Geochemical constraints on the tectonomagmatic evolution of the late Precambrian Fawakhir ophiolite, Central Eastern Desert, Egypt

Abstract

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 tholeftic 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 arc-type lavas, P-type MORB and boninitic rocks, suggesting that these rock units developed in a back-arc environment. The evolution of the Fawakhir ophiolite sequence from early tholeftes 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.