鄂尔多斯盆地高自然伽马值异常特征及主控因素研究

Study on feature of high natural gamma anomaly and main controlling factors in Ordos basin

为了解鄂尔多斯盆地浅部与深部高自然伽马异常特征的主控因素,本文从单孔测井曲线、典型剖面测井曲线对比、不同地层高自然伽马异常平面分布特征分析、放射性元素含量测试分析等方面,研究了该区高自然伽马异常的平面及纵向展布特征后认为:①铀含量变化与自然伽马幅值变化呈良好相关性,自然伽马异常主要是由铀含量增加直接引起,铀的活化和聚集呈现一定的地区差异;②自然伽马异常平面特征与地层沉积特征关系密切;③造成盆地高自然伽马异常特征的主控因素是盆地沉积环境的变迁和历经的构造运动,进而决定了铀的时空分布特征,盆地深部和浅部的铀异常也具有一定的关系。

In order to know the main controlling factors of high natural gamma anomaly in shallow and deep parts of Ordos basin, after studying the planar and vertical distribution feature of high natural gamma anomaly in the area from the aspects of correlation of logging traces in single hole and typical logging traces, analysis of planar distribution feature of high natural gamma anomaly in different strata and test analysis of the contents of radioelement, the paper considered: ①good correlation exists between the change of uranium contents and variation of natural gamma amplitude.The natural gamma anomaly mainly directly resulted from increasing the uranium content, and uranium activate and accumulation have certain regional difference; ②the planar feature of natural gamma anomaly is closely relative to stratigraphic sedimentary feature; ③the main controlling factors resulted in high natural gamma anomaly in the basin are changes of sedimentary environment and experienced structural movement, which further determined the feature of uranium time-space distribution, and uranium anomaly in shallow and deep parts of the basin also has some influence.