The Elements Geochemistry Characteristics Of Interlayer Oxidation Zone In Sandstone Type Uranium Deposits

In this dissertation, the author studied the element geochemistry characteristics of interlayer oxidized zone in sandstone type uranium deposits in our country. The dissertation is supported by "305"key project, studying the localization of interlayer oxidized zone and geochemical characteristics of U producing formation in Shihongtan deposit(the special serial number 2001BA609A-07-13). The author acquired some innovative outcomes and recognitions by systematically studying and comparison of major elements, trace elements, rare earth elements, isotopes and mineral fluid inclusions of sandstone type uranium deposits of typical Shihongtan interlayer oxidized zone in Yili basin and Turpan-Hami basin.(l)Interlayer oxidized zone and uranium mineralization forming uranium deposits were the results of the long term ground water-rock interaction on the low temperature and normal pressure condition, which was an opening system under nonequilibrium state. The interlayer oxidized zone and the concentration of uranium has the typical characters of low temperature geochemical processes. Interlayer oxidized zone can be defined from the bedrock to horizon C under hypergene weathering by such parameters as chemical metamorphosing (PC),index of chemical weathering (ICA) and index of mineral chemical differentiation (ICV).(2)Major elements can be divided into sensitive group, active, weak active and inert groups according to chemical metamorphosing parameter(PC) and fractional migration potential. For major elements of multivalent in the active group( Fe₂O₃, FeO) and U, the migration and concentration trend in interlayer oxidized zone is apparent. Interlayer oxidized zone can be divided accurately by Fe₂O₃, Fe₂O₃/FeO and U parameters (microscopic zoning). We can correct the field macroscopic color zoning by combining the macroscopic zoning and microscopic zoning. Univalent major elements components(Al₂O₃, SiO₂, K₂O, Na₂O) show remarkable activity at the process of interlayer oxidizing, their contents are variable and mingled in different zones and it can't be used in zoning. But we can speculate the developmental degree of interlayer oxidized zone and uranium mineralization according to the concentration trends and variation characteristics of sensitivity group, activity group and their ratios .(3)The comparatively steady elements such as lithiphile elements(Li, Rb, Cs, Ba , Cr, Pb etc), sulfophile elements(Co, Ni) and high field strength elements(Zr, Hf, Nb, Ta) change regularly at the process of interlayer oxidation except some radioactive elements(U, Th). Trace elements and rare earth elements commonly enrich in thin rock clast such as mudstone, in which the enriched elements species are more than those in the whole rock, which indicate that the regeneration action in caulking matter are more deep than that in whole rock at the process of interlayer oxidation, and the reallocate intention of trace elements in main minerlized rock in Tuha basin are more intensive than that in Yili basin at the process of deposition ,diagenesis and later changes .(4)The research of background value of major elements, trace elements, rare earth elements and organic carbon in main mineralized rock can indicate the deposition environment of mineral layers and later diagenetic change. The field geochemical background of elements can strongly control the...