The puzzling origin of the 6Li plateau

We discuss the Li-6 abundance evolution within a hierarchical model of Galaxy formation which correctly reproduces the [Fe/H] distribution of metal-poor halo stars. Contrary to previous findings, we find that neither the level (Li-6/H = 6 x 10(-12)) nor the flatness of the Li-6 distribution with [Fe/H] can be reproduced under the most favourable conditions by any model in which Li-6 production is tied to a (data-constrained) Galactic star formation rate via cosmic ray spallation. Thus, the origin of the plateau might be due to some other early mechanism unrelated to star formation.