Carbon Transport in a Faulted Metapelite Terrane During Continental Collision

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NabelekEAR-9980374This proposal is for study of carbonic fluid generation and transport in the Black Hills, South Dakota during Proterozoic metamorphism associated with the Trans-Hudson continental collision. The aim is to determine the composition and mass of fluids generated during prograde metamorphism of graphitic metapelitic from biotite to second sillimanite grade and to determine the pathways for expulsion of the fluids. Generation of carbon-bearing fluids during metamorphism of graphitic metapelites has received little attention compared to fluids generated by calc-silicate reactions, even though phase equilibria predicts that the metamorphic fluids must contain a significant carbonic component. The study will include XRD, Raman spectroscopic, and isotopic analysis of disseminated and fluid-deposited graphite over the range of grades, and will also include microthermometric, Ram spectroscopic, and stable isotope analysis of fluid inclusions in veins. The results will be interpreted in view of metamorphic reactions in the Black Hills, published graphite-fluid phase equilibria, and isotopic fractionations. The study will lead to a comprehensive model of carbonic fluid production and egress during regional metamorphic events associated with continental collisions. It will provide better understanding and quantification of the contribution of regional metamorphism to the global carbon cycle.