Usage of strain and vorticity analyses to interpret large‐scale fold mechanisms along the Sanandaj–Sirjan HP‐LT metamorphic belt, SW Iran

Abstract

3D finite strain analyses and kinematic vorticity measurements were carried out on the Loghon Anticline within the HP-LT Sanandaj-Sirjan metamorphic belt (Neyriz area, SW Iran). Rƒ/' and Fry methods were used on the strain markers (e.g. deformed fossils) to interpret geometric relationships between the fold axis, strain ellipsoid axes and shear zone boundaries. The results indicate the predominance of prolate strain in the anticline. Quantitative kinematic analyses show that the W k parameter is 0. 67 AE 0. 06 (i.e. pure-shear dominated non-coaxial flow). This study quantitatively supports the establishment of a dextral transpressive system, which is responsible for the development of the large-scale right-lateral shear zones that strike sub-parallel to the major folds. Flexural shear combined with regional dextral-shear is suggested to be the most common mechanism of folding in this area.

Deformations of Palaeozoic and Mesozoic rocks in southern Sirjan, Sanandaj–Sirjan Zone, Iran

“…3). The subsequent regional dextral-shearing, suggested for the Neyriz area (Sheikholeslami, 2008;Sarkarinejad et al, 2011), can also be generalized to the study area.…”

Vorticity analysis of the Palmi shear zone mylonites: new insights for the Alpine tectonic evolution of the Calabria–Peloritani terrane (southern Italy)

“…In spite of these controversial opinions, the 2D geometrical analysis of rigid porphyroclasts continues to be applied (e.g. Sarkarinejad et al ., ; Zhang and Teyssier, ; Cao et al ., ), also in combination with other vorticity techniques (e.g. Law et al ., ) to determine the vorticity of flow ( W m ) and consequently to assess whether deformation is dominated by simple or pure shear (e.g.…”

Structural and kinematic analyses of the basement window within the hinterland fold-and-thrust belt of the Zagros orogen, Iran

“…Inclined transpression was defined by Jones et al (2004) as isochronous contractional and dip-slip shearing that is a non-coaxial and non-plane strain deformation. An example of the classical crustal inclined transpression zone is the Zagros Thrust System, which involves ductile transpressional deformation (Mohajjel & Fergusson, 2000; Sarkarinejad, 2007; Sarkarinejad & Azizi, 2008; Sarkarinejad, Faghih & Grasemann, 2008; Sarkarinejad et al 2012; Sarkarinejad & Ghanbarian, 2014) resulting from relative motion between the Afro-Arabian continent and the Iranian microcontinent. Structural and kinematic analyses of the transpressional deformation indicate exhumation of the highly strained mylonitic shear zones associated with the nappes of the basement involved in the recently recognized hinterland fold-and-thrust belt of the Zagros orogen (Sarkarinejad & Alizadeh, 2009; Sarkarinejad & Ghanbarian, 2014) and improve our understanding of strain partitioning within the still active zone of inclined transpression in the Zagros Mountains.…”