Large Igneous Province

A Magmatic large province, with the English expression usually called Large Igneous Province ( LIP), is an area of the earth's crust that contains very large amounts of igneous rocks (up to the order of 1 million km3 on surfaces of several million km2), both intrusive and can be extrusiv and have formed in geologically short periods of time.

Most of the large igneous provinces consist of basalt, but some contain large amounts of rhyolite, such as the Columbia Plateau basalt in the western United States. This rhyolite typically has only a small water content and significantly higher eruption temperatures ( 850 ° C to 1000 ° C) in comparison to the resultant of island arcs rhyolites.

Some of the igneous large provinces are still more or less intact, such as the Deccan Traps, while others have crumbled by plate tectonic movements into parts, such as the Central Atlantic Magmenprovinz (Central Atlantic Magmatic Province, short CAMP ), now in Brazil, the eastern United States, Canada and West Africa are found.

Definition

The term Large Igneous Province goes to M. F. Coffin and O. Eldholm back in 1992. So that you referred to a number of areas, which are composed of mafic rocks, have an area of more than 100,000 sq km (slightly larger than Portugal), are triggered by processes that are not normal plate tectonics and sea floor spreading connected, and over a geologically short have formed time, typically in a million years or less.

According to the original definition of large igneous provinces include continental flood basalts, oceanic plateaus, large flight schools (which often represent an eroded volcanic province to the roots ) and sills as well as marked by volcanic activity passive continental margins. However, the definition of large igneous provinces is still in flux and is constantly being expanded and refined. Meanwhile, not only mafic rocks, but all igneous rocks are included in the definition, meet the condition of the formation of large quantities within a short geological time. Moreover, the inclusion of costs incurred by normal plate tectonic processes igneous rocks has been proposed, if they possess these characteristics. Also large granite intrusions like those of the South American Andes and the western North America are related to the magmatic United Provinces.

Be divided the magmatic United Provinces as suggested by Hetu C. Sheth from the year 2007 in the two groups caused by volcanism volcanic United Provinces (Large Volcanic Provinces or LVP) and the damages caused by plutonism Plutonian United Provinces (Large Plutonic Provinces, short LPP).

Theories of Education

The large extent of the magmatic United Provinces of often several million square kilometers and its volume up over a million cubic kilometers in connection with its geologically rapid development, which is an order of magnitude above the basalt emissions of the mid-ocean ridges, is not yet fully understood. They are often associated with active hotspots by a chain of volcanic islands or volcanoes. The cause of many, if not all igneous United Provinces, which are not caused by normal plate tectonics, mantle plumes therefore be adopted.

According to this hypothesis rise to large masses of hot material from the mantle. During the ascent they form a mushroom-shaped head, which is powered by a thin stalk with supplies. Does this hot mass on the underside of the lithosphere, it spreads out and melts, so as to form within one to two million years ago, large amounts of basaltic magma. The rising stem also creates a long chain of line-shaped volcano or volcanic island chains, because the lithosphere passes over him, the stem remains substantially stationary. The impingement of mantle plumes on the base of a lithospheric plate could this theory cause her fall apart, and be responsible for the occurrence of associated igneous United provinces on both sides of the resulting ocean. An example of this are the Paraná basalt in South America and the Etendeka basalt in Africa.

Other theories for the origin of large igneous provinces they lead back to the splitting ( delamination ) of eklogitischer lower crust, or lithosphere Nebenffekte powerful. Also contemplated is a meteorite impact.

Relations with extinction events

The emergence of large-scale magmatic provinces seems to stand in the Earth's history, in some cases with oceanic anoxic events or mass extinction in conjunction. Thus, the emergence of the Deccan Traps falls in the period of mass extinction at the Cretaceous - Tertiary boundary, that of the Karoo basalt and then connected with it Ferrar basalt Antarctica in the Jurassic extinction event at the boundary of the Pliensbachian / Toarcian. The emergence of the Central Atlantic Magma province should be responsible for the disappearance of many species at the transition from the Triassic and Jurassic, and the Siberian Trapp for the largest known mass extinction at the Permian-Triassic boundary.

Several mechanisms have been proposed to explain the link of the origin of magmatic provinces with major mass extinctions, including the release of large quantities of gaseous sulfate and resulting sulfuric acid in the atmosphere, which causes a decrease in temperatures. An example of this mechanism is the Laki eruption in Iceland in 1783, who had a decrease in the average temperatures in Europe result. The emergence of large quantities of magma in the ocean could reduce the oxygen content of the sea water either by direct reaction with hydrothermal solutions or indirectly caused by the release of large amounts of material that algal blooms, which use up the oxygen.

Examples of igneous United Provinces

Below magmatic United Provinces are listed that have been explored geologically.

Continental flood basalts

• Highlands of Ethiopia
• Columbia Flood Basalt
• Coppermine River basalt ( Canadian Shield )
• Deccan Traps (India)
• Paraná basalt and basalt Etendeka (Brazil - Namibia)
• Brazilian highlands
• Rio de la Plata craton (Uruguay )
• Karoo basalt and Ferrar basalt (South Africa - Antarctica )
• Siberian Trapp ( Russia)
• Emeishan Traps (West China)

Oceanic plateaus

• Wrangellia - Terran (Alaska and Canada)
• Caribbean igneous province Large ( Caribbean)
• Kerguelen Plateau (southern Indian Ocean)
• Ontong Java Plateau, Manihiki Plateau and Hikurangi Plateau ( Southwest Pacific )
• Jameson Land

Volcanic passive margins

• Arctic igneous province Large ( High Arctic Large Igneous Province, includes the volcanics of Ellesmere Iceland, the beach Fjord Formation, the alpha back, Franz Josef Land and Svalbard )
• North Atlantic igneous province Large ( includes basalts in Greenland, Iceland, Ireland, Scotland and the Faroe Islands)
• Central Atlantic Magmatic Province ( includes the eastern United States and Canada, northern South America and West Africa )

Transition swarms

• Mackenzie vein swarm ( Canadian Shield )
• Long -range gear Swarm ( Newfoundland and Labrador, Canada)
• Mistassini swarm -course (western Quebec, Canada)
• Matachewan swarm -speed ( Northern Ontario, Canada)

Sills

• Winagami - sill complex ( northwestern Alberta, Canada)