Typomorphic features of placer gold of the Sololi River basin (northeast of the Siberian platform)

Mineralogical features of placer gold and gold-sulfide ore occurrences of the Sololi river basin from the Sololi uplift of the Olenek arch have been studied. According to the typomorphic indicators, two types of gold are distinguished. The first type is gold of a tabular and lumpy shape, often with mineral indentation imprints. The inner structure is represented by granulation, and recrystallization, high-grade intergranular veins, and high-grade shells typical of the gold of intermediate reservoirs. This type of gold is characterized by a high fineness. The sources of this type of gold were gold-bearing intermediate reservoirs of the Permian and Riphean widely developed in the studied area. The second type of gold includes subrounded and poorly rounded gold, ore gold of hooked, tabular, crystalline and angular-lumpy shapes with a pitted-bumpy or flat surface, as well as large growths of gold with quartz. The fineness of this type of gold varies from low to very high. Its primary sources were probably quartz veins genetically related to the metamorphic rocks of the Eekit series and Precambrian rhyolites. Ore occurrence formed by the Late Permian clastic rocks during the processes of the Mesozoic tectonomagmatic activation is considered as an additional source of feeding. Establishment of indicators of low–temperature hydrothermal processes as mineral parageneses, such as mercury gold, cinnabar and barite, suggests shallow and low-temperature formation conditions of this ore occurrence.