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Bulk silicate Earth-like 142Nd and 182W mantle component sampled by 2.0 Ga Onega Basin picrites, Fennoscandia.

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Title: Bulk silicate Earth-like 142Nd and 182W mantle component sampled by 2.0 Ga Onega Basin picrites, Fennoscandia.
Authors: Puchtel, I.S.1 (AUTHOR) ipuchtel@umd.edu, Hellmann, J.L.1 (AUTHOR), Rizo, H.2 (AUTHOR), Blichert-Toft, J.3 (AUTHOR), Stepanova, A.V.4 (AUTHOR), Samsonov, A.V.5 (AUTHOR), Walker, R.J.1 (AUTHOR)
Source: Geochimica et Cosmochimica Acta. Mar2025, Vol. 393, p133-154. 22p.
Subjects: Rare earth metals, Siderophile elements, Mantle plumes, Oceanic crust, Mass transfer, Lherzolite
Abstract: In order to further evaluate the timing and possible mechanisms responsible for the transition from both positive and negative to no 142Nd and 182W anomalies in the Archean mantle, we obtained 142,143Nd, 176Hf, 186,187Os, 182W isotope and lithophile trace and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data for mantle plume-derived ∼2.0 Ga picrites and an associated differentiated mafic–ultramafic sill from the Onega Basin on the Fennoscandian Shield. The Onega Basin picrites share striking chemical similarities with the modern Kilauea picrites, featuring enrichments in light rare earth elements (LREE; La/Sm N = 1.5 ± 0.2), depletions in heavy rare earth elements (HREE; Gd/Yb N = 2.2 ± 0.1), positive high field strength element (HFSE) anomalies (Hf/Hf* = 1.2 ± 0.1, Nb/Nb* = 1.6 ± 0.1), and modern bulk silicate Earth (BSE)-like average W/Th = 0.20 ± 0.08 (2SD). Model calculations indicate that the parental picritic magmas were likely derived from 3 % equilibrium batch melting of a LREE-depleted garnet lherzolite PREMA-type mantle source containing a component of recycled oceanic crust. The 147Sm-143Nd, 176Lu-176Hf, and 187Re-187Os mineral-whole-rock isochron ages constrain precisely the timing of the Onega Basin lava emplacement at ∼1974 Ma. The corresponding initial ε143Nd = +3.0 ± 0.5 and ε176Hf = +2.8 ± 1.2 values indicate evolution of the Onega mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The lower ε176Hf relative to ε143Nd further implies decoupling of the two lithophile element isotope systems in the source. The initial μ186Os and γ187Os values are suprachondritic at +4.9 ± 2.1 and +2.9 ± 0.4, respectively, indicating evolution of the Onega mantle plume source with time-integrated slightly suprachondritic Pt/Os and Re/Os ratios. The μ142Nd = –1.1 ± 3.3 (2SD) and μ182W = 0.0 ± 4.8 (2SD) obtained for the Onega picritic magmas are unresolvable from the modern BSE values, implying that their mantle source had 142Nd and 182W compositions similar to those of the BSE. When considered together, the trace element systematics, suprachondritic Pt/Os and Re/Os ratios, and Hf-Nd isotopic decoupling are best explained in terms of incorporation into the Onega mantle plume source of 10–20 % recycled komatiite-basalt crust aged in the mantle for 1 to 2 Ga. These results provide new evidence that 142Nd and 182W anomalies that were common in the Archean mantle were effectively homogenized by 2.0 Ga ago on the scale of the mantle domains sampled by the Onega Basin magmas. This may have occurred due to the enhanced convective whole-mantle mass and heat transfer facilitated by processes of oceanic crust recycling that may have operated since at least the early Archean. [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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  Label: Title
  Group: Ti
  Data: Bulk silicate Earth-like 142Nd and 182W mantle component sampled by 2.0 Ga Onega Basin picrites, Fennoscandia.
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  Data: <searchLink fieldCode="AR" term="%22Puchtel%2C+I%2ES%2E%22">Puchtel, I.S.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> ipuchtel@umd.edu</i><br /><searchLink fieldCode="AR" term="%22Hellmann%2C+J%2EL%2E%22">Hellmann, J.L.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Rizo%2C+H%2E%22">Rizo, H.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Blichert-Toft%2C+J%2E%22">Blichert-Toft, J.</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Stepanova%2C+A%2EV%2E%22">Stepanova, A.V.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Samsonov%2C+A%2EV%2E%22">Samsonov, A.V.</searchLink><relatesTo>5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Walker%2C+R%2EJ%2E%22">Walker, R.J.</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Geochimica+et+Cosmochimica+Acta%22">Geochimica et Cosmochimica Acta</searchLink>. Mar2025, Vol. 393, p133-154. 22p.
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  Data: <searchLink fieldCode="DE" term="%22Rare+earth+metals%22">Rare earth metals</searchLink><br /><searchLink fieldCode="DE" term="%22Siderophile+elements%22">Siderophile elements</searchLink><br /><searchLink fieldCode="DE" term="%22Mantle+plumes%22">Mantle plumes</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanic+crust%22">Oceanic crust</searchLink><br /><searchLink fieldCode="DE" term="%22Mass+transfer%22">Mass transfer</searchLink><br /><searchLink fieldCode="DE" term="%22Lherzolite%22">Lherzolite</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: In order to further evaluate the timing and possible mechanisms responsible for the transition from both positive and negative to no 142Nd and 182W anomalies in the Archean mantle, we obtained 142,143Nd, 176Hf, 186,187Os, 182W isotope and lithophile trace and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data for mantle plume-derived ∼2.0 Ga picrites and an associated differentiated mafic–ultramafic sill from the Onega Basin on the Fennoscandian Shield. The Onega Basin picrites share striking chemical similarities with the modern Kilauea picrites, featuring enrichments in light rare earth elements (LREE; La/Sm N = 1.5 ± 0.2), depletions in heavy rare earth elements (HREE; Gd/Yb N = 2.2 ± 0.1), positive high field strength element (HFSE) anomalies (Hf/Hf* = 1.2 ± 0.1, Nb/Nb* = 1.6 ± 0.1), and modern bulk silicate Earth (BSE)-like average W/Th = 0.20 ± 0.08 (2SD). Model calculations indicate that the parental picritic magmas were likely derived from 3 % equilibrium batch melting of a LREE-depleted garnet lherzolite PREMA-type mantle source containing a component of recycled oceanic crust. The 147Sm-143Nd, 176Lu-176Hf, and 187Re-187Os mineral-whole-rock isochron ages constrain precisely the timing of the Onega Basin lava emplacement at ∼1974 Ma. The corresponding initial ε143Nd = +3.0 ± 0.5 and ε176Hf = +2.8 ± 1.2 values indicate evolution of the Onega mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The lower ε176Hf relative to ε143Nd further implies decoupling of the two lithophile element isotope systems in the source. The initial μ186Os and γ187Os values are suprachondritic at +4.9 ± 2.1 and +2.9 ± 0.4, respectively, indicating evolution of the Onega mantle plume source with time-integrated slightly suprachondritic Pt/Os and Re/Os ratios. The μ142Nd = –1.1 ± 3.3 (2SD) and μ182W = 0.0 ± 4.8 (2SD) obtained for the Onega picritic magmas are unresolvable from the modern BSE values, implying that their mantle source had 142Nd and 182W compositions similar to those of the BSE. When considered together, the trace element systematics, suprachondritic Pt/Os and Re/Os ratios, and Hf-Nd isotopic decoupling are best explained in terms of incorporation into the Onega mantle plume source of 10–20 % recycled komatiite-basalt crust aged in the mantle for 1 to 2 Ga. These results provide new evidence that 142Nd and 182W anomalies that were common in the Archean mantle were effectively homogenized by 2.0 Ga ago on the scale of the mantle domains sampled by the Onega Basin magmas. This may have occurred due to the enhanced convective whole-mantle mass and heat transfer facilitated by processes of oceanic crust recycling that may have operated since at least the early Archean. [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:
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    Identifiers:
      – Type: doi
        Value: 10.1016/j.gca.2025.01.013
    Languages:
      – Code: eng
        Text: English
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      Pagination:
        PageCount: 22
        StartPage: 133
    Subjects:
      – SubjectFull: Rare earth metals
        Type: general
      – SubjectFull: Siderophile elements
        Type: general
      – SubjectFull: Mantle plumes
        Type: general
      – SubjectFull: Oceanic crust
        Type: general
      – SubjectFull: Mass transfer
        Type: general
      – SubjectFull: Lherzolite
        Type: general
    Titles:
      – TitleFull: Bulk silicate Earth-like 142Nd and 182W mantle component sampled by 2.0 Ga Onega Basin picrites, Fennoscandia.
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              Text: Mar2025
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