Metamorfismo y deformación famatinianos en la Sierra de Chepes.

DAHLQUIST, J.A.; BALDO, E.G.

Ciudad Autónoma de Buenos Aires

Congreso; XIII Congreso Geológico Argentino y III Congreso Geológico de Hidrocarburos.; 1996

Asociación Geológica Argentina e Instituto Argentino del Petróleo y el Gas.

Ordovician granitoid suites intruded ill a lew-to-medium grade metased ime ntary seq uen ce. Remnants or the country rock s arc preserve d fanning isolated and dism embered outcrops within the granitoids. In the north -western sector of the Río de Las Cañas-Tuaní cross section- the metamorphic rocks preserved a well developed thermal event and associated deformation (M2-S2) related to the granitoid intrusion. Cordieritc porphyroblasts produced in this event recorded an older schistosity (S1) produced in a previous regional mctamorphism (M1) temperature range 400-700°C and a maximum pressure of 2.5 kb (10 km) were inferred from the progression of metamorphic zones towards the east and core of the range during M2, which indicate that the igneous units were emplaced between 7- 10 km. The analysis of mega and mesoscopic deformation as well as microscopic fabri c and mineralogy, indicate that development of the S2 fabric in the metamorphic rocks was syn -kiucmutica lly accompanied hygranitoid intrusion . As the age of the granite in the SCH have been recently assigned to the Ordovician (Llandeillan ?Caradocian, Pankhurst et al. 1996), the above observations extends that age to the thermal (M,) and deformation (S,) events. Comparison of the magmatic, thermal and metamorphic history of the SCH, Ulapes, Malanzan and Los Llanos with other sectors o f Sierras Pampeanas, suggest that they were part of a magmatic belt with collisional characteristics . This belt is extended from the Sierras de San Luis in the south to the Sistema de Famatina and the Puna in north-western Argentina.