Possible compositional effects on the electrical conductivity of olivine: A preliminary study

Abstract

Abstract:Volatile sensitive probes of the upper mantle, such as magnetotellurics, are being developed to overcome insensitivities in seismic and gravity subsurface mapping as part of an effort to identify the location of deeply buried ore deposits, in addition to more broadly understanding mantle temperature and water contents. An understanding of the conductivity of mantle minerals is an essential prerequisite to the full interpretation of magnetotelluric data. Current proton conduction models for simple mineral systems, such as olivine, show large discrepancies. The material used for these determinations, San Carlos peridotite, is not a single mineral phase and may have compositional variations. This could be one of the origins of these discrepancies. To test this hypothesis, a sample of San Carlos olivine was taken and separated out the mineral components using a combination of electrostatic rock disaggregation, magnetic susceptibility as well as manual separation. The separated fractions were characterised using petrography. Impedance data were collected as a function of temperature and pressure in a multi-anvil press from both the separated olivine material and the original mixture. Comparison of these values with literature data has been made.ii Acknowledgements:I wish to acknowledge the extensive and onerous effort that has gone into this work and the team of people who have taken time from their own work to guide, mentor and advise me. These people not only provided me with an amazing amount of academic help but also showed care and compassion during a personal illness suffered during the course of this thesis.To my supervisors, Associate Professor Simon Clark, Associate Professor Tracy Rushmer, Associate Professor Juan Carlos Afonso, I can never repay the immense amount of time you've given me over the past two years.Simon, I thank you for the guidance and tasks you set for me during the coursework component of this MRes, I do not think I would have anywhere near the grasp of this subject area I currently have without you challenging me. I wish to thank you also for the useful and informative discussion throughout the course of this research project. We may not have always agreed but they certainly helped me to understand how the project was evolving and how impactful and important all aspects of the project can be with a bit more hard work.Tracy, I wish to thank you for meeting with me regularly and helping me through the formalities at the beginning of this year. Your insight specifically into the way which a research project is planned and executed gave me a unique perspective in how I would carry out future work. I want to also thank you for giving me so much time and for the last minute edits that helped me make this thesis much more consistent. This was all while acting as an Associate Dean as well as having other students submitting this year.JC, I want to acknowledge the way you make people think about problems. I truly respect and appreciate the dedication you have to your students and your res...