Abstract
After an extensional stage giving rise to tholeiitic basalts and gabbros, the south western part of Kédougou Kéniéba Inlier (KKI) was affected by three phases of compressionnal deformation. The first phase (D1) was related to NE-SW stress that led to northeastward thrusting. Early granitoids would be implemented during this tectonic event. The second phase (D2) was due to East-West compressional stress that created combined strike sleep faults: NNW-SSE and NNE-SSW respectively sinistral and dextral. During this phase, some volcanic rocks and gabbros were mylonitized, hydrothermalized and transformed into quartzites. These quartzites were considered as sedimentary rocks in previous studies. Granitic plutons and andesites took place during this tectonic phase. D3 deformation occurred towards the end of the Eburnean orogeny. It would be held in two episodes. In the first episode, WNW-ESE stresses created conjugate shears: sinistral NNW-SSE and dextral NE-SW. In the second episode, stresses moved toward the NE-SW direction and made the resulting brittle structures arranged in NS dextral corridors.
Highlights
The Kédougou-Kéniéba Inlier (KKI) is part of the West African craton
The Kédougou-Kéniéba inlier consists mainly of Paleoproterozoic formations divided into two groups (Figure 1) (Bassot, [3]; Ndiaye et al, [4]; Theveniault et al, [5]): 1) To the west, the Mako group, considered as the oldest entity, is a tholeiitic volcanic complex (Dia, [6]; Diallo, [7]; Ngom, [8]; Dioh, [9]) cut by the Kakadian batholith dated around 2199 ± 68 Ma and 2168 Ma respectively by Bassot and Caen-Vachette, [10] and Dia, [6]; 2) To the east and above it, the Dialé-Daléma group dominated by sedimentary rocks and cut by an important calco-alcalin volcano-plutonic complex with a zircon age 2064 ± 30 Ma (Delor et al, [11])
Hirdes and Davis [14] obtained in the Kédougou-Kéniéba Inlier an age, 100 Ma lower than those ages found in the east (Ivory Coast, Ghana) and this led to subdividing the Paleoproterozoic of West Africa into two provinces: an older (2150 - 2190 Ma) eastern province (Ghana, Ivory Coast) and a younger (2080 - 2110 Ma)
Summary
The Kédougou-Kéniéba Inlier (KKI) is part of the West African craton. It is characterized by two domains. (Bessole, [1]; Black, [2]): 1) In the North, the dorsal Reguibat that spans Mauritania and western Algeria This dorsal contains both archean and paleoproterozoic formations: the first outcrops in the southwest and the second in the East, 2) In the South, the Leo dorsal occupies a vast area including southern Mali, Guinea, Ivory Coast, Niger, Burkina Faso and Ghana. Between these two dorsals, outcrops the Kédougou-Kéniéba inlier at the confines of Senegal and Mali. We emphasize the field geometric relationships between the main rocks of the southern part of the Mako group (Figure 2) and try to answer the following questions: 1) Is the Mako group affected by a single phase deformation as previously proposed [13]? 2) What is the origin of quartzite associated with volcano-plutonic rocks of the Mako group? Are they sedimentary rocks as formerly suggested [3]?
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