Abundance ratios in metal-rich halo and thick-disk stars

Recent determinations of precise abundance ratios for nearby halo and thick disk stars in the metallicity range -1.3 < [Fe/H] < -0.5 have revealed a s ignificant cosmic spread in the abundances of oxygen, magnesium, sodium, ni ckel, s-process and r-process elements relative to iron. Possible explanati ons of these variations are reviewed. In particular, it is discussed if the differences in abundance ratios are correlated with the kinematics of the stars, and hence can be used to identify stellar populations in the Galaxy.