Два типа ассоциаций минералов платиновой группы в золотоносных россыпях северо-западной части Кузнецкого Алатау

Translated title of the contribution: Two types of platinum group minerals assemblages from the gold-bearing placers are widespread in the northwest Kuznetsk Alatau

V. A. Gusev, G. Nesterenko, S. M. Zhmodik, D. K. Belyanin

Research output: Contribution to journalArticlepeer-review

Abstract

Quaternary gold-bearing alluvial placers are widespread in the northwest of the Kuznetsk Alatau and in the Kelbes region under study. They contain a small amount of platinum group minerals (PGM). The paper presents new data on the PGMs from the placers of Kelbes region.
The purpose of the study was to search of PGMs in the alluvial sediments, reveal the shape and relationship of PGMs in inter-growths, identify their composition and the type of platinum mineralization's primary source. The objects under study were PGMs from two alluvial placers. The first is located at the confluence of the Edinis and Nikolskaya rivers. The second is in the valley of the Sukhaya River. Optical and scanning electron microscopy was used for it.
The PGMs from the placers are mainly platinum-ferrous and ruthenium-iridium-osmium alloys (20 and 11 grains respectively). They have been found both as individual grains and inclusions in each other. Grains of Fe-Pt and Ru-Ir-Os alloys are different in their morphology. The surface of Fe-Pt alloys is smooth. The shape is rounded. On the contrary, the shape of Ru-Ir-Os alloys is tabular. The grains are often highly flattened. The minor PGMs of placers are braggite and sperrylite. We found only one individual grain of each mineral. Irarsite and laurite as well as unknown phase of Rh-1,Rh-00(Sb0,95As0,05)(1.00) were found as inclusions in the grains of Ru-Ir-Os alloys.
A ratio of Fe-Pt and Ru-Ir-Os alloys is various in Sukhaya and Edinis-Nikolskaya placers (3:2 and 5:1 respectively), and it isn't constant in the other placers of Kelbes region. This fact indicates that PGMs of the placers has different primary sources, at least two types.
Mineral paragenesis in Fe-Pt and Ru-Ir-Os alloys are characteristic features of the primary sources. Two paragenesis in PGMs of Sukhaya placer were found. They are isoferroplatinum inclusions in one of ruthenium grain (isoferroplatinum-ruthenium paragenesis) and osmium inclusion in one of isoferroplatimun grains (osmium-isopherroplatinum paragenesis). The first is a characteristic feature of ophiolite hyperbasites, the second is a feature of Ural-Alaskan-type intrusions.
Most Ru-Ir-Os alloys of Sukhaya placer are of Ru-rich to form the ruthenium trend on the Ru-Ir-Os diagram. There are inclusions of irarsite and laurite in Ru-Ir-Os alloys. These are characteristic features of the PGMs assemblage from ophiolite hyperbasites. Fe-Pt alloys of Sukhaya placer prevail over Ru-Ir-Os (their ratio being 3:2). This is typically for the placers, produced by Ural-Alaskan-type intrusion. Braggite (Pt, Pd, Ni)S is in the placer. Platinum sulfides are typical for the post-magmatic stage development of Ural-Alaskan-type intrusion. Braggite in ferroplatinum placers may be interpreted as a part of PGMs assemblage from Ural-Alaskan-type complexes.
The features of the PGMs assemblage from Edinis-Nikolskaya placer are characteristic only for Ural-Alaskan massifs. Native osmium is of Ru-poor. Fe-Pt alloys also prevail over Ru-Ir-Os, their ratio being 5:1. Well-faceted sperrylite is presented in the placer. Such sperry-lite is typical for the post-magmatic stage development of Ural-Alaskan-type intrusions, it's finding in ferroplatinum placers may indirectly point to the intrusions as a type of primary source. No mineral paragenesis was found.
Thus, the two different primary sources have formed the studied placers of the Kelbes region.
There are several large hyperbasite-basite massifs in the Kelbes region. The Kaygadat and the Uspensky massifs are closest to the studied placers. The Kaygadat massif belongs to the intrusion of the Ural-Alaska type according to M.Yu. Podlipsky and A.P. Krivenko. It may be the primary source of the PGMs in the placer of Edinis-Nikolskaya and Sukhaya. The Uspensky massif belongs to the ophio-lite type to the geological map data. It may be the primary source of the PGMs in the placer of Sukhaya River.
The data obtained supplement the available information on the PGMs bearing placers of the Kelbes region. They are also important for predicting primary mineralization both in the northwest Kuznetsk Alatau and beyond it.
Translated title of the contributionTwo types of platinum group minerals assemblages from the gold-bearing placers are widespread in the northwest Kuznetsk Alatau
Original languageRussian
Article number2
Pages (from-to)19-32
Number of pages14
JournalГеосферные исследования
Issue number1
DOIs
Publication statusPublished - Mar 2020

OECD FOS+WOS

  • 1.05 EARTH AND RELATED ENVIRONMENTAL SCIENCES
  • 1.05.KY GEOLOGY

State classification of scientific and technological information

  • 38 GEOLOGY

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