| Abstract: | The Central Asian metallogenic domain (CAMD) is a multi-core metallogenic system controlled by boundary strike-slip fault systems. The Balkhash metallogenic belt in Kazakhstan, in which occur many large and super-large porphyritic Cu-Mo deposits and some quartz vein- and greisen-type W-Mo deposits, is a well-known porphyritic Cu-Mo metallogenic belt in the CAMD. In this paper 11 molybdenite samples from the western segment of the Balkhash metallogenic belt are selected for Re-Os compositional analyses and Re-Os isotopic dating. Molybdenites from the Borly porphyry Cu deposit and the three quartz vein-greisen W-Mo deposits-East Kounrad, Akshatau and Zhanet-all have relatively high Re contents (2712-2772 μg/g for Borly and 2.267-31.50 μg/g for the other three W-Mo deposits), and lower common Os contents (0.670-2.696 ng/g for Borly and 0.0051-0.056 ng/g for the other three). The molybdenites from the Borly porphyry Cu-Mo depositand the East Kounrad, Zhanet, and Akshatau quartz vein- and greisen-type W-Mo deposits give average model Re-Os ages of 315.9 Ma, 298.0 Ma, 295.0 Ma, and 289.3 Ma respectively. Meanwhile, molybdenites from the East Kounrad, Zhanet, and Akshatau W-Mo deposits give a Re-Os isochron age of 297.9 Ma, with an MSWD value of 0.97. Re-Os dating of the molybdenites indicates that Cu-W-Mo metallogenesis in the western Balkhash metallogenic belt occurred during Late Carboniferous to Early Permian (315.9-289.3 Ma), while the porphyry Cu-Mo deposits formed at ～316 Ma, and the quartz vein-greisen W-Mo deposits formed at ～298 Ma. The Re-Os model and isochron ages thus suggest that Late Carboniferous porphyry granitoid and pegmatite magmatism took place during the late Hercy-nian movement. Compared to the Junggar-East Tianshan porphyry Cu metallogenic belt in northwestern China, the formation of the Cu-Mo metallogenesis in the Balkhash metallogenic belt occurred between that of the Tuwu-Yandong in East Tianshan and the Baogutu porphyry Cu deposits in West Junggar. Collectively, the large-scale Late Carboniferous porphyry Cu-Mo metallogenesis in the Central Asian metallogenic domain is related to Hercynian tectono-magmatic activities. |
