Volcanic Evolution of the Eastern Sector of the Cordillera de San Buenaventura: Geodynamic Implications for the Southern Puna

EMILCE BUSTOS; MARCELO ARNOSIO; WALTER BAEZ; GIANLUCA NORINI

Conferencia; Cities on Volcanoes 9; 2016

At the South of the Central Volcanic Zone of the Andes, in the Puna Plateau, the Cordillera de San Buenaventura (located at 27°S) marks the boundary between the normal subduction zone to the north and the flat subduction zone to the south. Volcanism in this area took place since 9 Ma to recent and can be stratigraphically summarized in four supersynthems, each one limited by first order unconformities, which respond to changes in the geodynamics of the area. San Buenaventura Supersynthem (9-7 Ma) groups rhyolitic ignimbritic units of calco-alkaline affinity emplaced on top of a metamorphic basement. The interaction of mantle and derived arc magmas with felsic lower crustal rocks produce crustal melts that erupted forming these rhyolitic ignimbrites. Then, the magmatic system changed, with the emplacement of arc related calco-alkaline products, forming stratovolcanoes complexes. This change of composition and eruptive style, from rhyolitic caldera-forming explosive activity to andesitic-dacitic effusive and explosive central volcanism, is marked by an angular unconformity at the base of the Lower La Hoyada Supersynthem (7.04 -