Petrology, geochronology and geochemistry of metallogenetic granite in Baiganhu W-Sn deposit, East Kunlun

Baiganhu tungsten-tin ore field is located in Ruoqiang County, Xinjiang. It is in the west of Qimantage mountain, East Kunlun and consists of four deposits of Baiganhu, Kekekaerde, Bashierxi and Awaer. These deposits are spatially associated with the Caledonian Bashierxi Magmatic Series. With particular focus on the Baiganhu deposit, we conducted detailed studies on the petrology, geochronology and geochemistry of the causative granite and discuss its characteristics, genetic type and the relationship with W-Sn mineralization. The causative granite is syenogranite based on slice identification. LA-MC-ICP-MS zircon U-Pb dating reveals that the syenogranite was emplaced at 413.6 +/- 2.4 Ma (MSWD = 0. 36, n = 30). Our and previously published ages and geochemical data of the plutons in the Baiganhu area together show that the S-type granites and A-type granites are coexisting in Bashierxi Magmatic Series and they were formed in a post-collisional setting during the Middle Silurian-Early Devonian (433 413Ma). Baiganhu syenogranite contains magmatic garnets and muscovites and the values of A/CNK and A/NK are in the range of 1.07 similar to 1.11 and 1.45 similar to 1.49, respectively, with a relatively low zircon saturated temperature and high field strength elements (HFSEs) content. Thus this pluton is peraluminous and high-K calc-alkaline S-type granite. It formed during the late stage of Bashierxi Magmatic Series and has a closely genetic connection with the tungsten-tin mineralization. We suggest that more attention should be payed to the buried or apophysis-like syenogranite during the further exploration for tungsten-tin in this area. Whereas the monzogranite and alkali feldspar granite contain homblendes and biotites which penetrate in the interstices between magmatic feldspar and quartz or even enclave magmatic quartz. They have relatively high K20 content (5.25% similar to 6.29%), with A/CNK ranging from 0.92 to 1.02, thus belong to metaluminous or weakly peraluminous shoshonite series. Their zircon saturated temperature (866 similar to 917 degrees C), all alkali content (8.30% similar to 9.69%), Sigma REE content (200 x 10(-6) similar to 413 x 10(-6)) and HFSEs content such as Zr, Nb, Ce and Y (Zr + Nb + Ce + Y = 556 x 10(-6) similar to 1006 x 10(-6)) all are obviously high thus belong to the shoshonite series A-type granites. It is inferred that rare and rare earth element mineralization related to A-type granite may be found in the Baiganhu and adjacent region.