Metamorphic evolution of eclogite facies rocks in Northern Hubei and Southern Henan, China

Eclogite fades rocks in this area are diverse in rock type. The field occurrence and rock-chemistry reflect theirin-situ origin. Based on their regional geology and field occurrence, two groups of eclogites are divided in terms of their peak temperature of metamorphism. Medium-temperature eclogites (MT), as Group B, occur in the Dabie Group. They were formed from epidote-amphibolite facies. The metamorphism of eclogite facies has two stages: the coesite eclogite facies stage (the peak condition:T = 600 -700°C,P = 2.7-3.0 GPa) and the glaucophane eclogite facies stage (the pressure decreases, may be lower than 2.5 GPa while the temperature has little change). Low temperature eclogites (LT), as Group C, occur in the Qijiaoshan Formation. They were formed from blue schist facies (the peak condition:T = 490–560°C,P< 1.5 GPa). The appearance of hydrous minerals in the eclogites indicates the important role of water in metamorphism. Medium-temperature eclogites are different from low-temperature ones in metamorphism. At last, the evolution of the high-pressure metamorphic belt is discussed as well. This research project was financially supported by the National Natural Science Foundation of China (No. 49372100).