Halogen concentrations and partitioning in subduction zone minerals at elevated pressures and temperatures

Abstract

Previous studies on volatile behaviour in the mantle have shown that the process of subduction represents an efficient barrier to the return of halogens (F, Cl, Br, I) to the upper mantle. However, this barrier, while efficient, is not complete. Halogen signatures have been found in material derived from the upper mantle, suggesting that halogens may persist within the subducting slab and be stored in mineral phases of the upper mantle. Candidate phases for the transfer to and potential fractionation and storage of halogens in the mantle are currently the subject of debate. To further knowledge of the halogen systematics of subduction zones, this project focuses on the geochemical analysis of suites of natural samples from the former subduction zone regions of the western and central Alps and western Norway. The Alpine suite represents subducted oceanic crust and may provide insight into the changes that occur in the slab during subduction. The Norway suite represents mantle wedge material and may provide information on halogens released from the slab during subduction. In addition to natural sample analyses, this project includes the experimental synthesis of high-pressure hydrous phases - humite-group minerals and lawsonite - to investigate the behaviour of fluorine in hydrous silicate minerals that could act as potential fluorine host phases at elevated pressures and temperatures. Oceanic, eclogite facies rocks from the western and central Alps contain variable concentrations of F (

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Ian Lyon (Supervisor), Raymond Burgess (Supervisor) & Alison Pawley (Supervisor)