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1.
Yongliang Xiong 《Aquatic Geochemistry》2008,14(3):223-238
Solubility experiments were conducted for the dissolution reaction of brucite, Mg(OH)2 (cr):
Experiments were conducted from undersaturation in deionized (DI) water and 0.010–4.4 m NaCl solutions at 22.5°C. In addition,
brucite solubility was measured from supersaturation in an experiment in which brucite was precipitated via dropwise addition
of 0.10 m NaOH into a 0.10 m MgCl2 solution also at 22.5°C. The attainment of the reversal in equilibrium was demonstrated in this study. The solubility constant
at 22.5°C at infinite dilution calculated from the experimental results from the direction of supersaturation by using the
specific interaction theory (SIT) is: with a corresponding value of 17.0 ± 0.2 (2σ) when extrapolated to 25°C. The dimensionless standard chemical potential (μ°/RT)
of brucite derived from the solubility data in 0.010 m to 4.4 m NaCl solutions from undersaturation extrapolated to 25°C is
−335.76 ± 0.45 (2σ), with the corresponding Gibbs free energy of formation of brucite, , being −832.3 ± 1.1 (2σ) kJ mol−1. In combination with the auxiliary thermodynamic data, the is calculated to be 17.1 ± 0.2 (2σ), based on the above Gibbs free energy of formation for brucite. This study recommends
an average value of 17.05 ± 0.2 in logarithmic unit as solubility constant of brucite at 25°C, according to the values from
both supersaturation and undersaturation.
Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the
United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000. 相似文献
2.
3.
Frank J. Millero Abzar Mirzaliyev Javid Safarov Fen Huang Mareva Chanson Astan Shahverdiyev Egon Hassel 《Aquatic Geochemistry》2008,14(4):289-299
The density ρ of Caspian Sea waters was measured as a function of temperature (273.15–343.15) K at conductivity salinities
of 7.8 and 11.3 using the Anton-Paar Densitometer. Measurements were also made on one of the samples (S = 11.38) diluted with water as a function of temperature (T = 273.15–338.15 K) and salinity (2.5–11.3). These latter results have been used to develop an equation of state for the Caspian
Sea (σ = ±0.007 kg m−3)
where ρ0 is the density of water and the parameters A, B and C are given by
Measurements of the density of artificial Caspian Sea water at 298.15 K agree to ± 0.012 kg m−3 with the real samples. These results indicate that the composition of Caspian Sea waters must be close to earlier measurements
of the major components. Model calculations based on this composition yield densities that agree with the measured values
to ± 0.012 kg m−3. The new density measurements are higher than earlier measurements. This may be related to a higher concentration of dissolved
organic carbon found in the present samples (500 μM) which is much higher than the values in ocean waters (~65 μM). 相似文献
4.
The activity of silica in kimberlites,revisited 总被引：1，自引：1，他引：0
Robert W. Luth 《Contributions to Mineralogy and Petrology》2009,158(2):283-294
The activity of silica in a silicate liquid in equilibrium with olivine and orthopyroxene decreases with increasing pressure. In contrast, the activity of silica in
an unbuffered silicate liquid changes little with pressure. Although the implications of these pressure dependencies have
been considered by previous authors in terms of inferring pressures of origin of magmas, less consideration has been given
to the implications of these dependencies on the evolution of the magma en route to the surface, or to the mantle through
which the magma passes. In this paper, a combination of Schreinemakers’ analysis in isothermal section and calculated reactions in space is used to (a) rationalize the absence of orthopyroxene xenocrysts in kimberlites and the relative abundance of olivine
“megacrysts” therein, (b) propose another reason for the paucity of xenocrystic mantle-derived carbonates in kimberlites,
(c) explain why clinopyroxene is much less reactive in the kimberlite melt than is orthopyroxene, and (d) explore the implications
of the relative stabilities of olivine, orthopyroxene, and clinopyroxene in kimberlitic magma for the mantle through which
the magma transits.
相似文献
| Robert W. LuthEmail: |
5.
Priscille Lesne Bruno Scaillet Michel Pichavant Jean-Michel Beny 《Contributions to Mineralogy and Petrology》2011,162(1):153-168
Experiments were conducted to determine CO2 solubilities in alkali basalts from Vesuvius, Etna and Stromboli volcanoes. The basaltic melts were equilibrated with nearly
pure CO2 at 1,200°C under oxidizing conditions and at pressures ranging from 269 to 2,060 bars. CO2 solubility was determined by FTIR measurements. The results show that alkalis have a strong effect on the CO2 solubility and confirm and refine the relationship between the compositional parameter Π devised by Dixon (Am Mineral 82:368–378,
1997) and the CO2 solubility. A general thermodynamic model for CO2 solubility in basaltic melts is defined for pressures up to 2 kbars. Based on the assumption that O2− and CO32− mix ideally, we have:
|
_boxclose_3^2 - ^m (P,T)X_^2 - ^m f__2 (P,T) K(P,T) = X__3^2 - ^m (P,T) ( X_^2 - ^m f__2 (P,T) ). \begin{gathered} K(P,T) = {\frac{{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)}}{{X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)}}} \hfill \\ K(P,T) = {{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)} \mathord{\left/ {\vphantom {{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)} {\left( {X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)} \right).}}} \right. \kern-\nulldelimiterspace} {\left( {X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)} \right).}} \hfill \\ \end{gathered} 相似文献
6.
Andreas G. Mueller 《Mineralium Deposita》2007,42(7):737-769
Five Cu–Au epidote skarns are associated with the Mt. Shea intrusive complex, located in the 2.7–2.6 Ga Eastern Goldfields
Province of the Archean Yilgarn craton, in greenstones bounded by the Boulder Lefroy and Golden Mile strike-slip faults, which
control the Golden Mile (1,435 t Au) at Kalgoorlie and smaller “orogenic” gold deposits at Kambalda. The Cu–Au deposits studied
are oxidized endoskarns replacing faulted and fractured quartz monzodiorite–granodiorite. The orebodies are up to 140 m long
and 40 m thick. Typical grades are 0.5% Cu and 0.3 g/t Au although parts are richer in gold (1.5–4.5 g/t). At the Hannan South
mine, the skarns consist of epidote, calcite, chlorite, magnetite (5–15%), and minor quartz, muscovite, and microcline. Gangue
and magnetite are in equilibrium contact with pyrite and chalcopyrite. The As–Co–Ni-bearing pyrite contains inclusions of
hematite, gold, and electrum and is intergrown with cobaltite and Cu–Pb–Bi sulfides. At the Shea prospect, massive, net-textured,
and breccia skarns are composed of multistage epidote, actinolite, albite, magnetite (5%), and minor biotite, calcite, and
quartz. Gangue and magnetite are in equilibrium with Co–Ni pyrite and chalcopyrite. Mineral-pair thermometry, mass-balance
calculations, and stable-isotope data (pyrite δ34SCDT = 2.5‰, calcite δ13CPDB = −5.3‰, and δ18OSMOW = 12.9‰) indicate that the Cu–Au skarns formed at 500 ± 50°C by intense Ca–Fe–CO2–S metasomatism from fluids marked by an igneous isotope signature. The Mt. Shea stock–dike–sill complex postdates the regional
D1 folding and metamorphism and the main phase of D2 strike-slip faulting. The suite is calc-akaline and comprises hornblende–plagioclase
monzodiorite, quartz monzodiorite, granodiorite, and quartz–plagioclase tonalite porphyry. The intrusions display a wide range
in silica content (53–73 wt% SiO2), in ratio (0.37–0.89), and in ratio (0.02–0.31). Chromium (62–345 ppm), Ni (23–158), Sr (311–1361 ppm), and Ba (250–2,581 ppm) contents are high, Sr/Y
ratios are high (24–278, mostly >50), and the rare earth element patterns are fractionated . These features and a negative niobium anomaly relative to the normal mid-ocean ridge basalt indicate that the suite formed
by hornblende fractionation from a subduction-related monzodiorite magma sourced from metasomatized peridotite in the upper
mantle. The magnesian composition of many intrusions was enhanced due to hornblende crystallization under oxidizing hydrous
conditions and during the subsequent destruction of igneous magnetite by subsolidus actinolite–albite alteration. At the Shea
prospect, main-stage Cu–Au epidote skarn is cut by biotite–albite–dolomite schist and by red biotite–albite replacement bands.
Post-skarn alteration includes 20-m-thick zones of sericite–chlorite–ankerite schist confined to two D3 reverse faults. The
schists are mineralized with magnetite + pyrite + chalcopyrite (up to 0.62% Cu, 1.6 g/t Au) and are linked to skarn formation
by shared Ca–Fe–CO2 metasomatism. Red sericitic alteration, marked by magnetite + hematite + pyrite, occurs in fractured porphyry. The biotite/sericite
alteration and oxidized ore assemblages at the Shea prospect are mineralogically identical to magnetite–hematite-bearing gold
lodes at Kambalda and in the Golden Mile. Published fluid inclusion data suggest that a “high-pressure”, oxidized magmatic
fluid (2–9 wt% NaCl equivalent, , 200–400 MPa) was responsible for gold mineralization in structural sites of the Boulder Lefroy and Golden Mile faults. The
sericite–alkerite lodes in the Golden Mile share the assemblages pyrite + tennantite + chalcopyrite and bornite + pyrite,
and accessory high-sulfidation enargite with late-stage sericitic alteration zones developed above porphyry copper deposits. 相似文献
7.
Amy E. Hofmann Michael B. Baker John M. Eiler 《Contributions to Mineralogy and Petrology》2013,166(1):235-253
In order to evaluate the effect of trace and minor elements (e.g., P, Y, and the REEs) on the high-temperature solubility of Ti in zircon (zrc), we conducted 31 experiments on a series of synthetic and natural granitic compositions [enriched in TiO2 and ZrO2; Al/(Na + K) molar ~1.2] at a pressure of 10 kbar and temperatures of ~1,400 to 1,200 °C. Thirty of the experiments produced zircon-saturated glasses, of which 22 are also saturated in rutile (rt). In seven experiments, quenched glasses coexist with quartz (qtz). SiO2 contents of the quenched liquids range from 68.5 to 82.3 wt% (volatile free), and water concentrations are 0.4–7.0 wt%. TiO2 contents of the rutile-saturated quenched melts are positively correlated with run temperature. Glass ZrO2 concentrations (0.2–1.2 wt%; volatile free) also show a broad positive correlation with run temperature and, at a given T, are strongly correlated with the parameter (Na + K + 2Ca)/(Si·Al) (all in cation fractions). Mole fraction of ZrO2 in rutile $ \left( {\mathop X\nolimits_{{{\text{ZrO}}_{ 2} }}^{\text{rt}} } \right) $ in the quartz-saturated runs coupled with other 10-kbar qtz-saturated experimental data from the literature (total temperature range of ~1,400 to 675 °C) yields the following temperature-dependent expression: $ {\text{ln}}\left( {\mathop X\nolimits_{{{\text{ZrO}}_{ 2} }}^{\text{rt}} } \right) + {\text{ln}}\left( {a_{{{\text{SiO}}_{2} }} } \right) = 2.638(149) - 9969(190)/T({\text{K}}) $ , where silica activity $ a_{{{\text{SiO}}_{2} }} $ in either the coexisting silica polymorph or a silica-undersaturated melt is referenced to α-quartz at the P and T of each experiment and the best-fit coefficients and their uncertainties (values in parentheses) reflect uncertainties in T and $ \mathop X\nolimits_{{{\text{ZrO}}_{2} }}^{\text{rt}} $ . NanoSIMS measurements of Ti in zircon overgrowths in the experiments yield values of ~100 to 800 ppm; Ti concentrations in zircon are positively correlated with temperature. Coupled with values for $ a_{{{\text{SiO}}_{2} }} $ and $ a_{{{\text{TiO}}_{2} }} $ for each experiment, zircon Ti concentrations (ppm) can be related to temperature over the range of ~1,400 to 1,200 °C by the expression: $ \ln \left( {\text{Ti ppm}} \right)^{\text{zrc}} + \ln \left( {a_{{{\text{SiO}}_{2} }} } \right) - \ln \left( {a_{{{\text{TiO}}_{2} }} } \right) = 13.84\left( {71} \right) - 12590\left( {1124} \right)/T\left( {\text{K}} \right) $ . After accounting for differences in $ a_{{{\text{SiO}}_{2} }} $ and $ a_{{{\text{TiO}}_{2} }} $ , Ti contents of zircon from experiments run with bulk compositions based on the natural granite overlap with the concentrations measured on zircon from experiments using the synthetic bulk compositions. Coupled with data from the literature, this suggests that at T ≥ 1,100 °C, natural levels of minor and trace elements in “granitic” melts do not appear to influence the solubility of Ti in zircon. Whether this is true at magmatic temperatures of crustal hydrous silica-rich liquids (e.g., 800–700 °C) remains to be demonstrated. Finally, measured $ D_{\text{Ti}}^{{{\text{zrc}}/{\text{melt}}}} $ values (calculated on a weight basis) from the experiments presented here are 0.007–0.01, relatively independent of temperature, and broadly consistent with values determined from natural zircon and silica-rich glass pairs. 相似文献
8.
Alexej N. Platonov Klaus Langer Stanislav S. Matsyuk 《Physics and Chemistry of Minerals》2008,35(6):331-337
In the course of a thorough study of the influences of the second coordination sphere on the crystal field parameters of the
3d
N
-ions and the character of 3d
N
–O bonds in oxygen based minerals, 19 natural Cr3+-bearing (Mg,Ca)-garnets from upper mantle rocks were analysed and studied by electronic absorption spectroscopy, EAS. The
garnets had compositions with populations of the [8]
X-sites by 0.881 ± 0.053 (Ca + Mg) and changing Ca-fractions in the range 0.020 ≤ w
Ca[8] ≤ 0.745, while the [6]
Y-site fraction was constant with x
Cr3+
[6] = 0.335 ± 0.023. The garnets had colours from deeply violet-red for low Ca-contents (up to x
Ca = 0.28), grey with 0.28 ≤ x
Ca ≤ 0.4 and green with 0.4 ≤ x
Ca. The crystal field parameter of octahedral Cr3+ 10Dq decreases strongly on increasing Ca-fraction from 17,850 cm−1 at x
Ca[8] = 0.020 to 16,580 cm−1 at x
Ca[8] = 0.745. The data could be fit with two model which do statistically not differ: (1) two linear functions with a discontinuity
close to x
Ca[8] ≈ 0.3,
9.
The diffusion of water in a peralkaline and a peraluminous rhyolitic melt was investigated at temperatures of 714–1,493 K
and pressures of 100 and 500 MPa. At temperatures below 923 K dehydration experiments were performed on glasses containing
about 2 wt% H2O
t
in cold seal pressure vessels. At high temperatures diffusion couples of water-poor (<0.5 wt% H2O
t
) and water-rich (~2 wt% H2O
t
) melts were run in an internally heated gas pressure vessel. Argon was the pressure medium in both cases. Concentration profiles
of hydrous species (OH groups and H2O molecules) were measured along the diffusion direction using near-infrared (NIR) microspectroscopy. The bulk water diffusivity
() was derived from profiles of total water () using a modified Boltzmann-Matano method as well as using fittings assuming a functional relationship between and Both methods consistently indicate that is proportional to in this range of water contents for both bulk compositions, in agreement with previous work on metaluminous rhyolite. The
water diffusivity in the peraluminous melts agrees very well with data for metaluminous rhyolites implying that an excess
of Al2O3 with respect to alkalis does not affect water diffusion. On the other hand, water diffusion is faster by roughly a factor
of two in the peralkaline melt compared to the metaluminous melt. The following expression for the water diffusivity in the
peralkaline rhyolite as a function of temperature and pressure was obtained by least-squares fitting:
10.
Dariusz Dobrzyński 《Aquatic Geochemistry》2007,13(3):197-210
A wide set of aqueous chemistry data (574 water analyses) from natural environments has been used to testify and validate
of the solubility of synthetic hydroxyaluminosilicate (HASB), Al2Si2O5(OH)4. The ground and surface waters represent regolith and/or fissure aquifers in various (magmatic, sedimentary and metamorphic)
bedrocks in the Sudetes Mts. (SW Poland). The solubility of HASB in natural waters was calculated using the method proposed by Schneider et al. (Polyhedron 23:3185–3191, 2004). Results confirm
usefulness and validity of this method. The HASB solubility obtained from the field data (logKsp = −44.7 ± 0.58) is lower than it was estimated (logKsp = −40.6 ± 0.15) experimentally (Schneider et al. Polyhedron 23:3185–3191, 2004). In the waters studied the equilibrium with
HASB is maintained at pH above 6.7 and at [Al3+] ≤ 10−10. Silicon activity (log[H4SiO4]) ranges between −4.2 and −3.4. Due to the calculation method used, the Ksp mentioned above cannot be considered as a classical solubility constant. However, it can be used in the interpretation of
aluminium solubility in natural waters. The HASB has solubility lower than amorphous Al(OH)3, and higher than proto-imogolite. From water samples that are in equilibrium with respect to HASB, the solubility product described by the reaction,
is calculated to be logKsp = 14.0 (±0.7) at 7°C. 相似文献
11.
The Influence of Redox Reactions on the Uptake of Dissolved Ce by Suspended Fe and Mn Oxide Particles 总被引：1，自引：0，他引：1
Laboratory experiments were conducted to evaluate the partitioning ofrare earth elements (REE) between solution and suspended
particles. Becauseof their strong tendency to complex, the REE can be used to study a varietyof marine processes and in particular
particle scavenging. In this study, anemphasis was placed on examining abiotic redox processes that influence theuptake of
dissolved Ce by particles. Batch sorption experiments wereconducted with REE and synthetic mineral phases over the range of
pH4–9. The solutions varied in ionic strength between 0 and 0.7 M andconsisted of individual solutes (NaNO3, NaCl, andNa2SO4), ionic mixtures that duplicate theseawater composition, and natural seawater. The uptake of REE from solutionwas also studied
at a Pt electrode coated with
using cyclic voltametry.
Experimental results are consistent with uptake of dissolved Ce onto
occurring by a combination of oxidativescavenging and surface complexation. The contribution of oxidativescavenging to the
removal of Ce from solution is most pronounced at acidicpH, where the strictly trivalent REE exhibit little propensity for
sorptiononto
. Sorption of dissolved Ce onto FeOOH occursin a manner analogous to that of the other strictly trivalent REE and nocontribution
from oxidative scavenging is observed on this mineral phase atlow pH. Our work also substantiates the hypothesis that anions
in solution,particularly
and Cl-, aswell as those adsorbed on the surface of the particles, influence the extentof Ce uptake by
.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Melchor González-Dávila J. Magdalena Santana-Casiano Frank J. Millero 《Aquatic Geochemistry》2007,13(4):339-355
The thermodynamic stability constants for the hydrolysis and formation of mercury (Hg2+) chloride complexes
13.
The chemical potential of oxygen (µO2) in equilibrium with magnesiowüstite solid solution (Mg, Fe)O and metallic Fe has been determined by gas-mixing experiments at 1,473 K supplemented by solid-cell EMF experiments at lower temperatures. The results give:
14.
The incorporation and diffusion of hydrogen in San Carlos olivine (Fo90) single crystals were studied by performing experiments under hydrothermal conditions. The experiments were carried out either at 1.5 GPa, 1,000°C for 1.5 h in a piston cylinder apparatus or at 0.2 GPa, 900°C for 1 or 20 h in a cold-seal vessel. The oxygen fugacity was buffered using Ni–NiO, and the silica activity was buffered by adding San Carlos orthopyroxene powders. Polarized Fourier transform infrared (FTIR) spectroscopy was utilized to quantify the hydroxyl distributions in the samples after the experiments. The resulting infrared spectra reproduce the features of FTIR spectra that are observed in olivine from common mantle peridotite xenoliths. The hydrogen concentration at the edges of the hydrogenated olivine crystals corresponds to concentration levels calculated from published water solubility laws. Hydrogen diffusivities were determined for the three crystallographic axes from profiles of water content as a function of position. The chemical diffusion coefficients are comparable to those previously reported for natural iron-bearing olivine. At high temperature, hydrogenation is dominated by coupled diffusion of protons and octahedrally coordinated metal vacancies
where the vacancy diffusion rate limits the process. From the experimental data, we determined the following diffusion laws (diffusivity in m2 s−1, activation energies in kJ mol−1):
for diffusion along [100] and [010];
for diffusion along [001]. These diffusion rates are fast enough to modify significantly water contents within olivine grains in xenoliths ascending from the mantle. 相似文献
15.
Sylvie Demouchy Stephen J. Mackwell David L. Kohlstedt 《Contributions to Mineralogy and Petrology》2007,154(3):279-289
Interdiffusion of Fe and Mg in (Mg,Fe)O has been investigated experimentally under hydrous conditions. Single crystals of
MgO in contact with (Mg0.73Fe0.27)O were annealed hydrothermally at 300 MPa between 1,000 and 1,250°C and using a Ni–NiO buffer. After electron microprobe
analyses, the dependence of the interdiffusivity on Fe concentration was determined using a Boltzmann–Matano analysis. For
a water fugacity of ∼300 MPa, the Fe–Mg interdiffusion coefficient in Fe
x
Mg1−x
O with 0.01 ≤ x ≤ 0.25 can be described by with and C = −80 ± 10 kJ mol−1. For x = 0.1 and at 1,000°C, Fe–Mg interdiffusion is a factor of ∼4 faster under hydrous than under anhydrous conditions. This enhanced
rate of interdiffusion is attributed to an increased concentration of metal vacancies resulting from the incorporation of
hydrogen. Such water-induced enhancement of kinetics may have important implications for the rheological properties of the
lower mantle.
16.
Redox-controlled iron isotope fractionation during magmatic differentiation: an example from the Red Hill intrusion, S. Tasmania 总被引：1，自引：1，他引：0
Paolo A. Sossi John D. Foden Galen P. Halverson 《Contributions to Mineralogy and Petrology》2012,164(5):757-772
This study presents accurate and precise iron isotopic data for 16 co-magmatic rocks and 6 pyroxene–magnetite pairs from the classic, tholeiitic Red Hill sill in southern Tasmania. The intrusion exhibits a vertical continuum of compositions created by in situ fractional crystallisation of a single injection of magma in a closed igneous system and, as such, constitutes a natural laboratory amenable to determining the causes of Fe isotope fractionation in magmatic rocks. Early fractionation of pyroxenes and plagioclase, under conditions closed to oxygen exchange, gives rise to an iron enrichment trend and an increase in $ f_{{{\text{O}}_{2} }} $ of the melt relative to the Fayalite–Magnetite–Quartz (FMQ) buffer. Enrichment in Fe3+/ΣFemelt is mirrored by δ57Fe, where VIFe2+-bearing pyroxenes partition 57Fe-depleted iron, defining an equilibrium pyroxene-melt fractionation factor of $ \Updelta^{57} {\text{Fe}}_{{{\text{px}} - {\text{melt}}}} \le - 0.25\,\permille \times 10^{6} /T^{2} $ . Upon magnetite saturation, the $ f_{{{\text{O}}_{2} }} $ and δ57Fe of the melt fall, commensurate with the sequestration of the oxidised, 57Fe-enriched iron into magnetite, quantified as $ \Updelta^{57} {\text{Fe}}_{{{\text{mtn}} - {\text{melt}}}} = + 0.20\,\permille \times 10^{6} /T^{2} $ . Pyroxene–magnetite pairs reveal an equilibrium fractionation factor of $ \Updelta^{57} {\text{Fe}}_{{{\text{mtn}} - {\text{px}}}} \approx + 0.30\,\permille $ at 900–1,000?°C. Iron isotopes in differentiated magmas suggest that they may act as an indicator of their oxidation state and tectonic setting. 相似文献
17.
A thermobarometer for sphene (titanite) 总被引：9，自引：0，他引：9
Leslie A. Hayden E. Bruce Watson David A. Wark 《Contributions to Mineralogy and Petrology》2008,155(4):529-540
Sphene and zircon are common accessory minerals in metamorphic and igneous rocks of very different composition from many different
geological environments. Their essential structural constituents, Ti and Zr, are capable of replacing each other to some degree.
In this paper we detail the results of high pressure–temperature experiments as well as analyses of natural sphene crystals
that establish a systematic relationship between temperature, pressure and Zr concentration in sphene. Calibrations of the
temperature and pressure relationships are presented as a thermobarometer. Synthetic sphene crystals were crystallized in
the presence of zircon, quartz and rutile at 1–2.4 GPa and 800–1,000°C from hydrothermal solutions. Crystals were analyzed
for Zr by electron microprobe (EMP). The experimental results define a log-linear relationship between equilibrium Zr content
(ppm by weight), pressure (GPa) and reciprocal absolute temperature:
The incorporation of Zr into sphene was found to be rather sensitive to pressure effects and also to the effects of kinetic
disequilibrium and growth entrapment that result in sector zoning. The Zr content of sphene is relatively insensitive to the
presence of both REEs and F-Al substitutions in sphene. To supplement and test the experimental data, sphenes from seven rocks
of well-constrained origin were analyzed for Zr by both EMP and ion microprobe (IMP). The sphene thermobarometer records crystallization
temperatures that are consistent with independent thermometry. When applied to natural sphene of unknown origin or growth
conditions, this thermobarometer has the potential to estimate temperatures with an approximate uncertainty of ±20°C over
the temperature range of interest (600–1,000°C). The Zr-in-sphene thermobarometer can also be used in conjunction with the
Zr-in-rutile thermobarometer to estimate both pressure and temperature of crystallization.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
18.
Yongjun Jiang Cheng Zhang Daoxian Yuan Gui Zhang Raosheng He 《Hydrogeology Journal》2008,16(4):727-735
The impact of land-use change on the quality of groundwater in the Xiaotjiang watershed, China was assessed for the period
1982–2004. Groundwater samples were collected from 30 monitoring points across the watershed, and were representative of the
various changes, determined by remote sensing and geographical information systems. The results indicate that 610 km2 (60% of the total watershed area) were subject to land-use change during the period. The most important changes were the
conversion of 135 km2 of forested land to cultivated land, and 211 km2 of unused land to cultivated land. The main impact was ascribed to diffuse pollution from fertilizers applied to newly cultivated
land, and from building development. Overall the groundwater pH value was significantly increased, as were the concentrations
of ions , , , , and Cl− in groundwater whilst the concentrations of Ca2+ and declined. More precisely, in the regions where forested land and unused land were converted into cultivated land, the pH
value and the concentrations of Mg2+, , , , , Cl− increased whilst the concentrations of Ca2+ and declined. However in the region where cultivated land was converted into construction land, the pH value and the concentrations
of Ca2+, Mg2+, , , , , , Cl− increased.
Résumé L’impact des changements de l’utilisation du territoire sur la qualité de l’eau souterraine dans le bassin versant de Xiaojiang, en Chine, a été évalué de 1982 à 2004. Des échantillons d’eau souterraine ont été récoltés à partir de 30 points d’observation éparpillés sur le bassin, représentant les divers changements déterminés par télédétection et système d’information géographique. Les résultats indiquent que 610 km2 (soit 60% de la surface du bassin) ont été sujets à des modifications de l’utilisation du territoire sur cette période. Les changements les plus importants furent la conversion de 135 km2 de forêt et 211 km2 de terres inutilisées en terres cultivées. Le principal impact est attribué à la pollution diffuse des engrais utilisés en agriculture et pour les batiments. De manière générale le pH de l’eau souterraine a augmenté significativement, ainsi que les concentrations des ions , , , , et Cl−, tandis que les concentration en Ca2+ et ont diminué. Plus précisément dans les régions transformées en terres cultivées, la valeur du pH et les concentrations en Mg2+, , , , , Cl− ont augmenté tandis que les concentrations en Ca2+ et ont diminué. Toutefois dans les régions cultivées converties en zones de construction, le pH et les concentrations en Ca2+, Mg2+, , , , , , Cl− ont augmenté. Resumen El impacto del cambio en uso de la tierra en la calidad del agua en la cuenca Xiaojiang, China fue evaluado para el periodo 1982–2004. Muestras de agua subterránea fueron tomadas de 30 puntos de monitoreo a través de la cuenca, y fueron representativas de los múltiples cambios, determinados por sensores remotos y sistemas de información geográfica. Los resultados indican que 610 km2 (60% del área total de la cuenca) estaban sujetos a cambios de uso de la tierra durante el periodo estudiado. Los cambios más importantes fueron la conversión de 135 km2 de bosques a tierra cultivada, y 211 km2 de tierra sin uso (ociosa) a tierra cultivada. El impacto principal fue causado por contaminación difusa de fertilizantes aplicados a la tierra recientemente cultivada, y a desarrollo de construcciones. En general el pH en agua subterránea creció significantemente, al igual que las concentraciones de los iones , , , , y Cl− en agua subterránea mientras que las concentraciones de Ca2+ y decrecieron. Mas precisamente, en las regiones donde bosque y tierra ociosa fueron convertidas en tierra cultivada, el valor de pH y las concentraciones de Mg2+, , , , , Cl− crecieron mientras las concentraciones de Ca2+ y decrecieron. Sin embargo en la región donde tierra cultivada fue convertida en construcciones, el valor de pH y las concentraciones de Ca2+, Mg2+, , , , , , Cl− crecieron.相似文献 19.
Hamdy H. Abd El-Naby 《Mineralium Deposita》2008,43(8):933-944
Uranium mineralization in the El Erediya area, Egyptian Eastern Desert, has been affected by both high temperature and low
temperature fluids. Mineralization is structurally controlled and is associated with jasperoid veins that are hosted by a
granitic pluton. This granite exhibits extensive alteration, including silicification, argillization, sericitization, chloritization,
carbonatization, and hematization. The primary uranium mineral is pitchblende, whereas uranpyrochlore, uranophane, kasolite,
and an unidentified hydrated uranium niobate mineral are the most abundant secondary uranium minerals. Uranpyrochlore and
the unidentified hydrated uranium niobate mineral are interpreted as alteration products of petscheckite. The chemical formula
of the uranpyrochlore based upon the Electron Probe Micro Analyzer (EPMA) is . It is characterized by a relatively high Zr content (average ZrO2 = 6.6 wt%). The average composition of the unidentified hydrated uranium niobate mineral is , where U and Nb represent the dominant cations in the U and Nb site, respectively. Uranophane is the dominant U6+ silicate phase in oxidized zones of the jasperoid veins. Kasolite is less abundant than uranophane and contains major U,
Pb, and Si but only minor Ca, Fe, P, and Zr. A two-stage metallogenetic model is proposed for the alteration processes and
uranium mineralization at El Erediya. The primary uranium minerals were formed during the first stage of the hydrothermal
activity that formed jasperoid veins in El Eradiya granite (130–160 Ma). This stage is related to the Late Jurassic–Early
Cretaceous phase of the final Pan-African tectono-thermal event in Egypt. After initial formation of El Erediya jasperoid
veins, a late stage of hydrothermal alteration includes argillization, dissolution of iron-bearing sulfide minerals, formation
of iron-oxy hydroxides, and corrosion of primary uranium minerals, resulting in enrichment of U, Ca, Pb, Zr, and Si. During
this stage, petscheckite was altered to uranpyrochlore and oxy-petscheckite. Uranium was likely transported as uranyl carbonate
and uranyl fluoride complexes. With change of temperature and pH, these complexes became unstable and combined with silica,
calcium, and lead to form uranophane and kasolite. Finally, at a later stage of low-temperature supergene alteration, oxy-petscheckite
was altered to an unidentified hydrated uranium niobate mineral by removal of Fe. 相似文献
20.
TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz 总被引：5，自引：2，他引：3
Jay B. Thomas E. Bruce Watson Frank S. Spear Philip T. Shemella Saroj K. Nayak Antonio Lanzirotti 《Contributions to Mineralogy and Petrology》2010,160(5):743-759
Quartz and rutile were synthesized from silica-saturated aqueous fluids between 5 and 20 kbar and from 700 to 940°C in a piston-cylinder
apparatus to explore the potential pressure effect on Ti solubility in quartz. A systematic decrease in Ti-in-quartz solubility
occurs between 5 and 20 kbar. Titanium K-edge X-ray absorption near-edge structure (XANES) measurements demonstrate that Ti4+ substitutes for Si4+ on fourfold tetrahedral sites in quartz at all conditions studied. Molecular dynamic simulations support XANES measurements
and demonstrate that Ti incorporation onto fourfold sites is favored over interstitial solubility mechanisms. To account for
the P–T dependence of Ti-in-quartz solubility, a least-squares method was used to fit Ti concentrations in quartz from all experiments
to the simple expression
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