Partitioning behavior of NI, CO, MO, and W between basaltic liquid and Ni‐rich metal: Implications for the origin of the moon and lunar core formation

Hillgren, V. J.

doi:10.1029/91gl02534

Cited by 29 publications

(6 citation statements)

References 11 publications

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“…Using D values obtained from parameterization, we estimated the concentrations of Mo, W, Ni, Co, Ru, Pd, and Au in the silicate portion of the lunar magma ocean during the conditions of core formation, following the method of Hillgren (), by applying the following mass balance equation:

C_{normalsil}^{i} = \frac{C_{bulk}^{i}}{(][x + false(1 - x false) (D_{\frac{normalmet}{normalsil}}^{i}))}

…”

Section: Discussionmentioning

confidence: 99%

Estimation of trace element concentrations in the lunar magma ocean using mineral‐ and metal‐silicate melt partition coefficients

Sharp

Righter

Walker

2015

Meteorit & Planetary Scien

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This study uses experimentally determined plagioclase‐melt D values to estimate the trace element concentrations of Sr, Hf, Ga, W, Mo, Ru, Pd, Au, Ni, and Co in a crystallizing lunar magma ocean at the point of plagioclase flotation. Similarly, experimentally determined metal‐silicate partition experiments combined with a composition model for the Moon are used to constrain the concentrations of W, Mo, Ru, Pd, Au, Ni, and Co in the lunar magma ocean at the time of core formation. The metal‐silicate derived lunar mantle estimates are generally consistent with previous estimates for the concentration of these elements in the lunar mantle. Plagioclase‐melt derived concentrations for Sr, Ga, Ru, Pd, Au, Ni, and Co are also consistent with prior estimates. Estimates for Hf, W, and Mo, however, are higher. These elements may be concentrated in the residual liquid during fractional crystallization due to their incompatibility. Alternatively, the apparent enrichment could reflect the inappropriate use of bulk anorthosite data, rather than data for plagioclase separates.

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C_{normalsil}^{i} = \frac{C_{bulk}^{i}}{(][x + false(1 - x false) (D_{\frac{normalmet}{normalsil}}^{i}))}

…”

Section: Discussionmentioning

confidence: 99%

Estimation of trace element concentrations in the lunar magma ocean using mineral‐ and metal‐silicate melt partition coefficients

Sharp

Righter

Walker

2015

Meteorit & Planetary Scien

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“…Most previous work on lunar siderophile elements has concluded that the Moon has undergone metal-silicate equilibration, and therefore likely possesses a small metallic core. These models differ in the size of the core and its composition (e.g., Brett 1973;Wänke et al 1977;Ringwood 1979;Drake et al 1984;Newsom 1984Newsom , 1986Ringwood and Seifert 1986;Wänke and Dreibus 1986;Hillgren 1991;O'Neill 1991;Righter and Drake 1996) and a summary of some of these models is presented in Table 3.15. Early models were based on the siderophileelement data reported by Wänke et al (1977).…”

Section: Core Formation Modelsmentioning

confidence: 99%

“…Subsequent Mo and Re analyses of lunar materials were considered in the modeling of Newsom (1984), who accounted for the lunar Re and Mo depletions with a 2-5 lunar wt% metallic core if the Moon accreted directly from the solar nebula, or a 0.5-1 lunar wt% core if it formed from material coming from the terrestrial mantle. Later work by Ringwood andSeifert (1986), O'Neill (1991) and Hillgren (1991) all argued that the 3 times larger depletion of Ni in the lunar mantle in comparison to the terrestrial mantle could be explained by a Ni-rich lunar core. These conclusions were based primarily on the assumption that the Moon was made of material from the primitive upper mantle of the Earth.…”

Section: Core Formation Modelsmentioning

confidence: 99%

The Constitution and Structure of the Lunar Interior

Wieczorek

2006

Reviews in Mineralogy and Geochemistry

445

449

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until the acquisition of thorium surface concentrations by the Lunar Prospector spacecraft. It now appears that the Moon possesses a fundamental asymmetry, stemming from the time of initial differentiation, with KREEP-rich rocks and mare volcanism having been concentrated on the Moon's Earth-facing hemisphere. Curiously, the elevations of the nearside hemisphere are about 2 km less than that of the far side. No matter the origin of the asymmetric distribution of KREEP-rich rocks, it appears that their associated high heat production fundamentally affected the post-magma-ocean magmatic history of the Moon's near side. Figure 3.1. One possible interpretation of the Moon's internal structure (a) just after magma-ocean crystallization and (b) near the end of mare basaltic volcanism. With the exception of a hemispheric dichotomy in crustal thickness and mare basaltic volcanism, this model, like many pre-Lunar Prospector models, represents the crust and mantle as being laterally uniform in composition. (a) The lunar magma ocean is assumed to have a depth of 550 km, the lower mantle is composed of "primitive" unmelted materials, and a small core is assumed. The sequences of major mineralogy as a function of radius in the mantle (olivine → olivine + pyroxene → ilmenite + olivine + pyroxene) and crust (plagioclase-rich in the upper crust and plagioclase + pyroxene + olivine in the lower crust), as well as the existence of a global KREEP-rich layer at the crust-mantle boundary, are a result of a fractionally crystallizing magma ocean. Complex processes, such as mantle overturn and asymmetric solidification of the magma ocean, are not considered in this model. (b) The lunar interior at ~3 Ga, emphasizing the nearside-farside dichotomy in both the distribution of mare basalts and the thickness of the lunar crust. (CM and CF represent the center of mass and center of figure, respectively, which are offset from each other by about 2 km). Compare with the more recent interpretations presented in Figure 3.27. [Used by permission of Springer, from McCallum (2001), Earth Moon Planets, Vol. 85-86, Figs. 2 and 4, pp. 256 and 260.] 1738 km 65 km Depleted Mantle Crust Core 550 km Plag Pl � Ol�Px KREEP Ilm� Ol�Px Ol Ol Px Primitive Mantle (a) Moon at~4.4 Ga South Pole-Aitken Basin Mare basalt (FeO~15-22 wt.%) Farside Nearside (b) Moon at~3 Ga � � �� 90 km Anorthositic Crust (FeO~4.5 wt.%) 40-50 km 40 km Incr. Fe Incr. Fe 1738 km 65 km Depleted Mantle Crust Core 550 km Plag Pl � Ol�Px KREEP Ilm� Ol�Px Ol Ol Px Primitive Mantle (a) Moon at~4.4 Ga South Pole-Aitken Basin Mare basalt (FeO~15-22 wt.%) Farside Nearside (b) Moon at~3 Ga � � �� 90 km Anorthositic Crust (FeO~4.5 wt.%) 40-50 km 40 km

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“…To ensure buffer capacity over long run durations, an additional piece of pure graphite was encapsulated inside the Pt container. The C-CO-CO 2 buffer results in an effective oxygen fugacity about 1 log unit above the IW buffer ($IW + 1) (French and Eugster, 1965;French, 1966;Wendlandt, 1982;Hillgren, 1991), with a reproducibility of the buffer conditions of at least IW + 1 ± 0.5 (French and Eugster, 1965).…”

Section: Methodsmentioning

confidence: 99%

“…LA-ICPMS measurements show no detectable Pt concentrations (below 1 ppb) in the starting material. We added about 1 wt% graphite powder to the starting mixture to function as an internal C-CO-CO 2 buffering system (see French and Eugster, 1965;French, 1966;Wendlandt, 1982;Hillgren, 1991). To ensure buffer capacity over long run durations, an additional piece of pure graphite was encapsulated inside the Pt container.…”

Section: Methodsmentioning

confidence: 99%

Experimental study of platinum solubility in silicate melt to 14GPa and 2273K: Implications for accretion and core formation in Earth

Ertel

Walter

Drake

et al. 2006

Geochimica et Cosmochimica Acta

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We determined the solubility limit of Pt in molten haplo-basalt (1 atm anorthite-diopside eutectic composition) in piston-cylinder and multi-anvil experiments at pressures between 0.5 and 14 GPa and temperatures from 1698 to 2223 K. Experiments were internally buffered at $IW + 1. Pt concentrations in quenched-glass samples were measured by laser-ablation inductively coupled-plasma mass spectrometry (LA-ICPMS). This technique allows detection of small-scale heterogeneities in the run products while supplying threedimensional information about the distribution of Pt in the glass samples. Analytical variations in 195 Pt indicate that all experiments contain Pt nanonuggets after quenching. Averages of multiple, time-integrated spot analyses (corresponding to bulk analyses) typically have large standard deviations, and calculated Pt solubilities in silicate melt exhibit no statistically significant covariance with temperature or pressure. In contrast, averages of minimum 195 Pt signal levels show less inter-spot variation, and solubility shows significant covariance with pressure and temperature. We interpret these results to mean that nanonuggets are not quench particles, that is, they were not dissolved in the silicate melt, but were part of the equilibrium metal assemblage at run conditions. We assume that the average of minimum measured Pt abundances in multiple probe spots is representative of the actual solubility. The metal/silicate partition coefficients (D met/sil ) is the inverse of solubility, and we parameterize D met/sil in the data set by multivariate regression. The statistically robust regression shows that increasing both pressure and temperature causes D met/sil to decrease, that is, Pt becomes more soluble in silicate melt. D met/sil decreases by less than an order of magnitude at constant temperature from 1 to 14 GPa, whereas isobaric increase in temperature produces a more dramatic effect, with D met/sil decreasing by more than one order of magnitude between 1623 and 2223 K. The Pt abundance in the Earth's mantle requires that D met/sil is $1000 assuming core-mantle equilibration. Geochemical models for core formation in Earth based on moderately and slightly siderophile elements are generally consistent with equilibrium metal segregation at conditions generally in the range of 20-60 GPa and 2000-4000 K. Model extrapolations to these conditions show that the Pt abundance of the mantle can only be matched if oxygen fugacity is high ($IW) and if Pt mixes ideally in molten iron, both very unlikely conditions. For more realistic values of oxygen fugacity ($IW À 2) and experimentally-based constraints on non-ideal mixing, models show that D met/sil would be several orders of magnitude too high even at the most favorable conditions of pressure and temperature. These results suggest that the mantle Pt budget, and by implication other highly siderophile elements, was added by late addition of a 'late veneer' phase to the accreting proto-Earth.

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Partitioning behavior of NI, CO, MO, and W between basaltic liquid and Ni‐rich metal: Implications for the origin of the moon and lunar core formation

Cited by 29 publications

References 11 publications

Estimation of trace element concentrations in the lunar magma ocean using mineral‐ and metal‐silicate melt partition coefficients

Estimation of trace element concentrations in the lunar magma ocean using mineral‐ and metal‐silicate melt partition coefficients

The Constitution and Structure of the Lunar Interior

Experimental study of platinum solubility in silicate melt to 14GPa and 2273K: Implications for accretion and core formation in Earth

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