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dc.contributor.authorBorlina, Cauê S.
dc.contributor.authorWeiss, Benjamin P.
dc.contributor.authorLima, Eduardo A.
dc.date.accessioned2020-04-08T15:44:24Z
dc.date.available2020-04-08T15:44:24Z
dc.date.issued2018-12-31
dc.identifier.issn0027-8424
dc.identifier.issn1091-6490
dc.identifier.urihttps://hdl.handle.net/1721.1/124534
dc.description.abstractZircon crystals from the Jack Hills, Western Australia, are one of the few surviving mineralogical records of Earth’s first 500 million years and have been proposed to contain a paleomagnetic record of the Hadean geodynamo. A prerequisite for the preservation of Hadean magnetization is the presence of primary magnetic inclusions within pristine igneous zircon. To date no images of the magnetic recorders within ancient zircon have been presented. Here we use high-resolution transmission electron microscopy to demonstrate that all observed inclusions are secondary features formed via two distinct mechanisms. Magnetite is produced via a pipe-diffusion mechanism whereby iron diffuses into radiation-damaged zircon along the cores of dislocations and is precipitated inside nanopores and also during low-temperature recrystallization of radiation-damaged zircon in the presence of an aqueous fluid. Although these magnetites can be recognized as secondary using transmission electron microscopy, they otherwise occur in regions that are indistinguishable from pristine igneous zircon and carry remanent magnetization that postdates the crystallization age by at least several hundred million years. Without microscopic evidence ruling out secondary magnetite, the paleomagnetic case for a Hadean–Eoarchean geodynamo cannot yet been made.en_US
dc.description.sponsorshipSeventh Framework Programme (European Commission) (Grant FP/2007-2013)en_US
dc.description.sponsorshipEuropean Research Council (Grant 320750)en_US
dc.description.sponsorshipNatural Environment Research Council (Great Britain) (Grant NE/P002498/1)en_US
dc.description.sponsorshipNational Science Foundation (U.S.) (Grant EAR1647504)en_US
dc.description.sponsorshipNational Science Foundation (U.S.). Division of Earth Sciences (Grant 1339051)en_US
dc.language.isoen
dc.publisherProceedings of the National Academy of Sciencesen_US
dc.relation.isversionof10.1073/pnas.1811074116en_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.sourcePNASen_US
dc.subjectMultidisciplinaryen_US
dc.titleSecondary magnetite in ancient zircon precludes analysis of a Hadean geodynamoen_US
dc.typeArticleen_US
dc.identifier.citationTnag, Fengzai et al. "Secondary magnetite in ancient zircon precludes analysis of a Hadean geodynamo." Proceedings of the National Academy of Sciences of the United States of America 116 (2019): 407-412 © 2019 The Author(s)en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Aeronautics and Astronauticsen_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciencesen_US
dc.relation.journalProceedings of the National Academy of Sciences of the United States of Americaen_US
dc.eprint.versionFinal published versionen_US
dc.type.urihttp://purl.org/eprint/type/JournalArticleen_US
eprint.statushttp://purl.org/eprint/status/PeerRevieweden_US
dc.date.updated2020-02-13T13:21:51Z
dspace.date.submission2020-02-13T13:21:53Z
mit.journal.volume116en_US
mit.journal.issue2en_US
mit.licensePUBLISHER_POLICY


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