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HILTON Umd 0117E 21218.Pdf ABSTRACT Title of Dissertation: GENETICS, AGES, AND CHEMICAL COMPOSITIONS OF IRON METEORITES Connor Hilton, Doctor of Philosophy, 2020 Dissertation directed by: Professor Richard Walker, Department of Geology Comparison of genetic isotopic compositions of iron meteorites with metal- silicate segregation ages suggests that the isotopic composition of the NC reservoir changed with time. By contrast, no such age-linked changes in the genetic isotopic compositions of iron meteorites from the CC reservoir are observed. Results of comparing bulk planetesimal genetic isotopic compositions with bulk planetesimal siderophile element chemical characteristics indicate that the processes responsible for isotopic heterogeneity in the early Solar System are not discerned by the siderophile element chemical characteristics of planetesimals. Iron meteorite parent bodies from the CC reservoir typically have smaller relative cores and a greater proportion of the Fe content in the mantle, consistent with the CC reservoir being a more oxidized environment, such as the outer Solar System, compared to the NC reservoir. The chemical characteristics of iron meteorite parent bodies, including bulk core FeS/Fe ratios and oxidation states, may form relationships with core formation ages, but whether these characteristics can account for potential differences in the formation ages of NC- and CC-type parent bodies presently cannot be constrained. GENETICS, AGES, AND CHEMICAL COMPOSITIONS OF IRON METEORITES by Connor D. Hilton Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2020 Advisory Committee: Professor Richard J. Walker, Chair Associate Professor Ricardo D. Arevalo Research Scientist Richard D. Ash Dr. Timothy J. McCoy Professor Alice Mignerey (Dean’s Representative) © Copyright by Connor Hilton 2020 Preface Portions of this dissertation have been previously published in peer-reviewed journals or are currently in preparation or revision. Specifically, chapters 2 and 3 have been published. Chapters 4 and 5 are currently in revision and in preparation, respectively. The contributions of each co-author to each chapter of this dissertation are outlined here. Chapter 2 Hilton C.D., Bermingham K.R., Walker R.J., McCoy T.J. (2019) Genetics, crystallization sequence, and age of the South Byron Trio iron meteorites: New insights to carbonaceous chondrite (CC) type parent bodies. Geochim. Cosmochim. Acta 251, 217-228. In this study, I collected all Os, Mo, Ru, and W isotope data and performed all trace element and thermal modeling. Katherine Bermingham provided guidance in the laboratory and Rich Walker collected the highly siderophile element and 187Os isotope data. Tim McCoy helped interpret the data. I wrote the first draft of this manuscript and edits were provided by co-authors. Chapter 3 Hilton C.D. and Walker R.J. (2020) New implications for the origin of the IAB main group iron meteorites and the isotopic evolution of the noncarbonaceous (NC) reservoir. Earth Planet. Sci. Lett. 540, 116248. ii I collected all Os, Pt, and W isotope data and wrote the first draft of this manuscript. Rich Walker helped interpret the data and edit the manuscript. Chapter 4 Hilton C.D., Ash R.D., and Walker R.J. (In revision) Origin of the Eagle Station Pallasites from the IIF iron meteorite core. Meteorit. Planet. Sci. In this study, I collected all highly siderophile element and Os isotope data and performed all trace element modeling. Richard Ash collected the siderophile element abundances by LA-ICP-MS. I interpreted all data and wrote the first draft of this manuscript. Richard Ash and Rich Walker provided edits. Chapter 5 Hilton C.D, Ash R.D., and Walker R.J. (In prep) Constraints on the chemical characteristics of the noncarbonaceous (NC) and carbonaceous (CC) nebular reservoirs. I collected highly siderophile element and Os isotope data for the IIAB, IID, and IIIF iron meteorites and performed all trace element modeling. The highly siderophile element and Os isotope data for the IIIAB iron meteorites were collected by a previous student under the supervision of Rich Walker. I interpreted all data and wrote the first draft of this manuscript. Richard Ash and Rich Walker provided edits. iii Acknowledgements I would like to thank Rich Walker, Ricardo Arevalo, Richard Ash, Tim McCoy, and Alice Mignerey for serving on my PhD committee as well as reading my dissertation and providing feedback. Rich Walker, Ricardo Arevalo, Richard Ash, and Tim McCoy are additionally thanked for their support throughout the proposal process and for their guidance over the course of this PhD. I am grateful for the funding provided by the University of Maryland and NASA for this dissertation and thankful for the meteorites provided to me by Arizona State University, the Cascadia Meteorite Laboratory, the Field Museum, the Maine Mineral and Gem Museum, the Russian Academy of Sciences, the Smithsonian Institution, and the University of California-Los Angeles. Rich Walker is especially recognized for his role as my PhD advisor and for all the work that entails. I am also grateful for the guidance and friendship that I have received from Richard Ash and Igor Puchtel, and for the support given to me by Michelle Montero, Suzanne Martin, and Todd Karwoski throughout graduate school. The past and present members of the Isotope Geochemistry Laboratory group, including Greg Archer, Katherine Bermingham, Emily Chiappe, Val Finlayson, Mitch Haller, Andi Mundl- Petermeier, Nao Nakanishi, Willie Nicklas, Hope Tornabene, and Emily Worsham, are thanked for their support and advice. I have fond memories of graduate school and, for that, I thank my fellow graduate students as well as the UMD Geology faculty and staff. I could not have completed my PhD without the support of my family, in particular my mother and sister, as well as my friends, old and new. Finally, I thank my fiancée, Anya, for her love and support, which iv helped me through this process immensely. I met Anya within the first two months of graduate school and she has been with me on this journey ever since. v Table of Contents Preface................................................................................................................................. ii Acknowledgements ............................................................................................................ iv Table of Contents ............................................................................................................... vi List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... ix List of Abbreviations ........................................................................................................ xii Chapter 1: Introduction and Goals ...................................................................................... 1 1.1 Driving questions ...................................................................................................... 1 1.2 Background ............................................................................................................... 1 1.3 Research goals .......................................................................................................... 7 Chapter 2: Genetics, crystallization sequence, and age of the South Byron Trio iron meteorites: New insights to carbonaceous chondrite (CC) type parent bodies .................. 9 2.1 Abstract ..................................................................................................................... 9 2.2 Introduction ............................................................................................................. 10 2.3 Materials and methods ............................................................................................ 13 2.4 Results ..................................................................................................................... 16 2.5 Discussion ............................................................................................................... 22 2.6 Conclusions ............................................................................................................. 39 2.7 Acknowledgements ................................................................................................. 41 2.8 Appendix 2 .............................................................................................................. 41 Chapter 3: New implications for the origin of the IAB main group iron meteorites and the isotopic evolution of the noncarbonaceous (NC) reservoir .............................................. 56 3.1 Abstract ................................................................................................................... 56 3.2 Introduction ............................................................................................................. 57 3.3 Methods................................................................................................................... 61 3.4 Results ..................................................................................................................... 64 3.5 Discussion ..............................................................................................................
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