Recent astronomical observations have shown that dust can get locally concentrated in protoplanetary disks, forming ring structures. The thermal processing of such regions could lead to dust evaporation and local enrichment of the solar gas in condensable elements. Previous studies focusing on major element behavior have shown that condensation of such dust-enriched gas could lead to the formation of a silicate melt with compositions resembling that of chondrules. However, previous studies focusing on dust-enriched environments were restricted to a limited set of elements. To study the mineralogical and chemical composition of condensates in these conditions, we have performed equilibrium calculations using the FactSageTM software for a dust-enriched solar gas. The calculations were done with dust-enrichment factors of 1 (solar composition), 10 and 100 at pressures ranging between 10-6 bar and 10-3 bar, for a CI-chondrite dust and a H-chondrite dust. The trace element condensation was accurately modelled with newly calculated activity coefficients in different solid and melt solutions. The available gas phase database was completed with new trace element species that are important to consider in oxidized conditions. The mineralogical sequence, melt composition and condensation temperature for all condensable elements were then quantified. Our calculations show that the iron contents of olivine in equilibrium with a gas that is x100 enriched in CI-dust is consistent with that of amoeboid olivine aggregates and chondrules. Furthermore, our estimated temperature at which fayalite can form in these conditions is higher than what was previously proposed, enabling diffusion and homogenization of iron in olivine. The calculated composition of refractory metals for a x10 and x100 CI-dust enriched gas at 10-4 bar is consistent with the measured compositions of refractory metal nuggets. The possibility for these grains to have formed in an H2O ice-enriched gas can be ruled out as the calculated fractionation patterns in this case did not match the observed compositions.

During the early history of the Solar System or in molecular clouds, dust particles were submitted to intense irradiation by protons, and helium nuclei accelerated to MeV energies or higher. The consequence of this irradiation on the isotope composition of solids at such energies is unknown, but major element modifications of chemical compositions suggest that there could be isotope fractionation associated with irradiation. In this study, we have analyzed the Si isotope composition of olivine layers produced by sputter deposition starting from San Carlos olivine. The deposits were irradiated by He2+ with a total fluence of 1.5 x 1017. The olivine deposits were analyzed prior to and after irradiation for Si isotopes by multicollector ICPMS. The Si isotope composition after sputter deposition (prior to He irradiation) was enriched in heavy Si isotopes with a mean delta 30Si value of 12.6 parts per thousand relative to the NBS-28 standard, whereas the irradiated olivine had lower delta 30Si values of 10.8 parts per thousand and 8.2 parts per thousand for the 200 keV and 6 MeV He irradiation, respectively. In both cases, the Si isotope fractionation are strictly mass-dependent. First, these results show that the process of sputter deposition induces a large enrichment in heavy Si isotopes that we attribute to a difference in the sticking coefficient of SiO isotopologues. Second, the effect of He irradiation is the reverse of what is expected from theoretical studies and numerical simulations of isotope fractionation under these irradiation conditions at lower energies (keV range). The enrichment in light Si isotopes could be due to redistribution processes and segregation that take place during the irradiation. This study suggests that Si isotopes could be powerful tracers of irradiation processes in astrophysical settings.

Context. Dust grains play a crucial role in the modeling of protostellar formation, particularly through their opacity and interaction with the magnetic field. The destruction of dust grains in numerical simulations is currently modeled primarily by temperaturedependent functions. However, a dynamical approach could be necessary to accurately model the vaporization of dust grains. Aims. We focused on modeling the evolution of dust grains during star formation, specifically on the vaporization of the grains by chemisputtering. We also investigated the evolution of non-ideal magnetohydrodynamic resistivities and the Planck and Rosseland mean opacities influenced by the grain evolution. Methods. We modeled the evolution of the dust by considering spherical grains at thermal equilibrium with the gas phase, composed only of one kind of material for each grain. We then took into account the exchange processes that can occur between the grains and the gas phase and that make the grain size evolve. We considered three materials for the grains: carbon, silicate, and aluminum oxide. Given a temporal evolution in temperature and density of the gas phase, we computed the evolution of a dust grain distribution. This evolution was then used to compute the non-ideal magnetohydrodynamic resistivities and the Planck and Rosseland mean opacities. Results. We observed a significant dependence of the sublimation temperature of the carbon grains on the dynamical evolution of the gas phase. The application of our method to trajectories where the temperature and density of the gas decrease after the sublimation of a portion of the grain distribution highlights the limitations of current vaporization prescriptions in simulations. Conclusions. The dynamical approach leads to more accurate results for the carbon grain quantity when the temperature and density of the gas evolve quickly. The dynamical approach application to collapse and disk evolution is then foreseen with its integration into hydrodynamic simulations.

Although Earth, together with other terrestrial planets, must have had an early-formed protocrust, the chemical composition of this crust has received little attention. The protocrust was extracted from an extensive magma ocean formed by accretion and melting of asteroidal bodies1. Both experimental and chronological data suggest that the silicate melt ascending from this magma ocean formed in equilibrium with, or after, metal was extracted to form Earth's core. Here we show that a protocrust formed under these conditions would have had incompatible (with respect to silicate minerals) trace-element characteristics remarkably similar to those of the current average continental crust. This has major implications for subsequent planetary evolution. Many geochemical arguments for when and how plate tectonics began implicitly assume that subduction is required to produce the continental trace-element signature. These arguments are severely compromised if this signature was already a feature of the Hadean protocrust.

The energy of the giant impact was large enough to generate an initially fully molten Moon. During the solidification of this lunar magma ocean (LMO), an anorthosite crust formed by flotation of light anorthite crystals. Lunar anorthosites show crystallization ages as young as 4.360 Gyr, suggesting a long-lived LMO or a rather young Moon. Existing models for LMO solidification are for a specific phase diagram based on one compositional model. However, the LMO solidification timescale depends on the lunar bulk composition and on the appearance of anorthite in the crystallization sequence.Here, we propose a physically robust 1D model for LMO evolution based on a simple anorthite/olivine-pyroxene eutectic phase diagram. Cumulates first settle at the ocean base for about a thousand years. This first stage results in an unstable thermal profile for the cumulates that can lead to their overturn. In the second stage, simultaneous crystallization of anorthite and cumulates leads to the formation of a buoyant lid that considerably slows down LMO cooling.We explore the impact of an initially hydrated composition, which reduces the stability of plagioclase, of the eutectic position and of the crust thermal conductivity. We show that cumulates overturn may reduce or extend the LMO solidification time depending on its duration. The total LMO solidification timescale ranges between 45 and 250 Myr. Given the most reliable age of 4.360 Gyr for FAN sample 60025, which derives from more than 99% of crystallization, we estimate an age of 4400 to 4560 Myr for the Moon.

Determining the age of the Moon, which is commonly considered as the termination of Earth accretion has been a complex challenge for geochronology. A number of methods have been used to delineate the age of the Moon based either on absolute chronology of lunar rocks or have relied on more indirect methods using short-lived nuclides such as Hf-182 that was present in the early history of the Solar System. Model ages usually require some assumptions that are sometimes controversial or harder to verify. In this study, new high precision Sr isotope data (2.4 ppm, 2SD) were obtained for a well -dated lunar anorthosite (60025) in order to better constrain the initial Sr-87/ Sr-86 of the bulk silicate Moon. This new data is then used to model the Sr isotope evolution of the Earth -Moon starting from the beginning of the Solar System. To comply with the Hf - W and stable isotope constraints, we then assume that the Earth and Moon were equilibrated at the time of Moon formation. By investigating systematically all the sources of uncertainties in our model, we show that compared with previous work on anorthosites, one can tighten the constraints on the youngest age of Moon formation to no >79 Ma after the beginning of the Solar System, i.e. the Moon cannot be younger than 4488 Ma.

Condensation processes, which are responsible for the main chemical differences between gas and solids in the Galaxy, are the major mechanisms that control the cycle of dust from evolved stars to planetary systems. However, they are still poorly understood, mainly because the thermodynamics and kinetic models of nucleation or grain growth lack experimental data. To bridge this gap, we used a large-volume three-phase alternating-current plasma torch to obtain a full high-temperature condensation sequence at an elevated carbon-to-oxygen ratio from a fluxed chondritic gas composition. We show that the crystallized suites of carbides, silicides, nitrides, sulfides, oxides and silicates and the bulk composition of the condensates are properly modelled by a kinetically inhibited condensation scenario controlled by gas flow. This validates the thermodynamic predictions of the condensation sequence at a high carbon-to-oxygen ratio. On this basis and using appropriate optical properties, we also demonstrate the influence of pressure on dust chemistry as well as the low probability of forming and detecting iron silicides in asymptotic giant branch C-rich circumstellar environments as well as in our chondritic meteorites. By demonstrating the potential of predicting dust mineralogy in these environments, this approach holds high promise for quantitatively characterizing dust composition and formation in diverse astrophysical settings. A high-power plasma torch was used to experimentally simulate the dust condensation process in carbon-rich stellar outflows. This approach holds promise for the quantitative characterization of dust composition and formation in diverse astrophysical settings.

A large-volume plasma torch has been used to experimentally simulate condensation in carbon-rich stellar outflows. Using the observed condensation sequence and appropriate optical properties, the feasibility of predicting dust mineralogy in these environments is demonstrated, offering a promising approach to the quantitative characterization of dust composition in various astrophysical settings.

The new Neoma MC-ICPMS/MS is equipped with a prefiltering system consisting of a double-Wien filter and a collision/reaction cell whose performances are challenged using different combinations of magnetic and electrostatic field values and adjustable slit apertures.

Geochemically enriched signatures in global oceanic basalts have long indicated a heterogeneous mantle source, but the role of lithologic heterogeneity in producing mantle partial melts, particularly fertile pyroxenite rocks, remains unclear. Uranium-series disequilibria in basalts are particularly sensitive to the increased garnet mode and melting rates of pyroxenite rocks, making the system a useful indicator of mantle lithologic heterogeneity in the melt region for oceanic basalts. Here we summarize evidence for the presence and importance of pyroxenite rocks in the upper mantle and their role in melt generation of mid-ocean ridge basalts and ocean island basalts, with a synthesis of U-series disequilibrium systematics in oceanic basalts and implications for global lithologic heterogeneity of the upper mantle. We further synthesize the melt modeling approaches for the interpretation of U-series disequilibria in basalts and demonstrate the use of numerical solution models for time-dependent reactive porous flow and dynamic melting during decompression of a two-lithology mantle in thermal equilibrium. Our model outcomes corroborate prior interpretations in favor of reactive porous flow and two-porosity transport for relatively homogeneous, peridotite-dominated mantle regimes, and further support contributions of pyroxenite partial melts to aggregated melts in order to reproduce the heterogeneous global basalt data. To most accurately predict the conditions of melting by comparison with measured data, two-lithology melting calculations should carefully consider the role of thermal equilibrium, mineral/melt partitioning, non-linear variations in mineral modes, and degree of melting during the melting process.

The measurement of radioactive xenon isotopes (radioxenon) in the atmosphere is a tool used to detect underground nuclear explosions, provided that some radioxenon escaped containment and that fractionation leading to the alteration of the relative proportions of these isotopes, is accounted for. After the explosion, volatilization followed by melting of the surrounding rocks produces a magma where the more refractory radioactive species get dissolved while the more volatile ones contribute to the gas phase that might escape. Indium, tin, antimony, tellurium and iodine are the main fission products involved in the decay chains leading to radioxenon. In this study, condensation as a function of temperature for these precursors of radioxenon were determined using thermodynamic calculations for systems with complex chemical composition corresponding to major environments of known underground nuclear explosions and for a range of pressure values representative of the cavity evolution. Our results illustrate a large difference between the relevant condensation temperatures for the radioxenon precursors and the tabulated boiling temperatures of the pure compounds often used as indicators of their volatility. For some precursory elements such as tin, the often-considered Heaviside function represents an oversimplification of the concept of condensation temperature, as condensation occurs over a temperature range as large as 2000 K. This results from the speciation of the elements in the gas phase mainly driven by the formation of oxides. Condensation also strongly depends on pressure while it moderately depends on the bulk chemical composition of the system. This study shows the importance and complexity of the condensation process following underground nuclear explosions. It also shows how thermodynamic computations allow the prediction of the quantity and the relative proportions of radioactive xenon isotopes in the gas phase in the presence of magma, before their potential emission to the atmosphere. Better detection, discrimination and understanding of underground nuclear explosions should arise by taking into account the fractionation resulting from the condensation of the radionuclides producing radioxenon in nuclear cavities.

The authors regret that a small error in the dynamic melting Matlab script used for this paper produced erroneous results for some of the included modeling outcomes.We have written an updated modeling program in python, which can be accessed in the ENKI and pyUserCalc

Accretion of terrestrial planets involved partial or global melting events such as magma oceans or magma ponds. Mars experienced large-scale differentiation very early in its history, as shown by its Sm-146-Nd-142 and Hf-182-W-182 record. The broad variations in epsilon Nd-142 and epsilon W-142 of SNC meteorites highlight the presence of mantle sources that must have remained isolated, at least partly, after the crystallization of a global magma ocean. In this study, we have investigated whether the crystallization of the martian magma ocean could have generated mantle reservoirs characterized by different silicon isotope signatures, as the fractionation of Si isotopes between minerals and melts is known to depend on pressure. Thus, the goal of this study was to investigate whether there were any relationships between magma ocean crystallisation and possible variations in the Si isotope record of SNC meteorites. High resolution silicon isotope measurements were performed on twelve meteorites from the Shergottite, Nakhlite and Chassignite groups using a Neptune Plus MC-ICP-MS in dry plasma mode. The delta Si-30 values are in good agreement with previous studies but display a narrower range of variations with a mean value at -0.46 parts per thousand +/- 0.07 (2SD). A magma ocean crystallization model shows that the range of delta Si-30 in SNCs is consistent with that generated by magma ocean crystallisation. In particular, there is a correlation between calculated Sm-147/Nd-144 for the moderately depleted mantle sources with delta Si-30 values; this correlation is consistent with the crystallization model if one includes trapped melt in the cumulates. In contrast, enriched shergottites displayed a very homogenous composition in Sm/Nd ratios, despite significant variability in delta Si-30. This observation could be related to either fluid-rock interactions or redox effect during magma differentiation. Altogether, silicon isotope compositions of SNC provide new constraints about magma ocean crystallization processes in Mars. (C) 2022 The Author(s). Published by Elsevier Ltd.

We present a new method for the chemical purification and the measurement of the isotopic composition of Cr by Thermal-Ionization Mass Spectrometry in various geological materials. The separation and purification protocol was adapted to match a wide range of geological and cosmochemical matrices and was tested with terrestrial reference materials, uranium-rich samples and meteorites. The total Cr yield was at least 86% and the Cr/U ratio went from 7.84 x 10(-5) to 5.72 x 10(3) after purification for uranium-rich materials. It also permitted an efficient removal of matrix elements such as Na and Mg and interfering elements such as Fe, Ti and V. Cr isotopic composition was measured using multistatic and multidynamic modes. The multidynamic mode displayed no improvement of the external reproducibility and internal precision compared with the multistatic mode, in contrast with what has been found with other isotope systems. This method gave a reproducibility of 5 ppm and 13 ppm (2 s.d.) for the Cr-53/Cr-52 and Cr-54/Cr-52 ratios respectively, over a period of several months, which represents an improvement of the long-term reproducibility compared with the other published methods. The accuracy of the protocol was tested by measuring terrestrial reference materials (AGV-1, AGV-2, BHVO-1 and BHVO-2) as well as extra-terrestrial samples (Bouvante, Stannern and Waconda), displaying good agreement with published data. This method is thus suited to detect any mass-independent fractionation or nucleosynthetic anomalies in geological materials. (C) 2022 Elsevier B.V. All rights reserved.

The Moon is thought to have formed from material ejected by a giant impact that took place at the end of Earth's accretion. The material ejected to space generated a large hot structure where material beyond the Roche limit accreted to form the Moon. It has long been known that the Moon is characterized by abundances in moderately volatile elements (MVE) lower than that of the Earth, while more recent studies have established that the concentrations in refractory elements are similar to the bulk Silicate Earth. The thermodynamic conditions that prevailed after this impact are poorly known and understanding the origin of the Moon-Earth differences in MVE requires a knowledge of the volatility of elements under these conditions. In this study, we reexamine the volatility of a large set of geochemically relevant elements and attempt to determine the P-T conditions under which volatiles were putatively separated from the liquid material. Our model predicts very different condensation temperatures due to higher pressures, compared with the conditions of the Solar Nebula and we extend the values of these temperatures to a wide number of trace elements (Se, Ag, Pt, Mo, W, Zn, Sn, Sb, Rb, Cs, U, Th, Cr, Ni, Co, Ga, Ge, Cu, and P). Our modeling shows that the observed lunar compositions cannot be explained by a single set of P and T conditions. Rather, it is best explained by a mixture between high-temperature condensates (~4000 K) and low temperature condensates (2000-2500 K). An important constraint is that for the low temperature condensates, liquid metal must have been stable and this is crucial for matching the abundance of volatile siderophile elements in the bulk Moon.