Petrografía y geoquímica de los granitoides de la quebrada del Arenoso, Sierra de La Huerta, Sierras Pampeanas Occidentales, San Juan, Argentina

PONTORIERO, SANDRA; CASTRO DE MACHUCA, BRÍGIDA

Tarija

Congreso; XII Congreso Geológico de Bolivia; 1996

Sociedad Geológica Boliviana

La Huerta range, San Juan province, Argentina, belongs to the Sierras Pampeanas System of precambrian-lower paleozoic age. Granitoid rocks from El Arenoso creek, in the eastern flank of the range are attributed tentatively to a syntectonic intrusive event of lower paleozoic age that affected the crystalline basement (Famatinian Orogeny: Early Ordovician). The granitic bodies are small and have elongated shapes. They were emplaced later during the main metamorphic-tectonic episode, in concordance with the foliation of the host rocks: tonalitic-dioritic gneisses and amphibolites of medium to high-grade (upper amphibolite to granulite facies). The granitoids are compositionally homogeneous and their composition is that of a medium-grained leucocratic monzogranite. Pegmatites closely related with the plutonic rocks are scarce and were identified in the surrounding metamorphic rocks. The granitoids underwent ductile deformation that caused a conspicuous foliated fabric which trends NNW-SSE, in concordance with the regional tectonic trend. The geochemical data point to a calc-alkaline and slightly peraluminous parent magma, with high silica and potassium contents. According to their characteristics, these rocks are thought to be orogenic-type granites related to a subduction process in a volcanic arc tectonic setting (VAG).