Isotopic evidence for internal oxidation of the Earth's mantle during accretion
The Earth's mantle is currently oxidised and out of chemical equilibrium with the core. The reasons for this and for the relatively oxidised state of Earth's mantle relative to the mantles of other terrestrial planets are unclear. It has been proposed that the oxidised nature and high ferr...
| Main Authors: | , , , , |
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| Format: | Journal article |
| Language: | English |
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2012
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| _version_ | 1826274802276499456 |
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| author | Williams, H Wood, B Wade, J Frost, D Tuff, J |
| author_facet | Williams, H Wood, B Wade, J Frost, D Tuff, J |
| author_sort | Williams, H |
| collection | OXFORD |
| description | The Earth's mantle is currently oxidised and out of chemical equilibrium with the core. The reasons for this and for the relatively oxidised state of Earth's mantle relative to the mantles of other terrestrial planets are unclear. It has been proposed that the oxidised nature and high ferric iron (Fe 3+) content of Earth's mantle was produced internally by disproportionation of ferrous iron (Fe 2+) into Fe 3+ and metallic iron by perovskite crystallisation during accretion. Here we show that there is substantial Fe isotope fractionation between experimentally equilibrated metal and Fe 3+-bearing perovskite (≥0.45‰/amu), which can account for the heavy Fe isotope compositions of terrestrial basalts relative to equivalent samples derived from Mars and Vesta as the latter bodies are too small to stabilise significant perovskite. Mass balance calculations indicate that all of the mantle's Fe 3+ could readily have been generated from a single disproportionation event, consistent with dissolution of perovskite in the lower mantle during a process such as the Moon-forming giant impact. The similar Fe isotope compositions of primitive terrestrial and low-titanium lunar basalts is consistent with models of equilibration between the mantles of the Earth and Moon in the aftermath of the giant impact and suggests that the heavy Fe isotope composition of the Earth's mantle was established prior to, or during the giant impact. The oxidation state and ferric iron content of the Earth's mantle was therefore plausibly set by the end of accretion, and may be decoupled from later volatile additions and the rise of oxygen in the Earth's atmosphere at 2.45Ga. © 2012 Elsevier B.V. |
| first_indexed | 2024-03-06T22:48:58Z |
| format | Journal article |
| id | oxford-uuid:5e28f5cd-88d9-410e-98ae-91f082dab7fc |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T22:48:58Z |
| publishDate | 2012 |
| record_format | dspace |
| spelling | oxford-uuid:5e28f5cd-88d9-410e-98ae-91f082dab7fc2022-03-26T17:38:48ZIsotopic evidence for internal oxidation of the Earth's mantle during accretionJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:5e28f5cd-88d9-410e-98ae-91f082dab7fcEnglishSymplectic Elements at Oxford2012Williams, HWood, BWade, JFrost, DTuff, JThe Earth's mantle is currently oxidised and out of chemical equilibrium with the core. The reasons for this and for the relatively oxidised state of Earth's mantle relative to the mantles of other terrestrial planets are unclear. It has been proposed that the oxidised nature and high ferric iron (Fe 3+) content of Earth's mantle was produced internally by disproportionation of ferrous iron (Fe 2+) into Fe 3+ and metallic iron by perovskite crystallisation during accretion. Here we show that there is substantial Fe isotope fractionation between experimentally equilibrated metal and Fe 3+-bearing perovskite (≥0.45‰/amu), which can account for the heavy Fe isotope compositions of terrestrial basalts relative to equivalent samples derived from Mars and Vesta as the latter bodies are too small to stabilise significant perovskite. Mass balance calculations indicate that all of the mantle's Fe 3+ could readily have been generated from a single disproportionation event, consistent with dissolution of perovskite in the lower mantle during a process such as the Moon-forming giant impact. The similar Fe isotope compositions of primitive terrestrial and low-titanium lunar basalts is consistent with models of equilibration between the mantles of the Earth and Moon in the aftermath of the giant impact and suggests that the heavy Fe isotope composition of the Earth's mantle was established prior to, or during the giant impact. The oxidation state and ferric iron content of the Earth's mantle was therefore plausibly set by the end of accretion, and may be decoupled from later volatile additions and the rise of oxygen in the Earth's atmosphere at 2.45Ga. © 2012 Elsevier B.V. |
| spellingShingle | Williams, H Wood, B Wade, J Frost, D Tuff, J Isotopic evidence for internal oxidation of the Earth's mantle during accretion |
| title | Isotopic evidence for internal oxidation of the Earth's mantle during accretion |
| title_full | Isotopic evidence for internal oxidation of the Earth's mantle during accretion |
| title_fullStr | Isotopic evidence for internal oxidation of the Earth's mantle during accretion |
| title_full_unstemmed | Isotopic evidence for internal oxidation of the Earth's mantle during accretion |
| title_short | Isotopic evidence for internal oxidation of the Earth's mantle during accretion |
| title_sort | isotopic evidence for internal oxidation of the earth s mantle during accretion |
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