Vein graphite deposits geological settings origi

Authors: F J Luque JM Huizenga E CrespoFeo H Wada L Ortega J F Barrenechea

Publish Date: 2013/09/22

Volume: 49, Issue: 2, Pages: 261-277

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Abstract

Graphite deposits result from the metamorphism of sedimentary rocks rich in carbonaceous matter or from precipitation from carbonbearing fluids or melts The latter process forms vein deposits which are structurally controlled and usually occur in granulites or igneous rocks The origin of carbon the mechanisms of transport and the factors controlling graphite deposition are discussed in relation to their geological settings Carbon in granulitehosted graphite veins derives from sublithospheric sources or from decarbonation reactions of carbonatebearing lithologies and it is transported mainly in CO2rich fluids from which it can precipitate Graphite precipitation can occur by cooling water removal by retrograde hydration reactions or reduction when the CO2rich fluid passes through relatively lowfO2 rocks In igneous settings carbon is derived from assimilation of crustal materials rich in organic matter which causes immiscibility and the formation of carbonrich fluids or melts Carbon in these igneoushosted deposits is transported as CO2 and/or CH4 and eventually precipitates as graphite by cooling and/or by hydration reactions affecting the host rock Independently of the geological setting vein graphite is characterized by its high purity and crystallinity which are required for applications in advanced technologies In addition recent discovery of highly crystalline graphite precipitation from carbonbearing fluids at moderate temperatures in vein deposits might provide an alternative method for the manufacture of synthetic graphite suitable for these new applicationsThis paper is a contribution from project CGL201016008 of the Spanish Ministry of Economy and Competitivity The authors acknowledge constructive criticisms of two anonymous referees as well as helpful suggestions by A Gilg Associate Editor and G Beaudoin Editor in Chief that helped to improve the paper We thank JL González Instituto de Geociencias for the excellent photographic artwork

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