| Content: Erlian basin is an important reservoir of not only oil, gas and coal, but alsosandstone type uranium. This thesis is based on mineralization theory of exogenic epigeneticsandstone type uranium. A metallogenic model of interlayer oxidation zone sandstone typeuranium deposits has been established by comprehensive analysis and research such as basicgeological data，sequence stratigraphy, depositional system, test results, especially the studyof characteristics on the tectonic setitng, depositional facies, sand body, oxidation zone,mineralization, ore-controlling factors. The following results and knowledge have beendrawn in this paper:1，the uranium ore-bodies lie in ancient valley sandbodies of the upper section of Saihanformation, Lower Cretaceous Seires. The orebody lithology is multi-graded sandstoneassembly with strong inhomogeneity, including sandy conglomerate, medium-coarse grainedsandstone, mid-fine grained sandstone, silty sandstone interbedded mudstone, sandyconglomerate. And the sandy conglomerate is the main composition. Braided irverfilling-combination and channel edge-combination is the main sedimentary microfacies ofthe ore-bearing strata, and it has a distinguished feature of well log.2，the uranium deposits are controlled mainly by the phreatic-interlayer oxidation zonedeveloped in sandstone-bodies of ancient Valley. The oxidation zone has an obviouszonation in the plane. The orebodies lie in grey sandstone near the forward line of oxidationzone. And the distirbution of the orebody is consistent with the direction of the front line ofoxidation zone in plane.3, in profile, the shapes of the orebodies are tabular and rolling，which controlled byfront line of phreatic-interlayer oxidation zone. And the spatial distirbution of ore-bodies iscontrolled by the development of palaeo valley section. Two main types of uranium ore havebeen determined by the appraisal result of ore in microscope: sandstone-type-ores andconglomerate-type-ores. Composition of ore, which contains more pyrite, organic carbon,clay etc.，is similar to that of wall rock. The content of the major trace-elements, such asSiOa, FeO, Fe2〇3，AI2O3，K2O, Na20，T1O2is high in the ore，and the content of the harmfulcomponent, such as CaO, MgO, CO2is low. Relatively，the trace elements, such as Ba，Rb，Ba is enrichment, however, Sr is loss.4，the metallogenic age of Bayanwula uranium deposits is44土5Ma (Paleocene Eocene(E2))，which has been determined by whole rock U-Pb isochron method, and the uraniumcontent of ore sample has been corrected by the uranium-radium equilibrium coeiffcient. Theexisting forms of the uranium in the ore are: adsorbed, minerals, and beairng, which havebeen found by the methods of radiograph, electron probe and scanning electron microscope.Adsorbed uranium is the main form, and the proportion of six-valence uranium is higher.5，associated elements in the ore-body and surrounding rock, such as selenium, rhenium,molybdenum, vanadium, scandium, etc., are enrichment, and rhenium, selenium, scandiumcan be utilized comprehensively. Rhenium and uranium are symbiotic relationship, andselenium deposited close to the oxidation side, and scandium enriched close to the reductionside.6，the mentallogic model of sandstone type uranium deposits in Bayanwula area hasbeen established based on study of ore controlling factors, such as oxidation zone, ancienthydrodynamics: The uranium deposits lie in ancient valley of the late of the EarlyCretaceous; the epigenesist metallogenic process consisted of3stages, enrichment,mineralization and ore-conservation, ran through the whole process of the generics,development and change of the valley; oxygen-uranium-beairng water coming from rechargearea seeped through the valley from lateral side，and moved along permeablesandstone-bodies caught in mudstone aquicludes, and then, uranium was precipitated andenriched by the reaction on reduction material in sandstone. This process is controlled by hydrodynamics conditions of the ancient Valley, reducing power and orogenic activity.The conclusion and understanding of the study have not only significant guiding on theexploration and development of sandstone type uranium deposits in Erlian Basin, but alsogreat significance to perfect metallogenic theory of the sandstone type uranium deposits. |
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