Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry
Mantle plumes are commonly perceived to have both a chemical and dynamic link with the subduction of ocean crust into the mantle. In principle, this should lead to the observation of chemical and isotopic signatures that are characteristic of ocean crust and marine sediments in ocean island basalts....
Published in: | Earth and Planetary Science Letters |
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2007
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Online Access: | https://researchers.mq.edu.au/en/publications/c6dda46a-3d03-41fd-bd59-e4c250fc6841 https://doi.org/10.1016/j.epsl.2007.10.008 http://www.scopus.com/inward/record.url?scp=36148962926&partnerID=8YFLogxK |
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ftmacquarieunicr:oai:https://researchers.mq.edu.au:publications/c6dda46a-3d03-41fd-bd59-e4c250fc6841 2024-06-23T07:53:56+00:00 Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry Nielsen, Sune G. Rehkämper, Mark Brandon, Alan D. Norman, Marc D. Turner, Simon O'Reilly, Suzanne Y. 2007-12-15 https://researchers.mq.edu.au/en/publications/c6dda46a-3d03-41fd-bd59-e4c250fc6841 https://doi.org/10.1016/j.epsl.2007.10.008 http://www.scopus.com/inward/record.url?scp=36148962926&partnerID=8YFLogxK eng eng info:eu-repo/semantics/restrictedAccess Nielsen , S G , Rehkämper , M , Brandon , A D , Norman , M D , Turner , S & O'Reilly , S Y 2007 , ' Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry ' , Earth and Planetary Science Letters , vol. 264 , no. 1-2 , pp. 332-345 . https://doi.org/10.1016/j.epsl.2007.10.008 article 2007 ftmacquarieunicr https://doi.org/10.1016/j.epsl.2007.10.008 2024-06-12T23:47:20Z Mantle plumes are commonly perceived to have both a chemical and dynamic link with the subduction of ocean crust into the mantle. In principle, this should lead to the observation of chemical and isotopic signatures that are characteristic of ocean crust and marine sediments in ocean island basalts. This study investigates the thallium (Tl) isotope systematics of lavas from Iceland and the Azores archipelago, in order to determine if their compositions were affected by admixing of ferromanganese sediments or upper ocean crust altered at low temperature. Such materials are known to display strongly fractionated Tl isotope signatures relative to the ambient upper mantle. Two samples from the island of Terceira in the Azores archipelago have Tl isotope compositions significantly different from normal mantle, and this suggests the presence of Fe-Mn sediments. Combined Pb and Tl isotope modelling indicates that the Tl anomalies are not a feature of the Azores plume but produced by assimilation of modern Fe-Mn sediments during magma ascent through the ocean crust. Excluding these two anomalous lavas from Terceira, the Iceland and Azores samples have identical Tl isotope compositions, with an overall mean of e{open} 205 Tl = - 1.5 ± 1.4 (2SD, n = 30) that is indistinguishable from the previously estimated upper mantle average (e{open} 205 Tl = - 2.0 ± 0.5). The near-constant Tl isotope compositions of the Iceland and Azores lavas may indicate that the respective mantle plume sources contain virtually no Fe-Mn sediments or altered upper ocean crust. Alternatively, it is possible that the lack of Tl isotope variation reflects quantitative removal of fractionated Tl from the slab during subduction and dehydration. A less straightforward explanation is that past marine environments produced sediments and altered marine basalts with nearly unfractionated Tl isotope compositions. All three scenarios have important implications and future Tl isotope studies will be able to identify the most feasible interpretation. Article in Journal/Newspaper Iceland Ocean Island Macquarie University Research Portal Earth and Planetary Science Letters 264 1-2 332 345 |
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Open Polar |
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Macquarie University Research Portal |
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ftmacquarieunicr |
language |
English |
description |
Mantle plumes are commonly perceived to have both a chemical and dynamic link with the subduction of ocean crust into the mantle. In principle, this should lead to the observation of chemical and isotopic signatures that are characteristic of ocean crust and marine sediments in ocean island basalts. This study investigates the thallium (Tl) isotope systematics of lavas from Iceland and the Azores archipelago, in order to determine if their compositions were affected by admixing of ferromanganese sediments or upper ocean crust altered at low temperature. Such materials are known to display strongly fractionated Tl isotope signatures relative to the ambient upper mantle. Two samples from the island of Terceira in the Azores archipelago have Tl isotope compositions significantly different from normal mantle, and this suggests the presence of Fe-Mn sediments. Combined Pb and Tl isotope modelling indicates that the Tl anomalies are not a feature of the Azores plume but produced by assimilation of modern Fe-Mn sediments during magma ascent through the ocean crust. Excluding these two anomalous lavas from Terceira, the Iceland and Azores samples have identical Tl isotope compositions, with an overall mean of e{open} 205 Tl = - 1.5 ± 1.4 (2SD, n = 30) that is indistinguishable from the previously estimated upper mantle average (e{open} 205 Tl = - 2.0 ± 0.5). The near-constant Tl isotope compositions of the Iceland and Azores lavas may indicate that the respective mantle plume sources contain virtually no Fe-Mn sediments or altered upper ocean crust. Alternatively, it is possible that the lack of Tl isotope variation reflects quantitative removal of fractionated Tl from the slab during subduction and dehydration. A less straightforward explanation is that past marine environments produced sediments and altered marine basalts with nearly unfractionated Tl isotope compositions. All three scenarios have important implications and future Tl isotope studies will be able to identify the most feasible interpretation. |
format |
Article in Journal/Newspaper |
author |
Nielsen, Sune G. Rehkämper, Mark Brandon, Alan D. Norman, Marc D. Turner, Simon O'Reilly, Suzanne Y. |
spellingShingle |
Nielsen, Sune G. Rehkämper, Mark Brandon, Alan D. Norman, Marc D. Turner, Simon O'Reilly, Suzanne Y. Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry |
author_facet |
Nielsen, Sune G. Rehkämper, Mark Brandon, Alan D. Norman, Marc D. Turner, Simon O'Reilly, Suzanne Y. |
author_sort |
Nielsen, Sune G. |
title |
Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry |
title_short |
Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry |
title_full |
Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry |
title_fullStr |
Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry |
title_full_unstemmed |
Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry |
title_sort |
thallium isotopes in iceland and azores lavas - implications for the role of altered crust and mantle geochemistry |
publishDate |
2007 |
url |
https://researchers.mq.edu.au/en/publications/c6dda46a-3d03-41fd-bd59-e4c250fc6841 https://doi.org/10.1016/j.epsl.2007.10.008 http://www.scopus.com/inward/record.url?scp=36148962926&partnerID=8YFLogxK |
genre |
Iceland Ocean Island |
genre_facet |
Iceland Ocean Island |
op_source |
Nielsen , S G , Rehkämper , M , Brandon , A D , Norman , M D , Turner , S & O'Reilly , S Y 2007 , ' Thallium isotopes in Iceland and Azores lavas - Implications for the role of altered crust and mantle geochemistry ' , Earth and Planetary Science Letters , vol. 264 , no. 1-2 , pp. 332-345 . https://doi.org/10.1016/j.epsl.2007.10.008 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.epsl.2007.10.008 |
container_title |
Earth and Planetary Science Letters |
container_volume |
264 |
container_issue |
1-2 |
container_start_page |
332 |
op_container_end_page |
345 |
_version_ |
1802645846939926528 |