Search

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.

The southern Dead Sea Transform (SDST) is an active left-lateral transform plate boundary that extends from the Sinai triple junction to the Lebanon restraining bend, separating the Arabian and Sinai plates. In this study, we analyze structural variations along the SDTS, and reproduce these variations in a 4D analogue model. From south to north, the structural styles along the SDTS indicate (1) rotational transtension within the Gulf of Aqaba, (2) pure strike-slip in Wadi Araba and Jordan River valley, and (3) pull-apart basins in the Dead Sea, Sea of Galilee and Hula basin. These different structural styles were replicated experimentally in an analogue model incorporating transtension with minor rotation along a kinked plate boundary. Our 4D model produced a deep southern depression with en echelon faults corresponding to the Gulf of Aqaba, a simple strike-slip fault system without vertical displacement reflecting the Wadi Araba and Jordan Valley, and a set of pull-apart basins reminiscent of the Dead Sea, Sea of Galilee and Hula basins. The accurate reproduction of the structural styles along this 600km-long plate boundary segment constrains the relative movement between the Arabian and Sinai plates to a simple combination of transtension with minor rotation, thereby negating the earlier hypothesis of Euler pole shift during the tectonic evolution of the SDST.

This study aims to characterize fracture permeability in altered Oligocene-Early Miocene basalts of the Jizan Group, which accumulated in half grabens during the continental rift stage of Red Sea evolution. Unlike fresh basalts, the Jizan Group was affected by low temperature hydrothermal metamorphism, which plugged the original matrix porosity in vesicles, breccias, and interflow layers with alteration minerals. On the other hand, the basalts are pervasively shattered by open closely spaced fractures in several directions. Characterization of these fractures is essential to reducing the fracture permeability uncertainty for mineral carbonation by the dissolved CO2 process such as Carbfix.Conventional measurements of fracture orientations and densities were initially taken at outcrops of the Jizan Group to characterize the fracture network. Photogrammetry of drone images covering larger areas were then used to create 3D models of the outcrops using Agisoft Metashape, which were analyzed for fracture geometries using Cloud Compare. The automated analysis of fracture orientations and densities compared well with conventional manual measurements. This gives confidence in semi-automated dronebased fracture characterization techniques in 3D, which are faster and less labor intensive, especially for characterization of large and difficult to reach outcrops.Our fracture characterization will be used to construct 3D fracture permeability models of the Jizan Group for combined physical and chemical simulation of injection of dissolved CO2 from industrial sources into basalts. This will provide essential parameters to mitigate geological risks and to determine depth, spacing, and injection rates in CO2 disposal wells.

Strike-slip motion is a fundamental tectonic process around the globe often resulting in prominent surface expressions. The full reconstruction and comprehension of strike-slip dominated structures can be a major challenge due to the complexity of the associated fault patterns. Further complexities occur when strike-slip dominated structures in the foreland interact with thrust belt fronts. Starting from a well-studied natural example (the Sciacca Fault Zone in the Sicilian Channel, Italy) we ran a set of analogue models simulating the interaction between strike-slip dominated fault zones and thrust structures using quartz sand as the analogue material and X-Ray Computed Tomography as a technique to carry out a 4D analysis of model internal structures. During a first phase, a thrust belt was created in our models, which was subsequently affected by a perpendicular fault system that underwent either pure strike-slip, 10°-, 20°-, 30°-transtensional, or 10°-, 20°-, 30°-transpressional motion. In general, transpressional models form pop-up structures, while the pure strike-slip model develops one sub-vertical fault bounded by two converging reverse faults. The 10˚-transtensional model generates a set of Riedel shear faults, which merge during the later stages of deformation. This model also shows a positive elevation change along the strike-slip dominated structures near the intersection with the thrust belt. The 20˚-transtensional model contains some Riedel shear faulting as well, but is dominated by two normal faults with steep dip angles and some minor sub-vertical strike-slip faults in between. This fault architecture is also observed in our 30˚-transtensional model. Three different tectonic regimes interacting with pre-existing and newly formed thrust front led to very different structural settings. These results were of help in better defining the tectonic regime that controlled the strike-slip dominated part of the Sciacca Fault Zone, but they show a fair match with other natural examples as well.