Understanding the formation of high metamorphic grade sequences from Archean Cratons is necessary for modelling Craton formation and evolution. In this study, we undertake a detailed review of the 1.28 Moz Au Katanning Gold Deposit granulite-facies host sequence, located in the southwestern Yilgarn Craton, Western Australia. To elucidate the nature of this granulite-facies gold deposit, a detailed geochemical, petrographic, and geochronological investigation was undertaken of its host gneissic sequence to establish a petrogenetic model of its formation. The high-grade metamorphic rocks that host gold mineralisation at the Katanning Gold Deposit can be divided into nine major lithological associations. These rocks are interpreted as mafic to felsic protoliths resembling modern BADR sequences which is consistent with extensional magmatism in a back arc setting. Zircon U-Pb dating yielded magmatic ages of a felsic and mafic gneiss at 2711 +/- 4 Ma and 2703 +/- 3 Ma, respectively, which are contemporaneous with the latest Archean volcanic events in the western Yilgarn Craton. The U-Pb ages of metamorphic zircon across four samples yielded a combined age of 2651 +/- 2 Ma, interpreted as the time of peak metamorphic conditions of similar to 700-900 degrees C and similar to 5-7 kbar for the entire sequence. Indicating rapid (c. 30 Myr) burial, marked by the maximum depositional age of a metasedimentary gneiss (2683 +/- 8 Ma) to granulite facies metamorphism, potentially implicating inversion of a closed back arc rift. This study provides a regional context for tectonic evolution of the southwestern Yilgarn Craton, reflecting on the role of high-grade metamorphism in Archean Cratons, and serves as a rare, detailed investigation into a large granulite-facies gold deposit.

Despite renewed interest in the energy resources of the Perth Basin, rift propagation, the evolution of fault activity and depocentre development along the Western Australian margin during rifting of East Gondwana are not well established. Rifting resulted in a series of predominantly NNW-SSE trending graben and half-graben extending from the Southern Carnarvon Basin in the north, through to the Perth Basin in the south. Gravity and magnetic data indicate two regions of greater structural complexity along this margin, with the northern of these regions data-poor. We investigate the more southerly region, commonly referred to as the northern Perth Basin, a Paleozoic to Mesozoic depocentre that developed through multiple phases of extension with variable extension directions, recording intracontinental rifting and eventual break-up of Australia and Greater India as part of the East Gondwana interior rift. Recently acquired seismic surveys that better image the pre-Mesozoic stratigraphy, together with legacy seismic and well data, have been utilised to create composite sections perpendicular and parallel to the rift axis. These composite sections reveal a progressive southward shift in fault activity and depocentres from the late Carboniferous through to the Early Cretaceous and that towards the south, many of the N-S trending fault segments previously thought to be active during the Cisuralian (early Permian) initiate much later in the Jurassic or Cretaceous. By contrast, E-W trending faults in the north of the basin, which formed perpendicular or at high angles to the rift axis, become throughgoing faults during the Late Triassic to Early Jurassic. Ultimately, these new interpretations provide evidence for episodic propagation of the rift system toward the south.

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.

We have discovered a presolar olivine from ALH 77307 with the highest ^25 Mg isotopic composition measured in a silicate to date ( δ ^25 Mg = 3025.1‰ ± 38.3‰). Its isotopic compositions challenge current stellar models, with modeling of magnesium, silicon, and oxygen showing a closest match to formation in a supernova (SN) where hydrogen ingestion occurred in the pre-SN phase. Presolar grains within primitive astromaterials retain records of processes and environmental changes throughout stellar evolution. However, accessing these records has proved challenging due to the average grain size (∼150 nm) of presolar silicates, their sensitivity to extraction agents, and instrumental restrictions, limiting the range of isotopic and chemical signatures which can be studied per grain volume. Here, we present the first known detailed geochemical study of a presolar silicate from a hydrogen-burning SN, studied in 3D without contributions to the analysis volume and at unprecedented spatial resolutions (<1 nm), essential for constraining physical and chemical processes occurring within this recently proposed stellar environment. From our results, we infer either (i) condensation within an environment depleted of heavy elements compatible with the olivine lattice under the pressure and temperature conditions during condensation, or (ii) during periods of limited mixing either near the end of the pre-SN phase or from a collapse so rapid localized pockets of different gas compositions formed.

Zircon with granular texture from hypervelocity impact structures can be used to estimate the thermodynamic conditions of impact processes, including pressure and temperature, and in some cases the timing of impact events via U-Pb geochronology. However, two disparate formation models have been proposed to explain the occurrence of zircon neoblasts that preserve systematic orientation relations; one involves zircon-reidite phase transformations (FRIGN zircon), whereas the other features melting and thermal dissociation of zircon in the absence of reidite. Distinguishing between these models is hampered by the lack of observational constraints on the intermediate transformation steps at nanoscale, and what processes give rise to observed systematic orientation relations among zircon neoblasts. Here we report new analyses of reidite-bearing and granular zircons from peak ring core samples of the Chicxulub impact structure using nanoscale methods. We describe lamellar and lense-like reidite habits associated with reidite twins in shocked zircon from impact melt-bearing breccia, along with the first observation of nanoscale zircon granules forming locally within preserved reidite lamellae. The crystallographic orientation of the zircon nano-granules matches the orientations predicted by the FRIGN zircon model, confirming they formed directly by solid-state reversion of reidite to zircon, and represent the earliest stages of the formation of granular zircon. Minor occurrences of baddeleyite at the interface of reidite and neoblastic zircon domains suggest that the reversion of reidite to zircon can occur together with local ZrSiO4 dissociation driven either by the loss of SiO2, which creates excess zirconia, or by local thermal dissociation of reidite. Other partially- and fully-granular zircon grains from the same impact melt-bearing breccia also preserve systematic orientation relationships among zircon neoblasts, consistent with having transformed directly from reidite. The observation that zircon neoblasts maintain systematic orientations from nanoscale to microscale in granular zircon supports the idea that neoblast orientations are encoded at the nucleation stage via solid state phase transformation. Observations in this study provide direct evidence to explain the nature of systematic high-pressure phase transitions involving zircon and have implications for unraveling the pressure-temperature history of zircon phase transitions in large impacts on Earth or other planetary bodies.

The study of Howardite-Eucrite-Diogenite (HED) meteorites provides unique insights into early planet formation and the impact events that shaped the early Solar System. However, unraveling the complex history of the HED parent body (hypothesized to be the asteroid 4 Vesta) from whole-rock samples is challenging since most HEDs are impact-related breccias comprising mixed lithic and mineral fragments that experienced variable deformation and alteration. Combining U-Pb geochronology, trace element geochemistry, and microstructural analysis of zircon can unravel magmatic, metamorphic and impact processes through time to decipher the HED parent body evolution. Here we present textural (EBSD), geochronological (Pb-207/Pb-206 SIMS dating) and geochemical data (Th/U, REE, Ti-in-zircon thermometry) on 61 zircon grains from melt breccia eucrites, unbrecciated/monomict/ polymict eucrites, howardites and diogenites. Diverse textures indicate variable histories of impact deformation and high-temperature recrystallization. Undeformed, fractured zircons preserve primary zoning (CL, Th/U, REE) indicating magmatic and metamorphic origins. At least three magmatic zircon grains (Th/U > 0.3) give( 207)Pb/Pb-206 ages of 4558-4565 Ma, suggesting primary differentiation in the parent body first million years. Twenty metamorphic zircon grains (Th/U < 0.3) date to 4420-4568 Ma, indicating prolonged thermal metamorphism from impact heating and/or crustal cooling. Impact-recrystallized granular zircon grains reveal major impacts during and just after the parent body differentiation (4500-4560 Ma), plus later events potentially linked to synchronous impacts in the Solar System (e.g. the Moon). Similarity of metamorphic and shocked zircon ages (circa 4550-4450 Ma) suggests impacts occurred for >= 100 million years after the parent body formed.

The Apollo 14 and 16 missions returned several samples commonly interpreted as crystalline impact melt, with ages of approximately 3800–3850 Ma. Previous work has suggested that these rocks formed in one or more pre-Imbrium basin forming impact(s). By contrast, recent ages determined for a range of lunar breccias provide compelling evidence that the Imbrium basin was formed at approximately 3920 Ma. Using an approach previously demonstrated in lunar basalts, Pb–Pb isochron ages are determined for two of these proposed impact melt samples (14078: 3848 ± 4 Ma; and 68415: 3834 ± 11 Ma). In the case of 14078, the least radiogenic Pb isotopic compositions measured here are interpreted as representing the initial Pb isotopic composition of the sample. This value indicates derivation from a source (or sources) with high 238U/204Pb ratios (approx. 2400), similar to those predicted for the Apollo 14 high-Al and very high-K basalts. It was not possible to determine an equivalent initial Pb isotopic composition for 68415, but Pb isotope evolution models indicate that the sample would have been derived from lithologies with lower 238U/204Pb source ratios (approx. 1000). In both cases, the samples are interpreted as having been formed by impacts local to the Apollo 14 and Apollo 16 landing sites.

The Ilkurlka structure is an similar to 12 km diameter buried circular aeromagnetic anomaly within the Officer Basin in Western Australia. Prior studies postulated a range of origins, including meteorite impact. We report the presence of pervasive deformation in the first drill cores from the structure. Brecciated sandstone and siltstone contain arrays of quartz grains with concussion fractures and rare shocked quartz grains with planar deformation features (PDF). Universal stage measurements of two quartz grains reveal one grain with PDF parallel to (0001) orientation and three PDF sets parallel to {10 (1) over bar 13}. A second grain contains three PDF sets parallel to {10 (1) over bar3} and one set parallel to {10 (1) over bar 14}. The shocked grains are interpreted to have formed in situ, rather than representing transported detrital shocked grains. These results suggest local shock compression of at least 10 GPa; however, preservation of primary porosity and overall paucity of shocked grains may indicate lower mean shock pressures. (U-Th)/He dating of 58 apatite grains from four samples across both cores shows a dominant age population at similar to 265 Ma and a minor age population at similar to 135 Ma. These dates overlap with regional events and thus do not provide an unambiguous impact age. An upper Carboniferous to lower Permian maximum impact age is provisionally proposed based on inferred missing target rock stratigraphy.

Over the Nullarbor Plain in South Australia, the Desert Fireball Network detected a fireball on the night of June 1, 2019 (7:30 pm local time), and 6 weeks later recovered a single meteorite (42 g) named Arpu Kuilpu. This meteorite was then distributed to a consortium of collaborating institutions to be measured and analyzed by a number of methodologies including SEM-EDS, EPMA, ICP-MS, gamma-ray spectrometry, ideal gas pycnometry, magnetic susceptibility measurement, mu CT, optical microscopy, and accelerator and noble gas mass spectrometry techniques. These analyses revealed that Arpu Kuilpu is an unbrecciated H5 ordinary chondrite, with minimal weathering (W0-1) and minimal shock (S2). The olivine and pyroxene mineral compositions (in mole%) are Fa: 19.2 +/- 0.2 and Fs: 16.8 +/- 0.2, further supporting the H5 type and class. The measured oxygen isotopes are also consistent with an H chondrite (delta O-17 parts per thousand = 2.904 +/- 0.177; delta O-18 parts per thousand = 4.163 +/- 0.336; Delta O-17 parts per thousand = 0.740 +/- 0.002). Ideal gas pycnometry measured bulk and grain densities of 3.66 +/- 0.02 and 3.77 +/- 0.02 g cm(-3), respectively, yielding a porosity of 3.0% +/- 0.7. The magnetic susceptibility of this meteorite is log chi = 5.16 +/- 0.08. The most recent impact-related heating event experienced by Arpu Kuilpu was measured by Ar-40/Ar-39 chronology to be 4467 +/- 16 Ma, while the cosmic ray exposure age is estimated to be between 6 and 8 Ma. The noble gas isotopes, radionuclides, and fireball observations all indicate that Arpu Kuilpu's meteoroid was quite small (maximum radius of 10 cm, though more likely between 1 and 5 cm). Although this meteorite is a rather ordinary ordinary chondrite, its prior orbit resembled that of a Jupiter Family Comet (JFC) further lending support to the assertion that many cm- to m-sized objects on JFC orbits are asteroidal rather than cometary in origin.

Abstract. Mineral hydration is an important geological process that influences the rheology and geochemistry of rocks and the fluid budget of the Earth's crust and mantle. Constant-stress differential compaction (CSDC) tests, dry and “wet” tests under confining pressure, and axial-stress tests were conducted for the first time to investigate the influence of triaxial stress on hydration in anhydrite–gypsum aggregates. Characterization of the samples before and after triaxial experiments was performed with optical and scanning electron microscopy, including energy-dispersive spectroscopy and electron backscatter diffraction mapping. Stress–strain data reveal that samples that underwent constant-stress differential compaction in the presence of fluids are ∼ 14 % to ∼ 41 % weaker than samples deformed under wet conditions. The microstructural analysis shows that there is a strong temporal and spatial connection between the geometry, distribution, and evolution of fractures and hydration products. The increasing reaction surface area in combination with pre-existing gypsum in a gypsum-bearing anhydrite rock led to rapid gypsification. The crystallographic orientations of newly formed vein gypsum have a systematic preferred orientation for long distances along veins, beyond the grain boundaries of wall-rock anhydrite. Gypsum crystallographic orientations in {100} and {010} are systematically and preferentially aligned parallel to the direction of maximum shear stress (45∘ to σ1). Gypsum is also not always topotactically linked to the wall-rock anhydrite in the immediate vicinity. This study proposes that the selective inheritance of crystal orientations from favourably oriented wall-rock anhydrite grains for the minimization of free energy for nucleation under stress leads to the systematic preferred orientation of large, new gypsum grains. A sequence is suggested for hydration under stress that requires the development of fractures accompanied by localized hydration. Hydration along fractures with a range of apertures up to 120 µm occurred in under 6 h. Once formed, gypsum-filled veins represent weak surfaces and are the locations of further shear fracturing, brecciation, and eventual brittle failure. These findings imply that non-hydrostatic stress has a significant influence on hydration rates and subsequent mechanical strength of rocks. This phenomenon is applicable across a wide range of geological environments in the Earth's crust and upper mantle.

Rubble piles asteroids consist of reassembled fragments from shattered monolithic asteroids and are much more abundant than previously thought in the solar system. Although monolithic asteroids that are a kilometer in diameter have been predicted to have a lifespan of few 100 million years, it is currently not known how durable rubble pile asteroids are. Here, we show that rubble pile asteroids can survive ambient solar system bombardment processes for extremely long periods and potentially 10 times longer than their monolith counterparts. We studied three regolith dust particles recovered by the Hayabusa space probe from the rubble pile asteroid 25143 Itokawa using electron backscatter diffraction, time-of-flight secondary ion mass spectrometry, atom probe tomography, and 40 Ar/ 39 Ar dating techniques. Our results show that the particles have only been affected by shock pressure of ca. 5 to 15 GPa. Two particles have 40 Ar/ 39 Ar ages of 4,219 ± 35 and 4,149 ± 41 My and when combined with thermal and diffusion models; these results constrain the formation age of the rubble pile structure to ≥4.2 billion years ago. Such a long survival time for an asteroid is attributed to the shock-absorbent nature of rubble pile material and suggests that rubble piles are hard to destroy once they are created. Our results suggest that rubble piles are probably more abundant in the asteroid belt than previously thought and provide constrain to help develop mitigation strategies to prevent asteroid collisions with Earth.

Hypervelocity impacts throughout Earth's history have profoundly affected the evolution of the continental crust. Accessory minerals like zircon are typically used to date impact events and rock-forming minerals like quartz are routinely used as shock barometers. However, feldspar group minerals – a major constituent of most crustal rocks – are generally underutilized in the documentation of impact-induced deformation and alteration. Alkali feldspar contains appreciable amounts of Pb and analysis of Pb isotopes in feldspar may offer the opportunity to identify impact-related isotopic modifications of shocked crustal target rocks and estimate their timing. Here, we apply a combination of laser ablation inductively coupled plasma (LA-ICP) and thermal ionization mass spectrometry (TIMS) Pb isotope analysis with imaging techniques, including electron backscatter diffraction (EBSD), cathodoluminescence (CL), and time of flight secondary ion mass spectrometry (ToF-SIMS), to shocked alkali feldspar from monzogranite in the oldest confirmed terrestrial impact structure (2229 ± 5 Ma) at Yarrabubba, Western Australia. Alkali feldspar preserves microstructures such as sub-planar and irregular fractures, sets of planar deformation bands that accommodate misorientations of up to ∼20°, sets of damage lamellae, and broad domains of lattice damage that can be linked to impact-related deformation. The Pb isotope compositions in alkali feldspar correlate with variations in electron diffraction band contrast – a proxy for crystallinity – and also the degree of misorientation and CL response. Less damaged alkali feldspar yields Pb model ages similar to the igneous zircon U–Pb crystallization age of the host monzogranite (∼2650 Ma), whereas younger Pb model ages correspond to zones of damage (high relative misorientation, low crystallinity, weak CL response). The observed Pb isotope behaviour implies radiogenic ingrowth of Pb, from decay of U and Th within damaged alkali feldspar, and therefore mixing with a grain-scale Pb reservoir that formed at the time of impact. The U and Th zonation in some shock-deformed alkali feldspar is broadly similar and follows the orientation of sub-planar fractures and damage lamellae. Detailed imaging reveals the zones of U and Th enrichment are associated with trains of monazite micro-inclusions, in conjunction with magnetite and/or hematite in places, which are inferred to have precipitated during impact-induced hydrothermal circulation. Hence, the Pb isotopic data record grain-scale hydrothermal alteration in superficially weakly altered monzogranite target rocks.

One of the most impassioned topics in large igneous province (LIP) research is how prolonged the duration of these large-scale magmatic events are, as LIP magmatism has considerable impact on models of associated reconstructions, of climate variability or tectonic events. High-precision geochronology is pivotal to LIP basalt emplacement rate, and thus to unravel the role these enormous magmatic events have throughout Earths geological and environmental history. Four high-precision 40Ar/39Ar plagioclase plateau ages for the Tasmanian dolerites (Ferrar) indicate ∼1.6 ± 0.4 Ma of resolvable, continuous magmatic activity; 184.27 ± 0.24 to 182.69 ± 0.54 Ma (2σ). The 40Ar/39Ar results provide evidence of distinctly older intrusions and a more prolonged duration than the observed 182.4-182.9 Ma age range and duration indicated by the main zircon record. Moreover, the precision of our 40Ar/39Ar results coupled with secondary electron microscopy analyses provide evidence of plagioclase crystal inheritance from slightly older magmatism entrained into younger magmatic pulses by exploiting pre-existing conduits. Numerical diffusion models, calculated for a theoretical age spectrum resulting from two slightly different plagioclase ages, provide an excellent match for measured data. Coupling geochemical data to the new age data indicates a silica and incompatible element evolution of the Ferrar magmatic system through time. The older generation of intrusions (ca. Zr: 92 ppm, SiO2: 53.67 wt.%) are seemingly less enriched in incompatible elements and silica than the youngest generation (ca. Zr: 147 ppm, SiO2: 56.5 wt.%). Here, we suggest that the magma chambers differentiated to more incompatible/silica-rich compositions saturating zircon only at evolved magmatic stages. This implies that plagioclase dates the full duration of magmatic Ferrar LIP activity of ca. 1.6 Myrs whilst zircon ages might be naturally biased and restricted to post-Zr saturation stage. The extended duration of Ferrar magmatism indicates that it is coeval with the Pliensbachian-Toarcian boundary. Therefore, we speculate that Ferrar (±Karoo) magmatism triggered the Pliensbachian-Toarcian extinction event and contributed to the Toarcian oceanic anoxic event, from which the environment did not begin to recover until only after the waning and cessation of Ferrar magmatic activity at ∼182 Ma, with zircon crystals recording the final flux of magma.

Lead isotopes are a powerful and versatile tool to elucidate fundamental geological problems related to the formation and evolution of continental crust. K‐feldspar is a popular target for Pb isotope measurement as it is prevalent in many rock types and tends to capture the initial Pb isotope composition of its parental magma. We present data for a new Pb isotope reference material: Albany K‐feldspar; as well as updated data for Shap K‐feldspar. Results of Pb double‐spike TIMS for Albany K‐feldspar are 206 Pb/ 204 Pb = 16.7872 ± 0.0062, 207 Pb/ 204 Pb = 15.5640 ± 0.0056, and 208 Pb/ 204 Pb = 36.6600 ± 0.0168 (2 s ). TIMS measurement results for Shap K‐feldspar indicate two isotopically distinct Pb populations. LA‐MC‐ICP‐MS, with a spatial resolution as high as 15 μm, indicates a homogeneous Pb isotopic composition in Albany K‐feldspar. In accord with previous studies, our results show that scatter in the measured Pb isotope ratios, related to the low natural isotopic abundance of 204 Pb, along with the effect of isobaric 204 Hg‐ 204 Pb interference, increases at lower count rates. However, the mean Pb isotope ratios measured via LA‐MC‐ICP‐MS using a range of spot sizes are in excellent agreement with TIMS results thus highlighting the feasibility of Pb isotope determination via LA‐MC‐ICP‐MS to access geological information preserved in small crystals, including mineral inclusions.

A quantitative understanding of grain shape preferred orientation (SPO) and grain boundary networks as fundamental characteristics of rocks and other crystalline solids is of major interest in geology and material science. Grain boundary networks contain useful information on the deformation history of polycrystalline aggregates, and their diagenetic and metamorphic histories. SPO can have a major impact on material characteristics such as permeability, acoustic velocity and mechanical strength, and on reaction surfaces. The objective of this study is to present a semi-automated toolbox of MATLAB™ scripts, named Grain Boundary Pattern Quantification (GBPaQ), that incorporate different methods for grain boundary pattern quantification for their application to, for example, seismic wave attenuation estimation. GBPaQ uses grain boundary statistics and calculates radial scan line intercepts. In this paper, GBPaQ is tested on two example grain boundary patterns, a granular texture and a foam texture with equant grains, which have been digitally stretched (deformed) to analyse their SPO evolution. The results show that a combination of grain ellipse, grain boundary segment orientation, and grain boundary segment intercept density rose diagrams provide a complete, detailed quantification of grain boundary pattern anisotropy. Grain boundary segment intercept (GBSI) analysis using GBPaQ yields a new grain boundary network parameter – the minimum intensity of grain boundary intercepts (Imin) – which follows a power law relationship with the average axial ratio of grain-fitted ellipses (r) during SPO development. We propose that Imin can be used for the quantitative analysis of SPO strength as a useful tool to assess the deformation history of polycrystalline aggregates. Further studies involving a broader range of different patterns and strain histories are necessary to fully investigate the potential of Imin versus r diagrams.