The Horizontal Loop Electromagnetic (HLEM) Response of Ifewara Transcurrent Fault,Southwestern Nigeria: A Computational Results

Abstract

The need to accurately interpret geological models that approximate mineralized zones in a Basement Complex terrain necessitate the development of horizon loop electromagnetic method (HLEM) forward modeling solutions for such scenarios. The focus of the present work is on finding rapid forward modeling solutions for synthetic HLEM data as an aid in exploration for moderate to deep conductive mineral exploration targets.The main thrust is obtaining idealized HLEM models that are required for geological interpretation of the subsurface in such environment. The original HLEM equations developed by Wesley were extended to represent a horizontally stratified earth with a conductive approximated by shear zone. From these equations a computer program was written to calculate the HLEM responses for optimal conductor model with known values of coil separations (L), depth of burial (z) and angle of dip of the target.The thin conductive model was used because it is simple and suitable for different geological scenarios. The accuracy of the approximate forward solution has been confirmed for HLEM systems with various geometric ranges, frequencies and conductivities. Three models having varying overburden thickness, dip angle of target and source-receiver separation were used in the forward modeling. The effect of varying the dip angle,overburden thickness and coil separation was studied in all the three models used. The result obtained from the forward modeling showed that variation of the dip angle gave rise to changes in the amplitudes of the anomalies generated, while that of overburden and coil separation gave rise to changes in anomaly shape. Also, the geometry and position of the causative body were precisely delineated.