干旱区生态环境知识资源中心

Airborne gamma radiometric and spectrometric surveys have shown that the Kab Amiri granite pluton is associated with an aero-gamma anomaly of magnitude equivalent to about 4 backgrounds. Detailed field studies including gamma spectrometric surveying, sampling, trenching and laboratory investigations revealed the following observations and conclusions. (1) The radioactive anomalies are associated with an episyenitized granite stock exposed to the south of the main pluton. (2) This western contact is controlled by a NW left-lateral major fault and its associated tension fracture systems. (3) The radioactive anomalous zones show many alteration features including muscovitization, sericitization, ferrogenation and carbonatization. (4) The uranium contents range between 16-28 ppm in the non-altered granites, and between 44-169 ppm in the radioactive zones. The Th is very much depleted ranging 1-5.5 ppm with no distribution pattern. (5) The U-deposition is believed to epigenetic since it is associated with the muscovitized and carbonatized episyenite which represent later stages in the episyenitization process itself that is characterized by strong K-leaching.