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| Format: | Dataset Open Access |
| Language: | en |
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2013
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| Online Access: | https://doi.org/10.1594/PANGAEA.806342 |
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| _version_ | 1867171813045305344 |
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| author | Bennett, Neil R Brenan, James M |
| author_facet | Bennett, Neil R Brenan, James M |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | The solubility of Re and Au in haplobasaltic melt has been investigated at 1673–2573 K, 0.1 MPa–2 GPa and IW-1 to +2.5, in both carbon-saturated and carbon-free systems. Results extend the existing, low pressure and temperature, dataset to more accurately predict the results of metal-silicate equilibrium at the base of a terrestrial magma ocean. Solubilities in run-product glasses were measured by laser ablation ICP-MS, which allows for the explicit assessment of contamination by metal inclusions. The Re and Au content of demonstrably contaminant-free glasses increases with temperature, and shows variation with oxygen fugacity (fO2) similar to previous results, although lower valence states for Re (1+, 2+) are suggested by the data. At 2 GPa, and Delta IW of +1.75 to +2, the metal-silicate partition coefficient for Re (DMet/Sil) is defined by the relation LogD[met/sil][Re] = 0.50(±0.022)*10**4/T(K)+3.73(±0.095) For metal-silicate equilibrium to endow Earth's mantle with the observed time-integrated chondritic Re/Os, (and hence 187Os/188Os), DMet/Sil for both elements must converge to a common value. Combined with previously measured DMet/Sil for Os, the estimated temperature at which this convergence occurs is 4500 (±900) K. At this temperature, however, the Re and Os content of the equilibrated silicate is ~100-fold too low to explain mantle abundances. In the same experiments, much lower Dmet/sil values have been determined for Au, and require the metal-silicate equilibration temperature to be <3200 K, as hotter conditions result in an excess of Au in the mantle. Thus, the large disparity in partitioning between Re or Os, and Au at core-forming temperatures argues against their mantle concentrations set solely by metal-silicate equilibrium at the base of a terrestrial magma ocean. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_806342 |
| institution | PANGAEA |
| language | en |
| publishDate | 2013 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Summary of phase compositions of experimental silicate melt, un-normalised analyses Bennett, Neil R Brenan, James M Aluminium oxide; Aluminium oxide, standard deviation; Barium oxide; Barium oxide, standard deviation; Calcium oxide; Calcium oxide, standard deviation; Electron microprobe (EMP); Elements, total; Gold; Gold, standard deviation; Iron; Iron, standard deviation; Iron oxide, FeO; Iron oxide, FeO, standard deviation; Laser-ablation inductively coupled plasma mass spectrometer (LA-ICP-MS); Magnesium oxide; Magnesium oxide, standard deviation; Nickel; Nickel, standard deviation; Rhenium; Rhenium, standard deviation; Sample code/label; Silicon dioxide; Silicon dioxide, standard deviation; Sodium oxide; Sodium oxide, standard deviation The solubility of Re and Au in haplobasaltic melt has been investigated at 1673–2573 K, 0.1 MPa–2 GPa and IW-1 to +2.5, in both carbon-saturated and carbon-free systems. Results extend the existing, low pressure and temperature, dataset to more accurately predict the results of metal-silicate equilibrium at the base of a terrestrial magma ocean. Solubilities in run-product glasses were measured by laser ablation ICP-MS, which allows for the explicit assessment of contamination by metal inclusions. The Re and Au content of demonstrably contaminant-free glasses increases with temperature, and shows variation with oxygen fugacity (fO2) similar to previous results, although lower valence states for Re (1+, 2+) are suggested by the data. At 2 GPa, and Delta IW of +1.75 to +2, the metal-silicate partition coefficient for Re (DMet/Sil) is defined by the relation LogD[met/sil][Re] = 0.50(±0.022)*10**4/T(K)+3.73(±0.095) For metal-silicate equilibrium to endow Earth's mantle with the observed time-integrated chondritic Re/Os, (and hence 187Os/188Os), DMet/Sil for both elements must converge to a common value. Combined with previously measured DMet/Sil for Os, the estimated temperature at which this convergence occurs is 4500 (±900) K. At this temperature, however, the Re and Os content of the equilibrated silicate is ~100-fold too low to explain mantle abundances. In the same experiments, much lower Dmet/sil values have been determined for Au, and require the metal-silicate equilibration temperature to be <3200 K, as hotter conditions result in an excess of Au in the mantle. Thus, the large disparity in partitioning between Re or Os, and Au at core-forming temperatures argues against their mantle concentrations set solely by metal-silicate equilibrium at the base of a terrestrial magma ocean. |
| title | Summary of phase compositions of experimental silicate melt, un-normalised analyses |
| topic | Aluminium oxide; Aluminium oxide, standard deviation; Barium oxide; Barium oxide, standard deviation; Calcium oxide; Calcium oxide, standard deviation; Electron microprobe (EMP); Elements, total; Gold; Gold, standard deviation; Iron; Iron, standard deviation; Iron oxide, FeO; Iron oxide, FeO, standard deviation; Laser-ablation inductively coupled plasma mass spectrometer (LA-ICP-MS); Magnesium oxide; Magnesium oxide, standard deviation; Nickel; Nickel, standard deviation; Rhenium; Rhenium, standard deviation; Sample code/label; Silicon dioxide; Silicon dioxide, standard deviation; Sodium oxide; Sodium oxide, standard deviation |
| url | https://doi.org/10.1594/PANGAEA.806342 |