Data for: Selenium isotope and S-Se-Te elemental systematics along the Pacific-Antarctic ridge: Role of mantle processes

This dataset includes Main Text Table 1-3 and Electronic Annex-Supplementary Tables S1-S3.Table 1. Selenium isotope composition and Se–Te abundances of geological reference materials and a randomly selected PAR MORB glass reported in this study and literature.Table 2. Selenium isotope composition, S–Se–Te abundances, and selected major element composition of the studied PAR glasses.Table 3. Summary of model parameters used for the near-fractional melting of a MORB mantle.Supplementary Table S1. Selenium isotope analysis of MH-495 (inter-laboratory standard solution; 30 ng mL−1 Se) during the course of this study.Supplementary Table S2. Compilation of trace element concentrations analyzed in this study (solution iQAP-Qc quadrupole ICP-MS) together with the major/trace element and radiogenic/stable isotope composition in the literature for the studied PAR glasses.Supplementary Table S3. Trace element concentrations of BHVO-2 (USGS reference material) analyzed in this study as a quality control standard

Data for: Selenium isotope and S-Se-Te elemental systematics along the Pacific-Antarctic ridge: Role of mantle processes

This dataset includes Main Text Table 1-3 and Electronic Annex-Supplementary Tables S1-S3.Table 1. Selenium isotope composition and Se–Te abundances of geological reference materials and a randomly selected PAR MORB glass reported in this study and literature.Table 2. Selenium isotope composition, S–Se–Te abundances, and selected major element composition of the studied PAR glasses.Table 3. Summary of model parameters used for the near-fractional melting of a MORB mantle.Supplementary Table S1. Selenium isotope analysis of MH-495 (inter-laboratory standard solution; 30 ng mL−1 Se) during the course of this study.Supplementary Table S2. Compilation of trace element concentrations analyzed in this study (solution iQAP-Qc quadrupole ICP-MS) together with the major/trace element and radiogenic/stable isotope composition in the literature for the studied PAR glasses.Supplementary Table S3. Trace element concentrations of BHVO-2 (USGS reference material) analyzed in this study as a quality control standard.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Selenium and tellurium in Reykjanes Ridge and Icelandic basalts: Evidence for degassing-induced Se isotope fractionation

Selenium behaves as a chalcophile and moderately volatile element during planetary accretion and magmatic processes on Earth. Together with the geochemically similar S and Te, Se is more volatile than most other moderately volatile elements and thus potentially becomes a new tracer to constrain the mechanism of volatile depletion in the Earth's mantle and other planetary bodies. As previously observed for several volatile elements, stable isotopes of Se are expected to fractionate upon eruptive outgassing of magmas. To understand the degassing behavior of Se and associated isotope fractionation, we report on Se and Te contents and Se isotope compositions (δSe) of submarine glasses across a range of distant ridge depth intervals along the Reykjanes Ridge and subglacial/subaerial basalts on Iceland (51–65°N; N = 22). Selenium (150–399 ng/g) and Te (2.61–14.5 ng/g) contents of the submarine glasses display progressive enrichment along the Reykjanes Ridge towards Iceland. This can be explained either by enhanced mantle melting towards Iceland or by enrichment of Se–Te contents in the mantle source due to the Icelandic plume–Reykjanes Ridge interaction. Both scenarios are equally plausible. The δSe values of submarine Reykjanes Ridge glasses range between −0.20 ± 0.08‰ and −0.08 ± 0.08‰ (on average −0.15 ± 0.07‰; 2SD, N = 15), which are unaffected by the Icelandic plume contribution and remain strictly within the previously reported average for depleted MORBs. These new data combined with literature δSe for depleted MORBs define a highly homogeneous depleted mantle composition δSe = −0.15 ± 0.11‰ (2SD, N = 44). On the other hand, we observed degassing of Se and Te to a variable extent (~40–95%) in submarine Reykjanes glasses at depths shallower than ~250 m and in subaerial/subglacial basalts on Iceland. Degassing-induced Se isotope fractionation shifted δSe of subaerial lavas towards heavier values (by up to ~0.44‰) well outside the range of submarine MORBs. However, when Se outgassing is associated with subglacial eruption, the outer glass rim of basalt preserves the primary/undegassed Se isotopic signature; whereas the pillow interior experiencing further Se loss (~50%) is enriched in heavier isotopes (−0.01 ± 0.12‰) relative to the outer glass rim (−0.22 ± 0.08‰). These observations are complemented by measurements of BHVO-2G from high-temperature heating experiments of the natural Hawaiian basalt BHVO-2, which show evaporation of 40% Se and 85% Te and resulting shift in δSe by ~+0.74‰. Degassing-induced Se isotope fractionation during volcanic eruption may be well explained by a simple Rayleigh distillation model with an empirical fractionation factor α of ~0.9998 (between volcanic gas and silicate melt). The results presented here show that Se isotope and Se–Te systematics can potentially contribute further constraints on degassing of chalcophile and volatile elements during terrestrial volcanism and large-scale planetary processes.We are especially grateful to Jean-Guy Schilling for his initial support and encouragement of the project, and to Katherine A. Kelley for providing us with all the samples. We acknowledge fruitful discussions with Ronny Schoenberg, Jabrane Labidi, and Timon Kurzawa, and lab support from Elmar Reitter and Maria Isabel Varas-Reus. We also thank Frances Jenner, Alex McCoy-West, and an anonymous reviewer for their through reviews and constructive suggestions, and Julie Prytulak for the efficient editorial handling. S. K. acknowledges financial support by the ERC Starting Grant O2RIGIN (636808)

Selenium isotope variations in orogenic garnet pyroxenites

Goldschmidt (2019), Barcelona (España), 18-23 august, 201

Moderate levels of oxygenation during the late stage of Earth’s Great Oxidation Event

The later stages of Earth's transition to a permanently oxygenated atmosphere during the Great Oxidation Event (GOE; ∼2.43–2.06 Ga) is commonly linked with the suggestion of an “oxygen overshoot” during the ∼2.22–2.06 Ga Lomagundi Event (LE), which represents Earth's most pronounced and longest-lived positive carbon isotope excursion. However, the magnitude and extent of atmosphere-ocean oxygenation and implications for the biosphere during this critical period in Earth's history remain poorly constrained. Here, we present nitrogen (N), selenium (Se), and carbon (C) isotope data, as well as bio-essential element concentrations, for Paleoproterozoic marine shales deposited during the LE. The data provide evidence for a highly productive and well-oxygenated photic zone, with both inner and outer-shelf marine environments characterized by nitrate- and Se oxyanion-replete conditions. However, the redoxcline subsequently encroached back onto the inner shelf during global-scale deoxygenation of the atmosphere-ocean system at the end of the LE, leading to locally enhanced water column denitrification and quantitative reduction of selenium oxyanions. We propose that nitrate-replete conditions associated with fully oxygenated continental shelf settings were a common feature during the LE, but nitrification was not sufficiently widespread for the aerobic nitrogen cycle to impact the isotopic composition of the global ocean N inventory. Placed in the context of Earth's broader oxygenation history, our findings indicate that O2 levels in the atmosphere-ocean system were likely much lower than modern concentrations. Early Paleoproterozoic biogeochemical cycles were thus far less advanced than after Neoproterozoic oxygenation

Moderate levels of oxygenation during the late stage of Earth's Great Oxidation Event

The later stages of Earth's transition to a permanently oxygenated atmosphere during the Great Oxidation Event (GOE; ∼2.43–2.06 Ga) is commonly linked with the suggestion of an “oxygen overshoot” during the ∼2.22–2.06 Ga Lomagundi Event (LE), which represents Earth's most pronounced and longest-lived positive carbon isotope excursion. However, the magnitude and extent of atmosphere-ocean oxygenation and implications for the biosphere during this critical period in Earth's history remain poorly constrained. Here, we present nitrogen (N), selenium (Se), and carbon (C) isotope data, as well as bio-essential element concentrations, for Paleoproterozoic marine shales deposited during the LE. The data provide evidence for a highly productive and well-oxygenated photic zone, with both inner and outer-shelf marine environments characterized by nitrate- and Se oxyanion-replete conditions. However, the redoxcline subsequently encroached back onto the inner shelf during global-scale deoxygenation of the atmosphere-ocean system at the end of the LE, leading to locally enhanced water column denitrification and quantitative reduction of selenium oxyanions. We propose that nitrate-replete conditions associated with fully oxygenated continental shelf settings were a common feature during the LE, but nitrification was not sufficiently widespread for the aerobic nitrogen cycle to impact the isotopic composition of the global ocean N inventory. Placed in the context of Earth's broader oxygenation history, our findings indicate that O2 levels in the atmosphere-ocean system were likely much lower than modern concentrations. Early Paleoproterozoic biogeochemical cycles were thus far less advanced than after Neoproterozoic oxygenation

Selenium isotopes as tracers of a late volatile contribution to Earth from the outer Solar System

International audienc