Metallogenic Model of Sandstone-Type Uranium Deposits in the Lower Section of Saihantala Formation, Western Ulanchabu Depression, Erlian Basin

Industrial uranium mineralization in deep strata has been newly discovered during the exploration of sandstone-type uranium deposits in Western Wulanchabu Depression, Erlian Basin, but its age attribution is still unclear. Sedimentary and sequence stratigraphy studies show that three-stage sequence A (lower Seihantala sequence) and sequence B (upper Seihantala sequence) are developed in the Saihantala Formation in Western Ulanchabu Depression. Sequence A can also be divided into low system tract (LST), lake spreading system tract (EST) and high system tract (HST). In the past, sandstone-type uranium deposits in Erlian basin were mainly produced in HST of sequence A and LST of sequence B, while the newly discovered industrial uranium mineralization in the western part of Wulanchabu depression was found in LST of sequence A through the paleontological, lithostratigraphic and sequence stratigraphic comparative studies. The LST metallogenic ability of sequence A depends on the size of reducing medium and skeleton sand body of coal-bearing rock series. The braided distributary channel sand body in braided river delta sedimentary system is the most favorable uranium reservoir. Nearly 100 kilometers of intermittent phreatic-interlayer oxidation zone was formed along the uranium-rich satellite rocks. The uranium metallogenic process can be divided into three stages:the pre-enrichment of uranium during early Cretaceous sedimentary period, the metallogenic process from late Cretaceous to Paleogene Paleocene, and the preservation of uranium from Paleogene Eocene to Quaternary. Finally, a trinity metallogenic model of "fault-controlled sand body-reverse-controlled oxidation-reduction-controlled ore body" has been established in this paper. The newly discovered industrial uranium mineralization layer is defined as LST of sequence A, which expands prospecting prospects in the western part of Ulanchabu Depression, Erlian Basin.