Hasil untuk "Mineralogy"

Viacheslav V. Klimenko, Varsha P. Kulkarni, Monique C. Aller

We present results from a mini-survey of dust spectral features arising in galaxies at redshifts $0.5 < z < 1.2$ in our James Webb Space Telescope (JWST) mid-infrared spectra of physically-unrelated background quasars. We analyze the JWST Mid-infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS) spectra of five quasars presented in Klimenko, Kulkarni, \& Aller 2025a (Paper I) to determine the best-fit silicate mineralogies. Template profile fits to the 10 $μ$m feature suggest the possible presence of crystalline silicates in three of the galaxies. This contrasts with the predominately amorphous silicate grains in the Milky Way diffuse interstellar medium (ISM). We also measure the extinction curves using existing data from UV to mid-IR. Combining our results with past Spitzer IRS studies, we find that (i) the 10~$μ$m silicate peak optical depth ($τ_{10}$) is about three times stronger than expected for the local diffuse ISM over the range $A_V =0.1-2.0$, with $τ_{10}/A_V$=$0.17\pm0.09$. (ii) The relative strength of the UV bump is similar to that in the local ISM. However, the ratio $τ_{10}/A_{2175}$ is larger ($\sim0.1-1$), and appears to decrease with $A_V$, approaching the Galactic ISM value ($\sim 0.1$) at $A_V\sim1.5-2$. (iii) No significant correlation of $τ_{10}/A_V$ with $R_V$. (iv) $τ_{10}$ is strongly correlated with the gas-phase Mg~II absorption strength for the quasar sightlines. Possible interpretations include that some quasar sightlines probe dust in the circumgalactic medium (CGM), and that dust grains may have been significantly reprocessed in the ISM and CGM under conditions that may differ from those in the local ISM.

Alexandre Gauvain, François Forget, Martin Turbet et al.

Surface runoff shapes planetary landscapes, but global hydrological models often lack the resolution and flexibility to simulate dynamic surface water bodies beyond Earth. Recent studies of Mars have revealed abundant geological and mineralogical evidence for past surface water, including valley networks, crater lakes, deltas and possible ocean margins dating from late Noachian to early Hesperian times. These features suggest that early Mars experienced periods allowing liquid water stability, runoff and sediment transport. To investigate where surface water could accumulate and how it may have been redistributed, we developed a global high-resolution (km-scale) surface hydrological model. The model uses a pre-computed hydrological database that maps topographic depressions, their spillover points, hierarchical connections between basins, and lake volume-area-elevation relationships. This database approach greatly accelerates simulations by avoiding repeated geomorphic processing. The model dynamically forms, grows, merges and dries lakes and putative seas without prescribing fixed coastlines, by transferring water volumes between depressions according to their storage capacities and overflow rules. We explore model behavior over the present-day Mars' topography measured by MOLA (Mars Orbiter Laser Altimeter) topography for a range of evaporation rates (from 0.1 m/yr to 10 m/yr) and total water inventories expressed as Global Equivalent Layer (from 1 mGEL to 1000 mGEL). 48 Simulations are iterated to reach the steady state. The model outputs the extent and depth of surface water bodies and identifies main drainage pathways using overflow fluxes as runoff indicators. Results show a transition toward a contiguous northern ocean between low (1-10 m) GEL values and increasing concentration of water in northern lowlands and major impact basins at higher GEL.

George Messinios, Konstantinos Koutroumbas, Olga Sykioti

In this study, we introduce a novel clustering-based methodology for mapping lunar surface mineralogy using hyperspectral data from the Moon Mineralogy Mapper (M³). The proposed methodology utilizes the Hapke photometric model to convert reflectance values to Single Scattering Albedo (SSA) values and constructs the distribution/histogram of the positions where the SSA signatures of the pixels in the entire image exhibit absorptions. Then, based on this histogram, an appropriate feature representation for each pixel is defined, oriented to the characterization of the pixel mineral composition. The k-means clustering algorithm is then applied on the new pixel representations. Mineral composition analysis for each cluster is then performed by evaluating whether the absorption features of each pixel match predefined absorption rules based on the spectral characteristics of eight selected typical minerals found on the Moon. Moreover, the proposed methodology provides mineral compositions within each pixel. The methodology is applied on an M³ dataset covering an area at the eastern Mare Serenitatis and the western Mare Tranquillitatis. The main results reveal spatial and compositional variations among clusters, and they are compatible with prior knowledge on various lunar maria basaltic compositions, demonstrating the reliability of the proposed methodology applied on planetary mineral exploration.

Elhadji Mory Traore, Akinade S. Olatunji, Mory Sidibe et al.

The Bougouni region in southwestern Mali hosts lithium-bearing pegmatites within the Paleoproterozoic Birimian greenstone belt. These pegmatites are classified into lithium-poor and lithium-rich types. Lithium-rich pegmatites are coarse-grained and abundant in spodumene, displaying high concentrations of lithium, cesium, and tantalum. They are characterized by minerals like potassic feldspar, spodumene, plagioclase, quartz, and white mica. Geochemical analysis reveals that the Bougouni pegmatites are silica-rich, resembling the Archean Tanco pegmatite, suggesting a more evolved magmatic history. Variations in aluminum and potassium content likely reflect differences in source materials and geological processes. Trace element compositions, including Rb, Sr, La, and U, provide unique geochemical signatures for each pegmatite field, indicating diverse mineralization processes and fluid-rock interactions.

S.I. Bryukhov, D.A. Artem’yev, I.A. Blinov et al.

The paper considers mineralogical and geochemical features of gold-sulfide mineralization of quartz veins in granites of the Katsbakh complex in the South Sukhtelya gold occurrence (South Urals). The sulfide content of quartz veins varies from 1 to 3 vol. %, rarely reaching 10 vol. %, and the average Au content is 5–10 g/t. Three types of native gold are identified: 1) in assemblage with Fe oxyhydroxides and in quartz (the fineness of 649–830 ‰), 2) in assemblage with tourmaline (the fineness of 870–888 ‰) and 3) in Fe oxyhydroxides in assemblage with fischesserite and in secondary Cu minerals. The sulfides include pyrite, chalcopyrite, sphalerite and galena. Pyrite is enriched in Ni, chalcopyrite contains Ag, Sn, and Sb, galena is rich in Se, Ag, Te, Bi, and Sb, and sphalerite has a higher amount of Cd, In, and Hg. The Au content of pyrite, chalcopyrite, and sphalerite is less than 0.1 ppm increasing up to 5 ppm in chalcocite and up to 168 ppm in Fe hydroxides. The ores formed during a gradual temperature decrease in a range from 400 to 200 °C, which corresponds to a sequence of mineral formation: pyrite → chalcopyrite → sphalerite → galena. The oxidation of sulfides resulted in the formation of the high-fineness native gold in assemblage with fishesserite.

Yan Shi, Jinyang Huo, Yuanyi Wang et al.

This investigation examines the impact of machine-made sand methylene blue (MB) values on mortar properties and microstructure through controlled clay type and content testing, encompassing macro-performances, microstructures, and mechanisms measuring compressive strength, flexural strength, drying shrinkage, frost resistance, impermeability, pore structure, microstructure, interfacial transition zones (ITZs), and hydration products. MB testing demonstrates that montmorillonite and illite exhibit a significant sensitivity divergence, where 1% montmorillonite achieves an MB value of 1.42, exceeding 1.40, while illite requires a 5% content to attain an MB of 1.50, complying with SL/T 352-2020 specifications. Increasing MB values induce an initial rise followed by a decline in 7d compressive strength yet a persistent increase in flexural strength for montmorillonite mortars, with both strength parameters decreasing at 28d and 90d. Illite mortars exhibit progressive declines in compressive and flexural strength across all curing ages (7d, 28d, and 90d) with rising MB values. SEM-EDS analyses reveal a deteriorating mortar microstructure, reduced paste compactness, and thickened ITZ under identical clay types as MB values increase. Combined XRD and TG-DTA analyses demonstrate a diminishing hydration degree and decreased hydration products in mortars with ascending MB values. Given a constant clay mineralogy, elevated MB values inhibit hydration-product formation, causing incomplete cement hydration reactions and deteriorated ITZ microstructures, consequently impairing mortar macro-performances.

Haijun Cao, Jian Chen, Xuejin Lu et al.

Abstract The Mg-pyroxene annulus in the South Pole–Aitken (SPA) basin holds crucial information about the lunar crustal evolution, yet its mineralogy and origin remain debate. Here we analyzed the mineralogy, exogenic ejecta, and soil evolution of the 2.8-billion-year-old Chang’e-6 samples from the SPA basin by Raman spectroscopic technique. The Chang’e-6 soils contain mare basalts and noritic exogenous ejecta (31–40 vol%), likely from Chaffee S crater. The derived mineralogy (63–67 vol% plagioclase and 25–27 vol% low-Ca pyroxene) of Mg-pyroxene annulus indicates a ferrous noritic lithology, attributed to a mixture of differentiated norite from the SPA impact melt sheet and re-deposited SPA crust (61–63 vol%). Ejecta accumulation facilitated glass formation, while small impacts induced quartz metamorphism, mixing mature basaltic soil with fresh ejecta, and leading to the fine-grained CE-6 soil. These findings provide new insights into the origin of SPA mafic anomalies and farside mare soil evolution.

Ahmed Gad, Hasan Arman, Saffet Yagiz et al.

Abstract This study characterized the mechanical behaviours of massive fractured (MLS), fossiliferous (FLS), and siliceous (SLS) limestone lithofacies under natural, dry, and saturated conditions. Uniaxial compressive strength (UCS), point load index (PLI), and indirect tensile strength (ITS) tests, along with petrographic, mineralogical, and geochemical analyses, were used to evaluate the impacts of the lithofacies composition and environmental conditions on rock strength. The results indicate that lithofacies composition, including mineralogy and texture, has a considerable effect on rock strength and durability. Under dry conditions, UCS values increased by up to ~ 200% in MLS and SLS relative to natural conditions, while saturation reduced UCS by 30–60% depending on lithofacies. Similar trends were observed in ITS, which decreased by up to 55% under saturation. The high silica content of SLS produced the most durable lithofacies, whereas the high porosity of FLS made it the most vulnerable to weakening from water exposure. MLS exhibited intermediate properties, as it loses strength considerably when existing fractures become saturated. Statistical analysis indicates that the CaO, SiO2, and MgO contents strongly influenced the rock mechanical properties. The study reveals relationships between lithofacies geochemistry, microstructural attributes (fractures, porosity, fossil interfaces), and mechanical responses under different moisture states. These insights allow for predictions about carbonate rock mechanical performance, making them crucial for geological research, engineering projects, industrial applications, and infrastructure design.

F. Tinaut-Ruano, J. de León, E. Tatsumi et al.

In the context of charge-coupled devices (CCDs), the ultraviolet (UV) region has mostly remained unexplored after the 1990s. Gaia DR3 offers the community a unique opportunity to explore tens of thousands of asteroids in the near-UV as a proxy of the UV absorption. This absorption has been proposed in previous works as a diagnostic of hydration, organics, and space weathering. Aims. In this work, we aim to explore the potential of the NUV as a diagnostic region for primitive asteroids using Gaia DR3. We used a corrective factor over the blue part of Gaia spectra to erase the solar analog selection effect. We identified an artificial relation between the band noise and slope and applied a signal-to-noise ratio (S/N) threshold for Gaia bands. Meeting the quality standards, we employed a Markov chain Monte Carlo (MCMC) algorithm to compute the albedo threshold, maximizing primitive asteroid inclusion. Utilizing one- and two-dimensional (1D and 2D) projections, along with dimensionality-reduction methods (such as PCA and UMAP), we identified primitive asteroid populations. We uncovered: (a) the first observational evidence linking UV absorption to the 0.7 μm band, tied to hydrated iron-rich phyllosilicates; and (b) a 2D space revealing a split in C-type asteroids based on spectral features, including UV absorption. The computed average depth (3.5 +- 1.0 %) and center (0.70 +- 0.03 μm) of the 0.7 μm absorption band for primitive asteroids observed with Gaia is in agreement with the literature values. In this paper, we shed light on the importance of the UV absorption feature to discriminate among different mineralogies (i.e., iron-rich phyllosilicates vs. iron-poor) or to identify taxonomies that are conflated in the visible (i.e., F-types vs. B-types). We have shown that this is a promising region for diagnostic studies of the composition of primitive asteroids.

هاشم شاهسونی

یکی از روش‌های ژئوفیزیکی که می‌توان برای اکتشاف ذخایری عمقی استفاده کرد روش مغناطیس‌سنجی است. مرسوم‌ترین ابزار اندازه‌گیری در روش مغناطیس‌سنجی زمینی، مغناطیس‌سنج‌های پروتون است. مغناطیس‌سنج‌های پروتون در مقایسه با حسگرهای میکروالکترومکانیکی گران قیمت و سنگین هستند و اندازه بزرگی دارند. همچنین نرخ نمونه‌برداری این مغناطیس‌سنج‌ها پایین است. این امر باعث می‌شود عملیات صحرایی زمان‌بر و هزینه‌بر باشد. با پیشرفت تکنولوژی، حسگرهای میکروالکترومکانیکی بسیار سبک و ارزان قیمت با نرخ نمونه‌برداری بالا و حساسیتی قابل قبول، معرفی شده‌اند. در این مطالعه یکی از این حسگرها راه‌اندازی شده و سپس برداشت‌هایی بر روی یک ذخیره کوچک آهن که در مجاورت روستای سرسیف در شهرستان سقز استان کردستان واقع است، انجام شده است. نتایج این برداشت‌ها با نتایج برداشت‌های انجام شده با استفاده از مغناطیس‌سنج پروتون مقایسه شده‌اند. این مقایسه نشان می‌دهد در برداشت‌های مغناطیس‌سنجی با استفاده از حسگرهای میکروالکترومکانیکی در محدوده مورد نظر، زمان برداشت حدود 5/8 ساعت و زمان برداشت بر روی همان پروفیل‌ها با استفاده از مغناطیس‌سنج پرتون حدود 30 ساعت است. همچنین هزینه برداشت با استفاده از حسگر به یک پنجم برداشت با مغناطیس‌سنج پروتون کاهش یافته است. به این ترتیب کاهش هزینه و زمان برداشت در یک عملیات مغناطیس‌سنجی که از اهداف این تحقیق است، برآورده شده است.

Livan García-Obregón, Luis Alberto Pérez García, Adrián Alujas-Díaz et al.

El estudio se centró en la influencia de la génesis geológica y el grado de cristalinidad en la cuantificación de fases minerales y contenido amorfo en arcillas cubanas. Se tomaron dos depósitos de arcilla con diferente génesis geológica y las muestras se caracterizaron mediante difracción de rayos X y técnicas de análisis de la fracción arcillosa. Se establecieron paragénesis dominantes para cada depósito, dominadas por caolinita, y se encontraron relaciones útiles entre diferencias estructurales y de tamaño de partículas con la génesis geológica, que pueden afectar una cuantificación adecuada. Se determinó que el nivel de meteorización condiciona el grado de cristalinidad, que a su vez tiene una fuerte relación con factores que inciden en una adecuada cuantificación. Finalmente, se establecieron los elementos fundamentales para formular una metodología integral para la adecuada caracterización y cuantificación de las fases arcillosas.

Ankushev M.N. , Alaeva I.P., Ankusheva P.S. et al.

The problem of the beginning of iron production in the Late Bronze Age of the Ural-Kazakhstan region is discussed. For this, 13 iron-bearing artefacts from nine settlements that functioned in the 2nd mil. BC were studied using the SEM-EDS and LA-ICP-MS methods: metal objects, metallurgical slags, and a bimetallic droplet. Most of the studied artefacts are not related to the iron metallurgy. High ferric impurities in copper metal products of the Late Bronze Age on the territory of the Southern Trans-Urals are caused by the use of iron-rich ore concentrates. The raw materials for these products were represented by mixed oxidized-sulphide ores from the cementation subzone of the volcanogenic massive sulphide and skarn copper deposits. Iron droplets, frequently found in the Late Bronze Age copper slag in the Ural-Kazakhstan region, are not directly related to iron metallurgy. They are by-products of the copper metallurgy formed in the process of copper extraction from the iron-rich components of the furnace charge or fluxes (brown iron ore, iron sulphides). The only artefacts that indicate direct smelting of metal from iron ore are the slag fragments from the Kent settlement. Presumably, oxidized martitized ore of the Kentobe skarn deposit or its nearby analogues was used to extract iron at the Kent settlement. Rare finds of iron slags from the Late Bronze Age, known only in the territory of Central Kazakhstan, confirm an extremely small scale of iron production. Iron ore had been already deliberately used for these experiments. However, iron metallurgy in the Ural-Kazakhstan region developed into a mature industry much later. The discovery of iron metallurgy based on the smelting of copper-sulphide ores in the Ural-Kazakhstan steppes is doubtful. The use of sulphide ores here is known from the 20th c. BC, and it was widespread. In the meantime, the first iron slags and products appear much later, and their finds are sporadic. The development of iron metallurgy on the basis of experiments with iron ores seems more likely.

Alireza Almasi, amir mahdavi, Jingwen Mao

Porphyry Cu deposits are typically oxidized. Oxygen fugacity (fO2) is a key factor, which controls the formation of porphyry Cu deposits. Trace element compositions of Cretaceous magmatic zircon grains (65.9-65.1 Ma) were determined from ore-bearing intrusive rocks of Gazu porphyry Cu deposit in the Tabas block. Then Ce4 +/Ce3+ of zircons were calculated, and estimated the oxygen fugacity of their parental magmas. The values of Ce4 +/Ce3+ in Gazu magmatic zircons are medium to low (range from 10 to 385 with an average of 110) which indicate a small deposit. The low oxygen fugacity values (average ∆FMQ ~ +1) of Gazu magma indicate that during the crystallization of magmatic zircons, the magma did not show high oxidized state (above hematite-magnetite buffer (HM) and ~ ΔFMQ + 4), which is not favorable for porphyry mineralization. This is confirmed by evidence such as magma generation due to metasomatized lithospheric mantle peridotite melting with low involving of the slab and mineralogy of deposit (lack of hematite-magnetite intergrowth and anhydrite). The contamination process during the ascent and emplacement had a decreasing effect on the oxygen fugacity of the Gazu emplaced bodies.

E. Fritsch, E. Fritsch, E. Balan et al.

<p>The OH stretching vibrational properties of eight serpentine samples from veins of the New Caledonian ophiolite have been investigated by Fourier-transform infrared spectroscopy (FTIR) in the mid-infrared and near-infrared ranges and by Raman spectroscopy. The samples were selected for their monophasic composition (Lz: lizardite; Ctl: chrysotile; and Atg: antigorite) making them representative of the three serpentine species. Comparison of fundamental and overtone spectra allowed us to interpret most of the observed bands and to propose consistent spectral decomposition in individual components. The OH stretching bands related to intrinsic vibrational properties of the minerals are distinguished from those associated with chemical substitutions in octahedral sites (mainly Fe and Ni for Mg substitutions). Observations made on the most symmetric Lz are consistent with previous interpretations and underline the effect of macroscopic parameters on OH stretching bands in the FTIR spectra. The major importance of the distribution of OH bond lengths in the broadening of the vibrational signals of the less symmetric and more distorted Atg is confirmed. The combination of the three spectroscopic methods makes it possible to unravel the occurrence of two different types of interlayer OH environments in Ctl nanotubes. One corresponds to the features observed at 3684 and 7171 cm<span class="inline-formula">⁻¹</span> in the fundamental and overtone spectra, respectively, and is similar to the local OH environment observed in Lz. The other corresponds to broader signals observed at 3693 and 7200 cm<span class="inline-formula">⁻¹</span> in the fundamental and overtone spectra, respectively. It reflects a distribution of OH bond lengths likely related to local structural misfits between adjacent layers in the tubular structure of Ctl.</p>

Pavol Matlovič, Julia de Leon, Hissa Medeiros et al.

Most of the currently known basaltic (V-type) asteroids are believed to be past or present members of the Vesta dynamical family. The rising discoveries of V-type asteroids that are not dynamically linked to the Vesta family suggest that a number of major basaltic bodies may have been present during the early stages of the solar system. In this work, we aim to provide a spectral analysis of 14 V-type candidates of various dynamical types, selected from the Moving Objects from VISTA Survey (MOVIS) catalogue. The computed visible and near-infrared (NIR) spectral parameters are used to investigate evidence of space-weathering or mineralogical differences from the expected basaltic composition. Based on the analysis of their visible spectra, we confirm 11 new V-type asteroids: six low-i asteroids - (3188) Jekabsons, (3331) Kvistaberg, (4693) Drummond, (7223) Dolgorukij, (9007) James Bond, and (29733) 1999 BA4; along with four inner-other asteroids - (5524) Lecacheux, (19983) 1990 DW, (51742) 2001 KE$_{55}$, and (90023) 2003 BD$_{13}$; as well as one fugitive - (2275) Cuitlahuac. Additionally, we analysed three peculiar outer main belt candidates based on their visible + NIR spectra. We confirm the diogenite-like composition of (2452) Lyot. The spectrum of asteroid (7302) is inconsistent with a basaltic composition and likely reflects an S-type body. The spectrum of (14390) 1990 QP$_{10}$ shows unique features that suggest a peculiar, unclassified composition. Overall, our results demonstrate the efficiency of the MOVIS catalogue in identifying V-type objects, with a success rate of over 85\%. The identification of V-types in the inner main-belt is more likely due to the presence of the Vesta family and other nearby asteroids that had escaped from the family. In the middle and outer main belt, where the amount of data is more limited, the proportion of false positives increases.

وهاب سرفرازی, شادمان محمدی بلبان اباد

در این مقاله،  روش شکست درزه ناممتد عمود بر‌هم با ایجاد بار نقطه‌ای برنده TBM توسط آزمایش‌های آزمایشگاهی و مدل‎سازی عددی مورد بررسی قرار می‌گیرد.  به‎این منظور، 4 نمونه آزمایشگاهی از جنس گچ با ابعاد 10*10*5 سانتی‎متر حاوی درزه ناممتد عمود بر‎هم آماده‎سازی شد. نمونه‌ها دارای دو درزه ناممتد با طول‌های 1 و 2 سانتی‎متر و عمود بر یکدیگر بودند. درزه کوچک‎تر دارای زاویه‌داری0، 45، 90 و 135 درجه نسبت به افق است. این نمونه‌ها زیر اثر بار نقطه‎ای برنده U شکل قرار گرفتند. هم‎زمان با مطالعات آزمایشگاهی، توسط نرم افزار FRANC2D شبیه‌سازی عددی نیز بر روی نمونه‌های حاوی درزه‌های ناممتد عمود برهم انجام شد. به‎طور کلی، 12 مدل عددی که الگوی هندسی آنها شبیه نمونه‌های آزمایشگاهی بود، ساخته شد.  نتایج نشان می‌دهد که آرایش درزه ناممتد T شکل، تاثیر به‌سزایی بر الگوی رشد و گسترش ترک دارد. نمونه در زوایای 45 و 135درجه نسبت به محور اعمال بار، کمترین مقاومت را دارد. با مقایسه الگوی شکست نمونه آزمایشگاهی و مدل عددی، می‌توان نتیجه گرفت که الگوی شکست مشابهی در نمونه آزمایشگاهی و مدل‌‌های عددی به‌وقوع پیوسته است.

Tamara de Riese, Paul D. Bons, Enrique Gomez-Rivas et al.

Crustal-scale fluid flow can be regarded as a bimodal transport mechanism. At low hydraulic head gradients, fluid flow through rock porosity is slow and can be described as diffusional. Structures such as hydraulic breccias and hydrothermal veins both form when fluid velocities and pressures are high, which can be achieved by localized fluid transport in space and time, via hydrofractures. Hydrofracture propagation and simultaneous fluid flow can be regarded as a “ballistic” transport mechanism, which is activated when transport by diffusion alone is insufficient to release the local fluid overpressure. The activation of a ballistic system locally reduces the driving force, through allowing the escape of fluid. We use a numerical model to investigate the properties of the two transport modes in general and the transition between them in particular. We developed a numerical model in order to study patterns that result from bimodal transport. When hydrofractures are activated due to low permeability relative to fluid flux, many hydrofractures form that do not extend through the whole system. These abundant hydrofractures follow a power-law size distribution. A Hurst factor of ~0.9 indicates that the system self-organizes. The abundant small-scale hydrofractures organize the formation of large-scale hydrofractures that ascend through the whole system and drain fluids in large bursts. As the relative contribution of porous flow increases, escaping fluid bursts become less frequent, but more regular in time and larger in volume. We propose that metamorphic rocks with abundant veins, such as in the Kodiak accretionary prism (Alaska) and Otago schists (New Zealand), represent regions with abundant hydrofractures near the fluid source, while hydrothermal breccias are formed by the large fluid bursts that can ascend the crust to shallower levels.

Robert Schouwstra, Johan Mocke, Michael Duncan et al.

Over the years the theft of material from platinum producers has mainly taken place from high-grade areas such as the precious- and base-metal refineries and the converter and smelting operations. At some concentrators, the metallic stream, which concentrated the larger platinum group mineral (PGM) grains using shaking tables (a gravity process), was also at risk due to its high grade. However, the processing of metallics was discontinued many years ago. The relative low grade of concentrator products has led to the belief that the concentrators are a low-risk area for theft. The final products are still very diluted by the gangue minerals, and to recover and purify the various metals contained in these products requires costly processing techniques (i.e., smelting and refining). High-grade stolen products are generally offered to small refineries who either further process, and package, or directly ship the material overseas for refining. In the case of stolen concentrates, the volume and value of the material would make that an unprofitable option. This assumption, as well as the risk the thieves run of being caught while removing large quantities of material from the concentrators, has resulted in management considering theft from concentrators of lesser importance than theft from the smelters or refineries. However, over the past few years investigations by protection services at concentrators have shown that high-grade platinum products are smuggled off-site. These products have been found on the concentrator as well as at illegal smelthouses where these type of products are processed further. Forensic investigations indicated that these upgraded products are much higher in grade than the normal concentrator products, characterised by high platinum contents, and contain high-density minerals such as galena (lead sulphide) and chromite. This suggests that these materials are significantly upgraded prior to smuggling these out of the operations. The method used by the perpetrators results in much of the value minerals being discarded, giving rise to concentrates that are atypical of Bushveld products. To better understand the process of upgrading these products and to get more information for the ‘fingerprinting’ database on the ‘at-risk products’, concentrator products were obtained from areas where material is stolen for further upgrading. This paper describes the upgrading process used by the illegal ‘processors’ and discusses the mineralogy and chemistry of the various products down the illegal processing chain. The study indicates that products containing coarse, liberated platinum-group minerals are the most favorable for upgrading. Flotation products with high precious metal grades and low chromite contents are preferred by the syndicate members. These are typically the first cells of the rougher banks, final concentrates, and the various cleaners and re-cleaners feeding into the final concentrates.

M. Popescu, J. Licandro, D. Morate et al.

The Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE) provide information about the surface composition of about 100,000 minor planets. The resulting visible colors and albedos enabled us to group them in several major classes, which are a simplified view of the diversity shown by the few existing spectra. We performed a serendipitous search in VISTA-VHS observations using a pipeline developed to retrieve and process the data that corresponds to solar system objects (SSo). The colors and the magnitudes of the minor planets observed by the VISTA survey are compiled into three catalogs that are available online: the detections catalog (MOVIS-D), the magnitudes catalog (MOVIS-M), and the colors catalog (MOVIS-C). They were built using the third data release of the survey (VISTA VHS-DR3). A total of 39,947 objects were detected, including 52 NEAs, 325 Mars Crossers, 515 Hungaria asteroids, 38,428 main-belt asteroids, 146 Cybele asteroids, 147 Hilda asteroids, 270 Trojans, 13 comets, 12 Kuiper Belt objects and Neptune with its four satellites. The colors found for asteroids with known spectral properties reveal well-defined patterns corresponding to different mineralogies. The distributions of MOVIS-C data in color-color plots shows clusters identified with different taxonomic types. All the diagrams that use (Y-J) color separate the spectral classes more effectively than the (J-H) and (H-Ks) plots used until now: even for large color errors (<0.1), the plots (Y-J) vs (Y-Ks) and (Y-J) vs (J-Ks) provide the separation between S-complex and C-complex. The end members A, D, R, and V-types occupy well-defined regions.

Vishnu Reddy, David Vokrouhlický, William F. Bottke et al.

We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovička et al. (2013). Using detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to 1999 NC43. We find about (1-3) x 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the about (10-3 -10-2) level. We also verified compositional link between Chelyabinska and 1999NC43. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode with the mean wobbling angle 20-30 deg. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the asteroid 1999 NC43 to be unlikely.