Abstract

GOMEZ, Anabel  and  RUBINSTEIN, Nora. Genesis of El Infiernillo Mining District, San Rafael Block, Mendoza. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.2, pp.231-238. ISSN 0004-4822.

El Infiernillo Mining District is located in the San Rafael Block (34º38'20";68º47'37"), province of Mendoza, Argentina. It is a porphyry Cu (Mo) type deposit which is hosted by a volcaniclastic sequence. It develops an alteration halo with a concentric pattern consisting of a central quartz neck surrounded by a potassic alteration zone and outwards a phyllic halo and small polymetallic veins. The potassic halo has a paragenesis of K-feldspar-quartz-(biotite). Three silicification phases are related to this alteration stage, one of them (with temperature between 550° and 390°C and salinity between 35 and 47 %) genetically linked to the copper mineralization. The phyllic alteration consists of quartz-illite-(rutile) with minor albite. The albitization process points out to an early phase of this phyllic stage. The fluid inclusions together with the textures of the quartz neck suggest the shallowing of the active hydrothermal system. The disseminated ore paragenesis consists of bornite, chalcopyrite-molibdenite, pyrite, (galena-sphalerite). The presence of molibdenite-quartz veins indicate the transition from the potassic to the phyllic stage while the pyrite-quartz ones point out to a transition to a fragile deformation regime during which the polymetallic veins, with a paragenesis of chalcopyrite- sphalerite, pyrite, (Ag) tetrahedrite, galena were formed. The petrologic characteristics of the volcaniclastic host rocks reveal that they correspond to the lower section of Choiyoi magmatic cycle. The magmatic and structural controls constrain the age of this ore deposit to the Early-Middle to Late Permian.

Keywords : Genesis; Cu (Mo) porphyry; Lower section; Choiyoi magmatic cycle.

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