Lunar regolith samples contain fragments of endogenic rocks and exogenous meteorites. We report the first discovery of a chondrule fragment preserved in Chang'e-5 (CE-5) regolith samples. Forsterite and enstatite phenocrysts have extremely high Mg# (> 99) and high Mn/Fe ratios in this chondrule fragment. Its glass mesostasis is heterogeneous and contains hydrogen and carbon, as indicated by Raman peaks. The mineral assemblage, chemical composition, and oxygen isotope anomaly of this fragment are similar to those of type-I chondrules from carbonaceous chondrites. This fragment and other chondritic relics with 3.4 Ga. This contrast suggests that there may have been a change of impactors to the Earth-Moon system during the Imbrian period. Furthermore, this CE-5 chondrule fragment is a direct record of volatile addition to the Moon's surface from meteorites during the Eratosthenian period.

As a moderately volatile, redox-sensitive chalcophile and siderophile element, Te and its isotopic composition can inform on a multitude of geochemical and cosmochemical processes. However, the interpretation of Te data from natural settings is often hindered by an insufficient understanding of the behavior of Te in high-temperature conditions. Here, we present the results of Te evaporation and isotopic fractionation in silicate melting experiments. The starting material was boron-bearing anorthite-diopside glass with 1 wt% TeO2. The experiments were conducted over the temperature range of 868-1459 degrees C for 15 min each, and at oxygen fugacities (logfO(2)) relative to the fayalite-magnetite-quartz buffer (FMQ) of FMQ-6 to FMQ+1.5, and in air. Evaporation of Te decreases with decreasing fO(2). For high-temperature experiments performed at > 1200 degrees C Te loss is accompanied by Te isotope fractionation towards heavier compositions in the residual glasses. By contrast, Te loss in experiments performed at temperatures 1200 degrees C is alpha(K) = 0.99993. At reducing conditions, Te likely substitutes as Te2- for O2- in the melt structure and becomes increasingly soluble at highly reducing conditions. Consequently, Te evaporation is not predicted for volcanic processes on reduced planetary bodies such as the Moon or Mercury. (C) 2022 Elsevier Ltd. All rights reserved.

Volatile lithophile elements are depleted in the different planetary materials to various degrees, but the origin of these depletions is still debated. Stable isotopes of moderately volatile elements such as Zn can be used to understand the origin of volatile element depletions. Samples with significant volatile element depletions, including the Moon and terrestrial tektites, display heavy Zn isotope compositions (i.e. enrichment of Zn-66 vs. Zn-64), consistent with kinetic Zn isotope fractionation during evaporation. However, Luck et al. (2005) found a negative correlation between delta Zn-66 and 1/[Zn] between CI, CM, CO, and CV chondrites, opposite to what would be expected if evaporation caused the Zn abundance variations among chondrite groups. We have analyzed the Zn isotope composition of multiple samples of the major carbonaceous chondrite classes: CI (1), CM (4), CV (2), CO (4), CB (2), CH (2), CK (4), and CK/CR (1). The bulk chondrites define a negative correlation in a plot of delta Zn-66 vs 1/[Zn], confirming earlier results that Zn abundance variations among carbonaceous chondrites cannot be explained by evaporation. Exceptions are CB and CH chondrites, which display Zn systematics consistent with a collisional formation mechanism that created enrichment in heavy Zn isotopes relative to the trend defined by CI-CK. We further report Zn isotope analyses of chondrite components, including chondrules from Allende (CV3) and Mokoia (CV3), as well as an aliquot of Allende matrix. All chondrules are enriched in light Zn isotopes (similar to 500 ppm on Zn-66/Zn-64) relative to the bulk, contrary to what would be expected if Zn were depleted during evaporation, on the other hand the matrix has a complementary heavy isotope composition. We report sequential leaching experiments in un-equilibrated ordinary chondrites, which show sulfides are isotopically heavy compared to silicates and the bulk meteorite by ca. +0.65 per mil on Zn-66/Zn-64. We suggest isotopically heavy sulfides were removed from either chondrules or their precursors, thereby producing the light Zn isotope enrichments in chondrules. (C) 2017 The Author(s). Published by Elsevier B.V.

High-precision magnesium (Mg) isotope data obtained using a large geometry high resolution MC-ICPMS are reported for 9 carbonaceous and ordinary chondrites, 9 eucrites and diogenites generally considered to originate from Asteroid 4 Vesta, together with 4 martian meteorites, and a variety of terrestrial and lunar materials. The variation in Mg isotopic composition found for mafic and ultramafic rocks, mafic minerals and chondrites is smaller than reported previously. The range of delta Mg-26 and delta Mg-25 of 0.6 parts per thousand and 0.3 parts per thousand defines a single mass-dependent fractionation line consistent with a homogeneous mix of nucleosynthetic components. Data for the Earth, Mars and Vesta display no systematic Mg isotopic differences despite large variations in the level of depletion in moderately volatile elements. Lunar mare basalts exhibit a significant range in delta Mg-26 (-0.53 parts per thousand to +0.05 parts per thousand) and delta Mg-25 (-0.27 parts per thousand to +0.02 parts per thousand) attributable to magmatic differentiation in the lunar magma ocean (LMO). Lunar basalts derived from early segregated cumulates and thought to be the most primitive are on average slightly similar to 0.17 parts per thousand (delta Mg-26) heavy relative to basalts from the Earth, Mars and Vesta. However, the difference is not well-resolved. More strikingly, all differentiated planets and planetesimals, as sampled, have Mg that is on average isotopically heavy compared with most chondrites analyzed thus far. Chondrules and CAIs also are generally heavy in terms of Mg, so this might reflect sorting of material in the proto-planetary disk. Such an explanation would be similar to one previously proposed (Hewins R. H. and Herzberg C. T. (1996) Earth Planet. Sci. Lett. 144, 1-7.) to explain the non-chondritic Si/Mg of the Earth. In this model chondrule-like objects separate from volatile rich planetary dust by accumulation in stagnant regions between eddies in the solar nebula. Small (similar to 1 km) planetesimals formed by accumulation of such molten material then develop into planetary embryos and thence to larger terrestrial planets by combinations of runaway growth and collisions. As such accumulation of molten chondrule-like droplets provides an explanation that obviates some of the dynamic difficulties associated with the onset of planetary accretion. The non-chondritic Mg isotopic composition of the Earth is consistent with data for Li and has important implications for Earth's bulk composition and putative hidden reservoirs. (C) 2007 Published by Elsevier B.V.