Evolution of trace element concentrations in felsic (meta-)igneous rocks from the Sioule region as a function of the differentiation index FeO + MgO + TiO₂. For comparison, the composition of early-Variscan cordierite-bearing peraluminous granitoids (CPG) of the Guéret Massif and mid-Variscan trachy-dacitic tuffs and lavas (“Tufs anthracifères” series) are shown (Cartannaz, 2006), in addition to the mean compositions of metasedimentary rocks of the Sioule series (n=13; Rocher et al., 2024).