MODELADO DE FLUIDOS DE LAS PEGMATITAS DE LA PORCIÓN SUR DEL DISTRITO COMECHINGONES, CÓRDOBA, A PARTIR DE NUEVOS DATOS DE ISÓTOPOS ESTABLES

DEMARTIS, MANUEL; CONIGLIO, JORGE; PINOTTI, LUCIO; D'ERAMO, FERNANDO; AGULLEIRO INSÚA, LEONARDO; MUÑOZ, ADRIEL; PETRELLI, HUGO

Universidad Nacional de Río Cuarto

Congreso; 10º Congreso de Mineralogía y Metalogenia; 2010

Universidad Nacional de Río Cuarto

In southern Comechingones Pegmatitic Field, Sierras Pampeanas of Córdoba, two types of pegmatites emplaced within the Guacha Corral Shear Zone (GCSZ) during the Famatinian orogeny were identified. P-T conditions and isotopic compositions of mineralizing fluids were calculated from O and H stable isotopes analyses of quartz-muscovite pair samples of both types of pegmatites. Type I pegmatites crystallized at ~600-700ºC and 5 kb. Calculated isotopic compositions for waters in equilibrium with quartz and muscovite from this type of pegmatites suggest processes of magma degassing. Type II pegmatites formed at ~2.5 kb, and a wide range of temperatures between 561 and 291ºC, probably evidence a transition from pegmatitic to hydrothermal stage. Calculated O and H isotopic compositions for waters in equilibrium with type II pegmatitic quartz-muscovite pairs suggest processes of mixing in variable proportions of magmatic-pegmatitic fluids with deeply recirculated meteoric solutions generated at high altitudes during deformation. Low D compositions of fluids equilibrated with type II pegmatite quartz-muscovite minerals can be explained by these processes, and constitute a conspicuous isotopic feature of many hydrothermal palaeozoic deposits of the Sierras Pampeanas Orientales.