Moho topography and Flexural response of Semail ophiolite in the Southern Oman Mountains: New constraints from teleseismic receiver functions and gravity anomalies

Abstract

The Semail Ophiolite in Oman represents one of the well-preserved ophiolite complexes globally and provides a unique window into the processes of obduction. The emplacement of Semail ophiolite onto the Arabian lithosphere is a result of intra-oceanic subduction, was strongly influenced by inheritance features preserved from pre-obduction tectonic processes. Therefore, a detailed characterization of the crustal architecture and rheological properties of the lithosphere are essential for improving our understanding of obduction processes. In this study, we investigated the crustal structure and Moho depth beneath the central Oman Mountains through analysis of P-wave receiver functions (PRFs) and Bouguer gravity anomalies. We utilize broadband seismic data recorded at 12 seismic stations spanning the ophiolite belt and surrounding regions (Ghaba basin and Saih Hatat Dome). PRFs analysis reveals noticeable lateral variations in Moho depths ranging from ∼39 km beneath the sedimentary basin to ∼46 km beneath the ophiolite belt, and decreasing to ∼30 km underneath Saih Hatat Dome (SHD). 2D forward modeling of Bouguer gravity anomalies (−36 to 91 mGal) constraints with seismological results shows flexural bending of the Moho topography and thin crust (∼ 30 km) beneath the SHD. The 2D forward flexural modelling analysis suggests that lithospheric flexure is due to the emplacement of the ∼5 km thick Semail Ophiolite. The presence of a thin crust beneath the SHD is caused by Permian rifting and thinning of the continental lithosphere. The observed high value of Vp/Vs (1.75 – 1.87) also provides support for Permian mafic intrusions to the lower crust. The Arabian lithosphere exhibits lower mechanical strength in the southern region (Te = 25 km) relative to the northern area, a characteristic likely inherited from pre-obduction magmatic processes. These results provide new geophysical constraints on the crustal architecture of the southern Oman Mountains and emphasize the role of surface loading in shaping lithospheric structure during ophiolite emplacement.