Quantification of a Granite Quarry by Electrical and Seismic Refraction Methods in the Locality of Nonkouagon (South of Ivory Coast)

Abstract

This study enabled us to assess the granite potential on the Nonkouagon site, with a view to meeting the need for supplies of aggregates (essential materials for infrastructure construction). To do this, we began by identifying the resistant zones, comparable to granitic formations, by means of resistivity maps and 2D profiles using the dipole-dipole device. Next, electrical boreholes were drilled with the Schlumberger device in the vicinity of these zones in order to determine the depositional stratigraphy and therefore the rooting depth of the massive rock, which varies between 6 and 30 m. Indeed, the electrical prospecting made it possible to highlight three lithological groups which are the filling sediments, the volcano-sediments and the basement (granites). The sedimentary formations correspond to the conductive zones, while the basement is represented by resistant zones. Finally, to confirm the results of the electrical method, seismic refraction was performed and the interpretation of the seismic section also showed three geological layers. The roof of the granite is observed from a depth of 16 m with a seismic velocity varying from 4.48 km/s to 4.72 km/s. The overlying layers are characterized by seismic velocity which vary from 3.84 km/s to 4.32 km/s for the saprolite and from 3.61 km/s to 3.76 km/s for the alterite. In addition, modelling of the granite areas made it possible to determine the volume of rock and to estimate the exploitable granite reserve at over one million tonnes.