Ion tracks in apatite at high pressures: the effect of crystallographic track orientation on the elastic properties of fluorapatite under hydrostatic compression     

Pascal Schouwink  Ronald Miletich  Angela Ullrich  Ulrich A. Glasmacher  Christina Trautmann  Reinhard Neumann  Barry P. Kohn 《Physics and Chemistry of Minerals》2010,37(6):371-387

Static elasticity measurements at high pressures were carried out on oriented fluorapatite single crystals, some of which contained oriented amorphous ion tracks (ITs) implanted with relativistic Au ions (2.2 GeV) from the UNILAC linear accelerator at GSI, Darmstadt. High-pressure experiments on irradiated and non-irradiated crystal sections were carried out in diamond-anvil high-pressure cells under hydrostatic conditions. In situ single-crystal diffraction was performed to determine the high-precision lattice parameters, simultaneously monitoring the widths of X-ray diffraction Bragg peaks. High-pressure Raman spectra were analyzed with respect to the frequency shift and widths of bands, which correspond to the Raman-active vibrational modes of the phosphate tetrahedra. Swift heavy ion irradiation was found to induce anisotropic lattice expansion and tensile strain within the host lattice dependent on the ion-track orientation. The relatively low Grüneisen parameter for the ν _1b(A _g) mode, which has been assigned to originate from the volume fraction of the amorphous tracks, and the γ(ν _1a)/γ(ν _1b) ratio reveals compressive strain on the amorphous ITs. The comparative compressibilities for the host lattice reveal approximately equivalent bulk moduli, but significantly different pressure derivatives (K _T = 88.4 ± 0.7 GPa, ∂K/∂P = 6.3 ± 0.3 for non-irradiated, K _T = 90.0 ± 1.7 GPa, ∂K/∂P = 3.8 ± 0.5 for irradiated samples). The axial compressibility moduli β ⁻¹ reveal significant differences, which correlate with the ion-track orientation [b_a ^{- 1} \beta_{a}^{ - 1}  = 240 ± 5 GPa, b_c ^{- 1} \beta_{c}^{ - 1}  = 361 ± 14 GPa, ∂( b_a ^{- 1} ) \left( {\beta_{a}^{ - 1} } \right) /∂P = 11.3 ± 1.2, ∂( b_c ^{- 1} ) \left( {\beta_{c}^{ - 1} } \right) /∂P = 11.6 ± 3.4 for irradiation ⊥(100); 246 ± 9 GPa, 364 ± 57 GPa, 9.5 ± 2.9, 14.7 ± 14.1 for irradiation ⊥(001), 230.7 ± 3.6 GPa, 373.5 ± 5.1 GPa, 19.2 ± 1.4, 20.1 ± 1.8 for no irradiation]. Line widths of XRD Bragg peaks in irradiated apatites confirm the strain of the host lattice, which appears to decrease with increasing pressure. By contrast, the bandwidths of Raman modes increase with pressure, and this is attributed to increasing strain gradients on the length scale of the short-range order. The investigations reveal considerable deviatoric stress on the [100]-oriented tracks due to the anisotropic elasticity, while the compression is uniform for the directions perpendicular to the tracks, which are aligned parallel to the c-axis. This difference might be considered to control the diffusion properties related to the annealing kinetics and its observed anisotropy, and hence to cause potential pressure effects on track-fading rates.  相似文献   

Complexation of Pb(II) by Chloride Ions in Aqueous Solutions     

Robert H. Byrne  Wensheng Yao  Yanxin Luo  Frank J. Millero 《Aquatic Geochemistry》2010,16(3):325-335

Lead chloride formation constants at 25°C were derived from analysis of previous spectrophotometrically generated observations of lead speciation in a variety of aqueous solutions (HClO₄–HCl and NaCl–NaClO₄ mixtures, and solutions of MgCl₂ and CaCl₂). Specific interaction theory analysis of these formation constants produced coherent estimates of (a) PbCl⁺, \textPbCl₂⁰ {\text{PbCl}}_{2}^{0} , and PbCl₃⁻ formation constants at zero ionic strength, and (b) well-defined depictions of the dependence of these formation constants on ionic strength. Accompanying examination of a recent IUPAC critical assessment of lead formation constants, in conjunction with the spectrophotometrically generated formation constants presented in this study, revealed significant differences among various subsets of the IUPAC critically selected data. It was found that these differences could be substantially reduced through reanalysis of the formation constant data of one of the subsets. The resulting revised lead chloride formation constants are in good agreement with the formation constants derived from the earlier spectrophotometrically generated data. Combining these data sets provides an improved characterization of lead chloride complexation over a wide range of ionic strengths:

log \text Cl b 1 = 1. 4 9 1- 2.0 4 I 1/ 2 ( 1+ 1. 5 I 1/ 2 ) - 1 + 0. 2 3 8 I log \text Cl b 2 = 2.0 6 2- 3.0 6 I 1/ 2 ( 1+ 1. 5 I 1/ 2 ) - 1 + 0. 3 6 9 I log \text Cl b 3 = 1. 8 9 9- 3.0 6 I 1/ 2 ( 1+ 1. 5 I 1/ 2 ) - 1 + 0. 4 3 9 I. \begin{gathered} {\log}\,{}_{\text{ Cl}} \beta_{ 1} = 1. 4 9 1- 2.0 4\,I^{ 1/ 2} \left( { 1+ 1. 5\,I^{ 1/ 2} } \right)^{ - 1} +\,0. 2 3 8\,I \hfill \\ {\log}\,{}_{\text{ Cl}} \beta_{ 2} = 2.0 6 2- 3.0 6\,I^{ 1/ 2} \left( { 1+ 1. 5\,I^{ 1/ 2} } \right)^{ - 1} +\,0. 3 6 9\,I \hfill \\ {\log}\,{}_{\text{ Cl}} \beta_{ 3} = 1. 8 9 9- 3.0 6\,I^{ 1/ 2} \left( { 1+ 1. 5\,I^{ 1/ 2} } \right)^{ - 1} +\,0. 4 3 9\,I. \hfill \\ \end{gathered}  相似文献    7. Practical Estimates of Tensile Strength and Hoek–Brown Strength Parameter m i of Brittle Rocks      M. Cai 《Rock Mechanics and Rock Engineering》2010,43(2):167-184 By applying the Griffith stress criterion of brittle failure, one can find that the uniaxial compressive strength (σc) of rocks is eight times the value of the uniaxial tensile strength (σt). The Griffith strength ratio is smaller than what is normally measured for rocks, even with the consideration of crack closure. The reason is that Griffith’s theories address only the initiation of failure. Under tensile conditions, the crack propagation is unstable so that the tensile crack propagation stress (σcd)t and the peak tensile strength σt are almost identical to the tensile crack initiation stress (σci)t. On the other hand, the crack growth after crack initiation is stable under a predominantly compressive condition. Additional loading is required in compression to bring the stress from the crack initiation stress σci to the peak strength σc. It is proposed to estimate the tensile strength of strong brittle rocks from the strength ratio of R = \fracs\textc | s\textt | = 8\fracs\textc s\textci . R = {\frac{{\sigma_{\text{c}} }}{{\left| {\sigma_{\text{t}} } \right|}}} = 8{\frac{{\sigma_{\text{c}} }}{{\sigma_{\text{ci}} }}}. The term \fracs\textc s\textci {\frac{{\sigma_{\text{c}} }}{{\sigma_{\text{ci}} }}} accounts for the difference of crack growth or propagation in tension and compression in uniaxial compression tests. \fracsc sci {\frac{{\sigma_{c} }}{{\sigma_{ci} }}} depends on rock heterogeneity and is larger for coarse grained rocks than for fine grained rocks. σci can be obtained from volumetric strain measurement or acoustic emission (AE) monitoring. With the strength ratio R determined, the tensile strength can be indirectly obtained from | s\textt | = \fracs\textc R = \fracs\textci 8. \left| {\sigma_{\text{t}} } \right| = {\frac{{\sigma_{\text{c}} }}{R}} = {\frac{{\sigma_{\text{ci}} }}{8}}. It is found that the predicted tensile strengths using this method are in good agreement with test data. Finally, a practical estimate of the Hoek–Brown strength parameter m i is presented and a bi-segmental or multi-segmental representation of the Hoek–Brown strength envelope is suggested for some brittle rocks. In this fashion, the rock strength parameters like σt and m i, which require specialty tests such as direct tensile (or Brazilian) and triaxial compression tests for their determination, can be reasonably estimated from uniaxial compression tests.  相似文献    8. IR calibrations for water determination in olivine,r-GeO<Subscript>2</Subscript>, and SiO<Subscript>2</Subscript> polymorphs      Sylvia-Monique?ThomasEmail author  Monika?Koch-Müller  Patrick?Reichart  Dieter?Rhede  Rainer?Thomas  Richard?Wirth  Stanislav?Matsyuk 《Physics and Chemistry of Minerals》2009,36(9):489-509 Mineral-specific IR absorption coefficients were calculated for natural and synthetic olivine, SiO2 polymorphs, and GeO2 with specific isolated OH point defects using quantitative data from independent techniques such as proton–proton scattering, confocal Raman spectroscopy, and secondary ion mass spectrometry. Moreover, we present a routine to detect OH traces in anisotropic minerals using Raman spectroscopy combined with the “Comparator Technique”. In case of olivine and the SiO2 system, it turns out that the magnitude of ε for one structure is independent of the type of OH point defect and therewith the peak position (quartz ε = 89,000 ± 15,000  \textl \textmol\textH2\textO-1 \textcm-2\text{l}\,\text{mol}_{{\text{H}_2}\text{O}}^{-1}\,\text{cm}^{-2}), but it varies as a function of structure (coesite ε = 214,000 ± 14,000  \textl \textmol\textH2\textO-1 \textcm-2\text{l}\,\text{mol}_{{\text{H}_2}\text{O}}^{-1}\,\text{cm}^{-2}; stishovite ε = 485,000 ± 109,000  \textl \textmol\textH2\textO-1 \textcm-2\text{l}\,\text{mol}_{{\text{H}_2}\text{O}}^{-1}\,\text{cm}^{-2}). Evaluation of data from this study confirms that not using mineral-specific IR calibrations for the OH quantification in nominally anhydrous minerals leads to inaccurate estimations of OH concentrations, which constitute the basis for modeling the Earth’s deep water cycle.  相似文献    9. Li diffusion in zircon   总被引：2，自引：2，他引：0   D. J. Cherniak  E. B. Watson 《Contributions to Mineralogy and Petrology》2010,160(3):383-390 Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0–1.2 GPa) conditions has been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE+3 that might provide charge balance. Diffusion experiments performed in the presence of H2O–CO2 fluid were run in a piston–cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon with oxalic acid added to produce H2O–CO2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,γ)8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion normal to the c-axis over the temperature range 703–1.151°C at 1 atm for experiments run with the spodumene source: D\textLi = 7.17 ×10 - 7 exp( - 275 ±11 \textkJmol - 1 /\textRT)\textm2 \texts - 1. D_{\text{Li}} = 7.17 \times 10^{ - 7} { \exp }( - 275 \pm 11\,{\text{kJmol}}^{ - 1} /{\text{RT}}){\text{m}}^{2} {\text{s}}^{ - 1}.  相似文献    10. A double hardening thermo-mechanical constitutive model for overconsolidated clays   总被引：1，自引：1，他引：0   E. L. Liu  H. L. Xing 《Acta Geotechnica》2009,4(1):1-6 On the basis of a double hardening model for clays and available experimental results, a new thermo-elasto-plastic constitutive model for saturated clays is proposed to describe the effects of temperature and overconsolidation ratio on the mechanical properties of saturated clays. Two hardening parameters are introduced: sc￠ {\sigma}_{{\rm c}}^{\prime} and α. The proposed model is then applied to simulate the relevant important features of saturated clays with different overconsolidation ratios under different temperature and loading conditions. The model predictions are compared with available experimental results to demonstrate its accuracy and usefulness.  相似文献    11. Heat capacity of hydrous trachybasalt from Mt Etna: comparison with CaAl<Subscript>2</Subscript>Si<Subscript>2</Subscript>O<Subscript>8</Subscript> (An)–CaMgSi<Subscript>2</Subscript>O<Subscript>6</Subscript> (Di) as basaltic proxy compositions      D.?GiordanoEmail author  A.?R.?L.?Nichols  M.?Potuzak  D.?Di?Genova  C.?Romano  J.?K.?Russell 《Contributions to Mineralogy and Petrology》2015,170(5-6):48 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    12. On the problem of transport species of tungsten by hydrothermal solutions      A. F. Redkin  N. P. Kostromin 《Geochemistry International》2010,48(10):988-998 The solubility of pentatungstate of sodium (PTS) Na2W5O16 · H2O and sodium tungsten bronzes (STB) Na0.16WO3 in acid chloride solutions containing 0.026, 0.26, and 3.02m NaCl have been studied at 500°C, 1000 bar, given fO2 (Co-CoO, Ni-NiO, PTS-STB buffers), and constant NaCl/HCl ratio (Ta2O5-Na2Ta4O11 buffer). Depending on experimental conditions, the tungsten content in the solutions after experiments varied from 10−3 to 2 × 10−2 mol/kg H2O. Obtained data were used to calculate the formation constants of predominant tungsten complexes (VI, V): H3W3VIO123−, W3VO93−, [WVW4VIO16]3−, for reactions $ \begin{gathered} 3H_2 WO_4^0 \leftrightarrow H_3 W_3 O_{12}^{3 - } + 3H^ + \log K_p = - 7.5 \pm 0.1, \hfill \\ 3H_2 WO_4^0 \leftrightarrow W_3 O_9^{3 - } + 1.5H_2 O + 3H^ + + 0.75O_2 \log K_p = - 25.7 \pm 0.2, \hfill \\ 5H_2 WO_4^0 \leftrightarrow \left[ {W^V W_4^{VI} O_{16} } \right]^{3 - } + 3H^ + + 3.5H_2 O + 0.25O_2 \log K_p = - 4.6 \pm 0.1 \hfill \\ \end{gathered} $ \begin{gathered} 3H_2 WO_4^0 \leftrightarrow H_3 W_3 O_{12}^{3 - } + 3H^ + \log K_p = - 7.5 \pm 0.1, \hfill \\ 3H_2 WO_4^0 \leftrightarrow W_3 O_9^{3 - } + 1.5H_2 O + 3H^ + + 0.75O_2 \log K_p = - 25.7 \pm 0.2, \hfill \\ 5H_2 WO_4^0 \leftrightarrow \left[ {W^V W_4^{VI} O_{16} } \right]^{3 - } + 3H^ + + 3.5H_2 O + 0.25O_2 \log K_p = - 4.6 \pm 0.1 \hfill \\ \end{gathered}   相似文献    13. Foundations of cable car towers upon alpine glaciers      Wolfgang Fellin  Bernhard Lackinger 《Acta Geotechnica》2007,2(4):291-300 This paper presents a design approach for strip footings upon glacier ice. Safety against ultimate limit state is proved by the geotechnical slip-line field solution by Prandtl. Glacier ice at 0°C can be modelled as purely cohesive material. Statistical evaluation of uniaxial compression tests with high strain rate revealed a mean value of the cohesion of 600 kPa and a characteristic value c k = 355 kPa (5% fractile). With a coefficient of variation V c = 0.3, the partial safety factor turns out to be γ c = 1.9. An approximate solution for estimating the creep settlement rate is presented to check the serviceability limit state: with the width b of the strip foundation, p the foundation pressure and for ice at 0°C. Experiences on Stubai glacier with grate shaped footings showed that creep settlements occurring per year due to maximum foundation pressures 250 kPa did not influence the operation and the maintenance of the cable cars.  相似文献    14. High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle   总被引：9，自引：4，他引：5   C. Ballhaus  R. F. Berry  D. H. Green 《Contributions to Mineralogy and Petrology》1991,107(1):27-40 Synthetic spinel harzburgite and lherzolite assemblages were equilibrated between 1040 and 1300° C and 0.3 to 2.7 GPa, under controlled oxygen fugacity (f O 2). f O 2 was buffered with conventional and open double-capsule techniques, using the Fe−FeO, WC-WO2-C, Ni−NiO, and Fe3O4−Fe2O3 buffers, and graphite, olivine, and PdAg alloys as sample containers. Experiments were carried out in a piston-cylinder apparatus under fluid-excess conditions. Within the P-T-X range of the experiments, the redox ratio Fe3+/ΣFe in spinel is a linear function of f O 2 (0.02 at IW, 0.1 at WCO, 0.25 at NNO, and 0.75 at MH). It is independent of temperature at given Δlog(f O 2), but decreases slightly with increasing Cr content in spinel. The Fe3+/ΣFe ratio falls with increasing pressure at given Δlog(f O 2), consistent with a pressure correction based on partial molar volume data. At a specific temperature, degree of melting and bulk composition, the Cr/(Cr+Al) ratio of a spinel rises with increasing f O 2. A linear least-squares fit to the experimental data gives the semi-empirical oxygen barometer in terms of divergence from the fayalite-magnetite-quartz (FMQ) buffer:   相似文献    15. Experimental investigation of zoisite–clinozoisite phase equilibria in the system CaO–Fe2O3–Al2O3–SiO2–H2O      A. Brunsmann  G. Franz  W. Heinrich 《Contributions to Mineralogy and Petrology》2002,143(1):115-130 The system Ca2Al3Si3O11(O/OH)-Ca2Al2FeSi3O11(O/OH), with emphasis on the Al-rich portion, was investigated by synthesis experiments at 0.5 and 2.0 GPa, 500-800 °C, using the technique of producing overgrowths on natural seed crystals. Electron microprobe analyses of overgrowths up to >100 µm wide have located the phase transition from clinozoisite to zoisite as a function of P-T-Xps and a miscibility gap in the clinozoisite solid solution. The experiments confirm a narrow, steep zoisite-clinozoisite two-phase loop in T-Xps section. Maximum and minimum iron contents in coexisting zoisite and clinozoisite are given by Xpszo (max) = 1.9*10 - 4 T+ 3.1*10 - 2 P - 5.36*10 - 2{\rm X}_{{\rm ps}}^{{\rm zo}} {\rm (max) = 1}{\rm .9*10}^{ - 4} T{\rm + 3}{\rm .1*10}^{ - 2} P - {\rm 5}{\rm .36*10}^{ - 2} and Xpsczo (min) = (4.6 * 10 - 4 - 4 * 10 - 5 P)T + 3.82 * 10 - 2 P - 8.76 * 10 - 2{\rm X}_{{\rm ps}}^{{\rm czo}} {\rm (min)} = {\rm (4}{\rm .6} * {\rm 10}^{ - {\rm 4}} - 4 * {\rm 10}^{ - {\rm 5}} P{\rm )}T + {\rm 3}{\rm .82} * {\rm 10}^{ - {\rm 2}} P - {\rm 8}{\rm .76} * {\rm 10}^{ - {\rm 2}} (P in GPa, T in °C). The iron-free end member reaction clinozoisite = zoisite has equilibrium temperatures of 185ᇆ °C at 0.5 GPa and 0ᇆ °C at 2.0 GPa, with (Hr0=2.8ǃ.3 kJ/mol and (Sr0=4.5ǃ.4 J/mol2K. At 0.5 GPa, two clinozoisite modifications exist, which have compositions of clinozoisite I ~0.15 to 0.25 Xps and clinozoisite II >0.55 Xps. The upper thermal stability of clinozoisite I at 0.5 GPa lies slightly above 600 °C, whereas Fe-rich clinozoisite II is stable at 650 °C. The schematic phase relations between epidote minerals, grossular-andradite solid solutions and other phases in the system CaO-Al2O3-Fe2O3-SiO2-H2O are shown.  相似文献    16. The H<Subscript>2</Subscript>O solubility of alkali basaltic melts: an experimental study      Priscille Lesne  Bruno Scaillet  Michel Pichavant  Giada Iacono-Marziano  Jean-Michel Beny 《Contributions to Mineralogy and Petrology》2011,162(1):133-151 Experiments were conducted to determine the water solubility of alkali basalts from Etna, Stromboli and Vesuvius volcanoes, Italy. The basaltic melts were equilibrated at 1,200°C with pure water, under oxidized conditions, and at pressures ranging from 163 to 3,842 bars. Our results show that at pressures above 1 kbar, alkali basalts dissolve more water than typical mid-ocean ridge basalts (MORB). Combination of our data with those from previous studies allows the following simple empirical model for the water solubility of basalts of varying alkalinity and fO2 to be derived: \textH 2 \textO( \textwt% ) = \text H 2 \textO\textMORB ( \textwt% ) + ( 5.84 ×10 - 5 *\textP - 2.29 ×10 - 2 ) ×( \textNa2 \textO + \textK2 \textO )( \textwt% ) + 4.67 ×10 - 2 ×\Updelta \textNNO - 2.29 ×10 - 1 {\text{H}}_{ 2} {\text{O}}\left( {{\text{wt}}\% } \right) = {\text{ H}}_{ 2} {\text{O}}_{\text{MORB}} \left( {{\text{wt}}\% } \right) + \left( {5.84 \times 10^{ - 5} *{\text{P}} - 2.29 \times 10^{ - 2} } \right) \times \left( {{\text{Na}}_{2} {\text{O}} + {\text{K}}_{2} {\text{O}}} \right)\left( {{\text{wt}}\% } \right) + 4.67 \times 10^{ - 2} \times \Updelta {\text{NNO}} - 2.29 \times 10^{ - 1} where H2OMORB is the water solubility at the calculated P, using the model of Dixon et al. (1995). This equation reproduces the existing database on water solubilities in basaltic melts to within 5%. Interpretation of the speciation data in the context of the glass transition theory shows that water speciation in basalt melts is severely modified during quench. At magmatic temperatures, more than 90% of dissolved water forms hydroxyl groups at all water contents, whilst in natural or synthetic glasses, the amount of molecular water is much larger. A regular solution model with an explicit temperature dependence reproduces well-observed water species. Derivation of the partial molar volume of molecular water using standard thermodynamic considerations yields values close to previous findings if room temperature water species are used. When high temperature species proportions are used, a negative partial molar volume is obtained for molecular water. Calculation of the partial molar volume of total water using H2O solubility data on basaltic melts at pressures above 1 kbar yields a value of 19 cm3/mol in reasonable agreement with estimates obtained from density measurements.  相似文献    17. Primary fluids entrapped at blueschist to eclogite transition: evidence from the Tianshan meta-subduction complex in northwestern China   总被引：5，自引：1，他引：5   Jun Gao  Reiner Klemd 《Contributions to Mineralogy and Petrology》2001,142(1):1-14 Orthopyroxene and olivine exposed along the rim of a harzburgite xenolith from La Palma (Canary Islands) show polycrystalline selvages and diffusion zones that result from contact with mafic, alkaline, silica-undersaturated melts during at least 10-100 years before eruption. The zoned selvages consist of a fine-grained reaction rim towards the xenolith and a coarser grained, cumulate-like layer towards the melt contact. The diffusion zones are characterized by decreasing magnesium number from about 89-91 in the xenolith interior to 79-85 at the rims, and clearly result from Fe-Mg exchange with surrounding mafic melt. The width of the diffusion zones is 80-200 µm in orthopyroxene and 1,020-1,730 µm in olivine. Orthopyroxene also shows decreasing Al2O3 and Cr2O3 and increasing MnO and TiO2 towards the reaction rims. Textural relations and comparisons with dissolution experiments suggest that orthopyroxene dissolution by silica-undersaturated melt essentially ceased after days to weeks of melt contact, possibly because of decreasing temperature and formation of the reaction rims. The short dissolution phase was followed by prolonged growth of diffusion zones through cation exchange between xenolith minerals and melt across the reaction rims, and by the growth of cumulus crystals. The observations indicate that orthopyroxene xenocrysts and harzburgite xenoliths can survive in mafic, silica-undersaturated, subliquidus magmas at 1,050-1,200 °C and 200-800 MPa for tens of years. Modeling and comparison of the diffusion zones indicate that the average Fe-Mg interdiffusion coefficient DFeMg in orthopyroxene is 2 log units lower than that in olivine; at 1,130 °C and QFM-buffered oxygen fugacity, DFeMgopx = 3 ×10 - 19  m2  s- 1D_{FeMg}^{opx} = 3 \times 10^{ - 19} \,{\rm m}^2 \,{\rm s}^{{\rm - 1}} . The new data overlap well with recently published data for DFeMg in diopside, and indicate that DFeMg opxD_{FeMg\,}^{opx} (as predicted by previous authors) may be extrapolated to higher temperatures and oxygen fugacities. It is suggested that DFeMg opx D_{FeMg\,}^{opx} and DFeMg in Mn-poor ferromagnesian garnet are similar within 0.5 log units at temperatures between 1,050 and 1,200 °C.  相似文献    18. Thermal expansion of plagioclase feldspars      M. Tribaudino  R. J. Angel  F. Cámara  F. Nestola  D. Pasqual  I. Margiolaki 《Contributions to Mineralogy and Petrology》2010,160(6):899-908 The volume thermal expansion coefficient and the anisotropy of thermal expansion were determined for nine natural feldspars with compositions, in terms of albite (NaAlSi3O8, Ab) and anorthite (CaAl2Si2O8, An), of Ab100, An27Ab73, An35Ab65, An46Ab54, An60Ab40, An78Ab22, An89Ab11, An96Ab4 and An100 by high resolution powder diffraction with a synchrotron radiation source. Unit-cell parameters were determined from 124 powder patterns of each sample, collected over the temperature range 298–935 K. The volume thermal expansion coefficient of the samples determined by a linear fit of V/V 0 = α(T − T 0) varies with composition (X An in mol %) as: aV = 2.90( 4 ) ×10 - 5 - 3.0( 2 ) ×10 - 7 *X\textAn + 1.8( 2 ) ×10 - 9 *X\textAn2 \alpha_{V} = 2.90\left( 4 \right) \times 10^{ - 5} - 3.0\left( 2 \right) \times 10^{ - 7} *X_{\text{An}} + 1.8\left( 2 \right) \times 10^{ - 9} *X_{\text{An}}^{2}  相似文献    19. An evaluation of quartzite flow laws based on comparisons between experimentally and naturally deformed rocks   总被引：4，自引：0，他引：4   Greg Hirth  Christian Teyssier  James W. Dunlap 《International Journal of Earth Sciences》2001,90(1):77-87   相似文献    20. Magnesiochloritoid: Compressibility and high pressure structure refinement      Paola Comodi  Marcello Mellini  Pier Francesco Zanazzi 《Physics and Chemistry of Minerals》1992,18(8):483-490 The response of magnesiochloritoid to pressure has been studied by single crystal X-ray diffraction in a diamond anvil cell, using crystals with composition Mg1.3Fe0.7Al4Si2O10(OH)4. The unit cell parameters decrease from a = 9.434 (3), b = 5.452 (2), c = 18.136 (5) Å, β = 101.42° (2) (1 bar pressure) to a = 9.370 (7), b = 5.419 (5), c = 17.88 (1) Å, β = 101.5° (1) (42 kbar pressure), following a slightly anisotropic compression pattern (linear compressibilities parallel to unit cell edges: β a = 1.85, β b = 1.74, βc = 3.05 × 10?4 kbar?1) with a bulk modulus of 1480 kbar. Perpendicular to c, the most compressible direction, the crystal structure (space group C2/c) consists of two kinds of alternating octahedral layers connected via isolated SiO4 tetrahedra. With increasing pressure the slightly wavy layer [Mg1.3Fe0.7AlO2(OH)4] tends to flatten. Furthermore, the octahedra in this layer, with all cations underbonded, are more compressible than the octahedra in the (A13O8) layer with slightly overbonded aluminum. Comparison between high-pressure and high-temperature data yields the following equations: $$\begin{gathered} a_{P,T} = 9.434{\text{ }}{\AA} - 174 \cdot 10^{ - 5} {\text{ }}{\AA}{\text{kb}}^{{\text{ - 1}}} \cdot P \hfill \\ {\text{ }} + 9 \cdot 10^{ - 5} {\text{ }}{\AA}^\circ C^{ - 1} \cdot (T - 25^\circ C) \hfill \\ b_{P,T} = 5.452{\text{ }}{\AA} - 95 \cdot 10^{ - 5} {\text{ }}{\AA}{\text{kb}}^{{\text{ - 1}}} \cdot P \hfill \\ {\text{ }} + 5 \cdot 65 \cdot 10^{ - 5} {\text{ }}{\AA}^\circ C^{ - 1} \cdot (T - 25^\circ C) \hfill \\ c_{P,T} = 18.136{\text{ }}{\AA} - 549 \cdot 10^{ - 5} {\text{ }}{\AA}{\text{kb}}^{{\text{ - 1}}} \cdot P \hfill \\ {\text{ }} + 16 \cdot 2^{ - 5} {\text{ }}{\AA}^\circ C^{ - 1} \cdot (T - 25^\circ C) \hfill \\ \end{gathered} $$ with P in kbar and T in °C. These equations indicate that the unit cell and bond geometry of magnesiochloritoid at formation conditions do not differ greatly from those at the outcrop conditions, e.g. the calculated unitcell volume is 917.3 Å3 at P = 16 kbar and T=500 °C, whereas the observed volume at room conditions is 914.4 Å3. In addition, they show that the specific gravity increases from formation at depth to outcrop at surface conditions.  相似文献    设为首页 | 免责声明 | 关于勤云 | 加入收藏 Copyright©北京勤云科技发展有限公司  京ICP备09084417号