HR: 1400h
AN: V53B-01 [Abstracts]
TI: Plio-Quaternary calc-alkaline and adakitic post-subduction volcanism in the Gulf of California, Mexico: the effects of slab tearing and continental breakoff
AU: Pallares, C
EM: cpallare@sdt.univ-brest.fr
AF: Unite Mixte de Recherche 6538 Domaines oceaniques, Universite de Bretagne
Occidentale-Institut Universitaire Europeen de la Mer, Place Nicolas Copernic, Plouzane, F-29280, France
AU: * Calmus, T
EM: tcalmus@servidor.unam.mx
AF: Estacion Regional del Noroeste, Instituto de Geologia, Universidad Nacional Autonoma de
Mexico, Blvd Luis Donaldo Colosio y Madrid S/N, Hermosillo, Son 83000, Mexico
AU: Maury, R C
EM: Rene.Maury@univ-brest.fr
AF: Unite Mixte de Recherche 6538 Domaines oceaniques, Universite de Bretagne
Occidentale-Institut Universitaire Europeen de la Mer, Place Nicolas Copernic, Plouzane, F-29280, France
AU: Benoit, M
EM: mathieu.benoit@univ-brest.fr
AF: Unite Mixte de Recherche 6538 Domaines oceaniques, Universite de Bretagne
Occidentale-Institut Universitaire Europeen de la Mer, Place Nicolas Copernic, Plouzane, F-29280, France
AU: Aguillon-Robles, A
EM: aaguillonr@uaslp.mx
AF: Instituto de Geologia, Universidad Autonoma de San Luis Potosi, Av. Dr. Manuel Nava no.
5, Zona Universitaria, San Luis Potosi, SLP 78250, Mexico
AU: Bellon, H
EM: bellon@univ-brest.fr
AF: Unite Mixte de Recherche 6538 Domaines oceaniques, Universite de Bretagne
Occidentale-Institut Universitaire Europeen de la Mer, Place Nicolas Copernic, Plouzane, F-29280, France
AU: Perez-Segura, E
EM: efrenpese@yahoo.com
AF: Departamento de Geologia, Universidad de Sonora, Blvd. Transversal y Rosales,
Hermosillo, Son 83000, Mexico
AU: Bourgois, J
EM: bourgois@ccr.jussieu.fr
AF: Centre National de la Recherche Scientifique, Geosciences Azur, Case 124, Universite
Paris 6, 4, Place Jussieu, Paris Cedex 5, 75252, France
AU: Cotten, J
EM: Jo.Cotten@univ-brest.fr
AF: Unite Mixte de Recherche 6538 Domaines oceaniques, Universite de Bretagne
Occidentale-Institut Universitaire Europeen de la Mer, Place Nicolas Copernic, Plouzane, F-29280, France
AB:
The Gulf of California province has recorded a complex magmatic history after the subduction of Farallon plate
stopped during Late Miocene. Besides the MORB-type tholeiitic volcanism associated with the spreading
segments in the southern Gulf and alkaline volcanism in the northernmost Gulf province, calc-alkaline and
adakitic volcanism is also encountered in the central Gulf region, between 26.30 and 29°N. It occurs in
Isla San Esteban which is located at the southeastern margin of the Pliocene extinct spreading centre of Lower
Tiburon Basin. Isla San Esteban is entirely made of andesitic, dacitic and rhyolitic subaerial lava flows, domes,
and pyroclastic deposits which K-Ar ages range from 4.5 to 2.5 Ma. Two magmatic series are distinguished: a
medium-K calc-alkaline series which evolved from basaltic andesites to rhyolites by fractionation of plagioclase,
pyroxenes, titanomagnetite and apatite; and an adakitic series including adakites of andesitic composition and
dacites derived from them through separation of plagioclase and amphibole. The subduction imprint of the
magmatism in Isla San Esteban, together with that of other Pliocene and Quaternary medium-K calc-alkaline
volcanic centers located along the Main Gulf Escarpment, suggests the occurrence of subduction-modified
mantle and possibly of slivers of oceanic crust beneath the Peninsula and the Gulf of California. Their occurrence
may be linked to the development of a Late Miocene asthenospheric window south of 29°N. We propose
that this slab window derived from the progressive tearing of the slab southwards from the edge of the earlier
Californian asthenospheric window, between the remnant of the Magdalena plate, completely attached to the
Pacific plate since 7 Ma, and the still downgoing Farallon plate. The high thermal regime linked to the opening of
the Gulf of California combined with the deep asthenospheric window may have triggered the partial melting of
remnants of oceanic crust as well as that of metasomatized mantle which represent the sources of adakitic and
calc-alkaline magmas, respectively.
DE: 1000 GEOCHEMISTRY
DE: 1100 GEOCHRONOLOGY
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly