Tissot et al. (2016) — An analytical tour-de-force reporting the U isotope composition of refractory inclusions (oldest known SS solids), including Curious Marie: an extremely U-depleted inclusion, with a 235U excess of 59 ‰. These data brought definitive evidence that 247Cm was alive in the early solar nebula, and demonstrated that intermediate and high mass r-nuclides are presumably produced in the same site for most of the history of the Galaxy.

Tang et al. (2017) — A detailed followed up study using in-situ techniques (26Al-26Mg, 36Cl-36S) to constrain the formation and alteration ages of Curious Marie. The early alteration responsible for Cm/U fractionation allows up to decrease by a factor 5 the uncertainty on the initial 247cm abundance in the early SS. This work also provides evidence for the coexistence of 26Al and 36Cl in the early solar nebula, raising the possibility that, in addition to an irradiation origin, 36Cl could have also been derived from a stellar source.

Asael et al. (2013) — A multi-proxy stable isotope (Mo, Fe, U) case-study of shales from the upper Zaonega Formation (2.06 Ga, Fennoscandia) aiming to understand the evolving ocean redox conditions in the wake of the Great Oxidation Event. This study highlights the caveat of detrital correction for U paleo redox reconstructions using shales.

Tissot & Dauphas (2015) — Details the methods for high-precision measurement of U by double spike technique and introduces an error propagation tool using MonteCarlo simulations. This paper then carefully examines the composition of the crust, and establishes the mass and isotope budget of the modern ocean. It demonstrates that U isotopes do indeed act as tracer of global oceanic redox conditions.

Tissot et al. (2018) — We introduce a simple step-leaching protocol for bulk carbonate δ238U analysis, and apply it to 43 shallow-water carbonates from the Bahamas Platform (ODP Leg 166 Site 1009). The samples, formed in oxygenated waters over the last 1.5 Myr, show large down-core δ238U variations suggesting a strong eustatic control on 238U/235U. This study emphasizes the need for statistically meaningful data sets and proper consideration of the depositional environment for paleoredox reconstructions using the carbonate record.

Bonus: As the method also provides high-precision on 234U/238U ratios, the data also confirmed the existence of cyclical variations in seawater (234U/238U) over, at least, the last 2 glacial-interglacial events (0.23 Myr), which has implications for screening U-Th ages of carbonates.

Chen et al. (2021) — A study of the δ238U secular trends in carbonates and shales over the geologic record. This study explores the relationship between extent of marine anoxia and U residence time, and highlights the challenges inherent to applying knowledge of the modern marine U isotopic cycle to periods of Earth’s history when ocean-floor anoxia was much more extensive, and atmospheric oxygen content was significantly lower than present.

Kipp & Tissot (2022) — This contributions highlights the limitations and pitfalls of steady-state calculations or illustrative forward modeling to constrain past oceanic anoxia during transient or short lived (< 5 Myr) events, or when anoxia is widespread (as the proxy loses its sensitivity). This paper then introduces an inverse (Bayesian inference) modeling approach that enables robust quantification of seafloor anoxia within and amongst δ238U datasets. (See Download page for code).

Telus et al. (2012) — Multi-isotope (Fe, Zn, Mg, U) case-study of differentiated crustal rocks, including I- (igneous), and S-type (sedimentary) granites from the Lachlan Fold Belt (Australia). The nature and redox state of the protolith do not appear to influence the δ238U compositions of granitic rocks. The lack of a positive correlation between the δ26Mg, δ238U and δ56Fe rules out Soret diffusion as the origin of isotope variations in the studied systems.

Tissot & Dauphas (2015) — In this paper, new data on igneous samples and a thorough literature compilation are combined to carefully examine the U isotope composition of the crust.

Tissot et al. (2017) — We report the discovery of distinct δ238U and REE patterns between quenched (rapidly cooled) and plutonic (slowly cooled) angrites. This is best explained as the result of magmatic differentiation, providing evidence for U stable isotope fractionation during magmatic processes.

Tissot et al. (2019) — The first report of high-precision δ238U in single-zircon grains (previous studies pooled 100s to 1000s of grain for an analysis). We show that single-zircon δ238U measurements are not only possible but also broadly applicable, and could enable (i) improvements in precision/accuracy of U–Pb and Pb–Pb dates, (ii) accurate investigation of U-series disequilibrium contribution to U–Pb discordance, and (iii) accurate re-evaluation of U decay constants. Data on Hadean/Archean grains argues against the widespread existence of natural nuclear reactors (Oklo-like) in the early Earth.

Tissot & Ibañez-Mejia (2021) — A review article highlighting the striking features of the δ238U record of igneous rocks and minerals, and discussing the type of key multi-disciplinary investigations that are need to establish a robust interpretative framework for δ238U variations in igneous systems. We pose the question: could we turn these currently enigmatic U isotope variations into reliable probes of high-T processes?

Tissot et al. (2017) — 238U/235U variations impact the accuracy of Pb-Pb ages. This paper present high-precision U isotope data, accordingly corrects the Pb-Pb ages of angrites, and revisits the agreement between the relative chronologies inferred from short-lived radionuclides (26Al, 53Mn, 182Hf) and the absolute Pb-Pb clock. The discovery of distinct δ238U and REE patterns between quenched (rapidly cooled) and plutonic (slowly cooled) angrites is best explained as the result of magmatic differentiation, providing evidence for U stable isotope fractionation during magmatic processes.

Tissot et al. (2022) — A petrogenetic study of angrites, leveraging the rapidly growing number of known specimens (> 5x over 20 years). We find that volcanic angrites define two compositional groups readily related by fractional crystallization. Pressure experiments indicate that the parental melt of the evolved lavas last equilibrated at 6-9 bar, requiring a minimum radius for the angrite parent body (APB) of 600-700 km. Using the composition of the more primitive lavas we derived a self-consistent estimate of the major elements abundances in the APB, which suggest that the volatile-depleted nature of the APB is a primitive feature resulting from nebular fractionation at high-T (~1300–1400 K). We make the case that the APB represents the archetype of the first-generation of refractory-enriched planetesimals and embryos formed in the innermost part of the inner Solar System (<1 AU), and which accreted in the telluric planets.

Davis et al. (2018) — A study of titanium isotopes and Rare Earth Element (REE) pattern in texturally diverse CAIs from Allende. The correlated Ti isotope anomalies point to contributions from at least two sources, likely Type II supernovae for 46Ti and Type Ia or electron-capture supernovae for 50Ti. The finding that the CAIs with the highest ε50Ti anomalies also show more dispersion in their mass-dependent δ49Ti suggests that thermal processing (evaporation/condensation) and gas-dust decoupling may have been responsible for the presence of titanium isotope anomalies in CAIs and bulk meteorites of different groups.

Charlier et al. (2019) — The first combined nucleosynthetic, radiogenic and stable strontium isotope characterization of fine- and coarse-grained CAIs (using inclusions from Allende). All CAIs, regardless of texture, show apparent enrichment in 84Sr with variability far outside analytical uncertainties, testifying to some degree of heterogeneity in the CAI forming region. The similar magnitude of 84Sr excess in CAIs and carbonaceous chondrites, suggests that the inventories of Sr (and other refractory elements) in carbonaceous chondrites are dominated by a cryptic refractory dust component (CRD) that was formed early and near the Sun, and was subsequently transported outwards to the carbonaceous chondrite-forming region.

Pravdivsteva et al. (2020) — A step-pyrolysis study of noble gases in the Curious Marie CAI revealing the preservation of an s-process carrier in CAIs. This contrasts with the commonly held view that presolar grains are found solely in the fine-grained rims surrounding chondrules and in the low-temperature fine-grained matrix that binds the various meteoritic components together. The noble gases signatures are most consistent with SiC grains as the carriers. This study provides the first evidence that premolar grains were incorporated into fine-grained CAIs in the Allende carbonaceous chondrite at the time of their formation, and have survived parent-body processing.

Hu et al. (2021) — The first investigation of mass-dependent isotope effects of all multi-isotopic REEs in CAIs. (from Allende). The light isotope enrichment of the most refractory REEs and more subdued isotopic variations of the least refractory REEs argue against group II CAIs as product of equilibration condensation. Instead, a two-stage process involving fast evaporation of preexisting materials, followed by near-equilibrium recondensation is needed, possibly in events akin to FU Orionis– or EX Lupi–type outbursts of eruptive pre–main-sequence stars.

Charlier et al. (2021) — A step-leaching study of nine unmelted CAIs from Allende. The chemically resistant residues show extreme positive μ84Sr (up to +80,655) and 87Sr variations that cannot be explained by decay of 87Rb, pointing to the presence in fine-grained CAIs of a presolar carrier enriched in the p-nuclide (84Sr). We argue that this unidentified carrier controls the isotopic anomalies in bulk CAIs and outer solar system materials, which reinstates the chronological signif- icance of differences in initial 87Sr/86Sr between CAIs and volatile-depleted inner solar system materials.

Tompkins et al. (2020) — Details the analytical methods for Zr isotopic analysis of zircon and introduces the MTUR1 zircon standard for in-situ δ94/90Zr work.

Ibañez-Mejia & Tisot (2019) — Pioneering study showing that Zr-rich phases (i.e., zircon, baddeleyite) from the FC-1 gabbros of the Duluth Complex exhibit δ94/90Zr variability in excess of 5 ‰! These observations suggest that Zr stable isotopes in zircon may provide a powerful new tracer of magmatic differentiation and a means to probe the history of Zr removal from magmatic liquids during fractional crystallization.

Méheut et al. (2021) — Results from ab initio calculations showing that equilibrium Zr isotope effects are negligible at magmatic temperatures (Δ94/90Zr <0.05 ‰ between zircon and melt at > 700C). The extreme fractionations observed in zircon from the Duluth Gabbro (previous paper), can be explained instead as the result of kinetic isotopic fractionation effects within the diffusive boundary layers that develop in crystallizing magmas.