Silicic magmas (>65 wt.% SiO2) play an integral role in creating permanent continental crust. Understanding how silicic magmatic systems evolve can help us better understand the processes that control whether silicic magmas remain trapped within Earths crust or ultimately reach Earths surface, culminating in volcanic eruptions. In this study, I use elemental and isotopic compositions of major and accessory minerals from diverse rock types produced by silicic magmatism in southeast Iceland and southwest USA to investigate geochemical relationships between crystals and their associated melt(s).
I present an extensive partition coefficient dataset for 8 mineral phases from a high-silica rhyolite, and demonstrate that accessory minerals (zircon, titanite, chevkinite, and apatite) exert a strong control on the distribution of rare earth and high field strength elements in a magma, while major minerals (amphibole, biotite, plagioclase, sanidine) dominantly control large ion lithophile elements. In addition, I offer a mathematical expression to estimate the relative abundances of Eu and Ce in their multivalent states (2+, 3+, and 4+), which may yield insight into the oxidation state of magmas based on the occurrence Ce and Eu anomalies in coexisting mineral phases.
I conducted a detailed geochemical study of zircons from Icelandic intrusive rocks, and show that their compositions form a coherent array consistent with the signature of zircons from Icelandic silicic volcanic rocks. I demonstrate that oxygen isotopes and hafnium isotopes (εHf) provide strong evidence for the existence of isotopically diverse magmatic sources in the Icelandic crust, including the influence of meteoric-hydrothermal processes and recycling of highly altered crust as a major contributor to silicic magmas in many Icelandic silicic magmatic systems.
The results presented here offer an additional dimension in helping us better understand the accumulation of silicic magmas and subsequent evolution of silicic magmatic systems within the Earths crust.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-07172015-123921 |
| Date | 23 July 2015 |
| Creators | Padilla, Abraham De Jesus |
| Contributors | Dr. James H. Clarke, Dr. George M. Hornberger, Dr. David J. Furbish, Dr. Calvin F. Miller, Dr. Guilherme A.R. Gualda |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-07172015-123921/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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