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Petrological evidence for stepwise accretion of metamorphic soles during subduction infancy (Semail ophiolite, Oman and UAE).

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Title: Petrological evidence for stepwise accretion of metamorphic soles during subduction infancy (Semail ophiolite, Oman and UAE).
Authors: Soret, Mathieu1 mathieu.soret@ubc.ca, Agard, Philippe1,2, Dubacq, Benoît1, Plunder, Alexis1,3, Yamato, Philippe2,4
Source: Journal of Metamorphic Geology. Dec2017, Vol. 35 Issue 9, p1051-1080. 30p.
Subjects: Petrology, Ophiolites, Amphibolites, Subduction
Geographic Terms: Oman, United Arab Emirates
Abstract: Metamorphic soles are tectonic slices welded beneath most large-scale ophiolites. These slivers of oceanic crust metamorphosed up to granulite facies conditions are interpreted as forming during the first million years of intraoceanic subduction following heat transfer from the incipient mantle wedge towards the top of the subducting plate. This study reappraises the formation of metamorphic soles through detailed field and petrological work on three key sections from the Semail ophiolite (Oman and United Arab Emirates). Based on thermobarometry and thermodynamic modelling, it is shown that metamorphic soles do not record a continuous temperature gradient, as expected from simple heating by the upper plate or by shear heating as proposed in previous studies. The upper, high- T metamorphic sole is subdivided in at least two units, testifying to the stepwise formation, detachment and accretion of successive slices from the down-going slab to the mylonitic base of the ophiolite. Estimated peak pressure-temperature conditions through the metamorphic sole, from top to bottom, are 850°C and 1 GPa, 725°C and 0.8 GPa and 530°C and 0.5 GPa. These estimates appear constant within each unit but differing between units by 100-200°C and ~0.2 GPa. Despite being separated by hundreds of kilometres below the Semail ophiolite and having contrasting locations with respect to the ridge axis position, metamorphic soles show no evidence for significant petrological variations along strike. These constraints allow us to refine the tectonic-petrological model for the genesis of metamorphic soles, formed via the stepwise stacking of several homogeneous slivers of oceanic crust and its sedimentary cover. Metamorphic soles result not so much from downward heat transfer (ironing effect) as from progressive metamorphism during strain localization and cooling of the plate interface. The successive thrusts originate from rheological contrasts between the sole, initially the top of the subducting slab, and the peridotite above as the plate interface progressively cools. These findings have implications for the thickness, the scale and the coupling state at the plate interface during the early history of subduction/obduction systems. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Metamorphic Geology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 126068987
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  Data: Petrological evidence for stepwise accretion of metamorphic soles during subduction infancy (Semail ophiolite, Oman and UAE).
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  Data: <searchLink fieldCode="AR" term="%22Soret%2C+Mathieu%22">Soret, Mathieu</searchLink><relatesTo>1</relatesTo><i> mathieu.soret@ubc.ca</i><br /><searchLink fieldCode="AR" term="%22Agard%2C+Philippe%22">Agard, Philippe</searchLink><relatesTo>1,2</relatesTo><br /><searchLink fieldCode="AR" term="%22Dubacq%2C+Benoît%22">Dubacq, Benoît</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Plunder%2C+Alexis%22">Plunder, Alexis</searchLink><relatesTo>1,3</relatesTo><br /><searchLink fieldCode="AR" term="%22Yamato%2C+Philippe%22">Yamato, Philippe</searchLink><relatesTo>2,4</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Metamorphic+Geology%22">Journal of Metamorphic Geology</searchLink>. Dec2017, Vol. 35 Issue 9, p1051-1080. 30p.
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  Data: <searchLink fieldCode="DE" term="%22Petrology%22">Petrology</searchLink><br /><searchLink fieldCode="DE" term="%22Ophiolites%22">Ophiolites</searchLink><br /><searchLink fieldCode="DE" term="%22Amphibolites%22">Amphibolites</searchLink><br /><searchLink fieldCode="DE" term="%22Subduction%22">Subduction</searchLink>
– Name: SubjectGeographic
  Label: Geographic Terms
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Oman%22">Oman</searchLink><br /><searchLink fieldCode="DE" term="%22United+Arab+Emirates%22">United Arab Emirates</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Metamorphic soles are tectonic slices welded beneath most large-scale ophiolites. These slivers of oceanic crust metamorphosed up to granulite facies conditions are interpreted as forming during the first million years of intraoceanic subduction following heat transfer from the incipient mantle wedge towards the top of the subducting plate. This study reappraises the formation of metamorphic soles through detailed field and petrological work on three key sections from the Semail ophiolite (Oman and United Arab Emirates). Based on thermobarometry and thermodynamic modelling, it is shown that metamorphic soles do not record a continuous temperature gradient, as expected from simple heating by the upper plate or by shear heating as proposed in previous studies. The upper, high- T metamorphic sole is subdivided in at least two units, testifying to the stepwise formation, detachment and accretion of successive slices from the down-going slab to the mylonitic base of the ophiolite. Estimated peak pressure-temperature conditions through the metamorphic sole, from top to bottom, are 850°C and 1 GPa, 725°C and 0.8 GPa and 530°C and 0.5 GPa. These estimates appear constant within each unit but differing between units by 100-200°C and ~0.2 GPa. Despite being separated by hundreds of kilometres below the Semail ophiolite and having contrasting locations with respect to the ridge axis position, metamorphic soles show no evidence for significant petrological variations along strike. These constraints allow us to refine the tectonic-petrological model for the genesis of metamorphic soles, formed via the stepwise stacking of several homogeneous slivers of oceanic crust and its sedimentary cover. Metamorphic soles result not so much from downward heat transfer (ironing effect) as from progressive metamorphism during strain localization and cooling of the plate interface. The successive thrusts originate from rheological contrasts between the sole, initially the top of the subducting slab, and the peridotite above as the plate interface progressively cools. These findings have implications for the thickness, the scale and the coupling state at the plate interface during the early history of subduction/obduction systems. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Metamorphic Geology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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        Value: 10.1111/jmg.12267
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 30
        StartPage: 1051
    Subjects:
      – SubjectFull: Petrology
        Type: general
      – SubjectFull: Ophiolites
        Type: general
      – SubjectFull: Amphibolites
        Type: general
      – SubjectFull: Subduction
        Type: general
      – SubjectFull: Oman
        Type: general
      – SubjectFull: United Arab Emirates
        Type: general
    Titles:
      – TitleFull: Petrological evidence for stepwise accretion of metamorphic soles during subduction infancy (Semail ophiolite, Oman and UAE).
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            NameFull: Soret, Mathieu
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            NameFull: Agard, Philippe
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            NameFull: Dubacq, Benoît
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            NameFull: Plunder, Alexis
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            NameFull: Yamato, Philippe
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            – D: 01
              M: 12
              Text: Dec2017
              Type: published
              Y: 2017
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              Value: 35
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              Value: 9
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