The Late Cretaceous Epithermal Beqtakari Prospect; Bolnisi Mining District, Georgia, Lesser Caucasus

Beqtakari is a Au-Ag-Zn-Pb ± Cu prospect located in the Bolnisi mining district of Georgia, Lesser Caucasus. It is hosted by an intermediate to felsic calcalkaline volcanic system of Upper Cretaceous age. This study focuses on mineralogical and petrography observations and stable isotope analysis based upon detailed fieldwork mapping combined with drill core logging in order to characterize the volcanic lithofacies and the mineralizing fluid conditions. The mineralization is divided in two zones, the Au-Ag-rich zone, which is hosted in a strongly silicified rhyodacite and the precious and polymetallic mineralization which is hosted in hydrothermally altered autobreccia. Late dikes related to a rhyodacitic dome are cross-cutting the Au-Ag-rich unit. The latter mineralization is covered by a welded tuff unit called the proximal sub-formation of Gasandami. The genetic relationship of this proximal sub-formation with the silicified rhyodacitic unit remains to be determined. Sulphur isotope results from the mineralization stage shows distinct values between sulphates and sulphides. Geothermometry using δ34S of sulphate-sulphide pairs yield higher temperature than expected, implying reequilibrium or disequilibrium