Volcanism of the Triassic Cuyo Basin in the Calingasta-Barreal Valley, western Argentina

SEBASTIÁN ROCHER; FERNANDO ABARZÚA; CARLA C. TAPIA BALDIS; M. GIMENA LÓPEZ

San Juan

Jornada; III Jornadas de Geología de Precordillera; 2015

Departamento de Geología - Fac. de Ciencias Exactas, Físicas y Naturales - Universidad Nacional de San Juan

The Middle-Upper Triassic deposits of the Calingasta-Barreal valley, northern expression of the Cuyo Basin of western Argentina, contain the register of rift- related basic and silicic volcanism. The petrology of these rocks, particularly the silicic members, has been poorly documented as well as their relationships with previous magmatic events. Basalts consist in two lava flow units characterized by flow foliations, columnar jointing and vesicles at the top. Ignimbrites form two flow units which show small volume, massive structure, low grade of welding and high aspect ratio. Geochemically, basic rocks are alkaline basalts associated to partial melting of a mantle OIB like enriched source. Ignimbrites are high silica rhyolites, with alumina, alkalis and trace element compositions similar to A-type granites. Triassic bimodal volcanism of Cuyo Basin shows a distinctive extensional within-plate magmatic setting, different from the previous Choiyoi arc related to within-plate transitional rhyolite magmatism.