Density of hydrous carbonate melts under pressure, compressibility of volatiles and implications for carbonate melt mobility in the upper mantle

Ritter, Xenia; Sanchez-Valle, Carmen; Sator, Nicolas; Desmaele, Elsa; Guignot, Nicolas; King, Andrew; Kupenko, Ilya; Berndt, Jasper; Guillot, B.

doi:10.1016/j.epsl.2019.116043

Cited by 13 publications

(12 citation statements)

References 47 publications

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“…( B ) Density as a function of pressure for dolomite melt obtained from experiments and FPMD simulations in this study, and comparison with previous studies. Blue asterisk-neutral point, blue upward-pointing triangle-flotation point, blue solid line-EOS fitting based on experimental data at 1773 K, blue dotted line-EOS fitting at 2000 K, red circle-density data obtained by LDA, red square-density data obtained by GGA, red dashed line-EOS fitting at 2000 K for LDA, red dash-dot line-EOS fitting at 2000 K for GGA, green diamond-classical MD simulations data at 2073 K from Desmaele et al ( 23 ), dark green diamond-GGA simulation data at 1773 K from Desmaele et al ( 23 ), cyan cross-classical MD simulations data at 1100 K from Hurt ( 26 ), black star-density data of hydrous dolomite melt (with 10 wt% H 2 O) at 1474–1681 K from Ritter et al ( 35 ) measured by X-ray absorption method, gray dashed line-density of carbonated basaltic melt (with 5.0 wt% CO 2 ) from sink-float experimental results by Ghosh S. et al ( 36 ), gray dash-dot line-density of carbonated MgSiO 3 melt (with 5.2 wt% CO 2 ) from FPMD results by Ghosh D.B. et al ( 37 ).…”

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confidence: 99%

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High-pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle

Jing

Bajgain

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Deeply subducted carbonates likely cause low-degree melting of the upper mantle and thus play an important role in the deep carbon cycle. However, direct seismic detection of carbonate-induced partial melts in the Earth’s interior is hindered by our poor knowledge on the elastic properties of carbonate melts. Here we report the first experimentally determined sound velocity and density data on dolomite melt up to 5.9 GPa and 2046 K by in-situ ultrasonic and sink-float techniques, respectively, as well as first-principles molecular dynamics simulations of dolomite melt up to 16 GPa and 3000 K. Using our new elasticity data, the calculated VP/VS ratio of the deep upper mantle (∼180–330 km) with a small amount of carbonate-rich melt provides a natural explanation for the elevated VP/VS ratio of the upper mantle from global seismic observations, supporting the pervasive presence of a low-degree carbonate-rich partial melt (∼0.05%) that is consistent with the volatile-induced or redox-regulated initial melting in the upper mantle as argued by petrologic studies. This carbonate-rich partial melt region implies a global average carbon (C) concentration of 80–140 ppm. by weight in the deep upper mantle source region, consistent with the mantle carbon content determined from geochemical studies.

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“… 48 , 49 . Comparisons with other simulation results for dolomite melt ( 23 , 26 ), density results for hydrous dolomite melt ( 35 ) and carbonated silicate melt ( 36 , 37 ) are given in SI Appendix , Text S4 . Similarly, both LDA and GGA simulations give similar pressure dependences of sound velocity.…”

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confidence: 99%

High-pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle

Jing

Bajgain

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…The seminal observation here is that the window in which negatively buoyant hydrous melts can occur on top of 410 km is both narrow in pressure (confined to at most 3 GPa, or ∼90 km above the 410 km discontinuity: Figure 4e), and narrow in compositional space (with at most a few percent water). Carbon may well play a role in these liquids; but, because of the low densities of compressed hydrous carbonatites (Ritter et al., 2020), the carbon content of liquids is also likely to be limited by the dynamic requirement of neutral or negative buoyancy. Hence, our net interpretation is that hydrous melts (within fairly strict limits) can stably exist above 410 km depth: but, should they partially crystallize, or be progressively enriched in water by ongoing subduction, they will likely buoyantly escape.…”

Section: Hydrous Silicate Melt Densities and Their Implications For M...mentioning

confidence: 99%

Thermoelasticity of Water in Silicate Melts: Implications for Melt Buoyancy in Earth's Mantle

Zeff

Williams

2021

JGR Solid Earth

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A comprehensive analysis of experimental data and theoretical simulations on the partial molar volume of water in silicate melt indicates that finite strain theory successfully describes the compression of the H2O component dissolved in silicate melt at high pressures and temperatures. However, because of the high compressibility of the water component, a fourth order equation of state fit is required to accurately simulate experimental results on water's volume in silicate melts at a deep upper mantle, transition zone, and lower mantle pressures. Data from previous shock compression experiments on hydrous minerals in which melting occurs along the Hugoniot are used to provide an experimental constraint on the partial molar volume of water in silicate melt at deep mantle temperatures and pressures. The equation of state of the water component indicates that, depending on elastic averaging technique, the amount of water that could be present in neutrally or negatively buoyant mafic/ultramafic melts above the 410 km seismic discontinuity is upper‐bounded at 5.6 wt%: smaller than previously inferred, and consistent with melt being confined to a narrow depth range above the 410 km discontinuity. If melt is predominantly distributed along grain boundaries in low aspect ratio films, extents of melting as low as 2% could produce observed seismic velocity reductions. The ability of the lowermost mantle to contain negatively buoyant hydrous liquids hinges on the trade‐off between iron content and hydration: at these depths, substantially higher degrees of hydration could be present within partial melts.

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“…Water can be a major constituent of carbonatite magmas: 10 wt.% H 2 O is soluble at 1 kbar and even more at higher pressures (Keppler, 2003). Such hydrous carbonatitic fluids are very buoyant relative to ambient mantle (Ritter et al., 2020). Decarbonation reactions between ascending carbonatite magmas and silica‐rich wall rocks produce CO 2 when they reach 100‐80 km depth (Wyllie & Huang, 1975).…”

Section: Introductionmentioning

confidence: 99%

Thallium Isotopes Reveal Brine Activity During Carbonatite Magmatism

Horton

Nielsen

Shu

et al. 2021

Geochem Geophys Geosyst

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Carbonatite and carbonated silicate melts are thought to be widespread in oxidized regions of Earth's upper mantle (Dasgupta, 2013; Hammouda & Keshav, 2015), yet constitute only a minor fraction of the magmas that reach Earth's surface. Because volcanologists have witnessed active eruptions from only one carbonatite volcano-Ol Doinyo Lengai in Tanzania (Dawson et al., 1990)-our understanding of carbonatite volcanism is largely based on geological observations and experimental constraints. The latter are challenging to obtain because carbonatitic magmas and fluids that exsolve from them are difficult to quench in laboratory settings (e.g., Veksler & Keppler, 2000). Carbonatitic magmas can form by low-degree partial melting of carbonated mantle or by exsolution from, and immiscibility with, alkaline silicate magmas (Gittins, 1988; Hamilton et al., 1979; Wyllie, 1989). Water can be a major constituent of carbonatite magmas: 10 wt.% H 2 O is soluble at 1 kbar and even more at higher pressures (Keppler, 2003). Such hydrous carbonatitic fluids are very buoyant relative to ambient mantle (Ritter et al., 2020). Decarbonation reactions between ascending carbonatite magmas and silica-rich wall rocks produce CO 2 when they reach 100-80 km depth (Wyllie &

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Density of hydrous carbonate melts under pressure, compressibility of volatiles and implications for carbonate melt mobility in the upper mantle

Cited by 13 publications

References 47 publications

High-pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle

High-pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle

Thermoelasticity of Water in Silicate Melts: Implications for Melt Buoyancy in Earth's Mantle

Thallium Isotopes Reveal Brine Activity During Carbonatite Magmatism

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