Structures and microstructures related to steady-state mantle flow in the Neyriz ophiolite, Iran

Structural analysis in the well-exposed and well-preserved Neyriz ophiolite suggests that it is a relatively undisturbed piece of oceanic lithosphere. Detailed structural mapping of high-T deformation mantle flow revealed the presence of three elliptical shaped diapirs trending NW–SE. These diapirs are characterized by vertical mantle foliations associated with vertical plunging stretching lineations, which progressively incline toward parallelism with the gently NE-dipping Moho. The NW–SE direction of asthenospheric upwelling of diapirs is parallel with the orientations of the vertical sheeted dike complex. This suggests that the Neyriz ophiolite was created by two NW–SE palaeo-ridge axes. These palaeo-ridges are classified as fast-spreading ridges. These ridges are segmented by a dextral palaeo-transform fracture zone. This is consistent with fast-spreading ridges. Comparison between the Neyriz and Oman ophiolites reveals that they show similar characteristics. Most of the Oman palaeo-ridge systems are oriented NW–SE and NNW–SE. They also display similar sheeted dike complex orientations and crustal thickness variations. These two ophiolites originally were part of the Neo-Tethyan oceanic lithosphere and afterwards were separated by the Oman line during continental collision of the Iranian micro-continent and Afro-Arabian continent.