Zircon LA-ICP-MS U-Pb age of I type granitoids from Qiaohuote copper deposit in Central Tianshan of Xinjiang and its geological implications
Zircon LA-ICP-MS U-Pb age of I type granitoids from Qiaohuote copper deposit in Central Tianshan of Xinjiang and its geological implications
复制标题
作者：
Dong Lian
位于南天山缝合带北侧的乔霍特铜存款中出露了两种地球化学特征相似的花岗岩类，出露于乔霍特铜存款南侧的花岗闪长岩和以包体形式产出于火山岩中的Moylite均为I型花岗岩，均具钙碱性成分，以富集LILE、亏损HFSE和Eu、Ta、Nb负异常为特征，这些花岗岩类的LA-ICP-MS锆石年龄分别为450.4±1.1Ma和430.8±4.1Ma，地球化学和年龄数据表明，它们形成于俯冲环境，乔霍特地区南天山洋向北俯冲可能始于晚奥陶世（450 Ma），早志留世（431 Ma）仍有活动，花岗闪长岩的形成时代早于容矿火山岩，因此，乔霍特铜存款的成矿作用与花岗闪长岩无关。
Two kinds of granitoids with the similar geochemical characteristics outcrop in Qiaohuote copper deposit which lies on the north side of South Tianshan Suture Zone.The granodiorite outcropping on the south side of Qiaohuote copper deposit and the moylite occurring as an enclave in the volcanic rocks belong to I type granite.They both have calc-alkaline composition,and are characterized by enriched LILE and depleted HFSE and negative anomalies in Eu,Ta,Nb,and Ti.Tectonically,they are related to the northward subduction of South Tianshan Ocean beneath the southern margin of Central Tianshan terrane.LA-ICP-MS zircon ages of 450.4±1.1Ma and 430.8±4.1Ma were obtained from these granitoids.The geochemical and age dating data reported in this paper indicate that these granitoids were formed in a subduction environment,the northward subduction of South Tianshan Ocean may start at Late Ordovician (450Ma) and still be active during Early Silurian (431Ma) in Qiaohuote region.The age of granodiorite is earlier than the ore-host volcanic rocks,therefore,the metallization of Qiaohute copper deposit is independent of the granodiorite.