Adakitic and calc-alkaline lavas of Antisana volcano (Ecuador): petrogenetic hypothesis

Abstract:

Volcanic rocks from Antisana volcano (Ecuador) show a clear enrichment in Sr, Nb, Ti and P relative to normal calc-alkaline rocks. Furthermore, some of them show low heavy rare earth and Y concentrations, a feature of typical adakites. However, as the P-T conditions for adakite genesis are not appropriate beneath the volcano, we propose that these rocks are derived from the partial melting of an hydrated mantle, previously and heterogeneously metasomatised by adakitic magmas at shallower depth.L'etude des laves du volcan Antisana (Equateur) revele la presence de laves calco-alcalines, enrichies en Sr, Nb, Ti et P par rapport a des laves calco-alcalines normales. Certaines laves montrent egalement un appauvrissement net en terres rares lourdes, typique des adakites. Cependant, les conditions necessaires a la genese d'adakites n'etant pas reunies sous l'Antisana, nous proposons que ces roches a caractere adakitique soient issues de la fusion partielle d'un manteau hydrate, prealablement metasomatise de facon heterogene par des liquides adakitiques issus de la plaque plongeante.

Año de publicación:

1999

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