Slab break-off model for the Triassic syn-collisional granites in the Qinling orogenic belt, Central China: Zircon U-Pb age and Hf isotope constraints

摘要

Numerous Triassic granitoids in the Qinling orogenic belt related to the Late Triassic collision between the North China Craton (NCC) and the Yangtze Block (YB) are important for determining the crustal composition at depth and the geodynamic processes by which the orogen formed. Most of the Triassic plutons in the Qinling orogen were emplaced between 205 and 225Ma. The granitoid rocks from the southern margin of the NCC, North Qinling, South Qinling, and the northern margin of the YB that were emplaced during this interval have two-stage Hf model ages of 0.60-2.52Ga (average 2.19Ga), 0.90-2.66Ga (average 1.29Ga), 0.41-3.04Ga (average 1.48Ga), and 1.00-1.84Ga (average 1.34Ga), respectively, and mean epsilon(Hf)(t) values of -14.5, -0.32, -1.36, and -3.98, respectively. The Hf isotope compositions of the granitoids in different tectonic units differ significantly, mirroring the diverse history of crustal growth of the four units.