层序结构对吐哈盆地SHT砂岩型铀矿成矿的控制作用
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摘要
通过分析构造旋回对基准面旋回的控制作用,建立了基准面旋回中三级陆相层序界面岩性识别标志——冲蚀厚层砾岩、厚煤层、沉积韵律变异面等。依据地震反射特征与建立的层序界面岩性标志将研究区含铀建造中下侏罗统划分成3个三级层序、18个准层序。研究了层序结构与沉积体系对层间氧化带砂岩型铀矿成矿的控矿作用,认为层序界面控制层间氧化带砂岩型铀矿化发育的垂向层位,基准面上升初期的辫状河体系与基准面下降期的辫状河三角洲体系分布控制铀矿化空间分布,辫状河、辫状河三角洲体系中主河道砂体控制了铀矿体分布。指出砂岩型铀矿床找矿的核心是寻找辫状河、辫状河三角洲砂体分布。
Based on analyzing the control of tectonic cycles over the base￣level cycles,three￣level lithologic recognition indicators of terrestrial sequences interfaces are established in the base￣level cycles,i.e. the thick washouted gravel bed,thick seams and sedimentary rhythm variation surfaces. Uranium￣bearing formations of low￣middle Jurassic in the study areas are divided into 3 three￣level sequences and 18 sub￣sequences according to the characteristics of seismic reflection and the established lithologic recognition indicators. The control of sequence frameworks and sedimentary systems over the interlayer oxidation sandstone￣type uranium deposits is studied. It is suggested that the sequence interface controls the vertical horizon where the interlayer oxidation sandstone￣type uranium deposits developed. Spatial distribution of the uranium mineralization is controlled by the braided channel system in the ascending stage of the base￣level and braided channel and delta system in the descending stage of the base￣level. The distribution of orebodies is controlled by the main channel sandbody in the braided channel and braided channel delta sandbody. It is pointed out that the prospecting core of sandstone￣type uranium deposit is to find out the distribution of the braided channel and braided channel delta sandbody.
Based on analyzing the control of tectonic cycles over the base￣level cycles,three￣level lithologic recognition indicators of terrestrial sequences interfaces are established in the base￣level cycles,i.e. the thick washouted gravel bed,thick seams and sedimentary rhythm variation surfaces. Uranium￣bearing formations of low￣middle Jurassic in the study areas are divided into 3 three￣level sequences and 18 sub￣sequences according to the characteristics of seismic reflection and the established lithologic recognition indicators. The control of sequence frameworks and sedimentary systems over the interlayer oxidation sandstone￣type uranium deposits is studied. It is suggested that the sequence interface controls the vertical horizon where the interlayer oxidation sandstone￣type uranium deposits developed. Spatial distribution of the uranium mineralization is controlled by the braided channel system in the ascending stage of the base￣level and braided channel and delta system in the descending stage of the base￣level. The distribution of orebodies is controlled by the main channel sandbody in the braided channel and braided channel delta sandbody. It is pointed out that the prospecting core of sandstone￣type uranium deposit is to find out the distribution of the braided channel and braided channel delta sandbody.
引文
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沈守文,彭大钧,颜其彬,等.吐哈盆地层序地层学研究[J].沉积学报,2001,19(2):263—270.
威尔格斯CK.层序地层学原理[M].徐怀大,魏魁生,洪卫东,译.北京:石油工业出版社,1992.1—15.
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