Zircon U-Pb age and geochemistry of Early Cretaceous intrusive rocks in Maiba area of Xainza County, Tibet

Abstract:In this paper, the authors studied the intrusive rocks widely distributed in Carboniferous - Permian strata in Maiba area of Xainza County within northern Middle Gangdise belt, and obtained the LA-ICP-MS zircon U-Pb age of 110.8±0.9 Ma for graniteand age of 111.0±1.1 Ma for quartz monzonite, respectively. Both ages are consistent within the error range, suggesting that the granite and the quartz monzonite should be the product of the same magmatic activity. The intrusive rocks are characterized by highSiO2, supersaturated aluminum (A/CNK=1.05-1.38), and enrichment of Al, Th, LREE, with Th abundance being 14.8×10-6-28.4×10–6, implying that they are probably associated with the upper crust substances. Their cobweb curve is remarkably similar to that of the upper crust and acidic volcanic rocks resulting from crustal remelting of 110 Ma Zenong Group in Middle Gangdise belt. These data indicate that the intrusive rocks might be the remelting products caused by the dehydration of crustal materials.