Publications des scientifiques de l'IRD

Djerossem F., Berger J., Vanderhaeghe O., Isseini M., Ganne Jérôme, Zeh A. (2020). Neoproterozoic magmatic evolution of the southern Ouaddai Massif (Chad). BSGF-Earth Sciences Bulletin, 191, 34 [22 p.]. ISSN 0037-9409.

Titre du document
Neoproterozoic magmatic evolution of the southern Ouaddai Massif (Chad)
Année de publication
Type de document
Article référencé dans le Web of Science WOS:000595717200001
Djerossem F., Berger J., Vanderhaeghe O., Isseini M., Ganne Jérôme, Zeh A.
BSGF-Earth Sciences Bulletin, 2020, 191, 34 [22 p.] ISSN 0037-9409
This paper presents new petrological, geochemical, isotopic (Nd) and geochronological data on magmatic rocks from the poorly known southern Ouaddai massif, located at the southern edge of the so-called Saharan metacraton. This area is made of greenschist to amphibolite facies metasediments intruded by large pre- to syn-tectonic batholiths of leucogranites and an association of monzonite, granodiorite and biotite granite forming a late tectonic high-K calc-alkaline suite. U-Pb zircon dating yields ages of 635 +/- 3 Ma and 613 +/- 8 Ma on a peraluminous biotite-leucogranite (containing numerous inherited Archean and Paleoproterozoic zircon cores) and a muscovite-leucogranite, respectively. Geochemical fingerprints are very similar to some evolved Himalayan leucogranites suggesting their parental magmas were formed after muscovite and biotite dehydration melting of metasedimentary rocks. A biotite-granite sample belonging to the late tectonic high-K to shoshonitic suite contains zircon rims that yield an age of 540 +/- 5 Ma with concordant inherited cores crystallized around 1050 Ma. Given the high-Mg (59) andesitic composition of the intermediate pyroxene-monzonite, the very similar trace-element signature between the different rock types and the unradiogenic isotopic signature for Nd, the late-kinematic high-K to shoshonitic rocks formed after melting of the enriched mantle and further differentiation in the crust. These data indicate that the southern Ouaddai was part of the Pan-African belt. It is proposed that it represents a continental back-arc basin characterized by a high-geothermal gradient during Early Ediacaran leading to anatexis of middle to lower crustal levels. After tectonic inversion during the main Pan-African phase, late kinematic high-K to shoshonitic plutons emplaced during the final post-collisional stage.
Plan de classement
Géologie et formations superficielles [064] ; Géophysique interne [066]
Description Géographique
Fonds IRD [F B010080427]
Identifiant IRD