Natural gamma anomalies and their geological significance of the Jurassic Zhiluo Formation in Yulin area, Northern Shaanxi

Yulin area lies in the northeast part of northern Shaanxi slope of the Ordos Basin and adjacent to Dongsheng uranium mine in the north,in which high abnormal values of natural gamma-ray logging are found in the porous Zhiluo formation. Based on the study of relevant borehole histogram, well logging curves and the relationship between uranium content and well logging values, it is found that the high anomaly holes are relatively concentrated in the northern part of Yulin and the abnormal occurrence strata are mainly grey green siltstone. This area is featured in Lacustrine deposits in the north and fluvial deposits in the south. The high abnormal layer vertically occurs in the “Oxidation-reduction Transition Zone”of the interlayer oxidation zone and partly in the lower submember of the Zhiluo Formation,with a positive correlation between the uranium content of the samples and the corresponding logging values. Overall, there is a good prospect for uranium prospecting in northern Yulin