Crustal rheological properties provide evidence for large-scale heterogeneity in the extended Arabian Shield Crust at the Red Sea Margin

Abstract

A better knowledge of the Arabian Shield Crust at the Red Sea Margin (AS-RSM) is essential to build more realistic models for the rifting process. Here, we present, for the first time, a comprehensive study on rheological parameters of crust derived from the receiver function analysis results from 24 seismic stations across the AS-RSM. The elastic parameters computed for the upper and lower crust are: Vp, Vp/Vs, density (ρ), shear modulus (μ), Lame’s first constant (λ), Poisson’s ratio (σ), Young’s modulus (E), bulk modulus (K) and acoustic impedance (AI). Their cross-plots and mutual regression relations are investigated to deduce the dominant rock composition in the underlying crust prevalent in their respective regions: North, Central and South Red Sea Margin (NRSM, CRSM and SRSM). Primary results are: (i) the AS-RSM is highly heterogeneous in rheology, and their variances extend both laterally and vertically inside the crust, (ii) significant changes are expected in lithological distribution, rock composition and metamorphic status at crustal depths, (iii) the lower crust underlying the NRSM and the SRSM mostly consists of quartz diorite to diorite, while those for the CRSM (including the Jeddah Terrain, JT) are composed of amphibolite and gabbro metamorphosed to upper amphibolite facies, (iv) crustal rheological properties underneath NRSM and SRSM are quite akin and have lower values, but those under CRSM and JT are significantly higher, and (v) the elastic moduli values and their analysis can find prognostic applications in stress changes around the fault zones that dissect the AS-RSM at high angles. These faults owe their inheritance from the Red Sea spreading.