LA-ICP-MS zircon U-Pb age, geochemistry and genesis of Neoproterozoic granitoids in the Biezhentao Mountain of Wenquan County, Xinjiang

The Neoproterozoic granites of the Biezhentao Mountain in Wenquan County of Xinjang were studied in this paper.Four LA-ICP-MS zircon U-Pb ages of 910~950 Ma were obtained for granitic gneisses in the Biezhentao Mountain of Wenquan County of Xinjiang.These new zircon LA-ICP MS U-Pb ages, together with previously published data, indicate that the granites were emplaced during 910~950 Ma.A few inherited old zircons U-Pb ages of >1000 Ma were found in all dated samples; they may have derived from the source rocks. These granitoids are characterized by a very coarse grained and huge augen gneiss texture. Major element data indicate that they belong to peraluminous monzogranite, with SiO₂ (≥ 70%), K₂O+Na₂O (6.5%~8.9%), and K₂O > Na₂O, thus defined as calc-alkaline to shoshonitic rocks. These rocks show nearly parallel REE patterns with different abundances and distinct negative Eu anomalies. All the granitoids display similar spider diagrams with obvious negative anomalies of Ba, Nb, Ta, Sr, P and Ti, and obvious enrichment of Rb, Th, U, K. Sr-Nd data suggest that the protoliths of Neoproterozoic granitoids belong to peraluminous S-type granites. Zircon ε_Hf (t) values range from +1.7 to +5.7, with model ages (t_DM1) of 883~1351 Ma and model ages (t_DM2) of 891~1588 Ma. Furthermore, with the age information on the ancient terranes of Tarim basin, the authors hold that the Tianshan ancient block probably formed a part of Rodina supercontinent during Early Neoproterozoic period and these granitoid rocks were linked to lithospheric thickening.