergrowths are of triangular or orthogonal

patterns. Etched with acidic K2Cr207• Plain reflected light (X 92).

.... " @, . .~

Fig. 21. P-32.a (776oC., 10,000 p.s.i.). lntruded and unintruded parts.

Recrysta11ization and increase in grain size in chalcopyrite. A

few twins are present. Black areas are either pyrrho~ite or

po1ishing pits. Etched with 1:1 H20

2 and Nn

40H. Plain ref1ected

light (X 40). , ....

26

Fig. 22. P-1 (555 0 C., 25,400 p,s.i.). Pyrrhotite (black) grains surrounded

by reaction rims. The r~action rim (intergrowths of cubanite and

chalcopyrite) has sharp boundary with chalcopyrite •. The inter


boundaries. The intergrowths are of triangu1ar or orthogonal

pa~terns~ Etched with acidic K2Cr207• Plain ref1ected light (X 92).

c)

Fig. 21. P-32.a (776oC., 10,000 p.s.i.). Intruded and unintruded parts.

Recrystallization and increase in grain size in chalcopyrite. A

few twins are present. Black areas are either pyrrhotite or

polishing pits. Etched with 1:1 H20

2 and Nn4~H. Plain reflected

light (X 40).

,',

"

'- -.

.oI',,:C

,1

26

Fig. 22. P-l (555 0 C., 25,400 p,s.i.). Pyrrhotite (black) grains surrounded

by reaction rims. The reaction rim (intergrowths of cubanite and

chalcopyrite) has sharp boundary with c~~lcopyrite •. The inter


boundaries. The intergrowths are of triangular or orthogonal

patterns. Etched with acidic K2Cr207• plain reflected light (X 92).

27

colour when etched with K2Cr207 and was strongly anisotropic. The other type

had a pale brass yellow colour and was weakly anisotropic. The former

corresponds to cubanite and the latter to the surrounding chalcopyrite mass.

The lamellae occur as triangular and orthogonal intergrowths (Fig.22). They

end abruptly at the chalcopyrite grain boundaries (Fig.22). The reaction

rim had a sharp boundary with the surrounding chalcopyrite mass. The above

characteristics indicate that the growth of the cubanite lamellae were

controlled by the crystallographic planes of chalcopyrite. The lamellae at

the periphery of the halo were of larger size than the ones near to the

pyrrhotite grain. Partly altered pyrrhotite grains are intensely fractured

(Fig. 23). When the pyrrhotite reacted more intensely with chalcopyrite, no

fractures were noted and the pyrrhotite was changed to a black coloured mass.

In the experiments at 5750 C. and above, chalcopyrite showed domains

of two different optical directions when etched with acidic K2Cr207. The

domains appeared at 5750 C. but not at 562oC. (see figs.24, 25). These were

formed when the high-temperature cubic polymorph cooled to a low-temperature

tetragonal polymorphe The domains stop sharply at the grain boundaries in

chalcopyrite (Fig.25). (Note that the grain boundaries in chalcopyrite

cannot be recognized with this etching reagent without the aid of the

domains.) The domains occurred in alternate optical directions (c and a or

b) throughout the chalcopyrite mass and showed t~n relationships (poly-

synthetic twins). One had a brown colour with a greenish tinge (on etching

wi th K 2 Cr207) but the colour was not easily distinguishable from the colour

of cubanite. These were isotropic and were different from the strongly

anisotropic cubanite lamellae. The isotropic domains are those with the

"c" - crystallographic axis normal to the polished section. The other

domains had a pale brass yellow colour (on etching with K2Cr207) and were

28

Fig. 23. P.ll (527 oC., 20,000 p.s.i.). Pyrrhotite grain with reaction rim.

Pyrrhotite is intensely fractured. The reaction rim has sharp

boundary with chalcopyrite. No grain boundaries were brought out

in chalcopyrite. Etched with K2Cr207. Plain reflected light

(X 92).

Fig. 24. P-17 (562oC., 10,000 p.s.i.). Pyrrhotite grains with reaction rims

(cubanite-chalcopyrite intergrowths). Etched.with K2Cr207. Plain

reflected light (X 92)0

28

'.~.,

• • ~ .~~ 1 ••

Fig. 23. P-ll (527°C., 20,000 p.s.i.). Pyrrhotite grain with reaction rime

Pyrrhotite is intensely fractured. The reaction rim has sharp

boundary with chalcopyrite. No grain boundaries were brought out

in chalcopyrite. Etched with K2Cr207' Plain reflected light

Fig. 24.

(X 92).

P-17 (562oC., 10,000 p.s.i.). Pyrrhotite grains with reaction rims

(cubanite-chalcopyrite intergrowths). Etched with K2Cr207' Plain


29

Fig. 25. P-15 ~5750C., 10,000 p.s.i.). Intruded part.' Domains in chalcopy

rite. These are isotropic (whitish gray) and weakly anisotropic

(grayish white). The domains end abruptly at the grain boundaries

in chalcopyrite. Domains reveal twinning in chalcopyrite.

Pyrrhotite (black). Pyrite (white). Magnetite (gray). Etched with

K2Cr207. Plain reflected light (X 92).

Fig. 26. P-2 (6030C., 25,000 p.s.i.). Domains in chalcopyrite. They end

at the grain boundaries in chalcopyrite. The domains are isotropic

(whitish gray) and weakly anisotropic (grayish-white). They appear

as rods. The domains a~e in either triangular or orthogonal

patterns. Pyrrhotite (black). Pyrite (white). Magnetite (gray).

Etched with K2Cr207. Plain reflccted light ,(X 92).

0" . ..: ~ . '~

29

Fig. 25. P-15 (5750 C., 10,000 p.s.i.). lntruded part. Domains in chalcopy

rite. These are isotropic (whitish gray) and weakly anisotropic

(grayish white). The domains end abruptly at the grain boundaries

in chalcopyrite. Domains reveal twinning in chalcopyrite.

Pyrrhotite (black). Pyrite (white). Magnetite (gray). Etched with

K2Cr207. Plain reflected light (X 92).

Fig. 26. P-2 (603 0 C., 25,000 p.s.i.). Domains in chalcopyrite. They end

at the grain boundaries in chalcopyrite. The domains are isotropic

(whitish gray) and weakly anisotropic (grayish·white). Theyappear

as rads. The domains are in either triangular or orthogonal

patterns. Pyrrhotite (black). Pyrite (white). Magnetite (gray).

Etched with K2Cr207. Plain reflected light (X 92).

, . . ~, " "

:~.

'. " ~, ,

30

weakly anisotropic. The domains appear as rods with a magnification of

92 X (Fig.26) and show spindle shapes under oil immersion with a

magnification of 380 X (Fig.28). The domains were oriented parallel to the

sphenoid (112) face edges, and appeared either as orthogonal or triangular

patterns, depending upon the orientation of the polished section in relation

to the grains. No cubanite was recognized at and above 575 0 C.

The X-ray diffraction pattern (using the Guinier camera) showed

the characteristics of the low tempe rature tetragonal polymorph. Figs.

27A and B shmoJ the X-ray patterns for different experiments. From this it

can be concluded that the cubic polymorph has reverted, on quenching, to a

stable tetragonal polymorph, leaving domains as evidence of the phase change.

There are four different sizes of domains which decreased as the

temperature increased and the changes were observed at 6000 , 6250 , 6600 and

7000 C. (see figs. 28, 29, 30 and 31). No apparent difference in the size

o 0 of the domains was found between 700 C. and 800 C. (see figs. 31 and 32).

The size of the domains did not change with differential pressure.

The polymorphic change has very little effect on the mobility of

chalcopyrite in spite of the volume expansion which occurs during trans-

formation from tetragonal to cubic form.

Magnetite, small pyrite grains, and gangue were carried along the

direction of chalcopyrite flow. The pyrite grains of larger size were

fractured (Fig.33). When the sample was completely pyrite, as in the

experiment P-6b (SS2 0 C. and 20,000 p.s.i.), it was fractured in contact

with the mullite hole (Fig.34). The magnetite, pyrite and gangue did not

react with chalcopyrite under the Experimental conditions.

B. Heating experiments on polycrystalline chalcopyrite:

The grmoJth of domains \oJas suspected to be due to the differential

30

weakly anisotropic. The domains appear as rods with a magnification of

92 X (Fig.26) and show spindle shapes under oil immersion with a

magnification of 380 ~ (Fig.28). The domains were oriented parallel to the

sphenoid (112) face edges, and appeared either as orthogonal or triangular

patterns, depending upon the orientation of the polished section in relation

to the grains. No cubanite was recognized at and above 5750 C.

The X-ray diffraction pattern (using the Guinier camera) showed

the characteristics of the low temperature ·'tetragonal polymorph. Figs.

27A and B show the X-ray patterns for different experiments. From this it

can be concluded that the cubic polymorph has reverted, on quenching, to a

stable tetragonal polymorph, leaving domains as evidence of the phase change.

There are four different sizes of domains which decreased as the

temperature increased and the changes were observed at 6000 , 6250 , 6600 and

7000 C. (see figs. 28, 29, 30 and 31). No apparent difference in the size

of the domains was found between 7000

C. and 8000 C. (see figs. 31 and 32).

The size of the domains did not change with differential pressure.

The polymorphic change has very little effect on the mobility of

chalcopyrite in spi te of the volume expansion which occurs during trans

formation from tetragonal to cubic form.

Magnetite, small pyrite grains, and gangue were carried along the

direction of chalcopyrite flow. The pyrite grains of larger size were

fractured (Fig.33). When the sample was completely pyrite, as in the

experiment P-6b (552oC. and 20,000 p.s.i.), it was fractured in contact

with the mullite hole (Fig.34). The magnetite, pyrite and gangue did not

react with chalcopyrite under the experimental conditions.

B. Heating experiments on polycrystalline chalcopyrite:

The growth of domains was suspected to be due to the differential

~ e

1 1 a- l ' i~ ~ 0 r "1 ;;: ,'" ~~I:

1 Il 1 Il '1 Il 1 1"! . - -1 m

r1 r- 1 11 . :f

'So·c t [10 i -fIIa.cl t !<!II

il!

Figs. 27 A and B. X-ray diffraction photographs for chalcopyrite obtained with the Guinier

focussing camera, using Co~~radia~ion. The diffraction patterns at different

temperatures show the characteristics of low-temperature polymorph. [chalCOPY-

rite (Cp), pyrrhotite (Po), pyrite (?y) , magnetite (M)J. .

Fig.27A

Fig. 27 B

w .....

32

Fig. 28. P-2 (603°C., 25,000 p.s.i.). Domains in chalcopyrite. Theyappear

as spindles. They occur as orthogonal pattern (centre) or tri

angular pattern (upper left corner). They are isotropic (grayish

black) and weakly anisotropic (grayish white). Etched with

K2Cr207. Plain reflected light. Oil imme~sion (X 380).

Fig. 29. P-29 (626°C., 10,000 p.s.i.). Domains in chalcopyrite. The size

of the domains decreased.'as compared in Fig. 28. Grain boundary in

chalcopyrite at the centre. Pyrite (white). Etched'with K2Cr207•

Plain r~flected light. Oil immersion (X 386).

32

Fig. 28. P-2 (603 0 C., 25,000 p.s.i.). Domains in chalcopyrite. Theyappear

as spindles. They occur as orthogonal pattern (centre) or tri

angular pattern (upper left corner). They are isotropic (grayish

black) and weakly anisotropic (grayish white). Etched with

K2Cr207. Plain reflected light. Oil imme~sion (X 380).

Fig. 29. P-29 (626 oC., 10,000 p.s.i.). Domains in chalcopyrite. The size

of the domains decreased'as compared in Fig. 28. Grain boundary in

chalcopyrite at the centre. Pyrite (white). Etchedwith K2Cr207•

Plain reflected light. Oil immersion (X 386).

Fig. 30. P-33 (660°C., 10,000 p.s.i.). Domains in a chalcopyrite grain.

The domains are of triangular pattern. The size of the domains

decreased as compared in Fig. 29. Etched with K2Cr207~ Plain

reflected light. Oil immersion (X 386).

33

Fig. 31. P-25.a (700°C., 10,000 p.s.i.). Domains in chalcopyrite. The

size of the domains decre~sed as compared in Fig. 30. Etched with

K2Cr207• Plain reflected light. Oil immersion (X 386).

Fig. 30. P·33 (660°C., 10,000 p.s.i.). Domains in a chalcopyrite grain.

The domains are of triangular pattern. The size of the domains

decreased as compared in Fig. 29. Etched with K2

Cr20

7• Plain

reflected light. Oil immersion (X 386).

33

Fig. 31. P.25.a (700°C., 10,000 p.s.i.). Domains in chalcopyrite. The

size of the domains decreased as compared in Fig. 30. Etched with

K2Cr20 7• Plain reflected light. Oil immersion (X 386).

34

Fig. 32. P-31.b (800°C., 10,000 p.s.i.). Domains in chalcopyrite grains.

The si~e of the domains appears to be comparable with the one in

Fig. 31. Etched wi~h K2Cri07- Plain ref1ected 1ight. Oi1

immersion (X 386).

Fig. 33. P-5 (602°C., 20,000 p.s.i.). Pyrite intensely fractured. Domains

are formed in chalcopyrite. Etched with K2C~207. Plain ref1ected

1ight (X 33).

(

34

Fig. 32. Pa 3l.b (800°C., 10,000 p.s.i.). Domains in chalcopyrite grains.

The size of the domains appears to be comparable with the one in

Fig. 31. Etched with K2CrZ0 7• Plain reflected light. Oil

immersion (X 386).

Fig. 33. P-5 (602°C., 20,000 p.s.i.). Pyrite intensely fractured. Domains

are formed in chalcopyrite. Etched with K2Cr207. Plain reflected

light (X 33).

35

Fig. 34. P-6.b (552oC., ~O,OOO p.s.i.). Sample is pyrite and fractured in

contact with the mullite tube (shear fracture). The vertical

fractures may belong to the original samplé. Plain reflected

light (X 33).

Fig. 35. P-19 (525 0 C.). Pyrrhotite grains with reaction rim (intergrowths

of cubanite and chalcopY~ite). The size of the intergrowth

lamellae greatly decreased as compared in Fig. 22. 'No domains in

chalcopyrite (grayish white). Pyrite (white). Magnetite (dark gray).


C)

(

35

Fig. 34. P-6.b (552°C., 20,000 p.s.i.). Sample is pyrite and fractured in

contact with the mullite tube (shear fracture). The vertical

fractures may belong to the original sample. Plain reflected

light (X 33).

Fig. 35. P-19 (525°C.). Pyrrhotite grains with reaction rim (intergrowths

of cubanite and chalcopyrite). The size of the intergrowth

lamellae greatly decreased as compared in Fig. 22. No domains in

chalcopyrite (grayish white). Pyrite (white). Magnetite (dark gray).


t~ , ..

I~

l'

36

pressure. Two heating experiments, without external pressure, were performed

at 5250 and 6000C. The samples were heated in evacuated silica tubes and

quenched in water.

At 5250C. chalcopyrite was not changed except for the formation

of reaction rims around the pyrrhotite grains. The reaction rims consist of

cubanite-chalcopyrite intergrowths as in the differential pressure

experiments. However, the size of the 1ame11ae was smal1er than in a

co1d sea1 bomb experiment at 5250C (Fig.35).

In the experiment at 6000C., when the si1ica tube was opened su1fur

dioxide was given off. The 10ss of su1fur cou1d not be checked in the case

of gold capsules because the sma11 amount of sul fur gas trapped in the

capsule escapes during opening the samp1e. Domains were observed in

chalcopyrite as they were in the differentia1 pressure experiments. The

size of the domains was great1y decreased (see figs. 36 and 26) and was

o comparable with that in the differentia1 pressure experiment at 650 C. (see

figs.36 and 37). The discrepancy in the size of the domains may be due to:

1) the coo1ing rate (si1ica tubes cool rapid1y when compared to the co1d

sea1 bombs), and 2) the 10ss of su1fur which may be greater in the heating

experiments than in the differentia1 pressure experiments. As a resu1t of

'rapid coo1ing of the si1ica tubes the su1fur re1eased did not re-enter the

crystal structure of the chalcopyrite comp1ete1y. The X-ray pattern was that

of the low-temperature tetragona1 po1ymorph (Fig.38A).

From the above two experiments it can be conc1uded that differential

pressure has very 1itt1e or no influence in the deve10pment of the domains;

and that a critica1 temperature was needed for causing them.

C. Co1d sea1 bomb and heating experiments on single crystal chalcopyrite:

It was suspected that the origin of the domains in chalcopyrite may

37

Fig. 36. p-18 (600°C.). Domains in chalcopyrite. The size of the domains

greatly decreased as compared in Fig. 26. Domains are isotropic

(grayish black) and weakly anistropic (white). Pyrite (grayish

white). Pyrrhotite (black). Etched with K2Cr207• Plain reflected

light (X 92).

Fig. 37. P-10 (650°C., 10,000 p.s.i.). Domains in chalcopyrite. The size

of the domains greatly decreased as compared in Fig. 26, but same as

in Fig. 36. Domains reveal grain boundaries and twinning in

chalcopyrite. Pyrrhotite (black). Etched with K2

Cr20

7• Plain


37

Fig. 36. P-18 (600oC.). Domains in chalcopyrite. The size of the domains

greatly decreased as compared in Fig. 26. Domains are isotropic

(grayish black) and weakly anistropic (white). Pyrite (grayish

white). Pyrrhotite (black). Etched with K2Cr207

• Plain reflected

light (X 92).

Fig. 37. P-10 (650oC., 10,000 p.s.i.). Domains in chalcopyrite. The size

of the domains greatly decreased as compared in Fig. 26, but same as

in Fig. 36. Domains reveal grain boundaries and twinning in

chalcopyrite. Pyrrhotite (black). Etched with K2

CrZ0

7• Plain


@

Figs. 38 A and B. X-ray diffraction photographs for chalcopyrite obtained with the Guinier

focussing camera, using COk radiation. The diffraction patterns for chalcopy.

e

Fig. 38 A

Fig. 38 B

~ rite show the characteristics of low~temperature polymorphe {chalcopyrite (Cp),

original chalcopyrite (ori. Cp), single crystal chalcopyrite (S.C.Cp),

pyrrhotite (Po), pyrite (Py), magnetite (M)}.

w 00

39

b~ due to the presence of impurities, especially pyrrhotite which readily

reacts with chalcopyrite. In order to ascertain their origin more clearly,

tbree experiments were performed with single crystals.

In all the crystals, only pyrite impurities were presen~

confirmed with X-ray diffrac.tion (Fig.40). The crystals have sphenoidal

habit [112]. In chalcopyrite planes parallel to sphenoid faces (112) are

the slip planes. In differential pressure experiments the crystals were

oriented so that the sphenoid (112) surfaces were oriented at approximately

o 45 to the differential pressure i.e., the c-axis of the crystal would be

parallel to the maximum pressure.

Differential pressure experiments were carried out at 5500 and

6000 C. under a differential pressure of 20,000 p.s.i. The distance of

intrusion of a single crystal, with proper orientation for easy glide, was

approximately the same as in the polycrystalline chalcopyrite.

On etching with 1:1 H202 and NH40H, polished sections showed that

chalcopyrite was composed of randomly oriented grains, which revealed

recrystallization in the in.truded part and a minor portion outside the

mullite tube (Fig.39). At 6000 C. it showed recrystallization and increase in

grain size (Fig.40).

On etching with acidic K2Cr207, chalcopyrite at 6000 C. exhibited

grain boundaries and domains (Fig. 41) and the grain boundaries were not

revealed in the absence of the domains, as in the experiment at 5500 C. The

characteristics of the domains were the same as in the polycrystalline

chalcopyrite except that 1) the colour of the isotropie domains was brown,

differing from that of the polycrystalline material which was brown with a

green tinge; and 2) the size of the domains had considerably increased. The

variation in size could be explained by the larger size of the single crystal

.8

40

Fig. 39. P-22 (550°C., 20,000 p.s.i.). Single crystal chalcopyrite.

Recrysta11ization in chalcopyrite in the intruded part and a minor

portion outside the mu11ite tube. Mechanica1 twinning present

away from the mu11ite tube. Black areas are po1ishing pits.

Etched with 1:1 H202 and NH40H. P1ail1 reflected light (xi!).

Fig. 40. P-20 (602°C., 20,000 p.s.i.). Single crystal cha1co~yrite.

Recrysta11ization and increase in grain size .in chalcopyrite. One

twin in'the intruded part (right side bottom). High relief

rounded w.hite grains are pyrite. Etched with 1:1 H202 and NH40H.

Plain ref1ected 1ight (X 40).

40

Fig. 39. P-22 (550°C., 20,000 p.s.i.). Single crystal chalcopyrite.

Recrystallization in chalcopyrite in the intruded part and a minor

portion outside the mullite tube. Mechanical twinning present

away from the mullite tube. Black areas are polishing pits.

Etched with 1:1 H202 and NH40H. Plaib reflected light (X~).

Fig. 40. P-20 (602°C., 20,000 p.s.i.). Single crystal chalco~yrite.

Recrystallization and increase in grain size in chalcopyrite. One

twin in the intruded part (right side bottom). High relief

rounded w.hite grains are pyrite. Etched with 1:1 H202 and NH40H.


41

Fig. 41. P-20 (602oC., 20,000 p.s.i.). Single crystal chalcopyrite. Domains

in chalcopyrite. They occur either as triangu1ar or orthogonal

patterns. Domains are isotropic (grayish black) and weak1y

anisotropic (white). Domains revea1 grain boundaries and twinning

in chalcopyrite. Etched with K2C~207. Plain ref1ected 1ight (X 92).

Fig. 42. P-21 (600oC.). Single crystal chalcopyrite. Domains in chalcopy

rite. The domains occur as triangular patterns, each pattern

para11e1 to the sphenoid face (112) edge. One pattern is poorly

deve1oped. Domains are isotropic (grayish··black) and weakly

anisotropic (white). Etched withK2Cr207. Plain ref1ected light.

(X 92).

C' '.;

(

41

Fig. 41. P-20 (602oC., 20,000 p.s.i.). Single crystal chalcopyrite. Domains

in chalcopyrite. They occur either as triangular or orthogonal

patterns. Domains are isotropic (grayish black) and weakly

anisotropic (white). Domains reveal grain boundaries and twinning

in chalcopyrite. Etched with K2Cr207. Plain reflected light (X 92).

Fig. 42. P-21 (600oC.). Single crystal chalcopyrite. Domains in chalcopy

rite. The domains occur as triangular patterns, each pattern

parallel to the sphenoid face (112) edge. One pattern is poorly

developed. Domains are isotropic (grayish black) and weakly

anisotropic (white). Etched witn K2Cr207' Plain reflected light.

(X 92).

.... ,.

42

in which the domains grow more freely than in the polycrystalline mate rial

where the growth of the domains May have been retarded by the numerous grain

boundaries and the presence of impurities. The X-ray patterns, for the above

two experiments,.was that of the low-temperature tetragonal polymorph (Fig.

38B).

Together, the above two experiments reveal that the formation of

the domains was independant of impurities.

One heating experiment was performed at 6000 C. with a single

crystal to ascertain the cause of the discrepancy in the size of the domains

observed as compared with those in polycrystalline chalcopyrite between 6000

and 6250 C. The crystal was of sphenoidal habit [112J. The size of the

domains was the same as in the differential pressure experiment (see figs.

42 and 41).

When the sphenoid face was examined under the microscope,

3 patterns of domains were observed parallel to the sphenoid face edges

(Fig.42). One set was poorly developed. No sulfur odour was noticed, unlike

that in experim.ent with polycrystalline chalcopyrite. Because the size of

the sample was small compared to that of the polycrystalline material, no

vapour of sul fur was noted. This experiment shows that at a constant

temperature above the inversion temperature, differential pressure, cooling

rate and impurities (pyrite) have no apparent effect on the size of the

domains.

D. Explanations for the decrease in the amount of intrusion with increase

in temperature under a confining pressure of 10,000 p.s.i.

From the 10,000 p.s.i. curve (Fig.4) the amount of intrusion

appears to be a continuous function of the temperature until the temperature

reached 6500 C., beyond which the amount of intrusion decreased •. '. Chalcopyrite

43

deformed above and be10w 6500C. did not show differences·either in the

optica1 properties or in X-ray diffraction patterns (Fig.27A and B). The

decrease in the amount of intrusion with increasing temperature, from 6500C.

upwards, requires exp1anation.

In the experiments performed at 7000C. and above, su1fur gas or

su1fur dioxide was found in the gold capsules, which indicates that

considerable amounts of sul fur were re1eased from the chalcopyrite and not

fu11y resorbed on quenching.

In these experiments the amount of intrusion increased from 5250

to 650QC. and decreased from 65cPto 8000C. The chalcopyrite recrysta11ized

at 5620C. and 1arger grains resu1ted at and above 5750C. These changes in

structure shou1d have faci1itated intrusion.

According to Frueh (1959), sul fur 10ss begins in chalcopyrite

be10w 3000C. Hi11er and Probsthain (1956) found that the sul fur content of

chalcopyrite decreases, upon heating, continuous1y fram 4340 to 7500C. It

can be pointed out that the rate of 10ss of sul fur is great between 5800C.

and 6200C. It appears from the article that the sul fur is 10st permanent1y

fram the chalcopyrite. They have given the formula for chalcopyrite at

7200C. as CU17+x!e17+xS32 (X=0.6). However, in the present experiments, the

o rate of sulfur 10ss apparent1y was great only at about 650 C. as the samp1e

was under a confining pressure. At 7000C. marked 10ss of su1fur was evident

in the present experiments. Decreasein the amount of su1fur should decrease

the rate of f1owage, due to the concentration of meta1 ions in the structure.

If su1fur 10ss occurs between 5250C. and 6500C., the reduction in

mobility resu1ting from this must be increasing1y overshadowed by the effects

of recrystal1ization fram 5620 to 62SoC. as shown by the experimental results.

At 6500C. a reversa1 occursgiving a decrease in the amount of intrusion

44

with increased temperature. This appears to be accompanied by an increased

rate of sulfur loss. Also, in the present experiments, the chalcopyrite is

continuously under differential pressure which induces strain in the

recrystallized grains and the recrystallized grains deform plastically

throughout the experiment. A possible explanation of the relationships of

these phenomena is as follows:

When the sul fur vaporizes, the Cu and Fe atoms enter into the

chalcopyrite structure as interstitial atoms (impurities). Some adjustments

undoubtedly take place during recrystallization. Also, the individual

recrystallized grains tend to deform plastically with the movement of

dislocations. However, the Cu and Fe atoms obstruct the movement of the

dislocations in chalcopyrite and the chalcopyrite is ~~~~~. Thus

the resistance to deformation is increased and the amount of intrusion

decreases. In the temperature range from 5250 to 6250 C. loss of sulfur is

slight and the effects of recrystallization predominafe. Increasing sul fur

loss above 6500 C. leaves more cations in the structure, which retard the

deformation. This reveals why the amount of intrusion decreased continuously

as the temperature is increased from 6500 C. onwards.

A further factor appears to have some relevance. The sul fur

pressure from dissociation of chalcopyrite, building up in the gold tube

might oppose the intrusion. On page 14 it is shawn that the sul fur pressure

at 627 0 C. was on1y 12 p.s.i. but loss of sulfur becomes rapid at about 6500 C.

and this suggests that the dissociation pressures also were rapid. This

would retard the rate of intrusion. Thus the pressure inside the gold

capsule can aid in decreasing the amount of intrusion at higher temperatures.

E. Hardness tests:

The gradual decrease of the amount of intrusion was explained as

45

due to loss of sul fur. lt appeared probable that this wou1d be accompanied

by an increase in hardness. To examine this property, hardness tests were

made on al1 the samp1es. The resu1ts are given in Table 1. lt is evident

from figures 43, 44 and 45B that hardness and mobi1ity are not re1ated in

any simple manner. Specimens subjected to pressures of 10,000 p.s.i.,

20,000 p.s.i., or 25,000 p.s.i. a11 hardened abrupt1y at around 5750C • •

This is corre1ated with the phase change and with the development of

domains as described further be1ow. At pressures of 20,000 p.s.i. and

higher, chalcopyrite fi11ed the avai1ab1e space before temperatures of 6500C.

were reached. So the zone of decreased mobi1ity shown in the curve in

figure 45B for 10,000 p.s.i. confining pressure cou1d not be examined at

the higher pressures with the equipment used. The situation for 10,000

p.s.i. confining pressure was examined more fu11y and the relation shown in

figure 45B will be discussed in detai1.

The f1attening of the hardness curve (Fig.45B) between 5750 and

6600C. will be designated as Region A, the drop in hardness at 6750C as

Region B, and the curve beyond 6750C. as Region C.

Region A: The correlation of the sudden increase in hardness can be made

with the appearance of domains in the quenched samples. Domains.in

chalcopyrite were first observed and described by Frueh (1958). They were

formed as a resu1t of transformation from high temperature cubic form to

the tetragona1 form, on quenching. In the present experiments these were

observed at 57 SoC. When the domains are formed, the y cause strain which

hardens chalcopyrite. This a1so exp1ains the f1attening of the hardness

curve between 5750C. and 6600C. Harker (1944) noted thata simi1ar phase

change increased the hardness in a gold-copper a110y when it changed from

a face-~entered cubic structure to a base-centered tetragona1 structure.

,.. QI

~ ::J

260

z 240 !Il !Il QI C

-0 ,.. ~ !Il ,.. ~ 220 u

..-1 :>

'" CIl

~

e

l o

..-1 4-1 o;J N

..-1 .... .... o;J 4-1 !Il >. ,.. u ~

A r----~ ---1 1.!r-

t 1 1 1

1 , , 1 1

1 ____ A 1

A

A -T--A----i,-J 200 1 Temperature

i

Oc

4500 500 0 5500 600 0 6500

e

Fig. 43 is a plot of mean Vickers Hardness number against temperature. lIardness tests were made on samples from cold seal bomb experiments performed at various temperatures under a constant cor:fining pressure 25,000 p.s.i.

A - 25,000 p.s.i. confining pressure (Polycrystalline Chalcopyrite)

700Gl

,.. QI

'6 ~240

QI bO

l ~Œl _._ o CIl

~ ~----o

Fig. 44 is a plot of mean Vickers Hcrdness number against temperature. Hardness tests were made on samples from cold senl bomb experiments performed at various temperatures under a constant confining pressure

!Il !Il QI C

-0 ,.. CIl :x: ~ 220 QI ~ U

..-1 :> c CIl

I!]

N 1 ..-1 1 ::: 1

CIl 1 4-1 1 !Il 1 ~ 1 U 1

; El : @ )

----- ~

~ r::J

~ o ,

200 1 Tempera ture Oc

4500 5000 5500 6000 6500

..... ---------------------------------7000

20,000 P.s.!.

El - 20,000 p.s.i. confining pressure (Polycrystalline Chalcopyrite)

~ - 20,000 p. s. 1. confining pressure (Single Crystal Chalcopyrite)

.po 0\

2.0

~ s:; 0

1.5 .,-1

fil :l ,... .w s:;

H

4-1 0

-,

j (1) () s:;

1.0

i <-:: "-' fil

-..l e::::I

0.5

0 -..l .w CI! ~l

.,-1

.-1

.-1 cv .w fil :>... ,... () (1)

Il:::

c:y ,.,. ..... '6

o

1 . o 1

47

Increase in the rate of 10ss of sulfur~

o

Fig. 45A

o <:>

...... ..,.",-" 1

O--~--~--~~-+----------------------------__________ __ 260

240

220

(1) /

gj 0 0 / .c0 Region 1\., / ~ ____________ 0 __ ""\ /

{ 0 0~ :~ ;1 : 15 //

i 1 0 ~ / 'D, 00 c./

CI! '(1) Region //0 N l ,Il::: 0 ,.,. ~ 1 1 0 ,.,./ r;;l 1 Size (1) of Size (2) ,, __ .........

/ g

/ /

ri /

~ 1 the domains of the Size (3) 0:: :>... , domains the domain Size (4) of the domains ,... ,same.

~ g 1 ~ t:'\ Il::: ,

same. 1>2

same. 2 "73

same. 3)4

-- 0--- -,'L'-0..J Fig. 45B

200

5000

Fig. 45A

Fig. 45B

1

6000 Tempera ture Oc

is same as Fig. 4 showing the plot of intrusion against temperature under a confining pressure of 10,000 p.s.i. is a plot of mean Vickers Hardness numb~r against temperature. The hardness tests were made on the samples from cold seal bomb experiments performed at various temperatures under a constant confining pressure pf 10,000 p.s.i.

48

Region B: o

Unti1 660 C., the increase in hardness is exp1ainab1e by the

domains. At 6750C., the chalcopyrite hardness decreased.

On page 43 it is shawn that 10ss of sul fur becomes rapid at about

6500C. When the samp1e is coo1ed slow1y, the su1fur atoms shou1d recombine

with the Cu and Fe atoms, which were diffused into the chalcopyrite

structure as interstitia1 atoms, to restore the original structure. Above

6500C., the 10ss of su1fur atoms is so great that during the time of

quenching the y may not have time to recombine upon quenching to restore the

original structure. Most of the cations stay inside the still intact

chalcopyrite crysta1s. Some of the su1fur atoms are deposited around the

crysta1s 100se1y bound by a few cations migrating outward to form a softer

chalcopyrite. This resu1ts in a decrease in hardness as the temperature is

increased.

A further possible factor affecting hardness is suggested by the

fact that the domains formed in experiments at tempe ratures from 6000C. to

70'OoC. were sma11er with increase of temperature. The change in hardness

appears to be much more abrupt than the change in domain size. Whether or

not there is a cause-effect re1ationship between these two phenomena is a

prob1em still to be reso1ved.

o Region C: After a drop in hardness of chalcopyrite at 675 C., the hardness

increased progressive1y. (The amount of intrusion a1so decreased

progressively.) Here appears to be a direct correlation. The sul fur 10ss

continues to be greater and. greater as the temperature increased. The

progressive increase in hardness could be explained by the loss of sulfure

Due to loss of su1fur, chalcopyrite is work-hardened. With greater

amounts of sulfur 10ss as the temperature is increased,a gradual increase in

hardness occurs. As the size of the domains appears to be the same betWeen

49

00. 700 C. and 800 C., the strain energy caused by the doma1ns should be the same

as at 7000 C. and should not influence the increments in hardness. For this

reason, only the loss of sulfur should have caused increase in hardness.

50

EXPERIMENTS USING "TRI-AXIAL COMPRESSION" EQUIPMENT

This group of experiments were intended to explore the behaviour

of naturally occurring sulfides when subjected to differential pressures at

moderately elevated temperatures.


A differential pressure bomb was externally heated and a uni axial

compressive force was applied. The apparatus was designed and built at

McGill by Cameron (1956) and Wolofsky (1957) for carrying out open and

closed system experiments on mineraIs and rocks. In the present

investigation the experiments were performed in. a closed system. The

apparatus and the operational procedures are fully described by Wolofsky

(1957). Figures 46, 47, 48 and 49 show the tri-axial compression apparatus

in the operating condition, bomb fittings, assembled bomb, and bomb fittings'

with a deformed specimen, respectively. Only the essential features are

described below.

The sample jacket was cut to a length of 2.4 inches from a

commercially available hard drawn copper tube, having 0.6 inch external

diameter and 0.03 inch wall thickness. To prepare the sample, a piece of

ore cut with parallel end faces was either drilled with a diamond core bit

or ground on a rotating lap so as to fit into the jacket. The latter method

became necessary when the samples were small (especially single crystals).

The samples were ground according to the necessity of the experiment; i.e. the

orientation of the crystallographic direction of the sample, whether

parallel, perpendicular or at an angle to the direction of the applied force.

One or more of the discs were fitted into a copper jacket and the

charge was then placed in the bombe The bomb was heated electrically through

an external winding. When the desired temperature was reached, the sample

Temperature ____ _ controller

51

-·----Confining pressure gauge

-----Bomb

.. -,-----Furnace

ack gauge

-----ack

Fig. 46. Tri-Axial Compression apparatus in the operating condition.

Fig. 47. Bomb fitt~ngs (Tri-Axial Compression apparatus).

Lower piston Teflon washer Copper washer Copper jacket

Tempera ture ____ _ controller

----Confining pressure gauge

------Bomb

.-------Furnace

ack gauge

ack

Fig. 46. Tri-Axial Compression apparatus in the operating condition.

Fig, 47. Bomb fittings (Tri-Axial Compression apparatus) •

. . "' .. " -_.

Lower piston Teflon washer

1ûasher

jacket

51

52

piston

Fig. 48. Assembled bomb (Tri-Axial Compression apparatus).

formed sample

Fig. 49. Bomb fittings with deformed specimen (Tri-Axial Compression

apparatus).

(

52

P"------L()Wer piston

Fig. 48. Assembled bomb (Tri-Axial Compression apparatus).

Deformed sample

Fig. 49. Bomb fittings with deformed specimen (Tri-Axial Compression

apparatus).

53

was subjected to the desired compressive force by a piston driven upwards by

a jack into the jacket. As the samp1e yie1ds under a constant compressive

force, the piston enters the bomb. The temperature of the bomb was main

tained with ±10oC. When the piston had entered the bomb to its possibie

1ength the experiment was terminated (The piston was made progressive1y

1arger in diameter towards the bot tom, so that the bomb admitted a11 but

approximate1y one cm. of its 1ength. This faci1itated taking out the piston

from the bomb.) The bomb was coo1ed in the air. The force exerted by the

jack on the samp1e was n.oted in each run.

The compressive stress was ca1cu1ated by dividing the force by the

initial cross-sectiona1.area of the samp1e (0.28 sq. inches). The actua1

compressive stress values were a1ways 1ess for two main reasons: first, the

cross-sectiona1 area of the samp1e increases with the shortenin.g a10ng the

axis; second, frictiona1 resistance (between jacket and piston, between

bomb and piston) decreases with increasing temperature. These two reasons

a1so have to be taken into consideration when the stress values of

different experiments are compared. Wo10fsky (1957, pp. 97-101) discussed

the complications invo1ved in the compressive stress ca1cu1ations. The

compressive stress difference was obtained by subtracting the confining

pressure from the compressive stress.

The shortening of the samp1e was measured in each run after opening

the samp1e and the percentage of shortening was ca1cu1ated in each run. Even

though the ca1cu1ated compressive stress and the percentage of shortening do

not represent the actua1 values, the y do indicate in a rough quantitative

way the physica1 behaviour of the samp1es.

Serious difficu1ties were encountered in maintaining a sea1 at the

moving end of the bomb because the tef10n washer me1ts and vo1ati1izes at

54

o about 300 C. When the teflon melted, the seal could not be maintained

under high confining pressures. To avoid this difficulty Many of the

experiments were performed at lower confining pressures.

At elevated temperatures the copper jacket reacted with the

sulfides. To avoid this the sample, in some experiments, was wrapped in

aluminum foil and placed inside the copper jacket. Even then, minor

reaction took place between the copper jacket and the sulfides. Possible

solutions to this problem might be bo have the copper jacket gold plated,

or to use a thin aluminum jacket. The gold plating would be worthwhile if

the lower piston seal could be perfected. In case the gold plating method

fails, gold foil could be wrapped around the specimen, but the cost of the

experiment will be high.

An aluminum jacket was tried, but it presented difficulties in

polishing the sample because of its high ductility. The aluminum jacket

could be used providing that a th in strip of the aluminum is cut away from

the edge of the section before it is set in the mounting medium. The

difficulty with this is that part of the sample at the boundary breaks away.

Difficulties were met in making polished sections from some of the

deformed samples because the y were brittle and fractured. To avoid this,

small holes were drilled in the sample and impregnated with plastic

(Quickmount, Fisher Co.) in a vacuum. The specimen was th en cut with a

diamond saw. To make sure that the fractured grains were welded together,

one section was soaked in household cement (Lepage's) diluted in acetone and

then polished.

The mineraIs were identified using a reflecting microscope. A

Phillips X-ray diffractometer, with Fek radiation, was used to identify ~

doubtful mineraIs.

Results

The maximum tempe rature deemed safe for the equipment was 5000 C.

and at such tempe ratures the confining pressure could not be raised much

above 15,000 p.s.i. without damage to the bombe

55

The experiments are numbered K-l to K-19, and are arranged

according to the mineraI or mineraIs and the physical conditions under which

the experiments were performed. The physical conditions and results of

each experiment are described in detail and are summarized in Table II.

Experiment K - 13

Material: Galena cut from a single crystal perpendicular to a cube face.

Pyrite cut from a single crystal perpendicular to a cube face.

Thick and thin layers alternately of galena and pyrite. Several

discs were used to provide comparisons, especially between pieces

in different positions (Fig. 50).

Conditions: See table II. Confining pressure: 4,000 p.s.i.; Temperature:

Room Temperature; Compressive stress difference: 31,000 p.s.i.

Results: Megascopically the deformed specimen showed dominant shear failure

(Fig. 51). The thick galena and pyrite bands were generally fractured parallel

to the direction of the applied force and granulation took place along the

fractures. In the thick galena bands some fractures followed cleavage

planes at an angle of 45 0 to the direction of the applied force. The galena

was finely crushed along the fracture zones (Fig. 52). The thinner galena

and pyrite bands were fractured and intensely granulated. The crushed pyrite

grains were drawn into streaks between the galena bands (Fig.53).

In this experiment both the galena and pyrite were deformed by

fracturing accompanied by granulation. Though fracturing and granulation

were intense, the original ban ding was retained.

8 e

TABLE II. Tri-Axial Compression Experiments

Exp.No. Samp1e Tempera- Confining Time of Jack Compress- Length Percentage Remarks ~ ture oC. pressure. rune force. ive stress shortened. of

p. s. i. Hours lbs. difference. cm. shortening. p.s.i.

K-13 cubic ga1ena. Room 4,000 l~ 9,800 31,000 4.00-2.10 47.5 cubic pyrite. tempera- =1.90

ture

K-15 cubic ga1ena. 200 4,000 1~ 8,500 26,350 4.00-2.00 50.0 A1uminum foi1 wrapped cubic pyri te. =2.00 around the samp1e.

cubic ga1ena. K .. l7 massive 300 4,000 2~ 8,500 26,350 3.85-2.40 38.0 A1uminum foi1 wrapped

pyrite. =1.45 around the samp1e.

K-12 cubic ga1ena. 400 4,000 ~ 7,000 21,000 3.80-1.80 52.5 A1uminum foi1 wrapped cubic pyrite. =2.00 around the samp1e.

octahedra1 K-14 galena. 400 4,000 Ji 7,500 22,800 4.05-1.65 59.0 A1uminum foi1 wrapped

cubic pyrite. =2.40 around the samp1e.

schistose K-16 ga1ena. 400 4,000 2 7,500 22,800 4.20-2.35 44.0 A1uminum foi1 wrapped

cubic pyrite. =1.85 around the samp1e.

cubic ga1ena. K-18 basai. 400 5,000 ~ 8,500 25,350 3.95-2.35 40.5 A1uminum foi1 wrapped

pyrrhotite. =1.60 around the samp1e four times.

K-8 galena with

200 15,000 4 19,000 52,850 4.00-2.30 42.5 pyrrhotite. =1.70

Ut 0\

8 e

TABLE II continued

Exp. No. Samp1e Tempera .. Confining Time of Jack Compress .. Length Percentage Remarks ture oC. pressure rune force. ive stress shortened. of

p.s.i. Hours lbs. difference. cm. shortening. p.s.i.

ga1ena with K-9 pyrrhotite. 385 13,000 1 14,500 37,800 3.45-1.45 58 Lead pellets present out-

cubic ga1ena. =2.00 side the copper jacket.

ga1ena with K-lO pyrrhotite. 475 18,000 2 18,000 46,300 4.20-1.90 55 Lead pellets present out-

spha1erite =2.30 side the copper jacket.

ga1ena with K-ll pyrrhotite. 300 7,000 1 12,000 35,850 4.20-1.70 59.5

massive =2.50 pyrite.

basal K-19 pyrrhoti te.

mas s ive pyrite 400 5,000 ~ 10,000 30,200 3.75 .. 2.25 40.0 A1uminum foi1 wrapped =1.50 around the samp1e twice.

K-5 chalcocite 300 15,500 ~ 18,000 48,800 4.00-2.15 46.0 with bornite. =1.85

chalcopyrite room K-1 ore. tempera .. 23,500 4~ 30,000 83,800 3.80-2.10 45.0

massive pyrite. ture =1.70

cha1copyri. te K-3 ore. 200 14,500 3 3/4 18,000 49,800 4.30 .. 2.75 36.0

massive pyrite. =1.55

VI ......

e

Exp.No. Samp1e Tempera- Confining Time of ture oC. pressure. run.

p.s.i. Hours.

chalcopyrite K-2 ore 200 14,000 3/4

massive pyrite.

chalcopyrite K-4 ore 200 15,000 4·

massive pyrite

K-6 chalcopyrite 350 15,000 1~ ore.

K-7 chalcopyrite 350 15,500 1 ore.

TABLE II continued

Jack Compress-force. ive stress lbs. difference.

p. s. i.

19,500 55,650

18,500 51,100

18,000 49,300

17,000 45,200

Length shortened. cm.

4.10-2.25 =1.85

4.25-3.25 =1.00

3.90-1.80 =2.10

3.80-1.50 =2.30

Percentage of shortening.

45.0

24.0

54.0

60.0

e

Remarks

A1uminum foi1 wrapped around the samp1e twice.

\.Il 00

..

CUBIC GALENA----CUBI C PYRITE-----

--

CUBIC GALENA--

tuBIC PYRITE

CUBIC GALENA--

CUBI C PYRITE---

CUBI C GALENA----

-

CUBIC PYRITE---

Fig. 50

oj

,

1

Fig. 51

Fig. 50. K-13 (Roam temperature). Undeformed specimen showing different

positions of samples in a copper jacket (X 1).

59

Fig. 51. K-13 (Room temperature). Deformed specimen. Galena and pyrite

single crystals were cut perpendicular to their cube faces. Thick

and thin bands alternately of galena and pyrite are deformed. The

samples failed along a shear fracture.

Fig. 52. K-13 (Rpom temperature). Galena is intensely crushed along a

fracture zone. Plain reflected light (X 33).

CUBIC GALENA···

eUBI e PYRITE··_·

CUBIC GALENA··_·

CUBle PYRITE···

eUBI e GALENA··-·

eUBI e PYRITE-···

eUBI e GALENA-·--

· ·

·

eUBI e PYRITE ._. -

Fig. 50

j s" :

i

Fig. 51

Fig. 50. K-13 (Room temperature). Undeformed specimen showing different

positions of samples in a copper jacket (X 1).

59

Fig. 51. K-13 (Room temperature). Deformed specimen. Galena and pyrite

single crystals were cut perpendicular to their cube faces. Thick

and thin bands alternately of galena and pyrite are deformed. The

samples failed along a shear fracture.

Fig. 52. K-l3 (R~om tempe rature). Galena is intensely crushed along a

fracture zone. Plain reflected light (X 33).

"e ". ,.

60

Experiment K - 15

Materia1: As in K - 13. Thick and thin 1ayers a1ternate1y of ga1ena and

pyrite. Severa1 discs were used to provide comparisons,

especia11y between pieces in different positions (Fig. 54).

Conditions: See Table II. Confining pressure: 4,000 p.s.i.; Temperature:

200oC.; Compressive stress difference: 26,350 p.s.i.

Resu1ts: The specimen was not uniformly deformed. The copper sheath

buck1ed on one side a110wing the specimen to move around the piston (Fig. 55).

Megascopica11y ga1ena and pyrite bands were fractured para11e1 to the

direction of the applied force.

Cleavage planes along which granulation took place developed in the

ga1ena; the galena was a1so granulated where it was in contact with the

pyrite bands. Rows of triangular pits in the galena were smoothly curved

due to translation gliding along the planes parallel to (100). Granulation

in galena is less here than in the experiment at room temperature. The

pyrite bands were fractured, granulated and individual pyrite grains were

locally drawn out into streaks embedded in the galena (Fig. 56).

In this experiment the galena was deformed largely by fracturing

but translation gliding was present to a small extent. Pyrite was fractured,

granulated and sometimes drawn into streaks.

Experiment K - 17

Material: Galena as in K - 13. Pyrite cut from a sample containing

pyrrhotite, chalcopyrite, magnetite and gangue. Thick and thin

layers alternately of galena and pyrite. Several discs were used

to provide comparisons, especially between pieces in different

positions (Fig. 57).

Conditions: See Table II. Confining Pressure: 4,000 p.s.i.; Temperature:

61

Fig. 53. K-13 (Room temperature). Pyrite is granu1ated and the grains are

drawn into a streak between two ga1ena bands. Etched with 1:1 HN03•

plain ref1ected 1ight (X 33).

cualc GALENA----

cualc PYRITE---

cualc GALENA-

cualc PYR!TE----

cualc GALENA--cualc PYRITE---

cualC GALENA----

cualc PYR/TE----

Fig. 54

- ~ !

Fig. 55

Fig. 54. K-15 (200oC.). Undeformed specimen showing different positions of

samp1es in a copper jacke~ (X 1).

Fig. 55. K-15 (200oC.). Deformed specimen. Ga1ena and pyrite. single crysta1s

were cut perpendicu1ar to their cube faces. Thick and thin bands

a1ternaté1y of galena and pyrite are deformed.

62

Fig. 56. K-15 (200°C.). Pyrite is granu1ated and the grains are drawn into

a streak between two ga1ena bands. Etched with 1:1 RN03• Plain

ref1ected 1ight (X 33).

eUBle GALENA----

.MASSIVE pyRITE---- 1---;

eUBIC GALENA----

MASSIVE PYRITE-----I---;

C UBIC GALENA-----

MASSIVE PYRITE-----======1

eUBIC GALENA----

MASSIVE PYRITE----

Fig. 57 Fig. 58

Plastic

Fig. 57. K-17 (300°C.). Undeformed specimen showing samp1es in different

positions in a copper jacket (X 1).

Fig. 58. K-17 (300°C.). Single crystal ga1ena cut perpendicu1ar to a cube

face. Pyrite was cut from a massive samp1e. Thick and thin 1ayers

a1ternate1y of ga1ena and pyrite.

63

3000 C.; Compressive stress difference:: 26,350 p.s.i.

Results: Megascopically the pyrite and some galena was fractured sub-parallel

to the direction of the applied force (Fig. 58). Most deformation in the

galena was due to translation gliding along planes parallel to the cube

faces (Fig. 59). The rows of triangular pits in galena were gently curved,

and became contorted along the fractures. The galena was intensely crushed

in the fracture zones (Fig.60), and along the contact with pyrite (Fig.6l).

The pyrite bands were either fractured parallel to the applied

force or granulated. Some pyrite grains were streaked into the galena

(Fig. 62).

The copper jacket reacted with pyrite to a minor extent to form

chalcopyrite, bornite, and chalcocite. The replacing minerals have

gradational contacts.

This experiment shows that galena deformed mainly by translation

gliding, although minor fracturing occurred. Pyrite was fractured and

granulated.

Experiment K-12

Material: As in K - 13. Thick and thin layers alternately of galena and

pyrite. Several discs were used to provide camparisons,

especially between pieces in different positions (Fig.63).


4000 C.; Compressive stress difference: 21,000 p.s.i.

Results: Megascopically the specimen showed uniform lateral elongation but

the jacket was buckled on one side (Fig. 64).

The deformed samples showed poorly developed pinch and swell

structure. The pyrite in the thick layers was broken into blocks which were,

in places, displaced (Fig.65). Fractures varied from parallel to 300 fram

64

Fig. 59. K-17 (300°C.). The rows of triangu1ar pits curved smooth1y which

indicate gliding along planes para11el to the cube faces. Etched

with 1:1 HN03. Plain ref1ected 1ight (X 92).

Fig. 60. K-17 (300oC.). A fracture in galena. Rows of triangular pits

contorted a10ng the fracture zone. Ga1ena is crushed in the

fracture zone. Etched with 1:1 HN03• Plain ref1ected 1ight eX 33).

()

(

.. ----_. ... .. __ ..... ~._--~---

64

Fig. 59. K-17 (300°C.). The rows of triangular pits curved smoothly which

indicate gliding along planes parallel to the cube faces. Etched

wi th 1: l RN03. Plain reflected light (X 92).

Fig. 60. K-17 (300°C.). A fracture in galena. Rows of triangular pits

contorted along the fracture zone. Galena is crushed in the

fracture zone. Etched with 1:1 RN03• Plain reflected light (X 33).

e·

65

Fig. 61. K-17 (3000~). Ga1ena shows fracturing and granulation in contact

with pyrite. Plain reflected 1ight (X 3~).

Fig. 62. K-17 (300oC.). Pyrite is granulated and the grains; are drawn into

a streak a10ng the direction of movement of ga1ena. Galena is

cleaved in the center. Plain reflected light (X 33).

( \

65

Fig. 61. K-17 (300°c.). Galena shows fracturing and granulation in contact

with pyrite. Plain reflected light (X 33).

10.

• G'T\. ,.- -'

Fig. 62. K-17 (300°C.). Pyrite is granulated and the grains are drawn into

a streak along the direction of movement of galena. Galena is

cleaved in the center. Plain reflected light (X 33).

Fig. 63.

Fig. 64.

CUBIC GALEU···-

CUBIC PYRITE-·-

CUBIC GALfNA-

CUBIC PYRITE·--

CUBIC GALENA·····

CUBIC PYRITE····

CUBIC GUEN.\-···

CUBIC . PYRITe-·_·

Fig. 63 Fig. 64

K-l2 (400oC.). Undeformed specimen showing samples in different

positions in a copper jacket (X·.~) •

K-12 (400oC.). Deformed specimen~ Single crystal galena and

pyrite were cut perpendicular to cube faces. Thick and thin

layers alternately of galena and pyrite.

. _. 4 ........ _ .•• .. .-" . , .... ~ ... ;'<'

' .. ~ .. " •.. ' '"~" o·

.••. . .~ Q"

.1

66

.. ~

Fig. 65. ~l2 (400oC.). Pyrite band is broken into two blocks and the

blocks are displaced. Galena flowed around py~ite without showing

granulation. The rows of triangular pits smoothly curved where

pyrite is offset. Plain reflected light (X 92).

Fig. 63.

Fig. 64.

CUBIC G4LENA···- , eUBle PYRITE-···

CUBIC GALENA--

CUBIC PYRITE·--

eUBle G4LEN4-····

eUBle PVRITE·_··

CUBle G4LEN4-·--

C:UBIC PYRITE-·---

Fig. 63 Fig. 64

K-12 (400oC. ). Undeformed specimen showing samples in different

positions in a copper jacket (X 1.).

K-l2 (400oc.). Deformed specimen. SiIigle crystal galena and

pyrite were cut perpendicular to cube faces. Thick and thin

layers alternately of galena and pyrite.

66

Fig. 65. K-l2 (400oC.). Pyrite band is broken into two blocks and the

blocks are displaced. Galena flowed around pyrite without showing

granulation. The rows of triangular pits smoothly curved where

pyrite is offset. Plain reflected light (X 92).

67

the direction of the applied force. The galena curved smoothly around the

pyrite fragments without showing granulation. In the galena the rows of

triangular pits were intensely curved (Fig.66) and generally were oriented

at an angle of 300 to 600 to the direction of the applied force. Note a

fracture in galena (Fig. 67).

Where the aluminum foil broke, the copper jacket reacted strongly

with pyrite to form chalcopyrite, bornite, and chalcocite. The replacing

mineraIs have gradational contacts. Close to the copper jacket bornite

lamellae were present in the chalcocite. In one place, the chalcocite

appeared to intrude into galena along a cleavage plane (Fig.68) where it was

crystallized into sub-rounded grains (seen on etching with 1:1 HN03). This

indicates that the chalcocite had greater mobility than the galena. The

galena did not appear to tear the aluminum foil and come into contact with

copper.

The galena deformed by translation gliding. Thick pyrite layers

were fractured and thin layers were granulated. The galena flowed around

the pyrite.

Experiment K - 14

Material: Galena cut from a single crystal perpendicular to an octahedral

plane. Pyrite as in K - 13. Thick and thin layers alternately

of galena and pyrite. Several discs were used to provide

comparisons, especially between pieces in different positions

(Fig.69).


4000C.; Compressive stress difference: 22,800 p.s.i.

Results: Megascopically the specimen was deformed symmetrical1y in aIl

directions and the sample pieces were elongated paral1e1 to shear

()

(

68

Fig. 66. K-12 (400°C.). Galena flowed around pyrite. The rows of triangular

pits are intensely curved. Pyrite is fractured at an angle 10° to

30° to the direction of the applied force. Plain reflected light

(X 33).

Fig. 67. K-12(4000C.). A fracture, parallel to the direction of the applied

force, distorted by a sub-horizontal fracture, acquiring step-like

arrangement. Plain reflected light (X 92).

jacket

Fig. 68. ~l2 (400°C.). Chalcocite (dark gray) appears to intrude into

galena along a cleavage plane. Plain reflected light (X 33).

OCTAHEDRAL

CUBIC

· ..

OCTAHEORAL GALENA····

CUBIC PYRITE·-

OCTAHERDAL GALENIr--

CUBIC PYRITE---

· ·

OCTAHEDRAL GALENA-·--CUBIC PYRITE-·-·

Fig. 69

,

Î ~ ...... '-.

Fig. 70

Fig. 69. K-l4 (400oC.). Undeformed specimen showing samples in different

positions in a copper jacket (X 1). 1

69

Fig. 70. K-l4 (400°C.). Deformed specimen. Single crystal ga~ena cut

perpendicular to an octahedral plane and pyrite cut perpendicular

to cube face. Thick and thin layers alternately of galena and

(-:~ ... . ':)

,.\ ..

....

69

'---,...-- Ga lena

r jacket

Fig. 68. K-12 (400°C.). Chalcocite (dark gray) appears to intrude into

galena along a cleavage plane. Plain reflected light (X 33).

, , ~,

OCTAH E 0 RAL GALENA----: 1

CUBIC PYRITE---' 1

OCT4HEDRAL

CUBIC

OCTAHERD4L

CUBIC

OCT4HEDR4L

CUBIC

GALENA-----~' 1 PYRITE----- •

GALENA-----

A PYRITE-----i

GALENA----

"""····m Fig. 69 Fig. 70

Fig. 69. K-14 (400°C.). Undeformed specimen showing samples in different

positions in a copper jac~et (X l).

Fig. 70. K-14 (400°C.). Deformed specimen. Single crystal galena eut

perpendieular to an oetahedral plane and pyrite eut perpendicular

to cube face. Thiek and thin layers alternately of galena and

pyrite •

. , .

70

directions (Fig.70).

Pinch and swe1l structures were well developed, galena occupying

the pinched portions of the pyrite and vice versa (Fig.7l). The galena

deformed plastically without showing granulation. The rows of triangular

pits were intensely curved. A few fractures were present in galena and the

cleavage planes were smoothly curved ~(Fig. 72). The pyrite was fractured at

o an angle of approximate1y 30 to the direction of the applied force.

The copper jacket reacted with pyrite forming chalcopyrite, bornite

and chalcocite, similar to experimen~K - 12.

In this experiment the specimen deformed symmetrica1ly, showing

translation glidingin the galena and fracturing in pyrite.

Experiment K - 16

Material: Galena dense and fine grained with a schistose appearance. The

sample cut parallel to ga1ena's schistosity. Pyrite as in K-13.

Thick and thin layers alternately of ga1ena and pyrite. Several

dis cs were used to provide comparisons, especially between pieces

in different positions (Fig.73).


4000C.; Compressive stress difference: 22,800 p.s.i.

Results: The specimen was non-uniformly deformed and was less shortened

than in the experiment K-12 (compare figs. 74, 64). Galena was, in

general, a coherent mass, although a few fractures were present. No

triangular pits were observed in the galena because it was a fine grained

material. The thin galena bands were intensely deformed (thinned and thicken-.

ed) and a f10w texture is revea1ed on etching with 1:1 HN03 (Fig.75). The

flow texture has resulted from individual crystals of galena e10ngated

perpendicular to the direction of the applied force. The pyrite bands

.,.

Fig. 71. K-14 (400°C.). Figure shows pinch and swe11 structure. Ga1ena

occupied pinched part of pyrite. Plain ref1ected 1ight (X 33).

Fig. 72. K-14 (400°C.). Fractures in ga1ena. The fractures are smoothly

curved. Plain ref1ected 1ight (X 33).

71

C" . . : "/

Fig. 71. K-14 (400°C.). Figure shows pinch and swell structure. Galena

occupied pinched part of pyrite. Plain reflected light (X 33).

,

~". Fig. 72. K-14 (400°C.). Fractures in galena. The fractures are smoothly

curved. Plain reflected light (X 33).

71

STEEL GALENA·---

·

· ·

CU81C pyRITE····

STEEL GALENA····

CU81C pyRITE····

STEEL GALENA-···

CU81C PYRITE-···

STEEL GALEN"'·· . CU81C PYRITE-···

Fig. 73

!

l .

Fig. 74

Fig. 73. K-16 (400oC.). Undeformed specimen showing samples in different

positions in a copper jacket (X.).).

72

Fig. 74. K-16 (400oC.). Deformed specimen. Galena'cut perpendicular to

schistosity and single crystal pyrite cut perpendicular to a cube

face. Thick and thin layers alternately of galena and pyrite •

. Fig. 75. K-16 (400oC.). Pyrite is intensely granulated. Galena smoothly

flowed around pyrite. Elongated individual ~alena crystals,

perpendicular to the direction of the applied force, reveal flow

texture. Etched with 1:1 RN03

• Plain reflected light (X 33).

STEEL GALENA-·-·

·1 -j

:1

CUBIC PlRITE---·

S TE EL GALEN A--·

CUBIC PYRIT E·_·

STEEL GALENA·_··

CUBIC PYRITE·--

STEEL GALENA--·-

CUBIC PYRITE----

Fig. 73

l

, . 1

..

. ~ --Fig. 74

Fig. 73. K-16 (400°C.). Undeformed specimen showing samp1es in different

positions in a copper jacket (X ~).

Fig. 74. K-16 (400°C.). Deformed specimen. Ga1ena ·cut perpendicu1ar to

72

schistosity and single crystal pyrite cut perpendicu1ar to a cube

face. Thick and thin 1ayers a1ternate1y of ga1ena and pyrite.

Fig. 75. K-16 (400°C.). Pyrite is intense1y granu1ated. Ga1ena smooth1y

f10wed around pyrite. E10ngated individua1 ga1ena crysta1s,

perpendicu1ar to the direction of the app1ied force, revea1 f10w

texture. Etched with 1:1 RN03

• Plain ref1ected 1ight (X 33).

73

showed intense fracturing sub-parallel to the direction of the applied force,

accompanied by granulation. The galena flowed around the pyrite grains. In

places, fractures in the pyrite extended into the galena.

The copper jacket reacted with pyrite forming chalcopyrite, bornite

(Fig.76) and minor chalcocite, similar to the experiment K - 12.

The galena in this experiment deformed plastically and the pyrite

was fractured and granulated. Flow texture was preserved in the galena.

There was less shortening of the specimen than in experiment K - 12.

Experiment K - 18

Material: Galena as in the experiment K - 13. Pyrrhotite sample cut fram a

single crystal perpendicular to the basal plane (0001). Thick

and thin layers alternately of galena and pyrrhotite. Several

discs were used to provide camparisons, especially between pieces

in different positions (Fig.77).



Results: The specimen was buckled on one side (Fig.7S). Galena deformed by

translation gliding with minor fracturing especially along the contact with

the pyrrhotite. The rows of triangular pits in galena were gently curved.

The pyrrhotite bands were intensely fractured and granulated as

weIl as displaced by the fracture planes. These fracture planes make angles

from sub-parallel to 750 to the direction of the applied force. The fracture

planes making a 65 0 angle are Most pronounced and they cut across the basal

partings at an angle of approximately 45 0, as the basal planes themselves

make an angle less than 900 with the direction aD the applied force being

rotated, which was ohserved after deformation. The fracture planes displaced

the basal partings and produced undulating surfaces in pyrrhotite. The

Fig. 76. K-16 (400oC.). Galena has sharp but undulatory boundary with

chalcopyrite and bornite masse Plain reflected light (X 33).

',~""'I

LLI CUBIC GALENA'---'

BASAL PYRRHOTITE----.----I

ClJBIC GALENA----'

BASAL PYRHHOTITE---

CUBIC GALENA----

BASAL PYRRHOTITE---

CUBIC GALENA----

BASAl; P YRRHOTiTE-----I----f

Fig. 77 Fig. 78

Fig. 77. K-18 (400oC.). Undeformed specimen showing samples in different

positions in a copper jacket(X~).

74

Fig. 78. K-18 (400oC.). Deformed' specimen. Single crystal galena cut

perpendicular to a cube face and pyrrhotite perpendièular to a

basal p'arting (0001). Thick and thin layers alternately of galena

and pyrrhotite.

75

termination of basal partings along the fracture planes and undulations

produced an even continuous boundary (Fig.79). The above characteristic

feature indicates deformation in pyrrhotite by translation gliding along the

basal planes. The pyrrhotite granulated, in places, in contact with galena.

The galena flowed around the undulations in pyrrhotite. The basal partings

were moved fram perpendicular position to an angle of approximately 700 with

respect to the direction of the applied force. The deviation of the basal

partings was due to the differential movement of the specimen under the

deforming force. The basal partings, in places, were gently curved (Fig.80).

The copper jacket reacted with pyrrhotite forming troilite

(confirmed by X-ray diffraction), chalcopyrite, and minor bornite and

chalcocite. The chalcopyrite occurred as stringers (or blades) in troilite

parallel to the pyrrhotite basal planes (Fig.81). The troilite is yellower

than pyrrhotite and strongly anisotropie, showing optical continuity with

pyrrhotite. Chalcopyrite has a pale brass yellow colour, is weakly

anisotropie and extinguishes at an angle of approximately 300

fram that of

troilite. Bornite replaced chalcopyrite. The bornite showed recrystal

lization on etching with 1:1 RN03• Chalcocite replaced bornite.

This experiment shows that galena deformed by translation gliding,

and pyrrhotite mainly by fracturing accampanied by granulation. The

pyrrhotite, also, appeared to deform by gliding along its basal planes as

shown by smooth undulating surfaces in contact with galena.

Experiment K - 8

Material: Galena eut from a massive ore containing pyrrhotite grains, a few

Magnetite grains and gangue, the pyrrhotite grains appearing to

have a preferred orientation. The sample eut in such a way that

the observable orientation of the pyrrhotite grains would be

. -/

.-:~

76

Fig. 79. K-18 (400°C.). Fractures cut the basal partings in pyrrhotite at

approximately 45°. The termination of the basal partings along the

fracture 'planes and undulations form an even continuous boundary

which may indicate translation gliding in pyrrhotite along the

basal planes. Galena flowed around pyrrhotite undulating surfaces.


Fig. 80. K-18 (400°C.). Pyrrhotite shows undulating surfaces. The basal

partings are gently curv,ed. Galena flowed around pyrrhoti te.


® . \ ,~,

76

r ~

~ #" ~ , .

~.

• ~ .

Fig. 79. K-IB (400 0C.). Fractures cut the basal partings in pyrrhotite at

approximately 45 0 • The termination of the basal partings along the

fracture 'planes and undulations form an even continuous boundary

which may indicate translation gliding in pyrrhotite along the

basal planes. Galena flowed around pyrrhotite undulating surfaces.


Fig. BO. K-IB (400 0 C.). Pyrrhotite shows undulating surfaces. The basal

partings are gently curved. Galena flowed around pyrrhotite.


77

Fig. 81. K-18 (400°C.). Chalcopyrite stringers in troilite (FeS), parallel

to pyrrhotite basal partings. Plain reflected light (X 92).

1 III GALENA O.RE 1 Il

PYRRHOTITE GRAINS 1 ELONGATEO PARALLEL---- 1 TO THE AP PLI ED FORCE 1

MINOR SPHALERITE

1 Il

Fig. 82 Fig. 83

Fig. 82. K-8 (200°C.). Undeformed sample in a copper jacket OCO.

Fig. 83. K-8 (200°C.). Galena or~. contains pyrrhotite grains which appear

to have a preferred orientation. The specimen deformed by shear

fracturing.

(

77

Fig. 81. K-18 (400°C.). Chalcopyrite stringers in troilite (FeS), parallel

to pyrrhotite basal partings. Plain reflected light (X 92).

Il GALENA ORE 1: \ 1 1

PYRRHOTITE GRAINS

ELONGATED PARALLEL----, Il TO THE APPLIEO FORCE 1

MINOR SPHALERITE

1 Il

Fig. 82 Fig. 83

Fig. 82. K-8 (200°C.). Undeformed sample in a copper jacket~ ~).

Fig. 83. K-8 (200°C.). Galena ore. contains pyrrhotite grains which appear

to have a preferred orientation. The specimen deformed by shear

frac tu ring.

78

parallel to the direction of the applied force (Fig.82).



Results: The sample was deformed by shear fractures and part of it moved up

around the piston (Fig.83). The galena was granulated into small cubic and

sub-rounded grains. The cleaved galena crystals curved around the pyrrhotite

grains. The pyrrhotite grains were broken into smaller sub-rounded grains.

This experiment shows that the massive galena ore was deformed by

fracturing and granulation.

Experiment K - 9

Material: Galena ore as in the experiment Ke 8, and the sample cut similar

to K - 8. Single crystal galena cut perpendicular to a cube face.

Thick sample of galena ore and thin sample of single crystal

galena (Fig.84).



Results: The contact between the single crystal galena and galena ore is

smooth but undulatory (Fig.85). The rows of triangular pits in single

crystal galena were curved (Fig.86). The galena ore was a coherent mass,

and it also appears to have deformed plastically, though the movement planes

were difficult to distinguish, but it showed minor fracturing in contact with

the pyrrhotite grains. The pyrrhotite was broken into smaller grains which

were carried by galena along its flow direction.

The copper jacket reacted with galena forming lead and chalcocite

(Fig.87). Lead pellets were also present outside the copper jacket. The

formation of lead, under conditions such as those of this experiment, was

explained by Wagner and Wagner (1957) by a displacement reaction

Fig. 84.

Fig. 85.

CUB IC GAL ENA----

GAlENA ORE. PYRRHOTITE GRAINS

ElONGATED PARAllEL-TO THE APPLIED FORCE.

MIHOR SHPAlERITE.

Fig. 84

1

i

11//1 1/ /1

III , 1 1 / 1

K-9 (38s oe. ). Undeformed specimen

copper jacket (X 1).

K-9 (38Soe.). Deformed specimen.

79

Fig. 85

showing ga1ena samp1es in a

Single crystal ga1ena and ga1ena

ore defonned with e1ongation in one direction. The contact between

the two samp1es is smooth but undu1atory.

Fig. 86. K-9 (38Soe.). A fracture in single crystal ga1ena. Rows of

triangu1ar pits are intensely curved. Plain r~f1ected light (X 33).

80

Fig. 87. ~9 (38soe.). Pyrrhotite grains are drawn along the direction of

flow of lead and chalcocite. Plain reflected light (X 92).

SPH4LERITE·'" W ITH GALENA

GALENA ORE. Il Il PYRRHOTITE GRAINS 1 1 1

EL ONGArED PARALLEL-"-' 1 TO THE 4PPLIED FORCE 1

MlHOR SHP4LERITE@"

SPHAL ERIT E . WITH G4LEN4--

Fig. 88. K-lO (47SoC.). Undeformed specimen showing the positions of

samples in a copper jacket (X"~).

2 Cu(S) + PbS (S) ~ CU2S (S) + Pb (S,L).

They have shawn that the free energy change of the above displacement

reaction is zero at 279 ± 4°C. The free energy is negative ab ove this

temperature, thus supporting the feasibility of the reaction and stability

of the three phase system CU2S~.,Pb, PbS above 279 ± 4°C. They have also

shawn that the free energy of the displacement reaction is positive below

81

279 ± 4°C. and the system Cu, CU2S, PbS is stable. The present results follow

the above displacement reaction and lead was observed ab ove 3000C.

When aluminum foil was wrapped around the samples (K - 12 to K-18),

the copper did not react with the galena.

Pyrrhotite grains, present in the reaction zone, changed their

colour from brawnish-cream to pinkish-cream but possessed their original

anisotropism. Chalcocite invaded pyrrhotite grains along the openings

present in the grains. Magnetite grains were unaffected.

Under the conditions of this experiment the single crystal and

apparently the ga1ena ore deformed by translation gliding. Ga1ena carried

the pyrrhotite grains a10ng its direction of f10w. Lead and cha1cocite were

formed as a resu1t of the reaction between the copper and ga1ena.

Experiment K - 10

Materia1: Ga1ena ore as in K - 8, the samp1e cut in simi1ar fashion.

Massive sphalerite with considerable galena. Galena samp1e

between two sphalerite samp1es (Fig.88).


47SoC.; Compressive stress difference: 46,300 p.s.i.

Results: The type of deformation in the galena ore was difficult to

de termine. However, it appears to have deformed p1astically, and attained

a high mobility with movement at an angle of 400 to the direction of the

82

applied force. Sphalerite bands were crushed.

Lead and chalcocite were formed as in the experiment K - 9.

Chalcocite invaded the pyrrhotite along openings in grains. Chalcopyrite was

observed in two pyrrhotite grains, apparently formed as a result of reaction

between chalcocite and pyrrhotite.

The sphalerite in this experiment was crushed while the galena

appears to have deformed plastically.

Experiment K - 11

Material: Galena ore as in K - 8, the sample cut so that the observable

orientation of the pyrrhotite grains in galena would be

perpendicular to the direction of the applied force. Pyrite as

in K - 17. Galena and pyrite samples of the same size (Fig.89).



Results: Megascopically, the galena was elongated along the shear fractures

(Fig.90), and the pyrite was fractured. The galena had a sinuous boundar&

in contact with pyrite.

Galena was intensely granulated along the shear fractures. The

remainder of it was coherent. Pyrrhotite, in galena, was broken into small

grains which were drawn along the shear planes. The straight rows of small

pyrrhotite grains in the undeformed galena ore were curved around the pyrite

fragments, indicating that galena flowed plastically and carried the broken

pyrrhotite grains along its direction of flow (Fig.9l).

Minor chalcocite was formed as a result of reaction between the

copper jacket and galena. No lead was observed. The chalcocite was beginning

to invade the pyrrhotite along the openings in its grains. Copper reacted

with pyrite forming bornite and chalcocite (chalcopyrite may have been lost

MASSIVE PYRITE----

GAL.ENA ORE. PYRRHOTITE GRAINS

EL.ONGATEO NORMAL. --- - - -TO THE APPL.IED FORCE.

MINOR SPHAL.ERITE----

r

Fig. 89

83

Fig. 90

Fig. 89. K-ll (300oC.). Undeformed specimen showin~positions of samples in

a copper jacket (X.~).

Fig. 90. K-ll (300oC.). Deformed specimen. Pyrite is crushed and lost.

Galena ore is elongated along two shear directions and granulated

along shear planes. The contact between pyrite and galena ore is

undulatory.

Fig. 91. K-ll (300oC.). Galena flowed around a pyritè fragment. Pyrrhotite

grains in galena are carried along the direction of flow of galena

an~ thus, 'assume the shape of the pyrite fragment. Plain reflected light (}Ç 33).

84

fram the specimen while cutting the sample).

Experiment K - 19

Material: Pyrrhotite cut fram a single crystal perpendicular to a basal

plane (0001). Pyrite cut from a massive specimen containing

pyrrhotite, chalcopyrite, magnetite and gangue. Thick and thin

layers alternately of pyrrhotite and pyrite. Several discs were

used to provide camparisons, especially between pieces in

different positions (Fig.92).


400°C.; Compressive stress difference: 30,200 p.s.i.

Results: The specimen was broken into two blocks along a fracture plane.

The fracture plane makes an angle of 20° with the direction of the applied

force (Fig.93). On the left side of the fracture the samples have straight

line contact and were less deformed. On the right side, the samples were

intensely compressed and elongated laterally, the central part being less

deformed.

In the less deformed block, fracturing and granulation in the

samples were less. The fractures were sub-parallel to the direction of the

applied force. The basal partings in pyrrhotite were less deformed, and were

granulated where the fractures intersected them (Fig.94).

In the highly deformed block, part of the sample was intensely

fractured and granulated. Pyrrhotite was traversed Dy fracture planes making

an angle of approximately 60° to the direction of the applied force: the

basal partings in pyrrhotite moved from perpendicular position to angles of

about 500 to 700• In places, the fracture planes and basal partings were

gently curved (Fig.95). In one place, the contact between pyrrhotite and

pyrite was undulatory but both minerais were crushed leaving no clear boundary

Fig. 92.

Fig. 93.

BASAL P'rRRHOTITE----

MASSIVE PYRITE···-t----I

BASAL PYRRHOT ITE--.-·

MASSIVE PYRITE-•• - I-----t

BASAL PYRRHOTlTE--.-.

MASSIVE PYRITE----I-----t

BASAL PYRRHOTITE----.

MASSIVE PYRITE-·-·I----I

Fig. 92 Fig. 93

85

o K-19 (400 C.). Undeformed specimen showing positions of samp1es in a copper jacket (X ~).

K-19 (400oC.). Deformed specimen. PYrrhoti·te cut perpendicu1ar to

a basal parting (0001). Pyrite cut from a massive samp1e. Thick

and thin 1ayers a1ternate1y of pyrrhotite and pyrite. The deformed

specimen was cut by a fracture plane making an angle of 200 with the

direction of the app1ied force.

Fig. 94. K-19 (4000 C.). Pyrrhotite shows fracturing and granulation. A

fracture appears to have been disp1aced by the pyrrhotite basal

parting. Plain ref1ected 1ight (X 92).

86

Fig. 95. K-19 (4000C.). Fractures intersected the basal partings in

pyrrhotite at approximately 45°. The basal partings are smoothly


Fig. 96. K-19 (400°C.). Figure shows undulating boundary between pyrrhotite

and pyrite, but both minerals are crushed leaving no clear boundary.


( )

86

Fig. 95. K-19 (4000C.). Fractures intersected the basal partings in

pyrrhotite at approximately 45°. The basal partings are smoothly


Fig. 96. K-19 (400°C.). Figure shows undulating boundary between pyrrhotite

and pyrite, but bath mineraIs are crushed leaving no clear boundary.


87

(Fig. 96). (The undulating surface of pyrrhotite was interpreted as due to

gliding along its basal planes in the experiment K - 18.)

The copper jacket reacted with pyrrhotite forming troilite (FeS),

chalcopyrite stringers in troilite, bornite and chalcocite, similar to the

experiment K - 18. The copper jacket reacted with pyrite forming chalcopy

rite, bornite and chalcocite. Bornite contained relict chalcopyrite

stringers. Chalcocite contained exsolved bornite lamellae. A few relict

pyrite grains were present in the reaction zone. The replacing mineraIs

have gradational contacts.

In this experiment pyrrhotite and pyrite were intensely fractured

and granulated and there was no sign of plastic deformation.

Experiment K - 5

Material: Chalcocite containing considerable bornite, minor pyrite and

gangue. The bornite àistributed throughout the chalcocite

(Fig.97).


300oC.; Compressive stress difference: 48,800 p.s.i.

Results: Chalcocite was coherent but was cut by irregular fractures

believed to have formed while the specimen was cooling. The sample consisted

of exsolved bluish white chalcocite 1amellae in b1ue chalcocite (seen by

etching with 1:1 HN03). The chalcocite exhibited polyhedral cleavage, or

recrystallization (?), after etching with 1:1 HN03 (Fig.98). No f10w texture

was observed. Difficu1ties are invo1ved in attributing the texture to

recrysta1lization because the composition of the chalcocite was changed from

its stoichiom~tric composition.

The copper jacket and chalcocite strongly reacted with bornite and

pyrite. Bornite was part1y changed into chalcocite as we1l as cha1cocite

UJ CHACOCITE ORE

-CONTAINING---r BORNITE AND PYRITE 1

Fig. 97. K-5 (300°C.). Undeformed sample in a copper jacket (X:"~).

Fig. 98. K-5 (300°C.). Chalcocite shows grain boundaries (?) as revealed

88

after etching. On the right side, bornite lamellae are present in

chalcocite. Irregular f"ractures are believed to have formed while

cooling. Etched with 1:1 HN03• Plain reflected light (X 92).

0),' r·,,: ~ w

CHACOCIT E ORE -CONT AINING----:

BORNITE AND PYRITE :

1 .

m Fig. 97. K-5 (300oc.). Undeformed samp1e in a copper jacket (X 1).

Fig. 98. K-5 (300°C.). Cha1cocite shows grain boundaries (7) as revea1ed

88

after etching. On the right side, bornite 1ame11ae are present in

cha1cocite. Irregu1ar fractures are be1ieved to have formed whi1e

coo1ing. Etched with 1:1 RN03• Plain ref1ected light (X 92).

89

having bornite lamellae. In sequence from the center pyrite was observed to

have changed into chalcopyrite, chalcopyrite stringers in bornite, bornite,

and bornite 1amellae in chalcocite. The contacts between the various

replacing minerals weregradational.

In this experiment the cha1cocite sample has been deformed 1aterally,

but the exact nature of deforrnation could not be ascertained since it may

have recrystallized.

Experiment K - 1

Material: Ore composed of pyrrhotite (60%), chalcopyrite (30%), magnetite

and gangue (10%). Pyrite massive and containing minor amounts of

chalcopyrite, magnetite and gangue. Pyrite sample between two ore

samples (Fig.99).


Room Temperature; Compressive stress difference: 83,800 p.s.i.

Results: The ore samples deformed with shear fractures making an angle of

300 with the applied force. The pyrite sample was crushed and it was lost.

Pyrite, chalcopyrite and magnetite were broken into small grains

along the shear fractures. These were crushed into a fine grained mosaic at

the center of the specimen, and the granular mate rial was concentrated along

a shear direction (Fig.100). In the remainder of the specimen, the minerals

were fractured sub-parallel to the direction of the applied force. Both the

mixed ore and the pyrite were brittle under the conditions of the experiment.

Experiments K - 3, 2 & 4

Material: Massive chalcopyrite containing minor pyrite, magnetite and

gangue. Pyrite as in K - 1. Chalcopyrite and pyrite samp1es of

the same size (Figs. 101, 102 and 104).

Conditions: See table II. Temperatu~e: 2QOoC.; Confining pressures:

PYRRHOTITE -CHALCOP YRITE MAGNETITE ORE·--·

PYRITE--

PYRRHOTITE -CHALCOPYRITE MAG NET ITE ORC--

Fig. 99. K-l (Room temperature). Undeformed specil!.len showing sample

positions in a copper jacket (X 1).

90

Fig. 100. K-1 (Room temperature). Pyrrhotite-chalcopyrite-magnetite ore. The

figure shows intense granulation in a shear zone as a fine grained

mosaic. 'Plane refle~ted light (X 92).

PYRITE---

CHALCOPYRITE--ORE'

-

-

CHALCOPYRITEORE

J

1.

Fig. 101. K-3 (200°C.). Undeformed specimen showing positions of samp1es

in a copper .iacket (X 1).

91

J __ ~ •.. ~lcopyri te

CHALCOPYRIT E ___ • ORE

PYRITE··_·

CHALCORYRITE·--· ORE

Fig. 102

, te

•

Fig. 103

Fig. 102. K-2 (200°C.). Undeformed specimen showing positioI).s of samp1es in

a copper jacket (X 1).

Fig. 103. K-2 (200°C.). Deformed specimen. Chalcopyrite fails a10ng shear

fractures. Pyrite is broken into ha1ves.

92

l PYRITE-·· .

CHALCOPYRITE····

PYRITE···

l

Fig. 104. K-4 (200°C.). Undeformed specimen showing positions of samples in

a copper jacket (X-~).

Fig. 105. K-4 (200°C.). Figure shows brecciated chalcopyrite. The fractures

that are parallel to the applied force became convex, giving an

appearance of a fold. Plain reflected light (X 92).

93

14,500, 14,000, 15,000 p.s.i. respectively.

Results: Megascopically the chalcopyrite sample showed shear fracture and

the pyrite sample was broken into two halves parallel to the applied force

(Fig.l03).

The chalcopyrite sample was intensely fractured throughout the

specimen. The fractures are parallel to, or are at angles of about 300 to the

direction of the applied force. In the experiment K - 4, at one place, some

of the fractures that are parallel to the applied force are convex (Fig. 105).

These experiments show that the chalcopyrite ore was intensely

fractured and granulated. Pyrite was only fractured.

Experiment K - 6

Material: Chalcopyrite ore as in K - 2 (Fig.l06).

Conditions: See table II.' Confining pressure: 15,000 p.s.i.; Temperature:


Results: Chalcopyrite was intensely fractured, and magnetiteand pyrite

grains in it were, in places, fractured. The copper jacket strongly

reacted with chalcopyrite fonning intermediate products and very little

unreacted sample was left to study the deformational textures. The reaction

products formed successive zones with gradational contacts, in passing

outward, of bornite lamellae in chalcopyrite (Fig.l07), bornite, chalcocite

lamellae in bornite, troilite stringers and bornite lamellae in chalcocite

(Fig. lOB), troilite stringers and bluish white chalcocite lamellae in blue

chalcocite. The troilite (FeS) stringers are composed of small grains.

Troilite was confirmed by X-ray diffraction.

In the present experiment, the formation of troilite stringers can

be explained by the process presented by Sugaki and Tashiro (1956). They

observed drop-like pyrrhotite (FeS) masses in the bornite zone, when

CHALCOPYRITE WITH MINOR

PYRITE, MAGNETlTE--AND GANGUE

Fig. 106. K-6 (350°C.). Undeformed specimen~:l).

Fracture

~~~--Chalccpyrite

Bornite

Fig. 107. K-6 (350°C.). Chalcopyrite is fractured. Bornite lamellae are

present in chalcopyrite along certain directions. Etched with

acidic K2Cr207. Plain reflected light (X 92).

94

95

--'llornite Chalcocite

Fig. 108. K-6 (350oC.). Figure shows bornite lamellae and troilite stringers

in chalcocite. Bornite and chalcocite appear to replace troilite

stringers. Etched with 1:1 RN03• Plain reflected light (X 92).

IJJI 1 . • 1

i l, j

CHALCOPYRITE " W ITH NINOR

PYRITE. MAGNÉTlTE···_·

AND GANGUE

Fig. 109. K-7 (350oC.). Undeformed specimen (X 1).

96

chalcopyrite was heated in contact with a copper plate at 500oC. and above

and quenched in water. The drop-like mineraI did not reveal grain boundaries.

They explained its formation according to a formula

2 CuFeS2 --)~ CU2 S + 2 FeS + S. (1)

Copper and sulfur atoms, from the dissociated chalcopyrite, migrated to the

adjacent bornite solid solution and iron atoms from the bornite solid

solution reversely migrated into the chalcopyrite zone to form pyrrhotite.

Sneed et al. (1954, p.22) stated that chalcopyrite disintegrates on heating

at 400oC. and above in matte smelting according to the fonnula (1).

Another possible explanation of the fonnation of troilite stringers

is as follows: Copper reacts with chalcopyrite according to the formula

(2)

The chalcocite, in turn, reacts with chalcopyrite to fonn bornite:

(3)

In this stage the chalcocite, together with the copper atoms from the jacket,

migrates inwards by a process of solid state diffusion. The iron atoms from

the troilite are slow to migrate; thus the troilite was left behind as a

relict mineraI. MacDougall et al. (1961) described the ab ove phenomenon

from their experimental results; that is, that copper diffuses more readily

than iron. Probably because the chalcocite reacted directly with chalcopy

rite, no troilite was formed in the inner zones. Thus, the troilite was

observed, in the present experiment, only in the chalcocite-rich zones and

not in the bornite-rich zones. Probably a part of troilite (as free iron

and sulfur atoms) in the chalcocite zone was replaced to form bornite

lamellae. The bornite lamellae and chalcocite tended to replace the troilite

stringers (Fig. 108).

Irregular fractures were present in the reaction zone and inter-

97

mittent metallic copper stringers were observed in them. Sugaki and Tashiro

(1956) observed similar but continuous metallic copper stringers across

bornite lamellae. They explained their f~rmation as follows: The copper

atoms (from the copper plate) diffused in a solid state into chalcopyrite.

When the migration of the copper atoms was prevented by cracks in the

chalcopyrit~produced by expansion during heating, they segregated along the

edges of the cracks and filled them. In the present experiment the formation

of copper stringers can be explained by a similar process, except that the

fractures resulted from deformation. When the specimen was cooled the

fractures were further extended along their linear dimensionsaccounting for

the discontinuous nature of the copper stringers.

Experiment K - 7

Material: As in K - 6, with the addition of aluminum foil wrapped around

a sample to prevent reaction between the copper jaëket and

sulfides (Fig.109).


3500 C.; Compressive stress difference: 45,200.p.s.i.

Results: The sample was broken along shear planes at an angle of 25 0 to the

direction of the applied force. Chalcopyrite was brittle and irregularly

fractured. Magnetite grains were fractured in places.

The aluminum foil broke and the copper jacket reacted with the

chalcopyrite forming intermediate products. Copper reacted with chalcopy

rite forming bornite lamellae in the chalcopyrite. Min.or chalcocite and

bornite were formed close to the copper jacket. Magnetite grains acquired a

pinkish tinge. Native copper was observed in the fractures, in the

reaction zone, similar to the experiment K - 6. The reaction was restricted

mainly to the outer portions of the shear zones.

Chalcopyrite was brittle, and fractured under the conditions of

this experiment.

98

99

DISCUSSION OF RESULTS

In the two experimental methods used in this investigation it was

found that sulfide minerals are deformed by fracturing and by plastic flow.

Of the six sulfide minerals investigated pyrrhotite single crystals,

sphalerite and pyrite were deformed by fracturing only; chalcocite, galena

and chalcopyrite were deformed by fracturing at low temperatures and plastic

flow at higher temperatures, with an intermediate zone where both fracturing

and plastic flow occurred.

Fracturing occurs at low temperatures and pressures. Plastic

flow and mobility phenomena occur in the solid state below their melting

points under suitable pressure conditions. Davies (1965a,b) determined the

mobility of some sulfide minerals and concluded that the degree of mobility inverse1y as

varies approximately ~" the hardness of the minerals tested. Gill (1965)

summarizing the research on mechanical deformation of sulfides at McGill

University observed that there are complications involved in the degree of

mobility of a particu1ar sulfide due to variations in grain size, crystal

orientation, and transformations in crystal structure. In the present

experiments, the loss of sul fur in sulfides at high temperatures appears to

retard the degree of mobility.

Certain minerals deform plastically under pressure alone, but an

increase in temperature makes them more plastic by activating many crystal

planes and by decreasing the amount of stress necessary for deformation.

The deformational behaviour of each mineral is discussed

below.

Chalcocite: One experiment only was performed on chalcocite, at 3000 C. under

a confining pressure of 15,500 p.s.i. It deformed as a coherent mass but no

flow textures were observed whereby the movement of material could be traced.

100

It is not c1ear in this experiment if the cha1cocite had recrysta11ized.

However, at higher temperatures Soles (1959) and Davies (1965a) found that

complete recrysta11ization had taken place.

Ga1ena: Be10w 2000C. and with confining pressures ranging up to 15,000 p.s.i.

ga1ena deformed by fracturing,whi1e at about 4000c .. w-ith confining pressures

ranging up to 13,000 p.s.i. it deformed comp1ete1y by plastic f1ow. Evidence

of the plastic f10w in ga1ena waspreserved in the form of 1) curved rows of

triangu1ar pits, interpreted as having been produced by translation gliding

on (100) planes, 2) e10ngation of individua1 crysta1s in schistose ga1ena,

3) f1owage, without fracturing, around harder minera1s, and 4) streakingout·.

of fragments of the harder minera1s in its direction of f1ow. These resu1ts

compare favourab1y with those of Davies (1965b) who obtained mobi1ity in.

ga1ena at 4000

C. under a differentia1 pressure of 8,000 p.s.i.

Where the gliding planes (100) in the ga1ena crystal are oriented

so that they coincide with the maximum shear stress, the crystal is most

_easi1y deformed. When the glide planes do not coincide with the planes of

maximum shear stress the crystals are more difficult to deform even though

they deform plastica1ly. Previously sheared or schistose ga1ena is also

difficu1t to deform when the schistosity is not para11el to the planes of

maximum shear stress.

Sphalerite: In the one experiment performed on spha1erite, at 47SoC. and a

confining pressure of 18,000 p.s.i., the minera1 was found to be britt1e, 1

and deformed by fracturing only.

Pyrrhotite: Single crystals of pyrrhotite were compressed in two experiments

at a temperature of 4000C. and a confining pressure of 5,000 p.s.i.

Pyrrhotite has a distinct basal parting (Deer et al., 1962). Buerger (1928)

found from experiments on pyrrhotite that there is evidence for translation

101

gliding, when the basal planes are oriented at 450 to the axis of the load.

In the present experiments, the basal planes were rotated to a position

~pproximately at 45 0 to the direction of the applied force where trans-

lational gliding occurred. Where basal partings were at an angle to the

shear planes, the pyrrhotite was fractured only. Roberts (1965), in testing

o the mobility of massive pyrrhotite, found that it readily flowed at 666 C.

and 23,600 p.s.i. confining pressure. Although the limitations have not yet

been detennined, pyrrhotite may be assumed to fracture at lower temperatures

and pressures under a directed stress except when its basal planes are

suitably oriented for gliding. At higher temperatures and pressures it is

readily deformed by plastic flow.

Pyrite: Pyrite was subjected to compressive stresses in conjunction with

the testing of the other mineraIs. Temperatures up to 4000 C. and confining

pressures ranging up to 23,500 p.s.i. pyrite is a hard, brittle and

uncleavable mineraI. In aIL cases the pyrite was deformed by fracturing. In

cold seal bomb experiments at 5500 C. under a confining pressure of 20,000

p.s.i. there was still no evidence of flow. Davies (1965b) found that pyrite

did not become mobile at 6650C. under a confining pressure of 8,000 p.s.i.

Chalcopyrite: Under ordinary conditions at the earth's surface chalcopyrite

is brittle, poo rI y cleavable, and has a hardness of 3.5 • 4. It is a sulfur

deficient compound, deviating from its stoichiometric formula CuFeS2 (Merwin

and Lombard, 1937; Frueh, 1959).

In the experiments conducted, the chalcopyrite recrystallized at

5000 C. under a confining pressure of 25,000 p.s.i., 5400 C. under 20,000

p.s.i., and 562°C. under 10,000 p.s.i.

Chalcopyrite is dimorphous and changes from a tetragonal to cubic

structure at about 5750 C., which is in general agreement with the findings

102

of Cheriton (1952), Hil1er and Probsthain (1956), Donnay and Kul1erud (1958),

Frueh (1958), and Yund and Kul1erud (1961).

The cubic structure has been identified by other investigators by

means of a high-temperature X-ray camera. The cubic structure was not fixed

by quenching in the present experiments. However, the evidence of the

existence of the cubic polymorph at high temperatures is found in the form

of demains. Buerger (1945) named these demains transformation twins.

The demains are tetragonal and are oriented in the a, b or c directions of

the isemetrie form. They are paral1el to the edges of the sphenoid face

(112), giving an appearance of a triangu1ar pattern. Frueh (1958) in a

theoretieal discussion, showed that the demains develop from crystal1ites

with their tetrad axes approximately para1lel to eaeh of the three tetrad

axes of the original eubic crystal. When the section is eut perpendicu1ar

or parallel to the "c" - crystallographic axis, the pattern is of

orthogonal type. The demains have been shown to be due not to pressure,

pyrite impurities, or sul fur loss,but on1y to temperature. There are

four different sizes of domains which decreased as the tempe rature

increased, and the changes w~re observed at 6000 , 625 0 , 6600, and 7000 C.

These domains are visible only after etching with acidic K2Cr207• To

the authors knowledge there is no indication in the earlier literature

that demains had been observed under the microscope, although their

formation was theoretically interpreted (Buerger, 1945, 1951) and

recognized by X-ray diffraction (Frueh, 1958).

The experiments in the tri-axial apparatus were c,arried out to

temperatures 3500 C. and confining pressures up to 23,500 p.s.i. The

chalcopyrite deformed by fracturing on1y.

In the eold seal bemb experiments, where the chalcopyrite was

103

intruded into an open space, it fractured at temperatures up to 5000 C. under

confining pressures of 20,000 and 25,000 p.s.i.; above this temperature it

moved as coherent masse The results of these experiments are given in table

l and figures 4 and 5. In figure 4 it will be noted that the amount of

o intrusion decreases gradually with increasing temperature above 650 C.,

under a constant pressure of 10,000 p.s.i. This may have been caused by the

loss of sul fur fram the chalcopyrite and the consequent hardening of the

samples as explained in page 44. Frueh (1959) found fram resistivity

measurements that loss of sulfur begins below 3l00 C. Hiller and Probsthain

(1956) found fram high-temperature X-ray camera studies that when chalcopyrite

is heated above 5500 C., the sul fur content decreases continuously up to 750°C.,

which was the highest temperature reached. The end product at 720°C. the y

reported as CU17+xFe17+xS32(X=0.6). It can be pointed out fram their results

1 0o that the rate of loss of su fur is great between 580 C. and 620 C. Evolution

of sulfur was noted in the present investigation in a heating experiment at

6000C., and in differential pressure experiments at 7000 C. and above. From

the above evidences, it is reasonable to believe that sulfur loss could be

more above 650°C. and caused ::-hardening in chalcopyrite. To substantiate

this explanation, hardness tests were made on aIl samp1es. From these tests

it was found that the increase in hardness increased suddenly at 575°C. and

was almost constant between 575°C. and 660°C., th en dropped sudden1y at 675°C.,

and increased gradually in experiment's up to 800°C. Possible exp1anations

were offered on pp.44-49 •

Single chalcopyrite crysta1s intruded about the same amount as the

polycrystalline materia1 when the g1ide planes (112) were oriented at 45° to

the differential pressure. The polymorphie change in the chalcopyrite has

very litt1e effect on its mobi1ity in spite of a volume expansion which

104

occurs during phase change. Its mobility is affected mainly by temperature,

pressur~ and loss of sulfur.

In experiments using the tri-axial compression equipment, where

alternate bands of different sulfide minerals were used, the minerals that

deformed by plastic flow were moulded around the brittle ones that fractured.

In extreme cases, where the brittle minerals were granulated, they were

drawn out in streaks along the direction of flow of the plastic minerals.

From the experiments we would expect that the resistance to

deformation of these minerals in an ore would be in the following general

order: Chalcocite, galena, chalcopyrite, pyrrhotite, sphalerite and pyrite.

105

CONCLUSIONS

o 1) Chalcocite deformed as a coherent mass at 300 C. under a confining

pressure of 15,500 p.s.i. However, no flow texture is observable and it is

not clear if the chalcocite has recrystallized.

2) Galena was fractured at 2000 C. and confining pressures up to 15,000 p.s.i.,

and flowed plastically at about 4000 C. and confining pressures up to 13,000

p.s.i. Plastic flow in galena can be recognized by curved rows of triangular

pits interpreted as having been produced by translation gliding on (100)

planes; elongation of individual crystals in schistose galena; flowage,

without fracturing, around harder minerals; and streakingout of fragments of

the harder minerals in the major direction of flow.

Schistose galena, whose schistosity was parallel to the direction

of the applied force, offered greater resistance to deformation th an the

cube and octahedral face galena when those faces were normal to the direction

of the applied force. The octahedral face galena deformed symmetrically with

respect to the direction of the applied force. Cube face galena deformed

asymmetrically.

Lead and chalcocite were formed above 3000 Ce as a result of the

reaction between copper and galena.

3) Chalcopyrite fractured at lower, but flowed plastically at higher

temperatures and pressures and its mobility was directly controlled by the

temperature, pressure, and loss of sul fur. It became readily mobile above

475°C. and below 650°C. under confining pressures of 10,000 to 25,000 p.s.i.

The amount of intrusion decreased at 6500 C. and above,under a confining

pressure of 10,000 p.s.i., explainable by the loss of sul fur. To support

this explanation, hardness tests were made. However, the increase in

hardness deviated from orderly increment up to 650°C. and th en increased

lO6

progressively.

o 0 0 Recrystallization of chalcopyrite at 500 , 540 , and 560 C. under

confining pressures of 25,000, 20,000, and 10,000 p.s.i. respectively,

obliterated aIl evidences of flow textures.

The change fram tetragonal to cubic symmetry did not occur at

5620C., but did occur at 5750 C., under a differential pressure of 10,000

p.s.i. This symmetry change could not be fixed by quenching but evidence of

the higher symmetry is found in a camplex set of "domains"; this change does

not appear to affect the mobility of chalcopyrite. These domains indicate a

minimum temperature of 56oPC. for chalcopyrite on quenching. These domains

should be distinguished fram twins produced by mechanical deformation, and

cubanite-chalcopyrite intergrowths.

4) Single crystal pyrrhotite, with its basal planes (0001) normal to the

o direction of the applied force, was fractured and granulated at 400 C. and

a confining pressure of 5,000 p.s.i. There ia evidence of translation gliding

o when the basal planes were rotated to a position approximately at 45 with the

direction of the applied force.

o Copper reacted with pyrrhotite at 400 C. and formed troilite and

chalcopyrite. Chalcopyrite occurred as stringers parallel to the pyrrhotite

basal partings.

5) Sphalerite was fractured at 4750 C. under a confining pressure of

18,000 p.s.i.

6) Pyrite was fractured and granulated at temperatures up to 5500 C. under

confining pressures ranging up to 23,500 p.s.i.

7) When layers of galena and pyrite or pyrrhotite are alternated, the galena

flows around fractured pyrite or pyrrhotite. The pyrite and pyrrhotite are

always granulated and the grains are streaked out in the direction of flow

107

of the galena. When alternated layers are deformed at 400°C., both minerals

are crushed ..

108

APPLICATION TO GEOLOGY

Sulfide deposits having different origins are recognized and

accepted by most geologists. Some important types are: Cavity fillings

(tin-silver deposits at Potos~, Bolivia; Park and MacDiarmid, 1964, pp.350-

354), replacements (copper deposits at Bisbee, Arizona; Bateman, 1950. pp.

498-500), and syngenetic deposits (copper deposits at Kupferschiefer near

Mansfeld, Germany; Park and MacDiarmid, 1964, pp.384-385). These types of

deposits have been distinguished by, among other things, certain textural

criteria.

Many ore deposits are found in metamorphic terrains. From this

have arisen the following problems: 1) What is the relation of the

emplacement of the deposit, in time, with respect to the metamorphism and

2) if the deposit has been metamorphosed, what structural and textural

relations can be expected in the ore?:

The present investigations, together with others, have shown that:

1) Certain sulfide minerals, chalcocite, galena, chalcopyrite, and

pyrrhotite will flow under various temperatures and pressures, into open

spaces: vugs, fractures and fissures, well within the range of temperature

and pressures prevailing in regional metamorphism.

2) Some minerals are fractured and granulated even under high temperature

and pressure conditions, e.g., pyrite and arsenopyrite.

3) During flow, soft minerals deform by gliding and twinning. Hard

minerals are granulated and streaked out along the direction of major

movement; this may give the appearance of foliation and banding.

4) Many of the minerals that flow also recrystallize. This obliterates

sorne of the deformation textures. Where both brittle and soft minerals are

present in an ore that is recrystallized, the soft minerals form a recrystal-

lized mass enclosing fractured and streaked out fragments of the brittle

mineraIs.

109

5) A polymorphic change in a mineraI indicates that the mineraI has been

subject to a certain minimum temperature and pressure. The appearance of

domains in the chalcopyrite indicate temperatures above 560oC. under

confining pressures fram 10,000 to 25,000 p.s.i. However, the inversion

temperature of chalcopyrite varies over a wide range at rressures greater

than indicated above~ullerud, et al., 1965) since polymorphic inversions

always involve density (lattice-volume) changes (Park and MacDiarmid, 1964,

P.190).

Corroborations:

Gneissose or steel galena containing streaks of sphalerite, pyrite

and tetrahedrite has been ascribed to flow banding at Slocan, B. C. (Uglow,

1917) and at Couer d~Alene, Idaho ~aldsm~dt, 1925).

Ramdohr (1953, pp.14-l5) described the Rammelsberg deposit as

having been deformed and completely recrystallized. He described fractured

pyrite grains and lumps surrounded by soft recrystallized ores of chalco

pyrite, galena and sphalerite.

Kinkel (1962, pp.1116-ll2l) described the Ore Knob deposit,

N. Carolina, as having been recrystallized. He described plastic flow in

the softer pyrrhotite and chalcopyrite over small distances. He described

the massive pyrrhotite - chalcopyrite ore flow into tension cracks in the

wall rock and in rock fragments. He interpreted the recrystallized textures

in the vein mineraIs and wall rock as a result of a rising temperature

gradient along the ore channel, largely in the absence of directional stress.

The well-documented descriptions of ore deposits are substantiated

by the experimental results of the deformation of sulfide ores.

110

FURTHER WORK

Further work should be done ta determine the full range of pressure

temperature conditions under which individual mineral species begin ta flow

plastically. Only after this has been fully explored should work be done on

mixed ores.

For the single mineral experiments the cold seal bomb apparatus

is the easier ta use. For mixed ores the tri-axial compression apparatus

should be used because the samples required for these experiments are too

large for the cold seal bomb apparatus.

More detailed experiments in this field should be designed to:

1) Further the present investigation by studying the mobility

of chalcopyrite at temperatures below 4750 C. under confining pressures above

25,000 p.s.i.

2) Study the effect of different rates of cooling on the

appearance and size of the domains in chalcopyrite.

3) Further the investigation for determining the effect of loss

of sulfur on the mobility of chalcopyrite. Determine the partial vapour

pressures of air and sul fur in the gold capsules at different temperatures.

4) Investigate flow textures in minerals that will not recrystal

lize to use as markers.

and 5) Study the deformation characteristics of such common ore

minerals as sphalerite and pyrrhotite.

III

ACKNOWLEDGEMENTS

The writer is indebted to Dr. J. E. Gill, Department of Geological

Sciences, McGill University, who as the director of this research suggested

the topic and gave valuable advice and criticism, in the course of the

investigation and preparation of the thesis.

The writer is grateful to Mr. R. Davies who contributed greatly

to solving many problems relating to the experimental section and valuable

suggestions and encouragement given during the investigation.

Particular thanks are due to Dr. A. J. Frueh's helpful discussion

and solution of crystallographic and X-ray aspects of the problem.

The writer is grateful to Mr. W. H. Maclean for taking X-ray

diffraction photographs with the Guinier camera and for his encouragement

and critical discussion while preparing the manuscript.

The writer wishes to thank Dr. L. A. Clark for kindly allowing the

use of his laboratory and for obtaining samples from the economic geology

collection, Geology Department, McGill University; also to Dr. L.S. Stevenson,

Redpath Museum, McGill University, for 5 single crystals of chalcopyrite.

Thanks are due to Mr. W. J. Doig, technician in the Department of

Geological Sciences, McGill University, who gave invaluable assistance in

making several components of the apparatus and in solving many mechanical

prob1ems.

Thanks are due also to Dr. R. L. Stanton for suggesting an etching

reagent "HP2+NH40H" for chalcopyrite.

Financial assistance and costs of materia1s and some equipment were

met by National Research Council of Canada grant A 1511 without which this

investigation could not have been carried out.

The author acknow1edges Mr. R. Martin and Mr. K. Ogris for the

financia1 assistance and three months 1eave of absence, under a special

post-graduate study plan, from the Iron Ore Company of Canada.

In conclusion the author wishes to express his thanks to

Mrs. J. Jackson who carefu11y typed this thesis.

112

113

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118

APPENDIX

Previous experimental work on the deformation of sulfides:

Deformation experiments have been performed on su1fides, but they are

remarkably few compared to what have been done on rocks, roc~forming mineraIs,

and metals. An excellent bibliography of experimental work on rocks and rock-

forming mineraIs is given in a symposium on~ Deformation (Geo1ogica1

Society of America, Memoir 79,1960).

The ear1iest experiments on su1fide deformation were performed by

" Mügge (1898, pp. 123-138) on single crystals of galena. The method consisted

of compressing single crystals of galena of pre-determined orientation in

suitable wedges. He concluded that the galena deforms by translation on (100)

plane along the [110] direction.

Adams (1910) deformed a pyrite cube at room temperature for 17 minutes

by which time a maximum load of 43,000 lbs. was applied, using Kick's method.

The specimen. container, a copper tube, has an internaI diameter of 1 1/16

inches and wall thickness of 1/8 inches. The method consisted of compressing

the testing material in a soft matrix within a ductile metal tube. The pyrite

wa~ crushed and powdered without showing any trace of plastic deformation.

" Mugge (1920, pp.30-3l) subjected small crystals (1 - 3 mm) of

chalcopyrite to pressures of 10,000 to 25,000 atm. at room temperature and

obtained striae parallel to (Ill) which could be followed over several

surfaces. The character of the movement was found to be translational.

Veit (1922), using Kick's method, deformed sphalerite crystals at room

temperature under pressures of 4,700 and 7,800 atm. respectively. Sphalerite

flowed plastically by translation on the (Ill) plane along a translation

direction? [112J. Veit also deformed pyrite but there was no indication of

plastic deformation.

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Buerger (1928) performed severa1 experiments, using Kick's method, on

single crysta1s of ga1ena, spha1erite, chalcopyrite and pyrrhotite, at roam

temperature, emp10ying copper tubes (1.125 inches externa1 diameter) for

holding the samp1es. The samp1es were shortened at a rate of 0.03 inches per

minute unti1 a particu1ar load was reached in a specific time. He pointed

out that it is not possible to ca1cu1ate accurate1y the stresses set up in

the enc10sed specimen because many variables are invo1ved. He used crystal

structure to discuss the resu1ts.

" Buerger experimenta11y confirmed the resu1ts of Mugge (1898) on ga1ena.

The ga1ena was deformed p1astica11y (exhibiting slip 1ines) with re1ative1y /

great ease when loads of 36,000 and 37,700 lbs. were app1ied normal to an

octahedra1 face. No measurab1e deformation or production of slip 1ines was

observed when loads of 33,800, 51,000 and 57,000 lbs. were app1ied normal to

a cube face. In addition, he showed that deformation of galena invo1ves a

reorientation of crysta110graphic directions such that a [lllJ direction

tends to become para11e1 to the load.

Sphalerite deformed by twin-g1iding on (111) planes, when a load of

55,000 lbs. was app1ied normal to a cube face for 15 minutes, the character

of the movement being twinning contrary to Veit's (1922) conclusions.

Chalcopyrite was found to deform by translation on (111) when a load

of 46,000 lbs. was app1ied for 10 minutes normal to a basal pinacoid (or a

-prism plane, as it was not possible to distinguish them morpho1ogica11y).

Buerger cou1d not define the translation direction experimenta11y, but he had

predicted it as [110J fram a consideration of the atomic arrangement. He

exp1ained the un1ike deformation behaviour of the close1y related chalcopyrite

and spha1erite 1attices to be due to impurities in the spha1erite which caused

it to deform by secondary twinning.

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Pyrrhotite was broken without showing any sign of plastic deformation

when loads of 44,000 and 49,200 lbs. were applied parallel to the basal

planes; or when the basal planes were at 450 to the load axis for 12 and 27

minutes respectively. Pyrrhotite apparent1y deformed by gliding, when two

specimens were set in the tube in such a way that a specimen having basal

planes inclined at 450 to the axis of the load layon a specimen with basal

planes parallel to the load, and both were cornpressed under a load of 54,000

lbs. for 10 minutes. However, the experiment failed to give critical results.

Newhouse and Flaherty (1930) deformed a massive ore containing a large

percentage of chalcopyrite, some sphalerite and a little pyrite, at a rate of

0.03 inches per minute, modifying the apparatus used by Adams (1910).

Chalcopyrite was found to flow and sorne crystals were elongated normal to the

deforming pressure, apparently developing a preferred orientation. Many

small fractures were present as weIl. The sphalerite was fractured; and the

pyrite crysta1s were fractured into thin plates which were elongated in an

~n echelon fashion.

Osborne and Adams (1931) pub1ished three experiments on galena and

pyrrhotite which were carried out in 1912. The specimen was tight1y fitted

into a nickel steel tube of 0.81 inches in diameter and compressed in a

testing machine. Galena was subjected to a maximum pressure of 97,500

p.s.i. for 1 hour and 35 minutes and pyrrhotite to 192,000 p.s.i. for 2 hours

and 35 minutes, both at roorn temperature. The galena was medium·grained

having gneissic texture and was cut with its gneissosity paraI leI to the

cylinder axis. After deformation, galena lost its gneissosity and became

massive. Also, galena showed flowage by g1iding and twinning. The grain

size was found to have decreased considerably. Pyrrhotite was an

equigranular aggregate which on deformation was fractured, the grains showing

., 121

marginal brecciation.

Chervyakovskii (1952) performed experiments on pyrite, chalcopy-

rite and sphalerite to study deformation and recrystallization phenomena.

When the minerais were pressed under loads up to 30 tons/cm2 X-ray asterism*

appeared in Laue diagrams indicating easiest deformation in sphalerite and

resistance to deformation in pyrite. When the deformed sulfides were

tempered in vacuo at 5000 C. for 85 hours, asterism disappeared in sphalerite

.,and was distinctly less intense in chalcopyrite, while dis crete recrystal

lization reflection spots developed.

Robertson (1955) deformed a cylindrical pyrite specimen at room

temperature until it ruptured under a hydrostatic pressure 500 kg/cm2 and

found it to fail with double wedge shearing surfaces making an angle of 320

with the axis. The rupture strength was 5,070 kg/cm2 under compression.

Soles (1959) showed that chalcocite, digenite and bornite can be made

to flow into openings under differential pressure at 5500 C. in an excess

sulfur envirQnment. Chalcocite and digenite flowed around a piston showing

flow lines without fracturing. In a low sulfur environment, chalcocite

behaved as a brittle substance and showed no sign of flow texture. The

chalcocite was recrystallized in both environments, leaving no trace of

flow texture.

*When a metal or an alloy is plastically deformed, the crystal lattice

of each grain is strained so that elongated spots known as 'asterism' appear

in certain directions in Laue photographs. The deformed metal or alloy

upon annealing, or tempering results in strain-free grains, thus

recrystallizing. The recrystallized grains give rise to sharp Laue spots

(Hume-Rothery and Raynor, 1954, p.299).

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Davies (1965 a) annealed sulfides under differential pressures. He

showed the relationship between hardness and ease of plastic deformation;

chalcocite, bornite, and galena with hardness of 3 or less flowed readily

whi1e chalcopyrite and pyrrhotite with hardness 3.5 or greater were more

resistant to plastic deformation. Cha1cocite f10wed at 4190C. and above,

under a confining pressure of 8,000 p.s.i. Moreover, there was a marked

increase in mobi1ity above 5630C. It showed rapid recrysta11ization and grain

growth above 467oC. and no characteristic textures were preserved. The

recrysta11ization and grain growth were ascribed to the inversion of

hexagonal cha1cocite to a face-centered cubic po1ymorph. Bornite and ga1ena

were readi1y mobile at 640oC. under a confining pressure of 7,500 p.s.i.,

whi1e chalcopyrite and pyrrhotite were fractured under the same conditions.

Flow structure was preserved in ga1ena.

Roberts (1965), using Davies' (1965a) method, produced f10wage in

pyrrhotite at 824°C. and above under a confining pressure of 16,000 p.s.i.,

and at 666oC. and 23,000 p.s.i. Under the latter conditions pyrrhotite showed

1ess fracturing with prominent flow. It was recrystallized, but twin lamellae

were observed.

Davies (1965 b) verified his first results (1965 a) on pyrrhotite

and chalcopyrite and showed that they flowed readi1y under higher differential

pressures. Pyrrhotite flowed plastically with notable fracturing. Chalcopy

rite recrystal1ized leaving no trace of flow textures. Davies performed a

series of experiments on single crystals of galena at selected temperatures

and confining pressures and showed that the amount of movement was controlled

by the above two factors. He also showed the relation between hardness and

ease of plastic deformation of several sulfides and arranged them in a table

according to increasing ease of plastic deformation as:

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Pyrite, Arsenopyrite

Pyrrhotite

Chalcopyrite

Galena (single crystal - cube face perpendicu1ar to hole in mu11ite tube),

mo1ybdenite1[(OOOl) face perpendicu1ar to ho1e in mullite tube~

Chalcocite

Ga1ena (compressea powder), bornite.

M01ybdenite [(0001) face para11el to hole in mu1lite tube]

P01ymorphism in chalcopyrite:

Buerger and Buerger (1934) were the first to establish the

existence of two forms of chalcopyrite (low and high polymorphs) by a

thermal and X-ray study. The 10w-chalcopyrite is an ordered structure,

which on heating changes into a disordered structure (high-chalcopyrite).

Buerger (1945) theoretical1y demonstrated that an inversion from

a high to a low form, with fal1ing temperature, results in twins, which he

ca1led transformation twins. The low-temperature form has a symmetry which

is a sub-group of the symmetry of the high-temperature form. In 1951, he

c1assified this type of inversion, based on structural and thermodynamic

considerations, as displacive transformation,. which proceeds with a very high

speed.

Cheriton (1952) determined the critical temperature of disordering

for natural chalcopyrite as 5800 ± 200C., by means of a high-temperature

X-ray camera. He concluded that the order-disorder transformation in

chalcopyrite off ers no possibility as a direct geological thermometer in

sulfide deposits, since the rate of ordering is sufficiently rapid to

maintain equilibrium ev en in the most rapidly cooled sulfide deposit.

Hiller and Probsthain (1956) found,that the low-to-high temperature

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o transfonmation of chalcopyrite occurs at 550 C., by X-ray diffraction and

thenmal studies. The sulfur content decreases with increasing temperature.

The chalcopyrite at 7200 C. has a fonmula CU17+xF~~7+xS32(x=0.6) and has a

cubic structure even at room temperature.

Kullerud (1956) found that the inversion temperature depends upon

the composition of chalcopyrite.

Donnay and Kullerud (1958) obtained cubic, high temperature

chalcopyrite in the laboratory in the fonm of small single crystals, when a

sample of pure CuFeS2 was held at 6000 C. over a period of 21 months and then

quenched in water.

Frueh (1958) had shown that when certain mineraIs transfonm from a

high to a low temperature fonm of symmetry, nucleation and growth of the

ordered fonm result as domains and these will fonm with aefinitely related

orientations. When the domains bear a rational symmetrical relation to each

other, they are referred to as transfonmation twins (Buerger, 1945). In

chalcopyrite the domains will not fit perfectly together with their axes

parallel and perpendicular, because of the dimensional difference in the

sulfur frame work. In addition, there will be a small angular difference

along the c - axis. He stated that it might be difficult, if not impossible,

to distinguish growth twins from the domain structure brought about by

inversion. Frueh has shawn that the presence of the domains can be easily

recognized on X-ray diffraction records of specimens of high-temperature

history. However, he warned that the presence of domains should be

considered as evidence only and not proof of an earlier minimum temperature

(5500 C. and above in the case of chalcopyrite).

Yund and Kul1erud (1961) found the inversion to take place at

5470 + SoC. in synthetic chalcopyrite containing the maximum amount of sulfur

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at this temperature. ,

Budko and Kulagov (1963) reported the existence of a natural cubic

modification of chalcopyrite in Noril'sk deposit, U.S.S.R. They regarded the

presence of Zn in the lattice of cubic chalcopyrite as one of the possible

reasons for the survival of cubic symmetry at low temperatures.

Kullerud et al. (1965) determined, by differential thermal analysis,

that the inversion temperature decreased markedly with increasing pressure.

The negative slope of the inversion is on the average almost 40 C/kb, and

appeared to be as low as 4000 C. at 40 kbs.

PENDALA - EXPERIMENTAL DEFORMATION OF SULFIDE...

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