西金乌兰-金沙江缝合带西段印支期石英闪长岩LA-ICP-MS锆石U-Pb年龄与地球化学特征  

LA-ICP-MS U-Pb age of zircon and geochemical characteristics of Indosinian quartz diorite in the western section of Xijinwulan-Jinshajiang suture zone

作　　者：党勘峰 陈小刚 DANG Kanfeng;CHEN Xiaogang(Shangluo Northwest Nonferrous 713 Team Co.,Ltd.,Shangluo 726000,Shaanxi,China)

机构地区：[1]商洛西北有色七一三总队有限公司,陕西商洛726000

出　　处：《矿产与地质》2020年第3期486-497,共12页Mineral Resources and Geology

基　　金：青海省国土资源厅地质勘查基金项目“青海省称多县歇武地区I47E018006、I47E019006(青海部分);I47E020006(青海部分)三幅1∶5万区域地质矿产调查”(编号:KD2012-09)资助。

摘　　要：青海省玉树巴塘一带的达叶隆巴、尕兴隆石英闪长岩体出露于西金乌兰—金沙江缝合带西段,呈不规则长带状侵位于西金乌兰群中。通过锆石U-Pb年代学及岩石地球化学等研究,探讨其形成构造环境。结果表明:两个岩体中的石英闪长岩均形成于印支期[(211.3±1.1)Ma、(211.05±0.83)Ma],且具有相似的岩石地球化学特征,属钙碱性准铝质岩石系列,岩石富集Rb、K、Ba、La、Nd、Sm等大离子亲石元素(LILE),相对亏损P、Zr、Ti等高场强元素(HFSE),Mg、Fe含量较高,P2O5较低,TiO2含量较低,Na2O含量较高,K2O含量低,K2O/Na2O比值小于1。综合研究表明:达叶隆巴、尕兴隆石英闪长岩是形成于俯冲背景下的岛弧花岗岩,因此可以初步确定在西金乌兰—金沙江缝合带玉树巴塘一带,洋壳的俯冲作用至少持续到211.05 Ma(晚三叠世末),这一结果为西金乌兰—金沙江缝合带西段发生的板块运动过程提供了新的证据与时限约束。Dayelongba and Gaxinglong quartz diorites in the Yushu-Batang area of Qinghai Province are exposed in the western section of Xijinwulan-Jinshajiang suture zone and intrude in the Xijinwulan Group as an irregular long-band shape.Through the study of zircon U-Pb chronology and rock geochemistry,the tectonic formation environment is discussed.The result shows that the two quartz diorites are formed in the Indosinian period[(211.3±1.1)Ma,(211.05±0.83)Ma],and have the similar geochemical rock characteristics,which belongs to the calcareous alkaline quasi-aluminum rock series.The rock is enriched with large ion lithophile elements(LILE)such as Rb,K,Ba,La,Nd,Sm,and relatively depleted in high field strength elements(HFSE)such as P,Zr,and Ti.Mg and Fe contents are high,P2O5 and TiO2 contents are relatively low,Na2O content is high and K2O content is low,K2O/Na2O ratio is less than 1.Comprehensive research shows that Dayelongba and Gaxinglong quartz diorites are island arc granitoids formed in the subduction background.So it can be preliminarily determined that the subduction of the oceanic crust is at least continuing until 211.05 Ma(the end of the Late Triassic)in the Yushubatang area of Xijinwulan-Jinshajiang suture zone.The result has provided a new evidence and time constraint for the plate movement process in the western section of Xijinwulan-Jinshajiang suture zone.

关 键 词：LA-ICP-MS锆石U-PB测年 地球化学特征 西金乌兰—金沙江缝合带 玉树巴塘 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]