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Albitite Hosted Gold-Sulfide Mineralization:An Example from the Paleoproterozoic Aravalli Supracrustal Sequence, Bhukia Area, Western India
The Paleoproterozoic Debari supracrustals of the Aravalli Supergroup in the Bhukia area, Western India, host a possibly unique type of mesothermal gold-sulfide mineralization in ultrasodic albitite rocks along second generation deformation structures. Petrographic and petrochemical studies have indicated the ubiquitous presence of graphite, besides albite, in the mineralized lodes. The genetic link of sodic fluids in accumulation of sulfides and the role of graphite in mobilizing the 'invisible gold' from base metal sulfides to appreciable concentrations of native gold is suggested to have occurred in three stages, namely, (i) gold co-precipitated and localized in the crystal lattices of sulfide minerals during the initial phase of albitite-sulfide deposition; (ii) during the peak deformation and metamorphic stage and under reducing conditions the graphite catalyzed the lattice-bound gold to reconstitute it as substrates within first generation perforated pyrite, corroded arsenopyrite and pyrrhotite and (iii) further increase in shearing and associated hydrothermal activity, expelled the gold grains from sulfide systems to be precipitated along the grain boundaries of sulfides and/or quartzcarbonate veins.