Spinel Compositional Variation in the Crustal and Mantle Lithologies of the Othris Ophiolite

Spinels from cumulus and non-cumulus members of the 0thris ophiolite display a considerable variation in composition. Cumulus pierites and gabbros contain either a primary chromite and/or a reaction spinel formed by reaction with co-existing sili?ate,-" (Cr--A1 varia tion) or intercumulus liquid (Cr--Fe variation). Non-cumulus peridotites contain spinels which vary along a Cr--A1 trend. Harzburgites contain a Cr-spinel and lherzolites a more aluminous spinel. The oecurence of gabbroic segregations within the host lherzolite appears to affect the spinel chemistry. Spinels adjaeent to these plagioclase--diopside veinlets are richer in aluminium than the spinels scattered within the depleted therzolite surrounding the veinlet. [Protoelastic harzburgites contain a highly aluminous spinel phase either as an exsolution phase within pyroxenes or as a groundmass spinel.] The Cr--A1 variation of the peridotites is believed to have resulted from interaction with interstitial aluminous liquid--in situ basaltic melt from a fused peridotite ?