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1.
The solubility of Gd2Ti2O7 ceramic in acidic solutions (HCl and HClO4) was studied at 250°C and saturation vapor pressure within pH 2.5–5.2. The dissolution process occurs mainly via two reactions: 0.5 Gd2Ti2O7(cr) + 3H+ = Gd3+ + TiO2(cr) + 1.5 H2O at pH < 3 and 0.5Gd2Ti2O7(cr) + H+ + 0.5H2O = Gd(OH) 2 + TiO2(cr) at pH 3–5. The thermodynamic equilibrium constants were calculated at the 0.95 confidence level as log K (1) o = 4.12 ± 0.47; = ?0.97 ± 0.16 at 250°C. It was shown that Gd3+ undergoes hydrolysis in solutions with pH > 3, and the species Gd(OH) 2 + dominates up to at least pH 5. At pH < 3, Gd occurs in solutions as Gd3+. The second constant of Gd3+ hydrolysis was determined at 250°C as K o = ?5.09 ± 0.5, and the thermodynamic characteristics of the initial Gd2Ti2O7 solid phase were determined: S 298.15 o = 251.4 J/(mol K) and ΔfG 298.15 o = ?3630 ± 10 kJ/mol.  相似文献   

2.
Based on the synthesis of hydrogeochemical materials on Sb occurrence in carbonate and thermal waters and thermodynamic simulations, genetic analysis was conducted of the transformations of probable Sb migration species (particularly oxygen-bearing and sulfide ones), and their transformations were calculated depending on the main parameters of hydrogeochemical systems (\(P_{CO_2 } \), T, R/W, Eh, and pH). The oxygen 2HSbO 2 0 + 3H2S = Sb2S3 + 4H2O (2SbO 2 ? + 3HS? + 5H+ = Sb2S3 + 4H2O) and sulfide HSb2S 4 ? + H+ = Sb2S3 cr + H2S (Sb2S 4 2? + 2H+ = Sb2S3cr + H2S) models for the genesis of hydrogenic Sb2S3(cr) were simulated. Information on occurrences of carbonate and thermal waters in various regions worldwide was generalized, and the reasons were identified for the geochemical separation of As and Sb in carbonate and thermal waters. The causes and conditions of an increase in Sb concentrations in thermal waters were revealed, and Sb migration species in carbonate and thermal waters were identified for various parameters of hydrogeochemical systems. Variations in Sb speciation were demonstrated for hydrogeochemical systems depending on their boundary conditions (\(P_{CO_2 } \), T, and R/W). Models were outlined responsible for the precipitation of Sb2S3(cr) from carbonate and thermal waters.  相似文献   

3.
The paper presents the results of a thermochemical and thermal study of cancrinite, (Na6.93Ca0.545K0.01)Σ7.485[(Si6.47Al5.48Fe0.05)Σ12O24](CO3)1.25 · 2.30 H2O, and cancrisilite, (Na7.17 Ca0.01)Σ7.18[(Si7.26Al4.70Fe0.04)Σ12O24][(CO3)1.05(OH)0.21(PO4)0.04(SO4)0.01] · 2.635 H2O, from the Khibina-Lovozero Complex, Kola Peninsula, Russia. Stages of the thermal decomposition of these minerals were studied using IR spectroscopy. The enthalpies of formation of the minerals from elements were determined by melt drop solution calorimetry: Δ f H el 0 (298.15 K) = ?14 490 ± 16 kJ/mol for cancrinite and ?14302 ± 17 kJ/mol for cancrisilite. The values of Δ f H el 0 (298.15 K), S o(298.15 K), and Δ f H el 0 (298.15 K) are determined for cancrinite and cancrisilite of theoretical composition.  相似文献   

4.
For the first time, chemical characterization of PM10 aerosols was attempted over the Bay of Bengal (BoB) and Arabian Sea (AS) during the ICARB campaign. Dominance of SO 4 2? , NH 4 + and NO 3 ? was noticed over both the regions which indicated the presence of ammonium sulphate and ammonium nitrate as major water soluble particles playing a very important role in the radiation budget. It was observed that all the chemical constituents had higher concentrations over Bay of Bengal as compared to Arabian Sea. Higher concentrations were observed near the Indian coast showing influence of landmass indicating that gaseous pollutants like SO2, NH3 and NO x are transported over to the sea regions which consequently contribute to higher SO 4 2? , NH 4 + and NO 3 ? aerosols respectively. The most polluted region over BoB was 13°?19°N and 70°?90°E while it was near 11°N and 75°E over AS. Although the concentrations were higher over Bay of Bengal for all the chemical constituents of PM10 aerosols, per cent non-sea salt (nss) fraction (with respect to Na) was higher over Arabian Sea. Very low Ca2+ concentration was observed at Arabian Sea which led to higher atmospheric acidity as compared to BoB. Nss SO 4 2? alone contributed 48% of total water soluble fraction over BoB as well as AS. Ratios SO 4 2? /NO ? 3 over both the regions (7.8 and 9 over BoB and AS respectively) were very high as compared to reported values at land sites like Allahabad (0.63) and Kanpur (0.66) which may be due to very low NO.3 over sea regions as compared to land sites. Air trajectory analysis showed four classes: (i) airmass passing through Indian land, (ii) from oceanic region, (iii) northern Arabian Sea and Middle East and (iv) African continent. The highest nss SO 4 2? was observed during airmasses coming from the Indian land side while lowest concentrations were observed when the air was coming from oceanic regions. Moderate concentrations of nss SO2. 4 were observed when air was seen moving from the Middle East and African continent. The pH of rainwater was observed to be in the range of 5.9–6.5 which is lower than the values reported over land sites. Similar feature was reported over the Indian Ocean during INDOEX indicating that marine atmosphere had more free acidity than land atmosphere.  相似文献   

5.
Surface snow and lake water samples were collected at different locations around Indian station at Antarctica, Maitri, during December 2004–March 2005 and December 2006–March 2007. Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with low chemical content is 6.2 and of lake water with high chemical content is 6.5. The Na+ and Cl? are the most abundantly occurring ions at Antarctica. Considerable amount of SO 4 2? is also found in the surface snow and the lake water which is attributed to the oxidation of DMS produced by marine phytoplankton. Neutralization of acidic components of snow is mainly done by NH 4 + and Mg2+. The Mg2+, Ca2+ and K+ are nearly equally effective in neutralizing the acidic components in lake water. The NH 4 + and SO 4 2? occur over the Antarctica region mostly in the form of (NH4)2SO4.  相似文献   

6.
A new mineral, droninoite, was found in a fragment of a weathered Dronino iron meteorite (which fell near the village of Dronino, Kasimov district, Ryazan oblast, Russia) as dark green to brown fine-grained (the size of single grains is not larger than 1 μm) segregations up to 0.15 × 1 × 1 mm in size associated with taenite, violarite, troilite, chromite, goethite, lepidocrocite, nickelbischofite, and amorphous Fe3+ hydroxides. The mineral was named after its type locality. Aggregates of droninoite are earthy and soft; the Mohs hardness is 1–1.5. The calculated density is 2.857 g/cm3. Under a microscope, droninoite is dark gray-green and nonpleochroic. The mean (cooperative for fine-grained aggregate) refractive index is 1.72(1). The IR spectrum indicates the absence of S O 4 2? and C O 3 2? anions. Chemical composition (electron microprobe, partition of total iron into Fe2+ and Fe3+ made on the basis of the ratio (Ni + Fe2+): Fe3+ = 3: 1; water is calculated from the difference) is as follows, wt %: 36.45 NiO, 12.15 FeO, 17.55 Fe2O3, 23.78 H2O, 13.01 Cl, ?O=Cl2 ?2.94, total is 100.00. The empirical formula (Z = 6) is Ni2.16Fe 0.75 2+ Fe 0.97 3+ Cl1.62(OH)7.10 · 2.28H2O. The simplified formula is Ni3Fe3+Cl(OH)8 · 2H2O. Droninoite is trigonal, space group R \(\bar 3\) m, R3m, or R32; a = 6.206(2), c = 46.184(18) Å; V = 1540.4(8) Å3. The strong reflections in the X-ray powder diffraction pattern [d, Å (I, %) (hkl)] are 7.76(100)(006), 3.88(40)(0.0.12), 2.64(25)(202, 024), 2.32(20)(0.2.10), 1.965(0.2.16). The holotype specimen is deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 3676/1.  相似文献   

7.
The chemical composition of aerosols in the Marine Atmospheric Boundary Layer (MABL) of Bay of Bengal (BoB) and Arabian Sea (AS) has been studied during the spring and inter-monsoon (March-May 2006) based on the analysis of water soluble constituents (Na+, NH 4 + , K+, Mg2+, Ca2+, Cl?, NO 3 ? and SO 4 2? ), crustal elements (Al, Fe, and Ca) and carbonaceous species (EC, OC). The total suspended particulates (TSP) ranged from 5.2 to 46.6 μg m?3 and 8.2 to 46.9 μg m?3 during the sampling transects in the BoB and AS respectively. The water-soluble species, on average, accounted for 44% and 33% of TSP over BoB and AS respectively, with dominant contribution of SO 4 2? over both the oceanic regions. However, distinct differences with respect to elevated abundances of NH 4 + in the MABL of BoB and that of Na+ and Ca2+ in AS are clearly evident. The non-sea-salt component of SO 4 2? ranging from 82 to 98% over BoB and 35 to 98% over AS; together with nss-Ca2+/nss-SO 4 2? equivalent ratios 0.12 to 0.5 and 0.2 to 1.16, respectively, provide evidence for the predominance of anthropogenic constituents and chemical transformation processes occurring within MABL. The concentrations of OC and EC average around 1.9 and 0.4 μg m?3 in BoB and exhibit a decreasing trend from north to south; however, abundance of these carbonaceous species are not significantly pronounced over AS. The abundance of Al, used as a proxy for mineral aerosols, varied from 0.2 to 1.9 μg m?3 over BoB and AS, with a distinctly different spatial pattern — decreasing north to south in BoB in contrast to an increasing pattern in the Arabian Sea.  相似文献   

8.
The incorporation of hydrogen into ferrosilite, Fe-bearing enstatite and orthopyroxene containing different trivalent cations (Cr3+ and Al3+, Cr3+ and Fe3+) was investigated experimentally at 25 kbar. Hydrogen concentration was determined by FTIR-spectroscopy on oriented crystal sections and by secondary ion mass spectroscopy, whereas Mößbauer spectroscopy and optical spectroscopy were used to characterise the valence state of Fe in orthopyroxene. Results suggest that hydrogen incorporation in ferrosilite is achieved by a similar mechanism as in pure enstatite. In Cr-bearing samples, however, hydrogen incorporation is reduced by the presence of other trivalent cations by an increased tendency to form Tschermaks substitutions, e.g. Si T 4+ + Mg M1 2+ ? Al T 3+ + Cr M1 3+ . Thus, hydrogen solubility in natural orthopyroxenes from the Earth’s mantle, containing significant amounts of Cr3+, Al3+, and Fe3+, may be much more limited than expected from their trivalent cation content, as a large fraction of the trivalent cations does not participate in H-incorporating reactions as 2 Mg M1 2+ ? M M1 3+ + VM1 + H i + .  相似文献   

9.
The paper reports original thermochemical data on six natural amphibole samples of different composition. The data were obtained by high-temperature melt solution calorimetry in a Tian–Calvet microcalorometer and include the enthalpies of formation from elements for actinolite Ca1.95(Mg4.4Fe 0.5 2+ Al01)[Si8.0O22](OH)2(–12024 ± 13 kJ/mol) and Ca2.0(Mg2.9Fe 1.9 2+ Fe 0.2 3+ )[Si7.8Al0.2O22](OH)2, (–11462 ± 18 kJ/mol), and Na0.1Ca2.0(Mg3.2Fe 1.6 2+ Fe 0.2 3+ )[Si7.7Al0.3O22](OH)2 (–11588 ± 14 kJ/mol); for pargasite Na0.5K0.5Ca2.0-(Mg3.4Fe 1.8 2+ Al0.8)[Si6.2Al1.8O22](OH)2 (–12316 ± 10 kJ/mol) and Na0.8K0.2Ca2.0(Mg2.8Fe 1.3 3+ Al0.9) [Si6.1Al1.9O22](OH)2 (–12 223 ± 9 kJ/mol); and for hastingsite Na0.3K0.2Ca2.0(Mg0.4Fe 1.3 2+ Fe 0.9 3+ Al0.2) [Si6.4Al1.6O22](OH)2 (?10909 ± 11 kJ/mol). The standard entropy, enthalpy, and Gibbs free energy of formation are estimated for amphiboles of theoretical composition: end members and intermediate members of the isomorphic series tremolite–ferroactinolite, edenite–ferroedenite, pargasite–ferropargasite, and hastingsite.  相似文献   

10.
Batisivite has been found as an accessory mineral in the Cr-V-bearing quartz-diopside metamorphic rocks of the Slyudyanka Complex in the southern Baikal region, Russia. A new mineral was named after the major cations in its ideal formula (Ba, Ti, Si, V). Associated minerals are quartz, Cr-V-bearing diopside and tremolite; calcite; schreyerite; berdesinskiite; ankangite; V-bearing titanite; minerals of the chromite-coulsonite, eskolaite-karelianite, dravite-vanadiumdravite, and chernykhite-roscoelite series; uraninite; Cr-bearing goldmanite; albite; barite; zircon; and unnamed U-Ti-V-Cr phases. Batisivite occurs as anhedral grains up to 0.15–0.20 mm in size, without visible cleavage and parting. The new mineral is brittle, with conchoidal fracture. Observed by the naked eye, the mineral is black and opaque, with a black streak and resinous luster. Batisivite is white in reflected light. The microhardness (VHN) is 1220–1470 kg/mm2 (load is 30 g), the mean value is 1330 kg/mm2. The Mohs hardness is near 7. The calculated density is 4.62 g/cm3. The new mineral is weakly anisotropic and bireflected. The measured values of reflectance are as follows (λ, nm—R max ′ /R min ′ ): 440—17.5/17.0; 460—17.3/16.7; 480—17.1/16.5; 500—17.2/16.6; 520—17.3/16.7; 540—17.4/16.8; 560—17.5/16.8; 580—17.6/16.9; 600—17.7/17.1; 620—17.7/17.1; 640—17.8/17.1; 660—17.9/17.2; 680—18.0/17.3; 700—18.1/17.4. Batisivite is triclinic, space group P \(\overline 1\); the unit-cell dimensions are: a = 7.521(1) Å, b = 7.643(1) Å, c = 9.572(1) Å, α = 110.20°(1), β = 103.34°(1), γ = 98.28°(1), V = 487.14(7) Å3, Z = 1. The strongest reflections in the X-ray powder diffraction pattern [d, Å (I, %)(hkl)] are: 3.09(8)(12\(\overline 2\)); 2.84, 2.85(10)(021, 120); 2.64(8)(21\(\overline 3\)); 2.12(8)(31\(\overline 3\)); 1.785(8)(32\(\overline 4\)), 1.581(10)(24\(\overline 2\)); 1.432, 1.433(10)(322, 124). The chemical composition (electron microprobe, average of 237 point analyses, wt %) is: 0.26 Nb2O5, 6.16 SiO2, 31.76 TiO2, 1.81 Al2O3, 8.20 VO2, 26.27 V2O3, 12.29 Cr2O3, 1.48 Fe2O3, 0.08 MgO, 11.42 BaO; the total is 99.73. The VO2/V2O3 ratio has been calculated. The simplified empirical formula is (V 4.8 3+ Cr2.2V 0.7 4+ Fe0.3)8.0(Ti5.4V 0.6 4+ )6.0[Ba(Si1.4Al0.5O0.9)]O28. An alternative to the title formula could be a variety (with the diorthogroup Si2O7) V8Ti6[Ba(Si2O7)]O22. Batisivite probably pertains to the V 8 3+ Ti 6 4+ [Ba(Si2O)]O28-Cr 8 3+ Ti 6 4+ [Ba(Si2O)]O28 solid solution series. The type material of batisivite has been deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.  相似文献   

11.
In a group of minerals of reasonable complexity in which the structure topology is related but not identical, the general relation between structure topology and chemical composition is not known. This problem is of major significance. The structural hierarchy and stereochemistry are described for 27 titanium disilicate minerals that contain the TS (titanium-silicate) block, a central trioctahedral (O) sheet and two adjacent (H) sheets of [5]- and [6]-coordinated polyhedra and (Si2O7) groups and related delindeite. The TS block is characterized by a planar cell based on translation vectors, t 1 and t 2 , with t 1 ～ 5.5 and t 2 ～ 7 Å and t 1 ∧ t 2 close to 90°. The general formula of the TS block is A 2 P B 2 P M 2 H M 4 O (Si 2 O 7 ) 2 X 4 + n, where M 2 H and M 4 O = cations of the H and O sheets; MH = Ti (= Ti + Nb), Zr, Mn2+, Ca; MO = Ti, Zr, Mn2+, Ca, Na; A P and B P are cations at the peripheral (P) sites = Na, Ca, Ba; X = anions = O, OH, F; n = 0, 2, 4; the core part of the TS block is shown in bold and is invariant. Cations in each sheet of the TS block form a close-packed layer and the three layers are cubic close packed.There are three topologically distinct TS blocks, depending on the type of linkage of two H sheets and the central O sheet. The H sheets of one TS block attach to the O sheet in the same manner. All structures consist of a TS block and an I (intermediate) block that comprises atoms between two TS blocks. Usually, the I block consists of alkali and alkaline-earth cations, (H2O) groups and oxyanions (PO4)3?, (SO4)2? and (CO3)2?. These structures naturally fall into four groups, based on differences in topology and stereochemistry of the TS block. In Group I, Ti = 1 apfu Ti occurs in the O sheet, and (Si2O7) groups link to a Na polyhedron of the O sheet (linkage 1). In Group II, Ti = 2 apfu, Ti occurs in the H sheet, and (Si2O7) groups link to two M 2+ octahedra of the O sheet adjacent along t 2 (linkage 2). In Group III, Ti = 3 apfu, Ti occurs in the O and H sheets, and (Si2O7) groups link to the Ti octahedron of the O sheet (linkage 1). In Group IV, Ti = 4 apfu (the maximum possible content of Ti in the TS block), Ti occurs in the O and H sheets, and (Si2O7) groups link to two Ti octahedra of the O sheet adjacent along t 1 (linkage 3). The stability of the TS block is due to the ability of Ti (Nb) to have an extremely wide range in Ti (Nb)-anion bond lengths, 1.68–2.30 Å, which allows the chemical composition of the TS block to vary widely. In crystal structures so far known, only one type of TS block occurs in a structure. The TS block propagates close-packing of cations onto the I block. The general structural principles and the relation between structure topology and chemical composition are described for the TS-block minerals. These principles allow prediction of structural arrangements and possible chemical compositions, and testing whether or not all aspects of the structure and chemical formula of a mineral are correct. Here, I show how these principles work, and review recent results that show the effectiveness of these principles as a predictive technique.  相似文献   

12.
The specific heat capacity (C p) of six variably hydrated (~3.5 wt% H2O) iron-bearing Etna trachybasaltic glasses and liquids has been measured using differential scanning calorimetry from room temperature across the glass transition region. These data are compared to heat capacity measurements on thirteen melt compositions in the iron-free anorthite (An)–diopside (Di) system over a similar range of H2O contents. These data extend considerably the published C p measurements for hydrous melts and glasses. The results for the Etna trachybasalts show nonlinear variations in, both, the heat capacity of the glass at the onset of the glass transition (i.e., C p g ) and the fully relaxed liquid (i.e., C p l ) with increasing H2O content. Similarly, the “configurational heat capacity” (i.e., C p c  = C p l  ? C p g ) varies nonlinearly with H2O content. The An–Di hydrous compositions investigated show similar trends, with C p values varying as a function of melt composition and H2O content. The results show that values in hydrous C p g , C p l and C p c in the depolymerized glasses and liquids are substantially different from those observed for more polymerized hydrous albitic, leucogranitic, trachytic and phonolitic multicomponent compositions previously investigated. Polymerized melts have lower C p l and C p c and higher C p g with respect to more depolymerized compositions. The covariation between C p values and the degree of polymerization in glasses and melts is well described in terms of SMhydrous and NBO/T hydrous. Values of C p c increase sharply with increasing depolymerization up to SMhydrous ~ 30–35 mol% (NBO/T hydrous ~ 0.5) and then stabilize to an almost constant value. The partial molar heat capacity of H2O for both glasses (\( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{g}} \)) and liquids (\( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \)) appears to be independent of composition and, assuming ideal mixing, we obtain a value for \( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \) of 79 J mol?1 K?1. However, we note that a range of values for \( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \) (i.e., ~78–87 J mol?1 K?1) proposed by previous workers will reproduce the extended data to within experimental uncertainty. Our analysis suggests that more data are required in order to ascribe a compositional dependence (i.e., nonideal mixing) to \( C_{{{\text{p}}\;{\text{H}}_{2} {\text{O}}}}^{\text{l}} \).  相似文献   

13.
The crystal structures of synthetic K-dravite [XKYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)], dravite [XNaYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)], oxy-uvite [XCaYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W O], and magnesio-foitite [X?Y(Mg2Al)ZAl 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)] are investigated by polarized Raman spectroscopy, single-crystal structure refinement (SREF), and powder X-ray diffraction. The use of compositionally simple tourmalines characterized by electron microprobe analysis facilitates the determination of site occupancy in the SREF and band assignment in the Raman spectra. The synthesized K-dravite, oxy-uvite, and magnesio-foitite have significant Mg–Al disorder between their octahedral sites indicated by their respective average 〈Y–O〉 and 〈Z–O〉 bond lengths. The Y- and Z-site compositions of oxy-uvite (YMg1.52Al1.48(10) and ZAl4.90Mg1.10(15)) and magnesio-foitite (YAl1.62Mg1.38(18) and ZAl4.92Mg1.08(24)) are refined from the electron densities at each site. The Mg–Al ratio of the Y and Z sites is also determined from the relative integrated peak intensities of the Raman bands in the O–H stretching vibrational range (3250–3850 cm?1), producing values in good agreement with the SREF data. The unit cell volume of tourmaline increases from magnesio-foitite (1558.4(3) Å3) to dravite (1569.5(4)–1571.7(3) Å3) to oxy-uvite (1572.4(2) Å3) to K-dravite (1588.1(2) Å3), mainly due to lengthening of the crystallographic c-axis. The increase in the size of the X-site coordination polyhedron from dravite (Na) to K-dravite (K) is accommodated locally in the crystal structure, resulting in the shortening of the neighboring O1–H1 bond. In oxy-uvite, Ca2+ is locally associated with a deprotonated W (O1) site, whereas vacant X sites are neighbored by protonated W (O1) sites. Increasing the size of the X-site-occupying ion does not detectably affect bonding between the other sites; however, the higher charge of Ca and the deprotonated W (O1) site in oxy-uvite are correlated to changes in the lattice vibration Raman spectrum (100–1200 cm?1), particularly for bands assigned to the T 6O18 ring. The Raman spectrum of magnesio-foitite shows significant deviations from those of K-dravite, dravite, and oxy-uvite in both the lattice and O–H stretching vibrational ranges (100–1200 and 3250–3850 cm?1, respectively). The vacant X site is correlated with long- and short-range changes in the crystal structure, i.e., deformation of the T 6O18 ring and lengthening of the O1–H1 and O3–H3 bonds. However, X-site vacancies in K-dravite, dravite, and oxy-uvite result only in the lengthening of the neighboring O1–H1 bond and do not result in identifiable changes in the lattice-bonding environment.  相似文献   

14.
The behavior of the 0.1 mNaCl + 0.002 mHCl + 1.9 × 10?5 mUO2(NO3)2 solution was studied at pH from 2.7 to 11.0, 25°C, and 1 bar in an argon atmosphere. The curve of variations in U concentration exhibits two minima at pH = 6.6 ± 0.7 and 10.0 ± 0.5. These minima are related to the precipitation of schoepite and clarkeite, respectively. The experimental data were used to refine the stability constants of U(VI) (hydroxo) complexes. For the polymer species of U(VI) with charges from +2 to ?1, the method of additivity of thermochemical increments was used, and increments of the linear relation were determined for the calculation of the Gibbs free energies of formation (ΔfG 298.15 0 ) of respective homologue series. The proposed method was applied to calculate the ΔfG 298.15 0 of formation of U(VI) (hydroxo)complexes containing from one to five uranium atoms.  相似文献   

15.
Kamarizaite, a new mineral species, has been identified in the dump of the Kamariza Mine, Lavrion mining district, Attica Region, Greece, in association with goethite, scorodite, and jarosite. It was named after type locality. Kamarizaite occurs as fine-grained monomineralic aggregates (up to 3 cm across) composed of platy crystals up to 1 μm in size and submicron kidney-shaped segregations. The new mineral is yellow to beige, with light yellow streak. The Mohs hardness is about 3. No cleavage is observed. The density measured by hydrostatic weighing is 3.16(1) g/cm3, and the calculated density is 3.12 g/cm3. The wavenumbers of absorption bands in the IR spectrum of kamarizaite are (cm?1; s is strong band, w is weak band): 3552, 3315s, 3115, 1650w, 1620w, 1089, 911s, 888s, 870, 835s, 808s, 614w, 540, 500, 478, 429. According to TG and IR data, complete dehydration and dehydroxylation in vacuum (with a weight loss of 15.3(1)%) occurs in the temperature range 110–420°C. Mössbauer data indicate that all iron in kamarizaite is octahedrally coordinated Fe3+. Kamarizaite is optically biaxial, positive: n min = 1.825, n max = 1.835, n mean = 1.83(1) (for a fine-grained aggregate). The chemical composition of kamarizaite (electron microprobe, average of four point analyses) is as follows, wt %: 0.35 CaO, 41.78 Fe2O3, 39.89 As2O5, 1.49 SO3, 15.3 H2O (from TG data); the total is 98.81. The empirical formula calculated on the basis of (AsO4,SO4)2 is Ca0.03Fe 2.86 3+ (AsO4)1.90(SO4)0.10(OH)2.74 · 3.27H2O. The idealized formula is Fe 3 3+ (AsO4)2(OH)3 · 3H2O. Kamarizaite is an arsenate analogue of orthorhombic tinticite, space group Pccm, Pcc2, Pcmm, Pcm21, or Pc2m; a = 21.32(1), b = 13.666(6), c =15.80(1) Å, V= 4603.29(5) Å3, Z= 16. The strongest reflections of the X-ray powder diffraction pattern [\(\bar d\), Å (I, %) (hkl)] are: 6.61 (37) (112, 120), 5.85 (52) (311), 3.947 (100) (004, 032, 511), 3.396 (37) (133, 431), 3.332 (60) (314), 3.085 (58) (621, 414, 324). The type material of kamarizaite is deposited in the Mineralogical Collection of Technische Universität Bergakademie Freiberg, Germany, inventory number 82199.  相似文献   

16.
The concentration of the Al and Ti paramagnetic impurity centers in pre-ore and ore-stage quartz at the Peschanka porphyry copper–molybdenum–gold deposit in the Western Chukchi Peninsula, Russia were determined using electron paramagnetic resonance spectroscopy (EPR). The [AlO 4 - /h+]0 concentration in pre-ore and ore-stage quartz varies from 29 to 124 and from 13 to 101 at. ppm, respectively. The contents of the [TiO 4 - /Li+]0 and [TiO 4 - /H+]0 centers reach 20 and 6.3 at. ppm, respectively. Pre-ore quartz associated with the formation of biotite–potassium feldspar–quartz alteration and ore-stage quartz associated with the formation of quartz–sericite rocks followed by the ore deposition differ considerably in the Ti center content, especially the [TiO 4 - /H+]0 center. The [TiO 4 - /H+]0 concentration is much higher in the pre-ore quartz (>2 at. ppm) than that in the ore-stage quartz related to copper mineralization (<2 at. ppm). The [TiO 4 - /Li+]0 concentration also decreases from pre-ore to ore-stage quartz. Taking the data we obtained into account, the formation temperature of pre-ore and ore-stage quartz estimated from a titaniumin-quartz geothermometer is 590–470°C (weighted average 520°C) and 510–310°C (weighted average 430°C), respectively. The obtained temperature range of 590 to 310°C is similar to that determined from homogenization of fluid inclusions in quartz.  相似文献   

17.
We have analyzed the orbital light curve of the X-ray nova XTE J1118+480 in a “disk + hot line” model based on three-dimensional gas-dynamical computations of gas flows in interacting binary systems. As a result, we have been able to derive reliable parameters for the system: i = 80 ?4 +4 degrees, MBH = 7.1 ?0.1 +0.5 M⊙, M opt = 0.39 ?0.07 +0.15 M⊙.  相似文献   

18.
The crystal structure of the unstable mineral alumoklyuchevskite K3Cu3AlO2(SO4)4 [monoclinic, I2, a = 18.772(7), b = 4.967(2), c = 18.468(7) Å, β = 101.66(1)°, V = 1686(1) Å] was refined to R 1 = 0.131 for 2450 unique reflections with F ≥ 4σF hkl. The structure is based on oxocentered tetrahedrons (OAlCu 3 7+ ) linked into chains via edges. Each chain is surrounded by SO4 tetrahedrons forming a structural complex. Each complex is elongated along the b axis. This type of crystal structure was also found in other fumarole minerals of the Great Tolbachik Fissure Eruption (GTFE, Kamchatka Peninsula, Russia, 1975–1976), klyuchevskite, K3Cu3Fe3+O2(SO4)4; and piypite, K2Cu2O(SO4)2.  相似文献   

19.
Analysis of hydrogeochemical materials on As distribution in CO2-bearing (carbonate) waters in various regions and the thermodynamic simulation of geochemical processes in rock-CO2-bearing water systems made it possible to constrain the optimal conditions for As transfer from rocks into carbonate waters and the accumulation of this element in the waters. The problem was solved with regard for the various rates of As transitions from rocks to water: (a) high rates of As transitions from rocks in compliance with the ion exchange mechanism and (b) low rates of As transitions from rocks in compliance with the mechanism involving the decomposition of As-bearing minerals. Various mechanisms of As extraction from rocks result in the compositional diversity of the aqueous phase and various As migration species in CO2-bearing waters, which, in turn, control the equilibrium concentration levels of this element. The principally important boundary conditions of As enrichment in CO2-bearing waters are high \(P_{CO_2 } \) and R/W ratios in the geochemical systems, a preliminary increase in the Cl concentration in the CO2-bearing waters, and the origin of these waters at high-density heat fluxes. As migration species were simulated for the model solutions and real carbonate waters of various geochemical types, and it is demonstrated that the predominant As species are oxygen-bearing HAsO 2 0 , and AsO 2 ? at a subordinate role of the sulfide HAs2S 4 2? , and As2S 4 2? — species even at high Σ S2? in the system. Two models of the genesis of solid As sulfides in CO2-bearing waters are analyzed: (1) with oxygen-bearing species (HAsO 2 0 , and AsO 2 ? ), which occur most widely, and (2) with sulfide species (As2S 4 2? , HAs2S 4 ? , and As4S 7 2? ), which occur not as widely.  相似文献   

20.
The paper reports data obtained in the course of a comprehensive physicochemical study of Li-tosudite, a mixed-layer mineral from hydrothermally altered rocks in western Chukotka, Russia, whose formula was reliably established. The enthalpy of formation of Li-tosudite from Chukotka, Ca0.15(Li0.9Mg0.2Al6.0)[Si6.4Al1.6O20](OH)10 · 3.3H2O, from elements was experimentally determined by melt solution calorimetry in a high-temperature Calvet microcalorimeter: ΔfH el o (298.15 К) =–15087 ± 26 kJ/mol. The standard entropy and Gibbs free energy of formation of this mineral were evaluated.  相似文献   

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