Petrography, petrogenesis and geodynamic of Sawlava ophiolitic complex, NW of Iran

Zagros ophiolites are mainly exposed in Oman، Neyriz، Kermanshah، Kurdistan and north western of Iraq. The Sawlava ophiolitic complex is a member of Kurdistan ophiolites. In this research petrogenesis and geodynamic of this part of Zagros ophiolites have been investigated. Basalt، microgabbro، gabbro with serpentinized dunite and wherlite are the main rock units of the complex. The phenocryst in the basalta and the microgabbros are plagioclase and clinopyroxene and the main textures in the basalts are porphyric and microlitic-glassy whereas intersertal and microgranular are dominant in the microgabbros. The main minerals in the gabbros are clinopyroxene (augite-diopside)، plagioclase with labrador composition. In the peridotites، the major minerals are olivine (Fo= 88-91)، clinopyroxene (diopside-clinoenstatite) and chromin spinels (picotite). By analogy with the global standards، the obtained geochemical data reveal that basalts and microgabbros in Sawlava ophiolitic complex are tholeiitic in nature، and their magma source tends towards N-MORB and E-MORB. Gabbros are in tholeiite to calc-alkaline magma series and show the abyssal MORB to oceanic ARC features. The chemistry of peridotites shows the abyssal to supra-subduction zone source. The high volume of basalt-microgabbro، low Ti value and high content of Al and Cr# in peridoitite chromian spinels، reveal a high rate of partial melting (25-35%) indicating that the depleted mantle subjected to high degree of partial melting can be the Sawlava complex source. According to geochemical data a depleted mantle may be the source of Sawlava ophiolitic complex. This feature is more remarkable in the studied gabbros and peridotites. Comparing the lithological and geochemical characteristics of the studied ophiolites with some other complexes in the world documented that the complex under discussion formed in an oceanic back arc setting.