Sr-Nd isotopic diagram for calc-alkaline lavas/plutons from the French Massif Central (this study, Shaw et al., 1993; Cuney et al., 2001; Pin and Paquette, 2002) and for Brévenne back-arc magmatism (Pin and Paquette, 1997). Also shown, the composition of the Depleted Mantle (DM) at 360 Ma (calculated with the data of Salters and Stracke, 2004), the probable signature of the mantle wedge around 360 Ma as attested by calc-alkaline magmatism arc like magmatism. The green dotted mixing hyperbola represent mixing between Depleted Mantle and a UGU paragneiss to model mixing of the mantle source with sediments buried by subduction while the black mixing dotted curve simulates contamination of a depleted basalt by a UGU paragneiss to reproduce continental assimilation. Values in % indicate the relative mass of sedimentary component in the mix.