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Experimental and Analytical Studies of Partial Melting in Planetesimals and the Martian Mantle by Max Collinet B.Sc

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Experimental and analytical studies of partial melting in planetesimals and the Martian mantle by Max Collinet B.Sc. Geological Sciences, 2009 M.Sc. Geological Sciences, 2011 University of Liège, Belgium Submitted to the Department of Earth, Atmospheric, and Planetary Sciences in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Geology at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 2020 © 2020 Massachusetts Institute of Technology. All rights reserved. Signature of Author: Department of Earth, Atmospheric, and Planetary Sciences October 30, 2019 Certified by: Timothy L. Grove Robert R. Shrock Professor of Earth and Planetary Sciences Thesis Supervisor Accepted by: Robert D. van der Hilst Schlumberger Professor of Earth and Planetary Sciences Department Head 2 Experimental and analytical studies of partial melting in planetesimals and the Martian mantle by Max Collinet B.Sc. Geological Sciences, 2009 M.Sc. Geological Sciences, 2011 University of Liège, Belgium Submitted to the Department of Earth, Atmospheric, and Planetary Sciences on October 30th, 2019 in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geology Abstract Planetesimals and planetary embryos, the building blocks of planets, started to melt within a few million years of the formation of the solar system. This thesis explores, through experiments and the analysis of meteorites, the magmatic processes that affected those early-formed bodies. Chapter 1 presents low-pressure experiments that simulate the onset of melting of planetesimals made of different chondritic materials (H, LL, CI, CM and CV). H, LL and CI compositions, melted at lower temperature and produced partial melts with higher SiO2, Al2O3 and alkali element concentrations compared to CM and CV compositions. They formed unique trachyandesite achondrites upon crystallization. In Chapter 2, the experiments are compared to primitive achondrites, distinct groups of meteorites that represent the melting residues “left behind” within planetesimals. Cumulative evidence from trachyandesite achondrites and primitive achondrites suggests that the planetesimals that accreted in the inner solar system were not depleted in alkali elements relative to the composition of the sun’s photosphere. Chapter 3 is a detailed study of ureilites, the largest group of primitive achondrites. Twelve ureilites were analyzed to determine the chemical composition and relative proportions of olivine and pyroxene. Those analyses, together with additional experiments, constrain the initial Mg/Si ratio of the ureilite parent body. The experiments are used to develop a new geothermometer, based on the partitioning of Cr between olivine and pyroxene, which demonstrates that ureilites are residues of incremental melting. Chapter 4 is the first of two chapters describing igneous processes on Mars, a planet sometimes referred to as a planetary embryo due to its small size and early accretion age. It describes a high-pressure experimental study of the partial melting of the primitive Martian mantle and discusses the origin of rocks from the Martian crust. Finally, chapter 5 is a study of Fe-Mg isotopic fraction in the olivine of the “enriched” shergottite Northwest Africa 1068. The composition and crystallization history of the parental melt, which represents a melt extracted from the Martian mantle, are constrained by modeling diffusion and crystal growth simultaneously. Thesis Supervisor: Timothy L. Grove Title: Robert R. Shrock Professor of Earth and Planetary Sciences 3 4 Acknowledgments I have many people to thank for their help, support and encouragement, without which none of this work would have been possible. First, I want to thank my advisor and mentor, Tim Grove. Tim showed me how fun and exciting experimental petrology can be. By working with him, I learned how to perform careful experiments, interpret my results and communicate them orally and in writing. But more importantly, I learned that many worthwhile experimental projects are not flawlessly executed to prove a preconceived idea. They start with the identification of an important question, evolve with successive failures and have to be carried out with perseverance and a lot of curiosity. I am grateful for his unwavering kindness, patience and trust that I repeatedly tested by breaking equipment, misplacing tools and, of course, overtightening valves. I look forward to our future discussions and continued collaboration. Next, I want to thank Oli Jagoutz, the chair of my thesis committee and advisor for my second general project. Oli has always offered his guidance and has kindly listened to me talk about obscure meteorites while I was pushing back the redaction of our own project. I am also grateful to the other members of my thesis committee, Rick Binzel, Ben Weiss and Tim McCoy, for their precious comments and advice. The discussion we had during my defense was inspirational and motivates me to address many other questions related to the early history of the solar system and the differentiation of planetesimals. There are so many other members of the EAPS community, past and present, that I should acknowledge. I know that I will inevitable forget many and present my apologies to those. I thank Neel Chatterjee, for teaching me to use the microprobe. Mira Parsons and Heather Queyrouze, for their support and friendship. Taylor Perron, for his advice during my general exam. Matej Pec, for interesting discussions about melt migration. François Tissot, for sharing is knowledge of cosmochemistry. To my office mates, lab mates and other graduate student peers, Stephanie Brown, Alex Mitchell, Ben Mandler, Ben Klein, Niya Grozeva, Jean-Arthur Olive, Mike Eddy, Annie Bauer, Billy Shinevar, Marjorie Cantine, Maya Stokes, Eva Golos, Patrick Beaudry and Susana Hoyos, thank you for our numerous conversations and for sharing your experience with me. You all greatly helped me to navigate graduate school at MIT. While at MIT, I continued to receive the help and support of previous advisors and mentors. I thank Bernard Charlier, Olivier Namur and Jacqueline Vander Auwera for teaching my first petrology classes in Liège, introducing me to fundamental research, and for remaining in touch during those six years. I thank Etienne Médard and Bertrand Devouard for introducing me to meteorite research during my master at Clermont-Ferrand. I thank Francois Holtz, Harald Behrens and Stefan Weyer for hosting me for six months at the mineralogy institute of Hanover. To my parents, Monique and Roger, thank you for your constant encouragement and love and for fostering my curiosity from a very young age by taking me to the Alps and to the Astronomy club of Spa. To my sister, Odile, thank you for showing me the way and inspiring me with your discipline and dedication in everything you undertake. Your visits to Boston with Antoine and Léone were so much fun. To my wife Nina, thank you for keeping me grounded and supporting me relentlessly during the most difficult times of my PhD. Thank you for exploring New England with me and making me feel at home here. I love you and look forward to discover new places together very soon. 5 6 Table of Contents Abstract ...................................................................................................................................... 3 Acknowledgments ...................................................................................................................... 5 Table of Contents ....................................................................................................................... 7 Introduction .............................................................................................................................. 11 Chapter 1: Widespread production of silica- and alkali-rich melts at the onset of planetesimal melting ..................................................................................................................................... 17 Abstract ................................................................................................................................ 17 1. Introduction .................................................................................................................. 18 2. Experimental and analytical methods ............................................................................ 20 2.1. MHC-pressure vessel experiments ............................................................................. 20 2.2. Gas mixing furnace experiments ................................................................................ 20 2.3. Starting materials ....................................................................................................... 21 2.4. Electron microprobe analyses .................................................................................... 21 3. Results .......................................................................................................................... 22 3.1. Approach of equilibrium ............................................................................................ 22 3.2. Mineral compositions and proportions ....................................................................... 24 3.3. Temperatures and reactions of melting ....................................................................... 24 3.4. Composition of experimental melts ............................................................................ 26 4. Discussion ...................................................................................................................
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