INGEIS   05370
INSTITUTO DE GEOCRONOLOGIA Y GEOLOGIA ISOTOPICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Pumpellyita del Lago Futalaufquen, Chubut, Patagonia Argentina
Autor/es:
MARIA ELENA VATTUONE; LEAL, PABLO; LATORRE, CARLOS OSCAR
Lugar:
FCEyN-UBA
Reunión:
Congreso; VIII Congreso de Mineralogía y Metalogenia 2006; 2006
Institución organizadora:
Catedras de Mineralogía y Petrologia FCEyN-UBA
Resumen:
ABSTRACT: The aim of this contribution is to describe the mineralogical features, genesis and geodynamic implicances of Fe-pumpellyite in low grade metamorphic assemblages (pumpellyite-actinolite facies). This mineral together with chlorite, epidote, actinolite (+ albite – quartz) were found in Jurassic/Cretacic basaltic rocks where they appear in the groundmass or filling amygdules of several millimeters long. Optical properties allowed us to determine two varieties of pumpellyites: 1) fibrous habit, green colour, 2V =40° (+); γ:c =35°; β=1.72 and 2) prismatic or equant crystals of brown colour, 2V= 40°(+) to uniáx. (-) and β=1.69-1.72. Both optical characteristics and the chemical analyses corresponds to Fe rich pumpellyite. Green pumpellyite could have grown of primary chlorite meanwhile brown pumpellyite genesis seems to be related to poor Ca-pyroxene. The pumpellyite composition suggests that lithological units were generated in marginal basins under steep or moderate steep geothermal gradients with high ƒO2.
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