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The core-mantle differentiation process plays a pivotal role in redistributing material on a massive scale, shaping the long-term evolution of rocky planets. Understanding this process is crucial for gaining insights into the accretion and evolution of planets like Mars. However, the details of Mars's core-mantle differentiation remain poorly understood due to limited compositional data for its core and mantle. In this study, we aim to constrain the Martian core-mantle differentiation by examining FeO partitioning between core and mantle materials, incorporating improved Martian compositional data from the InSight mission. Using ab initio thermodynamic techniques, we calculated the FeO partition coefficient between liquid iron and silicate melt. Our results align with previous studies while also clarifying the factors affecting partitioning behavior. Based on these findings and estimates of oxygen concentration in the core, we infer that Mars's core and mantle likely differentiated at temperatures above 2440 K and pressures ranging from 14 to 22 GPa. Although these estimates are higher than previously reported, they are consistent with observed abundances of moderately siderophile elements and Mars's accretion models. [ABSTRACT FROM AUTHOR]

Highly siderophile element (HSE) contents of komatiites have been widely used to estimate the HSE composition of Earth's mantle. However, the interpretation of existing komatiite data is controversial, with some authors arguing that the Archean deep mantle komatiite source was impoverished in HSE due to slow admixture of a late accretion component, while others invoke a melting process that would allow observed komatiite abundances to be obtained from a mantle source with present-day HSE abundances. To obtain insight into this issue, we present new HSE abundance data for komatiites from the Gorumahishani greenstone belt of the Singhbhum Craton, eastern India. Our Sm-Nd and Re-Os isotope data indicate a ∼3.5 Ga age for these little-studied rocks, which provide extreme examples of Al-depleted and Ti-depleted komatiite varieties, juxtaposed over a short-length scale. The calculated parental melt compositions for the Al-depleted komatiites have 2.7 ± 0.2 ppb Ru, 3.4 ± 0.2 ppb Pt, and 3.2 ± 0.6 ppb Pd, whereas, for the Ti-depleted type these values are 4.4 ± 0.3 ppb Ru, 3.2 ± 0.6 ppb Pt, 3.0 ± 0.5 ppb Pd. These concentrations are similar to those found in most Archean komatiites at >3.4 Ga. For the Al-depleted samples, these values would correspond to mantle abundances equivalent to ∼38 % of modern Bulk Silicate Earth (BSE) Ru contents and ∼24 and ∼21 % of BSE Pt and Pd contents, respectively, if it is assumed that simple extrapolation of the measured values to the MgO content of fertile peridotite provides an adequate approximation of the HSE composition of the BSE. To examine the alternative model that the low contents of Ru, Pd and Pt in Gorumahishani komatiites could be obtained from a mantle source with BSE-like HSE contents, we apply a simple two-stage critical melting model using current experimental HSE partitioning coefficients. The Ru abundances of the Gorumahishani Al-depleted komatiitic magmas can be produced from the pooled melts of a fertile source with BSE-like Ru and S contents during the first melting stage. The Ru abundances of the Ti-depleted komatiitic magmas can then be produced from remelting the residue left by this first melting stage. On the other hand, Pt and Pd abundances cannot be successfully modelled for either the Al-depleted or the Ti-depleted komatiites using available partition coefficients, though our current understanding of Pt and Pd partitioning after sulfide exhaustion is limited. The use of komatiites to characterize the abundance and distribution of HSE in the early mantle critically depends on developing a better understanding of the partitioning behaviors of these elements between mantle sources and komatiitic magmas. [ABSTRACT FROM AUTHOR]

Pebble accretion provides new insights into Earth's building blocks and early protoplanetary disk conditions. Here, we show that mixtures of chondritic components : metal grains, chondrules, calcium-aluminum-rich inclusions (CAIs), and amoeboid olivine aggregates (AOAs) match Earth's major element composition (Fe, Ni, Si, Mg, Ca, Al, O) within uncertainties, whereas no combination of chondrites and iron meteorites does. Our best fits also match the ε 54Cr and ε 50Ti values of Earth precisely, whereas the best fits for chondrites, or components with a high proportion of E chondrules, fails to match Earth. In contrast to some previous studies, our best-fitting component mixture is predominantly carbonaceous, rather than enstatite chondrules. It also includes 15 wt% of early-formed refractory inclusions (CAIs + AOAs), which is similar to that found in some C chondrites (CO, CV, CK), but notably higher than NC chondrites. High abundances of refractory materials is lacking in NC chondrites, because they formed after the majority of refractory grains were either drawn into the Sun or incorporated into terrestrial protoplanets via pebble accretion. We show that combinations of Stokes numbers of chondritic components build 0.35–0.7 Earth masses in 2 My in the Hill regime accretion, for a typical pebble column density of 1.2 kg/m2 at 1 au. However, a larger or smaller column density leads to super-Earth or moon-mass bodies, respectively. Our calculations also demonstrate that a few My of pebble accretion with these components yields a total protoplanet mass inside 1 au exceeding the combined masses of Earth, Moon, Venus, and Mercury. Accordingly, we conclude that pebble accretion is a viable mechanism to build Earth and its major element composition from primitive chondritic components within the solar nebula lifetime. [ABSTRACT FROM AUTHOR]

Carbonated melts play a significant role in mobilizing lithophile and volatile elements in the Earth's mantle and mantle metasomatism. However, there has been limited investigation into their potential for mobilizing chalcophile and siderophile elements (CSEs). In this study, we experimentally determine the sulfide liquid–carbonated melt partition coefficients of CSEs (D CSE Sul / C _ m e l t ) for a range of elements, including Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, In, Sn, Re, and Pb, at 1300–1600 °C, 1.0–3.0 GPa, and oxygen fugacity (f O 2) close to the graphite-CO 2 fluid buffer. Furthermore, the D Sul / C _ m e l t values for lithophile elements Cr, Mn, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, and Ta (D LithoE Sul / C _ m e l t ) are also determined. The obtained D CSE Sul / C _ m e l t values are 34–1230 for Co, 380–75200 for Ni, 200–14900 for Cu and Ag, 0.5–28 for Zn and Mo, 42–98 for Se, 24–640 for Cd, 5–52 for In and Sn, 650–15200 for Re, and 22–2470 for Pb. The obtained D LithoE Sul / C _ m e l t values are below 1–10. The variations of D CSE Sul / C _ m e l t and D LithoE Sul / C _ m e l t are primarily influenced by the FeO tot content in the carbonated melts. A partitioning model was developed to parameterize D CSE Sul / C _ m e l t and D LithoE Sul / C _ m e l t as a multi-function of pressure, temperature, composition of the carbonated melt (mainly the FeO tot content), and composition of the sulfide liquid. Our parameterization can explain the observed large variations of D CSE Sul / C _ m e l t and D LithoE Sul / C _ m e l t for most of the trace elements studied. Using our D CSE Sul / C _ m e l t parameterization, we model the CSE and U–Th contents of low-degree partial melts of carbonated mantle peridotite and slab eclogite with sulfur concentrations ranging from 50 to 500 µg/g. The modeling results can generally explain the trace element patterns observed in natural kimberlites and carbonatites; however, the peridotite- or slab-derived carbonated melts have a low capability in mobilizing CSEs, which can extract less than 3 % of Cu, Ni, Co, Re, and Os, 3–30 % of Mo, Pb, and Se, but up to 30–50 % U and Th from the source lithology. Consequently, the influence of carbonatite metasomatism on the Cu, Ni, Co, Re, and Os systematics of the Earth's mantle is minimal, although local enrichments of CSEs may occur when sulfides precipitate from carbonated melts. Because of the elevated concentrations of U and Th and the corresponding U/Pb and Th/Pb ratios in the carbonated melts, the mantle lithology that has undergone metasomatism by these melts can become a geochemical reservoir with high 208Pb/206Pb ratios. However, the effect of carbonatite metasomatism on Re–Os isotopic systems of the mantle is minimal due to the low Re concentrations in the carbonated melts. Accordingly, the radiogenic Pb–Os isotopic signatures of HIMU ocean island basalts cannot be explained solely by carbonatite metasomatism in the mantle. [ABSTRACT FROM AUTHOR]

The short-lived 182Hf–182W system is widely used for constraining the chronology of the early Solar System, including the timing of the formation, thermal evolution, and differentiation of planetary bodies. Utilizing the full potential of the Hf–W system requires knowledge of the Hf/W ratio and W isotopic composition of primitive chondritic material. However, metal-silicate heterogeneity among chondritic samples can complicate accurately determining the Hf–W systematics of bulk chondrite parent bodies. Moreover, interpreting Hf–W data for chondrites may be complicated by potential nucleosynthetic W isotope anomalies. To this end, we report Hf/W ratios and W isotope compositions for bulk ordinary and enstatite chondrites, as well as the first such data for Rumuruti chondrites. We find that ordinary and Rumuruti chondrites show no resolvable nucleosynthetic anomalies, whereas resolved ε183W (i.e. , 0.01% deviation in 183W/184W from terrestrial standard) excesses in individual enstatite chondrites suggest the presence of nucleosynthetic W isotope anomalies in bulk meteorite samples originating in the inner Solar System. These anomalies necessitate corrections when accurately quantifying radiogenic 182W variations. Furthermore, several ordinary chondrites deviate in Hf/W ratios and W composition from the parent body compositions previously obtained from internal 182Hf–182W isochrons, indicating variations in the abundance of metal across different chondrite samples. Similarly, the Hf–W systematics of some enstatite chondrites also deviate from the parent body values, which can be attributed to the heterogeneous distribution of Hf carrier phases. The new observations highlight the challenges in obtaining Hf-W data that are representative of the chondrite parent bodies from individual chondrites, especially from metal-rich samples. By contrast, Rumuruti chondrites of variable petrologic types exhibit uniform Hf/W and 182W/184W ratios, suggesting that these samples are representative of their parent body. Whereas their Hf/W ratio is similar to that of carbonaceous chondrites, their W isotope composition is less radiogenic. This indicates that the Rumuruti precursor reservoir most likely had a significantly lower Hf/W ratio than the ratio measured in Rumuruti chondrites today. These findings underscore the importance of understanding the likely variations in Hf-W isotope systematics of iron meteorite parent bodies for accurately determining the timing of core formation. [ABSTRACT FROM AUTHOR]

The problem of the internal structure of the Moon plays a special role in understanding its geochemistry and geophysics. The principal sources of information about the chemical composition and physical state of the deep interior are seismic experiments of the Apollo expeditions, gravity data from the GRAIL mission, and geochemical and isotopic studies of lunar samples. Despite the high degree of similarity of terrestrial and lunar matter in the isotopic composition of several elements, the problem of the similarity and/or difference in the major-component composition of the silicate shells of the Earth and its satellite remains unresolved. This review paper summarizes and critically analyzes information on the composition and structure of the Moon, examines the main contradictions between geochemical and geophysical classes models for the mantle structure, both within each class and between the classes, related to the estimation of the abundance of Fe, Mg, Si, Al, and Ca oxides, and analyzes bulk silicate Moon (BSM) models. The paper describes the principles of the approach to modeling the internal structure of a planetary body, based on the joint inversion of an integrated set of selenophysical, seismic, and geochemical parameters combined with calculations of phase equilibria and physical properties. Two new classes of the chemical composition of the Moon enriched in silica (∼50% SiO2) and ferrous iron (11–13% FeO, Mg# 79–81) relative to the bulk composition of the silicate component of the Earth (BSE) are discussed: (i) models E with terrestrial concentrations of CaO and Al2O3 (Earth-like models) and (ii) models M with higher contents of refractory oxides (Moon-like models), which determine the features of the mineralogical and seismic structure of the lunar interior. A probabilistic distribution of geochemical (oxide concentrations) and geophysical (P-, S-wave velocities and density) parameters in the four-layer lunar mantle within the range of permissible selenotherms was obtained. Systematic differences are revealed between contents of major oxides in the silicate shells of the Earth and the Moon. Calculations were carried out for the mineral composition, P-, S-wave velocities, and density of the E/M models, and two classes of conceptual geochemical models: LPUM (Lunar Primitive Upper Mantle) and TWM (Taylor Whole Moon) with Earth's silica content (∼45 wt % SiO2) and different FeO and Al2O3 contents. Arguments are presented in support of the SiO2- and FeO-enriched (olivine pyroxenite) lunar mantle, which has no genetic similarity with Earth's pyrolitic mantle, as a geochemical consequence of the inversion of geophysical parameters and determined by cosmochemical conditions and the mechanism that formed the Moon. The dominant mineral of the lunar upper mantle is high-magnesium orthopyroxene with a low calcium content (rather than olivine), as confirmed by Apollo seismic data and supported by spacecraft analysis of spectral data from a number of impact basin rocks. In contrast, the P- and S-wave velocities of the TWM and LPUM geochemical models, in which olivine is the dominant mineral of the lunar mantle, do not match Apollo seismic data. The geochemical constraints in the scenarios for the formation of the Moon are considered. The simultaneous enrichment of the Moon in both SiO2 and FeO relative to the pyrolitic mantle of the Earth is incompatible with the formation of the Moon as a result of a giant impact from terrestrial matter or an impact body (bodies) of chondritic composition and is in conflict with modern scenarios of the formation of the Moon and with similarities in the isotopic compositions of lunar and terrestrial samples. The problem of how to fit these different geochemical factors into the Procrustean bed of cosmogonic models for the Earth–Moon system formation is discussed. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an essential element for life. Yet the processes of planet formation and early planetary evolution through which rocky planets like Earth obtained their atmospheric and surface nitrogen inventory are poorly understood. In order to understand the effect of early silicate differentiation of the rocky bodies on N inventory, here we study the elemental partitioning of N between the silicate minerals and melts. We conducted laboratory experiments using tholeiitic basalts and Fe + Si alloy mixtures at 1.5 – 4.0 GPa and 1300 to 1550 °C under graphite saturation at an oxygen fugacity range of IW–1.1 to IW–3.0. The experiments yielded an assemblage of Fe-rich alloy melt (am) + silicate melt (sm) + clinopyroxene (cpx) ± garnet (grt) ± orthopyroxene (opx) ± plagioclase (plag). Using electron microprobe, we determine that under the experimental conditions, N act as an incompatible element with D N c p x / s m (0.11 – 0.47) > D N p l a g / s m (0.41) > D N o p x / s m (0.25) > D N g r t / s m (0.06 – 0.21). The D N m i n e r a l / s m do not show any strong dependence on temperature, pressure, and melt composition. However, through comparison with previous estimates, it appears that with decreasing f O 2 , N becomes less incompatible. Under our experimental conditions of alloy melt-mineral equilibria, N behaves as a siderophile element (D N a m / m i n e r a l ranging from 4.1 to 60.6) with f O 2 playing the strongest control on D N a m / m i n e r a l . Our data suggest that under reducing conditions, in the early stages of a magma ocean (MO) and/or deeper mantle, silicate minerals would hold a non-negligible fraction of N as N becomes less atmophile and siderophile. Therefore, reduced parent bodies could also retain substantial N in the residual mantle during partial melting. The extraction of N from an internal MO or a solid planetary mantle is thus enhanced only as the system becomes more oxidizing, enriching the surficial reservoirs in N. Thus, Earth's N 2 -rich atmosphere may be intrinsically linked to its mantle oxidation, whereas other rocky planets of the Solar System, such as Mars and Mercury, may have retained a significant portion of their N inventory in nominally N-free mantle silicates through episodes of MO crystallization and mantle melting. [ABSTRACT FROM AUTHOR]

Over 20,000 meteorites have been recovered from hot deserts. The effects of hot desert weathering upon highly siderophile elements (HSE) have been little studied. We have investigated the effects of neutral to mildly acidic leaching of three L6‐type ordinary chondrites of different weathering grades on HSE concentrations and Re‐Os isotopic systematics. We have characterized the bulk sample HSE patterns of these meteorites and conducted leaching experiments with progressively longer leaching times to determine the possible effects of long‐term residence in a desert. The most weathered sample (NWA 14239) displayed greater HSE concentration homogeneity than the other samples and released lower quantities of HSEs during leaching. Water leaching was milder than acetic acid and did not significantly modify the Re‐Os isotopic systematics of the residue relative to the bulk sample of NWA 869. Short‐term leachates of the less weathered samples (Viñales and NWA 869) were characterized by low 187Os/188Os ratios, indicating the preferential dissolution of early solar system–formed phases such as non‐magnetic chondrules and matrix with low Re/Os that are no longer intact in the most weathered sample. Of the HSE, Pd is most resistant to both water and acetic acid leaching, with a maximum removal of ~5% Pd, while Re, Os, and Ir are most mobile with up to 40% removal. [ABSTRACT FROM AUTHOR]

The processes of planetary accretion and differentiation, whereby an unsorted mass of primitive solar system material evolves into a body composed of a silicate mantle and metallic core, remain poorly understood. Mass‐dependent variations of the isotope ratios of non‐traditional stable isotope systems in meteorites are known to record events in the nebula and planetary evolution processes. Partial melting and melt separation, evaporation and condensation, diffusion, and thermal equilibration between minerals at the parent body (PB) scale can be recorded in the isotopic signatures of meteorites. In this context, the acapulcoite–lodranite meteorite clan (ALC), which represents the products of thermal metamorphism and low‐degree partial melting of a primitive asteroid, is an attractive target to study the processes of early planetary differentiation. Here, we present a comprehensive data set of mass‐dependent Fe, Zn, and Mg isotope ratio variations in bulk ALC species, their separated silicate and metal phases, and in handpicked mineral fractions. These non‐traditional stable isotope ratios are governed by mass‐dependent isotope fractionation and provide a state‐of‐the‐art perspective on the evolution of the ALC PB, which is complementary to interpretations based on the petrology, trace element composition, and isotope geochemistry of the ALC. None of the isotopic signatures of ALC species show convincing co‐variation with the oxygen isotope ratios, which are considered to record nebular processes occurring prior to the PB formation. Iron isotopic compositions of ALC metal and silicate phases broadly fall on the isotherms within the temperature ranges predicted by pyroxene thermometry. The isotope ratios of Mg in ALC meteorites and their silicate minerals are within the range of chondritic meteorites, with only accessory spinel group minerals having significantly different compositions. Overall, the Mg and Fe isotopic signatures of the ALC species analyzed are in line with their formation as products of high‐degree thermal metamorphism and low‐degree partial melting of primitive precursors. The δ66/64Zn values of the ALC meteorites demonstrate a range of ~3.5‰ and the Zn is overall isotopically heavier than in chondrites. The superchondritic Zn isotopic signatures have possibly resulted from evaporative Zn losses, as observed for other meteorite parent bodies. This is unlikely to be the result of PB differentiation processes, as the Zn isotope ratio data show no covariation with the proxies of partial melting, such as the mass fractions of the platinum group and rare earth elements. [ABSTRACT FROM AUTHOR]

The Urucum iron- and manganese formation (IF-MnF) in the Santa Cruz Formation, Brazil, was deposited in a glacially influenced, late Neoproterozoic depositional environment. It has proven to be a reliable and robust archive for the late Neoproterozoic, allowing unique insights into the composition of seawater during an interval that is characterized by dramatic changes in the Earth's litho-, hydros-, atmo-, and biosphere, including several episodes of low-latitude glaciations. Here we present highly siderophile element data of the Urucum IF-MnF to evaluate elemental sources that affected the Neoproterozoic seawater from which the Urucum IF-MnF precipitated. High uncertainties associated with current dating attempts of this formation overlapped with the Marinoan glaciation (∼650–635 Ma) as well as the Gaskiers glaciation event (∼580 Ma). A Re-Os regression line defined by iron-, manganese-, and chert-rich samples of the Urucum formation is interpreted as an isochron, yielding a refined age estimate of 577 ± 38 Ma and an initial 187Os/188Os ratio of 0.122 ± 0.003. The proposed depositional age overlaps with previous published age data of the Urucum IF-MnF, but relates the Urucum IF-MnF to the Ediacaran Gaskiers glaciation and overlaps with the age of the Shuram CIE (∼567 Ma). An initial 187Os/188Os ratio of 0.122 ± 0.003 is interpreted to represent pristine Neoproterozoic seawater and supports strong hydrothermal input, probably related to rifting, that promoted ferruginous conditions in the Urucum seawater. In an alternative scenario, Re-Os isotope data for the Urucum IF-MnF could also be interpreted in a multi-component mixing scenario, defined by hydrothermally influenced water masses that sourced most metals within the Urucum basin and a crustal component that entered the Urucum seawater either as detrital admixture or via riverine loads. Although none of the scenarios can be ruled out, we consider the isochron scenario as more plausible. [ABSTRACT FROM AUTHOR]

The origin of volatile elements, the timing of their accretion and their distribution during Earth's differentiation are fundamental aspects of Earth's early evolution. Here, we present the result of a newly developed accretion and core formation model, which features the results of high P–T metal–silicate partitioning experiments. The model includes well-studied reference elements (Fe, Ni, Ca, Al, Mg, Si) as well as trace elements (V, Ga, Ag, Au, S) covering a wide range from refractory to volatile behavior. The accretion model simulates the different steps of planet formation, such as the effects of continuous, heterogenous core formation at high P–T, the effect of the Moon-forming giant impact and the addition of matter after the core formation was completed, the so-called "late veneer". To explore the "core formation signature" of the volatile depletion patterns and the quantitative influence of a late veneer, we modeled planets that would have formed from known materials, such as CI, CM, CV, CO, EH and EL meteorites, and from a hypothetical volatile depleted material, CI*. Some of the resulting planets are Earth-like in key properties, such as overall core size, major element composition, oxygen fugacity and trace element composition. The model predicts the chemical signatures of the main planetary reservoirs, the metallic core and bulk silicate planet (BSP) of the modeled planets, which we compare with the chemical signature of Earth derived previously from core formation models and mass balance-based approaches. We show that planets accreted from volatile depleted carbonaceous chondrites (CM, CV, CO and CI*) are closest in terms of major element (Si, Mg, Fe, Ca, Al, Ni) and also siderophile volatile element (Ge, Ga, Au) concentrations to the components from which Earth accreted. Chalcophile volatile elements (S, Ag), instead, require an additional process to lower their concentrations in the BSP to Earth-like concentrations, perhaps the late segregation of a sulfide melt. [ABSTRACT FROM AUTHOR]

The intersection of the Foundation Plume with the Pacific-Antarctic Ridge is a key location in global geodynamics where a mantle plume is approached by and interacting with a fast-spreading mid-ocean ridge. Here, we discuss a comprehensive major and trace element and Sr-Nd-Pb isotope dataset of new and existing samples from the young Foundation Seamount Chain (<5 Ma) and adjacent section of the Pacific-Antarctic Ridge. We use the geochemistry of axial, off-axis and intraplate lavas to map the spatial extent of plume dispersal underneath the ridge as well as the internal zonation of the upwelling plume. We show that the unusual length, increased crustal thickness and occurrence of silicic rocks on the axis of the Foundation Segment are the direct result of plume being tapped by the axial melting zone. We demonstrate that the plume is not homogeneous but shows a HIMU-like (high time-integrated [sup 238]U/[sup 204]Pb) OIB (Ocean Island Basalt) component characterized by [sup 206]Pb/[sup 204]Pb of up to 20.5 in its center and a more EM1-like (Enriched Mantle one) OIB component characterized by low U/Pb and [sup 206]Pb/[sup 204]Pb but high Rb/Nb and [sup 87]Sr/[sup 86]Sr towards its edges. Plume entrainment leads to a high magma supply rate that fosters the formation of silicic rocks and triggers the lengthening of the segment over time. However, plume dispersal is not symmetric as the geochemical tracers for the OIB component are extending <100 km northwards but >300 km southwards. We relate this to the current plate tectonic framework in which the obliquity between the migrating ridge and the absolute plate motions induces a sub-axial asthenospheric flow that preferentially channels plume material southwards. [ABSTRACT FROM AUTHOR]

Facing with serious carbon emission issues, the production of green H2 from electrocatalytic hydrogen evolution reaction (HER) has received extensive research interest. Almost all kinds of noble metal phosphides (NMPs) consisting of Pt‐group elements (i.e., Ru, Rh, Pd, Os, Ir and Pt) are all highly active and pH‐universal electrocatalysts toward HER. In this review, the recent progress of NMP‐based HER electrocatalysts is summarized. It is further take typical examples for discussing important impact factors on the HER performance of NMPs, including crystalline phase, morphology, noble metal element and doping. Moreover, the synthesis and HER application of hybrid catalysts consisting of NMPs and other materials such as transition metal phosphides, oxides, sulfides and phosphates, carbon materials and noble metals is also reviewed. Reducing the use of noble metal is the key idea for NMP‐based hybrid electrocatalysts, while the expanded functionality and structure‐performance relationship are also noticed in this part. At last, the potential opportunities and challenges for this kind of highly active catalyst is discussed. [ABSTRACT FROM AUTHOR]

Major- and trace-element data together with Nd and Sr isotopic compositions and 40Ar/39Ar age determinations were obtained for Late Cretaceous and younger volcanic rocks from north-central Colorado, USA, in the Southern Rocky Mountains to assess the sources of mantle-derived melts in a region underlain by thick (≥150 km) continental lithosphere. Trachybasalt to trachyandesite lava flows and volcanic cobbles of the Upper Cretaceous Windy Gap Volcanic Member of the Middle Park Formation have low εNd(t) values from −3.4 to −13, 87Sr/86Sr(t) from ~0.705 to ~0.707, high large ion lithophile element/high field strength element ratios, and low Ta/Th (≤0.2) values. These characteristics are consistent with the production of mafic melts during the Late Cretaceous to early Cenozoic Laramide orogeny through flux melting of asthenosphere above shallowly subducting and dehydrating oceanic lithosphere of the Farallon plate, followed by the interaction of these melts with preexisting, low εNd(t), continental lithospheric mantle during ascent. This scenario requires that asthenospheric melting occurred beneath continental lithosphere as thick as 200 km, in accordance with mantle xenoliths entrained in localized Devonian-age kimberlites. Such depths are consistent with the abundances of heavy rare earth elements (Yb, Sc) in the Laramide volcanic rocks, which require parental melts derived from garnet-bearing mantle source rocks. New 40Ar/39Ar ages from the Rabbit Ears and Elkhead Mountains volcanic fields confirm that mafic magmatism was reestablished in this region ca. 28 Ma after a hiatus of over 30 m.y. and that the locus of volcanism migrated to the west through time. These rocks have εNd(t) and 87Sr/86Sr(t) values equivalent to their older counterparts (−3.5 to −13 and 0.7038–0.7060, respectively), but they have higher average chondrite-normalized La/Yb values (~22 vs. ~10), and, for the Rabbit Ears volcanic field, higher and more variable Ta/Th values (0.29–0.43). The latter are general characteristics of all other post–40 Ma volcanic rocks in north-central Colorado for which literature data are available. Transitions from low to intermediate Ta/Th mafic volcanism occurred diachronously across southwest North America and are interpreted to have been a consequence of melting of continental lithospheric mantle previously metasomatized by aqueous fluids derived from the underthrusted Farallon plate. Melting occurred as remnants of the Farallon plate were removed and the continental lithospheric mantle was conductively heated by upwelling asthenosphere. A similar model can be applied to post–40 Ma magmatism in north-central Colorado, with periodic, east to west, removal of stranded remnants of the Farallon plate from the base of the continental lithospheric mantle accounting for the production, and western migration, of volcanism. The estimated depth of the lithosphere-asthenosphere boundary in north-central Colorado (~150 km) indicates that the lithosphere remains too thick to allow widespread melting of upwelling asthenosphere even after lithospheric thinning in the Cenozoic. The preservation of thick continental lithospheric mantle may account for the absence of oceanic-island basalt–like basaltic volcanism (high Ta/Th values of ~1 and εNd[t] > 0), in contrast to areas of southwest North America that experienced larger-magnitude extension and lithosphere thinning, where oceanic-island basalt–like late Cenozoic basalts are common. [ABSTRACT FROM AUTHOR]

Copper possesses very strong chacophile properties, but under the conditions found in meteorites, its behavior is like that of siderophile elements. The Suizhou meteorite is a highly shocked L6 chondrite. Troilite and taenite are considered the main primary carrier of copper in this meteorite, and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains. The Suizhou meteorite contains a few very thin shock melt veins. The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination, electron microprobe analyses, and high-resolution X-ray elemental intensity mapping. Our results show that metallic copper is abundant in the Suizhou chondritic rock. Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence, and those at the FeNi metal–troilite interface are the second most common case. The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare. Metallic copper grains are not observed within the Suizhou shock veins, Instead, Cu in elemental form is transferred through shock metamorphism into FeNi metal + troilite intergrowths. Four different occurrence types of Cu in the FeNi metal + troilite intergrowths have been identified: the concentrations of Cu in the FeNi + FeS intergrowths for four occurrence types are rather close, we estimate it might be lower than 1 wt%. [ABSTRACT FROM AUTHOR]

A melilite‐rich, compact type A Ca‐Al‐rich inclusion (CAI), KU‐N‐02, from the reduced CV3 chondrite Northwest Africa 7865, is mantled by an åkermanite‐poor layer. We carried out a combined study of petrographic observations and in situ O and Al–Mg isotopic measurements for KU‐N‐02. The core shows a typical texture of igneous compact type A CAIs. The mantle consists of spinel, åkermanite‐poor melilite, and perovskite. Individual mantle melilite crystals show reverse zoning toward the crystal grain boundary, in contrast to core melilite crystals showing normal zoning. The O isotopic compositions of the minerals in KU‐N‐02 plot along the carbonaceous chondrite anhydrous mineral line on a three O‐isotope diagram. The mantle and core spinel crystals are uniformly 16O‐rich (Δ17O ~ −23‰). The mantle melilite crystals exhibit variable O isotopic compositions ranging between Δ17O ~ −2‰ and −9‰, in contrast to the uniformly 16O‐poor (Δ17O ~ −2‰) core melilite. The mantle melilite crystals also exhibit variable δ25Mg values (δ25MgDSM‐3 ~ −2‰ to +3‰) compared with the nearly constant δ25Mg values of the core melilite (δ25MgDSM‐3 ~ +2‰). The mantle minerals are likely to have formed by condensation from the solar nebular gas after core formation. The Al–Mg mineral isochrons of the core and mantle give initial 26Al/27Al ratios of (4.66 ± 0.15) × 10−5 and (4.74 ± 0.14) × 10−5, respectively. The age difference between the core and mantle formation is estimated to be within ~0.05 Myr, implying that both melting and condensation processes in the variable O isotopically solar nebular environments occurred within a short time during single CAI formation. [ABSTRACT FROM AUTHOR]

India-Asia continental collision–induced volcanic gas emissions are thought to have played an important role in driving Cenozoic atmospheric CO2 variations, yet the details of how the deep carbon cycle may influence volcanic CO2 degassing are not understood. We present a novel study employing Mg-Zn-Mo isotopic compositions of Cenozoic ultrapotassic lavas from NW Tibet. The negative Mg-Zn isotope correlation (δ26Mg = −0.39‰ to −0.19‰; δ66Zn = +0.27‰ to +0.36‰), bolstered by petrographic analysis of mantle-derived xenoliths from these lavas, demonstrates that the ultrapotassic magmas originated from a lithospheric mantle source that had been enriched by recycled carbonate-bearing sediments rich in calcite and dolomite. Very low δ98Mo values (−0.78‰ to 0‰) relative to the average continental crust (δ98Mo = +0.10‰ to +0.35‰) further indicate that the sedimentary components were derived from the subducted Indian continental crust after its dehydration. Monte Carlo modeling estimates that the input flux of carbon (elemental C) from such sediments into the lithospheric mantle is ∼5.6 Mt/yr, with a predicted CO2 emission rate of ∼15.5 Mt/yr. We suggest that the still ongoing subduction of the Indian tectonic plate has played a crucial role in introducing substantial quantities of carbonate-rich sediments into the Tibetan lithospheric mantle, leading to the sequestration of large amounts of CO2 via carbonatite metasomatism. Hence, partial melting of such a carbon-rich mantle reservoir in an orogenic setting provides the positive feedback mechanism that can explain the high flux of volcanic CO2 during IndiaAsia collision. These findings not only highlight the importance of continental subduction, sediment recycling, and mantle metasomatism by carbon-rich melts/fluids in the generation of Tibetan ultrapotassic volcanism, but they also show how the deep carbon cycle influences volcanic CO2 degassing. [ABSTRACT FROM AUTHOR]

Fe isotope variations in rocky bodies reveal fundamental information about planetary evolution. However, experimental results have come to contradictory conclusions on the equilibrium Fe isotope fractionation between metal and silicate during core-mantle differentiation. Many different processes, including evaporation, core formation, partial melting and disproportion of mantle silicate, have been consequently proposed to explain the observed Fe isotope variations in rocky solar system bodies. Here we perform ab initio molecular dynamics simulations and find that the anharmonicity in iron strongly decreases the force constant of Fe at low pressures (<∼50 GPa), which even reverses the equilibrium Fe isotope fractionation between metal and silicate. We conclude that pyrolitic melt is always enriched in heavy Fe isotopes relative to liquid Fe-alloys, no matter what pressure. Therefore core-mantle differentiation will play a significant role in explaining the heavy Fe isotope compositions of the mantles of some rocky bodies (e.g., Earth, the ureilite parent body, and possibly the asteroid Vesta). As all previously proposed processes for Fe isotope fractionation can only enrich the mantle-derived rocks in heavy Fe isotopes, the near/sub-chondritic Fe isotope signatures of Mars and the aubrite parent body thus imply that iron sulfide enriched in light Fe isotopes may significantly contribute to the iron components of those meteoritic samples. [ABSTRACT FROM AUTHOR]

The earth is thought to have gone through complex physicochemical changes during the accretion and magma ocean stages. To better understand this evolution process at the fundamental level, we investigate the behavior of a bulk earth melt system by simulating the composition Fe35.7Mg19.0Si15.2O30.2 (in wt%) at high pressure. A deep neural network potential trained by first-principles data can enable accurate molecular dynamics simulation of large supercells that greatly enhances sampling for reliable evaluation of elemental partitioning. Our simulated system undergoes a phase separation in which the four elements clump together to different extents into two major domains. Based on the coordination and space-decomposition analyses, the inferred composition at 3000 K and 29.1 GPa contains 96.2, 0.1, 1.9 and 1.7 wt% of Fe, Mg, Si, and O, respectively, for the one domain and the corresponding elemental proportions are 3.0, 29.7, 22.0, and 45.3 wt% for the other domain. The predicted segregation thus leads to the formation of an iron-rich phase which corresponds to the metallic core and a magma ocean phase which corresponds to the silicate mantle. The metallic domain incorporates more silicon and more oxygen whereas the magma ocean domain gains more iron oxides at higher temperatures. Our predicted compositions compare favorably with those derived from experimental work for the equilibrium state metal and silicate reacting under high-pressure conditions. [ABSTRACT FROM AUTHOR]

Seafloor abyssal peridotites are products after partial melting and melt-rock interaction, providing constraints on upper mantle processes and heterogeneity. Despite extensive studies of ophiolitic peridotites and a burgeoning dataset for dredged abyssal peridotites, limited studies have been undertaken on abyssal peridotite drill core samples. This omission means a lack of comparison between modern ocean mantle lithosphere and that of ophiolites, where field context is possible in the latter, but not the former. Ocean Drilling Program (ODP) Leg 153 near the Kane fracture zone, and ODP Leg 209, near the Fifteen-Twenty fracture zone, both on the mid-Atlantic Ridge but ∼1000 km distant from one another, recovered serpentinized mantle peridotites. We report whole-rock major-, trace- and highly siderophile-element (HSE: Re, Pd, Pt, Ru, Ir, Os) abundances and 187Os/188Os ratios of peridotites from three cores (maximum depth of 200.8 m) from the two Legs to explore mantle heterogeneity within the Atlantic Ocean basin. Peridotites from ODP Leg 153 are relatively fertile, with Al 2 O 3 contents ranging from 1.1 to 2.7 wt%. They are characterized by relatively radiogenic 187Os/188Os (0.1259 ± 0.0017; 2 S.D.) and uniform HSE abundances. The ODP Leg 209 peridotites are highly refractory, with Al 2 O 3 contents ranging from 0.1 to 0.8 wt%, and imply that they record an extensively depleted mantle. They have 187Os/188Os of 0.1207 ± 0.0023 (2 S.D.) and fractionated HSE abundances, indicative of depletion occurring > 1 billion years ago. Marked heterogeneity both in the extent and timing of depletion are therefore evident along a large segment of the mid-Atlantic ridge that produces zero-age basalts. Measurement of Os isotopes in spatially associated mid-ocean ridge basalts (MORB) is challenging due to their sub ng/g Os contents. Instead, Nd isotopes of MORB are used to show that they are unlikely to have formed directly from abyssal peridotite-like sources. Abyssal peridotites therefore represent long-lived refractory residues during mantle upwelling with the sources of MORB being more enriched. Comparison between drilled abyssal peridotites and ophiolitic mantle reveals larger compositional variations in the latter. The overall higher melting extent in ophiolite mantle is likely reflective of a more complex life cycle than the modern oceanic lithosphere. [ABSTRACT FROM AUTHOR]

Noble gases record in their radiogenic/non-radiogenic isotope ratios the traces of accretion history and degassing events from the early Earth, including giant impacts and the magma ocean stage, to large-scale recent volcanism. The diffusional behavior of noble gases in silicate magmas is one of the essential parameters needed to correctly model devolatilization from the magma ocean and subsequent volcanic eruptions. Here, we study the diffusivity of He, Ne, Ar, Kr, and Xe in molten pyrolite using ab initio molecular dynamics. We find that the diffusivity of the noble gases decreases with increasing atomic size. The diffusion of Ar is comparable to that of Mg. We compute the partial molar volumes and find that at high pressure, He is almost one order of magnitude more compressible than the heavier noble gases. The analysis of the speciation of the noble gases in the melt indicates that the lifetime of the coordination polyhedra formed with O is not sensitive to the mass of the noble gases. Finally, we compute the electron localization function along the Xe–O interatomic vectors and show that there is no chemical bonding between the Xe and surrounding O atoms from the hosting silicate melt. [ABSTRACT FROM AUTHOR]

GEMS (glass with embedded metal and sulfides) are the dominant carrier of amorphous silicates in anhydrous interplanetary dust particles (IDPs) and one of the most suitable materials to study early solar system processes. Amorphous silicates in 105 GEMS from eight IDPs were analyzed regarding texture and chemical composition to reassess GEMS formation theories and genetic relationships to amorphous silicate material in meteorites. Petrography of bulk IDPs was investigated to understand GEMS' relationships to other IDP components. Furthermore, carbon and nitrogen isotopic compositions were measured. Nearly all GEMS are aggregates of several subgrains with variable amount of nanophase inclusions and different Mg- and Si-contents, while single GEMS are rare. The subgrains within aggregates are typically surrounded by one or more carbon rims with high density. The chemical compositions of GEMS amorphous silicates are subsolar for all major element/Si ratios but exhibit wide heterogeneity. This is not influenced by silicon oil from the capturing process of IDPs as assumed before, as a penetration of the silicon oil is excluded by high resolution EELS (electron energy loss spectroscopy) areal density maps of silicon. Furthermore, low Fe-content in GEMS amorphous silicates shows that these are not altered by aqueous activity on the parent body as it is the case for amorphous silicate material in primitive meteorites. The subsolar element/Si ratios and the wide chemical heterogeneity point to a non-equilibrium fractional condensation origin either in the early solar nebula or in a circumstellar environment and are not in agreement with homogenization via sputtering in the ISM. The close association with carbon around GEMS subgrains and as double-rims around GEMS aggregates argue for a multi-step aggregation after formation of the smallest GEMS subgrains in the ISM or the early solar nebula. Carbon acting as matrix material connecting GEMS and other IDP components has lower areal density as seen from carbon EELS areal density maps and isotopic anomalies varying at the nanometer scale, pointing to different origins and processing of materials to varying extent or at changing temperatures. To balance GEMS' subsolar element/Si ratios, a supersolar component in IDPs was assumed to account for the overall chondritic composition of bulk IDPs. Nevertheless, our bulk IDP analyses revealed subsolar, but variable, element/Si ratios for complete particles as well, depending on type and amount of mineral phases in each particle. Pyroxenes in the investigated particles can occur as elongated euhedral crystals, but are overall rare. The dominant crystalline fraction in the investigated IDP samples are equilibrated aggregates (EAs) that show the same chemical compositions as GEMS, indicating that the EAs are recrystallized GEMS grains and formed after GEMS formation as secondary phases. [ABSTRACT FROM AUTHOR]

Seafloor massive sulfides form in various marine hydrothermal settings, particularly within volcanic arcs, where magmatic fluids may contribute to the metal budget of the hydrothermal system. In this study, we focus on the Kolumbo volcano, a submarine volcanic edifice in the central Hellenic Volcanic Arc hosting an active hydrothermal system. Diffuse sulfate-sulfide chimneys form a Zn-Pb massive sulfide mineralization with elevated As, Ag, Au, Hg, Sb, and Tl contents. These elements have similar behavior during magmatic degassing and are common in arc-related hydrothermal systems. Trace-element data of igneous magnetite, combined with whole rock geochemistry and numerical modelling, highlights the behavior of chalcophile and siderophile elements during magmatic differentiation. We report that, despite early magmatic sulfide saturation, chalcophile element contents in the magma do not decrease until water saturation and degassing has occurred. The conservation of chalcophile elements in the magma during magmatic differentiation suggests that most of the magmatic sulfides do not fractionate. By contrast, upon degassing, As, Ag, Au, Cu, Hg, Sb, Sn, Pb, and Zn become depleted in the magma, likely partitioning into the volatile phase, either from the melt or during sulfide oxidation by volatiles. After degassing, the residual chalcophile elements in the melt are incorporated into magnetite. Trace-element data of magnetite enables identifying sulfide saturation during magmatic differentiation and discrimination between pre- and post-degassing magnetite. Our study highlights how magmatic degassing contributes to the metal budget in magmatic-hydrothermal systems that form seafloor massive sulfides and shows that igneous magnetite geochemistry is a powerful tool for tracking metal-mobilizing processes during magmatic differentiation. [ABSTRACT FROM AUTHOR]

The elemental and isotopic properties of garnet pyroxenites can yield information on lithospheric mantle composition, thermal state, and evolution. The 34Ma Kakanui Mineral Breccia in New Zealand contains spectacular but little-studied mantle peridotite and pyroxenite xenoliths that yield new insights into the evolution of a portion of the underlying mantle lithosphere of a former Gondwana margin. The moderately depleted and metasomatized spinel peridotites, as judged from spinel and olivine compositions and bulk rock major and platinum group element abundances, give mineral equilibration temperatures <1020°C and are derived from the middle to shallow (~35 to 50 km) lithospheric mantle when projected onto a 70 mW∙m−2 geotherm. These residues have low Re/Os and Re-depletion 187Os/188Os model ages that range from Eocene (0.05 Ga) to Paleoproterozoic (1.9 Ga), consistent with extraction from a lithospheric mantle comprising fragments with complex depletion histories. Although the peridotites have restricted δ18O (olivine +5.2 to 6.2), evidence for an isotopically heterogeneous mantle column in addition to the 187Os/188Os is seen in clinopyroxene 87Sr/86Sr (0.70244 to 0.70292), εNd (+4.1 to 18.8), 206Pb/204Pb (17.8 to 20.3), and εHf (+10 to +101). Higher metamorphic equilibrium temperatures of the garnet pyroxenites (Fe–Mg exchange of >1150°C) compared to the peridotites indicate their Eocene extraction was from towards the base of this isotopically heterogeneous mantle lithosphere. Pyroxenite bulk compositions point to cumulate origins, and the mineral isotope ratios of 87Sr/86Sr (0.70282 to 0.70294), εNd (+5.5 to 8.0) and 206Pb/204Pb (18.1 to 19.3) match many of the Zealandia metasomatized mantle peridotite xenoliths as well as the primitive intraplate basalts but not the garnet pyroxenite host magmas. In contrast to many global pyroxenite studies, the garnet pyroxenite 87Sr/86Sr and δ18O (+5.2 to 5.8) data provide no evidence for subducted crustal material in the primary magma source region, and Sm–Nd and Lu–Hf isotope data yield mid-Cenozoic ages that are probably related to isotope closure during eruption. An exception is one sample that yields a Lu–Hf isochron age of 111.9 ± 9.1 Ma, which corresponds to the convergence of the Lu–Hf isotope evolution curves of three other samples. Liquids calculated to have been in equilibrium with these cumulates have trace element compositions comparable to primitive alkaline intraplate basalts like those found at the surface of Zealandia. The new data, therefore, indicate that a pulse of intraplate magmatism occurred during or directly after the cessation of long-lived subduction on the former Zealandia Early Cretaceous forearc Gondwana margin, despite any volcanic surface exposure having been long eroded away. The lower lithospheric mantle emplacement of the garnet pyroxenites suggests that the source of the alkaline parent magmas was probably the convecting mantle, which supports conclusions that intraplate magmas in Zealandia have asthenospheric and lithospheric mantle sources. [ABSTRACT FROM AUTHOR]

White dwarf atmospheres are frequently polluted by material from their own planetary systems. Absorption features from Ca, Mg, Fe, and other elements can provide unique insights into the provenance of this exoplanetary material, with their relative abundances being used to infer accretion of material with core- or mantle-like composition. Across the population of white dwarfs, the distribution of compositions reveals the prevalence of geological and collisional processing across exoplanetary systems. By predicting the distribution of compositions in three evolutionary scenarios, this work assesses whether they can explain current observations. We consider evolution in an asteroid belt analogue, in which collisions between planetary bodies that formed an iron core lead to core- or mantle-rich fragments. We also consider layer-by-layer accretion of individual bodies, such that the apparent composition of atmospheric pollution changes during the accretion of a single body. Finally, we consider that compositional spread is due to random noise. We find that the distribution of Ca, Fe, and Mg in a sample of 202 cool DZs is consistent with the random noise scenario, although 7 individual systems show strong evidence of core-mantle differentiation from additional elements and/or low noise levels. Future surveys that detect multiple elements in each of a few hundred white dwarfs, with well-understood biases, have the potential to confidently distinguish between the three models. [ABSTRACT FROM AUTHOR]

Metasomatized sub-continental lithospheric mantle (SCLM) is increasingly proposed to control the formation of giant hydrothermal gold provinces. However, the key budgets for gold and volatile components in the SCLM under gold provinces remain poorly constrained, thus hindering definitive genetic models of gold metallogenesis. The Cenozoic hydrothermal orogenic gold deposits in the Ailaoshan gold belt in SE Tibet that are genetically related to metasomatized SCLM, and adjacent penecontemporaneous lamprophyre dikes that are suggested to have a similar source, provide a rare opportunity to resolve this source budget issue. Integrated data on siderophile elements of the lamprophyre dikes, volatile contents of their melt inclusions, and their whole-rock geochemistry are utilized to constrain the source they share with the gold deposits. The lamprophyre primary magmas are characterized by high H 2 O (3.6 wt%), Cl (up to ∼4700 ppm) and S (up to ∼3100 ppm) concentrations, with modeling suggesting that their mantle sources are also significantly enriched in volatiles (H 2 O > 1000 ppm, Cl > 60 ppm), overlapping with those of the most volatile-rich magmas and mantle endmembers in the earth. Excluding those dikes that were either affected by auriferous fluids or experienced sulfide separation, the dikes have variable but generally normal Au concentrations (0.10–3.33 ppb), with estimated mantle sources comprising less than 1 ppb Au. This range is lower than or comparable to that of Au contents of global mantle peridotites and the primitive upper mantle, indicating that metasomatism processes did not significantly fertilize the SCLM beneath the gold province with anomalously high Au. Consequently, it appears that high volatile contents of the metasomatized SCLM, which promoted generation of auriferous fluid, ore-metal extraction, subsequent fluid transfer and advection, had a more important, and previously underestimated role in formation of the gold deposits. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is the most abundant element in Earth's atmosphere, but is extremely depleted in the silicate Earth. However, it is not clear whether core sequestration or early atmospheric loss was responsible for this depletion. Here we study the effect of core formation on the inventory of nitrogen using laser-heated diamond anvil cells. We find that, due to the simultaneous dissolution of oxygen in the metal, N becomes much less siderophile (iron-loving) at pressures and temperatures up to 104 GPa and 5000 K, a thermodynamic condition relevant to the bottom of the magma ocean in the aftermath of the moon-forming giant impact. Using a core–mantle–atmosphere coevolution model, we show that the impact-induced processes (core formation and/or atmospheric loss) are unlikely to account for the observed N anomaly, which is instead best explained by the accretion of mainly N-poor impactors. The terrestrial volatile pattern requires severe N depletion on precursor bodies, prior to their accretion to the proto-Earth. [ABSTRACT FROM AUTHOR]

The Allalin gabbro of the Zermatt-Saas meta-ophiolite consists of variably metamorphosed Mg- to Fe-Ti-gabbros, troctolites, and anorthosites, which are crosscut by basaltic dykes. Field relationships of the various rock types and petrographic studies together with bulk rock and mineral chemical composition data allow the reconstruction of the complete geological history of the Allalin gabbro. With increasing magmatic differentiation, the incompatible element content in clinopyroxene increases (e.g., REEs and Zr by a factor of 5), whereas the Mg# decreases (from 86.4 to 74.6) as do the compatible element contents (e.g., Cr and Ni by factors of 3.5 and 5, respectively). Exhumation to shallower depths led to subsolidus ductile deformation and cooling of the gabbro followed by the intrusion of fine-grained basaltic dykes, which display chilled margins. Bulk rock data of these dykes reveal strong similarities in fluid-immobile trace element patterns to tholeiitic pillow basalts of the Zermatt-Saas and nearby meta-ophiolites. The recalculated REE patterns of the melt in equilibrium with igneous clinopyroxene is very similar to the REE patterns of the mafic dykes, indicating a cogenetic origin of pillow basalts, dykes, and gabbros. Together with the previously determined Jurassic intrusion age of the gabbro, our observations demonstrate that the Allalin gabbro intruded as a tholeiitic magma in a slow spreading MOR environment of the Piemonte-Ligurian ocean of the Alpine Tethys. Subduction of the Allalin gabbro resulted in different eclogitization extents of the Mg-gabbros as a function of variable hydration degrees. Metagabbros with low extents of hydration record incomplete eclogitization; the magmatic mineralogy (olivine + clinopyroxene + plagioclase) is preserved together with disequilibrium textures in the form of reaction coronae surrounding mineral boundaries. Metagabbros with high extents of hydration are completely eclogitized and display pseudomorphic replacement textures of magmatic minerals by eclogite-facies mineral assemblages, which required significant major to trace element transport across mineral domains. The locally variable extents of hydration took place near the sea floor, as recorded by the presence of Cl-apatite (6.28 wt% Cl), and an increase in B concentrations of minerals pseudomorphically replacing olivine (e.g., chlorite with 0.20–0.31 µg/g B and omphacite with 0.22–0.25 µg/g B) compared to magmatic olivine (0.12–0.16 µg/g B). Moreover, the chemical zonation pattern of metamorphic garnet coronae is different in completely eclogitized gabbros and gabbros with relic igneous minerals, in agreement with a main hydration event prior to subduction. The Allalin gabbro therefore represents a classical example of an oceanic gabbro formed in a slow spreading setting in the mid Jurassic that experienced heterogeneous hydration near the sea floor. Paleogene subduction of the gabbro to 70–80 km depth produced variably equilibrated gabbroic eclogites. In eclogite-facies Mg-gabbros, the water-rich minerals chlorite, talc, and chloritoid pseudomorphing magmatic olivine remained stable to these depths, revealing the potential relevance of hydrated Mg-gabbros as a fluid source at subarc depths in subduction zones. [ABSTRACT FROM AUTHOR]

Samples collected from the surface/subsurface of C-type asteroid 162173 Ryugu by the Hayabusa2 mission were nondestructively analyzed in three dimensions (3D). Seventy-three small particles (approximately 10–180 µm in size) were observed using X-ray nanotomography, with an effective spatial resolution of approximately 200 nm. Detailed descriptions of these samples in terms of mineralogy, petrology, and variations among particles were reported. The 57 most common particles consisted of a phyllosilicate matrix containing mineral grains, mainly magnetite, pyrrhotite, dolomite and apatite. The remaining particles were mostly monomineralic particles (pyrrhotite, dolomite, breunnerite, apatite, and Mg-Na phosphate) with two unique particles (calcite in a Al 2 Si 2 O 5 (OH) 4 matrix, and CaCO 3 , phyllosilicate, and tochilinite-chronstedtite inclusions in a carbonaceous material matrix). The results confirmed that the samples correspond to Ivuna-type carbonaceous chondrites (CI chondrites) or related materials. Many small inclusions of voids and carbonaceous materials were detected in pyrrhotite, dolomite, breunnerite, and apatite. However, no fluid inclusions were observed, except for those in pyrrhotite that have already been reported. Magnetite exhibited a wide variety of morphologies, from irregular shapes (spherulites, framboids, plaquettes, and whiskers) to euhedral shapes (equants, rods, and cubes), along with transitional shapes. In contrast, the other minerals exhibit predominantly euhedral shapes (pyrrhotite: pseudo-hexagonal plates, dolomite: flattened rhombohedrons, breunnerite: largely flattened rhombohedrons, and apatite: hexagonal prisms) or aggregates of faceted crystals, except for Mg-Na phosphate. The matrices were heterogeneous with variable phyllosilicate particle sizes, Mg/Fe ratios, density (1.7 ± 0.2 g/cm3), nanoporosities (36 ± 9 %), and abundances of nanograins of Fe(-Ni) sulfides. The macroporosity of the particles was estimated as 12 ± 4 %. The observed textural relationships among the minerals suggest a precipitation sequence of: magnetite (spherulite → plaquette/framboid → rod/equant) → pyrrhotite (pentlandite → pyrrhotite) → apatite → dolomite → breunnerite → coarse phyllosilicates. Fe-bearing olivine (or low-Ca pyroxene) might have precipitated later than dolomite, indicating a high Mg activity in the aqueous solution. This precipitation sequence corresponds to a transition from irregular crystal forms (as seen in some magnetite) to regular forms of euhedral crystals (observed in some magnetite and other minerals). Based on the precipitation sequence and mineral morphologies, together with previously reported observations, a model for aqueous alteration in the Ryugu parent body was proposed as follows: CO 2 -H 2 O ice, amorphous silicates (GEMS-like material), and some minerals (mostly metal, sulfides, and anhydrous silicates) accumulated to form the parent body of Ryugu. Amorphous silicates and Fe-Ni metal quickly dissolved into the melted ice to form a highly supersaturated aqueous solution. Poorly-crystalized phyllosilicate and spherulitic magnetite precipitated first, followed by plaquette/framboidal magnetites with decreasing degree of supersaturation due to precipitation. Pseudo-hexagonal pyrrhotite plates were formed by dissolution and reprecipitation under relatively low supersaturation. Subsequently, apatite, dolomite, and breunnerite precipitated in this order in response to decreasing supersaturation. [ABSTRACT FROM AUTHOR]

Abundant carbon was identified on Mercury by MESSENGER, which is interpreted as the remnant of a primordial graphite flotation crust, suggesting that the magma ocean and core were saturated in carbon. We re-evaluate carbon speciation in Mercury's interior in light of the high pressure-temperature experiments, thermodynamic models and the most recent geophysical models of the internal structure of the planet. Although a sulfur-free melt would have been in the stability field of graphite, sulfur dissolution in the melt under the unique reduced conditions depressed the sulfur-rich liquidus to temperatures spanning the graphite-diamond transition. Here we show it is possible, though statistically unlikely, that diamond was stable in the magma ocean. However, the formation of a solid inner core caused diamond to crystallize from the cooling molten core and formation of a diamond layer becoming thicker with time. A diamond layer that becomes thicker with time is generated from carbon exsolution at the core-mantle boundary of Mercury, owing to cooling of its metallic core and potentially the silicate magma ocean. [ABSTRACT FROM AUTHOR]

Rapakivi granite is characterized by its unique structure, which has important implications for tectonic settings, magmatic processes, and crust–mantle interactions. In this study, we conducted a combined analysis of the petrography, mineral chemistry, geochemistry, and zircon U–Pb dating and Lu–Hf isotopic compositions of the Niujiaoshan Early Paleozoic rapakivi-textured granite from the North Qinling Belt. Zircon U–Pb dating yielded a crystallization age of 447 ± 7 Ma, which is younger than the ultra-high-pressure (UHP) metamorphic age (~ 500 Ma) but similar to the granulite facies retrograde age (~ 450 Ma) of UHP eclogites and felsic gneisses in the North Qinling Belt. The rapakivi feldspar phenocrysts have ovoid K-feldspar cores, which are rich in mineral inclusions, such as amphibole, biotite, quartz, and plagioclase, indicating early crystallization. The ovoid K-feldspar cores are mantled by oligoclase, whreras the matrix comprises biotite, amphibole, and coarse-grained plagioclase. The amphibole and biotite in the granite are rich in Mg and are indicative of a crust–mantle origin. The εHf (t) values of the zircons range from − 2.04 to + 3.63, suggesting formation via crust–mantle interactions. The rapakivi-textured granite displays high-K meta-aluminous I-type granite affinity, with high SiO2, K2O, and Na2O contents. Based on the geological background and results of this study, we propose that the Niujiaoshan rapakivi-textured granite was formed via the mixing of crustal materials induced by upper mantle magma during the exhumation of the North Qinling UHP metamorphic terrane, which occurred in a post-orogenic setting. [ABSTRACT FROM AUTHOR]

The Doldrums transform system, located in the Equatorial Atlantic at 7–8°N, is a 110 km-wide multi-fault shear zone, with five active transform faults separated by four short intra-transform ridge segments (ITRs). The two central ITRs, ITR-2 and ITR-3, are significantly deeper than the peripheral ridge segments, suggesting differences in the thermal conditions of the sub-ridge mantle. New chemical and radiogenic isotope data from on-axis lavas erupted across the transform domain reveal that the basalts from ITR-3 are enriched in alkalis (Na 2 O + K 2 O = 4.3 wt%; Na 8 up to 3.7) and light rare earth elements (La/Sm) N = 0.86–0.97). However, these basalts have lower Sr and Pb isotope ratios than MORB from the Equatorial Atlantic (i.e., 87Sr/86Sr ∼ 0.70237 and 206Pb/204Pb ∼ 18), and relatively high Nd and Hf isotope ratios (143Nd/144Nd = 0.51315–0.51325; 176Hf/177Hf = 0.2832–0.28325). Hence, the mantle underlying ITR-3 is, on average, depleted in highly incompatible elements. Thermal models of the sub-ridge mantle show that it is also the coldest mantle region under the Doldrums system with the lowest crust production. Considering its location in the central transform domain, it is likely that the local mantle underwent melting beneath adjacent segments of the Mid-Atlantic Ridge (MAR) before remelting below ITR-3. We propose that the initial melting event beneath the MAR selectively removed the most fusible, geochemically enriched mantle components, leaving behind a predominantly peridotitic source, characterized by comparatively low Sr and Pb isotope ratios. Therefore, MORB from intra-transform ridge segments, such as those within the Doldrums transform system, provide a rare opportunity to constrain the isotopic composition of highly incompatible element depleted peridotitic mantle, which is a ubiquitous, but otherwise often camouflaged component of Earth's mantle. [ABSTRACT FROM AUTHOR]

Pyroxenites, comprising only approximately 2 %–10 % by volume of the upper mantle, are among the most important lithological heterogeneity in the mantle. The formation of pyroxenite veins within peridotites is often attributed to migrating melts which provides an important mechanism for crust-mantle interaction. The Re–Os isotope system provides valuable insight into crust-mantle interaction, as there is a significant contrast in 187Os/188Os between crustal and mantle rocks. Previous Os isotope studies have shown that the forearc mantle wedge mainly consists of highly heterogeneous ancient peridotites. However, limited Re–Os isotope data of forearc mantle pyroxenites exist. Here, two types of mantle pyroxenites from the New Caledonia forearc ophiolite were selected for a comparative study. Contrasting microtextures and geochemical compositions support that these pyroxenites were formed by different processes. The Massif du Sud pyroxenites, hosted in harzburgites, have a cumulate origin and crystallized from boninitic melts generated by remelting of depleted mantle during subduction initiation, whereas the Tiebaghi pyroxenites within the host lherzolites are the products of melt-peridotite reactions. Both types of pyroxenites display highly fractionated highly siderophile element (HSE) patterns. The Massif du Sud pyroxenites are strongly enriched in palladium group platinum-group elements (PPGE) relative to iridium group platinum-group elements (IPGE) with remarkable positive Pt anomalies, which are similar to those of primitive arc lavas and mantle wedge pyroxenite xenoliths. In contrast, the Tiebaghi pyroxenites have flat IPGE but variable PPGE and Re patterns. Compared to the forearc mantle peridotites, the Tiebaghi pyroxenites have higher Os isotope ratios. Ancient basaltic melt percolation followed by long-term (>1 Ga) radiogenic ingrowth can successfully produce the observed correlations of 187Os/188Os with Os or Al 2 O 3 contents. Besides, the oldest Re-depletion model age (T RD) of ∼1.35 Ga has been obtained for the host lherzolites. Therefore, the Tiebaghi pyroxenites and their host lherzolites probably represent a stranded old mantle relict that has undergone ancient partial melting and melt percolation events. Our study supports the presence of highly radiogenic mantle domains in the forearc and provides significant constraints on the role of ancient basaltic melt percolation for generating mantle heterogeneity. [ABSTRACT FROM AUTHOR]

Parent bodies of carbonaceous chondrites that initially contained metallic iron potentially exert strong reduction power during aqueous alteration to generate molecular hydrogen in excess of hydrogen solubility in water-rich fluids. The surplus hydrogen escapes from the system, which is subsequently supplied to overlying regions in planetesimals. Based on this concept, we conducted chemical equilibrium modeling of the aqueous alteration and simulated gaseous H 2 migration within the icy planetesimal that has a melted mantle and an icy shell during the early stages of radiogenic heating. In the chemical equilibrium modeling, we simulated the aqueous alteration of chondritic rocks at 0–350 °C and a water/rock mass ratio of 0.2–10 with initial CO 2 contents of 0–10 mol% in the fluid. The results showed that the mineral assemblage and solution composition change with the temperature, water/rock mass ratio, and initial fluid composition. The reproduced mineral paragenesis and abundance well explain those of carbonaceous chondrites. Furthermore, it was revealed that the initial H 2 fugacity of the system influences not only the stability of minerals and solution compositions, but also the preservation potential of organic molecules. Indeed, within these parameter spaces, the modeling results account for the organic/inorganic carbon-rich alterations reported for the Tagish Lake meteorite, Ceres, and Ryugu. Simulations of gaseous H 2 migration in a planetesimal revealed that gaseous H 2 in the deep interior can be transported to the interface with an icy shell even if the permeability is low. Moreover, it is highly possible that an H 2 -rich layer would have been widely formed just below the icy shell. Therefore, it is expected that H 2 -rich regions beneath the ice layer in planetesimals have substantial potential for the synthesis and preservation of organic molecules. These results imply that the alteration of carbonaceous chondrite parent bodies and C-complex asteroids is characterized by not only the type of parent bodies (e.g., formation age and distance from the Sun) but also the locations within their parent bodies. [ABSTRACT FROM AUTHOR]

The Moon's mare volcanism predominantly occurs within the Procellarum KREEP Terrane (PKT), which is widely thought to be associated with KREEP components within the lunar interior. The Chang'e-5 (CE-5) mission sampled a young (2 Ga) mare basalt Em4/P58 unit of northern Oceanus Procellarum. The geochemistry of the CE-5 mare basalt enables assessment of mantle source compositions which are essential to understand the thermo-chemical mechanism for prolonged volcanism during secular cooling of the Moon. Geochemical compositions of the CE-5 bulk soil, breccias, and basalt clasts from various depths within the drill core consistently display high concentrations of incompatible trace elements (ITE: ∼ 0.3 × high-K KREEP; ∼ 5 μg/g Th) with KREEP-like inter-element ratios, for example for La/Sm, Nb/Ta, and Zr/Y. Exotic impact ejecta, extensive magma differentiation (<70 % fractional crystallization) and significant assimilation of KREEP materials during magma transit and eruption cannot account for the ITE contents and ratios or radiogenic isotope compositions (e.g., εNd initial of + 8 to + 9 and εHf initial of + 40 to + 46) of the CE-5 basalts; instead, partial melting of their mantle source played a dominant role. The Chang'e-5 basalt is a chemically evolved low-Ti mare basalt (Mg# of ∼ 34) with enriched KREEP-like ITE compositions but high long-term time-integrated Sm/Nd and Lu/Hf ratios, which represent a hitherto unsampled type of mare basalt. It formed by melting of an augite-rich mantle source (late-stage magma ocean cumulates containing > 30–60 % augite, and little or no ilmenite), with a small amount of late-stage interstitial melt that resembles KREEP (∼1–1.5 modal %, equivalent to 0.2–0.3 μg/g Th in the mantle source). The voluminous mare basalts making up the Em4/P58 unit (>1500 km3) provide compelling evidence for large-scale, ITE enriched young mare magmatism within Oceanus Procellarum. In combination with remote sensing data and with the unique Th-rich Apollo 12 basalt fragment 12032,366–18 (impact ejecta likely from Oceanus Procellarum), this implies that significant portions of the FeO- and Th-rich mare regions of the western PKT may also have formed in a similar way. [ABSTRACT FROM AUTHOR]

Fifteen experiments at 1 atm pressure and 1400 °C have been conducted to determine partition coefficients between olivine and silicate melt ( D Ol - m e l t ) of the first-row transition elements (FRTEs, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn), Ga and Ge in the system FeO-CaO-MgO-Al 2 O 3 -SiO 2 (FCMAS). Bulk iron contents are varied between 0 and 10 wt.% FeO, and oxygen fugacity ranges from 2 log units below the iron-wüstite buffer (IW-2) to 2 log units above the quartz-fayalite-magnetite buffer (QFM + 2), covering a range of igneous processes involving olivine in terrestrial and lunar conditions. Results show that multi-valent Fe and V are redox-sensitive and more incompatible at oxidizing conditions, consistent with previous studies. The moderately volatile elements (Cu, Zn, Ga and Ge) become more volatile at reducing conditions. No correlation between partition coefficients and oxygen fugacity is observed for other multi-valent (Ti, Cr, Mn) and for homo-valent elements (Sc, Co and Ni). Most D Ol - m e l t show no sensitivity to bulk system iron contents, but D Cr Ol - m e l t is significantly higher in our experiments compared to D Cr Ol - m e l t derived from olivine-melt inclusion pairs in lunar samples with much higher FeO contents. D Ni Ol - m e l t values are nearly constant at a range of oxygen fugacities above the IW buffer, but abruptly decrease when the system is very reducing (below the IW buffer). As a result, D Co Ol - m e l t / D Ni Ol - m e l t ratios that are constant (∼0.3) at or above the IW buffer increase significantly (0.72–0.99) at IW-2. Using the newly derived partition coefficients, we re-assess two aspects of lunar basalt generation. First, we conclude that the Cr-rich nature of the olivines in lunar basalts compared to terrestrial basalts must be attributed to the Cr-nature of cumulate mantle source of lunar basalts, linked to the early crystallization of Cr-poor minerals olivine and orthopyroxene in the lunar magma ocean resulting in a shallow Cr-rich cumulates. Second, the higher Co/Ni ratios in olivine in high-titanium lunar basalts compared to olivine in low-titanium lunar basalts suggest the former were formed at more reducing conditions (below the IW buffer). [ABSTRACT FROM AUTHOR]

During their formation, terrestrial planets underwent a magma ocean phase during which their metallic cores segregated from their silicate mantles and their early atmospheres formed. These planetary formation processes resulted in a redistribution of the abundances of highly volatile elements (HVEs, such as H, C, N, and S) between the planets' metallic cores, silicate mantles, and atmospheres. This review presents the numerous experimental techniques used to simulate the conditions and identify the parameters that influenced the behavior of HVEs during planetary formation. We also review the analytical techniques used to characterize the different types of experimental samples and quantify the distribution of HVEs between metallic and silicate phases, as well as their solubilities in silicate glasses. This exhaustive review targets students and young researchers beginning their work on the subject, or, more generally, scientists seeking a better understanding of this field of research. [ABSTRACT FROM AUTHOR]

On the microscale, the Winchcombe CM carbonaceous chondrite contains a number of lithological units with a variety of degrees of aqueous alteration. However, an understanding of the average hydration state is useful when comparing to other meteorites and remote observations of airless bodies. We report correlated bulk analyses on multiple subsamples of the Winchcombe meteorite, determining an average phyllosilicate fraction petrologic type of 1.2 and an average water content of 11.9 wt%. We show the elemental composition and distribution of iron and iron oxidation state are consistent with measurements from other CM chondrites; however, Winchcombe shows a low Hg concentration of 58.1 ± 0.5 ng g−1. We demonstrate that infrared reflectance spectra of Winchcombe are consistent with its bulk modal mineralogy, and comparable to other CM chondrites with similar average petrologic types. Finally, we also evaluate whether spectral parameters can estimate H/Si ratios and water abundances, finding generally spectral parameters underestimate water abundance compared to measured values. [ABSTRACT FROM AUTHOR]

As part of an integrated consortium study, we have undertaken O, Cd, Cr, Si, Te, Ti, and Zn whole rock isotopic measurements of the Winchcombe CM2 meteorite. δ66Zn values determined for two Winchcombe aliquots are +0.29 ± 0.05‰ (2SD) and +0.45 ± 0.05‰ (2SD). The difference between these analyses likely reflects sample heterogeneity. Zn isotope compositions for Winchcombe show excellent agreement with published CM2 data. δ114Cd for a single Winchcombe aliquot is +0.29 ± 0.04‰ (2SD), which is close to a previous result for Murchison. δ130Te values for three aliquots gave indistinguishable results, with a mean value of +0.62 ± 0.01‰ (2SD) and are essentially identical to published values for CM2s. ε53Cr and ε54Cr for Winchcombe are 0.319 ± 0.029 (2SE) and 0.775 ± 0.067 (2SE), respectively. Based on its Cr isotopic composition, Winchcombe plots close to other CM2 chondrites. ε50Ti and ε46Ti values for Winchcombe are 3.21 ± 0.09 (2SE) and 0.46 ± 0.08 (2SE), respectively, and are in line with recently published data for CM2s. The δ30Si composition of Winchcombe is −0.50 ± 0.06‰ (2SD, n = 11) and is essentially indistinguishable from measurements obtained on other CM2 chondrites. In conformity with petrographic observations, oxygen isotope analyses of both bulk and micromilled fractions from Winchcombe clearly demonstrate that its parent body experienced extensive aqueous alteration. The style of alteration exhibited by Winchcombe is consistent with relatively closed system processes. Analysis of different fractions within Winchcombe broadly support the view that, while different lithologies within an individual CM2 meteorite can be highly variable, each meteorite is characterized by a predominant alteration type. Mixing of different lithologies within a regolith environment to form cataclastic matrix is supported by oxygen isotope analysis of micromilled fractions from Winchcombe. Previously unpublished bulk oxygen isotope data for 12 CM2 chondrites, when combined with published data, define a well‐constrained regression line with a slope of 0.77. Winchcombe analyses define a more limited linear trend at the isotopically heavy, more aqueously altered, end of the slope 0.77 CM2 array. The CM2 slope 0.77 array intersects the oxygen isotope field of CO3 falls, indicating that the unaltered precursor material to the CMs was essentially identical in oxygen isotope composition to the CO3 falls. Our data are consistent with earlier suggestions that the main differences between the CO3s and CM2s reflect differing amounts of water ice that co‐accreted into their respective parent bodies, being high in the case of CM2s and low in the case of CO3s. The small difference in Si isotope compositions between the CM and CO meteorites can be explained by different proportions of matrix versus refractory silicates. CMs and COs may also be indistinguishable with respect to Ti and Cr isotopes; however, further analysis is required to test this possibility. The close relationship between CO3 and CM2 chondrites revealed by our data supports the emerging view that the snow line within protoplanetary disks marks an important zone of planetesimal accretion. [ABSTRACT FROM AUTHOR]

Modeling the behavior of trace elements during lunar magma ocean solidification is important to further our understanding of the chemical evolution of the Moon. Lunar magma ocean evolution models rely on consistent datasets on how trace elements partition between a lunar silicate melt and coexisting minerals at different pressures, temperatures, and redox conditions. Here we report new experimental trace element partition coefficients (D) between clinopyroxene (cpx), pigeonite, orthopyroxene, plagioclase, olivine (ol), and silicate melt at conditions relevant for the lunar magma ocean. The data include Dcpx−melt at ambient and high pressures (1.5 GPa and 1310 °C), and partition coefficients at ambient pressure for pig, opx, ol, and pl. Overall, clinopyroxene is a phase that may control the fractionation of key geochemical trace element ratios, such as Lu/Hf and Sm/Nd, during the evolution of the lunar magma ocean. We explore the impact of the new silicate Dmineral−melt on the trace element evolution of the lunar magma ocean and we find that accessory phosphate minerals, such as apatite or whitlockite are of critical importance to explain the observed trace element and isotopic signature of the KREEP reservoir on the Moon. The new partition coefficients were applied to calculate the trace element evolution of the residual melts of the crystallizing lunar magma ocean and we propose a new trace element composition for the urKREEP reservoir. The new data will be useful for future thermo-chemical models in order to adequately predict the duration of the lunar magma ocean and the age of the Moon. [ABSTRACT FROM AUTHOR]

Calcium, aluminum-rich inclusions (CAIs) are the oldest solids dated that formed in the solar system. Most CAIs in unmetamorphosed chondritic meteorites (chondrites; petrologic type ≤3.0) have uniform solar-like 16O-rich compositions (Δ17O ∼ −24‰) and a high initial 26Al/27Al ratio [(26Al/27Al)0] of ∼(4–5) × 10−5, consistent with their origin in a gas of approximately solar composition during a brief (<0.3 Ma) epoch at the earliest stage of our solar system. The nature of O-isotope heterogeneity in CAIs (Δ17O range from ∼−24 up to ∼+5‰) from weakly metamorphosed chondrites (petrologic type >3.0) remains an open issue. This heterogeneity could have recorded fluctuations of O-isotope composition of nebular gas in the CAI-forming region and/or postcrystallization O-isotope exchange of CAI minerals with aqueous fluids on the chondrite parent asteroids. To obtain insights into possible processes resulting in this heterogeneity, we investigated the mineralogy, rare-earth element abundances, and O- and Mg-isotope compositions of a CAI from the CO3.1 chondrite Dar al Gani 083. This concentrically zoned inclusion has a Zn-hercynite core surrounded by layers of (from core to edge) grossite, spinel, melilite, and Al-diopside. The various phases have heterogeneous Δ17O (from core to edge): −2.2 ± 0.6‰, −0.9 ± 2.1‰, −13.7 ± 2.1‰, −2.6 ± 2.3‰, and −22.6 ± 2.1‰, respectively. Magnesium-isotope compositions of grossite, spinel, melilite, and Al-diopside define an undisturbed internal Al–Mg isochron with (26Al/27Al)0 of (2.60 ± 0.29) × 10−6. We conclude that the variations in Δ17O of spinel and diopside recorded fluctuations in O-isotope composition of nebular gas in the CAI-forming region prior to injection and/or homogenization of 26Al at the canonical level. The 16O depletion of grossite and melilite resulted from O-isotope exchange with asteroidal fluid, which did not disturb Al–Mg isotope systematics of the CAI primary minerals. [ABSTRACT FROM AUTHOR]

The Chinese spacecraft Chang'e-5 (CE-5) landed on the northern Ocean Procellarum and returned 1,731 grams of regolith. The CE-5 regolith is composed mostly of fragments of basalt, impact glass, agglutinates, and mineral fragments. The basalts could be classified as of a low-Ti and highly fractionated type based on their TiO2 content of ∼5.3 wt% and Mg# of ∼28. Independent of petrographic texture, the CE-5 basalts have a uniform eruption age of 2,030 ± 4 Ma, demonstrating that the Moon remained volcanically active until at least ∼2.0 Ga. Although the CE-5 landing site lies within the so-called Procellarum KREEP [potassium (K), rare earth elements (REE), and phosphorus (P)] Terrane, neither the CE-5 basalts nor the mantle source regions of those basalts were enriched in KREEP components, such as incompatible elements, water, sulfur, or chlorine. Therefore, it would be a new and stimulating task in the future to look for the triggering mechanism of the young volcanism on the Moon. The CE-5 spacecraft returned 1,731 grams of lunar regolith in December 2020. It was the first new lunar sample since the last collection in August 1976. CE-5 regolith is basaltic in chemical composition, with only ∼1% highland materials of anorthosite, Mg suite, alkali suite, and KREEP. The CE-5 basalt is low Ti and highly differentiated. It was extruded at ∼2.0 Ga, being the youngest lunar basalt identified so far from the Moon. The triggering mechanism of the ∼2.0 Ga lunar volcanism is not clearly understood because its mantle source was dry and contained low abundances of KREEP elements. [ABSTRACT FROM AUTHOR]

Rare earth elements (REE) are a class of increasingly used high-tech product components and new emerging environmental pollutants, which are accumulated, in particular, in marine biota. In this study, REE contents were estimated in shells of several molluscs common in the Black Sea. The summed REE contents in mollusc shells decreased in the following order of species: Magallana gigas = Anadara kagoshimensis > Flexopecten glaber ponticus ≥ Rapana venosa > Mytilus galloprovincialis, ranging from 0.46 to 1.9 mg·kg−1. Canonical analysis of principal coordinates allowed for the correct identification of species based on the REE composition in no fewer than 67% of the samples. The mollusc shells were anomalously enriched in Sc, Y, La, Eu and Tb, most likely due to anthropogenic contamination. The Y/Ho ratios in all samples were represented by two fit values: 23.2 (chondritic) and 67.6 (superchondritic, mainly associated with A. kagoshimensis). A new universal relationship linking the contents of three light and heavy REE in Black Sea mollusc shells was proposed: Ce0.3 Er0.7/Yb = 2.00 ± 0.46 (mean ± standard deviation). [ABSTRACT FROM AUTHOR]

Delivery of nitrogen (N), one of the most important elements for life, to Earth thought to have occurred via both undifferentiated and differentiated bodies, lasting at least 50–100 Ma from the birth of the Solar System. Therefore, to understand how Earth got its N, it is imperative to know the N budget of the earliest formed bodies in our Solar System. The best astromaterials available for providing constraints on N budget of the earliest formed planetesimals are the iron meteorites. However, iron meteorites are crystallized products of a liquid alloy and do not represent the N budget of the bulk cores of various iron meteorite parent bodies (IMPBs). Therefore, to determine how N partitioned between solid alloy (sa) and liquid alloy (la) (D N s a / l a ) during crystallization of molten metal alloy core, we present a series of equilibrium partitioning experiments at 1–2 GPa and 1150–1550 ℃ for various initial starting compositions having different sulfur (S), nickel (Ni), iron (Fe) and fixed nitrogen (N) concentrations. We observe that N changes from mildly incompatible to mildly compatible with increasing S concentration in the liquid alloy. Furthermore, we observed that N concentration in solid alloy decreases with increasing temperature, while pressure and Ni content showed almost no effect on the partitioning behavior of N. We used a regression model based on the results of our study and a previous study to establish a parameterization for D N s a / l a . Using our parameterized D N s a / l a , we determine potential siderophile element proxies of N in metallic systems and model the initial N budget of various IMPBs groups pertaining to the inner (Non-Carbonaceous (NC) reservoir) and outer Solar System (Carbonaceous (CC) reservoir). Between two possible end-member styles of IMPB differentiation (IMO – Internal Magma Ocean; EMO – External Magma Ocean), EMOs result in a higher initial N budget with a major fraction getting lost via atmospheric loss. Importantly, our calculations suggest a gradation in the N budget of CC and NC IMPBs with CC IMPBs hosting lesser N than NC IMPBs. Therefore, the early Solar protoplanetary disk likely showed a gradation in N both in its elemental and isotopic composition. [ABSTRACT FROM AUTHOR]

Al–Mg mineral isochron studies using secondary ion mass spectrometry (SIMS) have revealed the initial 26Al/27Al ratios, (26Al/27Al)0, for individual Ca‐Al‐rich inclusions (CAIs) in meteorites. We find that the relative sensitivity factors of 27Al/24Mg ratio for SIMS analysis of hibonite, one of the major constituent minerals of CAIs, exhibit variations based on their chemical compositions. This underscores the critical need for using appropriate hibonite standards to obtain accurate Al−Mg data. We measured the Al−Mg mineral isochron for hibonite in a fine‐grained CAI (FGI) from the Northwest Africa 8613 reduced CV chondrite by SIMS using synthesized hibonite standards with 27Al/24Mg of ~30, ~100, and ~400. The obtained mineral isochron of hibonite in the FGI yields (26Al/27Al)0 of (4.73 ± 0.09) × 10−5, which is identical to that previously obtained from the mineral isochron of spinel and melilite in the same FGI (Kawasaki et al., 2020). The uncertainties of (26Al/27Al)0 indicate that the constituent minerals in the FGI formed within ~0.02 Myr in the earliest solar system. The disequilibrium O‐isotope distributions of the minerals in the FGI suggest that the O‐isotope compositions of the nebular gas from which they condensed underwent a transitional change from 16O‐rich to 16O‐poor within ~0.02 Myr in the earliest solar system. Once formed, the FGI may have been removed from the forming region within ~0.02 Myr and transported to the accretion region of the parent body. [ABSTRACT FROM AUTHOR]

The unexpected discovery of felsic magma by the Iceland Deep Drilling Project-1 (IDDP-1) in the Krafla volcanic system (KVS) presents a unique opportunity to investigate pre-eruptive lithium (Li) dynamics and establish a more direct connection between magma reservoirs and volcanic deposits. Our study provides new insights into Li abundances and isotope compositions in bulk-rock, minerals, and groundmass glass from rhyolitic lavas at KVS, encompassing various stages of groundmass crystallisation. Additionally, we examined felsic cuttings retrieved from the IDDP-1 well, comprising crystal-poor obsidian and crystal-bearing to -rich 'felsite' particles. Groundmass glasses from surface lavas show limited variability in K/Na, indicating limited secondary hydration of the glasses and that their Li contents seem to not be affected by this post-eruptive process. Lithium inventories in groundmass glasses and minerals within lavas exhibit variations consistent with the cooling history of the deposit, resembling patterns seen in Snake River Plain ignimbrites. Lithium contents of glassy rhyolitic lavas, whether bulk-rock (avg. 27.2 ± 3.1 μg/g) or groundmass glass (average 28.4 ± 4.7 μg/g), and their bulk isotopic compositions (avg. δ7Li =+ 4.4 ± 0.2‰) overlap with those observed in IDDP-1 obsidian cuts (avg. 24.9 μg/g Li in bulk, 28.6 ± 1.5 μg/g in groundmass glass, and δ7Li = 4.5 ± 0.2‰). Glassy lavas lacking spherulites may potentially preserve pristine magmatic Li element and isotope compositions, while areas with extensive groundmass crystallisation reveal Li enrichments in phenocrysts. Plagioclases in slowly cooled parts of the deposit record a two-fold increase in Li contents compared to plagioclase found in glassy counterparts, along with evidence of open-system degassing marked by heavier bulk Li isotope compositions and lower bulk Li contents of the crystallised lava portions (avg. δ7Li = +7.2 ± 0.1‰ and 7 ± 0.8 μg/g Li) relative to bulk glassy lithologies (avg. δ7Li = +4.1 ± 0.1‰ and 28 ± 2 μg/g Li). Partition coefficients derived from IDDP-1 cuts successfully predict Li inventories in vitrophyres of rhyolites on the surface of the KVS. Lithium isotope compositions of the crystal-rich IDDP-1 cuts are significantly heavier (avg. δ7Li = +7.2 ± 0.2‰) than lavas and IDDP-1 obsidian cuts, casting doubt on the notion that the IDDP-1 rhyolitic magma could result from the melting of felsite lenses in the KVS. Lithium contents in groundmass glasses within IDDP-1 crystal-rich cuts show higher Li contents (avg. 55.1–60.7 μg/g), correlating with the higher crystal content and an increase in other incompatible elements (avg. 250 μg/g Rb) relative to obsidian cuttings (avg. 75 μg/g Rb). [ABSTRACT FROM AUTHOR]

Mantle xenoliths hosted in volcanic rocks from the island of Lutao offer a glimpse into the nature of the mantle beneath the northern Luzon volcanic arc. The xenoliths are spinel-bearing and composed mostly of harzburgite with one lherzolite and one olivine orthopyroxenite. The olivine (Fo92.5–88.9), orthopyroxene (Mg# = 94.6–89.2), and clinopyroxene (Wo49.1–38.1En57.0–45.4Fs3.0–11.0) compositions are similar to those of abyssal peridotites. The spinel compositions are variable and can be principally divided into high-Al (Cr# < 45) and low-Al (Cr# > 45) groupings. The whole rock compositions are similar to abyssal peridotite (Al2O3 = 0.95–2.07 wt %; Mg# = 88.5–90.9) and have U-shaped chondrite normalized rare earth element patterns. The Sr-Nd isotopes of the xenoliths are broadly chondritic (87Sr/86Sri = 0.704400–0.707908; εNd(t) = 0.0 − +1.5). The two-pyroxene equilibrium temperatures range from 900 to 1200 °C with the majority of temperature estimates >1000 °C. The olivine-orthopyroxene-spinel oxygen barometry estimates yielded ΔFMQ values from 0 to +2 and correspond to moderately oxidizing to oxidizing conditions. The xenoliths are likely derived from the Philippine Sea Plate lithospheric mantle that was modified by melt extraction and/or fluid enrichment processes. Trace element and isotopic mixing modeling indicate that 1–2% contamination by subducted South China Sea sediment can explain the Sr-Nd isotopic enrichment and Th and U elemental variability within the xenoliths assuming an initial composition similar to enriched depleted mid-ocean ridge mantle (E-DMM). The anomalously high two-pyroxene equilibrium temperatures of the Lutao xenoliths relative to other regions of the northern Luzon volcanic arc (Iraya <1000 °C) indicate that they were affected by a high-temperature event that was likely a consequence of recent intra-arc rifting that occurred after collision (<6 Ma) between the Luzon arc and the Eurasian margin. [ABSTRACT FROM AUTHOR]

The Apollo 15 low-titanium and Apollo 17 high-titanium pyroclastic glass beads are among the most primitive magmatically derived samples obtained from the Moon. Two key samples, the low-Ti Apollo 15426 green glass clod and the high-Ti Apollo 74220 orange glass are morphologically distinct, where the Apollo 15 beads are larger (~107 μm along maximum axis) and more fractured, and the Apollo 17 are smaller (~42 μm) and less fractured. In this study, holohyaline beads as well as crystallized beads were examined from both samples using petrography, electron microprobe analysis, and laser-ablation inductively coupled plasma mass spectrometry. Crystallized beads show compositional variability in major, minor, and trace elements and enable examination of magmatic mineral fractionation processes during cooling of both deposits. The Apollo 15426 beads experienced variable olivine crystallization, whereas the Apollo 74220 beads experienced both olivine and ilmenite crystallization. Holohyaline beads from both deposits show more limited major, minor, and trace element variability than their crystallized counterparts. Trace element abundance data for individual holohyaline beads show that in Apollo 74220, they are tightly clustered at ~30× Carbonaceous Ivuna chondrite [CI] with negative Eu anomalies and subchondritic Nb/Ta, interpreted to reflect the presence of late-stage magma ocean cumulates overturned into an otherwise primitive mantle source. Incompatible trace element abundances for holohyaline beads in 15426 are supra-chondritic from ~8× CI, to >80× CI, with pronounced relative depletions in Sr and Eu for the most incompatible element enriched beads, which represent a distinct bead group within the deposit. Apollo 15426 beads have elevated Ni and Co abundances at the edges of the beads compared to their centers. These data are interpreted to reflect a more complex magmatic evolution of the 15426 deposit, beginning with (i) initial magma generation, storage, and assimilation within shallower low- and high-Ca pyroxene bearing magma ocean cumulates (15B,C); (ii) mobilization of the earlier magmas by more recently generated primitive magmas (15A); (iii) eruption and crystallization of some beads (15D,E); and (iv) later jumbling of the deposit, possible impact contamination and addition of exotic basaltic bead components (J Group). In contrast, the 74220 data show no discernable difference between Ni and Co abundances at the edges and centers supporting prior observations for limited melt fractionation and an absence of meteoritic components. Both deposits are likely to have been formed in the presence of a transient atmosphere. Using 74220 melt compositions from this study, post-entrapment crystallization abundances range from 266 to 1130 μg/g for H2O, 36 to 68 μg/g for F, 441 to 832 μg/g for S, and 0 to 2.31 μg/g for Cl, consistent with prior studies and suggesting up to ~0.1 wt % H2O in the melt, with considerably less in the source. The role that late-stage magma ocean cumulates rich in ilmenite and high-Ca pyroxene might play in modifying this volatile element estimate, however, casts remaining doubt on the volatile element abundance and evolution of the primitive Moon. [ABSTRACT FROM AUTHOR]

During the Grand Finale orbits, Cassini's Cosmic Dust Analyzer (CDA) recorded in situ mass spectra of ice and mineral nanodust grains ejected from Saturn's main rings falling into the planet's atmosphere. We present a compositional analysis of the mineral dust fraction employing a spectral deconvolution method to determine the elemental composition of these grains. The results indicate a relatively homogenous composition of exclusively Mg-rich silicates, with Mg, Si, and Ca close to CI chondritic abundances but a significant depletion in Fe and only traces of organic material at best. The Fe depletion becomes even more pronounced when compared to Fe-rich interplanetary dust particles encountered by CDA in the Saturnian system, which are assumed to contaminate and darken the main rings over time. We discuss potential explanations for the depletion, from which we favour compositional alteration of the infalling dust grains by impact-triggered chemistry in combination with dynamical selection effects and instrumental bias as the most plausible ones. This might cause an accumulation of Fe in the main rings over time, most likely in the form of oxides. [ABSTRACT FROM AUTHOR]