Timeframe of eastern Paleo-Tethys closure: Constraint on the Songpan-Ganzi Complex by big data-based multiproxy provenance analysis

Abstract

The Songpan-Ganzi Complex (SGC) is one of the largest turbidite complexes on Earth. The source-to-sink processes of the SGC are closely linked to the closure of the Paleo-Jinsha Ocean in the eastern Paleo-Tethys realm, so the spatiotemporal transitions in SGC provenance provide the potential to constrain the closure time. A comprehensive multiproxy provenance investigation, integrating detrital zircon UPb geochronology, whole-rock SmNd isotope data, and paleocurrent analysis, shed light on the origin of the Triassic SGC turbidites. In this study, it was determined that a significant proportion (exceeding 70%) of the detrital material comprising the SGC turbidites was sourced from the northwestern margin of the Yangtze Craton and the Qinling Orogen. A comprehensive and quantitative provenance study revealed that the Songpan-Ganzi turbidites primarily originated from collisional orogenic belts at convergent continental plate margins and secondarily from magmatic arcs and other tectonic units surrounding the basin. In this study, it was demonstrated that the SGC contains important information on the convergence of Eurasia and the tectonic evolution of surrounding terranes. (1) The South Qinling Orogen experienced significant rapid exhumation during the Ladinian to early Carnian. (2) The closure of the Paleo-Jinsha Ocean most likely occurred during the transition period between the upper and lower members of the Zhuwo Formation (ca. 231 Ma, middle Carnian). (3) During the Late Triassic, the crust of the Yidun Terrane underwent significant vertical accretion, resulting in a topography exceeding that of the Jomda-Weixi arc by the late Norian.