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1.
Origin of Archean lamprophyre dykes,Superior Province,Canada: rare earth element and Nd−Sr isotopic evidence 总被引:1,自引:0,他引:1
Hornblende- and clinopyroxene-phyric lamprophyre dykes exposed in the Roaring River Complex, Superior Province are alkaline, nepheline-normative, basaltic compositions (>50 wt% SiO2), that range from primitive to fractionated [Mg/(Mg + total Fe)=0.66–0.40; Ni=200–35 ppm], and which have high abundances of light rare earth elements (REE) [(Ce/Yb)n=16–26, Cen=60–300; n = chondrite normalized], Sr (870–1,800 ppm), P2O5 (0.4–1.3 wt%), and Ba (150–900 ppm). Crystal fractionation of the lamprophyres produced coeval gabbro and clinopyroxenite cumulate bodies. A whole-rock Sm–Nd isochron for lamprophyres and gabbro-pyroxenite yields a crystallization age of 2,667±51 Ma Ma (I=0.50929±0.0004;
Nd = + 2.3 0.7). Whole-rock Sr isotope data are scattered, but suggest an initial 87Sr/86Sr ratio of 0.7012, similar to bulk Earth. The elevated levels of light REEs and Sr in the lamprophyres were not due to crustal contamination or mixing with contemporaneous monzodioritic magmas, but a result of partial melting of a mantle source which was enriched in these and other large-ion-lithophile elements (LILEs) shortly before melting. The lamprophyres were contemporaneous with mantle-derived, high-Mg, LILE-enriched monzodiorite to granodiorite of the Archean sanukitoid suite. Both suites have concave-downward light REE profiles, suggesting that depleted mantle was common to their source regions, but the higher light REE abundances, higher Ba/La ratios, and lower
Nd values (+1.3±0.3) of the parental monzodiorites suggest a more enriched source. The lamprophyres and high-Mg monzodiorites were derived from a mineralogically and compositionally heterogeneous, LILE-enriched mantle lithosphere that may have been part of a mantle wedge above a subducting plate in an arc environment. 相似文献
2.
Trace and rare earth elements in cassiterite — sources of components for the tin deposits of the Mole Granite,Australia 总被引:1,自引:0,他引:1
Trace and rare earth elements have been determined for cassiterite from deposits associated with the Mole Granite and hosted by granite, metasediments and metavolcanics. The REE of cassiterite is controlled by the REE of the the ore fluid and the rocks through which this fluid circulated. The REE distribution factor and LREE/HREE value of cassiterite is strongly influenced by the associated mineral assemblage, the fluid chemistry and the crystal chemical characteristics of the host mineral. Cassiterite from deposits hosted by granite have trace and rare earth element characteristics similar to those determined for the Mole Granite. Cassiterite from deposits hosted by metasediments or acid volcanics have most trace and rare earth element characteristics similar to those of the enclosing rocks and some characteristics similar to the Mole Granite. The ore fluid had chemical components derived from the parental granite and components acquired by passage through the metamorphosed aureole. 相似文献
3.
《Chemical Geology》1999,153(1-4):259-279
The corrosion of basaltic dykes from central Germany which intruded during the Tertiary into rock and potash salts of Upper Permian age (Zechstein) has been studied. The corrosion behavior of these glassy basalts can serve as a natural analogue for the long-term corrosion expected for nuclear waste glasses in a salt repository. Our data demonstrate mobility and fractionation of the rare earth elements (REE) during a postintrusive circulation of salt brines. The processes controlling this behavior of the REE were dissolution and reprecipitation of phosphates. The K–Ar data document the synintrusive assimilation of a salt phase followed by a postintrusive fluid circulation in the peripheral parts. This circulation removed the assimilated salt and imported highly radiogenic salt Ar which was integrated into newly formed sheet silicates. The central part of the dyke was not affected by this circulation and could retain a mantle gas phase. The Sr isotope data document a synintrusive assimilation of salt Sr and a strong exchange with salt fluids during the postintrusive corrosion which was strongest in a zone next to the chilled dyke margins. This locally stronger alteration is probably due to different cooling and shrinking rates of the basalt at the margins and in the core of the dyke which led to the formation of a highly permeable fractured zone. 相似文献
4.
Accumulations of rare earth elements (REEs) in human body through multiple pathways including food ingestion, air inhalation and dermal absorption have received considerable attention due to their chronic toxicity to human health. The distribution and fractionation of 14 REEs were conducted in soil, well water, human blood and hair in the vicinity of a large-scale mining site in southwest Fujian Province, China. The LREEs/HREEs ratios were 9.17 for soil, 2.18 for water, 36.93 for human blood and 7.24 for human hair, respectively. The distribution patterns of REEs in soil, human blood and hair samples were characterized by LREEs enrichment and HREEs depletion, but LREEs depletion and HREEs enrichment in water sample. LaN/YbN values of these samples ranged from 0.41 to 1.83, LaN/SmN values from 0.43 to 4.92, and GdN/YbN values from 0.81 to 4.71. Soil and human blood showed enrichments of Ce, Gd and Er, but water showed a depletion of Ce. In addition, the normalized patterns showed a weak negative anomaly of Eu in soil and a weak negative anomaly of Nd in human blood and hair. Consequently, enrichment and depletion of REEs differ significantly among soil, water and human blood and hair, thus the REEs after entering into human body can undergo fractionation effects. 相似文献
5.
《Applied Geochemistry》2001,16(3):375-386
The concentrations of the lanthanide rare earth elements (REE) and Pt group elements (PGE) were measured in the Kupferschiefer from the Polish Zechstein Basin at, and in proximity to, the Rote Fäule near the Lubin Mining District. The Rote Fäule is a zone of post-depositional oxidation characterized by the presence of extensive amounts of Fe(III) oxides replacing syn-sedimentary framboidal pyrite. Outward from the Rote Fäule, the remainder of the Kupferschiefer is composed of Cu- and Pb/Zn-mineralized shale surrounding the Rote Fäule and a non-mineralized pyritic black shale in the central basin.The leading hypothesis explaining the high concentrations of PGE, and REE in the Kupferschiefer states that PGE, REE and the associated base metals were mobilized by oxidizing Cl− brines which migrated outward from the Rote Fäule into the reduced Kupferschiefer. According to available thermodynamic data, PGE were in all likelihood present as chloro-complexes in these oxidizing brines, as geologically realistic concentrations of Pt, Pd and Au could be transported as chloro-complexes. The Eh of these brines decreased as they migrated further from the Rote Fäule and into the Kupferschiefer. Base metals and PGE were precipitated in the order of their decreased solubility in these brines. As a result, the concentrations of least soluble PGE (Pt) are highest in the Rote Fäule and in the transition zone adjacent to the Rote Fäule (e.g. [Pt]=202–537 ppb) while the concentrations of the more soluble metals in these brines (Ag, Cu, Pb, and Re) are highest in the reduced-mineralized Kupferschiefer. The sources of the PGE and REE are enigmatic. It is likely that the metals were derived either from the underlying Rotliegendes sandstones and volcanics, the Variscan basement rocks, or the Kupferschiefer shale whose metals were mobilized by saline, oxidizing fluids released during intra-continental rifting in the Triassic period. 相似文献
6.
Marshall J. Reed Philip A. Candela Philip M. Piccoli 《Contributions to Mineralogy and Petrology》2000,140(2):251-262
The partitioning of the rare earth elements between a peraluminous monzogranitic melt and a chloride-bearing, sulfur- and
carbon dioxide-free, aqueous volatile phase was examined experimentally as a function of chloride and major element concentrations
at 800 °C and 200 MPa. The light rare earth elements (e.g. La, Ce) partition into the aqueous volatile phase to a greater
extent than the heavy rare earth elements (e.g. Yb, Lu). Distribution of the rare earth elements and the major elements H,
Na, K, Ca, and Al between the melt phase (mp) and aqueous volatile phase (aq) is a function of the chlorine concentration
in the system, and our data are consistent with the rare earth and major elements occurring as chloride complexes in the aqueous
volatile phase. Apparent equilibrium constants for experiments at 800 °C and 200 MPa, K
′
REE,Na
aq/mp
, expressed as the ratio of the concentration of a given rare earth element in the aqueous volatile phase to the concentration
of the same element in the melt phase, divided by the cubed ratio of sodium in the aqueous volatile phase to the concentration
of sodium in the melt phase, decrease systematically with increasing atomic number from K
′
La,Na
aq/mp
= 0.41(±0.03) to K
′
Lu,Na
aq/mp
=0.11(±0.01), except for Eu. These experimentally derived apparent equilibrium constants for the rare earth elements can be
used in a numerical simulation of magmatic volatile exsolution. The simulation gave results consistent with the elemental
distribution in the potassic alteration zone of a deep porphyry copper deposit, but higher concentrations of heavy rare earth
elements are released into the magmatic aqueous solution than are captured in the secondary mineralization.
Received: 1 November 1999 / Accepted: 7 June 2000 相似文献
7.
《Journal of Asian Earth Sciences》2000,18(2):177-194
Results of different isotopic and trace element studies on three carbonatite–alkaline complexes (Amba Dongar, Mundwara and Sarnu-Dandali) of the Deccan flood basalt province, India, are presented. The Amba Dongar (Ambadungar) complex has been dated precisely to 65.0±0.3 Ma by the 40Ar–39Ar method. The minimum initial Sr isotopic ratio of alkaline rocks of Amba Dongar is found to be same as that of the coexisting carbonatites, suggesting their derivation from a common parent magma, probably through liquid immiscibility. The rare earth element abundance in these rocks also supports the liquid immiscibility hypothesis. Further investigation revealed that the parent magma of this complex has been contaminated (∼5%) by the lower crustal material, which is clearly reflected in the initial 87Sr/86Sr variation of alkaline rocks but not in the carbonatites. Sr study also suggests that the mantle source of Amba Dongar like the other two complexes is a Rb/Sr enriched source. The temporal and spatial relationships of all the three complexes with the Deccan flood basalts support the hypothesis of reunion plume origin for these. Fractional crystallization and subsequent hydrothermal/meteoric alteration are found to have controlled the stable carbon and oxygen isotopic variations in carbonatites. This study suggests that all the complexes have been derived from isotopically average mantle except for a particular batch of parent magma at Amba Dongar, which appears to have incorporated recycled crustal carbon. In a plume origin scenario such incorporation indicates the entrainment of 13C-enriched subcontinental lithospheric mantle by the plume. 相似文献
8.
赛马碱性杂岩体位于我国辽东半岛,是一个典型的铀-铌和稀土多金属矿化杂岩体,富含重稀土,其复杂的演化过程和稀土元素富集机制仍没有得到有效约束。本文对该碱性杂岩体中角闪辉石正长岩、正长岩、黑云正长岩、云霓霞石正长岩和异霞正长岩5类岩石及锆石的元素地球化学特征进行了系统研究,并开展了特征矿物包裹体的显微岩相学研究,旨在限定杂岩体母岩浆的演化路径,揭示稀土元素的富集机制。研究结果显示,赛马碱性杂岩体的母岩浆经历了由钾质碱性(角闪辉石正长岩、正长岩和黑云正长岩),到钾质过碱性(云霓霞石正长岩),向钠质过碱性(异霞正长岩)的充分演化。在演化过程中赛马碱性杂岩体母岩浆的体系状态发生了明显变化,碱性岩浆演化受流体不饱和的纯岩浆体系的控制,而过碱性岩浆岩则形成于流体过饱和的岩浆体系,且异霞正长岩母岩浆流体的饱和程度明显高于云霓霞石正长岩的母岩浆。研究还显示,钾质碱性岩浆稀土元素的地球化学行为主要受控于磷灰石等矿物的分离结晶,而成矿的钠质过碱性岩浆稀土、锆和铌等元素的富集成矿则主要受富CO_(2)的高盐度岩浆热液的控制。 相似文献
9.
Matías Mudarra Bartolomé Andreo Juan Antonio Barberá Jacques Mudry 《Environmental Earth Sciences》2014,71(2):507-523
Analysis of Total Organic Carbon (TOC) and NO3 ? contents in the water at six springs in the province of Malaga (Southern Spain), sampled under different hydrologic conditions, revealed two different hydrochemical behaviour patterns for these natural tracers of infiltration. TOC content increased during every recharge period, following the rapid arrival of water infiltrating through the soil. On the other hand, NO3 ? content only rose during the first flood episodes (normally in autumn), and fell during the winter and spring ones. This difference is consequence of the distinctive biogeochemical kinetics of nitrogen with respect to organic carbon, both in the soil and within the aquifer. Unlike the mineralisation undergone by TOC from the surface to the spring, the NO3 ? ion remains in the aquifer almost unaffected, due to the oxidizing conditions prevailing within the karst medium, which do not allow its denitrification and favour its preservation within the saturated zone. In non-polluted aquifers, TOC and NO3 ? have a common origin in the soil and can be used to determine infiltration processes and the hydrogeological functioning of karst aquifers. Their different hydrochemical evolution provides information about mineralization and degradation processes of organic matter within karst aquifers, which can be used to validate the vulnerability to contamination in this type of medium. 相似文献
10.
《Applied Geochemistry》1995,10(4):391-405
Extensive NO3− contamination of groundwater in the Abbotsford aquifer to levels above drinking water limits is a major problem in the Fraser Lowlands of southwestern British Columbia, Canada. Nitrate concentrations in the aquifer ranged from 0 to 151 mg/l NO3−, with a median concentration of 46 mg/l NO3−. Of 117 wells sampled, 54% had NO3− concentrations exceeding the drinking water limit of 45 mg/1. Approximately 80% of the study area had groundwater NO3− concentrations exceeding 40 mg/1 NO3−. Potential NO3− source materials were poultry manure N and synthetic NH4 based fertilizers. Theδ15N of solid poultry manure samples ranged between + 7.9 and + 8.6‰ (AIR). Four brands of synthetic fertilizers commonly used hadδ15N values between −1.5 and −0.6‰. Ammonia volatilization caused theδ15N of groundwater NO3− produced from poultry manure N to range between +8 and +16‰. Theδ18O values of groundwater NO3−, by contrast, mostly ranged between +2 and +5‰ (SMOW). This narrow range ofδ18O values fell within the expected range of NO3− produced by nitrification of reduced N forms such as poultry manure N and NH4 fertilizers, and had a similar range ofδ18O values as NO3− in the upper part of the unsaturated zone below raspberry fields and beneath former manure piles. Theδ15N-NO3− andδ18O-NO3− data confirmed that NO3− in the aquifer was predominantly derived from poultry manure and to a lesser extent from synthetic fertilizers. Theδ18O-NO3− data further suggested the nitrification process occurred mainly in the summer months, with the soil NO3− produced subsequently flushed into the aquifer during fall recharge. Theδ15N-NO3−andδ18O-NO3− data conclusively indicated that no significant bacterial denitrification is taking place in the Abbotsford aquifer. 相似文献
11.
The partitioning of Gd in the experimental system diopside-aqueous vapor as a function of temperature, pressure, composition of the phases, time, grain size, solid-liquid ratio and Gd concentration has been investigated. A radioactive tracer measurement was used to determine Gd concentration in the separated phases. Diposides were reacted with aqueous vapor containing tracer Gd and reversibility was tested by reacting Gd-doped diopsides with pure aqueous vapor. Equilibration of Gd between the bulk of the diopside and the liquid was found to be limited by the slow rate of Gd diffusion in diopside, maximum value of D = 2 × 10?15cm2sec?1 at 800°C and 1 kb. Depending on whether the diopside was previously synthesized or synthesized from an oxide mix during the experiment, Gd concentrations were zoned in the crystal such that higher concentrations existed at the edges or center, respectively. Equilibrium is difficult to achieve in these experiments, but at the optimum experimental conditions for equilibration, the Gd diopside-aqueous vapor distribution coefficient is 20 ± 6 (800°C, 1 kb) in approximate agreement with previous results of 55 ± 23. Changing the composition of the aqueous vapor indicated that possible mechanisms for Gd substitution included coupling of Gd3+ with H+ or Na+ replacing 2Ca2+, or substitution of 2Gd3+ for 3Ca2+ with formation of a cation vacancy. 相似文献
12.
Garnet is a vital mineral for determining constrained P–T–t paths as it can give both the P–T and t information directly. However, estimates of the closure temperature of the Sm–Nd system in garnet vary considerably leading
to significant uncertainties in the timing of peak conditions. In this study, five igneous garnets from an early Proterozoic
2414 ± 6 Ma garnet—cordierite bearing s-type granite—which was subjected to high-T reworking have been dated to examine their
diffusional behaviour in the Sm–Nd system. Garnets 8, 7, 6 and 2.5 mm in diameter were compositionally profiled and then dated,
producing two-point Sm–Nd isochron ages of 2412 ± 10, 2377 ± 5, 2370 ± 5 and 2365 ± 8 and 2313 ± 11 Ma, respectively. A direct
correlation exists between grain size and amount of resetting highlighting the effect of grain size on closure temperature.
Major element EMPA and LA-ICPMS REE traverses reveal homogenous major element profiles and relict igneous REE profiles. The
retention of REE zoning and homogenisation of major element zoning suggest that diffusion rates of REEs are considerably slower
than that of the major cations. The retention of REE zoning and the lack of resetting in the largest grains suggest that Sm–Nd
closure temperature in garnet is a function of grain size, thermal history and REE zoning in garnet. 相似文献
13.
太平洋深海沉积物中富集稀土元素(REY,包括钇),被认为是富有潜力的新型稀土资源。(含)沸石粘土、深海粘土和多金属软泥是主要的富含REY的沉积物类型,其中(含)沸石粘土和深海粘土在中、西北太平洋海盆大面积分布,而多金属软泥则多分布于靠近东太平洋洋脊热液活动的深海盆地中。目前关于中、西北太平洋海盆的深海粘土和(含)沸石粘土已有较多的研究,但关于多金属软泥中REY的研究较少。不同区域、不同类型深海沉积物中的稀土元素赋存状态有何差异?影响稀土富集的机制又是什么目前尚不清楚,也就进一步影响了对深海沉积物稀土资源的勘查和开发工作。本文分析对比了太平洋不同区域不同类型深海沉积物的地球化学特征及矿物学特征。结果表明,总体上,中、西北太平洋海盆深海沉积物中,尤其是(含)沸石粘土中的REY含量明显高于东太平洋海盆多金属软泥REY含量,其REY的富集主要与磷酸盐有关。超常富集REY(∑REY>2000×10^(-6))的沉积物中的CaO/P_(2)O_(5)比值趋向于一致(~1.4),几乎接近于磷灰石CaO/P2O5比值(~1.3),因此REY主要赋存载体为磷灰石,该区沉积物中REY的富集可能受到磷酸盐化的影响;东太平洋海盆多金属软泥明显受到热液影响,铁和锰的含量明显增加,但其∑REY含量集中于500×10^(-6)~800×10^(-6),不随铁和锰的增加而变化,REY的富集仍与磷酸盐关系密切,而与铁锰物质和铝硅酸盐关系不大。中、西北太平洋海盆富稀土的深海沉积物形成时处于较强的氧化环境,同时又有充足的含磷物质补给,才造成REY在该区沉积物中的超常富集;而东太平洋海盆多金属软泥虽然处于氧化环境,但缺少足够的磷补给,所以其∑REY含量通常低于中、西北太平洋海盆沸石粘土中∑REY含量。 相似文献
14.
Lars Olov Andersson 《Physics and Chemistry of Minerals》2010,37(7):435-451
A number of different impurities are located in the open channels of natural beryl crystals. The rare Maxixe beryl contains
an unusual amount of NO2. The isoelectronic CO2
− radical is found in the irradiated Maxixe-type beryl. The NO2 radicals are distributed in the Be–Al plane of the crystal, with the nitrogen atom close to the oxygens of the beryl cavity
wall. These oxygens repel the negative CO2
− radical, which is located at the center of the beryl cavity and rotates around its O–O axis, which is parallel to the crystal
c-axis. When there is a nearby alkali ion at the center of the beryl channel, it reorients the CO2
− radical so that its bisector is parallel to the c-axis and points toward the positive ion. Different signals are analyzed for Li+, Na+, and another counter-ion, which probably is Cs+. The related NO3 and CO3
− radicals are the color centers in the investigated deep blue beryls. The slow decay of the color, which makes these beryls
useless as gem stones, is related to the decay of the hydrogen atoms which are present in these crystals. Evidence is given
that NO3 is created in Maxixe beryl by a natural process, while CO3
− in Maxixe-type beryl has been created by irradiation. The temperature dependence of the EPR signals of these two radicals
was investigated, but a definitive proof that they rotate at the center of the beryl cavity could not be given. EPR signals
from some other radicals in beryl have been observed and described. 相似文献
15.
Acta Geochimica - Many carbonate-hosted talc mineralization, which are widespread in South China, exclusively developed in Carboniferous dolomitic limestone with many siliceous bands and nodules,... 相似文献
16.
《Geochimica et cosmochimica acta》1999,63(11-12):1709-1722
Particulate samples (>0.45 μm) from a neutrally buoyant hydrothermal plume at 9°45′N on the northern East Pacific Rise were collected using large volume in situ filtration and analyzed for Fe, Al, Mn, Ni, and fourteen rare earth elements (REE). The Sm/Fe ratio (a proxy for overall REE/Fe) and Nd/Er (light/heavy REE fractionation) increased moderately with decreasing particulate Fe. Chemically, the sense of these relationships matched that documented previously in the TAG plume on the Mid-Atlantic Ridge (German et al., 1990), although particulate Fe was about 10 fold lower at 9°45′N. Spatial trends relative to the vent source, however, were opposite of expectation because slow Fe(II) oxidation and Fe(III) colloid aggregation over this interval led to increased particulate Fe (10–26 nM) with distance from source (Field and Sherrell, submitted). After subtraction of non-plume background particle composition, plume particles at 9°45′N and TAG had indistinguishable ranges of light REE-enriched fractionation relative to ambient seawater and had very similar Sm/Fe (therefore Kd for Fe oxyhydroxides), demonstrating that plume particles in both oceans reflect to a first degree the local seawater REE composition. Within-plume REE variations at 9°45′N were investigated using a simple mixing model which accounts for the bulk Fe-Al-Mn variations in the plume using two endmembers: fresh hydrothermal oxyhydroxide precipitates and ridge-crest background particles (composed largely of locally resuspended sediment). Sm/Fe and Nd/Er plot linearly with mixing ratio (R > 0.96), implying that the observed REE trends result from mixing of these two endmembers. Extrapolation to the composition of pure hydrothermal precipitates suggests that Nd/Er is fractionated relative to seawater by a factor of 1.8 during adsorption onto fresh Fe oxyhydroxide particles. The ridge-crest background particles are 5 fold higher in Sm/Fe and Nd/Er is 2.49 relative to seawater, partly a result of enriched terrigenous component in the resuspended matter. A reinterpretation of REE at TAG reveals that positive curvature in REE vs. Fe plots, argued previously to reflect continuous REE uptake (i.e., increasing Kd; German et al., 1990), may result from local depletion of the dissolved REE pool by partitioning onto Fe particles at Fe > 100 nM. Similar drawdown effects could contribute to the variable degrees of curvature observed for all seawater-source particle-reactive species in plumes that are sampled at high particulate Fe concentration. In sum, REE behavior in hydrothermal plumes is more consistent with equilibrium adsorption and mixing of distinct particle types, than with kinetic uptake control. Precise measurements of REEs in modern ridge-crest metalliferous sediments could be compared to the endmember composition calculated from the plume data to evaluate long-term changes in REE of the hydrothermal component. 相似文献
17.
《地学前缘(英文版)》2022,13(2):101337
Geo-electric anomalies are generated during the process of stress accumulation and release associated with earthquakes. However, the mechanism of these anomalies remains equivocal. Based on the analysis of thermoelectric characteristics of semiconductor minerals of the earth’s deep crust such as graphite, ferrosilicon alloy, magnetite etc., we perform finite element analysis to evaluate the principles governing the thermoelectric power generated by minerals and rocks. The results show that graphite, ferrosilicon alloy and magnetite all exhibit Seebeck effect and can be superimposed. And the thermo-electric field can be enhanced with the activation temperature increases, the content of thermoelectric minerals increases, the size of aggregates increases, and the spacing of thermoelectric minerals grains decreases. Seismogenic processes would generate a similar thermal gradient. The natural semiconductor minerals in this thermal field show a thermoelectric effect, forming a thermoelectric field that interferes with the background electric field. This study indicates that thermoelectric effect may have an important influence on the formation of geoelectric field. 相似文献
18.
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. 相似文献
19.
Electron paramagnetic resonance (EPR) spectra of CO
3
3–
molecule-ions stabilized by Sc3+ in natural calcite were identified and studied at X-band frequencies and room temperature. The principal values of the g-tensor (g
xx= 1.9997, g
yy = 2.0030, g
zz = 1.9972) and the direction cosines of the g and A tensors for CO
3
3–
-Sc3+ center were found to be close to that for the well-known CO
3
3–
-Y3+ center. A quantitative comparison of different impurity contents in calcite samples and analysis of the intensities of forbidden transitions were used to identify Sc3+. An estimation of the unpaired electron spin density on the nuclei of paramagnetic centers confirms that both centers, CO
3
3–
-Sc3+ and CO
3
3–
-Y3+, have the same nature. 相似文献
20.
Khadija Semhi Osman A. E. Abdalla Salah Al Khirbash Tabisam Khan Salim Asaidi Sardar Farooq 《Arabian Journal of Geosciences》2009,2(2):143-150
Groundwater samples from six wells and various species of plants from soils developed on ophiolites were collected from an arid area (AlKhod area, Oman) and analyzed for trace elements including rare earth elements (REEs). The distribution patterns of REEs in plants indicated an enrichment in middle REEs (MREEs?=?Sm to Dy) and heavy REEs (HREEs?=?Ho to Lu), when they are normalized to the REE composition of the Post Archean Australian Shale (PAAS), with a significant negative anomaly in Ce and a positive anomaly in Eu. Compared to Oman ophiolites, the REEs in different species of plants are depleted in Ce and enriched in MREEs and slightly enriched in light REE (LREE?=?from La to Nd). Relative to PAAS, the distribution of REEs in groundwaters revealed similar patterns to the REE distribution in plants. The distribution patterns of REEs in plants relative to those in waters are nearly flat. These patterns suggest that the transfer of REEs from soil solutions to the groundwaters in Oman occurs without any significant fractionation. 相似文献