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1.
Divariant oxide plus metal assemblages potentially make useful redox sensors for use in hydrothermal and other high pressure experiments. Here we report the calibration of the (Ni, Mn)O/Ni redox sensor in which the Ni/NiO (NNO) oxygen buffer is displaced to lower oxygen chemical potentials (O2), by the solid solution of MnO in the oxide phase. This assemblage was chosen because: (1) it covers a useful range of O2; (2) the system can be calibrated very accurately. Values of O2 defined by the (Ni, Mn)O/Ni assemblage were determined electrochemically, from 900 to 1300 K, using calcia-stabilized zirconia solid electrolytes. The oxide compositions (8 in total, ranging from 0.1X
NiO0.8) were analysed afterwards by electron microprobe, and were checked for internal consistency by measuring the lattice parameters (a0), using powder XRD. The accuracies of the measurements, both assessed theoretically and established empirically, are (1): ±80J/mol in O2, ±0.0002 Å in a0 and ±0.002 to 0.005 in X
NiO. Activity-composition relations were fitted to the Redlich-Kister formalism. There is a slight asymmetry (corresponding to a subregular model) across the solution with A
0
G
=9577(±45) J/mol, and A
1
G
=–477(±80) J/mol. The experimental data were also used to derive the parameters Vex, Hex and Sex. There is no obvious relationship between excess volumes and enthalpies of mixing, nor between excess volumes and excess entropies. The experimental data from this study have been used to formulate the (Ni, Mn)O/Ni redox sensor expression: O2 = 2(NNO) + 2RTlnX
NiO + 2(1 – X
NiO)2[11483 – 1.697T] – 477(4X
NiO – 1)(900 < T(K) < 1300) where O2(NNO)=–478967+248.514T–9.7961 T In T, from O'Neill and Pownceby(1993a). 相似文献
2.
The assemblage NiO+Ni-Pd alloy has been calibrated as a precise oxygen fugacity sensor in the temperature range 850–1250 K at 1 bar, using an electrochemical technique with oxygen-specific CSZ electrolytes, and Ni+NiO and Cu+Cu2O as the reference electrodes. Nine compositions were studied, ranging from 0.12 to 0.83 X
Ni
alloy
. Steady EMFs, implying equilibrium, were rapidly achieved in all cells, and were found to be reversible on increasing and decreasing temperature with a precision approaching 0.1 mV. The estimated accuracy of the measurements on each cell is ±0.2 mV (1, corresponding to ±0.003 log-bar units in fo2 at 1273 K). Compositions of the Ni-Pd alloys were measured after each run by electron microprobe, and these compositions were then checked for internal consistency by measuring the lattice parameter by X-ray diffraction. Nickel-rich alloys show positive deviations from ideality and endothermic enthalpies of mixing, but palladium-rich compositions have exothermic enthalpies of mixing and strong negative deviations from ideality. The excess entropies of mixing are positive for all compositions, and correlate approximately with the excess volumes of mixing. The highly asymmetrical deviations from ideality are well described by a polynomial expression of the Redlich-Kister form, with three terms for the enthalpies, and two for the excess entropies and volumes of mixing. The experimental data from this study have been used to re-formulate the Ni-Pd oxygen fugacity sensor to give an expression;
O2
ss
=
O2
NNO
– 2RT ln X
Ni
alloy
– [2 · (1 – X
Ni
alloy
)2 · [(–2165–7.958 · T) + (9409 – 0.888 · T) · (4 X
Ni
alloy
– 1) + 2089 · (6 X
Ni
alloy
– 1) · (2 X
Ni
alloy
– 1)]](850<T<1300) where
O2
ss
is in J mol-1, T is in kelvins, and the expression for
O2
NNO
is that given by O'Neill and Pownceby (1993). Values in terms of log fo2 may be obtained from the above by dividing by RT ln 10. The estimated standard error in
O2
ss
is on the order of ±200 J mol-1, which is approximately ±0.01 log-bar units in fo2 at 1273 K. 相似文献
3.
《Applied Geochemistry》1997,12(1):97-103
Analyses for δ34S of 13 bedded, marine anhydrite samples from the “C” anhydrite member of the Red River Formation (Upper Ordovician) in the North Dakota portion of the Williston basin represent an addition of δ34S data to a portion of the S isotope age curve with few data. Previously published estimates of δ34S for Upper Ordovician marine sulfates apparently are limited to 4 samples from the Saskatchewan portion of the same basin. An adjusted mean value of +25.5‰ was calculated for all known Upper Ordovician δ34S determinations. This value is approximately 2 to 3‰ lighter than the previous estimate, which suggests that δ34S of the world ocean during the Upper Ordovician may have been lighter than previously thought. However, because all δ34S data are from one sedimentary basin, additional S isotopic data from several globally-distributed evaporite basins are needed to evaluate this hypothesis and further constrain δ34S for the Upper Ordovician. Similar re-examination of other portions of the S isotope age curve with limited amounts of data may increase our understanding of the secular variation in δ34S. 相似文献
4.
5.
The ion activity product of Fe and phosphate in interstitial waters from four sediment cores taken from Greifensee, Switzerland indicate the presence of vivianite [Fe3(PO4)2 · 8 H2O] in the solid phase. Analysis of the sediment using an electron microprobe and by electron microscopy revealed P-rich grains to be also enriched in Fe. The combined methods provide strong evidence that vivianite is forming authigenically in the sediments. Thermodynamic stability calculations demonstrate that the most stable Fe and phosphate minerals (pyrite, siderite and apatite) are not the ones controlling the pore water chemistry. The results emphasize the importance of rate processes of mineral formation in early diagenesis.Calculations based on the sediment phosphate concentration, and the degree of supersaturation of Fe and phosphate in the upper portion (0–15 cm) of the pore waters, indicate that the rate of vivianite mineral growth is controlled by a surface reaction rather than a diffusion mechanism. The response time of dissolved phosphate in the sediment pore waters with respect to mineral precipitation is on the order of 1–20 days. Less than 15% of the phosphate released by organic matter degradation at the sediment-water interface and below is retained in the sediments. 相似文献
6.
7.
Simulation results of the equilibrium state of systems water-carbonaceous chondrite material, water-primary mantle material,
water-ultramafic rock material, and water-mafic rock material open with respect to carbon dioxide and methane at 25°C, 1 bar
indicate that highly alkaline reduced aqueous solutions with K/Na > 1 can be formed only if water is in equilibrium with compositions
close to those of continental crust and primitive mantle. Yu.V. Natochin’s hypothesis that the living cell can be formed only
in an aqueous environment with K/Na > 1 leads to the conclusion that terrestrial life could arise and further evolve on the
Earth during the differentiation of primary chondritic material into the Earth’s core and mantle (during the first few million
years of the planet’s lifetime) in an alkaline (pH 9–10) reduced (Eh = −400–500 mV) aqueous solution at a temperature of 50–60°C,
in equilibrium with an N2-bearing atmosphere, which also contained CH4 (partial pressure from 10−2 to 10−8 bar), CO2 (partial pressure from 10−5 to 10−8 bar), NH3, H2, H2S, CO, and other gases. 相似文献
8.
9.
Trace and Rare Earth Element Distribution in Scheelite from the Cantung Tungsten Bearing Skarn Deposit, N.W.T. Canada: a Geometallurgical Analysis with Evidence from SEM and LA ICP-MS Analysis 
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10.
《Applied Geochemistry》1988,3(5):523-533
The transition metals Fe, Cu, Zn and Pb have diffused only 10–20 cm into the clay barrier at the Confederation Road landfill compared to 130 cm for porewater chloride. Other major dissolved species, including the alkali and alkaline earth metals, have also diffused out of waste landfill and into clay subsoils more rapidly than the metals. Redox potentials, Eh, indicate strongly reducing conditions (Eh= − 130 mV) in the clayey soil at the subsoil/waste interface and increase to +50 mV at a depth of 45 cm below the interface. pH values are close to 8 within the subsoil but the slightly lower values (7.8–8) near the interface may result from production of organic acids during degradation of the wastes. Thermodynamic analysis of subsoil pore waters indicates that Fe, Cu, Zn and Pb exist primarily as metal-hydroxy complexes of the forms [MeOH]+ and [Me(OH)2]0, although a complex of [PbCl]+ may be significant, but not predominant. The analysis also demonstrates that the dissolved transition metal concentrations of the subsoil pore waters are controlled at carbonate mineral saturation levels, whereas Fe concentrations in leachate solutions associated with the wastes are controlled at FeS2 saturation levels.Thermodynamic calculations and Eh-pH diagrams suggest that Fe(OH)2, Zn(OH)2 and Pb(OH)2 are not stable phases in the solids of the subsoil. This means that observed “hydroxide” phases reported in the selective dissolution analysis by Yanful and Quigley (1986) have to be re-evaluated. 相似文献
11.
Wang Wenli Institute of Natural History Beijing Natural History Museum Yang Zunyi 《《地质学报》英文版》1993,67(3)
A new insect family Liaoximordellidae (fam. nov.) has been named for a well-preserved specimen which was collected from the Upper Jurassic outcropping west of Daxinfangzi Village, Lingyuan County, Liaoning Province. The specimen can not be put into Mordellidae or Praemordellidae because it possesses some original and intermediate characters in morphology. It serves the study of mordellid evolution. Besides, the fossil group associated with the insect is important for the stratigraphic division of the Mesozoic in western Liaoning. 相似文献
12.
13.
P. K. Misra S. Kishore S. K. Singh A. K. Jauhri 《Journal of the Geological Society of India》2009,74(1):139-140
Discussion
Rhodophycean algae from the Lower Cretaceous of the Cauvery Basin, South India by P.K. Misra, S. Kishore, S.K. Singh and A.K. Jauhri. Jour. Geol. Soc. India, v.73, 2009, pp.325–334 相似文献14.
Mark S. Ghiorso 《Contributions to Mineralogy and Petrology》1990,104(6):645-667
A solution model is developed for rhombohedral oxide solid solutions having compositions within the ternary system ilmenite [(Fe
2+
s
Ti
4+
1–s
)
A
(Fe
2+
1–s
Ti
4+
s
)
B
O3]-geikielite [(Mg
2+
t
Ti
4+
1–t
)
A
(Mg
2+
1–t
Ti
4+
t
)
B
O3]-hematite [(Fe3+)
A
(Fe3+)
B
O3]. The model incorporates an expression for the configurational entropy of solution, which accounts for varying degrees of structural long-range order (0s, t1) and utilizes simple regular solution theory to characterize the excess Gibbs free energy of mixing within the five-dimensional composition-ordering space. The 13 model parameters are calibrated from available data on: (1) the degree of long-range order and the composition-temperature dependence of the
transition along the ilmenite-hematite binary join; (2) the compositions of coexisting olivine and rhombohedral oxide solid solutions close to the Mg–Fe2+ join; (3) the shape of the miscibility gap along the ilmenite-hematite join; (4) the compositions of coexisting spinel and rhombohedral oxide solid solutions along the Fe2+–Fe3+ join. In the course of calibration, estimates are obtained for the reference state enthalpy of formation of ulvöspinel and stoichiometric hematite (–1488.5 and –822.0 kJ/mol at 298 K and 1 bar, respectively). The model involves no excess entropies of mixing nor does it incorporate ternary interaction parameters. The formulation fits the available data and represents an internally consistent energetic model when used in conjuction with the standard state thermodynamic data set of Berman (1988) and the solution theory for orthopyroxenes, olivines and Fe–Mg titanomagnetite-aluminate-chromate spinels developed by Sack and Ghiorso (1989, 1990a, b). Calculated activity-composition relations for the end-members of the series, demonstrate the substantial degree of nonideality associated with interactions between the ordered and disordered structures and the dominant influence of the miscibility gap across much of the ternary system. The predicted shape of the miscibility gap, and the orientation of tie-lines relating the compositions of coexisting phases, display the effects of coupling between the excess enthalpy of solution and the degree of long-range order. One limb of the miscibility gap follows the composititiontemperature surface corresponding to the ternary
second-order transition. 相似文献
15.
Two New“Notostracans”,Chenops gen.nov.and Jeholops gen.nov. (Crustacea:Branchiopoda:?Notostraca) from the Yixian Formation,Northeastern China 总被引：1，自引：1，他引：0
<正>The Early Cretaceous Jehol biota of northeastern China contains a diverse group of notostracans, including two genera,Chenops and Jeholops,described here.Chenops is characterized by a combination of an ovate carapace,narrow anal plate,equant distal endites and endopod on the anterior thoracic limbs.In addition to the new species,Chenops yixianensis,the genus also provisionally includes Prolepidurus oblongus Oleynikov, 1968.Jeholops,however,is monotypic,represented by the new species Jeholops hongi.It is characterized by a combination of kazacharthran and notostracan features unique to this taxon.Both new genera are provisionally placed in the taxon Notostraca.More detailed work exploring the morphology of exceptionally-preserved branchiopod crustaceans is needed.The difficulties in placing fossil notostracans into a phylogenetic framework are discussed. 相似文献
16.
《Applied Geochemistry》1988,3(5):499-516
“Stratabound” disseminated pyritic Au ore bodies were produced by reactions between wall rocks and through-flowing fluids in Mesozoic epigenetic Au quartz vein systems in the Sierra Nevada metamorphic belt. Equilibrium relations among Fe-bearing carbonate and sulfide minerals were critical in determining which rock types were likely to host disseminated mineralization along portions of discordant veins. The compositions of metasomatic carbonates in hydrothermally altered wall rocks at Alleghany, California, U.S.A., were larely predetermined by the relative proportions of Fe, Mg and Ca in the unaltered wall rocks. Thus, coexisting solid solutions in the magnesite-siderite and dolomite-ankerite series from a variety of different wall rocks yield an empirical phase diagram for a large part of the Ca CO3MgCO3FeCO3 system at the temperature of metasomatism (325 ± 50°C). Because Fe,Mg-silicates were unstable in alteration zones adjacent to the veins, wall rock Fe was partitioned between carbonates and sulfides. Pyritization and disseminated Au mineralization occur in a variety of igneous and metasedimentary wall rocks in which the initial molar Fe/(Fe + Mg) ≧ 0.5. In altered wall rocks with initial molar Fe/(Fe + Mg) ≦ 0.5, Fe was incorporated almost entirely within Mg-rich carbonates (XFeCO3 ≦ 0.6 in magnesite-siderite solutions). It is proposed that the CO2-rich vein fluid responsible for the alteration and mineralization was partially buffered with respect to H2S/CO2/H2 ratios by equilibrium between pyrite and Mg0.4Fe0.6CO3 (+graphite?) as it traversed and altered intermediate volcanic and sedimentary rocks. This fluid then locally reacted with lower Fe/(Fe + Mg) rocks to form Fe-bearing dolomite + magnesite assemblages, and reacted with higher Fe/(Fe + Mg) rocks to form ankerite + pyrite assemblages. Gold precipitated from saturated solutions of bisulfide complexes partly in response to fluid desulfidation and reduction caused by the pyritization reactions. In terranes dominated by intermediate metavolcanic and metasedimentary rocks, favorable host rocks for this type of mineralization need not have high Fe contents, but do require high Fe/(Fe + Mg) ratios. They may include felsic volcanic and plutonic rocks, Fe-rich tholeiitic differentiates, banded Fe formations, and a variety of siliceous and argillaceous sedimentary rocks. Rocks which tend not to be heavily sulfidized because they have low initial Fe/(Fe + Mg) ratios include ultramafic and mafic igneous rocks, and some argillaceous sedimentary rocks. Exploration guidelines based on these principles may be useful elsewhere in the Sierra Nevada and in other comparable heterogeneous metamorphic terranes, if modified to reflect the dominant buffering rock types in a given fluid flow path. Carbonate-sulfide equilibria are capable of approximately buffering the carbonate-sulfide ratios of CO2-rich vein fluids (fCO2≧ 102.8 at 325°C, 200MPa or 2000 bar). The Alleghany fluid (fCO2 ≈ 103.2, or ∼ 10 mol % CO2) had a molar CO2/H2S ratio of approximately 103, assuming graphite saturation. At lower CO2 fugacities, Fe-bearing silicates entered the buffering assemblages. Carbonatization reactions could potentially de-sulfidize some wall rocks, releasing S (and associated metals?) to the fluid. This would be most likely to occur in pyrite-bearing mafic and ultramafic rocks and some argillites. 相似文献
17.
Geology of Ore Deposits - The Yalguba Ridge in Karelia is a reference geological object for studying Paleoproterozoic variolitic lavas. F. Yu. Levinson-Lessing—the prominent Russian... 相似文献
18.
PENG Zicheng LEUNG Po Lau YU Peter CHENG Peikai LI Mai 《《地质学报》英文版》2006,80(5):759-762
The microprobe EDXRF equipment was used for analysis of the major and trace elements in glaze layer-transitive layer-body layer of the celadon from the Altar Yao （Kiln） and Laohudong Yao in the Southern Song Dynasty （1127-1279 A.D.）, Zhejiang, China. The K values of the discriminant factor for the celadon wares are larger than 8, which means the celadon of the Altar Yao and Laohudong Yao are different from that of the Longquan Yao. The former two belong to the Guan Yao system （the Chinese imperial kilns）, but the latter to the Min Yao system （the Chinese popular kilns）. The principle component analysis shows their relationship between the Altar and Laohudong wares with provenance postulation. The thickness of the transitive layer in the Altar and Laohudong wares is obviously different, which reveals the microstructure characteristics of the celadon even though both kinds of wares belong to the imperial kiln system. 相似文献
19.
An equation of state (EOS) explicit in Helmholtz free energy has been improved to calculate the PVTx and vapor–liquid phase equilibrium properties of CH4–CO2 fluid mixture. This EOS, where four mixing parameters are used, is based on highly accurate EOSs recommended by NIST for pure components (CH4 and CO2) and contains a simple generalized departure function presented by Lemmon and Jacobsen (1999). Comparison with experimental data available indicates that the EOS can calculate both vapor–liquid phase equilibrium and volumetric properties of this binary fluid system with accuracy close to that of experimental data up to high temperature and pressure within full range of composition. The EOS of CH4–CO2 fluid, together with the updated Gibbs free energy model of solid CO2 (dry ice), is applied to calculate the CH4 content (xCH4) and molar volume (Vm) of the CH4–CO2 fluid inclusion based on the assumption that the volume of an inclusion keeps constant during heating and cooling. diagrams are presented, which describe phase transitions involving vapor, liquid and CO2 solid phases of CH4–CO2 fluid inclusions. Isochores of CH4–CO2 inclusions at given and Vm can be easily calculated from the improved EOS. 相似文献
20.
Peter B. Kelemen 《Journal of the Geological Society of India》2009,74(2):280-282