The origin of a primitive trondhjemite from the Trans-Mexican Volcanic Belt and its implications for the construction of a modern continental arc
Por:
Gomez-Tuena, A, Mori, L, Rincon-Herrera, NE, Ortega-Gutierrez, F, Sole, J, Iriondo, A
Publicada:
1 jun 2008
Resumen:
A remarkable suite of Miocene high-silica trondhjemites discovered in the central Trans-Mexican Volcanic Belt indicates that slab melts can ascend through the mantle and crust while suffering only minor compositional modifications. Despite carrying an assortment of deep crustal xenoliths, the trondhjemites preserve the most depleted isotopic compositions ever measured in the Mexican arc, with values that are nearly identical to those of the Pacific mid-oceanic-ridge basalts. These rocks also have high Sr/Y ratios, and extremely fractionated heavy rare earth element patterns at relatively high Mg number (Mg#), features that are all consistent with melts from the subducted oceanic crust that had only limited interaction with mantle peridotite during ascent. Nonetheless, modeling results indicate that these unusual geochemical features can be modified by more extensive mantle assimilation, resulting in compositions that could match those of more typical intermediate rocks from Mexico. The
Filiaciones:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Queretaro 76230, Mexico
Univ Nacl Autonoma Mexico, Inst Geol, Mexico City 04510, DF, Mexico
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