Fluid dynamics, structural, micro-structural, and kinematic analyses on the Kuh-e-Namak (Dashti) salt diapiric rectangular cuboid channel flow, Iran

Abstract

A study was conducted to investigate the Kuh-e-Namak (Dashti) salt diapir using fluid dynamics, structural, and microstructural, analyses. The study focused on transient flow caused by salt diapirism within the restraining bend of the Kazerun fault system. The salt diapir is located in Bushehr Province, Iran, and it was found that it represents Newtonian viscous flow within a rectangular cuboid channel, rather than a circular channel as previously thought. The study discovered that the salt diapir underwent laminar irrotational flow (Re = 1147.31) upward, with the symmetric parabola velocity profile dominated by Poiseuille flow. When loaded by sedimentary overburden, the salt tended to migrate. The upper part of the salt dome and diapiric flow transferred from irrotational laminar Poiseuille flow to transient Poiseuille-Couette and turbulent Poiseuille-Couette flows with a non-uniform asymmetric parabola profile. The drag sheath folds from diapiric flow showed monoclinic symmetry patterns, which led to a relative increase in the ellipticity of individual sheath fold rings to define the analogous eye-folds and cat ‘s-eye-folds. The presence of porphyroclasts or vortexes of σ, δ, and φ types in sheath folds indicates that the upper sections of the salt dome and diapir went through a Poiseuille-Couette flow or transient and turbulent flow during a later stage. The salt transient and turbulent flow can gradually lead to increased shear stress and high strain rates that are superposed by sub-simple shear, resulting in activation of the faults and consequently, the earthquake as we have seen in the destructive Kaki-Shonbe earthquake (Mw = 6.3).