Geology topics

I.-M. Chou

Publications and source records attributed to I.-M. Chou.

At least 37 records · Page 2Linked to original sources

USGS2007

PVTx properties of the CO 2 -H 2 O and CO 2 -H 2 O-NaCl systems below 647 K: assessment of experimental data and thermodynamic models

Evaluation of CO 2 sequestration in formation brine or in seawater needs highly accurate experimental data or models of pressure–volume–temperature-composition ( PVTx ) properties for the CO 2 –H 2 O and CO 2 –H 2 O–NaCl systems. This paper presents a comprehensive review of the experimental PVTx properties and the thermodynamic models of these two systems. The following conclusions are drawn from the review: (1) About two-thirds of experimental data are consistent with each other, where the uncertainty in liquid volumes is within 0.5%, and that in gas volumes within 2%. However, this accuracy is not sufficient for assessing CO 2 sequestration. Among the data sets for liquids, only a few are available for accurate modeling of CO 2 sequestration. These data have an error of about 0.1% on average, roughly covering from 273 to 642 K and from 1 to 35 MPa; (2) There is a shortage of volumetric data of saturated vapor phase. (3) There are only a few data sets for the ternary liquids, and they are inconsistent with each other, where only a couple of data sets can be used to test a predictive density model for CO 2 sequestration; (4) Although there are a few models with accuracy close to that of experiments, none of them is accurate enough for CO 2 sequestration modeling, which normally needs an accuracy of density better than 0.1%. Some calculations are made available on www.geochem-model.org .

Chemical Geology↗

USGS2007

A unified equation for calculating methane vapor pressures in the CH4-H2O system with measured Raman shifts

A unified equation has been derived by using all available data for calculating methane vapor pressures with measured Raman shifts of C-H symmetric stretching band (??1) in the vapor phase of sample fluids near room temperature. This equation eliminates discrepancies among the existing data sets and can be applied at any Raman laboratory. Raman shifts of C-H symmetric stretching band of methane in the vapor phase of CH4-H2O mixtures prepared in a high-pressure optical cell were also measured at temperatures between room temperature and 200 ??C, and pressures up to 37 MPa. The results show that the CH4 ??1 band position shifts to higher wavenumber as temperature increases. We also demonstrated that this Raman band shift is a simple function of methane vapor density, and, therefore, when combined with equation of state of methane, methane vapor pressures in the sample fluids at elevated temperatures can be calculated from measured Raman peak positions. This method can be applied to determine the pressure of CH4-bearing systems, such as methane-rich fluid inclusions from sedimentary basins or experimental fluids in hydrothermal diamond-anvil cell or other types of optical cell. ?? 2007 Elsevier Ltd. All rights reserved.

Geochimica et Cosmochimica Acta↗

USGS2006

A shock-induced polymorph of anatase and rutile from the Chesapeake Bay impact structure, Virginia, U.S.A

A shock-induced polymorph (TiO2II) of anatase and rutile has been identified in breccias from the late Eocene Chesapeake Bay impact structure. The breccia samples are from a recent, partially cored test hole in the central uplift at Cape Charles, Virginia. The drill cores from 744 to 823 m depth consist of suevitic crystalline-clast breccia and brecciated cataclastic gneiss in which the TiO2 phases anatase and rutile are common accessory minerals. Electron-microprobe imaging and laser Raman spectroscopy of TiO2 crystals, and powder X-ray diffraction (XRD) of mineral concentrates, confirm that a high-pressure, ??-PbO2 structured polymorph of TiO2 (TiO2II) coexists with anatase and rutile in matrix-hosted crystals and in inclusions within chlorite. Raman spectra of this polymorph include strong bands at wavenumbers (cm-1) 175, 281, 315, 342, 356, 425, 531, 571, and 604; they appear with anatase bands at 397, 515, and 634 cm-1, and rutile bands at 441 and 608 cm-1. XRD patterns reveal 12 lines from the polymorph that do not significantly interfere with those of anatase or rutile, and are consistent with the TiO2II that was first reported to occur naturally as a shock-induced phase in rutile from the Ries crater in Germany. The recognition here of a second natural shock-induced occurrence of TiO2II suggests that its presence in rocks that have not been subjected to ultrahigh-pressure regional metamorphism can be a diagnostic indicator for confirmation of suspected impact structures.

American Mineralogist↗

USGS2006

In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: A new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions

A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition. ?? 2006 Society for Applied Spectroscopy.

Applied Spectroscopy↗

USGS2006

Sulfates on Mars: A systematic Raman spectroscopic study of hydration states of magnesium sulfates

The martian orbital and landed surface missions, OMEGA on Mar Express and the two Mars Explorations Rovers, respectively, have yielded evidence pointing to the presence of magnesium sulfates on the martian surface. In situ identification of the hydration states of magnesium sulfates, as well as the hydration states of other Ca- and Fe- sulfates, will be crucial in future landed missions on Mars in order to advance our knowledge of the hydrologic history of Mars as well as the potential for hosting life on Mars. Raman spectroscopy is a technique well-suited for landed missions on the martian surface. In this paper, we report a systematic study of the Raman spectra of the hydrates of magnesium sulfate. Characteristic and distinct Raman spectral patterns were observed for each of the 11 distinct hydrates of magnesium sulfates, crystalline and non-crystalline. The unique Raman spectral features along with the general tendency of the shift of the position of the sulfate ??1 band towards higher wavenumbers with a decrease in the degree of hydration allow in situ identification of these hydrated magnesium sulfates from the raw Raman spectra of mixtures. Using these Raman spectral features, we have started the study of the stability field of hydrated magnesium sulfates and the pathways of their transformations at various temperature and relative humidity conditions. In particular we report on the Raman spectrum of an amorphous hydrate of magnesium sulfate (MgSO4??2H2O) that may have specific relevance for the martian surface. ?? 2006 Elsevier Inc. All rights reserved.

Geochimica et Cosmochimica Acta↗

USGS2006

An improved model for the calculation of CO2 solubility in aqueous solutions containing Na+, K+, Ca2+, Mg2+, Cl-, and SO42-

An improved model is presented for the calculation of the solubility of carbon dioxide in aqueous solutions containing Na+, K+, Ca2+, Mg2+, Cl-, and SO42- in a wide temperature-pressure-ionic strength range (from 273 to 533 K, from 0 to 2000 bar, and from 0 to 4.5 molality of salts) with experimental accuracy. The improvements over the previous model [Duan, Z. and Sun, R., 2003. An improved model calculating CO2 solubility in pure water and aqueous NaCl solutions from 273 to 533K and from 0 to 2000 bar. Chemical Geology, 193: 257-271] include: (1) By developing a non-iterative equation to replace the original equation of state in the calculation of CO 2 fugacity coefficients, the new model is at least twenty times computationally faster and can be easily adapted to numerical reaction-flow simulator for such applications as CO2 sequestration and (2) By fitting to the new solubility data, the new model improved the accuracy below 288 K from 6% to about 3% of uncertainty but still retains the high accuracy of the original model above 288 K. We comprehensively evaluate all experimental CO2 solubility data. Compared with these data, this model not only reproduces all the reliable data used for the parameterization but also predicts the data that were not used in the parameterization. In order to facilitate the application to CO2 sequestration, we also predicted CO2 solubility in seawater at two-phase coexistence (vapor-liquid or liquid-liquid) and at three-phase coexistence (CO2 hydrate-liquid water-vapor CO2 [or liquid CO2]). The improved model is programmed and can be downloaded from the website http://www.geochem-model.org/programs.htm. ?? 2005 Elsevier B.V. All rights reserved.

Marine Chemistry↗

USGS2005

Determination of goslarite-bianchite equilibria by the humidity-buffer technique at 0.1 MPa

Goslarite-bianchite equilibria were determined along four humidity-buffer curves at 0.1 MPa and between 27 and 36 ??C. Results, based on tight reversals along each humidity buffer, can be represented by ln K (??0.005)=19.643-7015.38/T, where K is the equilibrium constant and T is temperature in K. Our data are in excellent agreement with several previous vapor-pressure measurements and are consistent with the solubility data reported in the literature. Thermodynamic analysis of these data yields 9.634 (??0.056) kJ mol-1 for the standard Gibbs free energy of reaction, which is in good agreement with the value of 9.658 kJ mol-1 calculated from the thermodynamic data compiled and evaluated by Wagman et al. [Wagman, D.D., Evans, W.H., Parker, V.B., Schumm, R.H., Halow. I., Bailey, S.M., Churney, K.L., Nuttal, R.L., 1982. The NBS tables of chemical thermodynamic properties. Selected values for inorganic and C1 and C2 organic substances in SI units. J. Phys. Chem. Ref. Data 11, Suppl. 2].

Chemical Geology↗

USGS2005

Producing ammonium sulfate from flue gas desulfurization by-products

Emission control technologies using flue gas desulfurization (FGD) have been widely adopted by utilities burning high-sulfur fuels. However, these technologies require additional equipment, greater operating expenses, and increased costs for landfill disposal of the solid by-products produced. The financial burdens would be reduced if successful high-volume commercial applications of the FGD solid by-products were developed. In this study, the technical feasibility of producing ammonium sulfate from FGD residues by allowing it to react with ammonium carbonate in an aqueous solution was preliminarily assessed. Reaction temperatures of 60, 70, and 80??C and residence times of 4 and 6 hours were tested to determine the optimal conversion condition and final product evaluations. High yields (up to 83%) of ammonium sulfate with up to 99% purity were achieved under relatively mild conditions. The optimal conversion condition was observed at 60??C and a 4-hour residence time. The results of this study indicate the technical feasibility of producing ammonium sulfate fertilizer from an FGD by-product. Copyright ?? Taylor & Francis Inc.

Energy Sources↗

USGS2005

Acquisition and evaluation of thermodynamic data for bieberite-moorhouseite equilibria at 0.1 MPa

Published estimates for the equilibrium relative humidity (RH) at 25 deg;C for the reaction: bieberite (CoSO4??7H2O) = moorhouseite (CoSO4??6H2O) + H2O, range from 69.8 to 74.5%. To evaluate these data, the humidity-buffer technique was used to determine equilibrium constants for this reaction between 14 and 43 ??C at 0.1 MPa. Reversals along five humidity-buffer curves yield In K = 18.03-6509.43/T, where K is the equilibrium constant, and T is temperature in K. The derived standard Gibbs free energy of reaction is 9.43 kJ/mol, which agrees well with several previously reported values based on vapor-pressure measurements. It also agrees well with values calculated from the data derived mostly from calorimetric measurements. Previous studies indicated that the temperature of the invariant point for the assemblage bieberite-moorhouseite-aqueous solution-vapor is near 44.7 ??C, and our extrapolated data predict 91.1% RH at this temperature; the predicted position for the invariant point is in excellent agreement with those reported previously.

American Mineralogist↗

USGS2003

Acquisition and evaluation of thermodynamic data for morenosite-retgersite equilibria at 0.1 MPa

Metal-sulfate salts in mine drainage environments commonly occur as solid solutions containing Fe, Cu, Mg, Zn, Al, Mn, Ni, Co, Cd, and other elements. Thermodynamic data for some of the end-member salts containing Fe, Cu, Zn, and Mg have been collected and evaluated previously, and the present study extends to the system containing Ni. Morenosite (NiSO 4 -7H 2 O)- retgersite (NiSO 4 -6H 2 O) equilibria were determined along five humidity buffer curves at 0.1 MPa and between 5 and 22°C. Reversals along these humidity-buffer curves yield In K = 17.58-6303.35/T, where K is the equilibrium constant, and T is temperature in K. The derived standard Gibbs free energy of reaction is 8.84 kJ/mol, which agrees very well with the values of 8.90, 8.83, and 8.85 kJ/mol based on the vapor pressure measurements of Schumb (1923), Bonnell and Burridge (1935), and Stout et al. (1966). respectively. This value also agrees reasonably well with the values of 8.65 and 9.56 kJ/mol calculated from the data compiled by Wagman et al. (1982) and DeKock (1982), respectively. The temperature-humidity relationships defined by this study for dehydration equilibria between morenosite and retgersite explain the more common occurrence of retgersite relative to morenosite in nature.

American Mineralogist↗

USGS2003

Relaxation of the structure of simple metal ion complexes in aqueous solutions at up to supercritical conditions

Recently x-ray absorption fine structure (XAFS) studies of various ions in aqueous solutions showed a variation of cation-ligand bond lengths, often coupled with other structure changes, with increasing temperatures. Thus, the variations of the structure of several metal ion complexes with temperature based on observations from the X-ray absorption fine structure (XAFS) studies in the hope that it will stimulate the development of either first- principles theory or molecular dynamics simulations that might adequately describes these results are discussed.

Journal of Chemical Physics↗

USGS2003

Determination of epsomite-hexahydrite equilibria by the humidity-buffer technique at 0.1 MPa with implications for phase equilibria in the system MgSO4-H2O

Epsomite (MgSO 4 ·7H 2 O) and hexahydrite (MgSO 4 ·6H 2 O) are common minerals found in marine evaporite deposits, in saline lakes as precipitates, in weathering zones of coal and metallic deposits, in some soils and their efflorescences, and possibly on the surface of Europa as evaporite deposits. Thermodynamic properties of these two minerals reported in the literature are in poor agreement. In this study, epsomite-hexahydrite equilibria were determined along four humidity-buffer curves at 0.1 MPa and between 25 and 45°C. Results obtained for the reaction epsomite = hexahydrite + H 2 O, as demonstrated by very tight reversals along each humidity buffer, can be represented by ln K (± 0.012) = 20.001 - 7182.07/ T , where K is the equilibrium constant, and T is temperature in Kelvin. The derived standard Gibbs free energy of reaction is 10.13 ± 0.07 kJ/mol, which is essentially the same value as that calculated from vapor pressure measurements reported in the literature. However, this value is at least 0.8 kJ/mol lower than those calculated from the data derived mostly from calorimetric measurements.

Astrobiology↗

USGS2003

Hydrothermal diamond-anvil cell: Application to studies of geologic fluids

The hydrothermal diamond-anvil cell (HDAC) was designed to simulate the geologic conditions of crustal processes in the presence of water or other fluids. The HDAC has been used to apply external pressure to both synthetic and natural fluid inclusions in quartz to minimize problems caused by stretching or decrepitation of inclusions during microthermometric analysis. When the HDAC is loaded with a fluid sample, it can be considered as a large synthetic fluid inclusion and therefore, can be used to study the PVTX properties as well as phase relations of the sample fluid. Because the HDAC has a wide measurement pressure-temperature range and also allows in-situ optical observations, it has been used to study critical phenomena of various chemical systems, such as the geologically important hydrous silicate melts. It is possible, when the HDAC is combined with synchrotron X-ray sources, to obtain basic information on speciation and structure of metal including rare-earth elements (REE) complexes in hydrothermal solutions as revealed by X-ray absorption fine structure (XAFS) spectra. Recent modifications of the HDAC minimize the loss of intensity of X-rays due to scattering and absorption by the diamonds. These modifications are especially important for studying elements with absorption edges below 10 keV and therefore particularly valuable for our understanding of transport and deposition of first-row transition elements and REE in hydrothermal environments.

Acta Petrologica Sinica↗

USGS2003

An overview on current fluid-inclusion research and applications

This paper provides an overview of some of the more important developments in fluid-inclusion research and applications in recent years, including fluid-inclusion petrography, PVTX studies, and analytical techniques. In fluid-inclusion petrography, the introduction of the concept of 'fluid-inclusion assemblage' has been a major advance. In PVTX studies, the use of synthetic fluid inclusions and hydrothermal diamond-anvil cells has greatly contributed to the characterization of the phase behaviour of geologically relevant fluid systems. Various analytical methods are being developed and refined rapidly, with the Laser-Raman and LA-ICP-MS techniques being particularly useful for volatile and solute analyses, respectively. Ore deposit research has been and will continue to be the main field of application of fluid inclusions. However, fluid inclusions have been increasingly applied to other fields of earth science, especially in petroleum geology and the study of magmatic and earth interior processes.

Acta Petrologica Sinica↗

USGS2002

The structure of Yb 3+ aquo ion and chloro complexes in aqueous solutions at up to 500 °C and 270 MPa

We report here on X-ray absorption fine structure (XAFS) measurements used to determine the structure of the Yb 3+ ion in aqueous solutions over a range of temperatures from 25 to 500 °C and pressures up to 270 MPa. Fluorescence Yb L 3 -edge spectra were collected separately from nitrate (0.006 m Yb/0.16 m HNO 3 ) and chloride (0.006 m YbCl 3 /0.017 m HCl) aqueous solutions within a hydrothermal diamond anvil cell. The Yb−O distance of the Yb 3+ aquo ion in the nitrate solution exhibits a uniform reduction at a rate of 0.02 Å/100 °C, whereas the number of oxygens decreases from 8.3 ± 0.6 to 4.8 ± 0.7, in going from 25 to 500 °C. No evidence for nitrate complexes was found from measurements made on this solution. The Yb 3+ is found to persist as an aquo ion up to 150 °C in the chloride aqueous solution. In the 300−500 °C range, chloro complexes are found to occur in the solution, most likely of the type Yb(H 2 O) δ - n Cl n +3- n (δ ≈ 7). The Yb−Cl distance of the chloro ytterbium(III) complexes is found to decrease uniformly at a rate of about 0.02 Å/100 °C, whereas the number of chlorines increases from 0.5 ± 0.3 to 1.8 ± 0.2 in the 300−500 °C temperature range. Conversely, the Yb−O distance undergoes a lower uniform reduction at a rate of 0.007 Å/100 °C, whereas the number of oxygens decreases from 8.3 ± 0.5 to 5.1 ± 0.3 in going from 25 to 500 °C in the same solution.

Journal of Physical Chemistry A↗

USGS2002

Solubility relations in the ternary system NaCl-CsCl-H2O at 1 atm. 1. Solubilities of halite from 20 to 100 °C

Solubilities of halite in the ternary system NaCl-CsCl-H 2 O have been determined by the visual polythermal method at 1 atm from 20 to 100 °C along five constant CsCl/(CsCl + H 2 O) weight ratio lines. These five constant weight ratios are 0.1, 0.2, 0.3, 0.4, and 0.5. The maximum uncertainties in these measurements are ± 0.02 wt % NaCl and ± 0.15 °C. The data along each constant CsCl/(CsCl + H 2 O) weight ratio line were regressed to a smooth curve. The maximum deviation of the measured solubilities from the smooth curves is 0.06 wt % NaCl. Isothermal solubilities of halite were calculated from smoothed curves at 25, 50, and 75 °C.

Journal of Chemical and Engineering Data↗

USGS2002

Solubility relations in the system sodium chloride-ferrous chloride-water between 25 and 70.degree.C at 1 atm

Solubility relations in the ternary system NaCl-FeCl2-H2O have been determined by the visual polythermal method at 1 atm from 20 to 85??C along six composition lines. These she composition lines are defined by mixing FeCl2??4H2O with six aqueous NaCl solutions containing 5, 10, 11, 15, 20, and 25 wt % of NaCl, respectively. The solid phases encountered in these experiments were NaCl and FeCl2??4H2O. The maximum uncertainties in these measurements are ??0.02 wt % NaCl and ??0.15??C. The data along each composition line were regressed to a smooth curve when only one solid phase was stable. When two solids were stable along a composition line, the data were regressed to two smooth curves, the intersection of which indicated the point where the two solids coexisted. The maximum deviation of the measured solubilities from the smoothed curves is 0.14 wt % FeCl2. Isothermal solubilities of halite and FeCl2??4H2O were calculated from these smoothed curves at 25, 50, and 70 ??C.

Journal of Chemical and Engineering Data↗

USGS2002

Solubility relations in the system potassium chloride-ferrous chloride-water between 25 and 75.degree.C at 1 atm

Solubility relations in the ternary system KCl-FeCl2-H2O have been determined by means of the visual polythermal method at 1 atm from 18 to 75??C along 10 composition lines. Solubilities of sylvite were measured along five composition lines defined by mixing KCl with five aqueous FeCl2 solutions containing 10, 20, 30, 38, and 45 wt % of FeCl2, respectively. Solubilities of FeCl2??4H2O were also determined along five composition lines defined by mixing FeCl2??4H2O with five aqueous KCl solutions containing 5, 10, 14.98, 19.97, and 24.99 wt % KCl, respectively. The maximum uncertainties in these measurements are ??0.02 wt % in KCl, ??0.15 wt % in FeCl2, and ??0.15??C. The data along each composition line were regressed to a smooth curve. The maximum deviations of the measured solubilities from the smoothed curves are 0.22 wt % in KCl and 0.12 wt % in FeCl2. Isothermal solubilities of sylvite and FeCl2??4H2O were calculated from these smoothed curves at 25, 40, 50, 60, 70, and 75??C.

Journal of Chemical and Engineering Data↗