Revista de la Asociación Geológica Argentina
versión impresa ISSN 0004-4822
CONIGLIO, Jorge E et al. Structural control of vein-type fluorite deposits of Cerro Áspero batholith, Sierras Pampeanas of Córdoba. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.4, pp. 507-520. ISSN 0004-4822.
With over 1,000,000 t of total reserves, the high-K devonian granites of the Cerro Áspero batholith (440 km2) are the most important fluorite-bearing granitic suite in the Sierras Pampeanas. The epithermal fluorite veins, of Cretaceous age, fill in steeply dipping, NE, EW, and NW strike-slip regional fault zones, with thicknesses generally less than 3 metres. They can be continued up to 200 m deep below surface. The geometry and distributions of the veins were tectonically controlled by divergent shear zones, probably linked with the opening of the south Atlantic ocean. In the study area, this regional situation established a dextral simple shear system related to NNE lineaments, that is characterized by N70ºE striking extensional structures, less than 1 km long, and NE and NW striking shear systems, more than 4 km long. These shear systems show typical patterns of transcurrent faults such as stepovers, offsets, bends and horsetail splay. Four successive mineralizing stages were recognized on the basis of textural and structural analyses of the veins. The emplacement of these mineralizing stages were controlled by a discontinuous activity of dextral couple, with the minimum paleostress (σ3) always oriented toward NNW. The fact that some of the fluorite stages are absent in several veins in the investigated areas, confirm that the mineralized structures had different times of opening and sealing, and thus the depositional sequence established could be used as an effective prospection criteria. The main ore bodies are related to extensional zones (releasing bends) and extensional structures, which registered the whole mineralizing sequence.
Palabras clave : Vein-type fluorite deposits; Tectonic control; Simple shear; Eastern Sierras Pampeanas.