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Platinum-group minerals were concentrated using superpanning from two composite chromitite samples, which were collected from two old mines within the Othrys ophiolite. This method allows for the recovery of a broad spectrum of these rare and fine-grained minerals, and helps to better identify them and interpret their origin. Major differences between the east and west Othrys ophiolites were determined, probably as a result of their different origin and evolution. Primary Os-, Ir-, and Ru-bearing platinum-group minerals (IPGM)-alloys and the Rh-, Pt-and Pd-bearing platinum-group minerals (PPGM) occur only in the east Othrys chromitite, indicating an evolution from initially low f S2 conditions at shallower mantle levels with the subsequent implication of a S-saturated ascending fluid. In contrast, the absence of primary IPGM-alloys in west Othrys chromitite indicates that S saturation had been attained. The presence of erlichmanite suggests that sulphur fugacity eventually increased significantly in both suites. Substantial fluctuations of a fluid phase, likely related to serpentinising fluids, modified the platinum-group minerals (PGM) assemblage of west Othrys, and resulted in a large diversity of secondary PGM minerals. The limited number of secondary species developed in the east Othrys indicate that secondary processes were also different in the two suites.

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The Iti and Kallidromon ophiolites, in continental central Greece, consist mainly of an ophiolite mélange overthrust by variably serpentinized ultramafic rocks. They include lherzolite and harzburgite; dunite pods occur within the lherzolite at Kallidromon. All rock types display typical textures of Alpine-type mantle rocks. Spinel, olivine and pyroxene compositions are similar to analogous phases from oceanic peridotites. The lherzolite contains an aluminous spinel. The dunite and harzburgite contain two compositional variants of Cr-rich spinel, both commonly present in zoned grains, one with higher Cr# and a second with lower Cr#. Linear variations of Al 2 O 3 , CaO, V and Ni with MgO, coupled with incompatible and rare-earth-element depletion and mineral compositions, suggest prior events of partial melting in both the lherzolite and harzburgite. The LREE enrichment in the harzburgite, as well as the development of Cr-rich spinel and tremolite and the PGE distribution in both the dunite and harzburgite, are consistent with a history of melt-peridotite interaction. The melt is considered to have been of boninitic composition, generated in the mantle wedge above a subduction zone. The harzburgite was formed at values of smaller melt:rock ratio relative to the dunite owing to partial assimilation of clinopyroxene and orthopyroxene from the host lherzolite. The dunite is considered to have been formed by assimilation of clinopyroxene and orthopyroxene, and replacement of Al-rich spinel by Crrich spinel, when locally ponded boninitic melts reacted with the host lherzolite. In both the harzburgite and dunite, subsequent differentiation of magma resulted in the formation of compositional areas poorer in Cr in the spinel grains. The involvement of a boninitic melt and the significant contribution of H 2 O in the formation of the harzburgite and dunite, along with mineralogical evidence, particularly Fo-and Cr-rich olivine in the dunite and high-Cr spinel in both the dunite and harzburgite, suggest a subduction-related regime for the origin of the Iti and Kallidromon ophiolites. Moreover, covariation of Cr/Al and Ni/Al values similar to the well-known SSZ-type ophiolites of Vourinos support the above hypothesis. SommaiReLes massifs ophiolitiques de Iti et Kallidromon, en Grèce continentale centrale, contiennent surtout un mélange ophiolitique recouvert par chevauchement par des roches ultramafiques à degré de serpentinisation variable, par exemple lherzolite et harzburgite; des lentilles de dunite sont présentes dans la lherzolite à Kallidromon. Toutes les roches font preuve de textures typiques de roches mantelliques de type alpin. Les compositions de spinelle, olivine et pyroxène ressemblent aux phases analogues de péridotites océaniques. La lherzolite contient un spinelle alumineux. La dunite et la harzburgite contiennent des variantes de spinelle chromifère, les deux généralement présents dans les grains zonés, un avec une valeur de Cr# élevée, et l'autre ayant une valeur plus faible. Les variations linéaires en Al...

Serpentinites and serpentinised ultramafic rocks from the Pindos ophiolite complex, northwestern Greece, contain Cr-spinel