13 research outputs found
Le rapport isotopique de l'hydrogène dans le Système Solaire interne : A la recherche des sources physico-chimiques de l'eau planétaire
No full textCurrent dynamical models of Solar System formation and geochemical models agree on a likely chondritic origin for the terrestrial water. Indeed, primitive meteorites, called chondrites, have undergone an aqueous alteration process on their parent bodies. Moreover, these meteorites are one of the considered sources for the existence of water in lunar minerals. This thesis lies on hydrogen isotopic ratios and water contents measured using NanoSIMS in the carbonaceous chondrite Paris and lunar soils from the Apollo missions. Chondrules in Paris meteorite seem to have registered a water source distinct from the one of the parent body aqueous alteration. For the Moon, water retained in soils is majority formed by implantation of the solar wind hydrogen.Les modèles dynamiques actuels de formation du Système Solaire et les modèles géochimiques s’accordent sur une probable origine chondritique de l’eau terrestre. En effet, les météorites primitives, appelées chondrites ont subi un phénomène d’altération aqueuse sur leurs corps parents. De même, ces météorites sont une des sources envisagées à la présence d’eau dans les minéraux lunaires. Cette thèse s’appuie sur des mesures NanoSIMS des rapports isotopiques de l’hydrogène et des teneurs en eau dans la chondrite carbonée Paris et les échantillons de sols lunaires provenant d’Apollo 16 et 17. Les chondres de la météorite Paris semblent avoir enregistré une source d’eau distincte à l’eau d’altération du corps parent. En ce qui concerne la Lune, l’eau contenue dans les sols est majoritairement formée par l’implantation de l’hydrogène du vent solaire
Preservation of primordial signatures of water in highly-shocked ancient lunar rocks
No full textSpurred by the discovery of water in lunar volcanic glasses about a decade ago, the accessory mineral apatite became the primary target to investigate the abundance and source of lunar water. This is due to its ability to contain significant amounts of OH in its structure, along with the widespread presence of apatite in lunar rocks. There is a general understanding that crustal cumulate rocks of the lunar magnesian (Mg) suite are better candidates for recording the original isotopic compositions of volatile elements in their parental melts compared to eruptive rocks, such as mare basalts. Consequently, water-bearing minerals in Mg-suite rocks are thought to be ideal candidates for discerning the primary hydrogen isotopic composition of water in the lunar interior. Mg-suite rocks and most other Apollo samples that were collected at the lunar surface display variable degrees of shock-deformation. In this study, we have investigated seven Apollo 17 Mg-suite samples that include troctolite, gabbro and norite lithologies, in order to understand if shock processes affected the water abundances and/or H isotopic composition of apatite. The measured water contents in apatite grains range from 31 to 964 ppm, with associated δD values varying between −535 ±134‰ and +147 ±194‰(2σ). Considering the full dataset, there appears to be no correlation between H2O and δD of apatite and the level of shock each apatite grain has experienced. However, the lowest δD was recorded by individual, water-poor (∼100 ppm H2O), regardless of the complexity of the shock-induced nanostructures, there appears to be no evidence of water-loss or alteration in their δD. The weighted average δD value of 24 such water-rich apatites is −192 ±71‰, and, of all 36 analyzed spots is −209 ±47‰, indistinguishable from that of other KREEPy lunar lithologies or the Earth’s deep mantle. Despite experiencing variable degrees of shock-deformation at a later stage in lunar history, water-rich apatite in some of the earliest-formed lunar crustal material appears to retain the original isotopic signature of H in the Moon
Al Huwaysah 010: The most reduced brachinite, so far
No full textAl Huwaysah 010 is an ungrouped achondrite meteorite, recently referred to as abrachinite-like meteorite. This meteorite, showing a fine-grained assemblage of low-Ca pyroxene and opaque phases, is strongly reduced in comparison to other reduced brachinites. The occurrence of some tiny plates of graphite and oldhamite in this meteorite suggests that a partial melt residue has experienced a further reduction process. Olivine, the most abundant phase, is compositionally homogeneous (Fo83.3) as well as the clinopyroxene (En45.5Fs10.8Wo43.7) and the plagioclase (Ab69.5). Orthopyroxene (En85.4Fs13.9Wo0.7) also occurs but only in a fine intergrowth. Other accessory phases are Fe metal grains (Ni-free or Cr-bearing Fe-Ni alloy), troilite, chlorapatite, pentlandite (as inclusions in chromite). The sample shows two different closure temperatures: the highest (≈900°C) is determined via the olivine–chromite intercrystalline geothermometer and the lowest temperature (≈520°C) is determined via the pyroxene-based intracrystalline geothermometer. These temperatures may represent, respectively, the closure temperature associated with the formation and a subsequent impact event excavating the sample from the parental body. The visible to near-infrared (VNIR)reflectance spectra of Al Huwaysah 010 exhibit low reflectance, consistent with the presence of darkening components, and weak absorptions indicative of olivine and pyroxene. Comparing the spectral parameters of Al Huwaysah 010 to potential parent bodies characterized by olivine–pyroxene mineralogy, we find that it falls within the field previously attributed to the SIII type asteroids. These results lead us to classify the Al Huwaysah 010 meteorite as the most reduced brachinite, whose VNIR spectral features show strong affinities with those of SIII asteroids
MINERALOGIC AND Δ17O-ε54Cr ISOTOPIC COMPOSITION OF BRACHINITE NORTHWEST AFRICA 13489: A NEW METACHONDRITE WITH ‘CX’ CHONDRITE AFFINITY?
No full textReduction of OH contamination in quantification of water contents using NanoSIMS imaging
No full textInternational audienceQuantification of water content is relevant in various topics in geology and planetary sciences. NanoSIMS has capabilities for high spatial resolution imaging and offers opportunities to accurately quantify water contents at fine scale on small surface areas. The main concern using ion microprobe techniques is to estimate and minimize contribution of water contamination, from residual gas in the sample chamber, sticking onto the surface of the sample. Here we tackle a set of sputtering/analytical parameters and we evaluate their relative influence on theOH−/Si− ratio.We demonstrate that a high erosion rate, reached using a primary beamintensity of ~25 pA, is sufficient to lower this OH contamination for basaltic glass. This leads us to describe a procedure to correct for OH contamination and thus determine accurate values of OH/Si ratio in order to quantify water contents in silicate materials using NanoSIMS imaging
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Northwest Africa 16788: The Largest Known Individual Martian Meteorite—A New Olivine Microgabbroic Shergottite and Its Implications for Martian Magmatism
No full textWe present a comprehensive study of a new Martian meteorite, Northwest Africa (NWA) 16788, found in the Sahara Desert in July 2023. This specimen constitutes the largest known individual meteorite of Martian origin, with a total weight of ⁓25 kg. A detailed mineralogical and geochemical investigation identifies NWA 16788 as an enriched olivine microgabbroic shergottite. Petrographic analysis reveals a millimeter-sized cumulate texture, which is intermediate between poikilitic and gabbroic shergottites, primarily composed of pyroxene (⁓61 vol.%), maskelynite (shocked plagioclase, ⁓21 vol.%), and olivine (⁓15 vol.%). Pyroxene grains exhibit a distinctive zoning pattern, placing NWA 16788 within a small group of Martian meteorites and lunar samples that record unique cooling histories, suggesting that similar samples may be more prevalent within the Martian igneous rocks than previously recognized. High-precision analyses of bulk 143Nd/144Nd and 87Sr/86Sr isotopic composition, combined with trace element abundance, indicate that NWA 16788 originated from the partial melting of an enriched Martian mantle source. Electron backscatter diffraction analysis reveals a unimodal distribution of olivine grain misorientation, averaging ⁓4.6°, consistent with a high-energy single-impact event. Moreover, visible and near-infrared spectroscopy data acquired on NWA 16788 could aid in identifying potential locations of analogous igneous rocks on the Martian surface. Finally, this study proposes refinements to the current classification scheme of Martian meteorites, aiming to reduce taxonomic ambiguity and improve the alignment between Martian meteorites and Martian igneous rocks, based on data from Mars rovers
Terrestrial exposure of a fresh Martian meteorite causes rapid changes in hydrogen isotopes and water concentrations
No full textDetermining the hydrogen isotopic compositions and H2O contents of meteorites and their components is important for addressing key cosmochemical questions about the abundance and source(s) of water in planetary bodies. However, deconvolving the effects of terrestrial contamination from the indigenous hydrogen isotopic compositions of these extraterrestrial materials is not trivial, because chondrites and some achondrites show only small deviations from terrestrial values such that even minor contamination can mask the indigenous values. Here we assess the effects of terrestrial weathering and contamination on the hydrogen isotope ratios and H2O contents of meteoritic minerals through monitored terrestrial weathering of Tissint, a recent Martian fall. Our findings reveal the rapidity with which this weathering affects nominally anhydrous phases in extraterrestrial materials, which illustrates the necessity of sampling the interiors of even relatively fresh meteorite falls and underlines the importance of sample return missions
The hydrogen isotopic composition of lunar melt inclusions: An interplay of complex magmatic and secondary processes
No full textSince the discovery of water (a term collectively used for the total H, OH and H2O) in samples derived from the lunar interior, heterogeneity in both water concentration and its hydrogen isotopic ratio has been documented for various lunar phases. However, most previous studies have focused on measurements of hydrogen in apatite, which typically forms during the final stages of melt crystallisation. To better constrain the abundance and isotopic composition of water in the lunar interior, we have targeted melt inclusions (MIs), in mare basalts, that are trapped during the earliest stages of melt crystallisation. Melt inclusions are expected to have suffered minimal syn- or post-eruption modification processes, and, therefore, should provide more accurate information about the history of H in the lunar interior. Here, we report H-/18O- measurements as calibrated water concentrations, and hydrogen isotope ratios obtained by secondary ion mass spectrometry (SIMS) in a large set of basaltic MIs from Apollo mare basalts 10020, 10058, 12002, 12004, 12008, 12020, 12040, 14072 and 15016. Our results demonstrate that partially crystallised MIs from lunar basalts and their parental melts were influenced by a variety of processes such as hydrogen diffusion, degassing and assimilation of material affected by solar-wind implantation. Deconvolution of these processes show that lunar basaltic parental magmas were heterogeneous and had a broadly chondritic hydrogen isotopic composition with δD values varying between -200 and +200 ‰
Organics preserved in anhydrous interplanetary dust particles: Pristine or not?
No full textThe chondritic‐porous subset of interplanetary dust particles (CP‐IDPs) are thought to have a cometary origin. Since the CP‐IDPs are anhydrous and unaltered by aqueous processes that are common to chondritic organic matter (OM), they represent the most pristine material of the solar system. However, the study of IDP OM might be hindered by their further alteration by flash heating during atmospheric entry, and we have limited understanding on how short‐term heating influences their organic content. In order to investigate this problem, five CP‐IDPs were studied for their OM contents, distributions, and isotopic compositions at the submicro‐ to nanoscale levels. The OM contained in the IDPs in this study spans the spectrum from primitive OM to that which has been significantly processed by heat. Similarities in the Raman D bands of the meteoritic and IDP OMs indicate that the overall gain in the sizes of crystalline domains in response to heating is similar. However, the Raman ΓG values of the OM in all of the five IDPs clearly deviate from those of chondritic OM that had been processed during a prolonged episode of parent body heating. Such disparity suggests that the nonaromatic contents of the OM are different. Short duration heating further increases the H/C ratio and reduces the δ13C and δD values of the IDP OM. Our findings suggest that IDP OM contains a significant proportion of disordered C with low H content, such as sp2 olefinic C=C, sp3 C–C, and/or carbonyl contents as bridging material
Investigating the effects of high-temperature thermal energy storage on aquifer biogeochemistry
No full textInternational audienceHigh-temperature aquifer thermal storage energy (HT-ATES) is a key technology for reducing greenhouse gas emissions related to space heating and cooling by storing seasonal energy in the subsurface. However, such process could significantly affect aquifers geochemistry and microbial communities. Elevated temperatures influence geochemical equilibria, changing mineral solubility, potentially leading to clogging, organic matter or trace elements mobilization, while simultaneously affecting microbial community structures and functions. Biogeochemical processes in HT-ATES remain poorly understood, making dedicated laboratory experiments crucial to assess their operational and environmental impacts. As part of the Horizon Europe PUSH-IT project (https://www.push-it-thermalstorage.eu/), this study investigates how repetitive heating and cooling cycles induced by HT-ATES affect biogeochemical processes in the subsurface. To simulate HT-ATES conditions, a pressurized flow through experiment is conducted where groundwater from a monitoring HT-ATES well at TUDelft (Netherlands) is injected through aquifer sediments at varying temperatures.Preliminary analysis of aquifer sediments and water composition provide initial insights. Sediments are quartz rich with detectable amounts of carbonates and clay minerals. The groundwater is brackish Na-Cl type (~6 g/L salinity) under reducing conditions. Dissolved gases such as CH4 and CO2 are present, along with Fe, Mn, NH4 and elevated organic carbon concentrations. Initial microbial analysis showed a cell concentration of ~106 cell/mL and revealed a dominance of bacteria (89%) with key genus Nitrospina, a nitrite-oxidizing bacteria, suggesting a role in nitrogen cycling, alongside other taxa (six major phyla identified) potentially involved in metal and sulphate reduction and organic matter degradation.Throughout the experiments, geochemical parameters (pH, redox potential, conductivity, key redox-sensitive compounds) and microbial community composition (qPCR, 16S rRNA Illumina sequencing) are monitored in both circulating water and sediments. These results help understand the impacts of HT-ATES on biogeochemical evolution of storage aquifers and assess the long-term stability of these systems and implications on groundwater quality.Acknowledgements: Funded by the European Union under grant agreement 1011096566 (PUSH-IT project). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor CINEA can be held responsible for them
