Geological setting and resources of the major rare-earth-element deposits in Australia

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• 作者：Subhash Jaireth ; ^{Subhash.Jaireth@ga.gov.au" class="auth_mail} ; Dean M. Hoatson ; Yanis Miezitis
• 关键词：Australia's rare-earth-element deposits ; Rare-earth-element resources ; Mineral systems ; Heavy mineral sand
• 刊名：Ore Geology Reviews
• 出版年：October 2014
• 年：2014
• 卷：62
• 期：Complete
• 页码：72-128
• 全文大小：11371 K

文摘

The rare-earth elements (REE) are a group of seventeen speciality metals that have unique and diverse 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 in Australia are 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 distribution and concentration 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 spatial association with alkaline felsic igneous rocks, however, scandium in laterite profiles has a closer affinity with ultramafic/mafic igneous rocks.

A mineral-system approach has been used in this review to classify the major Australian REE deposits according to various mineralising criteria and/or associated geological events. This hierarchical classification framework has the advantage over more traditional descriptive classifications in that it has the benefits of attempting to understand those geological processes considered critical to the formation of a particular deposit type, and also it has a more predictive capacity for identifying potential new areas and types of REE mineralisation. The highest level of the classification 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.

The review summarises the geological factors considered important for the formation of REE deposits. These factors can be used to identify mappable features in databases, which in turn can be applied to produce mineral potential/prospectivity maps.