Compositional variation of olivine related to high–temperature serpentinization of peridotites: Evidence from the Oeyama ophiolite
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- NOZAKA Toshio
- Department of Earth Sciences, Okayama University
抄録
<p>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.</p>
収録刊行物
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- Journal of Mineralogical and Petrological Sciences
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Journal of Mineralogical and Petrological Sciences 113 (5), 219-231, 2018
一般社団法人 日本鉱物科学会
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詳細情報 詳細情報について
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- CRID
- 1390282763070409984
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- NII論文ID
- 130007506101
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- ISSN
- 13493825
- 13456296
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- Crossref
- CiNii Articles
- KAKEN
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- 抄録ライセンスフラグ
- 使用不可