Geophysical imaging of ophiolite structure in the United Arab Emirates

M Y Ali,T Ambrose,M P Searle,B Keats,S Pilia,A B Watts

doi:10.1038/s41467-020-16521-0

Abstract

The Oman-United Arab Emirates ophiolite has been used extensively to document the geological processes that form oceanic crust. The geometry of the ophiolite, its extension into the Gulf of Oman, and the nature of the crust that underlies it are, however, unknown. Here, we show the ophiolite forms a high velocity, high density, >15 km thick east-dipping body that during emplacement flexed down a previously rifted continental margin thereby contributing to subsidence of flanking sedimentary basins. The western limit of the ophiolite is defined onshore by the Semail thrust while the eastern limit extends several km offshore, where it is defined seismically by a ~40–45°, east-dipping, normal fault. The fault is interpreted as the southwestern margin of an incipient suture zone that separates the Arabian plate from in situ Gulf of Oman oceanic crust and mantle presently subducting northwards beneath the Eurasian plate along the Makran trench.

Highlights

The Oman-United Arab Emirates ophiolite has been used extensively to document the geological processes that form oceanic crust
Ophiolites, which comprise oceanic crust and mantle that have been thrust onto previously rifted continental margins prior to continental collision, are a key component of the Wilson cycle, a fundamental feature of which is the closing of ocean basins and the formation of mountains belts
The world’s largest and best known ophiolite is found in the Oman–United Arab Emirates (UAE) mountains[1,2,3], a 1–3 km high, 700 km long by 150 km wide mountain belt part of the Arabian plate

Summary

Introduction

The Oman-United Arab Emirates ophiolite has been used extensively to document the geological processes that form oceanic crust. Field mapping reveals a distinct thrust slice of high-temperature granulite facies rocks brought up by an out-of-sequence thrust within the mantle sequence of the ophiolite, raising the possibility that the crust beneath the ophiolite may presently comprise stacked units of Late Cretaceous granulites, similar to the Bani Hamid thrust sheet[11]. Despite these previous studies, the sub-surface geometry of the Oman–UAE ophiolite remains poorly known because previous gravity models are unconstrained seismically and seismic reflection profile data have difficulty in imaging its internal structure. We find the eastdipping Semail ophiolite is >15 km thick, flexed down the preexisting crust by >5 km, is presently underlain by folded and thickened continental crust and is bound to the east by a major normal fault, implying the ophiolite may not be rooted in the Gulf of Oman crust and mantle

Methods

Results

Conclusion