In this application note, CAMECA describe the analysis of a 4.4 billion year old zircon using atom probe tomography (APT).
Atom Probe Tomography (APT) is a powerful and promising elemental and isotopic analysis technique for the nanoscale characterization of geological and extraterrestrial materials. The only physical evidence from the earliest phases of Earth’s evolution comes from zircons, ancient mineral grains that can be dated using the U–Th–Pb geochronometer. Unfortunately, the accuracy of the zircon ages can be biased by poorly understood processes of intracrystalline Pb mobility.
In a study by J. Valley et al., APT was used to identify and map individual atoms in the oldest known intact mineral grain from Earth, a 4.4-Gyr-old Hadean zircon with a high temperature overgrowth that formed about 1Gyr after the mineral’s core. The analysis showed for the first time that isolated nanoclusters, measuring about 10 nm and spaced 10–50 nm apart, are enriched in incompatible elements including radiogenic Pb with unusually high 207Pb/206Pb ratios.
APT technology provided unique nanoscale lead isotopic ratio analysis. This groundbreaking work demonstrates how advanced microscopies like APT not only can provide understanding of the physical properties of materials but also contribute to the interpretation of historical events in unexpected ways. This nanoscale chemical length analysis has provided insight into gigascale geological events.
To find out more about APT technology, download the full application note.