PROGRESS IN THE ATOM PROBE ANALYSIS OF GEOLOGICAL MATERIALS

Compositional variations in minerals at the nanometer scale have proven to yield fundamental insights into a range of geological processes associated with nucleation and mineral growth, and the subsequent modification of mineral compositions by processes such as diffusion, deformation and recrystallization. However, only atom probe microscopy, a technique that allows the sub-nanometre, 3D imaging of atoms within a very small needle-shaped specimen, allows quantitative measurement of low abundance trace elements and isotopic signatures at the nanometer scale. Despite its widespread use in materials research and in the development of semiconductor devices, the application of atom probe microscopy to the geosciences is a recent development, with the number of publications surging in recent years. The pioneering study by Valley et al. (2014), which highlighted the heterogeneous distribution of Pb in Hadean zircons, has provided the inspiration that has driven this recent growth. In this presentation, we will highlight recent developments in the nanoscale geochemical and isotopic characterisation of a broad range of minerals by atom probe microscopy. These examples include the measurement of bulk and isotopic compositions of sub-micrometer primary inclusions, the identification of nanoscale isotopic reservoirs and their formation mechanisms, and the relationship between element mobility and defect formation. These results highlight the exciting range of potential applications from terrestrial and extra-terrestrial samples.

Reference: Valley, J.W., et al. (2014). Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography. Nat. Geosci. 7, 219-223.