Selected major oxides (a–c) and trace elements (d, e) vs. MgO diagrams comparing Vesuvius 79 AD juvenile whole-rock samples from this study with experimental melts obtained during the crystallisation of a tephrite liquid (sample VES6) by Pichavant et al. (2014) and with literature data (LOI < 4 wt %) for the syn- and post-caldera activity of Somma-Vesuvius (sources as in Figs. 4 and 10 plus Civetta et al., 2004, Aulinas et al., 2008 and Di Renzo et al., 2007). Insets in e and f display an enlarged Y-axis. The average composition of the alkali feldspar syenite assemblages modelled to have fractionated in the transition from the most evolved grey to the least evolved white pumice clasts (aS1) and from the least to the most evolved white pumice clasts (aS2) are also shown. See text for further explanations. Additional diagrams are reported in Figs S2.9 and S2.10.