The nature and location of the suture zone in the Rokelide orogen, Sierra Leone: Geochemical evidence

New insights on proterozoic tectonics and sedimentation along the peri-Gondwanan West African margin based on zircon U–Pb SHRIMP geochronology

“…In places relict pillow-structures have been identified in the mafic volcanics, indicating subaqueous deposition (Latiff, 1993;Latiff et al, 1997). Based on trace element geochemistry of mafic volcanics, the unit is interpreted by Lytwyn et al (2006) to reflect an oceanic affinity.…”

“…However, based on the geochronological data suggesting the presence of two Neoproterozoic orogens, the 650-600 Ma Bassaride and 600-550 Ma Rokelide orogens (Villeneuve, 2008;Villeneuve et al, 2010), and on geochemical data for one amphibolite suggesting an oceanic setting for the Marampa Group, Lytwyn et al (2006) proposed a model in which the Kenema Assemblage represents a microcontinent/arc complex developed offshore prior to the Bassaride Orogen, which was accreted to the West African Craton during the closure of an intervening oceanic basin during the Rokel-Kasila Orogen. Reliable age data possibly supporting the Bassaride Orogen are limited to a series of granitoid rocks and volcanics in the north of Guinea ( Fig.…”

Re-assessment of the northern Guinean “Koubia–Lessere unconformity” (KLU): Consequences on the geological correlations throughout West Africa

“…The main consequences are: the ''Koubia-Lessere'' unconformity (KLU) is not equivalent to the ''Walidiala Unconformity'' (WU), as previously assumed; the Walidiala unconformity (WU) separating the basement (including the Madina-Kouta sedimentary group) from the Bassaris groups (Termesse, Walidiala, Faleme and Panampou) is involved in the Bassaride tectonic orogen; the KLU that is separating the Bassaris groups from the overlying ''Mali'' and ''Rokel River'' groups is, at least, 100 Ma younger than previously accepted; volcanic intrusions occurred at many times, from the Mesoproterozoic to the Devonian. Accordingly: the ''Walidiala triade'' of the Taoudeni basin (Marinhoan glacial event) is not a correlative of the ''Toulel Sigon'' conglomeratic formations (Villeneuve, 1984) and the last one should be linked to an unknown Late Cambrian or Early Ordovician glacial event; the Bassaride belt is linked to the Panafrican-II (Cadomian) orogen; the Rokelide belt should be reinterpreted by taking in consideration that Allen (1969) and Latiff et al (1997) have demonstrated that the ''Rokel River'' group is unconformably covering the Marampa group, which is now linked to the Bassaride groups (Lytwyn et al, 2006); the tectonic event related to a sinistral strike-slip movement affecting the ''Mali'' and ''Rokel River'' groups is not linked to the main Rokelide metamorphic event (550-530 Ma) but to a younger one that occurred before the deposition of the ''Youkounkoun'' group (post-490 Ma and ante-Silurian).…”

History of the West African Neoproterozoic Ocean: Key to the geotectonic history of circum-Atlantic Peri-Gondwana (Adrar Souttouf Massif, Moroccan Sahara)

“…given by Lahondère et al (2005), while occurrences of metagabbros in the Bassaride Belt of central southern Senegal were dated at 621 ± 8 Ma by Fullgraf et al (2010). Further rocks related to Neoproterozoic oceanic crust in the Rokelides are described by Lytwyn et al (2006) and Villeneuve (2008). Another region comprising several ophiolitic structures is situated in the Anti-Atlas.…”