page_title: Fault gouge
section_title: Classifications of Fault Gouge
hierarchical_section_title: Fault gouge / Classifications of Fault Gouge
caption_attribution_description: Čeština: Mikroskopická fotografie muskovitu (bezbarvé krystaly) pod zkříženými nikoly v metagranitu. V pravé části se nacházejí krystaly biotitu Pod jedním nikolem.English: Muscovite in metagranite. In right part are grains of biotite. Photograph with crossed polars.
context_page_description: Fault gouge is a tectonite with a very small grain size. Fault gouge has no cohesion and it is normally an unconsolidated rock type, unless cementation took place at a later stage. A fault gouge forms in the same way as fault breccia, the latter also having larger clasts. In comparison to fault breccia, which is another incohesive fault rock, fault gouge has less visible fragments. Fault gouge is also classified as have particles that are smaller than 1mm in diameter. Therefore, fault gouge is commonly composed of clays which commonly consist of Illite, Montmorillonite, Saponite, Kaolinite, Vermiculite, Quartz, Chlorite, Muscovite, Biotite, and/or Feldspars.
  Gouge-filled faults can be weak planes in rock masses. If compressive stresses are enough these can cause compressive yielding or eventually rock fracture.
context_section_description: Gouge is usually classified by to characteristics, it may be classified based upon its chemical or mineralogical composition and by its particle size type. Other more specific properties as listed in the previously mentioned sections are not normally part of the naming nomenclature. However, all fault gouge is usually referred to as having a finer particle size than 1mm. Both particle size and mineralogical composition may be analyzed by use of petrology and petrographic thin sections analysis.
  Particle Size:
  Clay Gouge: Gouge is considered Clay Gouge if the clast size is between 63 - 125 µm.
  Granular Fault Gouge: Granular fault gouge is described as having particle sizes of 105 - 149 µm.
  Classifications based upon chemical or mineralogical composition:
  Technically speaking, fault gouge can be composed of almost any mineral or set of minerals depending upon the country rock in the region. Some common fault gouge compositions are listed below.
  Other:
  Simulated Fault Gouge: Simulated fault gouge simply refers to gouge that is being modeled rather than actually being measured in the field. It could also be in done in combination with samples from the field to generate simulation of the fault system.
caption: Muscovite in metagranite. In right part are grains of biotite. Photograph with crossed polars.
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