Provenance and uranium source tracing for uranium-bearing series in the south of Songliao Basin: Evidence from zircon UPb chronology and lithogeochemistry

Abstract

The study of uranium sources in sandstone-type uranium deposits has been significantly hindered by the absence of effective methodologies, thereby impeding uranium resource exploration efforts. This paper delves into the origin and evolution of sandstone-type uranium deposits, particularly in two newly discovered mineral localities in the southeastern Songliao Basin, employing zircon UPb geochronology and petrogeochemistry. Additionally, it examines the evolutionary history of these deposits within the Paleo-Asian Ocean tectonic domain. The research reveals that the uranium-bearing series in the study area primarily originate from intermediate-acid magmatic rocks located in the active belt of the northern margin of the North China Craton and the continental island arc tectonic environment. The detrital zircon in the uranium reservoir sandstone, with a peak age range of 270–236 Ma, bears witness to the orogenic events involving the subduction, closure, and collision of the Paleo-Asian Ocean and the back-arc ocean basin. Meanwhile, the peak age range of 181–154 Ma signifies the Paleo-Pacific Ocean subduction impact in the study area. A comprehensive comparative analysis of zircon UPb chronology and lithogeochemistry indicates that the highly differentiated granite (Baijiagou Pluton), which mixed with the crust in the Early Triassic syn-collisional orogenic environment, serves as a promising source of uranium in the study area. By utilizing the differences in weathering resistance between zircon and rock, specifically the stable Th/U ratio in zircon and the unstable Th/U ratio in rocks, this relationship can be used to trace favorable uranium sources. This method provides an effective approach for identifying uranium sources in the exploration of sedimentary uranium deposits. The ocean-arc system present on the active continental margins of the Paleo-Asian Ocean's northern and southern sides continuously facilitates the material cycle of uranium rich sediments and magmatic uranium elements. This process, coupled with multi-stage and multi-material magmatism, ultimately leads to the formation of a favorable uranium rich geological body. This serves as the material and uranium source basis for the formation of sedimentary uranium deposits in northern China.