[Mg/Fe] as a function of [Fe/H] for the stars in the solar neighbourhood, closer than 1 kpc from the Galactic plane (left panels) and between 1 kpc and 2 kpc from the plane (right panels). Different selections, according to the signal-to-noise ratio of the spectra, are shown at the top (S/N> 10) and the bottom (S/N> 35). The colour-code corresponds to the azimuthal velocity of the stars. The dashed blue (black) line corresponds to the best-fit model of the thick (thin) disc. The black “+” sign is located at [Mg/Fe] = 0 and [Fe/H] = 0 dex.