Geophysical Responses of Paleoproterozoic Rocks and Structures in Western Mali: Magnetic and Electromagnetics Data Analysis

The western part of Mali belongs to the West African Craton (WAC) which abounds in significant potential for gold resources hosted in the Birimian Paleoproterozoic formations. These formations and associated structures are most often masked by the thickness sedimentary and lateritic covers. It is why need to use of geophysical methods. The geophysical signatures of these geological formations are little studied specially in the Inlier of Kedougou Kenieba. Previous studies have proposed a magnetic signature model of geological structures in western Mali, allowing to characterize some gold-bearing structures. However, many auriferous structures have a low magnetic response requiring the use of other geophysical methods such as electromagnetism. This allows understanding the resistant or conductor character of structures. The electromagnetic and magnetic data will be analyzed out in order to characterize the geophysical signatures of the structures related to gold mineralization. These results will be calibrated to geological field data in order to consolidate the geophysical interpretation. This study helped to assess the degrees of magnetization and conductivity of rocks and linear structures within western Mali. Structures related to gold mineralization have low-to-moderate magnetism with a high conductivity. This geophysical signature model is well known in volcano-sedimentary rocks along the main shear zone as well as NE–SW trend faults. These results support previous work in western Mali and are also corroborated by surface geological data. The geology shows the presence of gold in quartz veins and facies bearing sulfide minerals. Generally, the massif sulfide minerals are known by their high influence on the conductivity of rocks.