Western University Scholarship@Western Scholarship@Western Electronic Thesis and Dissertation Repository 3-12-2018 10:30 AM Crystallization processes and solubility of columbite-(Mn), tantalite-(Mn), microlite, pyrochlore, wodginite and titanowodginite in highly fluxed haplogranitic melts Alysha G. McNeil The University of Western Ontario Supervisor Linnen, Robert L. The University of Western Ontario Co-Supervisor Flemming, Roberta L. The University of Western Ontario Graduate Program in Geology A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Alysha G. McNeil 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Earth Sciences Commons Recommended Citation McNeil, Alysha G., "Crystallization processes and solubility of columbite-(Mn), tantalite-(Mn), microlite, pyrochlore, wodginite and titanowodginite in highly fluxed haplogranitic melts" (2018). Electronic Thesis and Dissertation Repository. 5261. https://ir.lib.uwo.ca/etd/5261 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]. Abstract Niobium and tantalum are critical metals that are necessary for many modern technologies such as smartphones, computers, cars, etc. Ore minerals of niobium and tantalum are typically associated with pegmatites and include columbite, tantalite, wodginite, titanowodginite, microlite and pyrochlore. Solubility and crystallization mechanisms of columbite-(Mn) and tantalite-(Mn) have been extensively studied in haplogranitic melts, with little research into other ore minerals. A new method of synthesis has been developed enabling synthesis of columbite-(Mn), tantalite-(Mn), hafnon, zircon, and titanowodginite for use in experiments at temperatures ≤ 850 °C and 200 MPa, conditions attainable by cold seal pressure vessels. Solubilities of wodginite, titanowodginite, microlite and pyrochlore are compared to those for columbite-(Mn) and tantalite-(Mn) in a flux-rich haplogranitic melt of alumina saturation index (ASI) 1.0 at 700 – 850 °C and 200 MPa. The effect of melt composition on solubilities of wodginite, titanowodginite, and microlite compared to tantalite-(Mn) is also investigated in highly fluxed haplogranitic melts of ASI 1.0, 1.10, and 1.24, at 700 °C and 800 °C and 200 MPa. The log solubility product (logKsp) for tantalite-(Mn) is highest (-2.32 mol2/kg2) followed by columbite-(Mn) (-2.68 mol2/kg2), and pyrochlore (-3.71 mol3/kg3) titanowodginite (-3.73 mol3/kg3), wodginite (-3.77 mol3/kg3), and microlite (-3.78 mol3/kg3) are almost identical within error at 750 °C. However, the tantalum mineral-melt partition coefficient solubilities of wodginite, titanowodginite, and tantalite-(Mn) are identical within error; microlite is different because it contains a major melt cation, sodium, and columbite- (Mn) is less soluble than pyrochlore. Wodginite, titanowodginite, and pyrochlore have i similar temperature and compositional dependences to columbite-(Mn) and tantalite-(Mn), as described in previous studies, and microlite solubility conversely increases with ASI. Experiments crystallizing columbite-(Mn) through the interaction of a manganese- rich hydrothermal fluid with a niobium-rich pegmatite melt have demonstrated that fluid- melt interactions are a plausible mechanism for the crystallization of niobium and tantalum ore minerals. These experiments show that saturation can be reached from lower, more reasonable niobium melt concentrations than previous experiments and from higher concentrations of manganese in a hydrothermal fluid. This is significant because natural pegmatites contain evidence of hydrothermal processes during rare metal crystallization stages. Keywords: columbite-(Mn), tantalite-(Mn), microlite, pyrochlore, wodginite, titanowodginite, solubility, crystallization mechanisms, fluid-melt interactions, pegmatite ii Co-Authorship Statement This thesis is divided into six chapters, four of which are in manuscript format. The key elements of Chapter 2 were published in The Canadian Mineralogist in 2015 as the manuscript “Hydrothermal synthesis of columbite-(Mn), tantalite-(Mn), hafnon and zircon at 800-850 °C and 200 MPa” by McNeil, A.G., Linnen, R.L., and Flemming, R.L. This manuscript was researched and prepared by McNeil, A.G., and thesis supervisors Linnen, R.L., and Flemming, R.L., provided critical evaluation of the work as well as suggestions for improvement of the manuscript with regards to experiments completed and analysis of the products. Chapters 3, 4, and 5 have yet to be submitted for publication, but Linnen, R.L., and Flemming, R.L., will remain second and third authors for these papers respectively. Fayek, M., is fourth author on Chapter 5 as he assisted with SIMS analyses and data collection. These manuscripts were researched and written by McNeil, A.G. Evaluation and suggestions for experimental methods and data interpretations, as well as review of the manuscripts was provided by Linnen, R.L., and Flemming, R.L. Copyright permission for Chapter 2 is provided in Appendix A. iii Acknowledgments There have been so many people who have helped make the past six years of this doctoral project possible. First, I would like to thank my supervisors, Dr. Robert Linnen and Dr. Roberta Flemming for their advice and guidance throughout this thesis. This project would not have been possible without their financial, emotional, and academic support. Dr. Linnen also provided me with the opportunities to work on many different projects throughout my time at Western, to learn more than just what my thesis could teach me; and Dr. Flemming provided me with invaluable teaching experience that teaching assistants are usually not given, and for this I am truly grateful. I would also like to acknowledge the Society of Economic Geologists for a Graduate Student Fellowship Award granted to myself in support of this research, as well as The Mineralogical Association of Canada for a Student Travel Grant awarded for presentation of research at GAC-MAC 2014 in Fredericton, New Brunswick, Canada. I would also like to gratefully acknowledge a NSERC Discovery Grant to Dr. Robert Linnen for funding this research, and a Queen Elizabeth II Graduate Scholarship in Science and Technology to Alysha McNeil in support of this research. Secondly, I would like to thank my mom and dad, Grace and Bruce, who without all of your financial support, I would not have been able to complete this thesis. You have always supported me through the toughest of times for both this thesis and personal struggles, and I can never say thank you enough for everything you have done, not just during this thesis, but throughout my entire life. I would also like to thank my brother Steven, who is always up for lunch time meet ups and random phone calls to discuss school and life, and helps make hard days (or weeks, or months) go by that much faster. I would also like to iv thank my husband Alex. Words cannot express how much I appreciate everything you have done for me. From reading countless manuscripts and reports, to bringing food and keeping me company during late night lab work or teaching sessions. This thesis would not have happened without your unconditional love and support. I would like to thank all my family and extended family for their support throughout this thesis: my Grandparents Jean and Russ; my Nana Barbara; my in-laws Natalie and Craig; and my brother and sisters’ in-law Chelsey, Nathan and Haley; Oma and Opa Ursula and Fred; and Grandma June. I would like to thank my thesis examiners Dr. Audrey Bouvier, Dr. Tony Withers, Dr. Kim Baines, and Dr. Dan Marshall for their careful reading of my thesis and their constructive comments that improved the final version. I would also like to thank everyone who has helped me with parts of this thesis. Marc Beauchamp for all his assistance with electron microprobe analyses and results interpretations. Abdullah Aseri for his help and guidance with experiment design and protocol – especially in the early days when I knew nothing about experimental petrology. Alex Rupert for help with µXRD analyses. Dr. Tony Withers for use of his high temperature furnace and thesis advice. Dr. Paul Boyle for single crystal XRD analyses and interpretation. Dr. Brian Hart and Mary Jane Walzak at Surface Science Western for their assistance with SEM and Raman analyses, respectively. Ryan Sharpe at the University of Manitoba for his assistance with SIMS analyses. Ivan Barker for his assistance with grain picking and sample cutting. Laurisha Bynoe, Cassandra Beauchamp, Dr. Yonghua Cao and Sarah CoDyre for their moral support and helpful discussions over the years. I would also like to thank everyone in both the Mineralogy Research Group and Hydrothermal Geochemistry Research v Group, for listening to my presentations over the years and moral support over the duration of this thesis. Finally, I would like to thank Dr. Nikole Bingham – Koslowski for everything she has done for me over the past several years, including help with editing an immense amount of writing. Our daily lunch time discussions about thesis issues, life in general, or pretty much anything else were some of the best times I’ve had, not just at Western, but in my entire life. Social life is something that ends up getting neglected as graduate students and you made