Constraining the tectono-thermal evolution of the Egyptian Red Sea margin: linking observations from the proximal to the hyperextended rift domain

The evolution of the Red Sea rift system - one of the prototypical and conceptually most influential continental rifts - can be differentiated into several distinct rifting phases: (i) rift initiation at ~23 Ma along the entire Red Sea, (ii) onset of necking and hyperextension recorded by rapid syn-rift subsidence in the E. Miocene (~19 Ma), (iii) transition to oblique rifting and movement along the Aqaba transform in the M. Miocene (~14 Ma) likely leading to coupled hyperextension and mantle exhumation, and finally (iv) initiation of oceanic spreading in the S Red Sea at ~5 Ma. This study presents new U-Pb and (U-Th)/He data from both the proximal Egyptian margin and the distal hyperextended margin (Zabargad Island) constraining the thermal evolution during progressive continental rifting and oceanic rupture. (U-Th)/He data from transects across upper- and lower-plate portions of the Egyptian proximal margin between the Gulf of Suez and Sudan record the structural and temporal evolution of rift initiation and necking in the proximal margins. In contrast, data from the distal domain exposed on Zabargad preserves both E. Miocene hyperextension as well as Pliocene reheating during nascent oceanic spreading. Zabargad represents a rare exhumed portion of a highly-attenuated distal rifted margin that was subsequently uplifted along the oceanic Zabargad fracture zone. While zircon U-Pb data document the E. Miocene phase of hyperextension, rutile and apatite U-Pb data from basement samples, yielding ages from ~5-12 Ma, document the exhumation phase and, more significantly, the reheating of the distal margin during initial oceanic break-up. This reheating of the distal continental margin has not been documented in modern or fossil hyperextended margins. These new data provide important new constraints on the thermal and mechanical evolution of rift margins during both necking and oceanic break-up and provide critical new insights into the thermal evolution of the crust during the transition from continental hyperextension to oceanic spreading as well as the role that reheating plays in rift propagation. In summary, these new thermochronometric data from the Egyptian Red Sea provide unique new insights into the thermal evolution of progressive rifting and continental break-up of one of the most prototypical rift systems.