Science, Maths & Technology
An introduction to geology
...chemistries, rich in alkali elements such as sodium, potassium and calcium, and even carbonate igneous rocks called carbonatites, where instead of being dominated by silica they are over 50% carbonate. A modern carbonatite volcano is Ol Doinyo Lengai in Tanzania. There are also REE not associated with alkali igneous rocks and carbonatites, they are often associated with...