Zircon SHRIMP U-Pb dating and geological implication of the Sabei Tin ore-deposit from Eastern Junggar of Xinjiang， China

Abstract：The Sabei tin ore deposits in the eastern Junggar are mainly developed in the quartz veins of the biotite granites and alkali amphibole-bearing quartz veins of the alkali-enriched granites. Zircons were selected from the cassiterite-bearing quartz veins of the biotite granites for SHRIMP U-Pb zircon dating, and yielded an age of 324.2±3.4Ma, implying the tin mineralization age. This age approximates to the formation time of the Laoyaquan-Hongtujing and Sujiquan biotite granitic batholith with 358.6 Ma～304±2 Ma, and obviously is earlier than those of the Sabei alkali-enriched granites (306±3 Ma～314±5 Ma) and alkali amphibole-bearing quartz veins (263.6±3 Ma～307±11 Ma) . We propose the existence of at least two periods of tin-mineralization, which is consistent with the post-collisional plutonic rocks (330 Ma ~310 Ma and 305 Ma～280 Ma) in the eastern Junggar and correspond to the first two phases of the three post-collisional mineralization (340 Ma～330 Ma，300 Ma～285 Ma，270 Ma～260 Ma) in the northern Xinjiang Province. Accordingly, we conclude that, the formation of the Sabei tin ore deposits has a multi-phase feature and is related not only to the alkali granites, but also to the biotite granites; the above two types of tin deposits and related alkali-enriched granites were resulted from the late paleozoic post-collisional magmatic and metallogenic events in the northern Xinjiang Province, a tin metallogenic system associated with late paleozoic post-collsional alkalic granites may be well developed in the Kalamaili ore deposits zone.