How Salty Water Dictates the Pace of Earth's Deepest Geological Transformations
In short: Serpentinization is a vital process that reshapes the ocean floor and potentially fuels life on distant moons. Yet, scientists have long struggled to measure its speed. Recent experiments reveal that the salinity of circulating fluids acts as a master dial, slowing down these reactions as salt concentrations rise.
Serpentinization is a fundamental hydration process where ultramafic rocks, such as olivine, react with aqueous fluids at temperatures below 400 °C. This transformation produces a suite of minerals including serpentine, brucite, and magnetite. It is a major driver of mass exchange between the Earth's mantle and surface, significantly altering the physical and chemical properties of the oceanic lithosphere. Beyond Earth, this process is considered a key factor in the habitability of icy moons orbiting Jupiter and Saturn.
Despite its importance, the rates at which these reactions occur have remained poorly constrained, with previous studies yielding widely divergent results. To address this, researchers developed an innovative method using synthetic fluid inclusions as micro-reactors. By trapping fluids within olivine crystals at 650 °C and 5.5 kbar, they created controlled environments to monitor mineral precipitation in real time. These experiments, conducted at 280 °C, demonstrated that the reaction rate is strongly dependent on the salinity of the fluid.
The data shows that as salinity increases, the activity of water decreases, which directly inhibits the serpentinization process. This discovery provides a clearer understanding of how environmental factors influence the geochemical cycling of volatile species like water, carbon dioxide, and hydrogen sulfide. Because serpentinization also generates hydrogen and methane, which can support deep-sea chemotrophs, these findings offer critical insights into the potential for life in extreme environments, both on our planet and across the solar system.
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Sources
- Summary by Intellect · source: Effect of water activity on rates of serpentinization of olivine - Nature Communications
- Also: Serpentinization
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