The volcanic association of Las Lomadas area, Corona Chico Volcanites. Somún Curá Magmatism. Río Negro province, Argentina

Abstract

This contribution deals with the Corona Chico Vulcanites, within the Somun Cura Magmatic Province, northern Extra-Andean Patagonia. The studied area is located to the north of the Alta Sierra de Somun Cura Volcanic Complex and is made of several basaltic volcanic buildings of varied morphologies: spatter cones, tuff ring and long lava flows related to small shield volcanoes (of scutulum type). Petrographic characteristics as well as whole rock chemical composition suggest a time progressive increase in alkalis content and a shift from early transitional terms to basanitic rocks in the latest stages. A simulation of the source yielded for Las Lomadas rocks an astenospheric source in the garnet-spinel facies, with associated low partial melting percentages (< 7-8%). Within the studied rock set, the spatter cones sequence displays geochemical affinities with the basaltic component of Alta Sierra de Somun Cura Volcanic Complex.