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On July 15, 2021, a huge fireball was visible over Poland. After the possible strewn field was calculated, the first and so far only sample, with a mass of 350 g, was discovered 18 days after the fireball event. The Antonin meteorite was found August 3, 2021, on the edge of a forest close to a dirt road near Helenow, a small suburb of the city of Mikstat. The rock is an ordinary chondrite breccia and consists of equilibrated and recrystallized lithologies. The boundaries between different fragments are difficult to detect, and the lithologies are of petrologic type 5 and type 4. The rock is moderately shocked (S4) and contains local impact melt areas and thin shock veins. The low-Ca pyroxene and olivine are equilibrated (Fs20.6 and Fa24.0, respectively), typical of L chondrites. The L chondrite classification is also supported by O isotope data and the results of bulk chemical analysis. The Ti isotope characteristics confirm that Antonin is related to the noncarbonaceous (NC) meteorites. One of the studied thin sections shows an unusual metal–chondrule assemblage, perhaps indicating that the metal in the chondrite is heterogeneously distributed, which is, however, not clearly visible in the element abundances.

WOS:000600550100030; International audience; Chromium (Cr) isotopes play an important role in cosmochemistry and planetary science because they are powerful tools for dating (Mn-53-Cr-53 short-lived chronometry), tracing (Cr-54 nucleosynthetic anomalies) the origins of the materials, and studying the processes involved in volatile element fractionation and planetary differentiation (Cr stable isotopic fractionation). To use Cr isotopes for these purposes, it is essential to precisely know the compositions of the various chondritic reservoirs. However, the Cr isotope composition of Rumuruti (R) chondrites remains unknown. Here, we report high-precision mass-independent (average 2SE uncertainty of similar to 0.02 and similar to 0.06 for epsilon Cr-53 and epsilon Cr-54, respectively; epsilon indicates 10,000 deviation) and mass-dependent (uncertainty of average 0.03 parts per thousand for delta Cr-53; .delta indicates 1000 deviation) Cr isotope data for 12 bulk R chondrites of petrologic types 3-6 (including R chondrite breccias), and one R chondrite-like clast (MS-CH) in the Almahata Sitta polymict ureilite. All the R chondrites show homogeneous bulk epsilon Cr-54 values, -0.06 +/- 0.08 (2SD), similar only to those of the Earth-Moon system and enstatite chondrites. This first epsilon Cr-54 dataset for R chondrites provides significant addition to the epsilon Cr-54-A, Delta O-17 diagram, and positions them as a potential endmember for planetary precursors. The R chondrites possess a higher Mn-55/Cr-52 of 0.68 +/- 0.04 relative to most of carbonaceous chondrites and higher epsilon Cr-53 values 0.23 +/- 0.05 (2SD) relative to most of chondrite groups. This likely results from the lower chondrule abundance in R chondrites compared to that of ordinary and enstatite chondrites. The stable Cr isotope composition of R chondrites is homogeneous with a delta Cr-53 = -0.12 +/- 0.03%e (2SD). Combined with previous data of other groups of chondrites, we show that the stable Cr isotopic composition of all the chondrites is homogeneous with delta Cr-53 of -0.12 +/- 0.04%e (2SD, N = 42) and is independent of the petrologic type and redox conditions. The lack of mass-dependent fractionation between all groups of chondrites suggests that the average chondrite delta Cr-53 value is also representative for the initial composition of all differentiated planets in the Solar System. Finally, the MS-CH clast in Almahata Sitta has a Cr isotopic composition (epsilon Cr-53 = 0.18 +/- 0.04, epsilon Cr-54 = 0.16 +/- 0.07, and delta Cr-53 = -0.11 +/- 0.05%e) that is consistent (within error) with it being an R chondrite-like clast. (C) 2020 Elsevier Ltd. All rights reserved.

Basalts from high flux intra-plate volcanism (Iceland, Hawaii, Samoa) are characterised by 3He/4He that are significantly higher than those from the upper mantle sampled at mid-ocean ridges. The prevailing paradigm requires that a largely undegassed deep Earth is enriched in primordial noble gases (3He, 20Ne) relative to degassed convecting upper mantle. However, the He concentration and 3He/20Ne ratio of high 3He/4He oceanic basalts are generally lower than mid-ocean ridge basalts (MORB). This so called ‘He paradox’ has gained infamy and is used to argue against the conventional model of Earth structure and the existence of mantle plumes. While the paradox can be resolved by disequilibrium degassing of magmas it highlights the difficulty in reconstructing the primordial volatile inventory of the deep Earth from partially degassed oceanic basalts.Basalts from 26 to 11°N on the Red Sea spreading axis reveals a systematic southward increase in 3He/4He that tops out at 15 Ra in the Gulf of Tadjoura (GoT). The GoT 3He/4He overlaps the highest values of sub-aerial basalts from Afar and Main Ethiopian Rift and is arguably located over modern Afar plume. The along-rift 3He/4He variation is mirrored by a systematic change in incompatible trace element (ITE) ratios that appear to define two-component mixing between E-MORB and HIMU. Despite some complexity, hyperbolic mixing relationships are apparent in 3He/4He-K/Th-Rb/La space. Using established trace element concentrations in these mantle components we can calculate the concentration of He in the Afar plume mantle. Surprisingly it appears that the upwelling plume mantle has 5-20 times less He than the convecting asthenospheric mantle despite the high 3He/4He (and primordial Ne isotope composition). This contradicts the prevailing orthodoxy but can simply be explained if the Afar mantle plume is itself a mixture of primordial He-rich, high 3He/4He (55 Ra) deep mantle with a proportionally dominant mass of He-poor low 3He/4He HIMU mantle. This is consistent with the narrow range of Sr-Nd-Os isotopes and ITE ratios of the highest 3He/4He Afar plume basalts, and is in marked contrast to high 3He/4He plumes (e.g. Iceland) that do not have unique geochemical composition. The HIMU signature of the Afar plume basalts implies origin in recycled altered oceanic crust (RAOC). Assuming that no He is recycled and using established RAOC U and Th concentrations, the low He concentration (< 5 x 1013 atoms/g He) of the He-poor mantle implies that the slab was subducted no earlier than 70 Ma and reached no more than 700 km before being incorporated into the upwelling Afar plume. We suggest that the Afar plume acquired its chemical and isotopic fingerprint during large scale mixing at the 670 km transition zone with the Tethyan slab, not at the core-mantle boundary.This study implies that large domains of essentially He-poor mantle exist within the deep Earth, likely associated with the HIMU mantle compositions. Further, it implies that moderately high-3He/4He (< 30 Ra) mantle plumes (e.g. Reunion) need not contain a significant contribution of deep mantle, thus cannot be used a priori to define primitive Earth composition.

The formation and differentiation of planetary bodies are dated using radioactive decay systems, including the short-lived 146Sm-142Nd (T½ = 103 or 68 Ma) and long-lived 147Sm-143Nd (T½ = 106 Ga) radiogenic pairs that provide relative and absolute ages, respectively. However, the initial abundance and half-life of the extinct radioactive isotope 146Sm are still debated, weakening the interpretation of 146Sm-142Nd systematics obtained for early planetary processes. Here, we apply the short-lived 26Al-26Mg, 146Sm-142Nd, and long-lived 147Sm-143Sm chronometers to the oldest known andesitic meteorite, Erg Chech 002 (EC 002), to constrain the Solar System initial abundance of 146Sm. The 26Al-26Mg mineral isochron of EC 002 provides a tightly constrained initial δ26Mg* of −0.009 ± 0.005 ‰ and (26Al/27Al)0 of (8.89 ± 0.09) × 10−6. This initial abundance of 26Al is the highest measured so far in an achondrite and corresponds to a crystallization age of 1.80 ± 0.01 Myr after Solar System formation. The 146Sm-142Nd mineral isochron returns an initial 146Sm/144Sm ratio of 0.00830 ± 0.00032. By combining the Al-Mg crystallization age and initial 146Sm/144Sm ratio of EC 002 with values for refractory inclusions, achondrites, and lunar samples, the best-fit half-life for 146Sm is 102 ± 9 Ma, corresponding to the physically measured value of 103 ± 5 Myr, rather than the latest and lower revised value of 68 ± 7 Ma. Using a half-life of 103 Ma for 146Sm, the 146Sm/144Sm abundance of EC 002 translates into an initial Solar System 146Sm/144Sm ratio of 0.00840 ± 0.00032, which represents the most reliable and precise estimate to date and makes EC 002 an ideal anchor for the 146Sm-142Nd clock.

International audience; On April 23rd, 2019, the Aguas Zarcas meteorite fall occurred in Costa Rica. Because the meteorite was quickly recovered, it contains valuable extraterrestrial materials that have not been contaminated by terrestrial processes. Our X-ray computed tomography (XCT) and scanning electron microscopy (SEM) results on various pre-rain fragments from earlier work (Kerraouch et al., 2020; 2021) revealed several distinct lithologies: Two distinct metal-rich lithologies (Met-1 and Met-2), a CM1/2 lithology, a C1 lithology, and a brecciated CM2 lithology consisting of different petrologic types. Here, we further examined these lithologies in the brecciated Aguas Zarcas meteorite and report new detailed mineralogical, chemical, isotopic, and organic matter characteristics. In addition to petrographic differences, the lithologies also display different chemical and isotopic compositions. The variations in their bulk oxygen isotopic compositions indicate that the various lithologies formed in different environments and/or under diverse conditions (e.g., water/rock ratios). Each lithology experienced a different hydration period during its evolution. Together, this suggests that multiple precursor parent bodies may have been involved in these processes of impact brecciation, mixing, and re-assembly. The Cr and Ti isotopic data for both the CM1/2 and Met-1 lithology are consistent with those of other CM chondrites, even though Met-1 displays a significantly lower ε50Ti isotopic composition that may be attributable to sample heterogeneities on the bulk meteorite scale and may reflect variable abundances of refractory phases in the different lithologies of Aguas Zarcas. Finally, examination of the organic matter of the various lithologies also suggests no strong evidence of thermal events, but a short-term heating cannot completely be excluded. Raman parameters indicate that the peak temperature has been lower than that for Yamato-793321 (CM2, ∼400 °C). Considering the new information presented in this study, we now better understand the origin and formation history of the Aguas Zarcas daughter body.

In the last 7 years, three meteorites (Blaubeuren, Cloppenburg, and Machtenstein) found in Germany were identified as chondrites. Two of these rocks had been recovered from the impact sites decades ago but were not considered to be meteorites. The aim of this study is to fully characterize these three meteorites. Based on the compositional data on the silicates, namely olivine and low‐Ca pyroxene, these meteorites fit nicely within the H‐group ordinary chondrites. The brecciated texture of Blaubeuren and Cloppenburg (both H4‐5) is perfectly visible, whereas that of Machtenstein, officially classified as an H5 chondrite, is less obvious but was detected and described in this study. Considering chondrites in general, brecciated rocks are very common rather than an exception. The bulk rock degree of shock is S2 for Blaubeuren and Machtenstein and S3 for Cloppenburg. All samples show significant features of weathering. They have lost their original fusion crust and more than half (W3) or about half (W2‐3) of their original metal abundances. The oxygen isotope compositions of the three chondrites are consistent with those of other H chondrites; however, the Cloppenburg values are heavily disturbed and influenced by terrestrial weathering. This is supported by the occurrence of the very rare hydrated iron phosphate mineral vivianite (Fe2+Fe2+2[PO4]2·8H2O), which indicates that the chondrite was weathered in a very wet environment. The terrestrial ages of Blaubeuren (~9.2 ka), Cloppenburg (~5.4 ka), and Machtenstein (~1.8 ka) show that these chondrites are very similar in their degree of alteration and terrestrial age compared to meteorite finds from relatively wet terrestrial environments. They still contain abundant metal, although, as noted, the oxygen isotope data indicate substantial weathering of Cloppenburg. The bulk compositions of the three meteorites are typical for H chondrites, although terrestrial alteration has slightly modified the concentrations, leading in general to a loss of Fe, Co, and Ni due to preferential alteration of metals and sulfides. As exceptions, Co and Ni concentrations in Machtenstein, which has the shortest terrestrial age, are typical for H chondrites. The chemical data show no enrichments in Ba and Sr, as is often observed in different meteorite groups of desert finds., European Regional Development Fund http://dx.doi.org/10.13039/501100008530, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

We report new high-precision stable K isotope data for three martian meteorites, one lunar meteorite, one ordinary chondrite, four terrestrial igneous United States Geological Survey (USGS) reference materials, and twenty howardite–eucrite–diogenite [HED] meteorites. The three martian meteorites define a relatively narrow δ41K range with an average of −0.36 ± 0.12‰ (2 SD) that is slightly heavier than the Bulk Silicate Earth (BSE) K isotopic composition (−0.48 ± 0.03‰). Except for the four Northwest Africa samples which were terrestrially contaminated, all HED meteorites reveal substantial 41K enrichment compared to BSE, lunar samples, martian meteorites, and chondrites. We propose that the average δ41K (+0.36 ± 0.16‰) obtained from HED meteorites is representative of Bulk Silicate 4-Vesta. The coupled volatile depletion and heavy K isotope enrichment in 4-Vesta could be attributed to both nebula-scale processes and parent-body events. The asteroid 4-Vesta is likely to have accreted from planetary feedstocks that have been significantly volatile-depleted prior to the major phases of planetary accretion in the early Solar System, with secondary effects of K loss during accretionary growth and magma ocean degassing.

International audience; Several studies have shown the evidence of GBCAs’environmentalpollution and Gd3+toxicity both in aquatic organisms and humans. This short communication provides a roadmap using recent quan-titative data on GBCAs’consumption, medical use and waste, towardsenvironmental pollution mitigation and sustainable development

Kersantite is the international designation for hypabyssal lamprophyres essentially made up of dark micas and plagioclase. Kersantites from the type locality (Kersanton hamlet) and the W-Armorican surrounding area are Serpukhovian/Bashkirian in age. They are systematically associated in the field with hypabyssal microgranodiorites, both types being intruded synchronously as syn-compressional magmatic bodies that postdated pre-tectonic Tournaisian/Visean dolerites. The kersantitic amphibole compositions can be used to constrain the crystallization pressures and oxygen fugacities (redox conditions much more oxidizing than the Ni-NiO buffer). The oscillatory zoning observed in clinopyroxene phenocysts is consistent with a magma chamber repeatedly refilled by mafic liquid. The melting source of the W-Armorican kersantites corresponded to a lithospheric mantle located in the spinel-garnet transition zone (75–85 km depth), highly metasomatized by fluids probably released by a subducted sediment-bearing slab. Microgranodiorites could result from intimate mixing between mantle- and crust-derived magmas, with cordierite as possibly melting phase. The emplacement of dolerites with anorogenic geochemical signature prior to kersantites/microgranodiorites implies upwelling of the asthenospheric mantle up to a relatively high level, probably as the result of an extension induced by either roll back of the subducted lithospheric slab or delamination of the overriding plate. The heat input associated to the long-lasted asthenosphere rise could have favored (1) the formation of early dolerites between 347 and 330 Ma; and then, (2) the genesis of syn-compressional kersantites and microgranodiorites between 330 and 310 Ma, once the overlying lithospheric mantle was metasomatized by crust-derived fluids. This magmatic sequence marked the beginning of the Avalonia-Armorica collision, just prior to the main Variscan compressional event in this zone at c. 315 Ma.

International audience; Glassy ejecta are associatedto a limited number of impact craters, and yet hold key information about hypervelocity impact processes. Here we report on the discovery of a similar to 650 km(2) impact glass strewnfield in the Central Depression of the Atacama Desert. These cm-sized splash-form objects, that we refer to as atacamaites, are essentially composed of a dacitic glass formed by high-temperature melting of local magmatic rocks, with the addition of a variable iron meteorite contamination, 5 wt.% on average. The most likely nature for the impactor is the IIAB iron group. The fission-track plateau method, on two samples, yielded a mean formation age of 7.83 +/- 0.26 Ma. No associated impact crater has been discovered so far, suggesting it may be a relatively small, km-sized crater. The glassy nature, aerodynamic shapes, elevated formation temperature, and low water content are reminiscent of tektites. However, their small size, heterogeneity, oxidation state, significant contamination by the impactor, and likely more proximal provenance distinguish them from tektites. Atacamaites have no equivalent among the few known terrestrial ejected impact glasses, and increase the intriguing diversity of such products that we propose to name "tektoids".

Dynamic models of solar system evolution suggest that D-type asteroids formed beyond Saturn's orbit and represent invaluable witnesses of the prevailing conditions in the outer solar system. Here, we report a comprehensive petrographic and isotopic characterization of the carbonaceous chondrite Tarda, a recent fall recovered in the Moroccan Sahara. We show that Tarda shares strong similarities with the D-type-derived chondrite Tagish Lake, implying that Tarda represents a rare sample of D-type asteroids. Both Tarda and Tagish Lake are characterized by the presence of rare 16O-rich chondrules and chondrule fragments, high C/H ratios, and enrichments in deuterium, 15N, and 13C. By combining our results with literature data on carbonaceous chondrites related to C-type asteroids, we show that the outer solar system 4.56 Gy ago was characterized by large-scale oxygen isotopic homogeneities in (i) the water–ice grains accreted by asteroids and (ii) the gas controlling the formation of FeO-poor chondrules. Conversely, the zone in which D-type asteroids accreted was significantly enriched in deuterium relative to the formation regions of C-type asteroids, features likely inherited from unprocessed, D-rich, molecular-cloud materials.

We performed a petrologic, geochemical, and oxygen isotopic study of the lowest FeO ordinary chondrite, Yamato (Y) 982717. Y 982717 shows a chondritic texture composed of chondrules and chondrule fragments, and mineral fragments set in a finer-grained, clastic matrix, similar to H4 chondrites. The composition of olivine (Fa11.17 ± 0.48 (1σ)) and low-Ca pyroxene (Fs11.07 ± 0.98 (1σ)Wo0.90 ± 0.71(1σ)) are significantly more magnesian than those of typical H chondrites (Fa16.0-20, Fs14.5-18.0), as well as other known low-FeO OCs (Fa12.8-16.7; Fs13-16). However, the bulk chemical composition of Y 982717, in particular lithophile and moderately volatile elements, is within the range of OCs. The bulk siderophile element composition (Ni, Co) is within the range of H chondrites and distinguishable from L chondrites. The O-isotopic composition is also within the range of H chondrites. The lack of reduction textures indicates that the low olivine Fa content and low-Ca pyroxene Fs content are characteristics of the precursor materials, rather than the result of reduction during thermal metamorphism. We suggest that the H chondrites are more compositionally diverse than has been previously recognized.

Basaltic rocks generated by upwelling mantle plumes display a range of trace element and isotope compositions indicative of strong heterogeneity in deep material brought to Earth surface. Helium isotopes are an unrivalled tracer of the deep mantle in plume-derived basalts. It is frequently difficult to identify the composition of the deep mantle component as He isotopes rarely correlate with incompatible trace element and radiogenic isotope tracers. It is supposed that this is due to the high He concentration of the deep mantle compared to degassed/enriched mantle reservoirs dominating the He in mixtures, although this is far from widely accepted. The modern Afar plume is natural laboratory for testing the prevailing paradigm.The 3He/4He of basalt glasses from 26°N to 11°N along the Red Sea spreading axis increases systematically from 7.9 to 15 Ra. Strong along-rift relationships between 3He/4He and incompatible trace element ratios are consistent with a binary mixture between moderately enriched shallow asthenospheric mantle in the north and plume mantle evident in basalts from the Gulf of Tadjoura, Djibouti (the Ramad enriched component of Barrat et al. 1990). The high-3He/4He basalts have trace element-isotopic compositions that are similar, but not identical, to the high 3He/4He (22 Ra) high Ti (HT2) flood basalts erupted during the initial phase of the Afar plume volcanism (Rogers et al. in press). This suggests that the deep mantle component in the modern Afar plume has a HIMU-like composition. From the hyperbolic 3He/4He-K/Th-Rb/La mixing relationships we determine that the upwelling deep mantle has 3-5 times higher He concentration than the asthenosphere mantle beneath the northern Red Sea.Barrat et al. 1990. Earth and Planetary Science Letters 101, 233-247.

In order to propose an optimal analytical procedure specific to ferromanganese (Fe-Mn) oxides, we investigated different modes of data acquisition using inductively coupled plasma mass spectrometry (ICP-MS). The results of trace element and Rare Earth Element (REE) determination in eight Fe-Mn nodules and crusts (FeMn-1, GSMC-1, GSMC-2, GSMC-3, GSPN-2, GSPN-3, NOD-A-1 and NOD-P-1) are presented here. The analytical procedure involves chemical dissolution of the Fe-Mn oxides and addition of a thulium (Tm) spike. The correction of measured values from potential isobaric interferences was investigated using both corrections based on mono-elemental solutions, and data acquisition in the high-resolution mode. The obtained results show that the high-resolution acquisition mode is unnecessary to achieve high quality data for REE in Fe-Mn oxides. Using our revised method, we provide a consistent set of precise and accurate values for eight widely used but poorly characterized certified reference materials.

On September 12, 2019 at 12:49:48 (UT) a bolide was observed by hundreds of eye-witnesses from the Netherlands, Germany, Belgium, Denmark and the UK. One day later a small meteorite stone was found by accident in Flensburg. The presence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the found object to cosmic rays in space linking it clearly to the bolide event. An exceptionally short exposure time of ~5000 years was determined. The 24.5 g stone has a fresh black fusion crust, a low density of -9 m³/kg). The rock consists of relict chondrules and clusters of sulfide and magnetite grains set in a fine-grained matrix. The most abundant phases are phyllosilicates. Carbonates (~3.9 vol.%) occur as calcites, dolomites, and a Na-rich phase. The relict chondrules (often surrounded by sulfide laths) are free of anhydrous silicates and contain abundant serpentine. Lithic clasts are also surrounded by similar sulfide laths partly intergrown with carbonates. ⁵³Mn-⁵³Cr ages of carbonates in Flensburg indicate that brecciation and contemporaneous formation of the pyrrhotite-carbonate intergrowths by hydrothermal activities happened no later than 4564.6±1.0 Ma (using D'Orbigny as Mn-Cr anchor). This corresponds to 2.6±1.0 or 3.4±1.0 Ma after CAIs, depending on the exact age CAI age. This is the oldest dated evidence for brecciation and carbonate formation, which likely occurred during parent body growth and incipient heating due to ²⁶Al. The O isotope composition of Flensburg reveals that it plots at the ¹⁶O-rich end of the CM chondrite field and in the transition field to the CV-CK-CR chondrites. This is unexpected since the O-isotope compositions of strongly aqueously-altered chondrites are generally found to be at the ¹⁶O-poor end of the CM range. The mass-dependent Te isotopic compositionof Flensburg is slightly different from mean CM chondrites and is most similar to those of the ungrouped C2 chondrite Tagish Lake. On the other hand, the 50Ti and 54Cr isotope nomalies indicate that Flensburg is similar to CM chondrites, as do the ~10 wt.% H₂O. Yet, the bulk Zn, Cu, and Pb concentrations are about 30% lower than those of mean CM chondrites. The He, Ne and, Ar isotopes of Flensburg show no solar wind contribution; its trapped noble gas signature is similar to that of CMs with a slightly lower concentration of ²⁰Netr. Based on the bulk H, C and N elemental abundances and isotopic compositions, Flensburg is clearly unique among the analyzed chondrites as it has the lightest bulk H and N isotopic compositions of any type 1 or 2 chondrite. The number of soluble organic compounds in Flensburg is even lower than that of the brecciated CI chondrite Orgueil. The extraordinary significance of Flensburg is given by the observation that it represents the oldest chondrite sample, in which the contemporaneous episodes of aqueous alteration and brecciation are 81 perfectly visible. The characterization of a large variety of carbonaceous chondrites with different alteration histories is important for interpreting returned samples from the OSIRIS-REx and Hayabusa 2 missions.

International audience; Radiogenic strontium isotopes are routinely used in provenance studies, but their application to sediments is often complicated by various grain size and weathering effects, which can influence measured 87Sr/86Sr ratios. Here, we report Sr isotopic data for a large number of sediment samples (n = 61) from the world's largest rivers and other river catchments draining particular geological and climatic settings; using both clay-rich (20 °C, intense feldspar weathering leads to the preferential incorporation of unradiogenic Sr into secondary clay minerals; a process which results in negative Δ87Sr/86Sr Clay-Silt values. In addition to climate forcing, the degree of size-dependent Sr isotope decoupling is also shown to be dependent on the type of weathering regime in watersheds, being more pronounced in low-elevation environments (< 2000 m), where transport-limited conditions and the presence of thick soil sequences can be associated with intense silicate weathering, than in high mountain regions (> 4000 m) dominated by kinetically-limited weathering regimes.While further studies will be required to test the validity of these conclusions at the local scale of weathering profiles, these findings suggest that combined Sr isotopic analyses of separate size fractions could be used as a new weathering proxy in sediment records, ideally complementing the conventional use of radiogenic Sr isotopes as provenance tracers. Finally, our results are also used to re-assess the mean Sr flux and 87Sr/86Sr composition of the suspended sediment exported to the ocean yearly, yielding a global flux-weighted average of 0.7160, identical to that proposed earlier in the seminal study of Goldstein and Jacobsen (1988).

Main-group pallasites (MGPs) are meteorites mainly composed of Fe-Ni metal and olivines, the latter being considered as one of the largest sampling of extraterrestrial mantle material available for study on Earth. We analysed the rare earth element (REE) concentrations of olivines from six MGPs to understand better the processes of formation of their parent mantle. All the investigated samples display very low REE abundances, and enrichments in both light REEs and heavy REEs. We interpret the light REE enrichments as a fingerprint of terrestrial contamination. The least contaminated olivines have higher heavy REE enrichments than those inferred for olivines directly crystallised in a magma ocean. Such enrichments in heavy REEs are possible if the mantle of the MGPs parent body is a residue of partial melting from a chondritic source. Alternatively, re-melting of magma ocean cumulates would explain both the homogeneity of the Ä17O values of MGPs, and the heavy REE enrichments of the olivines.

The 11th Symposium on Polar Science/Ordinary sessions: [OA] Antarctic meteorites, Poster presentations, Mon. 16 Nov. - Fri. 18 Dec.

The 11th Symposium on Polar Science/Ordinary sessions: [OA] Antarctic meteorites, Poster presentations, Mon. 16 Nov. - Fri. 18 Dec.

A major breakthrough in the field of rare earth element (REE) geochemistry has been the recent discovery of their utility to microbial life, as essential metalloenzymes catalyzing the oxidation of methanol to formaldehyde. Lanthanide-dependent bacteria are thought to be ubiquitous in marine and terrestrial environments, but direct field evidence of preferential microbial utilization of REE in natural systems is still lacking. In this study, we report on the REE and trace element composition of the tube of a siboglinid worm collected at a methane seep in the Gulf of Guinea; a tube-dwelling annelid that thrives in deep-sea chemosynthetic ecosystems. High-resolution trace element profiles along the chitin tube indicate marked enrichments of lanthanum (La) and cerium (Ce) in its oxic part, resulting in REE distribution patterns that depart significantly from the ambient seawater signature. Combined with various geochemical and microbiological evidence, this observation provides direct support for an active consumption of light-REE at cold seeps, associated with the aerobic microbial oxidation of methane. To further evaluate this hypothesis, we also re-examine the available set of REE data for modern seep carbonates worldwide. While most carbonate concretions at cold seeps generally display REE distribution patterns very similar to those for reduced pore waters in marine sediments, we find that seafloor carbonate pavements composed of aragonite commonly exhibit pronounced light-REE enrichments, as inferred from high shale-normalized La/Gd ratio (>~0.8), interpreted here as possibly reflecting the signature of lanthanide-dependent methanotrophic activity. This finding opens new perspectives for revisiting REE systematics in ancient seep carbonates and other microbialites throughout the Earth's history. In particular, the geochemical imprint of aerobic methane oxidation could be possibly traced using REE in Archaean stromatolites and other archives of Precambrian seawater chemistry, potentially providing new insights into the oxygenation of early Earth's oceans and associated microbiogeochemical processes.

International audience; Methane is an important greenhouse gas whose emissions into the oceans and atmosphere are regulated by relatively unconstrained anaerobic and aerobic microbial processes. The aerobic pathway for methane oxidation is thought to be largely dependent upon the use of rare earth elements (REE), but to date the effects of this process on their abundances in bacteria or in organisms living in symbiosis with methanotrophs remain to be evaluated. Here we show that deep sea chemosynthetic mussels prospering at methane seeps display distinctive lanthanum enrichments linked to the enzymatic activities of their symbionts. These results demonstrate that methanotrophy is able to fractionate efficiently REE distributions in organisms and possibly in the environment. Lanthanum anomalies recorded in ancient sediments are potential chemical fossils that could be used in the geological record for tracking early evidence of microbial life.

International audience; The origin(s) of the chassignites and nakhlites, closely related martian olivine and augite cumulates, respectively, are much debated. Northwest Africa (NWA) 8694 is the third chassignite to be discovered and the most ferroan, containing 85% olivine (Fo54). Its O-isotope compositions (δ18O ∼ 4.4‰, Δ17O ∼ 0.30‰) are typical of other martian meteorites. It has adcumulate texture and contains cumulus chromite, poikilitic pigeonite (En56Fs37Wo7) and mesostasis (trapped interstitial liquid). The latter contains pyroxene and plagioclase (An23 Ab70 Or8) plus rare K- feldspar (Or74), and has a trachyandesitic to trachytic bulk composition. Melt inclusions in olivine contain a variety of phases including biotite and rare amphibole. Olivine, chromite, and pigeonite compositions are intermediate between those of the other chassignites and those of the nakhlites. Augite, which appears to mantle pigeonite, has a composition overlapping that in nakhlite NWA 998 and some other nakhlites at (En41-40Wo38-39). The augite lamellae in pigeonite 1–2 μm in apparent width, and the survival of Ca zoning in olivine, suggest a near-surface cooling environment. The bulk-rock REE concentrations in the three chassignites do not correlate with Mg# but depend on the abundance of trapped liquid. The form of REE patterns calculated for olivine subtraction is very like those of nakhlite mesostases, but the observed concentrations of LREE in NWA 8694 trapped liquid have a very steep slope. This is explained by undersampling of baddeleyite and zirconolite that occur near olivine contacts with mesostasis. Though pyroxene is unzoned, its trace element variations indicate fractional crystallization. The range of olivine compositions in the three chassignites (Fo79-54) is too large to result from the crystallization sequential growth of olivine from a single magma undergoing fractional crystallization. The Ge/Si ratios show degassing of NWA 8694 which sets this chassignite apart from other chassignites and nakhlites, implying a unique batch of magma for its genesis. Many potential parent liquids are capable of generating the NWA 8694 olivine composition, though not its alkaline mesostasis. We calculated that Nakhla parent liquid NA01a (Stockstill et al., 2005) with 10% Nakhla core olivine added would produce both olivine crystals and alkaline daughter liquids with compositions matching those of NWA 8694. This meteorite is a chassignite cumulate containing nakhlitic mesostasis, a direct link between the chassignites and the nakhlites and the association of dunitic to trachytic compositions is reminiscent of terrestrial shield volcanoes. Chassignites and nakhlites were possibly formed when solidification fronts on chamber walls were disrupted, mainly as side eruptions of olivine-charged magmas from the deeper zones, and augite-charged fractionated magmas from nearer the summit of a volcano resembling Piton de la Fournaise on Earth.

Background and purpose Assess the evolution of gadolinium consumption and magnetic resonance imaging (MRI) scanners in France and Western Brittany (France) and compare regional practices between public and private hospitals for each organ specialty. Material and methods We collected data from national and universal health registries, and Western Brittany's health care structures, between 2011 and 2018, about the number of MR imaging exams and machines, the number of delivered GBCAs (gadolinium-based contrast agents), prescriptions and administration protocols. Results Over the last eight years, we observed an increase in the number of MRI machines implemented in France (62%), correlated with the increase of annual gadolinium consumption (amount of delivered GBCAs in kg, 64%), without modification of the annual quantity of gadolinium used per machine (2.7 kg in 2018). In Western Brittany, gadolinium impact is assigned to neuroimaging exams (50% CI95% [45;56] of all the contrast-enhanced exams), followed by thorax and abdomen exams (23% CI95% [18;28]). The ratio of injected exams to all exams is greater in public than in private hospitals (respectively 48% CI95% [46;49] versus 29% CI95% [26;30]). Conclusion Gadolinium consumption is increasing, correlated with the increase in the number of examinations carried out. Regionally, the main impact comes from neuroimaging exams. No change in practices has been observed in recent years despite some warnings about gadolinium deposits and environmental consequences.

We report on the mass-independent Cr isotope compositions of 11 main group ureilites and an ureilitic trachyandesite (ALM-A). The 54Cr/52Cr ratios for main group ureilites vary from −1.06±0.04 to −0.78±0.05 and averaged at −0.91±0.15 (2SD, N=18) including the data from literature. We argue that this variation reflects primitive mantle heterogeneities within the ureilite parent body (UPB). As such, this body did not experience a global-scale magma ocean, which is consistent with heterogeneous O isotope in ureilites. Furthermore, the ε54Cr values, Mn/Cr ratios, C isotope ratios, Mg# values, and Fe/Mn ratios in the olivine cores of ureilites are correlated with each other, which suggests the mixing of ureilite precursors from at least two reservoirs, rather than a smelting process or the oxidation from ice melting. All the ureilite samples (including the ALM-A) fall on a well-defined 53Mn–53Cr isochron corresponding to a 53Mn/55Mn ratio of (6.02 ± 1.59)×10−6, which translates to an age of 4566.7±1.5 Ma (within 2 Ma after calcium-aluminum-rich inclusions; CAIs) when anchored to the U-corrected Pb–Pb age for the D’Orbigny angrite. This old age indicates early partial melting on the UPB, consistent with the early accretion of the UPB (within 1 Ma after CAIs) predicted by thermal modeling. Furthermore, there is a 4∼5 Ma age difference between the external isochron in this study and internal isochron ages for the feldspathic clasts in polymict ureilites, which likely reflects an impact history during the early evolution of the UPB.

The Tenth Symposium on Polar Science/Special session: [OA] Antarctic meteorites, Thur. 5 Dec. / 3F Multipurpose conference room, National Institute of Polar Research

International audience; Fractional crystallization of basalts produces a variety of ultramafic cumulates poor in incompatible elements. Inorder to discuss the effect of trapped liquids on the concentrations of incompatible elements in these cumulates,we studied a series of dunites and pyroxenites from the Piton de la Fournaise (La Réunion Island, Indian Ocean).These rocks have a high variability in the abundance of these elements, which is only partially explained by theirproportions of olivines and pyroxenes. Mass balance calculations indicate that≈0.25 to 1 wt% of trapped meltsare required to account for the budget of the highly incompatible element abundances such as U, Rb, Nb orlight Rare Earth Elements (REE). Using our results, we revisited the REE geochemistry of chassignites, a groupletof Martian meteorites. Chassignites are mineralogically, texturally and chemically very similar to the dunitesfrom La Réunion Island, which can be seen as very close terrestrial analogs. The variations of REE abundancesand ratios in Chassigny, one of the three known chassignites, can be explained by inhomogeneous distributionof trapped melts in this meteorite at the scale of the size of the fragments (typicallyb1 g) used for the chemicalanalyses. Using these variations, we deduced the shape of the REE pattern and abundances of the Chassigny par-ent melt.

Planetary formation models show that terrestrial planets are formed by the accretion of tens of Moon- to Mars-sized planetary embryos through energetic giant impacts. However, relics of these large proto-planets are yet to be found. Ureilites are one of the main families of achondritic meteorites and their parent body is believed to have been catastrophically disrupted by an impact during the first 10 million years of the solar system. Here we studied a section of the Almahata Sitta ureilite using transmission electron microscopy, where large diamonds were formed at high pressure inside the parent body. We discovered chromite, phosphate, and (Fe,Ni)-sulfide inclusions embedded in diamond. The composition and morphology of the inclusions can only be explained if the formation pressure was higher than 20 GPa. Such pressures suggest that the ureilite parent body was a Mercury- to Mars-sized planetary embryo., Ureilites are a type of meteorite that are believed to be derived from a parent body that was impacted in the early solar system. Here, the authors analyse inclusions within diamonds from a ureilite meteorite and find that they must have formed at above 20 GPa suggesting the parent body was Mercury- to Mars-sized.

We analyzed the C isotopic compositions of 32 unbrecciated ureilites, which represent mantle debris from a now disrupted, C-rich, differentiated body. The δ 13 C values of their C fractions range from −8.48 to +0.11‰. The correlations obtained between δ 13 C, δ 18 O and Δ 17 O values and the compositions of the olivine cores, indicate that the ureilite parent body (UPB) accreted from two reservoirs displaying distinct O and C isotopic compositions. The range of Fe/Mg ratios shown by its mantle was not the result of melting processes involving reduction with C (“smelting”), but was chiefly inherited from the mixing of these two components. Because smelting reactions are pressure-dependent, this result has strong implications for the size of the UPB, and points to a large parent body, at least 690 km in diameter. It demonstrates that C-rich primitive matter distinct from that represented by carbonaceous chondrites was present in some areas of the early inner Solar System, and could have contributed to the growth of the terrestrial planets. We speculate that differentiated, C-rich bodies, or debris produced by their disruption, were an additional source of volatiles during the later accretion stages of the rocky planets, including Earth.

On February 6, 2016 at 21:07:19 UT, a very bright fireball was seen over the eastern part of Denmark. The weather was cloudy over eastern Denmark, but many people saw the sky light up-even in the heavily illuminated Copenhagen. Two hundred and thirty three reports of the associated sound and light phenomena were received by the Danish fireball network. We have formed a consortium to describe the meteorite and the circumstances of the fall and the results are presented in this paper. The first fragment of the meteorite was found the day after the fall, and in the following weeks, a total of 11 fragments with a total weight of 8982 g were found. The meteorite is an unbrecciated, weakly shocked (S2), ordinary H chondrite of petrologic type 5/6 (Bouvier et al. 2017). The concentration of the cosmogenic radionuclides suggests that the preatmospheric radius was rather small similar to 20 cm. The cosmic ray exposure age of Ejby (83 +/- 11 Ma) is the highest of an H chondrite and the second highest age for an ordinary chondrite. Using the preatmospheric orbit of the Ejby meteoroid (Spurny et al. 2017) locations of the recovered fragments, and wind data from the date of the fall, we have modeled the dark flight (below 18 km) of the fragments. The recovery location of the largest fragment can only be explained if aerodynamic effects during the dark flight phase are included. The recovery location of all other fragments are consistent with the dark flight modeling.

Angrite meteorites are some of the oldest materials in the solar system. They provide important information on the earliest evolution of the solar system and accretion timescales of protoplanets. Here, we show that the 54Cr/52Cr ratio is homogeneously distributed among angrite meteorites within 13 parts per million, indicating that precursor materials must have experienced a global-scale melting such as a magma ocean. The 53Cr/52Cr and Mn/Cr ratios are correlated, which is evidence for an initial 53Mn/55Mn ratio of (3.16 ± 0.11) × 10−6. When anchored to the U-corrected Pb–Pb age for the D’Orbigny angrite, this initial 53Mn/55Mn corresponds to an absolute age of 4563.2 ± 0.3 Ma, i.e., 4.1 ± 0.3 Ma after Ca–Al-rich inclusion-formation. This age is distinct from that of the volatile depletion events dated by the 87Sr/86Sr initial ratio and therefore must correspond to the age of crystallization of the magma ocean and crust formation of the angrite parent body (APB), which can also constrain a slightly bigger size of APB than that of Vesta. Furthermore, this age is similar to those obtained from internal isochrons of the oldest volcanic angrites that cooled rapidly at the surface of the parent body (with ages of 4564 ∼ 4563 Ma), while older than those obtained from plutonic angrites (4561 ∼ 4556 Ma) that cooled down slowly, located deeper within the parent body. This implies that cooling of the APB took at least ∼8 Myr after its differentiation.

The Ureilite Parent Body (UPB) was a C-rich planetary embryo disrupted by impact. Ureilites are fragments of the UPB mantle and among the most numerous achondrites. Zinc isotopic data are presented for 26 unbrecciated ureilites and a trachyandesite (ALM-A) from the same parent body. The δ66Zn values of ureilites range from 0.40 to 2.71‰ including literature results. Zinc isotopic compositions do not correlate with the compositions of olivine cores, with C and O isotopic compositions, with Zn abundances, nor with shock grades. The wide range of δ66Zn displayed by the ureilites is chiefly explained by evaporation processes that took place during the catastrophic breakup of the UPB. During breakup, the high temperatures of the UPB mantle allowed Zn to evaporate, regardless of the intensity the shock suffered by the ureilitic debris. For the most shocked of them, post-shock heating permitted greater evaporation, and heavier Zn isotopic compositions. The surface of the UPB was certainly much colder than the mantle before the breakup. Therefore, crustal rocks were probably less prone to Zn evaporation. ALM-A, the sole crustal rock analyzed at present, has a δ66Zn value (0.67‰) significantly higher than those of regular chondrites. This result indicates that its mantle source displayed already non-chondritic Zn isotopic compositions before the breakup of the UPB.

International audience; Based on the high abundance of fine-grained material and its dark appearance, NWA 11024 was recognized as a CM chondrite, which is also confirmed by oxygen isotope measurements. But contrary to known CM chondrites, the typical phases indicating aqueous alteration (e.g., phyllosilicates, carbonates) are missing. Using multiple analytical techniques, this study reveals the differences and similarities to known CM chondrites and will discuss the possibility that NWA 11024 is the first type 3 CM chondrite. During the investigation, two texturally apparent tochilinite-cronstedtite intergrowths were identified within two thin sections. However, the former phyllosilicates were recrystallized to Fe-rich olivine during a heating event without changing the textural appearance. A peak temperature of 400-600 degrees C is estimated, which is not high enough to destroy or recrystallize calcite grains. Thus, calcites were never constituents of the mineral paragenesis. Another remarkable feature of NWA 11024 is the occurrence of unknown clot-like inclusions (UCLIs) within fine-grained rims, which are unique in this clarity. Their density and S concentration are significantly higher than of the surrounding fine-grained rim and UCLIs can be seen as primary objects that were not formed by secondary alteration processes inside the rims. Similarities to chondritic and cometary interplanetary dust particles suggest an ice-rich first-generation planetesimal for their origin. In the earliest evolution, NWA 11024 experienced the lowest degree of aqueous alteration of all known CM chondrites and subsequently, a heating event dehydrated the sample. We suggest to classify the meteorite NWA 11024 as the first type 3 CM chondrite similar to the classification of CV3 chondrites (like Allende) that could also have lost their matrix phyllosilicates by thermal dehydration.

Gadolinium-based contrast agents (GBCAs), routinely used in magnetic resonance imaging (MRI), end up directly in coastal seawaters where gadolinium concentrations are now increasing. Because many aquatic species could be sensitive to this new pollution, we have evaluated the possibility of using shellfish to assess its importance. Gadolinium excesses recorded by scallop shells collected in Bay of Brest (Brittany, France) for more than 30 years do not reflect the overall consumption in GBCAs, but are largely controlled by one of them, the gadopentetate dimeglumine. Although its use has been greatly reduced in Europe over the last ten years, gadolinium excesses are still measured in shells. Thus, some gadolinium derived from other GBCAs is bioavailable and could have an impact on marine wildlife.