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Title: Faulting of natural serpentinite: Implications for intermediate-depth seismicity

Abstract

The seismic potential of serpentinites at high pressure was investigated via deformation experiments on cored natural serpentinite samples, during which micro-seismicity was monitored by recording Acoustic Emissions (AEs). Deformation was performed at pressures of 3–5 GPa, using a Deformation-DIA device, and over a wide range of temperatures, both within and outside antigorite's stability field. Below 400 °C, serpentinite deformation involves “silent” semi-brittle mechanisms, even in cases where strain localization is observed. At high temperature (i.e., above 600 °C), despite conditions propitious to dehydration embrittlement (i.e., fast strain rates and reaction kinetics), joint deformation and dehydration lead to ductile shear, without generation of AEs. Brittle behavior was observed in a narrow temperature window ca. 500 °C. In this latter case, AEs are consistently observed upon faulting and extremely sharp strain localization is observed in recovered samples. The resulting microstructures are consistent with the inverse ductile-to-brittle transition proposed by Proctor and Hirth (2016) in antigorite. This may therefore be a source of seismicity in subducting slabs at mantle pressures and temperatures from 500 to 600 °C. However, the acoustic signal observed here is orders of magnitude weaker than what is obtained at low PT conditions with brittle failure, consistently with low radiationmore » efficiency of serpentinite faulting (Prieto et al., 2013) and suggests that other mechanisms are responsible for large intermediate-depth earthquakes. In fact, the present results are in line with a recent study (Ferrand et al., 2017), that suggests that intermediate earthquakes are likely induced by mechanical instabilities due to dehydration in partly hydrated peridotites.« less

Authors:
; ORCiD logo; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFFOREIGN
OSTI Identifier:
1372241
Resource Type:
Journal Article
Resource Relation:
Journal Name: Earth and Planetary Science Letters; Journal Volume: 474; Journal Issue: C
Country of Publication:
United States
Language:
ENGLISH
Subject:
58 GEOSCIENCES; high pressure; acoustic emission; serpentinite dehydration; intermediate depth earthquakes; synchrotron x-ray diffraction; deformation-DIA

Citation Formats

Gasc, Julien, Hilairet, Nadège, Yu, Tony, Ferrand, Thomas, Schubnel, Alexandre, and Wang, Yanbin. Faulting of natural serpentinite: Implications for intermediate-depth seismicity. United States: N. p., 2017. Web. doi:10.1016/j.epsl.2017.06.016.
Gasc, Julien, Hilairet, Nadège, Yu, Tony, Ferrand, Thomas, Schubnel, Alexandre, & Wang, Yanbin. Faulting of natural serpentinite: Implications for intermediate-depth seismicity. United States. doi:10.1016/j.epsl.2017.06.016.
Gasc, Julien, Hilairet, Nadège, Yu, Tony, Ferrand, Thomas, Schubnel, Alexandre, and Wang, Yanbin. Fri . "Faulting of natural serpentinite: Implications for intermediate-depth seismicity". United States. doi:10.1016/j.epsl.2017.06.016.
@article{osti_1372241,
title = {Faulting of natural serpentinite: Implications for intermediate-depth seismicity},
author = {Gasc, Julien and Hilairet, Nadège and Yu, Tony and Ferrand, Thomas and Schubnel, Alexandre and Wang, Yanbin},
abstractNote = {The seismic potential of serpentinites at high pressure was investigated via deformation experiments on cored natural serpentinite samples, during which micro-seismicity was monitored by recording Acoustic Emissions (AEs). Deformation was performed at pressures of 3–5 GPa, using a Deformation-DIA device, and over a wide range of temperatures, both within and outside antigorite's stability field. Below 400 °C, serpentinite deformation involves “silent” semi-brittle mechanisms, even in cases where strain localization is observed. At high temperature (i.e., above 600 °C), despite conditions propitious to dehydration embrittlement (i.e., fast strain rates and reaction kinetics), joint deformation and dehydration lead to ductile shear, without generation of AEs. Brittle behavior was observed in a narrow temperature window ca. 500 °C. In this latter case, AEs are consistently observed upon faulting and extremely sharp strain localization is observed in recovered samples. The resulting microstructures are consistent with the inverse ductile-to-brittle transition proposed by Proctor and Hirth (2016) in antigorite. This may therefore be a source of seismicity in subducting slabs at mantle pressures and temperatures from 500 to 600 °C. However, the acoustic signal observed here is orders of magnitude weaker than what is obtained at low PT conditions with brittle failure, consistently with low radiation efficiency of serpentinite faulting (Prieto et al., 2013) and suggests that other mechanisms are responsible for large intermediate-depth earthquakes. In fact, the present results are in line with a recent study (Ferrand et al., 2017), that suggests that intermediate earthquakes are likely induced by mechanical instabilities due to dehydration in partly hydrated peridotites.},
doi = {10.1016/j.epsl.2017.06.016},
journal = {Earth and Planetary Science Letters},
number = C,
volume = 474,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2017},
month = {Fri Sep 01 00:00:00 EDT 2017}
}