Integrative structural study of the Kibuye-Gitarama-Gatumba area (West Rwanda): A contribution to reconstruct the Meso- and Neoproterozoic tectonic framework of the Karagwe-Ankole Belt

The geodynamic evolution of the Mesoprotemzoic Karagwe-Ankole Belt, situated in Central Africa, is largely unconstrained and topic of discussion. To overcome this knowledge gap, the tectonic history of the Western Domain has been studied, focusing on bedding, tectonic foliations and lineations, and quartz vein generations from the Kibuye-Gitarama-Gatumba area (West Rwanda). The results of our study reveal two fold generations, that are interpreted as the consequence of two separate compressional deformation events. The first fold generation (F-1) consists of regional-scale symmetrical folds, with a N30W to NS axial plane strike and variable foldcylindricity. The second generation (F-2) is expressed by local small-scale folds with a generally steep axial plane, superposed on the regional fold structure. The strike of the F-2 axial planes varies over the study area (N60W vs N20W), possibly linked to a buttressing effect from the rigid Gitarama batholith. Three quartz vein categories were determined: early quartz veins, strongly shortened or emplaced during F-1 (A-category), bedding-parallel, boudinaged quartz veins, deformed pre- to syn-F-2 (B-category) and undeformed, syn- to post-F-2 quartz veins (C-category). Based on geochronological data from literature, the first major compressional event can be connected to the Late Mesoproterozoic Rodinia assembly during the Stenian-Tonian, while the youngest tectonometamorphic event may represent the influence of the Late Neoproterozoic Gondwana assembly in the study area. This study furthermore demonstrates that the tectonic history of the Western Domain differs significantly from that of the Eastern Domain.

Automated summary

The study focuses on the tectonic history of the Mesoproterozoic Karagwe-Ankole Belt in Central Africa's Western Domain, revealing two generations of folding believed to be the result of two separate compressional deformation events. The development of quartz veins provides chronological data, showing differences in tectonic history between the Western and Eastern Domain in the study area.