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1.
Two parameters GO2– and HO2– are defined as the differences between respectively the Gibbs free energies and the enthalpies of formation of an oxide and its corresponding aqueous cation. The Gibbs free energies and enthalpies of formation of phosphates from their consituent oxides are shown to be linear functions of respectively GO2– and HO2– of their constituent cations.  相似文献   

2.
Fluoride-hydroxyl exchange equilibria between phlogopite-pargasite and phlogopite-tremolite mineral pairs were experimentally determined at 1,173K, 500 bars and 1,073–1,173 K, 500 bars respectively. The distribution of fluorine between phlogopite and pargasite was found to favor phlogopite slightly, G ex . (1,173 K)=–1.71 kJ anion–1, while in the case of phlogopite-tremolite, fluorine was preferentially incorporated in the mica, G ex . (1,073)=– 5.67 kJ anion–1 and G ex . (1,173K)=–5.84 kJ anion–1. These results have yielded new values of entropy and Gibbs energy of formation for fluortremolite, S f =–2,293.4±16.0JK–1 mol–1 and G f = –11,779.3±25.0 kJ mol–1, respectively. In addition, F-OH mineral exchange equilibria support a recent molten oxide calorimetric value for the Gibbs energy of fluorphlogopite, G f =–6,014.0±7.0 kJ mol–1, which is approximately 40 kJ mol–1 more exothermic than the tabulated value.This work performed in part at Sandia National Laboratories supported by the U.S. Department of Energy, DOE, under contract number DE-AC04-76DP00789  相似文献   

3.
The assemblage paragonite + quartz is encountered frequently in low- to medium-grade metamorphic rocks. With rising grade of metamorphism they react mutually to yield the condensed assemblage albite + Al2SiO5.The univariant curve pertaining to the equilibrium paragonite + quartz=albite + andalusite + H2O has been located experimentally. The reversed P H 2 O-T data are: 1 kb: 470–490° C 2 kb: 510–530° C 3 kb: 540–560° C 4 kb: 560–580° C 5 kb: 590–600° C The univariant curve pertaining to the equilibrium paragonite + quartz=albite + kyanite + H2O runs through the following P H 2 O-T-intervals: 5 kb: 570–625° C 6 kb: 600–630° C 7 kb: 620–640° C Thermodynamic calculations of S 298 0 , H f,298 0 and G f,298 0 of the phase paragonite from the experimental data presented above and those obtained from the equilibria of the reaction paragonite=albite + corundum + H2O (Chatterjee, 1970), agree within the limits of uncertainty. This prompts the idea that Zen's (1969) suggestion of a possible error of approximately 7 kcal in G f,298 0 of the Al2SiO5 polymorphs may in fact be due to an error of similar magnitude in G f,298 0 of corundum.A best estimate of S 298 0 , H f,298 0 and G f,298 0 of paragonite based on these considerations yield: S 298 0 : 67.61±3.9 cal deg–1 gfw–1 H f,298 0 : –1411.4±2.7 kcal gfw–1 G f,298 0 : –1320.9±4.0 kcal gfw–1 These numbers will be subject to change when better thermochemical data on corundum and albite are available.In medium-grade metamorphic rocks the assemblage paragonite + quartz is commonly found in stable coexistence with such other phases as muscovite, staurolite, andalusite, kyanite, but not with cordierite or sillimanite. However, the assemblage paragonite-sillimanite has been reported to be stable in the absence of quartz. All these petrologic observations can be explained on the basis of the stability data of the phases and phase assemblages concerned.  相似文献   

4.
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   

5.
The discrepancy between the tabulated Gibbs Energies of Formation for Al2SiO5 and corundum relative to muscovite and kaolinite is considered to lie principally with the latter two minerals. New values for heat of formation of gibbsite [Gbs] will affect the tabulated H f 0 , G f(298,1) 0 for the other aluminous minerals which are referred to gibbsite as calorimetric aluminum reference. Gibbs Energy Difference Functions, calculated from phase equilibria in the system CaO-Al2O3-SiO2-(H2O-CO2), can be used to estimate consistent H f 0 , G f(298,1) 0 values for aluminous minerals. A self consistent data set is presented referred to G f(298,1) 0 [Corundum]=–378.08 kcal mol–1. Two independent values for G f(298,1) 0 [Anorthite]=–961.52 and –960.29 kcal, from a recalculation of the H f 0 [Anor] based upon the revised H f(298,1) 0 [Gbs]=–309.325 kcal mol–1 and from measurement of silica activity on the anorthite-saturated part of the CaO-Al2O3-SiO2 liquidus, respectively, are considered to show the magnitude of the discrepancy and are used in the calculations.  相似文献   

6.
A new thermodynamic formulation of the Fe–Ti oxide geothermometer/oxygen barometer is developed. The method is based upon recently calibrated models for spinel solid solutions in the quinary system (Fe2+, Mg)(Al,Fe3+,Cr)2O4–(Fe2+, Mg)2TiO4 by Sack and Ghiorso, and rhombohedral oxides in the quaternary system (Fe2+,Mg,Mn)TiO3–Fe2O3 (this paper). The formulation is internally consistent with thermodynamic models for (Fe2+,Mg)-olivine and -orthopyroxene solid solutions and end-member thermodynamic properties tabulated by Berman. The constituent expressions account for compositional and temperature dependent cation ordering and reproduce miscibility gap features in all of the component binaries. The calibration does not account for the excess Gibbs energy resulting from compositional and temperature dependent magnetic ordering in either phase. This limits application of the method to assemblages that equilibrated at temperatures above 600° C. Practical implementation of the proposed geothermometer/oxygen barometer requires minimal use of projection algorthms in accommodating compositions of naturally occurring phases. The new formulation is applied to the estimation of temperature and oxygen fugacity in a wide variety of intermediate to silicic volcanic rocks. In combination with previous work on olivine and orthopyroxene thermodynamics, equilibration pressures are computed for a subset of these volcanics that contain the assemblage quartz, oxides and either ferromagnesian silicate. The calculated log10 f O 2-T relations are reflected in coexisting ferromagnesian mineral assemblages. Volcanics with the lowest relative oxygen fugacity (log10 f O 2) are characterized by the assemblage olivine-quartz, those with slightly higher log10 f O 2 s, by the assemblage orthopyroxene-quartz. The sequence proceeds with the necessary phases biotite-feldspar, then hornblende-quartz-clinopyroxene, and finally at the highest log10 f O 2 s, sphene-quartz-clinopyroxene. Quantitative analysis of these trends, utilizing thermodynamic data for the constituent phases, establishes that, in most cases, the T-log10 f O 2value computed from the oxides is consistent with the compositions of coexisting silicate phases, indicating that phenocryst equilibrium was achieved prior to eruption. There is, however, considerable evidence of oxide-silicate disequilibrium in samples collected from more slowly cooled domes and obsidians. In addition, T-log10 f O 2trends from volcanic rocks that contain biotite and orthopyroxene are interpreted to imply a condition of Fe2+–Mg exchange disequilibrium between orthopyroxene and coexisting ferromagnesian silicates and melt. It is suspected that many biotite-feldspar-quartz-orthopyroxene bearing low temperature volcanic rocks inherit orthopyroxene xenocrysts which crystallized earlier in the cooling history of the magma body.The problem is probably at least as complex as that of the feldspars... A.F. Buddington (1956)  相似文献   

7.
The marble- and metavolcanic-hosted Pb–Zn–(Ag–Sb–As) deposits of the Hällefors district, located in the Palaeoproterozoic Bergslagen ore province, south central Sweden, comprise both stratabound sulphides and discordant, Ag-rich sulphide–sulphosalt veins. The complex sulphide–sulphosalt assemblages of the Alfrida-Jan Olof mines at Hällefors were investigated by a combination of ore microscopy, electron-microprobe analysis, and in situ laser sulphur isotope analysis. The massive ore is characterized by positive and homogeneous 34S (+1.4 to +2.7 V-CDT), whereas vein-hosted sulphides and sulphosalts exhibit similar, but generally less positive to slightly negative 34S (–0.6 to +2.0). Comparison of the observed ore mineral assemblages with calculated phase equilibria in the system Fe–As–S–O–H and isotopic fractionation as a function of temperature, oxygen fugacity and pH indicates that the vein-type mineralization was formed from relatively reduced and rather alkaline hydrothermal fluids. At these reduced conditions, fractionation of 34S via changes of fO2 is insignificant, and thus the isotopic signatures of the vein minerals directly reflect the composition of the sulphur source. We therefore conclude that the vein-type ore essentially inherited the sulphur isotope signature from the pre-existing massive sulphides via metamorphic remobilization at approximately 300–400°C and 2–3 kbar. Scales of remobilization observable are on the order of about 5 mm to 30 cm. Overall, the sulphide–sulphosalt assemblages from the Alfrida-Jan Olof mines exhibit 34S values which are comparable to a majority of metasupracrustal-hosted deposits in the Bergslagen province, thereby suggesting a common origin from ca. 1.90–1.88 Ga volcanic-hydrothermal processes.Editorial handling: S. Nicolescu  相似文献   

8.
Late Hercynian U-bearing carbonate veins within the metamorphic complex of La Lauzière are characterized by two parageneses. The first is dominated by dolomite or ankerite and the second by calcite and pitchblende. Fluids trapped in the dolomites and ankerites at 350–400° C are saline waters (20 to 15 wt % eq. NaCl) with D –34 to –49. In the calcite they are less saline (17 to 8 wt % eq. NaCl) and trapped at 300–350° C with D –50 to –65. All fluids contain trace N2, CO2 and probably CH4. The carbonates have 13C –8 to –14. and derived their carbon from organic matter. Evolution of the physico-chemical conditions from dolomite (ankerite) to calcite deposition was progressive.H and O-isotope studies indicate the involvement of two externally derived fluids during vein development. A D-rich ( –35) low fO2, saline fluid is interpreted to have come from underlying sediments and entered the hotter overlying metamorphic slab and mixed with more oxidizing and less saline U bearing meteoric waters during regional uplift. This evidence for a sedimentary formation water source for the deep fluid implies that the metamorphic complex overthrusted sedimentary formations during the Late-Hercynian.  相似文献   

9.
Sulfur isotope ratios have been determined in 27 selected volcanic rocks from Iceland together with their whole rock chemistry. The 34S of analyzed basalts ranges from –2.0 to +0.4 with an average value of –0.8 Tholeiitic and alkaline rocks exhibit little difference in 34S values but the intermediate and acid rocks analyzed have higher 34S values up to +4.2 It is suggested that the overall variation in sulfur isotope composition of the basalts is caused by degassing. The small range of the 34S values and its similarity to other oceanic and continental basalts, suggest that the depleted mantle is homogeneous in its sulfur isotope composition. The 34S of the depleted mantle is estimated to be within the range for undegassed oceanic basalts, –0.5 to +1.0  相似文献   

10.
In pelitic rocks, under conditions of low f O 2 and low f H 2 O, the stability of the mineral pair cordierite-garnet is limited by five univariant reactions. In sequence from high pressure and low temperature to high temperature and low pressure these are: cordierite+garnet hypersthene+sillimanite+quartz, cordierite+garnet hypersthene+sapphirine+quartz, cordierite+garnet hypersthene+spinel+quartz and cordierite+garnet olivine+spinel +quartz. In this sequence of reactions the Mg/Mg+Fe2+ ratio of all ferro-magnesian minerals involved decreases continuously from the first reaction to the fifth. The five univariant boundaries delimit a wide P-T range over which cordierite and garnet may coexist.Two divariant equilibria in which the Mg/Mg+ Fe2+ ratio of the coexisting phases are uniquely determined by pressure and temperature have been studied in detail. P-T-X grids for the reactions cordierite garnet+sillimanite+quartz and cordierite+hypersthene garnet+quartz are used to obtain pressure-temperature estimates for several high grade metamorphic areas. The results suggest temperatures of formation of 700–850° C and load pressures of 5–10 kb. In rare occasions temperatures of 950–1000° C appear to have been reached during granulite metamorphism.On the basis of melting experiments in pelitic compositions it is suggested that Ca-poor garnet xenocrysts found in calc-alkaline magmas derive from admixed pelitic rocks and did not equilibrate with the calc-alkaline magma.  相似文献   

11.
Hydrothermally-altered mesozonal synmetamorphic granitic rocks from Maine have whole-rock 18O (SMOW) values 10.7 to 13.8. Constituent quartz, feldspar, and muscovite have 18O in the range 12.4 to 15.2, 10.0 to 13.2, and 11.1 to 12.0, respectively. Mean values of Q–F ( 18Oquartz– 18Ofeldspar)=2.4 and Q–M ( 18Oquartz– 18Omuscovite)=3.3 are remarkably uniform (standard deviations of both are 0.2). Measured Q–F and Q–M values demonstrate that the isotopic compositions of the minerals are altered from primary magmatic 18O values but that the minerals closely approached oxygen isotope exchange equilibrium at subsolidus temperatures. Analyzed muscovites have D (SMOW) values in the range –65 to –82.Feldspars in the granitic rocks are mineralogically altered to either (a) muscovite+calcite, (b) muscovite+calcite+epidote, (c) muscovite+epidote, or (d) muscovite only. A consistent relation exists between the assemblage of secondary minerals and the oxygen isotope composition of whole rocks, quartz, and feldspar. Rocks with assemblage (a) have whole-rock 18O>12.1 and contain quartz and feldspar with 18O>13.8 and >11.4, respectively. Rocks with assemblages (b), (c), and (d) have whole-rock 18O<11.4 and contain quartz and feldspar with 18O< 13.1 and <11.0, respectively. The correlation suggests that the mineralogical alteration of the rocks was closely coupled to their isotopic alteration.Three mineral thermometers in altered granite suggest that the hydrothermal event occurred in the temperature range 400°–150° C, 100°–150° C below the peak metamorphic temperature inferred for country rocks immediately adjacent to the plutons. Calculations of mineral-fluid equilibria indicate that samples with assemblage (a) coexisted during the event with CO2-H2O fluids of and 18O=10.8 to 12.2 while samples with assemblages (b), (c), or (d) coexisted with fluids of and 18O=9.4 to 10.1. Compositional variations of the hydrothermal fluids were highly correlated: fluids enriched in CO2 were also enriched in 18O. Because CO2 was added to the granites during hydrothermal alteration and because fluids enriched in CO2 were enriched in 18O, some or all of the variation in 18O of altered granites may have been caused by addition of 18O to the rocks during the hydrothermal event. The source of both the CO2 and 18O could have been high-18O metasedimentary country rocks. The inferred change in isotopic composition of the granites is consistent with depletion of the metacarbonate rocks in 18O close to the plutons and with large volumes of fluid that were inferred from petrologic data to have infiltrated the metacarbonate rocks during metamorphism.A close approach of minerals to oxygen isotope exchange equilibrium in altered mesozonal rocks from Maine is in marked contrast to hydrothermally-altered epizonal granites whose mineral commonly show large departures from oxygen isotope exchange equilibrium. The difference in oxygen isotope systematics between altered epizonal granites and altered mesozonal granites closely parallels a differences between their mineralogical systematics. Both differences demonstrate the important control that depth exerts on the products of hydrothermal alteration. Deeper hydrothermal events occur at higher temperature and are longer-lived. Minerals and fluid have sufficient time to closely approach both isotope exchange and heterogeneous chemical equilibrium. Shallower hydrothermal events occur at lower temperatures and are shorter-lived. Generally there is insufficient time for fluid to closely approach equilibrium with all minerals.  相似文献   

12.
Ternary clinopyroxenes have been synthesized in the plane Di-CaTs-En. The variation of their crystallographic parameters has allowed the development of three determinative grids, which utilize b-, 2 22¯1–2 310 and 2 330 –2 202 respectively. These grids show significant differences in comparison with the previously proposed ones. Present results have been used to review some data on clinopyroxenes equilibria in the system CaO-MgO-Al2O3-SiO2 (CMAS) (Biggar 1969; Bruno and Facchinelli 1978; Herzberg 1978; O'Hara and Schairer 1963; Boyd 1969). In particular the petrogenic grid correlating P, T and CaTs content of clinopyroxenes in spinel-lherzolite assemblage (Herzberg 1978) has been revised, and consequently equilibrium temperatures rise by one hundred degrees.  相似文献   

13.
Mo mineralization within the Galway Granite at Mace Head and Murvey, Connemara, western Ireland, has many features of classic porphyry Mo deposits including a chemically evolved I-type granite host, associated K- and Si-rich alteration, quartz vein(Mace Head) and granite-hosted (Murvey) molybdenite, chalcopyrite, pyrite and magnetite mineralization and a gangue assemblage which includes quartz, muscovite and K-feldspar. Most fluid inclusions in quartz veins homogenize in the range 100–350°C and have a salinity of 1–13 eq. wt.% NaCl. They display Th-salinity covariation consistent with a hypothesis of dilution of magmatic water by influx of meteoric water. CO2-bearing inclusions in an intensely mineralized vein at Mace Head provide an estimated minimum trapping temperature and pressure for the mineralizing fluid of 355°C and 1.2 kb and are interpreted to represent a H2O-CO2 fluid, weakly enriched in Mo, produced in a magma chamber by decompression-activated unmixing from a dense Mo-bearing NaCl-H2O-CO2 fluid. 34S values of most sulphides range from c. 0 at Murvey to 3–4 at Mace Head and are consistent with a magmatic origin. Most quartz vein samples have 18O of 9–10.3 and were precipitated from a hydrothermal fluid with 18O of 4.6–6.7. Some have 18O of 6–7 and reflect introduction of meteoric water along vein margins. Quartz-muscovite oxygen isotope geothermometry combined with fluid inclusion data indicate precipitation of mineralized veins in the temperature range 360–450°C and between 1 and 2 kb. Whole rock granite samples display a clear 18O-D trend towards the composition of Connemara meteoric waters. The mineralization is interpreted as having been produced by highlyfractionated granite magma; meteoric water interaction postdates the main mineralizing event. The differences between the Mace Head and Murvey mineralizations reflect trapping of migrating mineralizing fluid in structural traps at Mace Head and precipitation of mineralization in the granite itself at Murvey.  相似文献   

14.
A parameter GO2– is defined as the difference between the Gibbs free energy of formation from the elements of a given oxide and its corresponding aqueous cation. The Gibbs free energies of formation of compounds such as sulfates, nitrates or carbonates, from their constituent oxides, are shown to be linear functions of GO2– values of their constituent cations.  相似文献   

15.
Ilmenite macrocrysts in olivine melilitites from Namaqualand-Bushmanland, South Africa, have decomposed by subsolidus reduction to form oriented Mg-titanomagnetite along {0001} ilmenite planes. Residual ilmenite contains 10–11 wt% MgO, 1 wt% MnO, and 0.1 wt% Cr2O3. This macrocryst assemblage is mantled by an annulus of Mg-titanomagnetite, followed by an overgrowth of radiating magnetite + perovskite. Terminal compositions of these magnetites are similar to groundmass spinels, and to the outermost margins of magnetite macrocrysts that have very high Fe3+ core contents. The assemblages are remarkably similar to oxide intergrowths in kimberlites and an upper mantle derivation is proposed for ilmenite macrocrysts in these melilitites. Oxidation states in the source regions are also very similar, whether on-or off-craton, being slightly above FMQ (NNO), but reduced to FMQWM with the onset of decompression, volatile loss, and carbonate immiscibility. In the case of the melilitites, late stage, low pressure crystallization above NNO precipated abundant magnetite + perovskite. The oxide fO2 data are consistent with, and refine the fO2 estimates obtained previously for the behavior of Fe/Mg and Ni contents in olivine from the same suite of samples.  相似文献   

16.
Summary The crystal structures of hydrothermally grown CuSO4 · H2O and CuSeO4 · H2O were determined by single crystal X-ray methods [Space group ,a = 5.037 (1), 5.129 (1) Å,b = 5.170(1), 5.527(1)Å,c = 7.578(2), 7.469(2)Å, = 108.62(1), 103.98(1)°, = 108.39(1), 106.52(1)°, = 90.93(1), 97.19(1)°; Z = 2; Rw = 0.026, 0.030 for 2065, 2235 reflections with sin / 0.90 Å–1]. The Cu atoms are [4 + 2]-coordinated to O atoms. These elongated octahedra are corner connected via the H2O molecule to form chains. The formal units 1 [Cu2O8(H2O)2]12- are interconnected by [XO4]2- groups (X=S,Se) and hydrogen bonds (bond lengths 2.72–2.83 Å). The crystal structures show pseudomonoclinic symmetry and are strongly related to the structure type of kieserite.[/p]
Die Kristallstrukturen von CuSO4 · H2O und CuSeO4 · H2O und ihre Beziehungen zum Kieserit
Zusammenfassung Die Kristallstrukturen von hydrothermal gezüchtetem CUSO4 · H2O und CuSeO4. H2O wurden an Einkristallen mittels Röntgenbeugung bestimmt [Raumgruppe ;a = 5.037(1), 5.129(1)Å,b = 5.170(1), 5.527(1)Å,c = 7.578(2), 7.469 (2) Å, = 108.62(1), 103.98(1)°, = 108.39(1), 106.52(1)°, = 90.93(1), 97.19(1)°; Z = 2; RW = 0.026, 0.030 für 2065, 2235 Reflexe mit sin / 0.90)Å–1]. Die Cu-Atome werden durch O-Atome [4+2]-koordiniert. Diese gestreckten /lOktaeder sind miteinander über Ecken durch die H2O-Moleküle zu Ketten verknüpft. Die formalen Einheiten 1 [CU2O8(H2O)2]12– werden durch [XO4]2–-Gruppen (X = S, Se) und Wasserstoffbrücken (Bindungslängen 2.72–2.83Å) miteinander verbunden. Die Kristallstrukturen zeigen pseudomonokline Symmetrie und sind sehr nahe mit dem Strukturtyp des Kieserits verwandt.

With 1 Figure  相似文献   

17.
The mineral paragonite, NaAl2[AlSi3O10 (OH)]2, has been synthesized on its own composition starting from a variety of different materials. Indexed powder data and refined cell parameters are given for both the 1M and 2M1 polymorphs obtained. The upper stability limit of paragonite is marked by its breakdown to albite + corundum + vapour. The univariant equilibria pertaining to this reaction have been established by reversing the reaction at six different pressures, the equilibrium curve running through the following intervals: 1 kb: 530°–550° C 2 kb: 555°–575° C 3 kb: 580°–600° C 5kb: 625°–640° C 6 kb: 620°–650° C 7 kb: 650°–670° C.Comparison with the upper stability limit of muscovite (Velde, 1966) shows that paragonite has a notably lower thermal stability thus explaining the field observation that paragonite is absent in many higher grade metamorphic rocks in which muscovite is still stable.The enthalpy and entropy of the paragonite breakdown reaction have been estimated. Since intermediate albites of varying structural states are in equilibrium with paragonite, corundum and H2O along the univariant equilibrium curve, two sets of data pertaining to the entropy of paragonite (S 298 0 ) as well as the enthalpy ( H f,298 0 ) and Gibbs free energy ( G f,298 0 ) of its formation were computed, assuming (1) high albite and (2) low albite as the equilibrium phase. The values are: (1) (2) S 298 0 67.8±3.9 cal deg–1 gfw–1 63.7±3.9 cal deg–1 gfw–1 H f,298 0 –1417.9±2.7 kcal gfw–1 –1420.2±2.6 kcal gfw–1 G f,298 0 –1327.4±4.0 kcal gfw–1 –1328.5±4.0 kcal gfw–1.Adapted from a part of the author's Habilitationsschrift accepted by the Ruhr University, Bochum (Chatterjee, 1968).  相似文献   

18.
The 18O and D values in mud-volcanic waters of the Taman Peninsula and Kakhetia vary from +0.7 to +10.0 and from –37 to –13 , respectively. These values increase as the Greater Caucasus is approached. The increase in 18O and D also positively correlates with fluid generation temperatures based on hydrochemical geothermometers. This is accompanied by changes in the chemical composition of waters, in which contents of alkali metals, HCO– 3 ion, and boron increase, while the content of halogen ions (Cl, Br, J) decreases. Changes in the isotopic composition of water are also accompanied by the increase of 13 in methane and decrease of 11 B in clays. Analysis of formal models of the evolution of isotopic composition of mud-volcanic waters showed that mud volcanoes are recharged by freshened water from the Maikop paleobasin with an inferred isotopic composition of D –40 and 18 O –6. Based on this assumption, the 18O and D values observed in mud-volcanic waters can be explained not only by processes of distillation and condensation in a closed system, but also by combined processes of isotopic reequilibration in the water-illite-methane system.Translated from Litologiya i Poleznye Iskopaemye, No. 2, 2005, pp. 143–158.Original Russian Text Copyright © 2005 by Lavrushin, Dubinina, Avdeenko.  相似文献   

19.
Stibnite mineralisation in the antimony province of New England can be divided into Central type ores (veins of stibnite + quartz ± berthierite) and Peripheral type ores of stibnite + quartz + native antimony ± berthierite. The Central stibnites have 34SCDT values of –5±2 (1) which may represent equilibrium precipitation from mantle sulfur at about 200°C. Peripheral stibnites have 34S values between 0 and –25, with a large group at 0±2. They represent precipitation from a limited supply of mantle sulfur and the acquisition of sedimentary sulfur. We consider that the different ore types were produced from distinct ore solutions derived from two immiscible melts. These originated in the deep mantle, were mobilised by tectonic activity and supplied the antimony and most of the sulfur to the ores.  相似文献   

20.
Measurements were made of the hydrogen isotope ratios of hydrous silicates (mica and amphibole) and whole rocks, and the carbon isotope ratios of graphite and carbonaceous matter in the metamorphic rocks from the northern Kiso district in central Japan.D values of hydrous silicates in the graphite-bearing metapelites are always higher than those in graphite-free schists, even though the sample localities of the two rock-types are very close. Hydrogen isotopic equilibrium has been attained between the coexisting minerals.D/H ratios of water in the metamorphic fluids seem to depend strongly on the presence or absence of graphite and seem to be not constant throughout the district. The district is divided into three areas of low (metamorphic zones I, II), medium (zones IIIa–V) and high 13Cgr value (zones VIa–VII) areas. In the high 13Cgr values area, the carbon contents of the graphite-bearing rocks decrease slightly from zones VIa to VII, whereas the 13Cgr values increase sharply from the upper part of zone VIa to VIb. TheD values of biotite in these graphite-bearing rocks are higher than those in the medium 13Cgr area. This suggests that methane enriched inH and12C is produced and liberated by the devolatilization reactions between muscovite, graphite and water. The fluid produced is composed of water, methane and a subordinate amount of carbon dioxide, and its logfO2 value is deduced to be about 1.2 lower than that defined by the FMQ buffer. In the medium 13Cgr area, the 13C values of graphite are nearly constant (–20.8), while the Fe2O3/(Fe2O3 + FeO) ratio of the graphite-bearing rocks apparently decreases with increasing metamorphic grade.D differences in hydrous silicates between graphite-bearing and graphite-free rocks are observed. These facts are interpreted to mean that methane was produced in addition to water and carbon dioxide, and that its generation ( ratio of the fluid was about 2) had practically no isotope effect on the graphite. In the low 13Cgr area, the carbon contents of the rocks decrease clearly from zones I to IIIa. TheD and 13Cgr values of the non-metamorphosed shales are much lower than those of the low grade graphite-bearing metapelites. This suggests that methane is produced and liberated from the rocks even at the incipient stage of metamorphism.  相似文献   

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