THE GRANITIC GNEISSES AND ITS TECTONIC SETTING FROM THE NORTHERN PART OF ULTRA HIGH PRESSURE METAMORPHIC BELT IN EASTERN DABIE SHAN
Wu Weiping\ Xu Shutong\ Jiang Laili\ Liu Yican\ Su Wen\ Shi Yonghong (Anhui Institute Of Geology, Hefei 230001) Fan Lianghong,Chen Jinmiao and Shen Huanxi (No. 311 Geological Team of Anhur Bureau of Geology and Mineral Resources,Qianshan 246306)
The main characteritics of the granitic gneisses from the northern Dabie Shan are as follows: (1) rich in SiO 275%,K 2O+Na 2O8%,and K 2ONa 2O. (2) intrusive conact with the metamorphic crustal rocks, contain antilogues and typhonic inclusions. (3) lepide-granoblastic texture with relic magmatic texture, gneissic structure with augen of K-feldspar and LS type shape-fabric in shear zone. (4)amphibolite facies metamorphism. With some metamorphic mineral such as biotite, hornblende and a few garnet, muscovite, epidote,ect. (5) 629Ma (zircon U-Pb). These indicate that the granitic gneisses are different from the aegirine-bearing meta-granitoid in the ultrahigh pressure metamorphic belt. So, the former may be the underthrust basement of the Yangtze continental plate.