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1.
本文在对普通培养条件下异养微生物粪产碱杆菌(Alcaligenes faecalis,A.faecalis)反硝化特征研究的基础上,运用电化学方法于一定电势下(-0.15 V、-0.06 V、+0.06 V vs.NHE)模拟半导体矿物导带光电子能量,探讨不同能量的光电子对A.faecalis反硝化特性及细胞生长代谢的影响。实验显示,在普通培养条件下,A.faecalis在有氧和无氧环境中均不能还原NO-3,但还原NO-2效果明显。在模拟光电子实验体系中,A.faecalis可在不同电势(-0.15 V、-0.06 V、+0.06 V)的阴极石墨电极表面附着并形成具有反硝化活性的菌膜;其中,外加电势为-0.15V的实验组菌膜量最多,其NO-3去除率也最高,10天达到52%;-0.06 V体系略低,NO-3去除率为30.5%,+0.06 V体系菌膜量最少,其NO-3去除效果也最差,仅为10.6%。而在不添加微生物的电化学体系中,3个外加电势下的NO-3浓度均未发生明显变化。本实验研究结果证明了一定能量的半导体矿物光电子可影响土壤异养微生物A.faecalis的生长代谢及反硝化行为。  相似文献   

2.
Post-metamorphic CO2-rich fluid inclusions in granulites   总被引：2，自引：0，他引：2  
In granulite-facies samples from the Adirondack Mountains, NY, estimates of peak-metamorphic CO2 fugacities based on mineral equilibria are not consistent with estimates based on data for high-density, CO2-rich fluid inclusions. Of the 21 Adirondack samples investigated for this study, all contain CO2-rich inclusions. Inclusions occur in quartz, apatite, and garnet. They range in size from 3 to 50 m and are without visible H2O. In a few of the inclusions, freezing point determinations and preliminary Laser Raman spectroscopy show the presence of small amounts (<3%) of other fluids (N2 and H2S). CO2 liquid-vapor homogenization temperatures are between –46 and +31° C, corresponding to densities between 1.14 and 0.5 gm/cc. Some of these densities are consistent with peak-metamorphic entrapment (1.06 to 1.1 gm/cc).Peak metamorphic fluid compositions in these samples are inferred from fluid-buffering equilibria that restrict the fugacity of CO2 (f CO2) directly (i.e., calcite+quartz+wollastonite) or buffer the fugacity of oxygen (f O2). Assemblages that bufferf O2 are important because knowledge off O2 places an upper limit onf CO2. In 13 of the 21 samples, estimates of peak-metamorphic fluid compositions based on these equilibria show that the mole fraction of CO2 (XCO2) in equilibrium with the rock was low, in some cases less than 0.2.The contradiction of mineral equilibria and fluid inclusion data shows that the inclusions record post-metamorphic conditions. At present, there are no criteria to distinguish these primary appearing CO2-rich inclusions from those found in other granulite-facies terranes. Therefore, inferences of pressure-temperature conditions and peakmetamorphic fluid compositions based on fluid inclusions must be viewed with caution.  相似文献   

3.
The Dongping gold deposit is located near the center of the northern margin of the North China Craton. It is hosted in the Shuiquangou syenite and characterized by large amounts of tellurides. Numerous studies have addressed this deposit; the mineral paragenesis and ore‐forming processes, however, are still poorly studied. In this contribution, a new mineral paragenesis has been evaluated to further understand ore formation, including sulfides (pyrite, chalcopyrite, galena, sphalerite, molybdenite, and bornite), tellurides (altaite, calaverite, hessite, muthmannite, petzite, rucklidgeite, sylvanite, tellurobismuthite, tetradymite, and volynskite), and native elements (tellurium and gold). Molybdenite, muthmannite, rucklidgeite, and volynskite are reported for the first time in this deposit. We consider the Dongping gold deposit mainly formed in the Devonian, and the ore‐forming processes and the physicochemical conditions for ore formation can be reconstructed based on our newly identified ore paragenesis, that is, iron oxides → (CO2 effervescence) → sulfides → (fTe2/fS2 ratio increase) → Pb‐Bi‐tellurides → (condensation of H2Te vapor) → Au‐Ag‐tellurides → (mixing with oxidizing water) → carbonate and microporous gold → secondary minerals → secondary minerals. The logfO2 values increase from the early to late stages, while the fH2S and logfS2 values increase initially and then decrease. CO2 effervescence is the main mechanism of sulfides precipitation; this sulfidation and condensation of H2Te vapor lead to deposition of tellurides. The development of microporous gold indicates that the deposit might experience overprint after mineralization. The Dongping gold deposit has a close genetic relationship with the Shuiquangou syenite, and tellurium likely originated from Shuiquangou alkaline magmatic degassing.  相似文献   

4.
A sedimentary formation perturbated by supercritical CO2 reacts by dissolving primary minerals and forming new secondary phases. In this process CO2 may be trapped in stable carbonate minerals and may thereby be immobilized for long time spans. The potential for mineral trapping can be estimated by solving kinetic expressions for the reservoir minerals and possible secondary phases. This is, however, not trivial as kinetic data are uncertain or even lacking for the minerals of interest. Here, the rate equations most commonly used for CO2 storage simulations have been solved, and the rate parameters varied, to obtain sensitivity on the total amount of CO2 stored as mineral carbonate. As various expressions are in use to estimate growth rates of secondary carbonates, three formulations were compared, including one taking into account mineral nucleation preceding growth. The sensitivity studies were done on two systems, the Utsira Sand being representative for a cold quartz-rich sand (37 °C, 100 bar CO2), and the Gulf Coast Sediment, being representative for a medium temperature quartz–plagioclase-rich system (75 °C, 300 bar CO2).The simulations showed that the total predicted CO2 mineral storage is especially sensitive to the choice of growth rate model and the reactive surface area. The largest sensitivity was found on α, fraction of total surface area available for reactions, with a reduction of one order of magnitude for all reacting phases leading to 3–4 times lower predicted CO2 mineral storage. Because the reactive surface area is highly uncertain for natural systems, the range in predicted results may be even larger. The short-term predictions (<100–1000 a), such as the onset of carbonate growth, were highly sensitive to nucleation and growth rates. Moreover, the type of carbonate minerals formed was shown to be model dependent, with the simplest model predicting an unlikely carbonate assemblage at low temperature (i.e., formation of dolomite at 37 °C). Therefore, to use kinetic models to upscale short-term (<months) laboratory experiments in time, to identify the past reactions and physical conditions of natural CO2 storage analogues, and finally to predict the potential for CO2 trapping in existing and future storage projects, more knowledge has to be collected, especially on the reactive surface area of CO2 storage reservoirs, and on the rate of secondary carbonate nucleation and growth.  相似文献   

5.
Abstract Natural, pure CO2 inclusions in quartz and olivine (c. Fo90) were exposed to controlled fH2 conditions at T= 718–728°C and Ptotal= 2 kbar; their compositions were monitored (before and after exposures) by microsampling Raman spectroscopy (MRS) and microthermometry. In both minerals exposed at the graphite–methane buffer (fH2= 73 bar), fluid speciations record the diffusion of hydrogen into the inclusions. In quartz, room-temperature products in euhedral isolated (EI type) inclusions are carbonic phases with molar compositions of c. CO2(60) + CH4(40) plus graphite (Gr) and H2O, whereas anhedral inclusions along secondary fractures (AS type) are Gr-free and contain H2O plus carbonic phases with compositions in the range c. CO2(60) + CH4(40) to CO2(10) + CH4(90). EI type inclusions in olivine evolved to c. CO2(90–95) + CH4(5–10) without Gr, whereas AS type inclusions have a range of compositions from CO2(90) + CH4(10) ± Gr to CH4(50) + H2(50) ± Gr; neither H2O nor any hydrous species was detected by optical microscopy or MRS in the olivine-hosted products. Differences in composition between and among the texturally distinct populations of inclusions in both minerals probably arise from variations in initial fluid densities, as all inclusions apparently equilibrated with the ambient fH2. These relations suggest that compositional variability among inclusions in a given natural sample does not require the entrapment of multiple generations of fluids. In addition, the absence of H2O in the olivine-hosted inclusions would require the extraction of oxygen from the fluids, in which case re-equilibration mechanisms may be dependent on the composition and structure of the host mineral. Many of the same samples were re-exposed to identical P–T conditions using Ar as the pressure medium, yielding ambient fH2= 0.06 bar. In most inclusions, the carbonic fluids returned to pure CO2 and graphite persisted in the products. Reversal of the mechanisms from the prior exposure at fH2= 73 bar did not occur in any inclusions but the AS types in olivine, in which minor CO2 was produced at the expense of CH4 and/or graphite. The observed non-reversibility of previous mechanisms may be attributed to: (1) slower fluid–solid reactions compared to reactions in the homogeneous fluid phase; (2) depressed activities of graphite due to poor ordering; and/or (3) low ambient fO2 at the conditions of the second run.  相似文献   

6.
The stability of merwinite (Mw) and its equivalent assemblages, akermanite (Ak)+calcite (Cc), diopside (Di)+calcite, and wollastonite (Wo)+monticellite (Mc)+calcite was determined at T=500–900° C and P f=0.5–2.0 kbar under H2O–CO2 fluid conditions with X CO 2=0.5, 0.1, 0.05, and 0.02. Merwinite is stable at P f=0.5 kbar with T>700° C and X CO 2<0.1. At P f=2.0 kbar, the assemblage Di+Cc replaces merwinite at all T and X CO 2 conditions. At intermediate P f=1 kbar, the assemblage Ak+Cc is stable above 707° C and Wo+Mc+Cc is stable below 707° C. The univariant curve for the reaction Di+Cc=Wo+Mc+CO2 is almost parallel to the T axis and shifts to low P f with increasing X CO 2, with the assemblage Di+Cc on the high-P f side. The implications of the experimental results in regard to contact metamorphism of limestone are discussed using the aureole at Crestmore, California as an example.  相似文献   

7.
Heating and freezing studies on fluid inclusions in quartz from mineralized quartzfeldspar reef reveal the presence of type A CO2-H2O (H2O>50% by volume), type B CO2-H2O (H2O<50% by volume), type C pure CO2 and type D pure aqueous inclusions. Types A, B and C are primary and/or psuedo-secondary inclusions while type D are secondary. Types A and B homogenize on heating into different phases at similar temperatures ranging between 307 and 476°C, indicating entrapment from boiling hydrothermal solutions. Type D inclusions homogenize into a liquid phase at temperatures between 88 and 196°C. Boiling of hydrothermal solutions led to the formation of a CO2-rich phase of low density and salinity that coexisted with another dense and saline aqueous phase with very little CO2 dissolved in it. Ore and gangue mineral assemblage of primary ores indicate that ore deposition was characterized by logf O 2=?34.4 to ?30.2 atm, logf S 2=?11.6 to ?8.8 atm and pH=4.5 to 6.5.  相似文献   

8.
An economic and environmentally friendly approach of overcoming the problem of fossil CO2 emissions would be to reuse it through fixation into biomass. Carbon dioxide (CO2), which is the basis for the formation of complex sugars by green plants and microalgae through photosynthesis, has been shown to significantly increase the growth rates of certain microalgal species. Microalgae possess a greater capacity to fix CO2 compared to C4 plants. Selection of appropriate microalgal strains is based on the CO2 fixation and tolerance capability together with lipid potential, both of which are a function of biomass productivity. Microalgae can be propagated in open raceway ponds or closed photobioreactors. Biological CO2 fixation also depends on the tolerance of selected strains to high temperatures and the amount of CO2 present in flue gas, together with SOx and NOx. Potential uses of microalgal biomass after sequestration could include biodiesel production, fodder for livestock, production of colorants and vitamins. This review summarizes commonly employed microalgal species as well as the physiological pathway involved in the biochemistry of CO2 fixation. It also presents an outlook on microalgal propagation systems for CO2 sequestration as well as a summary on the life cycle analysis of the process.  相似文献   

9.
Rhythmic zoning is ubiquitous in igneous rocks. Based on polymerization and regular solution models, a non-ideal, disequilibrium and non-linear interface equation has been established to describe the process of crystal growth:f = 1/[1 + (β/x s )(1 -x s )exp(-W / RT)(1 - 2f)] wheref and xs represent respectively the mole fraction of a component in the crystal and melt at the interface;W the total exchange energy;R the gas constant; andT the temperature; β=k B /k A , withk A andk B representing respectively the rate constants of components A and B. Results of numerical simulation of the equation demonstrate that a domain of triple valuedness exists ifW / RT < -2. This model, together with the mass balance equation, explains reasonably the rhythmic phenomena in silicate solid solutions, indicating that self-organization is responsible for this process during mineral growth.  相似文献   

10.
The reaction chlorite+dolomite=spinel+ forsterite+calcite+CO2+H2O has been studied with hydrothermal equipment technique in a C-O-H fluid at P fluid=1,000, 2,000 and 3,000 bars and fo2 controlled by NB or QFM buffer. The equilibrium conditions for the reaction has been determined as log K=–57,119/T+95.77+0.9860(P-1)/T(bar,°K). The mineral mixtures had an excess of dolomite. The composition of the chlorite among the reaction products has been analysed and found to have a higher Al/Si ratio than clinochlore.  相似文献   

11.
Three successive metamorphic stages M1, M2 and M3 have been distinguished in polymetamorphic granulite facies quartz-feldspathic gneisses from the Seiland Igneous Province, Caledonides of northern Norway. An early period of contact metamorphism (M1; 750–950°C, ca. 5 kbar) was followed by cooling, accompanied by strong shearing and recrystallization at intermediate-P granulite facies conditions (M2; 700–750°C, 5–6kbar). High-P granulite facies (M3; ca. 700°C, 7–8 kbar) is related to recrystallization in narrow ductile shear zones and secondary growth on M2 minerals. On the basis of composition, fluid inclusions in cordierite, quartz and garnet can be divided into three major types: (1) CO2 inclusions; (2) mixed CO2–N2 inclusions; (3) N2 inclusions. Fluid chronology and mineral assemblages suggest that the earliest inclusions consist of pure CO2 and were trapped at the M1 contact metamorphic episode. A carbonic fluid was also present during the intermediate-P granulite facies M2 metamorphism. The CO2-rich inclusions in M2 garnet can be divided into two generations, an early lower-density and a late higher-density, with isochores crosscutting the P-T box of M2 and M3, respectively. The nitrogen-rich fluids were introduced at a late stage in the fluid evolution during the high-P M3 event. The mixed CO2–N2 inclusions, with density characteristics compatible with M3 conditions, are probably produced from intersection between pre-existing pure CO2 inclusions and N2 fluids introduced during M3. The fluid inclusion data agree with the P-T evolution established from mineral assemblages and mineral chemistry.  相似文献   

12.
A massive white sepiolite deposit at Amboseli precipitated from magnesium and silica released during the ground water dolomitization of an earlier lacustrine sepiolite. Kerolite has since formed in proximity to the massive sepiolite as an alteration product of sepiolite and as a ground water precipitate when the pH is below 8. Authigenic sepiolite also occurs in the overlying younger sediments. Kerolite is likely to occur but has not yet been positively identified.Presently, ground waters within the Amboseli Basin are supersaturated with respect to sepiolite and kerolite. This supersaturation results from the weathering of alkaline olivine basalts on the edge of the basin. The precipitation of sepiolite and/or kerolite does not control ground water compositions in the basin. These reactions are slow compared to other aqueous-mineral reactions such as those maintaining carbonate mineral equilibria. Equilibrium between disordered-dolomite and calcite buffers the log a Mg2+/(a H+)2 as a function of log f CO 2 in ground waters in the proximity of the massive sepiolite. This reaction can help explain the presence of sepiolite associated with dolomites in other near-surface deposits besides Amboseli.  相似文献   

13.
 Electrical conductivity of lherzolite (65% olivine), measured as a function of time after changes in the oxygen fugacity (f o2) of the surrounding CO2/CO atmosphere, is used to infer the diffusivity of the point defects responsible for conduction in olivine. A total of 63 equilibration runs at temperatures of 900, 1000, 1100, and 1200 ∘C were fit using nonlinear parameter estimation to recover time constants (directly related to diffusivity) and conductivity steps. An observed f o2 dependence in the time constants associated with re-equilibration implies two defect species of fixed diffusivity but with f o2-dependent concentrations. Although the rate-limiting step may not necessarily be associated with a conducting defect, when time constants are converted to diffusivities, the magnitudes and activation energies agree extremely well with the model for magnesium vacancies (the slower species) and small polarons (holes localized on Fe3+) derived by Constable and Roberts (1997). This earlier study used an independent method of simultaneous modeling of thermopower and electrical conductivity as a function of f o2 and temperature, on data from a different type of sample (a dunite). We observe that at high f o2 where polarons dominate over magnesium vacancies in the defect population, re-equilibration is dominated by magnesium vacancy diffusion, and vice versa (at low f o2 magnesium vacancies dominate and re-equilibration proceeds at the faster rate associated with polaron mobility). We interpret this to suggest association between the cation vacancies and polarons, as has been suggested by Tsai and Dieckmann (1997), making the concentration of the minority defect the rate-limiting step in the oxidation/reduction reactions. Received: 18 October 2000 / Accepted: 7 May 2002  相似文献   

14.
Fluid inclusions in quartz veins within Proterozoic metamorphic rocks in the Black Hills, South Dakota, were examined by microthermometry and Raman spectroscopy to assess the evolution of fluid compositions during regional metamorphism of organic-rich shales and late-orogenic magmatism, both of which were related to the collision of the Wyoming and Superior crustal blocks. Fluid inclusions occur in veins that began to be generated before or during regional compression and metamorphism that reached at least garnet-grade conditions, and in veins within the aureole of the Harney Peak Granite (HPG), where temperatures reached second-sillimanite grade conditions. Early veins in the schists have undergone recrystallization during heating and deformation that modified the composition of early CH4 or CO2 and N2-dominated inclusions. These fluids were apparently trapped under conditions of immiscibility with a saline aqueous fluid phase. They are interpreted to represent components generated during maturation of organic matter and dehydration of phyllosilicates during incipient metamorphism at reducing fO2 conditions. Most inclusions in the quartz veins are, however, secondary CO2-bearing. They imply a transition to higher fO2 conditions with increasing temperature of regional metamorphism. The fO2 conditions may have been controlled by the mineral assemblage in the host metapelites. The prevalence of bimodal distributions of trapped CO2-N2 and aqueous endmembers in the biotite and garnet zones also suggests that two immiscible fluid phases existed during the regional metamorphism.In the aureole of the HPG, graphite was evidently consumed by influx of magmatic fluids. CO2-H2O fluid inclusions dominate, but they have significantly less N2 than inclusions at lower metamorphic grades. All inclusions define secondary trails in mostly unstrained quartz. The bimodality of inclusion compositions is not as well defined as at lower grades, with many inclusions containing intermediate CO2-H2O compositions. This suggests that a single fluid phase existed at the high temperatures in the granite aureole, but then unmixed during cooling. A set of late quartz veins with graphitized and tourmalinized selvages in the granite aureole contains CH4-bearing inclusions with little N2. The existence of CH4 in these inclusions is attributed to complexing of magmatic B with hydroxyl anions taken from the CO2-H2O fluid phase, effectively causing reduction in fO2 and promoting precipitation of graphite.  相似文献   

15.
Thef o 2 of the equilibrium between graphite and C−O fluid has been determined from 15–30 kbar and 1100–1400°C using a sliding redox sensor consisting of (Ni, Mn) O+Ni metal. The equilibrium composition of oxide coexisting with metal was approached from both directions in each experiment with convergence to within 1 mol% NiO. Since, in theP−T range of the experiments, C−O fluids are >90% CO2 our measurements off o 2 translate into determinations of CO2 fugacity with an uncertainty of ±0.1 log units. These new determinations of theP−T−f o 2 plane of GCO equilibrium are in excellent agreement with the mainly unreversed measurements of Ulmer and Luth (1991) using pure metal-metal oxide sensors and with the equation of state of Saxena and Fei (1987). Modified forms of the Redlich-Kwong (MRK) equation of state (Holloway 1977; Flowers 1979; Kerrick and Jacobs 1981) predict higher values off o 2 for the GCO equilibrium than determined experimentally. This implies that CO2 is more compressible than the MRK predicts. Editorial responsibility: V. Trommsdorff  相似文献   

16.
Mn silicate-carbonate rocks at Parseoni occur as conformable lenses within metapelites and calc-silicate rocks of the Precambrian Sausar Group, India. The host rocks are estimated to have been metamorphosed at uppermost P-T conditions of 500–550°C and 3–4 kbar. The Mn-rich rocks contain appreciable Fe, reflected in the occurrence of magnetite(1) (MnO 1%), magnetite(2) (MnO 15%) and magnetite(3) (MnO 10%). Two contrasting associations of pyroxmangite, with and without tephroite, developed in the Mn silicate-carbonate rocks under isothermal-isobaric conditions. The former assemblage formed in relatively Fe-rich bulk compositions and equilibrated with a metamorphic fluid having a low X CO 2 (<0.2), and the latter equilibrated with a CO2-rich fluid. Rhodochrosite+magnetite(1)+quartz protoliths produced the observed mineral assemblages on metamorphism. Partitioning of major elements between coexisting phases is somewhat variable. Fe shows preference for tephroite over pyroxmangite at the ambient physical conditions of metamorphism. Oxygen fugacity during metamorphism was monitored at or near the QFM buffer in tephroite bearing domains, and the fluid composition was buffered by mineral reactions in respective domains. As compared to other metamorphosed Mn deposits of the Sausar Group, the Mn silicate-carbonate rocks at Parseoni were, therefore, metamorphosed at much lower f O 2 through complex mineral-fluid interactions.  相似文献   

17.
Fluid inclusions and mineral associations were studied in late-stage charnockitic granites from the Bjerkreim-Sokndal lopolith (Rogaland anorthosite province). Because the magmatic and tectonic evolutions of this complex appear to be relatively simple, these rocks are a suitable case for investigation of the origin and evolution of granulitic fluids. Fluid inclusions, primarily contained in quartz, can be divided into four types: carbonic (type I), N2-bearing (type II), CO2+H2O (type III) and aqueous inclusions (type IV). For each type, the role of leakage and fluid mixing are discussed from microthermometric and Raman spectrometric data. The most striking features of CO2-rich inclusions (the predominant fluid) is the presence of graphite in numerous, trail-bound inclusions (Ib) and its absence in a few isolated, very dense (d=1.16), pure CO2 inclusions (Ia) and in the late carbonic inclusions (Ic). Fluid chronology and mineral assemblages suggest that carbonic Ia inclusions represent the first fluid (pure CO2) trapped at or close to magmatic conditions (T=780–830° C, fO2=10-15 atm and P=7.4±1 kb), outside the graphite stability field. In contrast, type Ib inclusions enclosed graphite particles from a channelized fluid during retrograde rock evolution (P=3–4 kb and T=600° C). Decreases in T-fO2 could explain a progressive evolution from a CO2-rich fluid to an H2O-rich fluid in a closed C–O–H system. However, graphite destabilization observed in type Ic inclusions implies some late introduction of external water during the last stage of retrogression. The main results of this study are the following: (1) a carbonic fluid was present in an early stage of rock evolution (probably in the charnockitic magma) and (2) this granulite occurrence offers good evidence of crossing the graphite stability field during post-magmatic evolution.  相似文献   

18.
C-O-H-S fluid composition and oxygen fugacity in graphitic metapelites   总被引：4，自引：0，他引：4  
Abstract C-O-H fluid produced by the equilibration of H2O and excess graphite must maintain the atomic H/O ratio of water, 2:1. This constraint implies that all thermodynamic properties of the fluid are uniquely determined at isobaric-isothermal conditions. The O2, H2O and CO2 fugacities (fo2, fH2O and fCO2) of such fluids have been estimated from equations of state and fit as a function of pressure and temperature. These fugacities can be taken as characteristic for graphitic metamorphic systems in which the dominant fluid source is dehydration, e.g. pelitic lithologies. Because there are no compositional degrees of freedom for graphite-saturated fluids produced entirely by dehydration, the variance of the dehydration process is not increased in comparison with that in non-graphitic systems. Thus, compositional ‘buffering’of C-O-H fluids by dehydration equilibria, a common petrological model, requires that redox reactions, decarbonation reactions or external, H/O ± 2, fluid sources perturb the evolution of the metamorphic system. Such perturbations are not likely to be significant in metapelitic environments, but their tendency will be to increase the fO2 of the fluid phase. At high metamorphic grades, pyrite desulphidation reactions may cause a substantial reduction of fH2O and slight increases in fO2 and fCO2 relative to sulphur-free fluid. At low metamorphic grade, sulphur solubility in H/O ± 2 fluids is so low that pyrite decomposition must occur by sulphur-conserving reactions that cause iron depletion in silicates, a common feature of sulphidic pelites. With increasing temperature and sulphur solubility, pyrite desulphidation may be driven by dehydration reactions or infiltration of H2O-rich fluids. The absence of magnetite and the assemblages carbonate + aluminosilicate or pyrite + pyrrhotite + ilmenite from most graphitic metapelites is consistent with an H/O = 2 model for GCOH(S) fluid. For graphitic rocks in which such a model is inapplicable, a phase diagram variable that defines the H/O ratio of GCOH(S) fluid is more useful than the conventional fO2 variable.  相似文献   

19.
The eutectic mineral assemblage calcite-dolomite-periclase-apatite-forsterite-magnesioferrite-pyrrhotite-alabandite in a carbonatite dike within the Oka complex, Quebec, buffers the fugacities (and partial pressures) of all gas species in C-O-H-S-F, assuming vapor saturation. At the inferred eutectic (640° C, 1 kbar), the most important gas species and their partial pressures (bars) were: H2O, 882; CO2, 110; H2, 4.6; H2S, 2.7; CO, 0.5; and CH4, 0.1. Oxygen fugacity was near the QFM buffer, logf(O2)=–18.6, and sulfur fugacity was near the QFM-pyrrhotite buffer, logf(S2)=–5.9. Fluorine fugacity was low, logf(F2)=–43.9, consistent with the absence of fluoride minerals other than apatite. Presence of a water-rich gas phase is consistent with experiments on synthetic carbonatite systems (e.g. Fanelli et al. 1981), although compositions of the gas phase in published experiments cannot be determined exactly.Contribution no. 390 from the Mineralogical Laboratory, The University of Michigan  相似文献   

20.
The Vilarelho da Raia-Chaves region, located in northern Portugal adjacent to the Spanish border, is characterized by both hot and cold CO2-rich mineral waters issuing from springs and drilled wells. The present paper updates the conceptual circulation model of the Vilarelho da Raia cold CO2-rich mineral waters. Vilarelho da Raia mineral waters, dominated by Na and HCO3 ions, have formed mainly by interaction with CO2 of deep-seated mantle origin. The δ 18O, δ 2H and 3H values indicate that these waters are the result of meteoric waters infiltrating into Larouco Mountain, NW of Vilarelho da Raia, circulating at shallow depths in granitic rocks and moving into Vilarelho da Raia area. The conceptual geochemical and geophysical circulation model indicates that the hot and cold CO2-rich mineral waters of Chaves (76 °C) and Vilarelho da Raia (17 °C) should be considered manifestations of similar but not the same geohydrological systems. Electronic Publication  相似文献   

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