Compositional insights into exsolved mineral phases: Atom Probe Tomography at the exsolution boundary.

Understanding the nanoscale composition and exsolution behaviour of iron oxides is crucial for interpreting paleomagnetic signals and the thermochemical history of volcanic rocks. This study employs Atom Probe Tomography (APT) and Transmission Electron Microscopy (TEM) to investigate the nanoscale features of exsolved iron oxides within a volcanic basalt sample.

We investigate an intergrowth of ilmenite, titanohematite, and rutile, using 3D chemical mapping to precisely determine exsolution boundaries and quantify compositional transitions between the minerals with atomic-scale precision. TEM analyses complement these findings, offering structural and morphological context to the chemical variations. Preliminary results reveal distinct exsolution zones characterized by well-defined compositional gradients and interfacial features. These findings offer novel perspectives on the nanoscale architecture of exsolved iron oxides, providing a foundation for more accurate interpretations of paleomagnetic data.

While this study currently focuses on ilmenite-titanohematite-rutile systems, ongoing research will incorporate data from a magnetite-ilmenite assemblage, expanding our understanding of the broader mineralogical and magnetic structure of the sample. This research will be particularly valuable for researchers who may not be extensively familiar with the capabilities of APT in resolving nanoscale compositions and mineral phase relationships within geological samples.