Zircon U-Pb Dating From Elliger Temple Group, And Its Geological Significance,Midwest Inner Mongolia

The research zone is located in the Northern Inner Mongolia, which is close to the China-Mongolia border region. Geotectonically, the studied area lies in Central Asian Orogenic Belt, the junction of Siberian plate and North China plate. It is one of the areas with the most intense proliferation of Phanerozoic in the whole world. Based on the analysis of previous study, the formation of the studied area is closely related with the evolution of the Paleoasian Ocean. The time and position that Paleoasian final splited is a debatable point. One is that Paleoasian is finally split in the southern Erenhot — northern Xilinhot or southern Erenhot — Hegen mountain line. Another view is that it is finally split in the junction of Doyle Temple—Xilamulun suture. In recent years, the study found that the age composition of Erenhot Elliger Temple Group which is widely exposed in the southwestern region of is complicated. The predecessors holds controversial views on the structural attribution. The essay starts on the U-Pb age structure of Elliger Temple Group and it also provides time and material source evidence through the analysis on the contrast of morphological characteristics and regional zircon provenance in order to reveal the closing time and location of the ancient Asian ocean.The results show that Elliger Temple Group mainly shows by the low-temperature dynamic metamorphism, forming a combination of lower greenschist facies rocks. Its rock group is mainly made of metamorphic rocks composed by sericite quartz schist, metamorphic sandstone, carbonaceous slate, quartzite, tuff change, change rhyolite and crystalline limestone. It is reveled that Elliger Temple Group holds the same peak age of 420 ~ 540 Ma and the same chronological feature with the arc magmatic rocks of Baolidao island in the north side. Research on the four ancient zircons aged as 1519 Ma, 1554 Ma, 1698 Ma, 1718 Ma shows that they have no connection with the ancient zircons aged as 2000 Ma ~ 3800 Ma on Siberian plate,north and northeast sections plots so it proves that the emergence of the ElligerTemple Group has nothing to do with the cleavage of the ancient Craton. The diorite mylonite is obtained from the sheets of the samples during the institution. It shows that its invasion age is 520 Ma. These results indicate that Elliger Temple Group should be disintegration as ancient metamorphic crystalline basement, melange and metamorphic intrusive rocks. Through the comparation on the features of the Ondor Temple Group and Elliger Temple Group, it is found that the northern Ondor Temple Group has with the same characteristics with the Elliger Temple Group.Through the analysis of blue schist 383 Ma(Xu Bei et al.,2001) obtained by the previous group, The Ondor Temple Group and the Elliger Temple Group belongs to the same tectonic unit on the other integrated regional studies. The main magmatic zircons provenance is derived from the Paleozoic island arc magmatic rocks erosion,accompanied by the formation of subduction distributed grid Elliger Temple —Sunitezuoqi line of tectonic melange. Combined with the blue schist found during the research and on the conjecture of the age composition, it can be conferred that the closing position of Paleoasian should be the Elliger Temple Group-Sunitezuoqi cell line and the closing time should be Devonian.