Promethium (Pm) is the last facet in the lanthanides to assume dhcp framework at ambient conditions. The is likewise the only radioactive facet besides technetium through stable bordering elements. The occupational of Haire et al. (1990), whereby they acquired Pm-147 as a reactor byproduct is summary here. An extended discussion ~ above the compare of Pm with that that Sm, Nd, and actinide materials is offered in this work. Pm has been compressed to 60 GPa in a diamond anvil cell and also EDXD was employed in observing the structural changes in Pm. The lattice parameters that this pm sample in ~ ambient conditions are offered as a = 0.364 nm, c = 1.180 nm.
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The very first phase transition in pm from dhcp come fcc has actually been report at 10 GPa. The next change occurred about 18 GPa and Pm is shown to exhibition a dfcc framework which in this study has actually been secure at 60 GPa. The authors allude out changes in diffraction patterns in between 50 and also 60 GPa and also attribute them to a possible indication of more phase change. Upon releasing the pressure, the dfcc structure returned to fcc and also with part hysteresis, back to dhcp. Numbers 15 and 16 show the diffraction patterns at miscellaneous pressures and EOS of pm to 60 GPa, respectively. The authors point out the smooth nature of the fit and the lack of big discontinuities in the volume to come to the conclusion that the f-electron delocalization that is watched in the neighboring aspects of pm is not checked out in its situation up come 60 GPa.
Figure 15. Succession of diffraction spectra of afternoon representative of miscellaneous structures (A) dhcp spectrum listed below 10 GPa, (B) fcc spectra in between 10 and also 18 GPa, (C) spectra at 29 GPa, (D) spectra in ~ 50 GPa, and also (E) spectra in ~ 60 GPa (Haire et al., 1990).
Figure 16. Loved one volume of the three forms of Pm together a role of pressure. Bulk modulus and its press derivative space calculated to it is in 38 GPa and 1.4, dong (Haire et al., 1990).
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RADIOCHEMICAL methods | Overview
K. Buchtela, in Encyclopedia the Analytical science (Second Edition), 2005
Artificially produced Radionuclides
Man has artificially created radioelements (technetium, promethium, transuranium elements) and also many radioactive isotopes of the naturally arising elements. Thus, the herbal radioactivity top top the planet is come some extent increased by synthetic radioactive materials. Plenty of analytical research works focus on the determination of fabricated radionuclides, their migration, pathways, and build-up in the environment. The aim of this analysis research occupational is either to know about fate, pathway, and also metabolism of materials or to attain information about possible environmental security problems.
Radionuclides are produced by atom reactions. This nuclear reactions can take place between highly increased atomic nuclei or in between nuclei and nucleons (e.g., protons). To conquer the Coulomb barrier the charged nuclei or nucleons need to be listed with high kinetic energies. This is completed by the use of accelerator equipment such as cyclotrons, synchrotrons, and linear accelerators. Generally nuclear reactors are offered for radionuclide production due to the fact that the uncharged neutrons present in huge amount in nuclear reactors are communicate easily v the target nuclei.
By nuclear reactions nonradioactive elements can be reinvented to a radioactive species to enable their perceptible qualitative and quantitative decision (activation analysis).
The productivity of such a nuclear reaction, expressed by the resulting task of the product, is offered by
whereby A is the resulting activity, NT the number of target atoms, Φ the flux thickness of particles bombarding the target per unit the time and also area, σ the cross-section the the target nuclei, λ the decay continuous of the product, and also t the reaction time.
After the nuclear reaction, the target material typically has to it is in purified to eliminate by-products. Then, the product is supplied for the production and synthesis that ‘radiochemicals’. The resulting materials are provided for applications in atom medicine, research, and also industry.
Radiochemicals are easily accessible from a series of companies. Usually the purchase, handling, and use space subjected to license procedures. Details of together licensing actions depend on the legislation of the country and have to be strictly observed.
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John W. Arblaster, in Handbook on the Physics and Chemistry of rarely Earths, 2013
9.2 Condensed Phases
Unfortunately, the irradiate lanthanides do not show satisfactory periodic trends in properties and even praseodymium and neodymium, which space isostructural through promethium, show fairly poor agreement as to their physics properties. However, the ratio of the enthalpies of transformation and melting for neodymium together selected in ar 8 over at 0.415 ± 0.021 agrees with the worth of 0.415 obtained for promethium by Angelini and Adair (1974, 1976). Therefore, choosing the summation that the entropies of transition and blend for neodymium in ~ 8.325 J/(mol K) leads to one enthalpy of change for promethium that 3090 J/mol and an enthalpy of fusion of 7450 J/mol.
Heat capacity values for the body-centered cubic and also liquid phases because that lanthanum to samarium display a poor correlation, yet from these, a value of 44 J/(mol K) is selected for both phases because that promethium. Based largely on neodymium, a warm capacity value of 27.5 J/(mol K) is selected because that the alpha phase at 298.15 K and also 45.5 J/(mol K) at 1163 K based upon a warmth capacity difference of 1.5 J/(mol K) at the transition temperature. An intermediate worth of 35.0 J/(mol K) at 750 K is likewise selected based upon the neodymium details heat curve. These 3 values were supplied to represent the warm capacity that the alpha phase as
Ward and also Hill (1976) estimate the entropy in ~ 298.15 K to it is in 71.5 J/(mol K) which is accepted and also agrees with a worth of 71 J/(mol K) approximated by Morss (1976).
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The rarely earth aspects comprise 15 lanthanide facets (atomic number, Z = 57–71) as well as yttrium (Z = 39) and scandium (Z = 21) although promethium (Z = 61) does not show up in nature because of its radiation instability (Fig. 1). They are really coherent team in terms of chemical behavior and have freshly been based on intense investigation in the field of maritime geochemistry. All rare earth facets occur together a trivalent state with exemption of Ce4 + and also Eu2 +. In the lanthanide series, the progressive filling the electron in the shielded inner 4f covering with enhancing atomic number leads to steady decrease in the ionic radii from La3 + come Lu3 +, i m sorry is referred to as ‘the lanthanide contraction’. Consequently, small but systematic transforms in chemical properties allow them to be offered for unique tracers in studying basic processes the govern the to ride bicycle of rarely earth elements in the ocean. For instance, the more heavier lanthanides were predicted to be much more strongly complexed in seawater and also hence much more resistant to removal by scavenging the particulate matter. Yttrium mimics the hefty lanthanides, particularly holmium, due to the fact that of similarity in the ionic radii, its geochemical actions is frequently discussed in addition to that of rarely earth facets (Bau, 1996), back Y may decouple through holmium throughout estuarine mixing processes (Tepe and Bau, 2016; Bau et al., 1995; Lawrence and Kamber, 2006). However, Sc is a dramatically smaller cation through a geochemical behavior that different from other rare earths. In many literature, therefore, “rare earth facets (REEs)” generally include only lanthanides and also Y, and Sc is treated separately.
Two elements, Ce and Eu deserve to take the other oxidation states. In seawater, the result Ce4 + hydrolyzes readily and tends to be eliminated by scavenging. Because that this reason, seawater is commonly depleted in Ce loved one to that expected from bordering La and also Pr, conversely, Ce is frequently enriched in part authigenic minerals such together manganese nodules and also phosphorites. Europium have the right to be diminished to Eu2 +, a cation that have the right to be segregated from various other REEs, throughout magmatic processes. Anomalous concentration of Eu are not unusual in various igneous and also sedimentary rocks. However, reduction of Eu go not normally take ar within the ocean, although an Eu enrichment has often be encountered in hydrothermal fluids venting in ~ mid-oceanic ridges. The anomalous actions of Ce due to oxidation–reduction reactions have the right to be best and quantitatively evaluated loved one to the trivalent next-door neighbors (La and Pr) in the lanthanides collection without significant influence the the other processes affecting your oceanic distributions. This is a notable advantage of the element over the other shift metals, such together Mn and Fe, i m sorry behave individually influenced by the oxidation states.
On the other hand, heavy rare earth facets (HREEs) room quasi-conservative in ~ intermediate and also deep water masses in the open s or in the shelf water, and they have recently been supplied as water massive tracers come identify and also quantify the mix of various water masses (e.g. Hatta and Zhang, 2006; Zheng et al., 2016; Zhang et al., 2018). In addition, over there is one geochemically essential isotope of the lanthanides, 143Nd, which is produced by decay of 147Sm with a half-life the 10.6 × 1011 years. Organic variation that 143Nd/144Nd in terrestrial products occurs relying on mantle/crust segregation of Sm and Nd, and the age of the rocks. Thus, the 143Nd/144Nd ratio may be offered to restrict the resources of the REEs and also track water mass mixing in ~ the s (e.g. Lacan and Jeandel, 2005; Jeandel et al., 2013).
In addition, current investigations have indicated the enrichment that anthropogenic Gd anomalies in rivers and coastal waters, reflecting the intake of Gd chelates as comparison agents in magnetic resonance imaging (Bau, 1996; Bau et al., 2006; Campos and Enzweiler, 2016; Kulaksız and also Bau, 2007, 2011a,b, 2013; Nozaki et al., 2000a,b; Ogata and also Terakado, 2006). Because that example, in san Francisco Bay, the anthropogenic Gd substantially raised from 8.27 come 112 pmol kg− 1 end the past two decades. Anthropogenic Gd serves together a conservative tracer of dissolve wastewater-derived substances, i m sorry is in contrast to the nonconservative characteristics of herbal REEs in estuarine and coastal waters (Hatje et al., 2016).
The rarely earth aspects comprise fifteen lanthanide facets (atomic number, Z=57–71) and also yttrium (Z=39) and also scandium (Z=21), back promethium (Z=61) does not show up in nature because of its radiation instability (Figure 1). Lock are an extremely coherent team in terms of chemical behavior and also have recently been subjected to intense investigation in the ar of marine geochemistry. All rare earth elements occur as a trivalent state with exception of Ce4+ and Eu2+. In the lanthanide series, the steady filling that electron in the shielded inner 4f covering with boosting atomic number leader to progressive decrease in the ionic radii from La3+ to Lu3+, i m sorry is dubbed ‘the lanthanide contraction’. Consequently, tiny but systematic transforms in chemistry properties enable them come be used for unique tracers in studying fundamental processes the govern the cycle of rare earth facets in the ocean. Because that instance, the more heavier lanthanides were predicted come be an ext strongly complexed in seawater and hence much more resistant to removal through scavenging the particulate matter. Yttrium mimics the heavy lanthanides, an especially holmium, since of similarity in the ionic radii. However, Sc is a dramatically smaller cation with a geochemical actions that different from various other rare earths. In most literature, therefore, ‘rare earth aspects (REEs)’ generally encompass only lanthanides and also Y, and Sc is cure separately.
Two elements, Ce and Eu deserve to take the various other oxidation states. Although Ce is generally well accommodated within the strictly trivalent lanthanide collection in igneous rocks, oxidation reaction of Ce3+ to Ce4+ proceeds in oxygenated aqueous systems. In seawater, the resulting Ce4+ hydrolyzes readily and tends come be gotten rid of by scavenging. For this reason, seawater is frequently depleted in Ce relative to that expected from neighboring La and Pr, vice versa, Ce is regularly enriched in some authigenic minerals such as manganese nodules and also phosphorites. Europium can be reduced to Eu2+, a bigger cation that deserve to be segregated from various other REEs, during magmatic processes. Anomalous concentration of Eu space not unusual in miscellaneous igneous and sedimentary rocks. However reduction of Eu walk not normally take ar within the ocean, return an Eu enrichment has frequently be encountered in hydrothermal fluids venting in ~ midoceanic ridges. The anomalous behavior of Ce because of oxidation–reduction reactions deserve to be best and quantitatively evaluated loved one to the trivalent next-door neighbors (La and Pr) in the lanthanides collection without significant influence the the various other processes affecting your oceanic distributions. This is a notable advantage of the facet over the other shift metals, such together Mn and also Fe, i m sorry behave individually influenced by the oxidation states.
In addition, there room two geochemically essential isotopes the the lanthanides, 143Nd and 138Ce. The 143Nd is developed by decay of 147Sm v a half-life that 10.6×1011 years. Natural variation that 143Nd/144Nd in terrestrial products occurs depending on mantle/crust distinction of Sm and Nd, and the period of the rocks. Thus, the 143Nd/144Nd ratio might be used to restrict the sources of the REEs and also mixing in ~ the ocean. Likewise, the 138Ce/142Ce proportion may likewise be provided to dominate homogenization the the aspect by oceanic mixing because the 138Ce is developed by 138La decay (half-life, 2.97×1011 years). However, the 138Ce/142Ce ratio has actually not been well exploited in maritime geochemistry yet, due to the fact that of its smaller herbal variation as compared to the of Nd isotopes and analytical difficulty.
No data concerning the Pm–C phase diagram can be uncovered in the literature. The writer of Ref. <3> assumed the it need to be similar to the step diagrams the other at an early stage lanthanides and also proposed a theoretical phase chart of the promethium–carbon system, i m sorry is presented in Fig. 7. According to this projection, 2 binary carbides are likely to type in the system: Pm2C3 with a narrow homogeneity an ar (Pu2C3 framework type, a = 8.450–8.475 Å (Pm-rich–C-rich boundary)) and also PmC2 having actually two polymorphic forms: HT-βPmC2 (KCN-type structure) and also LT-αPmC2 (CaC2-type structure, a = 3.795, c = 6.365 Å). The highest possible solubility of carbon in βPm and αPm in ~ high temperatures is predicted not to exceed 8 and also 5 at.%, respectively.
Athanas Simon Macheyeki, ... Feng Yuan, in used Geochemistry, 2020
126.96.36.199.3.3 Rare-earth elements
REEs room a repertoire of 17 chemical facets in the periodic Table that occur together in nature. Lock display comparable chemical properties. The 17 REEs room lanthanum (La=57), cerium (Ce=58), praseodymium (Pr=59), neodymium (Nd=60), promethium (Pm=61), samarium (Sm=62), europium (Eu=63), gadolinium (Gd=64), terbium (Tb=65), dysprosium (Dy=66), holmium (Ho=67), erbium (Er=68), thulium (Tm=69), ytterbium (Yb=70), lutetium (Lu=71), scandium (Sc=21), and also yttrium (Y=39). The uses of REE in mineral exploration are detailed in chapter 2, varieties of ore deposits and their origin.
The lanthanides happen in the earth’s crust at concentration exceeding some generally used industrial elements making the ax ‘rare earths’ something of a misnomer. Because that example, yttrium, cerium, lanthanum, and neodymium are existing in the Earth’s late at higher concentrations than lead. That the 15 lanthanides, only promethium go not occur in nature. Back the lanthanides space not therefore rare, they space only economically feasible to mine in a couple of places (e.g., China, north America, and also Australia) and also their raised use in emerging an innovation applications has made lock a highly an important commodity. All of the lanthanides have comparable physical and also chemical properties and also are often explained as a group. In ~ the lanthanide group, however, there space differences between the toxicity the the in`dividual lanthanide elements and their compounds. Because of their typically low toxicity and use in arising technologies, specifically renewable energy, the lanthanides are often referred to as the ‘green elements’. Table 1 contains a review of the lanthanide elements, their chemical abstract solutions numbers, and also other information.
Table 1. Lanthanide elements, usual compounds, and other information
|Synonyms||Rare earths, rare earth metals|
|Chemical/pharmaceutical/other class||Transition metals, the environment-friendly elements|
|Representative chemicals||Cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), prometheum (Pm), praseodymium (Pr), samarium (Sa), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and also yttrium (Y)|
|Chemical abstract solutions registry number||Cerium (7440-45-1), dysprosium (7429-91-6), erbium (7440-52-0), europium (7440-53-1), gadolinium (7440-54-2), holmium (7440-60-0), lanthanum (7439-91-0), lutetium (7440-94-3), neodymium (7440-00-8), prometheum (7440-12-2), praseodymium (7440-10-0), samarium (7440-19-9), scandium (7440-20-2), terbium (7440-27-9), thulium (7440-30-4), ytterbium (7440-64-4), and also yttrium (7440-65-5)|
|Molecular formula (common compounds)||Cerium chloride: CeCl3; Cerium oxide: Ce2O3; Cerium nitrate: Ce(NO3)3; Gadolinium oxide: Gd2O3; Lanthanum carbonate: La2(CO3)3; Lanthanum oxide: La2O3;Yttrium oxide: Y2O3|
Volker Zepf, in rare Earths Industry, 2016
1.1 What REEs Are
The worldwide Union of Pure and also Applied Chemistry classifies REEs together a group of 17 facets in the third group that the periodic table of facets (Connelly, 2005). The REEs thus incorporate scandium (Sc, atomic number 21), yttrium (Y, 39), and the lanthanides, which are lanthanum (La, 57), cerium (Ce, 58), praseodymium (Pr, 59), neodymium (Nd, 60), promethium (Pm, 61), samarium (Sm, 62), europium (Eu, 63), gadolinium (Gd, 64), terbium (Tb, 65), dysprosium (Dy, 66), holmium (Ho, 67), erbium (Er, 68), thulium (Tm, 69), ytterbium (Yb, 70), and also lutetium (Lu, 71). Promethium is no usually contained in the discussion because it is the just radioactive REE and also principally the does not happen in nature. Next to the umbrella term “REE,” the elements are further grouped right into light REEs (LREEs) and also heavy REEs (HREEs), and also some writer such as Kingsnorth (2010) add a medium class of REEs (MREEs). The attributions to these teams are not distinct: the United claims (US) Geological survey (USGS) calls La to Gd the LREEs and Tb come Lu and Y the HREEs (USGS, 2014). Kingsnorth, however, offers La come Nd as LREEs, afternoon to Gd together MREEs, and also Tb to Lu to add Y as HREEs (Kingsnorth, 2010). Introduction of the three groups may come to be common due to the fact that the brand-new Chinese tax rates differentiate amongst LRE, MRE, and also HRE, i.e., light, medium, and high rare earth–rich concentrates (Argus, 2015).
The term “rare earth” traces back to the moment of discovery of the elements, at roughly 1800. The origin and also reason because that calling the materials “rare” room not explicit, but the etymological explanation given by Reiners (2001) is helpful. She says that the adjective “rare” was provided from the fifteenth century onward for something strange, extraordinary, and astonishing (Reiners, 2001). Thus, “rare” go not describe a rarely occurrence but to a weird habitus of the materials. Today, the short concentrations that REEs in ore bodies might be taken into consideration as gift rare. “Earth,” however, is clearly a common word because that oxidic materials in the nineteenth century.
Rare earth facets (REEs) stand for the group of 17 aspects comprising 15 lanthanides, plus yttrium (Y) and scandium (Sc) (Table 1). Amongst the REEs, yttrium was discovered very first in 1794 through a end up chemist, Johan Gadolin who isolated one oxide and called the “yttria,” in a mineral gathered from a quarry near the village of Ytterby in Sweden. The turned out to it is in a mixture of number of oxides of rare earths, consisting of yttrium oxide. The an initial individual REE to it is in isolated to be cerium (Jöns Jacob Berzelius and Wilhelm Hisinger, 1803). Most other REEs were isolated personally in the 19th century, and also the critical naturally occurring one—Lu—was diverted in 1907. The took over 150 years from to an initial REE to the final exploration of promethium in 1947. Due to the fact that promethium is a radioactive element, created from decays of turbulent isotopes that europium and also uranium, with the longest half-life the 17.7 years for 145Pm, the element does not happen in the Earth's late in detectable concentrations. For this reason, promethium is excluded from the factor to consider in this review.
Table 1. Names and also Symbols of the Rare earth Elements
|Sc||Scandium||Sc3 +: 0.87|
|Y||Yttrium||Y3 +: 1.02|
|La||Lanthanum||La3 +: 1.16|
|Ce||Cerium||Ce3 +: 1.14, Ce4 +: 0.87|
|Pr||Praseodymium||Pr3 +: 1.13|
|Nd||Neodymium||Nd3 +: 1.11|
|Sm||Samarium||Sm3 +: 1.08|
|Eu||Europium||Eu2 +: 1.25, Eu3 +: 1.07|
|Gd||Gadolinium||Gd3 +: 1.05|
|Tb||Terbium||Tb3 +: 1.04|
|Dy||Dysprosium||Dy3 +: 1.03|
|Ho||Holmium||Ho3 +: 1.02|
|Er||Erbium||Er3 +: 1.00|
|Tm||Thulium||Tm3 +: 0.99|
|Yb||Ytterbium||Yb3 +: 0.99|
|Lu||Lutetium||Lu3 +: 0.98|
Data resource for ionic radii (Shannon, R.D., 1976. Revised reliable ionic radii and systematic studies of interatomic ranges in halides and chalcogenides. Acta Crystallogr. A32, 751–767).
REEs never occur individually but collectively they are uncovered in miscellaneous minerals in the Earth's crust. This is a herbal verification that these facets partition likewise in melts, fluids, and also minerals on the earth. Exceptions space cerium (Ce) and europium (Eu), which may take various valence states (Ce4 + and Eu2 +) depending upon the oxidation state the the melts or fluids in addition to trivalence common of REEs. Thus, this characteristics is provided to assess relative redox conditions in some mineral or rock equipment (Henderson, 1996) and affects the concentration the REEs in minerals and ores in herbal environments. Scandium is usually uncovered separately from other rare earths and, therefore, choose promethium is not thought about in this review.
The ionic radii the trivalent REE ions are about 1 Å, which are compatible to those that Ca2 +, Na+, Th4 +, etc., and also are substantially larger than those of various other trivalent ions such as B3 +, Al3 +, and Fe3 + (Miyawaki and also Nakai, 1996). Ionic radii the the trivalent REE ions space systematically reduced from La to Lu with increasing atomic number. Slight differences of the ionic radii the REE ion (Table 1) also impact the partitioning that REEs right into the minerals. The ionic radius of Y3 + is similar to the heavy REE ions, bring about the similarity that chemical actions of yttrium with the REEs with larger atomic numbers.
The REEs space electropositive so your compounds are generally ionic. Native a mineralogical standpoint, these compounds are oxides, halides, carbonates, phosphates, and also silicates. Because REE ionic radii are reasonably large, substitution reactions generally involve large cations such as calcium or strontium even though some additional charge balancing is frequently necessary.
The REEs are shift metals. In the change metals, the s orbital of the outermost covering is filled before filling that the reduced electron shells is complete. In atoms of the period six shift elements, the 6s orbital is filled prior to the 5d and 4f orbitals. In the lanthanides, the is the 4f orbitals that are being filled, so the configuration of the valence electrons is comparable in every the REEs, for this reason all exhibit similar chemical behavior.
Because of high ionic dues and big radii, REEs behave together incompatible elements in magma, so that the REEs are more concentrated in the melt, conversely, compatible elements such as iron and also magnesium are an ext incorporated into minerals in the early on stages of fractional crystallization. This geochemical behavior leads come enrichment of REEs in felsic igneous rocks formed from the residual melt in the later stages of spring crystallization. The level of incompatibility varies; lighter REEs are an ext incompatible 보다 the heavier ones.
REEs are frequently classified right into light and also heavy groups, with scandium unclassified (Henderson, 1996). The grouping different with various study scopes such together electron configuration, mineralogy, chemistry behavior, etc. Because that example, Ni et al. (1995) classified the REEs into “cerium-group” type (La-Gd), yttrium-group kind (Tb-Lu and also Y) top top the communication of the partitioning the REEs in monazite (La-Gd) and also xenotime (Tb-Lu and Y). In this review, we classify them into light rare earth facets (LREEs: La-Eu) and heavy rare earth facets (HREEs: Gd-Lu and also Y), since Gd is selectively integrated into HREE minerals choose xenotime. We also note the “light” and “heavy” are most commonly and also properly offered with “lanthanides,” and also strictly speak a “heavy rarely earth” is inaccurate because that Y, i m sorry is lighter than any of the lanthanides.
The subject of this testimonial is REE mineralogy and also resources, that which significant REE minerals room monazite and xenotime in addition to bastnäsite. Later, REE concentrations and also contents exchange mail to complete of La come Lu and Y. REO (total REE oxides) refers to the total of La to Lu and also Y oxides in rocks and also ores, including divalent and also tetravalent, when REE2O3 represents the full of trivalent La-Lu and also Y oxides in REE minerals.
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Geochemically, REEs are more abundant in the Earth's crust 보다 the underlying mantle and more common in the upper continental crust 보다 the reduced crust. The variety of REEs in the continent crust varies from 43 (Ce) to 0.3 ppm (Tm, Lu), and light REEs (93 ppm) are more abundant than the hefty ones (32 ppm) (Rudnick and Gao, 2003). Lock reported the REEs (147 ppm in total) are more abundant 보다 copper (27 ppm), tin (1.7 ppm), and molybdenum (0.8 ppm) in the continent crust. This is because the incompatible REEs are concentrated in partial melts that have actually crystallized to kind the continental crust, and light REEs are larger in ion radius 보다 the hefty ones (Table 1), characterizing much more incompatible nature of LREEs 보다 HREEs.