The story of rare earth elements (REEs): Occurrences, global distribution, genesis, geology, mineralogy and global production

3 DIPARTIMENTO DI SCIENZE DELLA TERRA, UNIVERSITY OF TRIESTE, VIA E. WEISS 8, I-34127 TRIESTE, ITALY 4 INSTITUTO DE GEOCIENCIAS, UNIVERSIDADE DE SAO PAULO, C.P. 30627, 01051 SAO PAULO, SP, BRAZIL 5 DIPARTIMENTO DI SCIENZE DELLA TERRA, ‘LA SAPIENZA’ UNIVERSITY, PIAZZALE ALDO MORO 5, I-00185, ROME, ITALY 6 ISTITUTO DI MINERALOGIA, PETROGRAFIA E GEOCHIMICA, UNIVERSITY OF PALERMO, VIA ARCHIRAFI 36, I-90100,

Potassic and Sodic Igneous Rocks from Eastern Paraguay: their Origin from the Lithospheric Mantle and Genetic Relationships with the Associated Parana flood tholeiites

The rare earth elements are unusual when defining giant-sized ore deposits, as resources are often quoted as total rare earth oxide, but the importance of a deposit may be related to the grade for individual, or a limited group of the elements. Taking the total REE resource, only one currently known deposit (Bayan Obo) would class as giant (>1.7 × 10 7  tonnes contained metal), but a range of others classify as large (>1.7 × 10 6 tonnes). With the exception of unclassified resource estimates from the Olympic Dam IOCG deposit, all of these deposits are related to alkaline igneous activity – either carbonatites or agpaitic nepheline syenites. The total resource in these deposits must relate to the scale of the primary igneous source, but the grade is a complex function of igneous source, magmatic crystallisation, hydrothermal modification and supergene enrichment during weathering. Isotopic data suggest that the sources conducive to the formation of large REE deposits are developed in subcontinental lithospheric mantle, enriched in trace elements either by plume activity, or by previous subduction. The reactivation of such enriched mantle domains in relatively restricted geographical areas may have played a role in the formation of some of the largest deposits (e.g. Bayan Obo). Hydrothermal activity involving fluids from magmatic to meteoric sources may result in the redistribution of the REE and increases in grade, depending on primary mineralogy and the availability of ligands. Weathering and supergene enrichment of carbonatite has played a role in the formation of the highest grade deposits at Mount Weld (Australia) and Tomtor (Russia). For the individual REE with the current highest economic value (Nd and the HREE), the boundaries for the large and giant size classes are two orders of magnitude lower, and deposits enriched in these metals (agpaitic systems, ion absorption deposits) may have significant economic impact in the near future.

https://cris.brighton.ac.uk/ws/files/406833/geoscience%20frontiers%20REE%20smith%20et%20al.pdf

From mantle to critical zone: A review of large and giant sized deposits of the rare earth elements

Fenites associated with carbonatite complexes: A review

Primary and secondary niobium mineral deposits associated with carbonatites

The Araxa complex (16 km 2 ) comprises carbonatites forming a central core and a complex network of concentric and radial dykes as well as small veins; additionally, it includes mica-rich rocks, phoscorites and lamprophyres. Fenites also occur and are represented by Proterozoic quartzites and schists of the Araxa Group. The petrographic study of 130 borehole samples indicates that the complex is basically made up by two rock-types, carbonatites and mica-rich rocks, and subordinately by a third unit of hybrid composition. Carbonatites range chemically in composition, the most abundant type being magnesiocarbonatites. Dolomite and calcite correspond to the chief constituents, but other carbonate phases, including the Ce-group RE minerals, are also recognized. Phosphates and oxides are widespread accessories whereas silicate minerals consist of olivine, clinopyroxene, mica and amphibole. Mica-rich rocks are represented by abundant glimmeritic rocks and scarce cumulitic phlogopite-, olivine- and diopside-bearing pyroxenites. Hybrid rocks mainly contain phlogopite and tetraferriphlogopite as cumulus and intercumulus phases, respectively; carbonate minerals may also be found. Chemical data indicate that the carbonatites are strongly enriched in REE and have lower contents of Nb, Zr, V, Cr, Ni and Rb compared to the mica-rich rocks. The higher K, Nb and Zr contents of the latter rocks are believed to be related to metasomatic processes (glimmeritization) of the pyroxenites. Similar REE patterns for carbonatites and mica-rich rocks seem to suggest that they are related to a single

/pdf/petrography-and-mineral-chemistry-of-carbonatites-and-mica-31pnxatkbd.pdf

Petrography and mineral chemistry of carbonatites and mica-rich rocks from the Araxá complex (Alto Paranaíba Province, Brazil)

The Pariquera Açu K-alkaline complex and southern Brazil lithospheric mantle source characteristics

The paper describes the Corsica and Sardinia Late Hercynian dyke magmatism, which developed in two partially overlapping main phases of calc-alkaline and basaltic rock-suites. The two episodes were accompanied by rhyolitic dykes. Dyke activity began in Corsica around 320 Ma ago and ended in Sardinia about 230 Ma ago. Field data and geochronology suggest that the onset of hypabyssal magmatism occurred soon after the emplacement of the various Hercynian granitoid plutons, but almost always after complete solidification of the host rock. Petrography and mineral chemistry show significant differences between calc-alkaline, basaltic and rhyolitic rocks. The behaviour of trace elements with different degrees of incompatibility show intermediate characters for calc-alkaline magmatism, between those of intraplate basalt and volcanic-arc products. The nature of the source of the calc-alkaline rocks, tholeiitic and transitional basalt, suggests derivation from a subcontinental enriched lithospheric mantle. Crustal contamination during magma ascent appears to have played a minor role. Alkaline rocks (basanite, alkali basalt and their fractionated types: hawaiite and mugearite) show incompatible element distribution and initial Sr and Nd isotopic ratios typical of mantle-derived astenospheric unconlaminated magmas. Three rock-groups of felsic dykes are present: peraluminous, metaluminous and peralkaline rhyolite. The first, similar to S-type granite, have been related to partial melting of a metapelitic crustal source. The metaluminous rhyolite shows remarkable similarities with the calc-alkaline granitoid of the Sardinia-Corsica Batholith, and is linked to melting processes of a basic-intermediate meta-igneous source. The peralkaline rhyolite shows anorogenic features, a strong affinity with A-type granite, and a mantle signature with possible crustal involvement. The dyke magmatism reflects the evolution of mantle sources from erogenic up to anorogenic types, predating the Tethys opening and the beginning of the Alpine cycle.

Late to post-hercynian dyke activity in the Sardinia-Corsica Domain : A transition from orogenic calc-alkaline to anorogenic alkaline magmatism

/pdf/mantle-sources-and-differentiation-of-alkaline-magmatic-mbzdep6y19.pdf

Gianbosco Traversa

Papers

Petrography and mineral chemistry of carbonatites and mica-rich rocks from the Araxá complex (Alto Paranaíba Province, Brazil)

The Pariquera Açu K-alkaline complex and southern Brazil lithospheric mantle source characteristics

Late to post-hercynian dyke activity in the Sardinia-Corsica Domain : A transition from orogenic calc-alkaline to anorogenic alkaline magmatism

Mantle sources and differentiation of alkaline magmatic suite of Lages, Santa Catarina, Brazil

Petrological and geochemical studies of alkaline rocks from continental Brazil. 1. The phonolite suite from Piratini, RS