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1.
Fluid inclusions in quartz have been synthesized from Na2SO4 and NaF solutions at 700–800°C and 1 and 2 kbar using the fracture healing method. Some experiments have been carried out
in the presence of albite gel. Microthermometry of the synthesized inclusions showed that under experimental conditions, the
fluid was heterogeneous and reactive in respect to quartz and albite. Soluble sodium silicates formed in the presence of (alumino)silicate
matter, whereas malladrite appeared when fluid interacted with NaF. When the fluid was entrapped in inclusions cooled from
400 to 250°C, it became heterogeneous again. Appearance of the second liquid phase depended on the composition of the (alumino)silicate
phase. It has been shown that three noncrystalline phases coexist at such a low temperature. Silicate matter affects heterogeneous
fluid equilibria, even when the salts of the second type are contained in fluid in insignificant amounts. Fluid immiscibility
appears to be more widespread than is commonly suggested and is the most important mechanism of matter redistribution, including
ore substances. 相似文献
2.
Fluid inclusions in quartz were synthesized by the method of crack healing at 2 kbar and temperatures of 500, 700, 750, and 800°C from solutions containing sodium fluoride (±chloride). Critical phenomena occur in the saturated solution of NaF. Thermometric and cryometric measurements were carried out. Fluid interaciton with quartz was observed under all the parameters of our experiments with the formation of intermediate compounds, which were also sometimes trapped in inclusions. Based on the results of cryometric investigations of inclusions synthesized from solutions of different concentration, the solubility of NaF was estimated as 3.9 wt % at 500°C. It was shown that at temperatures higher than 700°C, heterogeneous entrapment occurred in most cases. Complex unmixing processes took place in the inclusions synthesized under the conditions of the upper heterogeneous region. All our observations suggest that coarse dispersed emulsions of two liquids exist in the upper heterogeneous region: an essentially aqueous phase and a water-rich silicate-dominated phase.At temperatures of 206–389°C, liquid immiscibility occurred in the presence of vapor, and three equilibrium noncrystalline (fluid) phases coexisted. Under the experimental conditions, the addition of NaCl to the fluidgenerating mixture did not exert a significant influence on the phase state of fluorine-bearing fluid. 相似文献
3.
The phase state of the fluid in the H2O–KF ± KCl ± NaF system is studied in the presence of quartz for an experimental assay of the mutual influence of various salts of the fluid-forming mixture on heterogeneous fluid equilibria. The fluid inclusions were synthesized in quartz by the fracture healing method from solutions with KF + KCl and KF + NaF mixtures at 1 or 2 kbar and 700, 750, or 800°C. The results of the fluid inclusion study indicate a heterogeneous state of the fluid and variation in the fluid composition during experiments as a result of its interaction with quartz. The increase in temperature and pressure, as well as variation in the proportions of the salt contents in the fluid-forming mixture, changed the course of chemical reactions. After all the experiments, a glassy phase was observed in some types of inclusions. It is known that aqueous KF or KCl solutions, the solubility of which increases during heating, are characterized by phase equilibria of systems of the first type (Valyashko, 1990), when liquid and vapor are equilibrated for a heterogeneous state of the fluid. In this case, some inclusions should homogenize to vapor. However, no similar inclusions were observed in contrast to denser fluid phases (liquids), which are typical of the upper heterogeneous area of systems of the second (P–Q) type. Some inclusions host solid phases, the solubility of which decreases as the temperature increases. The results of experiments in the presence of KF + NaF solutions showed that the amount of inclusions of heterogeneous entrapment increases at higher temperatures simultaneously with a decrease in the H2O content of the glassy phase. 相似文献
4.
Heterogeneous fluid equilibria in the second-type H2O-Na2CO3 system in the presence of SiO2 or SiO2 + NaAlSi3O8 were studied experimentally. Phase diagrams of the second-type systems are briefly described. Fluid inclusions in quartz
were synthesized by healing of fractures in 1 M Na2CO3 solution at 700°C and under 1, 2, and 3 kbar pressure. Some runs were carried out in the presence of albite gel. The microthermomemtric
study of the synthesized inclusions showed that under experimental conditions the fluid was heterogeneous and did not remain
inert with respect to quartz and albite. Some inclusions contained a glass-like phase, and liquid released from this phase
by heating. Having been heated, some inclusions revealed liquid immiscibility. Comparison of the water-silicate-sodium carbonate
system with similar systems containing sodium sulfate and fluoride (Kotel’nikova and Kotel’nikov, 2008, 2010) shows that they
have much in common. In all cases, the aqueous salt-bearing fluid did not remain inert relative to the quartz under relatively
low PT conditions. The inclusions entrapped in the upper heterogeneous region revealed immiscibility in the presence of vapor within
a temperature range of 200 to 400°C. The solutions of various concentrations, including oversaturated solutions in the presence
of solid phase, underwent recurrent heterogenization. Near 400°C, vapor is either dissolved in one of immiscible liquids or
absorbs this liquid. When heating progresses to higher temperature, inclusions commonly become unsealed. 相似文献
5.
Prograde and retrograde history of eclogites from the Eastern Blue Ridge, North Carolina, USA 总被引：4，自引：1，他引：4
Abstract The prograde metamorphism of eclogites is typically obscured by chemical equilibration at peak conditions and by partial requilibration during retrograde metamorphism. Eclogites from the Eastern Blue Ridge of North Carolina retain evidence of their prograde path in the form of inclusions preserved in garnet. These eclogites, from the vicinity of Bakersville, North Carolina, USA are primarily comprised of garnet–clinopyroxene–rutile–hornblende–plagioclase–quartz. Quartz, clinopyroxene, hornblende, rutile, epidote, titanite and biotite are found as inclusions in garnet cores. Included hornblende and clinopyroxene are chemically distinct from their matrix counterparts. Thermobarometry of inclusion sets from different garnets record different conditions. Inclusions of clinozoisite, titanite, rutile and quartz (clinozoisite + titanite = grossular + rutile + quartz + H2O) yield pressures (6–10 kbar, 400–600 °C and 8–12 kbar 450–680 °C) at or below the minimum peak conditions from matrix phases (10–13 kbar at 600–800 °C). Inclusions of hornblende, biotite and quartz give higher pressures (13–16 kbar and 630–660 °C). Early matrix pyroxene is partially or fully broken down to a diopside–plagioclase symplectite, and both garnet and pyroxene are rimmed with plagioclase and hornblende. Hypersthene is found as a minor phase in some diopside + plagioclase symplectites, which suggests retrogression through the granulite facies. Two‐pyroxene thermometry of this assemblage gives a temperature of c. 750 °C. Pairing the most Mg‐rich garnet composition with the assemblage plagioclase–diopside–hypersthene–quartz gives pressures of 14–16 kbar at this temperature. The hornblende–plagioclase–garnet rim–quartz assemblage yields 9–12 kbar and 500–550 °C. The combined P–T data show a clockwise loop from the amphibolite to eclogite to granulite facies, all of which are overprinted by a texturally late amphibolite facies assemblage. This loop provides an unusually complete P–T history of an eclogite, recording events during and following subduction and continental collision in the early Palaeozoic. 相似文献
6.
The Degdekan and Gol’tsovsky gold-quartz deposits are located in the southeastern Yana-Kolyma gold belt. The orebodies occur as quartz veins hosted in metaterrigenous rocks and cut by postmineral basic-intermediate dikes. It was established that metamorphism of sulfides and gangue quartz was restricted to a few centimeters off the dike contact. According to sulfide geothermometers, the metamorphic temperatures close to the contact of dikes attained 700°C at the Degdekan deposit and were no higher than 491°C at the Gol’tsovsky deposit. The formation of the forbidden assemblage of quartz and loellingite and its fine-grained texture indicate that the thermal effect on the Degdekan ore was short-term. The prolonged heating of the ore at the Gol’tsovsky deposit gave rise to the aggradation recrystallization of quartz and the formation of equilibrium sulfide aggregates that show only insignificant differences in composition from the primary phases. The average homogenization temperature of primary and pseudosecondary fluid inclusions is 206 ± 40°C in the unmetamorphosed veins and 257 ± 33°C in the metamorphosed veins. The salinity of fluids in the primary and pseudosecondary inclusions in quartz veins of both types varies from 0.5 to 14.0 wt % NaCl equiv. The melting temperature of liquid CO2 in the carbon dioxide inclusions, ranging from ?57.0 to ?60.8°C, suggests an admixture of CH4 and/or N2. The unmetamorphosed quartz veins were formed at a fluid pressure varying from 0.7 to 1.3 kbar, while quartz veins at the contact with dikes crystallized at a pressure of 0.8–1.5 kbar. The results of gas chromatography showed the presence of CO2 and H2O, as well as N2 and CH4. The average bulk of volatiles contained in the fluid inclusions in quartz from the metamorphosed veins is 1.5–2 times lower than in the unmetamorphosed veins; this proportion is consistent with the occurrence of decrepitated gas inclusions in the heated quartz. 相似文献
7.
Melt inclusions and aqueous fluid inclusions in quartz phenocrysts from host felsic volcanics, as well as fluid inclusions in minerals of ores and wall rocks were studied at the Cu-Zn massive sulfide deposits in the Verkhneural’sk ore district, the South Urals. The high-temperature (850–1210°C) magmatic melts of volcanic rocks are normal in alkalinity and correspond to rhyolites of the tholeiitic series. The groups of predominant K-Na-type (K2O/Na2O = 0.3–1.0), less abundant Na-type (K2O/Na2O = 0.15–0.3), and K-type (K2O/Na2O = 1.9–9.3) rhyolites are distinguished. The average concentrations (wt %) of volatile components in the melts are as follows: 2.9 H2O (up to 6.5), 0.13 Cl (up to 0.28), and 0.09 F (up to 0.42). When quartz was crystallizing, the melt was heterogeneous, contained magnetite crystals and sulfide globules (pyrrhotite, pentlandite, chalcopyrite, bornite). High-density aqueous fluid inclusions, which were identified for the first time in quartz phenocrysts from felsic volcanics of the South Urals, provide evidence for real participation of magmatic water in hydrothermal ore formation. The fluids were homogenized at 124–245°C in the liquid phase; the salinity of the aqueous solution is 1.2–6.2 wt % NaCl equiv. The calculated fluid pressure is very high: 7.0–8.7 kbar at 850°C and 5.1–6.8 kbar at 700°C. The LA-ICP-MS analysis of melt and aqueous fluid inclusions in quartz phenocrysts shows a high saturation of primary magmatic fluid and melt with metals. This indicates ore potential of island-arc volcanic complexes spatially associated with massive sulfide deposits. The systematic study of fluid inclusions in minerals of ores and wall rocks at five massive sulfide deposits of the Verkhneural’sk district furnished evidence that ore-forming fluids had temperature of 375–115°C, pressure up to 1.0–0.5 kbar, chloride composition, and salinity of 0.8–11.2 (occasionally up to 22.8) wt % NaCl equiv. The H and O isotopic compositions of sericite from host metasomatic rocks suggest a substantial contribution of seawater to the composition of mineral-forming fluids. The role of magmatic water increases in the central zones of the feeding conduit and with depth. The dual nature of fluids with the prevalence of their magmatic source is supported by S, C, O, and Sr isotopic compositions. The TC parameters of the formation of massive sulfide deposits are consistent with the data on fluid inclusions from contemporary sulfide mounds on the oceanic bottom. 相似文献
8.
We present a study of carbonate-bearing polyphase inclusions in garnets from leucocratic granitoids intruding metapelitic granulites of the Southern Marginal Zone (SMZ) of the Neoarchean Limpopo high-grade complex, South Africa, during the post-peak stage (2710–2650 Ma; U-Pb ages for zircons and monazites). Ternary feldspar thermometry suggests that the granitoid magma cooled from temperatures 800–900 °C at a pressure of ca. 6.5 kbar. Abundant CO2 fluid inclusions in quartz and T-XCO2 phase equilibria modeling via PERPLE_X imply action of an essentially carbonic fluid in the granitoids. Cores of almandine-rich garnet grains from the granitoids contain polyphase carbonate-bearing inclusions with a distinct negative crystal shape. The major carbonate in the inclusions is a strongly zoned magnesite-siderite variety, whereas pyrophyllite is the predominant silicate phase. Raman spectra of unexposed inclusions revealed a presence of CO2, as well as CH4 and H2O. The carbonate-bearing inclusions coexist with larger polyphase inclusions composed of biotite, quartz, K-feldspar, plagioclase, sillimanite, which are interpreted as relics of granitic melts. Modeling the mineral assemblage preserved within the carbonate-bearing inclusions shows that their present mineral and chemical compositions are a product of interaction of the trapped aqueous‑carbonic fluid with host garnet during cooling below 400 °C. Despite strong modifications, the inclusions bear evidence for initial saturation of the fluid with Mg‑carbonate. This is taken as an evidence for an origin of the fluids by devolatilization of the Mg-rich carbonate-bearing ultrabasic greenstone rocks of the Kaapvaal Craton that were buried under the SMZ. Being generated at temperatures between 650 and 700 °C, the fluid subsequently participated in anatexis and coexisted with the granite magma during exhumation and interaction of the SMZ granulites with cratonic rocks. 相似文献
9.
The study focuses on analysis of primary and secondary fluid inclusions present in quartz veins hosted in the phyllites to explore the stress and temperature conditions at the time of formation of metasediment sequences of the of Parsoi Formation, central India. The results reveal the two-phase liquid-rich fluid inclusions that indicate that the intrusions of quartz veins in phyllite may have taken place between the temperature from 168.8°C to 256.3°C with an average of 205.55°C from a magmatic moderately saline fluid (3.7 to 18.29 wt. % NaCl equiv.). The final ice-melting temperatures ranges from -14.6°C to -2.2°C which indicate that the aqueous fluids are mainly H2O-NaCl. The density distribution of fluid inclusions rich in liquid H2O only are unimodel and low in natures and appears to be entrapped between pressure 1.666 to 2.125 kbar at depth of 200m. The study supports epithermal nature of fluid inclusions. The characteristic of fluid inclusions along with lithological and structural peculiarities, nature of structural features may be helpful in exploring the future potential zone of gold mineralization in similar types of area. 相似文献
10.
I.S. Peretyazhko S.Z. Smirnov A.R. Kotel’nikov Z.A. Kotel’nikova 《Russian Geology and Geophysics》2010,51(4):349-368
The phase state of fluid in the system H3BO3–NaF–SiO2–H2O was studied at 350–800 °C and 1–2 kbar by the method of synthetic fluid inclusions. The increase in the solubility of quartz and the high reciprocal solubility of H3BO3 and NaF in water fluid at high temperatures are due to the formation of complexes containing B, F, Si, and Na. At 800 °C and 2 kbar, both liquid and gas immiscible phases (viscous silicate-water-salt liquid and three water fluids with different contents of B and F) are dispersed within each other. The Raman spectra of aqueous solutions and viscous liquid show not only a peak of [B(OH)3]0 but also peaks of complexes [B(OH)4]–, polyborates [B4O5(OH)4]2–, [B3O3(OH)4]–, and [B5O6(OH)4]–, and/or fluoroborates [B3F6O3]3–, [BF2(OH)2]–, [BF3(OH)]–, and [BF4]–. The high viscosity of nonfreezing fluid is due to the polymerization of complexes of polyborates and fluorine-substituted polyborates containing Si and Na. Solutions in fluid inclusions belong to P–Q type complicated by a metastable or stable immiscibility region. Metastable fluid equilibria transform into stable ones owing to the formation of new complexes at 800 ºC and 2 kbar as a result of the interaction of quartz with B-F-containing fluid. At high concentrations of F and B in natural fluids, complexes containing B, F, Si, and alkaline metals and silicate-water-salt dispersed phases might be produced and concentrate many elements, including ore-forming ones. Their transformation into vitreous masses or viscous liquids (gels, jellies) during cooling and the subsequent crystallization of these products at low temperatures (300–400 °C) should lead to the release of fluid enriched in the above elements. 相似文献
11.
Claudia Cannatelli 《Mineralogy and Petrology》2012,104(3-4):177-195
Mantle peridotites from the Veneto Volcanic Province (VPP) have been investigated in order to constrain P-T conditions of mantle events, determine the style of the metasomatic reactions, and the compositions of the metasomatic agents. Studied rocks show dominant protogranular and transitional textures; only one sample shows effect of pyrometamorphism. Clinopyroxenes in protogranular lherzolites show depleted LREE patterns, while those of transitional rocks are characterised by spoon-shaped REE patterns (La up to 60 times chondrite), and variable enrichments in LILE. Two generations of fluid inclusions are recognised: 1) Type I (CO2 ± CO ± C fluid) found only in orthopyroxene of transitional xenoliths which may contain very small amphibole; 2) Type II (CO2-rich fluid) found in all minerals of all xenoliths. Most of inclusions homogenize to liquid, with ThL ranging between ?44 and 31°C. The densest CO2 fluid inclusions (d?=?1.13?g/cm3), indicates a trapping pressure of ~10?kbar at 800°C. We propose that the mantle beneath the VVP equilibrated at pressures of 10?kbar, at about 800°C. Traces of an aqueous fluid preserved as fluid inclusions in orthopyroxene suggest the existence of an older subduction related metasomatic event and the occurrence of two stages metasomatism in the lithosphere beneath the SE Alps. 相似文献
12.
The Khtada Lake. British Columbia, metamorphic complex consists of high grade amphibolite and metasedimentary units with development of gneiss, migmatite and homogeneous autochthonous plutons. Maximum metamorphic conditions are estimated to have exceeded 5 kbar and 700°C.Fluid inclusions in matrix quartz are highly variable in density and composition, ranging from apparently pure CO2 (gas or liquid or both at room temperature) through CO2 + H2O ± CH4 mixtures to inclusions which are entirely aqueous. They occur along cracks, in groups without planar features and as isolated inclusions. The latter and some which occur in groups, are interpreted to most nearly approximate, in density and composition, the fluids present during the peak of metamorphism.The density and fluid composition data are derived from direct observations of phase changes between ? 180 and + 380°C and from the application of published experimental data in the system CH4-CO2-H2O-NaCl. The most dense, pure CO2 inclusions indicate a pressure of entrapment at 5 kbar, if a temperature of 700°C is assumed. This is in close agreement with the minimum P-T estimates from the mineral assemblages. Methane was positively identified in inclusions in graphite-bearing specimens. Salt content is concluded to be about 5–6 wt% NaCl equivalent in the aqueous phase in both aqueous and CO2 + H2O inclusions. There is evidence of immiscible separation of CO2-rich and H2O-rich fluids at temperatures at least as high as 375°C. 相似文献
13.
The Southern Marginal Zone of the Limpopo Belt in South Africa is characterised by a granulite and retrograde hydrated granulite terrane. The Southern Marginal Zone is, therefore, perfectly suitable to study fluids during and after granulite facies metamorphism by means of fluid inclusions and equilibrium calculations. Isolated and clustered high-salinity aqueous and CO2(-CH4) fluid inclusions within quartz inclusions in garnet in metapelites demonstrate that these immiscible low H2O activity fluids were present under peak metamorphic conditions (800-850 °C, 7.5-8.5 kbar). The absence of widespread high-temperature metasomatic alteration indicates that the brine fluid was probably only locally present in small quantities. Thermocalc calculations demonstrate that the peak metamorphic mineral assemblage in mafic granulites was in equilibrium with a fluid with a low H2O activity (0.2-0.3). The absence of water in CO2-rich fluid inclusions is due to either observation difficulties or selective water leakage. The density of CO2 inclusions in trails suggests a retrograde P-T path dominated by decompression at T<600 °C. Re-evaluation of previously published data demonstrates that retrograde hydration of the granulites at 600 °C occurred in the presence of H2O and CO2-rich fluids under P-T conditions of 5-6 kbar and ~600 °C. The different compositions of the hydrating fluid suggest more than one fluid source. 相似文献
14.
Phase equilibria in the ternary system H2O-CO2-NaCl were studied at 800 °C and 9 kbar in internally heated gas pressure vessels using a modified synthetic fluid inclusion
technique. The low rate of quartz overgrowth along the `b' and `a' axes of quartz crystals was used to avoid fluid inclusion
formation during heating, prior to attainment of equilibrium run conditions. The density of CO2 in the synthetic fluid inclusions was calibrated using inclusions in the binary H2O-CO2 system synthesised by the same method and measured on the same heating-freezing stage. In the two-phase field, two types
of fluid inclusions with different densities of CO2 were observed. Using mass balance calculations, these inclusions are used to constrain the miscibility gap and the orientation
of two-phase tie-lines in the H2O-CO2-NaCl system at 800 °C and 9 kbar. The equation of state of Duan et al. (1995) approximately describes the P-T section of the ternary system up to about 40 wt% of NaCl. At higher NaCl concentrations the measured solubility of CO2 in the brine is much smaller than predicted by the EOS. A “salting out” effect must be added to the equation of state to
include coulomb interaction in the model of Anderko and Pitzer (1993) and Pitzer and Jiang (1996). The new experimental data
together with published data up to 5 kbar (Shmulovich et al. 1995) encompass practically all subsolidus crustal P-T conditions. A feature of the new experimental results is the large compositional range in the H2O-CO2-NaCl system occupied by the stability fields of halite + CO2-rich fluid ± H2O-NaCl brine. The prediction of halite stability in equilibrium with CO2-rich fluid in deep-crustal rocks is supported by recent petrological and fluid inclusion studies of granulites.
Received: 29 June 1998 / Accepted: 17 March 1999 相似文献
15.
The phase state of fluid in the H2O-NaF-Na2SO4 system in the presence of silicates (quartz and albite) was experimentally explored using the method of synthetic fluid inclusions in quartz at 700°C and pressures of 1 and 2 kbar. Parallel experiments were conducted under identical conditions with either two silicates (quartz and albite) or quartz only. The presence of albite affects heterogeneous fluid equilibria both at different pressures and at different solution compositions. This indicates high solubilities of silicates in a saltwater fluid containing NaF and Na2SO4. The absence of inclusions homogenizing to a gas phase in the experimental products provides compelling evidence that liquid-liquid rather than liquid-vapor equilibria are characteristic of the H2O-SiO2-NaF-Na2SO4 and H2O-SiO2-NaF-Na2SO4-NaAlSi3O2 systems in the heterogeneous region. It can be concluded that critical equilibria in saturated solutions can exist in these systems. In addition, it was shown that the phase diagrams of these systems are complicated by the formation of immiscible liquids in the presence of vapor. This allowed us to conclude that there are two critical curves describing equilibria with two different salts. Fluids containing two salts (NaF and Na2SO4) are similar to fluids containing only one of these salts: (a) two liquids are in equilibrium under the parameters of the upper heterogeneous region, (b) each of them can in turn undergo unmixing at decreasing temperature and pressure, and (c) owing to chemical interaction between silicate and fluid components, a glassy phase can be formed and trapped in inclusions. 相似文献
16.
C. CASQUET 《Journal of Metamorphic Geology》1986,4(2):117-130
Abstract The Berzosa fault is a major ductile shear zone, the Berzosa Shear Zone (BSZ), which separates the ‘Ollo de Sapo’anticline from the inner higher-grade crystalline axis of the Iberian Hercynian Belt. This shear zone is the site of abundant early kinematic quartz (± Al-silicates) segregations, rich in fluid inclusions. Host rocks are medium-grade staurolite schists and sillimanite gneisses. Fluid inclusions in selected quartz segregations across the Berzosa shear zone have been studied by microthermometric methods as well as, in some instances, by Raman analysis. The recorded fluid inclusion history begins at the end of an intense secondary recrystallization period during late-peak metamorphic conditions and lasts until late in the uplift history of the zone. Three types of inclusions have been found, which in a time sequence are: CO2± H2O; H2O+salt (B-type); and, N2+CH4. Three types of B inclusion may be distinguished in turn, depending on whether they were trapped during an earlier dynamic-recovery phase (B1-type), formed later as intergranular trails (B2-type), or were trapped apparently along with N2+CH4 in clusions from a heterogeneous fluid (B3-type). Considerations from isochores confirm that CO2± H2O inclusions were trapped during late-peak and high-T retrograde metamorphic conditions (in the range 650–500°C and 5–2 kbar), whilst N2+CH4 inclusions, along with the B3-type of inclusions, formed at low-pressures (<1 kbar) and temperatures (± 300°C). B2-type inclusions were trapped chronologically between these two in a period in which strong inverse lateral thermal gradients developed in the zone. Inferred P-T paths for the area are convex to the T-axis. 相似文献
17.
The transformations (density, composition, or shape alterations) of fluid inclusions under isobaric cooling and isothermal
compression have been experimentally modeled. The H2O-CO2-CH4 inclusions used in the model experiments have been synthesized in quartz at 1 or 3 kbar and 700°C. The parameters of the
model experiments were as follows: for isobaric cooling, 700–400°C at 1 or 3 kbar; for isothermal compression, 1–3 and 3–5
kbar at 400 and 700°C, respectively. The shape of the inclusion walls changed as a result of the experiments because of the
dissolution and reprecipitation of the host phase. The intensity of these changes was directly affected by the pressure and
temperature differences and the amount of the aqueous phase in the inclusions. Fluid densities increased in many inclusions
in the run products: the increase ranged from insignificant (0.06 g/cm3) to fairly noticeable (0.15 g/cm3). The composition of the fluid inclusions also changed. The results of the experiments, in particular of those carried out
with a labeled fluid, show that the penetration of a denser external fluid into inclusions with a lower fluid density is the basic reason
for the increase in the density and change in the composition of fluid inclusions. In several experiments, the methane concentration
changed with an attendant change in the melting temperature of carbon dioxide but without noticeable changes in the carbon
dioxide homogenization temperature.
Original Russian Text ? O.V. Vasyukova, V.I. Fonarev, 2006, published in Geokhimiya, 2006, No. 12, pp. 1266–1278. 相似文献
18.
Fluid inclusions have been studied in three pegmatite fields in Galicia, NW Iberian Peninsula. Based on microthermometry
and Raman spectroscopy, eight fluid systems have been recognized. The first fluid may be considered to be a pegmatitic fluid
which is represented by daughter mineral (silicates)-rich aqueous inclusions. These inclusions are primary and formed above
500 °C (dissolution of daughter minerals). During pegmatite crystallization, this fluid evolved to a low-density, volatile-rich
aqueous fluid with low salinity (93% H2O; 5% CO2; 0.5% CH4; 0.2% N2; 1.3% NaCl) at minimum P–T conditions around 3 ± 0.5 kbar and 420 °C. This fluid is related to rare-metal mineralization. The volatile enrichment may
be due to mixing of magmatic fluids and fluids equilibrated with the host rock. A drop in pressure from 3 ± 0.5 to 1 kbar
at a temperature above 420 °C, which may be due to the transition from predominantly lithostatic to hydrostatic pressure,
is recorded by two-phase, water-rich inclusions with a low-density vapour phase (CO2, CH4 and N2). Another inclusion type is represented by two-phase, vapour-rich inclusions with a low-density vapour phase (CO2, CH4 and N2), indicating a last stage of decreasing temperature (360 °C) and pressure (around 0.5 kbar), probably due to progressive
exhumation. Finally, volatile (CO2)-rich aqueous inclusions, aqueous inclusions (H2O-NaCl) and mixed-salt aqueous inclusions with low Th, are secondary in charac- ter and represent independent episodes of hydrothermal fluid circulation below 310 °C and 0.5 kbar.
Received: 14 October 1999 / Accepted: 5 October 1999 相似文献
19.
Gerald Doppler Ronald J. Bakker Miriam Baumgartner 《Contributions to Mineralogy and Petrology》2013,165(6):1259-1274
The mobility of H2O and D2O by diffusion through quartz is illustrated with H2O-rich fluid inclusions synthesized at 600 °C and 337 MPa, within the α-quartz stability field. Inclusions are re-equilibrated at the same experimental conditions within a pure D2O fluid environment. Consequently, a gradient in volatile fugacities is the only driving force for diffusion, in the absence of pressure gradients and deformation processes. Up to 100 individual inclusions are analyzed in each experiment before and after re-equilibration by microscopic investigation, microthermometry, and Raman spectroscopy. Changes in fluid inclusion composition are obtained from the ice-melting temperatures, and density changes are obtained from total homogenization temperatures. After 1-day re-equilibration, inclusions already contain up to 11 mol % D2O. A maximum concentration of 63 mol % D2O is obtained after 40-day re-equilibration. D2O concentration profiles in quartz are determined from the concentration in inclusions as a function of their distance to the quartz surface. These profiles illustrate that deep inclusions contain less D2O than shallow inclusions. At equal depths, a variety of D2O concentration is observed as a function of fluid inclusion size: Small inclusions are stronger effected compared with large inclusions. A series of 19-day re-equilibration experiments are performed at 300, 400, 500, and 600 °C (at 337 MPa), at the same conditions as the original synthesis. The threshold temperature of diffusion is estimated around 450 °C at 337 MPa, because D2O is not detected in inclusions from re-equilibration experiments at 300 and 400 °C, whereas maximally 26 mol % D2O is detected at 500 °C. Our study indicates that the isotopic composition of natural fluid inclusions may be easily modified by re-equilibration processes, according to the experimental conditions at 600 °C and 337 MPa. 相似文献
20.
The Motuo area is located in the east of the Eastern Himalayan Syntaxis. There outcrops a sequence of high-grade metamorphic rocks, such as metapelites. Petrology and mineralogy data suggest that these rocks have experienced three stages of metamorphism. The prograde metamorphic mineral assemblages(M1) are mineral inclusions(biotite + plagioclase + quartz ± sillimanite ± Fe-Ti oxides) preserved in garnet porphyroblasts, and the peak metamorphic assemblages(M2) are represented by garnet with the lowest XSps values and the lowest XFe# ratios and the matrix minerals(plagioclase + quartz ± Kfeldspar + biotite + muscovite + kyanite ± sillimanite), whereas the retrograde assemblages(M3) are composed of biotite + plagioclase + quartz symplectites rimming the garnet porphyroblasts. Thermobarometric computation shows that the metamorphic conditions are 562–714°C at 7.3–7.4 kbar for the M1 stage, 661–800°C at 9.4–11.6 kbar for the M2 stage, and 579–713°C at 5.5–6.6 kbar for the M3 stage. These rocks are deciphered to have undergone metamorphism characterized by clockwise P-T paths involving nearly isothermal decompression(ITD) segments, which is inferred to be related to the collision of the India and Eurasia plates. 相似文献