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对采自宜昌三峡地区南华纪沉积岩中碎屑锆石进行了U-Pb定年,新元古代锆石U-Pb年龄在833Ma、785Ma出现高峰,说明此时期有两期大规模岩浆活动.结合前人的Hf同位素结果,新元古代锆石U-Pb年龄与εHf(t)值关系图表明:910～890Ma之间锆石εHf(t)值表现为高正值(≈10,接近亏损地幔演化值),890～840Ma锆石εHf(t)值明显降低,并有负值出现,另外在890Ma处有年龄峰出现.笔者认为扬子和华夏板块的拼合可能在890Ma发生了由俯冲到陆-陆或陆-弧的碰撞,之前的高εHf(t)值由洋壳俯冲造成,之后碰撞作用陆壳物质熔融造成了εHf(t)值的降低;840～800Ma的锆石εHf(t)值有正也有负,800～780Ma的锆石εHf(t)值小于0,780～750Ma的锆石εHf(t)值大于0.这些数据与830～795Ma、780～745Ma两期地幔柱事件吻合.
U-Pb dating of detrital zircons collected from the Nanhuaji sedimentary rocks in the Three Gorges area of Yichang shows that the Neoproterozoic zircon U-Pb ages peak at 833 Ma and 785 Ma, indicating that there are two large-scale magmatic activities during this period The results of Hf isotope analysis and U-Pb ages of Neoproterozoic zircons show that the εHf (t) values of zircons between 910 and 890Ma show high positive values (≈10, close to the depleted mantle evolution ), The value of εHf (t) of zircon from 890 ~ 840Ma obviously decreased and negative value appeared, and another peak appeared at 890Ma.The authors believe that the combination of Yangtze and Huaxia plate may occur from subduction to land-land in 890Ma Or the land-arc collision, the previous high εHf (t) value is caused by the subduction of the oceanic crust, and then the εHf (t) value decreases due to the melting of the collision continental crust material. The εHf (t) value of zircon from 840 to 800 Ma The negative εHf (t) values of zircons with 800-780 Ma zircons with εHf (t) less than 0,780-750 Ma are greater than 0. These data are consistent with the mantle plume events of 830-795 Ma and 780-745 Ma.