Petrogenesis and crustal evolution of the Tasiast TTG suite (SW Reguibat Shield, Mauritania). Implication for crustal growth in the West African craton

The Mauritanian Tasiast unit in the Southwestern Reguibat Archean Shield (North of West African craton = WAC) consists mainly gneiss dated between 3.07 and 2.91 Ga. We present new field petrographic observations combined with whole-rock geochemical data on gneisses to understand their petrogenesis, tectonic setting, evolution continental crust WAC. These provide firm evidence two distinct orthogneisses: trondhjemite high-K granite affinities. Geochemical characters suggest that (1) trondhjemites magma source were originally derived from polybaric partial melting at thickened occurred over a range P–T conditions, covering stability fields garnet amphibolite rutile eclogite. composition is attributed mixing major melts: one originating eclogitic facies region (high Nb/Ta) other garnet-amphibolite (low leaving garnet, amphibole, residue. (2) Compared trondhjemite, granites high K2O Rb contents, low Na2O, Al2O3 Sr contents basaltic oceanic was not material. Moreover, relationships trondhjemites. Hence, marked together stages during growth area.