内蒙古温其根乌兰蛇绿混杂岩中枕状玄武岩特征及锆石U-Pb年龄

Geological characteristics and zircon U-Pb age of pillow basalt of ophiolitic mélange in Wenqigenwulan,Inner Mongolia

内蒙古温其根乌兰蛇绿混杂岩是内蒙古索伦山-苏左旗-锡林浩特蛇绿岩带的西段部分,岩石组合包括枕状玄武岩、蛇纹岩、菱镁岩、硅质岩、浅变质粉砂质碎屑岩、碳酸盐岩等,岩石呈大小不等的构造岩块产出。枕状玄武岩具高Na2O、低K2O,富集Th、Ta、Nb,亏损K、Sr、Rb、Yb等元素,∑REE含量低,δEu=1.22~1.28,显示正Eu异常等大洋中脊玄武岩特征。LAMC-ICP-MS锆石U-Pb年龄为475.8±1.6Ma,为研究华北板块北缘的大地构造演化提供了新的证据。

The ophiolitic melange in Wenqigenwulan lies in the western part of Solon Mountain-Sonid Left Banner-Xilin Hot zone in Inner Mongolia. The rocks consist of pillow basalt, serpentinite, magnesitite, silicalite, shallow metamorphic silty clastic rock and carbonate. The rock occurs as different sizes of tectonic blocks. Geochemistry of pillow basalt shows high Na20, low K20, enrichment of Th, Ta, Nb, and depletion of K, Sr, tkb, Yb. REE values are low, and 8 Eu values vary from 1.22 to 1.28 with the features of MORB. The zircon U-Pb age is 475.8±1.6Ma. The geology and geochemistry and zircon U-Pb dating of the pillow basalt pro- vide new evidence for the tectonic evolution at the northern edge of North China Craton.