和海洋地球科学学院，山东青岛266100;

2. 青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室，山东青岛266100;

3. 日照市应急管理局，山东日照276800

闪岩进行了LA-ICP-MS 锆石U-Pb 年代学研究。斜长角闪岩中的锆石均呈自形-半自形，内部结构清

晰，发育有典型岩浆成因的振荡生长环带，结合较高的Th /U 比值，表明锆石的岩浆成因特征。测年

结果显示: 斜长角闪岩的加权平均年龄为( 444 ± 2) Ma，是陇山群中首次获得的早志留世火山岩的

年龄。结合区域地质资料，认为北祁连构造带陇山群应解体为古元古代—新元古代古老结晶基底岩系

和早古生代变质火山-沉积岩系两套地质体。

Techniques，MOE and College of Marine Geosciences，Ocean University of China，Qingdao 266100，Shandong，China;

2. Laboratory for Marine Mineral Resources，Qingdao National Laboratory for Marine Science and Technology，Qingdao 266100，

Shandong，China;

3. Rizhao Emergency Management Bureau，Rizhao 276800，Shandong，China

Qilian orogen，LA-ICP-MS zircon U-Pb dating of amphibolite in Longshan Group in Tianshui area has been studied．Zircons in amphibolite are euhedral-subhedral with clear internal structure，and typical magmatic oscillatory growth zones are developed． Combined with the high Th /U ratios，zircons are of magmatic origin． The results show that the weighted average age of amphibolite is ( 444 ± 2) Ma，which is the first age of Early Silurian volcanic rocks in Longshan Group． Based on the regional geological data，the authors suggest that the Longshan Group in the North Qilian orogen should be disintegrated into two sets of geological bodies:Paleoproterozoic-Neoproterozoic

ancient crystalline basement rocks and Early Paleozoic metamorphic volcanic-sedimentary rocks．