Abstract

ARAGON, E. et al. The Estrechura Andesites from the Middle Rio Chubut Volcanic-Pyroclastic Complex (Paleocene-Middle Eocene). Rev. Asoc. Geol. Argent. [online]. 2004, vol.59, n.4, pp.619-633. ISSN 0004-4822.

The Estrechura Andesites show a basalt-trachyte tholeiitic transitional trend. Liquid immiscibility is present from basalts to trachytes. Thus, basalts and trachybasalts are interpreted as the fractionating magmas; the trachyandesites are the enriched (mix) residual magma - immiscible liquid; and the trachytes are the segregated immiscible liquid at the magma chamber top. Even though it is a water poor system, the concentration of volatile in one of the immiscible liquids enables few ignimbrite extrusions that carry non-vesiculated perlitic magma blebs in pumice core. The depth of the magma chamber emplacement is estimated to be close to the 4,5 kilometers.

Keywords : Skarn; Ca - Fe; Cretaceous; Chubut; Argentina.

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