Episodic Paleoproterozoic (～2.45, ～1.95 and ～1.85Ga) mafic magmatism and associated high temperature metamorphism in the Daqingshan area, North China Craton: SHRIMP zircon U-Pb dating and whole-rock geochemistry

摘要

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.