Electromagnetic Survey for Mapping Subsurface Conductors in Jos Plateau

This study applies frequency-domain electromagnetic surveying to map subsurface conductive anomalies associated with tin-bearing alluvial deposits and basement geology in Jos Plateau, Plateau State, North Central Nigeria. The Jos Plateau is Nigeria's most historically significant mining area, with extensive cassiterite and columbite production from residual and alluvial placers. Post-mining land rehabilitation and artisanal mining management require knowledge of alluvial conductor distribution, thickness, and spatial extent. This study deploys a Geonics EM34 system in both horizontal and vertical dipole modes at station spacings of 20 metres along 18 east-west traverses covering approximately 4.2 square kilometres in selected abandoned mining pits near Barkin Ladi and Bokkos districts. Apparent conductivity profiles are processed for power-line coupling removal and smoothed using a 3-point moving average. Plan maps of apparent conductivity at 10-metre and 20-metre effective depths are generated. Findings reveal a network of elongated, high-conductivity anomalies in the range of 60 to 180 millisiemens per metre trending northeast-southwest, corresponding spatially with mapped alluvial valleys identified in geological reports. These are interpreted as water-saturated tin-bearing sand and gravel deposits that constitute remnant mineable material in post-artisanal areas. Three discrete conductivity highs exceeding 150 millisiemens per metre are recommended for follow-up test pitting and sampling. The study demonstrates that EM34 surveying can efficiently prioritise exploration targets in the complex alluvial terrain of the Jos Plateau.

Keywords: electromagnetic survey, tin-bearing alluvial deposits, Jos Plateau, EM34, subsurface conductors.