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

The ophiolitic mélange 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 Na2O, low K2O, enrichment of Th, Ta, Nb，and depletion of K, Sr, Rb, Yb. REE values are low, and δEu 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 provide new evidence for the tectonic evolution at the northern edge of North China Craton.