Ag-Sb deposits of the Yustid depression, eastern Russia and northwest Mongolia

Ag-Sb deposits of a new economic district that occurs on the boundary of the southeastern Altay Republic of eastern Russia and northeast Mongolia are herein described. Mineralization of this region is divided into two periods—(1) Late Hercynian (Mo-W deposits) and (2) Mesozoic (Sn-W, as well as Ni-Co-As, Ag-Sb, and Sb-Hg deposits). The deposits of main economic interest, silver-antimony, consist of siderite-sulfosalt veins and vein zones that occur in contact-metamorphosed coal-bearing terrigenous rocks of Devonian age. These veins occur to depths of up to 900 m, and occur along strike for 3 to 3.5 km; their thicknesses range up to 12 m. The deposits are mineralogically and geochemically similar to silver deposits of the Yakutian, Pamir, Slovakian, Coeur D'Alene (USA), and Freiberg (Germany) ore districts. The main ore minerals are quartz, carbonate, and Ag-tetrahedrite, with minor chalcostibnite, chalcopyrite, bournonite, zinkenite, arsenopyrite, and pyrite. Sulfides are characterized by widespread isomo...