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A Mineralogical Study of the Hemo-Ilmenite Ore from Lac Tio a Mineralogical Study of the Hemo—Ilmenite Ore

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A Mineralogical Study of the Hemo-Ilmenite Ore from Lac Tio a Mineralogical Study of the Hemo—Ilmenite Ore GM 35775 A MINERALOGICAL STUDY OF THE HEMO-ILMENITE ORE FROM LAC TIO A MINERALOGICAL STUDY OF THE HEMO—ILMENITE ORE FROM LAC TIO, QUEBEC by Michel Bergeron Ministère de l'Énergie et des Ressources Gouvernement du Québec Documentation Technique QUE: 1980 MAPS 0 5 No. QM: 36/1S Feb. 73 I A MINERALOGICAL STUDY OF HEMO-ILMENITE ORE FROM LAC TIO, OUEBEC ABSTRACT The Lac Tio orebody consista of a large deposit of massive hemo-ilmenite within andesine anorthosite rocks. The deposit has been mined continuously since 1951 by the Quebec Iron and Titanium Corporation. It is located some 22 miles north of Havre St-Pierre, a small sea port on the north coast of the St.Lawrence River. The purpose of this work has been to study in detail the mineralogy and chemistry of the hemo-ilmenite ore in order to detect possible chemical and mineralogical variations within the orebody. The work involved the systematic study of 135 specimens cif ore by X-ray diffraction, the complete chemical analyses of 48 high purity hemo- ilmenite concentrates, and the microscopic and electron probe exam- ination of some 40 polished sections. Our study shows that the Fe-Ti ore is almost entirely made up of hemo-ilmenite, of average composition 70% ilmenite and 30% hematite, unmixed to a regular intergrowth of hematite and ilmenite. Microprobe analyses and crystal chemical considerations indicate that the average composition of the unmixed phases is : (144.11814n. 00.4Fe.873 C1.004)Ti°3 203. Other minerals identified in the ore and (Fe,971y.014 A1 012Cr.004) consist of accessory amounts of plagioclase (An46, commonly antiperthitic), pleonaste spinel, and pyrite, as well as minor or trace quantities of magnetite, chlorite, hypersthene, zalcite, zircon, corundum, apatite, chalcopyrite, millerite, pyrrhotite, Co-Ni sulphides (linaeite series), II rutile and anatase. rrimary magnetite is almost absent in the ore; the most common magnetite is secondary in origin and together with anatase and rutile has formed at the expense of hemo-ilmenite during the subsolidus stage. The study of the variation of the hemp-ilme:.tite chemistry throughout the orebody indicates that the mineral deviates little from the average composition. All attempts to find regular or stratigraphic variations of the minor elements (Mg, Mn, Cr, Al, V) of the hemo-ilmenite were unsuccessful. The geology End origin of the deposit is reviewed in the light of our data. It is suggested that the ore crystallized from an oxide melt that separated by liquid immiscibility early in the evolution of the regional anorthosit:e mass{,f. From textural evidence it is concluded that b emo-ilmenite accumulated by crystal settling. The lack of fraction- ation trends in the ore is attributed to repeated injections of oxide magmas and to a slow rate of crystallization which favored adcumslus growth of the hemo-ilmenite crystals. ETUDE MINERALOGIQUE D;: MINERAI D'HEMO-ILMENITE DU LAC TIO QUEBEC Résumé Le gisement du Lac Tio est constitué d'un amas massif d'hémo- ilménite â l'intérieur d'un complexe anorthositique de type anorthosite A and.ésine. Ce dépôt, exploité depuis 1951 par la société Fer et Titane du Québec, est situés environ 22 milles au nord de Havre St-Pierre, petit port de mer sur la rive nord du fleuve St-Laurent. L"objectif de ce travail était de déceler d'éventuelles varia- tions minéralogiques et chimiques dans le gisement par une étude détail- lée de la composition du minerai. Le travail est basé sur l'é,ude systé- matique de 135 échantillons de minerai par diffraction des rayons-X, sur l'analyse chimique de 48 concentrés d'hémo-ilménite de très grande pureté et sur l'examen au microscope et à la microsonde d'environ 40 sections polies. Nous avons montré que le minerai de fer et de titane est com- posé presqu'exclusivement d'hémo-ilménite qui se présente sous forme d'une intercroissance lamellaire régulière formée d'environ 70% d'ilmé- nite et de 30% d'hématite. Les analyses à la microsonde et les données ct'istallochimiques in-liguent que la composition moyenne de chacune des .W4)TiO3 et phases exsudeés est la suivante (Mg.118M.004Fe.873Ca .004)203. Les minéraux. - c.essoires identifiés dans (Fe.0.,1V.014M .012G1 le minerai sont le plagioclase (An46, communément an~::lperthitique), le spinelle de type pléonaste et la pyrite. De petites quantités, voire des traces, de magnétite, chalcopyrite, chlorite;, rutile, hyperathène, pyrrho- IV tine, anatase, zircon, corindon, apatite, willerite,calci:e et des sul- fures de cobalt et de nickel (série linaeite) sont aussi 1résentes. La magnétite primaire est presque inexistante dans le minerai, la magnétite la plus commune dans le minerai est d'origine secondaire: islle s'est formée, tout comme le rutile et l'anatase, à varti.r d'hémo-iiménite lors du stade subsolidus. L'étude des vari itior i. de la compositaio. chimique de l'hémo-ilménite dans le gisement montre qu'elle s'écarte p:u de la composition moyenne. Tous nos efforts visant à prouver l'existence de variations régulières ou stratigraphiques dans les éléments mi•aeurs (Mg, Mn, Cr, Al, V) d:~ i'hémo-ilménite ont été infructueux. Une étude de la genèse et de l'histoire du gisement à la lumière de nos résultats, nous amène à considérer que le minerai a cristallisé à partir d'un fondu d'oxydes ("ore magma") qui ze serait formé par immisci- bilit:é au tout début de l'évolution du massif anorthositique régional. Les données texturales du minerai n7us portent à conclure que le liquide magmatique injecté dans l'anorthosite solidifiée a cristallisé par cris- tallisat-`.on fractionnée sous l'influence de la gravité. L'absence de variations stratigraphiques dans le minerai est attribuée à des injections répétées de magma et à un taux de cristallisation plutôt lent favorisant ainsi une croissance "adcumulus" des cristaux d'hémo-ilménite. m'Ans a matneaao:visxawmimmaimasianfiauaAial ■ ,dHUM~~es~►~~~e~~ ri~wa~s oo~ V TABLE OF CONTENTS 2241 ABSTRACT INTRODUCTION 1 Chapter I GEOLOGY OF THE LAC ALLARD AREA 3 1.1 Introduction 3 1.2 Location 3 1.3 Previous Work and History of the Area 6 1.4 Physical Geography 8 1.5 General Geology . .. 10 1.5.1 "Grenville Series" of Retty (1944) ....... 12 1.5.1.1 Quartzite 12 1.5.1.2 Hornblende Gneiss and Biotite Gneiss 12 1.5.1.3 Garnetiferous Gneiss 12 1.5.1.4 Less Common Rocks of the "Grenville Series" in the Area 12 1.5.2 "Morin Series" of Retty (1944) 13 1.5.2.1 Anorthosite ., 13 1.5.2.2 Anorthosite with Coarse Pyroxene Crystals 14 1.5.2.3, Ilmenite Rich Anorthosite 114 1.5.2.4 Anorthosite Dykes 15 1.5.3 Granitic Rocks 15 1.5.4 Diorite, Gabbro and Metagabbro 4,1 15 1.5.5 Pleistocene and Recent 15 1.6 Structural Geology 17 1.7 Economic Geology 18 1.7.1 Introduction 18 1.7.2 The Lac Tio Deposit 19 1.7.2.1 General Mineralogy and Chemistry of the Lac Tio Deposit ........... 22 1.7.2.2 Faulting of the Lac Tic Oreboc1r .. 26 1.7.2.3 Magnetic Property of the Lac Tio Hemo--Ilmenite ....."..........w.... 32 __ Yaffe Chapter II MINERALOGY OF THE LAC TIO HEMO-I_LMENITE DEPOSIT 35 2.1 Introduction 35 2.2 Description of Minerals 35 2.2.1 Hemo-Ilmenite 35 2.2.1.1 General Megascopic and Microscopic Characteristics 35. 2.2.1.2 Chemical Composition of Hlmo-I2menite 39 2.2.1.3 Minor Element Distribution in Unmixed Ilmenite and Hematite ... 47 2.2.1.4 Lattice Parameters and Composition of Unmixed Hematite and Ilmenite 44 2.2.1.5 Distribution and Variation of ilmenite and Hematite in the Ore7lody 49 2.2.2 Plagiaiciase . .... 51 2.2.3 Sulphides . 54 2.2.3.1 General Distribution . .. 54 2.2.3.2 Chemistry of the Sulphides ......... 56 2.2.1+ Spinel 5T 2.2.5 Magnetite 61 2.2.6 Rutile and Anatase 65 2.2.7 Chlorite and Biotite 68 2.2.8 Apatite, Corundum and Zircon 71 2.2.9 Hypersthene and Calcite 75 2.3 Mineralogical Summary 75 Chapter III GEOCHEMISTRY OF HEMO-ILMENITES FROM THE LAC TIO DEPOSIT 8o 3.1 Introduction 80 3.2 Selection and Preparation of Material for Study 80 3.3 Analytical Methods and Preparation of an Hemo- Ilmenite Standard 83 3.4 Chemistry of Hemo-Ilmenites in the Deposit 85 3.5 Chemical Variations of Hemo-Ilmenite in the Orebody 87 3.6 Inter-element Correlations in Hemo-Ilmenites 94 3.7 Synopsis of Hemo-Ilmeni.se Chemistry 103 romaimummiummull VII Page Chapter IV CERTAIN ASPECTS OF THE PETROLOGY AND ORIGIN OF THE LAC TIO DEPOSIT 106 4.1 Introduction 106 4.2 Metallogenic Traits of the Lac Tio Deposit ' 106 4.3 Crystallization and Evolution of the Hemo-ilmenite Magma 109 4.4 Subsolidus Evolution of the Hemo•-Ilmenite 114 4.5 Concluding Statement 118 BIBLIOGRAPHY 119 ACKNOWLEDGEMENTS . 124 APPENDICE: I Preparation and Chemical Analysis of 48 Lac Tio Hemo- Ilmenite Concentrates 125 II Preparation and Chemical Analysis of a Hemo-Ilmenite Standard 132 III Distribution of FeO, Fe203, A1203 and Cr203 in the Lac Tio Orebody 136 1MOSN®~i i " "I~HCMMOAIOMMIEL VIII TABLE DES MATIERES Page RESUME III INTRODUCTION 1 Chapitre I GEOLOGIE DE LA REGION DU LAC ALLARD 3 1.1 Introduction, ...,, 3 1.2 Situation .. 3 1.3 Travaux antérierars et histoire de la région 6 1.14 Géographie physique 8 1.5 Géologie généra:.e DO 10 1.5.1 "Série de Grenville" d'apras Retty(1944).
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