干旱区生态环境知识资源中心

The objective is aimed at identifying significant U and Th anomalies, the amount of re-mobilization of U and Th, the structural framework of the granite pluton and the distribution of spectrometric anomalies. The study revealed that the granite pluton could be represented as a single radio-lithologic unit excluding abnormal measurements exceeding (X) over bar+2S. It also revealed the existence of eight strong spectrometric anomalies. Observed values of eU correlate well with eTh, r=0.72, while the correlation between eU/eTh and eU is lacking, r=0.190. Meanwhile, there is a negative correlation between eU/eTh and eTh, r=-0.335. This deficiency in correlation suggests a limited or zero remobilization of uranium, which was partly governed by magmatic processes. An interpretative basement structural map of the study-area showed some striking features: four NW-trending faults of first-order magnitude (probably shear zones); three NE-trending faults of second-order magnitude; a series of third-order magnitude faults trending in different directions and, questionably, strike-slip faults as well as some basic and acidic dykes. Most of the radioactive anomalies were found within or near the major contact faults which may act as channels for mineralized fluids from the subsurface. These fluids possess increased concentrations of U and/or Th which could exist in appropriate chemical and/or structural traps. The U and Th anomalies were found to be associated with the northern and southern parts of the granite pluton respectively. The difference between the northern and southern parts of the granite pluton may be attributed to differences in radioelement content, the effect of partial and/or complete digestion of older rocks, or to different levels of erosion.