A M?ssbauer effect study of Fe³⁺ bearing γ-Fe₂SiO₄     

Zhe Li  I. Shinno  Danian Ye  Pingqiu Fu  Yueming Zhang 《中国科学D辑(英文版)》2001,44(1):34-46

Three synthetic Fe³⁺ bearing λ-Fe₂SiO₄ were analyzed using electron probe method, and the M?ssbauer spectra of the samples at 298 K, 150 K, and 95 K were measured. Each spectrum at three temperatures is composed of two doublets. These two doublets are assigned to Fe²⁺ in the octahedral sites and Fe³⁺ in the tetrahedral sites, respectively. Site occupancies were determined. The results show that Fe³⁺ and a small amount of Si⁴⁺ are in the tetrahedral and octahedral sites, respectively. The average bond lengths of the octahedral and tetrahedral sites were calculated according to the equations primarily given by Hill et al., O’Neill and Navrotsky and modified by the authors. Furthermore, the octahedral and tetrahedral bond lengths were used to calculate cell parameters and oxygen parameters. In addition, Fe³⁺ line broadening in the M?ssbauer spectra of Fe³⁺ bearing λ-Fe₂SiO₄ were interpreted by using the next nearest neighbor effects  相似文献   

Tetrahedral occupancy of ferric iron in (Mg,Fe)O: Implications for point defects in the Earth's lower mantle     

Kazuhiko Otsuka  Catherine A. McCammon  Shun-ichiro Karato 《Physics of the Earth and Planetary Interiors》2010,180(3-4):179-188

We investigated the concentration and site occupation of ferric iron (Fe³⁺) in (Mg,Fe)O to understand the influence of point defects on transport properties such as atomic diffusion, electrical conductivity and viscosity. We conducted Mössbauer spectroscopy of (Mg_0.8Fe_0.2)O single crystals synthesized at temperatures from 1673 to 2273 K and pressures from 5 to 15 GPa with Re–ReO₂ and Mo–MoO₂ oxygen fugacity buffers. The isomer shift of the Mössbauer spectra suggests that Fe³⁺ occupies mostly the tetrahedral site at reduced conditions and both the octahedral and tetrahedral sites at oxidized conditions. We formulate a thermodynamic model of point defect dissolution in (Mg,Fe)O which suggests that unassociated tetrahedral Fe³⁺ is more stable than unassociated octahedral Fe³⁺ at high-pressure and low oxygen fugacity due to the effect of configurational entropy. The pressure dependence of Fe³⁺ concentration indicates a change in the dominant site occupancy of Fe³⁺: (1) Fe³⁺ in the tetrahedral site, (2) Fe³⁺ in the octahedral site, and (3) defect clusters of Fe³⁺ and cation vacancy, in the order of increasing oxygen fugacity and decreasing pressure. This is in reasonable agreement with previously reported experiments on Fe³⁺ concentration, Mg–Fe interdiffusivity and electrical conductivity. We consider it plausible that (Mg,Fe)O accommodates Fe³⁺ in the tetrahedral site down to the lower mantle. Based on our results and available experimental data, we discuss the solubility competition between Fe³⁺ and protons (H⁺), and its implications for transport properties in the lower mantle.  相似文献   

Iron oxidation state in lower mantle mineral assemblages: I. Empirical relations derived from high-pressure experiments     

C.A. McCammon  S. Lauterbach  F. Seifert  P.A. van Aken 《Earth and Planetary Science Letters》2004,222(2):435-449

The oxidation state of iron can significantly influence the physical and chemical properties of lower mantle minerals. To improve methods for estimation of Fe³⁺/∑Fe, synthetic assemblages of (Mg,Fe)(Si,Al)O₃ perovskite and (Mg,Fe)O ferropericlase were synthesised from oxide starting mixtures in Re or Fe capsules at 26 GPa and 1650-1850 °C using a multianvil press. (Mg,Fe)(Si,Al)O₃ majorite was also present in some of the run products. Both electron energy loss spectra (EELS) and Mössbauer spectra were measured for each run product, and a robust fitting method was developed for Mössbauer spectra using EELS results as a standard that enabled Fe³⁺/∑Fe of (Mg,Fe)(Si,Al)O₃ perovskite to be determined from Mössbauer spectra of multiphase assemblages. There is a close to linear variation between Fe³⁺/∑Fe and Al concentration in (Mg,Fe)(Si,Al)O₃ perovskite, independent of oxygen fugacity. The concentration of Fe³⁺ in (Mg,Fe)O increases with increasing iron concentration along curves of constant oxygen fugacity, where higher oxygen fugacity stabilises greater Fe³⁺ concentrations. Fe²⁺/Mg partition coefficients calculated from chemical composition data corrected for measured Fe³⁺/∑Fe showed values nearly identical within experimental error for all samples, and independent of Al concentration and oxygen fugacity. Simple empirical relations were derived to calculate Fe³⁺/∑Fe in (Mg,Fe)(Si,Al)O₃ perovskite and (Mg,Fe)O ferropericlase samples for which no Mössbauer or EELS data were available, and tested by applying them to calculation of Fe²⁺/Mg partition coefficients from literature data for (Mg,Fe)(Si,Al)O₃ perovskite-(Mg,Fe)O assemblages where only total iron concentrations had been measured. Results showed Fe²⁺/Mg partition coefficients that were equal to existing values within experimental error, hence confirming the validity of the empirical relations.  相似文献   

Cation distribution in synthetic titanomaghemites     

J.B. O&#x;Donovan  W. O&#x;Reilly 《Physics of the Earth and Planetary Interiors》1978,16(3):200-208

Because of the difficulties of laboratory simulation of maghemitization, few studies have been carried out and the results of such studies are not in good agreement. Of particular interest is the evolution of the cation distribution with degree of non-stoichiometry. This indicates how the maghemitization process takes place at the atomic level. In the present study a suite of titanomagnetite specimens containing a range of concentration of Mg²⁺ ions were maghemitized and the possible cation distribution inferred from saturation magnetization measurements. Although a unique cation distribution cannot be obtained from such measurements, the observed data are consistent with the following model, except for high degrees of oxidation and high Mg concentration: (1) Ti⁴⁺ and vacancies in B sites only; (2) a random distribution of Mg²⁺ which remains frozen in during maghemitization; (3) availability for oxidation of tetrahedral site Fe²⁺ 20% of that of octahedral site Fe²⁺; and (4) deficient moment of the oxidized specimens due to small particle size.  相似文献   

Iron oxidation state in lower mantle mineral assemblages: II. Inclusions in diamonds from Kankan, Guinea     

C.A McCammon  T Stachel 《Earth and Planetary Science Letters》2004,222(2):423-434

Inclusions of ferropericlase and former (Mg,Fe)(Si,Al)O₃ perovskite in diamonds from Kankan, Guinea believed to originate in the lower mantle were studied using Mössbauer spectroscopy to determine Fe³⁺/ΣFe. Fe³⁺ concentration in the (Mg,Fe)(Si,Al)O₃ inclusion is consistent with empirical relations relating Fe³⁺/ΣFe to Al concentration, supporting the inference that it crystallised in the perovskite structure at lower mantle conditions. In ferropericlase there is a nearly linear variation of trivalent cation abundance with monovalent cation abundance, suggesting a substitution of the form Na_0.5M_0.5³⁺O (M=Fe³⁺, Cr³⁺, Al³⁺). Excess positive charge is likely balanced by cation vacancies, where their abundance is observed to increase with increasing iron concentration, consistent with high-pressure experiments. The abundance of cation vacancies is related to oxygen fugacity, where ferropericlase inclusions from Kankan and São Luiz (Brazil) are inferred to have formed at conditions more oxidising than Fe-(Mg,Fe)O equilibrium, but more reducing than Re-ReO₂ equilibrium. Fe²⁺/Mg partition coefficients between (Mg,Fe)(Si,Al)O₃ and ferropericlase were calculated for inclusions co-existing in the same diamond using Mössbauer data and empirical relations based on high-pressure experimental work. Most values are consistent with high-pressure experiments, suggesting that these inclusions equilibrated at lower mantle conditions. The measured ferropericlase Fe³⁺ concentrations are consistent with diamond formation in a region of redox gradients, possibly arising from the subduction of oxidised material into reduced lower mantle. Reduction of carbonate to form ferropericlase and diamond is consistent with a slight shift of Kankan δ¹³C values to isotopically heavy compositions compared to the worldwide dataset, and could supply the oxygen necessary to satisfy the high Fe³⁺ concentration in (Mg,Fe)(Si,Al)O₃ perovskite, as well as account for the high proportion of ferropericlase in the lower mantle paragenesis. The heterogeneity of lower mantle diamond sources indicates that the composition of lower mantle diamonds do not necessarily reflect those of the bulk mantle.  相似文献   

The location of Fe³⁺ ions in forsterite (Mg₂SiO₄)     

S. Zeira  S.S. Hafner 《Earth and Planetary Science Letters》1974,21(2):201-208

The electron spin resonance spectrum of Fe³⁺ in a single crystal of forsterite was studied. Two distinct patterns of about equal intensities were observed which are due to Fe³⁺ at two distinct positions with 4a (M1)and4c (M2or Si) symmetry of Pbnm. The assignment of the 4c pattern to Fe³⁺ ions at the Si position cannot be excluded by symmetry but it is unlikely. The Hamiltonian parameters A and E/D are consistent with the conclusion that Fe³⁺ in this crystal is disordered over two distinct octahedral positions.  相似文献   

Sedimentary geochemistry and provenance of the Lower and Middle Devonian Laojunshan Formation,the North Qilian Orogenic Belt     

XU YaJun  DU YuanSheng    YANG JiangHai & HUANG Hu Key Laboratory of Biogeology  Environmental Geology of China Education Ministry  China University of Geosciences  Wuhan  China  State Key Laboratory of Geological Processes  Mineral Resources 《中国科学:地球科学(英文版)》2010,(3)

The Laojunshan Formation is a suite of molasse formed during the rapid uplift of the North Qilian Orogenic Belt (NQOB). Forty-one samples of sandstone have been collected from the Sunan and Minle sections in the western sector and the Gulang and Jingyuan sections in the eastern sector of the NQOB belt. Geochemical analyses of those samples indicated: 1) The MgO+Fe2O3T and Al2O3/SiO2 values are higher, and K2O/Na2O ratios are lower in the western sector than those in the eastern sector. 2) All of them are de...  相似文献   

对橄榄石相变形核率的估算   总被引：2，自引：2，他引：0       下载免费PDF全文

王曙光  宁杰远  叶国扬  楼小挺  刘平江 《地球物理学报》2007,50(1):122-125

地幔主要矿物橄榄石［(Mg089Fe011)2SiO4］的相变与深源地震的解释以及俯冲带和周围地幔的相互作用相关. 其中,形核率和长大率是刻画其相变动力学的两个重要参数. 因为实验技术的原因,目前人们还没有基于实验数据给出橄榄石的形核率. 本文首先通过对挤碰物理图像的分析,对边界形核情形的相变动力学理论中表征挤碰程度的无量纲参数进行了修正. 在此基础上,根据已有的实验资料,首次对橄榄石相变的形核率进行了估计. 通过对形核率数据的拟合,可以得到形核率参数K0和γ1/3. 得到两个形核率参数的变化范围分别为K0=55×1021～87×1027s-1·m-2·K-1,γ1/3=0～020 J·m-2,最佳拟合值为：K0=69×1024s-1·m-2·K-1,γ1/3=016 J·m-2.  相似文献   

A laboratory study of meteor smoke analogues: Composition, optical properties and growth kinetics     

Russell W. Saunders  John M.C. Plane   《Journal of Atmospheric and Solar》2006,68(18):2182-2202

Meteoric smoke forms in the mesosphere from the recondensation of the metallic species and silica produced by meteoric ablation. A photochemical flow reactor was used to generate meteoric smoke mimics using appropriate photolytic precursors of Fe and Si atoms in an excess of oxidant. The following systems were studied: (i) Fe+O₃/O₂, (ii) Fe+O₃/O₂+H₂O, (iii) Fe+Si/SiO+O₃/O₂ and (iv) Si/SiO+O₃/O₂. The resulting nano-particles were captured for imaging by transmission electron microscopy, combined with elemental analysis using X-ray (EDX) and electron energy loss (EELS) techniques. These systems generated particle compositions consistent with: (i) Fe₂O₃ (hematite), (ii) FeOOH (goethite), (iii) Fe₂SiO₄ (fayalite) and (iv) SiO₂ (silica). Electron diffraction revealed that the Fe-containing particles were entirely amorphous, while the SiO₂ particles displayed some degree of crystallinity. The Fe-containing particles formed fractal aggregates with chain-like morphologies, whereas the SiO₂ particles were predominantly spherical and compact in appearance. The optical extinction spectra of the Fe-containing particles were measured from 300 nm<λ<650 nm. Excellent agreement was found with the extinction calculated from Mie theory using the refractive indices for the bulk compounds, and assuming that the fractal aggregates are composed of poly-disperse distributions of constituent particles with radii ranging from 5 to 100 nm. These sizes were confirmed from measurements of the particle size distributions and microscopic imaging. Finally, the particle growth kinetics of the Fe-containing systems exhibit unexpectedly rapid agglomerative coagulation. This was modelled by assuming an initial period of coalescent particle growth resulting from diffusional (Brownian) coagulation to form primary particles; further growth of these particles is then dominated by long-range magnetic dipole–dipole interactions, leading to the fractal aggregates observed. The atmospheric implications of this work are then discussed.  相似文献   

Temperature and pressure effects on⁴⁰Ar³⁹Ar systematics     

M. Ozima  I. Kaneoka  M. Yanagisawa 《Earth and Planetary Science Letters》1979,42(3):463-472

The effects of thermal and compressional treatment on⁴⁰Ar-³⁹Ar systematics have been investigated on three artificially heated biotite samples (heated for 1 hour at 700°C and 860°C in air and 700°C in vacuum respectively) and uniaxially compressed granite (p = 1400bar) and basalt samples (p = 1650bar). The⁴⁰Ar-³⁹Ar results for the disturbed samples are compared with those for undisturbed samples. Except for the vacuum-heating case, the effects of the disturbances may be interpreted as the combined effect of a partial loss of radiogenic⁴⁰Ar from the sample and an incorporation of air Ar into the sample. Common diagnostic effects are (1) reduction of the total fusion age, (2) distortion of the age spectrum and, if the degree of the partial Ar loss is small, (3) approximate preservation of the isochron age, and (4) reduction of the intercept value (⁴⁰Ar/³⁶Ar) in the isochron plot.The features observed in the age spectra of artificially disturbed samples are rather common in geologically disturbed samples, suggesting that the artificial disturbances simulate the effects of geological disturbances on⁴⁰Ar-³⁹Ar systematics.  相似文献   

Experimental study of gold activation-transportation in the process of potash metasomatism-alteration——North China platform gold deposit taken as an example     

WANG Yurong  HU Shouxi 《中国科学D辑(英文版)》2001,44(1)

Chemical reactions of plagioclase, biotite and their singleminerals, as well as a mineral mixture of (plagioclase +biotite+quartz), with KCl and (KCl+KHCO3) solutions were carried out at 150400℃ and 5080 MPa. Experiments show that alkaline fluid promotes plagioclase’s changing into potash feldspar, while acid fluid helps plagioclase, potash feldspar and biotite alteration form chlorite and sericite. After chemical reaction the acidity-alkalinity of solutions often changes reversely. It was observed that gold dissolved from the tube wall and recrystallized on the surfaces of biotite and pyrite. Therefore the transportation and enrichment of gold are related to the elementary effect of the fluid-mineral interfaces. Fe3+-Fe2+, as an oxidition-reduction agent, and volatile components Cl? and CO2 play important roles in the reaction process.  相似文献   

Structure of volcanic glasses from the NMR-EPR perspective: a preliminary application to the Neapolitan Yellow Tuff     

R. Petrini  C. Forte  G. Contin  C. Pinzino  G. Orsi 《Bulletin of Volcanology》1999,60(6):425-431

Glass samples from alkali-trachytic pumice of the Lower Member (LM, level LM1) and Upper Member (UM) of the Neapolitan Yellow Tuff at Campi Flegrei Caldera were studied by nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy. The EPR data show that the relative occupancy of the different iron sites varies in samples from the Lower Member LM1 and Upper Member of the eruptive sequence. The LM1 glasses are characterized by a more homogeneous distribution of the cationic site population of iron compared with UM and by a different Fe³⁺/Al³⁺ substitution in the C_2v symmetrical sites of the silicate framework. ²⁹Si MAS NMR spectra on glasses indicate that LM1 glasses are more depolymerized than UM glasses, indicating the existence of structurally distinct magma batches. ²⁷Al MAS NMR spectra indicate the occurrence in UM glasses of aluminum in both tetrahedral and octahedral coordination; the observed Al^VI is believed to be a primary feature of the glass, since ²⁷Al CP-MAS NMR experiments do not reveal detectable esa-hydrated Al. The Al in sixfold coordination could be ascribed either to the more abundant alkali–OH terminations in UM, in which alkalies would be extracted from their charge-balance role for Al, thus altering its fourfold structural position, or to permanent compaction during fast cooling and decompression of high-pressure melts. ²³Na CP-MAS NMR experiments indicate the existence of Na–OH groups in both LM1 and UM glasses, relatively more abundant in the latter. Although preliminary, the results indicate the possible application of atomic-scale studies to variables that determine the regimes of explosive volcanism. Received: 1 July 1998 / Accepted: 1 October 1998  相似文献   

A  3.5 Ga record of water-limited, acidic weathering conditions on Mars     

Joel A. Hurowitz  Scott M. McLennan 《Earth and Planetary Science Letters》2007,260(3-4):432-443

The secondary mineral budget on Earth is dominated by clay minerals, Al-hydroxides, and Fe-oxides, which are formed under the moderate pH, high water-to-rock ratio conditions typical of Earth's near-surface environment. In contrast, geochemical analyses of rocks and soils from landed missions to Mars indicate that secondary mineralogy is dominated by Mg (± Fe, Ca)-sulfates and Fe-oxides. This discrepancy can be explained as resulting from differences in the chemical weathering environment of Earth and Mars. We suggest that chemical weathering processes on Mars are dominated by: (1) a low-pH, sulfuric acid-rich environment in which the stoichiometric dissolution of labile mineral phases such as olivine and apatite (± Fe–Ti oxides) is promoted; and (2) relatively low water-to-rock ratio, such that other silicate phases with slower dissolution rates (e.g., plagioclase, pyroxene) do not contribute substantially to the secondary mineral budget at the Martian surface. Under these conditions, Al-mobilization is limited, and the formation of significant Al-bearing secondary phases (e.g., clays, Al-hydroxides, Al-sulfates) is inhibited. The antiquity of rock samples analyzed in-situ on Mars suggest that water-limited acidic weathering conditions have more than likely been the defining characteristic of the Martian aqueous environment for billions of years.  相似文献   

Metal-olivine associations and NiCo contents in two Apollo 12 mare basalts     

R.H. Hewins  J.I. Goldstein 《Earth and Planetary Science Letters》1974,24(1):59-70

Olivine crystals in mare basalts 12004,8 and 12022,12 are normally zoned with Cr-poor rims. The Ni content of rare 2–10-μm metal inclusions in olivine decreases markedly as Fe/Mg in their immediate olivine hosts increases. Each metal grain appears to have been enclosed by late olivine almost immediately after it crystallized. The fractionation trend for the olivine and metal contrasts with the subsolidus equilibration trend for pallasites. For the basalts, not even local equilibration of Fe, Ni and Co at metal/olivine interfaces can be detected by microprobe. Ni and Co concentrations range from about 300 ppm in olivine cores to about 70 ppm in rims. The limits of detection, at 95% confidence, are 36 ppm (Ni) and 25 ppm (Co). The distribution of Ni and Co in olivine, like that of Mg and Cr, records the depletion of these elements in the melt.Fractional solidification models, using the Ni and Co concentrations of the whole rock, and Ni and Co concentrations of the earliest formed olivine, metal and “opaques” as initial compositions, allow metal and olivine compositions to be predicted if the order of crystallization is known. Conversely the order of crystallization can be established if known olivine and metal compositions are reproduced. Calculated Ni and Co contents for metal and olivine in these basalts correspond to observed concentrations only where metal precipitation is delayed until the liquid has crystallized 4–5 wt.% olivine.  相似文献   

Oxidation state of iron in plagioclase from lunar basalts     

S.S. Hafner  D. VirgoD. Warburton 《Earth and Planetary Science Letters》1971

Mossbauer spectra of⁵⁷Fe at 77 and 295°K in the plagioclase from basalts 10044 and 12021 show that iron is in the high-spin ferrous state and located at at least two distinct positions with different coordination numbers. Some excess resonant absorption is probably due to Fe³⁺ although the Fe³⁺ doublet could not be positively resolved. The ratio Fe³⁺/(Fe²⁺ + Fe³⁺) is estimated to be between 0.02 and 0.1.  相似文献   

地震动滞回能量谱衰减规律研究   总被引：2，自引：0，他引：2  

公茂盛  翟长海  谢礼立  章文波 《地震工程与工程振动》2004,24(2):8-14

本文选用美国西部California州15次较大地震中的266条强地震动记录,利用衰减关系建立了滞回能量谱,分析了场地条件、延性系数、震级及距离等参数对滞回能量谱的影响。研究发现,场地条件对滞回能量谱影响很大,随着场地变软,滞回能量谱变大,与A B类场地相比,C类场地的滞回能量谱平均要高出70％左右,D类场地则要高出170％左右。随着延性系数的增大,滞回能量谱有增大的趋势,尤其是当延性系数由2变到4或6时更为明显,但当延性系数增加到一定程度时,滞回能量谱的差别不大,延性系数为4和6时的滞回能量谱差别不大,甚至在周期较大时,延性系数为6的滞回能量谱反而小于延性系数为4时的滞回能量谱。另外,研究结果表明,大的震级和小的距离对结构产生比较大的滞回能量需求。利用本文结果,可以估计未来地震中结构物所遭受滞回能量的大小。  相似文献   

High-pressure phase transformations in the system of MgSiO₃-FeSiO₃     

Li-Chung Ming  William A. Bassett 《Earth and Planetary Science Letters》1975,27(1):85-89

Two synthetic pyroxenes (FeSiO₃, MgSiO₃) and five natural pyroxenes with compositions of about Fs₈₀En₂₀, Fs₆₀En₄₀, Fs₅₀En₅₀, Fs₄₀En₆₀, and Fs₂₀En₈₀ have been subjected to pressures up to250 ± 50kbars at a temperature of about1500 ± 200°C in a diamond anvil cell heated by an infrared laser beam. After quenching and unloading X-ray data analysis indicates that (1) those with Mg less than 50% undergo the following reactions: 2(Mg,Fe)SiO₃ (pyroxene) → (Mg,Fe)₂SiO₄ (spinel) + SiO₂ (stishovite) → 2(Mg,Fe)O (magnesiowu¨stite) + SiO₂ (stishovite) with increase of pressure, and (2) those with Mg higher than 60%, undergo the following reactions: 2(Mg,Fe)SiO₃ (pyroxene) → (Mg,Fe)₂SiO₄ (spinel) + SiO₂ (stishovite) → 2(Mg,Fe)SiO₃ (hexagonal phase) → 2(Mg,Fe)O (magnesiowu¨stite) + SiO₂ (stishovite) with increase of pressure.  相似文献   

Disproportionation of spinels to mixed oxides: significance of cation configuration and implications for the mantle     

I.N.S. Jackson  R.C. Liebermann  A.E. Ringwood 《Earth and Planetary Science Letters》1974,24(2):203-208

Experimental study of the phase boundary for the disproportionation of the inverse spinel Mg₂SnO₄ into its isochemical mixed oxides indicates a slope dP/dT = 40 ± 10bars/°K. This positive slope is consistent with the large entropies of inverse (relative to normal) spinels predicted from high-temperature entropy-molar volume systematics. Thermodynamic data do not support the existence of a distinctly negative slope for the proposed disproportionation of Mg₂SiO₄ normal spinel. Evidence from X-ray and phase equilibria studies suggests the possibility that Si⁴⁺, Mg²⁺, and Fe²⁺ share the octahedral sites in silicate spinels under mantle conditions. The consequences of this partial inverse character are a positive slope for the postulated spinel-mixed oxide phase boundary near 650 km depth, removal of a widely accepted constraint on mantle-wide convection, and anomalous elasticity-density behaviour within the transition zone.  相似文献   

The occurrence state of vanadium in the black shale-hosted vanadium deposits in Shangling of Guangxi Province,China     

《Acta Geochimica》2015,(4)

The Shangling vanadium deposit, which occurs in the Lower Devonian Tangding formation black rock series strata, has V2O5 reserves of more than 1.5 million tons and prospective reserves of more than 2 million tons. Preliminary studies on the occurrence state of vanadium(V) in this deposit have been conducted by artificial heavy minerals concentrates, leaching experiments, scanning and transmission electron microscopy and X-ray powder diffraction.These experiments have revealed no independent vanadium mineral occurrences in the Shangling vanadium deposit and the percentages of water-soluble vanadium, hydrochloric acid soluble vanadium and HF soluble vanadium were1.93 %, 21.42 % and 76.47 %, respectively. Based on our data and earlier research, we estimate that the valences state of V absorbed onto the surface of organic matter or clastic particles are +5 and +4, accounting for 10.00 % and13.35 % of the total amount of V, respectively and the valences state of V that exist in the octahedral crystal lattice of authigenic illite include +3 and +4, accounting for71.64 % and 4.83 % of the total amount of V, respectively.By calculating the correlation between the total organic carbon and V, we infer that after deposition and before entering the crystal lattice of illite, V occurs in the form of humate complex or is adsorbed by organic matter. About4.24 % of the Al is in the octahedral crystal lattice of illite,which was replaced by the vanadium under the metallogenic environments of Shanglin.  相似文献   

High-pressure X-ray diffraction studies on β- and γ-Mg₂SiO₄     

Seishiro Mizukami  Akihito Ohtani  Naoto Kawai  Eiji Ito 《Physics of the Earth and Planetary Interiors》1975,10(2):177-182

Pressure effects on the lattice parameters of β- and γ-Mg₂SiO₄ have been measured at room temperature and at pressures up to 100 kbar using a multi-anvil high-pressure X-ray diffraction apparatus. The volume changes (ΔV/V₀) at 90 kbar are 5.4 · 10^?2 and 4.2 · 10^?2 for β- and γ-Mg₂SiO₄, respectively. Isothermal bulk moduli at zero pressure have been calculated from least-square fits of the data to straight lines. They turn out to be 1.66 ± 0.4 and 2.13 ± 0.1 Mbar for β- and γ-Mg₂SiO₄, respectively. The α → γ transition obeys Wang's linear V_φ?ρ relation but the α → β transition does not.  相似文献