Crustal structure beneath the volcanic field in the Tihamat Plains, Saudi Arabia: An integrated model constrained by gravity modelling and receiver function results

摘要

The Tertiary Tihamat-Asir-Volcanic-Zone (TAVZ) in the Tihamat Plains (TP) at the Arabian Shield margin north of the southern Red Sea is largely obscured by Quaternary alluvium and salt deposits, but partly exposed. We integrate available gravity data in the TP which is represented by three semi-circular Bouguer Anomaly (B.A.) highs with peak values of 30 mgal, situated at distances of similar to 50 km. This feature suggests prevailing anomalous crustal masses under the TP and were investigated using: (i) Digital Elevation Model (DEM); (ii) radially averaged spectral estimates on the causative source body depths within the crust; (iii) tilt-angle derivatives with horizontal derivatives of the tilt-angle values; and (iv) a theta map to define the edge of the continental crust in offshore Jizan. 2D gravity models for two traverses, the Mansiyah-Baysh Traverse (MBT) and Suq-Al-Ahad Traverse (SAAT), were constructed across the TAVZ, constrained by Receiver Function (REF) results from ten broadband seismic stations. Additional constraints for gravity interpretation come from the physical properties derived from REF results for the upper and lower crust. Our integrated crustal model infers a zone of Moho uplift approximately similar to 40 km wide, with vertical relief of 10-12 km at depths of similar to 37-45 km, where the average density of the crust is appreciably higher. Gravity models indicate a large volcanic field beneath the TP extending along the coast of the Red Sea. We find that crustal modification is an outcome of crust-mantle interaction owing to an elevated thermal regime under the TP.