Sandstone-type uranium deposits are developed in the Naomugeng depression of the Erlian Basin.The ore-bearing strata is the Lower Cretaceous Saihan Formation.In this paper,the rock characteristics of the sandstones of the Saihan Formation have been identified through microscopic observation and rock geochemistry,the sedimentary parent rocks of the Saihan formation in the study area have been demonstrated,and the sedimentary environment of the Saihan Formation has been discussed.The research shows that the sandstone of Saihan Formation is mainly composed of lithic sandstone and gritstone,which are mainly composed of plagioclase,potassium feldspar,quartz and debris.The interstitial material is mainly argillaceous,followed by clay minerals.The composition of major elements,rare earth elements and trace elements is similar between ore-bearing sandstones and non-ore-bearing sandstones,and the ore-bearing sandstones are mainly controlled by the oxidation-reduction conditions of the system.The sandstone has obvious negative Eu anomaly and is a right-leaning type of light rare earth enrichment,enriched in Ba,Ta,Ce,Sm enrichment,moderate depleted in Sr,K,Zr,Hf,and strong depleted of Ti.The overall variation characteristics are not different from the average upper crust.The element geochemical characteristics indicate that the sedimentary parent rocks of Saihan Formation sandstone are mainly granitic rocks,formed in a dry and hot climate,more alkaline,transition-reduction terrestrial freshwater environment.When Fe2+/Fe3+values are 0.2～0.3,the U content reaches the highest value,indicating the REDOX state controls the enrichment or depletion of uranium.
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