Trondhjemit

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The Trondhjemite (rarely also Trondheimite ) is an igneous rock from the group of Plutonites . The name was introduced in 1916 by Victor Moritz Goldschmidt after an occurrence near the city of Trondheim and denotes a light variety of the Tonalite .

composition

In the QAPF diagram , the Trondhjemites are in the same field as the Tonalites.

The main components are quartz and oligoclase from the mixed series of plagioclase . The content of dark components is generally low; Biotite and some hornblende as well as augite are the most common. It is characterized by the content of idiomorphic titanite crystals, which can account for up to 1% of the total rock. Apatite , orthite , magnetite and zirconium can be included as further accessory components .

Education and occurrence

The rock occurs worldwide mainly in the archaic cratons , mostly in a metamorphic form. Trondhjemites form together with tonalites and granodiorites when basaltic crust melts in subduction zones and form the so-called TTG (trondhjemite-tonalite-granodiorite) complexes, which often make up the oldest components of the cratons.

Types of Trondhjemites

literature

  • Wolfhard Wimmenauer: Petrography of igneous and metamorphic rocks . Enke, Stuttgart 1985, ISBN 3-432-94671-6 , pp. 92 f .
  • Walter Maresch & Olaf Medenbach: Steinbach's natural guide rocks . Mosaik, Munich 1996, ISBN 3-576-10699-5 , p. 50 .

Individual evidence

  1. ↑ Brief description , accessed on March 1, 2010
  2. ↑ Kent C. Condie (Ed.): Archean Crustal Evolution . Elsevier, Amsterdam 1994, ISBN 0-444-81621-6 .
  3. ↑ Mesoarchean tonalite-trondhjemite-granodiorite (TTG) associations (English), accessed on March 1, 2010