High-pressure granulite from Western Kunlun,northwestern China Its metamorphic evolution,zircon SHRIMP U-Pb ages and tectonic implication
High-pressure mafic granulites occurring as lenticular bodies within garnet-amphibolites in Kangxiwar Fault have been first reported in this paper. The P-T conditions of two metamorphic stages were obtained using calibrated geothermal barometers and ThermoCalc Program. The peak metamorphic condition of these high-pressure granulites is about 760―820℃, 1.0―1.2 GPa and the retrograde metamorphic condition is about 620―720℃, 0.7―0.8 GPa. The petrological studies show that they have a near-isobaric cooling P-T path which suggests that the Western Kunlun underwent initial crustal thickening, subsequent exhumation and cooling. The SHRIMP zircon U-Pb dating gives two groups of ages for high-pressure granulites. One is 177±6 Ma which is obtained from the rim of the zircon. We consider this age should be the metamorphic age. And the other is 456±30 Ma which is obtained from the core of the zircon and should be the protolith age. The formation of these high-pressure granulites in western Kunlun is closely correlated with the evolution of the Paleo-Tethys and has important implications for the research on Tethys and Paleo-Asian tectonic zone.
© BJSHRIMP 2013 - bjshrimp.cn