The abundance and distribution of sulfur (S) is of key importance for the occurrence and interpretation of geochemical processes. For example, the abundance and distribution of S controls potential sulfide or sulfate precipitation from silicate melts and therefore the cycles of sulfide/sulfate-loving elements such as Se, Te, Bi, the composition and properties of volcanic gases and the composition of planetary metallic cores. On the other hand, the measurement of sulfur in ancient (extra)-terrestrial rocks provides important clues to the processes of volatile loss and delivery in the early solar system. Prior to the project, the distribution of S in the deep interior and in small planetesimals were not well constrained. The main objectives / research questions from the SuChaMa project were therefore:
1. How much S can be stored in the deep terrestrial interior? The project has successfully studied the potential of S storage in the deep Earth by sulfide liquids, by analyzing and interpreting previous experiments at pressures and temperatures relevant to the deep Earth. The sulfur content at sulfide saturation was quantified and used to assess whether sulfide liquid saturation during differentiation of the Earth would be a likely process. The interpretation of previous experimental data showed that it is unlikely that a sulfide liquid segregated from the terrestrial silicate magma ocean in its early history.
2. How much S is lost during planetary accretion from metal-rich planetesimals? Another important aspect of the project was to investigate the potential evaporative loss from S from metal-rich planetesimals. For this purpose, high-temperature evaporation experiments were performed in a furnace, at vacuum and room pressures. Geochemical analyses of the run products provided the first experimental constraints on S evaporation from metal melts. The experiments show that S behaves volatile, but significantly less so as commonly assumed.
The geochemical interpretation of experiments and the conducted evaporation experiments were not only novel, they were thus critical in quantifying the flux of S in the terrestrial planets.
The Institute for Mineralogy at the University of Münster provided the much-needed modern and reliable experimental and analytical equipment, as well as the outstanding technical and scientific personnel. The project was therefore an excellent match, and it is expected that the project results reinforce the reputation of the University of Münster as one of Europe’s leading institutes for application of experimental petrology to planetary science.
