Modeling and Observations of High-silica Magmatic Systems on Earth and Mars

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EGGERS-DISSERTATION-2021.pdf (41.48 MB)
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Eggers, Gabriel L.
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Dufek, Josef
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http://hdl.handle.net/1853/67158
Abstract
On Earth, evolved felsic crust is commonly associated with plate tectonics, specifically subduction zones, and the role of water in modulating melting conditions and phase equilibria in the mantle and crust. As Mars lacks evidence of both plate tectonics and extensive water, felsic rock is unexpected there. However, new studies via remote sensing and in situ observation indicate a wider range of primary rock compositions on Mars, suggesting an incomplete understanding of how these materials form. Nili Patera, a caldera on the Syrtis Major shield volcano, has been a locus of compositional research on Mars, including the first detection of bedrock spectrally consistent with evolved felsic material. Using visible/near-infrared data from the CRISM instrument aboard the Mars Reconnaissance Orbiter, the extent of this feldspathic terrane in Nili Patera is mapped and its relation to surrounding mafic units is investigated. This provides important controls such as the areal extent (a proxy for volume) and relative age that can be used to constrain its magmatic formation history. A high-silica magma system on Earth, the Laguna del Maule volcanic field in Chile, is also studied. A stochastic magmatic model unifying dynamics and compositional understanding of magma system evolution is used to generate numerous realizations using known Laguna del Maule conditions and exploring a range of unknown magmatic fluxes in the crust. Forward models are developed and used to transform the magmatic model outputs to observable geophysical signals in gravity, magnetotellurics, and seismic velocity, which are evaluated against field measurements to determine a probable history of the Laguna del Maule magmatic system and investigate current arguments about the structure and supports of shallow, silicic systems. Together, these studies elucidate our understanding of how high-silica systems can form and evolve in disparate conditions.
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2021-07-27
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