How phyllosilicate mineral structure affects fault strength in Mg‐rich fault systems

The clay mineralogy of fault gouges has important implications for the frictional properties of faults, often identified as a major factor contributing to profound fault weakness. This work compares the frictional strength of a group of Mg‐rich minerals common in the Mg‐Al‐Si‐O compositional space (...

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Bibliographic Details
Published in:Geophysical research letters 2017-06, Vol.44 (11), p.5457-5467
Main Authors: Sánchez‐Roa, C., Faulkner, D. R., Boulton, C., Jimenez‐Millan, J., Nieto, F.
Format: Article
Language:English
Subjects:
Aluminum
Argon
Atomic structure
Bonding strength
Chemical bonds
Chemistry
Clay
Clay minerals
Continuity
Control stability
Crystal structure
Crystallography
Crystals
Fault detection
fault gouge
Faults
frictional strength
Identification
Interactions
Magnesium
Mineralogy
Minerals
Molecular structure
Palygorskite
phyllosilicates
Properties
Saponite
Sepiolite
Strength
Structural stability
Talc
Tests
Water chemistry
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Summary:The clay mineralogy of fault gouges has important implications for the frictional properties of faults, often identified as a major factor contributing to profound fault weakness. This work compares the frictional strength of a group of Mg‐rich minerals common in the Mg‐Al‐Si‐O compositional space (talc, saponite, sepiolite, and palygorskite) by conducting triaxial frictional tests with water or argon as pore fluid. The studied minerals are chemically similar but differ in their crystallographic structure. Results show that fibrous Mg‐rich phyllosilicates are stronger than their planar equivalents. Frictional strength in this group of minerals is highly influenced by strength of the atomic bonds, continuity of water layers within the crystals, and interactions of mineral surfaces with water molecules, all of which are dictated by crystal structure. The formation and stability of the minerals studied are mainly controlled by small changes in pore fluid chemistry, which can lead to significant differences in fault strength. Key Points The crystal structure of Mg‐rich phyllosilicates has a strong influence on their frictional strength Water distribution in phyllosilicate mineral structure affects frictional behavior Pore fluid chemistry directly influences Mg‐rich phyllosilicate distribution and fault strength
ISSN:0094-8276
1944-8007
DOI:10.1002/2017GL073055