LA-ICPMS zircon U-Pb geochronological constraints on the tectonothermal evolution of the Early Paleoproterozoic Dakendaban Group in the Quanji Block, NW China

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.