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Abstract This article describes condensation of the elements and use of condensation temperatures to plot and interpret Earth’s apparent volatility trend. Major points covered include the following. (1) Updated 50% condensation temperatures (T₅₀) for all naturally occurring elements, Tc, and Pu are tabulated at 10⁻²to 10⁻⁸bar total pressure for solar composition material. (2) Condensation temperatures are mainly controlled by the Gibbs energy of condensation reactions and also by the Gibbs energy of ideal mixing if elements (compounds) condense in a solution. The additional Gibbs energy change due to non-ideal solution, i.e., activity coefficients ≠1, is a secondary effect. (3) The theoretically correct relationship between condensation temperature and fraction condensed ($$\alpha _{\mathrm{M}}$$ ${\alpha }_M$) is derived from mass balance and chemical thermodynamic considerations. For major elements the condensation temperature is inversely proportional to log (1-$$\alpha _{\mathrm{M}}$$ ${\alpha }_M$). For trace elements dissolving in solid solution the condensation temperature is inversely proportional to log [(1-$$\alpha _{\mathrm{M}}$$ ${\alpha }_M$)/$$\alpha _{\mathrm{M}}$$ ${\alpha }_M$]. (4) The maximum amount of element condensed per K⁻¹, i.e., the maximum in [d$$\alpha _{\mathrm{M}}$$ ${\alpha }_M$/d(1/T)] is at the inflection point in the logistic (sigmoid) curve for an element, which is also at (or close to) the 50% condensation temperature. (5) Plots of normalized elemental abundances versus 50% condensation temperatures (volatility trends) are qualitative indicators of elemental fractionations due to volatility because they do not use the theoretically correct and quantitative relationship between condensation temperature and fraction condensed. (6) Volatility trend plots for average elemental abundances in CM, CO, CV, CR, H, L, LL, EH, EL chondrites show different “trends” for moderately and highly volatile elements, which may be linear, curved, a step function, or plateau. A comparison of three abundance sets for CM and CV chondrites shows trends depend on which elements are plotted, which data sources are used, and which temperature range is considered. (7) Proposed mechanisms for volatile element depletion in carbonaceous chondrites and the Earth are reviewed. (8) Some possible implications of volatile element abundances in the bulk silicate Earth are discussed. 

Abstract We studied a thin section of Lewis Cliff (LEW) 87223, an unusual EL3‐related, enstatite chondrite (EC) that has primary and secondary features not observed in other ECs. We studied its metal‐rich nodules, possible shock features, and chondrules, eight of which are Al‐rich chondrules (ARCs). LEW 87223 has petrologic and compositional features similar to EL3s. Enstatite is the dominant mineral; chondrule boundaries are well defined; Si content of metal (0.5–0.6 wt%) is consistent with typical EL3; it has Cr‐bearing troilite, oldhamite, and alabandite; and its O‐isotopic composition is similar to other ECs. However, metal abundance in LEW 87223 (~13 vol%) is slightly higher than in other EL3s and its metal nodules are texturally and mineralogically different from other ECs. Both high and low Ni metals are present, and its alabandite has higher Fe (27.8 wt% Fe) than in other EL3s. Silicates appear darkened in plane polarized light, largely due to reduction of Fe from silicate. A remarkable feature of LEW 87223 is the high abundance of ARCs, which contain Ca‐rich plagioclase and varying amounts of Na‐rich plagioclase along chondrule edges and as veins. This suggests Na metasomatism and the possibility of hydrothermal fluids, potentially related to an impact event. LEW 87223 expands the range of known EC material. It shows that ECs are more diverse and record a wider range of parent body processes than previously known. LEW 87223 is an anomalous EL3, potentially the first member of a new EC group should similar samples be discovered. 

We have measured the absolute doubly differential angular sputtering yield for 20 keV Kr+ impacting a polycrystalline Cu slab at an incidence angle of θi = 45° relative to the surface normal. Sputtered Cu atoms were captured using collectors mounted on a half dome above the sample, and the sputtering distribution was measured as a function of the sputtering polar, θs, and azimuthal, ϕs, angles. Absolute results of the sputtering yield were determined from the mass gain of each collector, the ion dose, and the solid angle subtended, after irradiation to a total fluence of ∼1 × 1018 ions/cm2. Our approach overcomes shortcomings of commonly used methods that only provide relative yields as a function of θs in the incidence plane (defined by the ion velocity and the surface normal). Our experimental results display an azimuthal variation that increases with increasing θs and is clearly discrepant with simulations using binary collision theory. We attribute the observed azimuthal anisotropy to ion-induced formation of micro- and nano-scale surface features that suppress the sputtering yield through shadowing and redeposition effects, neither of which are accounted for in the simulations. Our experimental results demonstrate the importance of doubly differential angular sputtering studies to probe ion sputtering processes at a fundamental level and to explore the effect of ion-beam-generated surface roughness. 

Dynamic models of the protoplanetary disk indicate there should be large-scale material transport in and out of the inner Solar System, but direct evidence for such transport is scarce. Here we show that the ε 50 Ti-ε 54 Cr-Δ 17 O systematics of large individual chondrules, which typically formed 2 to 3 My after the formation of the first solids in the Solar System, indicate certain meteorites (CV and CK chondrites) that formed in the outer Solar System accreted an assortment of both inner and outer Solar System materials, as well as material previously unidentified through the analysis of bulk meteorites. Mixing with primordial refractory components reveals a “missing reservoir” that bridges the gap between inner and outer Solar System materials. We also observe chondrules with positive ε 50 Ti and ε 54 Cr plot with a constant offset below the primitive chondrule mineral line (PCM), indicating that they are on the slope ∼1.0 in the oxygen three-isotope diagram. In contrast, chondrules with negative ε 50 Ti and ε 54 Cr increasingly deviate above from PCM line with increasing δ 18 O, suggesting that they are on a mixing trend with an ordinary chondrite-like isotope reservoir. Furthermore, the Δ 17 O-Mg# systematics of these chondrules indicate they formed in environments characterized by distinct abundances of dust and H 2 O ice. We posit that large-scale outward transport of nominally inner Solar System materials most likely occurred along the midplane associated with a viscously evolving disk and that CV and CK chondrules formed in local regions of enhanced gas pressure and dust density created by the formation of Jupiter.