Lower crustal melting during thrust faulting and arc volcanism in the late miocene to pliocene Payenia Volcanic Province

Abstract

In the late Miocene to Pliocene period, the Payenia volcanic province of southern Mendoza, Argentina, was a ected by a shallowly subducting Nazca slab, which caused compression and uplifting of the San Rafael Block (SRB) in the Andean foreland in eastern Payenia and thrusting in the Malargüe Fold and Thrust belt (MFTB) in the eastern Andean Cordillera of western Payenia (Ramos et al. 2014). The slab shallowing led to a broadening of the arc with arc-type volcanism extending up to 500 km behind the trench (Kay et al. 2006, Litvak et al. 2015). Volcanism mainly occurred in the western sector around the MFTB in the Sierra de Palauco (Dyhr et al. 2013) and in the eastern sector on the SRB (Litvak et al. 2015). The lavas from the Palauco and SRB regions fall in two groups: 1) a low Sr/Y group (Sr/Y < 55) comprising trachy-basalts to trachytes with classical arc-type trace element patterns; and 2) a high Sr/Y group (Sr/Y = 53-165) comprising andesites to rhyolites with distinctly low trace element contents except for high positive Ba, Sr and Pb anomalies.