Features of the Tanalyk gold placer and its primary sources (the Baymak ore-placer cluster, Southern Urals)

Abstract

The article presents the results of a study of the Tanalyk placer, which is part of the Baymak ore-placer cluster. It is shown that gold is predominantly bright yellow in color and has lump-shaped, wedge-shaped, plate-shaped and wire-rod-shaped forms. In terms of granulometric composition, it belongs to the large and medium class and is characterized mainly by medium roundness. The uniformity of morphological varieties of gold in different lithological and stratigraphic horizons indicates the inheritance of gold from ancient deposits to young ones. Placer gold is of high quality and has a fairly consistent composition; the main impurity here is silver, the content of which varies from 0.2 to 9%. The average fineness of gold in the placer in the following areas: Baymak pond – 938, Shurinsky log – 935, Aktash log – 943, Tanalyk (lines 1502-1559) – 917. Hypergene new formations on the surfaces of gold grains are represented by high-fineness rims. A common feature for gold of all size classes is the presence in the depressions and on their surface of films of iron and manganese hydroxides, crusts of fine-grained quartz, chlorite, and less commonly biotite, in which a large number of microparticles of very high-fine gold measuring 0.1–0.5 μm were found. The typomorphism of schlich gold, its composition and features of the internal structure indicate that the main source of gold was gold-quartz mineralization in the zones of wall-metasomatites of the Kul-Yurt-Tau gold-pyrite deposit, gold-polymetallic and gold-barite deposits Grafskoye, Troitsk and Novo-Troitsk. The junction points of diagonal neotectonically active lineaments with meridional magma- and ore-supplying faults form polychronic and polygenic through ore-concentrating structures. Dispersed gold occurrences in these structures are placer-forming and serve as the main source of the formation of large placers.