Flow banding

Flow banding

Flow banding is a geological term to describe bands or layers that can sometimes be seen in rock that formed from the substance molten rock or magma.

Flow banding is caused by friction of the viscous magma which is in contact with a solid rock interface, usually the wall rock to an intrusive chamber or if the magma is erupted, the surface of the earth across which a lava is flowing.

The friction and viscosity of the magma causes phenocrysts and xenoliths within the magma or lava to slow down near the interface and become trapped in a viscous layer. This forms laminar flow, which manifests as a banded, streaky appearance.

Flow banding is the result of a process of fractional crystallization which occurs by convection, if the crystals which are caught in the flow-banded margins are removed from the melt. This can change the composition of the melt in large intrusions, leading to differentiation.

In ultramafic to mafic layered intrusions flow banding can occur with crystal accumulation, forming pseudo-sedimentary structures.

Flow banding can also occur due to disturbances in the field of flow thus forming a haemotomtic flow band, these are common in the region of upper Iceland, there are many good Icelandic videos in which this rare phenomenon can be observed.

See also:
* Cumulate rocks
* Fractional crystallization


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • flow banding — GLOSSARY OF VOLCANIC TERMS A foliation commonly observed in intermediate and felsic lavas, that results from shearing of the lava during laminar flow (Cas and Wright, 1987, p. 78). In rhyolite flows, flow banding is commonly exhibited by… …   Glossary of volcanic terms

  • banding — The process of differential staining of (usually) metaphase chromosomes of cells to reveal the characteristic patterns of bands that permit identification of individual chromosomes and recognition of missing segments; each of the 22 pairs of… …   Medical dictionary

  • pulmonary artery banding — an operation to provide constriction of the pulmonary artery with a band to reduce pulmonary blood flow and relieve congestive heart failure in children with congenital heart defects that produce left to right shunts between ventricles or the… …   Medical dictionary

  • Igneous differentiation — In geology, igneous differentiation is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement or eruption. Contents 1 Definitions 1.1 Primary melts 1.2… …   Wikipedia

  • Geology of Jersey — The geology of Jersey is characterised by the Late Proterozoic Brioverian volcanics, the Cadomian Orogeny, and only small signs of later deposits from the Cambrian and Quaternary periods. The kind of rocks go from conglomerate to shale, volcanic …   Wikipedia

  • Meteorological history of Hurricane Jeanne — Hurricane Jeanne Category 3 hurricane (SSHS) The path of Hurricane Jeanne Formed September 13, 2004 Dissipated …   Wikipedia

  • rhyolite — ALASKA VOLCANO OBSERVATORY GLOSSARY Volcanic rock (or lava) that characteristically is light in color, contains 69% silica or more, and is rich in potassium and sodium. GLOSSARY OF VOLCANIC TERMS A volcanic rock containing greater than 68% silica …   Glossary of volcanic terms

  • Law of superposition — The law of superposition (or the principle of superposition) is a key axiom based on observations of natural history that is a foundational principle of sedimentary stratigraphy and so of other geology dependent natural sciences: The principle… …   Wikipedia

  • Phenocryst — A phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of a porphyritic igneous rock. Phenocrysts often have euhedral forms either due to early growth within a magma or by post… …   Wikipedia

  • Ultramafic to mafic layered intrusions — are found in typically ancient cratons and are rare but worldwide in distribution. The intrusive complexes exhibit evidence of fractional crystallization and crystal segregation by settling or floating of minerals from a melt. Ideally the… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”