Grain size distributions of fault rocks: A comparison between experimentally and naturally deformed granitoids

Keulen, Nynke; Heilbronner, Renée; Stünitz, Holger; Boullier, Anne-Marie; Ito, Hisao

doi:10.1016/j.jsg.2007.04.003

Cited by 144 publications

(127 citation statements)

References 60 publications

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“…A switch or competition between a splitting (transgranular) type breakage mechanism and abrasion type mechanism has previously been suggested from micro-structural observations of sheared glacial tills (Hooke and Iverson, 1995) laboratory and natural faults (e.g. STORTI et al, 2003;RAWLING and GOODWIN, 2003;HAYMAN, 2006;KEULEN et al, 2007;BJØRK et al, 2009) and basal shear zones of rockslides (HENDERSON et al, 2010). Our observations certainly support these interpretations, and indicate scenarios where a given comminution mechanism is likely to be favored.…”

Section: Discussionsupporting

confidence: 83%

“…STORTI et al, 2007;HEILBRONNER and KEULEN, 2006;STÜ NITZ et al, 2010) and grain size distributions (e.g. SAMMIS et al, 1987;BLENKINSOP, 1991;RAWLING and GOODWIN, 2003;STORTI et al, 2003;BILLI, 2005;KEULEN et al, 2007;SAMMIS and KING, 2007) of the gouge grains. One feature that many fault gouges have in common is that the grain size distribution follows a power law.…”

Section: Introductionmentioning

confidence: 99%

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Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge

Mair

Abe

2011

Pure Appl. Geophys.

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Abstract-The microstructural state and evolution of fault gouge has important implications for the mechanical behaviour, and hence the seismic slip potential of faults. We use 3D discrete element (DEM) simulations to investigate the fragmentation processes operating in fault gouge during shear. Our granular fault gouge models consist of aggregate grains, each composed of several thousand spherical particles stuck together with breakable elastic bonds. The aggregate grains are confined between two blocks of solid material and sheared under a given normal stress. During shear, the grains can fragment in a somewhat realistic way leading to an evolution of grain size, grain shape and overall texture. The 'breaking up' of the fault gouge is driven by two distinct comminution mechanisms: grain abrasion and grain splitting. The relative importance of the two mechanisms depends on applied normal stress, boundary wall roughness and accumulated shear strain. If normal stress is sufficiently high, grain splitting contributes significantly to comminution, particularly in the initial stages of the simulations. In contrast, grain abrasion is the dominant mechanism operating in simulations carried out at lower normal stress and is also the main fragmentation mechanism during the later stages of all simulations. Rough boundaries promote relatively more grain splitting whereas smooth boundaries favor grain abrasion. Grain splitting (plus accompanying abrasion) appears to be an efficient mechanism for reducing the mean grain size of the gouge debris and leads rapidly to a power law size distribution with an exponent that increases with strain. Grain abrasion (acting alone) is an effective way to generate excess fine grains and leads to a bimodal distribution of grain sizes. We suggest that these two distinct mechanisms would operate at different stages of a fault's history. The resulting distributions in grain size and grain shape may significantly affect frictional strength and stability. Our results therefore have implications for the earthquake potential of seismically active faults with accumulations of gouge. They may also be relevant to the susceptibility of rockslides since non-cohesive basal shear zones will evolve in a similar way and potentially control the dynamics of the slide.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge

Mair

Abe

2011

Pure Appl. Geophys.

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“…A pure tectonically related mechanical diminution or abrasion scenario (Jébrak, 1997;Keulen et al, 2007;Mort and Woodcock, 2008;Wright et al, 2009) Another scenario comprises the dissolution of local patches of sulphates which requires a brine density flow (Anderson and Kirkland, 1980) triggered by pressurized meteoric water exploring a present fracture system. The potential presence of some sulphate minerals is supported by the presence of celestite laths within and next to the SSB fabric.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Relationship between karstification and burial dolomitization in Permian platform carbonates (Lower Khuff — Oman)

Beckert

Vandeginste

John

2016

Sedimentary Geology

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Please cite this article as: Beckert, Julia, Vandeginste, Veerle, John, Cédric M., Relationship between karstification and burial dolomitization in Permian platform carbonates (Lower Khuff -Oman), Sedimentary Geology (2016Geology ( ), doi: 10.1016Geology ( /j.sedgeo.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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“…Veins are dilatant structures, typically fractures, filled with minerals that precipitated from fluid (see review of [1], and references therein). Hydraulic breccias are fragmented rocks where the fragmentation is mainly caused by chaotic fracturing due to fluid overpressure [2][3][4][5], as opposed to tectonic breccias where the diminution is due to tectonic stresses, typically along faults [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Transport efficiency and dynamics of hydraulic fracture networks

2015

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Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous Darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant "viscous" parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/f α behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

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Grain size distributions of fault rocks: A comparison between experimentally and naturally deformed granitoids

Cited by 144 publications

References 60 publications

Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge

Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge

Relationship between karstification and burial dolomitization in Permian platform carbonates (Lower Khuff — Oman)

Transport efficiency and dynamics of hydraulic fracture networks

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