Subsurface Cavity Detection Using 2d Electrical Resistivity Tomography At Some Mining Sites In Jos, Northcentral Nigeria

Abstract

The study area is located in Jos South Local Government Area of Plateau State, northcentral Nigeria. Artisanal mining activity is dominant in the area with a form of sub-surface extraction of the tin through underground cavities. This research aimed at detecting subsurface cavity using 2D Electrical Resistivity Tomography (ERT) at some mining sites in the study area. Campus Omega Terra-meter was used for the survey and Wenner-Schlumberger electrode configuration was adopted with inter- electrode spacing for the various sites ranged from 2m, 5m, and 10m. Active and non-active mine sites was selected for the study and field data where interpreted using the RES2DINV software. The smoothness constrain in version formulation was adopted. In Kuru area an oval shaped high resistivity values of about 736 to 1448Ωm suggests an air-filled cavity and a low resistivity values of 49.1 to 33Ωm indicates water filled cavity while control profile shows a low resistivity values of 64.6 to 98.7Ωm at a depth of 31.9m as a very good aquifer, for locating a deep well. In NTA college area, three geoelectric materials namely: clay, lateritic and sandy clay were observed. The resistivity value of about 77.7Ωm which was lower than ressistivity value of the host country rocks of 236Ωm suggests a water filled cavity and lower resistivity value of 97.2Ωm at Profile 2 attested to water filled cavity while resistivity value of above 822Ωm may indicate extension of air-filled cavity at Control Profile. A high resistivity value of 1483Ωm characterised the top soil at a depth of about 7m at control profile in Dura-Du area and A low resistivity value 80.1 to 122 Ωm at depth of about 13m to 15.9m indicates fresh water. The 2D ERT geophysical method has been used succefully to identify air-filled, water-filled and fresh water zones in the study area