The Skaergaard intrusion is a layered igneous intrusion in the Kangerlussuaq area, East

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is ...

. It comprises various rock types including

gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ...

, ferro diorite,

anorthosite Anorthosite () is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most ...

and

granophyre Granophyre ( ; from ''granite'' and ''porphyry'') is a subvolcanic rock that contains quartz and alkali feldspar in characteristic angular intergrowths such as those in the accompanying image. The texture is called granophyric. The texture can b ...

Discovered by

Lawrence Wager Lawrence Rickard Wager, commonly known as Bill Wager, (5 February 1904 – 20 November 1965) was a British geologist, explorer and mountaineer, described as "one of the finest geological thinkers of his generation"Vincent and best remembered for ...

in 1931 during the British

Arctic The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada ( Yukon, Northwest Territories, Nunavut), Danish Realm ( Greenland), Finland, Iceland ...

Air Route Expedition led by Gino Watkins, the intrusion has been important to the development of key concepts in

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

petrology Petrology () is the branch of geology that studies rocks and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous and metamorphic petrology are commonly taught together ...

, including

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...

differentiation and fractional crystallisation and the development of layering. The Skaergaard intrusion formed when

tholeiitic The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma ...

magma was emplaced about 55 million years ago,Brooks, CK, Gleadow, AJW (1977) ''A fission-track age for the Skaergaard intrusion and the age of the East Greenland basalts''. Geology, v. 5, p. 539-540. during the initial opening of the

North Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe a ...

. The body represents essentially a single pulse of magma, which crystallized from the bottom upward and the top downward. The intrusion is characterized by exceptionally well-developed

cumulate Cumulate rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Cumulate rocks are named according to their texture; cumulate texture is diagnostic of the conditions of formation of this group ...

layering defined by variations in the abundance of crystallizing

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...

and

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With ...

. The Skaergaard is perhaps the simplest and smallest of a group of gabbroic complexes of similar age that occur along the central coast of East Greenland, which together with coeval

flood basalt A flood basalt (or plateau basalt) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot reac ...

s are part of the North Atlantic

large igneous province A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation ...

References

External links

''The (virtual) Skaergaard Intrusion''
Geology of Greenland Arctic research Layered intrusions Paleogene magmatism {{regional-geology-stub

See also

References

External links