Magmatic and subsolidus deformation in the Mamil Choique Granitoids, SW North Patagonian Massif

LÓPEZ DE LUCHI, M.G., ; CERREDO, M.E.; RAPALINI, A.E.

Salta

Simposio; 12th Reunión de Microtectónica y Geologia Estructural; 2004

Comisión de Tectónica-AGA

Permian granitoids constitute almost the 60% of the Sierra de Mamil Choique. They were intruded by partially porphyric monzogranites located at the eastern sector of the Sierra and by undeformed Permian high Rb/Sr granite. The deformed granitoids display a magmatic planar fabric and banding that were overprinted by two regional folding events. Solid-state deformation in the pluton produced both crystal-plastic and brittle features. D3, that developed at upper-green schist facies, is a folding phase associated with SC structures and protomylonite microstructures. S-surfaces are defined by the pre-existing foliation whereas the cross-cutting C-surfaces are associated with small biotite flakes. In higher strained domains an unevenly distributed protomylonite texture is present with biotite fishes and rounded plagioclase porphyroclasts partially enveloped by microshears with new crystallized biotite, muscovite and quartz. D3 is bracketed between 325/300-278Ma. The younger folding D4 is characterized by upright fragile folds of fairly constant NE strike with axis plunging both to the NE and SW. Mamil Choique granitoids are either ferromagnetic (107-1105 x 10-5 SI) or paramagnetic (2-44 x 10-5 SI). P para% (4.1-21.5) is due to biotite. Planar magnetic fabrics dominate over linear (Flinn parameter