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1.
《Chemie der Erde / Geochemistry》2022,82(4):125915
Thermodynamic properties of several TeO2 polymorphs and metal tellurites were measured by a combination of calorimetric techniques. The most stable TeO2 polymorph is α-TeO2, with its enthalpy of formation (ΔfHo) selected from literature data as ?322.0 ± 1.3 kJ·mol?1. β-TeO2 is metastable (in enthalpy) with respect to α-TeO2 by +1.40 ± 0.07 kJ·mol?1, TeO2 glass by a larger amount of +14.09 ± 0.11 kJ·mol?1. >200 experimental runs and post-synthesis treatments were performed in order to produce phase-pure samples of Co, Cu, Mg, Mn, Ni, Zn tellurites. The results of the hydrothermal and solid-state syntheses are described in detail and the products were characterized by powder X-ray diffraction. The standard thermodynamic data for the Te(IV) phases are (standard enthalpy of formation from the elements, ΔfHo in kJ·mol?1, standard third-law entropy So in J·mol?1·K?1): Co2Te3O8: ΔfHo = ?1514.2 ± 6.0, So = 319.2 ± 2.2; CoTe6O13: ΔfHo = ?2212.5 ± 8.1, So = 471.7 ± 3.3; MgTe6O13: ΔfHo = ?2525.8 ± 7.9, So = 509.2 ± 3.6; Ni2Te3O8: ΔfHo not measured, So = 293.3 ± 2.1; NiTe6O13: ΔfHo = ?2198.7 ± 8.2, So = 466.5 (estimated); CuTe2O5: ΔfHo = ?820.2 ± 3.3, So = 187.2 ± 1.3; Zn2Te3O8: ΔfHo = ?1722.5 ± 4.0, So = 299.3 ± 2.1. The solubility calculations show that the Te(IV) concentration in an aqueous phase, needed to produce such phases, must be at least 3–5 orders of magnitude higher than the natural Te background concentrations. The occurrence of these minerals, as expected, are restricted to hotspots of Te concentrations. In order to produce more reliable phase diagrams, more work needs to be done on the thermodynamics of potential competing phases in these systems, including Te(VI) phases. 相似文献
2.
Henrik Friis Adrian A. Finch C. Terry Williams John M. Hanchar 《Physics and Chemistry of Minerals》2010,37(6):333-342
The photoluminescence properties of synthetic zircon, ZrSiO4, doped with REE3+ (REE = Pr, Sm, Eu, Gd, Dy, Ho, Er) were investigated using combined excitation and emission spectroscopy. All samples showed
luminescence characteristics of intra-ion energy transitions, similar to other lanthanide-doped materials. However, the relative
intensities were dependent on the energy of excitation and the presence of charge-transfer bands were inferred from excitation
spectra. From the data, we conclude that the lanthanides in zircon occur in more than one type of coordination. Energy transfer
between different lanthanides was observed in some co-doped samples and emissions that were unassigned in previous studies
have been assigned to specific lanthanides based on excitation spectroscopy. 相似文献
3.
4.
Mag. Ronald Miletich 《Mineralogy and Petrology》1993,48(2-4):129-145
Summary The crystal structures of copper-substituted manganese-denningites, Mn(Mn1–x
Cu
x
)(Te2O5)2 (0 x 1), were refined in space groupP42/nbc from single-crystal X-ray data. Single crystals with different degree of Cu-substitution suitable for X-ray investigation were synthesized under hydrothermal conditions, varying the Cu/Mn ratio and thepH-value. One main feature of the crystal structure is the distribution of Mn and Cu atoms among an eight and a six-coordinated site, respectively. Bond strength calculations support the site occupancies of the MnO8-polyhedra and MeO6-octahedra (Me = Cu., Mn1–x
). The decrease in length of the four Me[6]-O bonds clearly correlates with the increase of the Cu-substitution resulting in a distortion of the octahedra according to the Jahn-Teller effect of divalent copper. The stronger decrease of the lattice parameterc as compared toa is probably due to the variations of the bond lengths.
Dedicated to Prof Dr. Josef Zemann on the occasion of his 70th birthday
With 10 Figures 相似文献
Kupfer-substituierte Mangan-Denningite, Mn(Mn1–x Cu x )(Te2O5)2 (0 x 1): Synthese und Kristallchemie
Zusammenfassung Die Kristallstrukturen von Kupfer-substituierten Mangan-Denningiten, Mn(Mn–x Cu x )(Te2O5)2 (0 x 1) wurden mittels Einkristall-Röntgenbeugungsdaten in der RaumgruppeP42/nbc verfeinert. Geeignete Einkristalle mit unterschiedlich starker Cu-Substitution wurden unter hydrothermalen Bedingungen durch Variieren des Cu/Mn-Verhältnisses bzw. despH-Wertes dargestellt. Ein wesentlicher struktureller Gesichtspunkt ist die Verteilung der Mn und Cu-Atome auf eine acht- bzw. sechskoordinierte Punktlage. Die Verringerung von vier Me[6]-O Bindungslängen ist klar korrelierbar mit zunehmender Cu-Substitution, und führt zu einer Verzerrung der Oktaeder gemäß dem für zweiwertiges Kupfer bekannten Jahn-Teller Effekt. Bindungsstärkenberechnungen belegen die Besetzung der MnO8-Polyeder und MeO6-Oktaeder (Me = Cu x Mn1–x ). Die bevorzugte Verkleinerung der Gitterkonstantec gegenübera kann auf die Variationen der Bindungslängen zurückgeführt werden.
Dedicated to Prof Dr. Josef Zemann on the occasion of his 70th birthday
With 10 Figures 相似文献
5.
Bo PENG Shurong XIE Meilian XIAO Fucheng WU Zhi SONG 《中国地球化学学报》2006,25(B08):23-24
The Taojiang Mn ore deposit was exploited in the early 1960s, and waste rocks were developed since then. Because the Mn ores were hosted within the metal-enriched black shales （Peng et al., 2004）, the continuous mining has led to the exposure of an immense quality of black shales, which might cause serious impacts on environments. The present study deals with this environmental issue with samples from the waste rocks, and from the surrounding soils and surface water. The mineralogy of the waste rock was studied using EMPA, then a large number of elements in all waste rock, soil, and water samples were analyzed at a wide range of concentrations with high accuracy using an Elan6000 ICP-MS machine at Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The waste rock is composed mostly of black shales, with minor Mn carbonates. Both black shales and Mn carbonates of the waste rock contain many sulfide minerals, mainly pyrite, with minor galena, sphalerite, chalcopyrite, and others. The waste rocks are enriched in many metals including Sc, V, Cr, Co, Ni, Fe, Mn, Cu, Zn, Pb, Th, U, Mo, Sb, Sn, Tl, and others, and the metals are mostly hosted within the sulfides. Weathering of waste rocks might cause emission of the following metals： V, Cd, Ni, Th, U, Mo, Sb, Tl, Sc, Cr, Cu, Zn, Sn, and minor Co, and Pb. The surrounding soils are highly enriched in Cr, Co, Cu, Zn, Mn, Mo, Cd, Tl, and Pb, with the enrichment factors of 2.67.3.8, 7.26, 7.27, 8.2, 5.7, 13, and 5.4, respectively. The element ratios （Rb/Cs, Fe/Mn, Nb/Zr, Hf/Zr, and Ba/Sr） and REE distribution patterns of the soils are similar to those of the waste rocks and bedrocks. 相似文献
6.
本文首先详细研究了含Mn2 和Fe3 的致色矿物菱锰矿、鲕状赤铁矿、云母赤铁矿和镜铁矿的可见光吸收光谱及其一阶导数谱,鲕状赤铁矿、云母赤铁矿和镜铁矿的可见光吸收一阶导数谱的红光区的吸收谷的位置的变化表明随赤铁矿结晶度的降低,吸收谷由586.4nm移至577.4nm,而菱锰矿展示出了Mn2 的因电子跃迁产生的四个典型吸收及其一阶导数谱上577nm的吸收谷的强度比赤铁矿相应谷的强度低一个数量级,表明其电子跃迁的致色机理与赤铁矿的染色机理完全不同。依据赤铁矿的结晶度和鲕状赤铁矿与大洋红层中赤铁矿的沉积成因相似的原则遴选出鲕状赤铁矿为含Fe3 致色矿物,依据菱锰矿是和方解石具有相似结构且为红色的原则选取菱锰矿为含锰致色矿物,并佐以化学纯氧化镁为基体配制了一系列的含菱锰矿、鲕状赤铁矿和菱锰矿及鲕状赤铁矿的两相或三相混合物。详细研究了三类混合物的可见光吸收光谱的一阶导数谱,发现含菱锰矿和含鲕状赤铁矿在573nm附近均存在一吸收谷,鲕状赤铁矿的重量分数低至0.05%时仍可见一明显吸收谷且该吸收谷移至565nm附近,菱锰矿在低至0.50%时也可见这一吸收且在低至0.11%时仍可显示出菱锰矿的信息,其575nm的吸收峰未见偏移;混合物可见光一阶导数吸收谱上鲕状赤铁矿的575nm附近的吸收谷的强度随鲕状赤铁矿的重量分数的升高而增强,而所有的配制混合物中该吸收谷的位置低于577.4nm的事实也表明为使致色矿物和氧化镁混合均匀的研磨降低了赤铁矿的结晶度。本研究表明Mn2 的电子跃迁激发和细小、结晶差的赤铁矿的染色共同造就了意大利白垩纪远洋红色灰岩的红色。 相似文献
7.
N. V. Chukanov R. K. Rastsvetaeva S. N. Britvin A. A. Virus D. I. Belakovskiy I. V. Pekov S. M. Aksenov B. Ternes 《Geology of Ore Deposits》2011,53(8):767-774
A new heterophyllosilicate mineral schüllerite was found in the L?hley basalt quarry in the Eifel volcanic region, Germany,
as a member of the late mineral assemblage comprising nepheline, leucite, augite, phlogopite, magnetite, titanite, fresnoite,
barytolamprophyllite, fluorapatite, perovskite, and pyrochlore. Flattened brown crystals of schüllerite up to 0.5 × 1 × 2
mm in size and their aggregates occur in miarolic cavities of alkali basalt. The mineral is brittle, with a Mohs hardness
3–4 and perfect cleavage parallel to (001). D
calc = 3.974 g/cm3. Its IR spectrum is individual and does not contain bands of OH−, CO32− or H2O. Schüllerite is biaxial (−), α = 1.756(3), β = 1.773(4), γ = 1.780(4), 2V
meas = 40(20)°. Dispersion is weak, r < ν. Pleochroism is medium X > Y > Z, brown to dark brown. Chemical composition (electron microprobe, mean of five-point analyses, Fe2+/Fe3+ ratio determined by the X-ray emission spectroscopic data, wt %): 3.55 Na2O, 0.55 K2O, 3.89 MgO, 2.62 CaO, 1.99 ArO, 28.09 BaO, 3.43 FeO, 8.89 Fe2O3, 1.33 Al2O3, 11.17 TiO2, 2.45 Nb2O5, 26.12 SiO2, 2.12 F, −0.89 -O=F2, 98.98 in total. The empirical formula is (Ba1.68Sr0.18K0.11Na1.05Ca0.43Mn0.47Mg0.88Fe0.442+Fe1.023+Ti1.28Nb0.17Al0.24)Σ7.95Si3.98O16.98F1.02. The crystal structure was refined on a single crystal. Schüllerite is triclinic, space group P1, unit cell parameters: a = 5.4027(1), b = 7.066(4), c = 10.2178(1)?, α = 99.816(1), β = 99.624(1), γ = 90.084(1)°, V = 378.75(2) ?3, Z = 1. The strongest lines of the X-ray powder diffraction pattern [d, ?, (I, %)]: 9.96(29), 3.308(45), 3.203(29), 2.867(29), 2.791(100), 2.664(46), 2.609(36), 2.144(52). The mineral was named in honor
of Willi Schüller (born 1953), an enthusiastic, prominent amateur mineral collector, and a specialist in the mineralogy of
Eifel. Type specimens have been deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow,
registration no. 3995/1,2. 相似文献
8.
《Applied Geochemistry》2000,15(6):725-735
An investigation of the chemistry of surface precipitates on stream pebbles and Potamopyrgus (Hydrobia) jenkinsi (Smith) shells has been undertaken on samples collected from a contaminated river in SW England, UK. Samples were analysed by LA-ICP-AES to evaluate the technique as a suitable method to use on small environmental samples, and to determine if the Pb/Fe and Zn/Mn ratios of the coatings on the two substrates were comparable. The ratios in the coatings are similar in these samples types, but are generally higher on the pebble samples. Results have been compared to a previous investigation of pebble coating chemistry in the river, and are shown to have the same spatial distribution but very different absolute values due to changes in environmental conditions in the river over time. 相似文献
9.
10.
Haitaite-(La), (La, Ce)(U4+, U6+, Fe2+)(Fe3+, Al)2(Ti, Fe2+, Fe3+)18O38, is a new member of the crichtonite group. It is named after the Haita Village in the Miyi County of Sichuan Province, China, where the mineral was discovered. The mineral occurs as black opaque centimeter-sized aggregates in the external contact zone between the Neoproterozoic (~800 Ma) alkali feldspar granite and the Mesoproterozoic (~1700 Ma) micaschist. In the studied sample, haitaite-(La) is associated with other minerals, including ilmenite, magnetite, rutile, zircon, brannerite and uraninite. The new mineral is a black, metallic phase and has a Mohs hardness of 6, with a density of 4.99 g/cm3 (calculated) and 5.03 g/cm3 (measured). Haitaite-(La) is opaque in transmitted light and grayish-white under reflected light, with a reflectivity between 22.5% and 16.42% in the 400–700 nm band (SiC, in the air). The compositions of the mineral were measured by EPMA, the U4+/U6+ ratio was determined by X-ray photoelectron spectroscopy and the Fe2+/Fe3+ ratio was determined by M?ssbauer spectroscopy. Haitaite-(La) is trigonal, belongs to R3ˉ and has unit-cell parameters a = 10.3678(5) ?, c = 20.8390(11) ?, V = 1939.9(2) ?3, Z = 3. The crystalline structure is composed of octahedra with 9 layers of close-packed octahedra (M1, M3, M4, M5), tetrahedra (M2) and contains large 12-coordinated M0 sites. 相似文献
11.
12.
Th. Fehr R. Hochleitner A. Laumann E. Schmidbauer J. Schneider 《Physics and Chemistry of Minerals》2010,37(3):179-189
Mineralogical analysis, electrical conductivity and thermopower are reported for monocrystalline heterosite (Fe3+, Mn3+)PO4 with the orthorhombic olivine-type structure. The 57Fe Mössbauer spectrum could be adequately described using two Fe3+ doublets. By impedance spectroscopy (20 Hz–1 MHz) the electrical DC conductivity σDC and AC conductivity σAC were determined parallel (∥) and perpendicular to the [001] direction (space group Pnma) in the range ～160–440 K. The graph log σDC?1/T shows a slightly bent curve in both directions with activation energies of E A ～0.30 and ～0.15 eV in the high and low temperature ranges, respectively. The reduced E A is associated with electronic conduction; σDC ∥ [001] follows Mott’s T 1/4 variable range hopping law at lower temperatures with hopping between localized levels. The values of σAC are increased relative to σDC at high frequencies and low temperatures, obeying Jonscher’s universal dynamic response law; for σAC ∥ [001], the variation with temperature of the frequency exponent is in fair agreement with the model of small polaron hopping. The absolute thermopower Θ is negative and low between ～295 and ～440 K, Θ does hardly vary with temperatures in both directions; the temperature independency of Θ ∥ [001] is consistent with the small polaron hopping model. 相似文献
13.
Hugh S. C. O'Neill 《Contributions to Mineralogy and Petrology》1998,133(3):284-296
The partitioning of Fe2+ and Mn2+ between (Fe, Mn)TiO3 and (Fe, Mn)2SiO4 solid solutions in the system FeO-MnO-TiO2-SiO2 has been experimentally investigated at 1100 ∘C and pressures of 1 bar and 25 kbar, over a wide range of Fe/Mn ratios, using electron microprobe analysis of quenched run
products. The ilmenite solid solution in this system is within analytical uncertainty a simple binary between FeTiO3 and MnTiO3, but the olivine solid solution appears to contain up to 2.5 wt% TiO2. The Fe-Mn partitioning results constrain precisely the difference in the thermodynamic mixing properties of the two solid
solutions. If the mixing properties of (Fe, Mn)2SiO4 solid solutions are assumed to be ideal, as experimentally determined by Schwerdtfeger and Muan (1966), then the ilmenite
is a regular, symmetric solution with W
ilm
Fe-Mn=1.8±0.1 kJ mol−1. The quoted uncertainty does not include the contribution from the uncertainty in the mixing properties of the olivine solution,
which is estimated to be ±1.8 kJ mol−1, and which therefore dominates the uncertainty in the present results. Nevertheless, this result is in good agreement with
the previous experimental study of O'Neill et al. (1989), who obtained W
ilm
Fe-Mn=2.2±0.3 kJ mol−1 from an independent method. The results provide another item of empirical evidence supporting the proposition that solid
solutions between isostructural end-members, in which order-disorder effects are not important, generally have simple thermodynamic
mixing properties, with little asymmetry, modest excess entropies, and excess enthalpies approximately proportional to the
difference in the molar volumes of the end-members.
Received: 11 February 1998 / Accepted: 29 June 1998 相似文献
14.
《Geoforum》2017
REDD+ is a global scale climate change mitigation program aiming at creating financial values for carbon stored in forests. According to the proponents, REDD+ is an effective, efficient, and equitable mechanism for reducing emissions from deforestation and forest degradation. Some scholars question this assumption, and some call for further analysis to understand how REDD+ can contribute to economic, environmental, and social goals, and what are the synergies and trade-offs between them. The purpose of this paper is to contribute to the debate about whether REDD+ projects can be brought to accommodate economic (efficiency), environmental (effectiveness), and social (equity) concerns at the same time by drawing on own field results from a REDD+ project in Cambodia. The paper follows three tracks. The first is to develop and explain the conceptual and analytical framework for our empirical investigations. The second is to explain the field results. The third track is to discuss what general lessons can be learnt. Our case illustrates some of the mechanisms that are likely to work against the willingness and ability of REDD+ projects to ensure local people’s net-gains, and the risk that effectiveness and equity will suffer if REDD+ projects rely solely on the private market. Our case thus indicates a tension between the objectives of creating financial value from carbon stored in trees through the private market, and environmental and social equity concerns. However, we call for more comparative studies of REDD+ projects, and hope our conceptual framework can assist such studies. 相似文献
15.
A. Dúzs-Moore P. B. Leavens R. E. Jenkins II N. M. Altounian 《Mineralogy and Petrology》2003,79(3-4):225-241
Summary Wollastonite occurs abundantly at the Sterling Hill Fe–Zn–Mn ore deposit, Ogdensburg, New Jersey, one of the few occurrences of wollastonite in regionally metamorphosed rocks; it is absent from the surrounding Franklin marble. Wollastonite occurs in two distinct bands along the inner margins of the synclinal ore deposit. Minerals associated with wollastonite include calcite, grossular-andradite, diopsidic pyroxene, alkali feldspar, and rarely vesuvianite, quartz or bustamite. Assuming the generally accepted values of 750°C at 5kbar at Sterling Hill during metamorphism in the Grenville Orogeny, thermodynamic modeling of reactions involving garnet and wollastonite suggest XCO2 0.35 in the wollastonite-bearing rocks. Infiltrating metamorphic fluid rich in H2O was necessary for the formation of wollastonite; at XCO2 of 0.35, the calculated minimum volumetric water:rock ratio is 0.51. The source of the water is believed to be the dehydration of water-rich phases in adjacent ores or mafic rocks. The chemical compositions, textures, stratigraphy, and calculated metamorphic conditions show that wollastonite formed from calcite and quartz at the peak of the Grenville Orogeny.Present address: Maryland State Highway AdministrationReceived August 18, 2002; revised version accepted February 5, 2003 相似文献
16.
Xiaoyu ZHAO Wuyi WANG Hairong LI Fujian FENG Lizhen WANG 《中国地球化学学报》2006,25(B08):80-81
Brick-tea-type fluorosis is a peculiar endemic disease in China, which had been discovered in minority areas of western China since 1980, and distributed mainly in Tibet, Inner Mongolia, Gansu, Xinjiang, Qinghai and parts of Sichuan Province. The prevalence rate of fluorosis in Tibetan and Mongolian nationality people was higher. Epidemiological investigation showed that fluorosis morbidity and degrees were different in different brick-tea drinking areas, and it was probably caused by drinking various kinds of brick tea from different regions. Therefore, we collected 33 samples of brick tea from six provinces where minority nationalities were accustomed to drinking a large quantity of brick tea. F concentrations were determined by the combustion hydrolysis-ion selective electrode method. The results showed that among the brick teas, the F concentrations ranged from the minimum 74.1 mg/kg in Yunnan Province to the maximum 991.2 mg/kg in Sichuan Province. Besides, there was a great difference among the various kinds of brick tea, and F concentrations decreased in the order of Kang brick tea, Green brick tea, Black brick tea, Mi brick tea, Fu brick tea, Chitsu ping tea, Puerh tea, and Tuo tea. The average F concentration in brick teas was 431.92 mg/kg. 相似文献
17.
18.
康振川 《吉林大学学报(地球科学版)》1984,(3)
在Franckeit矿物中发现了一种新型硫化物(Zn0.5 Mn0.25 Fe0.25) S,用电子衍射、微区分析和高分辨结构像,证明它是一种ZnS型结构的多型体,其堆积序列为……AB AB AB AB CA……,其成分由X光能谱测定为:34.9±0.1％Zn,15.5±0.1％Fe,14.8±0.1％Mn,34.7±0.1％S。 相似文献
19.
20.
Shkolnik S. I. Letnikova E. F. Brusnitsyn A. I. Lepekhina E. N. Ivanov A. V. Perova E. N. 《Doklady Earth Sciences》2021,497(1):195-199
Doklady Earth Sciences - Isotope study of ore-bearing rocks at Fe–Mn rift deposits of the Atasu and Zhezdy (Dzhezdy) ore districts in Central Kazakhstan has been carried out for the first... 相似文献