Release of oxidizing fluids in subduction zones recorded by iron isotope zonation in garnet

Subduction zones are key regions of chemical and mass transfer between the Earth’s surface and mantle. During subduction, oxidized material is carried into the mantle and large amounts of water are released due to the breakdown of hydrous minerals such as lawsonite. Dehydration accompanied by the release of oxidizing species may play a key role in controlling redox changes in the subducting slab and overlying mantle wedge. Here we present measurements of oxygen fugacity, using garnet–epidote oxybarometry, together with analyses of the stable iron isotope composition of zoned garnets from Sifnos, Greece. We find that the garnet interiors grew under relatively oxidized conditions whereas garnet rims record more reduced conditions. Garnet δ56Fe increases from core to rim as the system becomes more reduced. Thermodynamic analysis shows that this change from relatively oxidized to more reduced conditions occurred during lawsonite dehydration. We conclude that the garnets maintain a record of progressive dehydration and that the residual mineral assemblages within the slab became more reduced during progressive subduction-zone dehydration. This is consistent with the hypothesis that lawsonite dehydration accompanied by the release of oxidizing species, such as sulfate, plays an important and measurable role in the global redox budget and contributes to sub-arc mantle oxidation in subduction zones

Precision measurement of CP\it{CP} violation in the penguin-mediated decay Bs0→ϕϕB_s^{0}\rightarrow\phi\phi

A flavor-tagged time-dependent angular analysis of the decay $B_s^{0}\rightarrow\phi\phi$ is performed using $pp$ collision data collected by the LHCb experiment at % at $\sqrt{s}=13$ TeV, the center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The $\it{CP}$-violating phase and direct $\it{CP}$-violation parameter are measured to be $\phi_{s\bar{s}s} = -0.042 \pm 0.075 \pm 0.009$ rad and $|\lambda|=1.004\pm 0.030 \pm 0.009$, respectively, assuming the same values for all polarization states of the $\phi\phi$ system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using $pp$ collisions at center-of-mass energies of 7 and 8 TeV, yielding $\phi_{s\bar{s}s} = -0.074 \pm 0.069$ rad and $|lambda|=1.009 \pm 0.030$. This is the most precise study of time-dependent $\it{CP}$ violation in a penguin-dominated $B$ meson decay. The results are consistent with $\it{CP}$ symmetry and with the Standard Model predictions.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-001.html (LHCb public pages

Magnesium isotope evidence that accretional vapour loss shapes planetary compositions

It has long been recognized that Earth and other differentiated planetary bodies are chemically fractionated compared to primitive, chondritic meteorites and, by inference, the primordial disk from which they formed. However, it is not known whether the notable volatile depletions of planetary bodies are a consequence of accretion1 or inherited from prior nebular fractionation2. The isotopic compositions of the main constituents of planetary bodies can contribute to this debate3, 4, 5, 6. Here we develop an analytical approach that corrects a major cause of measurement inaccuracy inherent in conventional methods, and show that all differentiated bodies have isotopically heavier magnesium compositions than chondritic meteorites. We argue that possible magnesium isotope fractionation during condensation of the solar nebula, core formation and silicate differentiation cannot explain these observations. However, isotopic fractionation between liquid and vapour, followed by vapour escape during accretionary growth of planetesimals, generates appropriate residual compositions. Our modelling implies that the isotopic compositions of magnesium, silicon and iron, and the relative abundances of the major elements of Earth and other planetary bodies, are a natural consequence of substantial (about 40 per cent by mass) vapour loss from growing planetesimals by this mechanism

Precision measurement of CP violation in the penguin-mediated decay Bs0→ϕϕ

A flavor-tagged time-dependent angular analysis of the decay B 0 s → ϕ ϕ is performed using p p collision data collected by the LHCb experiment at the center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6     fb − 1 . The C P -violating phase and direct C P -violation parameter are measured to be ϕ s ¯ s s s = − 0.042 ± 0.075 ± 0.009     rad and | λ | = 1.004 ± 0.030 ± 0.009 , respectively, assuming the same values for all polarization states of the ϕ ϕ system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using p p collisions at center-of-mass energies of 7 and 8 TeV, yielding ϕ s ¯ s s s = − 0.074 ± 0.069     rad and | λ | = 1.009 ± 0.030 . This is the most precise study of time-dependent C P violation in a penguin-dominated B meson decay. The results are consistent with C P symmetry and with the standard model predictions

Determination of tin equilibrium isotope fractionation factors from synchrotron radiation experiments

A method of determination of the reduced isotopic partition function ratio (beta-factor) from the partial density of state (PDOS) obtained by inelastic nuclear resonant X-ray scattering (INRXS) in synchrotron radiation experiments has been established. The method has been demonstrated by the example of tin isotopes. The tin beta-factors for CaSnO3, SnO2, SnO have been computed from the INRXS-derived PDOSs. ln beta(122/116Sn) =(0.390 +/- 0.0076)x - (0.00160 +/- 0.0000242)x(2) + (1.099 +/- 0.0573) - 10(-5)x(3)) for SnO ln(beta 122/116Sn) = (0.771 +/- 0.0150)x - (0.00392 +/- 0.000061)x(2) + (3.548 +/- 0.287). 10(-5)x(3) for SnO2 ln beta(122/116Sn) = (0.776 +/- 0.0157)x - (0.00334 +/- 0.000064)x(2) + (2.561 +/- 0.157). 10(-5)x(3) for CaSnO3 Equilibrium Sn-122/116 isotope fractionation between di- and tetravalent tin compounds is about 0.4 parts per thousand at 1000 K and about 4.1 parts per thousand at room temperature and can be measured by modern multicollector inductively-coupled plasma mass-spectrometers. Tin beta-factors reveal dependence on oxidation state previously detected for iron isotopes. A comparison of the tin beta-factors for SnO2 obtained on the basis of the INRXS-derived PDOS with those obtained by the Mossbauer spectroscopy method shows that both methods give similar results, but application of synchrotron radiation provides more accurate and reliable data. Equilibrium stable isotope fractionation of transition metals between different oxidation state compounds is not negligible even for elements as heavy as tin. Copyright (c) 2005 Elsevier Ltd

Redox-controlled iron isotope fractionation during magmatic differentiation: An example from the Red Hill intrusion, S. Tasmania

This study presents accurate and precise iron isotopic data for 16 co-magmatic rocks and 6 pyroxene-magnetite pairs from the classic, tholeiitic Red Hill sill in southern Tasmania. The intrusion exhibits a vertical continuum of compositions created by in situ fractional crystallisation of a single injection of magma in a closed igneous system and, as such, constitutes a natural laboratory amenable to determining the causes of Fe isotope fractionation in magmatic rocks. Early fractionation of pyroxenes and plagioclase, under conditions closed to oxygen exchange, gives rise to an iron enrichment trend and an increase in fo2 of the melt relative to the Fayalite-Magnetite-Quartz (FMQ) buffer. Enrichment in Fe3+/ΣFemelt is mirrored by δ57Fe, where VIFe2+-bearing pyroxenes partition 57Fe-depleted iron, defining an equilibrium pyroxene-melt fractionation factor of Δ57 Fepx-melt ≤ -0.25‰ × 106/T2 Upon magnetite saturation, the fo2 and δ57Fe of the melt fall, commensurate with the sequestration of the oxidised, 57Fe-enriched iron into magnetite, quantified as Δ57 Femtn-melt= +0.20‰ × 106/T2 Pyroxene-magnetite pairs reveal an equilibrium fractionation factor of Δ57 Femtn-px= ≈ + 0.30‰ at 900-1,000 °C. Iron isotopes in differentiated magmas suggest that they may act as an indicator of their oxidation state and tectonic setting. © 2012 Springer-Verlag.Paolo A. Sossi, John D. Foden, Galen P. Halverso