%0 Journal Article
%A Ignacio San José, Cristina de
%A Castiñeiras García, Pedro
%A Márquez González, Álvaro
%A Oyarzun Muñoz, Roberto
%A Lillo Ramos, F. Javier
%A López Ruiz-Labranderas, Iván
%T El Chichón Volcano (Chiapas Volcanic Belt, Mexico)Transitional Calc-Alkaline to Adakitic-Like Magmatism:Petrologic and Tectonic Implications
%D 2003
%@ 0020-6814
%U https://hdl.handle.net/20.500.14352/57116
%X The rocks of the 1982 eruption of El Chichón volcano (Chiapas, Mexico) display a series ofgeochemical and mineralogical features that make them a special case within the NW-trendingChiapas volcanic belt. The rocks are transitional between normal arc and adakitic-like trends. Theyare anhydrite-rich, and were derived from a water-rich, highly oxidized sulfur-rich magma, thus verymuch resembling adakitic magmas (e.g., the 1991 Pinatubo eruption). We propose that these rockswere generated within a complex plate tectonic scenario involving a torn Cocos plate (Tehuantepecfracture zone) and the ascent of hot asthenospheric mantle. The latter is supported by an outstandingnegative S-wave anomaly widely extending beneath the zone, from 70 to 200 km in depth. The adakitic-like trend would be derived from the direct melting of subducting Cocos plate, whereas thetransitional rocks would have resulted from the mixing of two poles, one reflecting a mantle source,and the other, the already mentioned adakitic melts. The basaltic source would also account for thehigh sulfur content and 34S values of the El Chichón system (about +5.8), as result of a contributionof SO2 in fluids released from an underlying mafic magma.
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