scholarly journals Fault gouge graphitization as evidence of past seismic slip

Geology ◽  
2017 ◽  
Vol 45 (11) ◽  
pp. 979-982 ◽  
Author(s):  
Li-Wei Kuo ◽  
Fabio Di Felice ◽  
Elena Spagnuolo ◽  
Giulio Di Toro ◽  
Sheng-Rong Song ◽  
...  
Keyword(s):  
Fault Gouge ◽  
Seismic Slip

Progressive illitization in fault gouge caused by seismic slip propagation along a megasplay fault in the Nankai Trough

Geology ◽  
2011 ◽  
Vol 39 (11) ◽  
pp. 995-998 ◽  
Author(s):  
A. Yamaguchi ◽  
A. Sakaguchi ◽  
T. Sakamoto ◽  
K. Iijima ◽  
J. Kameda ◽  
...  
Keyword(s):  
Nankai Trough ◽  
Fault Gouge ◽  
Seismic Slip

Nanocrystalline slip zones in calcite fault gouge show intense crystallographic preferred orientation: Crystal plasticity at sub-seismic slip rates at 18–150 °C

Geology ◽  
2013 ◽  
Vol 41 (8) ◽  
pp. 863-866 ◽  
Author(s):  
Berend A. Verberne ◽  
Johannes H.P. de Bresser ◽  
André R. Niemeijer ◽  
Christopher J. Spiers ◽  
D.A. Matthijs de Winter ◽  
...  
Keyword(s):  
Crystal Plasticity ◽  
Fault Gouge ◽  
Preferred Orientation ◽  
Slip Rates ◽  
Crystallographic Preferred Orientation ◽  
Seismic Slip

scholarly journals The effect of water on strain localization in calcite fault gouge sheared at seismic slip rates

2017 ◽  
Vol 97 ◽  
pp. 104-117 ◽  
Author(s):  
Marieke Rempe ◽  
Steven Smith ◽  
Thomas Mitchell ◽  
Takehiro Hirose ◽  
Giulio Di Toro
Keyword(s):  
Strain Localization ◽  
Fault Gouge ◽  
Slip Rates ◽  
Seismic Slip ◽  
Effect Of Water

Deciphering deformation mechanisms during seismic slip along wet carbonate faults

2020 ◽  
Author(s):  
Markus Ohl ◽  
Helen E. King ◽  
Andre Niemeijer ◽  
Jianye Chen ◽  
Martyn Drury ◽  
...  
Keyword(s):  
Isotope Exchange ◽  
Ion Beam ◽  
Fault Gouge ◽  
Pore Fluid ◽  
Deformation Mechanisms ◽  
Hydration Reaction ◽  
Self Diffusion ◽  
Seismic Slip ◽  
Physico Chemical ◽  
Seismic Deformation

<p>Strong dynamic weakening at seismic slip velocities in experiments on calcite has been attributed to a combination of grain-size reduction and nanoscale diffusion. However, these experiments were performed mostly dry and it is unknown how fluid-rock interactions affect the deformation mechanisms. The resulting physico-chemical interactions are key in deciphering deformation mechanisms and rheological changes during and after (seismic) faulting in the presence of a fluid phase. It is the interaction of the nanoscale of granular fault materials with fluids that may drive changes in rheological behaviour and fault stability. Considering that faults in the upper crust are major fluid pathways, there is a particular need for deformation experiments under wet conditions that focus on the nanoscale interaction between gouge material and pore fluid.</p><p>In order to track and quantify potential fluid – mineral interaction processes in carbonate faults, we have conducted deformation experiments on calcite gouge with water enriched in <sup>18</sup>O (97 at%) as pore fluid. The fault gouge was deformed in a rotary shear apparatus at v = 1 m/s and a normal load of σ<sub>n</sub> = 2 and 4 MPa. Raman spectroscopy and nanoscale secondary ion mass spectrometry (nanoSIMS) were used to analyse isotope distribution in the post-experiment samples. The nanostructure was characterised in electron transparent thin foils, prepared in a focused ion beam – scanning electron microscope (FIB-SEM), using transmission electron microscopy (TEM).</p><p>Raman analyses confirm the incorporation of <sup>18</sup>O into the calcite crystal structure, as well as the presence of amorphous carbon. We identify three new band positions relating to the possible isotopologues of CO<sub>3</sub><sup>2-</sup> (reflecting <sup>16</sup>O substitution by <sup>18</sup>O). In addition, we detected portlandite (Ca(OH)<sub>2</sub>), pointing to the hydration reaction of lime (CaO) with water. Raman and NanoSIMS maps reveal that <sup>18</sup>O is incorporated throughout the deformed volume, implying that calcite breakdown and isotope exchange affected the entire fault gouge.</p><p>Considering the oxygen self-diffusion rates in calcite (Farver, 1994) we conclude that solid-state <sup>18</sup>O – isotope exchange cannot explain the observed incorporation of <sup>18</sup>O into the calcite crystals during wet, seismic deformation. The hydration of portlandite and, calcite containing <sup>18</sup>O implies the breakdown and decarbonation of the starting calcite and the nucleation of new calcite grains. Our results question the state and nature of calcite gouges during seismic deformation and challenge our knowledge of the rheological properties of wet calcite fault gouges at high strain rates. The observations suggest that the physico-chemical changes are a crucial part of the deformation mechanism and have implications for the development of microphysical models that allow us to quantitatively predict fault rheology.</p><p> </p><p> </p><p>References</p><p>John R. Farver, Oxygen self-diffusion in calcite: Dependence on temperature and water fugacity, Earth and Planetary Science Letters, Volume 121, Issues 3–4, 1994, Pages 575-587, doi:10.1016/0012-821X(94)90092-2.</p>

Simulating melting of fault gouge at the local scale

2020 ◽  
Author(s):  
Guilhem Mollon ◽  
Jerôme Aubry ◽  
Alexandre Schubnel
Keyword(s):  
Surrounding Medium ◽  
Fault Gouge ◽  
Laboratory Studies ◽  
Numerical Work ◽  
Seismic Slip ◽  
Sliding Interface ◽  
Seismic Fault ◽  
Melted Layer ◽  
Time Observation ◽  
Real Time Observation

<p>Melting of fault gouge during fast co-seismic slip has been widely documented in laboratory studies. Because the real-time observation and local probing of this phenomenon is experimentally out of reach at the present time, the implication of melting on fault weakening are not yet fully understood,. Physics-based numerical modelling of a synthetic sliding interface could thus be a way to bring a better understanding of this physico-mechanical process.</p><p>In this study, we present a numerical work paving the way towards such an understanding. It is implemented in MELODY, a numerical tool combining Discrete Element Method (DEM) and a Multibody Meshfree Approach (i.e. highly deformable DEM). In this model, a small patch of seismic fault filled with granular gouge (composed of perfectly rigid and incrompressible grains with realistic angular shapes) is simulated. By shearing this simulated fault, we produce highly deformable gouge particles within a melted layer.</p><p>Numerical results show that melting processes have strong consequences on the fault rheology, by reducing shear stress and favouring the localization of the deformation on the sliding interface. Results are compared with experimental observations on saw-cut faults deformed in triaxial conditions in the laboratory. Future developments including thermal diffusion within the gouge and in the surrounding medium are described.</p>

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