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Dating continental subduction beneath the Samail Ophiolite: garnet, zircon, and rutile petrochronology of the As Sifah eclogites, NE Oman
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  • Joshua Michael Garber,
  • Matthew Rioux,
  • Michael P. Searle,
  • Andrew Robert Cooper Kylander-Clark,
  • Bradley R Hacker,
  • Jeff David Vervoort,
  • Clare Warren,
  • Andrew Smye
Joshua Michael Garber
Penn State University

Corresponding Author:[email protected]

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Matthew Rioux
University of California, Santa Barbara
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Michael P. Searle
Oxford University
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Andrew Robert Cooper Kylander-Clark
University of California
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Bradley R Hacker
Department of Earth Sciences, University of California, Santa Barbara
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Jeff David Vervoort
Washington State University
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Clare Warren
Open University
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Andrew Smye
Penn State University
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Studies of the high-pressure (HP) As Sifah eclogites in the NE part of the Saih Hatat window, Oman, have used different radiometric dating results (Ar/Ar, Sm-Nd vs. U-Pb, Rb-Sr) to interpret disparate tectonic models for the timing, geometry, and cause of continental subduction – including its association with the Samail Ophiolite. To determine the absolute timing of continental subduction, we coupled geochronological and geochemical analyses of major (garnet) and accessory phases (zircon, rutile) from the highest-grade metamorphic rocks in the Saih Hatat (As Sifah eclogites). Early Permian (283.8+/-0.7 Ma) tuffaceous zircon cores are consistent with earlier interpretations that the As Sifah rocks were sourced from a distal portion of the Arabian continental margin. Data from a range of bulk compositions, metamorphic assemblages, and rock textures consistently suggest a single metamorphic event, with garnet growth starting by ~81 Ma and ceasing by ~77 Ma, with slight but consistent offsets in the timing of metamorphic (re)crystallization between different lithologies. These new data confirm previous structural, metamorphic, and geochronological interpretations for continental HP metamorphism in a single NE-dipping subduction zone beneath the already obducted Samail Ophiolite; there is no robust evidence for a ~110 Ma event or a continental-ward dipping subduction zone. Combined with literature constraints, our data suggest that the As Sifah unit was subducted and exhumed relatively slowly (~5 mm/yr) compared to other continental high-pressure settings - likely associated with the dragging to mantle depths by a mafic root, followed by long residence in the lower to middle crust.
Dec 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 12. 10.1029/2021JB022715