Abstract

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.

Keywords : Vein-type fluorite deposits; Tectonic control; Simple shear; Eastern Sierras Pampeanas.

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