Experimental Insights into the Formation of High-Mg Andesites in the Trans-Mexican Volcanic Belt

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Title: Experimental Insights into the Formation of High-Mg Andesites in the Trans-Mexican Volcanic Belt
Author: Weber, Rachel Maria, 1975-
Abstract: High-Mg basaltic andesites and andesites occur in the central Trans-Mexican Volcanic Belt, primarily in the region south of Mexico City, and their primitive chemical characteristics suggest equilibration with mantle peridotite. These lavas may represent either slab melts that re-equilibrated with peridotite during ascent or hydrous partial melts of a peridotite source. I have experimentally mapped the liquidus mineralogy for a high-Mg andesite from the Pelagatos cinder cone as a function of temperature and H20 content over a range of mantle wedge pressures. The results,concur with a published thermo barometer for peridotite melting and suggest that this composition could only be in equilibrium with a harzburgite residue at relatively high water contents and low pressures and temperatures. However, numerically adjusting the composition fo r equilibrium with more refractory mantle (Fo92) shifts these conditions to lower water content s and higher pressures and temperatures near where geodynamic models indicate peak mantle wedge temperatures.
Description: x, 86 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
URI: http://hdl.handle.net/1794/11768
Date: 2010-06


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