The origin and dynamics of nitrogen in the Earth's mantle constrained by 15N15N in hydrothermal gases

Ultrahigh-precision noble gas isotope analyses reveal pervasive subsurface fractionation in hydrothermal systems

“…This is opposite to any prediction based on the respective solubilities of these gases under ideal conditions ( 37 , 44 ), but consistent with observations for DTF as reported in this study (Fig. 2B), indicating that DTF is (one of) the primary cause(s) of δ 15 N variations in volcanic systems ( 43 ).…”

“…Here, we show that the observed trend is compatible with DTF of a gas phase that was stripped off a deep groundwater component with the elemental composition of AEW at ~50°C. This suggests that δ 15 N of N 2 , like noble gases, is affected by the same DTF processes that appear to be ubiquitous in volcanic gas systems worldwide ( 43 ).…”

The origin of nitrogen in Earth's mantle: Constraints from basalts 15N/14N and N2/3He ratios

“…Hydrothermal gases from the Yellowstone stratovolcano yield similar results. Nearzero d 15 N and MORB-like N2/ 3 He were shown to be associated with the plume signature using the D30 approach (Labidi and Young, 2022). A picture of MORB-like N2/ 3 He but nearzero d 15 N for the high 3 He/ 4 He mantle seems to emerge as a global feature.…”

“…5). Three other popping rocks have d 15 N ~-3‰ associated with near-zero D30 values, suggesting the extracted N2 is unaffected by air contamination (Labidi et al, 2020;Labidi and Young, 2022). Those popping rocks have high K2O/TiO2 ~ 0.35 (Jones et al, 2019).…”

“…Nitrogen isotope data for three popping rocks are also used, from Javoy and Pineau (1991) and Labidi et al, (2020). The latter study was selected as nitrogen isotope ratios were measured together with D30 values, an independent measure of air contamination for nitrogen in natural samples (Labidi and Young, 2022).…”