Top-left: positions of the ten OCs under study, projected on the Galactic plane. The Sun is located at (X,Y) = (0, 8.3). The shaded area indicates the Monoceros structure. Top-right: [Fe/H] against Galactocentric radius for all ten clusters. The crosses indicate previous metallicity determinations from high-resolution spectroscopy (see references in Sect. 2). Bottom row: same as top row, for [α/Fe] abundances (taken as the mean of Mg, Si, Ca, and Ti abundances).