Pseudotachylite
A pseudotachylite is an ultra-fine grained, glass-like material that is usually dark in color and occurs in the form of thin, planar veins or as a matrix in a breccia-like shattered bedrock. Externally, a pseudotachylite is similar to a black basalt glass ( tachylite ) or dark flint.
Emergence
When rock units are displaced at a tectonic fault in the upper, brittle areas of the earth's crust , minerals and mineral aggregates are mechanically broken up by the mutual friction and creeping movement on the fault surface. During this process, the affected rock sections are usually converted into cataclasites or kakirites . At very high rates of movement, however, local temperatures of up to 1000 ° C are reached due to the friction, which leads to the formation of molten rock. With rapid cooling, no crystals form , but the melt solidifies to form an amorphous rock glass. It mostly occurs in the form of thin ducts within cataclasites.
Independent of this genesis is a second group of pseudotachylites, which are related to impact structures and the formation of which can be traced back to shock wave metamorphosis .
classification
Tectonically formed pseudotachylite belongs to the group of ultra-cataclasites , while those formed by shock wave metamorphosis belong to the group of impactites .
swell
- GH Eisbacher: Introduction to Tectonics. S. 173, Enke Verlag, Stuttgart 1996. ISBN 3-432-99252-1
- P. Heitzmann: Kakirite, Kataklasite, Mylonite - On the nomenclature of metamorphic rocks with deformation structures. Eclogae geologica Helvetiae, Vol. 78, pp. 273-286, 1985
Individual evidence
- ↑ D. Fettes, J. Desmons: Metamorphic Rocks. A Classification and Glossary of Terms. Cambridge University Press, Cambridge 2011, ISBN 978-0-521-33618-5 , pp. 188 .