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dc.contributor.author
Vilella, Kenny
dc.contributor.author
Bodin, Thomas
dc.contributor.author
Boukaré, Charles-Edouard
dc.contributor.author
Deschamps, Frédéric
dc.contributor.author
Badro, James
dc.contributor.author
Ballmer, Maxim D.
dc.contributor.author
Li, Yang
dc.date.accessioned
2020-12-11T11:05:36Z
dc.date.available
2020-12-11T03:56:48Z
dc.date.available
2020-12-11T11:05:36Z
dc.date.issued
2021-01-15
dc.identifier.issn
0012-821X
dc.identifier.issn
1385-013X
dc.identifier.other
10.1016/j.epsl.2020.116685
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/455896
dc.description.abstract
Seismic observations have suggested the presence of two Large Low Shear Velocity Provinces (LLSVPs) in the lowermost mantle whose nature and origin are still debated. Several studies have tried to infer their potential composition using seismic observations with the hope to identify their formation mechanism. In particular, compositions enriched in iron (∼12–14 wt%) and bridgmanite (∼90 vol%) have been identified as promising candidates. Interestingly, these characteristics are somewhat consistent with the cumulates produced by the solidification of a primitive magma ocean, except that the iron enrichment should be much larger (>20 wt%). Here, we provide a reappraisal of potential LLSVPs compositions based on an improved mineralogical model including, in particular, the effects of alumina. We systematically investigate the effects of six parameters: FeO and Al2O3 content, proportion of CaSiO3 and bridgmanite (so that the proportion of ferropericlase is implicitly investigated), Fe3+/∑Fe and temperature contrast between far-field mantle and LLSVPs. From the 81 millions cases studied, only 79000 cases explain the seismic observations. Nevertheless, these successful cases involve a large range of parameters with, for instance, FeO content between 12–25 wt% and Al2O3 content between 3–17 wt%. We then apply a principal component analysis (PCA) to these cases and find two robust results: (i) the proportion of ferropericlase should be low (<6 vol%); (ii) the formation of Fe3+-bearing bridgmanite is much more favored compared to other iron-bearing components. Following these results, we identify two end-member compositions: a Bm-rich and a CaPv-rich one. For each end-member composition, a large range of parameters is possible. We note, however, that a low temperature contrast (<500 K) is favored, and that a certain proportion between FeO content, Al2O3 and oxidation state should be maintained. Finally, we discuss different scenarios for the formation of LLSVPs and propose that investigating the mineral proportion produced by each scenario is the best way to evaluate their relevance. For instance, the solidification of a primitive magma ocean may produce FeO and Al2O3 contents similar to those suggested by our analysis. However, the mineral proportion of such reservoirs is not well-constrained and may contain a larger proportion of ferropericlase than what is allowed by our results. © 2020 Elsevier
en_US
dc.language.iso
en
en_US
dc.publisher
Elsevier
en_US
dc.title
Constraints on the composition and temperature of LLSVPs from seismic properties of lower mantle minerals
en_US
dc.type
Journal Article
dc.date.published
2020-12-02
ethz.journal.title
Earth and Planetary Science Letters
ethz.journal.volume
554
en_US
ethz.journal.abbreviated
Earth Planet. Sci. Lett.
ethz.pages.start
116685
en_US
ethz.size
12 p.
en_US
ethz.identifier.wos
ethz.identifier.scopus
ethz.publication.place
Amsterdam
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::02506 - Institut für Geophysik / Institute of Geophysics::03698 - Tackley, Paul / Tackley, Paul
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::02506 - Institut für Geophysik / Institute of Geophysics::03698 - Tackley, Paul / Tackley, Paul
ethz.date.deposited
2020-12-11T03:56:53Z
ethz.source
SCOPUS
ethz.eth
yes
en_US
ethz.availability
Metadata only
en_US
ethz.rosetta.installDate
2020-12-11T11:05:45Z
ethz.rosetta.lastUpdated
2022-03-29T04:34:31Z
ethz.rosetta.versionExported
true
ethz.COinS
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