Reducing conditions are typical of incipient serpentinization in which sulfides and alloys break down to form secondary phases. Sulfides and alloys are the main hosts of platinum group elements (PGEs) in serpentinites, and the role of serpentinization in the remobilization of these elements is controversial. Here, we replicated early serpentinization using cold-seal pressure vessels, reacting a mixture of olivine, synthetic laurite, and water at 50 MPa and temperatures of 250-350 degrees C for durations of 1-4 d. Olivine reacts partially to form serpentine and brucite. Laurite breaks down to form RuSx with variable Ru:S ratios plus euhedral FeS grains. There are no systematic relationships among temperature, time, water content, and the composition of the Ru phase. No neoformed Ru phases were identified, consistent with limited Ru mobility during serpentinization. Silicate mineral assemblages and breakdown of primary laurite are consistent with observations in natural and experimental systems where incipient serpentinization occurred at highly reducing conditions. The results are consistent with decoupling of Ir group PGEs and Pd group PGEs during serpentinization and suggest that serpentinization may affect PGEs differently in different geodynamic settings, with consequences for global PGE cycling.

Olivine low-angle grain boundaries (LAGBs) influence the upper mantle properties, but the role of geometry in their structure and chemical composition remains largely unexplored. Here, we characterise and compare three tilt LAGBs with a 4.5° misorientation angle but different misorientation axes in a mantle xenolith. Electron backscatter diffraction (EBSD) was used to characterise three olivine grains, containing one LAGB aligning with the (001)[100] slip system, and two LAGBs with (010)[100] slip. Within the (010)[100] LAGBs, transmission electron microscopy (TEM) shows dislocation cores regularly spaced at 5.8 nm. Direct dislocations imaging in the (001)[100] LAGB was hindered by lamella orientation. Atom probe tomography (APT) reveals segregation of Al, Ca, Fe, H and Ti to the LAGBs, accompanied by Mg depletion. In the (010)[100] LAGBs, the segregated elements are concentrated in linear arrays ( 5.8 nm spacing), consistent with segregation to dislocations. In the (001)[100] LAGBs, although segregated elements appear evenly distributed, 2D profiles show regularly spaced features at 4.8 nm along the boundary, indicative of dislocation spacing. Interfacial excess calculations reveal differences in elemental segregation between boundaries. The (001)[100] LAGB has greater H segregation, while the LAGB in the seemingly smaller grain exhibits decreased Al, Ca and Fe enrichment. These findings suggest that LAGB geometry influences elemental segregation. Because these geometries are associated with specific mantle fabrics, the segregation patterns may influence differences in phase transitions, creep behaviour, electrical conductivity, and seismic properties in the upper mantle.

Many materials, including those containing platinum group elements and noble metals, form nanometer-thick plates (nanoplates) in a range of natural environments, including ore deposits and serpentinites. Materials research uses metallic nanoplates, such as 2D metal oxide/sulfide in applications ranging from superconductors to biomedical engineering, because of their unique properties. A few techniques with sufficient spatial resolution can analyze these nanomaterials, such as nano-secondary ion mass spectroscopy. An alternative is atom probe tomography (APT), which provides in situ major and trace element data with nanometer-scale resolution and can analyze nanoplates. This research describes a novel method to produce APT samples from geological nanoplates using focused ion beam (FIB) lift-out. The redeposited material is used to fill voids at the interface between the plate and the substrate, consolidating the wedge that is lifted out for analysis. A case study of APT specimen preparation from a ∼500-nm-thick FeS plate, separated from an olivine substrate, by voids, ≤20 µm3 in volume, is described. The method produces robust specimens that yield millions of atoms during APT analysis. This method can be applied to nanoplates of different compositions and thicknesses from a broad range of materials, and to free-standing films supported by window structures.

Sulfides and sulfosalts in base-metal (Cu, Pb, Zn) deposits are significant reservoirs for trace elements, providing critical insights into ore genesis. Despite several studies in the literature on euhedral chalcopyrite and tennantite, their colloform equivalents, commonly consisting of mixtures of euhedral and acicular crystals, remain largely understudied from a geochemical perspective. This study investigates the micro- to nanoscale composition and distribution of trace-elements in colloform chalcopyrite and tennantite from two distinct hydrothermal environments: the Cordilleran lodes of Butte (Leonard mine; USA) and the low-temperature stratabound Zn-Pb deposit of Lisheen (Ireland). At both localities, chalcopyrite and tennantite are significantly enriched in Ge, Ga, Ag, and Pb (up to several 1000 s ppm), with zonal distributions at the microscale. However, the mode of occurrence differs in the two deposits. At Butte, Ge, Ga, Ag, Pb, and Tl are mainly incorporated into the crystal structure of euhedral grains, with Ge showing a positive correlation with Ga, Pb and Tl. While at Lisheen, Ge, Ag, and Pb are concentrated in thin colloform bands, further nanoscale investigations reveal that Ge is hosted within numerous nanoscale renierite inclusions (ideal formula = [(Cu,Zn)11(Ge,As)2Fe4S16]), rather than the acicular tennantite crystal structure (< 50 ppm Ge). These inclusions are cogenetic with micro- to nanoscale size fluid inclusions enriched in H2O, K, and Ca. In this case, these nanoscale renierite inclusions are interpreted to have formed either through exsolution or through the entrapment of a dense liquid under high levels of fluid supersaturation. In both case studies, acicular chalcopyrite exhibits a distinct <110> crystallographic preferred orientations (CPO) with a girdle on {001}. Acicular textures in both tennantite and chalcopyrite are consistently depleted in trace elements (Ge, Ga, Ag, Pb; <50 ppm). We suggest that the spatial distribution of trace elements is strongly influenced by a complex variety of parameters such as fluid composition, precipitation conditions (temperature, pH, supersaturation, growth kinetics). These results demonstrate that euhedral chalcopyrite and tennantite from high to intermediate sulfidation assemblages in magmatic-hydrothermal and sedimentary-hosted systems can host significant Ge and Ga concentrations. Detailed multiscale examination of sulfide microtextures is critical for interpreting the complex chemical zoning, potentially resulting in a better understanding of ore-forming processes.

Oscillatory zoning — alternating high- and low-impurity (trace element) zones — is a hallmark of magmatic zircon from felsic systems and preserves the history of magmatic systems. Although commonly attributed to fluctuations in temperature, pressure, or melt composition, the mechanisms driving this zoning remain uncertain. Here, we show that high-impurity growth zones, which appear homogeneous when imaged with a scanning electron microscope (SEM), actually consist of finer-scale growth zones when viewed at the nanoscale - and still finer zones are revealed at the atomic scale. The apparent homogeneity in SEM images results from electron beam convolution, where features smaller than the beam’s interaction volume cannot be resolved. Backscattered electron images have higher spatial resolution than cathodoluminescent images, but high-impurity zones imaged with both are found to consist of finer zones at the atomic scale when imaged with atom probe tomography. Adjacent low-impurity zones are homogeneous across all scales. We interpret these observations as evidence of impurity poisoning during near-equilibrium zircon growth. Faceted crystal growth at low supersaturation leads to rejection of impurities, except for those allowed by equilibrium partitioning. Rejected impurities accumulate on the crystal surface, blocking normal incorporation of atoms and temporarily halting growth. When supersaturation exceeds a critical threshold, growth resumes, trapping the adsorbed impurities and forming a high-impurity zone. These findings not only help to resolve the origin of oscillatory zoning in zircon but also establish a generalizable mechanism of impurity poisoning during near-equilibrium crystal growth, redefining how mineral records are interpreted in igneous systems and beyond.

Fault strength evolves during the earthquake cycle in response to transient, temperature-sensitive weakening and restrengthening. However, the micro- to atomic-scale structural and geochemical processes underpinning these strength changes are poorly understood. We used atom probe tomography (APT), scanning/transmission electron microscopy (S/TEM), and transmission Kikuchi diffraction (TKD) to characterize two previously studied hematite fault mirrors from the footwall damage zone of the Wasatch fault (Utah, USA) that developed during seismic slip. S/TEM and TKD analyses confirm these mirrors comprise euhedral micro- to nanoscale hematite grains with a crystallographic preferred orientation. APT reveals that elements relatively incompatible in the hematite lattice (e.g., Ca, Si, Ti, and Al) segregate to grain boundaries, triple junctions, and isolated intragrain dislocations during nucleation and grain boundary migration associated with transient high temperatures during slip. Triple junctions host higher solute concentrations than grain boundaries, consistent with their higher interfacial energy. Although element-decorated dislocations are few in the APT data, S/TEM reveals abundant undecorated dislocations near the fault mirror surface, indicating that most intragrain defects formed under cooler conditions where solute redistribution was limited. The abundance of later intragrain defects and low-angle boundaries (observed in TKD) suggests that the grain-boundary network became mechanically stronger relative to crystal interiors and may favor intragrain strain accommodation during subsequent deformation. These datasets enable discrimination between coseismic and lower-temperature fault slip and reveal how atomic-scale element mobility contributes to fault restrengthening.

Abstract Liquid immiscibility is commonly invoked to explain differentiation between mafic and silicic melts, but its physical effects are rarely visible at macroscopic scales. In this study, we show that the distinctive blue coloration of the Blue Dragon pahoehoe lava flow in Craters of the Moon National Monument and Preserve (Idaho, USA) results from Rayleigh scattering caused by nanoscale Fe-rich glass domains dispersed within a Si-rich glass matrix. Atom probe tomography and electron beam imaging demonstrate that these domains occur as spherical or tubular structures ∼10–50 nm in diameter. Droplet-like and bicontinuous intergrowths result from binodal and spinodal decomposition, respectively. The presence of these textures only in the near-surface glass layer of the Blue Dragon flow suggests that their development is controlled by cooling and melt compositional variations at crystal boundaries. The Blue Dragon nanoscale structures are analogous to those in synthetic opaline glasses and rare natural examples such as blue fulgurites and impact glasses. Nanoemulsions of immiscible liquids also form in other quenched lavas, but Blue Dragon represents the only documented case of naturally occurring blue volcanic glass. Its rarity reflects the need for (1) melt compositions sufficiently enriched in Fe to enter the miscibility gap upon cooling, (2) quenching rates that promote phase separation yet inhibit microlite formation, and (3) preservation of near-surface flow layers. Although eruptions of Fe-rich lavas such as Blue Dragon are uncommon for terrestrial volcanic systems, basaltic melts may commonly enter the immiscibility gap upon magma differentiation.

We present a novel focused ion beam (FIB) method (METIS-Fa: multi-technical measurements of electron transparent materials using an In sandwich-a FIB approach), for preparing geometrically symmetric atom probe tomography (APT) needles from ∼70 to 100 nm thin transmission electron microscopy (TEM) FIB foils. The METIS-Fa method uses a FIB instrument and In to bolster the TEM foil for subsequent production of APT needles. This method is the first to enable geometrically symmetric APT sample preparation, allowing optimal conditions for each technique in a correlated, site-specific TEM and APT study, with an overall 66% success rate out of nine needles. METIS-Fa was tested on a synthetic basaltic silicate; epoxy; terrestrial silicate (San Carlos Olivine) and oxide (corundum); meteoritic silicates from Miller Range (MIL) 090019 and Acfer 094; and a presolar stardust grain from the meteorite Allan Hills (ALH) 77307. The extraterrestrial grains demonstrated the ability to target individual grains (>100 nm in size). The high-quality TEM and APT data presented in this study demonstrates the method's reproducibility and benefits. METIS-Fa provides access to atomic, trace element, and mineralogical characterization of organic and inorganic materials, with broad applicability to material science, geosciences, planetary science, and medical science.

We studied a rare platinum-group element (PGE)-bearing phase occurring as inclusions in Pt-Fe alloys from placer deposits, previously referred to as "iridium oxide," but lacking confirmation of actual Ir oxide. X-ray absorption spectroscopy confirms that the studied Ir-O phase contains genuine IrO2, with iridium in a formal oxidation state of 4+ and an Ir-O bond distance of 1.95 +/- 0.02 & Aring;, matching synthetic rutile-type IrO2. Atom probe tomography reveals that IrO2 forms thin films along boundaries between metallic PGE-rich domains, which are separated by oxide-rich regions composed of Ca, Mn, Fe, K, and V oxides. Mass-balance constraints indicate that Rh, Ru, and Pt occur mainly as metals, while Os is partly oxidized. Formation of IrO2 from Os-Ir-Ru alloys requires extremely oxidizing conditions, estimated at approximately fayalite-magnetite-quartz (FMQ) + 5 to +10. While such conditions could potentially develop during hydrothermal alteration, there is limited geological evidence for such high fO2 values in natural environments. The coexistence of iridium oxide and metallic Ru contradicts thermodynamic predictions, which suggest Ru should oxidize prior to Ir. This discrepancy indicates that conventional equilibrium thermodynamics, where pressure, temperature, and chemical potential are the controlling intensive variables, may not predict natural redox behaviour. Alternative mechanisms, including kinetically controlled reactions, extremely limited length-scales of equilibrium, or a role for electrochemical work, may permit localized Ir oxidation. The results provide rare in-situ evidence for PGE oxidation and Os-Ir mobility within the lithosphere, with implications for PGE distribution and Os isotope systematics in mantle and crustal rocks.

Arsenopyrite is a major host of refractory Au in ore deposits, and remobilisation of Au from this mineral has been proposed as a significant process leading to the formation of secondary native Au mineralisation. However, the processes for Au remobilisation in arsenopyrite remain poorly constrained. In this study, we apply state-of-the-art post-acquisition pattern matching algorithms to resolve artefacts associated with arsenopyrite pseudosymmetry. This approach improved data quality enabling robust crystallographic interpretations. By using a correlative approach including microstructural characterisation, geochemical, textural and nanoscale investigations from two orogenic Au deposits, we report two mechanisms for Au remobilisation, both controlled by dislocations. In the Obuasi Au deposit, arsenopyrite shows evidence of re-equilibration with a sharp reaction front between Aurich and Au-poor arsenopyrite. Dislocations are systematically present in proximity to the front, suggesting that they act as fast diffusion pathways for mass exchange, instead of porosity as previously proposed. In the Fosterville Au deposit, a small amount of crystal-plastic deformation in arsenopyrite generated low-angle boundaries that are depleted in Au compared to undeformed arsenopyrite. Dislocations along the low-angle boundaries are enriched in trace elements such as Ni, but are depleted in Au, suggesting that the presence of dislocations may selectively remobilise Au. In summary, our results highlight the fundamental role of crystal defects in controlling Au remobilisation during coupled dissolution-reprecipitation and crystal-plastic deformation.

Accurate measurements of Hf isotope ratios in zircon rely on adequate correction for isobaric interferences, which increase in complexity as the ratio of heavy rare earth elements (HREE) to Hf increases. Currently, synthetic high‐HREE zircons are commonly used to bracket the highest naturally occurring HREE/Hf zircon grains during laser ablation‐based measurement but these are in limited supply. We present results for Grey Hill zircon, a new high 176 Yb/ 177 Hf zircon with a weighted mean age of 482.97 ± 0.17 Ma (2s). We show that Hf is homogeneously distributed at the microscale in Grey Hill zircon, whereas Yb is heterogeneously distributed in oscillatory‐ and sector‐zones following observed cathodoluminescence patterns. Atom probe tomography measurements show that Hf and Yb are homogeneously distributed at the nanoscale. Chemical abrasion solution multi‐collector inductively coupled plasma‐mass spectrometry (CA‐S‐MC‐ICP‐MS) yielded a mean 176 Hf/ 177 Hf of 0.282854 ± 0.000023 (2 s , n = 15), with a correlation to 176 Lu/ 177 Hf that corresponds to radiogenic ingrowth since ca . 483 Ma. If analyses are back‐calculated to the crystallisation age, the CA‐S‐MC‐ICP‐MS data yield a 176 Hf/ 177 Hf (t) of 0.282805 ± 0.000010 (2 s ), which we recommend be used as the reference ratio for Grey Hill zircon. Non‐abraded, in situ LA‐MC‐ICP‐MS analyses yielded results consistent with the CA‐S‐MC‐ICP‐MS mean. Importantly, LA‐MC‐ICP‐MS analyses do not show any correlation with HREE, and there is no apparent difference in measured 176 Hf/ 177 Hf between pristine and altered domains. The grains have 176 Yb/ 177 Hf (0.094–0.48) and 176 Lu/ 177 Hf (0.0028–0.014) ratios that are much higher than all commonly used natural reference materials. Thus, Grey Hill zircon is a useful natural reference material for LA‐MC‐ICP‐MS Hf isotope measurement to guarantee accurate isobaric interference correction across the full spectrum of naturally occurring zircon grains. Grey Hill zircon concentrates can be requested from the authors.

Trace elements in sulfides are commonly used to determine the physicochemical conditions of ore deposit formation. The thermodynamic models underpinning these studies rely on the assumption that trace elements are incorporated into the mineral's crystal structure, however recent atomic-scale investigations suggest that this assumption may be erroneous, especially in metamorphosed environments. Here, in primary undeformed colloform sphalerites from two Pb-Zn deposits in South-China, we study the microstructural, geochemical, and nanoscale distribution of trace elements. Our results show that colloform sphalerite hosts trace elements such as Ge (up to 5671 ppm) and Ga (up to 16307 ppm) in nanoscale polyphase inclusions (mainly 10-20 nm), comprising an aqueous solution and solid phases such as galena and pyrite. These Ge(-Ga) polyphase inclusions are rich in light elements and halogens (H, Li, Na, Cl, K) and heavier metals such as Mn and Pb, accounting for 5 %-78 % of the trace element budget in bulk sphalerite. We propose a model whereby the rapid crystallization of colloform sphalerite favors the preservation of elevated trace element concentrations in nanoscale fluid inclusions (i.e., Ga, Ge, Pb, Mn) that are in apparent thermodynamic disequilibrium with sphalerite. A nucleation mechanism is proposed involving the entrapment of dense liquid composed of an intermediate high-density disordered state under supersaturation conditions. Based on a global geochemical data compilation of colloform sphalerite, we show significant enrichment of Pb in colloform sphalerite and multiple positive correlations between Pb and Ge. This suggests that Pb-Ge-rich nanoscale dense-liquid inclusions may be a prevalent carrier for trace elements observed in colloform sphalerite textures. Similar colloform textures resulting from supersaturated solutions in minerals such as pyrite or quartz may also contain trace element-rich nanoscale inclusions. Presence of these nanoscale inclusions appears to have a minimal effect on the estimated formation conditions derived from sphalerite chemistry (temperature, fS2). This study highlights the value of chemical mapping in revealing temperature variations in sphalerite.

The study of the structure and geochemistry of olivine crystal defects is important but difficult because of their nanometer size and the analytical limitations of most techniques. Laser-assisted atom probe tomography (APT) is capable of sub-nanometer resolution, quantitative geochemical analysis and 3D reconstruction of olivine defects, but optimal analytical conditions and data reconstruction strategies have not been sufficiently studied. Here, we investigate the effect of different laser pulse energy (LPE) and crystal orientations on the quality and reconstruction parameters of APT data using specimens from two San Carlos olivine grains. Our findings show that increased LPE reduces the background noise, percentage of multiple hit events, and applied electric field, as shown by the Mg2+/Mg+ ratio, but increases the peak tails. The major element compositions show inaccuracies under all LPEs but exhibit higher consistency for higher LPEs. We determine that a LPE of 150pJ is the best compromise for optimal data quality in olivine. Using scanning electron microscopy imaging before and after APT analyses, we suggest that the Mg2+/Mg+ ratio can be used as a guide to estimate the electric field parameter and results in more accurate reconstructions.

Evaporation or freezing of water-rich fluids with dilute concentrations of dissolved salts can produce brines, as observed in closed basins on Earth1 and detected by remote sensing on icy bodies in the outer Solar System2,3. The mineralogical evolution of these brines is well understood in regard to terrestrial environments4, but poorly constrained for extraterrestrial systems owing to a lack of direct sampling. Here we report the occurrence of salt minerals in samples of the asteroid (101955) Bennu returned by the OSIRIS-REx mission5. These include sodium-bearing phosphates and sodium-rich carbonates, sulfates, chlorides and fluorides formed during evaporation of a late-stage brine that existed early in the history of Bennu's parent body. Discovery of diverse salts would not be possible without mission sample return and careful curation and storage, because these decompose with prolonged exposure to Earth's atmosphere. Similar brines probably still occur in the interior of icy bodies Ceres and Enceladus, as indicated by spectra or measurement of sodium carbonate on the surface or in plumes2,3.

Stainless steels like 304SS are commonly used in pressurized water reactor primary water environments due to their excellent resistance to stress corrosion cracking (SCC). However, SCC susceptibility has been observed in cold-worked 304SS. Cold-rolling introduces a high density of defects, such as deformation bands or dislocations, into the microstructure; applied stress, even if macroscopically below the yield stress, can result in regions with high localized stresses. Cold-worked and non-cold-worked samples were exposed to 360 degrees C simulated PWR primary water for 1500 h with and without active loading. Corrosion susceptibility of dislocations and deformation bands induced by cold-rolling and/or applied stress was studied using high-resolution (analytical) transmission electron microscopy. Deformation bands were generated in all specimens examined in the study. Penetrative oxidation was observed in some deformation bands in each specimen. The depth of penetrative deformation band oxidation frequently exceeded the depth of grain boundary oxidation in all specimens. However, deformation band oxides generally were narrowly confined to the deformation band plane. Highly Nirich regions were observed beyond all oxidation fronts. Surface oxides were thicker in the specimens exposed under active loading. The implications of these findings at surfaces for deformation bands intersecting stress corrosion crack paths are discussed.

Accurate measurements of Hf isotope ratios in zircon rely on adequate correction for isobaric interferences, which increase in complexity as the ratio of heavy rare earth elements (HREE) to Hf increases. Currently, synthetic high-HREE zircons are commonly used to bracket the highest naturally occurring HREE/Hf zircon grains during laser ablation-based measurement but these are in limited supply. We present results for Grey Hill zircon, a new high 176Yb/177Hf zircon with a weighted mean age of 482.97 +/- 0.17 Ma (2s). We show that Hf is homogeneously distributed at the microscale in Grey Hill zircon, whereas Yb is heterogeneously distributed in oscillatory- and sector-zones following observed cathodoluminescence patterns. Atom probe tomography measurements show that Hf and Yb are homogeneously distributed at the nanoscale. Chemical abrasion solution multi-collector inductively coupled plasma-mass spectrometry (CA-S-MC-ICP-MS) yielded a mean 176Hf/177Hf of 0.282854 +/- 0.000023 (2s, n = 15), with a correlation to 176Lu/177Hf that corresponds to radiogenic ingrowth since ca. 483 Ma. If analyses are back-calculated to the crystallisation age, the CA-S-MC-ICP-MS data yield a 176Hf/177Hf(t) of 0.282805 +/- 0.000010 (2s), which we recommend be used as the reference ratio for Grey Hill zircon. Non-abraded, in situ LA-MC-ICP-MS analyses yielded results consistent with the CA-S-MC-ICP-MS mean. Importantly, LA-MC-ICP-MS analyses do not show any correlation with HREE, and there is no apparent difference in measured 176Hf/177Hf between pristine and altered domains. The grains have 176Yb/177Hf (0.094-0.48) and 176Lu/177Hf (0.0028-0.014) ratios that are much higher than all commonly used natural reference materials. Thus, Grey Hill zircon is a useful natural reference material for LA-MC-ICP-MS Hf isotope measurement to guarantee accurate isobaric interference correction across the full spectrum of naturally occurring zircon grains. Grey Hill zircon concentrates can be requested from the authors.

Monazite and zircon grains from the ultra-high temperature (UHT) granulite of the Andriamena unit in the centre north of Madagascar, previously investigated using micro-drilled single grain isotopic dissolution geochronology and in-situ electron microprobe chemical dating by Paquette et al. (2004), are reinvestigated using high spatial resolution techniques: atom probe tomography (APT), transmission electron microscopy (TEM), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and secondary ion mass spectrometry (SIMS). The dated grains are located in quartz, garnet belonging to the peak UHT metamorphic assemblage and in retrograde coronitic texture composed of biotite, cordierite and orthoamphibole. Monazite grains show complex discordant trends with several radiogenic Pb (Pb*) loss dispersions, that were previously interpreted as recording at least four geologic episodes occurring from the Archean (~2.7 Ga) to the Proterozoic-Cambrian (~0.5 Ga). Multiscale investigations with SIMS, TEM and APT have been carried out on monazite and LA-ICP-MS on zircon. Zircon grains hosted in garnet and those in quartz record concordant ages at 2758 ±28 Ma and 2609 ±51 Ma, respectively. Monazite grains show age dispersion and a Pb*-loss trend correlated with the grain petrographic position. Grains located in garnet and quartz present less Pb*-loss than those located in the coronitic texture. The discordia indicates a crystallisation age at 2555 ±71 Ma and monazite grains hosted in quartz and garnet record a disturbance event at 1053 ±246 Ma. TEM investigations show that monazite located in quartz and garnet contain numerous Pb-bearing nanophases compared to monazite located in coronitic texture. There is an inverse correlation between the number of Pb-bearing nanophases and the percentage of Pb*-loss in monazite grains. 232Th/208Pb ratio obtained with APT in monazite matrix (i.e. excluding Pb-bearing nanophases) located in quartz and garnet indicated a mean age of 1092 ±127 Ma. This date is interpreted as a hitherto undetected geochronological record in Andriamena unit.

Samples returned from the carbonaceous asteroid (162173) Ryugu by the Hayabusa2 mission revealed that Ryugu is composed of materials consistent with CI chondrites and some types of space weathering. We report detailed mineralogy of the fine-grained Ryugu samples allocated to our "Sand" team and report additional space weathering features found on the grains. The dominant mineralogy is composed of a fine-grained mixture of Mg-rich saponite and serpentine, magnetite, pyrrhotite, pentlandite, dolomite, and Fe-bearing magnesite. These grains have mineralogy comparable to that of CI chondrites, showing severe aqueous alteration but lacking ferrihydrite and sulfate. These results are similar to previous works on large Ryugu grains. In addition to the major minerals, we also find many minerals that are rare or have not been reported among CI chondrites. Accessory minerals identified are hydroxyapatite, Mg-Na phosphate, olivine, low-Ca pyroxene, Mg-Al spinel, chromite, manganochromite, eskolaite, ilmenite, cubanite, polydymite, transjordanite, schreibersite, calcite, moissanite, and poorly crystalline phyllosilicate. We also show scanning transmission electron microscope and scanning electron microscope compositional maps and images of some space-weathered grains and severely heated and melted grains. Although our mineralogical results are consistent with that of millimeter-sized grains, the fine-grained fraction is best suited to investigate impact-induced space weathering.