CONICET | Buscador de Institutos y Recursos Humanos

ABSTRACT: Granitic pegmatites emplacement from southern Comechingones pegmatitic field, Córdoba. Southern Comechingones pegmatiticfield is composed of zoned Be-Nb-Ta-U−granite pegmatites with mostly lenticular morphologies, hosted in mylonitic rocksof the Guacha Corral shear zone. Important orientation changes in the host rock mylonitic foliation were identified, thus definingan anastomosed general pattern of the shear zone both at the outcropping and regional scale. Pegmatites were mostlyconformably emplaced within mylonitic foliation. Discordant pegmatites were also described. An internal planar fabric definedby the orientation of quartz, feldspar and muscovite from the intermediate zone of the granitic pegmatites was developedduring the Guacha Corral shear zone deformation. Mineral stretching lineations in pegmatites generally coincide with thatof the mylonitic host rocks. Structural analysis suggest that pegmatites of the Comechingones pegmatitic field were emplacedsynkinematically with the ductile amphibolite facies deformational event of the Guacha Corral shear zone, developed underprogressive simple shear deformation. Almost pure reverse sense of shear with westward tectonic transport characterizedthis deformational event, developed during Famatinian orogeny. Anastomosed general pattern of the mylonitic foliation in theGuacha Corral shear zone was the responsible for the origin of the spaces in which pegmatites and granites emplaced. Theserocks then cooled and crystallized simultaneously with progressive deformation. Moreover, discordant pegmatites constituteRiedel shear model T extensional fractures, and represented ascent magma channels. These structures would have been progressivelysheared and rotated from their original orientation, until they were subparalell to the enclosing mylonitic foliation,outcropping at present time as almost conformably pegmatites.Keywords: Emplacement, Comechingones pegmatitic field, Guacha Corral shear zone

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