Inhomogeneous chemical evolution of the Galactic halo

The considerable scatter of heavy element abundances observed in low-metallicity stars, as well as the peculiar abundances observed in some halo stars (e.g. CS 22892-052), support the hypothesis of an inhomogeneous enrichment of the Galactic halo at early times. Moreover the presence of r-process elements in low-metallicity stars is indicative of a prompt enrichment of the Galaxy by early generations of massive stars. In this contribution, we present the results of a Monte Carlo model for the dynamical and chemical Galactic evolution of halo gas, in particular for Fe and elements mostly produced by r-process nucleosynthesis, like Eu.