Origin of Lherzolitic Peridotites in Ab-Bid Ultramafic Complex (Hormozgan Province); Products of Mantle Metasomatism or Partial Melting Processes?

Abstract

<span>Lherzolite is one of the main units in the Ab-Bid ultramafic complex from Esfandagheh-HadjiAbad coloured mélange (South of Iran). The complex contains harzburgite, dunite, lherzolite and pyroxenite dykes and the lherzolites mainly occur in the margins. In the field, lherzolites occur as weakly foliated coarse-grained peridotites with shiny pyroxene grains and cut by neumerous pyroxenitic veins. Textural features such as elongation and undoluse extinction of minerals and porphyroclastic grains indicate that the lherzolites were part of the upper mantle and experienced high P-T deformational events. Mineral chemistry data such as Cr# values in spinels (10/33-14/04) and fo contents of olivines (90/49-93/51) from the Ab-Bid lherzolites suggest that these rocks belong to the mantle. Evidences such as CaO (1/18-3/23) and MgO (39/53-43/65) contents of whole rock compositions, Cr# (10/33-14/04) and Mg# (74/20-78) values of spinels, besides textural features and REE normalized patterns show that they have past a complex petrological history. At the first stage, they have partially melted (< 10%) in an abyssal environment, then, they refertilized by ascending melts and enriched in LREE. Tectonomagmatic discrimination diagrams indicate that Ab-Bid lherzolites belong to the abyssal peridotites and their petrogenetic evolutions are similar to those from MOR type peridotites. Our data document the dependence of Esfandagheh-HadjiAbad coloured mélange to the Neotethyan oceanic lithosphere in the south of Iran.</span>