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Irina Tretyakova, Institute of geology and mineralogy SB RAS (Russian Federation)
Geliy Fedoseev, Institute of geology and mineralogy SB RAS (Russian Federation)
Eugeniy Naumov, Institute of geology and mineralogy SB RAS (Russian Federation)
Alexander Borisenko, Institute of geology and mineralogy SB RAS (Russian Federation)
Vladimir Lebedev, Tuva Institute for Exploration of Natural Resources SB RAS (Russian Federation)
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Abakan ore cluster in the South Khakassia (Central Siberia) is the sample object for decision of questions of genesis of cobalt mineralization, age and relationship with magmatism. Different types of ore (magnetite, Ni-Co-As, Cu-Co, Pb-Zn-Cu) are spatially unite in this ore cluster. The general sequence of events in this region is: intrusions of granites and granosyenite skarn with Fe-mineralization gabbro dikes Ni-Co-mineralization in carbonate veins Cu-Co-As-mineralization.
The other hydrothermal cobalt districts are characterized by occurrences of different types of cobalt ores (viz. Co-As, Ni-Co-As, Cu-Co etc.). As a rule, occurrences are zoned, commonly in the sequence: arsenic sulphosalts Pb-Zn (Co-bearing) barite. Geochemical and temperature features allow the zoned cobalt deposits to be subdivided into two types, namely:
1. High temperature cobalt mineralization (Co-As Cu-Co-As Pb-Zn (Co-bearing) Ba)
2. Low-temperature nickel-cobalt mineralization (Ni-Co-As Cu-Co-As Cu, Pb, Zn, Ba (Co-bearing) Ba).
For example, the main type of hydrothermal cobalt mineralization at the Abakan ore cluster is Ni-Co-As mineralization, but Cu-Co?sulphosalt veins are widespread at the periphery.
The hydrothermal cobalt deposits in the South Khakassia and in other regions are characterized by high concentrations of Au, Ag, and PGE (Kharadgul deposit- Au up to 1.2 ppm, Ag up to 486 ppm, Pt up to 0.12 ppm, Pd up to 0.98 ppm). High PGE concentrations are typical in high-temperature Co-As deposits that are usually related to basic intrusions, whereas high contents of Au and Ag occur in low-temperature Ni-Co-As ores related to granites.
The age of granites of the Abakan ore cluster (437.2±4.4 Ma) was determined by U-Pb method (SHRIMP, zircon). Dating of cobalt deposits (Abakanskoe (409.1±4.9 Ma), Kharadgul (379.9±3.8 Ma) was carried out by sericite from ore quartz-sericite-carbonate veins (Ar-Ar-method). According to data by Mal'kovets (2001) and Lavrenchuk (2003) the ages of basic intrusions of Minusinsk depression are 392±11 Ma (Novaya Kuzurba, Ar-Ar-method) and 405.8±1.2 Ma (Chernaya Sopka, Ar-Ar).
With regard to all available information about age of cobalt deposits in Altai-Sayan orogenic area three main epochs of cobalt mineralization are recognized: Late-Mesozoic (J3 -Ê1), Early-Mesozoic (Ð2-Ò1) and Middle-Paleozoic (D-C1). Cobalt mineralization of Abakan ore cluster was formed in Middle-Paleozoic epoch. In this stage also Khovu-Aksy major cobalt deposit was appeared.
The work was supported by RFBR (grants 07-05-00803, 07-05-00988, 06-05-64789) and grant of the Ministry for Russian Science and Education DSP.2.1.1.702.
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