Las Andesitas Estrechura del Complejo Volcánico Piroclástico del Río Chubut Medio (Paleoceno-Eoceno Medio)

The Estrechura Andesites from the Middle Rio Chubut Volcanic-Pyroclastic Complex (Paleocene-Middle Eocene). 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.