# Fen Complex

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{{Short description|Region in Norway}}
{{Expand Norwegian}}
The '''Fen Complex''' ({{langx|no|Fensfeltet}}) in [Nome](/source/Nome%2C_Norway), [Telemark](/source/Telemark), [Norway](/source/Norway) is a region noted for an unusual suite of [igneous rocks](/source/igneous_rocks). Several varieties of [carbonatite](/source/carbonatite) are present in the area as well as [lamprophyre](/source/lamprophyre), [ijolite](/source/ijolite) and other highly alkalic rocks. It is the type locality for [fenite](/source/fenite), a [metasomatic](/source/metasomatism) rock commonly found around carbonatite and alkali intrusives.<ref name=Mindat>{{cite web |url=http://www.mindat.org/loc-14357.html |title=Fen Complex, Nome, Telemark, Norway |publisher=Mindat }}</ref>

The Fen Complex is a roughly circular area about three kilometres in diameter. It is located just west of the [Oslo graben](/source/Oslo_graben). [Radiometric](/source/Radiometric) age dating on the carbonatites gave an age of 539 +/- 14 Myr. The host rocks for the intrusions are middle [Proterozoic](/source/Proterozoic) [granite](/source/granite)s and [gneiss](/source/gneiss) and the complex was associated with the [Cambrian](/source/Cambrian) [rift](/source/rift)ing of the [craton](/source/craton)ic rocks.<ref name=Faure>Faure, Gunter (2000) ''Origin of Igneous Rocks'', Springer, pp. 319-321 {{ISBN|3-540-67772-0}}</ref>

The complex is a protected location because of the [rare minerals](/source/rare-earth_mineral) and rock types found there. The rocks were first described by [Waldemar Christofer Brøgger](/source/Waldemar_Christofer_Br%C3%B8gger_(geologist)) in 1921.<ref name=Mindat/> In 2026, Rare Earths Norway reported an updated estimate of 15.9 million metric tons of rare earth oxides, an 81% increase from a 2024 estimate of 8.8 million tons. The deposit includes significant amounts of [neodymium](/source/neodymium) and [praseodymium](/source/praseodymium), elements used in permanent [magnets](/source/Rare-earth_magnet) for technologies such as [electric vehicles](/source/electric_vehicles) and [wind turbines](/source/wind_turbines).<ref>{{cite news |title=Rare earths: Norway says estimate for deposit, Europe's biggest, jumps 81% |url=https://www.reuters.com/business/energy/rare-earths-norway-says-estimate-deposit-biggest-europe-jumps-81-2026-03-03/ |work=Reuters |date=3 March 2026}}</ref>

In regard to case work on mining permits: In Q2 2026, the Norwegian government said that it is taking over the case-work - from the municipality.<ref>https://e24.no/naeringsliv/i/M7PmW5/fensfeltet-vaar-store-bekymring-er-at-det-tar-for-lang-tid. E24.no. Retrieved 2026-06-01</ref>

==See also==
*[Alnö Complex](/source/Aln%C3%B6_Complex)
*[Kattsund-Koster dyke swarm](/source/Kattsund-Koster_dyke_swarm)
*[Kola Alkaline Province](/source/Kola_Alkaline_Province)
*[Norra Kärr](/source/Norra_K%C3%A4rr)
*[Särna alkaline complex](/source/S%C3%A4rna_alkaline_complex)

==References==
{{Reflist}}
{{Coord|59.2677|9.2779|region:NO-38|format=dms|display=title}}

{{Geology of Fennoscandia}}

Category:Carbonatite occurrences
Category:Geography of Telemark
Category:Petrology
Category:Geology of Norway
Category:Cambrian magmatism
Category:Volcanoes of Norway

{{regional-geology-stub}}
{{Telemark-geo-stub}}

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Adapted from the Wikipedia article [Fen Complex](https://en.wikipedia.org/wiki/Fen_Complex) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Fen_Complex?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.