Gold and platinum group metals in skarns of the Ol’ginsk and Dal’negorsk ore districts of Primorye and some issues of metallogeny of the southern Sikhote Alin region

Abstract

The Triassic‐Jurassic carbonaceous sequence of Sikhote Alin includes metalliferous sediments represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues [3, 4], siliceous rocks with pyrophanite (“brown cherts”), tin‐iron ores, “ilmenite‐ biotite‐feldspar” (metamorphosed clayey) rocks, and “itabirites.” They are characterized by high contents of Au, Ag, Pt, and Pd [2] and the ubiquitous presence of minerals of these elements. Hydrothermally altered sandstones, as well as siliceous‐clayey and siliceous rocks, which are associated with syngenetic metalliferous rocks, contain grains of gold, silver, argentite, platinum, Pd-platinum, itenbohaardite, and other minerals of noble metals. It should be mentioned that identifications of all minerals mentioned in this paper have been confirmed by microprobe analyses. Another type of hydrothermal ores is represented by Mn-rich amphibole‐pyroxene rocks that contain native gold, silver, Pdplatinum, and other minerals of gold, silver, and platinum group metals (PGM). Hydrothermal ores are products of the regeneration of metalliferous rocks due to the evolution of Late Cretaceous granitoid massifs. The amphibole‐pyroxene rocks formed after calcareous sandstones, which are probably of Late Triassic age [3]. The southern Sikhote Alin region incorporates numerous Late Cretaceous skarn and vein (cavity-filling) deposits of lead, zinc, silver, tin, tungsten, and iron. Skarns are characterized by high concentrations of Mn derived from manganese rocks [1]. Similarly as other metalliferous rocks, the manganese rocks are enriched in Pb, Zn, Ag, Sn, W, and Fe. Hydrothermal deposits of these metals define the metallogenic profile of the southern Sikhote Alin region. Manganese and other metals mentioned above were probably derived from metalliferous rocks of the Triassic‐Jurassic carbonaceous sequence. The metalliferous rocks and associated hydrothermal rocks contain Au and PGM. For example, these metals are concentrated in amphibole‐pyroxene rocks of the Shirokaya Pad area of the Ol’ginsk district. These rocks are analogues of the adjacent manganiferous