Volcanic centres in the Alta Sierra of Somún Curá and surroundings, Patagonia, Argentina

REMESAL, MARCELA B.; MARO, GUADALUPE; MACKERN, ALAN; PARICA, CLAUDIO; SALANI, FLAVIA

Congreso; 22st Colloquim on Latin American Earth Sciences (LAK); 2011

The oligocene Somún Curá basaltic plateau covers a large area in the north of the Extra-andean argentine Patagonia. the mostly Miocene post-plateau volcanic associations are distributed over the plateau either as bimodal volcanic complexes (Salani et al., 2008) or as monogenetic basaltic centres. alta Sierra of Somún Curá (aSvC) is the youngest bimodal volcanic complex; it shows a typical alkaline basalt-trachyte association of intraplate geochemistry. although major and trace elements display fairly linear trends, the conspicuous disequilibrium textures as well as some chemical features may suggest that other petrogenetic processes beside fractional crystallization controlled the evolution of the series. the aSvC is surrounded by minor monogenetic centres emplaced over the oligocene Somún Curá plateau; these mostly basaltic centres show several petrologic types (Remesal et al, 2007). Morphological studies makes evident that there are effusions with different rheological features (spatter cones, short lava flows, long lava flows, etc.). The evaluation of the structural control based on satellite images (false colour and RGB bands combined), along with aerial photographs and field data, allowed us to compile and classify around 200 vents within an area of 3000 km2. The distribution of these vents defines two main directions: one of nE-SW strike and the other SE-nW oriented. Both directions result parallel to two major lineaments recognized to the south of aSvC: abdala and telsen alignments which cut across the Jurassic to Cenozoic volcano-sedimentary record (Franchi et al.,1977; Lapido & Page, 1979; Cortés, 1987 Ardolino & Franchi, 1996). Most of the large bimodal post-plateau complexes located south of aSvC are also arranged along a SE-nW oriented belt (Remesal et al., 2011)