Compositional variation of olivine related to high-temperature serpentinization of peridotites: Evidence from the Oeyama ophiolite

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Abstract

Compositional variation of olivine in serpentinized peridotites provides a significant constraint on modeling the redox conditions of serpentinization and the tectonothermal history of ophiolites. Here I report the variations of Fe, Mg, Mn, and Ni contents of olivine from the Oeyama ophiolite, SW Japan and show textural and chemical evidence for compositional modification of olivine related to high-temperature (T ) serpentinization. The Fe- enrichment of olivine adjacent to antigorite without significant magnetite formation indicates a reducing condition for high-T serpentinization. Systematic variations of forsterite (Fo) component with distance from antigorite suggest Mg-Fe volume diffusion took place in olivine porphyroclasts under the conditions of high-T serpentinization. In addition, a similar diffusion pattern of Mn to Fe results in a retrograde trend in MnO-Fo diagram, which could be a useful indicator of high-T serpentinization. Retrograde antigorite is different from prograde antigorite in having a shape of elongated blade, lacking a significant amount of magnetite inclusion, and being more ferrous than lizardite. The existence of retrograde antigorite provides another piece of evidence for high-T serpentinization even if olivine has been decomposed by intense low-T serpentinization. Approximate estimation of time required for the observed Mg-Fe diffusion profiles of olivine porphyroclasts reveals that a cooling duration under the conditions of high-T serpentinization was much longer than that of amphibolite- facies metasomatism previously reported. This suggests a long residence time of the forearc peridotites within the serpentinized mantle wedge following rapid exhumation immediately after the amphibolite-facies metasomatism.

Original languageEnglish
Pages (from-to)219-231
Number of pages13
JournalJournal of Mineralogical and Petrological Sciences
Volume113
Issue number5
DOIs
Publication statusPublished - Jan 1 2018

Fingerprint

serpentinization
ophiolite
olivine
antigorite
forsterite
magnetite
metasomatism
amphibolite facies
lizardite
blades
redox conditions
wedges
exhumation
Japan
Earth mantle
residence time
diagrams
histories
inclusions
trends

Keywords

  • High-temperature serpentinization
  • Olivine composition
  • Retrograde antigorite
  • Retrograde olivine
  • Volume diffusion

ASJC Scopus subject areas

  • Geophysics
  • Geology

Cite this

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title = "Compositional variation of olivine related to high-temperature serpentinization of peridotites: Evidence from the Oeyama ophiolite",
abstract = "Compositional variation of olivine in serpentinized peridotites provides a significant constraint on modeling the redox conditions of serpentinization and the tectonothermal history of ophiolites. Here I report the variations of Fe, Mg, Mn, and Ni contents of olivine from the Oeyama ophiolite, SW Japan and show textural and chemical evidence for compositional modification of olivine related to high-temperature (T ) serpentinization. The Fe- enrichment of olivine adjacent to antigorite without significant magnetite formation indicates a reducing condition for high-T serpentinization. Systematic variations of forsterite (Fo) component with distance from antigorite suggest Mg-Fe volume diffusion took place in olivine porphyroclasts under the conditions of high-T serpentinization. In addition, a similar diffusion pattern of Mn to Fe results in a retrograde trend in MnO-Fo diagram, which could be a useful indicator of high-T serpentinization. Retrograde antigorite is different from prograde antigorite in having a shape of elongated blade, lacking a significant amount of magnetite inclusion, and being more ferrous than lizardite. The existence of retrograde antigorite provides another piece of evidence for high-T serpentinization even if olivine has been decomposed by intense low-T serpentinization. Approximate estimation of time required for the observed Mg-Fe diffusion profiles of olivine porphyroclasts reveals that a cooling duration under the conditions of high-T serpentinization was much longer than that of amphibolite- facies metasomatism previously reported. This suggests a long residence time of the forearc peridotites within the serpentinized mantle wedge following rapid exhumation immediately after the amphibolite-facies metasomatism.",
keywords = "High-temperature serpentinization, Olivine composition, Retrograde antigorite, Retrograde olivine, Volume diffusion",
author = "Toshio Nozaka",
year = "2018",
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doi = "10.2465/jmps.180420",
language = "English",
volume = "113",
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T1 - Compositional variation of olivine related to high-temperature serpentinization of peridotites

T2 - Evidence from the Oeyama ophiolite

AU - Nozaka, Toshio

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N2 - Compositional variation of olivine in serpentinized peridotites provides a significant constraint on modeling the redox conditions of serpentinization and the tectonothermal history of ophiolites. Here I report the variations of Fe, Mg, Mn, and Ni contents of olivine from the Oeyama ophiolite, SW Japan and show textural and chemical evidence for compositional modification of olivine related to high-temperature (T ) serpentinization. The Fe- enrichment of olivine adjacent to antigorite without significant magnetite formation indicates a reducing condition for high-T serpentinization. Systematic variations of forsterite (Fo) component with distance from antigorite suggest Mg-Fe volume diffusion took place in olivine porphyroclasts under the conditions of high-T serpentinization. In addition, a similar diffusion pattern of Mn to Fe results in a retrograde trend in MnO-Fo diagram, which could be a useful indicator of high-T serpentinization. Retrograde antigorite is different from prograde antigorite in having a shape of elongated blade, lacking a significant amount of magnetite inclusion, and being more ferrous than lizardite. The existence of retrograde antigorite provides another piece of evidence for high-T serpentinization even if olivine has been decomposed by intense low-T serpentinization. Approximate estimation of time required for the observed Mg-Fe diffusion profiles of olivine porphyroclasts reveals that a cooling duration under the conditions of high-T serpentinization was much longer than that of amphibolite- facies metasomatism previously reported. This suggests a long residence time of the forearc peridotites within the serpentinized mantle wedge following rapid exhumation immediately after the amphibolite-facies metasomatism.

AB - Compositional variation of olivine in serpentinized peridotites provides a significant constraint on modeling the redox conditions of serpentinization and the tectonothermal history of ophiolites. Here I report the variations of Fe, Mg, Mn, and Ni contents of olivine from the Oeyama ophiolite, SW Japan and show textural and chemical evidence for compositional modification of olivine related to high-temperature (T ) serpentinization. The Fe- enrichment of olivine adjacent to antigorite without significant magnetite formation indicates a reducing condition for high-T serpentinization. Systematic variations of forsterite (Fo) component with distance from antigorite suggest Mg-Fe volume diffusion took place in olivine porphyroclasts under the conditions of high-T serpentinization. In addition, a similar diffusion pattern of Mn to Fe results in a retrograde trend in MnO-Fo diagram, which could be a useful indicator of high-T serpentinization. Retrograde antigorite is different from prograde antigorite in having a shape of elongated blade, lacking a significant amount of magnetite inclusion, and being more ferrous than lizardite. The existence of retrograde antigorite provides another piece of evidence for high-T serpentinization even if olivine has been decomposed by intense low-T serpentinization. Approximate estimation of time required for the observed Mg-Fe diffusion profiles of olivine porphyroclasts reveals that a cooling duration under the conditions of high-T serpentinization was much longer than that of amphibolite- facies metasomatism previously reported. This suggests a long residence time of the forearc peridotites within the serpentinized mantle wedge following rapid exhumation immediately after the amphibolite-facies metasomatism.

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