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Tracing mantle metasomatism: Geochemical and isotopic clues from Neo-Tethyan suprasubduction zone ophiolite.

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Title: Tracing mantle metasomatism: Geochemical and isotopic clues from Neo-Tethyan suprasubduction zone ophiolite.
Authors: Xiong, Fahui1 xiongfahui@126.com, Zoheir, Basem2 basem.zoheir@gmail.com, Xu, Xiangzhen1, Liu, Zhao3, Qiu, Tian1, Yang, Jingsui1
Source: Geological Society of America Bulletin. Nov2025, Vol. 137 Issue 11/12, p4629-4648. 20p.
Subject Terms: *Ophiolites, *Peridotite, *Isotopic analysis, *Tethys (Paleogeography), *Earth's mantle, *Analytical geochemistry, *Subduction, *Subduction zones
Geographic Terms: Tibet (China)
Abstract: Scientific diamond drilling into the Purang massif, located in the western YarlungZangbo suture zone, Southwest Tibet, provides critical insights into the petrographic and geochemical evolution of Neo-Tethyan suprasubduction zone ophiolites. This study integrates structural, geochemical, and petrological data to reconstruct the formation and subsequent evolution of peridotites and associated lithologies, with implications for broader geodynamic processes. The massif predominantly consists of harzburgite, along with subordinate lherzolite, pyroxenite, and dunite (ca. 130 Ma), all of which are variably serpentinized (loss on ignition [LOI] of up to ∼11 wt%). Geochemical features, including high MgO (42.68– 46.24 wt%), low Al2O3 (0.7–1.18 wt%), and U-shaped rare earth element patterns, point to initial formation in a mid-ocean ridge setting with ∼10%–15% partial melting, which produced Cr- and Mg-enriched residues (Cr# 0.3–0.4; Mg# 0.88–0.92). Subsequent interactions with hydrous melts in a suprasubduction zone environment, combined with distal subduction components, led to the formation of high-Cr chromitites (Cr2O3 ≤ 60%), dunite pods, and clinopyroxene-bearing harzburgite. Re-Os isotopic data (187Os/188Os: 0.12479–0.12846; γOs: −2.74 to 0.12) and pressure-temperature estimates (2.0–2.7 GPa, 745–1067 °C) suggest a polyphase genesis involving melt percolation and mantle interaction. Platinum-group element (PGE) patterns show Pt and Pd depletion and enrichment in iridium-group PGEs in dunite, which reflects fractionated melts. Additionally, Mg isotopic data (δ26Mg: −0.67‰ to −0.22‰) emphasize the role of metasomatic processes, which indicates interaction with isotopically light fluids during subduction and mantle modification. This study provides compelling evidence of the multiphase genesis of the Purang peridotites, and shows they were shaped by midocean ridge extension, subduction dynamics, plume-induced lithospheric modification, and detachment faulting. These findings refine models of mantle evolution, oceanic lithosphere formation, and subduction zone dynamics, and highlight how detachment faulting, coupled with the emplacement of the Purang ophiolite, contributed to the evolution of oceanic lithosphere in the NeoTethyan realm. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
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  Data: Tracing mantle metasomatism: Geochemical and isotopic clues from Neo-Tethyan suprasubduction zone ophiolite.
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  Data: <searchLink fieldCode="AR" term="%22Xiong%2C+Fahui%22">Xiong, Fahui</searchLink><relatesTo>1</relatesTo><i> xiongfahui@126.com</i><br /><searchLink fieldCode="AR" term="%22Zoheir%2C+Basem%22">Zoheir, Basem</searchLink><relatesTo>2</relatesTo><i> basem.zoheir@gmail.com</i><br /><searchLink fieldCode="AR" term="%22Xu%2C+Xiangzhen%22">Xu, Xiangzhen</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Liu%2C+Zhao%22">Liu, Zhao</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Qiu%2C+Tian%22">Qiu, Tian</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Yang%2C+Jingsui%22">Yang, Jingsui</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Geological+Society+of+America+Bulletin%22">Geological Society of America Bulletin</searchLink>. Nov2025, Vol. 137 Issue 11/12, p4629-4648. 20p.
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  Data: *<searchLink fieldCode="DE" term="%22Ophiolites%22">Ophiolites</searchLink><br />*<searchLink fieldCode="DE" term="%22Peridotite%22">Peridotite</searchLink><br />*<searchLink fieldCode="DE" term="%22Isotopic+analysis%22">Isotopic analysis</searchLink><br />*<searchLink fieldCode="DE" term="%22Tethys+%28Paleogeography%29%22">Tethys (Paleogeography)</searchLink><br />*<searchLink fieldCode="DE" term="%22Earth's+mantle%22">Earth's mantle</searchLink><br />*<searchLink fieldCode="DE" term="%22Analytical+geochemistry%22">Analytical geochemistry</searchLink><br />*<searchLink fieldCode="DE" term="%22Subduction%22">Subduction</searchLink><br />*<searchLink fieldCode="DE" term="%22Subduction+zones%22">Subduction zones</searchLink>
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  Label: Geographic Terms
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  Data: <searchLink fieldCode="DE" term="%22Tibet+%28China%29%22">Tibet (China)</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Scientific diamond drilling into the Purang massif, located in the western YarlungZangbo suture zone, Southwest Tibet, provides critical insights into the petrographic and geochemical evolution of Neo-Tethyan suprasubduction zone ophiolites. This study integrates structural, geochemical, and petrological data to reconstruct the formation and subsequent evolution of peridotites and associated lithologies, with implications for broader geodynamic processes. The massif predominantly consists of harzburgite, along with subordinate lherzolite, pyroxenite, and dunite (ca. 130 Ma), all of which are variably serpentinized (loss on ignition [LOI] of up to ∼11 wt%). Geochemical features, including high MgO (42.68– 46.24 wt%), low Al2O3 (0.7–1.18 wt%), and U-shaped rare earth element patterns, point to initial formation in a mid-ocean ridge setting with ∼10%–15% partial melting, which produced Cr- and Mg-enriched residues (Cr# 0.3–0.4; Mg# 0.88–0.92). Subsequent interactions with hydrous melts in a suprasubduction zone environment, combined with distal subduction components, led to the formation of high-Cr chromitites (Cr2O3 ≤ 60%), dunite pods, and clinopyroxene-bearing harzburgite. Re-Os isotopic data (187Os/188Os: 0.12479–0.12846; γOs: −2.74 to 0.12) and pressure-temperature estimates (2.0–2.7 GPa, 745–1067 °C) suggest a polyphase genesis involving melt percolation and mantle interaction. Platinum-group element (PGE) patterns show Pt and Pd depletion and enrichment in iridium-group PGEs in dunite, which reflects fractionated melts. Additionally, Mg isotopic data (δ26Mg: −0.67‰ to −0.22‰) emphasize the role of metasomatic processes, which indicates interaction with isotopically light fluids during subduction and mantle modification. This study provides compelling evidence of the multiphase genesis of the Purang peridotites, and shows they were shaped by midocean ridge extension, subduction dynamics, plume-induced lithospheric modification, and detachment faulting. These findings refine models of mantle evolution, oceanic lithosphere formation, and subduction zone dynamics, and highlight how detachment faulting, coupled with the emplacement of the Purang ophiolite, contributed to the evolution of oceanic lithosphere in the NeoTethyan realm. [ABSTRACT FROM AUTHOR]
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=enr&AN=190288092
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1130/B38301.1
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 20
        StartPage: 4629
    Subjects:
      – SubjectFull: Ophiolites
        Type: general
      – SubjectFull: Peridotite
        Type: general
      – SubjectFull: Isotopic analysis
        Type: general
      – SubjectFull: Tethys (Paleogeography)
        Type: general
      – SubjectFull: Earth's mantle
        Type: general
      – SubjectFull: Analytical geochemistry
        Type: general
      – SubjectFull: Subduction
        Type: general
      – SubjectFull: Subduction zones
        Type: general
      – SubjectFull: Tibet (China)
        Type: general
    Titles:
      – TitleFull: Tracing mantle metasomatism: Geochemical and isotopic clues from Neo-Tethyan suprasubduction zone ophiolite.
        Type: main
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          Name:
            NameFull: Xiong, Fahui
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            NameFull: Zoheir, Basem
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            NameFull: Xu, Xiangzhen
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            NameFull: Liu, Zhao
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            NameFull: Qiu, Tian
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            NameFull: Yang, Jingsui
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            – D: 01
              M: 11
              Text: Nov2025
              Type: published
              Y: 2025
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              Value: 137
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              Value: 11/12
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            – TitleFull: Geological Society of America Bulletin
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