Mineralogical and geochemical features of heavy concentrates from creeks of the North-Western end of the Оkhotsk terrane (Khabarovsk Krai)

Abstract

The work presents the mineralogical and geochemical features of heavy concentrates from eight gold-bearing tributaries of the Anmandykan 2nd Creek in Khabarovsk krai: West otvilok, East otvilok, Somnitelny, Smezhny, Perevalny, Sobol, Vstrechny and Khvory. The mineral composition of heavy concen-trates of the right creeks differs from those of the left ones by a signifcantly higher percentage of minerals of the garnet group, sulfdes and native gold and a lower content of zircon and amphiboles. Garnets in heavy concentrates have different compositions and belong to the almandine and grossular-andradite series. Native gold grains in placers are yellow, small, mostly weak and medium-rounded, often with inclusions of quartz, feldspar, pyrite, iron oxides and hydroxides, and zircon. The native gold grains have low fneness and contain only Ag. The native gold grains are rimmed by thin, intermittent, porous aggregates of high-fneness gold. Two gold placer mineral assemblages are identifed, which include native gold, chalcopyrite, sphalerite and pyrite in assemblage 1 and native gold, scheelite and minerals of the garnet group (mainly of the grossular-andradite composition) in assemblage 2. Our data allow the forecast of the presence of two primary gold sources of gold-quartz-sulfde and skarn types. The comparison of results of mineralogical and geochemical studies showed their suitability and expressiveness for the interpretation of geological and metallogenic features of the studied area.