西天山察哈乌苏侵入体LA-ICP-MS锆石U-Pb年龄、Hf同位素特征及其地质意义

LA-ICP-MS zircon U-Pb ages and Hf isotopic characteristics of Chahawusu intrusion in West Tianshan,Xinjiang,and their geological implication

早石炭世末期,阿拉套山一带的洋盆由西往东逐渐闭合,310 Ma以后该地区进入后碰撞伸展阶段。察哈乌苏侵入体处在阿拉套山的西段,侵位于上泥盆统托斯库尔他乌组碎屑岩中,岩性以二长花岗岩为主,少量钾长花岗岩。LA-ICP-MS锆石U-Pb测年结果和Hf同位素组成表明察哈乌苏岩体二长花岗岩的206 Pb/238 U加权平均年龄为(312.7±3.6)Ma,岩体的形成时代属于晚石炭世初期阶段,岩浆可能来自亏损地幔的部分熔融,演化过程中遭受了地壳物质混染,可能为同碰撞挤压向后碰撞伸展转换阶段、张性构造环境下岩浆活动的产物。

The ocean basin in the Alataw area gradually closed from west to east at the end of Early Carboniferous.After 310 Ma,the area entered into a post-collision extension stage.The Chahawusu intrusion is located at the western section of the Alataw Mountains,and invaded into the clastic rocks of the Upper Devonian Toskuertawu Formation.Its lithology is dominated by monzogranite with a small amount of potassium feldspar granite.LA--ICP-MS zircon U--Pb dating results and Hf isotopic compositions show that the 206 Pb/238 U weighted average age of the monzogranite is(312.7±3.6)Ma,indicating the Chahawusu pluton was emplaced at the early stage of Late Carboniferous.The primary magma was likely derived from partial melting of a depleted mantle and was then contaminated by crustal materials during magma evolution processes.The Chahawusu pluton may be the product of magma activities under the extensional tectonic environment in the transitional stage from syn-collision compression to post-collision extension.