PETROGRAPHIC AND STRUCTURAL CHARACTERIZATION OF ROCKS OUTCROPPING IN THE MAVUMA BLOCK IN ONSHORE OF THE COASTAL BASIN OF THE DEMOCRATIC REPUBLIC OF CONGO

This research provides a petrographic and structural characterization of surface rocks in the Mavuma block, located in the terrestrial zone of the coastal basin of the Democratic Republic of Congo (DRC). The region analysed exhibits lithological diversity, incorporating both metamorphic and sedimentary rock units.
Petrographic examination of nine thin sections revealed various lithological facies, including gneisses, mica schists, amphibolites, quartzites, quartz arenites, mica metaquartzites, siltstones, grainstones, calcite-cemented sandstones, and eyed gneisses. Microscopic analysis revealed mineralogical and textural properties that suggest different rock formation mechanisms. Structural research, in conjunction with thin section examination, reveals that most crystallophyllian rocks are affected by widespread deformation characterised by extensively developed schistosity. However, some gneissic units show evidence of various deformation phases, indicating a more complicated metamorphic history.
The reconstructed structure reveals a preferred NNE-SSW direction of tectonic planes. Examination of the stress regime and fault displacement data reveals that the analysed region was mainly influenced by extensional tectonics, manifested by normal faults and associated vulnerable structures. There are also indications of previous compressive deformation, as shown by foliation features.