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Tracing Proterozoic arc mantle Hf isotope depletion of southern Fennoscandia through coupled zircon U–Pb and Lu–Hf isotopes

Petersson, Andreas LU ; Bjärnborg, Karolina LU ; Scherstén, Anders LU ; Gerdes, Axel and Næraa, Tomas LU (2017) In Lithos 284-285. p.122-131
Abstract

Constraints on the composition of the depleted mantle Sm–Nd and Lu–Hf crust formation ages have a long history of scientific debate. When calculating mantle extraction ages, and constructing crustal growth models, a linear evolution of incompatible trace elements in a depleted mantle since > 4 Ga is routinely used. Mantle depletion however varies regionally and over time and subduction of sediments and oceanic crust renders a mantle-wedge variously enriched relative to a modelled depleted mantle. Here we show that primitive mantle-derived subduction related gabbroic intrusions from southern Fennoscandia have Hf isotope compositions that are enriched relative to a MORB-like linear depleted mantle evolution curve. Extrapolation of... (More)

Constraints on the composition of the depleted mantle Sm–Nd and Lu–Hf crust formation ages have a long history of scientific debate. When calculating mantle extraction ages, and constructing crustal growth models, a linear evolution of incompatible trace elements in a depleted mantle since > 4 Ga is routinely used. Mantle depletion however varies regionally and over time and subduction of sediments and oceanic crust renders a mantle-wedge variously enriched relative to a modelled depleted mantle. Here we show that primitive mantle-derived subduction related gabbroic intrusions from southern Fennoscandia have Hf isotope compositions that are enriched relative to a MORB-like linear depleted mantle evolution curve. Extrapolation of primitive Paleoproterozoic gabbro suites enables the construction of a regional mantle evolution curve, providing improved constraints on model ages, crustal residence times and the fraction of juvenile versus reworked continental crust. Convergent margins are assumed to be one of the main sites of continental crust growth, and using an overly depleted mantle source yield model ages that are too old, and hence cumulative crustal growth models show too much crust generation early in the Earth's history. The approach of using the Hf isotope composition of zircon from primitive subduction related gabbroic intrusions as a proxy for mantle Hf isotope composition, piloted in this study, can be applied to other convergent margins.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Depleted mantle, Fennoscandia, Mantle enrichment, convergent margin, U–Pb–Hf
in
Lithos
volume
284-285
pages
10 pages
publisher
Elsevier
external identifiers
  • scopus:85018562784
  • scopus:85018562784
  • wos:000405252300008
ISSN
0024-4937
DOI
10.1016/j.lithos.2017.04.010
language
English
LU publication?
yes
id
3f90b676-48c4-4c0d-88d5-636abad3a951
date added to LUP
2017-05-12 07:56:53
date last changed
2018-03-29 09:28:37
@article{3f90b676-48c4-4c0d-88d5-636abad3a951,
  abstract     = {<p>Constraints on the composition of the depleted mantle Sm–Nd and Lu–Hf crust formation ages have a long history of scientific debate. When calculating mantle extraction ages, and constructing crustal growth models, a linear evolution of incompatible trace elements in a depleted mantle since &gt; 4 Ga is routinely used. Mantle depletion however varies regionally and over time and subduction of sediments and oceanic crust renders a mantle-wedge variously enriched relative to a modelled depleted mantle. Here we show that primitive mantle-derived subduction related gabbroic intrusions from southern Fennoscandia have Hf isotope compositions that are enriched relative to a MORB-like linear depleted mantle evolution curve. Extrapolation of primitive Paleoproterozoic gabbro suites enables the construction of a regional mantle evolution curve, providing improved constraints on model ages, crustal residence times and the fraction of juvenile versus reworked continental crust. Convergent margins are assumed to be one of the main sites of continental crust growth, and using an overly depleted mantle source yield model ages that are too old, and hence cumulative crustal growth models show too much crust generation early in the Earth's history. The approach of using the Hf isotope composition of zircon from primitive subduction related gabbroic intrusions as a proxy for mantle Hf isotope composition, piloted in this study, can be applied to other convergent margins.</p>},
  author       = {Petersson, Andreas and Bjärnborg, Karolina and Scherstén, Anders and Gerdes, Axel and Næraa, Tomas},
  issn         = {0024-4937},
  keyword      = {Depleted mantle,Fennoscandia,Mantle enrichment, convergent margin,U–Pb–Hf},
  language     = {eng},
  month        = {07},
  pages        = {122--131},
  publisher    = {Elsevier},
  series       = {Lithos},
  title        = {Tracing Proterozoic arc mantle Hf isotope depletion of southern Fennoscandia through coupled zircon U–Pb and Lu–Hf isotopes},
  url          = {http://dx.doi.org/10.1016/j.lithos.2017.04.010},
  volume       = {284-285},
  year         = {2017},
}