MN-RICH GARNET IN ECLOGITES FROM THE VOLTRI-GROUP (ITALY)

A detailed microprobe study has been performed on garnet occurring in six eclogite samples from the same small outcrop near Vara Inferiore ( Voltri Group, Italy). All garnets are strongly zoned and display compo sitional variations which are shown to be related to the grain size. T he unusual MnO enrichment at the core of the largest grains, as well a s the MnO depletion at the rims and in the smallest grains, lead to th e conclusion that nucleation and growth of garnet took place at differ ent times and continued throughout the eclogite metamorphic stage duri ng increasing temperature conditions, pressure being nearly constant.