Labou I., Benoit M., Baratoux Lenka, Gregoire M., Ndiaye P. M., Thebaud N., Beziat D., Debat P. (2020). Petrological and geochemical study of Birimian ultramafic rocks within the West African Craton : insights from Mako (Senegal) and Loraboue (Burkina Faso) lherzolite/harzburgite/wehrlite associations. Journal of African Earth Sciences, 162, p. art. 103677 [29 p.]. ISSN 1464-343X.
Titre du document
Petrological and geochemical study of Birimian ultramafic rocks within the West African Craton : insights from Mako (Senegal) and Loraboue (Burkina Faso) lherzolite/harzburgite/wehrlite associations
Année de publication
2020
Auteurs
Labou I., Benoit M., Baratoux Lenka, Gregoire M., Ndiaye P. M., Thebaud N., Beziat D., Debat P.
Source
Journal of African Earth Sciences, 2020,
162, p. art. 103677 [29 p.] ISSN 1464-343X
In Archean and Paleoproterozoic greenstone belts, ultramafic (UM) rock occurrences are commonly found in close association within basic and differentiated magmatic series. In the Kedougou-Kenieba Inlier (West African Craton), UM rocks are interbedded within the Birimian (2.1 Ga) Mako tholeiitic series (basalts, gabbros). UMs are typically lherzolite, harzburgite and wehrlite, characterized by their cumulative textures and relative pro-portions of chromite, olivine, clinopyroxene, amphibole +/- orthopyroxene. Geochemical study (Major, REE and trace elements in whole rocks and mineral (mainly clinopyroxene and amphibole) and Sr/Nd isotopic records suggest the existence of different types of complexes. The first one consists of lherzolite + harzburgite assemblages whereas the second one consists of isolated wehrlite massifs. Both complexes highlight two different geodynamic environments, the first association being significantly more juvenile or mantle-related than isolated wehrlites which show more evolved geochemical signatures. UM rocks (dunite + wehrlite) of Loraboue (greenstone belt of Boromo, Burkina Faso) associated with calcalkaline series display the same mineralogical composition as the Mako UM rocks but exhibit a different whole rock composition characteristic of mature island-arc magmas and showing U-shaped REE pattern for both clinopyroxene and host rock, and a clear negative Nb anomaly. The Mako UMs suggest that this portion of the Birimian crust was built in an oceanic context evolving from a MORB-like domain to an increasingly mature volcanic arc domain.
Plan de classement
Géologie et formations superficielles [064]
;
Géophysique interne [066]
Description Géographique
SENEGAL ; BURKINA FASO ; MAKO ; LORABOUE
Localisation
Fonds IRD [F B010077869]
Identifiant IRD
fdi:010077869
