Igneous life cycles: geochemistry of magma from mantle to surface and back again

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dc.contributor.advisorLee, Cin-Tyen_US
dc.creatorAllen, Sydney Marieen_US
dc.date.accessioned2023-09-01T21:05:04Zen_US
dc.date.created2023-08en_US
dc.date.issued2023-08-11en_US
dc.date.submittedAugust 2023en_US
dc.date.updated2023-09-01T21:05:05Zen_US
dc.description.abstractMaterial from within the Earth is cycled and recycled from the interior of the Earth to the surface in igneous rocks. The chemistry of igneous rocks record snapshots of this complex history. Here, we use three major projects to assess important processes in this life cycle. Continental arc volcanism generates a wide diversity of magma compositions, but the tempos of compositional variation are unclear. Here, we investigate a 7-million year record of volcanic ash layers in the Cretaceous Eagle Ford Group to investigate temporal changes in ash composition on <100 kyr timescales. We apply an empirical Ti/Zr-SiO2 relationship to Ti/Zr measurements of 52 Eagle Ford bentonites to reconstruct of ash protolith SiO2 of altered bentonites. Ash compositions fluctuate between periods of high and low silica volcanism over ~100 kyr timescales. If the temporal variability of these ashes represents broad snapshots of the Cordilleran continental arc, these results suggest that continental arc systems may undergo episodic changes in the extent of magmatic differentiation or the nature of eruption on rapid (<100 kyr) timescales. Slow-slip megathrust events in the Hikurangi forearc region, New Zealand, may be related to seamount subduction. We examine differences in the clast origins, depositional settings, and diagenetic histories of volcaniclastic units to highlight the heterogeneity of volcanic systems on the Hikurangi Plateau. The presence of voluminous hydrous clays within thick, altered volcaniclastic units provides a ready source for excess pore fluids that may enable slow-slip events along the Hikurangi subduction zone. Alkaline magmatism at Mountain Pass, CA has attracted attention due to its spatial and temporal association with a REE-rich, economically important carbonatite. However, questions remain about the origins of magma here. We present geochemical data for 121 primitive alkaline igneous rocks to allow a more complete picture of these uncommon igneous compositions. Examining primitive magma composition affords a glimpse into the early stages of magma generation to understand the origins and early histories of alkaline magmatism here. We argue for the importance of pyroxenite melting and suggest that metasomatism related to earlier subduction in this region were significant influences on mama compositions.en_US
dc.embargo.lift2024-02-01en_US
dc.embargo.terms2024-02-01en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.citationAllen, Sydney Marie. "Igneous life cycles: geochemistry of magma from mantle to surface and back again." (2023) Diss., Rice University. https://hdl.handle.net/1911/115278.en_US
dc.identifier.urihttps://hdl.handle.net/1911/115278en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectcontinental arc volcanismen_US
dc.subjectbentoniteen_US
dc.subjectEagle Ford Groupen_US
dc.subjectvolcanic temposen_US
dc.subjectvolcaniclasticen_US
dc.subjectHikurangien_US
dc.subjectslow-slipen_US
dc.subjectdiagenesisen_US
dc.subjectIODP Expedition 375en_US
dc.subjectMountain Passen_US
dc.subjectultrapotassic magmatismen_US
dc.titleIgneous life cycles: geochemistry of magma from mantle to surface and back againen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentEarth Scienceen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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