Structure of the metamorphic sole to the Oman Ophiolite, Sumeini Window and Wadi Tayyin: implications for ophiolite obduction processes
Published:January 01, 2014
R. J. Cowan, M. P. Searle, D. J. Waters, 2014. "Structure of the metamorphic sole to the Oman Ophiolite, Sumeini Window and Wadi Tayyin: implications for ophiolite obduction processes", Tectonic Evolution of the Oman Mountains, H. R. Rollinson, M. P. Searle, I. A. Abbasi, A. I. Al-Lazki, M. H. Al Kindi
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Two localities where the inverted metamorphic sole of the Oman Ophiolite are best exposed, Sumeini Window and Wadi Tayyin, have been mapped and sampled in greater detail. In both areas an inverted pressure and temperature profile is exposed beneath the Semail Thrust, the base of the ophiolite, from garnet+clinopyroxene-bearing granulite to hornblende+plagioclase amphibolite down through epidote amphibolite and a variety of greenschist facies metasediments, dominantly cherts, marbles and quartzites. Thermobarometry on garnet- and clinopyroxene-bearing amphibolites immediately beneath the contact with mantle sequence harzburgites shows that the upper sole rocks formed at pressure–temperature (P–T) conditions of 770–900 °C and 11–13 kbar, equivalent to depths of 30–40 km in oceanic lithosphere. Heat for metamorphism can only have been derived from the overlying mantle sequence peridotites. Pressures are higher than can be accounted for by the thickness of the ophiolite (15–20 km). Timing of peak metamorphism was synchronous with the formation of the ophiolite gabbroic–trondhjemite crustal sequence and eruption of the pillow lavas (Cenomanian; 96–95 Ma). Metamorphic sole rocks have been structurally repeated by imbricate thrusting, casting doubt on previous estimates of thermal gradients. All the data support a subduction zone setting for metamorphism and a supra-subduction zone environment for ophiolite formation during the Cenomanian.
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Tectonic Evolution of the Oman Mountains
The Oman Mountains contain one of the world's best- exposed and best-understood fold–thrust belts and the largest, best-exposed and most intensively studied ophiolite complex on Earth. This volume presents new international research from authors currently active in the field focusing on the geology of the Oman Mountains, the foreland region, the carbonate platforms of Northern and Central Oman and the underlying basement complex. In addition there is a particular focus on geoconservation in the region. The volume is divided into three main sections that discuss the tectonics of the Arabian plate using insights from geophysics, petrology, structural geology, geochronology and palaeontology; the petrology and geochemistry of the Oman Ophiolite and the sedimentary and hydrocarbon systems of Oman, drawing on the geophysics, structure and sedimentology of these systems. The volume is enhanced by numerous colour images provided courtesy of Petroleum Development Oman.