GEOCHEMISTRY OF CHROMITITES AND HOST ROCKS FROM THE PINDOS OPHIOLITE COMPLEX, NORTHWESTERN GREECE

Representative chromite samples of schlieren and massive ore types from various localities of the Pindos ophiolite complex were analyzed for platinum-group elements (PGE), S, Ni, Co and Cu, and mineral chemistry. Host dunites and harzburgite were also analyzed for the chalcophile elements. The chromite ores show a wide compositional variation. The Cr/(Cr + Al) ratio ranges from 0.47 to 0.83 while Mg/ (Mg + Fe2+) ranges between 0.42 and 0.73, but two populations can be distinguished (the high-Cr and high-Al types), which show a more restricted variation. Ranges of PGE contents (in ppb) are: Os = 8-150, Ir = 4-320, Ru = 15-550, Rh = 2-82, Pt = 3-150 and Pd = 1.5-20. Gold ranges between 1 and 13 ppb. The PGE and less chalcophile elements (Ni, Co and Cu), the incompatible/compatible element ratios, the PGE/S ratio and PGE patterns provide valuable information for the discrimination of chromite ores with a similar major-element composition. A fractionation trend in both chromitites and associated dunites can be used for stratigraphic orientation in the mantle sequences of ophiolite complexes and evaluation of their chromite potential.