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- Title
In situ TEM nanomechanical testing of antigorite plasticity and faulting.
- Authors
Idrissi, Hosni; van der Werf, Thomas; Samaee, Vahid; Lumbeeck, Gunnar; Pardoen, Thomas; Schryvers, Dominique; Cordier, Patrick
- Abstract
It is now recognized that large earthquakes are preceded and followed by a wide range ofevents, e.g. bursts of low-frequency earthquakes (LFEs), tremors, which can release as muchstrain as megathrust earthquakes. These events are related to creeping parts of the faultinterface for which some recent models have inferred the possibility of viscosities of theorder of some 1017 Pa.s. However, the detailed mechanisms associated with these events arepoorly known. In this study we adopt the mineral physics point of view and address the issueof the mechanical properties of antigorite which, among serpentines, is an importantcomponent of fault rheology. Given its particular crystal structure and its complexmicrostructure, the rheology of antigorite is still poorly understood. Standard ductileprocesses involving dislocation glide have been reported, but other mechanisms like kinking,delamination, which can lead to a semi-brittle behaviour are likely to contribute as well.Consequently, the type of rheological law that is adapted to this mineral is still a matter ofdebate. Recently, the development of a new generation of advanced instruments for quantitativein situ TEM nanomechanical testing has open a new field of investigation of mechanicalproperties in the transmission electron microscope (TEM). The major advantage of thistechnique is to provide a direct, visual access, to the deformation mechanisms as theyoperate while recording the mechanical response in-situ inside the microscope.In the present work, small beams (4×1×0.1 μm3) of antigorite are prepared byFocused Ion Beam and deformed in tension in the TEM. Cyclic deformation isapplied in the load control mode using the PI-95 TEM picoindenter holder and thePush-to-Pull (PTP) device (Bruker.Inc). Automated crystal orientation mapping in TEM(ACOM-TEM) was used prior to the in-situ tensile TEM tests in order to obtainstatistical information regarding the local orientation of the grains and the nature of theinterfaces. Despite applied stresses close to 1 GPa, no dislocation activity could be observed. Incontrast, significant plasticity, largely recoverable, resulted from the development of damageat interfaces. We propose that due to the crystal structure of antigorite, the interfacesrepresent a key factor in controlling its mechanical properties.
- Subjects
CRYSTAL orientation; ANTIGORITE; ION beams; TENSILE tests; CRYSTAL structure
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article