Abundance ratios for additional α‐elements (Si, Ca, Ti) plotted against [Fe/H]. The lower panel shows the mean α‐element abundance ratio, taken here as ﹩[ \alpha / \mathrm{Fe}\,] =\frac{1}{3}( \left[\mathrm{Mg}\,/ \mathrm{Fe}\,\right]+\left[\mathrm{Ca}\,/ \mathrm{Fe}\,\right]+\left[\mathrm{Ti}\,/ \mathrm{Fe}\,\right]) ﹩. The symbols are the same as in Fig. 3.