Gold composition and PTX formation conditions of the tardan-2 gold-sulphide-quartz ore manifestation in beresites (Eastern Tuva)

We considered the mineralogical and geochemical peculiarities of native gold, the conditions of ore formation and genesis of Tardan-2 gold occurrence situated in berezitized plagiogranites and granodiorites. We identified that Tardan-2 belongs to low-sulfide gold-quartz beresite-listwänite formation type with the wide variations in the gold fineness from 834 to 201 % (607 %, in average) and evolution of native gold composition from medium-fineness gold to mercury kustelite. According to the composition of the Au-bearing assemblages, the Tardan-2 corresponds to the gold-bismuth-sulfosalt-chalcopyrite mineral type with Bi mineralization and minerals of the Au-Ag-Hg series. We determined that the Au-bearing assemblages was formed in the hypabyssal facies environment (depth 2,1-3,0 km; P 0,73-0,98 kbar) due to Na, K and Mg chloride fluids with salinity of 8,7-1,7 wt. % NaCl equiv. and temperatures of 280-120 °C.