Publications des scientifiques de l'IRD

Couzinie S., Menot R. P., Doumnang J. C., Paquette J. L., Rochette P., Quesnel Y., Deschamps Pierre, Menot G. (2020). Crystalline inliers near Lake Iro (SE Chad) : post-collisional Ediacaran A(2)-type granitic magmatism at the southern margin of the Saharan Metacraton. Journal of African Earth Sciences, 172, 103960 [18 p.]. ISSN 1464-343X.

Titre du document
Crystalline inliers near Lake Iro (SE Chad) : post-collisional Ediacaran A(2)-type granitic magmatism at the southern margin of the Saharan Metacraton
Année de publication
2020
Type de document
Article référencé dans le Web of Science WOS:000590387100009
Auteurs
Couzinie S., Menot R. P., Doumnang J. C., Paquette J. L., Rochette P., Quesnel Y., Deschamps Pierre, Menot G.
Source
Journal of African Earth Sciences, 2020, 172, 103960 [18 p.] ISSN 1464-343X
The structure and evolution of the continental crust in the southern part of the Saharan Metacraton (central Africa) is poorly known due to extensive laterite and sediment cover as well as geographic isolation. We report on a series of five crystalline inliers newly discovered near Lake Iro (south-eastern Chad) that offered the opportunity to unravel the nature of the local basement in this area. Two spatially determined petrographic types are exposed in the inliers: a medium-grained porphyritic amphibole-biotite granite and a biotite microgranite with typical embayed (rhyolitic) quartz phenocrysts, both containing fine-grained melanocratic igneous enclaves. Some porphyritic granites display evidence for low temperature deformation along N60 shear zones. The Lake Iro igneous rocks are typified by their ferroan mineralogy, define a ferman alkali-calcic metaluminous to weakly peraluminous potassic association, and exhibit elevated HFSE (Zr, Nb, Y) and REE contents. Therefore, they are best classified as A(2)-type granites. They are variably ferromagnetic with total magnetization lower than 1 A/m. The Lake Im granites most likely correspond to a single subvolcanic-plutonic silicic complex because: (i) firstorder geochemical modelling indicates that the microgranites can be generated by 30% fractional crystallization of a two feldspar-amphibole assemblage from a porphyritic granite melt and (ii) both granite types yield zircon U-Pb emplacement ages consistent within a 575.3 +/- 5.6 to 581.3 +/- 3.8 Ma time frame. The Lake Iro granites thus represent the oldest of a series of post-collisional igneous associations exposed in southern Chad and nearby countries which, collectively, show that the amalgamation of the constituent blocks of the southern Saharan Metacraton is older than 580 Ma.
Plan de classement
Géologie et formations superficielles [064] ; Géophysique interne [066]
Description Géographique
TCHAD ; SAHARA
Localisation
Fonds IRD [F B010080541]
Identifiant IRD
fdi:010080541
Contact
  • Coordonnées :
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    Horizon Pleins textes
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