Discussion on the basement properties and east boundary of the Ergun massif
Zhang Li1, Liu Yongjiang1, Li Weimin1, Han Guoqing1,2, Zhang Jindai3, Guo Qingyin3, Li Changhua4
1. College of Earth Sciences, Jilin University, Changchun 130061;
2. University of Salzburg, Institute of Geology and Geography, Salzburg A-5020, Austria;
3. Department of China Geology and Mining, CNNC, Beijing 100013;
4. No.240 Institute of Nuclear Industry, Shenyang 110032
Northeast China is the critical area for solving the tectonic evolution of the East-Asian continent,it has thus drawn much attention.In recent years,the debates on the Ergun massif has been very intense,especially,the basement properties and the eastern boundary of Ergun massif.In this paper,the zircon LA-ICP-MS U-Pb dating for granitic gneiss of the Taiping Forest has been obtained,the zircon age mainly concentrates in the range of 840～830 Ma、800～780 Ma and 730～720 Ma,probably corresponds to three stages of magmatic event in Neoproterozoic.The weighted mean 206Pb/238U age of 21 analyzed zircon points yielded 779±20 Ma(MSWD=8.3),indicates that the original rock has emplaced and crystallized in Neoproterozoic; one zircon analysis shows U-Pb isotope age of 494±10 Ma,with the Th/U ratio is 0.06,suggesting that the zircon should be metamorphic origin,and this age therefore may be the metamorphic age of granite gneiss.Combine with the ages of granitoid that previously reported in Ergun massif and Xing'an massif,we concluded that only the Ergun massif has experienced the Neoproterozoic magmtic event; In addition,the Hf isotopic characteristics of granite in the Ergun massif and the Xing'an massif,obviously show different stages of initial evolution of the crust.Subsequent to the period of the collision between the Ergun massif and the Xing'an massif along the Tahe-Xiguitu suture zone in early Early Paleozoic,the two massifs have experienced Paleozoic magmatism together.The conclusions presented here significantly differ from the previous reported viewpoint that the Ergun massif and the Xing'an massif sutured along the Derbugan Fault.