Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes
The importance of subduction zone magmatism for Archean crustal evolution is highly debated, particularly with regard to the direct melting of subducted slabs. The debate centers largely around trace element geochemical observations. Among the fluid mobile elements, boron is widely accepted to be on...
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ftqueensland:oai:eprints.qut.edu.au:126167 2024-02-04T10:00:56+01:00 Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes Mohan, M. R. Kamber, B. S. Piercey, S. J. 2008 https://eprints.qut.edu.au/126167/ unknown Elsevier BV doi:10.1016/j.epsl.2008.07.042 Mohan, M. R., Kamber, B. S., & Piercey, S. J. (2008) Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes. Earth and Planetary Science Letters, 274(3-4), pp. 479-488. https://eprints.qut.edu.au/126167/ Science & Engineering Faculty Consult author(s) regarding copyright matters This work is covered by copyright. Unless the document is being made available under a Creative Commons Licence, you must assume that re-use is limited to personal use and that permission from the copyright owner must be obtained for all other uses. If the document is available under a Creative Commons License (or other specified license) then refer to the Licence for details of permitted re-use. It is a condition of access that users recognise and abide by the legal requirements associated with these rights. If you believe that this work infringes copyright please provide details by email to qut.copyright@qut.edu.au Earth and Planetary Science Letters boron arsenic archean subduction TTG petrogenesis trondhjemite-granodiorite ttg acid volcanic-rocks b-be systematics rb-sr ages west greenland southern india continental-crust trace-elements dharwar craton mantle evolution Geochemistry & Geophysics Contribution to Journal 2008 ftqueensland https://doi.org/10.1016/j.epsl.2008.07.042 2024-01-08T23:45:12Z The importance of subduction zone magmatism for Archean crustal evolution is highly debated, particularly with regard to the direct melting of subducted slabs. The debate centers largely around trace element geochemical observations. Among the fluid mobile elements, boron is widely accepted to be one of the most sensitive tracers of subduction zone processes. In modern subduction zone magmas, the B/Be ratio can be used to constrain supra-subduction zone mantle metasomatism. We present the first systematic database for concentrations of fluid mobile elements (Li, Be, B, and As) in 60 Archean granitoids spanning similar to 3.8 to similar to 2.5 Ga in age. The behavior of the very fluid mobile B and As relative to the similarly incompatible Be and Pr, respectively, demonstrates that two end-member types of Archean felsic magmas existed. Those with low fluid mobile element abundances have the steepest La/Yb, lowest W/Th and highest Nb/Ta and Sc concentrations, features compatible with an origin as direct slab melts that ascended through the mantle. On the other end of the spectrum are TTG with strong B and As enrichment, which in all regards other than their high La/Yb cannot be distinguished from modern arc melts. In between these extremes are TTG that share some characteristics with each end-member. These could have formed by melting of underplated basaltic eclogite at the base of the crust, in fluid-mobile element poor mantle above (hot) subduction zones where B and As were lost at shallow depth, or they could represent differentiates from very hydrous basaltic precursors in which garnet and amphibole replace olivine and pyroxene as the earliest crystallizing phases. The diversity of geochemical signatures of Archean granitoids suggests that they have formed in a wide range of geodynamic environments. (C) 2008 Elsevier B.V. All rights reserved. Article in Journal/Newspaper Greenland Queensland University of Technology: QUT ePrints Greenland Earth and Planetary Science Letters 274 3-4 479 488 |
institution |
Open Polar |
collection |
Queensland University of Technology: QUT ePrints |
op_collection_id |
ftqueensland |
language |
unknown |
topic |
boron arsenic archean subduction TTG petrogenesis trondhjemite-granodiorite ttg acid volcanic-rocks b-be systematics rb-sr ages west greenland southern india continental-crust trace-elements dharwar craton mantle evolution Geochemistry & Geophysics |
spellingShingle |
boron arsenic archean subduction TTG petrogenesis trondhjemite-granodiorite ttg acid volcanic-rocks b-be systematics rb-sr ages west greenland southern india continental-crust trace-elements dharwar craton mantle evolution Geochemistry & Geophysics Mohan, M. R. Kamber, B. S. Piercey, S. J. Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes |
topic_facet |
boron arsenic archean subduction TTG petrogenesis trondhjemite-granodiorite ttg acid volcanic-rocks b-be systematics rb-sr ages west greenland southern india continental-crust trace-elements dharwar craton mantle evolution Geochemistry & Geophysics |
description |
The importance of subduction zone magmatism for Archean crustal evolution is highly debated, particularly with regard to the direct melting of subducted slabs. The debate centers largely around trace element geochemical observations. Among the fluid mobile elements, boron is widely accepted to be one of the most sensitive tracers of subduction zone processes. In modern subduction zone magmas, the B/Be ratio can be used to constrain supra-subduction zone mantle metasomatism. We present the first systematic database for concentrations of fluid mobile elements (Li, Be, B, and As) in 60 Archean granitoids spanning similar to 3.8 to similar to 2.5 Ga in age. The behavior of the very fluid mobile B and As relative to the similarly incompatible Be and Pr, respectively, demonstrates that two end-member types of Archean felsic magmas existed. Those with low fluid mobile element abundances have the steepest La/Yb, lowest W/Th and highest Nb/Ta and Sc concentrations, features compatible with an origin as direct slab melts that ascended through the mantle. On the other end of the spectrum are TTG with strong B and As enrichment, which in all regards other than their high La/Yb cannot be distinguished from modern arc melts. In between these extremes are TTG that share some characteristics with each end-member. These could have formed by melting of underplated basaltic eclogite at the base of the crust, in fluid-mobile element poor mantle above (hot) subduction zones where B and As were lost at shallow depth, or they could represent differentiates from very hydrous basaltic precursors in which garnet and amphibole replace olivine and pyroxene as the earliest crystallizing phases. The diversity of geochemical signatures of Archean granitoids suggests that they have formed in a wide range of geodynamic environments. (C) 2008 Elsevier B.V. All rights reserved. |
format |
Article in Journal/Newspaper |
author |
Mohan, M. R. Kamber, B. S. Piercey, S. J. |
author_facet |
Mohan, M. R. Kamber, B. S. Piercey, S. J. |
author_sort |
Mohan, M. R. |
title |
Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes |
title_short |
Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes |
title_full |
Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes |
title_fullStr |
Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes |
title_full_unstemmed |
Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes |
title_sort |
boron and arsenic in highly evolved archean felsic rocks: implications for archean subduction processes |
publisher |
Elsevier BV |
publishDate |
2008 |
url |
https://eprints.qut.edu.au/126167/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland |
genre_facet |
Greenland |
op_source |
Earth and Planetary Science Letters |
op_relation |
doi:10.1016/j.epsl.2008.07.042 Mohan, M. R., Kamber, B. S., & Piercey, S. J. (2008) Boron and arsenic in highly evolved Archean felsic rocks: Implications for Archean subduction processes. Earth and Planetary Science Letters, 274(3-4), pp. 479-488. https://eprints.qut.edu.au/126167/ Science & Engineering Faculty |
op_rights |
Consult author(s) regarding copyright matters This work is covered by copyright. Unless the document is being made available under a Creative Commons Licence, you must assume that re-use is limited to personal use and that permission from the copyright owner must be obtained for all other uses. If the document is available under a Creative Commons License (or other specified license) then refer to the Licence for details of permitted re-use. It is a condition of access that users recognise and abide by the legal requirements associated with these rights. If you believe that this work infringes copyright please provide details by email to qut.copyright@qut.edu.au |
op_doi |
https://doi.org/10.1016/j.epsl.2008.07.042 |
container_title |
Earth and Planetary Science Letters |
container_volume |
274 |
container_issue |
3-4 |
container_start_page |
479 |
op_container_end_page |
488 |
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1789966476624527360 |