Kelyphite

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Kelyphite as bright zones around already decomposed garnet crystals in the serpentinite of Zöblitz

As Kelyphit be (according to the current definition of the International Union of Geological Sciences ) decomposition products called variable composition ringförmigi around garnet crystals form. The term is seldom used for such formations around olivine or pyroxe crystals . Kelyphites consist of symplectic intergrowths of different minerals and are a structural feature ( kelyphitic structure ) in metamorphic rocks.

Term, foreign language terms

The term was coined in 1882 by the Austrian mineralogist Johann Albrecht Schrauf (1837-1897). It goes back to the Greek word κέλυφος for nutshell.

Foreign-language terms are: English: kelyphite , French: kélyphite , Russian: келифит, коронит, Portuguese: kelifít , Polish: kelyfit , Czech: kelyfit .

Occur

The most common and well-known manifestations are outer edge zones ( corona-like formations) around garnet crystals in metamorphic rocks (mostly mafic and ultramafic rocks). This is a mixture of the newly formed and intergrown minerals. Completely decomposed garnet crystals have changed color and are made entirely of Kelyphites. The shape of the former crystal aggregate has largely been preserved.

This structural feature typically occurs in serpentinite rocks , gneisses and rocks of the green slate facies and has a significant influence on rock formation at higher concentrations and progressive metamorphosis .

Kelyphitization can also be observed in feldspars .

Common kelyphitic end products made from garnet crystals are plagioclase , spinel (containing chromium), phlogopite , chlorite , orthopyroxene , clinopyroxene and amphibole (hornblende). According to the older view, kelyphite is a mixture of augite , bronzite , hercynite and hornblende.

  • Kelyphitic zone in the Zöblitzer serpentinite (image width approx. 25 mm)

  • Decomposed garnet crystals, partially kelyphitized (image width approx. 90 mm)

  • Kelyphitz zone on considerably destructured garnet crystals
    (image width approx. 80 mm)

  • Completely kelyphitized grenade as a white band in Zöblitzer serpentinite (image width approx. 410 mm)

Individual evidence

  1. ↑ D. Fettes, J. Desmond (Ed.): Metamorphic Rocks. A classification and glossary of terms. Cambridge University Press, Cambridge 2007, ISBN 978-0-521-33618-5 , pp. 166 .
  2. ^ FJ Loewinson-Lessing / EA Struve: Petrografitscheski Slowar . Moskwa 1937, p. 145
  3. ↑ TO Krishtofovicha (Red.): Geologitscheski Slowar. Tom 1 . Moskva 1960 p. 312

literature

  • AN Krishtofovicha (Red.): Geologitscheski Slowar. Tom 1 . Moskva 1960
  • FJ Loewinson-Lessing / EA Struve: Petrografitscheski Slowar . Moscow 1937
  • Roland Vix: Rock determination in the field . Munich 2005 ISBN 3-8274-1513-6
  • Wolfhard Wimmenauer: Petrography of igneous and metamorphic rocks . Stuttgart (Enke) 1985 ISBN 3-432-94671-6

Web links

Commons : Kelyphite  - collection of images, videos and audio files