For a better understanding of aqueous fluids in subduction zones

Nature journal has published a paper by Branco Weiss fellow Matthieu Emmanuel Galvez with the title “Implications for metal and volatile cycles from the pH of subduction zone fluids”.

While water-based chemical reactions are essential to Earth’s surface chemistry, water is also crucial to our planet’s inner chemical dynamics. Subduction zones, where oceanic plate tectonics sink into the Earth’s interior, are the most important geodynamic setting where surface water is delivered to the deep Earth. There, it promotes melting of the crust and mantle and contributes to the global recycling of volatile elements and metals. The transport and exchange — the cycles — of these elements on Earth are controlled by the chemistry of aqueous fluids, and they participate in forming the energetic and mineral resources that fuel our societies. Consequently, characterizing the reactivity of supercritical aqueous solutions in subduction zones is a problem of both scientific and societal relevance in Earth science, but has long been a major challenge.

In their research, Matthieu Emmanuel Galvez and his team used thermodynamic models of fluid–rock equilibria at elevated pressure and temperature to predict the sensitivity of the pH of subduction zone fluids to a range of parameters, such as pressure, temperature, rock composition and mineralogies. The pH and ionic composition of fluids in the deep Earth are critical properties that provide insight into the exchange of volatiles, such as C, and metals between the surface and the Earth’s interior over geological time. The published findings provide a perspective on the controlling reactions that have coupled metal and volatile cycles in subduction zones for more than 3 billion years.

Read the paper in Nature and on the Nature website:
Galvez ME, Connolly JAD, Manning CE. Implications for metal and volatile cycles from the pH of subduction zone fluids. Nature 539, 420–424 (2016). DOI: 10.1038/nature20103

Read the news on the Deep Carbon Observatory website