云南中甸地区雪鸡坪同碰撞石英闪长玢岩锆石SHRIMP U-Pb定年及其意义

Zircon SHRIMP U-Pb dating of the syn-collisional Xuejiping quartz diorite porphyrite in Zhongdian, Yunnan, China, and its geological implications.

对金沙江缝合带东侧雪鸡坪同碰撞石英闪长玢岩进行了岩石学、岩石化学、稀土元素、锆石SHRIMPU-Pb定年等研究,石英闪长玢岩锆石SHRIMPU-Pb年龄为215Ma。结合前人的资料,认为金沙江洋盆闭合、板块碰撞的时间应为266Ma,碰撞阶段的年龄范围为266～215Ma。对无老核的岩浆型锆石的形成条件、结构简单的典型纯岩浆型锆石定年的测试点数量等方面也进行了讨论。

This paper deals with the petrological, petrochemical and REE studies of the Xuejiping syn-coUisional quartz diorite porphytite on the eastern side of the Jinshajiang suture zone. Its zircon SHRIMP U-Pb dating gives an age of 215 Ma. Based on this age, combined with previous data, the authors believe that the Jinshajiang ocean basin closed at 266 Ma and that the collision stage took place at 266--214 Ma. The conditions for the formation of rnagmatic zircon （zircon without an older core） and the number of analyzed spots for the dating of typical, pure magmatic type zircon with a simple structure are also discussed.