Closure of the Paleo‐Asian Ocean in the Middle‐Late Triassic (Ladinian‐Carnian): Evidence From Provenance Analysis of Retroarc Sediments
Dongfang Song, Wenjiao Xiao, Brian F. Windley, Qigui Mao, Songjian Ao, Hao Wang, Rui Li
Abstract
Abstract A major current debate in Asian tectonics concerns the time of closure of the Paleo‐Asian Ocean (PAO) and the collision between the Central Asian arcs and the Tarim and North China cratons (NCC). This has led to much uncertainty about the reconstruction of proto‐Asia and tectonic configuration of northeast Pangea. Here we report Triassic provenance change in the foreland of the Alxa Block by field‐based zircon U‐Pb and Hf isotopic analysis. Nonmarine sediments, unconformable on or in fault contact, with the Alxa basement yield Precambrian and Paleozoic–Triassic detrital zircon ages with maximum depositional ages of Middle‐Late Triassic (∼244–224 Ma). Hf isotopic data indicate that Middle Triassic sandstones were sourced from the NCC basement and a continental arc, whereas Late Triassic sediments received an additional input from a juvenile arc. This provenance change in the foreland sedimentation indicates that the final closure of the PAO was in the Middle‐Late Triassic.