Petrology, geochemistry, and petrogenesis of mafic dykes from the Kermanshah Ophiolite in Sahneh-Harsin area of Western Iran

Abstract

The Kermanshah ophiolite complex is a part of the Mediterranean–Zagros–Oman Tethyan ophiolites, located in the structural–tectonic zone of western Iran in the northern part of the Zagros main thrust. Doleritic sheeted dykes are well exposed within the ophiolite in the south of Sahneh. These dykes contain high MgO, Na2O, low TiO2 (2O5, and K2O contents, and high FeOt/MgO and LILE/HFSE ratios. The geochemical data show that the parent magma of these dykes was an initial melt, tholeiitic subalkaline in nature; with LIL elements-enriched signature. N-MORB-normalized multi-element plots indicate nearly flat patterns for HFSE and enrichment in LILE; patterns of incompatible trace elements demonstrate an island arc affinity for these dykes. The enrichment of the LILE in comparison with HFSE suggests the involvement of a crustal component driven by fluids along the subduction zone. Several geochemical parameters suggest that the dykes of Kermanshah Ophiolite exhibit transitional characteristics between mid-ocean ridge basalt and island-arc tholeiite. High LILE/HFSE ratio negate suggest a mid-ocean ridge setting for these dykes; it is, therefore, proposed that the dykes may have originated in a back-arc basin tectonic setting or supra-subduction zone.