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The Laibid pop-up structure is located in the highly deformed sub-zone of the Sanandaj-Sirjan Zone, western Iran. In this zone, structural trends are parallel to the Zagros fold-thrust belt (NW-SE), but the pop-up structure has a different trend of E-W and is surrounded by several fault sets, which are the youngest deformational event. Comparison between the fold axes and axial plains of the inner and outer part of the pop-up structure and also coaxial interference patterns of polyfolding show a continuous deformation in the study area. It seems that during Late Jurassic, due to right lateral transpression movement resulting from the collision of the Iranian and the Afro-Arabian continents, three folding stages formed and passively rotated in a continuous deformation condition. [ABSTRACT FROM AUTHOR]

Abstract: Kilometre-scale subparallel folds in the NW–SE trending Shahdad fold-and-thrust belt show active thin-skinned deformation produced by late Pliocene–Quaternary compressional tectonics between the Yazd and Lut blocks of the central microcontinent of southeast Iran. The Shahdad fold-and-thrust belt developed in a Miocene–Quaternary sedimentary sequence with gypsiferous marl overlain by well-stratified gypsiferous siltstone, sandstone, and conglomerate. The geometry of the fold-and-thrust belt is shown in four regional cross sections, which demonstrate common fault-propagation folds developed above thrusts splays and associated with curving ridges. In the northeast, incipient thrusts and back thrusts have developed at the tip of the blind northeast-dying-out sole thrust. However, further west, a major back thrust has brought to the surface the lower part of the stratigraphic succession (Malakhordeh thrust). In some fault-related folds, parts of the folds have been eroded and syntectonic sedimentary strata containing younger gypsiferous conglomerates have been deposited over an unconformity surface. These younger layers are also flexed above the underlying fault-propagation fold as the result of renewed slippage along the active fault. Collapsing has developed in the hinge zones of these folds. The sole detachment fault has developed through the lower plastic gypsiferous marls near their contact with the underlying Paleocene–Eocene volcanic rocks of the Lut block. [Copyright &y& Elsevier]

The Sanandaj–Sirjan Zone contains the metamorphic core of the Zagros continental collision zone in western Iran. The zone has been subdivided into the following from southwest to northeast: an outer belt of imbricate thrust slices (radiolarite, Bisotun, ophiolite and marginal sub-zones, which consist of Mesozoic deep-marine sediments, shallow-marine carbonates, oceanic crust and volcanic arc, respectively) and an inner complexly deformed sub-zone (late Palaeozoic–Mesozoic passive margin succession). Rifting and sea-floor spreading of Tethys occurred in the Permian to Triassic but in the Sanandaj–Sirjan Zone extension-related successions are mainly of Late Triassic age. Subduction of Tethyan sea floor in the Late Jurassic to Cretaceous produced deformation, metamorphism and unconformities in the marginal and complexly deformed sub-zones. Deformation climaxed in the Late Cretaceous when a major southwest-vergent fold belt formed associated with greenschist facies metamorphism and post-dated by abundant Palaeogene granitic plutons. In the southwest of the zone a Late Cretaceous island arc—passive margin collision occurred with ophiolite emplacement onto the northern Arabian margin similar to that in Oman. Final closure of Tethys was not completed until the Miocene when Central Iran collided with the northeast Arabian margin. [Copyright &y& Elsevier]

Abstract: The Khoy Ophiolitic Complex as a part of the Tethyan ophiolites is exposed in the northwestern part of the Iranian-Azerbaijan province, extending to the Anatolian ophiolites in southeastern Turkey. Petrography, geochemistry and microstructural studies of the residual mantle sequence in the Khoy Ophiolitic Complex provide important information about the degree of partial melting and deformation in the oceanic mantle lithosphere. Ultramafic tectonites dominantly composed of lherzolite and clinopyroxene-bearing harzburgite (TiO2 =0.012–0.024 wt.%; Al2O3 =1.36–1.81 wt.%). Chondrite-normalized rare-earth-element patterns are characteristically U-shaped. These peridotites can be divided into two types: (1) type 1 peridotites with Al-rich spinels (Cr number of 0.16–0.26, and Mg number of 0.64–0.76), resembling the fertile abyssal peridotites, supposed to have originated as the residue from<15% partial melting and mid-ocean ridge (MORB) magma extraction; (2) type 2 peridotites, representing characteristics of the depleted abyssal or supra-subduction-zone peridotites, with Cr-rich spinels (Cr number of 0.31–0.60 and Mg number of 0.51–0.72). This type of peridotite has undergone>20% partial melting, followed by segregation of basaltic magmas. Microstructural fabrics of olivine grains in peridotites highlight a sequence of dislocation creep on the (010) [100] slip system, plus subsidiary slip along the (001) [100] slip system. These systems, as well as coarse and fine-grained porphyroclastic textures, indicate deformation at high temperatures of ∼1000–1250°C. The observed subsidiary (001) [100] slip system is considered to have been triggered by elevated H2O activity, and that deformation phases took place in a wet subduction-related environment. The geochemical and microstructural data suggest that the mantle sequence of the Khoy Ophiolitic Complex is consistent with a supra-subduction-zone environment in relation to a slow-spreading back-arc basin. [Copyright &y& Elsevier]