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1.
Near-liquidus crystallization experiments have been carried out on two basalts (12.5 and 7.8 wt% MgO) from Soufriere, St Vincent
(Lesser Antilles arc) to document the early stages of differentiation in calc-alkaline magmas. The water-undersaturated experiments
were performed mostly at 4 kbar, with 1.6 to 7.7 wt% H 2O in the melt, and under oxidizing conditions (ΔNNO = −0.8 to +2.4). A few 10 kbar experiments were also performed. Early
differentiation of primitive, hydrous, high-magnesia basalts (HMB) is controlled by ol + cpx + sp fractionation. Residual
melts of typical high-alumina basalt (HAB) composition are obtained after 30–40% crystallization. The role of H 2O in depressing plagioclase crystallization leads to a direct relation between the Al 2O 3 content of the residual melt and its H 2O concentration, calibrated as a geohygrometer. The most primitive phenocryst assemblage in the Soufriere suite (Fo 89.6 olivine, Mg-, Al- and Ti-rich clinopyroxene, Cr–Al spinel) crystallized from near-primary (Mg# = 73.5), hydrous (∼5 wt% H 2O) and very oxidized (ΔNNO = +1.5–2.0) HMB liquids at middle crustal pressures and temperatures from ∼1,160 to ∼1,060°C. Hornblende
played no role in the early petrogenetic evolution. Derivative HAB melts may contain up to 7–8 wt% dissolved H 2O. Primitive basaltic liquids at Soufriere, St Vincent, have a wide range of H 2O concentrations (2–5 wt%). 相似文献
2.
The water content of low-K tholeiitic basalt magma from Iwate volcano, which is located on the volcanic front of the NE Japan arc, was estimated using multi-component thermodynamic models. The Iwate lavas are moderately porphyritic, consisting of ~8 vol.% olivine and ~20 vol.% plagioclase phenocrysts. The olivine and plagioclase phenocrysts show significant compositional variations, and the Mg# of olivine phenocrysts (Mg#78–85) correlates positively with the An content of coexisting plagioclase phenocrysts (An 85–92). The olivine phenocrysts with Mg# > ~82 do not form crystal aggregates with plagioclase phenocrysts. It is inferred from these observations that the phenocrysts with variable compositions were primarily derived from mushy boundary layers along the walls of a magma chamber. By using thermodynamic calculations with the observed petrological features of the lavas, the water content of the Iwate magma was estimated to be 4–5 wt.%. The high water content of the magma supports the recent consensus that frontal-arc magmas are remarkably hydrous. Using the estimated water content of the Iwate magma, the water content and temperature of the source mantle were estimated. Given that the Iwate magma was derived from a primary magma solely by olivine fractionation, the water content and temperature were estimated to be ~0.7 wt.% and ~1,310 °C, respectively. Differentiation mechanisms of low-K frontal-arc basalt magmas were also examined by application of a thermodynamics-based mass balance model to the Iwate magma. It is suggested that magmatic differentiation proceeds primarily through fractionation of crystals from the main molten part of a magma chamber when it is located at <~200 MPa, whereas magma evolves through a convective melt exchange between the main magma and mushy boundary layers when the magma body is located at >~200 MPa. 相似文献
3.
Basaltic glasses included in olivine phenocrysts from Kilauea volcano contain concentrations of H 2O, CO 2, and S similar to glassy Kilauean basalt dredged from the deep sea floor and greater than vesicular, subaerial Kilauean basalt. Our result contrasts with earlier reports that inclusions of basaltic glass in phenocrysts have little or no H 2O and large ratios of . Our analysed inclusions of glass are larger than 100 micrometers thick and similar in chemical composition to the host glass surrounding the olivine crystals indicating that the trapped melts are representative of the bulk liquid from which the crystals grew. Crystallization of about 2–8% of olivine from the melts after they were trapped is indicated by slight departures from the experimentally established equilibrium distribution of Mg and Fe between olivine and liquid. The measured concentrations of CO 2 correspond to phenocryst crystallization pressures of about 1.3 kbar for a subaerial basalt and about 5 kbar for a submarine basalt, consistent with geophysical models of Kilauea volcano. The compositions of volcanic gas predicted from our analyses are consistent with restored compositions of actual Kilauean gases. The rate of sulfur emission predicted from our analyses is greater than the sulfur dioxide emission rate observed during repose, but probably consistent with total degassing including eruptive episodes. The concentrations of H 2O, K 2O, Cl, and P in parental Kilauean basalt can be derived from upper mantle phlogopitic mica, pargasitic amphibole and apatite with compositions close to those of natural primary minerals in ultramafic xenoliths from continental kimberlites, or solely from apatite and phlogopitic mica with near 0.47 ± 0.03, slightly higher than the range of values reported. The amounts of phlogopitic mica and pargasitic amphibole contributing volatiles to Kilauean tholeiite is about 10 percent by mass of the parental liquid, or about 5% if the source does not include amphibole. In view of an estimated 20% of partial melting of mantle source rock to produce Kilauean tholeiites, there may be about 2 weight percent of mica plus amphibole in part of the mantle beneath Kilauea, or about 1 weight percent of phlogopitic mica if amphibole is absent. 相似文献
4.
花岗岩岩浆中的H2O含量通过影响熔体物理化学性质, 进而控制了花岗岩岩浆的结晶粒度、岩浆侵位深度以及某些金属元素迁移、富集的过程。因此, 对花岗岩熔体包裹体开展H2O含量的定量研究具有重要的地质意义。目前, 测试花岗岩岩浆中H2O含量的方法可分为间接估算和直接测量两种方法。间接估算法, 如利用花岗岩熔体的粘度和岩浆中H2O溶解度模型进行岩浆H2O含量估算, 其H2O含量数据的准确性严重依赖于花岗岩熔体组成、熔体包裹体精确的温压参数; 直接测量法, 如利用傅里叶变换红外光谱(FTIR)、电子探针(EPMA)、二次离子探针(SIMS)等对熔体包裹体H2O含量直接开展原位微区分析, 这些测试技术具有样品制备繁琐、H2O容易泄漏、红外光谱分析光斑大, 测试结果受控因素较多等特点, 容易降低测试精度。激光拉曼测试法作为直接测量法中的重要技术, 具有样品制备简单, 原位、无损分析测试的特点, 本文认为激光拉曼在花岗岩岩浆H2O含量的定量研究中具有较好的应用和推广前景。今后, 可尝试建立热液金刚石压腔+激光拉曼原位检测熔体包裹体H2O含量的测试方法。 相似文献
5.
Exposed, subduction-related magmatic arcs commonly include sections of ultramafic plutonic rocks that are composed of dunite, wehrlite, and pyroxenite. In this experimental study we examined the effects of variable H 2O concentration on the phase proportions and compositions of igneous pyroxenites and related ultramafic plutonic rocks. Igneous crystallization experiments simulated natural, arc magma compositions at 1.2 GPa, corresponding to conditions of the arc lower crust. Increasing H 2O concentration in the liquid changes the crystallization sequence. Low H 2O concentration in the liquid stabilizes plagioclase earlier than garnet and amphibole while derivative liquids remain quartz normative. Higher H 2O contents (>3%) suppress plagioclase and lead to crystallization of amphibole and garnet thereby producing derivative corundum normative andesite liquids. The experiments show that alumina in the liquid correlates positively with Al in pyroxene, as long as no major aluminous phase crystallizes. Extrapolation of this correlation to natural pyroxenites in the Talkeetna and Kohistan arc sections indicates that clinopyroxenes with low Ca-Tschermaks component represent near-liquidus phases of primitive, Si-rich hydrous magmas. Density calculations on the residual solid assemblages indicate that ultramafic plutonic rocks are always denser than upper mantle rocks in the order of 0.05 to 0.20 g/cm 3. The combination of high pressure and high H 2O concentration in the liquid suppresses plagioclase crystallization, so that ultramafic plutonic rocks form over a significant proportion of the crystallization interval (up to 50% crystallization of ultramafic rocks from initial, mantle-derived liquids). This suggests that in subduction-related magmatic arcs the seismic Moho might be shallower than the petrologic crust/mantle transition. It is therefore possible that calculations based on seismic data have overestimated the normative plagioclase content (e.g., SiO 2, Al 2O 3) of igneous crust in arcs. 相似文献
6.
The solubility of molybdenum (Mo) was determined at temperatures from 500 °C to 800 °C and 150 to 300 MPa in KCl-H 2O and pure H 2O solutions in cold-seal experiments. The solutions were trapped as synthetic fluid inclusions in quartz at experimental conditions, and analyzed by laser ablation inductively coupled plasma mass spectrometry (LA ICPMS).Mo solubilities of 1.6 wt% in the case of KCl-bearing aqueous solutions and up to 0.8 wt% in pure H 2O were found. Mo solubility is temperature dependent, but not pressure dependent over the investigated range, and correlates positively with salinity (KCl concentration). Molar ratios of ∼1 for Mo/Cl and Mo/K are derived based on our data. In combination with results of synchrotron X-ray absorption spectroscopy of individual fluid inclusions, it is suggested that Mo-oxo-chloride complexes are present at high salinity (>20 wt% KCl) and ion pairs at moderate to low salinity (<11 wt% KCl) in KCl-H 2O aqueous solutions. Similarly, in the pure H 2O experiments molybdic acid is the dominant species in aqueous solution. The results of these hydrothermal Mo experiments fit with earlier studies conducted at lower temperatures and indicate that high Mo concentrations can be transported in aqueous solutions. Therefore, the Mo concentration in aqueous fluids seems not to be the limiting factor for ore formation, whereas precipitation processes and the availability of sulfur appear to be the main controlling factors in the formation of molybdenite (MoS 2). 相似文献
7.
New volatile data (CO 2, H 2O, He, Ne, and Ar) are presented for 24 submarine basaltic glasses from the Kolbeinsey Ridge, Tjörnes Fracture Zone and Mohns Ridge, North Atlantic. Low CO 2 and He contents indicate that magmas were strongly outgassed with the extent of degassing increasing toward the south, as expected from shallower ridge depths. Ne and Ar are significantly more abundant in the southernmost glasses than predicted for degassed melt. The strong atmospheric isotopic signal associated with this excess Ne and Ar suggests syn- or posteruptive contamination by air. Degassing, by itself, cannot generate the large variations in δ 13C values of dissolved CO 2 or coupled CO 2-Ar variations. This suggests that δ 13C values were also affected by some other processes, most probably melt-crust interaction. Modelling indicates that degassing had a negligible influence on water owing to its higher solubility in basaltic melt than the other volatiles. Low H 2O contents in the glasses reflect melting of a mantle source that is not water-rich relative to the source of N-MORB.Before eruption, Kolbeinsey Ridge melts contained ∼400 ppm CO 2 with δ 13C of −6‰, 0.1 to 0.35 wt.% H 2O, 3He/ 4He ∼11 RA, and CO 2/ 3He of ∼2 × 10 9. We model restored volatile characteristics and find homogeneous compositions in the source of Kolbeinsey Ridge magmas. Relative to the MORB-source, He and Ne are mildly fractionated while the 40Ar/ 36Ar may be low. The 3He/ 4He ratios in Tjörnes Fracture Zone glasses are slightly higher (13.6 RA) than on Kolbeinsey Ridge, suggesting a greater contribution of Icelandic mantle from the south, but the lack of 3He/ 4He variation along the Kolbeinsey Ridge is inconsistent with active dispersal of Icelandic mantle beyond the Tjörnes Fracture Zone. 相似文献
8.
Experiments up to water pressures of 21 kbar have been undertaken to bracket the reactions chlorite + quartz = talc + kyanite + H 2O, chlorite + quartz = talc + cordierite + H 2O, and talc + kyanite + quartz = cordierite ± H 2O by reversed runs in the system MgO-Al 2O 3-SiO 2-H 2O (MASH). These reaction curves intersect at an invariant point (IP1) at PH 2O = 6.4 ± 0.2 kbar and a temperature of 624 ± 4°C. The curve of the chlorite + quartz breakdown to talc + kyanite + H 2O at water pressures above 6.4 kbar shows a negative dP/dT, with the slope decreasing with rising pressure, whereas the slope of the breakdown curve to talc + cordierite + H 2O at water pressures is clearly positive. The composition of the chlorite solid solution reacting with quartz has been estimated to be approximately Mg 4.85Al 1.15[Al 1.15Si 2.85O 10](OH) 8 over the entire pressure range investigated. The composition of the talc solid solution forming by the breakdown of chlorite + quartz appears to be Mg 2.94Al 0.06[Al 0.06Si 3.94O 10](OH) 2 at PH 2O = 2kbar. With increasing pressure, the Al content of talc decreases, reaching a value of about 0.06 atoms per formula unit at P,H 2O = 21 kbar. As a consequence of the new experimental data, the existing phase topologies of the MASH-system and K 2O-MASH-system have been revised. For example, the invariant point IP1 and the univariant reaction curve kyanite + talc + H 2O = chlorite + cordierite are stable. For this reason, the development of medium- to high-temperature metamorphic rocks compositionally approximating the MASH-system must be reconsidered. The whiteschists from Sar e Sang, Afghanistan, are treated as an example. The application of the present experimental data to metamorphic rocks of more normal composition requires the examination of the influence of further components. This leads to the conclusion that the introduction of Fe 2+ into magnesian chlorite extends its stability field in the presence of quartz by 10°-15°C in comparison with pure Mg-chlorite. 相似文献
9.
Garnet and omphacite from ultrahigh-pressure eclogites from the Dabie orogen, eastern China were investigated by Micro-FTIR. The results show that all garnet and omphacite grains contain structural water occurring as hydroxyl (OH), with H 2O contents varying from 14 to 1915 ppm (H 2O wt) and from 105 to 695 ppm, respectively. Within the same sample, the water contents are either homogeneous at the grain scale or vary systematically from higher in the core to lower in the rim. Low water contents at crystal rims possibly result from hydroxyl exsolution after pressure decrease upon rock exhumation. The δD values of omphacites are between −108.4‰ and −114.2‰, and independent of water contents. Heterogeneous water contents of garnet occur at the centimeter scale and fluid mobility during UHP metamorphism was very limited. The estimated whole-rock water content based on mineral H 2O contents is between 260 and 750 ppm, thereby implying that eclogitic rocks formed during continental subduction have the potential to recycle (at least) several hundreds ppm water to mantle depths. The preserved chemical differences likely indicate that the eclogitic rocks resided at mantle conditions for a limited time span, and imply that they were exhumed shortly after subduction. The water released during decompression might represent the early-stage retrograde fluid. 相似文献
10.
Polymerization of silicate and aluminate tetrahedra in glasses,melts and aqueous solutions—II. The network modifying effects of Mg2+ , K+, Na+, Li+, H+, OH−, F−, Cl−, H2O,CO2 and H3O+ on silicate polymers
The effect of the group IA and VIIA ions, as well as Mg 2+, and the molecules H 2O, CO 2, H 3O + and OH ? on the energy of the Si-O bond in a H 6Si 2O 7 cluster has been calculated using semiempirical molecular orbital calculations (CNDO/2). Three types of elementary processes, i.e. substitution, addition, and polymerization reactions have been used to interpret data on the dynamic viscosity, surface tension and surface charge, hydrolytic weakening, diffusivity, conductivity, freezing point depression, and degree of polymerization of silicates in melts, glasses, and aqueous solutions. As a test of our calculational procedure, observed X-ray emission spectra of binary alkali silicate glasses were compared with calculated electronic spectra. The well known bondlength variations between the bridging bond [Si-O(br)] and the non-bridging bond [Si-O(nbr)] in alkali silicates are shown to be due to the propagation of oscillating bond-energy patterns through the silica framework. A kinetic interpretation of some results of our calculations is given in terms of the Bell-Evans-Polanyi reaction principle. 相似文献
11.
A new microscope vacuum heating stage and gas analyzer has been developed for measurement of H 2O, CO 2, SO 2, and noncondensable gas (H 2, CO, N 2, Ar, CH 4, etc.) evolved from samples, particularly natural glass, at temperatures up to 1280°C. The gas evolved upon heating to 1280δC is collected in a liquid nitrogen cold trap. Gas components are identified by the characteristic vapor pressure and temperature ranges over which solid and vapor are in equilibrium during sublimation of individual components. The masses of CO 2, SO 2, and H 2O derived from samples and blanks are calculated using the ideal gas law, the molecular weights of the components, and the gauge constant (i.e. the ratio of the number of moles of a gas to its partial pressure in the constant volume). Results obtained by repeated determinations of H 2O, CO 2, and SO 2 evolved from a submarine basaltic glass from Kilauea volcano, Hawaii, (average sample mass = 3 × 10 ?3 g) gave probable errors for the determinations of H 2O (0.23%), CO 2 (0.025%), and S (0.071%) equal to 4, 10, and 8% respectively, of the concentrations. Determinations of H 2O in smaller samples of H 2O-poor basaltic pumice show a linear proportionality (0.063%) between the measured H 2O and the sample mass over the range 0.1 × 10 ?6 to 1.7 × 10 ?6 g H 2O. Comparisons of H 2O determinations by this technique with those obtained by Penfield, gas chromatic, microcoulometric, and vacuum fusion techniques used elsewhere show reasonably good agreement. Determinations of SO 2 by this technique agree reasonably well X-ray fluorescence and electron microprobe determinations of sulfur. Determinations of CO 2 by the present technique are reproducible but cannot be compared directly to measurements made in other labs because of differences in samples analyzed. The principle advantages of this analytical technique are the very small sample required, the simultaneous determination of H 2O, CO 2, SO 2 and noncondensable gas, the avoidance of calibration procedures dependent on chemical standards, and the visual observations that can be made during sample outgassing. 相似文献
12.
Experiments were conducted to test the hypothesis that higher silica rhyolites of the St. Francois Mountains, Missouri, USA are products of fractional crystallization of lower silica granitic magmas. Experiments were carried out at pressures of 0.5 and 1.0 kb under water-saturated conditions, temperatures ranged from 800° to 925°C and the oxygen fugacity for all experiments were maintained at, or near, the nickel-nickel oxide (NNO) buffer level. Results of experiments with Butler Hill granite indicate that fractionation of near liquidus silicate phases, orthopyroxene and plagioclase, causes an enrichment of SiO2 in the residual melts. Mineralogical and chemical compositions of the experimental charges are similar to that of higher silica Grassy Mountain rhyolites of the St. Francois Mountains. Experiments also show that at pressures of 1.0 Kb or higher orthopyroxene reacts with the hydrous melt to produce biotite which is a common phase in the plutonic rocks of the St. Francois Mountains. 相似文献
13.
The Koralpe of the Eastern European Alps experienced high-temperature/low-pressure metamorphism (∼650 °C and 6.5 kbar) during the Permian and eclogite facies metamorphism (∼700 °C and 14 kbar) during the Eo-Alpine (Cretaceous) metamorphic event. In the metapelitic Plattengneiss shear zone that constitutes much of the Koralpe, the second metamorphism caused only partial re-equilibration of the assemblages formed during the first metamorphism. It is shown here that the Eo-Alpine mineral assemblage, garnet + biotite + muscovite + plagioclase + quartz (with or without kyanite), formed under low water activity conditions that are consistent with the level of dehydration that occurred during the Permian event. This implies that the rocks were essentially closed-system from the peak of the Permian metamorphism through the Eo-Alpine event. The evolution of water content of the rocks is traced through time: that prograde dewatering during the Permian metamorphic event terminated at the metamorphic peak with a water content around 3–4 mol.%. The water content remained then constant and led to water-undersaturation during the subsequent Eo-Alpine metamorphism. From the water content and activity evolution a post-peak isothermal decompression path close to the solidus is inferred for the Eo-Alpine event. 相似文献
14.
Speciation of aqueous magnesium in the system MgO-SiO 2-H 2O-HCl in supercritical aqueous fluids has been investigated using standard rapid-quench hydrothermal techniques and a modification of the Ag + AgCl buffer method (Frantz and Eugster, 1973. Am. J. Sci. 267, 268–286). A concentric double-capsule charge was utilized. The outer gold capsule contained the assemblage talc + quartz + Ag + AgCl + H2O- MgCl2 fluid; the inner platinum capsule, Ag + AgCl + H2O- HCl fluid. During the experiments, and thus equilibrated between the two capsules. After quenching, measurement of the chloride concentration in the fluid in the inner capsule and total magnesium in the fluid in the outer capsule defines the concentrations of HCl and Mg that coexist with talc + quartz in the outer capsule. Changes in the measured molality of HCl as a function of the total magnesium concentration at constant P and T were used to identify the predominant species of magnesium in the hydrothermal fluid. Experimental results showed that at 2000 bar, MgCl° 2 is the predominant species above 550°C and Mg 2+, below 400°C. Data at intermediate temperatures when combined with the dissociation constant for HCl were used to obtain the dissociation constant for MgCl° 2. The results of these experiments were combined with results from experiments using Ag + AgCl in conjunction with the oxygen buffer, hematite-magnetite, to obtain the equilibrium constant for the reaction from which the difference in Gibbs free energy of MgCl° 2 and HC1° was obtained as a function of temperature at 1000, 1500 and 2000 bar pressure, Solubility constants for brucite. forsterite, chrysotile, and talc were calculated. 相似文献
15.
Dualite, Na30(Ca,Na,Ce,Sr)12(Na,Mn,Fe,Ti)6Zr3Ti3MnSi51O144(OH,H2O,Cl)9, a new zircono-titanosilicate with a modular eudialyte-like structure from the Lovozero alkaline Pluton, Kola Peninsula, Russia
Dualite has been found at Mount Alluaiv, the Lovozero Pluton, the Kola Peninsula in peralkaline pegmatoid as sporadic, irregularly
shaped grains up to 0.3–0.5 mm across. K-Na feldspar, nepheline, sodalite, cancrinite, aegirine, alkaline amphibole, eudialyte,
lovozerite, lomonosovite, vuonnemite, lamprophyllite, sphalerite, and villiaumite are associated minerals. Dualite is yellow,
transparent or translucent, with conchoidal fracture. The new mineral is brittle, with vitreous luster and white streaks.
The Mohs hardness is 5. The measured density is 2.84(3) g/cm 3 (volumetric method); the calculated density is 2.814 g/cm 3. Dualite dissolves and gelates in acid at room temperature. It is nonfluorescent. The new mineral is optically uniaxial and
positive; ω = 1.610(1), ɛ = 1.613(1). Dualite is trigonal, space group R3 m. The unit cell dimensions are a = 14.153(9), c = 60.72(5) ?, V = 10533(22) ?, Z = 3. The strongest reflections in the X-ray powder pattern [ d, ? ( I,%)( hkl)] are as follows: 7.11(40)(110), 4.31(50)(0.2.10), 2.964(100)(1.3.10), 2.839(90)(048), 2.159(60)(2.4.10, 0.4.20), 1.770(60)(2.4.22,
4.0.28, 440), 1362(50)(5.5.12, 3.0.42). The chemical composition (electron microprobe, H 2O calculated from X-ray diffraction data) is as follows, wt %: 17.74 Na 2O, 0.08 K 2O, 8.03 CaO, 1.37 SrO, 0.29 BaO, 2.58 MnO, 1.04 FeO, 0.79 La 2O 3, 1.84 C 2O 3, 0.88 Nd 2O 3, 0.20 Al 2O 3, 51.26 SiO 2, 4.40 TiO 2, 5.39 ZrO 2, 1.94 Nb 2O 5, 0.58 Cl, 1.39 H 2O,-O = 0.13 Cl 2; they total is 99.67. The empirical formula calculated on the basis of 106 cations as determined by crystal structure is
(Na 29.79Ba 0.1K 0.10) Σ30(Ca 8.55Na 1.39REE 1.27Sr 0.79) Σ12 · (Na 3.01Mn 1.35Fe 0.872+Ti 0.77) Σ6(Zr 2.61Nb 0.39) Σ3 (Ti 2.52Nb 0.48) Σ3(Mn 0.82Si 0.18) Σ1(Si 50.77Al 0.23) Σ51 O 144[(OH) 6.54(H 2O) 1.34·Cl 0.98] Σ8.86). The simplified formula is Na 30(Ca,Na,Ce,Sr) 12(Na,Mn,Fe,Ti) 6Zr 3Ti 3 MnSi 51O 144 (OH,H 2O,Cl) 9). The name dualite is derived from Latin dualis (dual) alluding to the dual taxonomic membership of this mineral, which is at the same time zirconosilicate and titanosilicate.
The crystal structure is characterized by two module types (alluivite-like and eudialyte-like) alternating along a threefold
axis with a doubled c period relative to eudialyte and close chemical affinity to rastsvetaevite (Khomyakov et al., 2006a) and labyrynthite (Khomyakov
et al., 2006b). According to the authors’ crystal chemical taxonomy of the eudialyte group, the new mineral belongs to one
of three subgroups characterized by a 24-layered structural framework. Dualite is a mineral formed during the final stages
of peralkaline pegmatite formation. The type material of dualite is deposited at the Fersman Mineralogical Museum, Russian
Academy of Sciences, Moscow.
Original Russian Text ? A.P. Khomyakov, G.N. Nechelyustov, R.K. Rastsvetaeva, 2007, published in Zapiski Rossiiskogo Mineralogicheskogo
Obshchestva, 2007, Pt CXXXVI, No. 4, pp. 68–73.
Approved by the Commission on New Minerals and Mineral Names, International Mineralogical Association, July 8, 2005. 相似文献
17.
We present here new measurements of sulfur dioxide and hydrogen sulfide emissions from Vulcano, Etna, and Stromboli (Italy), made by direct sampling at vents and by filter pack and ultraviolet spectroscopy in downwind plumes. Measurements at the F0 and FA fumaroles on Vulcano yielded SO 2/H 2S molar ratios of ≈0.38 and ≈1.4, respectively, from which we estimate an H 2S flux of 6 to 9 t · d −1 for the summit crater. For Mt. Etna and Stromboli, we found SO 2/H 2S molar ratios of ≈20 and ≈15, respectively, which combined with SO 2 flux measurements, suggest H 2S emission rates of 50 to 113 t · d −1 and 4 to 8 t · d −1, respectively. We observe that “source” and plume SO 2/H 2S ratios at Vulcano are similar, suggesting that hydrogen sulfide is essentially inert on timescales of seconds to minutes. This finding has important implications for estimates of volcanic total sulfur budget at volcanoes since most existing measurements do not account for H 2S emission. 相似文献
18.
Plagioclase feldspar/magmatic liquid partition coefficients for Sr, Ba, Ca, Y, Eu 2+, Eu 3+ and other REE have been determined experimentally at 1 atm total pressure in the temperature range 1150–1400°C. Natural and synthetic melts representative of basaltic and andesitic bulk compositions were used, crystallizing plagioclase feldspar in the composition range An 35–An 85. Partition coefficients for Sr are greater than unity at all geologically reasonable temperatures, and for Ba are less than unity above approximately 1060°C. Both are strongly dependent upon temperature. Partition coefficients for the trivalent REE are relatively insensitive to temperature. At fixed temperature they decrease monotonically from La to Lu. The partition of Eu is a strong function of oxygen fugacity. Under extreme reducing conditions DEu approaches the value of DSr. 相似文献
19.
A set of correlations for the volumetric properties and enthalpies of phases in the system H 2O-NaCl as a function of temperature, pressure, and composition has been developed that yields accurate values from 0 to 1000 °C, 1 to 5000 bar, and 0 to 1 XNaCl. The volumetric properties of all fluid phases from low-density vapor to hydrous salt melts and single-phase binary fluids at high pressures and temperatures, can be described by a simple equation
20.
Realistic simulations of fluid flow in geologic systems have severely been hampered by the lack of a consistent formulation for fluid properties for binary salt-water fluids over the temperature-pressure-composition ranges encountered in the Earth’s crust. As the first of two companion studies, a set of correlations describing the phase stability relations in the system H 2O-NaCl is developed. Pure water is described by the IAPS-84 equation of state. New correlations comprise the vapor pressure of halite and molten NaCl, the NaCl melting curve, the composition of halite-saturated liquid and vapor, the pressure of vapor + liquid + halite coexistence, the temperature-pressure and temperature-composition relations for the critical curve, and the compositions of liquid and vapor on the vapor + liquid coexistence surface. The correlations yield accurate values for temperatures from 0 to 1000 °C, pressures from 0 to 5000 bar, and compositions from 0 to 1 XNaCl (mole fraction of NaCl). To facilitate their use in fluid flow simulations, the correlations are entirely formulated as functions of temperature, pressure and composition. 相似文献
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