The composition of liquids coexisting with dense hydrous magnesium silicates at 11–13.5GPa and the endpoints of the solidi in the MgO–SiO2–H2O system

Melekhova, Elena; Schmidt, Max W.; Ulmer, Peter; Pettke, Thomas

doi:10.1016/j.gca.2007.03.034

Cited by 36 publications

(27 citation statements)

References 42 publications

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“…12-13 GPa (Melekhova et al, 2007). Model fits to the data use the melt formulation of Silver and Stolper (1985), with r=1 and K=K(T) (see discussion in main text).…”

Section: Ex-situ Observationsmentioning

confidence: 99%

“…It should be noted that the periclase liquidus field 375 and periclase-forsterite cotectic are poorly constrained by the data. The low temperature extension of the cotectic is chosen to fit the reported Mg:Si ratios of melts in equilibrium with forsterite and various DHMS phases at 13.5 GPa (Melekhova et al, 2007). Previous work on hydrous phase stability and Mg:Si ratios for cotectic melts are also included (Melekhova et al, 2007).…”

Section: The Mgo-siomentioning

confidence: 99%

“…The low temperature extension of the cotectic is chosen to fit the reported Mg:Si ratios of melts in equilibrium with forsterite and various DHMS phases at 13.5 GPa (Melekhova et al, 2007). Previous work on hydrous phase stability and Mg:Si ratios for cotectic melts are also included (Melekhova et al, 2007). Our melt model in the MSH system serves as a useful tool for investigating melting at high pressures in the mantle.…”

Section: The Mgo-siomentioning

confidence: 99%

“…The original H 2 O contents of the partial hydrous melts are normally estimated by mass balance and/or by deficits in microprobe totals (e.g. Ohtani et al, 2000;Demouchy et al, 2005;Litasov et al, 2011;Melekhova et al, 2007). Mass balance alone depends on being able to accurately estimate the volume proportions of solid phases and quench phases, recognise 50 and subtract quench overgrowths where they exist, and calculate the effective ambient-pressure density of the melt.…”

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confidence: 99%

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Hydrous melting and partitioning in and above the mantle transition zone: Insights from water-rich MgO–SiO2–H2O experiments

Myhill

Frost

Novella

2017

Geochimica et Cosmochimica Acta

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Abstract Hydrous melting at high pressures affects the physical properties, dynamics and chemical differentiation of the Earth. However, probing the compositions of hydrous melts at the conditions of the mantle transition zone has traditionally been challenging. In this study, we conducted high pressure multianvil experiments at 13 GPa between 1200 and 1900 • C to investigate the liquidus in the system MgO-SiO 2 -H 2 O. Water-rich starting compositions were created using platinic acid (H 2 Pt(OH) 6 ) as a novel water source. As MgO:SiO 2 ratios decrease, the T-X H2O liquidus curve develops an increasingly pronounced concave-up topology. The melting point reduction of enstatite and stishovite at low water contents exceeds that predicted by simple ideal models of hydrogen speciation. We discuss the implications of this work on the behaviour of melts in the deep upper mantle and transition zone, and present new models describing the partitioning of water between the olivine polymorphs and associated hydrous melts.

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“…12-13 GPa (Melekhova et al, 2007). Model fits to the data use the melt formulation of Silver and Stolper (1985), with r=1 and K=K(T) (see discussion in main text).…”

Section: Ex-situ Observationsmentioning

confidence: 99%

Section: The Mgo-siomentioning

confidence: 99%

Section: The Mgo-siomentioning

confidence: 99%

mentioning

confidence: 99%

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Hydrous melting and partitioning in and above the mantle transition zone: Insights from water-rich MgO–SiO2–H2O experiments

Myhill

Frost

Novella

2017

Geochimica et Cosmochimica Acta

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“…Such features, when they come into play, influence melting phase relations and chemical transport/fractionation, irrespective of particular tectonic settings. However, the lack of knowledge in the relevant phase equilibria appears to be particularly grim in rock types consisting of hydrous, carbonated mantle peridotite and harzburgite (although see Falloon and Green [1990], Gudfinnsson et al [2008], Keshav and Gudfinnsson [2009], and Mibe et al [2009]), especially given the fact that there continue to be considerable disagreements as to where supercritical (second critical end‐points or singularities) features develop in the system MgO‐SiO 2 ‐H 2 O [ Luth , 1993; Melekhova et al , 2007; Mibe et al , 2007]. Hence given these fundamental uncertainties in the influence of water (with or without CO 2 ) on melting phase relations, the suggestion that water gets expelled (or nearly so) from the rocks during subduction, while carbonate escapes melting‐related events and thereby undergoes subduction to great depths in the Earth [ Dasgupta and Hirschmann , 2004], requires some attention.…”

Section: A Note On the Survival Of Carbonate To Moderately Great Deptmentioning

confidence: 99%

Experimentally dictated stability of carbonated oceanic crust to moderately great depths in the Earth: Results from the solidus determination in the system CaO‐MgO‐Al₂O₃‐SiO₂‐CO₂

Keshav¹,

Guðfinnsson²

2010

J. Geophys. Res.

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[1] Solidus melting phase relations are reported for carbonated eclogite in the system CaO-MgO-Al 2 O 3 -SiO 2 -CO 2 at 12 to 25 GPa. From 12 to 16 GPa, melts are in equilibrium with clinopyroxene, stishovite, garnet, aragonite, and magnesite. At 20 and 25 GPa, melts are in equilibrium with garnet, stishovite, calcium-alumino silicate, calcium perovskite, and magnesite. Melting reactions demonstrate that from 12 to 16 GPa, stishovite is in reaction with the melt. At 20 and 25 GPa, garnet and stishovite together are produced upon melting of model, carbonated eclogite. At 20 and 25 GPa, calcium perovskite is also the phase that contributes the most toward liquid production. Melt compositions at all pressures are carbonatitic, with roughly 37-40 wt% dissolved CO 2 . From 12 to 16 GPa, the liquids are calciocarbonatites with Ca# molar of ∼69-71; liquid compositions become less calcic with Ca# of ∼52-55 at 20 and 25 GPa. Given these melting phase relations, suitable subduction zone adiabats do not intersect the solidus of model carbonated eclogite at depths investigated in the present study. Hence, on this basis, it is fair to say that carbonated eclogite possibly avoids melting in subduction zone settings, thereby delivering carbonate to at least moderate depths in the Earth. However, owing to local heating events, small-degree melting of carbonated eclogite is not completely precluded, and the liquids liberated from this melting can be viewed as agents of chemical mass transfer in the deep Earth. At present, however, geochemical consequences of subduction-related melting of carbonated eclogite are difficult to evaluate.Citation: Keshav, S., and G. H. Gudfinnsson (2010), Experimentally dictated stability of carbonated oceanic crust to moderately great depths in the Earth: Results from the solidus determination in the system CaO-MgO-Al 2 O 3 -SiO 2 -CO 2 ,

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The homogeneous mixing of MgO and H₂O at extreme conditions

Kovačević

González‐Cataldo

Militzer

2023

Contrib. Plasma Phys

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Investigating water worlds presents a unique opportunity to understand the fundamental processes of planetary formation and evolution. One key aspect is characterizing the interactions between water and rock under the pressures and temperatures present within these worlds. Investigating the conditions for the homogeneous mixing of these materials is imperative to characterizing bulk properties and evolution of water‐rich exoplanets. Here we use density functional molecular dynamics simulations to study MgO‐H2O mixtures at high pressure–temperature conditions where H2O occurs in solid, superionic, or liquid form. MgO, the representative rocky material, can be either solid or liquid. We start from 500 K at 120 GPa, increasing the temperature step by step up to 8000 K. By inspection, we determine the temperature at which MgO‐HO homogeneously mix in our simulations. At 6000 K and 174 GPa is when we find the system to homogeneously mix. This heat‐until‐it‐mixes approach provides us with an upper bound on the temperature for the mixing of MgO and H2O. We find that homogeneous mixing occurs at sufficiently low temperatures to be relevant for the collisional growth of a water‐rich planet.

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The composition of liquids coexisting with dense hydrous magnesium silicates at 11–13.5GPa and the endpoints of the solidi in the MgO–SiO2–H2O system

Cited by 36 publications

References 42 publications

Hydrous melting and partitioning in and above the mantle transition zone: Insights from water-rich MgO–SiO2–H2O experiments

Hydrous melting and partitioning in and above the mantle transition zone: Insights from water-rich MgO–SiO2–H2O experiments

Experimentally dictated stability of carbonated oceanic crust to moderately great depths in the Earth: Results from the solidus determination in the system CaO‐MgO‐Al₂O₃‐SiO₂‐CO₂

The homogeneous mixing of MgO and H₂O at extreme conditions

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The composition of liquids coexisting with dense hydrous magnesium silicates at 11–13.5GPa and the endpoints of the solidi in the MgO–SiO2–H2O system

Cited by 36 publications

References 42 publications

Hydrous melting and partitioning in and above the mantle transition zone: Insights from water-rich MgO–SiO2–H2O experiments

Hydrous melting and partitioning in and above the mantle transition zone: Insights from water-rich MgO–SiO2–H2O experiments

Experimentally dictated stability of carbonated oceanic crust to moderately great depths in the Earth: Results from the solidus determination in the system CaO‐MgO‐Al2O3‐SiO2‐CO2

The homogeneous mixing of MgO and H2O at extreme conditions

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Experimentally dictated stability of carbonated oceanic crust to moderately great depths in the Earth: Results from the solidus determination in the system CaO‐MgO‐Al₂O₃‐SiO₂‐CO₂

The homogeneous mixing of MgO and H₂O at extreme conditions