USGS Science⌕ Search

Geology topics

B. S. Hemingway

Publications and source records attributed to B. S. Hemingway.

At least 37 records · Page 2Linked to original sources
USGS1990

Thermodynamic properties for bunsenite, NiO, magnetite, Fe3O4, and hematite, Fe2O3, with comments on selected oxygen buffer reactions

Smoothed values of the heat capacities and derived thermodynamic functions are given for bunsenite, magnetite, and hematite for the temperature interval 298.15 to 1800 K. The Gibbs free energy for the reaction Ni + 0.5O2 = NiO is given by the equation ??rG0T = -238.39 + 0.1146T - 3.72 ?? 10-3T ln T and is valid from 298.15 K to 1700 K. The Gibbs free energy (in kJ) of the reaction 2 magnetite + 3 quartz = 3 fayalite + O2 may be calculated from the equation ??rG0T = 474.155 - 0.16120 T in kJ and between 800 and 1400 K. The Gibbs free energy (in kJ) of the reaction 6 hematite = 4 magnetite + O2 may be calculated from the following equations: ??rG0T = 496.215 - 0.27114T, ??rG0T = 514.690 - 0.29753T, ??rG0T = 501.348 - 0.2854T. -from Author

American Mineralogist↗
USGS1990

Heat capacities and thermodynamic properties of annite (aluminous iron biotite)

The heat capacities have been measured between 7 and 650 K by quasi-adiabatic calorimetry and differential scanning calorimetry. At 298.15 K and 1 bar, the calorimetric entropy for our sample is 354.9??0.7 J/(mol.K). A minimum configurational entropy of 18.7 J/(mol.K) for full disorder of Al/Si in the tetrahedral sites should be added to the calorimetric entropy for third-law calculations. The heat capacity equation [Cp in units of J/mol.K)] Cp0 = 583.586 + 0.075246T - 3420.60T-0.5 - (4.4551 ?? 106)T-2 fits the experimental and estimated heat capacities for our sample (valid range 250 to 1000 K) with an average deviation of 0.37%. -from Authors

American Mineralogist↗
USGS1989

Heat capacities and entropies at 298.15 K of MgTiO3 (geikielite), ZnO (zincite), and ZnCO3 (smithsonite)

Heat capacities of synthetic MgTiO3 (geikielite), ZnO (zincite), and natural crystals of smithsonite (ZnCO3) were measured between 9 and 366 K using an automatic adiabatically shielded calorimeter. At 298.15 K the standard molar entropies Smo of MgTiO3, ZnO, and ZnCO3 are (74.64 ?? 0.15), (43.16 ?? 0.09), and (81.19 ?? 0.16) J??K-1??mol-1, respectively. Debye temperatures for MgTiO3 and ZnO calculated from our Cp, mo values below 20 K are (900 ?? 20) K and (440 ?? 25) K respectively. Heat capacities for MgTiO3 and ZnO were combined with enthalpy increments from the literature to derive heat-capacity equations for these phases from 260 to about 1800 K. The heat capacities of MgTiO3 between 260 and 1720 K were fitted with an average deviation of 0.3 per cent by the equation: C??p,m/(J??K-1??mol-1) = 222.5-0.05274(T/K)-6.092x105(T/K)-1-1874.6(T/K) -1/2+1.878x10-5(T/K)2 and for ZnO the equation: C??p,m/(J??K-1??mol-1) = 53.999+7.851x10-4(T/K)-5.868x105(T/K)-2 -127.50(T/K)-:1/2+1.9376x10-6(T/K)2 fits the heat capacities in the temperature interval of 250 to 1800 K with an average deviation of 0.7 per cent. ?? 1989.

Journal of Chemical Thermodynamics↗
USGS1988

Thermophysical properties of ilvaite CaFe22+Fe3+Si2O7O (OH); heat capacity from 7 to 920 K and thermal expansion between 298 and 856 K

The heat capacity of ilvaite from Seriphos, Greece was measured by adiabatic shield calorimetry (6.4 to 380.7 K) and by differential scanning calorimetry (340 to 950 K). The thermal expansion of ilvaite was also investigated, by X-ray methods, between 308 and 853 K. At 298.15 K the standard molar heat capacity and entropy for ilvaite are 298.9??0.6 and 292.3??0.6 J/(mol. K) respectively. Between 333 and 343 K ilvaite changes from monoclinic to orthorhombic. The antiferromagnetic transition is shown by a hump in Cp0with a Ne??el temperature of 121.9??0.5 K. A rounded hump in Cp0between 330 and 400 K may possibily arise from the thermally activated electron delocalization (hopping) known to take place in this temperature region. ?? 1988 Springer-Verlag.

Physics and Chemistry of Minerals↗
USGS1987

Heat capacity measurements for cryolite (Na3AlF6) and reactions in the system NaFeAlSiOF

The heat capacity of cryolite (Na 3 AlF 6 ) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S 0 298 = 238.5 J / mol K "> S 0 298 = 238.5J/mol K S 0 T − S 0 298 = 145.114 ln T+ 193.009∗10 −3 T− 10.366∗ 10 5 T 2 − 872.89 J / mol K (273−836.5 K ) "> S 0 T −S 0 298 = 145.114lnT+ 193.009∗10 −3 T−10.366∗ 10 5 T 2 − 872.89J/mol K(273−836.5K) Δ S Trans = 9.9 J / mol K "> ΔS Trans = 9.9J/mol K S 0 T − S 0 298 =198.414 ln T+73.203∗ 10 −3 T−63.814∗ 10 5 T 2 −1113.11 J / mol K (836.5−1153 K ) "> S 0 T −S 0 298 =198.414 ln T+73.203∗ 10 −3 T−63.814∗10 5 T 2 −1113.11J/mol K(836.5−1153K) with the transition temperature between α- and β-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system Na Fe Al Si O F. The resultant phase diagrams allow constraints to be placed on the f O 2 , f F 2 , a SiO 2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log f O 2 is approximately −19.2, log f F 2 is −31.9 to −33.2, and a SiO 2 is −1.06 at assumed P T "> PT conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland.

Geochimica et Cosmochimica Acta↗
USGS1987

Heat capacities of synthetic hedenbergite, ferrobustamite and CaFeSi2O6 glass

Heat capacities have been measured for synthetic hedenbergite (9–647 K), ferrobustamite (5–746 K) and CaFeSi 2 O 6 glass (6–380 K) by low-temperature adiabatic and differential scanning calorimetry. The heat capacity of each of these structural forms of CaFeSiO 6 exhibits anomalous behavior at low temperatures. The X-peak in the hedenbergite heat-capacity curve at 34.5 K is due to antiferromagnetic ordering of the Fe 2+ ions. Ferrobustamite has a bump in its heat-capacity curve at temperatures less than 20 K, which could be due to weak cooperative magnetic ordering or to a Schottky anomaly. Surprisingly, a broad peak with a maximum at 68 K is present in the heat-capacity curve of the glass. If this maximum, which occurs at a higher temperature than in hedenbergite is caused by magnetic ordering, it could indicate that the range of distortions of the iron sites in the glass is quite small and that coupling between iron atoms is stronger in the glass than in the edge-shared octahedral chains of hedenbergite. The standard entropy change, S o 298.15 − S o 0 , is 174.2 ± 0.3, 180.5 ± 0.3 and 185.7 ± 0.4 J/mol·K for hedenbergite, ferrobustamite and CaFeSi 2 O 6 glass, respectively. Ferrobustamite is partially disordered in Ca-Fe distribution at high temperatures, but the dependence of the configuratonal entropy on temperature cannot be evaluated due to a lack of information. At high temperatures (298–1600 K), the heat capacity of hedenbergite may be represented by the equation C o p (J/mol·K) = 3 l 0.46 + 0.01257 T -2039.93 T −1 2 − 1.84604× l0 6 T −2 "> −12− 1.84604× 10 6 T −2 and the heat capacity of ferrobustamite may be represented by C o p (J/mol·K) = 403.83−0.04444T+ 1.597× 10 −5 T 2 −3757.3T −1 2 "> C o p (J/mol·K)= 403.83−0.04444T+ 1.597× 10 −5 T 2 −3757.3T −12 .

Geochimica et Cosmochimica Acta↗
USGS1987

Origin of coffinite in sedimentary rocks by a sequential adsorption-reduction mechanism.

Coffinite is the dominant ore mineral in the V-U ores of the Tony-M mine in the Henry Mts mineral belt of the Colorado Plateau. This orebody was formed at a density-stratified solution interface between uranyl-ion-bearing meteoric water and a saline fluid which was locally reducing. The localization of U at this solution interface occurred by adsorption onto the surfaces of detrital minerals, this adsorption being related to the pH difference between the two fluids. Experimental evidence is presented showing that the adsorption facilitated the reduction of uranium to U(IV). This adsorbed, reduced uranium bonded with aqueous silica in the ore zone to form coffinite. The high concentration of silica (as a monomeric species) in the ore-forming solution stabilized coffinite in preference to uraninite.-R.A.H.

Bulletin de Mineralogie↗
USGS1987

Quartz: heat capacities from 340 to 1000 K and revised values for the thermodynamic properties.

New heat-capacity data for quartz have been measured over the T interval 340-1000 K by differential scanning calorimetry. The data were combined with recent heat-content and heat-capacity data to provide a significantly revised set of thermodynamic properties for alpha -quartz and to resolve the problem of disparate heat-content and heat-capacity data for alpha - and beta -quartz.-J.A.Z.

American Mineralogist↗
USGS1986

The heat capacity of a natural monticellite and phase equilibria in the system CaO-MgO-SiO2-CO2

The heat capacity of a natural monticellite (Ca 1.00 Mg .09 Fe .91 Mn .01 Si 0.99 O 3.99 ) measured between 9.6 and 343 K using intermittent-heating, adiabatic calorimetry yields C p 0 (298) and S 298 0 of 123.64 ± 0.18 and 109.44 ± 0.16 J · mol −1 K −1 respectively. Extrapolation of this entropy value to end-member monticellite results in an S 0 298 = 108.1 ± 0.2 J · mol −1 K −1 . High-temperature heat-capacity data were measured between 340–1000 K with a differential scanning calorimeter. The high-temperature data were combined with the 290–350 K adiabatic values, extrapolated to 1700 K, and integrated to yield the following entropy equation for end-member monticellite (298–1700 K): S T 0 ( J · mol −1 K −1 ) = S 298 0 + 164.79 In T + 15.337 · 10 −3 T + 22.791 · 10 5 T −2 − 968.94. Phase equilibria in the CaO-MgO-SiO 2 system were calculated from 973 to 1673 K and 0 to 12 kbar with these new data combined with existing data for akermanite ( Ak ), diopside ( Di ), forsterite ( Fo ), merwinite ( Me ) and wollastonite ( Wo ). The location of the calculated reactions involving the phases Mo and Fo is affected by their mutual solid solution. A best fit of the thermodynamically generated curves to all experiments is made when the S 0 298 of Me is 250.2 J · mol −1 K −1 less than the measured value of 253.2 J · mol −1 K −1 . A best fit to the reversals for the solid-solid and decarbonation reactions in the CaO-MgO-SiO 2 -CO 2 system was obtained with the ΔG 0 298 ( kJ · mole −1 ) for the phases Ak (−3667), Di (−3025), Fo (−2051), Me (−4317) and Mo (−2133). The two invariant points − Wo and − Fo for the solid-solid reactions are located at 1008 ± 5 K and 6.3 ± 0.1 kbar, and 1361 ± 10 K and 10.2 ± 0.2 kbar respectively. The location of the thermodynamically generated curves is in excellent agreement with most experimental data on decarbonation equilibria involving these phases.

Geochimica et Cosmochimica Acta↗
USGS1986

Low-temperature heat capacity of diopside glass (CaMgSi2O6): A calorimetric test of the configurational-entropy theory applied to the viscosity of liquid silicates

Heat-capacity measurements have been made between 8 and 370 K on an annealed and a rapidly quenched diopside glass. Between 15 and 200 K, Cp does not depend significantly on the thermal history of the glass. Below 15 K Cp is larger for the quenched than for the annealed specimen. The opposite is true above 200 K as a result of what is interpreted as a secondary relaxation around room temperature. The magnitude of these effects, however, is small enough that the relative entropies S(298)−S(0) of the glasses differ by only 0.5 J/mol K, i.e. , a figure within the combined experimental uncertainties. The insensitivity of relative entropies to thermal history supports the assumption that the configurational heat capacity of the liquid may be taken as the heat capacity difference between the liquid and the glass (Δ Cp ). Furthermore, this insensitivity allows calculation of the residual entropies at 0 K of diopside glasses as a function of the fictive temperature from the entropy of fusion of diopside and the heat capacities of the crystalline, glassy and liquid phases. For a glass with a fictive temperature of 1005 K, for example, this calorimetric residual entropy is 24.3 ± 3 J /mol K, in agreement with the prediction made by RICHET (1984) from an analysis of the viscosity data with the configurational-entropy theory of relaxation processes of Adam and Gibbs (1965). In turn, all the viscosity measurements for liquid diopside, which span the range 0.5-4· 10 13 poise, can be quantitatively reproduced through this theory with the calorimetrically determined entropies and Δ Cp data. Finally, the unclear significance of “activation energies” for structural interpretations of viscosity data is emphasized, and the importance of Δ Cp and glass-transition temperature systematics for determining the composition and temperature dependences of the viscosity is pointed out.

Geochimica et Cosmochimica Acta↗
USGS1986

Heat capacities and thermodynamic functions for beryl, Be3Al2Si6O18, phenakite, Be2SiO4, euclase, BeAlSiO4(OH), bertrandite, Be4Si2O7(OH)2, and chrysoberyl, BeAl2O4.

The heat capacities of beryl, phenakite, euclase and bertrandite have been measured between approx 5 and 800 K by combined quasi-adiabatic cryogenic calorimetry and differential scanning calorimetry. The heat capacities of chrysoberyl have been measured from 340 to 800 K. The resulting data have been combined with solution and phase-equilibrium experimental data and simultaneously adjusted using the programme PHAS20 to provide an internally consistent set of thermodynamic properties for several important beryllium phases. The experimental heat capacities and tables of derived thermodynamic properties are presented.-J.A.Z.

American Mineralogist↗
USGS1986

Akermanite: phase transitions in heat capacity and thermal expansion, and revised thermodynamic data.

A small but sharp anomaly in the heat capacity of akermanite at 357.9 K, and a discontinuity in its thermal expansion at 693 K, as determined by XRD, have been found. The enthalpy and entropy assigned to the heat-capacity anomaly, for the purpose of tabulation, are 679 J/mol and 1.9 J/(mol.K), respectively. They were determined from the difference between the measured values of the heat capacity in the T interval 320-365 K and that obtained from an equation which fits the heat-capacity and heat-content data for akermanite from 290 to 1731 K. Heat-capacity measurements are reported for the T range from 9 to 995 K. The entropy and enthalpy of formation of akermanite at 298.15 K and 1 bar are 212.5 + or - 0.4 J/(mol.K) and -3864.5 + or - 4.0 kJ/mol, respectively. Weak satellite reflections have been observed in hk0 single-crystal X-ray precession photographs and electron-diffraction patterns of this material at room T. With in situ heating by TEM, the satellite reflections decreased significantly in intensity above 358 K and disappeared at about 580 K and, on cooling, reappeared. These observations suggest that the anomalies in the thermal behaviour of akermanite are associated with local displacements of Ca ions from the mirror plane (space group P421m) and accompanying distortion of the MgSi2O7 framework.-L.C.C.

Canadian Mineralogist↗
USGS1985

The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O

Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO 3 ) from 5 to 1000 K. These measurements yield S 298 0 = 108.9 J /( mol · K ). Calculations from published experimental data on the reduction of ilmenite yield Δ 298 0 ( I 1) = −1153.9 kJ /( mol · K ). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of ƒO 2 ">ƒ ƒO2 are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookite ss and hematite-ilmenite ss . Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling.

Geochimica et Cosmochimica Acta↗
USGS1985

Low-temperature molar heat capacities and entropies of MnO2 (pyrolusite), Mn3O4 (hausmanite), and Mn2O3 (bixbyite)

Pyrolusite (MnO2), hausmanite (Mn3O4), and bixbyite (Mn2O3), are important ore minerals of manganese and accurate values for their thermodynamic properties are desirable to understand better the {p(O2), T} conditions of their formation. To provide accurate values for the entropies of these important manganese minerals, we have measured their heat capacities between approximately 5 and 380 K using a fully automatic adiabatically-shielded calorimeter. All three minerals are paramagnetic above 100 K and become antiferromagnetic or ferrimagnetic at lower temperatures. This transition is expressed by a sharp ??-type anomaly in Cpmo for each compound with Ne??el temperatures TN of (92.2??0.2), (43.1??0.2), and (79.45??0.05) K for MnO2, Mn3O4, and Mn2O3, respectively. In addition, at T ??? 308 K, Mn2O3 undergoes a crystallographic transition, from orthorhombic (at low temperatures) to cubic. A significant thermal effect is associated with this change. Hausmanite is ferrimagnetic below TN and in addition to the normal ??-shape of the heat-capacity maxima in MnO2 and Mn2O3, it has a second rounded maximum at 40.5 K. The origin of this subsidiary bump in the heat capacity is unknown but may be related to a similar "anomalous bump" in the curve of magnetization against temperature at about 39 K observed by Dwight and Menyuk.(1) At 298.15 K the standard molar entropies of MnO2, Mn3O4, and Mn2O3, are (52.75??0.07), (164.1??0.2), and (113.7??0.2) J??K-1??mol-1, respectively. Our value for Mn3O4 is greater than that adopted in the National Bureau of Standards tables(2) by 14 per cent. ?? 1985.

Journal of Chemical Thermodynamics↗
USGS1985

Low-temperature heat capacity and entropy of chalcopyrite (CuFeS2): estimates of the standard molar enthalpy and Gibbs free energy of formation of chalcopyrite and bornite (Cu5FeS4)

The heat capacity of CuFeS2 (chalcopyrite) was measured between 6.3 and 303.5 K. At 298.15 K, Cp,mo and Smo(T) are (95.67??0.14) J??K-1??mol-1 and (124.9??0.2) J??K-1??mol-1, respectively. From a consideration of the results of two sets of equilibrium measurements we conclude that ??fHmo(CuFeS2, cr, 298.15 K) = -(193.6??1.6) kJ??mol-1 and that the recent bomb-calorimetric determination by Johnson and Steele (J. Chem. Thermodynamics 1981, 13, 991) is in error. The standard molar Gibbs free energy of formation of bornite (Cu5FeS4) is -(444.9??2.1) kJ??mol-1 at 748 K. ?? 1985.

Journal of Chemical Thermodynamics↗