Rare Earth Elements- A Review

This article presents a description of Rare-earth elements (REE) which are a collection of seventeen metals that have distinctive and varied chemical, magnetic, and luminescent properties that make them strategically important in a number of high-technology industries. Consequently, the REE are increasingly becoming more attractive commodity targets for the mineral industry. This paper presents a comprehensive review of the distribution, geological characteristics and resources of Australia's major REE deposits. REE are generally associated with igneous, sedimentary, and metamorphic rocks in a wide range of geological environments. Elevated concentrations of these elements have been documented in various heavy-mineral sand deposits (beach, dune, marine tidal, and channel), carbonatite intrusions, (per)alkaline igneous rocks, iron-oxide breccia complexes, calc-silicate rocks (skarns), fluorapatite veins, pegmatites, phosphorites, fluviatile sandstones, unconformity-related uranium deposits, and lignites. The dissemination and deliberation of REE in these deposits are influenced by various rock-forming processes including enrichment in magmatic or hydrothermal fluids, separation into mineral species and precipitation, and subsequent redistribution and concentration through weathering and other surface processes. The lanthanide series of REE (lanthanum to lutetium) and yttrium show a close genetic and three-dimensional association with alkaline felsic igneous rocks, however, scandium in laterite profiles has a closer empathy with ultramafic/mafic igneous rocks. The highest level of the cataloguing comprises four general ‘mineral-system association' categories, regolith, basinal, metamorphic, and magmatic, which in turn contain sixteen ‘deposit type' members, namely: regolith-carbonatite-associated; ultramafic/mafic rock-associated; basinal- heavy mineral sand deposits in beach, high dune, offshore shallow marine tidal, and tidal environments; phosphorite; lignite; unconformity-related; metamorphic -calc-silicate; and magmatic- (per)alkaline rocks; carbonatite; pegmatite; skarn; apatite and/or fluorite veins; and iron-oxide breccia complex.