A reassessment of the iron isotope composition of the Moon and its implications for the accretion and differentiation of terrestrial planets
| العنوان: | A reassessment of the iron isotope composition of the Moon and its implications for the accretion and differentiation of terrestrial planets |
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| المؤلفون: | Tomáš Magna, Franck Poitrasson, Clive R. Neal, Thomas Zambardi |
| المساهمون: | Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS) |
| المصدر: | Geochimica et Cosmochimica Acta Geochimica et Cosmochimica Acta, Elsevier, 2019, 267, pp.257-274. ⟨10.1016/j.gca.2019.09.035⟩ Geochimica et Cosmochimica Acta, 2019, 267, pp.257-274. ⟨10.1016/j.gca.2019.09.035⟩ |
| بيانات النشر: | HAL CCSD, 2019. |
| سنة النشر: | 2019 |
| مصطلحات موضوعية: | Basalt, Olivine, 010504 meteorology & atmospheric sciences, Stable isotope ratio, Lunar mare, Geochemistry, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Isotope fractionation, Planetary science, 13. Climate action, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, engineering, Terrestrial planet, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences |
| الوصف: | The Fe isotope composition of planetary bodies may provide constraints on their accretion modes and/or differentiation processes, but to do so, the Fe isotope systematics of key planetary reservoirs needs to be determined. To investigate this for the Moon, we measured the Fe isotope compositions for a suite of 33 bulk lunar mare basalts and highland rocks. Combined with published data, a compendium of 73 different lunar bulk rocks reveals a statistically significant Fe isotope difference between low-Ti and high-Ti mare basalts, yielding average δ57Fe = 0.127 ± 0.012‰ (2SE; n = 27) and δ57Fe = 0.274 ± 0.020‰ (2 SE; n = 25), respectively, relative to the IRMM-14 isotopic reference material. As lunar basalts are thought to reflect the Fe isotope composition of their respective mantle sources, the estimated relative proportion of the low-Ti and high-Ti source mantle suggests that the lunar upper mantle δ57Fe value should be close to 0.142 ± 0.026‰. Whilst the composition of highland rocks (ferroan anorthosites and Mg-suite rocks) should provide a more global view of the Moon, the calculation of the mean δ57Fe value of 15 available highland rock analyses yields δ57Fe = 0.078 ± 0.124‰. Such a value is not defined precisely enough to be of critical use for comparative planetology. Ferroan anorthosites and Mg-suite rocks also give unresolvable means. It appears that Fe isotope heterogeneity among the lunar highland rocks is caused by non-representatively too small sample aliquots of coarse-grained rocks. It can also be the result of mixed lithologies for some. When the (kinetic) effect of olivine tending towards low δ57Fe and feldspar with predominantly high δ57Fe is cancelled, a more precise δ57Fe value of 0.094 ± 0.035‰ is calculated. It is indistinguishable from the mean δ57Fe of impact melts and is also similar to the upper lunar mantle estimate obtained from mare basalts. Collectively, this newly determined Fe isotope composition of the bulk Moon is indistinguishable from that of the Earth, and heavier than those reported for other planetary bodies. This planetary isotope relationship is only observed for silicon given the currently available mass-dependent stable isotope database. Because both iron and silicon reside in the Earth’s metallic core in significant quantities, this may point to the involvement of metallic cores of the Earth and Moon in the interplanetary Fe and Si isotope fractionation. Rather than via high-pressure metal–silicate fractionation at the core–mantle boundary, this would more likely be achieved by partial vaporization of the liquid outer metallic core in the aftermath of a Moon-forming giant impact. |
| اللغة: | English |
| تدمد: | 0016-7037 |
| DOI: | 10.1016/j.gca.2019.09.035⟩ |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4721609dad764fcee0aa4df75cb70991 https://hal.archives-ouvertes.fr/hal-02399041/document |
| Rights: | OPEN |
| رقم الانضمام: | edsair.doi.dedup.....4721609dad764fcee0aa4df75cb70991 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 00167037 |
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| DOI: | 10.1016/j.gca.2019.09.035⟩ |