Preliminary Geological Mapping, Petrographic, and Structural Studies of Precambrian Basement Complex Rocks in Part of Chulwe-Matale, South Kivu, DR Congo

Abstract

A geological map is a veritable planning tool for the economic development of any nation. This map contains the distribution of various types of bedrock in the area. A geological map of Congo’s geographic landmass has been produced since 1974 with the recently updated map of Kivu (Eastern part of Congo) in February 2018. This map largely omits some local geology of interest, possibly owing to its large area coverage. Thus, local geologic mapping must be encouraged to bridge this lacuna; the focus of this study. Field traversing and rock sample collections were carried out and thin sections of the different rock types were prepared and mounted on glass slides for microscopic observation. Geological mapping revealed that the study area is made of ferruginous, graphitic sandstone schists and quartzite with interbedded metadoleritic sills. The petrographic studies revealed the mineral assemblages of quartz-feldspars-muscovite and olivine-pyroxene and plagioclase feldspars respectively for the first and the second group geological units. The structural investigations come out of two deformation phases: the strike-slip type would be at the origin of the cleavages and folds. It’s related to the D1 of the Kibarian orogeny. The second is an extensive phase responsible for the NW-SE fracturation mapped in the study area. The Matale discordance crosses all these lithologies, a later phase is possible. This discontinuity would have acted in the region studied by switching the lithology units from NE-SW to ENE-WSW orientation. This research recommends that the Chulwe-Matale formations would be typical of the Lower Kibarian (Bugarama group) but the geochronology and geochemical data are lacking to confirm this hypothesis.