  We present a preliminary local thermodynamic equilibrium (LTE) abundance
analysis of the template halo red giant HD122563 based on a realistic,
three-dimensional (3D), time-dependent, hydrodynamical model atmosphere of the
very metal-poor star. We compare the results of the 3D analysis with the
abundances derived by means of a standard LTE analysis based on a classical,
1D, hydrostatic model atmosphere of the star. Due to the different upper
photospheric temperature stratifications predicted by 1D and 3D models, we find
large, negative, 3D-1D LTE abundance differences for low-excitation OH and Fe I
lines. We also find trends with lower excitation potential in the derived Fe
LTE abundances from Fe I lines, in both the 1D and 3D analyses. Such trends may
be attributed to the neglected departures from LTE in the spectral line
formation calculations.
