Re-Os Dating of Molybdenites from the Cu-Mo-W Deposits in the Balkhash Metallogenic Belt,Kazakhstan and Its Geological Significance

Анотація

The Balkhash metallogenic belt in Kazakhstan,with the occurrence of many porphyritic Cu-Mo deposits and some quartz-vein greisen W-Mo deposits,is a very famous porphyritic Cu-Mo metallogenic belt in the Central Asian Metallogenic domain which is represented as a multiple core metallogenic system controlled by the boundary strike-slip fault system. In this paper 11 molybdenite samples from the western Balkhash metallogenic belt were selected for Re-Os isotopic dating. The molybdenites from the porphyritic Borly Cu-Mo deposit,and East Kounrad,Zhanet and Akshatau quartz-vein greisen W-Mo deposits,gave average model Re-Os ages of 315.9 Ma,298.0 Ma,295.0 Ma and 289.3 Ma,respectively. Meanwhile,the molybdenites from East Kounrad,Zhanet and Akshatau W-Mo deposits gave a Re-Os isochron age of 297.9 Ma,with MSWD of 0.97. Re-Os dating of molybdenites indicates that the Cu-Mo-W metallogenesis in the western Balkhash metallogenic belt formed during Late Carboniferous to Early Permian (315.9~289.3 Ma),while the porphyry Cu-Mo deposits formed at ~315.9 Ma,and quartz-vein greisen W-Mo deposits formed at ~297.9 Ma. The Re-Os model and isochron ages suggest that Late Carboniferous porphyry granitoid and pegmatite magmatism during Late Hercynian movement. Comparing to the Juggar-East Tianshan porphyry Cu metallogenic belt in northwestern China,the time of the Cu-Mo metallogenesis in Balkhash metallogenic belt,is between that of Tuwu-Yandong and Baogutu porphyry Cu deposits in East Tianshan and west Junggar. Concluded,the large-scale porphyry Cu-Mo metallogenesis in Central Metallogenic Domain centralized in Late Carboniferous due to Hercynian tectonic-magmatic activities.

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