Halogens in the Earth's mantle: Concentrations in nominally halogen-free mantle minerals and element partitioning during partial melting

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It has been well known for some time that nominally water-free minerals can store significant amount of water in Earth's mantle. This has fundamentally improved our understanding of Earth's interior as even small amounts of water are known to substantially affect phase stability, melting relations, and rheology of the mantle. The proposed project now aims to investigate, for the first time, element concentrations of Fluorine (F) and Chlorine (Cl) in a variety of mantle minerals. This could be important, as F and Cl are expected to have similar effects as water in the mantle, especially in regards to partial melting and rheological properties. F and Cl concentrations in nominally halogen-free mantle minerals are very low and will be measured with specifically designed in-situ methods, called secondary ion mass spectroscopy (SIMS). To better understand the geochemical behaviour of F and Cl in mantle rocks, and derived basalts, we will also determine the partitioning of F and Cl between mantle minerals and basaltic melts. These partition coefficients will help to understand how halogens behave during partial melting of the mantle and during fractionation of basalt.