Dramatic P-wave velocity drop due to micro-cracking during antigorite dehydration at high-pressure
Abstract
Tomographic and receiver functions studies reveal widespread zones of high elastic wave velocity ratios (V p /V s ) in subducting lithospheres, commonly interpreted as zones of elevated pore fluid pressure produced by dehydration of hydrous minerals at depth. In addition, high-resolution tomographic models reveal sharp P-wave velocity decreases in these areas, which cannot be reconciled with the densification of mineral assemblages expected under such pressure conditions but instead indicate a significant contribution of released fluids to bulk elastic properties during dehydration. Here we report pronounced compressional wave velocity (V p ) drops during antigorite dehydration in high-pressure, high-temperature experiments representative of subduction zone conditions. The rate and amplitude of V p decreases depend on dehydration kinetics, ranging from moderate, longlasting decrease under slow, near-equilibrium conditions (high pressurelow temperature) to fast, largeamplitude drop when the reaction is overstepped. Dehydration systematically produces anastomosing fracture networks and micro-cracks decorated with ultrafine grained reaction products. Effective medium modeling of a volume undergoing progressive antigorite dehydration, with fluid-filled cracks at pressures above 2.0 GPa, reproduces both the V p reductions observed in laboratory experiments and the elevated V p /V s ratios imaged in subducting slabs at depth when results are extrapolated to natural seismic frequencies. Together, experiments and velocity models therefore show that antigorite dehydration at high pressure occurs along fractures, forming transient fluid pathways that may locally weaken the rock.
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BibTeX
@article{baisset2026dramatic,
title = {{Dramatic P-wave velocity drop due to micro-cracking during antigorite dehydration at high-pressure}},
author = {Marie Baïsset and Arefeh Moarefvand and Julien Gasc and Loïc Labrousse and Alexandre Schubnel},
journal = {Earth and Planetary Science Letters},
year = {2026},
month = sep,
doi = {10.1016/j.epsl.2026.120325},
url = {https://insu.hal.science/insu-05766620v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Dramatic P-wave velocity drop due to micro-cracking during antigorite dehydration at high-pressure
AU - Marie Baïsset
AU - Arefeh Moarefvand
AU - Julien Gasc
AU - Loïc Labrousse
AU - Alexandre Schubnel
PY - 2026
DA - 2026/09/28
JO - Earth and Planetary Science Letters
DO - 10.1016/j.epsl.2026.120325
UR - https://insu.hal.science/insu-05766620v1
AB - Tomographic and receiver functions studies reveal widespread zones of high elastic wave velocity ratios (V p /V s ) in subducting lithospheres, commonly interpreted as zones of elevated pore fluid pressure produced by dehydration of hydrous minerals at depth. In addition, high-resolution tomographic models reveal sharp P-wave velocity decreases in these areas, which cannot be reconciled with the densification of mineral assemblages expected under such pressure conditions but instead indicate a significant contribution of released fluids to bulk elastic properties during dehydration. Here we report pronounced compressional wave velocity (V p ) drops during antigorite dehydration in high-pressure, high-temperature experiments representative of subduction zone conditions. The rate and amplitude of V p decreases depend on dehydration kinetics, ranging from moderate, longlasting decrease under slow, near-equilibrium conditions (high pressurelow temperature) to fast, largeamplitude drop when the reaction is overstepped. Dehydration systematically produces anastomosing fracture networks and micro-cracks decorated with ultrafine grained reaction products. Effective medium modeling of a volume undergoing progressive antigorite dehydration, with fluid-filled cracks at pressures above 2.0 GPa, reproduces both the V p reductions observed in laboratory experiments and the elevated V p /V s ratios imaged in subducting slabs at depth when results are extrapolated to natural seismic frequencies. Together, experiments and velocity models therefore show that antigorite dehydration at high pressure occurs along fractures, forming transient fluid pathways that may locally weaken the rock.
SN - 0012-821X
ER -