Structure of H2O-saturated peralkaline aluminosilicate melt and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to 800°C and ∼800MPa

Mysen, Bjørn O.

doi:10.1016/j.gca.2010.04.024

Cited by 44 publications

(37 citation statements)

References 94 publications

(152 reference statements)

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“…It follows, therefore, that for fluids in equilibrium with quartz in the system SiO 2 -NaOH-H 2 O, the silicate polymerization with Q 0 and Q 1 species is similar to that in SiO 2 -H 2 O fluid spectra at higher pressures (Mysen et al 2013). It also resembles the aqueous fluids in the equilibrium with alkali aluminosilicate melt under similar temperature and pressure conditions (Mysen 2010). …”

Section: Resultsmentioning

confidence: 65%

“…Pressure could not, therefore, be calculated from the PVT data of pure H 2 O. Furthermore, silicate components dissolved in the fluid also affect the equation of state of H 2 O (Mysen 2010). Instead, the pressure was measured with the one-phonon Raman line from a chip of synthetic carbon-13 diamond placed inside the sample chamber.…”

Section: Methods/experimentalmentioning

confidence: 99%

“…Composition and structure of silicate-saturated aqueous fluids at high temperature and pressure have been determined experimentally for pure SiO 2 -H 2 O systems as well as for some more complex silicate and aluminosilicate compositions (Newton and Manning 2002;Kessel et al 2005;Mibe et al 2008Mibe et al , 2011Mysen 2010). From those experiments, it is evident that silicate solubility in aqueous fluids depends on the presence of other components in addition to SiO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Mysen

2018

Prog Earth Planet Sci

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Aqueous fluids in the Earth's interior are multicomponent systems with silicate solubility and solution mechanisms strongly dependent on other dissolved components. Here, solution mechanisms that describe the interaction between dissolved silicate and other solutes were determined experimentally to 825°C and above 1 GPa with in situ vibrational spectroscopy of aqueous fluid while these were at high temperature and pressure. The silicate content in Na-bearing, silicate-saturated aqueous fluid exceeds that in pure SiO 2 at high temperature and pressure. Silicate species were of Q 0 (isolated SiO 4 tetrahedra) and Q 1 (dimers, Si 2 O 7 ) type. The temperature dependence of its equilibrium constant, K = X Q1 /(X Qo ) 2 , yields enthalpies of 22 ± 12 and 51 ± 17 kJ/mol for the SiO 2 -H 2 O and Na-bearing fluids. In contrast, in Ca-bearing fluids, the solubility is more than an order of magnitude lower, and only Q 0 species are present. The present data together with other published experimental information lead to the conclusion that the silicate solubility in aqueous fluids in equilibrium with mafic rocks such as amphibolite and peridotite is an order of magnitude lower than the solubility in fluids in equilibrium with felsic rocks such as andesite and rhyolite compositions (felsic gneiss) under similar temperature and pressure conditions. The silicate speciation also is more polymerized in the felsic systems. This difference is also why second critical end-points in the Earth are at lower temperature and pressure in felsic compared with mafic systems. Alkali-rich fluids formed by dehydration of felsic rocks also show enhanced high field strength element (HFSE) solubility because alkalis in such solution form oxy complexes with the HFSE cations. Fluids formed by dehydration of felsic rocks in the Earth's interior are, therefore, more efficient transport agents of silicate materials than fluids formed by dehydration of mafic and ultramafic rocks, whether for major, minor, or trace elements.

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Section: Resultsmentioning

confidence: 65%

Section: Methods/experimentalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Mysen

2018

Prog Earth Planet Sci

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“…Equivalent OH/H 2 O for melt were not obtained for reasons discussed above. However, the overall degree of silicate polymerization as a function of water fugacity, using the NA10-H 2 O data from Mysen (2010) for calibration, results in an equivalent f H2O quite similar to that of pure H 2 O (Fig. 12b).…”

Section: Discussionmentioning

confidence: 89%

“…3). This is less than the proportion of OH groups in pure silicate-H 2 O systems at similar temperatures and pressures, where this proportion often exceeds 10% (Mysen 2010). In fact, by using the relationship between proportion of OH in fluid, expressed as A 4500 /(A 4500 + A 5200 ) from the FTIR data, and fugacity of H 2 O for the same silicate composition and pure H 2 O (Mysen 2010) (see Fig.…”

Section: Discussionmentioning

confidence: 99%

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

Mysen

2018

Prog Earth Planet Sci

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Understanding what governs the speciation in the C-O-H-N system aids our knowledge of how volatiles affect mass transfer processes in the Earth's interior. Experiments with aluminosilicate melt + C-O-H-N volatiles were, therefore, carried out with Raman and infrared spectroscopy to 800°C and near 700 MPa in situ in hydrothermal diamond anvil cells. The measurements were conducted in situ with the samples at the desired temperatures and pressures in order to avoid possible structural and compositional changes resulting from quenching to ambient conditions prior to analysis. Experiments were conducted without any reducing agent and with volatiles added as H 2 O, CO 2 , and N 2 because both carbon and nitrogen can occur in different oxidation states. Volatiles dissolved in melt comprise H 2 O, CO 3 2-, HCO 3 -, and molecular N 2 , whereas in the coexisting fluid, the species are H 2 O, CO 2 , CO 3 2-, and N 2 . The HCO 3 -/CO 3 2-equilibrium in melts shift toward CO 3 2-groups with increasing temperature with ΔH = 114 ± 22 kJ/mol. In fluids, the CO 2 abundance is essentially invariant with temperature and pressure. For fluid/melt partitioning, those of H 2 O and N 2 are greater than 1 with temperature-dependence that yields ΔH values of − 6.5 ± 1.5 and − 19.6 ± 3.7 kJ/mol, respectively. Carbonate groups, CO 3 2-are favored by melt over fluid. Where redox conditions in the Earth's interior exceed that near the QFM oxygen buffer (between NNO and MW buffers), N 2 is the stable nitrogen species and as such acts as a diluent of both fluids and melts. For fluids, this lower silicate solubility, in turn, enhances alkalinity. This means that in such environments, the transport of components such as high field strength cations, will be enhanced. Effects of dissolved N 2 on melt structure are considerably less than on fluid structure.

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Structure and equilibria among silicate species in aqueous fluids in the upper mantle: Experimental SiO₂–H₂O and MgO–SiO₂–H₂O data recorded in situ to 900°C and 5.4 GPa

et al. 2013

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[1] Experiments to determine silicate structural species in silicate-saturated aqueous fluids in equilibrium with silica polymorphs (quartz and coesite), enstatite, and enstatite + forsterite in the SiO 2 -H 2 O and MgO-SiO 2 -H 2 O systems have been carried out in situ in the 0.4-5.4 GPa and 700-900°C pressure and temperature ranges, respectively. MicroRaman spectroscopy was the structural probe. In the SiO 2 -H 2 O system (1.6-5. ). The expression 2Q 1 ⇌ Q 0 + Q 2 describes the equilibrium among these species with ΔH and ΔV values from the isochoric temperature and isothermal pressure dependence of its equilibrium constant,, range from À23 to À69 kJ/mol and À1 to À2 cm 3 /mol, respectively. In the system MgO-SiO 2 -H 2 O the calculated silica solubility, using literature algorithms, is approximately 50% of that in the SiO 2 -H 2 O system at similar temperature and pressure. Only Q 1 and Q 0 species were detected in the MgO-SiO 2 -H 2 O fluids, whether in equilibrium with enstatite + forsterite (P < 3 GPa) or enstatite only (P > 3 GPa). The temperature and pressure dependence of the equilibrium constant, K = X Q1 /X Q0 , for this system yields average values of ΔH = 40 ± 5 kJ/mol and ΔV = À2.3 ± 0.4 cm 3 /mol. The speciation of silicate in aqueous fluids resembles that in hydrous melts as a function of temperature and pressure at deep crustal and upper mantle temperature and pressure conditions, and they become increasingly similar with depth. As the silicate speciation and solubility in the aqueous fluid depend on silicate composition, the pressure and temperature at which complete miscibility occurs will also vary with silicate composition. The structural similarity between fluids and melts will also lead to fluid/melt element partition coefficients trending toward 1 and mineral/fluid partition coefficients trending toward mineral/melt values in the upper mantle as the silicate-H 2 O systems approach complete miscibility with increasing temperature and pressure.

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Structure of H2O-saturated peralkaline aluminosilicate melt and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to 800°C and ∼800MPa

Cited by 44 publications

References 94 publications

Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

Structure and equilibria among silicate species in aqueous fluids in the upper mantle: Experimental SiO₂–H₂O and MgO–SiO₂–H₂O data recorded in situ to 900°C and 5.4 GPa

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Structure of H2O-saturated peralkaline aluminosilicate melt and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to 800°C and ∼800MPa

Cited by 44 publications

References 94 publications

Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

Structure and equilibria among silicate species in aqueous fluids in the upper mantle: Experimental SiO2–H2O and MgO–SiO2–H2O data recorded in situ to 900°C and 5.4 GPa

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Structure and equilibria among silicate species in aqueous fluids in the upper mantle: Experimental SiO₂–H₂O and MgO–SiO₂–H₂O data recorded in situ to 900°C and 5.4 GPa