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Mass transfer into the leading edge of the mantle wedge: Initial results from Oman Drilling Project Hole BT1B
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  • Peter B Kelemen,
  • Juan Carlos de Obeso,
  • James Andrew Leong,
  • Marguerite Godard,
  • Keishi Okazaki,
  • Alissa Jeanne Kotowski,
  • Craig Manning,
  • Eric T Ellison,
  • Manuel D Menzel,
  • Janos Urai,
  • Greg Hirth,
  • Matthew Rioux,
  • Daniel Fritz Stockli,
  • Romain Lafay,
  • Andreas Beinlich,
  • Jude A. Coggon,
  • Nehal H. Warsi,
  • Juerg Matter,
  • Damon Teagle,
  • Katsuyoshi Michibayashi,
  • Eiichi Takazawa,
  • Zaher Al Sulaimani,
  • Michelle Harris
Peter B Kelemen
Columbia University

Corresponding Author:[email protected]

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Juan Carlos de Obeso
University of Calgary
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James Andrew Leong
Lamont Doherty Earth Observatory
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Marguerite Godard
Universite de Montpellier
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Keishi Okazaki
Japan Agency for Marine-Earth Science and Technology
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Alissa Jeanne Kotowski
McGill University
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Craig Manning
University of California Los Angeles
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Eric T Ellison
University of Colorado
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Manuel D Menzel
RWTH Aachen University
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Janos Urai
RWTH Aachen University
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Greg Hirth
Brown University
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Matthew Rioux
University of California, Santa Barbara
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Daniel Fritz Stockli
University of Texas at Austin
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Romain Lafay
University of Montpellier
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Andreas Beinlich
University of Bergen
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Jude A. Coggon
National Oceanography Centre
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Nehal H. Warsi
Alara Resources Ltd.
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Juerg Matter
University of Southampton
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Damon Teagle
National Oceanography Centre Southampton
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Katsuyoshi Michibayashi
Nagoya University
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Eiichi Takazawa
Niigata University
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Zaher Al Sulaimani
Oman Water Society
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Michelle Harris
University of Plymouth
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Abstract

This paper provides an overview of research on core from Oman Drilling Project Hole BT1B and the surrounding area, plus new data and calculations, constraining processes in the Tethyan subduction zone beneath the Samail ophiolite. The area is underlain by gently dipping, broadly folded layers of allochthonous Hawasina pelagic sediments, the metamorphic sole of the Samail ophiolite, and Banded Unit peridotites at the base of the Samail mantle section. Despite reactivation of some faults during uplift of the Jebel Akdar and Saih Hatat domes, the area preserves the tectonic “stratigraphy” of the Cretaceous subduction zone. Gently dipping listvenite bands, parallel to peridotite banding and to contacts between the peridotite and the metamorphic sole, replace peridotite at and near the basal thrust. Listvenites formed at less than 200°C and (poorly constrained) depths of 25 to 40 km by reaction with CO2-rich, aqueous fluids migrating from greater depths, derived from devolatilization of subducting sediments analogous to clastic sediments in the Hawasina Formation, at 400-500°. Such processes could form important reservoirs for subducted CO2. Listvenite formation was accompanied by ductile deformation of serpentinites and listvenites – perhaps facilitated by fluid-rock reaction – in a process that could lead to aseismic subduction in some regions. Addition of H2O and CO2 to the mantle wedge, forming serpentinites and listvenites, caused large increases in the solid mass and volume of the rocks. This may have been accommodated by fractures formed as a result of volume changes, perhaps mainly at a serpentinization front.