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Early Earth & Zircon Research – UW-Madison (March 2014)

 


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Valley et al 2014, Nature Geoscience

Valley, J. W., A. J. Cavosie, T. Ushikubo, D. A. Reinhard, D. F. Lawrence, D. J. Larson, P. H. Clifton, T. F. Kelly, S. A. Wilde, D. E. Moser, and M. J. Spicuzza (2014), Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography, Nature Geoscience vol. 7, p 219-223.

http://dx.doi.org/10.1038/ngeo2075
          Nature Geoscience, Feb. 23, 2014 (PDF)
          App.  1 - 6  PDF
         Appendix 7:  oxygen three-isotope analyses  (Excel Spreadsheet)
         News & Views by Samuel Bowring (PDF)

Selected Web Sites (March 2014)
          Ars Technica    Article by Scott Johnson (MS in Geology, UW-Madison)
          UW News
           NPR- Morning Edition

Videos at:
          Slate,
          Test Tube
          Examiner
         CNN World News

Cathodoluminescence image of a 400-mm zircon. Conventional U-Pb geochronology shows this is the oldest known (4.4 Ga, billion years) concordant zircon from Earth. At nm-scale, the 207Pb/206Pb ratios show that clusters formed by heating and diffusion 1-Ga after crystallization of the zircon. Incompatible elements are concentrated in alpha-recoil damaged domains, which form groups of 6-8 clusters due to U- and Th-series decay chains. These first nano-geochronology results rule out Pb-mobility biasing of the Hadean age and confirms chemical homogenization of the silicate Earth before 4.4 Ga. (credit:  John Valley, University of Wisconsin)

Cathodoluminescence image of a 400-micron zircon. Conventional U-Pb geochronology shows this is the oldest known (4.4 Ga, billion years) concordant zircon from Earth (Valley et al. 2014, Nature Geoscience). At nm-scale, the 207Pb/206Pb ratios show that clusters formed by heating and diffusion 1-Ga after crystallization of the zircon. Incompatible elements are concentrated in alpha-recoil damaged domains, which form groups of 6-8 clusters due to U- and Th-series decay chains. These first nano-geochronology results rule out Pb-mobility biasing of the Hadean age and confirms chemical homogenization of the silicate Earth before 4.4 Ga. (credit: John Valley, University of Wisconsin)

Atom Probe Tomography- Movies:

3-D rotating images of Pb (207Pb and 206Pb only) and Y measured by APT in specimen #2 from the core of zircon 01JH36-69 from Jack Hills, Western Australia. Scale in nm with no vertical exaggeration.


Atoms of Y including background for the full 1000-nm-long specimen shown in Fig. 3A.


Y & Pb for the enlarged ~100 nm domain shown in Fig. 3B. Only data from within the 3-at.% Y contour are shown to accentuate clusters.