Fluvial Placer Deposit (REE)
Physical Process - Ground surface
Synonym
Alluvial placer deposit
Required Geological Setting
Neogene and Quaternary sediments
Occurrence
Fluvial placer deposits where rare earth element (REE) minerals are selectively concentrated by water flows of rivers based on the difference of specific density. The REE fluvial placer deposits are at downstreams of REE containing REE miarolitic pegmatites, abyssal pegmatites, muscovite-rare-element pegmatites, rare-element pegmatite (allanite), rare-element pegmatite (euxenite), and rare-element pegmatite (gadolinite). The REE fluvial placer deposits are formed on the riverbeds at a gently flowing stream in fissures of riverbed slabs or at upstreams of obstacles such as boulders in water.
Mineral Assemblages (Abyssal pegmatites)
Zircon, Euxenite-(Y), Samarskite-(Y), Fergusonite-(Y), Thorite
Mineral Assemblages (REE miarolitic pegmatites)
Cassiterite, Xenotime-(Y), Monazite-(Ce), Fergusonite-(Y), Topaz