Precambrian High-Pressure Metamorphic Rocks within the Collision Zone of the Yangtze and Cathaysia Blocks, China: Jadeite/Glaucophane-Type Facies

Precambrian high-pressure metamorphic rocks are found as blocks in the serpentinized peridotite of the northeastern Jiangxi ophiolitic melange, which is located within the Precambrian collision zone between the Yangtze and Cathaysia blocks in southern China. These rocks consist of jadeite-quartz-albite schists and blueschists. Crossite in the blueschists has yielded two K-Ar ages and a 40Ar/39Ar age of ∼ 800 Ma. The petrography, mineral chemistry, metamorphic evolution, and pressure-temperature (P-T) conditions of these high-pressure metamorphic rocks are described here. The high-pressure metamorphic facies series may be divided into two categories in order of ascending pressure: (1) a high-pressure intermediate type, and (2) a jadeite-glaucophane type (Miyashiro, 1961). Precambrian high-pressure metamorphic rocks belonging to this first type—the high-pressure intermediate facies—have been reported previously (Liou et al., 1989, 1990; Nakajima et al., 1990). These rocks are characterized by stability of g...

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