Precise Li abundances in metal-poor stars: depletion in the Spite plateau

We present Li abundances for 73 stars in the metallicity range —3.5 < [Fe/H] < — 1.0 using improved IRFM temperatures (Casagrande et al. 2009) with precise E(B-V) values obtained mostly from interstellar Nal D lines, and high-quality equivalent widths (aEw ~ 3%). At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance ALi = 2.64 dex (MARCS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (ALi = 2.72) from standard BBN.