关键词: 含铀矿砂岩, 成岩作用, 成岩环境, 介质条件, 铀矿成因机制, 鄂尔多斯盆地

Abstract: The uranium-bearing sandstones in Dongsheng area were basically classified into four types including yellowish brown-red sandstones in the oxidation zone,gray sandstones and altered grayish green sandstones in the primary ore zone,and light gray-grayish white "bleaching" sandstones by using the data of field geological survey,observation and description of drilling cores,identification and quantitative statistics of thin sections and polished sections under microscope.The igneous and mudstone fragments in the sandstones were attributed to the uranium resources.Uranium mineralization was controlled by the oxidation-reduction interface and occurred under the medium condition changing from acidic oxidation to alkaline reduction during diagenesis and epigenesis periods.Generation of uranium was closely related to migration and escaping of natural gas and may be also relevant to hydrothermal solution activities during epigenesis period.Secondary or regenerated zircons closely coexisted with the intergranular smectite and chlorite cements and micro pyrite,which show α trace of absorbed uranium.It implies that formation of these zircons may be related with uranium enrichment in origin.Part of the feldspar fragments replaced by kaolinite and dissolution of early carbonate cements resulted in loss of strontium is the main reason for the "bleaching" sandstones with low content of strontium.

Key words: uranium-bearing sandstones, diagenesis, diagenetic environment, medium condition, uranium mineralization mechanism, Ordos Basin