The Sudbury Ores: fheir Minerology eind Origin by J. E.HAWTEY Mil.l,er Memorial ResearchProfess or D epartmentof Geologi.calSciences Queen'sUnivers'ity, Kingston, Canad.a MineralogicalAssociction of Cqnqdq 1962 PntNmo gv Uxrvnnsrtv or TonoNro Pnsss Tononro, CaNane Fusl-rssrn sv MTNeRALocIcALAssocIATroN or Caxaoe Aoonsss ALL coMMuNIcATroNsro Socnrr.n'nv, Mrsrnanocrcer- Assocretrorq or Canaoe. 300 Lesnrroi{ Sr., OrrAwA PREFACE In this volume the writer has attempted to bring together the results of some thirty years of part-time research on various aspects of the great Sudbury ore deposits, carried out in association with several generations of his students whose names, listed below, are unfortunately too numerous to include as co-authors. Although they may thus appear to be "silent partners" in the undertaking, specific references to their individual con- tributions, which have been very real, will be found throughout the paper. As every teacher directing research soon realizes, the part played by his students is an invaluable one, not only by virtue of their discovery of new facts, but also by the clarifying influence of prolonged discussions, the recognition and elimination of woolly thinking and faulty hypotheses, and by the many fruitful suggestions which inevitably emerge to be tested by further study or experiment. The volume is divided into three parts, the reasons for which will become apparent. Throughout most of the investigation the mineralogical and chemical features of the ores were the main concern. The fortunate appointment of Dr. R. L. Stanton as a post-doctorate National Research Council Fellow allowed a fairly complete review of this phase of the work in 1957--8.The results of this are given largely in Part II under the joint authorship of Hawley and Stanton. In this section the various classifi- cations of the ores and their relations to the rocks in which they are found are considered, the descriptive mineralogy of the ores is detailed and illustrated, and the distribution of metals and minerals throughout the field is indicated. Such studies, however, have serious limitations when one comes to their interpretation unless there is available a well documented and authenticated geological succession of events into which they can be integrated. Probably only those familiar with the region are aware of the confused state of the published geological literature of Sudbury and the many unrefuted ideas which have either been discarded for some years or seriously questioned by field geologists. It was thus imperative that the geological problems existing in the area be reviewed to establish as clearly as possible the premises on which a theory of origin of the ores could be based. This has been particularly aided by recent advances in dating techniques, by further detailed mapping by the Ontario Depart- ment of Mines, by a very significant paper on the Frood-Stobie deposit and two Guide Books on the area, and to some extent by certain thesis \/l PREFACE studies, Part I is accordingly devoted chiefly to a consideration of the geological problems and premises to portray the geological setting. Part II is a factual study of the ores and minerals as noted. Part III is the writer's interpretation of the data presented. The latter begins with a summary of the history of events leading to and following the deposition of the ores. This has given rise to a dual classification of the processes involved-those which are truly magmatic and those which simply represent very minor post-magmatic ore effects produced in their long subsequent Precambrian history. The evidence for both is considered in some detail. In such a contribution as this it naturally falls to the writer to assume full responsibility for the ideas advanced and especially for the appraisal of the geological history. The contributions of his co-workers and in fact of all who have written at one time or another on these outstanding deposits are however acknowledged as forming the foundation on which the final conclusions are based. RESEARCH CONTRIBUTORS As stu.d,entsG. A. Harcourt 1932-33 H. F. Zurbrigg 1932-33 G. L. Colgrove 1939-40 A. M. Clarke 194546 D. F. Hewitt 1946-47 V. A. Haw 194748 C. L. Lewis 1949-50 Y. Rimsaite 1950-53 W. O. J. GroeneveldMeijer 1953-54 E. C. Speers(d,ecaased') 1954-56 R. M. Ginn 1955-56 J. F. Sadler 1957-58 Ian Nichol 1957-58 A. Y. Smith 1959-60 A. J. Naldrett 1960-61 Others Dr. R. L. Stanton Dr. C. E. Michener Dr. A. R. Graham Queen's[Jnhters'ity J. E. Hawlnv Sebtember1961 CONTENTS Panr I-TuB Gnor,ocrcar,Srmruc . I A. txtnonucrloN AND ACKNoWLEDGEMENTS I B. cBor.ocrcAr- PRoBLEMSAND PREMISES 3 1. crupnar, STATEMENT 3 2. rEanunBs oursIDE TrrE NIcKELIRRUPTIVE 8 (a) Stratigraphy and Intrusives 8 (b) The Granite Problem I (c) The Sudbury Breccias t4 3.FEATURES WITHIN THE BASIN 18 4. THE NICITfi'L IRRUPTIVE 2L o. POST-IIURONIAN AND LATE PRECAMBRIAN FEATURES 27 Penr II-TuB Facts: Tno Onns, THErR MrNEneLs, Msralos aNo DrstnreurroN (by J. E. Hawley and R. L. Stanton) 30 A. THtr ORE DEPOSITS 30 1. CLASSIFICATION oF THE oRE DEPOSITS 30 2. ptrvsrcal rYPES 32 (o) Disseminated Ores 32 (D) Massive Ores 33 (c) Immiscible-Silicate-SulphideOre 34 (d) Breccia Ores 35 (e) Vein and Stringer Ores 37 3. cBxgtrc cLASSIFIcATIoNS 38 B. THE MINERALS (DESCR IPTIvE MINERALOGY) 4l 1. uBtar-r,rc MINERALS 4+ (o) Major Metallic Minerals 4+ Pyrrhotite 44 Pentlandite 50 (i) Properties and composition 50 (ii) Cell edge of pentlandite oo (iii) Mode of occurrence . oo Chalcopyrite , . 59 Cubanite 62 vl1t CONTENTS (b) Minor Metallic Minerals 64 Magnetite 64 Ilmenite and Intergrowths with Magnetite 65 Pyrite 66 (i) Earlv pyrite 67 (ii) Reaction pyrite 67 (iii) Hypogene replacement pyrite 69 (iv) Pink nickeloan pyrite 70 (v) Late types of pyrite, hypogene or supergene(?) 7I Nickel-Arsenic-bearing Minerals: Gersdorffite, Niccolite, Maucherite 74 (i) Gersdorffite 75 (ii) Niccolite 78 (iii) Maucherite 81 Heazlewoodite (?) 82 Bornite 83 Valleriite 85 Sphalerite 86 Stannite 87 Violarite 88 Marcasite 89 Millerite 91 Hematite 92 (c) Minerals of the Precious Metals and their Associates 92 Sperrylite 93 Palladium Bisrnuthides: Michenerite. Froodite and Mineral C 94 (i) Michenerite 94 (ii) Froodite 95 (iii) Mineral C 95 Native Gold (Electrum) 96 Native Silver 97 Hessite 98 Mineral B-Schapbachite (?) 98 Galena 99 Parkerite 101 Tetradymite r02 Native Bismuth 103 Mineral A (Bismuthinite ?) t04 (d) Mineral SpeciesReported but not Confirmed t04 Chalcocite 104 Molybdenite 104 CONTENTS 1X Tetrahedrite 104 Smaltite t04 Danaite 105 Native Copper 105 Graphite 105 Cassiterite 105 2. Nolc-I,rprallrc MTNERALS 105 (a) Gangue Minerals, Inclusions and Products of Wall Rock Alteration 105 Quartz r07 Carbonates 109 Biotite 109 Amphiboles 110 Garnets 111 Pyroxenes 111 Chlorite 111 (D) SecondarySupergene Minerals (non-metallic) 111 c. RELATroNsrrrps oF oRE MTNERALSTo RocK FoRMTNG MTNERALS 112 D. DISTRIBUTION OF METALS AND MINERALS IN THE ORES 115 l. coppon-NrcKEl-rRoN AND Tr{ErR MTNERAL RATros 116 2. cosar,t AND sELENTuM 119 (o) Cobalt 119 (6) Selenium LzL 3. rnp PREcrous METALs . I22 (o) The Platinum Metals t22 (b) Gold and Silver t27 4, lEAl, ZINC, TIN, BISMUTH, ANTIMoNv AND TELLURIUM t28 Panr Ill-ImrpnpnorarroNs: TnB Hlsronv aNo OnrcrN or Tns Suosunv Onrs 146 A. HISTORY OF EVENTS AND CLASSIFICATION OF PROCESSES IN- voLvED rN FoRMATToNoF THE ones (suruuRnv) 146 1. srcnrprcaNT pRE-oREEvENTs .. I47 2. rNrnusroN oF sULpHIDE-BEARTNGrRRUprrvE AND FoRMA- TroN oF MAGMATTcoRES 148 3. posr-lrecMATrc oRE EFFEcrs .. 150 (o) Hypogene Alterations and Local Remobilization by Post-Ore Granite 150 CONTENTS (b) "Secondary Hvdrothermal" Mineralization and Altera- tions 150 (c) Remobilization by Keweenawan Trap and . Diabase Dykes 151 (d) SupergeneAlterations 151 B. THE MAGMATIC ORES 151 1. BvrorNcs oF oRES FoRMEDIN sITU L52 (o) Disseminated Ore in Norite and Quartz Diorite 1"52 (b) DisseminatedSilicates in Sulphide r54 2. svrrBxco oF TNJECTEDoRES 156 3. ruBonptrcAl- CONSIDERATIoNSAND COMPARISONS .. 160 4. BvrosNcr oF THE TExTURES AND PARAGENESIS OF TIIE MAGMATIC ORES 163 (o) The Early Minerals 165 (b) The Major Minerals 169 Pyrrhotite 169 Pentlandite Intergrowths t70 Chalcopyrite and Intergrowths L76 Sphalerite (Sphalerite-Stannite) 178 (c) The Late Minerals-Cu-Ni-1inerals-Cu-Ni-As"Bi-Te-Pb and Precious Metals 179 5. BvrnoNcB oF TrrE DrsrRIBUTroN oF METALSAND zoNING 181 C. POST.MAGMATIC ORE EFFECTS 188 L. gvpocrNE ALTERATToNS AND LOCAL REMOBILIZATION BY POST-ORE GRANITE 188 (o) Pseudo-eutectic Intergrowths of Nickel Arsenides and Sulphides 188 (b) RemobilizedPentlandite-Pyrite Breccia Ore 190 2. "sECoNoARy rryDRorHERMAL" MINERALTzATIoN AND ALTERATION 191 3. r-ocer, REMoBrLrzATroNEFFEcrs NEAR KEwEENAwAN DYKEs t92 4. suppncoNE ALTERATIoNS 193 D. STIMMARY AND CONCLUSIONS 196 RerrnrlqcBs 202 TABTESAND I!.LUSTRATIONS TABLES 1, Tentative Table of Precambrian Events and Formations Sudbury District o 2. Minerals in the Sudbury Ores +l 3. Cobalt and Nickel Content of Specially Purified Pyrrhotite and Pentlandite 47 4. Nickel, Cobalt and Silver Content of Pyrrhotite in Sudbury Deposits . 49 o. ChemicalAnalyses of Sudbury Pentlandite. 51 6. Nickel, Cobalt and Ni,/Co Ratiosin Sudbury Pentlandites(after Naldrett) 52 n Cobalt and Nickel in Falconbridgeand East Mine Pentlandites 53 8. Analysesof Sudbury Chalcopyrite 60 o Partial Analysesof Sudbury Pyrites. 68 10.Partial Analyses of Gersdorffite /o 11.Partial Analvses of Marcasite ol 1' Qualitative SpectrographicAnalyses of Galena 101 13.Copper-Nickeland Mineral Ratios ,. 116 14.Cobalt-NickelContent of CommonSudbury Ore Minerals 119 15.Seleniumcontent of SudburySulphide Minerals . I2I 16.Approximate Amounts and Ratios of Platinum Metals in Common Ore Minerals of Sudburv 124 17.Platinum Metals in Minerals and Ore in an Offset Deposit, Sudbury 125 18.Comparison of Ratios: Platinum Metals in Magmatic Sulphide Ores with Production from Sudbury L26 19.Silver Content of Sudbury Sulphides L27 20.Schematic Presentation of Crystallization Historl' of the Sudbury Irruptive and Associated Magmatic Ores t64 2t.