Copper-molybdenum porphyry deposits of Russia (Sib eria) and Mongolia were formed within the interaction zone of the Siberian conti nent with Paleo-As ian (Pt 2-Pz 2), Paleo-Tethys (Pz 3) and Mongolo-Okhotsk (Pz 2-Mz) ocean s. Ore-beari ng magmatic (porphyry) complexes, which are closely associated in time and space with Cu-Mo mineralization, are represented by small stocks (up to 1 km 2) and numerous dikes of basic to acid composition. Rb-Sr and 40 Ar/ 39 Ar dating fix three temporal periods of activity o f ore-form ing process within Siberia and Mongolia which resulted in a wide appearance of C u-Mo porphyry mineralization. A series of large-scale deposits was formed at t ha t time: 1) Early Devonian (Mo-porphyry Sora deposit, Kuznetsk-Alatau; Cu-Mo- porp hyry Aksug deposit, Tuva), 2) Triassic (Cu-Mo-porphyry Erdenetuin-Obo, Northe rn Mongolia), 3) Late Jurassic (Cu-Mo-porphyry Zhireken and Shakhtama deposits, Eastern Transbaikalia). The deposits of small size were formed between these periods (Cu-Mo-porphyry Tsagan-Suburga, Cu-porphyry Kharmagtai deposits in Southern Mongolia, etc.). C u- Mo-porphyry deposits within Siberia and Mongolia as a whole were formed with a regular periodicity at 20～30 Ma intervals. Large copper-molybdenum porphyry deposits are characterized by the manifestat ion of multiple ore-forming processes which are related to separate pulses of o r e-bearing magmatism. Three pulses of ore-bearing magmatism are established at th e large scale Erdenetuin-Obo deposit: I-250～240 Ma, II-225～220 Ma, III-225 ～195 M a. Every magmatic pulse is accompanied by ore mineralization. The Erdenet ore di strict includes three deposits of different sizes. Large-scale deposits are in principle multi-stage formations. They are charac terized by the repeated manifestation of ore-bearing magmatism and the ore-for mi ng processes during the long period of geological time within a relatively limit ed space.
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