Magmatic Differentiation in Arc and Mid-Ocean Ridge Settings Thesis by Madeline Janine Lewis In Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2021 (Defended May 18, 2021) ! ii © 2021 Madeline Janine Lewis ORCID: 0000-0001-7968-2822 ! iii ACKNOWLEDGEMENTS This thesis is the result of many years of education and encouragement from advisors, peers, family, and colleagues, of which there are too many to individually name. I would like to specifically thank many of those who have helped me reach this point, and broadly acknowledge all others who have inspired and assisted me along the way. I would firstly like to thank my PhD advisors Paul Asimow and Claire Bucholz for their endless support and constructive criticism that has helped me grow significantly as a researcher. I am also grateful for the collaboration and mentorship from members of my thesis advisory committee !Woody Fischer, George Rossman, and Ed Stolper! throughout my time at Caltech. The work presented here would not be possible without the excellent analytical support from Nathan Dalleska, Chi Ma, and Yunbin Guan. I am also incredibly thankful to the support staff and residents of the Arms Building, and particularly Mark Garcia for his help with preparation for many class field trips and research fieldwork and for forgiving my return of mud- covered vehicles. I am grateful to collaborators within and beyond Caltech, including Sarah McCart for much work put into characterization and analysis of sediment cores, to Dave Lund for spear- heading the sediment cores projects, to Oli Jagoutz for helpful conversation and manuscript comments, to Ayman Maurice for providing samples and interpretations of BIFs, and to Juliet Ryan-Davis for analyses for our semi-overlapping Sierra Nevada batholith projects. I would also like to thank the many field assistants who have helped me collect, and more importantly carry rocks over mountains: Joe Biasi, Juliet Ryan-Davis, Allyson Trussell, Emma Sosa, Matt Barickman, Sam Newall, and last but not least, my mom Liane Lewis. ! iv Finally, I would like to thank my family and friends for their never-ending encouragement. The 2015-16 Pit, the residents of second floor Arms, and the Caltech dining and arts folks have all been wonderful in creating social and creative outlets. I cannot express how much the support from my parents has helped me to reach this point. Thank you for always letting me play in the dirt, taking me on my first trips to the Sierras, paying for my undergraduate education, and making many Sunday dinners during grad school. And lastly, I thank my husband Joe for your love and support, and for always being there for me when I need it most. ! v ABSTRACT The compositional variation of igneous rocks and construction of Earth’s crust is the result of magmatic differentiation !crystallization, melting, and assimilation mechanisms that cause the composition of magmas to change over time. This thesis investigates magma generation and evolution at both convergent and divergent plate boundaries. The resulting magmatic arcs and mid-ocean ridges create the vast majority of Earth’s crust, though the details of crustal construction and the specific processes that generate the observed magmatic and volcanic products are complex. Accordingly, this work uses the geochemical signatures encoded in rocks and minerals to explain magmatic differentiation histories in multiple tectonic settings. Here, I present five main studies that utilize field and textural observations, geochemical analyses, and computational modeling to investigate the compositional structure of the crust beneath magmatic arcs and mid-ocean ridges. In addition, this work explores the pyroclastic and sedimentary products dispersed by magmatically heated hydrothermal fluids in submarine environments. Chapters 2 and 3 investigate the crystallization histories of mafic intrusions in the eastern-central Sierra Nevada batholith paleo-continental arc, California. This work has implications for the compositional and temporal generation of both mafic and evolved magmas throughout the batholith and in other continental arcs. Chapters 4 and 5 explore records of submarine volcanic ash deposits associated with explosive mid-ocean ridge eruptions from the East Pacific Rise and Pacific-Antarctic Ridge, as well as the effects that sea level change has on melting of the mantle, eruption styles, and the compositional evolution of mid-ocean ridge magmas. Chapter 6 examines the mineral hosting of rare earth elements (REEs) in the Wadi Karim banded iron formation, and the implications of element mobility on interpretations based on REE abundances. ! vi PUBLISHED CONTENT AND CONTRIBUTIONS The chapters of this thesis, exempting the Introduction, were each prepared as individual manuscripts or portions of manuscripts (in the case of Chapter 4). The term “we” is used throughout this text in reference to the following co-authors: CHAPTER 2: Lewis MJ, Bucholz CE, Jagoutz OE (submitted to CMP, Jan 2021) Evidence for Polybaric Fractional Crystallization in a Continental Arc: Hidden Lakes Mafic Complex, Sierra Nevada Batholith, California. (in review for Contributions to Mineralogy and Petrology) MJL participated in conception of this project, collected samples, completed field mapping, analyzed samples, completed fractionation modeling, interpreted results, and wrote most of the manuscript. CHAPTER 4: Adapted from: Lund DC, Seeley EI, Asimow PD, Lewis MJ, McCart SE, Mudahy AA (2018) Anomalous Pacific‐Antarctic Ridge Volcanism Precedes Glacial Termination 2. Geochemistry, Geophysics, Geosystems 19(8):2478-2491 https://doi. org/10.1029/2017GC007341 ! Sections included here consist of only the portions of the project for which MJL completed the geochemical analyses, modeling, and drafting of the manuscript. All other analyses and interpretations from the project (completed by co-authors) are cited as Lund et al. (2018) in the text. MANUSCRIPTS IN PREPARATION WITH CO-AUTHORS CHAPTER 3: Lewis MJ, Ryan-Davis JR, Bucholz CE. Mafic Intrusions Reveal a Mantle Driver of Arc Episodicity and Crustal Thickening in the Sierra Nevada Batholith. (in preparation for Geology) MJL led the conception of the project, fieldwork, geochronology, bulk-rock analyses, and manuscript preparation. CHAPTER 5: Lewis MJ, McCart SE, Asimow PD, Lund DC. Multiple Sills Tapped by Explosive Eruptions from the East Pacific Rise: Ties to Sea Level Variation. (in preparation) MJL completed sample preparation and analysis, interpreted results, completed fractionation modeling, and drafted the manuscript. CHAPTER 6: Lewis MJ, Asimow PD, Fischer WW, Maurice AE. Hosting of REE in Accessory Minerals in the Wadi Karim BIF: Implications for the Preservation of Bulk-rock Trace Element Signatures in Iron Formation. (in preparation for Precambrian Research) MJL completed SEM maps and in-situ compositional analyses, completed REE budget calculations, interpreted results, and wrote much of the manuscript. ! vii TABLE OF CONTENTS Acknowledgements .................................................................................................................... iii Abstract ...................................................................................................................................... v Published Content and Contributions ........................................................................................ vi Table of Contents ....................................................................................................................... vii List of Figures ....................................................................................................................... xi List of Tables ......................................................................................................................... xiii Chapter 1: Introduction .......................................................................................................... 1 1.1 Background .......................................................................................................................... 2 1.2 Dissertation Summary .......................................................................................................... 3 1.3 Remaining Questions and Potential Future Directions ........................................................ 8 1.4 References Cited .................................................................................................................. 11 Chapter 2: Evidence for Polybaric Fractional Crystallization in a Continental Arc: Hidden Lakes Mafic Complex, Sierra Nevada Batholith, California ............................................... 15 2.1 Abstract ............................................................................................................................... 16 2.2 Introduction ......................................................................................................................... 16 2.2.1 Geologic Setting .................................................................................................... 19 2.3 Field Relationships............................................................................................................... 20 2.3.1 Norites ................................................................................................................... 21 2.3.2 Anorthosites .........................................................................................................