Abundance ratio [Mg/Fe] as a function of [M/H], colour-coded by the FWHM_CCF of the cross-correlation function. Both panels contain the same number of stars. Strong saturated lines (left, with less dispersed sequences) are less sensitive to spectral line-broadening than non-saturated lines (right). The [Mg/Fe] abundances were derived by performing the continuum placement around a local wavelength interval of 5 Å.