Abstract:

 The highpressure metamorphic belt in central Qiangtang is located in Longmu CoShuanghu suture zone, and composed of eclogite, blue schist and garnet muscovite schist. Its formation process has important significance for the study of tectonic evolution of this suture zone. In 2008, the author found the jadeite garnet twomica schist in the Hunanshan petrofabric, Zhanjin group, which is a new highpressure metamorphic rock type. In this paper, we do a detailed research on petrology, mineralogy and metamorphism of this rock, and consider that this jadeite garnet twomica schist has undergone at least two stages of metamorphism. The first stage was greenschist facies at T=425434 ℃, p=300500 MPa, in which formed the early schistosity S1; the second stage was highpressure metamorphism of blueschist facies at T=472481 ℃, p=12001700 MPa, in which formed the schistosity S2 of main rock period. These rocks were formed in one period of blueschist facies metamorphism and deformation, ranging from 218 Ma to 220 Ma, which was produced by the tectonic movement of the eclogite exhumation.

Key words: high pressure metamorphic belt, jadeite, blueschist facies, exhumation, central Qiangtang