ESTRATIGRAFÍA Y GEOQUÍMICA DEL VOLCANISMO DE COMPOSICIÓN INTERMEDIA (MIOCENO SUPERIOR- PLIOCENO) EN EL EXTREMO ORIENTAL DE LA CORDILLERA DE SAN BUENAVENTURA (PUNA AUSTRAL)

Stratigraphy and geochemistry of the intermediate composition volcanism (Upper Miocene-Pliocene) at the eastern portion of the Cordille- ra de San Buenaventura (Southern Puna). The San Buenaventura mountain range is composed by volcanic units with composition ranging between acid to intermediate and age ranging from Upper Miocene to Holocene. They cover a Neoproterozoic-Lower Paleozoic metamorphic basement with some plutonic intrusions and Ordovician sediments with intercalated volcanic rocks. The La Hoyada Volcanic Complex of intermediate composition outcrops at the eastern part of the range. This complex in- cludes explosive and effusive high-K calc-alkaline rocks with compositions between andesite-trachyandesite and dacites. Based on field observations and new geochemical and geochronological data it was feasible to partially reconstruct the stratigraphy of this complex divided into at least two volcanic sequences between ca. 7-2.5 Ma. In comparison with the calc-alkaline rocks from the frontal volcanic arc between 25° and 27° lat S it is possible to assign them the similar origin from mantle sources with a crustal component.