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MRD-10 Large ore provinces of Central Asia

The age of gold-sulfide (Au-As) and gold-telluride mineralization of the Eastern Kazakhstan and correlation with magmatism

Evgeniy Naumov, Institute of geology and mineralogy SB RAS (Russian Federation)
Alexander Borisenko, Institute of geology and mineralogy SB RAS (Russian Federation)
Konstantin Kovalev, Institute of geology and mineralogy SB RAS (Russian Federation)
Yuriy Kalinin, Institute of geology and mineralogy SB RAS (Russian Federation)
Irina Tretyakova, Institute of geology and mineralogy SB RAS (Russian Federation)
 

Eastern Kazakhstan is one of the very promising gold-ore regions of the Central Asia. Large commercial deposits of Au-sulfide (Au-As) (Bakyrchik, Bolshevik, Suzdal, etc.) and Au-Te (Sekisovskoye) types, and also whole series of small and average deposits of Au-sulfide-Q, Au-Sb, and Au-skarn types are revealed in the structures of this region. Two main ore complexes of gold mineralization can be recognised in the Eastern Kazakhstan: 1) Cu-Mo (Au) porphyry, Au-Te, Au-Ag assosiated with diorite-plagiogranite intrusions; 2) Au-sulfide-Q and Au-sulfide (Au-As) and Au-Sb-Hg. The same types of deposits occurs in adjacent areas of NW China.
The earliest among them is Cu-Mo (Au) porphyry mineralization - 310 Ma (Re-Os, Song H.X. et al., 2007). The Au-Te mineralization closely associated with Cu-porphyry systems frequently form independent industrial deposits. The age of one of Au-Te deposits (Sekisovsloye) is dated at 306.6±3.8 Ma (Ar-Ar, sericite). Mineralization of Au-As (±Sb, Hg) geochemical type is represented by the several occurrences, which are characterised by different temperatures and are situated at the different levels of the ore-forming system. The ages of Au-As mineralization are within the interval of 290-270 Ma (Ar-Ar, sericite). The most part of them is localized in the Eastern-Kalba ore belt in black shales and grey sedimentary Carboniferous host rocks.
The model of the formation of these deposits consists of several stages, including processes of accumulation of the enriched by Au, Ag, Sb carbonaceous terrigenous rocks, their conversion at the stage of diagenesis, catagenesis of sediments and formation of shear zone, and hydrothermal-metasomatic processes related to the Later Paleozoic (C₃-P) magmatism. This multistage model of the Au-As mineralization forming is evidenced by geochemical data, isotope composition (C, S), and isotope-geochronological (Ar-Ar) data.