Quantifying the Volume Changes During Serpentinization of Peridotite using Hydrothermal Laboratory Experiments and X-ray Microtomography

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

The interaction of mantle rocks with aqueous fluids (i.e. serpentinization) is a widespread hydrothermal process associated with tectonic plate boundaries. By adding significant amounts of water to mantle rocks, serpentinization causes a decrease in rock density and mechanical strength. As a result serpentinization is believed to play a major role in the formation and breakup of continents, seafloor spreading and subduction. The hydration of mantle rocks impacts the global geochemical cycles of volatiles, most notably water and carbon dioxide, with strong implications for Earth's climate, mantle melting in volcanic arcs and the seismicity of subduction zones. Serpentinization has operated throughout most of Earth's history and has, via the production of hydrogen, created geochemical conditions capable of supporting microbial life in extreme subsurface environments. Despite its key role in a number of global geological processes, the most basic relations between chemical mass transfer during serpentinization and associated changes in rock volume have remained poorly quantified. This project is designed to improve our understanding of these processes. The overall objective of this research is to link changes in fluid composition and mineralogy to concomitant changes in volume as a function of time and temperature using a combination of hydrothermal laboratory experiments, mineral and fluid analysis, X-ray microtomography (µ-CT), and geochemical modeling. In particular this project will resolve whether serpentinization can be regarded as an isochemical or an isovolumetric process, a long-standing and strongly debated question in serpentinization research. The results of this study will have important ramifications for our understanding of the geochemistry, emplacement and deformation of serpentinite in a wide range of geological settings.