Provenance and tectonic significance of Lower Triassic clastic sedimentary rocks of the West Qinling Orogenic Belt, Central China

The West Qinling Orogenic Belt (WQOB) in central China witnessed the closure of the Paleo-Tethys Ocean and the subsequent amalgamation between the North China Block and the South China Block during the Permian-Jurassic. However, the pre-closure Triassic tectonic evolution of the WQOB remains poorly constrained. Thick Triassic sedimentary successions are well preserved in the Xiahe-Hezuo district and provide significant infor-mation for investigating the tectonic setting in the WQOB. Here we present U-Pb ages and Hf isotopic compo-sitions of detrital zircons from a pebbly slate of clastic sedimentary rock that comprises the Longwuhe Formation of the WQOB, the Xiahe-Hezuo district, Central China. The detrital zircon U-Pb ages vary from 2525 Ma to 244 Ma and are distributed in five periods, i.e., 2525-2225 Ma, 2013-1676 Ma, 1127-883 Ma, 501-438 Ma, and 330-244 Ma. The youngest detrital zircon age peak of ca. 250 Ma constrains the maximum depositional age of the Longwuhe Formation to the Early Triassic. Provenance analysis indicates that the WQOB, the eastern Qilian Orogenic Belt, and the southern North China Block serve as the main source of the pebble-bearing slate. The detrital zircon of 330-281 Ma in the WQOB implies likely the presence of an Early Triassic continental arc. Integrated results of the regional structure, geochronology, and geochemistry of the Triassic granites in the WQOB suggest that the Longwuhe Formation was probably deposited in a forearc setting at ca. 250 Ma and followed immediately by arc magma intrusion in Early Triassic. Thus, the WQOB was possibly generated as a continental arc associated with the northward subduction of the Qinling Paleo-Tethys Ocean lithosphere during the Early Triassic.