TYPOMORPHISM OF PLACER GOLD OF THE KASMINSKO-URSKY ORE DISTRICT (NORTH-EASTERN SALAIR)
V.V. Kolpakov1, P.A. Nevolko1, V.S. Vesnin1, P.A. Fominykh1
V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia
Keywords: Salair, gold, placers, typomorphism, morphology, fineness, impurity elements, hypergene transformation, mineral inclusions, primary sources, isoferroplatinum
Abstract
The morphology, chemical composition, ore and placer mineral associations of gold placers of the Ursky ore cluster and the less studied Kasminsko-Chesnokovsky prospective area of northeastern Salair indicate numerous and diverse primary sources, and the presence of gold in intermediate collectors. The fineness of 970-1000‰ is mainly due to hypergene-transformed gold. Placers were formed mainly due to quartz, quartz-carbonate, quartz-(carbonate)-sulfide veins and stockworks of the gold stage of mineralization, including superimposed on barite-polymetallic, with fine and finely dispersed gold, mineralization of the Ursky ore cluster and on dikes of the main composition. One of the sources of gold is also metasomatites (carbonate-micaceous, quartzites, quartz-albite-epidote, with rutile), accompanying gold ore bodies, or not associated with them. Differences in the typomorphic properties of placer gold are due to different contributions of primary sources. In the placers of the upper part of the Ur River, the Zvonchikha River, this is probably predominantly gold mineralization superimposed on dikes of the main composition. The gold has a high fineness (>910‰), it contains copper impurity (up to 1-6 wt.%) and, in one case, inclusion of Pd telluride. Quartzites are also a possible source of Au (as at the Kopna deposit). In the lower part of the Ur river placer, the Au fineness and the amount of copper-bearing gold decrease, and the frequency of occurrence of gold with mercury impurity increases. Gold mineralization is probably superimposed on polymetallic or localized in the rocks of the pechorkinsky complex. Polymetallic gold-bearing mineralization is indicated by the presence of gold with a fineness below 820‰ (as at the Iyunsky deposit). The sources of gold in the placers of the Chesnokovka and Kurnichikha rivers, in addition to mineralization associated with basic dikes, are mineralization characterized by gold with a fineness of 820-910‰ (including very small and fine), usually containing mercury impurity. These may be quartz veins and metasomatites on terrigenous rocks of the Suenginsky formation, known in the area. Inclusions in gold of placers of the Kasminsko-Ursky ore district are represented by minerals of sulfide ores, metasomatites, weathering crusts. In the gold of the Kasminsko-Chesnokovsky area, in contrast to the gold of the Ursky ore cluster, no inclusions of copper minerals (chalcopyrite, bornite, covellite, tennantite), common in pyrite-polymetallic ores, were found. The typomorphic properties of gold of the Aprelsky deposit reflect the multiplicity of sources, among them there are quartz veins, metasomatites on rocks of the Pecherkinsky formation, possibly mineralization superimposed on polymetallic. The sources of gold of the Khristinovsky Yama placer are probably diverse and similar to those of the placers of the Ur and Zvonchikha rivers. The isoferroplatinum grain from the Khristinovsky Yama placer can be attributed to the vilyuisky type.
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