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117-650: There are three important reasons to study the South China Block. First, South China hosts a great deal of rare-earth element (REE) ores . Second, the South China Block is a key component of the Rodinia supercontinent . Therefore, such study helps us understand more about the supercontinent cycle . Third, almost all major known clades of Triassic marine reptiles have been recovered from the South China sedimentary sequences. They are important to understand

234-549: A fissile material . The principal sources of rare-earth elements are the minerals bastnäsite ( RCO 3 F , where R is a mixture of rare-earth elements), monazite ( XPO 4 , where X is a mixture of rare-earth elements and sometimes thorium), and loparite ( (Ce,Na,Ca)(Ti,Nb)O 3 ), and the lateritic ion-adsorption clays . Despite their high relative abundance, rare-earth minerals are more difficult to mine and extract than equivalent sources of transition metals (due in part to their similar chemical properties), making

351-491: A mantle plume origin. For example, the picrites is proved to represent a high temperature primary magma. In addition, the basalt shows isotopic similarity with ocean island basalt (OIB) which is formed by a mantle plume triggered by subducted oceanic crust. The Indosinian (Triassic) and Yanshanian (Jurassic-Cretaceous) Movement represents the Mesozoic deformation and magmatism event. There are several characteristics about

468-609: A CO 2 -rich primary magma, by fractional crystallization of an alkaline primary magma, or by separation of a CO 2 -rich immiscible liquid from. These liquids are most commonly forming in association with very deep Precambrian cratons , like the ones found in Africa and the Canadian Shield. Ferrocarbonatites are the most common type of carbonatite to be enriched in REE, and are often emplaced as late-stage, brecciated pipes at

585-418: A Permian magmatic arc There are some doubts on the starting time of Pacific plate westward subduction.  The Permian synchronous arc magmatism has not been discovered along the coastal Provinces of Southeast China yet. They are only reported in the southern part of the South China Block. 2. Occurrence of Jurassic adakitic rock A conventional way to generate magma is by melting in the mantle wedge which

702-532: A component of magnets in hybrid car motors." The global demand for rare-earth elements (REEs) is expected to increase more than fivefold by 2030. The REE geochemical classification is usually done on the basis of their atomic weight . One of the most common classifications divides REE into 3 groups: light rare earths (LREE - from 57 La to 60 Nd), intermediate (MREE - from 62 Sm to 67 Ho) and heavy (HREE - from 68 Er to 71 Lu). REE usually appear as trivalent ions, except for Ce and Eu which can take

819-665: A few percent of yttrium). Uranium ores from Ontario have occasionally yielded yttrium as a byproduct. Well-known minerals containing cerium, and other LREE, include bastnäsite , monazite , allanite , loparite , ancylite , parisite , lanthanite , chevkinite, cerite , stillwellite , britholite, fluocerite , and cerianite. Monazite (marine sands from Brazil , India , or Australia ; rock from South Africa ), bastnäsite (from Mountain Pass rare earth mine , or several localities in China), and loparite ( Kola Peninsula , Russia ) have been

936-759: A great magmatic accretionary belt along the present-day southern margin of North America, Greenland, and Baltica. It includes the 1.8–1.7 Ga Yavapai, Central Plains and Makkovikian Belts, 1.7–1.6 Ga Mazatzal and Labradorian Belts, 1.5–1.3 Ga St. Francois and Spavinaw Belts , and 1.3–1.2 Ga Elzevirian Belt in North America; the 1.8–1.7 Ga Ketilidian Belt in Greenland; and the 1.8–1.7 Transscandinavian Igneous Belt, 1.7–1.6 Ga Kongsberggian-Gothian Belt, and 1.5–1.3 Ga Southwest Sweden Granitoid Belt in Baltica. Other cratonic blocks also underwent marginal outgrowth at about

1053-720: A long distance from another block that was once close to the Cathaysia Block . Another competing idea suggests that the Cathaysia Block was formed during the assembly of the Columbia supercontinent in the Paleoproterozoic. There are two pieces of evidence. The Cathaysia Block was possibly contiguous with East Antarctica, Laurentia and Australia. It is suggested that the Late Archean oval-shaped detrital zircons were brought from those blocks. The study of

1170-544: A maximum number of 25 was estimated. The use of X-ray spectra (obtained by X-ray crystallography ) by Henry Gwyn Jeffreys Moseley made it possible to assign atomic numbers to the elements. Moseley found that the exact number of lanthanides had to be 15, but that element 61 had not yet been discovered. (This is promethium, a radioactive element whose most stable isotope has a half-life of just 18 years.) Using these facts about atomic numbers from X-ray crystallography, Moseley also showed that hafnium (element 72) would not be

1287-432: A melt phase if one is present. REE are chemically very similar and have always been difficult to separate, but the gradual decrease in ionic radius from light REE (LREE) to heavy REE (HREE), called the lanthanide contraction , can produce a broad separation between light and heavy REE. The larger ionic radii of LREE make them generally more incompatible than HREE in rock-forming minerals, and will partition more strongly into

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1404-404: A melt phase, while HREE may prefer to remain in the crystalline residue, particularly if it contains HREE-compatible minerals like garnet . The result is that all magma formed from partial melting will always have greater concentrations of LREE than HREE, and individual minerals may be dominated by either HREE or LREE, depending on which range of ionic radii best fits the crystal lattice. Among

1521-507: A mine in the village of Ytterby in Sweden ; four of the rare-earth elements bear names derived from this single location. A table listing the 17 rare-earth elements, their atomic number and symbol, the etymology of their names, and their main uses (see also Applications of lanthanides ) is provided here. Some of the rare-earth elements are named after the scientists who discovered them, or elucidated their elemental properties, and some after

1638-414: A quarry in the village of Ytterby , Sweden and termed "rare" because it had never yet been seen. Arrhenius's "ytterbite" reached Johan Gadolin , a Royal Academy of Turku professor, and his analysis yielded an unknown oxide ("earth" in the geological parlance of the day ), which he called yttria . Anders Gustav Ekeberg isolated beryllium from the gadolinite but failed to recognize other elements in

1755-456: A rare-earth element. Moseley was killed in World War I in 1915, years before hafnium was discovered. Hence, the claim of Georges Urbain that he had discovered element 72 was untrue. Hafnium is an element that lies in the periodic table immediately below zirconium , and hafnium and zirconium have very similar chemical and physical properties. During the 1940s, Frank Spedding and others in

1872-404: A separate group of rare-earth elements (the terbium group), or europium was included in the cerium group, and gadolinium and terbium were included in the yttrium group. In the latter case, the f-block elements are split into half: the first half (La–Eu) form the cerium group, and the second half (Gd–Yb) together with group 3 (Sc, Y, Lu) form the yttrium group. The reason for this division arose from

1989-420: A similar effect. In sedimentary rocks, rare-earth elements in clastic sediments are a representation of provenance. The rare-earth element concentrations are not typically affected by sea and river waters, as rare-earth elements are insoluble and thus have very low concentrations in these fluids. As a result, when sediment is transported, rare-earth element concentrations are unaffected by the fluid and instead

2106-423: A temperature of 400 °C (752 °F). These elements and their compounds have no biological function other than in several specialized enzymes, such as in lanthanide-dependent methanol dehydrogenases in bacteria. The water-soluble compounds are mildly to moderately toxic, but the insoluble ones are not. All isotopes of promethium are radioactive, and it does not occur naturally in the earth's crust, except for

2223-515: A trace amount generated by spontaneous fission of uranium-238 . They are often found in minerals with thorium , and less commonly uranium . Though rare-earth elements are technically relatively plentiful in the entire Earth's crust ( cerium being the 25th-most-abundant element at 68 parts per million, more abundant than copper ), in practice this is spread thin across trace impurities, so to obtain rare earths at usable purity requires processing enormous amounts of raw ore at great expense, thus

2340-462: A valence of 3 and form sesquioxides (cerium forms CeO 2 ). Five different crystal structures are known, depending on the element and the temperature. The X-phase and the H-phase are only stable above 2000 K. At lower temperatures, there are the hexagonal A-phase, the monoclinic B-phase, and the cubic C-phase, which is the stable form at room temperature for most of the elements. The C-phase

2457-499: Is aided by the fluid release from the subducted slab. However, adakitic rock is formed from melting the slab directly.  Recent research shows that slab melting is possible in flat-slab subduction.   Of the ten known flat slab regions worldwide, at least eight are linked to occurrences of adakitic magmas. However, there is no known Late Jurassic adakitic rock in South China. 3. Triassic Tectonic regime Rare-earth element The rare-earth elements ( REE ), also called

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2574-467: Is also disagreement on the tectonic setting of the rocks. (e.g. intra-oceanic arc versus continental arc, backarc versus forearc). Despite so, only divergent double subduction system can provide plausible explanation on two key observations in the Jiangnan Orogen. After the amalgamation, it is widely recognized that continental rifting and widespread 800—760 Ma bimodal magmatism occurred in

2691-465: Is called the bixbyite structure, as it occurs in a mineral of that name ( (Mn,Fe) 2 O 3 ). As seen in the chart, rare-earth elements are found on Earth at similar concentrations to many common transition metals. The most abundant rare-earth element is cerium , which is actually the 25th most abundant element in Earth's crust , having 68 parts per million (about as common as copper). The exception

2808-466: Is clear evidence that the final time of the amalgamation of the South China Block is much later than 900 Ma. Therefore, it was not located in the central part of Rodinia . The evidence comes from lithological and structural records. On the other hand, the South China Block may be located in the periphery of Rodinia . It might be next to northern India and western Australia. When the Tolo Terrane

2925-482: Is composed of mainly Neoproterozoic basement rocks. Rare occurrence of Paleoproterozoic rocks and Mesoproterozoic rocks are reported in southwest Zhejiang and Hainan Island respectively. Paleozoic magmatism is not common in the South China Block. However, a late Permian Emeishan large igneous province is reported in the western margin of the Yangtze Block . Mesozoic magmatism is very extensive, especially in

3042-431: Is estimated to have been approximately 12,900 km (8,000 mi) from north to south at its broadest part. The eastern coast of India was attached to western North America , with southern Australia against western Canada . In the Paleoproterozoic most of South America was rotated such that the western edge of modern-day Brazil lined up with eastern North America, forming a continental margin that extended into

3159-611: Is high, weathering forms a thick argillized regolith, this process is called supergene enrichment and produces laterite deposits; heavy rare-earth elements are incorporated into the residual clay by absorption. This kind of deposit is only mined for REE in Southern China, where the majority of global heavy rare-earth element production occurs. REE-laterites do form elsewhere, including over the carbonatite at Mount Weld in Australia. REE may also be extracted from placer deposits if

3276-440: Is only fragmentary study on the formation of the Cathaysia Block due to sparse Precambrian outcrop. Unlike the Yangtze Block , no Archean outcrop and basement are identified in the Cathaysia Block . However, the finding of Late Archean detrital zircons led scientists to speculate the existence of an unexposed Archean basement. This idea is challenged by the fact that the zircons are oval in shape. They were possibly transported

3393-445: Is possible to observe the serial trend of the REE by reporting their normalized concentrations against the atomic number. The trends that are observed in "spider" diagrams are typically referred to as "patterns", which may be diagnostic of petrological processes that have affected the material of interest. According to the general shape of the patterns or thanks to the presence (or absence) of so-called "anomalies", information regarding

3510-443: Is synthetically produced in nuclear reactors. Due to their chemical similarity, the concentrations of rare earths in rocks are only slowly changed by geochemical processes, making their proportions useful for geochronology and dating fossils. Rare-earth elements occur in nature in combination with phosphate ( monazite ), carbonate - fluoride ( bastnäsite ), and oxygen anions. In their oxides, most rare-earth elements only have

3627-517: Is the highly unstable and radioactive promethium "rare earth" is quite scarce. The longest-lived isotope of promethium has a half-life of 17.7 years, so the element exists in nature in only negligible amounts (approximately 572 g in the entire Earth's crust). Promethium is one of the two elements that do not have stable (non-radioactive) isotopes and are followed by (i.e. with higher atomic number) stable elements (the other being technetium ). The rare-earth elements are often found together. During

South China Craton - Misplaced Pages Continue

3744-464: Is thought to be the suture between the Cathaysia Block and the Tolo Terrane. The Tolo Channel Fault in Hong Kong possibly represents a trace of the suture . Therefore, the newly defined unit is named the Tolo Terrane. The study of the formation of the Yangtze Block is challenging due to rare Archean outcrops. It is believed that it was formed at around 3.8 – 3.2 Ga. The timing is earlier than

3861-476: The Cathaysia block . This section focuses on how the components of the South China Block were formed. The South China Block is traditionally divided into the Yangtze Block in the northwest and the Cathaysia Block in the southeast. The northeast-trending Jiangshan-Shaoxing Fault represents the boundary (i.e. suture ). It starts from Jiangshan through Shaoxing to Pingxiang. However, the southern extension of

3978-802: The Gawler Craton . In China, a 1.8–1.4 Ga accretionary magmatic zone, called the Xiong’er belt (Group), extends along the southern margin of the North China Craton. Columbia began to fragment about 1.5–1.35 Ga, associated with continental rifting along the western margin of Laurentia (Belt-Purcell Supergroup), eastern India (Mahanadi and the Godavari), southern margin of Baltica (Telemark Supergroup), southeastern margin of Siberia ( Riphean aulacogens ), northwestern margin of South Africa (Kalahari Copper Belt), and northern margin of

4095-563: The Oddo–Harkins rule : even-numbered REE at abundances of about 5% each, and odd-numbered REE at abundances of about 1% each. Similar compositions are found in xenotime or gadolinite. Well-known minerals containing yttrium, and other HREE, include gadolinite, xenotime, samarskite , euxenite , fergusonite , yttrotantalite, yttrotungstite, yttrofluorite (a variety of fluorite ), thalenite, and yttrialite . Small amounts occur in zircon , which derives its typical yellow fluorescence from some of

4212-595: The Proterozoic core of Laurentia plus Baltica. Because Hoffman published his name earlier than Rogers and Santosh published theirs, there have been calls to use Nuna rather than Columbia , on the basis of scientific precedence. However, Nuna was essentially equivalent to an earlier Nena , and neither clearly referred to an early supercontinent as Columbia did, rather than merely the core of this earlier supercontinent. Other earlier speculative continents included Hudsonland and Arctica , but Rogers and Santosh were

4329-829: The Yangtze Block and the Cathaysia Block in the Neoproterozoic. The unified South China Block experienced four important events in the Phanerozoic. They are called the Wuyi-Yunkai Movement (Early Paleozoic), the Emeishan flood basalt magmatism (Late Paleozoic), the Indosinian Movement (Triassic) and the Yanshanian Movement (Jurassic-Cretaceous). The three movements created an array of deformation, magmatism and metamorphism in

4446-533: The rare-earth metals or rare earths , and sometimes the lanthanides or lanthanoids (although scandium and yttrium , which do not belong to this series, are usually included as rare earths), are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals . Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes. Scandium and yttrium are considered rare-earth elements because they tend to occur in

4563-476: The suture may represent a lateral shearing event rather than a collision event. Such a mechanism may be analogous to the sliver-plate tectonics of the Sumatran Subduction Zone . If this is correct, the Tolo Terrane should be considered as part of the Cathaysia Block , rather than a distinct unit. Following the traditional definition, the South China Block was formed by the collision between

4680-486: The upper mantle (200 to 600 km depth). This melt becomes enriched in incompatible elements, like the rare-earth elements, by leaching them out of the crystalline residue. The resultant magma rises as a diapir , or diatreme , along pre-existing fractures, and can be emplaced deep in the crust , or erupted at the surface. Typical REE enriched deposits types forming in rift settings are carbonatites, and A- and M-Type granitoids. Near subduction zones, partial melting of

4797-428: The "heavy" group from 6.965 (ytterbium) to 9.32 (thulium), as well as including yttrium at 4.47. Europium has a density of 5.24. Rare-earth elements, except scandium , are heavier than iron and thus are produced by supernova nucleosynthesis or by the s-process in asymptotic giant branch stars. In nature, spontaneous fission of uranium-238 produces trace amounts of radioactive promethium , but most promethium

South China Craton - Misplaced Pages Continue

4914-568: The 4 f orbital which acts against the electrons of the 6 s and 5 d orbitals. The lanthanide contraction has a direct effect on the geochemistry of the lanthanides, which show a different behaviour depending on the systems and processes in which they are involved. The effect of the lanthanide contraction can be observed in the REE behaviour both in a CHARAC-type geochemical system (CHArge-and-RAdius-Controlled ) where elements with similar charge and radius should show coherent geochemical behaviour, and in non-CHARAC systems, such as aqueous solutions, where

5031-615: The Cambrian sandstone from the Yangtze Block and the Cathaysia Block shows a mixed zircon provenance, which indicates sediment could travel from one block to another one. This argued against the presence of a vast ocean. The Emeishan flood basalt magmatism represents the most significant geological feature in Southwest China. The duration of the basalt magmatism is geologically short (i.e. 1.0-1.5 Ma). Petrological and geochemical results provide indisputable evidence for supporting

5148-550: The Cambrian. Following the "Missing-link" hypothesis, the South China Block was placed in the interior of Rodinia . During the Rodinia break-up, the South China Block drifted northward in the middle Neoproterozoic. Subsequently, it collided with the northwest India Craton in the Gondwana margin by the Cambrian. The Qiangtang Terrane was sandwiched between the South China Block and India Craton during collision. The North India Orogen

5265-543: The Indosinian Movement (Triassic) and the Yanshanian Movement (Jurassic-Cretaceous). They led to extensive deformation and magmatism. On the other hand, the Late Paleozoic Emeishan flood basalt magmatism is an important event in the western part of the block. South China Block is formed by the assembly of both the Yangtze and Cathaysia blocks along the northeasterly trending Jiang-Shao Fault. However,

5382-506: The LREE. This has economic consequences: large ore bodies of LREE are known around the world and are being exploited. Ore bodies for HREE are more rare, smaller, and less concentrated. Most of the current supply of HREE originates in the "ion-absorption clay" ores of Southern China. Some versions provide concentrates containing about 65% yttrium oxide, with the HREE being present in ratios reflecting

5499-401: The Mesozoic tectonic movement. Flat slab subduction is usually caused by the arrival of buoyant oceanic plateau (i.e. thicker oceanic crust). As the flat slab penetrated beneath the continental crust, the fold and thrust belt migrated inland, resulting in the younging trend towards the continent. The coeval magmatism could only occur in the front of the flat slab. No magmatism could occur in

5616-572: The North China Block (Zhaertai-Bayan Obo Belt). The fragmentation corresponded with widespread anorogenic magmatic activity, forming anorthosite - mangerite - charnockite - granite suites in North America, Baltica, Amazonia, and North China, and continued until the final breakup of the supercontinent at about 1.3–1.2 Ga, marked by the emplacement of the 1.27 Ga Mackenzie and 1.24 Ga Sudbury mafic dyke swarms in North America. Other dyke swarms associated with extensional tectonics and

5733-678: The Rogers and Santosh configuration, whereas the fits of India, East Antarctica, South Africa, and Australia with Laurentia are similar to their corresponding fits in the configuration of Rodinia . This continental configuration is based on the available geological reconstructions of 2.1–1.8 Ga orogens and related Archean cratonic blocks, especially on those reconstructions between South America and west Africa; western Australia and southern Africa; Laurentia and Baltica; Siberia and Laurentia; Laurentia and central Australia; East Antarctica and Laurentia; and North China and India. Of these reconstructions,

5850-758: The South China Block was formed. Traditionally, the South China Block was formed by the collision between the Yangtze Block and the Cathaysia Block in the Neoproterozoic. They collided to form the Jiangnan Orogen. If the Tolo Terrane does exist, the final formation time should be pushed forward to the Jurassic. There are four major controversies about the amalgamation process. There are two schools of thought. A great deal of single-sided subduction systems have been proposed. The diversity arises from different subduction manner including orthogonal subduction, oblique subduction or change in subduction polarity . There

5967-427: The South China Block. The Wuyi-Yunkai Movement (Ordovician-Silurian) represents the first Phanerozoic tectonic event in the South China Block. Two models have been proposed. They are the intraplate model and Cambrian ocean model. Nowadays, more and more scientists advocate for the intraplate model. There are four key characteristics of the Wuyi-Yunkai Movement. This model suggests that this tectonic event occurred in

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6084-486: The South China Block. Two models have been proposed. The South China Block possibly serves as this missing link (i.e. the "missing link" hypothesis). They suggest the head of the mantle plume , which was sited beneath the South China Block, led to rifting and bimodal magmatism since 825 Ma. The discovery of 825 Ma komatiitic basalts in Yiyang, which is indicative of a hot mantle source, provides an indisputable evidence for

6201-620: The Tolo Terrane is at the initial stage. Most of the evidence comes from Hong Kong. The Tolo Terrane possibly represents a fragment of the Qiangtang Terrane . When the South China Block collided with the India Craton in the Cambrian, the Qiangtang Terrane was sandwiched between those two blocks. During the collision, a fragment (i.e. Tolo Terrane) was calved off from the Qiangtang Terrane. This section focuses on how

6318-530: The United States (during the Manhattan Project ) developed chemical ion-exchange procedures for separating and purifying rare-earth elements. This method was first applied to the actinides for separating plutonium-239 and neptunium from uranium , thorium , actinium , and the other actinides in the materials produced in nuclear reactors . Plutonium-239 was very desirable because it is

6435-449: The accompanying HREE. The zirconium mineral eudialyte , such as is found in southern Greenland , contains small but potentially useful amounts of yttrium. Of the above yttrium minerals, most played a part in providing research quantities of lanthanides during the discovery days. Xenotime is occasionally recovered as a byproduct of heavy-sand processing, but is not as abundant as the similarly recovered monazite (which typically contains

6552-462: The age of supercontinent assembly. The Columbia assembled through a global collision event during 2.1-1.8 Ga. Therefore, the constituent continental blocks of the Columbia should record a larger population of 2.1-1.8 Ga detrital zircon. In fact, The Kunyang Group in the Yangtze Block shows this pattern. However, the position of the block is poorly known. It possibly connected with North China, western Australia and/or northwestern Laurentia. There

6669-500: The anhydrous rare-earth phosphates, it is the tetragonal mineral xenotime that incorporates yttrium and the HREE, whereas the monoclinic monazite phase incorporates cerium and the LREE preferentially. The smaller size of the HREE allows greater solid solubility in the rock-forming minerals that make up Earth's mantle, and thus yttrium and the HREE show less enrichment in Earth's crust relative to chondritic abundance than does cerium and

6786-497: The boundary remains unclear. Before they collided together to form the South China block in the Neoproterozic, both of them were part of the Columbia supercontinent . Recent studies have proposed that the South China Block is possibly divided into three instead of two units. The newly defined unit is termed the Tolo Terrane, which is next to the eastern margin of the Cathaysia Block . The northeast-trending Zhenghe–Dapu fault

6903-652: The break-up of Columbia include the Satakunta-Ulvö dyke swarm in Fennoscandia and the Galiwinku dyke swarm in Australia. An area around Georgetown in northern Queensland, Australia , has been suggested to consist of rocks that originally formed part of Nuna 1.7 Ga in what is now northern Canada. In the initial configuration of Rogers and Santosh (2002), South Africa, Madagascar , India, Australia, and attached parts of Antarctica are placed adjacent to

7020-871: The core of igneous complexes; they consist of fine-grained calcite and hematite, sometimes with significant concentrations of ankerite and minor concentrations of siderite. Large carbonatite deposits enriched in rare-earth elements include Mount Weld in Australia, Thor Lake in Canada, Zandkopsdrift in South Africa, and Mountain Pass in the USA. Peralkaline granites (A-Type granitoids) have very high concentrations of alkaline elements and very low concentrations of phosphorus; they are deposited at moderate depths in extensional zones, often as igneous ring complexes, or as pipes, massive bodies, and lenses. These fluids have very low viscosities and high element mobility, which allows for

7137-408: The crude yttria and found the same substances that Mosander obtained, but Berlin named (1860) the substance giving pink salts erbium , and Delafontaine named the substance with the yellow peroxide terbium . This confusion led to several false claims of new elements, such as the mosandrium of J. Lawrence Smith , or the philippium and decipium of Delafontaine. Due to the difficulty in separating

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7254-740: The crystallization of large grains, despite a relatively short crystallization time upon emplacement; their large grain size is why these deposits are commonly referred to as pegmatites. Economically viable pegmatites are divided into Lithium-Cesium-Tantalum (LCT) and Niobium-Yttrium-Fluorine (NYF) types; NYF types are enriched in rare-earth minerals. Examples of rare-earth pegmatite deposits include Strange Lake in Canada and Khaladean-Buregtey in Mongolia. Nepheline syenite (M-Type granitoids) deposits are 90% feldspar and feldspathoid minerals. They are deposited in small, circular massifs and contain high concentrations of rare-earth-bearing accessory minerals . For

7371-413: The difference in solubility of rare-earth double sulfates with sodium and potassium. The sodium double sulfates of the cerium group are poorly soluble, those of the terbium group slightly, and those of the yttrium group are very soluble. Sometimes, the yttrium group was further split into the erbium group (dysprosium, holmium, erbium, and thulium) and the ytterbium group (ytterbium and lutetium), but today

7488-409: The electron structure is also an important parameter to consider as the lanthanide contraction affects the ionic potential . A direct consequence is that, during the formation of coordination bonds, the REE behaviour gradually changes along the series. Furthermore, the lanthanide contraction causes the ionic radius of Ho (0.901 Å) to be almost identical to that of Y (0.9 Å), justifying the inclusion of

7605-651: The element showing the anomaly and the predictable one based on the average of the normalized concentrations of the two elements in the previous and next position in the series, according to the equation: where [ REE i ] n {\displaystyle [{\text{REE}}_{i}]_{n}} is the normalized concentration of the element whose anomaly has to be calculated, [ REE i − 1 ] n {\displaystyle [{\text{REE}}_{i-1}]_{n}} and [ REE i + 1 ] n {\displaystyle [{\text{REE}}_{i+1}]_{n}}

7722-510: The establishment of the Columbia supercontinent. This is supported by the preserved ancient crustal remnant (i.e. 3.8 Ga detrital zircon derived from the South China Block). Yangtze Block later became part of the Columbia , but its position has only been constrained poorly. The U-Pb crystallization age distribution of 7000 detrital zircons is characterized by several peaks over the history of Earth spans. Those peaks coincide with

7839-417: The existence of an unknown element. The fractional crystallization of the oxides then yielded europium in 1901. In 1839 the third source for rare earths became available. This is a mineral similar to gadolinite called uranotantalum (now called " samarskite ") an oxide of a mixture of elements such as yttrium, ytterbium, iron, uranium, thorium, calcium, niobium, and tantalum. This mineral from Miass in

7956-505: The fits of Baltica and Siberia with Laurentia; South America with west Africa; and southern Africa with western Australia are also consistent with paleomagnetic data . A new configuration of Columbia was reconstructed by Guiting Hou (2008) based on the reconstruction of giant radiating dike swarms. Another configuration has been suggested by Chaves and Rezende (2019) supported on available paleomagnetic data and fragments of 1.79-1.75 Ga large igneous provinces . Rogers and Santosh proposed

8073-511: The following observations apply: anomalies in europium are dominated by the crystallization of feldspars . Hornblende , controls the enrichment of MREE compared to LREE and HREE. Depletion of LREE relative to HREE may be due to the crystallization of olivine , orthopyroxene , and clinopyroxene . On the other hand, the depletion of HREE relative to LREE may be due to the presence of garnet , as garnet preferentially incorporates HREE into its crystal structure. The presence of zircon may also cause

8190-433: The form of Ce and Eu depending on the redox conditions of the system. Consequentially, REE are characterized by a substantial identity in their chemical reactivity, which results in a serial behaviour during geochemical processes rather than being characteristic of a single element of the series. Sc, Y, and Lu can be electronically distinguished from the other rare earths because they do not have f valence electrons, whereas

8307-566: The fractionation of trace elements (including rare-earth elements) into the liquid phase (the melt/magma) into the solid phase (the mineral). If an element preferentially remains in the solid phase it is termed 'compatible', and if it preferentially partitions into the melt phase it is described as 'incompatible'. Each element has a different partition coefficient, and therefore fractionates into solid and liquid phases distinctly. These concepts are also applicable to metamorphic and sedimentary petrology. In igneous rocks, particularly in felsic melts,

8424-405: The geographical locations where discovered. A mnemonic for the names of the sixth-row elements in order is "Lately college parties never produce sexy European girls that drink heavily even though you look". Rare earths were mainly discovered as components of minerals. Ytterbium was found in the "ytterbite" (renamed to gadolinite in 1800) discovered by Lieutenant Carl Axel Arrhenius in 1787 at

8541-448: The heavy rare-earth elements (HREE), and those that fall in between are typically referred to as the middle rare-earth elements (MREE). Commonly, rare-earth elements with atomic numbers 57 to 61 (lanthanum to promethium) are classified as light and those with atomic numbers 62 and greater are classified as heavy rare-earth elements. Increasing atomic numbers between light and heavy rare-earth elements and decreasing atomic radii throughout

8658-403: The interior of the unified South China Block. The far-field stress associated with distant continental collisions led to crustal thickening and metamorphism (460–445 Ma) in the interior of the South China Block. The rocks in the lower portion of the lithosphere might be converted into eclogite (i.e. a very dense rock) due to the high pressure burden. This portion of the lithosphere eventually

8775-470: The latter among the REE. The application of rare-earth elements to geology is important to understanding the petrological processes of igneous , sedimentary and metamorphic rock formation. In geochemistry , rare-earth elements can be used to infer the petrological mechanisms that have affected a rock due to the subtle atomic size differences between the elements, which causes preferential fractionation of some rare earths relative to others depending on

8892-418: The logarithm to the base 10 of the value. Commonly, the rare-earth elements are normalized to chondritic meteorites , as these are believed to be the closest representation of unfractionated Solar System material. However, other normalizing standards can be applied depending on the purpose of the study. Normalization to a standard reference value, especially of a material believed to be unfractionated, allows

9009-472: The main grouping is between the cerium and the yttrium groups. Today, the rare-earth elements are classified as light or heavy rare-earth elements, rather than in cerium and yttrium groups. The classification of rare-earth elements is inconsistent between authors. The most common distinction between rare-earth elements is made by atomic numbers ; those with low atomic numbers are referred to as light rare-earth elements (LREE), those with high atomic numbers are

9126-474: The margin of Rodinia . On the one hand, the South China Block is proposed to be located between eastern Australia and western Laurentia in the interior of Rodinia (i.e. "Missing-link" hypothesis). Several lines of evidence support this hypothesis. Rodinia assembled through global collision events from 1300 Ma to 900 Ma. It is expected that the central part of Rodinia should not record any later collision event since it had already amalgamated. However, there

9243-521: The marine recovery after the Permian-Triassic mass extinction . The South China Block was formed by collision between the Yangtze Block and Cathaysia Block in the Neoproterozoic. On the one hand, the central and eastern part of the South China Block experienced three important Phanerozoic tectonic events. In the Chinese literature, they are named the Wuyi-Yunkai Movement (Early Paleozoic),

9360-522: The metals (and determining the separation is complete), the total number of false discoveries was dozens, with some putting the total number of discoveries at over a hundred. There were no further discoveries for 30 years, and the element didymium was listed in the periodic table of elements with a molecular mass of 138. In 1879, Delafontaine used the new physical process of optical flame spectroscopy and found several new spectral lines in didymia. Also in 1879, Paul Émile Lecoq de Boisbaudran isolated

9477-640: The most part, these deposits are small but important examples include Illimaussaq-Kvanefeld in Greenland, and Lovozera in Russia. Rare-earth elements can also be enriched in deposits by secondary alteration either by interactions with hydrothermal fluids or meteoric water or by erosion and transport of resistate REE-bearing minerals. Argillization of primary minerals enriches insoluble elements by leaching out silica and other soluble elements, recrystallizing feldspar into clay minerals such kaolinite, halloysite, and montmorillonite. In tropical regions where precipitation

9594-478: The name Columbia for a hypothetical supercontinent preceding Rodinia. They chose the name because critical evidence for the supercontinent was provided by the relationship between the Columbia region of North America (centered on the state of Washington ) and east India. The naming is not universally accepted. In 1997, P.F. Hoffman proposed the name Nuna (from Inuit "lands bordering the northern oceans") for

9711-415: The name "rare" earths. Because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals . Consequently, economically exploitable ore deposits are sparse. The first rare-earth mineral discovered (1787) was gadolinite , a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from

9828-560: The new element samarium from the mineral samarskite . The samaria earth was further separated by Lecoq de Boisbaudran in 1886, and a similar result was obtained by Jean Charles Galissard de Marignac by direct isolation from samarskite. They named the element gadolinium after Johan Gadolin , and its oxide was named " gadolinia ". Further spectroscopic analysis between 1886 and 1901 of samaria, yttria, and samarskite by William Crookes , Lecoq de Boisbaudran and Eugène-Anatole Demarçay yielded several new spectral lines that indicated

9945-424: The normalized concentration, [ REE i ] sam {\displaystyle {[{\text{REE}}_{i}]_{\text{sam}}}} the analytical concentration of the element measured in the sample, and [ REE i ] ref {\displaystyle {[{\text{REE}}_{i}]_{\text{ref}}}} the concentration of the same element in the reference material. It

10062-427: The normalized concentrations of the respectively previous and next elements along the series. The rare-earth elements patterns observed in igneous rocks are primarily a function of the chemistry of the source where the rock came from, as well as the fractionation history the rock has undergone. Fractionation is in turn a function of the partition coefficients of each element. Partition coefficients are responsible for

10179-432: The observed abundances to be compared to the initial abundances of the element. Normalization also removes the pronounced 'zig-zag' pattern caused by the differences in abundance between even and odd atomic numbers . Normalization is carried out by dividing the analytical concentrations of each element of the series by the concentration of the same element in a given standard, according to the equation: where n indicates

10296-524: The ore. After this discovery in 1794, a mineral from Bastnäs near Riddarhyttan , Sweden, which was believed to be an iron – tungsten mineral, was re-examined by Jöns Jacob Berzelius and Wilhelm Hisinger . In 1803 they obtained a white oxide and called it ceria . Martin Heinrich Klaproth independently discovered the same oxide and called it ochroia . It took another 30 years for researchers to determine that other elements were contained in

10413-414: The others do, but the chemical behaviour is almost the same. A distinguishing factor in the geochemical behaviour of the REE is linked to the so-called " lanthanide contraction " which represents a higher-than-expected decrease in the atomic/ionic radius of the elements along the series. This is determined by the variation of the shielding effect towards the nuclear charge due to the progressive filling of

10530-528: The overlying crust rebounded. The crust is therefore stretched (i.e. extensional setting). At the same time, a surge of mantle upwelling occurred. This created widespread within-plate igneous rock. Then, oceanic crust with "normal" thickness arrived on the subduction zone. It is expected that the subduction angle would be increased due to less buoyancy. Therefore, the oceanic crust would roll back. This created an oceanward younging Cretaceous magmatism. However, this model faces several challenges. 1. Occurrence of

10647-399: The presence of a mantle plume . However, there is alternative genesis of komatiites like hydrous melting in the subduction zone. Moreover, no Neoproterozoic Large Igneous Province has been identified in the South China Block. There is no consensus about the position of the South China Block in the Rodinia supercontinent. The main controversy is whether it was located in the interior or at

10764-446: The principal ores of cerium and the light lanthanides. Enriched deposits of rare-earth elements at the surface of the Earth, carbonatites and pegmatites , are related to alkaline plutonism , an uncommon kind of magmatism that occurs in tectonic settings where there is rifting or that are near subduction zones. In a rift setting, the alkaline magma is produced by very small degrees of partial melting (<1%) of garnet peridotite in

10881-440: The processes at work. The geochemical study of the REE is not carried out on absolute concentrations – as it is usually done with other chemical elements – but on normalized concentrations in order to observe their serial behaviour. In geochemistry, rare-earth elements are typically presented in normalized "spider" diagrams, in which concentration of rare-earth elements are normalized to a reference standard and are then expressed as

10998-421: The rare-earth elements relatively expensive. Their industrial use was very limited until efficient separation techniques were developed, such as ion exchange , fractional crystallization, and liquid–liquid extraction during the late 1950s and early 1960s. Some ilmenite concentrates contain small amounts of scandium and other rare-earth elements, which could be analysed by X-ray fluorescence (XRF). Before

11115-404: The rear part of the slab. Therefore, the synchronic igneous rocks shows a similar younging trend. As time passed by, the oceanic slab is converted to a dense rock (i.e. eclogite). Therefore, the flat slab started to break off and sink. At the same time, it exerted a downward pull on the overlying continental crust to create a broad basin with a lake. When the slab was fully detached from the crust,

11232-479: The rock retains the rare-earth element concentration from its source. Columbia (supercontinent) Columbia , also known as Nuna or Hudsonland , is a hypothetical ancient supercontinent . It was first proposed by John J.W. Rogers and M. Santosh in 2002 and is thought to have existed approximately 2,500 to 1,500 million years ago (Ma), in the Paleoproterozoic era. The assembly of

11349-485: The same ore deposits as the lanthanides and exhibit similar chemical properties, but have different electrical and magnetic properties . The term 'rare-earth' is a misnomer because they are not actually scarce, although historically it took a long time to isolate these elements. These metals tarnish slowly in air at room temperature and react slowly with cold water to form hydroxides, liberating hydrogen. They react with steam to form oxides and ignite spontaneously at

11466-667: The same time. In South America, a 1.8–1.3 Ga accretionary zone occurs along the western margin of the Amazonia Craton, represented by the Rio Negro, Juruena, and Rondonian Belts. In Australia, 1.8–1.5 Ga accretionary magmatic belts, including the Arunta, Mount Isa, Georgetown, Coen, and Broken Hill Belts, occur surrounding the southern and eastern margins of the North Australia Craton and the eastern margin of

11583-636: The seafloor, bit by bit, over tens of millions of years. One square patch of metal-rich mud 2.3 kilometers wide might contain enough rare earths to meet most of the global demand for a year, Japanese geologists report in Nature Geoscience ." "I believe that rare[-]earth resources undersea are much more promising than on-land resources," said Kato. "[C]oncentrations of rare earths were comparable to those found in clays mined in China. Some deposits contained twice as much heavy rare earths such as dysprosium,

11700-493: The sedimentary parent lithology contains REE-bearing, heavy resistate minerals. In 2011, Yasuhiro Kato, a geologist at the University of Tokyo who led a study of Pacific Ocean seabed mud, published results indicating the mud could hold rich concentrations of rare-earth minerals. The deposits, studied at 78 sites, came from "[h]ot plumes from hydrothermal vents pull[ing] these materials out of seawater and deposit[ing] them on

11817-419: The sequential accretion of the Earth, the dense rare-earth elements were incorporated into the deeper portions of the planet. Early differentiation of molten material largely incorporated the rare earths into mantle rocks. The high field strength and large ionic radii of rare earths make them incompatible with the crystal lattices of most rock-forming minerals, so REE will undergo strong partitioning into

11934-497: The series causes chemical variations. Europium is exempt of this classification as it has two valence states: Eu and Eu . Yttrium is grouped as heavy rare-earth element due to chemical similarities. The break between the two groups is sometimes put elsewhere, such as between elements 63 (europium) and 64 (gadolinium). The actual metallic densities of these two groups overlap, with the "light" group having densities from 6.145 (lanthanum) to 7.26 (promethium) or 7.52 (samarium) g/cc, and

12051-401: The southern Ural Mountains was documented by Gustav Rose . The Russian chemist R. Harmann proposed that a new element he called " ilmenium " should be present in this mineral, but later, Christian Wilhelm Blomstrand , Galissard de Marignac, and Heinrich Rose found only tantalum and niobium ( columbium ) in it. The exact number of rare-earth elements that existed was highly unclear, and

12168-427: The southern edge of Scandinavia . Columbia was assembled along global-scale 2.1–1.8 Ga collisional orogens and contained almost all of Earth 's continental blocks. Some of the events associated with the assembly of Columbia are: Following its final assembly at c. 1.82 Ga, Columbia underwent long-lived (1.82–1.5 Ga), subduction -related growth via accretion at key continental margins, forming at 1.82–1.5 Ga

12285-482: The southwestern extension of this suture is poorly understood due to poor exposure. Yangtze Block contains several Archean—Paleoproterozoic crystalline basements (e.g. Kongling Complex ). The igneous rocks are unconformably overlain by weakly metamorphosed Neoproterozoic sequences (e.g., Banxi Group) and unmetamorphosed Sinian units. In contrast, the Cathaysia block does not contain any Archean basement. Instead, it

12402-766: The subducting plate within the asthenosphere (80 to 200 km depth) produces a volatile-rich magma (high concentrations of CO 2 and water), with high concentrations of alkaline elements, and high element mobility that the rare earths are strongly partitioned into. This melt may also rise along pre-existing fractures, and be emplaced in the crust above the subducting slab or erupted at the surface. REE-enriched deposits forming from these melts are typically S-Type granitoids. Alkaline magmas enriched with rare-earth elements include carbonatites, peralkaline granites (pegmatites), and nepheline syenite . Carbonatites crystallize from CO 2 -rich fluids, which can be produced by partial melting of hydrous-carbonated lherzolite to produce

12519-433: The supercontinent was likely completed during global-scale collisional events from 2,100 to 1,800 Ma. Columbia consisted of proto- cratons that made up the cores of the continents of Laurentia , Baltica , Ukrainian Shield , Amazonian Craton , Australia , and possibly Siberia , North China , and Kalaharia as well. The evidence of Columbia's existence is provided by geological and paleomagnetic data. Columbia

12636-399: The system under examination and the occurring geochemical processes can be obtained. The anomalies represent enrichment (positive anomalies) or depletion (negative anomalies) of specific elements along the series and are graphically recognizable as positive or negative "peaks" along the REE patterns. The anomalies can be numerically quantified as the ratio between the normalized concentration of

12753-479: The time that ion exchange methods and elution were available, the separation of the rare earths was primarily achieved by repeated precipitation or crystallization . In those days, the first separation was into two main groups, the cerium earths (lanthanum, cerium, praseodymium, neodymium, and samarium) and the yttrium earths (scandium, yttrium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). Europium, gadolinium, and terbium were either considered as

12870-484: The two ores ceria and yttria (the similarity of the rare-earth metals' chemical properties made their separation difficult). In 1839 Carl Gustav Mosander , an assistant of Berzelius, separated ceria by heating the nitrate and dissolving the product in nitric acid . He called the oxide of the soluble salt lanthana . It took him three more years to separate the lanthana further into didymia and pure lanthana. Didymia, although not further separable by Mosander's techniques,

12987-442: The underlying Cathaysia sedimentary sequences. They were derived from the rock in the India Craton and East African orogen. This suggested a close proximity between the South China Block and India Craton. This model suggests that there was a Cambrian ocean between the Yangtze Block and the Cathaysia Block . Closure of the ocean led to collision between those two blocks and subsequent deformation, magmatism and metamorphism. However,

13104-425: The western margin of North America, whereas Greenland, Baltica (Northern Europe), and Siberia are positioned adjacent to the northern margin of North America, and South America is placed against West Africa . In the same year (2002), Zhao et al. proposed an alternative configuration of Columbia, in which the fits of Baltica and Siberia with Laurentia and the fit of South America with West Africa are similar to those of

13221-491: Was broken away. It sank into the mantle since it was heavy. This triggered mantle upwelling and subsequent decompression melting. The mantle was melted to generate mafic magma . The mafic magma underplated and melted the over-thickened crust to generate Silurian granitic intrusions. The driving force of such internal deformation was attributed to the South China Block-India Craton collision in

13338-411: Was created during the continental collision. This collision is believed to be the driver for the intracontinental deformation in the South China Block. The collision history is constrained by sedimentary provenance study. The Ediacaran-Cambrian sedimentary rocks in the Cathaysia Block showed an exotic provenance. They were not derived from the Yangtze Block , continental blocks nearby or recycling of

13455-492: Was in fact still a mixture of oxides. In 1842 Mosander also separated the yttria into three oxides: pure yttria, terbia, and erbia (all the names are derived from the town name "Ytterby"). The earth giving pink salts he called terbium ; the one that yielded yellow peroxide he called erbium . In 1842 the number of known rare-earth elements had reached six: yttrium, cerium, lanthanum, didymium, erbium, and terbium. Nils Johan Berlin and Marc Delafontaine tried also to separate

13572-494: Was once thought to be in space group I 2 1 3 (no. 199), but is now known to be in space group Ia 3 (no. 206). The structure is similar to that of fluorite or cerium dioxide (in which the cations form a face-centred cubic lattice and the anions sit inside the tetrahedra of cations), except that one-quarter of the anions (oxygen) are missing. The unit cell of these sesquioxides corresponds to eight unit cells of fluorite or cerium dioxide, with 32 cations instead of 4. This

13689-546: Was split from the Qiangtang Terrane, it was removed from the collision system by a strike-slip fault . Then, It collided with the Cathaysia Block in the Middle-Late Jurassic. The assembly age is consistent with a major deformation event in Hong Kong (i.e. thrusting and metamorphism in northwestern Hong Kong). However, this idea is challenged by the rare coeval magmatism along the Zhenghe–Dapu fault. Therefore,

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