Geologic And Geochemical Reconnaissance Of Isla San Esteban- Post-Subduction Orogenic Volcanism In The Gulf Of California

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Journal Article: Geologic And Geochemical Reconnaissance Of Isla San Esteban- Post-Subduction Orogenic Volcanism In The Gulf Of California

Abstract
Isla San Esteban is a calc-alkaline volcanic island in the center of the Gulf of California, a zone of active continental rifting. Its rocks range in composition from andesitic to rhyolitic with dacitic flows and sills making up more than 80% of its volume. Most other islands of the north-central Gulf of California are fragments of continental crust and include extensive metamorphic and sedimentary, as well as igneous units. K-Ar age determinations have resulted in ages of 2.5 to 2.9 m.y. for samples from Isla San Esteban. These ages indicate that a volcano was erupting siliceous lava flows and pyroclastic units in the center of the Gulf of California 9.5 m.y. after subduction beneath the continental margin ceased and a minimum of 4.5 m.y. after extension began to open the Gulf. A site of young orogenic volcanism at one other location in the Gulf of California region is further evidence that a lag time of more than 9 m.y. may elapse between the end of subduction of a lithospheric plate and the last eruption of orogenic rocks. A fragment of subducted oceanic crust may be the source of the calc-alkaline magma and the complex tectonic setting of the region may provide the environment necessary for the unusual volcanism.

Author 
Dana L. Desonie








Published Journal 
Journal of Volcanology and Geothermal Research, 1992





DOI 
Not Provided
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Citation

Dana L. Desonie. 1992. Geologic And Geochemical Reconnaissance Of Isla San Esteban- Post-Subduction Orogenic Volcanism In The Gulf Of California. Journal of Volcanology and Geothermal Research. (!) .