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

DEMARTIS, M. *, CONIGLIO, J. E. **, PINOTTI, L. P. *, D`ERAMO, F. J. *, AGULLEIRO INSÚA, L. A. *, MUÑOZ, A. A.** Y PETRELLI, H. A. **

RIO CUARTO

Congreso; MinMeT 2010; 2010

Asociación Mineralógica Argentina- Dpto de Geología UNRC

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