Geosuture

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Geosutur , suture zone or just suture (from Latin sutura , seam ') is a term from geology that denotes the boundary or contact zone between formerly separate crustal blocks (e.g. continents , island arches or oceanic plateaus ) that are created by plate tectonic processes have collided with each other. Such collisions and thus the formation of sutures occur at converging plate boundaries after the oceanic crust previously located between the crustal blocks has been subducted .

Structurally, a suture is nothing more than an extensive fault zone . Investigations with the help of geophysical methods have shown that these fault zones can extend vertically into the upper mantle and laterally over many hundreds of kilometers. Geosutures are characterized by intensely deformed and metamorphically shaped rocks . In the ideal case, ophiolite complexes or ophiolitic rock suites in the broader sense (such as the ZEV rocks interpreted as meta- turbidites ) occur in the suture zone , which are the result of a partial shearing off of the oceanic crust that was previously between the collided crustal blocks. This is seldom the case, especially with older sutures, since the ophiolites there have been destroyed either by recent tectonics or by erosion since the formation of the suture.

Prime examples of sutures can be found today within the geologically young alpine fold mountains , u. a. the Alps and the Himalayas . Where the continental crust portions of the African plate or the Indian plate have collided with those of the Eurasian plate for about 50 million years, the oceanic crust of the Neotethys basin that was once in between has now been almost completely subducted. Some snippets of oceanic crust were autopsied on the Eurasian plate and can be found there today in the form of the ophiolites typical of geosutures. Due to its relatively old age, which means that the characteristic ophiolites are partly missing today, the search for sutures in the varistic is much more difficult.

literature

  • Wolfgang Frisch and Jörg Loeschke: Plate Tectonics . Income from research Volume 236, Wissenschaftliche Buchgesellschaft, Darmstadt 1992, ISBN 3-534-09410-7 .
  • Hans Murawski & Wilhelm Meyer: Geological dictionary . 10., rework. u. exp. Ed., P. 278, Enke Verlag, Stuttgart 1998, ISBN 3-432-84100-0 .
  • LT White, T. Ahmad, GS Lister, TR Ireland: Where does India end and Eurasia begin? Geochemistry Geophysics Geosystems. Vol. 12, No. 10, 2011, doi : 10.1029 / 2011GC003726 (only online).