Fluids in Earth’s surface environment are commonly present as an aqueous-vapour phase, and evaporation, boiling and liquid-vapour separation play a key role in element transport, from the evaporation of seawater, to the formation of metal ores, from porphyry to epithermal  Conventionally, it has been assumed that metals concentrate in the liquid phase and that boiling promotes the partitioning of volatile elements alone. However, over recent years this conventional understanding has been questioned and there is increasing evidence from experimental studies that a number of metal species are stable in aqueous vapour, and that in all cases, metal solubility may be orders of magnitude higher than predicted from volatility data alone . This is consistent with modelling  observations of metals in the vapour phase of fluid inclusions  and volcanic condensates . Consequently, the vapour phase is now considered as being capable of transporting substantial quantities of many metals in its own right.
If metal transport via the vapour phase is simply controlled by volatile behaviour, then in principle, isotope fractionation should occur, with lighter isotopes being lost more readily to the vapour phase than heavier isotopes. However, contrary to this expected behaviour our preliminary data for Fe stable isotopes in the vapour phase of fluids from the Reykjanes hydrothermal system in Iceland show preferential enrichment of the heavy isotopes of Fe. At this stage it is not clear whether this fractionation results from the precipitation of sulfide or other secondary phases during boiling, or metal speciation in the vapour phase
This project will involve the measurement of metal stable isotopes in the liquid and vapour phase from first, samples taken from a range of high-temperature hydrothermal systems hosted by basalt, gneiss and sediments in Iceland, Italy and Germany, combined with thermodynamic modelling of the dominant elemental species present, second experimental gas-liquid samples, involving evaporation and boiling experiments on a range of surface water compositions. These results will allow us to determine the role of volatile behaviour, metal speciation, and secondary phase precipitation in the segregation and transport of metals in the vapour phase.