LAUSR

The very low frequency electromagnetic (VLF-EM) method is a rapid and reliable geophysical method was used in the investigation for uranium bearing structures in the Proterozoic basement of the Dhofar region that may be a potential source and trap for uranium and associated minerals in Sultanate of Oman. Accordingly, the in-phase and out of phase components of VLF-EM field along 11 traverses were recorded at two different transmitter frequencies viz. 16 kHz and 16.4 kHz at an approximate line interval of 20 m with a measurement interval of 10 m. These measured components were subjected to Fraser and Karous-Hjelt filtering in order to decipher the nature and depth to the sub-surface conductor. The Fraser filtered in-phase VLF-EM components yield a strong amplitude almost over the top of the conductor. On the other hand, the Hjelt filtered responses yield the depth to the source in the range 10–80 m. Spectral analysis of selected a few traverses result the depth to source in the range 31–39 m. Analytical signal approach of total magnetic field of line-I substantiates this depth. The peaks of Fraser filtered stacked profiles delineate approximately the trend of the sub-surface fault which mimic the trend inferred from the combined interpretation of VLF-EM and magnetic anomalies. The results of Fraser and Karous-Hjelt filter output suggest a mineralized conductive sub-surface fault aligned along NW-SE. It may be noted that the random sampling of gamma ray spectrometer has recorded a maximum uranium concentration of up to 30–40 ppm prior to VLF-EM survey.