Western University Scholarship@Western Electronic Thesis and Dissertation Repository February 2015 Chromite Crystal Structure and Chemistry applied as an Exploration Tool Patrick H.M. Shepherd The University of Western Ontario Supervisor Dr. Roberta L. Flemming The University of Western Ontario Graduate Program in Geology A thesis submitted in partial fulfillment of the equirr ements for the degree in Master of Science © Patrick H.M. Shepherd 2015 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Geology Commons Recommended Citation Shepherd, Patrick H.M., "Chromite Crystal Structure and Chemistry applied as an Exploration Tool" (2015). Electronic Thesis and Dissertation Repository. 2685. https://ir.lib.uwo.ca/etd/2685 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Western University Scholarship@Western University of Western Ontario - Electronic Thesis and Dissertation Repository Chromite Crystal Structure and Chemistry Applied as an Exploration Tool Patrick H.M. Shepherd Supervisor Roberta Flemming The University of Western Ontario Follow this and additional works at: http://ir.lib.uwo.ca/etd Part of the Geology Commons This Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in University of Western Ontario - Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Chromite Crystal Structure and Chemistry Applied as an Exploration Tool (Thesis format: Integrated Article) by Patrick H.M. Shepherd Graduate Program in Earth Science A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science The School of Graduate and Postdoctoral Studies The University of Western Ontario London, Ontario, Canada © Shepherd 2014 Abstract Spinel group minerals have long been of interest in mineral exploration due to their use as indicator minerals. The unit cell parameter is a structural measurement primarily controlled by composition and this study has attempted to look at the applications of the unit cell parameter as a proxy for composition in exploration, with a focus on diamond exploration. The implementation of µXRD for this purpose required the creation the Slice Integration Technique to improve the signal to noise ratio from 2D data. The compositions of spinels can be approximated through their correlation with unit cell with some ambiguity. Possible applications include the discrimination of diamond inclusion-related compositions for diamond exploration, or in gemology and curatorial studies, where the nondestructive nature of µXRD is advantageous. Additional analysis of chromite indicator minerals was conducted using a field portable XRD which has demonstrated that unit cell data could be used in the field, in conjunction with other new field-portable technologies, such as XRF. Keywords Chromite, Unit Cell Parameter, Spinel, Mineral Exploration ii Acknowledgments No research undertaking is the result of a lone investigator’s efforts, and as such, there are a great many individuals who have contributed to this project and who have made its completion possible. I would first like to thank my supervisor Dr. Roberta Flemming, for her guidance and her willingness to always be available to help. I would also like to thank her for the opportunity to work in her X-ray lab as an RA, which has been a great experience and allowed me the ability to finish my thesis. I have benefited from her guidance during this project and her support. Matthew Izawa deserves special thanks for having been extremely helpful during the final months of the project. His emotional and academic support was indispensable in the process of solving a number of standard difficulties that were encountered during the research process, and his many discussions were of the utmost help. I am very grateful to Dr.Tom Nowicki for guidance and for graciously providing samples, and for much useful advice in understanding the industry. I would also like to thank Mineral Services Canada Inc for supplying samples. Many thanks also to Dave Edey, Mike Craig, Alysha McNeil, Annemarie Pickersgill, Bethany Dean, Trevor Weiss, Sarah CoDyre, Diego Uribe, Mike Bramble, Dr. Phil McCausland, Also deserving of recognition are Eleni and Sotiros Petrou, Ashley Piskor-Potter, Corey De Vlugt John Jardine, Catherine Jardine, Megan Simpson, Eva McGuire, Adam Helmers, Aaron Drahushchak, Steve Eckert, Ben Lamb, Cameron Beare, Charles Nolan, Justin Peter, Dan Freeman, Fr.Raymond DeSouza, Josh Vanleeuwen, Peter Ketelaars, Sean Wilson, David Johnson and the many other people who have been there to support me along my journey. Many thanks to Michael McTaggart-Cook for graciously giving his time in reading and editing the final draft of this thesis the evening before submission. iii Finally, my family has been an amazing source of support, especially my mother, who throughout my undergraduate degree and my masters degree has been there when I needed a quick edit, an ear to vent to or to ask for advice. Moreover, my sister Sarah has been a constant source of support. There is nothing like having a sister show up the night before thesis is due with a full dinner. iv Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iii Table of Contents ............................................................................................................... iii List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x List of Appendices ........................................................................................................... xiii Chapter 1 ............................................................................................................................. 1 1 Introduction .................................................................................................................... 1 1.1 Overview ................................................................................................................. 1 1.2 Spinel Structure and Unit Cell ................................................................................ 2 1.3 Spinel Indicator Minerals ........................................................................................ 4 1.4 Spinel petrogenetic indicators ................................................................................. 6 1.5 Kimberlites: History and Overview ........................................................................ 6 1.6 Exploration Target and Strategy ............................................................................. 9 1.7 Indicator Mineral Overview .................................................................................. 10 1.8 Diamond Indicator Mineral Discrimination .......................................................... 13 1.9 Kimberlite Chemical Trends ................................................................................. 14 1.10 Rationale for the Unit Cell Parameter as a Compositional Proxy ........................ 16 1.11 References ............................................................................................................ 17 Chapter 2 ........................................................................................................................... 24 2 Methods ........................................................................................................................ 24 2.1 Samples ................................................................................................................. 24 2.2 General Methods ................................................................................................... 25 2.2.1 Micro X-ray Diffraction ............................................................................ 25 v 2.2.2 Slice Integration Technique Overview ..................................................... 28 2.2.3 Error Determination .................................................................................. 28 2.2.4 Terra X-Ray Diffraction /X-Ray Fluorescence Methods .......................... 29 2.2.5 The Unit Cell Parameter Refinement ........................................................ 29 2.2.6 Electron Probe Micro-Analysis (EPMA) .................................................. 29 2.3 References ............................................................................................................. 33 Co-Authorship Statement.................................................................................................. 34 Chapter 3 ........................................................................................................................... 35 3 Signal enhancement through a maximum intensity projection using Slice Integration of 2D-XRD data: Applications to unstrained crystallites (>100 micron grain size) ...