GEOPHYSICAL SIGNATURE OF THE VIEN-TYPE URANIUM MINERALIZATION OF WADI EISHIMBAI, SOUTHERN EASTERN DESERT, EGYPT | ||||
| Journal of Egyptian Geophysical Society | ||||
| Volume 9, Issue 1, 2011, Page 23-36 PDF (5.44 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jegs.2011.384434 | ||||
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| Author | ||||
| I.M. Gaafar | ||||
| Nuclear Materials Authority, Cairo, Egypt, Email: gaafar_ibrahim@yahoo.com. | ||||
| Abstract | ||||
| The application of various geophysical tools with different responses succeeded in fixing U-mineralization in Wadi Eishimbai area. The area was studied using detailed ground spectrometric, magnetic and VLF-EM surveys. The interpretation of the obtained spectrometric maps clearly reflects the sharp increase of eU content. Meanwhile, the K- and Th-contents show sharp decreases. The eU/eTh ratio correlates positively with eU concentrations and negatively with eTh concentrations, indicating an increase in the U-potentiality than the surrounding granite. The N-S shear zone displays an eU content ranging from 20 to 140 ppm. The ENE- trending lamprophyre is characterized by elongated uranium anomalies trending in the E-W direction, with values >90 ppm. Equivalent uranium content of the brecciated granite attains values up to 700 ppm. The ground magnetic and VLF-EM surveys played important roles in providing structural information, which proved useful in geological mapping and mineral exploration for the discovery of the uranium mineralization in the study area. This study follows the expected subsurface extension of the Sela shear zone, under Wadi sediments. The ground total magnetic-intensity map shows a relatively narrow and an elongated shape for the lamprophyre anomaly which extends for about 600m in the Wadi towards the west direction. The filtered very low frequency electromagnetic (VLF-EM) contour maps of the two used frequencies (17.1 and 28.5 kHz) show an excellent agreement, indicating that the shear zone is distinguished with somewhat or relatively strong conductivity westwards, as an extension for the main shear zone. It is elongated in an ENE-WSW trend, and extends in the western direction, referring to the existence of conductive materials. Most of the NW-SE trending faults cause sudden changes in the magnetic and VLF-EM contour spacing over an appreciable distance, which suggests a discontinuity in depth due to their left-lateral strike-slip displacements. The interpreted faults, with an ENE-WSW trend represent the main trend of Sela shear zone, through which hydrothermal solutions flowed causing high alteration and uranium mineralization. | ||||
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