%0 Journal Article
%A Luque Del Villar, Francisco Javier
%A Rodas González, Magdalena
%T Constraints on graphite crystallinity in some Spanish fluid-deposited occurrences from different geologic settings
%D 1999
%@ 0026-4598
%U https://hdl.handle.net/20.500.14352/110842
%X Epigenetic, vein-type graphite mineralization originates by deposition from C—O—H fluids in high-temperature environments. Consequently, fluid-deposited graphite is uniformly highly crystalline in volumetrically large occurrences. This work examines the factors controlling graphite crystallinity in fluid-deposited occurrences with reference to some case studies from southern Spain where vein-type graphite is associated with a variety of host rocks. Possible causes influencing high crystallinity of graphite in these occurrences include: (1) large graphite occurrences are generated from large volumes of fluids that maintain their temperatures for long periods of time, which is easier at higher temperatures; (2) high temperature conditions are required for a fluid to precipitate a major part of its dissolved carbon during a small temperature decrease; (3) carbon is incorporated into C—O—H fluids mainly through devolatilization reactions which also require high temperatures; (4) highly crystalline graphite generated at high-T/high-P conditions is less susceptible to resorption as P decreases or by subsequent fluid flow; (5) graphite precipitation involves high activation energy that can be overcome only if the temperature is high enough. These causes can be extrapolated to most vein-type graphite deposits worldwide.
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