Publications

@article{eberhard_coupling_2025,

title = {Coupling antigorite deformation and dehydration in high-pressure experiments},

author = {Lisa Eberhard and Mattia Luca Mazzucchelli and Stefan Markus Schmalholz and Holger Stünitz and Ahmed Addad and Patrick Cordier and Oliver Plümper},

url = {https://doi.org/10.1007/s00410-025-02255-z},

doi = {10.1007/s00410-025-02255-z},

issn = {1432-0967},

year  = {2025},

date = {2025-08-01},

urldate = {2025-08-01},

journal = {Contributions to Mineralogy and Petrology},

volume = {180},

number = {9},

pages = {64},

abstract = {The dehydration of antigorite is an important reaction in subduction zones with implications on both geochemical and geophysical processes. In this experimental study we focus on the onset of antigorite dehydration and investigate various chemical and physical parameters as possible drivers for the fluid release. We performed hydrostatic and co-axial Griggs experiments on antigorite serpentinites with variable chemical composition and microstructures at high-pressure and high-temperature conditions across the antigorite dehydration (1.5 GPa, 620–670 °C). For these conditions, our thermodynamic models predict the formation of olivine from magnetite decomposition and partial dehydration of antigorite. Detailed analyses of the run products reveal limited magnetite decomposition. Antigorite dehydration is restricted to samples that have been deformed. Nano-sized olivine and orthopyroxene formed locally in oblique dehydration bands and exhibit neither a clear crystallographic preferred orientation nor a topotactic relation with precursor antigorite. We argue that limited local dehydration in our experiments is related to strain and variations in reaction kinetics. Systematic investigation excludes mineralogical and chemical heterogeneities, and temperature gradients as reaction driving potentials. The structural relation of the dehydration bands suggests deformation-related dehydration, which is supported by numerical simulations that couple reaction kinetics with mechanical work rate and self-consistently predict dehydration bands. In this scenario, strain concentration due to applied axial stress locally increases the internal energy of antigorite to reach the activation energy of the dehydration reaction, enabling dehydration. This study highlights the importance of coupled mechanical and chemical processes and provides a mechanistic framework for deformation-induced dehydration of antigorite.},

keywords = {Continuum modeling, mineral-fluid interaction, THMC},

pubstate = {published},

tppubtype = {article}

}

@article{mazzucchelli_fluid-mineral_2024,

title = {Fluid-mineral Equilibrium Under Nonhydrostatic Stress: Insight From Molecular Dynamics},

author = {Mattia L. Mazzucchelli and Evangelos Moulas and Boris J. P. Kaus and Thomas Speck},

url = {https://ajsonline.org/article/92881-fluid-mineral-equilibrium-under-nonhydrostatic-stress-insight-from-molecular-dynamics},

doi = {10.2475/001c.92881},

issn = {1945-452X, 0002-9599},

year  = {2024},

date = {2024-02-01},

urldate = {2024-02-01},

journal = {American Journal of Science},

volume = {324},

abstract = {The interpretation of phase equilibria and reactions in geological materials is based on standard thermodynamics that assumes hydrostatic and homogeneous stress conditions. However, rocks and minerals in the lithosphere can support stress gradients and nonhydrostatic stresses. Currently, there is still not an accepted macroscopic thermodynamic theory to include the effect of nonhydrostatic stress on mineral reactions, and the use of several thermodynamic potentials in stressed geological system remains under debate. In experiments under nonhydrostatic stress, it is often difficult to resolve the direct effect of differential stress on phase equilibria because pressure gradients may be developed. Such gradients can affect the metamorphic equilibria at the local scale. Here, we investigate the direct effect of a homogeneous, nonhydrostatic stress field on the solid-fluid equilibrium using molecular dynamics simulations at non-zero pressure and elevated temperature conditions. Our results show that, for simple single-component systems at constant temperature, the equilibrium fluid pressure of a stressed system is always larger than the value of fluid pressure at hydrostatic stress conditions. The displacement of the equilibrium value of the fluid pressure is about an order of magnitude smaller compared to the level of differential stress in the solid crystal. Thus, phase equilibria can be accurately predicted by taking the fluid pressure as a proxy of the equilibration pressure. On the contrary, the mean stress of the solid can deviate substantially from the pressure of the fluid in stressed systems at thermodynamic equilibrium. This has implications on the use of thermodynamic pressure in geodynamic models since the fluid pressure is a more accurate proxy for predicting the location of metamorphic reactions, while the equilibrium density of the solid has to be determined from its mean stress.},

keywords = {mineral-fluid interaction, molecular dynamics, thermodynamics},

pubstate = {published},

tppubtype = {article}

}