Provenance and tectonic setting of the Upper Cretaceous Yaojia Formation sandstones in the Hailijin area, southern Songliao Basin: Constraints from petrogeochemistry and zircon U-Pb chronology

Abstract

Objective Tracing the provenance of host clastic rocks is key for understanding uranium reservoir projection and uranium source evaluation of alluvial uranium ore. Methods The Hailijin uranium ore, of which the host rock is the Upper Cretaceous Yaojia Formation, is located in the southern part of Songliao Basin, northeastern China. This paper performed detailed petrography, whole-rock geochemistry and detrital zircon U-Pb geochronology of sandstone in the Yaojia Formation. Results Twenty-six samples collected from 16 drill holes display high contents of SiO2 and relatively low contents of Al2O3, Fe2O3, MgO, MnO, Na2O and TiO2, which plot in the area of lithic sandstone to sublithic sandstone, thus indicative of source rocks as the felsic components. The chemical index of alteration values range from 62.93 to 83.46, while the index of compositional variability values range from 0.4 to 1, which corresponds to moderate chemical weathering in a semiarid to semihumid climatic setting. The geochemical discriminant diagram shows that the tectonic background of the Yaojia Formation is a passive continental margin. Zircon U-Pb ages are mainly distributed at 180-110 Ma, 320-230 Ma and 2 536-1 738 Ma. Conclusion Combined with stratigraphy, magmatic records around the Songliao Basin and regional tectonic evolution, this study suggests that the sediments of the Yaojia Formation in the Hailijin were sourced from the Linxi area of the southern Great Xing'an Range.

Keywords

• songliao basin
• yaojia formation
• geochemistry
• zircon geochronology
• provenance analysis