Geochemical characteristics and their significances of rare-earth elements in deep-water well core at the Lingnan Low Uplift Area of the Qiongdongnan Basin

A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both∑REE and∑LREE （LREE is short for light-group REEs） fluctuate in a relatively wide range, while∑HREE （HREE is short for heavy-group REEs） maintains a relatively stable level. With the stratigraphic chronology becoming newer, both∑REE and∑LREE show a gradually rising trend overall. The∑REE of the core is relatively high from the bottom of Yacheng Formation （at a well depth of 4 207 m） to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China＇s neritic sediments and loess, with significant ＂continental ori-entation＂. The∑REE of the core is relatively low in the lower part of Yacheng Formation （at a well depth of 4 207-4 330 m）, as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrich-ment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift ar-eas; the continental margin materials from the north contributed only insignificantly; the provenance devel-oped to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement （34-25 Ma BP, early expansion of the South China Sea）, Baiyun Movement （23 Ma BP）, late expansion movement （23.5-16.5 Ma BP）, expansion-settlement transition, and other important events are all clearly recorded by the geochemi-cal characteristics of REEs in the core.

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu_(46)Zr_(47-x)Al_7M_x(M = Ce,Pr,Tb,and Gd) bulk metallic glasses

Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stability, and mechanical properties of Cu46Zr47-xA17Mx were investigated. The GFA of Cu46Zr47-xA17Mx （M = Ce, Pr） alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47-xA17Thx（X = 2, 4, and 5） amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47-xA17Gdx（x = 2, 4, and 5） increases with increasing Gd. Tx and Tp of all decrease. Tg is dependent on the rare-earth element and its content. ATx for most of these alloys decreases except the Cu46Zra2Al7Gd5 alloy. The activation energies △Eg, △Ex, and △Ep for the Cu46Zr42A17Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respec- tively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43A17Pr4 alloy presents the least, Hv 479. The compressive strength （at.f.） of the Cu46Zra3A17Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.

Influence of Rare-Earth Elements on ElectricalProperties of Pd

The influence of RE (RE = La, Ce. Pr. Nd, Sm, Eu, Gd. Tb. Dy, Er, Yb) additives with dilute concentrations on the electrical properties of Pd has been studied. All RE elements increase the specific resistivity (ρ) and decrease the resistance temperature coefficient (α) of Pd. and (ρ.α) Pd-RE ls equal to (ρ· α)Pd.The RE elements before Gd reduce the thermo-emf of Pd on Cu. other heavy RE enhance the thermo-emf.The experimental data of normalized Pd-0.1 at.-%RE alloys indicate that the effect of light RE additives on the specific resistivity of Pd is larger than that of heavy RE and Ce. Eu and Yb show anomalous strong effect. The valence and atomic size are main factors influencing the electrical properties.

INFLUENCE OF RARE-EARTH ELEMENTS ON THERMAL STABILITY OF PdSi_(16.5)GLASS

The influence of rare-earth elements,La,Ce,Pr,Nd,Sm,Eu,Gd,Dy,Ho,Er and Yb on the thermal stability of PdSi_(16.5) glass was studied systematically by means of DSC.All rare-earth elements,especially heavy ones,increase obviously the thermal stability parameters,including T_θ(T_g ,T_x ,T_g),T_(rg) and ΔE etc.The crystallization temperatures T_(p1) and T_(p2) increase linearly with the lanthanide constriction increasing,but Eu shows an anomalous influence:Pd-Si-Eu metallic glass possesses the highest thermal stability and the lowest concentration limit of glass forming among Pd-Si-R glasses.

Geochemistry of rare-earth elements and its significance in the study of climatic and environmental change in Barrow, Arctic Alaska

Geochemical characteristics of rare earth elements ( REE) and sedimentary features were studied in the borehole 96 7 1 from Elson Lagoon in Barrow, Arctic Alaska. The results show that total contents of REE (∑REE) are lower, suggesting that physical weathering is dominate, therefore, concentrations of rare earth elements are lower in the paleosediment environment. The chondrite normalized distribution patterns of REEs are characterized by light REE (LREE) enrichment and Eu depletion with the terrestrial sedimentary rock as the parent materials. In comparison with the borecore AB 67 in Elson Lagoon, the main conclusions for climatic and environmental changes are similar: before 1740 A.D., it was cold and dry with terrestrial properties, but the comparatively warming around 1400 A.D. and 1550 A.D. ; after 1740 A.D., it became warming, or markedly after 1821 A.D.; but it was cold around 1890 A.D. From 1904 A.D., it got warm again, but it was relatively cold around 1971 A.D..

Geochemical Behavior of Trace- and Rare-Earth Elements in the Hydrothermal Alteration Facies of the Cijulang Area, West Java, Indonesia

This study examines the behavior of trace- and rare-earth elements (REE) in different hydrothermal alteration facies (silicic, advanced argillic and argillic) of Cijulang high-sulfidation epithermal gold deposit, West Java, Indonesia. The results of the study indicate that remarkable differences in the behavior of trace elements and REE are observed in the studied alteration facies. All REE in the silicic facies are strongly depleted. In advanced argillic facies, Heavy rare-earth elements (HREE) are strongly depleted whereas light rare earth elements (LREE) are quite enriched. REE concentrations in the argillic facies show little or no variation with respect to fresh rock counterparts. A strong depletion of REE in the silicic facies is likely to be favored by the highly acidic nature of the hydrothermal fluids, the abundance of complexing ions such as Cl ˉ, F ˉ, and in the hydrothermal solutions and the absence of the secondary minerals that can fix the REE in their crystal structures. An apparent immobility of LREE in advanced argillic facies is possibly due to the presence of alunite. The immobility of REE in the argillic facies suggests the higher pH of the fluids, the lower water/rock ratios and the presence of the phyllosilicates minerals. -

Geochemistry of rare-earth elements in shallow groundwater, northeastern Guangdong Province, China

Shallow groundwater and hot springs were collected from northeastern Guangdong Province, Southeast China, to determine the concentrations and fractionation patterns of rare-earth elements(REE). The results show that the La, Ce and Nd of REEs are abundant in groundwater and rock samples, and the ∑REE contents in groundwater and rock samples range from 126.5 to 2875.3 ng/L, and 79.44 to 385.85 mg/L, respectively. The shallow groundwater has slightly HREE-enriched PAAS-normalized patterns. However, the granitic rocks PAAS-normalized patterns, with remarkable negative Eu anomalies, are different from that of shallow groundwater. The enrichment of HREE is considered to be controlled by REE complexation and readsorption for most groundwater has Ce and Eu positive anomalies. The Ce and Eu anomalies in groundwater are controlled by redox conditions. Moreover, the Fe-contain sediments dissolution and/or the reduction of Fe oxyhydroxides are another factor contributing to Ce anomalies. The Eu anomalies in groundwater are controlled by the preferential mobilization of Eu2+ during water-rock interaction compared to Eu3+.

Rare-Earth Elements and Genesis of Lamprophyres in the Laowangzhai Gold Orefield, Yunnan Province

The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailaotectonic zone, Yunnan Province, is a typical gold orefield where lamprophyres are temporallyand spatially related to gold mineratization. Major element data show that lamprophyres in theorefield are of alkalic series and can be divided into potassic and K-rich calc-alkaline lamprophyres. The rocks are enriched in rare-earth elenlents as compared with the primary mantle andmid-ocean ridge basalts(MORB). Modelled calculations by the least squares method of Petrological Mixing show that the mantle source for the lamprophyres is enriched in rare-earth elements. The geotectonic development of western Yunnan, Sr and Nd isotopic compeitions, incompatible element patterns and linear programing calculations indicate that the fluids were de-rived from dehydration of submaine sediments which are enriched in ALK, LREE and incompatible elements and then were carried to mantle wedges as a result of plate subduction. That isthe main factor leading to the formation of a metasomatic fertile mantle in the area studied.

Geochemical behavior of rare-earth elements and other major and minor elements in sound-producing and silent beach sands in Japan

The major element composition of sound-producing sand is reported together with rare-earth elements (REE) and other selected elements for the first time. Rare-earth element concentrations in beach sands from Miyagi and Tottori in Japan were determined by induction-coupled, argon-plasma spectrometry (ICP-MS) to characterize the REE of sound-producing and silent sands relative to the parental rocks. Sound-producing sand beaches are very common and all over in Japan: five beaches in Miyagi and 2 in Tottori are selected with other silent sand beaches in the areas. Both sound-producing sand and silent sand samples from Miyagi and Tottori contain more than 60wt% of SiO2 and are composed mainly of quartz and feldspar. Miyagi sand samples are characterized by light REE enrichment and flat chondrite-normalized patterns that are similar to those of local source sandstone. However, all sand samples from Miyatojima in Miyagi show positive Eu anomalies, a characteristic feature not shown in other sand samples from Miyagi. Tottori sand samples also are characterized by high REE contents and remarkable positive Eu anomalies. The sands containing lower REE contents are due to high quartz and feldspar contents. Miyatojima sand samples and Tottori sand samples have high REE contents and show remarkable positive Eu anomalies due to the presence of feldspar. The best results are obtained using all of the geological methods and the Principal Component Analysis (PCA) as a measure of the similarity between sound-producing sand and silent sand. The difference between sound-producing sand and silent sand is obtained from the PCA results.

Hydrothermal Redistribution of Rare-Earth Elements in Pingxiang Dacite, Guangxi

Distribution of the rare-earth elements (REE) in dacite has been studied so as to get a better understanding of the migration behavior of REE during alteration. Both unaltered and altered samples were collected in an unpolluted area of Guangxi Zhuang Autonomous Region, southwest China. The REE concentrations were analyzed by ICP-MS. It is concluded that the REE were enriched during dacite alteration in varying degrees. The chondrite-normalized REE patterns of altered samples approximately maintain the characteristics of unaltered samples. However, if we normalize the REE concentrations of altered samples with unaltered dacite, fractionation of REE will appear. The LREE are more enriched than HREE in all altered samples with the LREE possibly precipitated as carbonate minerals. Both positive and negative Eu anomalies exist. Enrichment, immobility and depletion are noticed for the element Lu. Heavy mineral alteration, difference in stability constant between carbonate LREE and HREE complexes, downward migration of weathering fluid and microenvironment change may be responsible for the fractionation of REE in the altered dacite.

Compositional Characteristics and Existing Forms of Major, Trace and Rare-earth Elements in Cassiterite, Dupangling Tin Ore Field, Guangxi

Trace elements in cassiterite, including Ta, W, Fe, Mn, Ti, Zr, V, Sc, Si, kl, In, Ga, Ge, Be,Bi, Ag, Sb, As, Cu, Pb, Zn, Co and REE, have been studied by many workers (Shan Zhenhua etal., 1988; Huang Zhou Tianren et al., 1987; Wu Qingsheng et al., l988; Hu Zening, 1988, Li Zhong-qing 1988 MingZhi et al.,1988; Wang Lihua et al., 1988, Liu Kanghuai, 1990). Up to now, however,most of the previous studiesareconcerned with tracoelement variations in cassiterites of diffirent occur-rences and colors from diffirent types of ore deposits, Data concerning the modes of occurrence of’ these trace elements are rare, except for the contention that Nb-Ta, F.2+-M.-F.3+ and W-F.3+ maysubstitute isomorphously for Sn as pointed out by Zhou Tianren et al. (1987) and Moller et al.(1988). In this paper we are concerned with the compositionaI characterishcs as well as the modes ofoccurrence of trace elements in cassiterites from quartz veins and greisens in the Dupangling tin field,Guangxi, based on mu1tivariate statistical analys es.Tin mineralization in the Dupang1ing area is found associated with the medium-to fine-grainedprotolithionite-albite granite and its outer contacts. Cassiterite occurs, with wolframite, both inquartz veins in the contact and in greisens within the granite.’ ) Spatially, greisens become dominantover quartz veins in going from the contact to the interior of the granite and with increasing depth.The greisens are of various shapes. The vein-shaPed and the sheet-shaped greisens at the top of thegranite are rich in quartz and the chambered greisens always constitute rich ores and contain abun-dant topaz or mica. Genetically, Sn, W ndneralizations associated with the protolithionite-albite gran-ite are considered to have been formed from fluid melt derived from the ore-forming magma re-sponsible for the

Geochemistry of the trace elements and rare-earth elements at the boundary between Cambrian Series 2 and Series 3 at Jianshan,South China:Paleoenvironmental and stratigraphic implications

The Jianshan section in Jianhe County,Guizhou Province,is a very important auxiliary section to the candidate stratotype at the boundary between Cambrian Series 2 and Series 3.Twenty four samples collected from the Jianshan section of the Kaili Formation were analyzed for the concentrations of trace element and rare-earth elements(REEs) by inductively coupled plasma mass spectrometry.The trace element and REE geochemical characteristics of the Kaili Formation at the Jianshan section show that trace element composition and REE distribution patterns across the section are covariant.Notably,at 44 m above the base of the Kaili Formation,most trace element contents and REEs concentrations are lower than those values observed below 44 m.Above 44 m,an increasing trend in the concentration of both trace elements and REEs is observed.These geochemical data indicate important,but subtle,changes at the 44 m horizon.If this is,in fact,verified by work in progress,geochemical criteria can provide additional supports for defining the top surface of Cambrian Series 2,especially in sections where Oryctocephalus indicus is absent.Trace element ratios,specifically Ni/Co,V/Cr,V/(Ni+V) and Th/U as well as Ce and Eu anomalies indicate that the sedimentary environment of the Kaili Formation at the Jianshan section was oxidizing,that benthic redox conditions were less oxic,and may have been influenced by freshwater as compared to the Balang area.Moreover,the Eu anomalies observed in the Kaili Formation are similar to the negative Eu anomalies observed in post-Archean sedimentary rocks,and reveal fluctuations in oxygen content from the bottom to the top of the Kaili Formation.

Distribution of Rare-earth Elements in the Shenzhen Bay and Dapeng Bay Modern Sediments

The aim of this paper is to study the REE geochemistry of the Shenzhen Bay (SZB) and Dapeng Bay(DPB) modern sediments, discuss their REE distribution patterns, reveal the REE geochemical difference between the two bays which share the same material source but are deposited in different sedimentary environments, and expound their dynamic changes.It can be concluded that the SZB and DPB sediments are essentially of continental source.Their REE distribution patterns are quite different from those of Pacific pelagic sediments, but are very similar to those of South Chi-na granites.Because of different sedimentary environments prevailing in the SZB and DPB, some REE fractionation would have taken place in the sediments of the two bays.

Toward understanding the role of genomic repeat elements in neurodegenerative diseases

Neurodegenerative diseases cause great medical and economic burdens for both patients and society;however, the complex molecular mechanisms thereof are not yet well understood. With the development of high-coverage sequencing technology, researchers have started to notice that genomic repeat regions, previously neglected in search of disease culprits, are active contributors to multiple neurodegenerative diseases. In this review, we describe the association between repeat element variants and multiple degenerative diseases through genome-wide association studies and targeted sequencing. We discuss the identification of disease-relevant repeat element variants, further powered by the advancement of long-read sequencing technologies and their related tools, and summarize recent findings in the molecular mechanisms of repeat element variants in brain degeneration, such as those causing transcriptional silencing or RNA-mediated gain of toxic function. Furthermore, we describe how in silico predictions using innovative computational models, such as deep learning language models, could enhance and accelerate our understanding of the functional impact of repeat element variants. Finally, we discuss future directions to advance current findings for a better understanding of neurodegenerative diseases and the clinical applications of genomic repeat elements.

Leaching behaviors of iron and aluminum elements of ion-absorbed-rare-earth ore with a new impurity depressant

Ion-absorbed rare-earth ore is an important mineral resource which is widely extracted by in-situ leaching process. And such process generates a significant amount of impurities such as aluminum and iron ions in leaching solution simultaneously. The surface characteristics and interactions by infrared spectroscopy and X-ray diffraction were studied to optimize the leaching conditions. It is found that the environment-friendly depressant LG-01 can react with the impurity ions through the formation of a new complex on the surface of leaching residues. Thus, it reduces significantly the concentration of impurity ions in leaching solution and improves the leaching rate of rare-earth ore. Moreover, a leaching rate of 95.6% and an impurity removal rate of 92% have been achieved under the optimized conditions.

Mechanism of interaction relation between the rare-earth element Ce and impurity elements Pb and Bi in Ag-based filler metal

The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can be easily produced between these three elements in the filler metal, which greatly limited the formation of the isolated phase Pb or Bi and also eliminated the bad effect of impurity elements Pb and Bi on the spreading property of Ag-based filler metal. The metallurgical and quantum-mechanical bond formation analysis show that a strong chemical affinity was existed between the rare-earth element Ce and impurity elements Pb and Bi, which was proved by the XRD analysis results.

Biological effect of rare-earth elements on anti-oxidation enzymes in wheat under acid rain stress

Based on pot-culture experiments, the biological effect of rare-earth elements (REE) on antioxidation enzymes of wheat under acid rain stress was studied. The results show that both acid rain and REE can affect the activity of anti-oxidation enzymes of wheat to different extents. Under the acid rain stress, anti-oxidation enzymes (CAT, SOD) of wheat showed single peak curve with the decrease of pH values. After REE were applled, variation of activities of anti-oxidation enzymes was relatively stable and the peak value of variation curve would move in the direction of increased acidity. Under low acidity of acid rain, REE could reduce the sensitivity of anti-oxidation enzymes of wheat to acid rain stress significantly and promote the resistance of anti-oxidation enzymes of wheat to acid rain.