Native Gold from Alluvial Sediments of the Kyvvozh Region and Its Possible Sources (Vol–Vym Uplift, Central Timan)

Abstract

The most possible genetic types of primary sources are determined on the basis of study of typomorphic features of gold from alluvial sediments of the Kyvvozh region of Central Timan, including economic placers. The size of gold particles widely varies, reaching small nuggets; there are rounded, weakly rounded, and nonrounded particles. Many of them underwent recurrent deformations in form of envelope curves, pits, and fractures. Most gold grains have high-fineness rims. Native gold always contains Ag and, locally, Cu, Pd, and Hg. There are frequent blocky gold particles with high-Ag veinlet zones. Native gold is intergrown with and contains inclusions of pyrite and galena and rarely minerals of the cobaltite–gersdorffite series, ankerite, galenobismuthite, native bismuth, and aurostibite, as well as sudovikovite PtSe₂, which is identified for the first time in the region. Three types of native gold are recognized: (1) homogenous Ag-bearing, (2) blocky with high-Ag veinlet zones, and (3) rare Ag-bearing with Cu and Pd. The morphology, composition, and structure of placer gold indicate its contribution from various (including proximal) sources. The NW-oriented zones of hydrothermal stringer-disseminated sulfide mineralization, which are partly exposed during placer exploitation, are most interesting. Native gold with Cu and Pd is most likely related to the derivatives of basic magmatism. The Vol–Vym, Tsil’ma, and Chetlas uplifts of Central Timan can be considered the promising for primary gold and deserve further study and searching works.