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Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth

Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

Description

Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The 176Lu-176Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the...[Show more]

dc.contributor.authorIizuka, Tsuyoshi
dc.contributor.authorYamaguchi, Takao
dc.contributor.authorHibiya, Yuki
dc.contributor.authorAmelin, Yuri
dc.date.accessioned2016-06-14T23:18:43Z
dc.identifier.issn0027-8424
dc.identifier.urihttp://hdl.handle.net/1885/102588
dc.description.abstractKnowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The 176Lu-176Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day 176Hf/177Hf and 176Lu/177Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess 176Hf due to the accelerated decay of 176Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial 176Hf/177Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess 176Hf and accurately represent the Lu-Hf system of the bulk Earth (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago.
dc.publisherNational Academy of Sciences (USA)
dc.rightsAuthor/s retain copyright
dc.sourcePNAS - Proceedings of the National Academy of Sciences of the United States of America
dc.titleMeteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume112
dc.date.issued2015
local.identifier.absfor040203 - Isotope Geochemistry
local.identifier.absfor020108 - Planetary Science (excl. Extraterrestrial Geology)
local.identifier.ariespublicationa383154xPUB1512
local.type.statusPublished Version
local.contributor.affiliationIizuka, Tsuyoshi, University of Tokyo
local.contributor.affiliationYamaguchi, Takao, The University of Tokyo
local.contributor.affiliationHibiya, Yuki, The University of Tokyo
local.contributor.affiliationAmelin, Yuri, College of Physical and Mathematical Sciences, ANU
local.bibliographicCitation.issue17
local.bibliographicCitation.startpage5331
local.bibliographicCitation.lastpage5336
local.identifier.doi10.1073/pnas.1501658112
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
local.identifier.absseo970102 - Expanding Knowledge in the Physical Sciences
dc.date.updated2016-06-14T08:28:32Z
local.identifier.scopusID2-s2.0-84928688712
dcterms.accessRightsOpen Access
CollectionsANU Research Publications

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