Geotectonic significance of the Marayes Viejo basalt based on K-Ar age dating; Western Pampean Ranges, San Juan province, Argentina

CASTRO DE MACHUCA, BRÍGIDA; SUMAY, CELINA; BRUNO, NATALIA; MEISSL, ESTELA; CONTE-GRAND, ALICIA

Pucón

Simposio; III South American Symposium on Isotope Geology; 2001

Servicio Nacional de Geología y Minería (SERNAGEOMIN) y Universidad de Chile

The absolute age of the Marayes Viejo Basalt (BMV) presented in this work, confirms the spatial relationships observed between the different lithostratigraphic units, and supports the conclusion that the magmatic activity in the area of the Marayes-El Carrizal basin, Western Sierras Pampeanas, is initiated in the Neopaleozoic, prior to the formation and filling of the basin. The radiometric age, stratigraphic position, petrographic and chemical characteristics, do not coincide with the characteristics of typical intraplate basalts of other Triassic basins described from the geologic terrain of the Pampean Ranges. On the contrary, they suggest an active subduction during Permian time for the western margin of the Pampean Ranges.