  NGC 3201 is a globular cluster suspected to have an intrinsic spread in the
iron content. We re-analysed a sample of 21 cluster stars observed with
UVES-FLAMES at the Very Large Telescope and for which Simmerer et al. found a
0.4 dex wide [Fe/H] distribution with a metal-poor tail. We confirmed that when
spectroscopic gravities are adopted, the derived [Fe/H] distribution spans ~0.4
dex. On the other hand, when photometric gravities are used, the metallicity
distribution from Fe I lines remains large, while that derived from Fe II lines
is narrow and compatible with no iron spread. We demonstrate that the
metal-poor component claimed by Simmerer et al. is composed by asymptotic giant
branch stars that could be affected by non local thermodynamical equilibrium
effects driven by iron overionization. This leads to a decrease of the Fe I
abundance, while leaving the Fe II abundance unaltered. A similar finding has
been already found in asymptotic giant branch stars of the globular clusters M5
and 47 Tucanae. We conclude that NGC 3201 is a normal cluster, with no evidence
of intrinsic iron spread.
