MINERALOGY AND CHEMISTRY OF CR-CHLORITES ASSOCIATED WITH CHROMITES FROM VAVDOS AND VASILIKA OPHIOLITE COMPLEXES (CHALKIDIKI, MACEDONIA, NORTHERN GREECE)

In the lower ultramafic unit of the Mesozoic Chalkidiki complex. serpe ntinized dunite is the predominant rock. Chromitites. mostly in the fo rm of layers, are hosted in this unit. Chromite grains are moderately to strongly deformed and are very often surrounded by a marginal zone of ferritchromite which is associated with a Cr-chlorite. Chromite gra ins. altered to ferritchromite. are partly or completely surrounded an d/or replaced by the Cr-chlorite which is also observed as thin fractu re-filling veins in the chromite grains. The mineralogy. chemistry and genesis of the Cr-chlorite from two chromite deposits, namely Vasilik a and Vavdos. is dicsussed. Optical and X-ray data, Mossbauer spectra and mineral microprobe analyses are presented. The examined Cr-chlorit e is a penninite to clinochlore and is believed to be parageneticaly r elated to the ferritchronlite, as indicated by the higher Cr/(Cr + Al) ratio and the lower Mg/(Mg + Fe) ratio in ferritchromite compared to that of parent chromite. The principal process of ferritchromite forma tion is associated with the transfer of Cr and Al from the chromite fo r the formation of Cr-chlorite.