Elemental geochemical characteristics of Jurassic uranium-bearing strata in Ningdong area, western Ordos basin

The geochemical characteristics of sedimentary rocks record important geological information during the process of rock deposition, are an effective tool for the study of the paleoenvironment, the tectonic setting and the attributes of provenance. This paper aims to the comprehensive study of the paleoenvironment, the tectonic setting and provenance attribute of lower section of Zhiluo Formation by testing and analyzing the content of major elements, trace elements, and rare earth elements of the sandstone and mudstone samples collected from the lower section of Middle Jurassic Zhiluo Formation in the eastern margin of Ordos basin using the method of XRF and ICP-MS. The research indicates that Sr content, Sr/Cu ratio, V/(V+Ni) ratio, U/Th ratio, and CIA as well as other geochemical indexes suggest the semi-arid and semi-humid paleoclimate of lower section of Zhiluo Formation, and the oxygen enrichment-secondary oxygen enrichment freshwater environments as the paleo-water conditions; The rare earth feature proves that the provenances of lower section of Zhiluo Formation may be mainly the Alashan ancient land in the northwest of the basin. The provenance lithology is mainly made up of gneiss, garnet shallow rock, unequal grain quartz sandstone and medium-grained quartz sandstone. The tectonic setting of provenance area is mainly related to the continental island arc, and the oceanic island arc.