Abstract
A recent investigation of the bolivianita Anahi mine reveals that the mineralization is the product of intracratonic thermal fluids which migrated along a deep lineament and through a basin with an Upper Proterozoic sediment filling. The mineralization is hosted by Cambrian limestone and related to a collapse structure. It occurs within caverns of dissolution, fractures and open spaces which were formed by karstic processes and circulation of thermal fluids. The different types of quartz precipitated by mixing of ascendant thermal fluids enriched in silica with descendent cold meteoric water close to the paleo-surface. The geometry of the mineralizacion follows the subterraneous morphology of the paleo-karst. The amorphous silica precipitated close or on top of the paleo-aquifer as opal-chalcedony with some disseminated pyrite. The crystalline gem quartz grew below this sinter cap. The exact age of the mineralization is unknown. But it is most likely that the process of selective dissolution of the Cambrian limestone started after its consolidation during a phase of continental uplift of the regolith under humid climate and continues until today. The migration of thermal fluids was probably induced by Upper Cretaceous alkaline igneous activity.
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