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Rationale: The analysis of the three sulfur stable isotope ratios ( 33 S/ 32 S, 34 S/ 32 S, 36 S/ 32 S) is routinely performed by gas-source isotope ratio mass spectrometry (IRMS) on the SF 6 gaseous molecule, collecting SF 5 + ions at m/z ~ 127, 128, 129 and 131. High precision and accuracy are commonly achieved owing to a lack of correction because fluorine has only one isotope and the inert nature of the SF 6 molecule. The analysis of the 36 S/ 32 S ratio is, however, complicated by the low abundance of 36 S (~0.015%) and the possible occurrence of trace amounts of fluorocarbon compounds leading to 12 C 3 F 5 + ions at m/z ~ 131, i.e. where 36 SF 5 + ions are collected., Methods: We used gas-source high-resolution IRMS to better characterize the nature of possible interferences, and we tested novel types of filaments in order to investigate their influence on possible interferences., Results: We confirm that the 12 C 3 F 5 + ion represents the main isobaric interference at m/z ~ 131. We also demonstrate that tungsten fluoride adducts are formed from the reaction of fluorine ions derived during fragmentation of the SF 6 molecule with the hot tungsten filament. These reactions lead to the formation of e.g. WF 5 + , WF 4 + , WF 3 + ions, including doubly charged ions. WF 4 ++ , in particular, leads to isobaric interference on m/z ~ 128, 129 and 131 from 180 WF 4 ++ , 182 WF 4 ++ and 186 WF 4 ++ ions, respectively. Because 180 W (0.12%) is at low abundance, its influence on δ 33 S measurements would remain negligible, but 182 W (26.5%) and 186 W (28.4%) lead to scale contraction for both δ 34 S and δ 36 S., Conclusions: Rather than correcting for these interferences, or working at high mass resolution, we suggest avoiding W isobaric interferences by using other types of filaments, with initial reports on both pure Re filaments and Y 2 O 3 -coated W filaments., (© 2024 John Wiley & Sons Ltd.)

Nitrogen is the main constituent of the Earth's atmosphere, but its provenance in the Earth's mantle remains uncertain. The relative contribution of primordial nitrogen inherited during the Earth's accretion versus that subducted from the Earth's surface is unclear 1-6 . Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare 15 N 15 N isotopologue of N 2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle δ 15 N (the fractional difference in 15 N/ 14 N from air), N 2 / 36 Ar and N 2 / 3 He. Our results show that negative δ 15 N values observed in gases, previously regarded as indicating a mantle origin for nitrogen 7-10 , in fact represent dominantly air-derived N 2 that experienced 15 N/ 14 N fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the 15 N 15 N data allow extrapolations that characterize mantle endmember δ 15 N, N 2 / 36 Ar and N 2 / 3 He values. We show that the Eifel region has slightly increased δ 15 N and N 2 / 36 Ar values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts 11 , consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has δ 15 N values substantially greater than that of the convective mantle, resembling surface components 12-15 , its N 2 / 36 Ar and N 2 / 3 He ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume δ 15 N values may both be dominantly primordial features.

Riverine dissolved sulfate (SO 4 2- ) sulfur and oxygen isotope variations reflect their controls such as SO 4 2- reduction and reoxidation, and source mixing. However, unconstrained temporal variability of riverine SO 4 2- isotope compositions due to short sampling durations may lead to mischaracterization of SO 4 2- sources, particularly for the pyrite-derived sulfate load. We measured the sulfur and triple-oxygen isotopes (δ 34 S, δ 18 O, and Δ' 17 O) of Mississippi River SO 4 2- with biweekly sampling between 2009 and 2013 to test isotopic variability and constrain sources. Sulfate δ 34 S and δ 18 O ranged from -6.3‰ to -0.2‰ and -3.6‰ to +8.8‰, respectively. Our sampling period captured the most severe flooding and drought in the Mississippi River basin since 1927 and 1956, respectively, and a first year of sampling that was unrepresentative of long-term average SO 4 2- . The δ 34 S SO4 data indicate pyrite-derived SO 4 2- sources are 74 ± 10% of the Mississippi River sulfate budget. Furthermore, pyrite oxidation is implicated as the dominant process supplying SO 4 2- to the Mississippi River, whereas the Δ' 17 O SO4 data shows 18 ± 9% of oxygen in this sulfate is sourced from air O 2 .

Molecular nitrogen (N 2 ) comprises three-quarters of Earth's atmosphere and significant portions of other planetary atmospheres. We report a 19 per mil (‰) excess of 15 N 15 N in air relative to a random distribution of nitrogen isotopes, an enrichment that is 10 times larger than what isotopic equilibration in the atmosphere allows. Biological experiments show that the main sources and sinks of N 2 yield much smaller proportions of 15 N 15 N in N 2 . Electrical discharge experiments, however, establish 15 N 15 N excesses of up to +23‰. We argue that 15 N 15 N accumulates in the atmosphere because of gas-phase chemistry in the thermosphere (>100 km altitude) on time scales comparable to those of biological cycling. The atmospheric 15 N 15 N excess therefore reflects a planetary-scale balance of biogeochemical and atmospheric nitrogen chemistry, one that may also exist on other planets.

Establishing the age of the Moon is critical to understanding solar system evolution and the formation of rocky planets, including Earth. However, despite its importance, the age of the Moon has never been accurately determined. We present uranium-lead dating of Apollo 14 zircon fragments that yield highly precise, concordant ages, demonstrating that they are robust against postcrystallization isotopic disturbances. Hafnium isotopic analyses of the same fragments show extremely low initial 176 Hf/ 177 Hf ratios corrected for cosmic ray exposure that are near the solar system initial value. Our data indicate differentiation of the lunar crust by 4.51 billion years, indicating the formation of the Moon within the first ~60 million years after the birth of the solar system.

Earth and the Moon are shown here to have indistinguishable oxygen isotope ratios, with a difference in Δ'(17)O of -1 ± 5 parts per million (2 standard error). On the basis of these data and our new planet formation simulations that include a realistic model for primordial oxygen isotopic reservoirs, our results favor vigorous mixing during the giant impact and therefore a high-energy, high-angular-momentum impact. The results indicate that the late veneer impactors had an average Δ'(17)O within approximately 1 per mil of the terrestrial value, limiting possible sources for this late addition of mass to the Earth-Moon system., (Copyright © 2016, American Association for the Advancement of Science.)

Doppler weather radar imaging enabled the rapid recovery of the Sutter's Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand's parameter = 2.8 ± 0.3). Sutter's Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted.