THE CASSITERITE-SULPHIDE DEPOSITS

OF WESTERN TASMANIA

oy

DAVID IM~ GROVES t B. Sc. (Hons).

(University of Tasmania)

A thesis submitted in partial fulfilment of the

re~uirements for the degree of

Doctor of Philosophy

mnVERSITY OF TASMANIA

HOBART

October 1968

This thesis contains no material which has been accepted

for the award of any other degree or diploma in any

university and to the best of my knowledge and belief

contains no copy or paraphrase of material previously

published or written by another person except where due,

reference is made in the text of the thesis.

DAVID IAN GROVES

University of Tasmania

Hobart

October 1968

TABLE OF CONTENTS

ABSTRACTACKNOWLEDGMENTS

INTRODUCTIONGEOLOGICAL HISTORY

INTRODUCTIONPROTEROZOICCAMBRIANORDOVICIANSILURIAN-DEVONIANDEVONIANPOST-LATE DEVONIAN

THE CASSITERITE-SULPHIDE DEPOSITSMT. BISCHOFF TIN MINEMt. Bischoff SequenceWaratah and Arthur River Sequences and Associated

Igneous RocksProterozoic-Cambrian_QontactStructure of_P~ot~rozoic and Cambrian Sequences

. Devonian Igneous RocksMineralization

(a) Tin Mineralization(b) Lead-Zinc-Silver Mineralization(c) Oxidation of the Orebodies

Post-mineralization ActivityCLEVELAND TIN MIIJECambrian Stratigraphy and Igneous RocksStructureDevonian Igneous RocksMineralization

(a) Tin Mineralization(b) Lead-Zinc-Silver Mineralization(c) Copper Mineralization

~. RENISON BELL TIN MINEDalcoath Quartzite and Renison Bell Shale

Page No.

14 ' .,

6999

1215161719212123

26293134373739414142424445464646474849

"Red Rock"Crimson Creek FormationDundas GroupCambrian Igneous RocksStructureDevonian Igneous RocksMineralization

(a) Tin Mineralization(b) Lead-Zinc-Silver 1lineralization(c) Copper Mineralization

'Post-mineralization Igneous RocksOTHER CASSITERITE-SULPHIDE DEPOSITSRazorback-Grand PrizeMt. LindsaySUMMARY

MINERAGRAPHY OF THE CASSITERITE-SULPHIDEDEPOSITS

INTRODUCTIONSYSTEMATIC MINERAL DESCRIPTIONSWolframiteCassiteriteH::.ematiteArsenopyritePyriteMarcasitePyrrhotiteChalcopyriteSphaleriteSta=iteTetrahedriteJamesoniteNative Bismutl!GalenaBoulangeritePyrargyrite

Page No.505252535456

57575960

60

62

62

6364

67

67

707070717172

7475

777880

82

82

83

83

83

83

Canfieldite

Franck_ei te

Vallerii te

Gold

Mar;netite

Solid So],ution

Page No.

84848485

85

85~NON-SULPHIDE COMPONENTS OF CASSITD~ITE-

SULPHIDE ORES 88

MT. BISCHOFF 88

Replacement Deposit 88

Fissure Veins 95

/ REnSON BELL 95CLEVELAlifD 96

GEOCHEMICAL STUDIES OF THE CASSITERITE­SULPHIDE ORES AN~ C01~ARISON WITH OTHERORES IN I'IESTERL'f 'l'AS1'fANIA 98

INTRODUCTION 98

COBALT AIm NICKEL IN IRON JULPHIDES 99

MINOR ELEMENTS IN SPHALERITE 101

Cadmium in Sphalerite 101

(a) Previous Investigations 101

(b) This Investigation 103

Manganese in Sphalerite 106

(a) Previous Investigations 106

(b) This Investigation 107

SELENIu1~ IN SULPHIDES 108

Previous Investigations 108

This Investigation 111

SU1~flARY 113

GEOBAR01ffiTRY, GEOTHERM01ffiTRY AJID THEPROBL~1 OF ZONING IN THE CASSITERITE-SULPHIDE DEPOSITS 115

GEOBARmffiTRY 115

V Geological Considerations 115

(a) Mt. Bischoff 115

(b) Cleveland 116

J (c) Renison Bell 116

Fluid Inclusion DataGEOTHERMOMETRY AND ZONINGIntroductionFluid Inclusion Studies at Mt. Bischoff

(a) Nature of the I!lClusions(b) Salinity Data(c) Temperature Data(d) Alkali Ratio Data(e) Summary and Conclusions

Temperature Indications from Sulphide Systems(a) The Fe-S System(b) The Fe-Zn-S System(c) The Fe-As-S System(d) Pyrite Geothermometer(e) Melting Points and Solid Solutions

Sulphur IsotopesTrace Elements

THE GRANITIC ROCKS AS30CIATED WITHCASSITERITE-SULPHIDE MI1illRAIIZATION

INTRODUCTIONSID!IlVIiUW OF STRUCTURE, PETROGRAPHY AND METAMORPHISMMeredith GraniteHeemskirk Granite

v Pine HillMt. BischoffRelationship between the Granitic RocksGEOCHEMISTRY OF GRANITIC ROCKSMajor Elements·Trace Elements

(a) Rubidium(b) Strontium-Barium( 0) Thorium-Uranium(d) L:i thium(e) Copper, Zinc and Lead(f) Tin

Page No.118121121123123124125130

133135

135140

145147148149151

155155158158160162164164166166172

173174176177178179

Page No.

181

181

181

185188188

190

193

J~TERATION OF GRANITIC ROCKSPetrography of the Rocks

(a) Mt. Bischoff,/ (b) Pine Hill

Geochemistry of Alteration(a) Mt. Bischoff

,/ (b) Pine HillSUWKARY AND CONCLUSIONS

APPE~IDIX A1. PETROGRAPHY OF GRANITIC ROCKSASSOCIATED WITH TIN MINBRALIZATION

MEREDITH GRANITEEven-grained AdamellitePorphyritic_AdamelliteSodaclase MicrograniteAlaskite AplitePorphyriesPegmatiteGreisenMT • BISCHOFFQuartz-Feldspar Porphyry

/ PINE HILLSodaclase AdamellitesSodaclase-Adamellite Porphyries,Quartz-Feldspar PorphyriesPegmatitesAPPENDIX A2. ANALYSIS o:e STRUCTURAL STATE AIIID

COMPOSITION OF FELDSPARSPOTASH FELDSPARSPLAGIOCLASEAPPERTIIX A3. PETROGRAPHY OF HORNFELSES FROM THE

PINE HILL CONTACT METMiORPHIC AUREOLEAPPE~IDIX A4. ANALYSIS OF GRANITIC ,~CKS AND

TOURMALINES

~ SMHPLE COLLECTIONSM;~LE PREPAP~TION

I ANALYSIS OF MAJOR ELEMENTSl TRACE ELEMENT ANALYSIS

207

207207

209

212

213214

215215

215215

217

217

219220

221

222

222

224

225

229229229

230234

../RESULTSAPPENDIX B1. ANALYSIS OF Cd AND Mn IN SPHALERITESAPPElillrx B2. ANALYSIS OF Se IN SULPHIDES:PREPARATIONANALYSISAPPENDIX C1. DETERMINATION OF IRON CONfENT OF

SPHALERITEAPPENDIX C2. PREPARATION AND ANALYSIS OF

PYRRHOTITE FROM CASSITERITE-SULPHIDEORE BODIES

APPE~mIX C3. SULPHUR ISOTOPE STUDIESAPpmmIX ])1. CRITERIA OF PARAGENESISSUCCESSIVE DEPOSITIONCross Cutting Relations

(a) Veinlets(b) Mineral Interfaces

InclusionsSDWLTANEOUS DEPOSITIONExsolution IntergrowthsInterlayeringPartial IdiomorphismEutectic TexturesAPPLICATION TO THIS INVESTIGATIONAPPElillIX D2. MODAL ANALYSIS OF ORES AND GRANITESMODAL ANALYSIS OF ORBSMODAL ANALYSIS OF GlVUJITBSAPPE~vIX D3. CHm~ICAL ANAIXSIS OF CARBONATE ROCKS

REFERENCES

Page No •236237241241241

245

248252253253253253254254255255255256256256258258260261263

LIST OF FIGURES

*

9

Precedingnumberedpage.

8Locality Map - TasmaniaGeological sketch map and localitymap of western Tasmania, afterSolomon (1965). .Geological map, Waratah-Mt. Meredith­Renison Bell area, compiled from varioussources.

Figure 1.Figure 2.

Figure 3.

1122

23

29

23

34

31

48

48

44

Figure 6.Figure 7.Figure

Figure

FigureFigure

Figure 4.

Figure 5.

Geological history of western Tasmania. 10Major structural elements, westernTasmania, after Solomon (1965).Geology - Waratah area.

Locality map, Mt. Bischoff.8. Geological map of ~t. Bischoff area,

a£ter Groves and Solomon (1964).Figure 9. Cross sections through Bischoff

Anticlinorium in the Waratah District. 2310. Geology - Greisen-Pig Flat, Mt. Bischoff.2511. Mt. Bischoff - cross section F. 2512. Detailed geological plan of sluiced

area, Don Hill, Mt, Bischoff.Figure 13. Diagrammatic representation of folding,

Don Hill, Mt. Bischoff.Figure 14. Structural elements - Nt. Bischoff.

Equal angle-lower hemisphere projection. 31Figure 15. Joints and lodes, Waratah area. Equal

angle-lower hemisphere projection.Figure 15A.A typical cross section through the

Cleveland Mine, from Cox (1968).Figure 16. Geological map of Renison Bell area,

compiled from various sources.Figure 17. Cross sections, Renison Bell, compiled

from various sources.Figure 18. Geology - Battery Workings, Renison

Bell. Geology by P.A. Hill andM. Solomon, 1961. 54

* In pocket at back of thesis

Figure 21 •Figure 22.

Figure 23.

Figure 24.

Figure 25.

Figure 26.

Figure 27.

Figure 19. Structural elements - Renison Bell. 54Equal angle-lower hemisphere projection,from P.A. Hill and M. Solomon, 1961.

Figure 20. Composition and structural type ofpyrrhotite, cassiterite-sulphide deposits,west coast, Tasmania. 76Exsolution textures, Cleveland. 86

Composition of dolomite and secondarycarbDnate, Mt. Bischoff and Renison Bell. 92

Distribution of Co and Ni in Tasmanianpyrites. 99Distribution of Cd and ~Hn in sphalerites,western Tasmania. 103Plot of average weight percent Fe and Cdin sphalerites, western Tasmania. 104Distribution of Se in sulphides, Tasmania. 111

Lines of equal density for aqueous 119solution and CO in terms of pressure andtemperature, fr6m data given by Klevstovand Lerr@lein (1959) and Kennedy (1954).

Figure 28. Frequency distribution of melting point 124determinations on inclusions carryingaqueous solutions, combined with salinityestimates expressed as weight percent NaCI.

Figure 29. Frequency distribution of filling 125temperatures of inclusions in fluorite andquartz from Mt. Bischoff.

Figure 30. Plot of salinity v. temperature of formationusing average values of primary inclusionsand values for individual primary inclusionsfor which both parameters were measured. 129

Figure 31. Composition of pyrrhotite and sphaleritein equilibrium with iron, pyrrhotite orpyrite as a function of fugacity ofsulphur and temperature. From Toulminand Barton (1964) and Barton and Toulmin(1966). 137

Figure 32. The composition of sphalerite inequilibrium with metallic iron and ironsulphide phases. Diagram from B00rman(1967). 140

Figure 33. Variation of parameters of possible 145thermometric significance with spatialposition at Mt. Bischoff and a comparisonwith the same parameters at Renison Belland Cleveland.

Figure 34. Distribution of Co and Ni in iron 152sUlphides, Mt. Bischoff and RenisonBell.

Figure 35. Relationship between Co and Ni in iron 152sulphides, Mt. Bischoff and RenisonBell.

158

159

170

169

167

172

169

176

188

Figure 38.

Figure 39.

Figure 40.

Figure 41.

Figure 42.

Figure 43.

Figure 37.

Figure 36. Properties of potash feldspar ingranitic rocks, Meredith, Mt. Bischoffand Pine Hill.Properties of plagioclase from MeredithGranite and Pine Hill.Plot of molecular quotients (x 100) ofK20 and Na20 and of FeO (total) againstMgO for granitic rocks, western Tasmania.Variation diagram (niggli values) ofgranitic rocks, western Tasmania.Generalized chemical trends of graniticrocks, western Tasmania.Plot of normative Or-Ab-SiO? ratios ofthe granitic rocks of weste~n Tasmania.Trace element relationships, graniticrocks, western Tasmania.Histograms showing frequency of Th/Uratios and plot of Th/U v. K/Rb ingranitic rocks, western Tasmania.Composition of unaltered and alteredgranitic rocks, Mt. Bischoff and RenisonBell.

Figure 45. Location of analysed rocks, Meredith 229Granite, Heemskirk Granite, Pine Hilland Mt. Bischoff.

Fi[<;ure 44.

Figure 46. Comparison of uyrrhotite composition, 249Mt. Bischoff.

Plate 1 •

Plate 2.

Plate 3.

Plate 4.

Plate 5.

Plate 6.

Plate 7.

Plate 8.

Plate 9.

Plate 10.

Plate 11.

Plate 12.

Plate 13.

Plate 14.

Plate 15.

Plate 16.

LIST OF PLATESPrecedingnumberedpage.

Flexural fold in quartzite and shale,Mt. Bischoff sequence, Mt. Bischoff. 24Agglomerate, BettIs Track 3 miles southof Corinna Road. 24Flow banding in quartz-feldspar porphyry,White Face Dyke, Mt. Bischoff. 36

Small swirl in altered quartz-feldsparporphyry, White Face Dyke, Mt. Bischoff. 36

Amygdale containing quartz s~hcrulites

in Cambrian spilite, Arthur River. 36Amygdale containing quartz sph·Gruli·t>csin Cambrian spilite, Arthur River.Crossed nicols. 36Steeply dipping Tertiary gravels, sandsand silts, Don Hill, Nt. Bischoff. 41Tourmaline nodules in gabbro, Pine Hill. 41Clastic grains of microcline and quartzin graphic intergrowth in hornfels,Crimson Creek Formation, Pine Hill. 52Relic auto clastic texture in clasticgrain from hornfels, Crimson CreekFormation, Pine Hill. 52Clusters of cassiterite crystals in talcand sellaite matrix, replacementdeposit, Mt. Bischoff. 70Concentration of granular cassiteritein quartz,from arsenopyrite-rich ore,from No.2 HOTizon, Renison Bell. 70Zoned arsenopyrite crJTstals withdilational veinlets of pyrrhotite,fromNo. 1 .Horizon, Renison Bell. 71Arsenopyrite crystals replaced bypyrrhotite ,from No.1 Horizon, RenisonBelL 71Euhedral pyrite replaced by pyrrhotite,from No. 1 Horizon, Renison Bell. 72Granular mass of second generationpyrite (+ marcasite) from hypogenealteration of pyrrhotite. From replacementdeposit, Mt. Bischoff. 72

Plate 17. Recrystallization of second generationpyrite and segregation of pyrite andcarbonate, from replacement deposit,Mt. Bischoff. 73

Plate 18. ~ticro-botryoidal supergene pyrite andmarcasite forming around fracture inpyrrhotite, from replacement deposit,Mt. Bischoff. 73

Plate 19. Colloform supergene pyrite replacingpyrrhotite, from replacement deposit,Mt. Bischoff. 74

Plate 20. Elongate lamellae of monoclinic pyrrhotitein an hexagonal pyrrhotite host, fromreplacement deposit, Mt. Bischoff. 74

Plate 21. Stannite along a sphalerite grainboundary with other irregular blebsof stannite, from replacement deposit,Mt. Bischoff. 79

Plate 22. Sphalerite containing irregular blebs ofstannite replaced by fibrous jamesonite,from replacement deposit, Mt. Bischoff. 79

Plate 23. Jamesonite replacing second generationpyrite and carbonate, from replacementdeposit, Mt. Bischoff. 82

Plate 24. Large acicular jamesonite crystalreplacing second generation pyrite andcarbonate, from replacement deposit,Mt. Bischoff. 82

Plate 25. Zoned tourmaline crystals in largefluorite crystal,from contact of quartz­feldspar porphyry and dolomite, Mt.Bischoff. 88

Plate 26. Zoned tourmaline crystals included insphalerite, carbonate and sellaite,fromreplacement deposit, Mt. Bischoff. 88

Plate 27. Small idioblastic corundum crystalsincluded in serpentine and carbonate, fromreplacement deposit, Mt. Bischoff. 89

Plate 28. Idioblastic garnet crystals replaced bytalc and quartz, from replacementdeposit, Mt. Bischoff. 89

Plate 29. Chondrodite replaced by serpentine,fromreplacement deposit, Brown Face, Mt.Bischoff. 90

Plate 30. Complex twinning in chondrodite crystalssurrounded by serpentine, from replacementdeposit, Brown Face, Mt. Bischoff. 90

Plate 31. Columnar wollastonite rimmed by carbonatewith inclusions of tourmaline, fromreplacement deposit, Mt. Bischoff. 90

Plate 32. Columnar wollastonite replaced bypyrrhotite and talc, from replacementdeposit, Mt. Bischoff. 90

Plate 33. Sellaite replaced by fluorphlogopite,from replacement deposit, Mt. Bischoff. 91

Plate 34. Rosettes of muscovite, quartz andcarbonate against coarse sellaite withinclusions of zoned tourmaline, fromreplacement deposit, Mt. Bischoff. 91

Plate 35. Chlorite rims around pyrrhotite andserpentine, from replacement deposit,Mt. Bischoff. 94

Plate 36.

Plate 37.

Plate 38.

Plate 39.

Plate 40.

Plate 41.

Plate 42.

Plate 43 •.

Sheaves of dolomite surrounding adolomite-quartz nucleus, from replacementdeposit, Mt. Bischoff. 94Fine grained chert cut by veinlets ofquartz and chlorite and patches ofpyrrhotite, from Cleveland. 96Quartz-chlorite aggregates with massivesulphides, from Cleveland. 96Inclusions containing mainly liquid CO?with a bubble of CO2 and a small quantItyof aqueous solution, Happy Valley, Mt.Bischoff. 118Inclusion containing solid daughterminerals, probably halite and sylvite,Brown Face, Mt. Bischoff. 118Negative crystal in fluorite filled withaqueous solution and vapour bubble,Pig Flat, Mt.· Bischoff. 123

Partially necked inclusion in fluorite,Pig Flat, ~t. Bischoff. 123Inclusions occupying a planar surface influorite, Slaughteryard Face, Mt. Bischoff.

123Plate 44. Aqueous inclusions with high vapour

bUbble/liquid ratios in fluorite ,Fook I sLode, Waratah. 123

Plate 45. Anhedral quartz phenocryst in quartz­tourmaline groundmass~from alteredporphyry, Pine Hill, rtenison Bell. 181

Plate 46. Carbonate and sphalerite replacing anorthoclase phenocryst, White Face Dyke,Mt. Bischoff. 181

Plate 47. Replacement of orthoclase phenocrystby carbonate, quartz and topaz, south endof White Face Dyke, Mt. Bischoff. 182

Plate 48. MUltiple cassiterite-topaz-quartzaggregate replacing an orthoclase phenocrystVfuite Face Dyke, Mt. Bischoff. 182

Plate 49. Radial aggregate of columnar topaz withinterstitial quartz in extensivelyaltered porphyry, White Face Dyke,Mt. Bischoff. 184

Plate 50. Euhedral zoned cassiterite with topazin extensively altered porphyry, WhiteFace Dyke, Mt. Bischoff. 184

Plate 51. Zoned plagioclase in adamellite, MeredithGranite. 207

Plate 52. Coarse string perthite in adamellite,Meredi th Grani te • 207

Plate 53. Graphic intergrowth of orthoclase andquartz in adamellite, Meredith Granite. 208

Plate 54. Contact of biotite-rich enclave withadamellite, Meredith Granite. 208

Plate 55. Orthoclase phenocryst in porphyry, WhiteFace Dyke, Mt. Bischoff. 215

Plate 56. Flow banding in porphyry, White Face Dyke,Mt. Bischoff. 215

Plate 57. Tourmaline associated with plagioclase,K-feldspar and quartz, ad~lellite, PineHilL 217

Plate 58. Coarse diopside crystals in carbonateand quartz matrix, calc-silicate hornfels,Gormanston Creek, 217

Plate 59. Skeletal garnet crystals and minordiopside in axinite, calc-silicatehornfels, Gormanston Creek. 226

Plate 60. Garnet with interstitial SUlphide,calc-silicate hornfels, Gormanston Creek. 226

LIST OF TABLES Precedingnumberedpage.

Table 1.

Table 2.

Analyses of sedimentary rocks of theMt. Bischoff sequence. 24Chemical analysis of post-mineralizationdyke-rock from Benison Bell and comparisonwith Jurassic chilled dolerite and Tertiarysaturated olivine basalt. 61

Table 3. Sulphide and oxide composition ofcassiterite-sulphide ores. 67

Table 4. Weight percentage of components incassiterite-sulphide ores, calculatedfrom modal analyses. 68

Table 5. Elemental composition (weight per cent)of sulphide phase of cassiterite-sulphideores calculated from modal analyses. 69

Table-6. Average Cd, Thill and Fe values insphalerites from western Tasmania. 103

Table 7. Filling temperatures and correctedtemperatures in fluorite and quartz,Mt. Bischoff. 127

Table 8. Alkali weight ratios of fluid inclusionfrom Mt. Bischoff and other occurrences. 131

Table 9. Homogenization temperatures forexsolution pairs (Edwards, 1954). 148

Table 10. Cobalt and nickel contents of ironsulphides from Mt. Bischoff and RenisonBell. 151

Table 11. Summary of isotopic dating of granites,western Tasmania. 155

Table 12. Average compositions of granitic rocksfrom meredith Granite, Heemskirk Granite,Pine Hill and Mt. Bis choff • 166

Table 13. Distribution of tin in biotites fromMeredith Granite and Heemskirk Granite. 180

Table 14. Partial analysis of topaz from Mt.Bischoff. 182

Table 15. Average compositions of unaltered andaltered granitic rocks, Mt. Bischoff andPine Hill. 188

Table 16. Modal analyses of even-grained rocks,Meredith Grani te • 208

Table 17. Modal analyses of sodaclase adamllitesfrom Pine Hill. 208

Table 32.

Table 31.

Table 33-.

Table 34-.

I

Table 18. Parameters of alkali feldspars in rocksfrom the Meredith Granite, Mt. Bischoffand Pine Hill. 223

Table 19. Optical parameters of plagioclases fromthe Meredith Granite and Pine HillComplex. 224

Table 20. Conditions of analysis of major elementsby X~ray fluorescence spectrography. 232

Table 21. Analysis of standard rocks with CO2 ,H20+ and H20- not determined independently.

233Table 22. Conditions of analysis of trace elements

by X-ray fluorescence spectrography. 234Table 23. Analysis of trace elements in standard

rocks using X-ray fluorescencespectrography. 236

Table 24. Major element analyses and trace elementanalyses of granitic rocks from theMeredith Granite. 236

Table 25. Niggli values and C.I.r.W. norms forgranitic rocks from the Meredith Granite. 236

Table 26. Major element and trace element analysesof porphyries from Mt. Bischoff. 236

Table 27. Major element and trace element analysesof granitic rocks from Pine Hill. 236

Table 28. Niggli values and C.I.P.W. norms forgranitic rocks from Mt. Bischoff andPine HilL 236

Table 29. Major element and trace elementanalyses of the Heemskirk Granite, fromBrooks and Compston (1965) and Blissett(1962). 236Niggli values and C.I.P.W. norms forgranitic rocks from the Heemskirk Granite.236Analyses of tourmalines from the MeredithGrani te" Mt. Bischoff and Pine Hill. 236

andCadmium/manganese analyses of Tasmaniansphalerites. 239Comparison of independent seleniumanalyses. 243Selenium analyses of sulphides fromwestern Tasmania. 244

Table 30.

Table 35. Mole per cent FeS determined fromunit cell edge of sphalerites (Cd andMn determined.) 246

Table 36.

Table 37.

Table 38.

Table 39.

Table 40.

Table 41.

Table 42.

Table 43.

Table 44.

Mole per cent FeS determined from unitcell edge of sphalerites (average Cd andMn values taken).Mole per cent FeS in sphalerites fromthe Magnet Mine (Edwards, 1960).Ranges and averages of weight per centFe in sphalerites from western Tasmania.Symmetry and composition of pyrrhotitescrushed in air.Symmetry and composition of pyrrhotitescrushed in shellite, from Mt. Bischoff,Renison Bell and Cleveland.J34S values for Mt. Bischoff, sulphidesanalysed by Dr. T.A. Rafter.J34S values for Rehison Bell.Replicate determinations on polishedsections 15-74 to 15-57 from No.1Horizon, Renison Bell.Precision of results expressed asvariance.

247

247

247

251

251

251

252

259

259Table 45. Modal analyses of cassiterite-sulphide

ores (volume per cent). 259Table 46. Percentage counting errors in the analysis

of carbonates. 261Table 47. Partial analyses of dolomites from Mt.

Bischoff and Renison Bell. 262Table 48. Partial analysis of carbonate rocks from

replacement ore-body and lode deposits,Waratah. 262

Table 49. Partial analysis of carbonate-rich lodefrom Renison Bell. 262

I

ABSTRACT

The cassiterite-sulphide deposits in Western Tasmania are stratiform

replacement deposits (Mt. Bischoff; Renison Bell; Cleveland; Mt. Lindsay),

fissure deposits with marg~nal replacement (Federal Lode, Renison Bell;

Razorback-Grand Prize), and fissure lodes (Mt. Bischoff), that consist

essentially of pyrrhotite with subordinate pyrite, arsenopyrite, chalcopyrite,

sphalerite and cassiterite. They are localized in dolomitic horizons of

Upper Proterozoic-Lower Cambrian age in faulted, complex anticlinal structures

These have been the loci for intrusion of cupolas and associated dyke

swarms of late Devonian granitic rocks, which have been extensively

topazized, tourmalinized and/or greisenized. The major and trace element

chemistry of these granitic rocks combined with isotopic dating indicates

that they probably represent the most highly fractionated portions of

penecontemporaneous, high-level, post-kinematic granitic batholiths

occurring throughout Western Tasmania. These granitic batholiths may

be interconnected at depth. The spatial association of the polyascendant

tin mineralization with these granitic rocks, and their associated pre­

joint tin mineralization, suggests that they are derived from a common

source.

Around the cassiterite-sulphide deposits are haloes of dispersed

Pb-Zn-Ag mineralization, which on the basis of field relationships is

considered to be related to the same granitic activity. A uniform

distribution of Co and Ni in Fe-sulphides, Cd in sphalerites, Se in

sulphides, and Mn in both the cassiterite-sulphide and Pb-Zn-Ag deposits

provides empirical support for a single metallogenic province covering

Western Tasmania in the late Devonian.

-2-

In the cassiterite~sulphidedeposits, cassiterite and wolframite have

generally crystallized before the earliest formed sulphides, which are pyrite

and arsenopyrite, followed by pyrrhotite. Chalcopyrite, sphalerite and

stannite were formed penecontemporaneously and were followed by tetrahedrite 1

jamesonite, bismuth and finally galena with associated canfieldite, frackeiite

boulangerite and pyrargyrite. At Mt. Bischoff pre-sulphide metasomatism

of dolomite at temperatures in excess of 4000 c resulted in formation of

tourmaline, quartz, wollastonite, chondrodite and garnet. These minerals

were subsequently replaced by sulphides and talc, fluorphlogopite, serpentine,

chlorite, Fe-Mn~g carbonates, fluorite and sellaite. Similar alteration

has occurred at Renison Bell and Cleveland but the pre-Sulphide phase is

limited to the formation of minor tourmaline, topaz and quartz.

A mineralogical and isotopic lateral zonation can be demonstrated at

Mt. Bischoff. The zonal and paragenetic sequences are essentially parallel.

Fluid inclusion studies demonstrate that the zoned sequence is partly a

function of declining temperature, with initial deposition of fluorite

up to 5800, decreasing to 2000 C in the marginal zone. It is probable that

the temperature, salinity and composition of the ore-forming fluids

were constantly changing during mineralization as an initially hot,

saline fluid was mixed with cooler, less saline meteoric and connate waters,

in conjunction with heat loss to the wall rocks. In general, compositional

changes in SUlphide systems within the zonal sequence are consistent with

cooling of the ore-forming fluid from temperatures as high as 7000 C to below

3000 C, with a sympathetic decline in fugacity of SUlphur and oxygen.

However some anomalies exist between interpretations based on the Fe-S and

Fe-Zn-S systems, and the Fe-As-S system. The other cassiterite-sulphide

-3-

deposits lack a well defined zonation with respect to both mineralogy and

isotopic composition of sulphur, but their initial deposition temperatures

are comparable or slightly lower than those at Mt. Bischoff. Ore

deposition was probably initiated by increasing alkalinity of the

ore-forming fluids caused by reaction with dolomitic host rocks.

-4­

ACKNOWLEDGMENTS

I am indebted to Drs. M. Solomon and J. van Moort for their

supervision, active co-operation and stimulating discussion during

this research. The assistance of Dr. Solomon and his research assistants,

Mrs. G. Sanders and Mr. S. Stevens in the time-consuming study of fluid

inclusions is gratefully acknowledged. The helpful discussions with

other staff members, Mr. M'.R. Banks, Dr. A. Spry and Dr. R. Varne is

acknowledged and advice and assist"lllce given by Mr. R. Ford 011 all

".spects of X-ray analysis was invaluable. I have also benefited from

discussions with colleagues at the University of Tasmania, particularly

Mr. D. Mc}',. Duncan who contributed valuable advice on feldspar mineralogy

and Mr,. G,. Loftus-Hills who collaborated in the investigation of some

trace elements in sulphides from West Tasmania.

I am also indebted to Mr. Symons, the Director of Mines, Mr. I.

Jennings and Mr,. J. Noldart of the Department of Mines, Tasmania for

active co-operation in all phases of this study and to Dr. Emyr Williams

for continued advice and encouragement. Invaluable assistance with

drafting was given by Mr. K. Kendall and his st~ff at the Department

of Mines and several chemical analyses were carried out at the

Department of Mines Assay Laboratory in Launceston under the supervision

of Mr. H. Wellington. Assistance with thin sections was freely given

by Mr. B. Cox and Mr. H. Peterson, and advice and assistance with

polishing procedures by Mr. M, Bowers of the Tasmanian Museum.

I am also grateful to Mines Exploration Pty. Ltd. and Mr. P.J.

Verwoerd, Renison Ltd. and Mr. R, Shakesby, and the Electrolytic

-5-

Zinc Co. and Mr. G.H. Griffiths, and Cl~veland Tin, for permission to

map and sample and for assistance in the field.

-6-

INTRODUCTION

This study of the cassiterite-sulphide deposits is part of a research

project on the geology and mineral resources of Western Tasmania that has

been supervised by Dr. M. Solomon. The research is partly a continuation,and re-examination of an investigation of the Waratah District by the

author for an honours B.Sc. in 1963.

The original scope of this thesis involved detailed investigation

of the cassiterite-sulphide ore-bodies, particularly at Renison Bell and

Mt. Bischoff. Difficulties arose with this programme based essentially

on the control of these mines by different companies, that have competing

exploration activities. As detailed mapping of the ore bodies and enclosing

rocks at Renison Bell and Cleveland was not allowed, the emphasis of the

research was centred on Mt. Bischoff, where censorship of informaticn

was less severe, and a comparison made with the other deposits, several

aspects of which were studied during this investigation. The main result

of these restrictions has been a more regional study, with particular

emphasis on the granitic rocks spatially associated with the tin deposits.

This t~esis cOntains a brief discussion of the regional geology

of the area enclosing the cassiterite-sulphide deposits and associated

granitic rocks. This is essential for an understanding of the regional

setting of the deposits and for estimation of limiting pressures during

mineralization. This discussion is primarily based on a regional

map which has been compiled from mapping carried out by the author at

intervals between 1962 and 1967, and by various officers of the Geological

Survey (Department of Mines, Tasmania) and Rio Tinto Mining Company.

-7-

The geological environment of the cassiterite-sulphide deposits is

described in detail. The section on Mt. Bischoff is based essentially

on work by the author, and the Renison Bell section on investigations

by Blissett (1962), Gilfillan (1965), Rubenach (1967), unpublished research

by Dr. M. Solomon and Prof.- P.A. Hill (Carlton University,Ottawa, Canada)

and detailed investigation of some aspects by the author. The section on

Cleveland is based on Cox and Glasson (1967) and on regional mapping by

the author.-

Detailed descriptions of the sUlphide ores and host-rock alteration

are presented and the geobarometry and geothermometry studied with

references to sphalerite and pyrrhotite compositions and fluid inclusion

studies in non-sulphide components. Geochemical studies of the ores have

been carried out by Mr.- G.- Loftus-Hills and the author,and the significance

of Cd and Mn in sphalerites and Ni, Co and Se in sulphides is briefly

discussed. A discussion of zoning at Mt. Bischoff is presented in terms

of the mineralogy, alteration, temperature and fugacity of sulphur and

oxygen,together with sulphur isotope studies by Drs. T.A. Rafter and

M. Solomon.

A geochemical study of the granitic rocks associated with the ore

deposits has been carried out and the relationships between spatially

separated occurrences is discussed. The distribution of tin in the

granitic rocks and its bearing on the tin mineralization is also

discussed.

The thesis is presented in two sections: (a) descriptions and

interpretations of the investigations described above, and (b) a series

of appendices in which details of methods of analysis are given, together

with tables of results.

-8-

Descriptive work which is not essential

to the main theme of the thesis, but on which the interpretation ofw~.-;/

geochemical work~is included in these appendices.

All specimen numbers referred to are those of the Geology Department,

University of Tasmania, unless otherwise stated.

o 10 20 30 ~c MILESL_ I : :

-BEULAH_DELORA/NE

_ ADAHSFIELD

CENTRAL

HIGHLANDS

ROUND- fir.

-LQRINNA

ULYERSTON,1£"'-'kO:,EUGENANA •

BURNIE

.fir. DARWIN

• 8ALrOVfl

o 20 40 60 KM.: , J ;

LOCALITY MAP -TASMANIA

Figure 1