National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2003

Composition and evolution of hydrothermal fluids

Butterfield, D.A., W.E. Seyfried, Jr., and M.D. Lilley

In Energy and Mass Transfer in Submarine Hydrothermal Systems, P.E. Halbach, V. Tunnicliffe, and J. Hein (eds.), Dahlem Workshop Report Volume 89, Free University of Berlin, Berlin, 123–161 (2003)

Aqueous fluids provide the link between the solid earth and the biosphere and are the primary vehicle for the transport of heat and chemical mass between the ocean and the oceanic lithosphere. Extensive exploration and sampling along mid-ocean ridges (MORs) have revealed a wide range in composition of hydrothermal fluids, and experimental studies have determined thermodynamic data for mineral-fluid systems that are analogous to submarine hydrothermal systems. The primary characteristics of basalt-hosted hydrothermal fluids can be understood and modeled with the processes of mineral-fluid equilibrium in a hot reaction zone, fluid phase separation and segregation, and mixing of different fluid reservoirs. Fluid composition and mineral-fluid thermodynamic data to constrain non-MOR basalt (MORB) hydrothermal systems need more development. Likewise, kinetic studies relevant to hydrothermal systems are limited, as is our knowledge of where thermodynamic equilibrium might cease to be the controlling factor, and reaction rates take over. This chapter reviews the spatial and temporal variability in fluid chemistry, the controls on fluid chemistry in MOR hydrothermal systems, the relation of diffuse fluids to high-temperature fluids, new methods in hydrothermal chemistry, and suggested ways to advance hydrothermal chemistry and related fields.

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