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1.
The water and bed-sediment pollution status of the Padma River was determined by analysis of representative samples for selected
metals and ions. Water and bed-sediment samples were collected at a T-dam, Rajshahi, Bangladesh, for 7 months. Water and silt-metal
content analysis was performed using atomic absorption spectrophotometry or other analytical methods. The data showed the
variation of the metal ion-levels in water as follows: Ca 17.11–48.37 ppm, Na 17.51–20.09 ppm, K 1.00–3.60 ppm, Cr 2.80–7.00 ppm,
and SO4 4.17–5.48 ppm; in bed sediment, the levels were Cr 35–1050 ppm and Pb 12–48 ppm. The occurrence of Na, K and Ca was in the
normal range (US EPA permissible limit), but the levels of Cr in water were much higher than the permissible limit. The SO4 ion content was well below the pollution level. The concentration of Pb in the bed sediment was within the permissible limit
for the standard International Atomic Energy Agency (IAEA) Soil-5a, but the concentration of Cr in the bed sediment was significantly
higher than the permissible limit for the standard IAEA Soil-5a. Thus the Padma river water was polluted with Cr. The occurrence
of some ions showed a monthly variation.
Received: 19 August 1999 · Accepted: 12 October 1999 相似文献
2.
Humberto Terrazas Salas Hermínio Arias Nalini Jr. Júlio César Mendes 《Environmental Geology》2006,49(4):520-526
One hundred samples of granitic rock were collected from granite traders in Belo Horizonte. Autoradiography, optical microscopy,
diffractometry, and chemical analysis (X-ray spectrometry, X-ray fluorescence, neutron activation, gravimetry, and electron
probe microanalysis) were used to determine the mineral assemblages and lithotypes. Autoradiographic results for several samples
showed the presence of monazite, allanite, and zircon. Chemical analysis revealed uranium concentrations ≤30 ppm and thorium
≤130 ppm. Higher concentrations generally correlated with high concentrations of light rare earths in silica-rich rocks of
granitic composition. Calculations were made of radioactive doses for samples, of floor tiles in a standard room, with total
concentration of uranium and thorium greater than 60 ppm. On the basis of calculations of 232 Th, 40 K, and 226 Ra from analysis of Th, K, and U, the doses calculated were between 0.11 and 0.34 mSv/year, which are much lower than the
acceptable international exposure standard of 1.0 mSv/year. 相似文献
3.
Samples of enstatite and forsterite were crystallized in the presence of a hydrous fluid at 15 kbar and 1100 °C. Water contents
in quenched samples were measured by 1H MAS NMR and by FTIR. If the samples were prepared in the same way, similar water concentrations were obtained by both methods.
There is no evidence that one or the other method would severely over or underestimate water contents in nominally anhydrous
minerals. However, measured water contents vary by orders of magnitude depending on sample preparation. The lowest water contents
are measured by polarized FTIR spectroscopy on clear, inclusion-free single crystals. These water contents probably reflect
the real point defect solubility in the crystals. Polycrystalline material shows much higher total water concentrations, presumably
due to hydrous species on grain boundaries, growth defects, and in submicroscopic fluid inclusions. Grinding the sample in
air further increases water concentration. This effect is even more pronounced if the sample is ground in water and subsequently
dried at 150 °C. Polarized FTIR measurements on clear single crystals of enstatite saturated at 15 kbar and 1100 °C give 199 ± 25 ppm
by weight of water. The spectra show sharp and strongly polarized bands. These bands are also present in spectra measured
through turbid, polycrystalline aggregates of enstatite. However, in these spectra, they are superimposed on much broader,
nearly isotropic bands resulting from hydrous species in grain boundaries, growth defects, and submicroscopic fluid or melt
inclusions. Total water contents for these polycrystalline aggregates are between 2000 and 4000 ppm. Water contents measured
by FTIR on enstatite powders are 5300 ppm after grinding in air and 12 600 ppm after grinding under water und subsequent drying
at 150 °C.
Received: 25 June 1999 / Revised, accepted: 4 October 1999 相似文献
4.
Factors controlling copper solubility and chalcopyrite deposition in the Sungun porphyry copper deposit, Iran 总被引：14，自引：0，他引：14
The Sungun porphyry copper deposit is hosted in a Diorite/granodioritic to quartz-monzonitic stock that intruded Eocene volcanosedimentary
and Cretaceous carbonate rocks. Copper mineralization is associated mainly with potassic alteration and to a lesser extent
with sericitic alteration. Based on previously published fluid inclusion and isotopic data by Hezarkhani and Williams-Jones
most of the copper is interpreted to have deposited during the waning stages of orthomagmatic hydrothermal activity at temperatures
of 400 to 300 °C. These data also indicate that the hydrothermal system involved meteoric waters, and boiled extensively.
In this work, thermodynamic data are used to delineate the stability fields of alteration and ore assemblages as a function
of fS2, fO2 and pH. The solubility of chalcopyrite was evaluated in this range of conditions using recently published experimental data.
During early potassic alteration (>450 °C), Copper solubility is calculated to have been >50 000 ppm, whereas the copper content
of the initial fluid responsible for ore deposition is estimated, from fluid inclusion data, to have been 1200–3800 ppm. This
indicates that initially the fluid was highly undersaturated with respect to chalcopyrite, which agrees with the observation
that veins formed at T > 400 °C contain molybdenite but rarely chalcopyrite. Copper solubility drops rapidly with decreasing temperature, and at
400 °C is approximately 1000 ppm, within the range estimated from fluid inclusion data, whereas at 350 °C it is only 25 ppm.
These calculations are consistent with observations that the bulk of the chalcopyrite deposited at Sungun is hosted by veins
formed at temperatures of 360 ± 60 °C. Other factors that, in principle, may reduce chalcopyrite solubility are increases
in pH, and decreases in fO2 and aCl−. Our analysis shows, however, that most of the change in pH occurred at high temperature when chalcopyrite was grossly undersaturated
in the fluid, and that the direction of change in fO2 increased chalcopyrite solubility. We propose that the Sungun deposit formed mainly in response to the sharp temperature
decrease that accompanied boiling, and partly as a result of the additional heat loss and decrease in aCl−, which occurred as a result of mixing of acidic Cu-bearing magmatic waters with cooler meteoric waters of lower salinity.
Received: 8 July 1998 / Accepted: 8 April 1999 相似文献
5.
To test whether invasive Spartina alterniflora marshes were functionally equivalent to native Scirpus mariqueter marshes, the present study used bottomless lift nets (20 m2) during 12 high-tide events from August to October 2008 to compare nekton densities and biomass between the two marsh types
in the Dongtan wetland. A total of eight species of fish, two species of shrimp, and three species of crab were collected.
So-iny mullet Chelon haematocheilus, keeled mullet Liza carinata, Asian freshwater goby Acanthogobius ommaturus, and ridge-tail prawn Exopalaemon carinicauda dominated samples from the two marsh types and accounted for over 90% of the total catch. There were significantly greater
densities and biomass (p < 0.05) of total nekton (all species combined) and two mullets (C. haematocheilus and L. carinata) in S. alterniflora marshes than in S. mariqueter marshes in August 2008, while no significant differences (p > 0.05) between the two marsh types were observed for densities and biomass of any species or total nekton in September and
October 2008. Non-metric multidimensional scaling ordination did not show clear separation of samples between the two marsh
types (r = 0.071, p = 0.159). Furthermore, there were no habitat-specific differences (p > 0.05) in the size distributions of the three numerically dominant species (C. haematocheilus, L. carinata, and A. ommaturus). We concluded that S. alterniflora marshes were utilized by nekton in a fashion similar to their utilization of native S. mariqueter marshes under similar physical conditions. 相似文献
6.
R. V. Fodor 《Mineralogy and Petrology》2000,69(3-4):213-225
Summary ?To enhance the ability to distinguish tholeiitic from alkalic magma parentages by mineral compositions, I determined trace-element
abundances in plagioclase separated from xenolithic gabbros of Mauna Kea volcano. These gabbros have origins in tholeiitic
and alkalic magmas of the Hamakua postshield stage of Mauna Kea volcanism. Chondrite-normalized rare-earth element (REE) patterns
for plagioclase show that highly calcic plagioclase, ≥ An78, from alkalic magma has greater light-REE/heavy-REE (LREE/HREE) ratios than less calcic plagioclase, An64–75, from tholeiitic magma (ratios, 22–33 vs < 20), suggesting that higher LREE/HREE ratios are inherent to plagioclase of alkalic
magmas. However, with compositional evolution (i.e., to lower An), plagioclase REE patterns are of limited use for distinguishing
tholeiitic from alkalic parentage because LREE/HREE ratios within each group increase and overlap in the range of ∼ 20–90.
Sr, Ba, Hf, and Ta can also discern parentages as their abundances in plagioclase largely reflect abundances inherent to their
parental magmas. The best expressions for identifying parentage use Sr abundances (Sr vs An; vs Ce/Yb; vs Sr/Ce), although
Hf, Ba, and Ta abundances vs An and vs Ce/Yb are also useful – the distinctions due to tholeiitic plagioclase having relatively
low Sr (∼ 500–1000 ppm), Ba (< 100 ppm), Hf (< 0.10 ppm), and Ta (< 0.05 ppm). These relationships help to distinguish between
the effects of differentiation on trace-element abundances in plagioclase and their abundances owed to intrinsic concentrations
in their magmas. They create compositional fields for tholeiitic and alkalic parentages that remain graphically separated
even though differentiation may have enriched the plagioclase in incompatible elements.
Received July 22, 1999;revised version accepted December 7, 1999 相似文献
Zusammenfassung ?Plagioklas aus tholeitischen und alkalischen Magmen von Hawaii: Unterscheidung aufgrund von REE, Sr, Ba, Hf und Ta Um die M?glichkeit der Unterscheidung tholeitischer von alkalischer Magmaherkunft durch Mineralzusammensetzungen zu verbessern, habe ich die Spurenelementverteilung in Plagioklasen, die von xenolithischen Gabbros des Mauna Kea Vulkans abgetrennt wurden, untersucht, Diese Gabbros entstammen tholeitischen und alkalischen Magmen des Hamakua “Post-Schild” Stadiums des Mauna Kea Vulkanismus. Chondritisch normalisierte Seltene Erd (SEE) Verteilungs-Muster für Plagioklase zeigen, dass stark kalzische Plagioklase, > An78, aus alkalischen Magmen h?here leichte SEE/schwere SEE (LSEE/HSEE) Verh?ltnisse zeigen, als weniger kalzische Plagioklase, An64–75 aus tholeitischem Magma (Verh?ltniszahlen 22–33 gegenüber < 20). Dies weist darauf hin, dass h?here LSEE/HSEE-Verh?ltnisse typisch für Plagioklase aus alkalischen Magmen sind. Im Zuge der Evolution der Zusammensetzungen (d.h. zu niedrigeren An-Werten hin), sind die SEE Verteilungsmuster von Plagioklasen weniger hilfreich um tholeitische von alkalischer Herkunft zu unterscheiden. Dies ist deshalb so, weil die Verh?ltniszahlen innerhalb jeder Gruppe zunehmen und im Bereich von 20–90 überlappen. Sr, Ba, Hf und Ta k?nnen auch dazu dienen, um die Herkunft der Plagioklase zu definieren, da ihre H?ufigkeit gro?teils auf H?ufigkeiten, die für die Ursprungsmagmen typisch sind, zurückgehen. Die besten Herkunft-Parameter sind die Sr H?ufigkeiten (Sr vs An; vs Ce/Yb; vs Sr/Ce), obwohl die H?ufigkeit von Hf, Ba und Ta gegen An und gegen Ce/Yb auch nützlich sind. Diese Unterscheidungen gehen darauf zurück, dass tholeitische Plagioklase relativ niedrige Sr (∼ 500–1000 ppm), Ba (< 500 ppm) Hf (< 0.10 ppm) und Ta (< 0.5 ppm) führen. Diese Beziehungen erleichtern die Unterscheidung zwischen den Auswirkungen der Differenzierung auf die Spurenelement-Verteilungsmuster in Plagioklasen und auf ihre H?ufigkeiten, die auf die intrisischen Konzentrationen in den Ursprungsmagmen zurückgehen. Sie definieren charakteristische Felder für tholeitische und für alkalische Herkunft, die graphisch separiert bleiben, auch wenn die Gehalte der Plagioklase an inkompatiblen Elementen durch Differenzierung zugenommen haben mag.
Received July 22, 1999;revised version accepted December 7, 1999 相似文献
7.
Summary ?The occurrence of divalent rare earth elements (Sm2+, Yb2+, Tm2+, and Ho2+) in natural fluorite is evaluated using a suite of 37 samples deriving mainly from Sn–W deposits in the Erzgebirge (Germany),
Central Kazakhstan, and the Mongolian Altai. Trace element composition was determined by ICP-AES and ICP-MS. The defect structure
of the samples was studied by cathodoluminescence (CL), electron paramagnetic resonance (EPR), and optical absorption spectroscopy.
Reduction of cubic Sm3+, Yb3+, Tm3+, and Ho3+ under radioactive irradiation produces the corresponding divalent centres. Our data suggest a preferable formation of Sm2+ and Yb2+ under thorium and of Tm2+ and Ho2+ under uranium irradiation. Irradiation (indicated by intense brownish (thorium) and deep purple (uranium) coloration of fluorite)
gives rise to a population of divalent centres in equilibrium with their decay. However, sporadic radioactive irradiation
and stabilisation of the divalent state of the REE by other electron defects were found in most cases.
Three models of stabilisation of Sm2+, Yb2+, Tm2+, and Ho2+ are discussed. The most effective mechanism for Sm, Yb, Tm, and Ho is coupling with Fe3+ centres (REE3++Fe2+ → REE2++Fe3+). Accordingly, the occurrence of Fe3+ centres in natural fluorite is regarded to indicate not an oxidising, but rather a reducing environment during fluorite precipitation.
Originally incorporated in the divalent form, Fe2+ was converted to Fe3+ by radioactive irradiation. Such a conclusion is in agreement with the finding of high contents of interstitial fluorine
providing tetragonal local compensation of trivalent REE centres in crystals with high Fe3+. If Fe is not present, compensation of divalent Sm, Yb, and Tm is achieved by radiogenic oxidation of Ce(Pr, Tb)3+ accompanied by charge transfer (REE3++Ce(Pr, Tb)3+ → REE2++ Ce(Pr, Tb)4+). Ho2+ is sometimes stabilised by a hole trapped by an electron localised on a F vacancy (Ho3++e− on □F → REE2++ self-trapped exciton). Because Sm2+ is optically active, the stabilisation by Fe3+ (stable up to temperatures above 350 °C) or Ce(Pr, Tb)4+ (unstable even under visible light) in samples may be determined by careful observations in the field.
Institut für Geotechnik, ETH Zürich, ETH-H?nggerberg, Zürich, Switzerland
Stanford Linear Accelerator Center, Menlo Park, CA, USA
Received January 8, 2002; revised version accepted June 10, 2002 相似文献
8.
Ronaldo Sousa Pedro Morais Carlos Antunes Lúcia Guilhermino 《Estuaries and Coasts》2008,31(6):1198-1207
The bivalve Pisidium amnicum (Müller 1774) is a common species in several European freshwater ecosystems. However, few Iberian watersheds are colonized
by this species, and the River Minho estuary is possibly the Iberian aquatic ecosystem with the larger population. In October
2004–2007, investigations on spatial and temporal variations in P. amnicum abundance and biomass were carried out at 16 sites along the River Minho tidal freshwater wetlands. Mean abundance and biomass
per site ranged from 0 to 750 ind m−2 and 0 to 7.42 g AFDW m−2, respectively. A clear decrease in the spatial distribution, abundance, and biomass was observed during the 4-year assessment.
Furthermore, a stepwise multiple regression model showed that organic matter and conductivity explained 50.2% of the variation
in P. amnicum abundance (R
2 = 0.502, F
[2, 15] = 7.569, p = 0.005). Ecological knowledge is essential to the implementation of future conservation plans for P. amnicum, and the results of this study are of paramount importance to identify habitats that should be protected in order to preserve
this species and provide scientific reference that may be useful in the development of management and/or restoration plans. 相似文献
9.
G. D. Gwanmesia J. Liu G. Chen S. Kesson S. M. Rigden R. C. Liebermann 《Physics and Chemistry of Minerals》2000,27(7):445-452
Dense isotropic polycrystalline specimens of majorite-rich garnets (Py100, Py62Mj38, Py50Mj50, Py21Mj79 and Mj100) along the pyrope (Mg3Al2Si3O12 = Py100)-majorite (MgSiO3 = Mj100) join were fabricated in a 2000-ton uniaxial split-sphere anvil apparatus (USSA-2000) at pressures from 10 to 18.5 GPa and
temperatures from 1200 to 1850 °C, within their stability fields in runs of 2–4-h duration, using hot-pressing techniques
developed by Gwanmesia et al. (1993). These specimens are single-phased, fine-grained (≤5 mm), free of microcracks, and have
bulk densities greater than 99% of the corresponding single-crystal X-ray density. Elastic compressional (P) and shear (S) wave velocities were determined at room pressure and temperature for these polycrystalline garnet specimens by phase comparison
ultrasonic interferometry. For Mj100, the P and S wave velocities are within 1% of the Hashin-Shtrikman averages calculated from the single crystal elastic moduli measured
by Brillouin spectroscopy. Both the elastic bulk modulus (K) and the shear modulus (G) decrease continuously with increasing majorite content from pyrope garnet (Py100) to pure majorite garnet (Mj100). The compositional dependence of K and G are given by K = 172.3 (40) − 0.085X, and G = 91.6 (10) − 0.038X, where X = mol% majorite), respectively, indicating that substitution of Si for Mg and Al decreases both K and G by about 5% along the solid solution series.
Received: 25 March 1999 / Accepted: 12 July 1999 相似文献
10.
Interactions between several silicate and metallic phases are studied by applying a self consistent thermodynamic approach
and using recent thermodynamic data. We compute proportions and compositions of oxidized silicates and of reduced metallic
phase in equilibrium at various temperatures and oxygen fugacities. The empirically observed activity-composition relationships
for ternary metallic alloys are used and their applications to a general thermodynamic expression for a non-regular ternary
system is explicitly discussed. We show that the stability limits of olivines and pyroxenes with respect to precipitation
of metallic phases under reducing conditions are directly related to the presence of nickel impurities. We precisely evaluate
the modifications of the stability limits as a function of nickel content. For typical mantle olivines [Fe/(Fe+Mg) = 0.1]
the stability limits are given for values of x
Ni= Ni/(Ni+Fe+Mg) ranging from 10 ppm to 1% by: ln f
O2=−39.83+ 7.86 ln x
Ni, ln f
O2=−14.68+6.21 ln x
Ni, at 900 K and 1600 K, respectively.
Received: 17 November 1999 / Accepted: 14 May 2000 相似文献
11.
The lattice constants of paragonite-2M1, NaAl2(AlSi3)O10(OH)2, were determined to 800 °C by the single-crystal diffraction method. Mean thermal expansion coefficients, in the range 25–600 °C,
were: αa = 1.51(8) × 10−5, αb = 1.94(6) × 10−5, αc = 2.15(7) × 10−5 °C−1, and αV = 5.9(2) × 10−5 °C−1. At T higher than 600 °C, cell parameters showed a change in expansion rate due to a dehydroxylation process. The structural refinements
of natural paragonite, carried out at 25, 210, 450 and 600 °C, before dehydroxylation, showed that the larger thermal expansion
along the c parameter was mainly due to interlayer thickness dilatation. In the 25–600 °C range, Si,Al tetrahedra remained quite unchanged,
whereas the other polyhedra expanded linearly with expansion rate proportional to their volume. The polyhedron around the
interlayer cation Na became more regular with temperature. Tetrahedral rotation angle α changed from 16.2 to 12.9°. The structure
of the new phase, nominally NaAl2 (AlSi3)O11, obtained as a consequence of dehydroxylation, had a cell volume 4.2% larger than that of paragonite. It was refined at room
temperature and its expansion coefficients determined in the range 25–800 °C. The most significant structural difference from
paragonite was the presence of Al in fivefold coordination, according to a distorted trigonal bipyramid. Results confirm the
structural effects of the dehydration mechanism of micas and dioctahedral 2:1 layer silicates. By combining thermal expansion
and compressibility data, the following approximate equation of state in the PTV space was obtained for paragonite: V/V
0 = 1 + 5.9(2) × 10−5
T(°C) − 0.00153(4) P(kbar).
Received: 12 July 1999 / Revised, accepted: 7 December 1999 相似文献
12.
Zircon reaction and stability of the U-Pb isotope system during interaction with carbonate fluid: experimental hydrothermal study 总被引：4，自引：0，他引：4
N. G. Rizvanova O. A. Levchenkov A. E. Belous N. I. Bezmen A. V. Maslenikov A. N. Komarov A. F. Makeev L. K. Levskiy 《Contributions to Mineralogy and Petrology》2000,139(1):101-114
The interpretation of metamorphically induced U-Pb isotopic discordance requires a thorough understanding of zircon-fluid
interactions. With this aim we have studied the behaviour of metamict and crystalline zircon phases and their U-Pb systems
by cathodoluminescence after treatment by 2M Na2CO3 solution at T = 200–800 °C and P = 1–5 kbar for 3–14 days, X-ray diffraction, microprobe and isotope dilution analysis. The data indicate that zircon transformation
under hydrothermal conditions depends on the experimental conditions and the degree of structural damage. Reconstitution of
defective and impurity-enriched zones of metamict zircon (homogenization of impure element concentrations and increase of
crystallinity) was observed at 400 °C and P = 1 kbar. Considerable lead and uranium loss occurred under these conditions. As a result of zircon dissolution, newly formed
baddeleyite accommodating U from 2M Na2CO3 solution and Zr-Na-silicate were recognized. This process intensified with increasing pressure. Study of crystalline zircon
indicates that migration of U and Pb took place only during dissolution of zircon at T above 650 °C. In the presence of carbonate-ions essential U and Pb amounts are lost from metamict zircon at a lower P-T than is typical for greenschist facies metamorphism.
Received: 4 October 1997 / Accepted: 6 December 1999 相似文献
13.
The hydroelectric reservoir of Petit Saut, French Guiana, was created in 1994–1995 by flooding 350 km2 of tropical forest. When sampled in 1999, the lake exhibited a permanent stratification separating the 3–5 m thick, oxygenated
epilimnion from the anoxic hypolimnion. The rate of anaerobic organic carbon mineralization below the oxycline was on the
order of 1 μmol C m−2 s−1 and did not show a pronounced difference between wet and dry seasons. Methanogenesis accounted for 76–83% of anaerobic carbon
mineralization, with lesser contributions of sulfate reduction and dissimilatory iron reduction. Upward mixing of reduced
inorganic solutes explained 90% of the water column O
2 demand during the dry season, while most O
2 consumption during the wet season was coupled to aerobic respiration of organic matter synthesized in the surface waters.
Inorganic mercury species represented 10–40% of total dissolved mercury in the epilimnion, but were of relatively minor importance
(≤10%) in the anoxic portion of the water column. Net production of soluble organic mercury compounds in the flooded soils
and anoxic water column did not vary significantly between wet and dry seasons. Methylmercury accounted for about 15% of total
dissolved mercury below the oxycline. Its estimated net production rate, 0.04 mg m−2 yr−1, is of the same order of magnitude as values reported for contaminated lakes and flooded terrestrial ecosystems. 相似文献
14.
Assessment of heavy-metal contamination of floodplain soils due to mining and mineral processing in the Harz Mountains, Germany 总被引：9，自引：2，他引：7
2 study area was assessed with respect to its heavy-metal load on the basis of the current guideline values. The heavy-metal
loads of the soils in the study area have ranges of <0.2–200 mg kg−1 for Cd, <10–30,000 mg kg−1 for Pb, 7–10,000 mg kg−1 for Cu and 50–55,000 mg kg−1 for Zn. Mobility of the heavy metals was determined by extraction at different pH values. The acid neutralisation capacity
(ANCx) at these pH values was also determined to estimate the probability that the pH can drop to pH=x. The ANC values in the study area ranged from 6 to 3000 mmol H+ kg−1, from −33 to 800 mmol H+ kg−1 and from −74 to 160 mmol H+ kg−1 for ANC3.5, ANC5.0 and ANC6.2, respectively. Together with pedological data, the extraction experiments permit differentiation between soil units that
have been placed in the same environmental hazard class on the basis of total heavy-metal loads.
Received: 10 August 1998 · Accepted: 14 August 1999 相似文献
15.
The cation distribution of Co, Ni, and Zn between the M1 and M2 sites of a synthetic olivine was determined with a single-crystal
diffraction method. The crystal data are (Co0.377Ni0.396Zn0.227)2SiO4, M
r
= 212.692, orthorhombic, Pbnm, a = 475.64(3), b = 1022.83(8), and c = 596.96(6) pm, V = 0.2904(1) nm3, Z = 4, D
x
= 4.864 g cm−3, and F(0 0 0) = 408.62. Lattice, positional, and thermal parameters were determined with MoKα radiation; R = 0.025 for 1487 symmetry-independent reflections with F > 4σ(F). The site occupancies of Co, Ni, and Zn were determined with synchrotron radiation employing the anomalous dispersion effect
of Co and Ni. The synchrotron radiation data include two sets of intensity data collected at 161.57 and 149.81 pm, which are
about 1 pm longer than Co and Ni absorption edges, respectively. The R value was 0.022 for Co K edge data with 174 independent reflections, and 0.034 for Ni K edge data with 169 reflections. The occupancies are 0.334Co + 0.539Ni + 0.127Zn in the M1 sites, and 0.420Co + 0.253Ni + 0.327Zn
in the M2 sites. The compilation of the cation distributions in olivines shows that the distributions depend on ionic radii
and electronegativities of constituent cations, and that the partition coefficient can be estimated from the equation: ln [(A/B)M1/(A/B)M2] = −0.272 (IR
A
-IR
B
) + 3.65 (EN
A
−EN
B
), where IR (pm) and EN are ionic radius and electronegativity, respectively.
Received: 8 April 1999 / Revised, accepted: 7 September 1999 相似文献
16.
Selenomethionine (SeM) is an organic toxicant that is present in seleniferous environments. No kinetic data is yet available
regarding SeM reactions in coal mine environments, where selenium (Se) toxicity is a potential concern. A kinetic study was
conducted on two reclaimed coal mine soils (Typic Torriorthents) from Wyoming having sandy and clayey textures. Four levels
of SeM treatments (0, 50, 100 μM, and plant amendment from the mine vegetation) were reacted with the soils for 4, 7, 14,
28, 42, 56, and 84 days to characterize the kinetic behavior of overall SeM disappearance from soil solutions. Detection of
SeM in soil solutions at the control level (0 μM SeM) indicated occurrence of indigenous SeM in the soils. In the plant-amended
soil solutions, much greater concentrations of SeM were observed as compared with the soil-only systems. This indicated the
plant material was a more potential source of SeM than the mine soils. A time-dependent loss in solution SeM concentrations
was observed for both soils under 0, 50, 100 μM SeM treatments. For the soil-plant mixtures, the solution SeM concentration
increased initially, reached a maximum after 14 days, and then decreased thereafter. In the plant-amended soil solutions,
SeM concentrations at all time intervals were higher for the sandy as compared to the clayey soil. At 50 and 100 μM SeM treatments,
the solution pH was linearly related to the percentages of SeM disappeared from the solutions; greater percentage of SeM was
removed from solutions at comparatively lower pH levels, which was ≥90% at pH 7.7 for both soils. Solution SeM concentrations
decreased exponentially with time following first-order kinetic reactions. Under all applications (except for the control),
C
0 (SeM concentration at t=0) values for the sandy soil were greater than those determined for the clayey soil, indicating higher solution SeM availability
for the former and more SeM retention by the latter at t=0. Comparison of C
0 in controls (0 μM SeM addition) suggested greater indigenous SeM in the clayey soil. For both soils, C
0 values under different treatments followed the order, (soil+100 μM)>(soil+50 μM)>(soil+0 μM). The specific reaction rate
constants (K
r) of SeM for both soils were similar (0.031 and 0.029 day–1 for sandy and clayey soils, respectively); low K
r values indicated that SeM loss from our reclaimed coal mine soil solutions would follow rather slow kinetics. The half-life
(t
0.5) of SeM varied from 15 to 55 days depending on treatment level. The knowledge obtained from this study should contribute
in developing time-based Se reclamation strategies in coal mine environments.
Received: 18 September 1995 · Accepted: 28 December 1995 相似文献
17.
Summary The “Geochemical Atlas of Austria” shows a notable positive geochemical arsenic anomaly in stream sediments of the Saualpe,
eastern Carinthia, Austria. Detailed investigation has shown that it is caused by an unusual kind of mineralization in brecciated
marbles. The mineralization consists predominantly of native arsenic (often in small, stellate aggregates) and realgar (±
minor orpiment). The As content may reach as much as 1.4 wt-%. The samples investigated do not contain any sulfarsenides and
arsenides, and do not show enrichments of other metals: e.g. gold contents are < 5 ppb, Hg contents ≤ 1.3 ppm, Sb contents
≤ 4 ppm. The atomic As/S ratio varies considerably, and surpasses in a number of samples a value of 2. The As mineralization
seems to be associated with the formation of late, extremely fine-grained quartz ± carbonate, penetrating the breccia, and
is evidently a very late event in the mineralization history of the region.
Received April 21, 1999; revised version accepted December 30, 1999 相似文献
Zusammenfassung Eine gediegen Arsen – Realgar Vererzung in Marmorender Saualpe, K?rnten, ?sterreich Der “Geochemische Atlas der Republik ?sterreich” zeigt in Bachsedimenten der Saualpe, ?stliches K?rnten, ?sterreich, eine bemerkenswerte positive geochemische Arsenanomlie. Die detaillierte Untersuchung zeigte, da? sie haupts?chlich durch eine ungew?hnliche Mineralisation in Marmorbrekzien verursacht ist. Diese besteht fast ausschlie?lich aus gediegen Arsen (oft in kleinen, sternf?rmigen Aggregaten) und Realgar (± wenig Auripigment). Der As-Gehalt kann 1.4 Gew.-% erreichen. Die untersuchten Proben sind frei von Sulfarseniden und Arseniden, und sie zeigen keine nennenswerten Anreicherungen an anderen Metallen: z. B. sind die Goldgehalte < 5 ppb, die Hg-Gehalte ≤ 1.3 ppm und die Sb-Gehalte ≤ 4 ppm. Das atomare As/S-Verh?ltnis schwankt betr?chtlich und überschreitet in einer Reihe von Proben den Wert 2. Diese As-Mineralisation scheint mit der Bildung von sp?tem, feinstk?rnigem Quarz ± Karbonaten verbunden zu sein und ist in der Mineralisationsgeschichte der Region offensichtlich ein sehr sp?tes Ereignis.
Received April 21, 1999; revised version accepted December 30, 1999 相似文献
18.
Near-infrared (NIR) absorption bands related to total water (4000 and 7050 cm−1), OH groups (4500 cm−1) and molecular H2O (5200 cm−1) were studied in two polymerised glasses, a synthetic albitic composition and a natural obsidian. The water contents of the
glasses were determined using Karl Fischer titration. Molar absorption coefficients were calculated for each of the bands
using albitic glasses containing between 0.54 and 9.16 wt.% H2O and rhyolitic glasses containing between 0.97 and 9.20 wt.% H2O. Different combinations of baseline type and intensity measure (peak height/area) for the combination bands at 4500 and
5200 cm−1 were used to investigate the effect of evaluation procedure on calculated hydrous species concentrations. Total water contents
calculated using each of the baseline/molar absorption coefficient combinations agree to within 5.8% relative for rhyolitic
and 6.5% relative for albitic glasses (maximum absolute differences of 0.08 and 0.15 wt.% H2O, respectively). In glasses with water contents >1 wt.%, calculated hydrous species concentrations vary by up to 17% relative
for OH and 11% relative for H2O (maximum absolute differences of 0.33 and 0.43 wt.% H2O, respectively). This variation in calculated species concentrations is typically greater in rhyolitic glasses than albitic.
In situ, micro-FTIR analysis at 300 and 100 K was used to investigate the effect of varying temperature on the NIR spectra of the
glasses. The linear and integral molar absorption coefficients for each of the bands were recalculated from the 100 K spectra,
and were found to vary systematically from the 300 K values. Linear molar absorption coefficients for the 4000 and 7050 cm−1 bands decrease by 16–20% and integral molar absorption coefficients by up to 30%. Depending on glass composition and baseline
type, the integral molar absorption coefficients for the absorption bands related to OH groups and molecular H2O change by up to −5.8 and +7.4%, respectively, while linear molar absorption coefficients show less variation, with a maximum
change of ∼4%. Using the new molar absorption coefficients for the combination bands to calculate species concentrations at
100 K, the maximum change in species concentration is 0.08 wt.% H2O, compared with 0.39 wt.% which would be calculated if constant values were assumed for the combination band molar absorption
coefficients. Almost all the changes in the spectra can therefore be interpreted in terms of changing molar absorption coefficient,
rather than interconversion between hydrous species.
Received: 17 December 1998 / Revised, accepted 8 July 1999 相似文献
19.
Raffaello Cioni 《Contributions to Mineralogy and Petrology》2000,140(1):40-54
The evolution of volatiles in the AD 79 magma chamber at Vesuvius (Italy) was investigated through the study of melt inclusions
(MI) in crystals of different origins. FTIR spectroscopy and EMPA were used to measure H2O, CO2, S and Cl of the different melts. This allowed us to define the volatile content of the most evolved, phonolitic portion
of the magma chamber and of the mafic melts feeding the chamber. MI in sanidine from phonolitic and tephri-phonolitic pumices
show systematic differences in composition and volatile content, which can be explained by resorption of the host mineral
during syn-eruptive mixing. The pre-eruption content of phonolitic magma appears to have been dominated by H2O and Cl (respectively 6.0 to 6.5 wt% and 6700 ppm), while magma chamber refilling occurred through the repeated injection
of H2O, CO2 and S-rich tephritic magmas (respectively 3%, 1500 ppm and 1400 ppm). Strong CO2 degassing probably occurred during the decompressional path of mafic batches towards the magma chamber, while sulphur was
probably released by the magma following crystallization and mixing processes. Water and chlorine strongly accumulated in
the magma and reached their solubility limits only during the eruption. Chlorine solubility appears to have been strongly
compositionally controlled, and Cl release was inhibited by groundmass crystallization of leucite, which shifted the composition
of the residual liquid towards higher Cl solubilities.
Received: 28 October 1999 / Accepted: 21 April 2000 相似文献
20.
Summary The 100 m thick and 700 m long Nadezhda sill-like gabbronorite body, emplaced in the mafic-ultramafic Lukkulaisvaara layered
intrusion, is associated with Cu-Ni-PGE mineralization that is mostly confined to mottled anorthosites developed from host
gabbronorites and norites along the margin of the entire body. PGE and Au show distinct positive correlation with Cu, Ni and
S suggesting that the noble metals are mainly controlled by sulphides. A mineralized layer about 1 m thick contains on average
0.74 wt.% S, 1.77 ppm Pt and 7.96 ppm Pd. Marginal location of PGE-rich sulphides and their absence in the Nadezhda body suggest
that the mineralizing process must have been gravity-independent and not related to the bulk saturation of the magma in sulphides.
We propose that the Nadezhda Cu-Ni-PGE mineralization formed as a result of local sulphide saturation that was achieved in situ at the margins as a result of the flux of ore-bearing fluids from the interior of the body towards its margins. The sulphides
became PGE-rich due to interaction with a large volume of ore-bearing fluids that were introduced into the Nadezhda body during
a juvenile stage of its development as a conduit through which a large volume of magma has passed on its way to the main chamber.
Authors’ addresses: R. M. Latypov and S. Yu. Chistyakova, Kola Science Centre, Geological Institute, Fersman Str. 16, 184200 Apatity, Russia; Present address: Department of Geosciences,
University of Oulu, P. O. Box 3000, Oulu, FIN-90014, Finland; T. T. Alapieti, Department of Geosciences, University of Oulu, P. O. Box 3000, Oulu, FIN-90014, Finland 相似文献