LAM-ICPMS U-PB AGES OF MESOZOIC VOLCANIC ROCKS IN DAXINGANLING AREA (NORTHEASTERN CHINA) AND THEIR TECTONIC SIGNIFICANCE

The Daxinganling Mesozoic tectono-magmatic belt is located in the east part of Inner Mongolia, northeastern China. The magmatic belt mainly consists of three volcanic Formations which are Manketouebo Formation, Manitu Formation and Baiyingaolao Formation. There are many different views about the forming age and tectonic setting of the three volcanic Formations. Especially, because of lackage of precise isotopic ages, they have been considered to be late Jurassic for a long time. In order to determine the detailed ages of the Mesozoic volcanic rocks in Daxinanling area, several samples including tuff, andesite and rhyolite are obtained from the three Formations for LAM-ICPMS zircon U-Pb dating. The crystallization ages of volcanic rocks are from 123~130Ma (6 samples), indicating that the volcanic rocks formed in early Cretaceous, which coincides with the massive volcanic eruption age along the eastern China. Furthermore, according to the geochemistry data of the volcanic rocks, most of samples are suggested to be arc-related lithogenesis, which is possibly caused by the subduction from the Pacific plate to Eurasian plate, but is not the lithospheric delamination during early Cretaceous.