U-Th-Pb SHRIMP AGES FOR THE MIOCENE PIRE MAHUIDA VOLCANIC COMPLEX, SOMÚN CURÁ MAGMATIC PROVINCE, PATAGONIA, ARGENTINA.

SALANI, F. M.; SANTOS S. JOAO ORESTES

San Pablo

Simposio; 9Th Southamerican Symposium on Isotope Geology; 2014

USPI

The Somún Curá Magmatic Province, Northeastern Extra-Andean Patagonia, is an extensive volcanic field developed through two effusive stages: the first one builds a mainly Oligocene large basaltic plateau; the second one is a post-shield stage which encompasses several large bimodal complexes, developed from late Oligocene through Miocene times. We are presenting the new geochronological information corresponding to a post-plateau complex: the Pire Mahuida Volcanic Complex (PMVC) (42º SL, 68º 30´W). This is a bimodal association made up mostly by acidic facies represented by rhyolite and andesite-dacite lava domes, rhyolite lava flows, acidic pyroclastic deposits, and a subordinated basaltic facies that overlies the acidic sequence. PMVC was built through several and recurrent magmatic stages related to two calderas and minor centers. Stratigraphy and morphology of felsic volcanics indicate at least two effusive phases for the lava flows and pyroclastics, being the lava domes attributed to a different event. U-Th-Pb SHRIMP determinations in zircons of two rhyolites from the volcanic field were performed at Curtin University of Technology, Perth, yielding an early Miocene age.