The Zabargad Fracture Zone and Mabahiss Deep, Northern Red Sea: new insights from new high-resolution bathymetric mapping

The Red Sea axis hosts an oceanic ultra-slow spreading ridge which is generally arranged into right-stepping segments. The largest apparent ridge offset runs at the transition between the northern and central Red Sea, amounts to ~ 100 km along a N-S trend, and is referred as to the Zabargad Fracture Zone (ZFZ). The ZFZ separates ridge segments characterized by exposed oceanic crust (the Mabahiss “Deep” in the north and the central Red Sea further south), but its nature and precise geometry are debated owing to the extensive Miocene evaporites that cover the basement structures. The ZFZ is the location of the most intensive seismic activity in the northern Red Sea, with a reported historical magnitude 6.5 earthquake. Due to its proximity with coastal communities, the ZFZ thus potentially poses a significant hazard. In order to better characterize the seismic potential of the ZFZ, we collected new high-resolution bathymetric data of the Mabahiss Deep and ZFZ, and use them to map the tectonic structures over both exposed-basement and salt-covered areas.Our findings reveal typical slow spreading-ridge features in the Mabahiss area, such as an axial MORB volcano with a summit caldera located in the middle of a 9 x15 km axial valley bounded by up to ~300-m-high normal fault escarpments. In addition, our results highlight a highly deformed salt cover in the ZFZ area and several salt diapirs outcropping near its eastern edge. The orientation of salt-deformation fabrics records a clear rotation from rift-parallel to rift-normal in the vicinity of the ZFZ, suggesting a potential control by underlying basement structures. Overall, the deformed area indicates that the ZFZ is a 70 km long and 15 km wide fracture zone, oriented roughly N-S, and potentially consisting of several NE-SW rift-perpendicular faults. These new data provide the first step to characterize the geometry and seismic potential of the ZFZ and to constrain the segmentation of the ridge axis in the northern Red Sea, emphasizing the importance of continued research to improve our understanding of this complex region and its potential impact on coastal communities.