Volatiles in Magmatic Systems

The isotope composition of magmatic volatiles and related isotope fractionation processes can be deduced by analyses of glasses, volcanic gases, and hot springs. The main process that can cause isotope fractionation of volatile compounds is degassing 

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The objective of this chapter is to review available stable isotopic data on seafloor hydrothermal systems. However, this goes far beyond a simple literature review because much new, previously unpublished data, collected by the author, is included. In addition, an important goal of this chapter is to interpret the stable isotope systematics of seafloor hydrothermal systems in the context of fluid-rock reactions and geochemical reaction calculations. Boiling and supercritical phase-separation, volcanic eruption and dike-emplacement events, addition of magmatic volatiles, and bacterial fractionation processes will be discussed where applicable. In addition to the commonly measured stable isotopes of C, O, H, and S, stable isotope ratios of B, Li, N, Cl, Cu, and Fe are included where data are available. Much new data has appeared since the last comprehensive overview of stable isotopes in seafloor hydrothermal systems (Shanks et al. 1995). This includes a wealth of information on hydrothermal systems related to volcanic arcs, back-arc spreading centers, seamounts, and serpentinized ultramafics. 

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