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MRD-10 Large ore provinces of Central Asia

Hydrothermal Ni-Co mineralization of central Asia: Geochemistry, age and correlation with magmatism

Alexander Borisenko, Institute of Geology and Mineralogy (Russian Federation)
Vladimir Lebedev, Tuva institute of complex natural resources development (Russian Federation)
Irina Tretiyakova, Institute of Geology and Mineralogy (Russian Federation)
Alexey Travin, Institute of Geology and Mineralogy (Russian Federation)
Galina Pavlova, Institute of Geology and Mineralogy (Russian Federation)
 

Several ore districts with economic Ni-Co mineralization of different types (Co-As skarn, Ag-Ni-Co-As, Cu-Co-As, Co-bearing Pb-Zn) are located in the structures of Central Asia. The Tuvinian (Khovu-Aksy, Chergak deposits, etc.) and Tien Shan (Aktapa, Akdjilga deposits, etc.) districts are the largest among them. Five main stages of Ni-Co ores formation have been recognized based on isotope-geochronological investigations (U-Pb, Ar-Ar, Rb-Sr dating): Middle Paleozoic - 410-395 and 350 Ma (Tuvinian and South-Khakassia ore districts), Early Permian 270-280 Ma (Tien Shan and East-Kazakhstan districts), Early Mesozoic - 256-242 Ma (Altai), Late Mesozoic - 118-120 Ma (Southern Tuva) and Eocene (Anarak district, Iran). The age of Ni-Co mineralization in these ore districts correlates the age of mafic and alkaline mafic plutonic and volcanic complexes as well as with the age of Ni-Co-Pt magmatic deposits (250 Ma for Norilsk district, 280 Ma for Eastern Tien Shan, 120 Ma for Aldan district), and Hg, Au-Hg mineralization (Tien Shan, Altai, Transbaikalia, Iran, etc.). Genetic links of Ni-Co mineralization with mantle mafic and alkaline mafic magmatism are evidenced by isotope-geochemical data including He isotope composition of the ore-forming fluids (³He/⁴He=0.6-6.16•10^-6). Ores of Co deposits of Central Asia have relatively high contents of Pt (up to n ppm), Pd (up to 1 ppm), and Hg (up to 0.15%), and contain Hg-silver, Hg-gold and patorite (Hg-palladium). Fluid inclusion study in the minerals of the Co deposits show that ores formed at wide temperature range from highly concentrated (Na, Fe, Ca, K) chloride solutions with CH₄-CO₂- N₂ containing gas phase.
The research was supported by RFBR grants 06-05-64789, 07-05-00803, and by DSP.2.1.1.702 grant from the Ministry for Russian Science and Education.