Geochemistry and petrogenesis of gabbroids in the Soleimanieh ophiolites, Sabzevar

The Soleimanieh ultramafic-mafic cumulate rocks (East of Sabzevar) include gabbronorites, amphibole gabbronorites, pegmatite gabbros, leucogabbronorites, norites, diorites and plagioclase bearing amphibole peridotites. The Cr-number of spinels in amphibole peridotites and olivine gabbronorites varies from 0.44 to 0.45 and 0.42 to 0.44 respectively. Geochemically, the gabbroic rocks are characterized by Mg# between 50 to 65% and their composition is directly related to modal abundances of the main rock-forming minerals. They have low TiO2 content, indicating boninitic to highly depleted island-arc tholeiitic affinities for their parental melts. The rocks have flat to depleted LREE patterns (relative to HREE). Enrichment in LILE and depletion in HFSE are characteristics of the Soleimanieh gabbroic rocks, showing formation of the rocks in a supra-subduction zone environment. Compared to the gabbroic rocks, the Sabzevar lavas have calc-alkaline characteristics and seem to be formed in a subducton zone environment.