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Fe isotope decoding of fluid-absent versus fluid-present melting of deeply subducted continental crust.

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Title: Fe isotope decoding of fluid-absent versus fluid-present melting of deeply subducted continental crust.
Authors: Er-Lin Zhu1, Qiong-Xia Xia1 qxxia@ustc.edu.cn, Yi-Xiang Chen1, Ren-Xu Chen1, Hao-Hong Shu1, Zhao-Ya Li1, Yong-Fei Zheng1
Source: Geology. Nov2025, Vol. 53 Issue 11, p924-928. 5p.
Subject Terms: *Iron isotopes, *Continental crust, *Migmatite, *Melting, *Orogenic belts, *Metamorphic rocks
Geographic Terms: China
Abstract: Fluid-present melting and fluid-absent melting are two primary mechanisms for the chemical differentiation of continental crust. However, it is still challenging to decode these processes with conventional geochemical methods. In this study, we present systematic Fe isotope data of anatectic migmatites and gneisses from the Dabie orogen, China, which were formed by different mechanisms of crustal anatexis. Fluid-present melting of biotite generates migmatites with restricted Fe3+/ΣFe (0.31-0.44) and homogeneous δ56Fe values (0.06‰-0.17‰). In contrast, fluid-absent melting of phengite produces migmatites and migmatitic gneisses with dramatic Fe3+/ΣFe (0.26-0.94) and δ56Fe (0.04‰-0.61‰) variations. Quantitative modeling of Fe distribution during partial melting reveals that Fe isotope fractionation is governed by source mineral assemblages under varying melting regimes. During fluid-absent melting, the reactant phengite has much higher Fe3+/ΣFe and δ56Fe values than the peritectic biotite, resulting in high and heterogeneous δ56Fe values in the complementary melt. In contrast, during fluid-present melting, the reactant biotite and peritectic amphibole have similarly low Fe3+/ΣFe and δ56Fe values, leading to low and homogeneous δ56Fe values in the complementary melt. This establishes Fe isotopes as a novel tracer for crustal anatexis, critical for understanding continental reworking and intracrustal differentiation. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
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DbLabel: Energy & Power Source
An: 189404222
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  Label: Title
  Group: Ti
  Data: Fe isotope decoding of fluid-absent versus fluid-present melting of deeply subducted continental crust.
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  Data: <searchLink fieldCode="AR" term="%22Er-Lin+Zhu%22">Er-Lin Zhu</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Qiong-Xia+Xia%22">Qiong-Xia Xia</searchLink><relatesTo>1</relatesTo><i> qxxia@ustc.edu.cn</i><br /><searchLink fieldCode="AR" term="%22Yi-Xiang+Chen%22">Yi-Xiang Chen</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Ren-Xu+Chen%22">Ren-Xu Chen</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Hao-Hong+Shu%22">Hao-Hong Shu</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Zhao-Ya+Li%22">Zhao-Ya Li</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Yong-Fei+Zheng%22">Yong-Fei Zheng</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Geology%22">Geology</searchLink>. Nov2025, Vol. 53 Issue 11, p924-928. 5p.
– Name: Subject
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  Data: *<searchLink fieldCode="DE" term="%22Iron+isotopes%22">Iron isotopes</searchLink><br />*<searchLink fieldCode="DE" term="%22Continental+crust%22">Continental crust</searchLink><br />*<searchLink fieldCode="DE" term="%22Migmatite%22">Migmatite</searchLink><br />*<searchLink fieldCode="DE" term="%22Melting%22">Melting</searchLink><br />*<searchLink fieldCode="DE" term="%22Orogenic+belts%22">Orogenic belts</searchLink><br />*<searchLink fieldCode="DE" term="%22Metamorphic+rocks%22">Metamorphic rocks</searchLink>
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  Label: Geographic Terms
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  Data: <searchLink fieldCode="DE" term="%22China%22">China</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Fluid-present melting and fluid-absent melting are two primary mechanisms for the chemical differentiation of continental crust. However, it is still challenging to decode these processes with conventional geochemical methods. In this study, we present systematic Fe isotope data of anatectic migmatites and gneisses from the Dabie orogen, China, which were formed by different mechanisms of crustal anatexis. Fluid-present melting of biotite generates migmatites with restricted Fe3+/ΣFe (0.31-0.44) and homogeneous δ56Fe values (0.06‰-0.17‰). In contrast, fluid-absent melting of phengite produces migmatites and migmatitic gneisses with dramatic Fe3+/ΣFe (0.26-0.94) and δ56Fe (0.04‰-0.61‰) variations. Quantitative modeling of Fe distribution during partial melting reveals that Fe isotope fractionation is governed by source mineral assemblages under varying melting regimes. During fluid-absent melting, the reactant phengite has much higher Fe3+/ΣFe and δ56Fe values than the peritectic biotite, resulting in high and heterogeneous δ56Fe values in the complementary melt. In contrast, during fluid-present melting, the reactant biotite and peritectic amphibole have similarly low Fe3+/ΣFe and δ56Fe values, leading to low and homogeneous δ56Fe values in the complementary melt. This establishes Fe isotopes as a novel tracer for crustal anatexis, critical for understanding continental reworking and intracrustal differentiation. [ABSTRACT FROM AUTHOR]
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1130/G52997.1
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 5
        StartPage: 924
    Subjects:
      – SubjectFull: Iron isotopes
        Type: general
      – SubjectFull: Continental crust
        Type: general
      – SubjectFull: Migmatite
        Type: general
      – SubjectFull: Melting
        Type: general
      – SubjectFull: Orogenic belts
        Type: general
      – SubjectFull: Metamorphic rocks
        Type: general
      – SubjectFull: China
        Type: general
    Titles:
      – TitleFull: Fe isotope decoding of fluid-absent versus fluid-present melting of deeply subducted continental crust.
        Type: main
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            NameFull: Er-Lin Zhu
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            NameFull: Qiong-Xia Xia
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            NameFull: Yi-Xiang Chen
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            NameFull: Ren-Xu Chen
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            NameFull: Hao-Hong Shu
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            NameFull: Zhao-Ya Li
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            NameFull: Yong-Fei Zheng
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            – D: 01
              M: 11
              Text: Nov2025
              Type: published
              Y: 2025
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              Value: 00917613
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              Value: 53
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              Value: 11
          Titles:
            – TitleFull: Geology
              Type: main
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