Comparative Study of Chromite Deposits from Troodos, Vourinos, North Oman and New Caledonia Ophiolites

Abstract

The comparative study of chromitites from Vourinos (Greece), Troodos (Cyprus), Semail (Oman), Tiebaghi and Massif du Sud (New Caledonia) ophiolitic complexes reveals that all studied chromite deposits are surrounded by dunite whose extent bears no relation to the size of the orebody. The dunite-chromitite contact may be gradational or sharp; in Oman, its sharpness is emphasized by the presence of interstitial silicates (plagioclase, pyroxenes) in chromitite which are missing in the surrounding dunite. The occurrence of PGM inclusions in disseminated chromite from dunite in the Vourinos and Tiebaghi ophiolites infers a genetic relationship between chromitites and their dunitic envelopes. In chromite deposits from Vourinos and Massif du Sud, olivine is the only interstitial phase. The Oman chromitites exhibit a complex interstitial assemblage with olivine, clinopyroxene, plagioclase and pargasitic amphibole. Silicate inclusions (olivine, orthopyroxene, clinopyroxene, plagioclase, pargasite, phlogopite, sodium equivalent of phlogopite, nepheline) are commonly observed in chromitites. Their distribution within the host crystal indicates that they were trapped during chromite crystallization. Tabular crystals of both pyroxenes found in some chromite bodies might result from epitaxial intergrowth or from exsolution.