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LA-ICPMS zircon U-Pb geochronological constraints on the tectonothermal evolution of the Early Paleoproterozoic Dakendaban Group in the Quanji Block, NW ChinaDOI: 10.1007/s11434-008-0265-x Keywords: Dakendaban Group,tectonothermal events,LA-ICPMS zircon U-Pb dating,Quanji Block,NE Qinghai-Tibet Plateau Abstract: The Quanji Block, situated between the northern margin of the Qaidam Block and the South Qilian orogenic belt in the NE Qinghai-Tibet Plateau, China, is thought to represent a remnant continental crust. In this study, LA-ICPMS U-Pb analyses of detrital zircon grains from two mesosomes in the migmatitic Dakendaban Group yield ages of 2467+28/ 26 Ma and 2474+66/ 52 Ma, respectively. Zircon grains from a leucosome give two distinct ages of 2471+18/ 16 Ma and 1924+14/ 15 Ma. Zircon from a granitic pegmatite that intruded into the Dakendaban Group yields an age of 2427+44/ 38 Ma. These data suggest that the Early Paleoproterozoic Dakendaban Group deposited between ~2.43 to ~2.47 Ga and has been subject to an intrusive event at 2.43 Ga, and regional metamorphism-anatexis at 1.92 Ga. The common lower intercept age of ~0.9 Ga probably records a significant Early Neoproterozoic event in the Quanji Block.
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