Fault breccia

Fault breccia

Fault breccia (IPA: /ˈbrɛtʃiə, ˈbrɛʃ-/, Italian: breach), or tectonic breccia is a breccia (a rock type consisting of angular clasts) that was formed by tectonic forces. Fault breccia has no cohesion, it is normally an unconsolidated rock type, unless cementation took place at a later stage. Sometimes a distinction is made between fault gouge and fault breccia, the first has a smaller grain size. [Twiss, R.J. & Moores, E.M., 2000 (6th edition): "Structural Geology", W.H. Freeman & co, ISBN 0-7167-2252-6; p. 55]

Zones of fault breccia and fault gouge in rocks can be a hazard for the construction of tunnels and mines, as the non-cohesive zones form weak places in the rock where a tunnel can collapse more easily.

Origin

Fault breccia is a tectonite, it forms by tectonic movement along a localized zone of brittle deformation (a fault zone) in a rock. The grinding and milling occurring when the two sides of the fault zone moving along each other results in a material that is made of loose fragments. Because of this fragmentation fault zones are easily infiltrated by groundwater. Minerals like calcite, epidote, quartz or talc can precipitate from the water depositing so the rock cements. However, when the tectonic movement along the fault zone continues the cement itself can be fragmented leading to a new gouge material containing neoformed clasts.

Deeper in the Earth's crust, where temperatures and pressures are higher, the rocks in the fault zone can still brecciate, but they keep their internal cohesion. The resulting type of rock is called a cataclasite.

ee also

*Breccia
*Cataclasite
*Fault (geology)

References


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Look at other dictionaries:

  • fault breccia — noun or fault rubble : a rock composed of angular fragments that have resulted from movement along a fault : crush breccia * * * Geol. angular rock fragments produced by fracture and grinding during faulting and distributed within or adjacent to… …   Useful english dictionary

  • fault breccia — Geol. angular rock fragments produced by fracture and grinding during faulting and distributed within or adjacent to the fault plane. [1890 95] * * * …   Universalium

  • fault breccia —    The assemblage of broken rock fragments frequently found along faults. The fragments may vary in size from inches to feet …   Lexicon of Cave and Karst Terminology

  • Breccia — (pronEng|ˈbrɛtʃiə, ˈbrɛʃiə, it. breach) is a rock composed of angular fragments of several minerals or rocks in a matrix, that is a cementing material, that may be similar or different in composition to the fragments. A breccia may have a variety …   Wikipedia

  • Fault gouge — is an unconsolidated tectonite (a rock formed by tectonic forces) with a very small grain size. Fault gouge has no cohesion, it is normally an unconsolidated rock type, unless cementation took place at a later stage. Fault gouge forms in the same …   Wikipedia

  • Fault (geology) — Part of a series on earthquakes Types Foreshock • Aftershock • Blind thrust Doublet • Interplate • …   Wikipedia

  • fault — /fawlt/, n. 1. a defect or imperfection; flaw; failing: a fault in the brakes; a fault in one s character. 2. responsibility for failure or a wrongful act: It is my fault that we have not finished. 3. an error or mistake: a fault in addition. 4.… …   Universalium

  • breccia —    1. Angular fragments of rock, commonly, but not inevitably, cemented by finer grained materials including silica, iron minerals, and calcite to form a new rock. Many fault planes are marked by zones of broken rock, either loose or re cemented …   Lexicon of Cave and Karst Terminology

  • fault rubble — noun see fault breccia …   Useful english dictionary

  • fault zone —    A fault that is expressed as a zone of numerous small fractures or of breccia or fault gouge. A fault zone may be as wide as hundreds of meters.    Compare: fault, fault line scarp.    GG …   Glossary of landform and geologic terms

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