Experimentally determined Si isotope fractionation between silicate and Fe metal and implications for Earth's core formation

Shahar, Anat; Ziegler, K.; Young, Edward; Ricolleau, A.; Schauble, E. A.; Fei, Yingwei

doi:10.1016/j.epsl.2009.09.025

Cited by 120 publications

(119 citation statements)

References 27 publications

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“…Oxygen fugacity can be controlled by surrounding sample materials with buffer materials. In order to study Si isotope fractionation between metal and silicate, piston-cylinder experiments were run between 0.54 and 1 GPa pressure and in a temperature range between 1450 and 1800°C by Shahar et al (2009Shahar et al ( , 2011 and Hin et al (2014). The latter study used a rotating piston-cylinder apparatus (Schmidt et al, 2006) that enabled improved density separation of metal and silicate phases.…”

Section: High-pressure Experimental Methodsmentioning

confidence: 99%

“…Georg et al, 2007;Shahar et al, 2009Shahar et al, , 2011Ziegler et al, 2010;Kempl et al, 2013a;Hin et al, 2014), driven by the different chemical bonding environment of Si in silicate rocks versus metallic liquid Georg et al, 2007). If Si isotope fractionation between metal and silicate is an equilibrium process, the heavier isotopes fractionate preferentially into the stiffer bonded phase, in this case the silicate.…”

Section: The Role Of Si Stable Isotopesmentioning

confidence: 99%

“…Shahar et al (2011) The isotope fractionation between metal and silicate, 30 Si sil-met , is reported and summarised in Table 2. The silicatemetal isotope fractionation of this data collection varies from 0.05‰ (± 0.02‰; 1 SE ) for a 1-minute piston-cylinder experiment by Shahar et al (2009) at 1800°C and 1 GPa up to 5.69‰ (± 0.10‰; 1 SE ) and 5.21‰ (± 0.10‰; 1 SE ) in the natural samples of Ziegler et al (2010) equilibrated in solid state over a couple of thousand years between ß850 and ß930°C. The analytical uncertainty in Table 2 is reported in terms of standard deviation or standard error, following the reporting in the individual studies.…”

Section: Literature Datamentioning

confidence: 99%

“…Shahar et al (2009Shahar et al ( , 2011 used experiments containing iron metal with 9 wt% Si and an oxide mixture simulating a BSE composition. The metal phase in their run products typically contained ß8 wt% Si (Shahar et al, 2009). The silicate run product was partially molten, containing both solid olivine grains and quenched melt (Shahar et al, 2011).…”

Section: Starting Materials and Compositionsmentioning

confidence: 99%

“…Experimental studies on Si isotope fractionation between metal and silicate were carried out by Shahar et al (2009Shahar et al ( , 2011 at pressures of 1 and 7 GPa, and temperatures between 1800 and 2200°C. Kempl et al (2013a) did experiments at 9 GPa and ß2150°C.…”

Section: The Role Of Hpt Experimentsmentioning

confidence: 99%

See 4 more Smart Citations

Silicon stable isotope fractionation between metal and silicate at high-pressure, high-temperature conditions as a tracer of planetary core formation

Kempl

Vroon

Wagt

et al. 2016

Netherlands Journal of Geosciences

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The largest differentiation event in Earth and other terrestrial planets was the high-pressure, high-temperature process of metal core segregation from a silicate mantle. The abundant element silicon (Si) can be partially sequestered into the metallic core during metal-silicate differentiation, depending on pressure, temperature and planetary oxidation state. Knowledge of the Si content of a planet's core can constrain the conditions of core formation, but in the absence of direct samples from planetary cores, quantifying core Si content is challenging. One relatively new tool to study core formation in terrestrial planets is based on combining measurements of the Si stable isotopic composition of planetary crust and mantle samples with measurements of the Si stable isotope fractionation between metal and silicate at high-temperature and high-pressure conditions. In this study we present the results of a small set of high-pressure, high-temperature (HPT) experiments and combine these with a review of literature data to investigate how the Si isotope fractionation behaviour between metal and silicate varies as a function specifically of experimental run time and temperature. We show that although there is no debate about the sign of fractionation, absolute values for Si isotope fractionation between metal and silicate are difficult to constrain because the experimental database remains incomplete, and because Si isotopic measurements of metals in particular suffer from the absence of a true inter-laboratory comparison. We conclude that in order to derive accurate quantitative estimates of the Si content of the core of the Earth or other planets a wide range of additional experiments will be required.

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Section: High-pressure Experimental Methodsmentioning

confidence: 99%

Section: The Role Of Si Stable Isotopesmentioning

confidence: 99%

Section: Literature Datamentioning

confidence: 99%

Section: Starting Materials and Compositionsmentioning

confidence: 99%

Section: The Role Of Hpt Experimentsmentioning

confidence: 99%

See 3 more Smart Citations

Silicon stable isotope fractionation between metal and silicate at high-pressure, high-temperature conditions as a tracer of planetary core formation

Kempl

Vroon

Wagt

et al. 2016

Netherlands Journal of Geosciences

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Equations of state in the Fe‐FeSi system at high pressures and temperatures

et al. 2014

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Earth's core is an iron-rich alloy containing several weight percent of light element(s), possibly including silicon. Therefore, the high pressure-temperature equations of state of iron-silicon alloys can provide understanding of the properties of Earth's core. We performed X-ray diffraction experiments using laser-heated diamond anvil cells to achieve simultaneous high pressures and temperatures, up to~200 GPa for Fe-9 wt % Si alloy and~145 GPa for stoichiometric FeSi. We determined equations of state of the D0 3 , hcp + B2, and hcp phases of Fe-9Si, and the B20 and B2 phases of FeSi. We also calculated equations of state of Fe, Fe 11 Si, Fe 5 Si, Fe 3 Si, and FeSi using ab initio methods, finding that iron and silicon atoms have similar volumes at high pressures. By comparing our experimentally determined equations of state to the observed core density deficit, we find that the maximum amount of silicon in the outer core is~11 wt %, while the maximum amount in the inner core is 6-8 wt %, for a purely Fe-Si-Ni core. Bulk sound speeds predicted from our equations of state also match those of the inner and outer core for similar ranges of compositions. We find a compositional contrast between the inner and outer core of 3.5-5.6 wt % silicon, depending on the seismological model used. Theoretical and experimental equations of state agree at high pressures. We find a good match to the observed density, density profile, and sound speed of the Earth's core, suggesting that silicon is a viable candidate for the dominant light element.

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Compression of Fe–Si–H alloys to core pressures

Tagawa

Ohta

Hirose

et al. 2016

Geophysical Research Letters

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We examined the compression behavior of hexagonal‐close‐packed (hcp) (Fe0.88Si0.12)1H0.61 and (Fe0.88Si0.12)1H0.79 (in atomic ratio) alloys up to 138 GPa in a diamond anvil cell (DAC). While contradicting experimental results were previously reported on the compression curve of double‐hcp (dhcp) FeHx (x ≈ 1), our data show that the compressibility of hcp Fe0.88Si0.12Hx alloys is very similar to those of hcp Fe and Fe0.88Si0.12, indicating that the incorporation of hydrogen into iron does not change its compression behavior remarkably. The present experiments suggest that the inner core may contain up to 0.47 wt % hydrogen (FeH0.26) if temperature is 5000 K. The calculated density profile of Fe0.88Si0.12H0.17 alloy containing 0.32 wt % hydrogen in addition to geochemically required 6.5 wt % silicon matches the seismological observations of the outer core, supporting that hydrogen is an important core light element.

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Experimentally determined Si isotope fractionation between silicate and Fe metal and implications for Earth's core formation

Cited by 120 publications

References 27 publications

Silicon stable isotope fractionation between metal and silicate at high-pressure, high-temperature conditions as a tracer of planetary core formation

Silicon stable isotope fractionation between metal and silicate at high-pressure, high-temperature conditions as a tracer of planetary core formation

Equations of state in the Fe‐FeSi system at high pressures and temperatures

Compression of Fe–Si–H alloys to core pressures

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