Everything about Large Igneous Province totally explained
Large Igneous provinces (LIPS) were originally defined by Coffin and Eldholm (1992) as areas of
Earth's surface that contain very large volumes of magmatic rocks (typically
basalt but including
rhyolites) erupted over extremely short
geological time intervals of a few million years or less. These provinces are not associated with normal
plate tectonic magmatism, ie,
mid-ocean ridges and
island arcs. LIPS include continental
flood basalts,
oceanic plateaus, large
dike swarms (the eroded roots of a volcanic province), and
volcanic rifted margins, recognized by the presence of dike swarms and "seaward dipping reflectors" -- seismically-imaged tabular features buried deep beneath sediment that lie parallel to a passive
continental margin along the
continental slope, and interpreted to represent
lava flows or sills that formed during rifting of the continent). Most LIPS consist of basalt, but some contain large volumes of associated rhyolite; the rhyolite is typically very dry compared to island arc rhyolites, with much higher eruption temperatures (850º to 1000º C) than normal rhyolites.
When created, LIPS often occupy a few million km² and have volumes on the order of 1 million km
3. In most cases, the majority of a LIP's volume is emplaced in less than 1 million years. One of the conundra of LIPS origins is to understand how enormous volumes of basaltic magma are formed and erupted over such short time scales, with effusion rates up to an order of magnitude greater than mid-ocean ridge basalts.
Theories of formation
Large igneous provinces are often linked to active
hotspots by linear chains of volcanic islands or volcanoes, leading to models that connect their origins to
mantle plumes. In this hypothesis, mantle plumes consist of a bulbous head and a thin tail that feeds hot mantle into the head. When the rising plume head encounters the lithosphere, it spreads out and melts catastrophically to form large volumes of basalt magma in 1-2 million years. Subsequent volcanism originates with the plume tail. The movement of lithosphere across the surface of the Earth in response to plate tectonics causes the plume tail volcanics to form linear island chains. The impact of the plume on the base of continental lithosphere may cause rifting and breakup of the continent, creating conjugate LIPS on opposite sides of an ocean basin (for example, the Parana-Etendeka pair of South America-Africa).
Alternate theories include delamination of eclogitic lower crust, edge effects of thick lithosphere, and meteorite impact (see
Mantle plumes for more complete discussion of alternate models).
Relationship to extinction events
Because a LIP may in several cases have occurred simultaneously with
oceanic anoxic events and
extinction events, it has been proposed that the volcanic byproducts of LIP formation may have had a profound and deleterious effect on the global environment, perhaps contributing to extinction events. The most important examples are the
Deccan Traps (
Cretaceous–Tertiary extinction event), the
Karoo-Ferrar (
Pliensbachian-Toarcian extinction), the
Central Atlantic Magmatic Province (
Triassic-Jurassic extinction event), and the
Siberian traps (
Permian-Triassic extinction event).
LIPS have two impacts on environment that can cause extinction: first, they release large volumes of sulfate gas that forms sulfuric acid in the atmosphere; this absorbs heat and causes substantial cooling (for example, the
Laki eruption in Iceland, 1783). Second, oceanic LIPS can reduce oxygen in seawater by either direct oxidation reactions with metals in hydrothermal fluids or by causing algal blooms that consume large amounts of oxygen (Kerr, 2005).
Examples of LIPs
These are well documented large igneous provinces in geological research.
Continental Flood basalts
Oceanic Plateaux
Caribbean large igneous province (Caribbean Sea)
Kerguelen Plateau (Indian Ocean)
Ontong Java Plateau, Manihiki Plateau and Hikurangi Plateau (southwest Pacific Ocean)
Jameson Land
Volcanic Rifted Margins
High Arctic Large Igneous Province (includes the Ellesmere Island Volcanics, Strand Fiord Formation, Alpha Ridge, Franz Josef Islands and Svalbard.)
North Atlantic Igneous Province (includes basalts in Greenland, Iceland, Ireland, Scotland, Faroes)
Central Atlantic Magmatic Province (eastern United States and Canada, northern South America, northwest Africa)
Dike Swarms
MacKenzie Dike Swarm, Coppermine basalts (Canada, Precambrian)Further Information
Get more info on 'Large Igneous Province'.
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