Petrology and geochemistry of the Neoproterozoic Siroua granitoids (central Anti-Atlas, Morocco): evolution from subduction related to within-plate magmatism

International audienceThe Siroua massif includes many plutons of Neoproterozoic age. The mineralogical and geochemical character of the plutons allows us to describe an evolution of the magmatism, in space and time, from a subduction-related type in the northern part, to a within-plate subalkaline type in the southern part. The first magmatic activity coeval with the closing of the Khzama oceanic basin in the north is little evolved and of oceanic type (dominantly gabbros and basalts). It is followed by a low potassic calc-alkaline magmatism (gabbro-diorites, tonalites and trondhjemites of Nebdas pluton) and by a voluminous highly potassic calcalkaline magmatism (Askaoun and Ifouachguel plutons) that marks the collisional period. The end of crustal uplift and the beginning of the extension is marked in the south by a sub-alkaline magmatism corresponding to the Ida ou Illoun, Imdghar and Affela N'ouassif granites. Magmatic activity, in the Siroua massif, is marked at the end of the Neoproterozoic (PIII) by a continental tholeiite with an alkaline affinity, which occurs as dykes crosscutting the Neoproterozoic granites, and later by dominantly alkaline granites

CO2 disposal into carbonate-dominated reservoirs: where and when Decarbonatation does occur ?

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Joints en graphite souple à usage industriel : étude de l’oxydation et prédiction du vieillissement

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Syn-collisional peraluminous magmatism in the rio Doce region: Mineralogy, geochemistry and isotopic data for the neoproterozoic Urucum Suite (eastern Minas Gerais State, Brazil)

International audienceThe Urucum Suite granitoids (Rio Doce region southeastern Brazil) contains four main facies: megafeldspar granites, deformed medium-to-coarse-grained granites, tourmaline, and pegmatitic facies. they intrude both the staurolite-garnet-muscovite-biotite schist of the Sao Tome formation (Rio Doce Group) and the Galileia metaluminous suite (596±4 Ma). Detailed structural studies suggest that the Urucum Suite emplaced during an important dextral strike-slip movement (D1 phase) of the Brasiliano orogeny (650-450 Ma). Modal and chemical mineralogical variations suggest an evolution from the megafeldspar facies to the pegmatitic facies. Whole-rock geochemistry indicates the peraluminous character of the Urucum suite granitoids, the evolution from the megafeldspar facies granites to pegmatite facies granites to pegmatitic facies granites and suggests the syn-collisional character of this suite. U-Pb zircon (582± 2 Ma) and monazite (576-573 ±4 Ma) data indicate that the Urucum Suite emplaced during the Brasiliano orogeny. The peraluminous nature of the Suite and isotopic rich character in the Rb-Sr (87 Sr/86 Sr = 0.7114 to 0.7165) and Sm Nd (eNd(T) = -7.4 and -8.2) systems indicate that it formed by partial melting of older intermediate to felsic crustal sources. Based on early Proterozoic model-ages (2.3 to 1.8 Ga) and on 2.0 ga U-Pb inherited signature, granitoids of the Suite are probably derived from a rocks with a long crustal residence (Transamazonian basement), without extensive mantle contributio