Episodic Paleoproterozoic (~2.45, ~1.95 and ~1.85 Ga) mafic magmatism and associated high temperature metamorphism in the Daqingshan area, North China Craton: SHRIMP zircon U-Pb dating and whole-rock geochemistry
In the Daqingshan area within the Khondalite Belt of the North China Craton, Paleoproterozoic gabbro and dolerite intrusions show amphibolite to granulite-facies metamorphism. U-Pb zircon dating and whole-rock geochemistry were undertaken on these rocks in order to understand the timing of mantle magmatism and thermal processes. Ten samples yielded zircon U-Pb formation ages of 2.46-2.44 Ga, 1.97-1.92 Ga and 1.84 Ga and metamorphic ages of 1.95-1.83 Ga. They are variable in geochemical composition with some being enriched in light rare earth and large ion lithosphere elements but depleted in Nb-Ta. Combined with previous results, it is concluded that mafic magmatism at 2.45-2.37 Ga and 1.97-1.92 Ga indicates two Paleoproterozoic extensional phases, with the latter accompanied by HT-UHT metamorphism as a result of underplating of mantle magma.