Single‐Crystal Elasticity of Antigorite at High Pressures and Seismic Detection of Serpentinized Slabs

Grafulha Morales, Luiz Fernando

Criniti, Giacomo

Kurnosov, Alexander

Boffa Ballaran, Tiziana

Speziale, Sergio

Marquardt, Katharina

Capitani, Gian Carlo

Marquardt, Hauke

DOI: https://doi.org/10.1029/2022GL099411
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10355
Criniti, Giacomo; 1 Bayerisches Geoinstitut University of Bayreuth Bayreuth Germany
Kurnosov, Alexander; 1 Bayerisches Geoinstitut University of Bayreuth Bayreuth Germany
Boffa Ballaran, Tiziana; 1 Bayerisches Geoinstitut University of Bayreuth Bayreuth Germany
Speziale, Sergio; 5 German Research Centre for Geosciences GFZ Potsdam Germany
Marquardt, Katharina; 6 Department of Materials Faculty of Engineering Imperial College London London UK
Capitani, Gian Carlo; 7 Department of Earth and Environmental Sciences University of Milano‐Bicocca Milano Italy
Marquardt, Hauke; 2 Department of Earth Sciences University of Oxford Oxford UK
Abstract
The subduction of serpentinized slabs is the dominant process to transport “water” into Earth's mantle, and plays a pivotal role for subduction dynamics. Antigorite, the most abundant serpentine mineral in subduction settings, may imprint a seismic signature on serpentinized slabs, making them seismically distinguishable from the dry, non‐serpentinized ones. However, the complete single‐crystal elasticity of antigorite has not been experimentally constrained at high pressures, hindering the use of seismological approaches to detect serpentinization in subducting slabs. Here, we report the full elastic stiffness tensor of antigorite by single‐crystal Brillouin spectroscopy and X‐ray diffraction up to 7.71(5) GPa. We use our results to model seismic properties of antigorite‐bearing rocks and show that their seismological detectability depends on the geometrical relation between seismic wave paths and foliation of serpentinized rocks. In particular, we demonstrate that seismic shear anisotropy shows low sensitivity to serpentinization for a range of relevant geometries.
Plain Language Summary: The subduction of serpentinized slabs plays a key role in the deep recycling of water into the Earth's interior. Antigorite is the main serpentine mineral in subducting slabs, and the most important carrier of water. Antigorite‐bearing rocks are predicted to have a distinct seismic signature, potentially allowing them to be detected with seismological approaches. However, our current knowledge on seismic properties of antigorite‐bearing rocks is limited, mostly hampered by a lack of experimental constraints on single‐crystal elasticity of antigorite at relevant pressures. In this study, state‐of‐the‐art techniques were employed to produce the first experimental description of the complete high‐pressure elasticity of antigorite single crystals. Our experimental data set was implemented in the modeling of seismic properties of antigorite‐bearing rocks at pressures relevant for subduction. Our results were used to discuss the relation between seismic wave path and shear wave anisotropy in serpentinized slabs, and challenge the use of shear wave splitting as a proxy for serpentinization in slabs.
Key Points:
Single‐crystal elasticity of antigorite at high pressures is determined by Brillouin spectroscopy and X‐ray diffraction experiments.
Seismic signature of serpentinized slabs is constrained in a relevant composition‐pressure space.
Serpentinization in slabs may be undetectable through shear wave anisotropy.