A Paleoproterozoic ultramafic-mafic assemblage and associated volcanic rocks of the Boromo greenstone belt: fractionates originating from island-arc volcanic activity in the West African craton

Diversity of the Palaeoproterozoic granitoids of the Kédougou inlier (eastern Sénégal): Petrographical and geochemical constraints

“…2) are represented by two series trending NNE-SSW: the western series of Mako overlain by the eastern series of Dialé-Daléma (Bassot, 1966(Bassot, , 1987. The series of Mako consist of: (i) in its western part of a thick sequence of basalts, locally pillowed, as well as dolerites and gabbros, of tholeiitic affinity, interlayered with immature detrital sediments and limestone; (ii) in its eastern part of basaltic, gabbroï c and ultramafic bodies of tholeiitic affinity, basalts and andesites of calc-alkaline affinity and immature metasediments (Bassot, 1966;Ngom et al, 1997); in this eastern part of the juxtaposition of tholeiitic and calc-alkaline magmatic suites similar to those described in the Baoulé-Mossi domain in Ghana by Sylvester and Attoh (1992) and in Burkina Faso by Béziat et al (2000). The Dialé-Daléma series comprise (Bassot, 1966(Bassot, , 1987 of detrital sedimentary pile (volcanoclastics, turbidites, mudstones and carbonates) interbedded with calc-alkaline volcanics.…”

“…1): (i) the northern Reguibat rise represented by both Archean and Palaeoproterozoic terrains (2.0 Ga); (ii) the southern Man rise consisting of the Archean formations of the Liberia nucleus and the Palaeoproterozoic formations of the Baoulé-Mossi domain (referred to as the Birimian); and (iii) the Kédougou and Kayes inliers only represented by the Birimian terrains. The Birimian terrains correspond to narrow linear to arcuate volcanic belts and wider sedimentary basins that were accreted around 2.0 Ga during the Eburnean orogeny Liégeois et al, 1991;Boher et al, 1992;Taylor et al, 1992;Hirdes et al, 1996;Doumbia et al, 1998;Béziat et al, 2000). This orogeny is also characterized by the emplacement of huge volumes of granitoids (Leube et al, 1990;Liégeois et al, 1991;Cheilletz et al, 1994;Hirdes et al, 1996;Doumbia et al, 1998;Oberthü r et al, 1998;Egal et al, 2002;Hirdes and Davis, 2002;Gasquet et al, 2003).…”

“…According to Junner (1940), Milési et al (1992), Ledru et al (1991), Feybesse and Milési (1994) and Ndiaye et al (1997), the metasedimentary series of the belts are from the Lower Birimian. On the other hand, Bassot (1966), Pouclet et al (1996) and Béziat et al (2000) propose that the bimodal volcanism underlay the metasediments. According to Abouchami et al (1990), Boher et al (1992) and Pouclet et al (1996), the tholeiitic lavas are related to an oceanic plateau environment, according to Sylvester and Attoh (1992) and Ama Salah et al (1996) they are related to a back-arc environment (Sylvester and Attoh, 1992;Ama Salah et al, 1996) and finally Dia et al (1997) and Béziat et al (2000) link them to an immature arc environment.…”

“…On the other hand, Bassot (1966), Pouclet et al (1996) and Béziat et al (2000) propose that the bimodal volcanism underlay the metasediments. According to Abouchami et al (1990), Boher et al (1992) and Pouclet et al (1996), the tholeiitic lavas are related to an oceanic plateau environment, according to Sylvester and Attoh (1992) and Ama Salah et al (1996) they are related to a back-arc environment (Sylvester and Attoh, 1992;Ama Salah et al, 1996) and finally Dia et al (1997) and Béziat et al (2000) link them to an immature arc environment. The overall tectonic regime is ascribed either to modern-like plate tectonic conditions, with dominant collision and thrusting (Ledru et al, 1994;Feybesse and Milési, 1994) or to Archean-like tectonics, with dominant transcurrent shearing and diapirism (Pons et al, , 1992(Pons et al, , 1995Vidal et al, 1996;Doumbia et al, 1998;Caby et al, 2000;Debat et al, 2003;Gasquet et al, 2003).…”

Structure and emplacement model for late-orogenic Paleoproterozoic granitoids: the Tenkodogo–Yamba elongate pluton (Eastern Burkina Faso)

“…According to the authors, (1) the metasedimentary series of greenstone-belt affinity, called here volcanic belts, are lying either below (Junner, 1940;Mil esi et al, 1992;Feybesse and Mil esi, 1994) or above (Bassot, 1966;Pouclet et al, 1996;Hirdes et al, 1996;B eziat et al, 2000) the volcanic series; (2) the volcanic series were emplaced either in the oceanic plateau context (Abouchami et al, 1991;Boher et al, 1992;Pouclet et al, 1996), in the back-arc context (Sylvester and Attoh, 1992;Ama Salah et al, 1996) or in both contexts (B eziat et al, 2000); and (3) the overall tectonic regime is ascribed either to modern plate tectonic conditions, with dominant collision and thrusting (Ledru et al, 1994;Feybesse and Mil esi, 1994) or to Archean-like tectonics, with dominant transcurrent shearing and diapirism (Pons et al, 1991(Pons et al, , 1992(Pons et al, , 1995Vidal et al, 1996;Doumbia et al, 1998;Caby et al, 2000). The granitoids constitute about 70% of the Birimian formation.…”