Author name: Nicole Métrich

Sulfur is a ubiquitous element whose variable valence states (S2-, S0, S4+, S6+) allow it to participate in a wide variety of geochemical and biogeochemical processes. Depending on its redox state and controlling species, sulfur dissolved in magma may be fractionated into a water-rich phase and sulfur-bearing minerals. Retrieving information on the original sulfur abundance and isotopic signature of a magma is challenging and requires deciphering the different processes that may have operated during its evolution en route to the surface. Advances made in thermodynamic modeling, experimentation on sulfur solubility and diffusion in silicate melts, and microanalytical techniques for probing sulfur’s speciation and isotopic signature at the micrometer scale are providing an outstanding picture of sulfur evolution in magmas.

Sulfur is a widely distributed element on Earth and in the solar system. Its multiple valence states (S2- to S6+) allow it to participate in numerous geochemical and biochemical processes. It may be one of the light elements in the Earth’s core and may have been crucial in core formation. Sulfur is an essential component in all life on Earth and likely supported earliest life. Sulfur geochemistry is used to understand the early evolution of Earth’s atmosphere and hydrosphere, and serves as a monitor of volcanic SO2 and H2S and as a tracer of anthropogenic sources of sulfur. Recent advances in the use of multiple sulfur isotopes (32S, 33S, 34S, and 36S) and in situ isotopic measurements will help to develop sulfur stable isotopes as a vital tracer in the Earth and planetary sciences and will provide applications for understanding inorganic and biogenic processes.