Abstract

The evolution of planetary magnetic fields are recorded in nanoscale magnetic inclusions found in geological materials. Traditional paleomagnetism focuses on the measurement and characterisation of ensemble magnetic properties found in bulk macroscopic samples. Owing to the development of high-sensitivity magnetometers and novel synchrotron techniques, a new paradigm in paleomagnetic studies is currently being established which allows for the study of rare and unique samples from the earliest eras of the earth’s and the solar system’s history. In these samples the critical questions revolve around the ability to establish a link between the nanostructural properties (composition, chemical ordering and distribution of magnetic inclusions) and the magnetic signal measured. This talk will explore how advanced microscopy techniques facilitate our understanding of these new systems and allows for exploration into the fundamental rock magnetic behaviour. First, we will discuss challenges in trying to establish the oldest measurement of the earth’s magnetic field using single grains of Zircon. I will present correlative experiments comparing magnetic maps with high resolution x-ray tomography which reveal some provoking relationships between the magnetic signal carriers and the host mineralogy. We develop this multi-scale approach further using FIB -nanoTomography to reveal the magnetic architecture in a single grain of olivine from a chondritic meteorite. This information provides a foundation for an estimate of the magnetic field present in the solar nebula – the accretionary disc of gas and dust that existed in the first 5 Myr of the solar system. Finally, I will present an in-depth study of a FeNi spinoidial decomposition system unique to meteoritic samples. This system is currently being used as a time resolved record of core dynamics on small planetary bodies. Using the atom probe tomography, STEM EDS tomography, and scanning precession electron diffraction we are able to revel the underlying structure and composition of this alloy. This seminar will highlight some of the challenging materials science questions encountered in paleomagnetic research.