Nitrogen distribution between aqueous fluids and silicate melts

Li, Yuan; Huang, Ruifang; Wiedenbeck, Michael; Keppler, Hans

doi:10.1016/j.epsl.2014.11.050

Cited by 56 publications

(45 citation statements)

References 45 publications

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“…We have compiled experimental results to augment the discussion in the previous section and to quantitatively describe the N solubility of geologic materials . Measurements have been made for N in minerals , silicate melt (Libourel et al, 2003;Mysen et al, 2008;Mysen and Fogel, 2010;Mysen et al, 2014), Fe-metal (Kadik et al, 2011;Roskosz et al, 2013), and aqueous fluids (Li and Keppler, 2014;Li et al, 2015). Experimental conditions are variable (e.g., different starting materials, presence of alkalis, etc.…”

Section: Resultsmentioning

confidence: 99%

The nitrogen budget of Earth

Johnson¹,

Goldblatt²

2015

Earth-Science Reviews

179

191

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We comprehensively compile and review N content in geologic materials to calculate a new N budget for Earth. Using analyses of rocks and minerals in conjunction with N-Ar geochemistry demonstrates that the Bulk Silicate Earth (BSE) contains ∼ 7 ± 4 times present atmospheric N (4 × 10 18 kg N, or PAN), with 27 ± 16 × 10 18 kg N. Comparison to chondritic composition, after subtracting N sequestered into the core, yields a consistent result, with BSE N between 17 ± 13 × 10 18 kg to 31 ± 24 × 10 18 kg N. Embedded in the chondritic comparison we calculate a N mass in Earth's core (180 ± 110 to 300 ± 180 × 10 18 kg) as well as present discussion of the Moon as a proxy for the early mantle.Significantly, our study indicates the majority of the planetary budget of N is in the solid Earth. We suggest that the N estimate here precludes the need for a "missing N" reservoir. Nitrogen-Ar systematics in mantle rocks and primary melts identify the presence of two mantle reservoirs: MORB-source like (MSL) and high-N. High-N mantle is composed of young, N-rich material subducted from the surface and identified in OIB and some xenoliths. In contrast, MSL appears to be made of old material, though a component of subducted material is evident in this reservoir as well.Taking into account N mass and isotopic character of the atmosphere and BSE, we calculate a δ 15 N value of ∼ 2 . This value should be used when discussing bulk Earth N isotope evolution. Additionally, our work indicates that all surface N could pass through the mantle over Earth history, and in fact the mantle may act as a long-term sink for N. Since N acts as a tracer of exchange between the atmosphere, oceans, and mantle over time, clarifying its distribution in the Earth is critical for evolutionary models concerned with Earth system evolution. We suggest that N be viewed in the same light as carbon: it has a fast, biologically mediated cycle which connects it to a slow, tectonically-controlled geologic cycle.

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Section: Resultsmentioning

confidence: 99%

The nitrogen budget of Earth

Johnson¹,

Goldblatt²

2015

Earth-Science Reviews

179

191

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“…Figure 1 shows that regardless of pressure or temperature, D N metal/silicate increases with increasing oxygen fugacity, as calculated from the composition of the coexisting quenched metal and silicate (Table S-1). The trend in Figure 1 can be rationalised if one assumes that under these very reducing conditions below the iron-wüstite buffer, nitrogen is mostly dissolved as N 3-ion in the silicate melt (Kadik et al, 2011(Kadik et al, , 2013Li et al, 2015), while it dissolves as interstitial N atoms in the metal (Häglund et al, 1993 Figure 1. We noticed that the silicates recovered from the multi-anvil experiments performed at 5.0 to 7.0 GPa were not completely glassy, but contained fine-grained quench crystals.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen isotope fractionation during terrestrial core-mantle separation

Li¹,

Marty²,

Shcheka³

et al. 2016

Geochem. Persp. Let.

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doi: 10.7185/geochemlet.1614The origin and evolution of the terrestrial nitrogen remains largely unresolved. In order to understand the potential influence of core-mantle separation on terrestrial nitrogen evolution, experiments were performed at 1.5 to 7.0 GPa and 1600 to 1800 °C to study nitrogen isotope fractionation between coexisting liquid Fe-rich metal and silicate melt. The results show that the metal/silicate partition coefficient of nitrogen D N metal/silicate ranges from 1 to 150 and the nitrogen isotope fractionation d15 N metal-silicate is −3.5 ± 1.7 ‰. Calculations show that the bulk Earth is more depleted in d 15 N than the present-day mantle, and that the presentday mantle d 15 N of −5 ‰ could be derived from an enstatite chondrite composition via terrestrial core-mantle separation, with or without the addition of carbonaceous chondrites. These results strongly support the notion that enstatite chondrites may be a main component from which the Earth formed and a main source of the terrestrial nitrogen. Moreover, in the deep reduced mantle, the Fe-rich metal phase may store most of the nitrogen, and partial melting of the coexisting silicates may generate oceanic island basalts (OIBs) with slightly positive d15 N values.

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“…However, it should be noted that the heterogeneous distribution of water in lunar mantle (e.g., Albarède et al, 2014;Robinson and Taylor, 2014) must cause different parts of the lunar mantle to degas carbon with different efficiencies, and extremely dry parts of the lunar mantle may not degas significant quantity of CH 4 . Furthermore, these calculated values of CH 4 contents in both lunar and Martian basalts may be maximum because other volatiles such as nitrogen at reduced conditions (Kadik et al, 2011;Li et al, 2013Li et al, , 2015 may compete for non-hydroxyl hydrogen. However, with 200-600 ppm H and log f O 2 of IW-2 to IW, our experiments indeed show 20-70 ppm CH 4 in silicate melt (see Fig.…”

Section: Degassing Of C-o-h Volatiles Via Partial Melting Of Reduced mentioning

confidence: 97%