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The ca. 3.5 Ga Bon Accord Ni deposit was located in the Barberton Greenstone Belt of the Kaapvaal Craton, South Africa, and contained a unique assemblage of Ni-rich minerals including trevorite (NiFe2O4). It was initially interpreted as a metamorphosed extraterrestrial body, recently ruled out by Cr isotope data, and subsequently as a fragment of the Archean Earth’s core. More recent suggestions have highlighted similarities between Bon Accord and Archean magmatic sulfide mineralization. We present a geochemical (rare earth element [REE], halogen, and highly siderophile element [HSE] abundance) and isotopic (noble gases, Zn, Cr, and Re-Os) study to elucidate the origin of this enigmatic body. Bon Accord is enriched in the REE relative to primitive mantle (PM), with a pattern resembling that of Aldepleted komatiites. The bulk material has >10 × PM Os and Ir, >100 × PM Ru, Pt, Pd, and Re, and radiogenic 187Os/188Os. Trevorite, silicates, and two bulk-rock samples are consistent with chondritic to sub-chondritic initial 187Os/188Os at the time of formation. The new REE data implicate a komatiite precursor in the formation of Bon Accord, and the HSE data bear striking similarities to those of Ni-enriched Archean magmatic sulfide deposits. Enrichment in the heavier Zn isotopes supports desulfurization of a sulfide (isotopically light) deposit during serpentinization to produce the trevorite-dominated body. We conservatively estimate this process could have mobilized as much as ~9.2 × 104 tonnes of H2S, offering an intriguing possibility for sourcing of the sulfur that fixes the historically important gold mineralization in the Barberton Greenstone Belt.

Volatile elements are key to understanding the accretion and differentiation processes that formed the terrestrial planets. Relative to the solar photosphere or carbonaceous Ivuna-type (CI) chondrites, the terrestrial planets are depleted in moderately volatile elements (MVEs), with the Earth being more depleted in MVEs than Mars. Mass-dependent and mass-independent stable isotope variations of MVEs, such as Zn, can be used to determine the origin of volatile depletion on Mars. Here we present Zn isotopic compositions of ten Martian meteorites, spanning the major petrologic groups, and show that the Zn isotope composition of the Martian mantle, representative of the Bulk Silicate Mars (BSM), has a δ66Zn (per mille deviation of the 66Zn/64Zn from the JMC-Lyon standard) of +0.50 ± 0.18. This is distinctly heavier than that of the Earth (+0.16 ± 0.06‰). The BSM Zn isotope composition could partly reflect fractionation during volatile loss by evaporation consistent with the isotopic composition of other volatile elements (e.g., K). The mass-independent Zn isotopic composition of Mars, ε66Zn (per 10,000 deviation of the 66Zn/64Zn from the terrestrial standard JMC-Lyon, normalized to 68Zn/64Zn) is intermediate between carbonaceous chondrites (CC) and non-carbonaceous chondrites (NC), but with stronger affinity to the NC compared to that of the Earth. Therefore, planets further from the Sun are not necessarily made from a higher fraction of CC-like material. ISSN:0012-821X ISSN:1385-013X

Potassium (K) is an essential electrolyte for cellular functions in living organisms, and disturbances in K+ homeostasis could lead to various chronic diseases (e.g. hypertension, cardiac disease, diabetes, and bone health). However, little is known about the natural distribution of stable K isotopes in mammals and its application to investigate the bodily homeostasis and/or as a biomarker for diseases. Here, we measured K isotopic compositions (δ41K, per mil deviation of 41K/39K from the NIST SRM 3141a standard) of brain, liver, kidney, and red blood cells (RBCs) from 10 mice (five females and five males) with three different genetic backgrounds. Our results reveal that different organs and RBCs have distinct K isotopic signatures. Specifically, the RBCs have heavy K isotopes enrichment with δ41K ranging from 0.67 to 0.08 ‰, while the brains show lighter K isotopic compositions with δ41K ranging from -1.13 to -0.09 ‰ compared to the livers (δ41K = -0.12 ± 0.58 ‰) and kidneys (δ41K = -0.24 ± 0.57 ‰). We found that the K isotopic and concentration variability is mostly controlled by the organs, with a minor effect of the genetic background and sex. Our study suggest that the K isotopic composition could be used as a biomarker for changes in K+ homeostasis and related diseases such as hypertension, cardiovascular, and neurodegenerative diseases.

Mercury (Hg) provides critical information on terrestrial planet formation and evolution due to its unique physicochemical properties and multiform isotopic compositions. Current knowledge of Hg is mainly limited to Earth's surface environments, and the understanding of Hg in the Earth's interior remains unclear. Accretionary orogens are major settings for continental crustal growth and crust-mantle interactions. We studied the Hg concentration and isotopic composition of igneous rocks in the eastern Central Asian orogenic belt, using Hg as a proxy to trace the recycling of surface materials in Earth's lithosphere. Our results show low Hg abundances in mafic through felsic igneous rocks (4.93 ± 4.35 ppb, standard deviation [SD], n = 267). Mafic rocks show slightly lower δ202Hg (−2.9‰ ± 0.5‰, SD, n = 24) than intermediate (−2.4‰ ± 0.8‰, SD, n = 58) and felsic (−1.5‰ ± 0.8‰, SD, n = 185) rocks, indicating a chemical stratification of Hg isotopic composition in the continental crust with isotopically lighter Hg in the lower part and heavier Hg in the upper part. Slightly positive Δ199Hg values are observed in mantle-derived mafic (0.07‰ ± 0.06‰, SD) and intermediate (0.06‰ ± 0.07‰, SD) rocks, which agree well with those reported for marine sediments, indicating the involvement of fluids or melts from the oceanic crust. Larger variations of Δ199Hg values (−0.26‰ to +0.21‰, average: 0.01‰ ± 0.08‰, SD, n = 185) are observed in felsic rocks, further indicating recycling of surface Hg from the marine reservoir via slab subduction (reflected by positive values) plus magmatic assimilation of terrestrial Hg (reflected by negative values). Our study demonstrates that Hg isotopes can be a promising tracer for the chemical dynamics of Earth's lithosphere.

The application of vanadium (V) stable isotopes to trace various geological and biological processes is an emerging field. Vanadium can exist in several redox states and in various could be used to trace its exchange between different phases during these processes. In order to provide a basis for interpreting natural data, we have computed theoretical isotope fractionation factors of V among various species relevant to geological and biological environments. To validate the accuracy of the calculations, we performed laboratory experiments to evaluate the V isotopic fractionation between organic and aqueous phases. The laboratoryscale experiment via liquid-liquid extraction with the aqueous phase of V in HCl and the organic phase of dicyclohexano-18-crown-6 (DC18C6) in 1,2-dichloroethane was performed. The magnitude of the isotope fractionation factor for the 51V/50V ratio between the aqueous and organic phases, which was found to vary between -0.1 and +1.35%o depending on HCl molarity, is well explained by our theoretical isotope fractionation factors (ln beta) obtained by the density functional theory method for V(IV) model molecules. We have also estimated the relative effect of the nuclear field shift (NFS) effect and the conventional mass-dependent isotope fractionation, where the NFS effect was found to be marginal (similar to 0.025%o) on the V isotope fractionation. This theoretical approach is applied to obtain ln beta for various V species relevant to geological and biological environments which are discussed with regard to understanding natural variations of the V isotopes. ISSN:2472-3452

New 187Re-187Os, 87Rb-87Sr, triple O-isotope isotope, bulk rock highly siderophile- (HSE: Os, Ir, Ru, Pt, Pd, Re), major- and trace-element abundance data are reported for a variety of carbonaceous, ordinary and enstatite chondrite meteorites. In addition, new mineral chemical data are reported for the Chelyabinsk LL5 ordinary chondrite fall for comparison with existing chondrite data and to investigate element sequestration into metal and mineral phases within some chondrites. The focus of the study is to link the variations observed in the HSE abundances and Re-Os isotopes with other isotopic and elemental data to explore the relative roles of sample sizes, terrestrial alteration and parent body processes more fully on chondrite meteorite compositions. Trace element variations in Chelyabinsk silicate, oxide and metal grains highlight the importance of geochemical heterogeneity imparted by mineralogical variations and mode effects, as well as sample size. Using a range of sample powder aliquot sizes, it is possible to show that this becomes significant for the HSE at

Zircon is often used to study granites (sensu lato) and continental crust because it is very resistant and can be analyzed for various isotope systems that provide time and source information about their parental melts. Granites with different petrological histories have distinct bulk-rock silicon isotope compositions but it is unclear if these differences are also detectable in zircon because of superimposed fractionation effects (e.g., related to temperature, silica content, magmatic processes). The present study explores the Si isotope signatures of zircon from various granite types to constrain their isotope fractionation behavior and uses them as igneous petrogenetic tools, and possibly as granite source discriminators when zircon is found in detrital sediments. Our results show that although Si isotope compositions in zircon can be modified by secondary (post-crystallization) processes such as alteration/weathering and metamorphism, they are primarily controlled by zircon-melt isotope fractionation, which depends on both zircon crystallization temperature and magma silica content. Once these fractionation effects are understood and filtered out, a pattern emerges between Si isotope signatures of zircons from different granite types that is consistent with theoretical and experimental results as well as with known Si isotope differences at the bulk-rock scale. Silicon isotope ratios in zircon can track magma evolution (e.g., temperature and SiO2 changes) and, hence, reveal complex processes that involved magma mingling, fractional crystallization, and/or multiple sources. This study, therefore, illustrates that Si isotopes in zircon can be used to investigate magma evolution and represents a useful complement to existing techniques in granite studies involving zircon (e.g., U-Th-Pb, Lu-Hf and O isotopes) provided that it is not used as a stand-alone technique.

Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37° ± 10°C, about 5.2 − 0.7 + 0.8 million (statistical) or 5.2 − 2.1 + 1.6 million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles that of the Sun’s photosphere than other natural samples do.

The chemical characteristics of magmatic Ni–Cu sulfide deposits in orogenic settings differ from those in cratons as they are characterized by extensive alteration, presence of hydrous minerals and typical normal mantle sulfur isotopes. How these characteristics are related to the mode of formation of the Ni–Cu sulfide deposits is still unknown. Here, we present petrological and mineralogical investigations of the Hongqiling Ni–Cu sulfide deposit, a typical representative of such numerous deposits in the Central Asian Orogenic Belt. Observations at various scales of field outcrops, hand specimens, thin sections and microscopes reveal that alterations are selectively exposed in silicate minerals, particularly olivine and pyroxenes that are close to ore bodies and sulfides. Such selective alteration is also related to sulfide type and abundance, and ore texture in the rocks/ores. It is worth noting that alteration of olivine and pyroxenes becomes weak when hydrous minerals (hornblende and phlogopite) are present. Profile analyses demonstrate that the olivine grains enclosed in or in contact with sulfides have compositional zonation with Fe, Mn, Sc and Zn concentrations higher when closer to the contacts with sulfides relative to the cores and contacts with other silicates, while those grains in sulfide-barren rocks show relatively homogeneous compositions. Similarly, the hornblende grains in contact with sulfide show distinct compositional variations. Sulfides in the rocks and ores are all free of alteration and have mantle-like sulfur isotopic compositions (pyrrhotite δ34S = −1.53 to 0.38‰; pentlandite δ34S = −1.28 to 0.25‰; chalcopyrite δ34S = −1.77 to 0.24‰). These features suggest that the selective alterations occurring in early crystallized phases were induced by sulfide melt intrusion and crystallization, instead of late-stage processes as previously thought. The sulfide melts segregated at the early stage of the magma evolution were presumably hydrous and buoyant in the silicate magma and therefore were transported upward and penetrated into silicate grains. The hydrous fluids were independent of the subducted material and metamorphic origin, and contained no significant crustal component in the late Triassic. Finally, when the sulfides crystallized, fluids would be released from the sulfide melts to hydrate surrounding mineral phases and rocks, because sulfides theoretically don’t accommodate hydrous components. The fluids also enhanced compositional exchanges between sulfides and silicates and accounted for the crystallization of hydrous minerals. From this perspective, fluids play a critical role in sulfide melt transportation and silicate compositional alteration, and selective alteration can be considered as a significant indicator of mineralization and exploration in mafic-ultramafic intrusions.

Copper (Cu) stable isotopes are useful for understanding pathways and tracing changes in Cu homeostasis, such as those induced by various diseases (e.g. liver cirrhosis, numerous forms of cancer, and neurodegenerative diseases). However, this utility relies on a baseline understanding of the natural distribution of Cu isotopes between organs of healthy organisms, which is not well-known at present. Here, the distribution of natural Cu isotopes in the brain, liver, red blood cells, plasma, kidneys, and muscle of 14 mice (7 males and 7 females) from three different genetic backgrounds is assessed. We show that the Cu isotopic composition of most mouse organs is isotopically distinct from one another. The most striking feature is the heavy isotope enrichment of the kidney (δ65Cu = 1.65 ± 0.06‰, 2SE), brain (δ65Cu = 0.87 ± 0.03‰, 2SE) and liver (δ65Cu = 0.71 ± 0.24‰, 2SE) compared to blood components, i.e. red blood cells (RBCs) (δ65Cu = 0.30 ± 0.06‰, 2SE), and plasma (δ65Cu = –0.61 ± 0.08‰, 2SE), with δ65Cu being the per mil deviation of the 65Cu/63Cu ratio from the NIST SRM 976 standard. Differences in genetic background do not appear to affect the isotopic distribution of Cu. Interestingly, male and female mice appear to have different Cu concentrations and isotopic compositions in their brain, plasma, muscle, and RBC. By demonstrating that organs have distinct isotopic compositions, our study reinforces the notion that Cu stable isotopes can be used to trace changes in homeostasis in diseases affecting Cu distribution, such as Alzheimer's disease, liver cancer, and possible chronic kidney failure.

The Ediacaran age (ca. 570 Ma) Shuram excursion, a ca. 12‰ depletion in δ¹³C_(carb), may record a dramatic oxidation of marine sediments associated with a reorganization of Earth’s carbon cycle closely preceding the rise of large metazoans. However, several geochemical indicators suggest it may instead record secondary processes affecting the sediments such as post-depositional alteration. The stable isotopic composition of iron incorporated within carbonates (δ⁵⁶Fe_(carb)) reveals an anomalous ⁵⁶Fe-depletion (down to -1.05‰) in strata containing the Shuram excursion, while the underlying and overlying strata have crustal ⁵⁶Fe-δ⁵⁶Fe_(carb) values. These depleted δ⁵⁶Fe_(carb) data during the Shuram excursion reflect incomplete reduction of iron oxides, limited by low ambient organic carbon contents. This elevated pulse of sedimentary iron oxides would consume the majority of the limited pool of organic carbon and therefore would give rise to very low net organic carbon burial during a time of enhanced detrital delivery of oxidized iron to the sediments. These results imply a syndepositional origin for the Shuram excursion, which represents a shift in the redox composition of Earth’s sedimentary shell toward more oxidizing conditions, perhaps removing a long-lived buffer on atmospheric oxygen.

The development of collision-cell multi-collection inductively-coupled-plasma mass-spectrometers has revolutionized K isotope chemistry, improving the sensitivity by over a factor of 10 compared to that of older generation instruments. The application of isotope chemistry of metals in medical science (isotope metallomics) has shown significant growth in the last few years with respect to the study of metal cycles in the body and/or as diagnostic tools for diseases affecting metal homeostasis. Given the major role that K plays in biology through the preservation of cellular homeostasis itself, the generation of nervous impulses, and the formation of glycogen in the liver, the development of K isotope metallomics is imminent and necessary. To this end, we report the first set of high precision K isotopic data for numerous widely available biological reference materials, spanning both land and sea animals, as well as various bodily organs (muscle, kidneys, and liver). Results indicate that land animals are globally enriched in the lighter isotopes compared to sea animals, and that K isotopes are fractionated by more than 1.5‰ between organs (bovine), highlighting that K isotopes could be used to study K cycles within the body. These novel data—and reference materials—could be used for future interlaboratory comparisons.

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.

Significance Zircon, a common accessory mineral in crustal rocks, records plentiful and critical information on the Earth’s history. The isotopes of its major component, Zr, could be another powerful but unexplored tracer. We apply high-precision, high–spatial-resolution, in situ laser ablation Zr isotope measurements of magmatic zircons in continental arc plutonic rocks. Single zircon grains show impressive internal zoning with lighter Zr isotopes in the core but heavier ones toward the rim, solving a fundamental but controversial issue on how zircon fractionates Zr isotope in evolving magmas. Our results also reveal a strong temperature dependence of Zr isotopic fractionation. The Zr isotope is thus very promising in deciphering the differentiation history of magmatic systems and possibly the continental crust through time., Zircons widely occur in magmatic rocks and often display internal zonation finely recording the magmatic history. Here, we presented in situ high-precision (2SD

This study presents high precision Zn stable isotope analyses for lower crustal rocks (9 granulites from Archean terrains and 30 lower crustal xenoliths) from the north margin of the North China Craton (NCC) to understand the behavior of Zn isotopes during deep crustal processes and the Zn isotopic composition of the lower continental crust (LCC). The lower crustal xenoliths range in composition from mafic to felsic with MgO contents of between 0.4 to 20.2 wt.%. The δ66Zn (the permil deviation of the 66Zn/64Zn ratio from the JMC-Lyon standard) values of lower crustal xenoliths range from −0.17‰ to 0.38‰. The lack of clear correlation of δ66Zn with geochemical indicators (e.g., Al2O3, Cr, Ba/La, 87Sr/86Sr and 143Nd/144Nd) indicates that assimilation of Precambrian lower crust, fluid metasomatism, and accumulation of pyroxene and plagioclase had a limited effect on Zn isotopic compositions of these lower crustal xenoliths. The δ66Zn values (0.18‰ to 0.34‰) of garnet-bearing mafic granulites decrease with increasing FeO(T) and V contents, which are likely results of the accumulation of Fe-Ti oxides. The average δ66Zn of the lower continental crust is estimated to be 0.29 ± 0.02‰ (95% SE) using lower crustal xenoliths from the Neogene Hannuoba basalts. This δ66Zn value is similar to the estimated value (0.28 ± 0.04‰, 95% SE) obtained from the granulites from Archean terrains, suggesting that there is no significant difference in the Zn isotopic composition between the Archean and present-day lower continental crust. Combining the δ66Zn data of the lower crustal xenoliths and granulite terrains and different weighting methods, the Zn isotopic composition of the lower continental crust is estimated to be 0.28 ± 0.04‰ (95% SE).

International audience; Metallomics is a rapidly evolving field of bio-metal research that integrates techniques and perspectives from other "-omics" sciences (e.g. genomics, proteomics) and from research vocations further afield. Perhaps the most esoteric of this latter category has been the recent coupling of biomedicine with element and isotope geochemistry, commonly referred to as isotope metallomics. Over the course of less than two decades, isotope metallomics has produced numerous benchmark studies highlighting the use of stable metal isotope distribution in developing disease diagnostics-e.g. cancer, neurodegeneration, osteoporosis-as well as their utility in deciphering the underlying mechanisms of such diseases. These pioneering works indicate an enormous wealth of potential and provide a call to action for researchers to combine and leverage expertise and resources to create a clear and meaningful path forward. Doing so with efficacy and impact will require not only building on existing research, but also broadening collaborative networks, bolstering and deepening cross-disciplinary channels, and establishing unified and realizable objectives. The aim of this review is to briefly summarize the field and its underpinnings, provide a directory of the state of the art, outline the most encouraging paths forward, including their limitations, outlook and speculative upcoming breakthroughs, and finally to offer a vision of how to cultivate isotope metallomics for an impactful future.

Variations of the stable Ca isotopic compositions (noted as δ44/40Ca relative to the SRM915a standard) of basalts are interpreted as effects of mantle sources. Mantle pyroxenites are a minor but integral part of the mantle and, as fusible components, they are important source rocks to understand chemical and isotopic heterogeneity in mantle-derived magmas. However, the effect of pyroxenites on the Ca isotopic composition of the mantle has been poorly constrained. To which extent mantle pyroxenites and their formation processes such as melt-peridotite reaction, particularly involving recycled crustal materials, lead to heterogeneity in δ44/40Ca of the mantle is unknown. Here, we report δ44/40Ca of different types of pyroxenites (spinel pyroxenites, garnet pyroxenites, and phlogopite-bearing spinel clinopyroxenites) and minerals separates, along with surrounding peridotites from Hannuoba xenoliths, North China Craton to address the issue. Initial 87Sr/86Sr ratio indicates that recycled crustal materials were incorporated into parental magmas of garnet pyroxenites (0.70391–0.70715) and phlogopite-bearing clinopyroxenites (0.7142–0.7149), consistent with previous conclusions from Sr-Nd isotopes. Overall, the δ44/40Ca of garnet pyroxenites ranges from 0.86‰ to 0.98‰ (average 0.90 ± 0.05‰, n = 10) and the host peridotites affected by the infiltrating melts from 0.87‰ to 0.93‰ (0.89 ± 0.04‰, n = 8). Each pair (n = 8) of garnet pyroxenite and host peridotite displays no measurable difference in δ44/40Ca. The spinel pyroxenites and phlogopite-bearing spinel clinopyroxenites also show similar δ44/40Ca (0.94 ± 0.06‰ and 0.98 ± 0.05‰, respectively). The indistinguishable δ44/40Ca among these different types of pyroxenites and surrounding peridotites suggest no obvious Ca isotope variations during silicate melt-peridotite interaction and fractional crystallization, even if recycled silicate materials were involved. These results indicate that the mantle source with variable proportions of pyroxenites in equilibrium conditions overall would show uniform δ44/40Ca. It implies that the basic magmas derived from such peridotite-pyroxenite source would display limited variations in δ44/40Ca, even if their radiogenic isotopes show strong heterogeneity. The conclusion is consistent with no systematic variations in the available δ44/40Ca of different basalt types such as DMM, EM1 and HIMU. However, garnets in mantle rocks of recent work and this study generally display heavier δ44/40Ca than co-existing clinopyroxenes, implying that melts generated by partial melting of mantle sources with abundant residual garnets may show lighter δ44/40Ca values than MORBs.

Significance We discovered a zircon record in a Martian meteorite that spans 4.2 Gyr, nearly the entire geologic history of Mars. Ancient zircons define a bimodal distribution with groupings at 4474 ± 10 Ma and 4442 ± 17 Ma, reflecting intense bombardment episodes triggered by the migration of the gas giant planets. A group of younger detrital zircons record ages from 1548.0 ± 8.8 Ma to 299.5 ± 0.6 Ma. The only plausible sources for these grains are the Elysium and Tharsis volcanic provinces that are the expressions of deep-seated mantle plumes. The chondritic-like Hf-isotope compositions of these zircons require the existence of a primitive and convecting mantle reservoir. Thus, these grains provide a tangible record of the deep Martian interior., Combining U–Pb ages with Lu–Hf data in zircon provides insights into the magmatic history of rocky planets. The Northwest Africa (NWA) 7034/7533 meteorites are samples of the southern highlands of Mars containing zircon with ages as old as 4476.3 ± 0.9 Ma, interpreted to reflect reworking of the primordial Martian crust by impacts. We extracted a statistically significant zircon population (n = 57) from NWA 7533 that defines a temporal record spanning 4.2 Gyr. Ancient zircons record ages from 4485.5 ± 2.2 Ma to 4331.0 ± 1.4 Ma, defining a bimodal distribution with groupings at 4474 ± 10 Ma and 4442 ± 17 Ma. We interpret these to represent intense bombardment episodes at the planet’s surface, possibly triggered by the early migration of gas giant planets. The unradiogenic initial Hf-isotope composition of these zircons establishes that Mars’s igneous activity prior to ∼4.3 Ga was limited to impact-related reworking of a chemically enriched, primordial crust. A group of younger detrital zircons record ages from 1548.0 ± 8.8 Ma to 299.5 ± 0.6 Ma. The only plausible sources for these grains are the temporally associated Elysium and Tharsis volcanic provinces that are the expressions of deep-seated mantle plumes. The chondritic-like Hf-isotope compositions of these zircons require the existence of a primitive and convecting mantle reservoir, indicating that Mars has been in a stagnant-lid tectonic regime for most of its history. Our results imply that zircon is ubiquitous on the Martian surface, providing a faithful record of the planet’s magmatic history.

Co-auteur étranger; International audience; This study reports the first Si isotope data measured in zircon using nanosecond laser ablation multiple collector inductively coupled plasma mass spectrometry. Long-term (>2 years) external reproducibility obtained on the 91500 zircon standard is 0.13‰ and 0.21‰ (2SD) for δ29Si and δ30Si (per mil deviation from the quartz reference NBS 28), respectively, and typical precision on a single run is on the order of 0.10‰ and 0.12‰ (2SE) for δ29Si and δ30Si, respectively. Our results show good consistency between laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and solution multiple collector inductively coupled plasma mass spectrometry (S-MC-ICP-MS)/secondary ionization mass spectrometry (SIMS) data demonstrating that the Si isotopic composition of zircon can be accurately measured by LA-MC-ICP-MS. Obtained δ30Si values on natural zircon standards range from −0.32 ± 0.23‰ (2SD) for 91500 to −0.47 ± 0.17‰ for MudTank, whereas the MUN (synthetic) zircon standards have lower δ30Si values around −2.0‰ (e.g. −2.08 ± 0.17‰ for MUN-1-2b). Silicon isotope measurements by LA-MC-ICP-MS open new possibilities for studying zircon formation in various geological contexts.

Copper is a metal that plays a central role in biology, for example, as co-factor in various redox enzymes. Its stable isotopic composition is being used as tracer of its transport in living organisms and as a biomarker for diseases affecting its homeostasis. While the application of copper stable isotopes to biological studies is a growing field, there are presently no biological standards that are systematically analyzed in the different laboratories, as it is the case for geological samples (e.g., by using widely available basalt samples). It is therefore paramount for the community to establish such standard. Copper also binds oxygen in the respiratory protein, hemocyanin, in the hemolymph of mollusks and arthropods and is thus critical to respiration for these species.Here, the Cu isotope composition of hemocyanin of different modern species of mollusks and arthropods (Megathura crenulate Keyhole limpet, Limulus polyphemus Horseshoe crab and Concholepas concholepas Chilean abalone), as well as theoretical constraints on the origin of these isotopic fractionations through ab initio calculations are reported.The isotopic fractionation factors for Cu(I) and Cu(II), both in hemocyanin and in seawater, predict an enrichment in the lighter isotope of Cu in the hemocyanin by over 1 permil compared to seawater. The hemocyanin of Chilean abalone and Horseshoe crab have Cu isotope compositions (δBecause these hemocyanin standard samples are widely available, they could serve in the future as inter-laboratory standards to verify the accuracy of the Cu isotopic measurements on biological matrices.

FeNi metals represent an important fraction of chondritic components that remains relatively unexplored within most carbonaceous chondrite groups. The compositions of these metals can place constraints on the nature of their precursor materials as well as the physicochemical conditions of chondrule formation. In this study, we have analyzed the major, minor and trace element compositions of metal grains from relatively unaltered carbonaceous chondrites NWA 801 (CR), Leoville (CV3.1), Paris (CM2.9), Maribo (CM2.8) and Bells (CM-an). We observe a predominant and constant sub-solar Co/Ni ratio of CR, CM and CM-an metal grains. In Ni versus Co space, the metal grains fall below modelled curves for equilibrium condensation of metals from a solar gas. From Ni versus Cr plots, we infer that Paris (and possibly Leoville) metal grains could have maintained a primary condensation signature, although for most grains, condensation must have occurred under disequilibrium conditions. CR and isolated CM-an metals mostly fall outside of the predicted condensation fields. Based on metal-silicate partition coefficients of Ni and Co that vary with pressure, we interpret their Co/Ni signatures as having a planetary origin, with presumable extraction by impact jetting. Considering that almost all CM and CR metal grains have the same Co/Ni ratio, we cannot rule out a planetary origin for CM metal grains. We relate the highly siderophile element (HSE) patterns of carbonaceous chondrite metal to mixing and subsequent equilibration of refractory metal nuggets (RMN), FeNi alloys and silicate chondrule precursors. As with the Co/Ni ratios, the HSE patterns of CM, CM-an, CR and CV metal grains are nearly identical, suggesting that the abundance and nature of the metal precursor materials were similar for carbonaceous chondrites. The overall volatility patterns of CV, CM and CR chondrites, suggest that the latter form under more oxidizing conditions than CV chondrites. The volatility patterns of Paris metal grains overlap with CV and CR chondrule metals, implying variable P-T-fO2 conditions during CM chondrule formation. Finally, we comment on the origin of metal grains in various petrological settings. Chondrule rim and isolated metal grains are likely derived and expelled from the equilibrated core metal and were subsequently altered to include and re-equilibrate with materials from the disk. Trace element analyses of the anomalous CM chondrite Bells metal grains show potential relationships with CM chondrite and CH chondrite metal for the chondrule cores and isolated grains, respectively. Small metal grains from CM chondrite Maribo, which are located in the chondrite matrix, potentially have distinct volatility patterns from CR and Paris isolated grains, hinting at a distinct origin for small metal grains and large chondrule-derived metal. Future work on carbonaceous chondrite metal should include an investigation of small (micron scale) versus large isolated metal grains.

Generally, terrestrial rocks, martian and chondritic meteorites exhibit a relatively narrow range in bulk and apatite Cl isotope compositions, with δ37Cl (per mil deviation from standard mean ocean chloride) values between − 5.6 and + 3.8 ‰. Lunar rocks, however, have more variable bulk and apatite δ37Cl values, ranging from ∼ − 4 to + 40 ‰. As the Howardite-Eucrite-Diogenite (HED) meteorites represent the largest suite of crustal and sub-crustal rocks available from a differentiated basaltic asteroid (4 Vesta), studying them for their volatiles may provide insights into planetary differentiation processes during the earliest Solar System history.\ud Here the abundance and isotopic composition of Cl in apatite were determined for seven eucrites representing a broad range of textural and petrological characteristics. Apatite Cl abundances range from ∼ 25 to 4900 ppm and the δ37Cl values range from − 3.98 to + 39.2 ‰. Samples with lower apatite H2O contents were typically also enriched in 37Cl but no systematic correlation between δ37Cl and δD values was observed across samples. Modelled Rayleigh fractionation and a strong positive correlation between bulk δ66Zn and apatite δ37Cl support the hypothesis that Cl degassed as metal chlorides from eucritic magmas, in a hydrogen-poor environment. In the case of lunar samples, it has been noted that δ37Cl values of apatite positively correlate with bulk La/Yb ratio. Interestingly, most eucrites show a negative correlation with bulk La/Yb ratio. Recently, isotopically light Cl values have been suggested to record the primary solar nebular signature. If this is the case then 4 Vesta, which accreted rapidly and early in Solar System history, could also record this primary nebular signature corresponding to the lightest Cl values measured here. The significant variation in Cl isotope composition observed within the eucrites are likely related to degassing of metal chlorides.

International audience; Although Solar System bodies exhibit large variations in their volatile element abundances, the mechanisms and conditions that lead to these variations remain ambiguous. The howardite-eucrite-diogenite (HED) meteorites that likely sample the asteroid 4 Vesta, provide evidence for extensive volatile depletion on their parent body. Isotopic variations in moderately volatile elements, such as Zn, have been used to track the origin of such volatile loss. Although not nominally volatile, Cr is useful because it has several oxidized gas species that render it volatile under the oxidizing conditions that characterize planetary accretion. As such, volatile loss of Cr has the potential to produce an isotopically light evaporation residue under an equilibrium regime. This contrasts with other moderately volatile elements that show heavy isotope enrichments in the residue following both kinetic or equilibrium fractionation. Here, we report the Cr stable isotope composition of 11 eucrites and four diogenites. The eucrites possess systematically lighter Cr isotope compositions than diogenites, which is onset by the accumulation of isotopically heavy Cr3+-rich orthopyroxene and spinel in diogenites during their magmatic evolution. We estimate for the primary eucrite melt with Mg# approximate to 50, a delta Cr-53 (Cr-53/Cr-52 deviation relative to NIST SRM 979 in per mile) of -0.22 +/- 0.03 parts per thousand (2SD), lighter than any chondritic meteorite group by similar to 0.1 parts per thousand This deficit may result from either partial melting with residual Cr3+-bearing phases (e.g. chromite) that retain heavy isotopes, or from vapor loss that occurred at equilibrium with a magma ocean on Vesta. Isotopic fractionation during partial melting would necessitate implausibly high Cr contents in the Vestan mantle, and oxygen fugacities high enough to stabilize chromite in the mantle source. Isotopic fractionation during evaporation would require an oxidized vapor and a reduced residue, as predicted by thermodynamic constraints on the composition of the vapor phase above a silicate magma ocean. Therefore, this Cr isotopic deficit between Vesta and chondrites may be caused by Cr loss at relatively high oxygen fugacity in a gas phase at equilibrium with the liquid from which it evolved. Temperatures of volatile loss are estimated to be lower than 2300 K, consistent with loss from a large-scale magma ocean model for formation of Vesta, which may be a common evolutionary stage in accreting planetesimals. (C) 2019 Elsevier Ltd. All rights reserved.

FM acknowledge funding from ERC grant agreement No. 101001282 (METAL), the UnivEarthS Labex program (numbers: ANR-10-LABX-0023 and ANR-11-IDEX-0005-02), the IPGP multidisciplinary program PARI, the Region île-de-France SESAME Grants no. 12015908, EX047016, and the IdEx Université de Paris grant, ANR-18-IDEX-0001 and the DIM ACAV+. The source of and timing of delivery of the volatile elements to Earth is a question that is fundamental to understanding how our planet evolved. Here, we show that primitive meteorites have resolved mass-independent Zn isotope anomalies from the terrestrial reservoir. Carbonaceous chondrites (CC), likely originating from the outer Solar System are distinct from non-CC, and Earth is intermediate between these two components. Modelling based on these data indicates that around 30% of Earth's budget of Zn and other moderately volatile material derives from the participation of 6% of CC-like materials during Earth's accretion, with the remaining coming from NC meteorites. This implies that, despite the relatively minor mass of Earth thought to derive from CC-like material, the CC component of Earth was relatively and significantly volatile-enriched; this is in line with the observation that the terrestrial elemental abundance pattern of moderately volatile elements could be explained by a carbonaceous source, and with the carbonaceous chondrite-like isotopic budget of more volatile-rich material accreted later in Earth's accretion history (e.g. Hg, Se, N, noble gases). Publisher PDF