The Earth’s deep chlorine (Cl) cycle remains poorly understood. A major amount of Cl is brought into the mantle by subduction, but a significant fraction is returned as Cl-rich brines, although high concentrations of Cl in parts of the mantle are attested to by inclusions in diamonds. Cl-rich brines likely play central roles in transporting elements to form magmatic ore deposits. The proposed research will investigate the deep Cl cycle from an experimental perspective, focusing on Cl partitioning and δ37Cl stable isotope fractionation between fluids, melts and relevant mantle phases. The high pressure-temperature experiments will be performed at the Australian National University, Australia and the University of Frankfurt, Germany, with Cl analyses and isotope fractionation enabled by state-of the-art instruments (SHRIMP in Canberra and SIMS in Heidelberg, Germany). These innovative experiments will help quantify the Earth’s deep halogen cycle, while also providing constrains to test hypotheses on magmatic ore deposit formation from a perspective that is significantly different from those currently available. During his Diploma (University of Mainz), PhD, and post doctoral studies (University of Münster; Sorbonne Université Paris) the applicant used a wide range of analytical and experimental methods, while gaining a profound knowledge of halogens, isotope fractionation, and phase equilibria of mantle and crust. He thus brings a wealth of theoretical, experimental and analytical experience to the project, which will compliment the expertise that he aims to acquire in ion microprobe techniques. Both the ANU and the University of Frankfurt would benefit from the applicant’s research experience, which will be applied to a novel research direction. In return the applicant would greatly benefit from gaining ion probe analysis skills and deepening his knowledge about experiment petrology and ore geology at two of the world’s leading institutions in these fields.