The challenge: Catastrophic planetary collisions impacts during the Earth’s first 500 million years in the aftermath of the planetary collision that formed the Moon provided enough energy to melt the planet’s interior, creating planetary-scale volumes of liquid molten rock, or “magma oceans”. The subsequent cooling and crystallisation of these vast volumes of liquid rock determined the physical and chemical properties of the Earth's interior, which governs the structure and compostion of our planet today. However, we do not know exactly where and how the Earth’s magma oceans crystallised, and whether remnants of early magma ocean material, or the sulfur-rich melt that may have separated from it, are still preserved at the base of the Earth’s mantle today, where they may act as reservoirs for volatiles and rare metals. We also do not know if this residual material has remained inert throughout the course of Earth history or whether it has been sampled by mantle melting events, potentially transferring its precious cargo of volatiles and metals to the planet’s surface. A major issue is that the evidence for early magma ocean processes on Earth has been largely erased by the tectonic mixing processes that have operated over the past ~3 billion years. This lack of physical evidence limits our ability to test and refine planetary magma ocean models and we need geochemical tracing tools to unravel these processes.
Societal importance: The chemistry of the Earth's interior and surface are fundamentally linked via the processes of volatile gases being released from the interior such that understanding the chemical evolution of the Earth's interior is fundamental to understanding our planet's future long-term habitability. Understanding the chemistry of our planet's interior, particularly of metals closely associated with sulfur, is profoundly important to to understanding whether there is the potential for spatial-temporal controls on the distribution of precious metals (like platinum, gold and copper) in the Earth's interior and hence in deposits close to the surface.
Overall objectives: To develop a series of novel and robust stable isotope tracers that can be used to probe early differentiation and magma ocean events. To calibrate the behaviour of these systems experimentally and to apply these data to natural samples where we will develop internally-consistent thermodynamic equilibria models of stable isotope fractionation to help us to interpret the data and hence constrain the record of magma ocean crystallisation on Earth.
