Field-Based Evidence for Intra-Slab High-Permeability Channel Formation at Eclogite-Facies Conditions During...

Area of Science:

• Geochemistry
• Tectonics
• Metamorphic Petrology

Background:

• Fluid release from subducting oceanic lithosphere is crucial for subduction zone geodynamics, influencing volcanism, seismicity, and exhumation.
• Fundamental details of fluid composition, flow, and rock reactivity in subduction zones require further investigation.

Purpose of the Study:

• Investigate a multi-kilometer metasomatic system in Alpine Corsica to understand fluid-rock interactions.
• Quantify metasomatic mass changes, fluid fluxes, and carbon fluxes along intra-slab fluid pathways.

Main Methods:

• Mass balance analysis to quantify metasomatic changes.
• Analysis of fluid-mediated processes along a major intra-slab interface.
• Assessment of carbon fluxes associated with metasomatic events.

Main Results:

• Identified two distinct metasomatic stages resulting from deep fluid infiltration with consistent flow direction.
• Quantified significant metasomatic mass changes and high time-integrated fluid fluxes (10^4-10^5).
• Demonstrated that channelized fluids lead to carbon fluxes orders of magnitude higher than local dehydration reactions.

Conclusions:

• Major intra-slab interfaces act as fluid channels, facilitating episodic fluid flow.
• The studied metasomatic system is a natural analogue for predicted high permeability channels in numerical simulations.
• Channelized fluid flow significantly enhances carbon transport within subduction zones.