Upper panels: vector point diagrams, from Gaia proper motions, of stars belonging to the Mg-rich and Mg-poor sequences (left and right, respectively). Lower panels: longitudinal proper motion component versus heliocentric radial velocity of stars belonging to the Mg-rich and Mg-poor sequences (left and right, respectively). In each panel, the Spearman correlation coefficient ρ_s and its respective p-value are quoted. In all panels, mean error bars in proper motions and velocity are smaller than point sizes.