Post-Pampean cooling and the uplift of the Sierras Pampeanas in the west of Cordoba (Central Argentina)

Abstract

An extensive survey on the cooling history by K/Ar biotite and muscovite dating of the basement rocks of the Sierras de Cordoba ( Argentina) and San Luis (Argentina) was carried out and interpreted in terms of a differential uplift history of the different blocks. Large pegmatitic muscovites from the Sierras de Cordoba record Late Cambrian to Early Ordovician ages. Beginning of cooling in the Sierra de San Luis is documented by muscovite booklets from pegmatites yielding ages between 448 Ma and 438 Ma. The limit between those age domains is marked by the Los Tuneles and Guacha Corral shear zones accommodating the vertical displacement. Constraints by K/Ar mica ages and structural observations suggest two principal phases of compression around 480 Ma and 430 Ma. The latter coincides with the final collision of the Cuyania Terrane to the western outboard of Gondwana. The Pachango Shear Zone, which cuts the Los Tuneles Shear Zone records the latest phase of ductile deformation in the Late Silurian.