鄂尔多斯盆地彬县地区铀矿化特征及油气关系OA

Binxian area is located in the southern part of Ordos Basin and is currently a key exploration sector for Zhiluo Formation of Middle Jurassic in the southern region of the basin.To clarify the relationship between uranium mineralization and hydrocarbons in Zhiluo Formation of Binxian area,this study integrates methods such as microscopic identification,electron probe analysis,trace element analysis,and hydrocarbon component analysis,based on field investigations and core logging.The results indicate that lower member sandstones of Zhiluo Formation in Binxian area exhibit red and gray-green alterations,with the gray-green alteration being formed by the reduction of previously oxidized sandstone.Uranium mineralization is distributed in the paleo-interlayer oxidation zone and on the gray sandstone side of the redox transition zone.The ore-bearing sandstones are primarily gray medium-grained sandstones,coarse-grained sandstones,and pebbly coarse-grained sandstones.The uranium minerals are mainly coffinite and pitchblende,occurring interstitially between detrital grains or associated with pyrite.Uranium shows significant positive correlations with V,Re,Mo,organic C,and Se.The hydrocarbons in the lower member sandstones are primarily derived from deep-seated cracked natural gas of early crude oil.The hydrocarbon-bearing gases enhanced the reducing capacity of the sandstones,and provided sufficient reductants for subsequent uranium mineralization.