Written byMiki Huynh
Cathodoluminescence image of a 400-μm zircon and the 3-D map made by atom-probe tomography of a group of ~10-nm clusters of radiogenic atoms of 207Pb (yellow) and 206Pb (green) from the core of this crystal. Credit: John Valley, University of Wisconsin.
A recently designed probe takes the analysis of Hadean-age zircon to the level of a single atom, broadening scientists’ understanding of the ancient mineral and its relation to the history of Earth.
In his Presidential Address to the Mineralogical Society of America last July, John Valley of the NAI Can 6 Team at the University of Wisconsin-Madison wrote about development of new instruments and a combination of atom-probe tomography (APT) and secondary ion mass spectrometry (SIMS). APT magnifies sections of zircon up to a million times smaller than SIMS and identifies the mass and three-dimensional position of individual atoms. Paired with SIMS observations, the atom probe provides a fuller picture of the atomic distribution, age, effects from radiation, and crystallization and thermal history of the zircon. These findings support theories about crust formation and the existence of habitable oceans on a relatively cool Earth earlier than 4.3 billion years ago.
The full paper, “Nano- and micro-geochronology in Hadean and Archean zircons by atom-probe tomography and SIMS: New tools for old minerals,” is available through the Mineralogical Society of America.