Native gold from alluvial deposits of the Kyvvozhsky district and its probable primary sources (Volsko-Vymskoe rise, Middle Timan)

Abstract

Based on the study of typomorphic features of gold from alluvial deposits of the Kyvvozh region of Middle Timan, including industrial placers, the most probable genetic types of primary sources were determined. The size of gold particles varies widely, reaching the size of small nuggets; along with rounded ones, there are weakly rounded and unrounded particles. Many of them have undergone repeated deformations in the form of envelope-shaped bends, dents and tears. Most gold coins have high-fineness rims. Gold always contains Ag, sometimes Cu, Pd and Cu. Gold particles with a block structure with high-silver vein zones are often found. In intergrowths with gold and in the form of inclusions are noted in it pyrite, galena, and occasionally minerals of the cobaltine-gersdorfite series, ankerite, galenobismutite, native bismuth, aurostibite, and also sudovikovite (PtSe2), which was first identified in the region. Three types of gold have been identified: 1 – homogeneous silver-containing, 2 – block with highly silvery vein-like zones, 3 – rare silver-containing with impurities of Cu, Pd. The morphology, composition and structure of placer gold indicate its entry into placers from various sources, including nearby sources. Of greatest interest are the zones of development in Riphean rocks of hydrothermal veinlet-disseminated sulfide mineralization, oriented in the northwest direction, partially exposed during the development of placers. Gold with Cu and Pd impurities is most likely associated with derivatives of mafic magmatism. The Volsko-Vymskoe, as well as the Tsilemskoe and Chetlasskoe uplifts of Middle Timan can be considered promising in terms of primary gold content and deserve further study and prospecting.