Document Type: Original Article

Authors

1 Department of Geology, Zahedan Branch, Islamic Azad University, Zahedan, Iran

2 Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran

3 Department of Geology, Mashhad Branch, Islamic Azad University, Mashhad, Iran

Abstract

Nosrat-Abad ophiolitic extrusive sequence, located in the Sistan Suture Zone, in south eastern Iran. The extrusive sequence, contains pillow lava, sheet flow and related volcanic-clastic breccias which have undergone low-grade metamorphism. This association shows calc alkaline to tholeiitic affinities. Interpretation of the geochemical data and behavior of the elements in different diagrams reveals two distinct domains in the Nosrat-abad ophiolitic extrusive sequence. The sheet flows are depleted in HFSE similar to those of SSZ. However, the enrichment of the pillow lavas in LILE could be attributed to an enriched mantle source or melting of metasomatized sediments above the subducted slab. It appears that two subduction components (fluids-melt), caused the diversity seen in the chemical composition of the study rocks. The MORB to subduction chemical characteristics of the Nosrat-Abad ophiolitic extrusive sequence could be explained by a shift in the tectonic settings from the mid-ocean ridge to the marginal basin in Sistan during the Late Cretaceous period.

Keywords