Abstract
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 2.46–2.44Ga, 1.97–1.92Ga and 1.84Ga and metamorphic ages of 1.95–1.83Ga. 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 2.45–2.37Ga and 1.97–1.92Ga indicates two Paleoproterozoic extensional phases, with the latter accompanied by HT–UHT metamorphism as a result of underplating of mantle magma.
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