On new potentially ore-bearing Kakhtarminsky area in Eastern Sayan nickel-platinum-bearing province

The Kakhtarminsky potentially ore-bearing region (POR) in the Eastern Sayan is situated in thearrangement of the Herma-Kakhtarminsky tectonic ledge in the Lower Devonian volcanic rocks of the Agul depression. Precambrianmetamorphic and igneous formations prevail in the structure of the protrusion. Its northern part is composed of Riphean and Paleozoicgranitoids and gabbroids of the Berezovsky and Verkhnekrasninsky massifs, and the southern part is a fragment of the synclinalstructure. The wings of this structure are presented by gneisses and schists, containing bodies of amphibolites and granulites. This factallows to compare it with the gneisses and schists of the Archaean Khaylaminsky series of the Biryusinsky block. The nuclear (central)part of the synclinal structure is formed by the rocks of the lower Kuskunaksky series of the Karagansky complex. These rocks are alsoprevalent within the Kansky block. The sequence consists predominantly of amphibolite, amphibole and biotite gneisses, rarely marblesand quartzite. More than 20 bodies of ultramafic rocks are found in the nuclear part of the syncline and near it; they are classified assubvolcanic facies of ultramafic volcanics. The bodies have a linear, lens and ellipsoid shapes with the size of up to 4.0 sq.km on thesurface. According to their morphology and size they are similar to the ore-bearing Kingashsky massif. High-magnesian dunites are alsoprevalent in their composition. Spots of sulphides are established in relatively large massifs. The zone of sulphide mineralization withnickel content from 0.19 to 0.4%, chromium up to 0.7%, platinum up to 1 g/t, palladium up to 0.5 g/t is identified in the area bygeophysical methods. The ore bodies within the sulphide zone stretch along the surface in the first kilometers, and have up to onehundred meters of the apparent power. Taking into account the area of mineralized rocks and the content of the ore elements, forecastresources by category amounted to P2 are: nickel - 1,000,000 tons, copper - 30,000 tons, cobalt - 6,000 tons, gold - 38 tons, platinum -51 tons and palladium - 25 tons. Geological-tectonic position, composition, petrochemical and geochemical characteristics of theKakhtarminsky ultramafic rocks indicate their formation resemblance to the ore-bearing ultramafic rocks of the Kingashsky orejunction; and metamorphic sequences are correlated with the Idarsky greenstone belt of the Kansky and Biryusinsky blocks, containingthe Kingashsky ore district. A number of direct forecasting and search features are established in the Kakhtarminsky POR that indicatethe possibility of opening here a field of sulphide-nickel mineralization with the associated gold-platinum ore. There are findings ofsperrylite from the alluvial streams draining ultramafic massifs, and on the binary diagrams most of the spots of the analysis ofKakhtarminsky dunites and peridotites almost coincide with the Kingashsky trend. Thus, these data allow us to consider theKakhtarminsky POR as a new object of the East Sayan nickel-platinum province, promising to search for nickel sulphide withassociated precious metals. A number of features allow forecasting the discovery of deposits of nickel of the Mount Cate type in thebodies of dunites. The presence of linear (band) massifs of ultramafic rocks does not preclude the discovery of sulphide nickel depositswith low-copper content of the Kambaldinsky type here due to the powerful series of volcanic ultramafites (komatiites). The authorsrecommend to perform a complex geophysical study, detailed searches, including the electrical prospecting and magnetometry, searchroutes and exploration wells with a corresponding set of testing on the territory of Kakhtarminsky POR.

Keywords

Authors

References