  We present new FLAMES@VLT spectroscopic observations of 30 stars in the field
of the LMC stellar cluster NGC 1866. NGC 1866 is one of the few young and
massive globular cluster that is close enough so that its stars can be
individually studied in detail. Radial velocities have been used to separate
stars belonging to the cluster and to the LMC field and the same spectra have
been used to derive chemical abundances for a variety of elements, from [Fe/H]
to the light (i.e. Na, O, Mg...) to the heavy ones. The average iron abundance
of NGC 1866 turns out to be [Fe/H]= -0.43+-0.01 dex (with a dispersion of 0.04
dex), from the analysis of 14 cluster-member stars. Within our uncertainties,
the cluster stars are homogeneous, as far as chemical composition is concerned,
independent of the evolutionary status. The observed cluster stars do not show
any sign of the light elements 'anti-correlation' present in all the Galactic
globular clusters so far studied, and also found in the old LMC stellar
clusters. A similar lack of anti-correlations has been detected in the massive
intermediate-age LMC clusters, indicating a different formation/evolution
scenario for the LMC massive clusters younger than ~3 Gyr with respect to the
old ones. Also opposite to the Galactic globulars, the chemical composition of
the older RGB field stars and of the young post-MS cluster stars show robust
homogeneity suggesting a quite similar process of chemical evolution. The field
and cluster abundances are in agreement with recent chemical analysis of LMC
stars, which show a distinctive chemical pattern for this galaxy with respect
to the Milky Way. We discuss these findings in light of the theoretical
scenario of chemical evolution of the LMC.
