What is a nepheline syenite in geology ?

Nepheline syenite : definition

Streckeisen diagrams (or QAPF diagrams) - Classification of plutonic and volcanic rocks
It is a highly undersaturated grainy igneous rock, consisting mainly of alkali feldspars, usually perthitic microcline (on average 70%), and feldspathoids (mainly nepheline, more rarely sodalite, analcime or hauyne (on average 20 %), biotite, amphibole (riebeckite) and pyroxene  like aegirine, sometimes cancrinite. Apatite, titanitezirconfluorite and sometimes calcite, corundum and eudialyte are abundant, defining many varieties and allowing the exploitation of these rocks as ore of zirconium, rare earth elements or phosphorus.

Nepheline syenites draw small intrusive massifs associated with syenites, carbonatites or peridotites. Pegmatitic facies with large crystals, called pegmatitoids, frequently line the edges. Their volcanic equivalent is the phonolite.

The most famous deposits are those of the Kola Peninsula (Russia), Illimaussaq (Greenland) and the Arendal region (Norway).
Larvikite from Norway
Larvikite from Norway

ReCaptcha

This service is used to secure web forms of our website and required if you want to contact us. By accepting it you agree to Google's privacy policy: https://policies.google.com/privacy

Facebook

Our website allows you to like or share its content on Facebook social network. By activating and using it you agree to Facebook's privacy policy: https://www.facebook.com/policy/cookies/

YouTube

Integrated videos provided by YouTube are used on our website. By accepting to watch them you agree to Google's privacy policy: https://policies.google.com/privacy

Twitter

Integrated tweets and share services of Twitter are used on our website. By accepting and using these you agree to Twitter's privacy policy: https://help.twitter.com/en/rules-and-policies/twitter-cookies

PInterest

Our website allows you to share its content on PInterest social network. By activating and using it you agree to PInterest's privacy policy: https://policy.pinterest.com/en/privacy-policy/