An Application of Integrated Geophysical Approaches to Identified Heavy Metal Pathways at Gold Mining Site North – Western Nigeria
Abstract
Mining in terrestrial environment leave behind potential hazard especially if located near the populated center, with mines tailing ponds representing significant concern due to their potential for contaminant release and leachates plume formation. This study employs Electrical Resistivity Tomography [ERT], Induced polarization Image [IPI], Vertical Electrical Sounding [VES] and geochemical analysis. Eight [8] ERT and IP profiles were conducted within the study area, each of profile length 200 m and 5 m electrode spacing and 50 m inter profile spacing, using SAS 4000 Terrameter. The interpretation of the ERT results shows 3 layers , the first layer overburden consist of laterites and clay has apparent resistivity( <200Ω𝑚 ) and thickness 1.25 m to 13 m , the second layer weathered basement has apparent resistivity ( 341 Ωm to 620 Ωm ) and extend to a depth of 3 m to 28 m , the third layer fresh basement has apparent resistivity ( >1200 Ω𝑚 ) extend to a depth beyond 37 m . the IP- model delineated low chargeability layer ( 0.5msec to 3 msec ) to a depth of 10 m , moderate chargeability layer ( 3msec to 7msec ) to a depth of 30 m and high chargeability layer (>40𝑚𝑠𝑒𝑐 ) up to a depth of 34m .three shallow fracture zones were delineated ,identified by their low resistivity and chargeability at Profile 1 , Profile 5 and Profile 7 respectively , each 125 m from the beginning of the profile to a depth of 20 m , 15 m and 13 m respectively all within the weathered basement , VES data conducted at certain profile on ERT corroborated the ERT results, by identifying aquifer zones all within the weathered basement. Additionally results of geochemical analysis reveal high concentration of organic and inorganic parameters with elevated level of heavy metals such as Fe , Pb , As , and Mn respectively , in the mines leachates, indicating contamination of groundwater, revealing the pathways of contamination from the tailings to the local aquifer nearby ponds and river , are through these fructures/faults and joints.