PGE-BEARING GOLD-SULFIDE MINERALIZATION IN THE RYABINOVYI ALKALINE MASSIF, CENTRAL ALDAN, RUSSIA

This paper contains new data on the mineral composition of gold-sulfid e veinlet disseminated mineralization associated with the Ryabinovyi m ultiphase ring-type alkaline massif in the Aldan region of southern Ya kutia. The following minerals of platinum-group elements (PGE) were di scovered: and studied comprehensively: moncheite (platinum ditelluride ) and erlichmanite (iridium- and ruthenium-bearing osmium disulfide). They are associated with three bornite varieties distinct in optical p roperties and in Me/S and (Cu + Ag)/Fe ratios, djurleite and anilite-d igenite (silver-bearing minerals of the chalcocite group), carrollite (cobalt thiospinel), and tetrahedrite. PGE concentrations in igneous r ocks, alkaline metasomatites, and gold-sulfide ores of different types were analyzed by neutron activation and spectrochemical methods. The study of fluid inclusions shows that the gold-sulfide mineralization w as formed at temperatures of 400-160 degrees C with the involvement of two types of fluids: (a) a high-pressure (4.0-7.3 kbar) CO2-H2O fluid with high salinity and (b) an H2O-rich fluid with low salinity. Both fluids and metals participated in the formation of the PGE-rich gold-s ulfide mineralization and derived from a deep source.