“…They are outliers of an important crustal thickening related to the building of the Dahomeyides orogen [13] [19]. The internal units occurring in the benino-nigerian metacraton are described as gneisso-migmatitic and granitic complexes associated with meta-volcanosedimentary belts [9] [20] [21] [22]. These lithostructural sets result from involvement of a wide eburnean or paleoproterozoic domain during panafrican remobilization.…”
Section: Regional Geological Contextmentioning
confidence: 99%
“…The Dn phase is contemporaneous with the collision between the southeastern margin of the WAC and the benino-nigerian metacraton, 612.5 ± 0.8 My ago [24]. It is associated with a granulite facies metamorphic peak defined by parageneses stressing Sn foliation that is generally obliterated by subsequent planar structures [18] [22]. The Dn+1 phase corresponds to nappe emplacement with west vergence.…”
Thanks to detailed field investigations, microstructural and geochemical analysis and relationship with enclosing rocks, microfabrics, magmatic typology and metamorphic evolution of the Kantè sepentinites have been specified for the first time. The Kantè serpentinites in northern Togo constitute a mega-lens of ultrabasic rocks tectonically intercalated in the sericite chlorite schists of the Atacora structural unit. The brecciated, schitotose or massive rock facies are strongly marked by an S1 schistocity plane superimposed by a flat C shear plane linked to a west vergence thrusting movement. The parageneses that compose the metamagmatites are essentially serpentinous, containing plagioclase, opaque minerals (magnetite, chromite, spinel) and pyroxene porphyroblasts. These microfabrics represent relics of a probable gabbroic protolith. In fact, the geochemical characteristics of the Kantè serpentinites suggest that their magmatic typology is that of komatiites or tholeiitic basalts with oceanic arc affinities. They would have been emplaced in an active margin environment. The retromorphic evolution of the protolith corresponds to the phase of involvement in a major tangential contact during the panafrican tectogenesis.
“…They are outliers of an important crustal thickening related to the building of the Dahomeyides orogen [13] [19]. The internal units occurring in the benino-nigerian metacraton are described as gneisso-migmatitic and granitic complexes associated with meta-volcanosedimentary belts [9] [20] [21] [22]. These lithostructural sets result from involvement of a wide eburnean or paleoproterozoic domain during panafrican remobilization.…”
Section: Regional Geological Contextmentioning
confidence: 99%
“…The Dn phase is contemporaneous with the collision between the southeastern margin of the WAC and the benino-nigerian metacraton, 612.5 ± 0.8 My ago [24]. It is associated with a granulite facies metamorphic peak defined by parageneses stressing Sn foliation that is generally obliterated by subsequent planar structures [18] [22]. The Dn+1 phase corresponds to nappe emplacement with west vergence.…”
Thanks to detailed field investigations, microstructural and geochemical analysis and relationship with enclosing rocks, microfabrics, magmatic typology and metamorphic evolution of the Kantè sepentinites have been specified for the first time. The Kantè serpentinites in northern Togo constitute a mega-lens of ultrabasic rocks tectonically intercalated in the sericite chlorite schists of the Atacora structural unit. The brecciated, schitotose or massive rock facies are strongly marked by an S1 schistocity plane superimposed by a flat C shear plane linked to a west vergence thrusting movement. The parageneses that compose the metamagmatites are essentially serpentinous, containing plagioclase, opaque minerals (magnetite, chromite, spinel) and pyroxene porphyroblasts. These microfabrics represent relics of a probable gabbroic protolith. In fact, the geochemical characteristics of the Kantè serpentinites suggest that their magmatic typology is that of komatiites or tholeiitic basalts with oceanic arc affinities. They would have been emplaced in an active margin environment. The retromorphic evolution of the protolith corresponds to the phase of involvement in a major tangential contact during the panafrican tectogenesis.
“…They represent the frontal part of the Benino-Nigerian Shield that collided with the eastern margin of the WAC during the ultimate stage of the Dahomeyides edification [7]. The fracture network in the gneisso-migmatitic units is attributed to the two last Pan-African deformation phases [13] [14] [15]. These major fractures have probably influenced the coastal basin setting up.…”
The sandstone relics of probable Cretaceous age found around Tohoun show an extensional tectonics imprint associated with the Atlantic opening. This imprint consists of normal fault networks well expressed on two sites of outcrop and corresponds to three fracturing episodes materialized by families of conjugated planes striking E-W, NW-SE, and NE-SW. Striated plane data analysis shows three extensional axes successively N-S, NE-SW and NNW-SSE. The reconstructed paleostress tensors can be attributed to pre-to syn-rift phases responsible for the development of primary basin structures in the Gulf of Guinea. This preliminary analysis, concerning only fractures in the basal sequence relics, remains to be extended to the entire Togolese coastal basin to a better definition of the Atlantic dynamic.
“…The Bénin Republic, bound by coordinates 6°15′N–12°30′N and 1°00′E–3°40′E, is a West African country located in the inter-tropical zone, with a total land area of 112.622 km 2 . It is a strip of land, bordered by Niger, Burkina Faso, Togo, Nigeria and the Atlantic Ocean (Figure 1); with fairly rugged relief and an average altitude of 200 m. Figure 1 Geological map of the Volta Basin and the Pan-African Dahomeyides Belt (modified, Chala et al 2015). …”
Section: Introductionmentioning
confidence: 99%
“…Geological map of the Volta Basin and the Pan-African Dahomeyides Belt (modified, Chala et al 2015). …”
Gold in Benin occurs as primary and alluvial forms in various deposits and occurrences. The mineralisation has a regional distribution covering, in particular, the Atacora area (Natitingou) and the regions of Bembèrèkè, Djougou and Dunkassa which are between the 9th and 11th parallel north. The data collected during previous work allow us to recognise the main style of primary gold as being quartz-vein hosted. This style occurs principally in quartzite, mica schist, schist and amphibolite lithologies, outcropping in the criss-crossing of the faults and the rugged relief. The mineralised veins are milky, deformed and gold is associated with sulphides and tourmaline. In these veins, gold exhibits three forms: free native metal, tellurides, and combined or included in sulphides. These gold-bearing quartz veins would proceed from hydrothermal solutions related to granitic mass. Classical characteristics available about the primary gold mineralisation in Bénin are inadequate to better clarify its geodynamic context. However, it has some similarities with deposits of the Precambrian terranes in adjacent countries (Pourra deposit in Burkina Faso and Kalana deposit in Mali) which are characterised by epigenetic gold deposits in Precambrian metamorphic terranes. Also, the vein gold of Bénin are mostly located in Precambrian metamorphosed sedimentary and volcanic formations ; these could also have the epigenetic disseminated gold style like in some West African deposits (Ashanti deposit).
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