Mineralogy of a highly fractionated replacement unit from ?Angel? pegmatite, Comechingones pegmatitic field, Córdoba, Argentina. Argentina

DEMARTIS MANUEL, JOAN MELGAREJO DRAPER, PURA ALFONSO, JORGE CONIGLIO, LUCIO PINOTTI, FERNANDO DERAMO

Revista de la AGA

AGA

Lugar: Buenos Aires; Año: 2011 p. 68 - 70

0328-2767

The Comechingones Pegmatitic field (CPF), southeastern Pampean Pegmatitic Province (Galliski 1994a and b; Hub 1994 and 1995; Galliski 1999), locates in the northwestern Sierra de Comechingones, Córdoba province, Argentina. It is composed of a great number of Be?Nb?Ta?P?U-rich pegmatites of the rare-element class (some of them grading to the muscovite class), beryl?columbite?phosphate subtype (Galliski 1994a). These pegmatites were emplaced synkinematically during the compressive deformation of the crustal scale Guacha Corral shear zone (Demartis 2010). The pegmatites are generally well zoned. Border and wall zones are composed of fi ne- to mediumgrained quartz + muscovite ± microcline ± albite. Coarse- to very coarse-grained intermediate zones are composed of graphic microcline + quartz + muscovite ± albite ± garnet; phosphates and uranium minerals occur in these zones. Core is composed of milky quartz with subordinated microcline and muscovite, with accessory crystals of beryl and minerals of the columbite series. Replacement units are rare and have been found only in a few cases, as in the ?Ángel? pegmatite, and they generally affect graphic microcline + quartz intermediate zones. ?Ángel? pegmatite, cropping out in the southern part of the CPF (~ 32º 18? S and 64º 54? W), is particularly known because of its varied primary and secondary uranium mineralogy (Angelelli 1950). The aim of this contribution is to describe the extremely fractionated minerals from the replacement units. quartz + muscovite ± microcline ± albite. Coarse- to very coarse-grained intermediate zones are composed of graphic microcline + quartz + muscovite ± albite ± garnet; phosphates and uranium minerals occur in these zones. Core is composed of milky quartz with subordinated microcline and muscovite, with accessory crystals of beryl and minerals of the columbite series. Replacement units are rare and have been found only in a few cases, as in the ?Ángel? pegmatite, and they generally affect graphic microcline + quartz intermediate zones. ?Ángel? pegmatite, cropping out in the southern part of the CPF (~ 32º 18? S and 64º 54? W), is particularly known because of its varied primary and secondary uranium mineralogy (Angelelli 1950). The aim of this contribution is to describe the extremely fractionated minerals from the replacement units. fi ne- to mediumgrained quartz + muscovite ± microcline ± albite. Coarse- to very coarse-grained intermediate zones are composed of graphic microcline + quartz + muscovite ± albite ± garnet; phosphates and uranium minerals occur in these zones. Core is composed of milky quartz with subordinated microcline and muscovite, with accessory crystals of beryl and minerals of the columbite series. Replacement units are rare and have been found only in a few cases, as in the ?Ángel? pegmatite, and they generally affect graphic microcline + quartz intermediate zones. ?Ángel? pegmatite, cropping out in the southern part of the CPF (~ 32º 18? S and 64º 54? W), is particularly known because of its varied primary and secondary uranium mineralogy (Angelelli 1950). The aim of this contribution is to describe the extremely fractionated minerals from the replacement units.