New Ar-40/Ar-39 Geochronology Data Of The Fuping And Wutai Complexes: Further Constraints On The Thermal Evolution Of The Trans-North China Orogen

The Trans-North China Orogen has witnessed the assembly of the Western and Eastern blocks of the North China Craton during Late Paleoproterozoic. Numerous studies have focused on the subduction/collision timing and metamorphic evolution of the Trans-North China Orogen, whereas the thermal evolution and exhumation history are still poorly understood. The Fuping and Wutai Complexes are widely exposed of middle- to high-grade metamorphic rocks, which are excellent regions to investigate the thermal evolution and exhumation history of the Trans-North China Orogen. Previous U-Pb geochronological data of metamorphic zircon and monazite suggest that the peak granulite facies metamorphism in the Fuping Complex occurred during 1.92-1.80 Ga, and peak amphibolite facies metamorphism in the northeastern part of the Wutai Complex happened at 1.85-1.82 Ga. Here we report newly obtained hornblende Ar-40/Ar-39 age of 1813-1806 Ma in the Fuping Complex, and biotite Ar-40/Ar-39 age of 1802-1786 Ma in the northeastern part of the Wutai Complex, which representing the cooling ages. Combined with previous thermochronological data, the cooling rate of 2.0-8.5 degrees C/Ma was obtained for the middle to southern segments of the Trans-North China Orogen, possibly suggesting a moderate to fast exhumation relative to other Proterozoic orogens.