Horizontal loop electromagnetic and self-potential signatures of mineralized structures : a case study from Abu Rusheid Area, Southeastern Desert, Egypt

الملخص EN

Horizontal-loop electromagnetic (HLEM) and self-potential (SP) surveys were carried out at Abu Rusheid area, southeastern Desert, Egypt, to follow the extension of the exposed mineralized shear zone at depth and to detect any possible subsurface mineralization and its probable extension, as well as to reveal its structural setting, which may affect the distribution of radioactive and other associated minerals.

The HLEM data were collected using four frequencies (110, 440, 3250 and 14080 Hz) and two coil separations (80 and 140 m).

The interpretation of these data indicates the presence of two strong conductive zones trending in the NNW-SSE and NW-SE directions.

These strong conductors are dissected by a moderate conductive zone trending in the NE-SW direction.

The target parameters, as estimated from the HLEM data suggest that their widths range between 10 and 80 m, depths to the top are shallow and vary from 13.6 m to 58 m, dip angles range between 36° and 82° to both the east and west, and conductance (σt) changes from 18.4 to 135.2 Siemens (S).

A small area was selected for an SP survey to follow observed radiometric anomalies at depth.

The results indicated the existence of a series of conductive zones corresponding, in many places, to the previous identified radiometric zones.

The integration of the results revealed that, the SP and HLEM conductive anomalies are related to shear zones and faults, as well as lamprophyre and quartz veins.

Most of these anomalous zones are open towards the north which may attract the attention to the continuity of mineralization northwards.

In addition, the NNW-SSE, NW-SE and NE-SW trending structures are of prime importance and can be considered as significant targets for further field investigations.