Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Other literature type English OPEN
Molli, Giancarlo ; Menegon, Luca ; Malasoma, Alessandro (2017)

The switching in deformation mode (from distributed to localized) and mechanisms (viscous versus frictional) represent a relevant issue in the frame of crustal deformation, being also connected with the concept of the brittle-<q>ductile</q> transition and seismogenesis. In subduction environment, switching in deformation mode and mechanisms may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). On the other hand, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in the localization of deformation and shear zone development, thus representing a case in which switching deformation mode and mechanisms interact and relate to each other. This contribution analyzes an example of a crystal plastic shear zone localized by brittle precursor formed within a host granitic-protomylonite during deformation in subduction-related environment. The studied structures, possibly formed by transient instability associated with fluctuations of pore fluid pressure and episodic strain rate variations may be considered as a small scale example of fault behaviour associated with a cycle of interseismic creep and coseismic rupture or a new analogue for episodic tremors and slow slip structures. Our case-study represents, therefore, a fossil example of association of fault structures related with stick-slip strain accomodation during subduction of continental crust.
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