The Maniitsoq Norite Belt is a ~75 km x 15 km J-shaped belt of

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

norite Norite is a mafic Intrusive rock, intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite, orthopyroxene, and olivine. The name ''norite'' is derived from Norway, by its Norwegian name ''Norge''. Norite, also known ...

intrusions In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of Intrusive rock, intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety o ...

, located in the

Akia Terrane The Akia terrane is a tectonostratigraphic terrane located in the North Atlantic craton, North Atlantic Craton in southern West Greenland. The Akia terrane is bounded to the Southeast by the Eoarchean, Eo- to Neoarchean, Neo-archaean tectonostratigr ...

of the North Atlantic Craton,

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

, near the town of

Maniitsoq Maniitsoq () or Sukkertoppen is a town on Maniitsoq Island, western Greenland located in the Qeqqata municipality. With 2,534 inhabitants , it is the sixth-largest town in Greenland. History Archaeological finds indicate that the area ha ...

.Ravenelle, J. F., Weiershauser, L., and Cole, G. (2017). Report No.: 3CN024.004. Updated Independent Technical Report for the Maniitsoq Nickel-Copper-Cobalt-PGM Project, Greenland. Available at: https://s1.q4cdn.com/725069486/files/doc_downloads/technical_reports/Technical_Report_2017.pdf The belt is found as enclaves ranging from meter-scale pods to 8 km² large intrusive bodies within the ~3050 to 2990 Ma TTG and dioritic

gneisses Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under p ...

of the Akia terrane. and formed contemporaneously with the host gneisses between ~3013 and 3001 Ma The norites underwent high grade

granulite Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated ...

facies

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

at temperatures of ~800 °C and pressures of ~9 kbar (approximately 30 km depth) from ~3010 to 2980 Ma, soon after they were intruded. The norites were metamorphosed twice more at ~2.7 Ga and ~2.5 Ga. A wide variety of norite types are found within the belt, which can be broadly divided into two main groups with different

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

proportions and

chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...

compositions;

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

-rich 'norites' and

pyroxene The pyroxenes (commonly abbreviated 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 ions of calcium (Ca), sodium (Na), iron ( ...

-rich 'melanorites'. These are believed to have formed from fractional crystallisation of a single type of

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

, with accumulation of dense minerals such as pyroxene in the melanorites, and accumulation of less-dense minerals such plagioclase in the norites. Their geochemical compositions indicate that they crystallised from a

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

magma, derived from

partial melting Partial melting is the phenomenon that occurs when a rock is subjected to temperatures high enough to cause certain minerals to melt, but not all of them. Partial melting is an important part of the formation of all igneous rocks and some metamorp ...

of a depleted mantle source, which subsequently assimilated large amounts of continental crust. The Maniitsoq Norite Belt was interpreted to have formed in an ultra-hot

orogeny Orogeny () is a mountain-mountain formation, building process that takes place at a convergent boundary, convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is tectonic uplift, u ...

due to the combination of norite formation from depleted mantle melting and crustal assimilation, TTG formation due to melting in the crust, and high temperature metamorphism that immediately followed magmatism. The Maniitsoq Norite Belt has long been investigated for its nickel-copper-cobalt-platinum group element mineral potential. The belt was first explored by Kryolitselskabet Øresund A/S from 1959 to 1973, and subsequently investigated by Falconbridge Ltd., Nunaoil A/S, Cominco Ltd., NunaMinerals A/S, and most recently by North American Nickel Inc. Exploration was ongoing as of 2019 and planned until 2021.

References

{{reflist Geology of Greenland Igneous intrusions Mesoarchean magmatism Precambrian North America