A Study of Millerite from Cu-Ni-PGE Footwall Veins, Sudbury, ON: Crystal-Chemistry, Morphology, & Geological Implications by Thomas Edward Gore Thesis submitted in partial fulfilment of the requirements for the degree of Masters of Science in Geology The Faculty of Graduate Studies Laurentian University Sudbury, Ontario, Canada © Thomas Edward Gore, 2020 THESIS DEFENCE COMMITTEE/COMITÉ DE SOUTENANCE DE THÈSE Laurentian Université/Université Laurentienne Faculty of Graduate Studies/Faculté des études supérieures Title of Thesis Titre de la thèse A Study of Millerite from Cu-Ni-PGE Footwall Veins, Sudbury, ON: Crystal- Chemistry, Morphology, & Geological Implications Name of Candidate Nom du candidat Gore, Thomas Edward Degree Diplôme Master of Science Department/Program Date of Defence Département/Programme Geology Date de la soutenance May 20, 2020 APPROVED/APPROUVÉ Thesis Examiners/Examinateurs de thèse: Dr. Andrew McDonald (Supervisor/Directeur de thèse) Dr. Pedro Jugo (Committee member/Membre du comité) Approved for the Faculty of Graduate Studies Approuvé pour la Faculté des études supérieures Dr. David Lesbarrères Monsieur David Lesbarrères Dr. Daniel Marshall Acting Dean, Faculty of Graduate Studies (External Examiner/Examinateur externe) Doyen intérimaire, Faculté des études supérieures ACCESSIBILITY CLAUSE AND PERMISSION TO USE I, Thomas Edward Gore, hereby grant to Laurentian University and/or its agents the non-exclusive license to archive and make accessible my thesis, dissertation, or project report in whole or in part in all forms of media, now or for the duration of my copyright ownership. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also reserve the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by the professor or professors who supervised my thesis work or, in their absence, by the Head of the Department in which my thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that this copy is being made available in this form by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. ii ABSTRACT Millerite (-NiS) is a common accessory mineral in magmatic Cu-Ni-PGE deposits, such as those occurring in Sudbury, Ontario, Canada. In such localities, millerite develops as platy crystals, often forming large, cleavable masses. This is in stark contrast to the more widespread occurrence of millerite as a hydrothermal precipitate within vugs in carbonate basins, where it develops an acicular morphology, with crystals often exhibiting exaggerated aspect ratios (l:w > 20). The reason for these contrasting morphologies is attributed directly to the genesis of magmatic millerite that initially crystallizes as the high-temperature mineral crowningshieldite (-NiS), later inverting to millerite upon further cooling. The morphology exhibited by platy millerite is thus representative of crowningshieldite via a paramorphic relationship. Millerite of magmatic origin also frequently exhibits secondary twinning on {011̅2}, resulting from a post- crystallization increase in pressure. Development of these twins produces a variable response under BSE microscopy that is attributed to orientation contrast. KEYWORDS Millerite, NiS, magmatic sulphide, crystal structure, morphology, polymorph, crystal growth, twinning, backscatter coefficient, electron channelling iii ACKNOWLEDGEMENTS This project represents the culmination of years of work, not only my own, but of countless others who have provided their assistance along the way. This section is dedicated to them. To my supervisor, Dr. Andrew McDonald, I would like to convey my most sincere gratitude for supporting me not only in this project, but for guiding me through the fascinating world of mineralogy since I first stepped into his classroom in 2014. Without his tireless efforts reviewing shoddy abstracts and manuscripts, facilitating hours upon hours of discussion, and teaching me the invaluable skill of observation as a scientist, this project would have been impossible. To Dr. Pedro Jugo, who assisted me in designing the synthesis experiments, and generously allowed me access to and use of his experimental petrology laboratory. To Willard Desjardins, for preparing all of the polished thin sections examined over the course of this study. To Dr. William Zhe and Chris Beckett-Brown, who assisted greatly in collecting and processing EBSD data. To Rémy Poulin, who assisted in collecting PXRD data. To Brad Lazich, Andre Stewart, and Kevin Pieterse of Nickel Rim South mine, and Brian Gauvreau and Kyle Kauppi of Coleman mine for facilitating access to the mines and assisting with sample collection. To Erika Anderson and Ralph Rowe of the Canadian Museum of Nature for providing the representative samples of hydrothermal millerite for comparison. To all my fellow classmates and graduate students, for the years of camaraderie and passionate geological discussions. And finally to my family, for all the endless support they have given me over the years and helping me in pursuit of my passion. Our evolving scientific understanding of the world we live in is built on the shoulders of those who came before us. Their theories and propositions provide the foundations for our interpretations and understandings. Similarly, this project was not a singular undertaking, but was only achievable through the support of everyone mentioned above, and a great number of others who were not named explicitly. To all of them, I owe a depth of gratitude. Thank you. Thomas E. Gore iv TABLE OF CONTENTS THESIS DEFENCE COMMITTEE ............................................... ERROR! BOOKMARK NOT DEFINED. ABSTRACT ...................................................................................................................................... III ACKNOWLEDGEMENTS ................................................................................................................. IV TABLE OF CONTENTS ..................................................................................................................... V LIST OF FIGURES .......................................................................................................................... VII LIST OF TABLES ......................................................................................................................... VIII LIST OF EQUATIONS ................................................................................................................... VIII PREAMBLE ..................................................................................................................................... IX Chapter 1: ...................................................................................................................................... 1 Relationship Between the Crystal Chemistry & Morphology of Millerite ............................... 1 ABSTRACT ....................................................................................................................................... 2 1.0 INTRODUCTION ......................................................................................................................... 3 1.1 BACKGROUND ........................................................................................................................... 5 1.1.1 Structure & Morphology ........................................................................................... 5 1.1.2 Structure & Polymorphism of NiS ............................................................................. 7 1.1.3 Phase Equilibrium ................................................................................................... 11 1.1.3.1 THE FE-NI-S TERNARY SYSTEM ............................................................................11 1.1.3.2 THE FE-NI-CU-S QUATERNARY SYSTEM ...............................................................14 1.1.3.3 THE NI-S BINARY SYSTEM ....................................................................................16 1.1.4 Synthesis of -NiS ................................................................................................... 19 1.1.5 Notes on Magmatic vs. Hydrothermal Millerite ...................................................... 21 1.1.6 Sample Locations .................................................................................................... 22 1.2 METHODS ................................................................................................................................ 25 1.2.1 Chemistry................................................................................................................. 25 1.2.2 CVT Synthesis .......................................................................................................... 25 1.2.3 X-Ray Diffraction .................................................................................................... 26 1.3 OBSERVATIONS ....................................................................................................................... 27