Bromine concentrations in a heterogeneous Earth´s mantle

Volatile elements play a crucial role in geological processes within Earth`s mantle and crust. They influence for example the viscosity of melts, which in turn affects the nature of volcanic eruptions. On a global scale, volatile elements can significantly affect the mode of convection in the Earths mantle responsible for heat transport and planetary cooling. The heavy halogens, chlorine, bromine, and iodine, are particularly important due to their unique chemical properties which makes them excellent tracers for the distribution and transport of volatiles within the Earths mantle, as well as their recycling from the Earth`s surface back into the mantle in subduction zones. Despite their significance, knowledge about the quantities and distribution of bromine and iodine in the mantle remains limited. This is primarily due to their extremely low concentrations in the major minerals of the upper mantle and the lack of precise data describing their behavior during geological processes, such as partial melting. These gaps in understanding hinder to date a comprehensive view of the role of halogens in the global cycle of volatile substances. This research project aims to identify the primary minerals that store bromine in the rocks of the Earths upper mantle. Additionally, it seeks to enhance our understanding of the distribution and transport of bromine within the mantle and subduction zones To achieve these goals and accurately measure the extremely low concentrations of bromine in mantle minerals, the project will combine established analytical methods in an innovative way. First, samples will be irradiated with neutrons to convert bromine into krypton, a noble gas. Then, a UV-laser will be used to ablate minute amounts of sample material, which will subsequently be analyzed using noble gas mass spectrometry. This cutting-edge approach will enable precise determination of bromine concentrations in individual minerals from both natural and experimental samples. The analysis of natural samples will help identify the primary carriers of bromine in the mantle. Furthermore, high-pressure, high-temperature experiments simulating the formation of partial melts in the upper mantle will be conducted to determine and quantify the distribution of bromine within the Earths mantle. The project will also investigate how bromine is incorporated into the crystal structures of key mantle minerals and assess the influence of parameters such as pressure, temperature, and chemical composition. Ultimately, the data obtained will provide valuable insights into how volatile elements contributed to the enrichment of volatiles in the early Earth, thus laying the foundation for the origin of life.