Journal metrics

Journal metrics

  • IF value: 4.165 IF 4.165
  • IF 5-year value: 4.075 IF 5-year 4.075
  • CiteScore value: 4.28 CiteScore 4.28
  • SNIP value: 1.501 SNIP 1.501
  • SJR value: 1.060 SJR 1.060
  • IPP value: 4.21 IPP 4.21
  • h5-index value: 29 h5-index 29
  • Scimago H index value: 27 Scimago H index 27
Solid Earth, 8, 767-788, 2017
https://doi.org/10.5194/se-8-767-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
13 Jul 2017
Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica
Giancarlo Molli1, Luca Menegon2, and Alessandro Malasoma3 1Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria, 53, Pisa 56126, Italy
2School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth, UK
3TS Lab and Geoservices, Via Vecchia Fiorentina, 10, Cascina 56023, Pisa, Italy
Abstract. 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–ductile transition and seismogenesis. In a subduction environment, switching in deformation mode and mechanisms and scale of localization may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). However, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in some cases for the localization of deformation and shear zone development, thus representing a case in which switching deformation mechanisms and scale and style of localization (deformation mode) interact and relate to each other. This contribution analyses an example of a millimetre-scale shear zone localized by brittle precursor formed within a host granitic protomylonite. The studied structures, developed in ambient pressure–temperature (PT) conditions of low-grade blueschist facies (temperature T of ca. 300 °C and pressure P ≥ 0. 70 GPa) during involvement of Corsican continental crust in the Alpine subduction. We used a multidisciplinary approach by combining detailed microstructural and petrographic analyses, crystallographic preferred orientation by electron backscatter diffraction (EBSD), and palaeopiezometric studies on a selected sample to support an evolutionary model and deformation path for subducted continental crust. We infer that 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 to stick-slip strain accommodation during subduction of continental crust.

Citation: Molli, G., Menegon, L., and Malasoma, A.: Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica, Solid Earth, 8, 767-788, https://doi.org/10.5194/se-8-767-2017, 2017.
Publications Copernicus
Download
Short summary
We present a new case study on the role of brittle precursors in nucleating shear zone. Our studied sample shows a high-pressure, low-temperature (HP/LT) microscale ultramylonite developed by brittle precursors induced during deformation within a host HP/LT granitic mylonite. We infer that the studied structures may be considered as a small-scale example of fault structures related to stick-slip strain accommodation during subduction of continental crust.
We present a new case study on the role of brittle precursors in nucleating shear zone. Our...
Share