Tephrite
Tephrite (téphra, Greek = ash) are red-brown to black-gray cast rocks that have a fine-grained, fine-crystalline to porphyry structure. Phonolithic tephrites, sometimes called phonotephrites , are slightly lighter.
Rock description and mineral inventory
Tephrites consist of feldspar representatives ( nepheline or leucite ), anorthite-rich plagioclase (An 50-70 ), clinopyroxenes , amphiboles and subordinate alkali feldspars .
Olivines do not occur or only to a proportion of less than 10%. In this property, the tephrites differ from the olivine-rich basanites , which are in the same field of the line iron diagram (QAPF classification). Tephrites are related to basalt , with which they are often associated, in terms of their formation conditions and their appearance .
Tephrites have few or no speckles . In contrast, rock often contains pores in which zeolite minerals can occur. Peridotitic xenolites do not occur.
The term tephrite is rarely used in colloquial language, the rock is usually referred to as basalt .
history
Tephrites were first described scientifically in 1816 by Pierre Louis Antoine Cordier in the Journal des Mines (Vol. XV). Cordier was a French geologist who studied volcanic rocks. Further work on this was carried out later by Karl von Fritsch and Wilhelm Reiss as part of their rock research on Tenerife (published in 1868).
Occurrence
Tephrites occur as lava flows in massive or columnar form. But they also appear as slag and pyroclastic secretions.
In Germany, tephrites are found in the Eifel (e.g. as Mayener basalt lava ), Lausitz , in the Westerwald , on the Kaiserstuhl , Vogelsberg and in the Rhön . Other occurrences are, for example, from the Canary Islands and Madagascar , from Italy , Portugal , Greenland , Uganda , Kazakhstan and Colorado . known. A large deposit with an interesting loaf structure is located in northern Bohemia near Konojedy in the Dubí hora NSG .
use
Individual tephrites are used as floor coverings, block steps and facade panels.
literature
- Fritz Mangartz: Roman Basaltava mining between the Eifel and the Rhine (monographs of the Roman-Germanic Central Museum Mainz Volume 75, Vulkanpark-Forschungen Volume 7) , Verlag Schnell + Steiner, Regensburg 2008, ISBN 978-3-7954-1859-5
- Roland Vinx: Rock determination in the field . Munich (Elsevier) 2005 ISBN 3-8274-1513-6
- Wolfhard Wimmenauer: Petrography of igneous and metamorphic rocks . Stuttgart (Enke) 1985 ISBN 3-432-94671-6
Individual evidence
- ^ FJ Loewinson-Lessing / EA Struve: Petrografitscheski Slowar . Moskwa 1937, p. 335.
- ^ Wilhelm Meyer: Geology of the Eifel . 1st edition. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1986, ISBN 3-510-65127-8 , pp. 398 .
- ↑ rocks. ( Memento of the original from July 17, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Institute for Geological Sciences, FU Berlin.
- ↑ L. Melluso et al .: Petrogenesis of a basanite-tephrite-phonolite volcanic suite in the Bobaomby (Cap d'Ambre) peninsula, northern Madagascar. Journal of African Earth Sciences Vol. 49, No. 1-2, pp. 29-42, September 2007 doi : 10.1016 / j.jafrearsci.2007.06.002
- ↑ Foide. GeoMuseum TU Clausthal
- ↑ tephrite. Britannica Online.
