Meta granitoid from the High Ultrahigh Pressure Metamorphic Belt in the Dabie Mountains and Its Tectonic Significance
大别山东部榴辉岩带中的变质花岗岩及其大地构造意义

The metagranitoid found in the high ultrahigh pressure metamorphic belt ( HP UHPMB ) in the Dabie Mountains is alkali meta granite.It can be distinguished from the unmetamorphosed Mesozoic granite and the low pressure gneiss by the features: (1) the key metamorphic minerals:phengite and coronal garnet around albite; (2) mainly granoblastic with relic magmatic texture and gneissic structure on the margin;(3) deformed together with it's HP UHPMB country gneiss during second generation of fold; (4) chemically rich in SiO 2 and Na 2O,sometimes K 2O, the sum of Na 2O and K 2O content is more than 7%;(5) mineral assemblage showing amphibolite metamorphism; (6) chronologically being 181.Ma ( Rb Sr, Wr Bi ); (7) with UP UHPM rocks as xenolith. By these features it is concluded that the metagranitoid was occurred during the exhumation and as the special member of the UHPMB. It is very important for understanding the exhumation rate of the UHPMB.