The use of mineral chemistry in the study of origin and evolution of dunitic rocks from Ab-Bid ultramafic complex (East Haji Abad, Hormozgan Province)

Ab-Bid ultramafic complex is a part of Esfandagheh-HadjiAbad coloured mélange at the north of Hormozgan Province. It contains harzburgite, lherzolite, dunites, pyroxenite and chromitite. Dunites occur either as large and continuous masses or as dykes which have been intruded into the harzburgites. Mineral chemistry evidences show that the origin of these two types of dunites are completely different. Continuous dunites are similar to the residual mantle peridotites, while, dunitic dykes are the remnants of mantle channels and conducted the melts toward the upper levels. Dunitic dykes are produced by reaction of suprasubduction zone related  to boninitic melts with the harzburgites and they are replacive dunites, but the large and continuous dunites have formed by partial melting of the harzburgites in a suprasubduction zone setting and so they are residual dunites.