Metallicity distribution in the four different radial regions distinguishing between young (0−0.5 Gyr, upper panel), intermediate (4−5 Gyr, middle panel) and old stars (8−9 Gyr, bottom panel) for Oceanus (current locations). Coloured histograms follow the colour code explained in Fig. 8. The distributions are different for young stars compared to the similar distributions in the case of the old component. Intermediate-aged stars show an intermediate behaviour.