Nitrogen recycling in subduction zones

Recycled noble gas and nitrogen in the subcontinental lithospheric mantle: Implications from N-He-Ar in fluid inclusions of SE Australian xenoliths.

“…The MORB-type component is confirmed by our helium analyses (Table 1), which show a remarkably uniform 3 He/ 4 He ratio of 10.1 ± 0.2 × 10 -6 , that is within the range of the upper mantle helium isotopic ratio measured in MORBs (e.g., Craig and Lupton, 1981 (Marty, 1995 (Marty, 1995 Sano et al, 1998). tle and the atmosphere is not sufficient to explain the variable nitrogen isotopic ratios observed in the Australian xenoliths. This requires an additional N component.…”

Volatile element isotope systematics at Ontake volcano, Japan.

“…Thus helium and carbon isotope data were well documented in volcanic and hydrothermal systems. On the other hand, the nitrogen isotope data are very sparse in the literature (Fischer et al, 1998;Sano et al, 1998a). This is partly because nitrogen isotope signature of the upper mantle has not been well known until recently due to experimental difficulty (Marty and Humbert, 1997;Cartigny et al, 1997).…”

“…Thus, considering MORB and pristine diamond data, it is currently thought that nitrogen in the Earth's upper mantle is characterized by a δ 15 N value of -5 ± 2‰. Sano et al (1998a) has reported that the subducting sedimentary nitrogen may be characterized by a δ 15 N value of +7 ± 4‰ at convergent 36 Ar ratios of back-arc basin basalt glasses and phenocrysts in subareal volcanic rock. Recently the sedimentary δ 15 N value has been confirmed by a study on volcanic gas and hydrothermal fluid in island arc (Sano et al, 2001).…”

“…The magmatic and crustal end-members have 3 He/ 4 He ratios of 8.0R atm and 0.02R atm , respectively (Sano and Wakita, 1985). If we take also the δ 15 N values of magmatic = -3‰ and crustal end-members = +3‰, which are within the variations of mantle derived and subducting sedimentary nitrogen isotopes (Sano et al, 1998a), several mixing lines between the two hypothetical components can be drawn based on the variation of the ratio (r) of magmatic N 2 / 3 He ratio to crustal N 2 / 3 He ratio (see Fig. 5).…”

Water, Life, and Planetary Geodynamical Evolution

“…Much of this sedimentary nitrogen is returned into the atmosphere through arc volcanism. Thus, about 85% of arc volcanic nitrogen is of sedimentary origin (Sano et al 2001a). The total net (i.e.…”