Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province
The great majority of continental flood basalts (CFBs) have a marked lithospheric geochemical signature, suggesting derivation from the continental lithosphere, or contamination by it. Here we present new Pb and Os isotopic data and review previously published major element, trace element, mineral c...
Published in: | Earth and Planetary Science Letters |
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Online Access: | http://hdl.handle.net/10138/136492 |
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ftunivhelsihelda:oai:helda.helsinki.fi:10138/136492 2024-06-23T07:46:12+00:00 Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province Subduktion muokkaamaa merellistä kuorta sekoittuneena köyhtyneeseen vaippalähteeseen Karoon laakiobasalttiprovinssin alkulähteillä Heinonen, Jussi S. Carlson, Rick W. Riley, Teal R. Luttinen, Arto V. Horan, Mary F. Finnish Museum of Natural History Natural Sciences Unit 2014-11-05T13:07:01Z 13 application/pdf http://hdl.handle.net/10138/136492 eng eng Elsevier Scientific Publ. Co 10.1016/j.epsl.2014.03.012 Heinonen , J S , Carlson , R W , Riley , T R , Luttinen , A V & Horan , M F 2014 , ' Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province ' , Earth and Planetary Science Letters , vol. 394 , pp. 229-241 . https://doi.org/10.1016/j.epsl.2014.03.012 ORCID: /0000-0002-3129-0392/work/30885307 ORCID: /0000-0001-8998-4357/work/32341620 http://hdl.handle.net/10138/136492 f89c496a-bdfb-47df-88d8-010da8051c12 84897530604 000335613300023 info:eu-repo/semantics/openAccess openAccess Other natural sciences LARGE IGNEOUS PROVINCE CONTINENTAL FLOOD BASALTS KAROO MAGMATISM picrite mantle source crustal recycling Article acceptedVersion 2014 ftunivhelsihelda 2024-06-04T14:34:43Z The great majority of continental flood basalts (CFBs) have a marked lithospheric geochemical signature, suggesting derivation from the continental lithosphere, or contamination by it. Here we present new Pb and Os isotopic data and review previously published major element, trace element, mineral chemical, and Sr and Nd isotopic data for geochemically unusual mafic and ultramafic dikes located in the Antarctic segment (Ahlmannryggen, western Dronning Maud Land) of the Karoo CFB province. Some of the dikes show evidence of minor contamination with continental crust, but the least contaminated dikes exhibit depleted mantle –like initial εNd (+9) and 187Os/188Os (0.1244–0.1251) at 180 Ma. In contrast, their initial Sr and Pb isotopic compositions (87Sr/86Sr = 0.7035–0.7062, 206Pb/204Pb = 18.2–18.4, 207Pb/204Pb = 15.49–15.52, 208Pb/204Pb = 37.7–37.9 at 180 Ma) are more enriched than expected for depleted mantle, and the major element and mineral chemical evidence indicate contribution from (recycled) pyroxenite sources. Our Sr, Nd, Pb, and Os isotopic and trace element modeling indicate mixed peridotite-pyroxenite sources that contain ~10–30 % of seawater-altered and subduction-modified MORB with a recycling age of less than 1.0 Ga entrained in a depleted Os-rich peridotite matrix. Such a source would explain the unusual combination of elevated initial 87Sr/86Sr and Pb isotopic ratios and relative depletion in LILE, U, Th, Pb and LREE, high initial εNd, and low initial 187Os/188Os. Although the sources of the dikes probably did not play a major part in the generation of the Karoo CFBs in general, different kind of recycled source components (e.g., sediment-influenced) would be more difficult to distinguish from lithospheric CFB geochemical signatures. In addition to underlying continental lithosphere, the involvement of recycled sources in causing the apparent lithospheric geochemical affinity of CFBs should thus be carefully assessed in every case. The great majority of continental flood basalts (CFBs) have a ... Article in Journal/Newspaper Antarc* Antarctic Dronning Maud Land HELDA – University of Helsinki Open Repository Ahlmannryggen ENVELOPE(-2.500,-2.500,-71.833,-71.833) Antarctic Dronning Maud Land The Antarctic Earth and Planetary Science Letters 394 229 241 |
institution |
Open Polar |
collection |
HELDA – University of Helsinki Open Repository |
op_collection_id |
ftunivhelsihelda |
language |
English |
topic |
Other natural sciences LARGE IGNEOUS PROVINCE CONTINENTAL FLOOD BASALTS KAROO MAGMATISM picrite mantle source crustal recycling |
spellingShingle |
Other natural sciences LARGE IGNEOUS PROVINCE CONTINENTAL FLOOD BASALTS KAROO MAGMATISM picrite mantle source crustal recycling Heinonen, Jussi S. Carlson, Rick W. Riley, Teal R. Luttinen, Arto V. Horan, Mary F. Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province |
topic_facet |
Other natural sciences LARGE IGNEOUS PROVINCE CONTINENTAL FLOOD BASALTS KAROO MAGMATISM picrite mantle source crustal recycling |
description |
The great majority of continental flood basalts (CFBs) have a marked lithospheric geochemical signature, suggesting derivation from the continental lithosphere, or contamination by it. Here we present new Pb and Os isotopic data and review previously published major element, trace element, mineral chemical, and Sr and Nd isotopic data for geochemically unusual mafic and ultramafic dikes located in the Antarctic segment (Ahlmannryggen, western Dronning Maud Land) of the Karoo CFB province. Some of the dikes show evidence of minor contamination with continental crust, but the least contaminated dikes exhibit depleted mantle –like initial εNd (+9) and 187Os/188Os (0.1244–0.1251) at 180 Ma. In contrast, their initial Sr and Pb isotopic compositions (87Sr/86Sr = 0.7035–0.7062, 206Pb/204Pb = 18.2–18.4, 207Pb/204Pb = 15.49–15.52, 208Pb/204Pb = 37.7–37.9 at 180 Ma) are more enriched than expected for depleted mantle, and the major element and mineral chemical evidence indicate contribution from (recycled) pyroxenite sources. Our Sr, Nd, Pb, and Os isotopic and trace element modeling indicate mixed peridotite-pyroxenite sources that contain ~10–30 % of seawater-altered and subduction-modified MORB with a recycling age of less than 1.0 Ga entrained in a depleted Os-rich peridotite matrix. Such a source would explain the unusual combination of elevated initial 87Sr/86Sr and Pb isotopic ratios and relative depletion in LILE, U, Th, Pb and LREE, high initial εNd, and low initial 187Os/188Os. Although the sources of the dikes probably did not play a major part in the generation of the Karoo CFBs in general, different kind of recycled source components (e.g., sediment-influenced) would be more difficult to distinguish from lithospheric CFB geochemical signatures. In addition to underlying continental lithosphere, the involvement of recycled sources in causing the apparent lithospheric geochemical affinity of CFBs should thus be carefully assessed in every case. The great majority of continental flood basalts (CFBs) have a ... |
author2 |
Finnish Museum of Natural History Natural Sciences Unit |
format |
Article in Journal/Newspaper |
author |
Heinonen, Jussi S. Carlson, Rick W. Riley, Teal R. Luttinen, Arto V. Horan, Mary F. |
author_facet |
Heinonen, Jussi S. Carlson, Rick W. Riley, Teal R. Luttinen, Arto V. Horan, Mary F. |
author_sort |
Heinonen, Jussi S. |
title |
Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province |
title_short |
Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province |
title_full |
Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province |
title_fullStr |
Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province |
title_full_unstemmed |
Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province |
title_sort |
subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the karoo continental flood basalt province |
publisher |
Elsevier Scientific Publ. Co |
publishDate |
2014 |
url |
http://hdl.handle.net/10138/136492 |
long_lat |
ENVELOPE(-2.500,-2.500,-71.833,-71.833) |
geographic |
Ahlmannryggen Antarctic Dronning Maud Land The Antarctic |
geographic_facet |
Ahlmannryggen Antarctic Dronning Maud Land The Antarctic |
genre |
Antarc* Antarctic Dronning Maud Land |
genre_facet |
Antarc* Antarctic Dronning Maud Land |
op_relation |
10.1016/j.epsl.2014.03.012 Heinonen , J S , Carlson , R W , Riley , T R , Luttinen , A V & Horan , M F 2014 , ' Subduction-modified oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental flood basalt province ' , Earth and Planetary Science Letters , vol. 394 , pp. 229-241 . https://doi.org/10.1016/j.epsl.2014.03.012 ORCID: /0000-0002-3129-0392/work/30885307 ORCID: /0000-0001-8998-4357/work/32341620 http://hdl.handle.net/10138/136492 f89c496a-bdfb-47df-88d8-010da8051c12 84897530604 000335613300023 |
op_rights |
info:eu-repo/semantics/openAccess openAccess |
container_title |
Earth and Planetary Science Letters |
container_volume |
394 |
container_start_page |
229 |
op_container_end_page |
241 |
_version_ |
1802644503289397248 |