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Research Paper | Geology | Congo | Volume 11 Issue 11, November 2022 | Popularity: 5.2 / 10
A Unified Structural Framework for Major Shear Zone in the Ntem-Chaillu-Ivindo Blocks: Case of Tectonic and Structural Evolution of the Ivindo Basement, Northern Republic of Congo, Congo Craton
Alan Patrick Rodeck Loemba, Hardy Medry Dieu-Veill Nkodia, Urbain Fiacre Opo, Nicy Carmel Bazebizonza Tchiguina, Timothee Miyouna, Florent Boudzoumou
Abstract: The Ivindo Basement primarily outcrops within the Souanke and Bomalinga Provinces of the Republic of Congo and is part of an Archean Ntem-Chaillu-Ivindo block, in the western part of a greater Central African Congo Craton. Geological studies in the Ivindo Basement have focused on rock sample petrography, geochemistry and geochronology, revealing different supracrustal sequences (also referred to as greenstone belts) and granite-gneiss complexes, cross-cut byyounger mafic to ultramafic dykes. The supracrustals consist of metamorphosed volcano-sedimentary chlorite-sericite-schist sequences, banded iron formations and amphibolites. This paper offers an additional structural analysis of a reactivated regional shear zone across the Ivindo Basement. Our structural identifies three distinct phases of deformation, labelled D1-3. D1 was associated with horizontal NNW-SSE compression and is exposed at both Souanke and Bomalinga. This phase developed a ductile to brittle shear zone systems, with dextral WNW-ESE to NNW-SSE and E-W faults, together with sinistral N-S and NE-SW Riedel shears. D2 was only observed in Bomalinga and is mainly comprised of sinistral WNW-ESE and dextral NE-SW trending brittle shear zones; i.e., with an opposite sense of shear to D1. The transition between D1 and D2 is marked by changes in the kinematics of blocks and in-filling granitic intrusions. The D2 phase resulted from E-W horizontal shortening under an extensional strike-slip regime. Both D1 and D2 shear zones were reactivated as normal faults during a third, D3, deformation phase, experiencing E-W horizontal shortening and N-S radial extension. On a more regional scale, the mapped shear zones within the Ivindo Basement correlate with normal faults along the edge of the Proterozoic Sembe-Ouesso basin, as interpreted from a topographic map of ALOS as 500 m in depth surface rupture.
Keywords: Congo craton, Ivindo basement, shear zones, Archean, Republic of Congo
Edition: Volume 11 Issue 11, November 2022
Pages: 785 - 797
DOI: https://www.doi.org/10.21275/SR221101012735
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