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 language | English |
|---|---|
| Pages (from-to) | 219-231 |
| Number of pages | 13 |
| Journal | Journal of Mineralogical and Petrological Sciences |
| Volume | 113 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - Jan 1 2018 |
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Keywords
- High-temperature serpentinization
- Olivine composition
- Retrograde antigorite
- Retrograde olivine
- Volume diffusion
ASJC Scopus subject areas
- Geophysics
- Geology
Cite this
Compositional variation of olivine related to high-temperature serpentinization of peridotites : Evidence from the Oeyama ophiolite. / Nozaka, Toshio.
In: Journal of Mineralogical and Petrological Sciences, Vol. 113, No. 5, 01.01.2018, p. 219-231.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Compositional variation of olivine related to high-temperature serpentinization of peridotites
T2 - Evidence from the Oeyama ophiolite
AU - Nozaka, Toshio
PY - 2018/1/1
Y1 - 2018/1/1
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.
KW - High-temperature serpentinization
KW - Olivine composition
KW - Retrograde antigorite
KW - Retrograde olivine
KW - Volume diffusion
UR - http://www.scopus.com/inward/record.url?scp=85056413323&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85056413323&partnerID=8YFLogxK
U2 - 10.2465/jmps.180420
DO - 10.2465/jmps.180420
M3 - Article
AN - SCOPUS:85056413323
VL - 113
SP - 219
EP - 231
JO - Journal of Mineralogical and Petrological Sciences
JF - Journal of Mineralogical and Petrological Sciences
SN - 1345-6296
IS - 5
ER -