Cerro Corona 87Sr/86Sr ratios, High Range of Somún Curá, Extra Andean Patagonia.

REMESAL, M; MARO, G.; PARICA, C A,; MILLER, H

Hiedelberg

Simposio; 23rd Latin American Colloquium; 2014

Germany Research Foundation

Cerro Corona fits a shield volcano in the ?Alta Sierra de Somún Curá? (High Range of Somún Curá), the bimodal complex of youngest relative age in the Magmatic Province of Somún Curá. Its activity, mainly effusive, is represented by alkaline, basaltic, trachyandesitic-basaltic and trachytic lava flow, with a discontinuity of 2% in SiO2 between both groups. According the geochemistry analyses, the most compositional extremes are cogenetic. The geochemical modelling reveals that the trachytic magmas would be the consequence of fractional crystallization of trachyandesitic-basaltic liquids through a high degree of fractionation (~70%) of clinopyroxene, Fe and Ti oxides, plagioclase and apatite. The alkaline feldspar should be fractionated into a late stage of the evolution of the system together with the biotite, engaging the important role in the differentiation of most evolved trachytes. Furthermore, the presence of quite a lot of disequilibria textures, mainly in the phenocrysts of the trachytic rocks, which is evidence of alteration under the physical conditions in the magmatic reservoir, which suggests the influence of the emplacement of hottest magmas in the base of it with or without recharge (Maro and Remesal, 2012). The trachyandesitc-basaltic lavas building the main structure of the Cerro Corona are aphiric of intersertal texture composed by plagioclase, olivine, clinopyroxene and opaque minerals. They are characterized by high SiO2 (>50%) and low MgO (≈4%). The most differentiated rocks are porphiric with high content af anorthoclase, clinopyroxene, olivine, plagioclase, biotite and apatite. They have: SiO2 >57% and Mg