东昆仑南缘布青山地区得力斯坦花岗闪长岩LA-ICP-MS锆石U-Pb年龄及其地质意义

LA-ICP-MS zircon U-Pb dating of granodiorite from Delisitan of the Buqingshan area, southern margin of East Kunlun Mountains, and its geological implications

布青山构造混杂岩带地处青藏高原东北缘,是东昆仑南缘一条重要的构造单元边界,带内构造岩浆活动强烈,早古生代—晚古生代中酸性侵入岩较发育。采用LA-ICP-MS锆石U-Pb同位素测年技术,对研究区内得力斯坦花岗闪长岩进行高精度的年代学测试,获得^(206)Pb/^(238)U年龄加权平均值为414.3±1.8Ma,表明其侵位时间为晚志留世—早泥盆世。结合前人研究成果,认为得力斯坦花岗闪长岩是洋壳俯冲板块部分熔融的产物,暗示布青山地区原特提斯洋向北俯冲可能持续到晚志留世—早泥盆世,进而为研究东昆仑地区的地质构造演化提供新的约束。

The Buqingshan tectonic mélange,which is an important tectonic boundary on the southern margin of East Kunlun Mountains,is located in the northeast of the Tibetan Plateau.In this area,tectonic movement is active and Early Paleozoic-Late Paleozoic intermediate-acidic intrusive rocks are well developed.With high-precision geochronologic analysis,LA-ICP-MS zirconU-Pb dating was conducted for zircons from Delisitan granodiorite and,as a result,the206Pb/238U weighted average age of414.3±1.8Ma was obtained,which implies that the Delisitan granodiorite was formed in Late Silurian-Early Devonian period.Summary of previous researches shows that the granodiorite was the product of partial melting of the subducting oceanic crust,and this means that the Proto-Tethys oceanic crust of Buqingshan area was subducted northward from Cambrian until Late Silurian-Early Devonian.These results provide a new constraint for the study of tectonic evolution in the East Kunlun area.