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oai:docta.ucm.es:20.500.14352/571162025-08-08T17:20:45Zcom_20.500.14352_14col_20.500.14352_15

Ignacio San José, Cristina de Castiñeiras García, Pedro Márquez González, Álvaro Oyarzun Muñoz, Roberto Lillo Ramos, F. Javier López Ruiz-Labranderas, Iván 2023-06-20T16:49:00Z 2023-06-20T16:49:00Z 2003 0020-6814 https://hdl.handle.net/20.500.14352/57116 http://www.tandf.co.uk/journals/titles/00206814.asp The rocks of the 1982 eruption of El Chichón volcano (Chiapas, Mexico) display a series of geochemical and mineralogical features that make them a special case within the NW-trending Chiapas volcanic belt. The rocks are transitional between normal arc and adakitic-like trends. They are anhydrite-rich, and were derived from a water-rich, highly oxidized sulfur-rich magma, thus very much resembling adakitic magmas (e.g., the 1991 Pinatubo eruption). We propose that these rocks were generated within a complex plate tectonic scenario involving a torn Cocos plate (Tehuantepec fracture zone) and the ascent of hot asthenospheric mantle. The latter is supported by an outstanding negative 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 the transitional 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 the high sulfur content and 34S values of the El Chichón system (about +5.8), as result of a contribution of SO2 in fluids released from an underlying mafic magma. eng open access El Chichón Volcano (Chiapas Volcanic Belt, Mexico) Transitional Calc-Alkaline to Adakitic-Like Magmatism: Petrologic and Tectonic Implications journal article