Phyllosilicates formation in faults rocks: Implications for dormant fault-sealing potential and fault strength in the upper crust - Archive ouverte HAL Access content directly
Journal Articles Geophysical Research Letters Year : 2013

Phyllosilicates formation in faults rocks: Implications for dormant fault-sealing potential and fault strength in the upper crust

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Thibault Cavailhes
  • Function : Author
  • PersonId : 934353
Roger Soliva
  • Function : Author
  • PersonId : 862793
Pierre Labaume
Jean-Pierre Sizun
Delphine Charpentier
  • Function : Author
  • PersonId : 756797
  • IdRef : 059727020
Alain Chauvet
Bruno Scalabrino
  • Function : Author

Abstract

Phyllosilicate content and related permeability of fault zones form primary controls on hydraulic and mechanical behavior of the brittle crust. Hence, understanding and predicting the localization of these ubiquitous minerals is a major issue for fundamental and applied geosciences. We describe normal fault zones cutting a foreland arkosic turbiditic formation suffering high-T diagenesis and formed under conditions (~200°C) typical of deeply buried reservoirs and common within the seismogenic interval. Microstructural analyses show a large proportion of phyllosilicates (up to 34%) in the fault rock, derived from near-complete feldspar alteration and disaggregation during deformation. This study shows that even faults with offsets (~20 cm) much lower than bed thickness can have such large feldspar-to-phyllosilicate transformation ratios, implying that the origin of the phyllosilicates is purely transformation related. These results imply that the potential sealing capacity and strength of faults could be predicted from the host rock feldspar content. Where sealing capacity and fault strength can be related to phyllosilicate content, these properties can then also be inferred from the predicted phyllosilicate content: this opens up new horizons concerning the hydraulic and the mechanical behavior of the upper crust.
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hal-00903574 , version 1 (11-05-2021)

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Thibault Cavailhes, Roger Soliva, Pierre Labaume, Christopher Wibberley, Jean-Pierre Sizun, et al.. Phyllosilicates formation in faults rocks: Implications for dormant fault-sealing potential and fault strength in the upper crust. Geophysical Research Letters, 2013, 40 (16), pp.4272-4278. ⟨10.1002/grl.50829⟩. ⟨hal-00903574⟩
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