Batholith
A batholith ( ancient Greek βάθος bathos , German 'depth' and λίθος líthos , German 'stone' ) is a spacious and complexly structured igneous rock body with an outcrop width of more than 100 km 2 on the surface , which widens towards the bottom.
Batholiths are irregularly shaped intrusive bodies ( plutons ), which displace the rock they penetrate, thermally change mineralogically ( contact metamorphosis ) and sometimes also melt it. Batholiths do not arise from a single igneous intrusion, but are usually made up of many successive plutonic intrusions.
Volcanogenic batholiths
Eroded former volcanic chains usually show a complex structure of intrusions in their root area , which represent batholiths in their overall appearance. These intrusions are part of the magmatic activity of volcanic chains and represent a larger volume fraction of the material extracted from the earth's mantle than the volcanic material emerging at or near the earth's surface ( lavas and pyroclastics ). A well-known example is the Sierra Nevada Batholith in the USA, which is also home to Yosemite National Park .
Orogenous batholiths
During orogeny , rocks can melt without intrusion from the Earth's mantle. The anatectic deep igneous rocks formed in this way can in a few cases reach sizes similar to volcanogenic batholiths, but have a different chemical composition than the latter: They are often enriched in potassium and their composition corresponds to average values of the continental crust .
Occurrence
Batholites occur in all areas of the earth where extensive magmatic activity has taken place. Examples of batholiths are:
- Adamello -Batholith, Alps
- Aral granite batholite, Chinese Altai
- Chinamora batholith, Zimbabwe
- Coast Plutonic Complex, Coast Mountains and Cascade Mountains , Canada / USA
-
Cornubian batholith in Cornwall , England
- Land's End Granite , batholith under Cornwall, extension 68,000 km³
- Patagonian batholith, Andes
- Sierra Nevada Batholith, USA
literature
- Myron G. Best: Igneous and Metamorphic Petrology . WH Freemann & Company, San Francisco 1982, ISBN 0-7167-1335-7 , pp. 127 .
- Werner Zeil: Brinkmann's outline of geology, first volume: General geology . 12th edition. Ferdinand Enke Verlag, Stuttgart 1980, ISBN 3-432-80592-6 , p. 180 .
- Dieter Richter: General Geology . 3. Edition. de Gruyter Verlag, Berlin - New York 1985, ISBN 3-11-010416-4 , pp. 270 .