TRAPPED CARBON DIOXIDE IN EAST ANTARCTIC GRANULITES : EVIDENCE FROM FLUID INCLUSIONS

概要

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Charnockites from the Skallen area in the Lutzow-Holm Bay region of East Antarctica show carbonic fluid inclusions trapped within garnet, feldspar and quartz. Microthermometric and micro-Raman laser analyses characterize these fluids to be pure CO_2. With a maximum density of 1.05g/cm^3,these fluids are inferred to represent the traces of the ambient fluid which effected the reduction of water activites and dehyrated large segments of the Gondwanian deep crust. A sympathetic decrease in the densities of carbonic fluids trapped within early to late crystallizing minerals is recorded. This defines an uplift path which crossed higher to lower density isochores, in close correspondence with the T-convex metamorphic P-T trajectory computed for this terrane from mineral phase equilibria constraints. We provide the first direct evidence for the infiltration of CO_2 in the East Antarctic granulites, a well established mechanism believed to have been instrumental in generating charnockites in the other Gondwana continents.
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