Quartz Structure Research Articles

Study of the sensitivity of ZrO2 and ZnO layers electrochemically deposited on a quartz resonator

A study is presented on the sensitivity of electrochemically deposited ZrO2 and ZnO on a quartz resonator. The nanostructured ZrO2 and ZnO layers are deposited by electrochemical method on the Au electrodes of the quartz resonators. The deposition of the electrochemical layers of ZrO2 and ZnO is carried out in aqueous solution of (ZrOCl2 (5. 10-3 M) and KCl (0.1 M) for ZrO2 and (ZnCl2 (5. 10-3 M) and KCl (0.1 M) for ZnO) at 70°C and (vs SCE) using a three-electrode electrochemical cell. The structure of the ZrO2 and ZnO layers deposited on the polished surface of quartz resonator is studied by Scanning Electron Microscopy (SEM) and optical profilometry. The influence of the roughness on the ZrO2 and ZnO sorption properties is investigated. The sorption ability of the ZrO2 and ZnO layers is defined by measuring the resonant frequency shift (ΔF) of the quartz structure in the presence of different concentration of methanol, ethanol and ammonia (0 - 25000 ppm).

Petrological, geochemical, and microfacies analysis of the Sylhet limestone, Bengal Basin, Bangladesh: implication for depositional environment and diagenesis

The fossiliferous Sylhet limestone formation of the Eocene age in the Bengal Basin is important for scientific and geoheritage study. This formation is exposed in the two locations of Bengal Basin; however, it is least studied. In this study, petrological, geochemical, and microfacies analysis of the Sylhet limestone was carried out by analyzing twenty-eight (28) samples from the two exposed sections and two underground (boreholes) in the Bengal Basin. The microscopic and XRD analysis shows that the calcite is the most dominant mineral in the studied samples along with some amount of dolomite, siderite, ankerite, pyrite, and quartz. The presence of the crystal structure of calcite, dolomite, quartz, and pyrite was confirmed through SEM-EDX. Geochemical results show that the samples are composed of high CaO (14.296 to 53.326%) with a significant amount of Fe2O3 (0.095 to 18.482%), Al2O3 (0.664 to 7.357%), K20 (0.83 to 2.274%), MgO (0.157 to 8.109%), and SiO2 (0.08 to 0.451%). Beside the major oxides, some minor and trace elements including Sr, Mn, Zr, Zn, Sc, Co, V, Ba, Ni, and Cu were also measured. Among these, Sr, V, Mn, and Cu concentration within the Sylhet limestone directly indicates its depositional environment at a shallow continental shelf in open marine condition and its diagenetic change to convert as dolomitic limestone. Geochemical characteristics indicate that the Sylhet limestone is highly dolomitized with high Ca/Mg ratio and was deposited in a low-energy shallow continental shelf marine depositional environment. Higher values of the Ca/Mg ratio of the studied samples also confirm lower salinity during its deposition. The presence of silica in the limestone was observed with a positive/negative correlation with Ca which implies that the silica is derived either from a terrestrial source due to increases of sediment supply during the Middle Eocene for the consequences of the Indo-Asian plate Himalayan Collision or dissolution from the siliceous shells of fossils that replace the calcite. Eight (08) microfacies (MFT) types were identified based on abundance of foraminifera or calcareous algae (e.g., Nummulites sp., Discocyclina sp., Alveolina sp., Quinqueloculina sp., Cibicides sp., Lenticulina sp., Ovulites sp.) which are similar to grainstone/packstone carbonate of 18 standard microfacies types (SMF 18). The observed SMF was deposited under restricted to open marine carbonate platform of shallow water depth at different hydrodynamic conditions.

Microstructural Analysis of Changes in the Morphology of Quartz Raw Materials of Different Genesis at Dry Milling

The influence of the genesis of quartz-containing rocks on the strength of particles and changes in morphology during destruction from the standpoint of the mineralogical approach in the development of the scientific direction "geonics" ("geomimetics") has been investigated. The kinetics of dry grinding of raw materials in a laboratory ball roller mill was carried out. The features of the formation and development of cracks, particle size distribution, changes in the morphology and microstructure of fragments have been studied. It was found that in natural quartz cracks develop along the surface, where the highest concentration of impurities creates a defect structure with destruction into small particles. The purest structure of hydrothermal quartz is susceptible to brittle fracture into fragments similar in morphology to the base particle. Reducing the defectiveness of the structure increases the strength of the crystals. The internal energy potential of techno genic raw materials is determined by its defective structure, which undergoes the greatest deformations during grinding, allowing obtaining the maximum values of the specific surface area and reduce the grinding time. A difference in the degree of crystallinity of quartz, which composes the polymineral techno genic raw materials, makes it possible to obtain the optimal granulometry of fine particles. The conducted research is aimed at identifying the mechanisms of destruction of quartz rocks and can be used in solving engineering problems not only in construction materials science, but also in geotechnics.

Application of ATR-FTIR spectroscopy in tandem with chemometrics for assessing the firing conditions of Hellenistic and Roman ceramic shards excavated from the ancient city of Stratonikeia in South-Western Turkey

The use of attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectra combined with chemometrics were tested to assess the firing conditions of the shard samples excavated from the ancient city of Stratonikeia. Totally thirty-six principal component analysis (PCA) models were compared according to their ability to classify fifty-five shard samples. The PCA model using normal FTIR spectra ranged between 825 and 400 cm−1 with 25 smoothing points showed the best classification results by dividing the shard samples into five different groups (A, B, C, D, E) based on their different spectral information. To determine the firing conditions and the mineralogical compositions of the shard groups, the second-derivative ATR-FTIR spectra (two polynomial degrees and 11 smoothing points of Savitzky-Golay) between 1700 and 400 cm−1 was successfully used. It was determined that the minerals of pseudo-amorphous structure of meta-smectite, quartz, muscovite, gehlenite, and gypsum were the main phases in the shard samples fired in the oxidizing atmospheric conditions. The obtained findings indicate that the firing temperature is about 800–950 °C and 600–800 °C for the shard groups of A, B, C, and D and E, respectively.

Mineralogy and Geochemistry of Agates from Paleoproterozoic Volcanic Rocks of the Karelian Craton, Southeast Fennoscandia (Russia)

Agates of Paleoproterozoic volcanics (2100−1920 Ma) within the Onega Basin (Karelian Craton, Southeast Fennoscandia) were studied using optical and scanning electron microscopy, X-ray powder diffraction, X-ray fluorescence spectrometry XRF, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and C-O isotope analysis. Agate mineralization is widespread in the lavas gas vesicles, inter-pillow space of basalts, picrobasalts, basaltic andesites, as well as agglomerate tuffs. Agates are characterized by fine and coarse banding concentric zoning; moss, spotted, veinlet, and poor-fancy texture types were identified. Agate mineralization is represented by silicates, oxides, and hydroxides, carbonates, phosphates, sulfides, and sulfates. Among the silica minerals in agates only chalcedony, quartz and quartzine were found. The parameters of the quartz structure according to the X-ray diffraction data (well-develops reflections (212), (203), (301), large crystallite sizes (Cs 710–1050 Å) and crystallinity index (CI 7.8–10.3) give evidence of multi-stage silica minerals recrystallization due to a metamorphic (thermal) effect. The decreasing trend of trace element concentration in the banded agates from the outer zone to the core suggests a chemical purification process during crystallization. C-O isotope characteristic of agate-associated calcite reflects primary magmatic origin with the influence of hydrothermal activity and/or low-thermal meteoric fluids. Agates were formed under low PT-parameters and related to hydrothermal activity on the first stage of Svecofenian orogeny within 1780−1730 Ma. Thus, it can be believed that the temporal gap between continental flood basalts outflow and agate formation is about 190 Ma.

Quartz metastability at high pressure: what new can we learn from polarized Raman spectroscopy?

The pressure dependence of the polarized Raman scattering of quartz was studied under hydrostatic conditions up to 9 GPa. We extended the available pressure calibrations, usually limited to the two most intense peaks, to a larger number of modes, providing polynomial functions that describe the relationship between pressure P and wavenumber shift $$\Delta \omega$$ for the 128-, 206-, 265-, 464-, 696-, 809-, 1080- and 1161- $$\hbox {cm}^{-1}$$ modes. For the first time, the pressure behavior of the LO-TO splitting is characterized up to 9 GPa under hydrostatic conditions. The pressure-induced wavenumber changes and derived phonon compressibilities show that longitudinal and transverse modes can be used interchangeably for the calculation of strains through the Gruneisen tensor to derive the strains in crystals, such as mineral inclusions, under non-hydrostatic conditions. A careful examination of the linewidths as a function of pressure shows that they are sensitive to the metastability of the quartz structure with respect to the high-pressure silica polymorphs. It is proposed that strong multiphonon interactions contribute to the stability of the structure of quartz at ambient conditions.

Luminescent properties of Eu3+-doped silica nanophosphors derived from rice husk

Rice husk nanosilica (RH-SiO2) doped with europium (RH-SiO2: Eu3+) was produced by the sol-gel method. X-ray Diffraction patterns show amorphous silica with increased crystallinity as the concentration of Eu increases. Phase transformation occurred with the addition of Eu3+ ion due to the presence of oxygen vacancy as well as strain in the lattice imposed by the larger size of the dopant ion in the lattice. The quartz structure emerged at a relative low concentration (1 mol%) and increased with Eu3+ content and at 3 mol% doping, the cristabolite phase emerged. No Eu3+ phase was observed. Scanning Electron Microscopy review agglomerates of nano-sized particles and Transmission Electron Microscopy show dispersed spherical nanoparticles measuring an average size of 35 nm. Fourier Transform Infra-red spectroscopy confirms the presence of SiO2. The surface area of the nanophosphor measured by Brunauer-Emmett-Teller is 189.64 m2/g. Photoluminescence (PL) analysis shows Eu3+ ion transitions leading to red emission. The asymmetry ratio and Judd-Ofelt intensity parameters indicate a low symmetry environment for the Eu3+ in the RH-SiO2 nanophosphors. The Ω2 values increase with increasing Eu3+ concentration, suggesting an increase in structural deformation or transformation of SiO2. The International Commission on Illumination (CIE) chromaticity coordinates values are close to the national television standard committee (NTSC) standards for red phosphors, which confirms the suitability of these red nanophosphors for display applications.

Influence of crystal structure on constitutive anisotropy of silica sand at particle-scale

In spite of recent advanced geotechnical research regarding the influence of particle-scale morphology and fabric on the constitutive behavior of silica sands, there is still no published literature that investigated the influence of crystal structure of sand particles on their constitutive behavior. The main constituent of silica sand particles is quartz mineral, which has a trigonal crystal system and hexagonal lattice. This paper investigates the influence of quartz crystal structure on the constitutive response of silica sand particles using 3D X-ray diffraction (3DXRD), synchrotron micro-computed tomography (SMT), and 3D finite element (FE) analysis. Unconfined uniaxial compression experiments on single particles of synthetic silica cubes exposed the notion of constitutive anisotropy caused by the crystal structure of quartz. Since the silica cubes have simple regular geometry 1mm3, they were loaded in different directions with respect to their crystal local planes. The crystal structure was also identified for a natural silica sand specimen composed of 2705 particles and loaded in confined uniaxial compression. Physical limitations of the experimental measurements made a strong case for the use of 3D FE analysis to study how the change in crystal local orientation of individual sand particles can fundamentally produce anisotropy in the constitutive response of natural sand specimens. The 3D FE analysis was validated to accurately model the crystal-based constitutive anisotropy in silica particles using the results of the silica cube experiments. The analysis was then executed on 3D FE meshes that closely matched the physical shape and fabric of the 2705 particles in the natural sand specimen. Both the experiments and 3D FE analysis showed that the crystal structure of quartz essentially causes a directional anisotropy in the constitutive behavior of silica particles.

Molecular simulation and microtextural characterization of quartz dissolution in sodium hydroxide

This study uses empirical experimental evidence and Material Studio simulations to explain the interaction of sodium hydroxide (NaOH) with quartz. Density functional theory (DFT) calculations were carried out using the Cambridge Serial Total Energy Package. In addition, quartz grains subjected to dissolution in NaOH were characterized using scanning electron microscopy. The so-called O-middle termination in the quartz tetrahedron structure, typified by a solitary exposed oxygen atom at the surface, is the most susceptible SiO2 terminations to NaOH attack, as it is associated with the lowest surface energy. The adsorption energy values are − 1.44 kcal/mol and − 5.90 kcal/mol for a single atom layer and five-layered atomic structure, respectively. The DFT calculation reveals intramolecular energy is the dominant adsorption energy, followed by a weak van der Waals energy. The NaOH adsorbed on quartz (001) surface constitutes a lower band gap of 0.138 eV compared to cleaved quartz (001) surface (0.157 eV). In addition, the energy range of NaOH adsorbed on quartz is wider (− 50 to 10 eV), compared to (001) quartz (− 20 to 11 eV). The dissolved quartz showed the precipitation of sorbed silicate phases due to incongruent reactions, which indicates new voids and etch pits can be created through the cleaving of the sodium silicates sorbed into the quartz surface. The adsorption energy for NaOH interactions with reservoir sandstone was significantly higher compared to the solitary crystal grains, which can be attributed to the isotropic deformation of a single crystal, and non-uniform deformations of adjacent grains in granular quartz of sandstone reservoir. It can be inferred that exposure to NaOH will affect the structure and reactivity of quartz. The quartz surface textural study indicates that dissolution of crystalline (granite) and clastic rocks (sandstone) is critical to the development of voids, which will improve permeability by providing channels and routes for the passage of hydrothermal and reservoir fluids.

Using mechanical activation of quartz to enhance the compressive strength of metakaolin based geopolymers

The present work synthesized geopolymer with quartz mechanical activated at different time, and the strengthening mechanism of geopolymer by activated quartz was investigated. The changes of quartz before and after activation and the microstructure of geopolymer was explained by the determinations of particle size, specific surface area and the concentration of reactive Si, as well as XRD, XPS and NMR measurement. With the activation time of quartz increasing from 0 to 60 min, the compressive strength of geopolymer increased from 31.5 to 55.2 MPa. The results showed that increase of quartz reactivity is mainly due to the formation of the Si-centered radicals and non-bridging oxygen on the surface rather than the changes in physical property or crystal structure of quartz. The high activity tetrahedra Si with non-bridge oxygen on the surface of quartz replace the tetrahedra Al in geopolymer gel, which lead to a Si-rich gel formed around quartz and the improvement of compressive strength.

Research on a Micro-Processing Technology for Fabricating Complex Structures in Single-Crystal Quartz.

Single-crystal quartz material is widely applied in the manufacture of resonators and sensors, but it is difficult to process because of its high hardness. A novel way to fabricate single-crystal quartz structures is proposed in this paper; the method includes quartz-on-silicon (QoS) technology and inductively coupled plasma (ICP) etching, which makes it feasible to fabricate complex structures with crystal quartz. The QoS method encompasses the bonding of silicon and quartz, followed by the thinning and polishing of quartz, which can enable the fabrication of an ultra-thin quartz wafer on silicon. In this way, instead of the conventional wet etching with hydrofluoric acid, the quartz layer can be easily etched using the ICP dry-etching method. Then, the structure of the pure quartz material is obtained by removing the silicon wafer. In addition, the silicon layer can be processed into the appropriate structure. This aspect overcomes the difficulty of processing a complex structure of single-crystal quartz with different crystal orientations. Thin single-crystal quartz wafers of Z-cut with a thickness of less than 40 μm were obtained by using this method, and a complex three-dimensional structure with an 80 μm width was also acquired by the ICP etching of the quartz wafer. The method can be applied to make both crystal-oriented quartz-based sensors and actuators, such as quartz resonant accelerometers.

Impact of surface complexation and electrostatic interactions on pH front propagation in silica porous media

The coupled effects of pH and ionic strength impact a variety of geochemical processes in the subsurface. In this study, we investigate the interactions of H+ and major ions at the surface-solution interface of silica porous media under advection-dominated flow-through conditions. A series of 21 column experiments were performed by systematically injecting solutions of different pH and ionic strengths. Three types of porous media (i.e., two natural sands and quartz beads) were considered in order to explore differences in surface/solution interactions among quartz materials. Multiple lines of evidence were used to characterize the geochemical processes taking place during the flow-through experiments: (i) breakthrough curves of pH and major ions were measured at the column outlets; (ii) the natural sand surfaces were characterized by chemical extractions and scanning electron microscopy and the quartz structure was analyzed by XRD; (iii) reactive transport modeling was performed to quantitatively interpret the experimental results.We observed strong reactivity of the quartz surface characterized by significant release of protons when interacting with the major ions. The results also show significant differences in the quantity of protons emitted from the surfaces of the three silica porous media, as well as in the shape of the pH breakthrough curves. Reactive transport modeling was based on a multicomponent ionic transport formulation and on surface complexation description of the solid/solution interactions. The surface complexation model included the individual contributions of quartz and Fe/Al oxides present in the sand coatings with the component additive approach. For each medium, a single set of surface complexation parameters capable of reproducing the experimental dataset (i.e., 7 columns) was calibrated by parallelizing the simulations of the flow-through experiments. This approach allowed us to capture the pH and ionic species behavior within a large range of ionic strengths (i.e., [0–100] mM). The SCMs quantitatively show that H+ is released from quartz upon adsorption of Na+ and that the protonation of the oxides surfaces retards the pH front. Differences in acidity behavior between the silica surfaces seem to be primarily controlled by differences in surface topology, crystal structure of quartz and/or various presence of aluminosilicates. This study demonstrates that the reactivity and diversity of quartz surfaces in silica porous media and the complex interplay with oxide surfaces in the coatings control the transport of aqueous charged species in flow-through systems.

Adsorption of gold cyanide on quartz

The adsorption of gold cyanide onto the surface of quartz (101) is discussed based on experimentation combined with quantum chemistry calculations. Adsorption tests were conducted by using gold cyanide and quartz power. Atomic absorption, infrared spectroscopy, energy-dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy were used to characterize the elemental content in solution and species adsorbed onto the quartz surface. The adsorption of Au(CN)2− onto the surface of quartz was simulated by using quantum chemical calculations based on density functional theory (DFT) and implemented in the CASTEP module of Materials Studio. The optimal functional quartz structure is obtained with the functional GGA-PBESOL, which gives a k-point set of 3 × 3 × 4 and a cutoff energy of 440 eV. The calculated energy of the adsorption of Au(CN)2− onto the surface of quartz (101) is −463.39 kJ/mol. The calculated Au1-O12 distance is 2.097 Å, and the Au1-O20 distance is 2.079 Å, which indicates that Au(CN)2− adsorbs onto the quartz surface. A Mulliken population analysis indicates that some charge transfer from the Au1 atom of Au(CN)2− to the O12 and O20 atoms in the quartz. A population analysis of the bond indicates that Au atoms bond to O atoms on the quartz surface. Quantum chemistry calculations are consistent with the results of adsorption experiments, which show that Au(CN)2− adsorbs onto the quartz surface. Some gold cyanide is thus adsorbed onto quartz during cyanide leaching of gold ore, which affects the extraction of gold.

A Weak Form Nonlinear Model for Thermal Sensitivity of Love Wave Mode on Layered Structures.

A precise theoretical model for the thermal sensitivity of Love wave mode is significant in the structure design, temperature compensation, and the prediction of thermal behavior. This article proposes a weak form nonlinear model to calculate the thermal sensitivity of Love waves on arbitrary layered structures. The third-order material constants, as well as the thermal stress and strain tensors between the substrate, electrodes, and wave-guiding layer, are considered in the model. The 9 ×9 effective elastic and the 3 ×9 effective piezoelectric matrixes are imported into the nonlinear constitutive equations and boundary conditions using weak form expressions. A temperature-compensated Love wave mode resonator on a layered ZnO/interdigital transducer (IDT)/quartz structure is obtained. The theoretical model is verified through the comparison of experimental and analytical results. The model is beneficial for the design of Love wave devices and sensors.

Diatomite inspired nanostructured quartz as a piezoelectric material

Diatomite continues to fascinate the scientific community with widespread applica tion in the energy sector. However, these applications have not encompassed all energy segments. Herein, we report a soft chemistry approach to synthesize nanostructured quartz from diatomite for piezoelectric applications. The synthesis parameters will be varied to understand the effects on the structure and formation of quartz. Preliminary results confirm that diatomite is a siliceous material with a neat nanoscale morphology. The formation of nanostructured quartz from diatomite will expand the range of applications of diatomite in energy related applications.

Helium diffusion as sine-Gordon kink in disordered quartz structure

Discrete model (local chains approach) reveals the influence of heterogeneity of structure on the movement of a helium atom in the form of a soliton Frenkel-Kontorova. The transition to the field form of this equation - to the Klein-Fock-Gordon equation or, simply, to the sine-Gordon equation, allows us to calculate the diffusion coefficient of such a soliton, taking into account the collective nature of the movement of the atom and the accompanying reversible displacements of the atoms of the environment through the medium in the form of a soliton and taking into account the details of the structure of nanostructures.

EBSD and CL Study of Deformed Quartz Grains in Rocks: An Example for one Strain Fringe Structure From Iron Quadrangle.

Kinematic indicators, including certain strain fringes, represent an important group of structures related to the progressive deformation in rocks. The evolution of these fibrous textures can be explained by the combination of multiple mechanisms of deformation and fluid flow, mainly controlled by the orientation of the strain field and the morphology of the grains. In general, the observations are done with an optical microscope and compared with computational models of growth. This work proposes a combination of crystallographic and cathodoluminescence data obtained in rocks from banded iron formations of the Iron Quadrangle in Brazil to represent an example of how complementary analytical techniques can be useful to understand geological problems. The chosen sample exhibits a strain fringe structure of quartz around a clast of magnetite partially transformed into goethite and hematite. Through the crystallographic data it was possible to identify the grain boundary morphology and domains of low deformation areas. On the other hand, the cathodoluminescence signal evidenced the occurrence of grains with a higher concentration of crystalline defects.

Studying internal structure of quartz by broadband ultrasonic tomography under cyclic compression

The article considers the possibility of studying and identifying defects in the internal structure of synthetic quartz crystals using the parameters of acoustic emission and laser-ultrasound tomography. In the course of cyclic compressive loading, the nature of the propagation of discontinuities in a sample was investigated. It is revealed that the properties of the material, the inhomogeneity of which is associated with the presence of microdefects and anisotropy, change in the initial stages of mechanical load. With repeated application of the load on the sample, previously formed defects cause significant changes in its internal structure. With the help of numerical modeling, the obtained results were verified.

The Xe‐SiO2 System at Moderate Pressure and High Temperature

AbstractXenon (Xe), the heaviest of the stable noble gases, is missing by a factor of 20 relatively to other noble gases, when comparing the Earth's and Mars's atmospheres with chondrites. In this work, the possibility of Xe retention in quartz, a major mineral of the continental crust, is tested. The Xe‐SiO2 system is investigated from 0.7 to 2.7 GPa and up to 1900 K, by in situ X‐ray powder diffraction and infrared spectroscopy. Experimental data are complemented by ab initio calculations to retrieve Xe incorporation mechanisms. An excess of quartz unit cell volume up to 4.2% is observed, consistent with a Xe for Si substitution in the quartz structure. Xe has a linear oxygen environment composed of two O atoms located at 1.98–2.00 Å from the Xe atom. Moreover, a new phase is evidenced above Xe melting curve at 0.8–1.0 GPa. The new (Xe,Si)O2 phase is orthorhombic and corresponds to an elongation of the quartz unit cell. In this phase, Xe substitutes for Si with a nearly planar oxygen environment composed of four O atoms located at 2.06–2.09 Å from the Xe atom. Xe incorporation in SiO2 proves to be significant, as previously shown for olivine. Xe incorporation is therefore expected to occur in the whole range of lithospheric silicate minerals. These findings emphasize the need to consider Xe incorporation in crust and upper mantle minerals as a process to store and fractionate xenon, in the framework of the “missing xenon” issue.

Shocked quartz in polymict impact breccia from the Upper Cretaceous Yallalie impact structure in Western Australia

AbstractYallalie is a ~12 km diameter circular structure located ~200 km north of Perth, Australia. Previous studies have proposed that the buried structure is a complex impact crater based on geophysical data. Allochthonous breccia exposed near the structure has previously been interpreted as proximal impact ejecta; however, no diagnostic indicators of shock metamorphism have been found. Here we report multiple (27) shocked quartz grains containing planar fractures (PFs) and planar deformation features (PDFs) in the breccia. The PFs occur in up to five sets per grain, while the PDFs occur in up to four sets per grain. Universal stage measurements of all 27 shocked quartz grains confirms that the planar microstructures occur in known crystallographic orientations in quartz corresponding to shock compression from 5 to 20 GPa. Proximity to the buried structure (~4 km) and occurrence of shocked quartz indicates that the breccia represents either primary or reworked ejecta. Ejecta distribution simulated using iSALE hydrocode predicts the same distribution of shock levels at the site as those found in the breccia, which supports a primary ejecta interpretation, although local reworking cannot be excluded. The Yallalie impact event is stratigraphically constrained to have occurred in the interval from 89.8 to 83.6 Ma based on the occurrence of Coniacian clasts in the breccia and undisturbed overlying Santonian to Campanian sedimentary rocks. Yallalie is thus the first confirmed Upper Cretaceous impact structure in Australia.