Abstract

RUBINSTEIN, Nora; GOMEZ, Anabel  and  KLEIMAN, Laura. Caracterización litofacial y geoquímica de las Volcanitas del área del distrito minero El Infiernillo, Mendoza. Rev. Asoc. Geol. Argent. [online]. 2013, vol.70, n.3, pp.382-389. ISSN 0004-4822.

El Infiernillo mining district is a porphyry Cu (Mo) type deposit located in the northern part of the San Rafael Massif. It is hosted by a volcaniclastic sequence which corresponds to the Choiyoi Magmatic Cycle. This volcaniclastic sequence comprises three ignimbritic facies of dacitic-trachyandesitic composition, a dacitic laccolith and a set of andesitic dykes. The geochemical characteristics of the ignimbrites and the laccolith are similar to those of volcanic rocks belonging to the lower section of Choiyoi Magmatic Cycle from other mineralized and non mineralized areas of the San Rafael Massif. These rocks have a geochemistry typical of an arc-related magmatism over a thickened crust. Conversely, the geochemistry of the andesitic dykes is similar to the volcanics of the upper section of Choiyoi Magmatic Cycle. The ore deposit develops an alteration halo with a concentric pattern consisting of a central quartz neck surrounded by a potassic alteration zone followed by a phyllic outer halo and small polymetallic veins. The phyllic alteration affecting the ignimbrites led to losses of Na and Ca and gains of Mg, Si, Fe and K and these chemical changes are revealed by its alteration mineralogy. The geologic setting allows constraining the age of the El Infiernillo ore deposit close to the Early-Late Permian limit.

Keywords : Lithofacies; Geochemistry; Volcaniclastic sequence; Lower section; Choiyoi Magmatic Cycle; San Rafael Massif.

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