Volcanic evolution of the eastern sector of the Cordillera de San Buenaventura: Geodynamic implications for the Souther Puna.

EMILCE BUSTOS; BAEZ, WALTER ARIEL; GIANLUCA NORINI; ARNOSIO MARCELO

Puerto varas

Congreso; Cities on Volcanoes 9; 2016

IAVCEI

At the South of the Central Volcanic Zone of the Andes, in the Puna Plateau, the Cordillerade San Buenaventura (located at 27°S) marks the boundary between the normal subductionzone to the north and the flat subduction zone to the south. Volcanism in this area took placesince 9 Ma to recent and can be stratigraphically summarized in four supersynthems, eachone limited by first order unconformities, which respond to changes in the geodynamics ofthe area. San Buenaventura Supersynthem (9-7 Ma) groups rhyolitic ignimbritic units ofcalco-alkaline affinity emplaced on top of a metamorphic basement. The interaction ofmantle and derived arc magmas with felsic lower crustal rocks produce crustal melts thaterupted forming these rhyolitic ignimbrites. Then, the magmatic system changed, with theemplacement of arc related calco-alkaline products, forming stratovolcanoes complexes. Thischange of composition and eruptive style, from rhyolitic caldera-forming explosive activity toandesitic-dacitic effusive and explosive central volcanism, is marked by an angularunconformity at the base of the Lower La HoyadaSupersynthem (7.04 -