Rare-element Pegmatite (Amblygonite)

Abbreviation

REL-Li

Classification

Amblygonite subtype < Complex type < Lithium subclass < (LCT family) < Rare-element class < Granitic pegmatite

Required Geological Setting

Plutonic rocks

Occurrence

Pegmatites formed by fractional crystallization of S-type granite magma associated with upper Greenschist facies to Amphibolite facies in Barrovian-type middle-P metamorphism. It is considered that the complex type pegmatites are formed by extremely fractionated magma. The rare-element class pegmatites emplaced at shallow depth, and most of pegmatites are reported from active continental margin granites in compressional crustal settings such as the Pacific 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 amblygonite subtype is characterized by abundant Li, P, and F. Li is included mostly in amblygonite, and other Li-bearing aluminosilicates are rare.

Mineral Assemblages (Major minerals)

Quartz, Orthoclase, Microcline, Albite, Muscovite, (Almandine)

Mineral Assemblages

Amblygonite, Beryl, Columbite-(Fe), Tantalite-(Fe), (Lepidolite, Pollucite)