Metallogenic Conditions And Prospecting Prediction Of Sandstone Type Uranium Deposits In Zhongji Area,Northern Ordos Basin

Ordos basin is an important Mesozoic oil-bearing sedimentary basin uranium gas in the past,the mineral exploration process,a large number of radioactive anomalies were found in the Middle Jurassic Zhiluo Formation in the lower section of the coarse sandstone,the previous studies show that the radioactive anomaly characteristics mainly caused by radioactive uranium,the coarse sandstone for the uranium rich fluvial sand body,because the change of sedimentary facies and sedimentary environment,the horizon is relatively stable,but the uranium content of large changes,how to carry out uranium prospecting and mining district in a certain area of useful information and guide the prospecting work is particularly important.Based on sandstone type uranium metallogenic regularity Ordos northern basin at this time,the Zhongji area as an example,a detailed analysis of the sedimentary characteristics and tectonic conditions and rock material composition and formation environment of uranium metallogenic background,on the basis of systematically summarizes the uranium metallogenic feature the Zhongji area,analyzes the causes of uranium mineralization,the establishment of the metallogenic model and prospecting in the study area,and the next step prospecting direction indicator.Petrological and geochemical analysis results show that the study area,have a good group of original sedimentary period of uranium source conditions,the original source from the north or the northeast area of the middle Yin Mountain of granite,characteristics of petrology with arc active continental margin magmatic arc-the evolution of the mature.The rock composition with active continental margin(mature island arc magmatic arc evolution)petrology characteristics.Through geological analysis,it is considered that the Mesozoic strata in the Zhongji area are monoclinic strata,and the interlayer oxidation zones exists in the Zhiluo Formation of the Middle Jurassic strata.From the northern denudation area with oxygenated water and from the southern deep fault with reductive organic fluids,for sandstone type uranium ore formation in the region are provided for reducing agent,oxidizing agent and uranium metallogenic material,is conducive to the enrichment of uranium.Ore formation sand body is mainly located in the lower member of Zhiluo Formation,especially the river bifurcation and intersection zone facilitates fluid multiphase transformation,thus favorable gray gray white minerotect distribution is limited,uranium and oxygen bearing water infiltration and reduction of oil and gas fluid up to the key the distribution of uranium mineralization.From the analysis of tectonic sedimentary evolution and geochemical characteristics of rocks,that uranium mineralization in chronological order can be divided into three stages: Middle Jurassic host rock formation stage,early Cretaceous crustal uplift and oxygenated fluid transformation and superposition enrichment stages,and the late Cretaceous tectonic formation and deep fluid superposition mineralization stages.Based on the analysis of metallogenic geological conditions,the metallogenic model of uranium in this area is summarized,It is considered that the uranium metallogenic model in the Zhongji area is a model of the combination of reductive fluid invasion and interlayer oxidation,In the Zhongji area,Yuanjiatan-Kang Jiabalou area is the first grade favorable metallogenic area,and Bianjiahao-Lijiapan area is the second grade favorable mining area.