Caracterización metamórfica de unidades metapelíticas de la Serie Occidental de La Cordillera de la Costa: el afloramiento de Infiernillo, Pichilemu, Chile

SEBASTIÁN OSVALDO VERDECCHIA; GILDA COLLO; FRANCISCO MUÑOZ; CAMILO PALAPE

San Miguel de Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

Asociación Geológica Argentina

The western series of Carboniferous-Permian metamorphic basement of central Chile are integrated by a high-pressure and low-temperature succession represented by blueschist, greenschist, metapelites and metarenites. In the metapelites, the main metamorphic M1 event is characterized by growth of white mica, which orientation defines a S1 foliation (D1, subparallel to a S0 primary foliation), and is overlapped by two fragile deformation stages without mineral growth. The crystallo-chemical white mica b parameter was calculated in all samples, with values between 9.028 and 9.056 Å, representative of high-pressure gradient. These values argues against a retrograde origin for the white mica, and could be linked to the metamorphic event associated with the accretionary evolution during the Early Carboniferous to Late Triassic subduction beneath the southwestern Gondwana margin.