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Chen X.,Chinese Academy of Geological Sciences | Chen Z.,Chinese Academy of Geological Sciences | Han S.,Chinese Academy of Geological Sciences | Wang Z.,Chinese Academy of Geological Sciences | And 4 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2013

The Balkhash metallogenic zone in Kazakhstan is an important porphyry Cu-Mo metallogenic belt in the Central Asia metallogenic domain. In this paper, zircon SHRIMP U-Pb dating, major, rare earth and trace elemental geochemistry, and Sr and Nd isotope tracing of porphyry granitoids from Kounrad, Borly and Aktogai large and super-large porphyry Cu deposits, provide important informations on porphyry Cu metallogenic time and tectonic environment of the zone. Two stages of metallogenesis, one at ~327 Ma with the formation of Kounrad and Aktogai deposits, and the other at ~316 Ma with Borly deposit, are determined. The porphyry granitoids from this zone are mainly high K calc-alkaline series volcanic arc granite, some of them are adakite-like in trace element geochemistry. εSr(t) and εNd(t) of granitoids from three deposits are in the ranges of-6.35-34.03 and -0.46-5.53, respectively. Their Sr-Nd isotopic signatures indicate that porphyry granitoids from Kounrad and Borly were derived from a mixing source between the depleted mantle and the ancient continental crust, whereas that from Aktogai were derived from the depleted mantle directly. Via comparison of the Balkhash metallogenic zone and Junggar metallogenic zone, they are considered to be formed in the same Late Paleozoic Balkhash-Junggar porphyry Cu-Mo Metallogenic zone.


Chen X.-H.,Chinese Academy of Geological Sciences | Chen Z.-L.,Chinese Academy of Geological Sciences | Han S.-Q.,Chinese Academy of Geological Sciences | Wang Z.-H.,Chinese Academy of Geological Sciences | And 6 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2012

The Balkhash metallogenic belt in Kazakhstan, with many porphyritic Cu-Mo deposits and some quartz-vein greisen Mo-W deposits, is a famous porphyritic Cu-Mo metallogenic belt in Central Asian metallogenic domain. Three typical Mo-W deposits such as East Kounrad, Akshatau, and Zhanet, are studied in this paper through the application of geothermochronology. Zircon SHRIMP U-Pb geochronology yields ages of 293.6±2.7 Ma (alkaline granite), 306±1 Ma (granodiorite), and 304±4 Ma (porphyry monzonite), for East Kounrad, Akshatau, and Zhanet deposits respectively, belonging to the tectonic-magmatism in the Late Hercynian. 40Ar/ 39Ar thermochronology gives the cooling ages at 292±3 Ma for biotite from Akshatau, and 288.8±3.6 Ma and 278±5 Ma for K-feldspars from Akshatau and East Kounrad, respectively. Apatite fission track dating of granitoids gives low temperature cooling ages of 92.1±5.7 Ma, 92.2±5.0 Ma and 80.3±4.9 Ma, for East Kounrad, Akshatau, and Zhanet deposits, respectively, suggesting the uplifting and exhumation of Mo-W deposits together with the granitoids during the Late Cretaceous. The geochronological data and thermal history modeling presented in this paper, together with metallogenic information from previous studies, reveal the entire thermo-history, from the intrusion of plutons and Mo-W metallogenesis in the abyssal system in the Late Carboniferous and the Early Permian, through regional cooling, to the exhumation of the deposits in the Late Cretaceous, in the western part of Balkhash metallogenic belt.

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