%0 Journal Article
%A Crespo Feo, María Elena
%A Luque Del Villar, Francisco Javier
%A Fernández Barrenechea, José María
%A Rodas González, Magdalena
%T Mechanical graphite transport in fault zonesand the formation of graphite veins
%D 2005
%@ 0026-461X
%U https://hdl.handle.net/20.500.14352/50265
%X This paper describes a vein-shaped graphite occurrence in which, for the first time, the geological,mineralogical and isotopic evidence support its formation by physical remobilization of previouslyformed syngenetic graphite. The deposit studied is located in the Spanish Central System and it occursalong the contact between a hydrothermal Ag-bearing quartz vein and a graphite-bearing quartzitelayer. The characteristics of this occurrence differ from those of fluid-deposited vein-type graphitemineralization in that: (1) graphite flakes are oriented parallel to the vein walls; (2) graphitecrystallinity is slightly lower than in the syngenetic precursor (graphite disseminated in the quartzite);and (3) the isotopic signatures of both types of graphite are identical and correspond to biogeniccarbon. In addition, the P-T conditions of the hydrothermal Ag-bearing quartz veins in the study area(P <1 kbar, and T up to 360ëC) contrast with the high degree of structural order of graphite in the vein.Therefore, physical remobilization of graphite can be regarded as a suitable alternative mechanism toaccount for some cases of vein-shaped graphite deposits. Such a mechanism would require a previousconcentration of disseminated syngenetic graphite promoted, in this case, by the retrograde solubility ofquartz. This process would generate monomineralic graphite aggregates enhancing its lubricantproperties and permitting graphite to move in the solid state along distances in the range of up toseveral metres.
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