Tectonic setting and provenance analysis of the Yaojia Formation in the northeastern Songliao Basin, NE China: constraints from sandstone geochemistry, Hf isotopes, and zircon U–Pb chronology

Abstract

The Songliao Basin is rich in uranium ores, and the Yaojia Formation, which is dominated by gray fine-grained sandstones, contains the main ore-bearing stratum. Rocks in the formation contain high SiO2, Al2O3, and total alkali, with enrichment in Rb, Th, U, K, and light rare earth elements but are depleted in high field strength elements, similar to upper crustal rocks. U–Pb dating of zircon grains from sandstones in the formation yielded four groups of ages, including 99–182, 202–245, 284–365, and 1800–1900 Ma. These ages combined with the Hf isotope composition, geochemical characteristics, and regional history suggest that the Yaojia Formation rocks are associated with passive and active continental margin settings. These clastic rocks originate principally from felsic rocks in the Zhangguangcailing–Xiao Xing'anling area, and these were deposited in oxic freshwater environments.