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

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 10 CG 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.

Enhancing the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect with sodium dodecyl sulfate surfactant

Ameliorating the problem of low leaching efficiency,long leaching period,and high agent consumption should be studied to efficiently exploit ion-absorbed rare earth ore resources.In this study,the surfactant sodium dodecyl sulfate(SDS) is used to enhance the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect for the first time.The effects of surfactant concentration,leaching agent dosage,solution flow velocity,and solution pH on the leaching rate were explored,and the mechanism of SDS was discussed.Under the optimum conditions,the addition of a small amount of SDS(mass fraction0.04%) can increase the leaching rate by about 5%,shorten the leaching period,and reduce the consumption of the leaching agent.SDS significantly ameliorates the seepage effect of the ore body by reducing the surface tension of the leaching agent and ameliorating the wettability of the mineral surface.This effect is the main factor that improves the leaching efficiency.DFT(density functional theory) calculation results show that SDS can react with rare earth ions,which reduces the adsorption strength on clay mineral surfaces.Hence,rare earth ions are easily exchanged by ammonium ions,and mass transfer is enhanced.

Rare Earth Element Geochemistry on Magmatic Rocks and Gold Deposits in Shizishan Ore-Field of Tongling, China

REE geochemical characteristics of the magmatic rocks and gold deposits in Shizishan ore-field of Tongling were studied. Three types of the magmatic rocks have almost the same chondrite-normalized REE patterns, Eu and Ce anomalous values, and ∑REE, ∑LREE/∑HREE regular changes, which indicates that their magmas come from the same source and their digenetic mechanism is fractional crystallization. In three gold deposits, the mineral ores and related altered rocks have similar chondrite-normalized REE patterns and sharp Eu positive anomalous values. The REE contents reduced from the magmatic rocks to skamization or alteration magmatic rocks, skam type ores, sulphide type ores, wall-rocks limestone or marble. The REE geochemical characteristics of the ores and related rocks show that primary fluids originated from magmatic differentiation in lower pressure of shallow crust, ore-forming hydrothermal solutions gained REE and mineralization elements further from leaching the magmatic rocks, then superimposed and reformed the limestones or marbles and deposited ore-forming material.

Rare earth element geochemistry of hydrothermal deposits from Southwest Indian Ridge

The REE compositions of hydrothermal deposits and basalt samples from the Southwest Indian Ridge （SWIR） were determined with ICP-MS. The results show that there are significant differences between different types of samples although all samples show relative LREE enrichment. The contents of REE in hydrothermal sulfides and alterated rocks samples are lower （from 7.036× 10^-6 to 23.660×10^-6）, while those in the white chimney deposits are relatively higher （ranging from 84.496 × 10^-6 to 103.511 × 10^- 6）. Both of them are lower than basalts. Chondrite-normalized REE distribution patterns show that sulfides and alterated rocks samples are characterized by significant positive Eu anomalies. On the contrary, white chimney deposits have obvious negative Eu anomalies, which may be caused by abundant calcite existing in the white chimney samples. Both the content and distribution pattern of REE in sulfides suggest that REE most possibly is originally derived from hydrothermal fluids, but influenced by the submarine reducing ore-forming environment, seawater convection, mineral compositions as well as the constraint of mineral crystallizations.

State of rare earth elements in the rare earth deposits of Northwest Guizhou,China

We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No independent rare earth minerals were detected by scanning electron microscope. Elements detected by the electronic probe for the in situ micro-zone of the sample included: O,Al, Si, Ca, Mg, Fe, Ti, K, Na, S, Cl, C, Cu, Cr, V, and Pt.Rare earth elements were not detected by electron probe.(NH_4)_2 SO_4,(NH_4)Cl, NaCl, and H_2 SO_4 were used as reagents in chemical leaching experiments that easily leached out rare earth elements under the action of 10%reagent, indicating that the rare earth elements in ore are mainly in the ionic state rather than present as rare earth minerals.

Geochemical Characteristics of Rare Earth Elements in Gejiu Tin Polymetallic Deposits, Yunnan Province, China

In order to get a better understanding of metallogeny, the geochemical characteristics of REE and trace element for Gejiu tin polymetallic deposits were studied by comparing concentrations of REE and trace elements in different type ores and rocks, including skarn-type ore, bedded-type ore, vein-type ore, altered granite, country rocks. Results of this study indicated that the metallogenic matters for different type ores in the study area might be derived from the same origin source, which may be mainly related to granitic activities. Furthermore, there are some differences in concentrations of REE in different ores due to their different depositional mechanism during that time. LREE concentrations were enriched relatively in the vein-type ores and the bedded-type ores with relatively low total REE concentrations, whereas total REE concentrations were higher in the skarn-type ores with LREE and HREE concentrations in wide variation ranges.

Rare earth elements and yttrium in ferromanganese deposits from the South China Sea:distribution,composition and resource considerations

Ferromanganese nodules and crusts contain relatively high concentration of rare earth elements（REE） and yttrium（REY）,with a growing interest in exploitation as an alternative to land-based REY resources.On the basis of comprehensive geochemical approach,the abundance and distribution of REY in the ferromanganese nodules from the South China Sea are analyzed.The results indicate that the REY contents in ferromanganese deposits show a clear geographic regularity.Total REY contents range from 69.1×10^-6 to 2 919.4×10^-6,with an average value of 1 459.5×10^-6.Especially,the enrichment rate of Ce content is high,accounting for almost 60% of the total REY.This REE enrichment is controlled mainly by the sorption of ferromanganese oxides and clay minerals in the nodules and crusts.Moreover,the total REY are higher in ferromanganese deposits of hydrogenous origin than of diagenetic origin.Finally,Light REE（LREE） and heavy REE（HREE） oxides of the ferromanganese deposits in the study area can be classified into four grades： non-enriched type,weakly enriched type,enriched type,and extremely enriched type.According to the classification criteria of rare earth resources,the Xisha and Zhongsha platform-central deep basin areas show a great potential for these rare earth metals.

Trace Elements and Rare Earth Elements of Sulfide Minerals in the Tianqiao Pb-Zn Ore Deposit,Guizhou Province,China

Trace elements and rare earth elements（REE） of the sulfide minerals were determined by inductively-coupled plasma mass spectrometry.The results indicate that V,Cu,Sn,Ga,Cd,In,and Se are concentrated in sphalerite,Sb,As,Ge,and Tl are concentrated in galena,and almost all trace elements in pyrite are low.The Ga and Cd contents in the light-yellow sphalerites are higher than that in the brown and the black sphalerites.The contents of Ge,Tl,In,and Se in brown sphalerites are higher than that in light-yellow sphalerites and black sphalerites.It shows that REE concentrations are higher in pyrite than in sphalerite,and galena.In sphalerites,the REE concentration decreases from light-yellow sphalerites,brown sphalerites,to black sphalerites.The ratios of Ga/In are more than 10, and Co/Ni are less than 1 in the studied sphalerites and pyrites,respectively,indicating that the genesis of the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis associated with hydrothermal genesis.The relationship between LnGa and LnIn in sphalerite,and between LnBi and LnSb in galena,indicates that the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis.Based on the chondrite-normalized REE patterns,δEu is a negative anomaly（0.13-0.88）,andδCe does not show obvious anomaly（0.88-1.31）;all the samples have low total REE concentrations（〈3 ppm） and a wide range of light rare earth element/high rare earth element ratios（1.12-12.35）.These results indicate that the ore-forming fluids occur under a reducing environment.Comparison REE compositions and parameters of sphalerites,galenas,pyrites,ores,altered dolostone rocks,strata carbonates,and the pyrite from Lower Carboniferous Datang Formation showed that the ore-forming fluids might come from polycomponent systems,that is,different chronostratigraphic units could make an important contribution to the ore-forming fluids.Combined with the tectonic setting and previous isotopic geochemistry evidence,we conclude that the ore-deposit genesis is hydrothermal,sedimentary reformed,with multisources characteristics of ore-forming fluids.

A new type of rare earth elements deposit in weathering crust of Permian basalt in western Guizhou, NW China

A new type of rare earth elements （REEs） deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ∑RE2O3 0.065%-1.086%. This type of REEs deposit was widely distributed with steady horizon and thickness of 3-4 m. The ore-bearing weathering crust （kaolinite） of the three discovered REEs deposits belonged to the third episode of the Emeishan basalt eruption. The new type of REEs deposit was suggested that basalt （tuff） weathering could lead to the enrichment of the rare earth elements. Therefore, it is of important economic significance to explore REEs deposits in the weathering crust of basalt （tuffs） in Yunnan, Guizhou, and Sichuan Provinces.

Rare Earth Elements Geochemistry of Laowan Gold Deposit in Henan Province: Trace to Source of Ore-Forming Materials

The compositions of REE in quartz and pyrite from the main stage of the Laowan gold deposit in Henan Province and that in quartz from Laowan granite were determined by inductively coupled plasma-mass-spectrometry （ICP-MS） to trace the source of ore-forming materials. Meanwhile, the REE compositions of the deposit ore, granite and metamorphic wall rock were also considered for comparative studies in detail. The range of ∑REE of quartz and pyrite from the deposit ores is 4.18 × 10^-6- 30.91 × 10^-6, the average of ∑REE is 13.39 × 10^-6, and the average of ∑REE of quartz in the Laowan granite is 6.68 × 10^-6. There is no distinct difference of REE parameters between the deposit ore quartz and granite quartz. The quartz in gold deposit has the same REE particular parameters as quartzes from Laowan granite, such as δEu, δCe, （La/Yb）N and （La/Sm）N, partition degree of LREE to HREE, especially, the chondrite-normalized REE patterns, but no similarity to those from metamorphic wall rock, which shows that ore-forming hydrothermal fluid is mainly the fluid coming from the Laowan granite magma, rather than metamorphic fluid. Meanwhile, comparison studies on REE features between minerals from the deposit ores and related geological bodies in the deposit show that REE characteristics of minerals can serve as an indicator of ore-forming fluid properties and sources, while the REE characteristics of the bulk samples （such as deposit ores, granites and wall rocks） can not trace the source of the ore-forming materials exactly.

Geochemistry of Rare Earth Elements of Anqing Copper Deposit in Anhui Province

The geochemical features of REE were studied by comparing the copper ore with the skarn, the diorite and the stratum, to trace the source of metallogenic materials in Anqing copper deposit, Anhui. The origin of metallogenic hydrothermal fluids was studied through simulating REE pattern of the balanceable hydrothermal fluids. The results indicate that the metallogenic materials come from the diorite and the metallogenic hydrothermal fluids come from the dioritic magma. The results also show that the rare earth elements are relatively mobile during metallization.

Geochemistry of Rare Earth Elements in Xikeng Ag-Pb-Zn Ore Deposit, South Anhui, China

In this paper, a comparative study is done on the geochemical charateristics of REE in ore, ore-hosted rocks of Lantian group, granite related to ore deposit, and altered rocks for tracing origin of ore-forming materials. The result indicates that the ore-forming fluid and ore-forming materials for Xikeng silver-polymetallic ore deposit were derived from Yixian granite's magmatic activity. Water-rock reaction of the hydrothermal fluid with the carbonate-rich stratum led the altered rock to relatively enrich in HREE.

Rare Earth Element and Trace Element Features of Gold-bearing Pyrite in the Jinshan Gold Deposit,Jiangxi Province

Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements（LREE;159.556 ppm） and lower HREE（12.108 ppm）.TheΣLREE/ΣHREE ratio is 12.612 and（La/Yb）_N is 11.765.These indicate that pyrite is rich in LREE.The（La/Sm）_N ratio is 3.758 and that of（Gd/Yb）_N is 1.695.These are obvious LREE fractionations.The rare earth element（REE） distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks（regional metamorphic rocks）,but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio（average value 0.38） of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with Cl〉F.

Geochemistry of Rare Earth Elements in Hydrothermal Ore Deposit in Heishan Area,Shaanxi Province

The study on rare earth elements in hydrothermal ore deposit in Heishan area indicates that the REE concentration in rock with very weak negative Ce and Eu anomaly is far higher than those in ore. The REE pattern in ore is characterized by very low REE concentration, typical enrichment in LRE and distinctive negative Eu and Ce anomaly. δ Eu and δ Ce values vary from 0 51～0 6 to 0 71～0 77 and 0 84～0 88 to 0 60～0 78, respectively, as shown in samples from Fe Cu ore to Au ore. Different δ Eu and δ Ce values reveal that temperature gradually decreases and oxygen fugacity gradually increases when ore bearing hydrothermal solution evolves from early to late stage. It is likely that REE in solution is mainly transported in the forms of(RE(CO 3) 3F) 4- , (RE(CO 3)F 2) -, (RE(F,Cl) 2) + , (RE(CO 3) 3) 3- and (RE(CO 3) 4) 5- complexes.

Beneficiation Studies of a Rare Earth Ore from the Olserum Deposit

The Olserum deposit located in Sweden hosts an indicated mineral resource of 4.5 million tonnes at 0.6% total rare earth oxides (TREO), exhibiting a relatively high proportion of heavy rare earth elements (HREE). The mineralogy and beneficiation of a composite drill core sample from the Olserum deposit were studied. Monazite and xenotime were found by the mineralogical analyses to be the target minerals for beneficiation of REEs and most (96.9%) of REEs in the ore are carried by monazite (68.5%) and xenotime (28.4%). Because xenotime carries 84.7% of heavy REEs (Y, Gd, Dy) in the ore it is more valuable mineral than monazite. A beneficiation process was developed which includes grinding, wet low intensity magnetic separation (WLIMS) for removal of magnetite and REEs flotation consisting of one stage of roughing and two stages of cleaning. Selective flotation collector of REE minerals and suitable grinding size of feed material were determined by testwork. The REE concentrate and tailings were chemically and mineralogically characterized. The studies of process mineralogy showed that the REE-bearing minerals, monazite and xenotime, and apatite were successfully enriched from the concentrations of 0.6%, 0.31% and 2.6% in the feed to those of 17.0%, 8.9% and 65.0% in the concentrate with the recoveries of 79.0%, 81.3% and 71.0%, respectively.

Geochemistry of Rare Earth Elements in Aktishikan Gold Deposit,Xinjiang

The characteristics and the models of rare earth elements in the geological bodies and the hydrothermal water balanced with the adamellite were comprehensively studied in Aktishikan gold deposit,Nurt area of Altay,Xinjiang.And the behavior of rare earth elements during metasomatic alteration was discussed by using the isocon method of Grant.The results show that the rare earth elements are inert during metasomatic alteration,the hydrothermal water has no relation to the magmatic water,and the gold material sources mainly stem from the wall rock.

Geochemical Behavior of Rare Earth Elements in Jianchaling Ore Depositin Shaanxi Province

Studies on rocks and ores of Jianchaling ore deposit, southern Shaanxi, show that REE patterns in the ores clearly differ from that in ultrabasic and acidic rocks. The REE pattern in Ni ore is similar to that in Au ore and is characterized by typical enrichment in LREE and sharp negative Eu and Ce anomalies, indicating that Ni ore and Au ore were formed from the same hydrothermal solution. δ Eu and δ Ce variations reflect that Ni ore is formed at higher temperature and relative reduction environment, and Au ore at lower temperature and relative oxidation environment. The characteristics imply that the ore forming materials were derived from the ultrabasic rock and the hydrothermal solution is a post magmatic acidic solution.

Effect of Rare Earth Elements on Depositing Rate of Nickel Alloy Brush Plating Coatings

The effect of four kinds of rare earth elements on the depositing rate of Ni-based alloy brush plating coatings was investigated. The results indicate that all of the selected rare earth elements increase the depositing rate of Ni-based alloy coatings, and Sm increases the depositing rate most obviously. There is an optimum amount of rare earth addition in the plating solution. With the change of plating voltage to a certain extent, the results reveal no differences. The mechanism of the increase of the depositing rate was analyzed.

Rare Earth Elements Geochemistry of Dongtian Gold Deposit in Western Guangdong

Yunkai uplifted area is one of the important metallogenic areas in Guangdong and Guangxi Provinces, in which many gold, silver, tungsten, tin, lead, zinc, molybdenum, and iron deposits were found. Dongtian gold deposit in the middle of Yunkai uplifted area, western Guangdong Province, is chosen as an example of those deposits. Comparative studies on the chondrite-normalized REE patterns and ΣREE, LREE/HREE, δ Eu , δ Ce , N La/Yb , and N La/Sm of auriferous quartz veins, altered gneiss type gold ores, Caledonian gneissic biotite granite, and Late Yanshanian granite porphyry were made. The results indicate that the source of the metallogenic materials of the auriferous quartz veins and the altered gneiss type gold ores are the same, and both of them come from the gneissic biotite granite. Metallogenic epoch of the deposit is estimated to be Caledonian period.