We document the discovery of an active, shallow, seafloor hydrothermal system (known as the Seven Sisters Vent Field) hosted in mafic volcaniclasts at a mid-ocean ridge setting. The vent field is located at the southern part of the Arctic mid-ocean ridge where it lies on top of a flat-topped volcano at ~130 m depth. Up to 200 deg C phase-separating fluids vent from summit depressions in the volcano, and from pinnacle-like edifices on top of large hydrothermal mounds. The hydrothermal mineralization at Seven Sisters manifests as a replacement of mafic volcaniclasts, as direct intraclast precipitation from the hydrothermal fluid, and as elemental sulfur deposition within orifices. Barite is ubiquitous, and is sequentially replaced by pyrite, which is the first sulfide to form, followed by Zn-Cu-Pb-Ag bearing sulfides, sulfosalts, and silica. The mineralized rocks at Seven Sisters contain highly anomalous concentrations of ‘epithermal suite’ elements such as Tl, As, Sb and Hg, with secondary alteration assemblages including silica and dickite. Vent fluids have a pH of ~5 and are Ba and metal depleted. Relatively high dissolved Si (~7.6 mmol/L Si) combined with low (0.2–0.4) Fe/Mn suggest high-temperature reactions at ~150 bar. A delta-13C value of -5.4 permil in CO2 dominated fluids denotes magmatic degassing from a relatively undegassed reservoir. Furthermore, low CH4 and H2 (<0.026 mmol/kg and <0.009 mmol/kg, respectively) and 3He/4He of ~8.3 R/Racorr support a MORB-like, sediment-free fluid signature from an upper mantle source. Sulfide and secondary alteration mineralogy, fluid and gas chemistry, as well as delta-34S and 87Sr/86Sr values in barite and pyrite indicate that mineralization at Seven Sisters is sustained by the input of magmatic fluids with minimal seawater contribution. 226Ra/Ba radiometric dating of the barite suggests that this hydrothermal system has been active for at least 4670 +/- 60 yr.

The southeastern sector of the Hafafit Metamorphic Complex, southern Eastern Desert of Egypt comprises infrastructural orthogneisses of tonalite and syenogranite parentage, amphibolites, and a volcano-sedimentary association. These are overthrust by an obducted suprastructural ophiolite nappes via the Nugrus thrust. The protolith of the biotite–hornblende-gneisses was formed during island-arc accretion, while that of the garnet–biotite gneisses were formed in a within-plate regime, consistent with a transition to a post-collisional setting. The volcano-sedimentary association comprises interbedded and intercalated highly foliated metapelitic schists, metabasites, and leucocratic gneisses, deposited in a back-arc basin. The metapelites and the leucocratic gneisses originated from immature Fe-shales and arkoses derived from intermediate-mafic and acidic igneous rocks, respectively, via weak chemical weathering in a tectonically active island arc terrane. The intercalated amphibolites were derived from tholeiitic basalts generated in a back-arc setting.

The volcano-sedimentary association was metamorphosed under upper-amphibolite facies conditions with pressures of 9–13 kbar and temperatures of 570–675 °C, as derived from conventional geothermobarometry and pseudosection calculation. A steep, tight clockwise P–T path is constrained and a geothermal gradient around 20 °C/km is estimated for the peak metamorphism. We assume that deformation and metamorphism are due to crustal thickening during the collision of East and West Gondwana, where peak metamorphism took place in the middle to lower crust at 33 km average crustal depth. This was followed by a subsequent quasi-isothermal decompression due to rapid exhumation during wrench tectonics. Sinistral transcurrent shearing with extensional denudation resulted in vertical ductile thinning that was accompanied by heat input from magmatism, as indicated by a higher geothermal gradient during retrograde metamorphism and exhumation of the complex.

U–Pb data from magmatic zircons yields protolith ages of 731 ± 3 Ma for the biotite–hornblende gneisses and 646 ± 12 Ma for the garnet–biotite gneisses. Conforming to field evidence, our geochronology data point to a depositional age of the volcano-sedimentary cover at around 650 Ma. The age of metamorphism is constrained by a low Th/U ratio of a zircon grain crystallized at an age of 597 ± 6 Ma.

We investigated the role of N₂-fixation by the colony-forming cyanobacterium, Aphanizomenon spp., for the plankton community and N-budget of the N-limited Baltic Sea during summer by using stable isotope tracers combined with novel secondary ion mass spectrometry, conventional mass spectrometry and nutrient analysis. When incubated with ¹⁵N₂, Aphanizomenon spp. showed a strong ¹⁵N-enrichment implying substantial ¹⁵N₂-fixation. Intriguingly, Aphanizomenon did not assimilate tracers of ¹⁵NH₄⁺ from the surrounding water. These findings are in line with model calculations that confirmed a negligible N-source by diffusion-limited NH₄⁺ fluxes to Aphanizomenon colonies at low bulk concentrations (<250 nm) as compared with N₂-fixation within colonies. No N₂-fixation was detected in autotrophic microorganisms <5 μm, which relied on NH₄⁺ uptake from the surrounding water. Aphanizomenon released about 50% of its newly fixed N₂ as NH₄⁺. However, NH₄⁺ did not accumulate in the water but was transferred to heterotrophic and autotrophic microorganisms as well as to diatoms (Chaetoceros sp.) and copepods with a turnover time of ~5 h. We provide direct quantitative evidence that colony-forming Aphanizomenon releases about half of its recently fixed N₂ as NH₄⁺, which is transferred to the prokaryotic and eukaryotic plankton forming the basis of the food web in the plankton community. Transfer of newly fixed nitrogen to diatoms and copepods furthermore implies a fast export to shallow sediments via fast-sinking fecal pellets and aggregates. Hence, N₂-fixing colony-forming cyanobacteria can have profound impact on ecosystem productivity and biogeochemical processes at shorter time scales (hours to days) than previously thought.

The Jabal Al-Hassir ring complex in the southern Arabian Shield is an alkaline granite complex comprising an inner core of biotite granite that outwardly becomes a porphyritic sodic-calcic amphibole (ferrobarroisite–katophorite) granite. A combined study of mineral chemistry and single zircon Hf–O zircon isotope analyses was carried out to infer the magma sources of the Neoproterozoic post-collisional A-type granitoids in Saudi Arabia. The granitic rocks show high positive initial ɛHf(t) values of +7.0 to +10.3 and δ¹⁸O values of +5.8‰ to +7.4‰ that are consistent with melting of a juvenile crustal protolith that was formed during the Neoproterozoic assembly of the Arabian-Nubian Shield (ANS). Crustal-model ages (Hf-t_NC) of 0.71–0.94 Ga indicate minor contribution from an older continental crust in the formation of the Jabal Al-Hassir granitic rocks (crystallization age = 620 ±3 Ma), but any such component is likely to be Neoproterozoic in age. Temperature and oxygen fugacity (ƒO₂) estimates suggested that the Jabal Al-Hassir A-type granite magma was generated at high temperature (820–1050 °C) and low ƒO₂. Geochemical characteristics (e.g., low ƒO₂), geochronological data, and Hf and O isotope compositions, indicate that the magmas of the Neoproterozoic A-type granites of the Jabal Al-Hassir ring complex were likely generated by crustal partial melting of a juvenile Neoproterozoic lower crustal tholeiitic rocks, following collision between East and West Gondwana in the final stages of the evolution of the Arabian Shield.

This study explores the suitability of apatite as a tracer of the source(s), chemistry, and evolution of ore-forming hydrothermal fluids. This is tested by analysing the halogen (F, Cl, Br, and I), stable Cl isotopic, and trace element compositions of fluorapatite from the regional-scale Olserum-Djupedal rare earth element (REE) phosphate mineralisation in SE Sweden, which is dominated by monazite-(Ce), xenotime-(Y), and fluorapatite. The primary hydrothermal fluid flow system is recorded in a sequence from proximal granite-hosted to distal metasediment-hosted fluorapatite. Along this sequence, primary fluorapatite shows a gradual increase of Cl and Br concentrations and in (Gd/Yb)N, a decrease of F and I concentrations, a decrease in δ37Cl values, in (La/Sm)N, and partly in (La/Yb)N and (Y/Ho)N. Local compositional differences of halogen and trace element concentrations have developed along rims and in domains adjacent to fractures of fluorapatite due to late-stage partial reaction with fracture fluids. These differences are insignificant compared to the larger deposit-scale zoning. This suggests that apatite can retain the primary record of the original ore-forming fluid despite later overprinting fluid events. The agreement between Br/Cl and I/Cl ratios of apatite and those of co-existing fluid inclusions at lower temperatures indicates that only a minor fractionation of Br from I occurs during apatite precipitation. The halogen ratios of apatite can thus be used as a first-order estimate for the composition of the ore-forming fluid. Taking the small fractionation factors for Cl isotopes between apatite and co-existing fluid at high temperatures into account, we propose that the Cl isotopic composition of apatite and the halogen ratios derived from the apatite composition can be used jointly to trace the source(s) of ore-forming fluids. By contrast, most trace elements incorporated in apatite are affected by the host rock environment and by fluid-mineral partitioning due to growth competition between co-crystallising minerals. Collectively, apatite is sensitive to changing fluid compositions, yet it is also able to record the character of primary ore-forming fluids. Thus, apatite is suitable for tracing the origin, chemistry, and evolution of fluids in hydrothermal ore-forming settings.

Deep crustal felsic xenoliths from classic Scottish Midland Valley localities, carried to the surface by Permo-Carboniferous magmatism, are shown for the first time to include metaigneous varieties with dioritic and tonalitic protoliths. Four hypotheses regarding their origin have been evaluated: (1) Precambrian basement; (2) Permo-Carboniferous underplating; (3) ‘Newer Granite’ magmatism; (4) Ordovician arc magmatism. U–Pb zircon dating results rule out the Precambrian basement and Permo-Carboniferous underplating hypotheses, but establish that the meta-igneous xenoliths represent both ‘Newer Granite’ and Ordovician (to possibly Silurian) arc magmatism. The metadiorite xenoliths are shown to have protolith ages of c. 415 Ma with εHft zircon values ranging from +0·1 to +11·1. These are interpreted to represent unexposed ‘Newer Granite’ plutons, based on age, mineralogical, isotopic and geochemical data. This shows that Devonian ‘Newer Granite’ magmatism had a greater impact on the Midland Valley and Southern Uplands crust than previously realized. Clinopyroxene–plagioclase–quartz barometry on the metadiorites from the east and west of the Midland Valley yielded a similar pressure range of c. 5–10 kbar, and a metadiorite from the east yielded a minimum two-feldspar temperature estimate of c. 793–816°C. These results indicate that the metadiorites once resided in the middle–lower crust. In contrast, two metatonalite xenoliths have a Late Ordovician protolith age (c. 453 Ma), with zircon εHft values of +7·8 to +9·0. These are interpreted as samples of a buried Late Ordovician magmatic arc situated within the Midland Valley. Inherited zircons with similar Late Ordovician ages and εHft=453 values (+1·6 to +10·8) are present in the metadiorites, suggesting that the Devonian ‘Newer Granites’ intruded within or through this Late Ordovician Midland Valley arc. A younger protolith age of c. 430 Ma from one of the metatonalites suggests that arc activity continued until Silurian times. This validates the long-standing ‘arc collision’ hypothesis for the development of the Caledonian Orogen. Based on U–Pb zircon dating, the metatonalite and metadiorite xenoliths have both experienced metamorphism between c. 400 and c. 391 Ma, probably linked to the Acadian Orogeny. An older phase of metamorphism at c. 411 Ma was possibly triggered by the combined effects of heating owing to the emplacement of the ‘Newer Granite’ plutons and the overthrusting of the Southern Uplands terrane onto the southern margin of the Midland Valley terrane.

Shergottite Northwest Africa (NWA) 8159 is a basaltic rock derived from a mantle source with chemical characteristics that are unique in the martian meteorite suite. To further investigate this source reservoir, the Pb isotope compositions of plagioclase/maskelynite, pyroxene, phosphates, and shock melt-glass in NWA 8159 have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Due to the limited spread in Pb isotope data, these Pb isotope compositions have been used to calculate an imprecise PbPb isochron age of 3.4 ± 2.1 Ga (2σ), which is broadly consistent with the crystallization age of 2.37 ± 0.25 Ga determined previously by 147Sm143Nd. The lack of radiogenic in-growth within individual minerals since 2.4 Ga means that this sample is depleted in U, which is in agreement with NWA 8159's positive initial ε143Nd. An initial Pb composition was calculated using an x-y weighted average of the least radiogenic Pb isotope population measured in the sample. This initial Pb composition is not consistent with the model for Pb growth in the shergottite mantle at 2.4 Ga. This composition is, however, consistent with the model for the Nakhla-Chassigny mantle. Using the latter model, a source μ (238U/204Pb) of 2.6 ± 0.6 has been calculated. This μ-value is in contrast with the other depleted shergottites (1.4-1.5) and falls significantly off the array of source ε143Nd vs. μ defined by the rest of the martian meteorite suite and thus, necessitates a differentiation history distinct from the other martian meteorites. Sequestering Pb in sulphides during differentiation is the only mechanism to fractionate U from Pb and create a low-μ reservoir. Consequently, the relatively high μ-value of the source of NWA 8159 is in contrast with the positive initial ε143Nd and indicates that its mantle source region likely lacked significant sulphur. This is consistent with the lack of sulphides in the sample itself and could have played a role in its complicated oxidation history.

The triple oxygen isotope compositions of phosphate grains in six martian meteorites have been measured by Secondary Ion Mass Spectrometry (SIMS) and combined together with their chlorine isotope and halogen concentrations have been used to constrain hydrosphere-lithosphere interactions on Mars. These samples include three enriched shergottites (Zagami, Roberts Massif 04262 and Larkman Nunatak 12011), one depleted shergottite (Tissint), an orthopyroxenite (Allan Hills 84001), and a regolith breccia (Northwest Africa 7533). The phosphates measured here have a range in δ18O [(18O/16O)sample/(18O/16O)Standard-1] × 103] from +1.0 to +6.8‰ and could be a result of indigenous mantle values, mixing with martian water, or replacement reactions taking place on the surface of Mars. Three samples have a Δ17O [δ17O-1000(1 + δ18O /1000)0.528-1] in equilibrium with the martian mantle (ALH 84001, Tissint, and Zagami), while three samples (LAR 12011, RBT 04262, and NWA 7533) have an elevated positive Δ17O outside of analytical uncertainty of the martian fractionation line (MFL). The phosphates in the latter group also have positive and negative δ37Cl [(37Cl/35Cl)sample/(37Cl/35Cl)standard – 1] × 103] and enrichments in halogens not seen in the rest of the sample suite. Perchlorate formation on Earth fractionates Cl in both positive and negative directions and generates a correlated positive Δ17O. Further, perchlorate has been detected in wt% amounts on the martian surface. Thus, these results strongly suggest the presence of multiple Cl isotope reservoirs on the martian surface that have interacted with the samples studied here over the last ca. 2 Ga of geologic time. The weighted average of Δ17O measurements from phosphate grains (n = 13) in NWA 7533, which are the explicit result of exchange reactions on the martian surface, yields a statistically robust mean value of 1.39 ± 0.19‰ (2σ, MSWD = 1.5, p = 0.13). This value likely represents an accurate estimate for an oxidized surface reservoir on Mars.

Martian meteorite NWA 7533 is a regolith breccia that compositionally resembles the Martian surface measured by orbiters and landers. NWA 7533 contains monzonitic clasts that have zircon with U–Pb ages of 4.428 Ga. The Pb isotopic compositions of plagioclase and alkali feldspars, as well as U–Pb isotopic compositions of chlorapatitein the monzonitic clasts of NWA 7533 have been measured by Secondary Ion Mass Spectrometry (SIMS). The U–Pb isotopic compositions measured from the chlorapatitein NWA 7533 yield an age of 1.357 ±81Ga(2σ). The least radiogenic Pb isotopic compositions measured in plagioclase and K-feldspar lie within error of the 4.428 Ga Geochron. These data indicate that the monzonitic clasts in NWA 7533 are a product of a differentiation history that includes residence in areservoir that formed prior to 4.428 Ga with a μ-value (238U/204Pb) of at least 13.4 ±1.7 (2σ)and aκ-value (232Th/238U) of ∼4.3. This μ-value is more than three times higher than any other documented Martian reservoir. These results indicate either the Martian mantle is significantly more heterogeneous than previously thought (μ-value of 1–14 vs. 1–5) and/or the monzonitic clasts formed by the melting of Martian crust with a μ-value of at least 13.4. Therefore, NWA 7533 may contain the first isotopic evidence for an enriched, differentiated crust on Mars.

The Pb isotope composition of a nuclear fallout debris particle has been directly measured in post-detonation materials produced during the Trinity nuclear test by a secondary ion mass spectrometry (SIMS) scanning ion image technique (SII). This technique permits the visual assessment of the spatial distribution of Pb and can be used to obtain full Pb isotope compositions in user-defined regions in a 70 μm × 70 μm analytical window. In conjunction with backscattered electron (BSE) and energy-dispersive spectroscopy (EDS) mapping of the same particle, the Pb measured in this fallout particle cannot be from a major phase in the precursor arkosic sand. Similarly, the Pb isotope composition of the particle is resolvable from the surrounding glass at the 2σ uncertainty level (where σ represents the standard deviation). The Pb isotope composition measured in the particle here is in excellent agreement with that inferred from measurements of green and red trinitite, suggesting that these types of particles are responsible for the Pb isotope compositions measured in both trinitite glasses. 

Five Hadean (> 4 Ga) aged zircon grains from the Jack Hills metasedimentary belt have been investigated by a secondary ion mass spectrometry scanning ion image technique. This technique has the ability to obtain accurate and precise full U-Pb systematics on a scale < 5 μm, as well as document the spatial distribution of U, Th and Pb. All five of the grains investigated here have complex cathodoluminescence patterns that correlate to different U, Th, and Pb concentration domains. The age determinations for these different chemical zones indicate multiple reworking events that are preserved in each grain and have affected the primary crystalized zircon on the scale of < 10 μm, smaller than conventional ion microprobe spot analyses. In comparison to the spot analyses performed on these grains, these new scanning ion images and age determinations indicate that almost half of the spot analyses have intersected several age and chemical domains in both fractured and unfractured parts of the individual crystals. Some of these unfractured, mixed domain spot analyses have concordant ages that are inaccurate. Thus, if the frequency of spot analyses intersecting mixed domains here is even close to representative of all other studies of the Jack Hills zircon population, it makes the interpretation of any trace element, Hf, or O isotopic data present in the literature tenuous. Lastly, all of the grains analysed here preserve at least two distinguishable 207Pb/206Pb ages. These ages are preserved in core-rim and/or complex internal textural relationships in unfractured domains. These secondary events took place at ca. 4.3, 4.2, 4.1, 4.0, 3.7, and 2.9 Ga, which are coincident with previously determined statistically robust age peaks present in this zircon population.

The initial Pb compositions of one enriched shergottite, one intermediate shergottite, two depleted shergottites, and Nakhla have been measured by Secondary Ion Mass Spectrometry (SIMS). These values, in addition to data from previous studies using an identical analytical method performed on three enriched shergottites, ALH 84001, and Chassigny, are used to construct a unified and internally consistent model for the differentiation history of the Martian mantle and crystallization ages for Martian meteorites. The differentiation history of the shergottites and Nakhla/Chassigny are fundamentally different, which is in agreement with short-lived radiogenic isotope systematics. The initial Pb compositions of Nakhla/Chassigny are best explained by the late addition of a Pb-enriched component with a primitive, non-radiogenic composition. In contrast, the Pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the Martian mantle that can be modeled based on recent results from the Sm–Nd system. The shergottites have been linked to a single mantle differentiation event at 4504 Ma. Thus, the shergottite Pb isotopic model here reflects a two-stage history 1) pre-silicate differentiation (4504 Ma) and 2) post-silicate differentiation to the age of eruption (as determined by concordant radiogenic isochron ages). The μ-values (238U/204Pb) obtained for these two different stages of Pb growth are μ1 of 1.8 and a range of μ2 from 1.4–4.7, respectively. The μ1-value of 1.8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto Earth, suggesting this is the initial μ-value for inner Solar System bodies. When plotted against other source radiogenic isotopic variables (Sri, γ187Os, ε143Nd, and ε176Hf), the second stage mantle evolution range in observed mantle μ-values display excellent linear correlations (r2 > 0.85) and represent a spectrum of Martian mantle mixing-end members (depleted, intermediate, enriched).

The full U-Pb isotopic systematics in a complex lunar zircon ‘Pomegranate’ from lunar impact breccia 73235 have been investigated by the development of a novel Secondary Ion Mass Spectrometry (SIMS) scanning ion imaging (SII) technique. This technique offers at least a four-fold increase in analytical spatial resolution over traditional SIMS analyses in zircon. Results from this study confirm the hypothesis that the Pomegranate zircon crystallized at 4.302 ± 0.013 Ga and experienced an impact that formed, U-enriched zircon around primary zircon cores at 4.184 ± 0.007 Ga (2σ, all uncertainties). The increase in spatial resolution offered by this technique has facilitated targeting of primary zircon that was previously inaccessible to conventional spot analyses. This approach has yielded results indicating that individual grains with a diffusive distance of less than ~4 μm have been reset to the young impact age, while individual grains with a diffusive distance larger than ~6 μm have retained the old crystallization age. Assuming a broad range in cooling rate of 0.5–50 °C/year, which has been observed in a suite of similar lunar breccias, a maximum localized temperature generated by the impact that reset small prima- ry zircon and created new, high-U zircon is estimated to be between 1100 and 1280 °C.

The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive d³⁷Cl anomalies (+1.1 to +2.5 ‰).  These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative d³⁷Cl anomalies (-0.2 to -5.6 ‰).  Phosphates with the largest negative d³⁷Cl anomalies display zonation where the rims of the grains are enriched in all halogens and have significantly more negative d³⁷Cl anomalies indicating interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average d³⁷Cl of -0.6 ‰, which suggests a similar Cl isotope composition between Mars, the Earth, and the Moon. The only process known to fractionate Cl isotopes, both positively and negatively, is formation of perchlorate, which has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have also been observed on the Martian surface, has been active throughout Martian history. 

The ~1.6 Ga Tirohan Dolomite of the Lower Vindhyan in central India contains phosphatized stromatolitic microbialites. We report from there uniquely well-preserved fossils interpreted as probable crown-group rhodophytes (red algae). The filamentous form Rafatazmia chitrakootensis n. gen, n. sp. has uniserial rows of large cells and grows through diffusely distributed septation. Each cell has a centrally suspended, conspicuous rhomboidal disk interpreted as a pyrenoid. The septa between the cells have central structures that may represent pit connections and pit plugs. Another filamentous form, Denaricion mendax n. gen., n. sp., has coin-like cells reminiscent of those in large sulfur-oxidizing bacteria but much more recalcitrant than the liquid-vacuole-filled cells of the latter. There are also resemblances with oscillatoriacean cyanobacteria, although cell volumes in the latter are much smaller. The wider affinities of Denaricion are uncertain. Ramathallus lobatus n. gen., n. sp. is a lobate sessile alga with pseudoparenchymatous thallus, “cell fountains,” and apical growth, suggesting florideophycean affinity. If these inferences are correct, Rafatazmia and Ramathallus represent crown-group multicellular rhodophytes, antedating the oldest previously accepted red alga in the fossil record by about 400 million years.

Abstract SIMS Th–Pb dating of hydrothermal fissure-vein monazite-(Ce) has the unique potential to date multiple tectonic events under low-grade metamorphic brittle/ductile conditions over large time frames. Monazites-(Ce) from brittle fault systems in the Eastern Alps allow us to constrain their Cretaceous activity over 20 Ma within single crystals, recording all major tectonic events. Eo-Alpine formation of the fluid-filled fissure-veins occurred 90 Ma ago at 352 ± 19°C and 342 ± 42 MPa. This corresponds to peak conditions during regional metamorphism of the Cretaceous collisional nappe stacking. Several stages of dissolution–reprecipitation/recrystallization record fault activity between 84 and 70 Ma. Corresponding fluid inclusions indicate conditions of 229 ± 10°C and 143 ± 20 MPa. This correlates with the formation of sedimentary basins during post-orogenic extension associated with strike-slip movements. The results strengthen the hypothesis that many large fault systems in the Eastern Alps developed during the Cretaceous orogeny and became reactivated during Neogene Alpine tectonics.

Chain-forming diatoms are key CO2-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate and ammonium assimilation in two field populations of chain-forming diatoms (Skeletonema and Chaetoceros) at low-nutrient concentrations under still conditions and turbulent shear using secondary ion mass spectrometry combined with stable isotopic tracers and compared our data with those predicted by mass transfer theory. Turbulent shear significantly increases cell-specific C assimilation compared to still conditions in the cells/chains that also form fast-sinking, aggregates rich in carbon and ammonium. Thus, turbulence simultaneously stimulates small-scale biological CO2 assimilation and large-scale biogeochemical C and N cycles in the ocean.

Paired isotope dilution – thermal ionization mass spectrometry (ID-TIMS) and secondary ion mass spectrometry (SIMS) zircon U–Pb data elucidate geochronological relations in the historically important Knaben molybdenum mining district, Sveconorwegian Orogen, south Norway. This polyphase district provided c. 8.5 Mt of ore with a grade of 0.2%. It consists of mineralized quartz veins, silica-rich gneiss, pegmatites and aplites associated with a heterogeneous, locally sulphide-bearing, amphibolites facies gneiss called Knaben Gneiss, and hosted in a regional-scale monotonous, commonly weakly foliated, granitic gneiss. An augen gneiss at the Knaben I deposit yields a 1257±6 Ma magmatic zircon age, dating the pre-Sveconorwegian protolith of the Knaben Gneiss. Mineralized and non-mineralized granitic gneiss samples at the Knaben II and Kvina deposits contain some 1488–1164 Ma inherited zircon and yield consistent intrusion ages of 1032±4, 1034±6 and 1036±6 Ma. This age links magmatism in the district to the regional 1050–1020 Ma Sirdal I-type granite suite, corresponding to voluminous crustal melting during the Sveconorwegian orogeny. A high-U, low-Th/U zircon rim is present in all samples. It defines several age clusters between 1039±6 and 1009±7 Ma, peaking at c. 1016 Ma and overlapping with a monazite age of 1013±5 Ma. The rim records protracted hydrothermal activity, which started during the main magmatic event and outlasted it. This process was coeval with regional high-grade Sveconorwegian metamorphism. Molybdenum deposition probably started during this event when silica-rich mineralizing fluids or hydrous magmas were released from granite magma batches. An analogy between the Knaben district and shallow, short-lived porphyry Mo deposits is inappropriate.

Zircon U–Pb geochronological data in 18 samples from Finnmarksvidda and one sample from the Repparfjord Tectonic Window, northern Norway, constrain the evolution of the Palaeoproterozoic Kautokeino Greenstone Belt and neighbouring units in a Fennoscandia context. The Jergul Complex is an Archaean cratonic block of Karelian affinity, made of variably gneissic, tonalite–trondhjemite–granodiorite–granite plutonic rocks formed between 2975 ± 10 and 2776 ± 6 Ma. It is associated with the Archaean Goldenvárri greenstone–schist formation. At the base of the Kautokeino Greenstone Belt, the Masi Formation is a typical Jatulian quartzite, hosting a Haaskalehto-type, albite–magnetite-rich, mafic sill dated at 2220 ± 7 Ma. The Likčá and Čáskejas formations represent the main event of basaltic magmatism. A synvolcanic metagabbro dates this magmatism at 2137 ± 5 Ma. The geochemical and Nd isotopic signature of the Čáskejas Formation (eNd = +2.2 ± 1.7) is remarkably similar to coeval dykes intruding the Archaean Karelian Craton in Finland and Russia (eNd = +2.5 ± 1.0). The Čáskejas Formation can be correlated with the Kvenvik Formation in the Alta–Kvænangen Tectonic Window. Two large granite plutons yield ages of 1888 ± 7 and 1865 ± 8 Ma, and provide a maximum age for shearing along two prominent NNW–SSE-oriented shear zones recording Svecokarelian transpression. The Bidjovagge Au–Cu deposit formed around 1886 to 1837 Ma and is also related to this NNW–SSE-oriented shear system. The Ráiseatnu Complex is mainly composed of granitic gneisses formed between 1868 ± 13 and 1828 ± 5 Ma, and containing metasediment rafts and zircon xenocrysts ranging from c. 3100 to 2437 Ma. The Kautokeino Greenstone Belt and Ráiseatnu Complex are interpreted as Palaeoproterozoic, pericontinental, lithospheric domains formed during rifting between Archaean cratonic domains. They accommodated oblique convergence between the Karelian and the Norrbotten Archaean cratons during the Svecokarelian orogeny.

Hafnium and oxygen isotopic compositions measured in-situ on U-Pb dated zircon from Archaean sedimentary successions belonging to the 2.9–2.8 Ga Belingwean/Bulawayan groups and previously undated Sebakwian Group are used to characterize the crustal evolution of the Zimbabwe Craton prior to 3.0 Ga. Microstructural and compositional criteria were used to minimize effects arising from Pb loss due to metamorphic overprinting and interaction with low-temperature fluids. 207Pb/206Pb age spectra (concordance >90%) reveal prominent peaks at 3.8, 3.6, 3.5, and 3.35 Ga, corresponding to documented geological events, both globally and within the Zimbabwe Craton. Zircon δ18O values from +4 to +10‰ point to both derivation from magmas in equilibrium with mantle oxygen and the incorporation of material that had previously interacted with water in near-surface environments. In εHf-time space, 3.8–3.6 Ga grains define an array consistent with reworking of a mafic reservoir (176Lu/177Hf ∼0.015) that separated from chondritic mantle at ∼3.9 Ga. Crustal domains formed after 3.6 Ga depict a more complex evolution, involving contribution from chondritic mantle sources and, to a lesser extent, reworking of pre-existing crust. Protracted remelting was not accompanied by significant mantle depletion prior to 3.35 Ga. This implies that early crust production in the Zimbabwe Craton did not cause complementary enriched and depleted reservoirs that were tapped by later magmas, possibly because the volume of crust extracted and stabilised was too small to influence (asthenospheric) mantle isotopic evolution. Growth of continental crust through pulsed emplacement of juvenile (chondritic mantle-derived) melts, into and onto the existing cratonic nucleus, however, involved formation of complementary depleted subcontinental lithospheric mantle since the early Archaean, indicative of strongly coupled evolutionary histories of both reservoirs, with limited evidence for recycling and lateral accretion of arc-related crustal blocks until 3.35 Ga.

Lead and multiple sulphur isotope compositions were measured in-situ by SIMS on sulphide minerals from phoscorites and carbonatites of the ca. 2.06 Ga Phalaborwa Complex in South Africa. Additionally, sulphide mineral separates and bulk-rock samples were analyzed with IRMS methods to confirm SIMS data. Lead isotope ratios define a trend stretching from unradiogenic to highly radiogenic ratios corresponding to a Pb–Pb regression date of 2054 ± 99 Ma. This apparent date is consistent with the timing of emplacement and thus provides an age estimate for the sulphide mineralization. The least radiogenic Pb isotope compositions overlap, and the regression line intersects, a hypothetical mixing line between MORB mantle and an upper crustal reservoir at ca. 2.1 Ga, suggesting that either a significant quantity of crustal Pb contributed to sulphide mineralization, or that sulphidic xenomelts were derived from an isotopically enriched mantle source. Sulphur isotope ratios of individual sulphide minerals obtained by SIMS are highly variable (δ34S: −15 to +15‰ V-CDT) and, importantly, reveal the contribution of pre-Great Oxidation Event (GOE) atmospheric sulphur with mass-independent isotope fractionation (Δ33S = δ33S–[(1+δ34S)0.515-1]×1000 ≠0.0‰). Mass-independent sulphur isotope fractionation is also revealed by sulphur isotope ratios measured on sulphide mineral separates (Δ33S: 0.2 to 0.7‰) and bulk rock samples (Δ33S: 0.2 to 0.4‰). Generally, the range of sulphur isotope ratios obtained with SIMS is much larger than that observed in non-SIMS data, possibly reflecting isotopic variability at the μm scale, resolvable only with microbeam measurements. Various sources and mechanisms by which supracrustal material may have been incorporated into mantle-derived carbonatite-phoscorite magmas are assessed, taking into account that geological evidence for the presence of sedimentary material available for assimilation during shallow-level magma emplacement is lacking. Given the variability in S and Pb isotopic compositions, it is inferred that pre-GOE surficial Pb and S were not derived from asthenospheric mantle contaminated with supracrustal materials. Instead, whole rock trace element compositions, in concert with published geochemical and petrological evidence, are consistent with interaction of asthenospheric, plume-derived melt with compositionally heterogeneous lithospheric mantle that was metasomatically modified by fluids and melts released from a subducting slab. Despite geochemical and geochronological similarities with the 2055 Ma Busvheld Complex, lead and sulphur isotope data for both complexes are resolvably different, pointing to distinct lithospheric mantle sources involved in sulphide mineralization.

The most abundant components of primitive meteorites (chondrites) are millimeter-sized glassy spherical chondrules formed by transient melting events in the solar protoplanetary disk. Using Pb-Pb dates of 22 individual chondrules, we show that primary production of chondrules in the early solar system was restricted to the first million years after the formation of the Sun and that these existing chondrules were recycled for the remaining lifetime of the protoplanetary disk. This finding is consistent with a primary chondrule formation episode during the early high-mass accretion phase of the protoplanetary disk that transitions into a longer period of chondrule reworking. An abundance of chondrules at early times provides the precursor material required to drive the efficient and rapid formation of planetary objects via chondrule accretion.

The formation of a primordial crust is a critical step in the evolution of terrestrial planets but the timing of this process is poorly understood. The mineral zircon is a powerful tool for constraining crust formation because it can be accurately dated with the uranium-to-lead (U–Pb) isotopic decay system and is resistant to subsequent alteration. Moreover, given the high concentration of hafnium in zircon, the lutetium-to-hafnium (176Lu–176Hf) isotopic decay system can be used to determine the nature and formation timescale of its source reservoir (1,2,3) Ancient igneous zircons with crystallization ages of around 4,430 million years (Myr) have been reported in Martian meteorites that are believed to represent regolith breccias from the southern highlands of Mars (4,5) These zircons are present in evolved lithologies interpreted to reflect re-melted primary Martian crust4, thereby potentially providing insight into early crustal evolution on Mars. Here, we report concomitant high-precision U–Pb ages and Hf-isotope compositions of ancient zircons from the NWA 7034 Martian regolith breccia. Seven zircons with mostly concordant U–Pb ages define 207Pb/206Pb dates ranging from 4,476.3 ± 0.9 Myr ago to 4,429.7 ± 1.0 Myr ago, including the oldest directly dated material from Mars. All zircons record unradiogenic initial Hf-isotope compositions inherited from an enriched, andesitic-like crust extracted from a primitive mantle no later than 4,547 Myr ago. Thus, a primordial crust existed on Mars by this time and survived for around 100 Myr before it was reworked, possibly by impacts (4,5) to produce magmas from which the zircons crystallized. Given that formation of a stable primordial crust is the end product of planetary differentiation, our data require that the accretion, core formation and magma ocean crystallization on Mars were completed less than 20 Myr after the formation of the Solar System. These timescales support models that suggest extremely rapid magma ocean crystallization leading to a gravitationally unstable stratified mantle, which subsequently overturns, resulting in decompression melting of rising cumulates and production of a primordial basaltic to andesitic crust (6,7).

Pillow basalt and chert form integral lithologies comprising many Archean greenstone belt packages. To investigate details of these lithologies in the >3.7 Ga Isua Greenstone Belt, SW Greenland, we measured silicon isotope compositions of quartz crystals, by secondary ion mass spectrometry, from a quartz-cemented, quartz-amygdaloidal basaltic pillow breccia, recrystallized chert and chert clasts thought to represent silica precipitation under hydrothermal conditions. The recrystallized chert, chert clasts and quartz cement have overlapping δ³⁰Si values, while the δ³⁰Si values of the quartz amygdules span nearly the entire range of previously published values for quartz precipitates of any age, despite amphibolite facies metamorphism. We suggest that the heterogeneity is derived from kinetic isotope fractionation during quartz precipitation under disequilibrium conditions in a hydrothermal setting, consistent with the pillow breccia origin. On the basis of the present data, we conclude that the geological context of each sample must be carefully evaluated when interpreting δ³⁰Si values of quartz.

Silica-rich Precambrian rocks often preserve geochemical information and microfossil remnants from the early biosphere and could play a critical role in the formation of early crust. Because these rocks are important geochemical and paleontological archives, we need to better constrain their geochemical and isotopic attributes and generate a refined picture of the evolving Archean silica cycle. Here, we investigate a series of sub- to greenschist facies Si-rich Archean rocks from the ~ 2.7 Ga Abitibi greenstone belt, Canada, that represent chemical sedimentary rocks and rocks formed via silica-addition through the process of silicification. We report data for major and trace element geochemistry, multi-crystal silicon and oxygen isotopes of quartz using isotope ratio mass spectrometry, and texture-specific silicon isotope values measured using secondary ion mass spectrometry on Neoarchean chemical sedimentary rocks, their silicified equivalents, and associated silicified volcanic rocks. We find that in such a well-preserved terrane we can utilize petrographic textures and geochemical attributes to establish rock origin, distinguishing siliceous rocks that form via chemical sedimentation from those that form via silicification. Chemical sedimentary rocks display a wide range of 30Si-depleted silicon isotopes values that vary with stratigraphy similar to other Archean iron formation. Silicified volcanic rocks possess 30Si-enriched values, similar to Archean silicified basalts. We conclude that because silicon isotope values of iron formation shift toward 30Si-enriched values up stratigraphy, basinal changes in the composition of the silicon isotope reservoir may be preserved. Silicon isotope values of silicified volcanic rocks by contrast, likely represent precipitation from an isotopically heavy silicon reservoir, influenced by downward percolating seawater and upward moving convecting fluids interacting with host volcanic rock (basalt or andesite). Overall, we confirm that Neoarchean silicified rocks are 30Si-enriched like their Paleoarchean counterparts.

Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core−rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

New field, geochemical, and geochronological data from the Segama Valley Felsic Intrusions (SVFI) of Sabah, north Borneo, shows them to be arc-derived tonalites; not windows or partial melts of a crystalline basement beneath Sabah. U-Pb zircon ages date emplacement in the Triassic and Jurassic: 241.1 ± 2.0 Ma, 250.7 ± 1.9 Ma, 178.7 ± 2.4 Ma, and 178.6 ± 1.3 Ma; contemporaneous with peaks in magmatism and detrital zircons in Sarawak and west Kalimantan (west Borneo). Isotopic data for Sr, Nd, and Pb from whole rocks, and for Hf and O from zircon all show mantle and/or MORB affinities indicating a mantle-derived origin. Enrichment of fluid mobile trace elements and trace element ratios indicate that the most likely setting for this is in a continuation of the Sundaland continental arc. There is no evidence in the field, geochemical, or zircon U-Pb data for continental basement in the Segama Valley region. The intrusive nature of the Segama Valley tonalites constrains the emplacement age of their supra-subduction zone host rocks to at least the Triassic. This new data expands the Triassic and Jurassic extent of Borneo and the Sundaland arc, and challenges models of Borneo's development predominantly through allochthonous terrane accretion in the Cretaceous. Instead, we propose a model of protracted autochthonous growth through supra-subduction zone crustal extension and associated magmatism.

Mangaia hosts the most radiogenic Pb-isotopic compositions observed in ocean island basalts and represents the HIMU (high µ = ²³⁸U/²⁰⁴Pb) mantle end-member, thought to result from recycled oceanic crust. Complete geochemical characterization of the HIMU mantle end-member has been inhibited due to a lack of deep submarine glass samples from HIMU localities. We homogenized olivine-hosted melt inclusions separated from Mangaia lavas and the resulting glassy inclusions made possible the first volatile abundances to be obtained from the HIMU mantle end-member. We also report major and trace element abundances and Pb-isotopic ratios on the inclusions, which have HIMU isotopic fingerprints. We evaluate the samples for processes that could modify the volatile and trace element abundances postmantle melting, including diffusive Fe and H₂O loss, degassing, and assimilation. H₂O/Ce ratios vary from 119 to 245 in the most pristine Mangaia inclusions; excluding an inclusion that shows evidence for assimilation, the primary magmatic H₂O/Ce ratios vary up to ∼200, and are consistent with significant dehydration of oceanic crust during subduction and long-term storage in the mantle. CO₂ concentrations range up to 2346 ppm CO₂ in the inclusions. Relatively high CO₂ in the inclusions, combined with previous observations of carbonate blebs in other Mangaia melt inclusions, highlight the importance of CO₂ for the generation of the HIMU mantle. F/Nd ratios in the inclusions (30 ± 9; 2σ standard deviation) are higher than the canonical ratio observed in oceanic lavas, and Cl/K ratios (0.079 ± 0.028) fall in the range of pristine mantle (0.02–0.08).

Integrated petrography, mineralogy, geochronology and geochemistry of cold seep carbonate crusts and free gas from the Alvheim channel elucidate diagenetic carbonate precipitation and related seepage histories in the central North Sea. Free gas isotope characteristics coupled with carbonate δ¹³C values as low as − 66‰ VPDB, indicate a predominantly microbial methane source with minor thermogenic contribution. We estimate that ~ 70% of the carbon sequestered into carbonate precipitates was derived from local oxidation of methane. The early stage of crust growth is represented by microcrystalline aragonite and Mg-calcite (10 to 40% mol MgCO₃) cementing seafloor sediments consisting of clays, quartz, feldspar, and minor detrital low Mg-calcite and dolomite. Typical association of aragonite cement with coarse-grained detritus may reflect elevated fluid flow and flushing of fine particles prior to cementation close to the seafloor. Middle rare earth element enrichment in early generation microcrystalline cements containing framboidal pyrite indicates diagenetic precipitation within the zone of anaerobic methane oxidation contiguous to iron reduction. The later generation diagenetic phase corresponds to less abundant radial fibrous and botryoidal aragonite which lines cavities developed within the crusts. In contrast to early generation cements, late generation cavity infills have rare earth elements and Y patterns with small negative Ce anomalies similar to seawater, consistent with carbonate precipitation in a more open, seawater dominated system. Aragonite U–Th ages indicate carbonate precipitation between 6.09 and 3.46 kyr BP in the northern part of the channel, whereas in the southern part precipitation occurred between 1.94 and 0.81 kyr BP reflecting regional changes in fluid conduit position.

Abstract Miller Range (MIL) 13317 is a heterogeneous basalt-bearing lunar regolith breccia that provides insights into the early magmatic history of the Moon. MIL 13317 is formed from a mixture of material with clasts having an affinity to Apollo ferroan anorthosites and basaltic volcanic rocks. Noble gas data indicate that MIL 13317 was consolidated into a breccia between 2610 ± 780 Ma and 1570 ± 470 Ma where it experienced a complex near-surface irradiation history for ~835 ± 84 Myr, at an average depth of ~30 cm. The fusion crust has an intermediate composition (Al2O3 15.9 wt%; FeO 12.3 wt%) with an added incompatible trace element (Th 5.4 ppm) chemical component. Taking the fusion crust to be indicative of the bulk sample composition, this implies that MIL 13317 originated from a regolith that is associated with a mare-highland boundary that is KREEP-rich (i.e., K, rare earth elements, and P). A comparison of bulk chemical data from MIL 13317 with remote sensing data from the Lunar Prospector orbiter suggests that MIL 13317 likely originated from the northwest region of Oceanus Procellarum, east of Mare Nubium, or at the eastern edge of Mare Frigoris. All these potential source areas are on the near side of the Moon, indicating a close association with the Procellarum KREEP Terrane. Basalt clasts in MIL 13317 are from a very low-Ti to low-Ti (between 0.14 and 0.32 wt%) source region. The similar mineral fractionation trends of the different basalt clasts in the sample suggest they are comagmatic in origin. Zircon-bearing phases and Ca-phosphate grains in basalt clasts and matrix grains yield 207Pb/206Pb ages between 4344 ± 4 and 4333 ± 5 Ma. These ancient 207Pb/206Pb ages indicate that the meteorite has sampled a range of Pre-Nectarian volcanic rocks that are poorly represented in the Apollo, Luna, and lunar meteorite collections. As such, MIL 13317 adds to the growing evidence that basaltic volcanic activity on the Moon started as early as ~4340 Ma, before the main period of lunar mare basalt volcanism at ~3850 Ma.

Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO₂ fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO₂-dominated vapour phase. The CaO-rich glasses have extremely low δ¹¹B values down to −41.5‰, reflecting preferential partitioning of ¹⁰B into the assimilating melt. Loss of ¹¹B from the reaction site occurs via the CO₂ vapour phase generated during carbonate dissolution, which transports ¹¹B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ¹¹B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

Measurement of oxygen isotope ratios in common silicate minerals such as olivine, pyroxene, feldspar, garnet, and quartz is increasingly performed by Secondary Ion Mass Spectrometry (SIMS). However, certain mineral groups exhibit solid solution series, and the large compositional spectrum of these mineral phases will result in matrix effects during SIMS analysis. These matrix effects must be corrected through repeated analysis of compositionally similar standards to ensure accurate results. In order to widen the current applicability of SIMS to solid solution mineral groups in common igneous rocks, we performed SIMS homogeneity tests on new augite (NRM-AG-1) and enstatite (NRM-EN-2) reference materials sourced from Stromboli, Italy and Webster, North Carolina, respectively. Aliquots of the standard minerals were analysed by laser fluorination (LF) to establish their δ¹⁸O values. Repeated SIMS measurements were then performed on randomly oriented fragments of the same pyroxene crystals, which yielded a range in δ¹⁸O less than ± 0.42 and ± 0.58‰ (2σ) for NRM-AG-1 and NRM-EN-2, respectively. Homogeneity tests verified that NRM-AG-1 and NRM-EN-2 do not show any crystallographic orientation bias and that they are sufficiently homogeneous on the 20 μm scale to be used as routine mineral standards for SIMS δ¹⁸O analysis. We subsequently tested our new standard materials on recently erupted pyroxene crystals from Merapi volcano, Indonesia. The δ¹⁸O values for Merapi pyroxene obtained by SIMS (n = 204) agree within error with the LF-derived δ¹⁸O values for Merapi pyroxene but differ from bulk mineral and whole-rock data obtained by conventional fluorination. The bulk samples are offset to higher δ¹⁸O values as a result of incorporation of mineral and glass inclusions that in part reflects crustal contamination processes. The Merapi pyroxene SIMS data, in turn, display a frequency peak at 5.8‰, which allows us to estimate the δ¹⁸O value of the primary mafic magma at Merapi to ~ 6.1‰ when assuming closed system differentiation.

Despite the intense cratering history of the Moon, very few traces of meteoritic material have been identified in the more than 380 kg of samples returned to Earth by the Apollo and Luna missions. Here we show that an ~200-µm-sized fragment collected by the Luna 16 mission has extra-lunar origins and probably originates from an LL chondrite with similar properties to near-Earth stony asteroids. The fragment has not experienced temperatures higher than 400 °C since its protolith formed early in the history of the Solar System. It arrived on the Moon, either as a micrometeorite or as the result of the break-up of a bigger impact, no earlier than 3.4 Gyr ago and possibly around 1 Gyr ago, an age that would be consistent with impact ages inferred from basaltic fragments in the Luna 16 sample and of a known dynamic upheaval in the Flora asteroid family, which is thought to be the source of L and LL chondrite meteorites. These results highlight the importance of extra-lunar fragments in constraining the impact history of the Earth–Moon system and suggest that material from LL chondrite asteroids may be an important component.