The Role of Manganese As a Controller of Gold Mineralization/Abstract

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The San José de Las Malezas quartz-gold deposit is located on the North side of the Cuban Ophiolitic Complex, within the Structural-Facial Zone "Zaza", Province of Villa Clara, Cuba. In the area of the deposit there is a well developed listwaenitic zone that begins with (i) massive and relatively little altered serpentinites that pass into (ii) iron-altered serpentinites which are in gradational contact with (iii) completely carbonatized rocks and (iv) a core of silicified rocks and quartz veins. Copper and gold mineralizations are associated with these quartz bodies, but binary correlation analysis of geochemical data suggests that the ores are genetically independent of one another. In concordance with the proposed genetic model supported by thermodynamic calculations and field observations, copper is thought to be introduced by a hydrothermal process, whereas gold was leached from the serpentinites. The evolution of manganese minerals from anaerobic to aerobic species provoked a reducing environment which hampered the precipitation of gold and other ores inside and near the serpentinites. Accordingly, a significant negative correlation between gold and manganese in similar areas of hydrothermally altered serpentinites, may be good indicators of possible gold concentrations.

The mechanical transportation of very small and thin scales of native gold from the serpentinites by the fluids is also suggested as a possible mechanism to explain the presence of this kind of scales inside the iron-altered zone.