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The Fawakhir ophiolitic sequence is composed mainly of serpentinites, metagabbros, boninitic metagabbros and metavolcanics. The serpentinites have geochemical features similar to those of depleted-mantle peridotites. Major and trace element characteristics show that the ophiolitic metagabbro and metavolcanic rocks are of tholeiitic to calc-alkaline affinity. REE abundances in the metagabbros and metavolcanics are characterised by flat to fractionated patterns. The Fawakhir ophiolitic sequence shows a spectrum of compositions ranging from are-type lavas, P-type MORE and boninitic rocks, suggesting that these rock units developed in a back-are environment. The evolution of the Fawakhir ophiolite sequence from early tholeiites to later boninitic-type magmas may suggests that these rocks could be generated by fractional fusion and melt extraction during ascent of the magma source within a mantle melting column. The boninites were generated from a more refractory mantle source relative to the other rocks. (C) 1999 Elsevier Science Limited. All rights reserved.