Hasil untuk "Mineralogy"

D. Hillel, J. Hatfield

Lélia Libon, Alessandra Ravasio, Silvia Pandolfi et al.

FeO (wüstite), which exhibits complex electronic and structural properties with increasing pressure and temperature, is a key mineralogical phase for understanding deep planetary interiors. However, direct measurements of its spin state at high-pressure and temperature remain challenging in static compression experiments. Here, we employ laser-driven shock compression to extend the FeO principal Hugoniot up to $\sim$900 GPa and perform in situ X-ray diffraction and X-ray emission spectroscopy up to 250 GPa, probing FeO's crystal structure and spin state. We demonstrate a continuous spin crossover of iron in FeO over a broad pressure range, with the high-spin state persisting beyond Earth's core-mantle boundary (CMB) conditions. These observations provide new experimental constraints on iron spin state at extreme conditions essential for geophysical models of (exo)planetary interiors.

E. Nagel, J. Köhler, M. Zechmeister et al.

We present the first planet mass measurement obtained with CRIRES+ radial velocity (RV) observations using the K-band gas cell. Our target, LHS 3844 b (TOI-136), is a transiting super-Earth with radius $R_b=1.286^{+0.043}_{-0.044}R_\oplus$ and an orbital period of $P_b = 0.462929709^{+0.000000044}_{-0.000000042}$d, placing it in the class of ultra-short-period (USP) planets. The host star LHS 3844 is an old ($7.8\pm1.6$Gyr), slowly rotating ($P_{rot} = 130.0^{+16.9}_{-13.4}$d) M5.0 dwarf with $M_\star = 0.151\pm0.014M_\odot$ at a distance of 15pc (V=15.2mag, K=9.2mag). Combining our CRIRES+ RVs with archival ESPRESSO spectra, and confirming the signal in each dataset independently, we detected periodic RV variations with a semi-amplitude $K_b=6.95^{+0.55}_{-0.60}$m/s, implying a planetary mass of $m_b = 2.37\pm0.25M_\oplus$ and a bulk density of $ρ_b = 6.15^{+0.60}_{-0.61}$gcm$^{-3}$, consistent with a predominantly rocky composition. We further found excess RV variability that may be attributed to stellar jitter or to an additional planetary signal, for which we identified a tentative super-Earth candidate with a period of $\approx6.88$d. Owing to its proximity to its M-dwarf host, LHS 3844 b experiences intense irradiation and is unlikely to retain a substantial H/He envelope. Interior modeling places an upper limit on the iron-core mass fraction, which is consistent with an Earth-like rocky composition. With an emission spectroscopy metric of 28, LHS 3844 b is a prime JWST target for atmospheric and surface characterization and the most promising surface-characterization target known. Phase-curve spectroscopy may reveal its surface mineralogy and enable the first robust detection of exoplanet surface spectral features. Our results demonstrate that near-infrared RVs obtained with CRIRES+ enable robust mass measurements of super-Earths orbiting late M dwarfs.

Philipp Baumeister, Francesca Miozzi, Claire Marie Guimond et al.

Most our knowledge about rocky exoplanets is based on their measure of mass and radius. These two parameters are routinely measured and are used to categorise different populations of observed exoplanets. They are also tightly linked to the planet's properties, in particular those of the interior. As such they offer the unique opportunity to interpret the observations and potentially infer the planet's chemistry and structure. Required for the interpretation are models of planetary interiors, calculated a priori, constrained using other available data, and based on the physiochemical properties of mineralogical phases. This article offers an overview of the current knowledge about exoplanet interiors, the fundamental aspects and tools for interior modelling and how to improve the contraints on the models, along with a discussion on the sources of uncertainty. The origin and fate of volatiles, and their role in planetary evolution is discussed. The chemistry and structure of planetary interiors have a pivotal role in the thermal evolution of planets and the development of large scale properties that might become observables with future space missions and ground-based surveys. As such, having reliable and well constrained interior models is of the utmost importance for the advancement of the field.

Hassan Kamaleldin M.

Chert, a primarily silica-bearing sedimentary rock, is often found in limited layers within the Earth's lithosphere. Optical microscopy, X-ray diffraction, major and trace element analyses were used to study chert samples from Gebel El-Khashab—an Oligocene formation consisting of fluvial sands and chert gravels together with silicified wood fragments and tree trunks in east Cairo, Egypt. The chert samples are quartz ± goethite ± moganite, with no evidence of an opal precursor. They are characterized by a variety of silica fabrics, comprising microcrystalline quartz, megaquartz, and chalcedonic quartz. The microcrystalline quartz is most common and likely formed inorganically by direct precipitation from solution. Several trace components are recognized in microcrystalline fabrics, including: (1) calcite, (2) detrital quartz and zircon, (3) echinoderms and other unidentified fossils, (4) organic textures, and (5) organic-rich structures that are potential fossil morphologies. The preservation of echinoderm fossils and organic morphologies point to primary deposition of silica. The chert samples studied here averaged 95 wt.% SiO2, 2 wt.% Fe2O3T, 0.5 wt.% CaO, 0.11 wt.% MnO, 0.1 wt.% Al2O3, 0.03 wt.% MgO, 0.02 wt.% TiO2, 0.02 wt.% K2O, and 0.03 wt.% Na2O. The low total rare earth element content (3 ppm), high Eu anomalies, low Y/Ho values and the discrimination diagrams Al–Fe–Mn, Fe/Ti–Al/(Al + Fe + Mn), and Al2O3/TiO2–Al/(Al + Fe + Mn) indicate the hydrothermal origin of silica in these cherts. The hydrothermal silica-derived cherts were deposited close to the mid-oceanic ridge, as indicated by the Al2O3/(Al2O3 + Fe2O3T) and the Fe2O3T/TiO2–Al2O3/(Al2O3 + Fe2O3T) association diagram. The chert deposits were transported in Oligocene to their current setting. The positive Ce anomalies of some chert samples point to an influence of a terrestrial material source.

Christopher Small, Daniel Sousa

The statistical and topological properties of spectral feature spaces are direct expressions of the populations of spectra they represent. Characterization of the topology and dimensionality of spectral feature spaces provides both quantitative and qualitative insight into their information content. Understanding the characteristics and information content of a spectral feature space is essential to modeling and interpretation of the target properties of spectra. The reflectance of crystalline substrates, specifically sands and evaporites, is of immediate relevance to remote sensing of the diversity of soils and terrestrial substrates more generally. The objective of this analysis is to characterize the topology and spectral dimensionality of spectroscopic feature spaces composed of a diversity of co-occurring sands and evaporites worldwide. To achieve this, we construct a composite spectral feature space as a mosaic of 30 desert environments imaged by NASA’s EMIT spaceborne imaging spectrometer and compare the global and local structure of the aggregate spectral feature space using a combination of linear and nonlinear dimensionality reduction. The 3D (>99%) variance partition of the EMIT mosaic indicates that the spectral diversity of sand and evaporite reflectances is determined primarily by albedo and spectral continuum–related to mineralogy, moisture content and illumination geometry. The spectral feature space defined by the low order principal components clearly distinguishes low and high albedo sand endmembers with multiple internal clusters indicating distinct spectral continuum shapes. The same feature space also contains a continuum of evaporite endmembers with no apparent clustering but a strong dependence of albedo and continuum curvature on moisture content. In contrast, 2D and 3D UMAP embeddings of the same feature space clearly distinguish at least 18 spectrally separable clusters interspersed amidst two continua of tendrils. One continuum is associated with multiple sand albedo gradients in the Gobi Desert while the other corresponds to a variety of low albedo basement outcrops in multiple granules. Together, these observations indicate that the EMIT spectrometer is able to clearly distinguish spectrally separable reflectance features in both the spectral continuum and narrowband absorptions, suggesting that the geographically distinct crystalline substrates included in the study are mineralogically distinct and completely spectrally separable.

Mustafa Berkay Doğan

This study examines the effect of variations in dry rock bulk modulus (Kdry) on compressional wave velocity (Vp) using Gassmann fluid substitution theory and various fluid mixing laws in the context of CO2 sequestration in the Utsira formation at the Sleipner Field. Significant changes in Vp, exceeding 600 m/s, were observed, particularly when applying the Gassmann-Wood law, which demonstrated heightened sensitivity to saturation variations. In contrast, the Gassmann-Brie approach, utilizing an empirically selected constant, produced more stable and reliable results. This study emphasizes that relying solely on the Gassmann-Wood equation for Kdry calculations may result in inaccurate predictions, particularly for CO2-saturated formations. To mitigate this, laboratory measurements of Kdry are recommended to enhance the reliability of predictions. Furthermore, initial saturation conditions critically affect the Vp calculations, underlining the importance of selecting an appropriate mixing law to ensure accurate assessments during CO2 injection and storage.

J. Varga, L. B. F. M. Waters, M. Hogerheijde et al.

Context. Rocky planets form by the concentration of solid particles in the inner few au regions of planet-forming disks. Their chemical composition reflects the materials in the disk available in the solid phase at the time the planets were forming. Aims. We aim to constrain the structure and dust composition of the inner disk of the young star HD 144432, using an extensive set of infrared interferometric data taken by the Very Large Telescope Interferometer (VLTI), combining PIONIER, GRAVITY, and MATISSE observations. Methods. We introduced a new physical disk model, TGMdust, to image the interferometric data, and to fit the disk structure and dust composition. We also performed equilibrium condensation calculations with GGchem. Results. Our best-fit model has three disk zones with ring-like structures at 0.15, 1.3, and 4.1 au. Assuming that the dark regions in the disk at ~0.9 au and at ~3 au are gaps opened by planets, we estimate the masses of the putative gap-opening planets to be around a Jupiter mass. We find evidence for an optically thin emission ($τ<0.4$) from the inner two disk zones ($r<4$ au) at $λ>3\ μ$m. Our silicate compositional fits confirm radial mineralogy gradients. To identify the dust component responsible for the infrared continuum emission, we explore two cases for the dust composition, one with a silicate+iron mixture and the other with a silicate+carbon one. We find that the iron-rich model provides a better fit to the spectral energy distribution. Conclusions. We propose that in the warm inner regions ($r<5$ au) of typical planet-forming disks, most if not all carbon is in the gas phase, while iron and iron sulfide grains are major constituents of the solid mixture along with forsterite and enstatite. Our analysis demonstrates the need for detailed studies of the dust in inner disks with new mid-infrared instruments such as MATISSE and JWST/MIRI.

Jeffrey P. Gay, Estelle E. Ledoux, Matthias Krug et al.

Abstract Seismic anisotropy is a powerful tool to map deformation processes in the deep Earth. Below 660 km, however, observations are scarce and conflicting. In addition, the underlying crystal scale mechanisms, leading to microstructures and crystal orientations, remain poorly constrained. Here, we use multigrain X‐ray diffraction in the laser‐heated diamond anvil cell to investigate the orientations of hundreds of grains in pyrolite, a model composition of the Earth's mantle, at in situ pressure and temperature. Bridgmanite in pyrolite exhibits three regimes of microstructures, due to transformation and deformation at low and high pressure. These microstructures result in predictions of 1.5%–2% shear wave splitting between 660 and 2,000 km with reversals in fast S‐wave polarization direction at about 1,300 km depth. Anisotropy can develop in pyrolite at lower mantle conditions, but pressure has a significant impact on the plastic behavior of bridgmanite, and hence seismic observations, which may explain conflicting anisotropy observations.

D. V. Semenova, V. G. Vladimirov, I. V. Karmysheva et al.

The first U-Pb isotope-geochronological data were obtained on the age of early collisional granitoids of the Matut massif (Western Sangilen, SE Tuva). The rocks that have been studied are assigned to magnesian, calc-alkaline, high-potassium, and low-peraluminious varieties. LA-ICP-MS analysis on two zircon samples showed that the Matut granite massif formation age corresponds to 522 Ma (U/Pb, LA-ICP-MS, zircons, 520±3 Ma (sample KT-1070) and 524±3 Ma (sample KT-1324)). Thus, the Matut massif granitoids are among the most ancient in Western Sangilen and were formed at the early collisional stage of the structural evolution of the region. Based on the data obtained, an assessment was made of the duration of collisional orogeny on the northwestern margin of the Tuva-Mongolian massif. The initiation to collapse period of the orogen is at least 80 million years.

Ali Shebl, Mahmoud Abdellatif, Mohamed Badawi et al.

Abstract Integrating various tools in targeting mineral deposits increases the chance of adequate detection and characterization of mineralization zones. Selecting a convenient dataset is a key for a precise geological and hydrothermal alteration mapping. Remote sensing and airborne geophysical data have proven their efficiency as tools for reliable mineral exploration. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced land imager (ALI), Landsat 8 (L8), and Sentinel 2 data are widely-used data among various types of remote sensing images in resolving lithological and hydrothermal alteration mapping over the last two decades. ASTER is a well-established satellite in geological remote sensing with detailed Short-wave infrared (SWIR) range compared to visible and near-infrared region (VNIR) that controls iron-associated alteration detection. On contrary, ALI has excellent coverage of the VNIR area (6 bands), but does not possess the potentiality of ASTER for the SWIR and thermal regions. Landsat 8 is widely used and highly recommended for lithological and hydrothermal alteration mapping. The higher spatial (up to 10 m) resolution of Sentinel 2 MSI has preserved its role in producing accurate geological mapping. Notwithstanding the foregoing, implementing the four datasets in a single study is time-consuming. Thus, an important question when commencing an exploration project for hydrothermal alterations-related mineralization (orogenic mineral deposits in the current research) is: which dataset should be adopted to fulfill proper and adequate outputs? Here the four widely recommended datasets (ASTER, ALI, L8, and sentinel 2) have been tested by applying the widely-accepted techniques (false color combinations, band ratios, directed principal component analysis, and constrained energy minimization) for geological and hydrothermal alteration mapping of Gabal El Rukham-Gabal Mueilha district, Egypt. The study area is covered mainly by Neoproterozoic heterogeneous collection of ophiolitic components, island arc assemblage, intruded by enormous granitic rocks. Additionally, airborne magnetic and radiometric data were applied and compared with the remote sensing investigations for deciphering the structural and hydrothermal alteration patterns within the study area. The results demonstrated a different extent from one sensor to another, highlighting their varied efficacy in detecting hydrothermal alterations (mainly hydroxyl-bearing alterations and iron oxides). Moreover, the analysis of airborne magnetic and radiometric data showed hydrothermal alteration zones that are consistent with the detected alteration pattern. The coincidence between high magnetic anomalies, high values of the K/eTh ratio, and the resultant alterations confirm the real alteration anomalies. Over and above that, the remote sensing results and airborne geophysical indications were verified with fieldwork and petrographic investigations, and strongly recommend combining ASTER and Sentinel 2 results in further investigations. Based on the outputs of the current research, we expect better hydrothermal alteration delineation by adopting the current findings as they sharply narrow the zones to be further investigated via costly geophysical and geochemical methods in mineral exploration projects.

Viktor Sharapov, Yuri Semenov, Grigory Kuznetsov et al.

This study focuses on the ability of spinel crystals in ultramafic xenoliths, like zircon, to store the primary composition and structure when exposed to magma fluid flows or the thermal heating of ultramafic fragments in magma flows during volcanic eruptions. Mantle ultramafic rock xenoliths from explosives of the Avacha Volcano in Kamchatka have different facies of their metasomatic changes above the magma chamber. An alternative hypothesis of their source is from fragments of layered mafic intrusions containing spinels, which store initial petrogenetic records of the original magma melt. Experiments were conducted to prove this idea using a Budker Institute of Nuclear Physics (INP SB RAS) unit. Large scales of change in the composition and structure of spinel crystals were caused by the hot fluids from melted xenolith sites.

Evgeny Galuskin, Irina O. Galuskina, Vadim Kamenetsky et al.

AbstractOsbornite (TiN) is extremely rare in nature (commonly found in enstatite meteorites) and has not yet been identified correctly to form naturally in terrestrial settings. Due to its thermodynamic stability and thermal shock resistance, TiN has wide industrial applications, mainly as coatings. However, as the melting temperature of TiN is very high (~3000°С), coatings are produced at much lower temperatures via physical or chemical vapor deposition. Also, anthropogenic analogues of osbornite are often observed in pyrometallurgical slags. Therefore, it is critical to distinguish between anthropogenic and naturally occurring osbornite. A detailed petrographic study was undertaken on in situ osbornite found within unusual gehlenite-bearing breccias from wadi Zohar, Negev Desert of the pyrometamorphic Hatrurim Complex. The Hatrurim Complex, which extends through Israel, Palestine, and Jordan within the Dead Sea Rift zone, mainly comprises larnite, gehlenite, and spurrite rocks. Osbornite, in close association with iron phosphides, barringerite, and schreibersite, occurs at contacts between gehlenite, paralava, and calcinated clasts of host sedimentary rocks. Based on investigation of pseudowollastonite and Fe-P series phases, osbornite is formed at low pressure, extremely high temperatures (~1200-1500°С), and reduced conditions, following pyrolysis of organic matter contained in the sedimentary protolith. This is the first identification of in situ osbornite in terrestrial rocks and indicates that high-temperature and highly reduced conditions, which are common for meteorites, may occur at/near the Earth’s surface as a result of sustained pyrometamorphism in particular settings. Our findings also provide relevant data and criteria for comparing osbornite occurrences elsewhere and ultimately evaluating their origins.

Ruslan A. Maksarov, Ilya R. Prokopiev, Anna G. Doroshkevich et al.

In this paper, we present the results of a mineralogical study of the ores of the Karalveem deposit in the northeast of Russia (Central and Ruslovy areas). Gold mineralization is characterized by two types of ores: gold-quartz-arsenopyrite (quartz veins with native gold and sulfide mineralization) and gold-sulfide (metasomatites) in gabbrodolerite. In most samples, both types of ores are combined, making these complex ores are of particular interest. The main ore mineral is arsenopyrite; secondary and accessory minerals include pyrite, rutile, ilmenite, galena, chalcopyrite, monazite, sphalerite, and native gold. Native gold in quartz-sulfide and gold-sulfide ore types is present in a free form as microveinlets, micron-size segregations in the host rock, or as microinclusions in sulfides. Both ore types are characterized by the similar chemical composition of ore minerals: the fineness of gold in the gold-sulfide type is 870–900 ‰, in veins – 840–910 ‰. The trace ele- ment composition of pyrite and arsenopyrite from metasomatites and quartz veins is also alike. Based on this, it was concluded that the productivity of gold-sulfide and gold-quartz-arsenopyrite ores was formed by a single impulse.

Mervat M. Eltantawy, Mikhail A. Belokon, Elena V. Belogub et al.

A novel method of 3D self‐organization of patterns made of biomimetic hydroxyapatite (HA) in agar matrix is reported. The model system involves gradual ion diffusion and phase transitions of calcium phosphates. Herein, HA is precipitated for the first time in the agar gel matrix via single‐diffusion gel growth technique to aggregate the inorganic Liesegang rings (LRs). These patterns are formed as periodic structures through precipitation reaction and arise during the reagent diffusion in a polymer matrix. The concentrations of these inner and outer electrolytes, as well as pH and temperature effects on the morphologies, periodicity, stability, and number of LRs, are studied. In this study, the periodic HA Liesegang ring structures (HA LRs) are fabricated via a diffusion‐limited aggregation process. These patterns influence the C2C12 cell growth and allow to obtain the patterns formed by the cell tissue. This method can be prospective for the generation of 3D gradients in materials/3D gradient materials generation for studying the interface tissue engineering, systematic cell–biomaterial interaction, as well as for the fabrication of the stimuli‐responsive gradients to control/mimic migration of cells during the wound healing.

Diane E. Moore, David A. Lockner

Abstract We conducted triaxial friction tests at hydrothermal conditions (25°C–350°C) on gouges of peridotite and its principal mineral constituents olivine and orthopyroxene. Pore‐fluid chemistry was varied by the use of peridotite, granite, or quartzite driving blocks (representing wall rock) housing the gouge layer. Samples sheared at slow rates initially strengthen to a peak value, and then weaken toward a residual strength. The transition is accompanied by a change from velocity‐weakening to velocity‐strengthening behavior marked by a series of small stress drops. The extent of weakening varies with the ultramafic mineralogy and with the chemical environment established by the driving block lithology. The strengths of olivine and olivine‐rich peridotite gouges decrease substantially (to μ ∼ 0.25–0.30), and that of orthopyroxene to a lesser extent, at temperatures ≥200°C when sheared between crustal driving blocks. Less weakening is observed in the peridotite‐block experiments; the minimum strength of the peridotite gouges (μ ∼ 0.5) occurs at 250°C, the temperature at which olivine hydration rates are near their maximum in ultramafic rocks. The strength reductions in all experiments are attributed to solution‐transfer (pressure solution) processes that come to predominate over cataclastic mechanisms during shear. The lower pH of fluids in contact with silica‐saturated crustal rocks enhances the weakening of olivine‐rich gouges. In these short‐duration experiments, secondary phyllosilicate mineral growth was of a limited extent and varied with gouge and wall‐rock mineralogy and with temperature. Over geologic time spans, however, the alteration assemblages will assume an increasingly important role in fault‐zone behavior.

R. Miyawaki, F. Hatert, M. Pasero et al.

Koki Okajima, Kenji Nagata, Masato Okada

We propose a Markov chain Monte Carlo-based deconvolution method designed to estimate the number of peaks in spectral data, along with the optimal parameters of each radial basis function. Assuming cases where the number of peaks is unknown, and a sweep simulation on all candidate models is computationally unrealistic, the proposed method efficiently searches over the probable candidates via trans-dimensional moves assisted by annealing effects from replica exchange Monte Carlo moves. Through simulation using synthetic data, the proposed method demonstrates its advantages over conventional sweep simulations, particularly in model selection problems. Application to a set of olivine reflectance spectral data with varying forsterite and fayalite mixture ratios reproduced results obtained from previous mineralogical research, indicating that our method is applicable to deconvolution on real data sets.

Juan Ruiz-Quintana, Alain Carballo-Peña, José Nicolás Muñoz-Gómez et al.

To increase the geological knowledge of the weathering crust of the Cajálbana nickel lateritic deposit, its mineralogical and geochemical characterization was performed, with the purpose of determining the presence of rare earth elements and other metals of interest, not contemplated in the preliminary studies. Composite samples were taken from six mineralogical wells drilled in the research area. The samples were analyzed using X-ray diffractometry and chemical analysis of basic elements and by ICP-MS, for 26 chemical elements. Anomalous concentrations of scandium and samarium were revealed, which exceed four times the clarke value of the first and ten times that of the second. The existence of anomalous contents of scandium of 104,32 ppm and samarium of 82,18 ppm in the limonite horizon, with a total concentration of ETR in this horizon of 191,25 ppm, increases the potential value of the lateritic resources of the deposit Cajálbana.

A. Süssenberger, S. T. Schmidt, F. H. Schmidt et al.

<p>This study reports on reaction processes in a transition zone from contact to regional metamorphism by using Raman spectroscopy on carbonaceous matter (RSCM), illite “crystallinity” (Kübler index, KI), chlorite geothermometry, and thermal modeling. The thermal effect due to the emplacement of the Torres del Paine intrusion (TPI, assembly time of ca. 150&thinsp;kyr) had different consequences for inorganic and organic compounds of the host rock. The thermal alteration of the pre-intrusive regional metamorphosed host rock is documented by elevated RSCM temperatures, high-temperature chlorite generations, and the appearance of epidote and retrograde Fe-rich chlorite. Microprobe analysis on chlorite indicates incomplete re-equilibration as evidenced by various chlorite populations of individual contact metamorphic samples. This study indicates that the maturity of organic matter is the most reliable and unequivocal indicator on timescales of several thousand years to determine the lateral extension of the TPI contact aureole. Raman geothermometry reveals that the lateral extension of the contact-influenced zone expands up to a distance of 1.5&thinsp;km and, thus, expands to ca. 1.1&thinsp;km further out than the macroscopically mappable hornfels contact aureole. The best match between measured (Raman geothermometry) and calculated (thermal modeling) <span class="inline-formula">Δ<i>T</i>_max</span> values (<span class="inline-formula">Δ<i>T</i>=54</span>&thinsp;<span class="inline-formula">^∘</span>C) is achieved with a total intrusion assembly time of 150&thinsp;kyr, a magmatic temperature of 800&thinsp;<span class="inline-formula">^∘</span>C, a two-batch model (batch repose time of 10&thinsp;kyr) with five pulses per batch, short heating durations (3&thinsp;kyr), and long pulse repose times (15&thinsp;kyr).</p>