Distribution of the selected sample in the ([M/H], [Mg/Fe]) plane at different ages and locations in the Galaxy (R_g). Two chemical sequences appear for ages younger than ∼ 11–12 Gyr, corresponding to the classical thick (blue stars) and thin (red circles) disc components. Each panel corresponds to a bin in the (age, R_g) space, dividing the Galactic disc into two regions: inner (R_g ≤ 7.5 kpc; top row) and outer (R_g > 7.5 kpc; bottom row). The blue and red crosses in the bottom-right corner of each panel represent the mean estimated errors in [Mg/Fe] and [M/H] for the thick and thin disc population, respectively, at that particular radius and time. The average R_g and z_max for each population are given at the top of each panel. The whole working sample is shown by the dotted grey points.