[ESAC Seminar] Gage Coon

“Experimental serpentinization of dunite rock cores”

Serpentinization occurs due the hydration of ultramafic rocks in various tectonic settings. This hydration has been proposed as a source of geological hydrogen that could be engineered as a carbon-free energy carrier. However, the details of the hydrogen generation are complex and remain poorly understood. Water availability often limits reaction progress as the fluid-rock interactions modify permeability and generate grain-scale stresses due to the volumetric increase associated with the reaction. Most laboratory studies to date rely on powdered samples instead of solid rock cores and hence do not capture the full dynamics of fluid-rock interactions in natural settings. This study investigates how water availability and temperature influence serpentinization in intact dunite cores. Stress relaxation experiments were conducted in a Griggs-type solid medium deformation apparatus at 1.3 GPa confining pressure and 300–400 °C temperature for durations of 0 to 11 days with water contents ranging from 2 to 4 wt% relative to rock mass. The rocks were first loaded to ~200 MPa differential stress and left to creep. Microstructural analysis of post-experiment thin sections confirmed significantly increased serpentine content compared to the starting material and intricate fracture networks likely caused by both the volumetric increase during serpentinization as well as creep deformation. Continuous ultrasonic monitoring tracked in-situ P-wave velocity evolution (Vp), which decreased in one experiment from approximately 7.7 to 6.9 km/s over 11 days at 400 °C. These results connect observed seismic velocity changes to fluid–rock reactions in the deep lithosphere and provide constraints on serpentinization kinetics in intact ultramafic rocks.

ESAC Early-Career Seminar Series —

A forum for students and postdocs to share recent research, hone presentation skills, and build community among peers, sponsored by the EAPS Student Advisory Committee. Open to current EAPS graduate and undergraduate students and postdocs. Typically hosted on Thursdays during the semester, including pizza lunch.

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