Hasil untuk "Mineralogy"

František Teťák, Katarína Korábová, Dušan Laurinc

In 1986, the KLK-1 (Klanečnica) borehole was drilled northwest of Moravské Lieskové as part of a regional oil and gas exploration programme. The well reached a total depth of 662 m and was intended to verify the occurrence and potential accumulation of hydrocarbons within the Drietoma anticline, a geophysically indicated structural high in the St. Hrozenkov–Drietoma area. The drilled succession was originally assigned to the Svodnice Fm. of the Biele Karpaty Unit down to 75 m, and to the Zlín Fm. of the Rača Unit below this depth. However, a re-examination of the preserved core material suggests that the presence of glauconitic sandstones and an inferred middle to late? Eocene age do not support the previous correlation with the Rača Unit. The lower interval of the borehole, below approximately 90 m, is here reinterpreted as belonging to the Bystrica Mb. of the Bystrica Unit. The borehole cores reinterpretation is supported by the abundant occurrence of larger foraminifera, lithologically variable quartz-glauconitic sandstones, and thick beds of dark grey silty claystones to marlstones, all characteristics also of the Bystrica Mb. Furthermore, the western extent of the Bystrica Unit does not appear to terminate at the Nezdenice Faults, as previously supposed, but continues westwards beneath the Biele Karpaty Unit, albeit to a limited subsurface extent.

Petrov N.F., Kupriyanova E.V., Alaeva I.P. et al.

Materials of archaeological excavations of the Bronze Age sites contain many items, the functions of which are quite difficult to determine. The subject of this study is a group of artifacts that, in our opinion, are related to the production of ornaments: ceramic saucers with signs, molds, cross-shaped pendants. A number of molds and ceramic saucers contain prints similar in form to cross-shaped pendants — the only type of molded ornaments in the Bronze Age of the Southern Trans-Urals and Kazakhstan. At the same time, the dimensions of negatives on the molds and saucers do not match in size with known finds of cross-shaped pendants, which does not allow considering them as working specimens used for casting these ornaments. Regarding ceramic saucers, various versions about their functions, from ritual to production (molds), have been proposed. The X-ray fluorescence analysis of the inside of the prints on ceramic saucers recorded past contact with metal — tin and lead, and to a lesser extent with copper. Various types of scientific analyses have found that tin and lead are concentrated in large quantities in bronze alloys, used for making cross-shaped pendants. Based on this, a hypothesis has been proposed regarding their possible application combining the ritual and utilitarian aspects, i.e. their potential use in rituals related to the production of ornaments.

J. S. Martin, J. Kobus, J. Varga et al.

The T-Tauri type young stellar object RY Tau exhibits a dust depleted inner cavity characteristic of a transition disk. We constrain the spatial distribution and mineralogy of dust in the RY Tau protoplanetary disk in the inner few astronomical units using spectrally resolved interferometric observations in the L, M, and N bands obtained with VLTI/MATISSE. Employing a 2D temperature gradient model we estimate the orientation of the inner disk finding no evidence of significant misalignment between the inner and outer disk of RY Tau. Successively, we analyze the chemical composition of silicates depending on spatial region in the disk and identify several silicate species commonly found in protoplanetary disks. Additionally, a depletion of amorphous dust grains toward the central protostar is observed. Monte Carlo radiative transfer simulations show that hot dust close to the protostar and in the line of sight to the observer, either in the uppermost disk layers of a strongly flared disk or in a dusty envelope, is necessary to model the observations. The shadow cast by a dense innermost disk midplane on the dust further out explains the observed closure phases in the L band and to some extent in the M band. However, the closure phases in the N band are underestimated by our model, hinting at an additional asymmetry in the flux density distribution not visible at shorter wavelengths.

Rena A. Lee, Fei Dai, Andrew W. Howard et al.

We report the confirmation of TOI-6324 b, an Earth-sized (1.059 $\pm$ 0.041 R$_\oplus$) ultra-short-period (USP) planet orbiting a nearby ($\sim$20 pc) M dwarf. Using the newly commissioned Keck Planet Finder (KPF) spectrograph, we have measured the mass of TOI-6324 b 1.17 $\pm$ 0.22 M$_\oplus$. Because of its extremely short orbit of just $\sim$6.7 hours, TOI-6324 b is intensely irradiated by its M dwarf host, and is expected to be stripped of any thick, H/He envelope. We were able to constrain its interior composition and found an iron core mass fraction (CMF = 27$\pm$37%) consistent with that of Earth ($\sim$33%) and other confirmed USPs. TOI-6324 b is the closest to Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase curve and secondary eclipse observations (Emission Spectroscopy Metric = 25) which may reveal its surface mineralogy, day-night temperature contrast, and possible tidal deformation. From 7 sectors of TESS data, we report a tentative detection of the optical phase curve variation with an amplitude of 42$\pm$28 ppm.

Marcel M. Popescu, Eri Tatsumi, Javier Licandro et al.

The near-Earth asteroid (98943) Torifune, previously designated 2001 CC$_{21}$, is the flyby target of the Hayabusa2 extended mission, nicknamed Hayabusa2$\#$ (SHARP: Small Hazardous Asteroid Reconnaissance Probe). The ground-based telescope observations offer a key science input for the mission's scientific investigation. During 2022 - 2024 this asteroid was at visible apparent magnitudes brighter than 18.5, allowing for a detailed characterization using ground-based telescope observations. We determined its rotation period $P~=~5.021516\pm0.000106$ h and its absolute magnitude H = 18.78 $\pm$ 0.14 and. The large number of lightcurves allows to estimate its axes ratio, its convex shape and its pole orientation $λ= 301^{\circ} \pm 35^{\circ}$, $β= {89^{+1}_{-6}}^{\circ}$ and $ε= 5^{\circ} \pm 3^{\circ}$ which indicate a prograde rotation. We report the semi-axis of the equivalent ellipsoid, $a$ = 0.42$^{+0.08}_{0.06}$ km, $b$ = 0.16$^{+0.05}_{0.04}$ km, and $c$ = $0.17\pm0.03$ km. Consequently, the volume equivalent diameter is $D_{eq}$ = $0.44 \pm 0.06$ km . Using observations conducted simultaneously with four broadband filters, we determined $(g-r) = 0.663 \pm 0.022$ mag, $(r-i) = 0.177 \pm 0.012$ mag, and $(i-z_s) = -0.061 \pm 0.032$ mag. Additionally, we found that Torifune exhibits no detectable large-scale heterogeneity. We classified the object using a high signal-to-noise ratio spectrum (over the visible and near-infrared region) as Sq-type in the Bus-DeMeo taxonomy. We estimate a mineralogy similar to LL/L ordinary chondrites, with an ol/(ol+px) = 0.60, a Fa content of 28.5 mol$\%$, and a Fs content of 23.4 mol$\%$. The spectral data indicate a surface affected by moderate space weathering effects.

Á. Kóspál, P. Ábrahám, V. V. Akimkin et al.

Accretion variability is ubiquitous in YSOs. While large outbursts may strongly affect the disk, the effects of moderate bursts are less understood. We aim to study the physical response of the disk around the eccentric binary system DQ Tau to its periodic accretion changes. We organized a multi-wavelength campaign centered on four JWST/MIRI spectra. We targeted three periastrons (high accretion state) and one apastron (quiescence). We used optical and near-infrared spectroscopy and photometry to measure how the accretion luminosity varies. We decomposed the multi-epoch SEDs into stellar, accretion, and rim components. We fitted the solid-state features using various opacity curves and the molecular features using slab models. We find the inner disk of DQ Tau to be highly dynamic. The temperature, luminosity, and location of the inner dust rim vary in response to the movement of stars and the L_acc variations. This causes variable shadowing of the outer disk, leading to an anti-correlation between the rim temperature and the strength of the silicate feature. The dust mineralogy remains constant, dominated by large amorphous olivine and pyroxene grains, with smaller fractions of crystalline forsterite. The excitation of CO (1550-2260 K), HCN (880-980 K), and hot H2O (740-860 K) molecules as well as the luminosity of the [NeII] line correlate with the accretion rate, while the warm (650 K) and cold (170-200 K) H2O components are mostly constant. CO emission, originating from a hot (>1500 K) region likely within the dust sublimation radius, is most sensitive to L_acc changes. In comparison with other T Tauri disks, DQ Tau is highly C-poor and displays moderately inefficient pebble drift. We conclude that even moderate accretion rate changes affect the thermal structure in the planet-forming disk regions on short timescales, providing a crucial benchmark for understanding disk evolution.

Milaushkin M. V., Mal’kovets V. G., Gibsher A. A. et al.

The article presents results of a study of the chemical composition of garnet xenocrystals from a concentrate of the heavy fraction of kimberlites from the Yubileinaya pipe and Ottorzhenets kimberlite body. Samples from porphyry kimberlites and autolithic kimberlite breccias were taken for analysis from the Yubileinaya pipe. Significant differences are noted in the studied samples of peridotite garnets from the Yubileinaya kimberlite pipe and the Ottorzhenets body. Compared to the Yubileinaya pipe, the Ottorzhenets body exhibits a decreased amount of garnets of the harzburgite-dunite paragenesis in the composition range of Cr2O3 > 8.5 wt. % and CaO < 3 wt. %. On this basis, we assume that the Ottorzhenets body is not a displaced fragment of the Yubileinaya pipe, but belongs to a new unknown kimberlite body. We also assume that the diamond-bearing potential of the primary Ottorzhenets body is reduced compared to the Yubileinaya pipe, which is consistent with the information on the diamond content, according to the data of ALROSA (PJSC).

I. R. Prokopyev, A. G. Doroshkevich, M. D. Varchenko et al.

The Srednyaya Zima alkaline-ultramafic carbonatite complex is located in the Eastern Sayan and is a part of the area of manifestation of Neoproterozoic rare-metal alkaline-carbonatite magmatism along the southern and southeastern margins of the Siberian craton. Mineralogical studies of calciocarbonatites of the Srednyaya Zima complex have shown the presence of primary magmatic mineral phases of calcite, biotite (annite-phlogopite), ilmenite, and fluorapatite. Pyrochlore, zircon, burbankite, magnetite, rutile, titanite, strontianite, and barite were identified of the accessory minerals. The chemical composition of the magmatic minerals of the Srednyaya Zima carbonatites is similar to the mineral composition of the closely aged carbonatite complexes Belaya Zima and Arbarastakh. The rare-element and structural analysis of zircon from carbonatites showed the presence of two zones – a magmatic core and areas of recrystallization. U-Pb dating of igneous zircon showed the age interval of its crystallization – 637±4 Ma, which coincides with the geochronology of the formation of alkali-ultramafic rare-metal complexes along the southern margin of the Siberian craton. The formation of Neoproterozoic alkaline-carbonatite complexes is associated with tectonic events of the breakup of the Rodinia supercontinent.

Duccio Fanelli, Luca Bindi, Lorenzo Chicchi et al.

Neural networks are gaining widespread relevance for their versatility, holding the promise to yield a significant methodological shift in different domain of applied research. Here, we provide a simple pedagogical account of the basic functioning of a feedforward neural network. Then we move forward to reviewing two recent applications of machine learning to Earth and Materials Science. We will in particular begin by discussing a neural network based geothermobarometer, which returns reliable predictions of the pressure/temperature conditions of magma storage. Further, we will turn to illustrate how machine learning tools, tested on the list of minerals from the International Mineralogical Association, can help in the search for novel superconducting materials.

Mikhail Zolotov

Sulfur-bearing species play crucial roles in atmospheric physical-chemical processes, atmosphere-surface interactions, and the geological evolution of Venus. This chapter provides a comprehensive overview of (1) instrumental data on the abundance and speciation of sulfur in atmospheric and crustal materials, (2) the behavior of sulfur-bearing species in the mesosphere, clouds, and lower atmosphere, (3) chemical and mineralogical aspects of atmosphere-surface interactions, and (4) the fate of sulfur during the formation, differentiation, and geological evolution of Venus, including volcanic degassing, gas-solid reactions at the surface, a proposed aqueous period, and subsequent evolution. The chapter also outlines key questions and discusses further exploration of Venus in the context of sulfur-relevant investigations.

Sergey N. Britvin, Oleg S. Vereshchagin, Natalia S. Vlasenko et al.

The lack of benchmark data on the real minerals, native ammonium carriers in Solar System gives rise to controversial opinions on extraterrestrial ammonium reservoirs. We herein report on discovery of the first mineral carrier of meteoritic ammonium and show its relevance to the compositional and spectral characteristics of cometary and asteroidal bodies. Chemically distant from previously inferred volatile organics or ammoniated phyllosilicates, it is an aqueous metal-ammonium sulfate related to a family of so-called Tutton salts. Nickeloan boussingaultite, (NH4)2(Mg,Ni)(SO4)2 6H2O, occurs in Orgueil, a primitive carbonaceous chondrite closely related to (162173) Ryugu and (101955) Bennu, the C-type asteroids. The available spectroscopic, chemical and mineralogical data signify that natural Tutton salts perfectly fit into the role of ammonium reservoir under conditions of cometary nuclei and carbonaceous asteroids.

Bajda Tomasz, Rogowska Melania, Pawłowska Agnieszka

Minerals from the phosphate groups are used in environmental engineering as thermodynamically stable vehicles for heavy metals such as zinc. The hopeite Zn3(PO4)2·4H2O was synthesized and characterized by X-ray diffraction and scanning electron microscopy. The solubility of the hopeite was measured at 25°C. The average solubility product, log Ksp, for the reaction Zn3(PO4)2·4H2O ⇔ 3Zn2+ + 2PO43- + 4H2O at 25°C is –35.72 ± 0.03. The free energy of formation, ΔG°f,298, calculated from this measured solubility product is –3597.4 ± 1.0 kJ mol-1. The immobilization of zinc in the hopeite structure offers the possibility of developing an effective method for removing Zn from wastewater, water and soils.

Richard H. Worden, James E. P. Utley

Porosity and permeability define the reservoir quality of a sandstone. Porosity and permeability are controlled by primary sedimentary characteristics and subsequent diagenetic modification. Grain size, sorting, detrital mineralogy, and matrix content are defined at the point of deposition. Bioturbation, infiltration, continued alteration of reactive minerals and soft sediment deformation can occur soon after deposition and, together with the primary characteristics, these condition, or define, how a sediment will behave during subsequent burial. Diagenetic modifications include compaction, initially mechanical and then chemical, mineral growth and, in some cases, grain dissolution and development of secondary pores. Porosity and permeability typically decrease as diagenesis progresses. Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) approaches can be applied to study many aspects of sandstone diagenesis including detrital mineralogy, grain size, sorting, grain shape, grain angularity and matrix content. SEM-EDS is also useful for defining quantities and location in the pore network of cements that are mineralogically distinct from detrital grains (e.g., calcite, dolomite, siderite, or anhydrite). SEM-EDS can be useful for studying clay mineral cements, especially when they occur in patches bigger than 5–10 μm. In sandstones, SEM-EDS is not so useful when the cements are mineralogically identical to detrital grains (e.g., quartz cement in quartz sandstones) where additional signals such as cathodoluminescence (CL) may be required. Macro- and meso-pores can be quantified using SEM-EDS but, on its own, it cannot automatically measure micro-porosity as it is below the minimum 1 µm spatial resolution of the approach. Mechanical compaction, a key process that causes porosity-loss in sandstones, is not easily quantified using SEM-EDS. Nonetheless, together with additional routine techniques, SEM-EDS can be used to solve most problems associated with sandstone diagenesis and reservoir quality.

A. Loges, G. Scholz, N. de Sousa Amadeu et al.

<p>The mutual influence of F and OH groups in neighboring sites in topaz (Al<span class="inline-formula">₂</span>SiO<span class="inline-formula">₄</span>(F,OH)<span class="inline-formula">₂</span>) was investigated using magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. The splitting of <span class="inline-formula">¹⁹</span>F and <span class="inline-formula">¹</span>H NMR signals, as well as the OH Raman band, provides evidence for hydrogen bond formation within the crystal structure. Depending on whether a given OH group has another OH group or fluoride as its neighbor, two different hydrogen bond constellations may form: either OH<span class="inline-formula">⋯</span>O<span class="inline-formula">⋯</span>HO or F<span class="inline-formula">⋯</span>H<span class="inline-formula">⋯</span>O. The proton accepting oxygen was determined to be part of the SiO<span class="inline-formula">₄</span> tetrahedron using <span class="inline-formula">²⁹</span>Si MAS NMR. Comparison of the MAS NMR data between an OH-bearing and an OH-free topaz sample confirms that the <span class="inline-formula">¹⁹</span>F signal at <span class="inline-formula">−</span>130 ppm stems from F<span class="inline-formula">⁻</span> ions that take part in H<span class="inline-formula">⋯</span>F bonds with a distance of <span class="inline-formula">∼</span> 2.4 Å, whereas the main signal at <span class="inline-formula">−</span>135 ppm belongs to fluoride ions with no immediate OH group neighbors. The Raman OH sub-band at 3644 cm<span class="inline-formula">⁻¹</span> stems from OH groups neighboring other OH groups, whereas the sub-band at 3650 cm<span class="inline-formula">⁻¹</span> stems from OH groups with fluoride neighbors, which are affected by H<span class="inline-formula">⋯</span>F bridging. The integrated intensities of these two sub-bands do not conform to the expected ratios based on probabilistic calculations from the total OH concentration. This can be explained by (1) a difference in the polarizability of the OH bond between the different hydrogen bond constellations or (2) partial order or unmixing of F and OH, or a combination of both. This has implications for the quantitative interpretation of Raman data on OH bonds in general and their potential use as a probe for structural (dis-)order. No indication of tetrahedrally coordinated Al was found with <span class="inline-formula">²⁷</span>Al MAS NMR, suggesting that the investigated samples likely have nearly ideal <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Al</mi><mo>/</mo><mi mathvariant="normal">Si</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d0bd312d27fa3264f4721ed1a8b84140"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-34-507-2022-ie00004.svg" width="28pt" height="14pt" src="ejm-34-507-2022-ie00004.png"/></svg:svg></span></span> ratios, making them potentially useful as high-density electron microprobe reference materials for Al and Si, as well as for F.</p>

الناز گراوندی, سروش مدبری, پوریا گراوندی et al.

کانسارهای آهن زرنان- چوره‌ناب در 5 کیلومتری شمال شرق شهر زنجان و در کوه‌‌های طارم، بین روستاهای زرنان و چوره‌ناب واقع ‌است. مطالعات کانی‌شناسی و همچنین مشاهدات صحرایی نشان می‌دهد که کانی‌سازی آهن بیشتر از نوع منیتیتی است، البته کانی‌های هماتیت و گوتیت نیز به ‌صورت کم در اثر هوازدگی و دگرسانی تشکیل ‌شده‌اند. کانه‌زایی آهن در این محدوده به ‌صورت رگه‌ها و عدسی‌هایی در توده نفوذی الیگوسن تشکیل ‌شده است. در سنگ‌های ولکانیکی نیز کانی‌زایی به صورت رگه‌ای با وسعت کم مشاهده می‌شود. ضخامت رگه‌ها بین 5/0 تا حدود 15 متر و طول آن‌ها تا حدود 200 متر قابل ‌پیگیری است. مطالعات ژئوفیزیکی به روش مغناطیس‌سنجی در 5240 ایستگاه در وسعت 8 کیلومترمربع برای تعیین نواحی پر پتانسیل کانی‌سازی آهن و همچنین بررسی گسترش عمقی کانی‌سازی انجام شد. در این پژوهش نقشه‌های مغناطیس کل، برگردان به قطب، سیگنال تحلیلی و ادامه فراسو تهیه شد. نتایج به ‌دست ‌آمده از حفاری‌های انجام‌شده، انطباق بسیار خوبی با بررسی‌های مغناطیس‌سنجی دارد. بر اساس نتایج به‌ دست ‌آمده از این مطالعات، نُه بی‌هنجاری An1- An9 در محدوده مورد مطالعه شناسایی شد که بی‌هنجاری‌های An3، An8 و An9 سطحی‌تر و دارای گسترش عمقی حدود 40 متر هستند و دیگر بی‌هنجاری‌ها گسترش عمقی بیشتری دارند. نتیجه مدلسازی داده‌های مغناطیسی، تعیین موقعیت (محل و عمق تقریبی) و هندسه توده‌های مولد بی‌هنجاری مغناطیسی و موفق بودن مطالعات ژئوفیزیکی در اکتشاف در این منطقه است.

Olga Alexandrovna Doynikova

Yuzhu Ge, Giovanna Della Porta, Chelsea L. Pederson et al.

Similar carbonate fabrics may result from different pathways of precipitation and diagenetic replacement. Distinguishing the underlying mechanisms leading to a given carbonate fabric is relevant, both in terms of an environmental and diagenetic interpretation. Prominent among carbonate fabrics are aragonite botryoids and spherulites, typically interpreted as direct seawater precipitates and used as proxies for fluid properties and depositional environments. This study investigated μm to mm-scale Holocene botryoidal and spherulitic aragonite from marine and non-marine carbonate settings associated with microbial mats, and reports two distinct formation mechanisms: 1) early diagenetic replacement, and 2) primary precipitation via nanocrystal aggregation. In the intertidal microbial mats of Khawr Qantur (Abu Dhabi), botryoidal and spherulitic aragonite are replacement products of heavily micritized bioclasts. To form the botryoidal and spherulitic aragonite, skeletal rods and needles, resulting from disintegration of micritized bioclasts, recrystallize into nanocrystals during early marine diagenesis. These nanocrystals then grow into fibrous crystals, forming botryoidal and spherulitic aragonite. In the lacustrine microbial bioherms of the hypersaline Great Salt Lake (United States) and in the hydrothermal travertines of Bagni San Filippo (Italy), botryoidal and spherulitic aragonite evolve from nanocrystals via precipitation. The nanocrystals are closely associated with extracellular polymeric substances in microbial biofilms and aggregate to form fibrous crystals of botryoidal and spherulitic aragonite. The studied fabrics form a portion of the bulk sediment and show differences in terms of their formation processes and petrological features compared to the often larger (few mm to over 1 m) botryoidal and spherulitic aragonite described from open-marine reefal cavities. Features shown here may represent modern analogues for ancient examples of carbonate depositional environments associated with microbialites. The implication of this research is that botryoidal and spherulitic aragonite associated with microbial mats are relevant in paleoenvironmental interpretations, but must be combined with a detailed evaluation of their formation process. Care must be taken as the term “botryoidal and spherulitic aragonite” may in fact include, from the viewpoint of their nucleation and formation mechanism, similar fabrics originated from different pathways. At present, it seems unclear to which degree the μm to mm-scale botryoids and spherulites described here are comparable to their cm-to dm-size counterparts precipitated as cements in the open pore space of reefal environments. However, it is clear that the investigation of ancient botryoidal and spherulitic aragonite must consider the possibility of an early diagenetic replacement origin of these precipitates.

Alejandro Fonseca Duarte, Adriana Gioda

The purpose of this study was to determine the chemical and mineralogical composition of suspended sediments from the Acre River, located in the Purus Basin, upper Amazon basin, a region associated with the Fitzcarrald Arch. The elemental and mineralogical compositions of the sediments were assessed by using mass and atomic spectroscopy, and X-ray diffraction. A total of 46 samples were collected between 2008 and 2011 from four sites in the study area during wet and dry seasons. The suspended sediments contained feldspar, kaolinite, illite and quartz as well as the elements Hg, Zn, V, Ti, Si, Pb, Ni, Na, Mn, Mg, K, Fe, Cu, Cr, Cd, Ca, Al, S, and P in different proportions that were associated with the various weathering reactions linked to physical, chemical and biological processes in the region. The obtained results represent the first set of values and relationships regarding the mineralogy and chemical identification of the suspended sediments in the Acre River and can be used as a reference for the geochemical characteristics of the Purus Basin. Such regional studies will become increasingly necessary to observe the impacts of climate change and human activities on the suspended sediment load and composition of the Amazon River.

B. Rousseau, M. C. De Sanctis, A. Raponi et al.

We analyzed the surface of Vesta at visible wavelengths, using the data of the Visible and InfraRed mapping spectrometer (VIR) on board the Dawn spacecraft. We mapped the variations of various spectral parameters on the entire surface of the asteroid, and also derived a map of the lithology. We took advantage of the recent corrected VIR visible data to map the radiance factor at 550 nm, three color composites, two spectral slopes, and a band area parameter relative to the 930 nm crystal field signature in pyroxene. Using the howardite-eucrite-diogenite (HED) meteorites data as a reference, we derived the lithology of Vesta using the variations of the 930 nm and 506 nm (spin-forbidden) band centers observed in the VIR dataset. Our spectral parameters highlight a significant spectral diversity at the surface of Vesta. This diversity is mainly evidenced by impact craters and illustrates the heterogeneous subsurface and upper crust of Vesta. Impact craters also participate directly in this spectral diversity by bringing dark exogenous material to an almost entire hemisphere. Our derived lithology agrees with previous results obtained using a combination of infrared and visible data. We therefore demonstrate that it is possible to obtain crucial mineralogical information from visible wavelengths alone. In addition to the 506 nm band, we identified the 550 nm spin-forbidden one. As reported by a laboratory study for synthetic pyroxenes, we also do not observe any shift of the band center of this feature across the surface of Vesta, and thus across different mineralogies, preventing use of the 550 nm spin-forbidden band for the lithology derivation. Finally, the largest previously identified olivine rich-spot shows a peculiar behavior in two color composites but not in the other spectral parameters.

Pedram Abdolghader, Andrew Ridsdale, Tassos Grammatikopoulos et al.

Hyperspectral stimulated Raman scattering (SRS) microscopy is a label-free technique for biomedical and mineralogical imaging which can suffer from low signal to noise ratios. Here we demonstrate the use of an unsupervised deep learning neural network for rapid and automatic denoising of SRS images: UHRED (Unsupervised Hyperspectral Resolution Enhancement and Denoising). UHRED is capable of one-shot learning; only one hyperspectral image is needed, with no requirements for training on previously labelled datasets or images. Furthermore, by applying a k-means clustering algorithm to the processed data, we demonstrate automatic, unsupervised image segmentation, yielding, without prior knowledge of the sample, intuitive chemical species maps, as shown here for a lithium ore sample.