2-D Electrical Resistivity Survey for Cassiterite Potential Mapping in Jos-Bukuru Area, North Central, Nigeria

Aim: To use 2-D Electrical Resistivity method in Cassiterite Potential mapping in Jos-Bukuru Area, North Central, Nigeria.

Methodology: Locations suspected to have very high probability for cassiterite mineralisation from the cassiterite potential map produced for the study area were selected for 2-D electrical resistivity survey. 2-D Electrical resistivity survey was carried out to obtain resistance data. The configuration used here was the Wenner-Schlumberger. The measured resistance data collected in the field was converted to apparent resistivity values which were then iteratively subjected to inversion process using RES2DINV software, to generate the 2-D resistivity sections. Inversion was carried out with the robust model constraint. Forward resistivity calculation was executed by applying an iterative algorithm based on finite element method. Rock samples were also collected near the survey lines used for the 2-D electrical resistivity survey for petrography.

Results: The 2-D resistivity interpretation models revealed the probable average depth to cassiterite bearing alluvium to be least at Doi 2 (6 m) and greatest at Vom 1 (50 m). Suspected igneous intrusions and faults were observed within the subsurface of Kwang Rayfield 1 and 2, Doi 1 and 2, Rapkparak Shen and Kwata Zawan 1 and 2 profiles. The 2-D resistivity interpretation model for Vom 1 and 2 revealed probable depths to sub-basalt valley to be greater than 50 m and 45 m respectively. A loto (Hausa word for tunnel) mine was dug 295 m along Kwang Rayfield 1 survey line and was confirmed to contain some cassiterite bearing alluvium at 11.5 m deep. The probable depth to the cassiterite bearing alluvium from point A (295 m) on Kwang Rayfield 1 interpretation model is approximately 10 m. This depth in comparison with the depth in the loto mine at which cassiterite was found is correct to about 87%. Petrography revealed dominance of biotite, quartz and feldspar in hand specimen and thin section.

Conclusion: It can be concluded that though large lodes of cassiterite may have been extracted, there may still be some substantial amount of cassiterite deposits in the Jos - Bukuru area.