In the name of Allah.

Hello dear Dr Fotohi.

Rocks that originate from the melting of the continental crust, such as alkaline granites, are usually more enriched in rare earth elements than other igneous rocks. Of course, these types of rocks usually show enrichment in light rare earth elements such as cerium, lanthaium and neodymium. Apatites of hydrothermal origin, such as apatites of Kiruna-type iron deposits, show enrichment of light rare earth elements. Marine sedimentary apatites (phosphorites) show enrichment of heavy rare earth elements. In general, rare earth elements geochemically have a close relationship with uranium and thorium.

A technical document of the International Atomic Energy Agency titled Thorium Resources as Co- and By-products of Rare Earth Deposits was attached. I hope it will be useful to increase your knowledge about rare earth elements.