Indicator typomorphic features and potential sources of small-size placer gold from the Ebelyakh area (northeast Siberian platform)

Abstract

In order to detect potential sources studied are mineralogical-geochemical special features of the Billyakh River gold placer which belongs to the Ebelyakh diamondiferous area. It is shown that the main sources for the gold are auriferous reservoir rocks of Neogene-Quaternary age. The indicator typomorphic features of the gold include small size (less than 0.5 mm), scaly and platy forms, rough shagreen surface with casts of pressing minerals, and high fineness (900–999 ‰). The most highly informative feature is a strongly modified internal structure of the gold showing evidence of granulation and recrystallisation. Unrounded gold particles are also found in the study area, which suggests proximity of a primary source. They are characterized by a very small size (less than 0.2 mm), angular-cloddy forms, rough, porous surface, widely ranging fineness (535 to 999 ‰), heterogeneous chemical composition, and a complex, multi-phase internal structure. A potential primary source is predicted to be localized at the intersection of N—S and F—W-treading fault zones in the upper Billyakh River. This prediction is supported by the discovery in the river basin of Ebelyakh to disseminate gold-sulfide mineralization confined to the N—S-trending fault zone.