新疆昭苏布合塔铜(金)矿化区花岗质岩石锆石U-Pb年龄、地球化学特征及其成因

布合塔铜（金）矿化区位于新疆昭苏境内，大地构造位于那拉提构造带北缘西段。矿化区主要被二长花岗岩及石英闪长岩呈岩株状侵入，在花岗岩体边缘及与围岩接触带内均有铜（金）矿化。研究区2种岩体的锆石 LA-ICP-MS U-Pb测年结果分别为（434.5±4.6）Ma（二长花岗岩）、（445.7±5.1）Ma（石英闪长岩），为晚奥陶世—早志留世；元素地球化学测试结果显示，二者均属过铝质钾玄岩系列；二长花岗岩A/CNK值为1.35~1.42，石英闪长岩A/CNK值为1.47~1.71，具S型花岗岩特征；二者稀土元素特征较为相近，均显示轻稀土相对富集、具Eu负异常（δEu=0.67~0.80），微量元素均显示富集Ba、Th、U，亏损Nb、Ta等；地球化学分析表明，岩浆源岩主要为变杂砂岩，以部分熔融作用为主。结合区域大地构造背景及相关研究，总体认为该矿化区花岗质岩浆是由中天山板块与伊犁板块碰撞闭合之后的中下地壳部分熔融而成。

Zircon U-Pb Age and Geochemical Characteristics of Granites from Buheta Cu(Au) Mineralization District in Zhaosu County,Xinjiang Province

The Buheta Cu (Au) mineralization district is located to the west of the north margin of Nalati tectonic belt,Zhaosu County in Xinjiang Province.Monzogranite and quartz diorite are developed in this deposit,and the Cu-Au mineralization is found in the margin of the plutons and the contact zone between the plutons and wall rocks.The LA-ICP-MS zircon U-Pb dating results of monzogranite and quartz diorite are (434.5 ±4.6) Ma and (445.7 ±5.1) Ma,consistent with Late Ordovician to Early Silurian.According to the geochemical data,they belong to shoshonitic granites of peraluminous S-type with high A/CNK value of 1.35-1.42 and 1.47-1.71 respectively.The granites exhibit weak negative Eu anomalies(δEu=0.67-0.80),enrichment in LREE and large-ion lithophile elements (such as Ba、Th and U),and depletion of high strength elements(such as Nb and Ta).It suggests that the granites were generated from the partial melting of metagreywacke.Combined with the regional tectonic evolution,we conclude that the emplacement of granites in Buheta mineralization district was related to the post collision stage of the Middle Tianshan plate and the Yili plate through a partial melting of middle and lower crustal sedimentary rocks.