Mineralogical and geochemical characteristics of the Mesoproterozoic sedimentary rocks in Rwanda and their implication for hydrocarbon investigation

To reduce deforestation and ensure energy security for socioeconomic advancements, Rwanda must find alternatives to wood fuel. Widely developed metasedimentary mudstones gradually became a petroleum survey object due to the progress of petroleum exploration theories and practices in the Mesoproterozoic strata all over the world. In this study, extensive field and experimental work was conducted to explore the organic features of the Mesoproterozoic strata and their relationship with the geological background, which is important for a petroleum survey of such strata. The results show that (1) the Mesoproterozoic samples have low total organic carbon (TOC) and S1+S2 and (2) except for the high degree of thermal maturity (Ro ranging from 3.71 to 3.82, avg. 3.77), the low TOC is mainly caused by the hypoxia degree and dissolution of terrigenous clastic materials in shallow water environments related to the fluvial delta. Hence, the Gikoro and Pindura groups should be paid more attention in Northwestern Rwanda (offshore direction in paleography) in subsequent exploration work for their thicker mudstones.