【摘要】 西秦岭造山带北缘古元古界秦岭岩群中,新识别出新阳新元古代花岗质片麻岩,位于天水市西北部新阳镇东侧。花岗质片麻岩中锆石Th/U比值较高,阴极发光图像显示锆石内部振荡环带清晰,具岩浆成因特征。LA-ICP-MS锆石U-Pb同位素加权平均年龄为(938±4)Ma～(981±5)Ma,表明花岗质片麻岩形成于新元古代,反映了晋宁期西秦岭北缘存在一次构造热(俯冲碰撞)事件,可能是Rodinia超大陆的汇聚事件在西秦岭的响应。更多还原

【Abstract】 The Xinyang Neoproterozoic granitoid gneiss,identified from the Paleoproterozoic Qinling Group complex on the northern margin of the western Qinling orogen,is located to the east of Xinyang town of the northwestern Tianshui.The internal CL images of zircons in granitoid gneiss show that the zircons have higher Th/U ratios and clear oscillatory zoning,indicating an igneous origin.The acquired LA-ICP-MS zircon U-Pb weighted average ages (938 ±4 Ma and 981±5 Ma) indicate that the granitoid gneiss was formed in the Neoproterozoic and that a tectono-thermal event (subduction and collision) occurred on the northern edge of the West Qinling during the Jinningian,which is presumed to be the response of the convergence of the supercontinent Rodinia in the West Qinling.更多还原