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

John W. Valley

Charles R. Van Hise Professor
Stable Isotope Geochemistry and Metamorphic Petrology
(608) 263-5659
Email: valley@geology.wisc.edu
Office: 345 Weeks Hall

John Valley-Home | John Valley – CV | WiscSIMS | Stable Isotope Lab | Early Earth & Zircon Research | Useful Links

Cavosie2019JHReview Cavosie AJ, Valley JW, Wilde SA(2019) The Oldest Terrestrial Mineral Record: Thirty Years of Research on Hadean Zircon From Jack Hills, Western Australia. In: Earth’s Oldest Rocks. MJ Van Kranendonk (ed.), Elsevier, p 255-278. doi.org/10.1016/B978-0-444-63901-1.00012-5

Valley2015APT Valley JW, Reinhard DA, Cavosie AJ, Ushikubo T, Lawrence DF, Larson DJ, Kelly TF, Snoeyenbos D, Strickland A (2015) Nano- and Micro-geochronology in Hadean and Archean Zircons by Atom-Probe Tomography and SIMS: New Tools for Old Minerals. Am. Mineral, 100: 1355-1377. doi.org/10.2138/am-2014-5134.

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.