Absarokites from the Western Mexican Volcanic Belt : constraints on mantle wedge conditions


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dc.contributor.author Hesse, Marc
dc.coverage.spatial Western Mexico
dc.date.accessioned 2008-12-23T17:14:50Z
dc.date.available 2008-12-23T17:14:50Z
dc.date.issued 2002-08
dc.identifier.uri http://hdl.handle.net/1912/2599
dc.description Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 2002 en
dc.description.abstract We have investigated the near liquidus phase relations of a primitive absarokite from the Mascota region in Western Mexico. Sample M.102 was chosen because it has high MgO contents, a high Mg# and F090 olivine phenocrysts, indicating it is primitive mantle melt. High-pressure experiments on a synthetic analogue of the absarokite composition with a H2O content of either -1 7 wt% or -5.1 wt% were cared out in a piston cylinder apparatus. The composition with -1.7 wt% H2O is multiply saturated with olivine and orthopyroxene as liquidus phases at 1.6 GPa and 1400°C. At the same pressure clinopyroxene appears 30°C below the liquidus. With a H2O content of -5.1 wt% composition M.102 is multiply saturated with olivine and orthopyroxene on the liquidus at 1.7 GPa and 1300°C. Assuming batch melting, we suggest that absarokite M.102 segregated from a depleted lherzolite or harburgite residue at depth -50 km depth in the mantle wedge. Unlike most lavas in the region, the absarokite has not ponded and fractionated at the crust mantle interface (-35-40 km), and the temperatures of multiple saturation indicate that the mantle wedge beneath the Jalisco block is hotter than previously thought. The low degree batch melting of an original metasomatised harzburgite source, can produce the observed trace element abundances. The liquidus phase relations are not consistent with the presence of non-peridotitic veins at the depth of last equilibration. Therefore, we propose that the Mascota absarokites segregated at an apparent melt fraction of less than 5% from a depleted peridotitic source. They initially formed by a small degree of melting of a metasomatised original source at greater depth. en
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en
dc.relation.ispartofseries WHOI Theses en
dc.subject Volcanism en_US
dc.subject Submarine geology en_US
dc.title Absarokites from the Western Mexican Volcanic Belt : constraints on mantle wedge conditions en
dc.type Thesis en
dc.identifier.doi 10.1575/1912/2599

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