%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Djerossem, F.
%A Berger, J.
%A Vanderhaeghe, O.
%A Isseini, M.
%A Ganne, Jérôme
%A Zeh, A.
%T Neoproterozoic magmatic evolution of the southern Ouaddai Massif (Chad)
%D 2020
%L fdi:010080427
%G ENG
%J BSGF-Earth Sciences Bulletin
%@ 0037-9409
%K Central Africa Orogenic Belt ; Pan-African ; Saharan Metacraton ; peraluminous granites ; shoshonitic magmatism
%K TCHAD ; SAHARA
%K OUADDAI MASSIF
%M ISI:000595717200001
%P 34 [22 ]
%U https://www.documentation.ird.fr/hor/fdi:010080427
%> https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers20-12/010080427.pdf
%V 191
%W Horizon (IRD)
%X 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.
%$ 064 ; 066