Earth is the "blue planet", with over 70% of its surface covered in water and a further equivalent of up to 4 oceans in its interior. This abundance of water has a profound impact on the processes that shape our planet, as well as the development of the organisms that inhabit it. To understand this impact, it is necessary to know the properties and chemistry of the fluids involved. At present this information is largely unavailable. This project aims to develop mineral composition as a new tool to determine the composition of fluids using the systematic partitioning of elements between minerals and fluids. Whereas direct samples of fluids are rare, especially as age increases, the associated minerals are preserved. At present, this approach is limited because of a lack of mineral-fluid partition values at appropriate conditions. Moreover, partitioning depends strongly on the speciation of elements in the fluid and this is mostly unknown at elevated pressures and temperatures. In this project I will develop a model to predict element partitioning between minerals and fluids at elevated pressures and temperatures. I will use atomistic simulation techniques to model both the preference of an element to enter the mineral, and the element's speciation. Combined, this will allow me to determine the relative partition coefficients among elements and the changes therein with changing pressure, temperature and chemistry. I will combine this relative model with partitioning experiments to allow for quantitative modelling of fluids in subduction zones and mid-ocean ridges, which control element cycling between the Earth’s interior and surface. I will also reconstruct ocean chemistry back in time, especially for the early Earth where life developed. More generally, given the ubiquity of water-rock interaction in natural and industrial processes, this model will improve our understanding and modelling capability of a wide variety of processes in the Earth Sciences and beyond.
Fields of science
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