Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism
Radioactive decay of uranium and thorium produces He-4, whereas He-3 in the Earth's mantle is not produced by radioactive decay and was only incorporated during accretion-that is, it is primordial(1). He-3/He-4 ratios in many ocean-island basalts (OIBs) that erupt at hotspot volcanoes, such as...
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ftharvardudash:oai:dash.harvard.edu:1/3224717 2023-05-15T16:51:55+02:00 Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism Gonnermann, H. G. Mukhopadhyay, Sujoy 2007 application/pdf http://nrs.harvard.edu/urn-3:HUL.InstRepos:3224717 https://doi.org/10.1038/nature06240 en_US eng Nature Publishing Group http://dx.doi.org/10.1038/nature06240 http://www.people.fas.harvard.edu/~mukhop/publications.htm Nature Gonnermann, Helge M., and Sujoy Mukhopadhyay. 2007. Non-equilibrium degassing and a primordial source for helium in ocean-island volcanism. Nature 449: 1037-1040. 0028-0836 http://nrs.harvard.edu/urn-3:HUL.InstRepos:3224717 doi:10.1038/nature06240 Journal Article 2007 ftharvardudash https://doi.org/10.1038/nature06240 2022-04-04T12:42:09Z Radioactive decay of uranium and thorium produces He-4, whereas He-3 in the Earth's mantle is not produced by radioactive decay and was only incorporated during accretion-that is, it is primordial(1). He-3/He-4 ratios in many ocean-island basalts (OIBs) that erupt at hotspot volcanoes, such as Hawaii and Iceland, can be up to sixfold higher than in mid-ocean ridge basalts (MORBs). This is inferred to be the result of outgassing by melt production at mid-ocean ridges in conjunction with radiogenic ingrowth of He-4, which has led to a volatile-depleted upper mantle (MORB source) with low He-3 concentrations and low He-3/He-4 ratios(2-6). Consequently, high He-3/He-4 ratios in OIBs are conventionally viewed as evidence for an undegassed, primitive mantle source, which is sampled by hot, buoyantly upwelling deep-mantle plumes(3,6,7). However, this conventional model provides no viable explanation of why helium concentrations and elemental ratios of He/Ne and He/Ar in OIBs are an order of magnitude lower than in MORBs. This has been described as the 'helium concentration paradox'(8) and has contributed to a long-standing controversy about the structure and dynamics of the Earth's mantle. Here we show that the helium concentration paradox, as well as the full range of noble-gas concentrations observed in MORB and OIB glasses, can self-consistently be explained by disequilibrium open-system degassing of the erupting magma. We show that a higher CO2 content in OIBs than in MORBs leads to more extensive degassing of helium in OIB magmas and that noble gases in OIB lavas can be derived from a largely undegassed primitive mantle source. Earth and Planetary Sciences Version of Record Article in Journal/Newspaper Iceland Ocean Island Harvard University: DASH - Digital Access to Scholarship at Harvard Nature 449 7165 1037 1040 |
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Harvard University: DASH - Digital Access to Scholarship at Harvard |
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English |
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Radioactive decay of uranium and thorium produces He-4, whereas He-3 in the Earth's mantle is not produced by radioactive decay and was only incorporated during accretion-that is, it is primordial(1). He-3/He-4 ratios in many ocean-island basalts (OIBs) that erupt at hotspot volcanoes, such as Hawaii and Iceland, can be up to sixfold higher than in mid-ocean ridge basalts (MORBs). This is inferred to be the result of outgassing by melt production at mid-ocean ridges in conjunction with radiogenic ingrowth of He-4, which has led to a volatile-depleted upper mantle (MORB source) with low He-3 concentrations and low He-3/He-4 ratios(2-6). Consequently, high He-3/He-4 ratios in OIBs are conventionally viewed as evidence for an undegassed, primitive mantle source, which is sampled by hot, buoyantly upwelling deep-mantle plumes(3,6,7). However, this conventional model provides no viable explanation of why helium concentrations and elemental ratios of He/Ne and He/Ar in OIBs are an order of magnitude lower than in MORBs. This has been described as the 'helium concentration paradox'(8) and has contributed to a long-standing controversy about the structure and dynamics of the Earth's mantle. Here we show that the helium concentration paradox, as well as the full range of noble-gas concentrations observed in MORB and OIB glasses, can self-consistently be explained by disequilibrium open-system degassing of the erupting magma. We show that a higher CO2 content in OIBs than in MORBs leads to more extensive degassing of helium in OIB magmas and that noble gases in OIB lavas can be derived from a largely undegassed primitive mantle source. Earth and Planetary Sciences Version of Record |
format |
Article in Journal/Newspaper |
author |
Gonnermann, H. G. Mukhopadhyay, Sujoy |
spellingShingle |
Gonnermann, H. G. Mukhopadhyay, Sujoy Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism |
author_facet |
Gonnermann, H. G. Mukhopadhyay, Sujoy |
author_sort |
Gonnermann, H. G. |
title |
Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism |
title_short |
Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism |
title_full |
Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism |
title_fullStr |
Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism |
title_full_unstemmed |
Non-Equilibrium Degassing and a Primordial Source for Helium in Ocean-Island Volcanism |
title_sort |
non-equilibrium degassing and a primordial source for helium in ocean-island volcanism |
publisher |
Nature Publishing Group |
publishDate |
2007 |
url |
http://nrs.harvard.edu/urn-3:HUL.InstRepos:3224717 https://doi.org/10.1038/nature06240 |
genre |
Iceland Ocean Island |
genre_facet |
Iceland Ocean Island |
op_relation |
http://dx.doi.org/10.1038/nature06240 http://www.people.fas.harvard.edu/~mukhop/publications.htm Nature Gonnermann, Helge M., and Sujoy Mukhopadhyay. 2007. Non-equilibrium degassing and a primordial source for helium in ocean-island volcanism. Nature 449: 1037-1040. 0028-0836 http://nrs.harvard.edu/urn-3:HUL.InstRepos:3224717 doi:10.1038/nature06240 |
op_doi |
https://doi.org/10.1038/nature06240 |
container_title |
Nature |
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449 |
container_issue |
7165 |
container_start_page |
1037 |
op_container_end_page |
1040 |
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1766042053371756544 |