Left: spatial distribution (top-left), CMD (top-right), and radial velocity vs. [ Fe / H ] distribution of the RAVE stars in a 35 degree field centered on NGC 1851. The cluster center of M 22 is indicated by an open (blue) circle. The [ Fe / H ], radial velocity, colors and magnitudes of the red giant branch stars of M 22 shown as triangles (blue in the online version) are taken from Marino et al. (2009), Da Costa et al. (2009), Alves-Brito et al. (2012) and Gratton et al. (2014). Right: [ Si / Fe ], [ Mg / Fe ] and [ Ti / Fe ] ratio of the same stars. The triangles (green in the online version) are elemental abundances of M 22 horizontal branch stars obtained from intermediate-resolution spectra by Gratton et al. (2014).