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

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 or ...

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

intrusions, located in the Akia Terrane of the

North Atlantic Craton The North Atlantic Craton (NAC) is an Archaean craton exposed in southern West Greenland, the Nain Province in Labrador, and the Lewisian complex in northwestern Scotland. The NAC is bounded by the Nagssugtoqidian orogen to the north and the 1.8 ...

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 t ...

, near the town of

Maniitsoq Maniitsoq (), formerly Sukkertoppen, is a town in 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 ...

.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 ( ) 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. Gneiss forms at higher temperatures an ...

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 w ...

facies

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

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 chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

proportions and

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...

compositions;

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 prope ...

-rich 'norites' and

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) ...

-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 is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

, with

accumulation Accumulation may refer to: Finance * Accumulation function, a mathematical function defined in terms of the ratio future value to present value * Capital accumulation, the gathering of objects of value Science and engineering * Accumulate (hi ...

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 occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the solid ...

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 building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

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