Abstract The 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.

Abstract The deep marine Grès d'Annot Formation is one of the best exposed analogues to sand-rich turbidite sub-surface systems. Provenance and reservoir heterogeneities have been investigated through a geochemical study of different areas and facies in this formation. Most compositions may be described as mixtures between carbonate and three clastic end-members, i.e. clay, framework grains and a subset of the heavy minerals (zircon, Tioxide, apatite, monazite). These end-members have a nearly uniform chemistry over the studied area and a granite-dominated provenance consistent with a Corsica-Sardinia source hypothesis. This rather uniform provenance makes the Annot Formation a favourable case for exploring the relationships between facies and geochemistry. Not only do different facies differ in average composition, but chemical variations at the bed scale fingerprint the depositional mechanism: archetypal (graded) turbidites and traction-dominated (over-bank) deposits display contrasting variation trends in geochemical plots. The local-scale variation patterns and the general relationship between grain size and chemistry are tentatively integrated in a single differentiation model, providing a rationale for the use of geochemistry in provenance studies, and a possible way to characterize sedimentary facies.