Typomorphism of placer gold of the Khatyrkhay ore-placer cluster (Upper-Amga area)

It is necessary to study typomorphism of placer gold, because it is an effective and promising trend for forecasting formation of possible types of gold deposits in poorly studied areas, which does not require considerable costs. A study of typomorphic features of placer gold of the Khatyrkhay ore-placer cluster (Upper-Amga area) allowed determining that it is characterized by mineralogical-geochemical features of the same type. Fine high-standard gold with similar morphologic features prevails in all placers. It is mainly poor rounded, has an irregular shape and ore outlook that is typical for autochthonous gold and close relation of auriferous placers to neighboring primary sources. Trace elements and microinclusions of ore and rock-forming minerals identified in placer gold reflect a specific character of mineral composition of the Khatyrkhay ore field that additionally confirm a conclusion about delivery of gold from the neighboring primary sources of the gold-sulfide formation. A discovery of such microinclusions as tellurides of bismuth (tellurobismuthite, galenobismuthite) indicates conditions of the formation of gold mineralization related to exocontact metasomatism with the intrusion of monzonite-syenite composition. Inner structures of gold of this ore-placer cluster are characterized by the middleand coarse-grained structure, sometimes the structures of full granulation and disintegration are observed in them, being signs of thermal metamorphism, formed during intraand post-ore transformations. Placer gold almost lacks high-standard shells and microveinlets that indicates short-term presence of alluvial gold in supergene conditions. In general, on the basis of the study of typomorphism of placer gold it is concluded that the assumed gold ore source of the Khatyrkhay placer field is the gold-skarn type of mineralization (Lebedinsky), manifested in skarnified rocks and beresitized granite gneisses.

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