Fluid inclusion geobarometry: Pressure corrections for immiscible H2O–CH4 and H2O–CO2 fluids

Hurai, Vratislav

doi:10.1016/j.chemgeo.2010.09.014

Cited by 21 publications

(5 citation statements)

References 57 publications

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“…A further notable prediction of the thermodynamic model is that at temperatures below 350-400 Ccorresponding to the stability field of pyrophyllite (Figure 10)-the residual fluid separates into two immiscible fluids: one fluid (F1) is nearly H 2 O pure (approximately 94 mol%) and the other (F2) is a CO 2bearing and is highly enriched in N 2 (up to 60 mol%) (Figure 10c and Table 3). This temperature range corresponds with the extended immiscibility field of the H 2 O-CO 2 system for a wide P-TX range (Diamond, 2001;Hurai, 2010). An immiscible H 2 O-rich fluid phase in the inclusion would further enhance both H 2 O-loss from the MFI and sheet silicate producing reactions due to the increased activity of water.…”

Section: Timing Of Mfi Crystallizationmentioning

confidence: 86%

“…The presence of a low-viscosity subduction channel, active between ca. 395 and 365 Ma, and fast exhumation of HP units with a rate comparable to plate motions has been inferred for the serpentinite-matrix mélange rocks, which occur in the lowest structural position of the COC ( Ábalos et al, 2003, 2010Novo-Fern andez et al, 2016).…”

Section: Geological Backgroundmentioning

confidence: 89%

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Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Spránitz

Padrón‐Navarta

Szabó

et al. 2022

Journal Metamorphic Geology

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Primary multiphase fluid inclusions (MFI) were studied in one eclogite and two granulites from the Cabo Ortegal Complex (COC, NW Spain) by means of Raman imaging, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM‐EDS) and Focused Ion Beam ‐ Scanning Electron Microscopy (FIB)‐SEM. Complementary, secondary MFI in pyroxenites from COC were also investigated. MFI hosted in eclogite and granulites occur along growth zones or in 3D clusters in garnet porphyroblasts suggesting a primary origin at high‐pressure (HP) metamorphic conditions. The mineral assemblage of MFI is mainly composed of Fe‐Mg‐Ca‐carbonates and phyllosilicates ± graphite ± quartz ± corundum ± pyrite ± apatite ± rutile and a fluid phase composed of nitrogen ± methane ± carbon‐dioxide. The mineral proportions vary among the lithologies. Dominant carbonates and hydrous silicates are interpreted as step‐daughter minerals (crystals formed in the MFI after entrapment as a result of fluid–host interaction), whereas apatite, quartz and rutile are considered in part as accidentally trapped minerals since they also occur as crystal inclusions together with MFI in each rock type. Quartz and corundum occur together in MFI in ultramafic granulite and are regarded as step‐daughter minerals in this lithology. These observations suggest that the MFI are products of post‐entrapment reactions of a homogeneous COHN fluid system with the host mineral. Thermodynamic calculations in the CaFMAS‐COHN system confirmed that bulk composition of the MFI in eclogite is similar to the host garnet+COHN composition except for a potential lost of H2O. Carbonation and hydration reaction between the host (i.e. garnet or pyroxene) and the fluid inclusion results in the consumption of all CO2 and part of the H2O from the fluid phase producing Ca‐Fe‐Mg‐carbonates and hydrous step‐daughter minerals, mostly pyrophyllite and chlorite. Nitrogen content of the originally trapped COHN fluid in eclogite was estimated to have a maximum value of 10 mol% at peak HP conditions and 30–40 mol% at retrograde conditions that is within the range of the observed MFI in the residual fluid (13–68 mol%). Pseudosection modelling confirmed the stability of the phase assemblage in the MFI in a specific low‐pressure, low‐temperature stability field (between 300°C and 400°C at pressures < 1 GPa), caused by H2O‐ and CO2‐consuming reactions possibly in a single step. Our findings indicate that such processes in the exhuming HP units may play a role in global nitrogen and carbon cycling as well as potentially contributing to nitrogen and methane supply to subsurface–surface environments during devolatilization in the forearc regions of convergent plate margins.

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Section: Timing Of Mfi Crystallizationmentioning

confidence: 86%

Section: Geological Backgroundmentioning

confidence: 89%

Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Spránitz

Padrón‐Navarta

Szabó

et al. 2022

Journal Metamorphic Geology

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“…For example, at 1150°C for ρ 𝐶𝑂 2 =0.8 g/cm 3 , the relatively simple empirical expression of Sterner and Pitzer (1994) gives 5.008 kbar, while the more complex thermodynamic model of Span and Wanger (1996) gives 4.956 kbar (~3% difference). However, the conversion between measured CO 2 density to depth is substantially less simple when trapped fluids contain other species, such as H 2 O or SO 2 (Hansteen and Klugel, 2008;Hurai, 2010). It is difficult to estimate the initial molar ratios of each species, and EOS for these mixed fluids are poorly constrained, if parameterized at all.…”

Section: Assessing and Comparing Modelsmentioning

confidence: 99%

Determining the Pressure – Temperature – Composition (P-T-X) conditions of magma storage

Wieser,

Gleeson,

Matthews

et al. 2024

Preprint

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Determining the pressures and temperatures at which melts are stored in the crust and upper mantle, and the major element composition, redox state and volatile contents of these melts, is vital to constrain the structure and dynamics of magmatic plumbing systems. In turn, constraining these parameters helps understand the geochemical and structural evolution of the Earth’s lithosphere, and periods of unrest at active volcanoes. We review common thermobarometers, hygrometers and chemometers based on mineral and/or liquid compositions, before discussing recent advances in melt and fluid inclusion barometry, Raman-based elastic thermobarometry, and thermodynamic modelling methods. Where possible, we investigate the accuracy and precision of each technique, and the implications for the application of each method to different research questions.

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“…The coexistence of LV-, VL-and V-type inclusions along the same healed microfractures (Figure 8) provides strong evidence that the fluids were entrapped under immiscible conditions at or below the CH 4 -H 2 O solvus. In fact, secondary inclusions in quartz have the following characteristics of heterogeneously trapped inclusions: (1) variable phase ratios at room temperature, ranging from gas-dominated to water-dominated compositions and (2) the gas-dominated inclusions homogenize towards the vapor-phase, and the water-dominated inclusions homogenize to liquid phase [54,55].…”

Section: Discussionmentioning

confidence: 99%

Fenitization at the Lovozero Alkaline Massif, NW Russia: Composition and Evolution of Fluids

Mokrushina,

Mikhailova,

Pakhomovsky

2023

Geosciences

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The 360–370 Ma old Lovozero massif (NW Russia) is a layered nepheline syenitic-foidolitic pluton. Despite its huge size (650 km2), the massif is surrounded by a narrow fenite aureole, and the most intensive fenitization is associated with pegmatites and hydrothermal veins that have intruded into the wall rocks. We studied petrography, petrochemistry, mineralogy and fluid inclusions along a profile crossing the direct contact of the Lovozero massif with country Archean gneiss. We found that the fluid responsible for fenitization was a heterogeneous mixture of two coexisting phases, an aqueous fluid with salinity 8.6–15.1 eq. wt.% NaCl and a methane fluid. The coexistence of these two fluids indicates immiscibility conditions at (or below) CH4–H2O solvus. The aqueous fluid affected both the endocontact alkaline rocks and country gneiss. In the endocontact, intense autometasomatic alterations of the early crystallized minerals occurred, for example, the natrolitization of nepheline and sodalite. Besides, the aqueous fluid transported Na2O, K2O, as well as P2O5, TiO2, H2O, F, Cl and S into the exocontact. These components were precipitated in the immediate vicinity of the massif contact, and the salinity of the aqueous fluid decreased to 0.53–3.06 eq. wt.% NaCl. We assume that there are two reasons for a narrow fenite aureole in the Lovozero massif: intense autometasomatic alterations and a decrease in the permeability of country rocks due to fluid immiscibility.

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Fluid inclusion geobarometry: Pressure corrections for immiscible H2O–CH4 and H2O–CO2 fluids

Cited by 21 publications

References 57 publications

Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Determining the Pressure – Temperature – Composition (P-T-X) conditions of magma storage

Fenitization at the Lovozero Alkaline Massif, NW Russia: Composition and Evolution of Fluids

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