Nano-kinematic indicators (Gulf of Aqaba, Saudi Arabia)

Abstract Strain and kinematic indicators are frequently investigated to assess the type, magnitude, and orientation of deformation fields. Typically, their analysis ranges from the outcrop to the thin section scale. The present study characterizes the structural and mineralogical development of a phyllosilicate-rich fault gouge from the core of a major strike-slip fault on the eastern margin of the Gulf of Aqaba. We used transmission electron microscopy and focused ion beam techniques to explore shear deformation structures down to the nanoscale. The fault gouge was differentiated at the micron-submicron scale into chlorite-rich and illite-rich bands. The observed nano-kinematic shear sense indicators were SC/SCC’ fabrics in phyllosilicate bands, inclined axial planes in kink-folded illite and chlorite plates, platy hematite clasts inclined against the shear direction, and a σ-type clast system with recrystallized material in strain shadow wings around the clasts. These indicators provide a consistent set of criteria to determine shear sense in phyllosilicate-rich fault gouges.