Magmatic response to early aseismic ridge subduction: the Ecuadorian margin case (South America)

Abstract:

A geochemical and isotopic study of lavas from Pichincha, Antisana and Sumaco volcanoes in the Northern Volcanic Zone (NVZ) in Ecuador shows their magma genesis to be strongly influenced by slab melts. Pichincha lavas (in fore arc position) display all the characteristics of adakites (or slab melts) and were found in association with magnesian andesites. In the main arc, adakite-like lavas from Antisana volcano could be produced by the destabilization of pargasite in a garnet-rich mantle. In the back arc, high-niobium basalts found at Sumaco volcano could be produced in a phlogopite-rich mantle. The strikingly homogeneous isotopic signatures of all the lavas suggest that continental crust assimilation is limited and confirm that magmas from the three volcanic centers are closely related. The following magma genesis model is proposed in the NVZ in Ecuador: in fore arc position beneath Pichincha volcano …

Año de publicación:

2003

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