  We present new observations of copper and zinc abundances in 90 metal-poor
stars, belonging to the metallicity range -3< [Fe/H] < -0.5. The present study
is based on high resolution spectroscopic measurements collected at the Haute
Provence Observatoire (R= 42000, S/N > 100). The trend of Cu and Zn abundances
as a function of the metallicity [Fe/H] is discussed and compared to that of
other heavy elements beyond iron. We also estimate spatial velocities and
galactic orbital parameters for our target stars in order to disentangle the
population of disk stars from that of halo stars using kinematic criteria. In
the absence of a firm a priori knowledge of the nucleosynthesis mechanisms
controlling Cu and Zn production, and of the relative stellar sites, we derive
constraints on these last from the trend of the observed ratios [Cu/Fe] and
[Zn/Fe] throughout the history of the Galaxy, as well as from a few well
established properties of basic nucleosynthesis processes in stars. We thus
confirm that the production of Cu and Zn requires a number of different sources
(neutron captures in massive stars, s-processing in low and intermediate mass
stars, explosive nucleosynthesis in various supernova types). We also attempt a
ranking of the relative roles played by different production mechanisms, and
verify these hints through a simple estimate of the galactic enrichment in Cu
and Zn. In agreement with suggestions presented earlier, we find evidence that
Type Ia Supernovae must play a relevant role, especially for the production of
Cu.
