Fluid-rock interaction and mantle wedge deformation across space and timescales – COLDNOSE

Here, I propose to conduct an original multidisciplinary project dedicated to imaging and modeling geological processes in the Cold Nose region. Samples from two natural laboratories (in the Urals and the Antilles), where such fossil Cold Noses are visible at the surface, will be used to document multiscale deformation mechanisms and fluid-rock interaction processes.

State-of-the-art analytical tools will be combined with field and structural data on these outcrops to decipher the geochemical and microstructural properties of hydrated mantle rocks (serpentinites). This dataset will serve as a guide to drive high-resolution thermomechanical numerical models to quantify critical parameters such as fluid migration velocity, effective viscosity and shear stresses at the base of the cold nose. Parameter tuning will be performed via self-consistent iterations based on our geological, petro-geochemical observations as well as seismological data and post-seismic GPS displacement modeling.

First results are expected for 2026.

Implications of this research include: (i) The impact on high-pressure fluid mobility, influencing global volatile budgets and their recycling in arc magmas. (ii) The debate on the amount and distribution of serpentinites in the cold nose and (iii) The deformation of the serpentinized cold nose at different time scales, affecting the modeled thermal structure of subduction zones, with consequences for rheological models of the interface. The COLDNOSE project will shed new light on the mechanisms rooted in this poorly understood region of subduction zones and will thus provide critical constraints for (i) the mechanisms at the source of fast and slow slip events (ii) the coupling and seismic hazard maps and finally (iii) increase our capabilities to identify areas likely to generate mega-ruptures in active subduction zones.

The understanding of stress distribution and seismic instabilities along the subduction interface region is critical to document coupling mechanisms and hence assess seismic hazard along convergent margins. Yet, the physical and mechanical processes rooted in the hydrated, serpentinized mantle above subduction zones (the “cold nose”) remain debated and poorly understood, despite fundamental consequences on the elastic loading of the seismogenic interface. Here I propose to lead an original multi-disciplinary project dedicated at imaging and modeling geological processes in the cold nose region. Samples from two natural laboratories (in the Polar Urals and in the Dominican Republic), where such fossil cold nose settings are now visible at the Earth’s surface, will be used to document multi-scale deformation mechanisms and fluid-rock interaction processes. State-of-the-art analytical tools will be combined with field and structural data on cold nose exposures to decipher geochemical and microstructural properties of hydrated mantle rocks (serpentinites). This wealth of data will serve as a guideline to run high-resolution thermo-mechanical numerical models aiming at understanding and quantifying critical parameters such as fluid migration velocity, effective viscosity and shear stresses on the deep subduction interface. Model refinement and parameter adjustment will be implemented via self-consistent iterations based on geological, petro-geochemical observations along with high-resolution seismological data and post-seismic geodetic modelling results. The COLDNOSE project will shed a new light on mechanisms rooted in this poorly known region of subduction zones and thus provide critical constrains for (i) fast and slow slip events source mechanisms (ii) locking and seismic hazard maps and ultimately (iii) increase our capabilities of identifying the areas susceptible to generate megathrust earthquake events.