Crystal chemistry of Cr-spinel from the Imandra layered pluton, Kola Peninsula

Cr-spinol from the Imandra layered pluton was studied by a variety of metho ds including mineralogical and petrographic investigations, microprobe, inf rared (IR) spectroscopy, XRD, and Mossbauer spectroscopy on Fe-57 nuclei. T he Imandra Cr-spinel is a multicomponent (Fe2+, Mg)(Cr, Al, Fe3+)(2)O-4 sol id solution, which underwent exsolution during cooling after being crystall ized to form two major cluster groups composed of chromite and spinel; the domain size was not larger than 6 mum. The concordant variation of chemical compositions in both cluster groups was governed by the equilibrium redist ribution of chemical elements according to the occupancy of energetically a dvantageous cation sites.