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1.
The Xihuashan tungsten deposit (South Jiangxi, China) is located on the border of a granitic stock composed of four intrusive units: γ inf2a sup5 , γ inf2b sup5 , γ inf2c sup5 and γ inf2e sup5 chronologically. The deposit is situated in γ inf2a sup5 and γ inf2b sup5 whose contact zone is marked by a stockscheider and by a sporadic fine-grained granite designated γ inf2b′ sup5 . The feldspathic episyenitic veins or masses located mainly in γ inf2b sup5 resulted from granite alteration. This alteration characterizes the fluid activity which followed previous mechanical action, remnant liquids draining under structural control. The quartz-bearing Xihuashan veins (Dayu mining district) are a typical wolframite-quartz vein deposit and have developed mainly in γ inf2b sup5 . The density of the veins and the huge mineralizations in γ inf2b sup5 can be explained by the carapace role played by γ inf2a sup5 , γ inf2b′ sup5 and the stockscheider. The deposit is formed by 615 economically valuable veins (medium grade: 1,08% in WO3) characterized by four stages of mineralization; a reverse vertical zoning is generally observed. Thus, the Xihuashan tungsten deposit possesses a metallogenic value contributing to the comprehension of metallogenic and structural phenomena related to the evolution of granitic masses.  相似文献   

2.
The sedimentation models for the upper part of the Tyumen Formation (the J2?C3 productive layers) and the Abalak Formation (J 1 2 and J 1 1 ) were constructed on the basis of data from lithological studies of Jurassic stratum cores (the Potanai oilfield in the northeast Shaim megaswell). The models show that the sedimentation environment sequentially changed from the continental to the deltaic, lagoonal, and shelf types through the Middle and Late Jurassic.  相似文献   

3.
Groundwater, surface water, soil and river sediment samples, and information on land use in the Nanfei River basin (NRB) of China have been analyzed to study the geochemistry, distribution, and mobilization of phosphorus. The distribution of phosphate (PO 4 3??/sup> ) and the relationships between PO 4 3??/sup> and several constituents in groundwater were studied. Partial correlation analysis relating PO 4 3??/sup> to types of land use was conducted using the data analyzing tool SPSS 15.0. The processes controlling the transport of PO 4 3??/sup> are discussed. The conclusions from this study are: (1) urban land use has obvious impact on PO 4 3??/sup> in groundwater, the average concentration of PO 4 3??/sup> being 4.37?mg/L, greater than that resulting from farmland and mixed land use, which have average PO 4 3??/sup> concentrations of 0.10 and 0.18?mg/L, respectively; (2) the partial correlation between PO 4 3??/sup> and types of land use is significant with a coefficient of 0.760; (3) the PO 4 3??/sup> concentrations in surface water are generally higher than those in groundwater, and the total phosphorus (TP) concentrations in river sediments are generally higher than those in soil samples; (4) groundwater is a carrier of PO 4 3??/sup> and is likely responsible for the redistribution of PO 4 3??/sup> in different regions of NRB.  相似文献   

4.
The temperature dependence of the lattice parameters of pure anorthite with high Al/Si order reveals the predicted tricritical behaviour of the \(I\bar 1 \leftrightarrow P\bar 1\) phase transition at T c * =510 K. The spontaneous strain couples to the order parameter Q° as x i∝S xQ i Q°2 with S xQ 1 =4.166×10?3, S xQ 2 =0.771×10?3, S xQ 3 =?7.223×10?3 for the diagonal elements. The temperature dependence of Q° is $$Q^{\text{o}} = \left( {1 - \frac{T}{{510}}} \right)^\beta ,{\text{ }}\beta = \tfrac{{\text{1}}}{{\text{4}}}$$ A strong dependence of T c * , S xQ i and β is predicted for Al/Si disordered anorthite.  相似文献   

5.
Electric dipole polarizabilities have been calculated from first principles of quantum mechanics for the BO 3 3? , CO 3 2? , NO 3 ? series and for NO 2 ? and LiNO3(g). Calculated trends in average polarizability and polarizability anisotropy in the BO 3 3? -NO 3 ? series are in agreement with experiment and can be qualitatively interpreted in terms of the varying energies of the a1′, a2″ and e′ symmetry unoccupied MO's of the oxyanions. Embedding a CO 3 2? ion in a D3h symmetry array of divalent cations reduces both the average polarizability and its anisotropy, particularly when diffuse s and p functions are included in the calculation. Calculations on the gas phase LiNO3 molecule and on the free NO 3 ? ion in the distorted geometry found in LiNO3(g) allow us to separate polarizability contributions internal to the NO 3 ? and Li+ ions from those which arise from the Li+-NO 3 ? interaction. The Li+-NO 3 ? interaction term so obtained is much smaller than the NO 3 ? contribution but is in turn larger than the Li+ contribution, suggesting that the inclusion of this interaction term is essential for obtaining accurate results for ion pairs. Although static polarizabilities are in reasonable agreement with experiment for NO 3 ? the wavelength dispersion of the polarizability is underestimated by about a factor of two, apparently as a result of inadequacies in the quantum mechanical method. Calculated values are also presented for 14N NMR shieldings in the nitrogen oxyanions but these are in only qualitative agreement with the experimental values. Similarly, calculated values of magnetic susceptibility are in only qualitative agreement with experiment although trends along the BO 3 3? -NO 3 ? series are properly reproduced.  相似文献   

6.
Ionic conductivity of polycrystalline calcite containing varying amounts of PO 4 3? ions was measured in the pressure range of 1–6 GPa and at room temperature. Electrical conductivity increased with pressure corresponding to the phase transition of calcite I to calcite II. The conductivity in calcite III decreased exponentially with pressure. Calculated activation volumes of the conductivity varied with PO 4 3? content in the range of 0.94–5.34 cm3/mol. This variation corresponded to the lattice parameter change of calcite I due to PO 4 3? incorporation and indicated the contribution of CO 3 2? -vacancies associated with PO 4 3? ions to the conductivity.  相似文献   

7.
Absorption bands are determined in polarized optical spectra of vivianite Fe3(PO4)2·8H2O, recorded at room and low temperatures. These bands are caused by spin-allowed d-d transitions in structurally nonequivalent Fe A 2+ (～11000 cm-1 (γ-polarization) (and) ～12000 cm-1 (β-polarization)) (and) Fe B 2+ (～8400 cm-1 (γ, α-polarization) and ～11200 cm-1 (α-polarization)) ions. A charge transfer band (CTB) Fe B 2+ +Fe B 3+ →Fe B 2+ +Fe B 2+ (～15000 cm-1) also determined, has polarizing features giving evidence of a change in the Fe B 2+ -Fe B 3+ bond direction, when compared with Fe B 2+ -Fe B 2+ . Bands of exchange-coupled Fe3+-Fe3+ pairs (～19400, ～20400, ～21300 and ～21700 cm-1) which appear on oxidation of Fe2+ in paired Fe B octahedra are also characterized.  相似文献   

8.
This paper presents the point-defect thermodynamics for fayalite and olivine solid solutions (Fe x Mg1?x )2SiO4. By means of thermogravimetry, the metal-to-oxygen ratio of these silicates has been determined as a function of oxygen potential, compositionx and temperature. Experiments were performed in the range of 1,000° C≦T≦1,280° C and 0.2≦x≦1.0. It is found that V Me ″ , Fe Me · and the associate {Fe′ Si ′ Fe Me · } are the majority defects. With this knowledge it is possible to calculate the nonstoichiometry at given temperature as a function of \(p_{O_2 } \) and \(a_{SiO_2 } \) . The cation vacancy concentration shows a \(p_{O_2 }^{1/5} \) -dependence (forx≧0.2) and increases at givenT and \(p_{O_2 } \) almost exponentially with compositionx. In the composition range studied here, the silicates show an oxygen excess, and FeO is more soluble in the olivine than SiO2.  相似文献   

9.
An experimental study of the particulars of the solubility and crystallization of brushite Ca(HPO4) · 2H2O from aqueous solution in conditions of a variable pH (6.0–3.0) and the contents of impurity ions (K+, Na+, NH 4 + , Mg2+, SO 4 2? , CO 3 2? ) has been conducted. It is established that brushite solubility markedly rises with a decrease in pH from 6 to 3 and slightly rises with an increase in Mg2+ and SO 4 2? concentrations. The enrichment in K+, Na+, and NH 4 + does not affect brushite solubility. The changeable chemistry of the medium results in variation of the synthetic crystal habit, from rhombic tabular to thickened prismatic crystals.  相似文献   

10.
The electron paramagnetic resonance (EPR) spectra of Fe3+ in a well cristallized kaolinite from Decazeville in France are well resolved. It is shown that in this sample there are mainly two slightly different spectra, well separated at low temperature and characterized at -150° C by the constants B 2 0 = 0.112 cm?1, B 2 2 = 0.0688 cm?1 for one and B 2 0 = 0.116 cm?1, B 2 2 = 0.0766 cm?1 for the second. These two spectra arise from Fe3+ substituted for Al3+ at the two octahedral positions in equal amounts. The temperature dependence of EPR spectra was studied and was explained by a modification of the octahedral sites.  相似文献   

11.
The non-ferroic triclinic to triclinic \(I\bar 1 - P\bar 1\) phase transition in anorthite is described in terms of the spontaneous onset of an order parameter η. A triclinic to triclinic phase transition can be driven by order parameters (representations) arising from the Γ, Z, X, U, V, R, Y, and T points of symmetry of the Brillouin zone. Each point leads to a set of two inequivalent representations and thus there is a total of sixteen inequivalent order parameters. However, only the R 1 + representation is consistent with the change from the body-centered to primitive cell (increase of primitive cell size of two) and also with the origin of the two space groups (inversion center) being at the same position. The R 1 + order parameter of the high symmetry triclinic phase \(P\bar 1_0\) (or equivalently \(I\bar 1\) ) causes a reciprocal lattice change and, in terms of the lower symmetry reciprocal lattice, the order parameter corresponds to the b* point. This is consistent with experimentally observed x-ray diffuse scattering. Using induced representation theory, microscopic distortions compatible with the R 1 + order parameter are obtained. Assuming a distortion in an arbitrary direction at the general 2(i) Wyckoff position (x0,y0,z0) of \(P\bar 1_0\) (the higher symmetry phase) induced representation theory demands an opposite displacement at the position (x0, y0, z0), an opposite displacement at (x0+1,y0+1,z0+1), and the same displacement at ( \(\bar x\) 0+1, \(\bar y\) 0+1, \(\bar z\) 0+1) of \(P\bar 1_0\) . This is also consistent with experiment. The presence of the weak c-type reflections above the transition is attributed to the fluctuating lower symmetry antiphase domains related by the translation (1/2, 1/2, 1/2).  相似文献   

12.
Laihuite reported in the present paper is a new iron silicate mineral found in China with the following characteristics:
  1. This mineral occurs in a metamorphic iron deposit, associated with fayalite, hypersthene, quartz, magnetitc, etc.
  2. The mineral is opaque, black in colour, thickly tabular in shape with luster metallic to sub-metallic, two perfect cleavages and specific gravity of 3.92.
  3. Its main chemical components are Fe and Si with Fe3+>Fe2+. The analysis gave the formula of Fe Fe 1.00 3+ ·Fe 0.58 2+ ·Mg 0.03 2+ ·Si0.96O4.
  4. Its DTA curve shows an exothermic peak at 713°C.
  5. The mineral has its own infrared spectrum distinctive from that of other minerals.
  6. This mineral is of orthorhombic system; space group:C 2h /5 ?P21/c; unit cell:α=5.813ű0.005,b=4.812ű0.005,c=10.211ű0.005,β=90.87°.
  7. The Mössbauer spectrum of this mineral is given, too.
  相似文献   

13.
Submarine groundwater discharge (SGD) was quantified at select sites in San Francisco Bay (SFB) from radium (223Ra and 224Ra) and radon (222Rn) activities measured in groundwater and surface water using simple mass balance box models. Based on these models, discharge rates in South and Central Bays were 0.3?C7.4?m3?day?1?m?1. Although SGD fluxes at the two regions (Central and South Bays) of SFB were of the same order of magnitude, the dissolved inorganic nitrogen (DIN) species associated with SGD were different. In the South Bay, ammonium (NH 4 + ) concentrations in groundwater were three-fold higher than in open bay waters, and NH 4 + was the primary DIN form discharged by SGD. At the Central Bay site, the primary DIN form in groundwater and associated discharge was nitrate (NO 3 ? ). The stable isotope signatures (??15NNO3 and ??18ONO3) of NO 3 ? in the South Bay groundwater and surface waters were both consistent with NO 3 ? derived from NH 4 + that was isotopically enriched in 15N by NH 4 + volatilization. Based on the calculated SGD fluxes and groundwater nutrient concentrations, nutrient fluxes associated with SGD can account for up to 16?% of DIN and 22?% of DIP in South and Central Bays. The form of DIN contributed to surface waters from SGD may impact the ratio of NO 3 ? to NH 4 + available to phytoplankton with implications to bay productivity, phytoplankton species distribution, and nutrient uptake rates. This assessment of nutrient delivery via groundwater discharge in SFB may provide vital information for future bay ecological wellbeing and sensitivity to future environmental stressors.  相似文献   

14.
Hydrotalcite-like solid solutions have been synthesized by coprecipitation in basic solutions with variable SO 4 2? /CO 3 2? ratios. Chemical determination of CO 3 2? in the interlayer was impossible because of the presence of minor hydromagnesite. SO 4 2? was determined both by chemical analysis and X-ray photoelectron spectroscopy (XPS), the two methods giving similar results. A Raman spectrometry gave additional data on the SO 4 2? /CO 3 2? ratio. Then, the stoichiometry of the anionic interlayers, X s , X c , and X OH were determined, and the influence of X s on the c′ parameter (increasing from c′=7.97 Å to c′=8.63 Å between X s =0 and X s =1) was characterized. In addition, a partitioning curve of SO 4 2? and CO 3 2? between aqueous solutions and hydrotalcite-like compounds was established. Its general shape strongly suggests a miscibility gap between a sulfate-rich end and a carbonate-rich solid solution (maximum SO 4 2? /CO 3 2? about 0.2). This result explains why most of the hydrotalcites synthesized during experimental alteration of basaltic glasses by sea-water (a sulfate-rich solution) are CO 3 2? -rich solid solutions.  相似文献   

15.
The complexation between gold and silica was experimentally, confirmed and calibrated at 200 °C: $$\begin{gathered} Au^ + + H_3 SiO_4^ - \rightleftharpoons AuH_3 SiO_4^0 \hfill \\ \log K_{(200^\circ C)} = 19.26 \pm 0.4 \hfill \\ \end{gathered} $$ Thermodynamic calculations show that AuH3SiO 4 0 would be far more abundant than AuCl 2 ? under physicochemical conditions of geological interest, suggesting that silica is much more important than chloride as ligands for gold transport. In systems containing both sulfur and silica, AuH3SiO 4 0 would be increasingly more important than Au (HS) 2 ? as the proportion of SiO2 in the system increases. The dissolution of gold in aqueous SiO2 solutions can be described by the reaction: $$\begin{gathered} Au + 1/4O_2 + H_4 SiO_4^0 \rightleftharpoons AuH_3 SiO_4^0 + 1/2H_2 O \hfill \\ log K_{(200^\circ C)} = 6.23 \hfill \\ \end{gathered} $$ which indicates that SiO2 precipitation is an effective mechanism governing gold deposition, and thus explains the close association of silicification and gold mineralization.  相似文献   

16.
The borate polyhedra BO 3 3? , B(OH)3, BO 4 5? , and B(OH) 4 ? are studied using the ab initio and multiple scattering Xα quantum mechanical methods. The ab initio self-consistent-field (SCF) molecular orbital (MO) method, at the minimum basis set level, predicts equilibrium B-O distances within 0.04 Å of their average values in solids so long as the polyhedron charge is small. Orbital energies from double zeta basis set ab initio calculations and analogies with isoelectric compounds are used to assign the X-ray spectra of BO 3 3? and to predict the valence region spectra of BO 4 5? . Contour maps of the difference between molecular and superimposed free atom electron densities show charge buildup along the B-O bond which is only slightly smaller than that observed in CO 3 2? .  相似文献   

17.
Electron paramagnetic resonance (EPR) measurements of natural anhydrite CaSO4, celestite SrSO4 and barite BaSO4 have revealed the presence of PO 3 2? and SO 3 ? radicals. Hyperfine structure from33S has been detected and measured for the first time. Low-symmetry effects, which are manifested in noncoincidence of g and hyperfine axes, were observed for SO 3 ? . The dynamics of one of the two SO 3 ? types in anhydrite has been investigated. Variations of spin Hamiltonian parameters with temperature have been attributed to thermally induced jumps between the two magnetically inequivalent sites of this center.  相似文献   

18.
Hydrogeochemical studies have been carried out in a coastal region, using multivariate statistical model, for better understanding the controlling processes that influence the aquifer chemistry. Two principal components (PC1 and PC2) are extracted from the data set of chemical variables (pH, TDS, Ca2+, Mg2+, Na+, K+, HCO 3 ? , Cl?, SO 4 2? , NO 3 ? and F?), which account for 79% of the total variation in the quality of groundwater. The PC1 (salinity controlled process) includes the concentrations of TDS, Mg2+, Na+, K+, Cl?, SO 4 2? and NO 3 ? , while the PC2 (alkalinity controlled process) comprises the concentrations of pH, HCO 3 ? and F?. The spatial distribution of PC scores identifies the locations of high salinity and alkalinity processes. The first process corresponds to the influences of geogenic, anthropogenic and marine sources, and the second one to the influence of water-soil-rock interaction. Thus, the present study shows the usefulness of multivariate statistical model as an effective means of interpretation of spatial controlling processes of groundwater chemistry.  相似文献   

19.
In 61 pairs of coexisting biotites and muscovites from the Central Alps total Al scatters considerably, but in both series a gradual increase is noticed with increasing metamorphic grade. The ratio Al Mu tot /Al Bi tot remains virtually constant (1.61 average for greenschist facies, 1.57 for amphibolite facies). Tetrahedral Al varies little in biotites and increases in muscovites-phengites with rising metamorphic grade; accordingly the ratio Al Mu IV /Al Bi IV increases slightly with grade. Far the best control of metamorphism is evidenced by octahedral Al. In the muscovite series, and still more pronounced in the biotite series, AlVI increases with increasing metamorphic grade. Consequently 1 $$K_D = \frac{{Al_{Mu}^{VI} }}{{Al_{Bl}^{VI} }}$$ decreases from 14 to 3. A map (Fig. 6) representing the regional distribution of the KD values locates a 100 km long and 23 km broad central zone with low KD. The outline of this central core almost coincides with the isograds anorthite-diopside-calcite and labradorite-pyroxene-hornblende of the Tertiary regional metamorphism; with some deviations this core also agrees with the zone in which phenomena of partial anatexis are observed. The KD values of micas from anateotic pegmatites agree with those of associated gneisses and schists. The study demonstrates that in the course of progressive regional metamorphism equilibrium has been approached to an unexpected extent and that the two micas coexisted in a strict sense.  相似文献   

20.
Exchange-mineral equilibria with Al and Fe3+ aqueous chloride solutions (aq.), Andr + AlCl aq 3 = FeCl aq 3 + Gros, (1) Psc + AlCl aq 3 = FeCl aq 3 + Czo, (2) were studied under the following experimental conditions: 500°;C and 580°;C and 1 and 2 kbar, respectively, with an overall concentration of metals in the aqueous solutions of about 0.5 M and pH 3. The mixing functions of the components in garnet and epidote were calculated from the experimental data. Thermodynamic treatment of experimental evidence for reaction (1) led to the conclusion that, within the accuracy of experiment, garnet in the andradite-grossularite series was an ideal solid solution. However, epidote solid solution markedly departed from the ideal, as was shown by concentration and pressure-temperature (PT) dependencies of Gibbs's molar excess energies and by mixing-volume concentration dependence.  相似文献   

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