Budget and cycle of halogens in the mantle

Despite their low concentrations in the Earth’s mantle, halogens are thought to play an important role in the evolution of magmatic systems, the transport of metals in magmatic systems, the degassing of volcanoes, and the interaction between volcanic gases and the Earth's atmosphere. Understanding of the high-temperature aspects of the halogen geochemical cycle and their role in igneous processes is thus a major step for using halogens as a geochemical tool. Indeed, as they are thought not to be (or only slightly) fractionated during magmatic evolution, they could provide information about their sources.
With the improvement of analytical techniques, I and Br, the rarest halogens started to be measured. Any dataset presents all of the halogen compositions combined with other key elements or isotopes, whereas it would help to understand the halogen behavior during magmatic processes. This project aims at acquiring the first large and complete dataset involving all halogens, using melt inclusions from different geological settings (island arc, ocean island). This dataset, documenting the heterogeneity at small and large scales of halogens in the Earth’s mantle, would provide new data to understand the halogens’ behavior at high temperature and would help to constrain the role of ocean crust recycling in the halogen cycle.
Better knowledge of the halogens’ behavior at high temperature could then be applied to other research field in geosciences, such as metamorphism (fluid/rock interaction) and cosmochemistry (Earth's starting halogens content; halogens degassing history; halogens fractionation in meteorites).

 

Supervisor
Anne-Sophie Bouvier

PhD student
Mélina Manzini

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