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Basalt Mo isotope evidence for crustal recycling in continental subduction zone.

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Title: Basalt Mo isotope evidence for crustal recycling in continental subduction zone.
Authors: Fang, Wei1 (AUTHOR), Dai, Li-Qun1,2,3 (AUTHOR) lqdai@ustc.edu.cn, Zheng, Yong-Fei1,2 (AUTHOR), Zhao, Zi-Fu1,2,3 (AUTHOR)
Source: Geochimica et Cosmochimica Acta. Oct2022, Vol. 334, p273-292. 20p.
Subjects: Subduction zones, Basalt, Igneous rocks, Isotopes, Mafic rocks, Continental crust, Laser ablation inductively coupled plasma mass spectrometry
Geographic Terms: China
Abstract: Highly variable molybdenum (Mo) isotope compositions are common in mafic arc magmas above oceanic subduction zones, but Mo isotopes of mafic magmas related to continental deep subduction have not yet been documented. Here, we report for the first time the Mo isotope composition of mafic igneous rocks above a typical continental subduction zone in east-central China, where the North China Block was subducted by the South China Block in the Triassic. Continental basalts of Early Cretaceous age show negative δ98Mo values of −0.98 to −0.16 ‰, significantly lower than the normal mantle value of −0.20 ± 0.01 ‰. These basalts also exhibit arc-like trace element compositions, high (87Sr/86Sr) i ratios of 0.7050 to 0.7058, negative ε Nd (t) values of −15.2 to −10.4, and negative ε Hf (t) values of −18.7 to −7.9. The light Mo isotope signatures are associated with enrichments in not only radiogenic Sr-Nd-Hf isotopes but also melt-mobile incompatible elements in the basalts. This indicates that the mantle source of these basalts would be generated by metasomatic reaction of the mantle wedge peridotite with felsic melts derived from partial melting of the deeply subducted continental crust. Given that continental crust usually exhibits heavy Mo isotope compositions, it would be dehydrated during its subduction to subarc depths. While the dehydration would have released isotopically heavy Mo fluids from the subducting crust, it leaves isotopically light Mo in the residual crust. The dehydrated continental crust underwent partial melting at subarc depths to produce felsic melts with low δ98Mo values, transferring the light Mo isotope signature into the mantle source of the basalts. Therefore, Mo isotopes in mafic igneous rocks are a powerful means to decipher the recycling of crustal components at convergent plate margins. Our study provides the first insight into Mo isotope recycling in continental subduction zones. [ABSTRACT FROM AUTHOR]
Copyright of Geochimica et Cosmochimica Acta is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
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PubTypeId: academicJournal
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  Data: Basalt Mo isotope evidence for crustal recycling in continental subduction zone.
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  Data: <searchLink fieldCode="AR" term="%22Fang%2C+Wei%22">Fang, Wei</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Dai%2C+Li-Qun%22">Dai, Li-Qun</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)<i> lqdai@ustc.edu.cn</i><br /><searchLink fieldCode="AR" term="%22Zheng%2C+Yong-Fei%22">Zheng, Yong-Fei</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Zhao%2C+Zi-Fu%22">Zhao, Zi-Fu</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Geochimica+et+Cosmochimica+Acta%22">Geochimica et Cosmochimica Acta</searchLink>. Oct2022, Vol. 334, p273-292. 20p.
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  Data: <searchLink fieldCode="DE" term="%22Subduction+zones%22">Subduction zones</searchLink><br /><searchLink fieldCode="DE" term="%22Basalt%22">Basalt</searchLink><br /><searchLink fieldCode="DE" term="%22Igneous+rocks%22">Igneous rocks</searchLink><br /><searchLink fieldCode="DE" term="%22Isotopes%22">Isotopes</searchLink><br /><searchLink fieldCode="DE" term="%22Mafic+rocks%22">Mafic rocks</searchLink><br /><searchLink fieldCode="DE" term="%22Continental+crust%22">Continental crust</searchLink><br /><searchLink fieldCode="DE" term="%22Laser+ablation+inductively+coupled+plasma+mass+spectrometry%22">Laser ablation inductively coupled plasma mass spectrometry</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: Highly variable molybdenum (Mo) isotope compositions are common in mafic arc magmas above oceanic subduction zones, but Mo isotopes of mafic magmas related to continental deep subduction have not yet been documented. Here, we report for the first time the Mo isotope composition of mafic igneous rocks above a typical continental subduction zone in east-central China, where the North China Block was subducted by the South China Block in the Triassic. Continental basalts of Early Cretaceous age show negative δ98Mo values of −0.98 to −0.16 ‰, significantly lower than the normal mantle value of −0.20 ± 0.01 ‰. These basalts also exhibit arc-like trace element compositions, high (87Sr/86Sr) i ratios of 0.7050 to 0.7058, negative ε Nd (t) values of −15.2 to −10.4, and negative ε Hf (t) values of −18.7 to −7.9. The light Mo isotope signatures are associated with enrichments in not only radiogenic Sr-Nd-Hf isotopes but also melt-mobile incompatible elements in the basalts. This indicates that the mantle source of these basalts would be generated by metasomatic reaction of the mantle wedge peridotite with felsic melts derived from partial melting of the deeply subducted continental crust. Given that continental crust usually exhibits heavy Mo isotope compositions, it would be dehydrated during its subduction to subarc depths. While the dehydration would have released isotopically heavy Mo fluids from the subducting crust, it leaves isotopically light Mo in the residual crust. The dehydrated continental crust underwent partial melting at subarc depths to produce felsic melts with low δ98Mo values, transferring the light Mo isotope signature into the mantle source of the basalts. Therefore, Mo isotopes in mafic igneous rocks are a powerful means to decipher the recycling of crustal components at convergent plate margins. Our study provides the first insight into Mo isotope recycling in continental subduction zones. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Geochimica et Cosmochimica Acta is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1016/j.gca.2022.08.008
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 20
        StartPage: 273
    Subjects:
      – SubjectFull: Subduction zones
        Type: general
      – SubjectFull: Basalt
        Type: general
      – SubjectFull: Igneous rocks
        Type: general
      – SubjectFull: Isotopes
        Type: general
      – SubjectFull: Mafic rocks
        Type: general
      – SubjectFull: Continental crust
        Type: general
      – SubjectFull: Laser ablation inductively coupled plasma mass spectrometry
        Type: general
      – SubjectFull: China
        Type: general
    Titles:
      – TitleFull: Basalt Mo isotope evidence for crustal recycling in continental subduction zone.
        Type: main
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            NameFull: Fang, Wei
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            NameFull: Dai, Li-Qun
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            NameFull: Zheng, Yong-Fei
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            NameFull: Zhao, Zi-Fu
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          Dates:
            – D: 01
              M: 10
              Text: Oct2022
              Type: published
              Y: 2022
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            – Type: issn-print
              Value: 00167037
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            – Type: volume
              Value: 334
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            – TitleFull: Geochimica et Cosmochimica Acta
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