Kakirit
Kakirite (named after the northern Swedish lake Kakir , name introduced by Fredrik Svenonius in 1900) are primary loose rock with a directionless, chaotic structure , which was created by fracture deformation as a result of tectonic stress. Kakirite and genetically similar rocks are summarized under the generic term rocks with deformation structures or cataclastic rocks .
Emergence
As a result of tectonic processes, discrete fracture surfaces , so-called fault or fault surfaces, arise in the mountains at relatively low temperatures . As a result of the movements, the rock at the fault areas is sometimes heavily stressed mechanically. This can fragment it and downright grind it. Kakirite is formed at low temperatures in a relatively shallow crust. It can be secondarily solidified (cemented) over time by separating calcium carbonate , silica or iron oxides and hydroxides from aqueous solutions circulating in the fault zone. At greater depths, where the rock plasticity increases due to higher temperatures and dynamic recrystallization is also involved in the formation of the cataclastic structure, a cataclasite is formed instead of the kakirite . At even greater depths, at even higher temperatures, mylonite is formed , which always has foliation (" foliation ") as a distinguishing feature from kakirite and cataclasite .
Properties and classification
The term kakirit refers exclusively to the structure, grain binding and genesis of the rock and is in fact independent of the mineral stock. Fault gouge is typically in the form of a cementless breccia with a certain amount of rock flour - matrix before. If the matrix proportion is relatively small, one speaks of a tectonic breccia if the majority of the rock fragments are relatively large (in the dm and cm range), and of a fracture breccia or rustle if the majority of the fragments are smaller (in the cm and mm Area) are. If fine and very fine material predominates, one speaks of rock flour or Störungsletten (Letten = clayey-loamy rock; English: fault gouge ).
Significance for geotechnics
Fault gouge is preparing for its softness and unpredictability in mining or tunneling the miners or miners often far more problems than the hardest rock formations.
The last time Kakirit deposits made headlines was between 2004 and 2005 during the construction of the Gotthard Base Tunnel . After particularly hard rock formations put excessive strain on the tunnel builders' tools, the penetration of a subsequent Kakiritz zone required extensive safety measures.
literature
- Peter Heitzmann: Kakirite, Kataklasite, Mylonite - On the nomenclature of metamorphic rocks with deformation structures . In: Eclogae Geologicae Helvetiae . tape 78 , no. 2 , 1985, pp. 273-286 , doi : 10.5169 / seals-165656 .
- Wolfhard Wimmenauer: Petrography of igneous and metamorphic rocks . Enke, Stuttgart 1985, ISBN 3-432-94671-6 , pp. 311 ff .
Individual evidence
- ↑ Fredrik Svenonius: Öfversikt af Stora Sjöfallets och angränsande fjälltrakters geologi. Geologiska Föreningen i Stockholm Förhandlingar, Vol. 22, No. 4, 1900, pp. 273–322, doi : 10.1080 / 11035890009446896
- ^ Adrian Schmid: Neat tunnel: All respect for the rock ( Memento from May 12, 2012 in the Internet Archive ). The Swiss Observer , Edition 1 of January 11, 2002