Sediment Provenance of the Intracontinental Ordos Basin in North China Craton Controlled by Tectonic Evolution of the Basin-Orogen System

摘要

The intracontinental Ordos Basin hosts many large uranium deposits, and its evolution was controlled by the surrounding orogenic belts during the Paleozoic to Mesozoic. Paleocurrent data of the Jurassic Zhiluo Formation reveal that its sedimentary detritus were transported dominantly from southwest to northeast in the basin. However, the detrital zircon age pattern of the Zhiluo Formation is similar to those of the Inner Mongolia Paleo-uplift, the Central Asian Orogenic Belt (CAOB), the Yinshan Block, and the Khondalite Belt to the north but is remarkably different from those of the Qinling Orogenic Belt (QOB) and the North Qilian Belt to the south. Discriminant diagrams using immobile elements also reveal that the detritus of the Zhiluo Formation are dominated by felsic volcanic rocks and andesitic arc rocks, consistent with rock types in its northern orogenic units. The Zhiluo sandstones show high chemical index of weathering values (68-83), suggesting long-distance transportation and intensive weathering. These lines of evidence demonstrate that rocks from the Zhiluo Formation were recycled from underlying Permian-Triassic sediments that were ultimately sourced from the northern orogenic units. The Ordos Basin has a three-stage growth that was controlled by the formation and tectonic evolution of the QOB to the south and the CAOB to the north during the Late Carboniferous to Jurassic.