Rare-element Pegmatite (Gadolinite)

Abbreviation

REL-REE

Classification

Gadolinite type < REE subclass < (NYF family) < Rare-element class < Granitic pegmatite

Occurrence

Pegmatites formed by fractional crystallization of I-type granite magma. Pegmatites are emplaced at shallow depth, and distribute at interior to marginal zones of granite batholiths. Most of pegmatites are reported from passive continental margin granites in extentional crustal settings such as the Atlantic Ocean. Textures of host rocks are clearly cut by pegmatites, and host rocks are subjected to contact metamorphism by granites or pegmatites. Pegmatites are massive and pockets are very rare. The Gadolinite type is characterized by abundant Y, Be, and heavy rare-earth elements such as Gd, Er, Yb.

Mineral Assemblages (Major minerals)

Quartz, Microcline, Albite, Muscovite

Mineral Assemblages

Gadolinite-(Y), Fergusonite-(Y), Samarskite-(Y), Zircon, Rutile, Fluorite, Ilmenite, (Zinnwaldite)