Origin and Obduction of the Oman Ophiolite

M.P. Searle, D.J. Waters.

In this project we are studying the petrogenesis and structure of the Oman Ophiolite, a slab of Late Cretaceous oceanic crust (radiolarian cherts, pillow lavas, sheeted dykes, gabbros and cumulate peridotite-gabbros) and upper mantle (depleted harzburgite  - dunite) that was emplaced, largely intact onto the passive continental margin of Arabia. The sub-ophiolite metamorphic sole beneath the Oman ophiolite consists of garnet + clinopyroxene amphibolites showing partial melt textures at the highest levels, epidote amphibolites and a variety of greenschist facies meta-sediments (marbles, quartzites) and meta-volcanics that were accreted to the base of the ophiolite slab. P-T conditions of peak metamorphism suggest a subduction-zone origin and U-Pb zircon and 40Ar-39Ar cooling ages suggest that metamorphism was contemporaneous with ophiolite formation implying a supra-subduction zone origin of the ophiolite. A thrust wedge of granulite facies sole rocks occurs in the Mahdah region where crustal anatexis has resulted in intrusion of garnet-cordierite-andalusite bearing leucogranites into the ophiolite.

Selected references:

High-Pressure metamorphism (eclogite, carpholite) in Oman

M.P. Searle, D.J. Waters in collaboration with I. Alsop (St.Andrews) P. Agard (Paris)

A unique belt of High-Pressure metamorphic rocks (As Sifah eclogites, blueschists and carpholite-bearing schists) occur in northeastern Oman at the deepest structural levels exposed in the Oman Mountains. Structural mapping combined with thermobarometry and U-Pb and 40Ar-39Ar geochronology show that the leading edge of the Arabian continental margin was dragged down the subduction zone to >80 km depth during the later stages of ophiolite obduction. Intense high-strain shear zones occur throughout the HP region with development of one of the World’s largest and best preserved sheath folds in Wadi Mayh. This project involves regional structural mapping and micro-structrual analysis in conjunction with thermobarometry and metamorphic modeling.

Selected references:

Oman Mountains fold and thrust belt, Oman and UAE.

M.P. Searle, in collaboration with M. Ali (Petroleum Institute, Abu Dhabi)

The foreland fold-thrust beneath the Oman Ophiolite comprises highly deformed deep-sea sedimentary and alkaline volcanic rocks and mélanges (Haybi complex) and Mesozoic passive margin sediments (Hawasina complex) that form a beautifully exposed imbricate thrust belt. Restoration of balanced cross-sections suggests that these rocks were emplaced approximately 300-400 km across the Arabian continental margin during the Late Cretaceous obduction of the ophiolite. Structural mapping in the mountains is combined with gravity, seismic and well data from the foreland to constrain the deep crustal structure of the thrust belt.

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Structure of the Musandam peninsula, Oman and UAE.

M.P. Searle, A.B. Watts

The northernmost peninsula of the Oman Mountains in Musandam shows the first stages of the continental collision of Arabia with Central Iran with thrust duplication of the entire Permian-Mesozoic shelf carbonates and pre-Permian basement along the Oligocene Hagab Thrust. Structural mapping, combined with gravity, seismic and well data from the Oman - United Arab Emirates foreland reveals the complex interaction of the Late Cretaceous thrust sheets folded over the Musandam mid-Tertiary culmination, with two foreland basins developed in front of the rising mountains, the Late Cretaceous Aruma basin, and the Oligocene Pabdeh basin.

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Structure of the Palmyride fold belt, Syria

M.P. Searle

The Palmyride fold belt in central Syria extend northeast away from the Dead Sea Fault and developed as a result of Tertiary inversion of an intra-continental basin combined with right-lateral transpression. Balanced and restored cross-sections across the box-folded structures from Damascus east to Tudmor (Palmyra) reveal low amounts of crustal shortening with dextral torque during the Late Tertiary. We are studying the timing of inversion and compression in comparison with the timing of motion along the Levant fracture or Dead Sea Fault system.

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Dead Sea Fault, Syria and Jordan

M.P. Searle

The Dead Sea Fault is a major left-lateral strike-slip fault bounding the western margin of Arabia stretching from the Red Sea - Gulf of Aqaba north through the Dead Sea pull-apart basin to the Yammouneh restraining bend in Lebanon northwards into Syria. The northern part of the Dead Sea Fault cuts the Syrian coastal range folds and terminates in the north in a major trans-tensional pull-apart basin (Al-Ghab depression). Structural mapping combined with 40Ar-39Ar dating of Neogene alkali basalts is used to constrain amounts of left-lateral strike-slip motion and throw across the bounding normal faults.