Typomorphism of fine placer gold and potential primary sources of the Anabar mineral subprovince (the North-East of the Siberian Platform)

Typomorphous features of placer gold in the basins of the Anabar and the Bolshaya Kuon- amka were investigated for the purpose of determining its indicator signs for the prediction of potential primary sources. It is shown that the main sources of gold are auriferous reservoir rocks of Neogene- Quaternary age. The indicator typomorphic features of this kind of gold are small size (–0,5 mm), scaly and platelet shape, coarse shagreen surface with the prints of mineral indentation, and high fineness (900– 999 ‰). The most informative feature is its strongly altered internal structure showing evidence of granula- tion and recrystallization. Autochthonous gold of ore habit is also found. Characteristic features of this type of gold are a very small size (–0,2 mm), angular-cloddy forms of individual particles, rough porous surface, widely ranging fineness (535 to 999 ‰), heterogeneous chemical composition, and a complex, multi-phase internal structure. This indicates the presence of neighboring primary sources. Hydrothermal-metasomatic formations with disseminated gold-sulfide mineralization, discovered at the sites of tectonic jointing of carbonate rocks developed in fault zones could be such sources. Considering epigenetic mineral associa- tions, quartz-potassium feldspar and quartz hydrothermal-metasomatic formations are identified. Ore min- eralization of disseminated type is represented (in decreasing order) by pyrite, gold, chalcopyrite, galena, sphalerite and silver. Gold is found in native form, and in association with pyrite (quartz metasomatites) and potassium feldspar (potash feldspar metasomatites). So, near-fault hydrothermal-metasomatic forma- tions with gold-sulfide impregnated mineralization were discovered for the first time at the territory under investigation. As a result of the studies, indicator typomorphous signs of the fine gold of proximal migration for these assumed indigenous sources were revealed.

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