Mineralogy Mapper Research Articles

Mineralogical mapping and lithological discrimination by using ASTER remote sensing data in the Chitral region, Khyber Pakhtunkhwa, Northern Pakistan

Mineralogical mapping and lithological discrimination by using ASTER remote sensing data in the Chitral region, Khyber Pakhtunkhwa, Northern Pakistan

Structural and mineralogical mapping using multispectral satellite data (Aster, Landsat 8 OLI, and Sentinel 2B) combined with field work in the Western High Atlas, Morocco

Structural and mineralogical mapping using multispectral satellite data (Aster, Landsat 8 OLI, and Sentinel 2B) combined with field work in the Western High Atlas, Morocco

Lunar mantle composition and timing of overturn indicated by Mg# and mineralogy distributions across the South Pole-Aitken basin

The South Pole-Aitken (SPA) basin, excavating more than 100 km depth, must have exposed extensive lunar mantle materials, making it a promising location for sampling mantle material. To investigate the distribution of potential mantle materials across the SPA basin, we mapped the distribution of Mg# and major minerals contents using Moon Mineralogy Mapping data and radiative transfer modeling. We found that the potential mantle material exposed by SPA is Mg-rich orthopyroxenite, and we identified the locations of seven mantle candidate sites. The Chang'E-6 sample return site is located near mantle candidate sites within the Apollo basin, making it promising to return the first unambiguous mantle sample. Our Mg# and mineral mapping results show that the SPA ejecta is enriched in low-Ca pyroxene (LCP) with Mg#≥85, consistent with a post-overturn upper mantle composition. The enrichment of LCP in the SPA upper mantle may result from a low content of dunite or incomplete overturn.

Integrated Remote Sensing for Geological and Mineralogical Mapping of Pb-Zn Deposits: A Case Study of Jbel Bou Dahar Region Using Multi-Sensor Imagery

This research applies remote sensing methodologies for the first time to comprehensively explore the geological and mineralogical characteristics of the Jbel Bou Dahar region. An integrated approach with multi-sensor satellite images, including ASTER, Landsat-8, and Sentinel-2 was applied with the aim to discriminate the different lithological units in the study area. We implemented a suite of well-established image processing techniques, including Band Ratios, Principal Component Analysis, and Spectral Angle Mapper, to successfully identify, classify, and map the spatial distribution of carbonate minerals, OH-bearing minerals, and iron oxide minerals. Due to its high spectral resolution in the short-wave infrared region (SWIR), the ASTER sensor provided the most accurate results for mapping carbonate and OH-bearing minerals compared to the Sentinel-2 and Landsat-8 sensors. Conversely, Sentinel-2 offers high spectral and spatial resolution in visible and near-infrared (VNIR) corresponding to the regions where iron oxide minerals exhibit their characteristic absorption peaks. The results confirm the advantages of remote sensing technologies in the geological and mineralogical exploration of the study area and the importance of selecting the appropriate sensors for specific mapping objectives.

Assessing the Suitability of Territories for Detailed Geological and Mineralogical Mapping Based on Statistical Methods for Processing Remote Sensing Data from the Landsat-8 Spacecraft: Using the Example of Southeastern Zabaykalsky Krai, Russia

Assessing the Suitability of Territories for Detailed Geological and Mineralogical Mapping Based on Statistical Methods for Processing Remote Sensing Data from the Landsat-8 Spacecraft: Using the Example of Southeastern Zabaykalsky Krai, Russia

Marker Minerals in Volcanics and Xenoliths—An Approach to Categorize the Inferred Magmatic Rocks Underneath the Present-Day Volcanic Landscape of Tenerife, Spain (NW African Rare Mineral Province)

A mineralogical mapping (terrain analysis) based on micro-mounts has been performed in the Archipelago of the Canary Islands, Spain. The rare elements Be, F, Li, Nb, Ta, Zr, Hf, and rare earth elements (REE) were investigated on the largest island of the Canary Islands Archipelago, Tenerife, Spain. This study forms a contribution to the metallogenetic evolution of the offshore area of the NW African Rare Mineral Province. The finds made at Tenerife were correlated by means of minero-stratigraphy with the adjacent islands La Gomera, Gran Canaria and Fuerteventura, where typical critical element host rocks, e.g., carbonatites, are exposed. At Tenerife, these hidden rock types are only indicated by a wealth of 128 compositional first-order marker minerals hosting Be, F, Zr, Nb, Ta, Zr, Hf, Li, Cs, Sn, W, Ti and REE plus Y and another 106 structural second-order marker minerals describing the geodynamic and morpho-structural evolution of Tenerife (Mn, Fe, Pb, U, Th, As, Sb, V, S, B, Cu, Zn, Mo, Au). Based upon the quantitative micro-mineralogical mapping of lithoclasts and mineralogical xenoliths (foid-bearing monzodiorite/gabbro, (nepheline) syenite, phonolite trachyte) in volcanic and volcaniclastic rocks, hidden intrusive/subvolcanic bodies can be delineated that are associated with contact-metasomatic, zeolitic and argillic alteration zones, as well as potential ore zones. Two potential types of deposits are determined. These are pegmatite-syenites with minor carbonatites bound to a series of agpaitic intrusive rocks that are genetically interlocked with rift zones and associated with a hotspot along a passive continental margin. Towards the east, the carbonatite/alkali magmatite ratio reverses at Fuerteventura in favor of carbonatites, while at Gran Canaria and La Gomera, shallow hypogene/supergene mineral associations interpreted as a marginal facies to Tenerife occur and a new REE discovery in APS minerals has been made. There are seven mineralizing processes different from each other and representative of a peculiar metallogenic process (given in brackets): Protostage 1 (rifting), stages 2a to 2d (differentiation of syenite–pegmatite), stages 3 to 4b (contact-metasomatic/hydrothermal mineralization), stages 5a to 5b (hydrothermal remobilization and zeolitization), stage 6 (shallow hypogene-supergene transition and kaolinization), and stage 7 (auto-hydrothermal-topomineralic mineralization). The prerequisites to successfully take this holistic approach in economic geology are a low maturity of the landscapes in the target area, a Cenozoic age of endogenous and exogenous processes amenable to sedimentological, geomorphological, volcano-tectonic and quantitative mineralogical investigations. The volcanic island’s mineralogical mapping is not primarily designed as a proper pre-well-site study on the Isle of Tenerife, but considered a reference study area for minero-stratigraphic inter-island correlation (land–land) and land–sea when investigating the seabed and seamounts around volcanic archipelagos along the passive margin, as exemplified by the NW African Craton and its metallogenic province. This unconventional exploration technique should also be tested for hotspot- and rift-related volcanic islands elsewhere on the globe for mineral commodities different from the ones under study.

Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts

Abstract. Soil dust aerosols are a key component of the climate system, as they interact with short- and long-wave radiation, alter cloud formation processes, affect atmospheric chemistry and play a role in biogeochemical cycles by providing nutrient inputs such as iron and phosphorus. The influence of dust on these processes depends on its physicochemical properties, which, far from being homogeneous, are shaped by its regionally varying mineral composition. The relative amount of minerals in dust depends on the source region and shows a large geographical variability. However, many state-of-the-art Earth system models (ESMs), upon which climate analyses and projections rely, still consider dust mineralogy to be invariant. The explicit representation of minerals in ESMs is more hindered by our limited knowledge of the global soil composition along with the resulting size-resolved airborne mineralogy than by computational constraints. In this work we introduce an explicit mineralogy representation within the state-of-the-art Multiscale Online Nonhydrostatic AtmospheRe CHemistry (MONARCH) model. We review and compare two existing soil mineralogy datasets, which remain a source of uncertainty for dust mineralogy modeling and provide an evaluation of multiannual simulations against available mineralogy observations. Soil mineralogy datasets are based on measurements performed after wet sieving, which breaks the aggregates found in the parent soil. Our model predicts the emitted particle size distribution (PSD) in terms of its constituent minerals based on brittle fragmentation theory (BFT), which reconstructs the emitted mineral aggregates destroyed by wet sieving. Our simulations broadly reproduce the most abundant mineral fractions independently of the soil composition data used. Feldspars and calcite are highly sensitive to the soil mineralogy map, mainly due to the different assumptions made in each soil dataset to extrapolate a handful of soil measurements to arid and semi-arid regions worldwide. For the least abundant or more difficult-to-determine minerals, such as iron oxides, uncertainties in soil mineralogy yield differences in annual mean aerosol mass fractions of up to ∼ 100 %. Although BFT restores coarse aggregates including phyllosilicates that usually break during soil analysis, we still identify an overestimation of coarse quartz mass fractions (above 2 µm in diameter). In a dedicated experiment, we estimate the fraction of dust with undetermined composition as given by a soil map, which makes up ∼ 10 % of the emitted dust mass at the global scale and can be regionally larger. Changes in the underlying soil mineralogy impact our estimates of climate-relevant variables, particularly affecting the regional variability of the single-scattering albedo at solar wavelengths or the total iron deposited over oceans. All in all, this assessment represents a baseline for future model experiments including new mineralogical maps constrained by high-quality spaceborne hyperspectral measurements, such as those arising from the NASA Earth Surface Mineral Dust Source Investigation (EMIT) mission.

Mapping the mineralogy in the Oxia Planum and Mawrth Vallis ExoMars landing sites – implications for aqueous alteration and paleoenvironmental evolution

Mineralogical studies constitute one of the main tools to investigate geological processes on Mars. Here, the mineralogy of the ExoMars landing sites Oxia Planum and Mawrth Vallis is analyzed based on multispectral datasets of the CRISM Compact Reconnaissance Imaging Spectrometer for Mars of Mars Reconnaissance Orbiter, TES Thermal Emission Spectrometer of Mars Global Surveyor and OMEGA Visible and Infrared Mineralogical Mapping Spectrometer of Mars Express are integrated and interpreted. Primary and secondary minerals of carbonates, oxides, silicates and sulphates mineral groups are characterized, with most minerals produced by aqueous alteration, with 35 mineral species identified, amongst which phyllosilicates are the dominant group. Coexisting mineral types point to distinct hydrothermal and alteration stages. Our investigation supports that water must have been present on early Mars on superficial and endogenous processes, causing direct precipitation and transformations of secondary minerals, with some not usually formed simultaneously. Hence, it is likely that species may have arisen at different times, due to changes of Martian climate. Some minerals may have formed in the subsurface. The Martian palaeoenvironments might include subaerial, underwater, and shallow subsurface hydrothermal systems, cold springs, alkaline lakes, sabkhas, and playas. Our results contribute to our understanding of the planned landing sites to prepare for what the ExoMars rover mission may encounter, highlighting the impact that water may have had on the mineral genesis, alteration processes and their astrobiological potential.

The method of medium-scale mineralogical mapping during diamond searching: a case study in the Ygyatta Region (Western Yakutia)

The analysis of mineralogical information has enabled the development of a novel mineralogical zoning method using GIS and statistics. The proposed method was applied to the Ygyatta Region located within the Yakut Diamond-bearing Province. A set of mineralogical characteristics was chosen to examine the information content and productivity of the terrigenous collectors, providing an exact identification of the development areas of the deposits and the locations of their primary sources during medium-scale forecasting. The developed GIS-integrated database of the mineralogical passports of mine workings was based on the identification of background and anomalous parameters in the mineralogical field. The latter, within the Ygyatta Region, was delineated using ModelBuilder. The proposed method demonstrates the ability to contour mineralogical taxa of the “node” and “section” ranks within the Ygyatta Region, leading to the identification of six mineralogical nodes and fifteen mineralogical sections. This method can be effective for medium-scale zoning, based on mineralogical data from other diamond-bearing areas.

Lithological discrimination and mineralogical mapping using Landsat-8 OLI and ASTER remote sensing data: Igoudrane region, jbel saghro, Anti Atlas, Morocco

This study aims to delineate the lithological formations, in addition to a mineralogical mapping comparing between the ASTER and Landsat-8 OLI sensors in the Igoudrane region. The research was accomplished using BR along with spectral profiles of minerals, PCA, MNF, ICA, XRD, and reflectance spectrometry. The BR measured with ASTER revealed the presence of amphibole, illite, smectite, muscovite, phengite, basic degree index SiO2, calcite, chlorite, epidote, dolomite, hydroxides, and ferrous silicates. Furthermore, Landsat-8 OLI BR highlighted areas with oxides, hydroxides, and laterite. The spectral profiles of minerals showed their absorption in the VNIR and SWIR regions. The muscovite and illite (phyllic alteration) are distinguished by Al–OH absorption at 2.20 μm. The argillitic alteration is additionally defined by muscovite, illite, and Kaolinite, where Kaolinite has a high absorption at 0.9 μm. Chlorite and carbonates characterized the propylitic alteration zone, with an absorption ranging between 2.3 μm and 2.35 μm due to CO3 and Mg–OH compositions. The oxidation (hematite and jarosite) was distinguished by absorption near 0.95 μm and 2.3 μm, respectively, whereas the goethite spectral profile exhibits absorption near 1.4 μm and 2.2 μm. The absorption of smectite is 1.4 μm, near 2.2 μm. The amphibole had absorption near 1.4 μm and 2.3 μm, whereas the pyroxene had absorption near 1.4 μm and 2.3 μm. The first three components of PCA, MNF, and ICA showed the highest eigenvalues and gave an appreciable discrimination of the lithologies, especially with ASTER. Moreover, the XRD quantified the mineralogy of the rocks, which were compared to the BR of ASTER. The reflectance spectrometry also provided alteration minerals, such as muscovite, phengite, illite, Fe–Mg chlorite, Fe-chlorite, iron oxides, hydroxides, hornblende, and calcite. Overall, the methodology adopted has shown great performance and strong potential for mapping alteration areas and lithological discrimination in similar arid regions.

An advanced thermal roughness model for airless planetary bodies

We present a combined reflectance and thermal radiance model for airless planetary bodies. The Hapke model provides the reflected component. The developed thermal model is the first to consistently use rough fractal surfaces, self-scattering, self-heating, and disk-resolved bolometric albedo for entire planets. We validated the model with disk-resolved lunar measurements acquired by the Chinese weather satellite Gaofen-4 at around 3.5–4.1 μm and measurements of the Diviner lunar radiometer at 8.25 μm and 25–41 μm, finding nearly exact agreement. Further, we reprocessed the thermal correction of the global lunar reflectance maps obtained by the Moon Mineralogy Mapper M3and employed the new model to correct excess thermal radiance. The results confirm the diurnal, latitudinal, and compositional variations of lunar hydration reported in previous and recent studies with other instruments. Further, we compared the model to lunar measurements obtained by the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) on board BepiColombo during a flyby maneuver on April 9, 2020: the measured and the modeled radiance variations across the disk match. Finally, we adapted the thermal model to Mercury for emissivity calibration of upcoming Mercury flyby measurements and in-orbit operation. Although a physical parameter must be invariant under various observation scenarios, the best lunar surface roughness fits vary between different datasets. We critically discuss possible reasons and conclude that anisotropic emissivity modeling has room for improvement and requires attention in future studies.

Mineralogical Mapping Using Remote Sensing and Geophysical Data in IMITER Anti-Atlas of Morocco

Mineralogical Mapping Using Remote Sensing and Geophysical Data in IMITER Anti-Atlas of Morocco

Territory Suitability Assessment for Conducting Detailed Geological and Mineralogical Mapping Based on Statistical Methods of Remote Sensing Data Processing Landsat-8: A Case Study in the Southeastern Transbaikalia, Russia

The work considers the suitability of using multispectral satellite remote sensing data Landsat-8 for conducting regional geological and mineralogical mapping of the territory of south-eastern Transbaikalia (Russia) in conditions of medium- low-mountain relief and continental climate. The territory was chosen as the object of study due to its diverse metallogenic specialization (Au, U, Mo, Pb-Zn, Sn, W, Ta, Nb, Li, fluorite). Diversity in composition and age of ore-bearing massifs of intrusive, volcanogenic and sedimentary rocks are also of interest. Statistical processing algorithms to increase spectral information content of satellite data Landsat-8 were used; they include: principal component analysis (PCA); minimum noise fraction (MNF) and independent component analysis (ICA). Eigenvector matrices analysed on the basis of statistical processing results and two-dimensional correlation graphs were built to compare thematic layers with geological material classes: oxide/hydroxide group minerals containing transition iron ions (Fe3+ and Fe3+/Fe2+); a group of clay minerals containing A1–OH and Fe, Mg–OH; minerals containing Fe2+ and vegetation cover. Pseudo-coloured RGB composites representing the distribution and multiplication of geological materials classes was generated and interpreted. Integration of informative thematic layers with using fuzzy logic model was carried out to construct a prospectivity map. Received map was compared with geological information, and positive conclusions about territory suitability for further remote mapping research of hydrothermally altered zones and hypergenesis products in order to localize areas promising for identifying hydrothermal-metasomatic mineralization were made.

Mineralogical constraints on the genesis of an alkalic-type epithermal Au-Te deposit: Tuvatu, Fiji

To study the characteristics and genetic constraints on alkalic-type epithermal Au mineralisation, here we use the example of the Tuvatu Au-Ag deposit in Fiji, with an emphasis on detailed, quantitative mineralogy. Tuvatu mineralisation is hosted in a weakly altered potassic monzonite in parallel sided-veins of K-feldspar, biotite, sericite, calcite, and quartz, with epidote-bearing propylitic or sericite-rich selvages. Petrographic study of core and automated SEM-based mineralogical mapping of thin sections have been utilised to update previous parageneses of the deposit. Automated SEM techniques enable identification of small amounts of obscure minerals that form minuscule grains, which would otherwise be very difficult to identify and measure. As a result, our data show that gold fineness is extremely high, with the mean and median Au content of native-Au and Au-Ag alloy being 96.7% and 100% respectively, yet precious-metal tellurides make up the majority of the Au deportment. Tellurides show evidence of multiple phases and zoning with depth. For the first time at Tuvatu, Pt- and Pd-tellurides have been identified. Tuvatu has a number of features in common with alkalic systems elsewhere, including quartz-poor, carbonate-rich veins and alteration, abundant and varied telluride minerals, high gold grades, and Pt-Pd occurrences. We suggest these characteristics are a result of relatively high temperature (250–300 °C) fluids and immiscible semi-metal melts fluxing into the shallow epithermal environment. High pH fluids lead to quartz-poor alteration, but mildly acidic conditions dominate in areas of high fluid flux, where the lower pH causes precipitation of tellurides with quartz. Boiling of the fluids produces zonation of tellurides with depth but leaves relatively subtle textural evidence compared to boiling in most epithermal systems, in common with other quartz poor, carbonate-rich alkalic epithermal deposits around the world.

Quartz veins and silver-containing crushing zones in the exocontact of Solur granite stock (Kularsky district, Yakutia)

The purpose of the work is a investigation of quartz varieties present in quartz veins and crushing zones in order to establish the formation conditions and the possibilities of using quartz varieties to study the distribution of mineralization during exploration. The work was stimulated by the discovery of gold and gold-silver mineralization in adjacent areas and the possibility of using some new methods for studying quartz. Research methods. Samples for the study were taken during the mineralogical mapping of the studied area in the course of work to assess the prospects for its ore potential. The characterization of quartz from veins and crushing zones was carried out on the basis of its field descriptions and laboratory microscopic study, as well as measurements of X-ray luminescence (RL) of vein quartz in the region of 350–550 nm. Fluid inclusions in quartz and sulfur isotope composition in sulfides from quartz veins were also studied. Results and conclusions. The granite stock, surrounded by a zone of contact hornfels with cordierite and andalusite, lies among terrigenous sedimentary rocks that have undergone metagenesis (anhimetamorphism). Veins of glassy coarse-grained quartz and recrystallized (granular) quartz are located directly in the granites, partially recrystallized gray quartz – among the contact cornea, and veins of deformed milky-white quartz - in terrigenous sedimentary rocks outside the contact halo. As the transition from veins located among granites to veins located outside the granite massif, the intensity of quartz RL decreases sharply. The nature of the RL indicates the probable presence in the crystal lattice of quartz from veins in granites of their own defects – vacancies of oxygen or silicon, and in gray and milkywhite quartz – cation-compensated [AlO4 /M+]-centers. Sulfide mineralization in quartz veins is mainly represented by arsenopyrite with an isotopic composition of sulfur close to the meteorite standard. In addition to quartz veins, later crushing zones with hydrothermal injection breccias are also common in the area. In breccia cement and in breccia-intersecting veins, early non-split hypidiomorphic quartz and later split comb-shaped and chalcedony quartz are present. In micro-cryptogrаined chalcedony quartz with grain size up to 0.05 mm contaminated with inclusions of finely crushed rock particles and kaolinite grains, the inclusions of the pyrargyrite – one of the main silver-containing minerals on a number of gold-silver deposits of the region – were found. Based on the known vertical zonality of epithermal gold-silver deposits with the confinement of kaolinite-containing ores and chalcedony quartz to the upper horizons of the deposits, and due to the presence of micro-cryptograined chalcedony quartz containing kaolinite and pyrargyrite in the considered crushing zones, it can be suggested that these crushing zones may be confined to the upper parts of the silver mineralization development zone.

Geochemical and mineralogical soil survey of the conterminous USA: a project retrospective

From 2007 to 2010, the United States Geological Survey (USGS) conducted a low-density (one site per 1600 km 2 ), geochemical and mineralogical soil survey of the conterminous USA ( c . 8 × 10 6 km 2 ). This project was initiated to address the lack of a national soil geochemical database that was a critical need for state and federal environmental agencies, public health specialists and those engaged in risk assessment of contaminated land. Sampling and analytical protocols were developed in consultation with stakeholders at a 2003 workshop, and pilot studies were carried out from 2004 to 2007. Sampling began in 2007 and concluded in 2010. Chemical and mineralogical analyses were completed in 2013, and the datasets were released to the public that same year. Geochemical and mineralogical maps were published in 2014, and an interactive website was released in 2019. The author was Project Chief for this effort throughout the lifetime of the study. The evolution of the project is discussed from its inception through to the publication of results and its impact. The lessons learned during the project are reviewed in the hope that applied geochemists who undertake such broad-scale geochemical mapping projects in the future will find them useful. Thematic collection: This article is part of the Continental-scale geochemical mapping collection available at: https://www.lyellcollection.org/topic/collections/continental-scale-geochemical-mapping

Pore systems and organic petrology of cretaceous Mowry and Niobrara source-rock reservoirs, Powder River Basin, Wyoming, USA

The Powder River Basin (PRB) is a world-class oil province, in large part thanks to contributions from premier source rocks, Cretaceous Mowry and Niobrara shales. Both formations are also unconventional reservoirs. A critical aspect of evaluating production potential and finding sweet spots is the nature of the pore systems in these fine-grained source-rock reservoirs. Variation by stratigraphic interval is important for selecting optimum target zones for horizontal wells. Understanding variation in pore type, size, and connectivity and relationships with mineralogy and fabric help in determining prospectivity in different parts of the basin. Deciphering controls on pore-system development helps predict intervals and locations of optimum reservoir quality.Imaging of Niobrara and Mowry samples from a range of thermal maturities provided observations and data on pore systems, organic matter (OM) types and associations with mineralogy and fabric, wettability, and microporosity associated with both diagenetic and detrital clays. Imaging techniques included scanning electron microscopy, organic petrography and correlative scanning electron microscopy, and mapping of mineralogy through energy dispersive spectroscopy.Mean solid bitumen (BRo) and vitrinite reflectance (VRo) values indicate all samples are in the oil window with values ranging from 0.52 to 1.15%. Organic fluorescence is prominent in amorphous OM, solid bitumen and some vitrinite in the early oil window. The fluorescence is extinguished at higher thermal maturity. Carbonate pellets (in Niobrara) mainly contain migrated solid bitumen and residual live oil and little or no terrigenous OM (vitrinite and inertinite). However, terrigenous OM is common in siliceous/argillaceous laminae in both formations, where it occurs with amorphous OM, some of which has converted in situ to a solid bitumen petroleum residue.One key finding is the widespread presence of migrated OM at very early oil window maturity. Distribution of such OM and associated wettability alteration is fabric-controlled, at all levels of thermal maturity studied. Clay morphology and abundance and supporting rigid mineral grain framework strongly influence pore development, preservation, and connectivity in both formations. Carbonate content is a good proxy for reservoir quality in Niobrara intervals due to association of porous solid bitumen with calcareous fecal pellets. High recrystallized microquartz content is associated with the best reservoir intervals in the Mowry.

Soil crusting: New insight from synchrotron 2D micro X-ray diffraction mapping of clay-particle orientation and mineralogy

Our understanding of soil crusting and its detrimental consequences is mainly based on the analysis of morphological changes occurring at the soil surface. Such changes are usually assessed at spatial scales ranging from a few millimeters to that of the field. The inner-reorganisation within the topsoil during soil crusting primarily involves the redistribution of clay particles. Their mineralogy and arrangement remain however delicate to determine by the sole use of microscope observations. To overcome these limitations, we developed an innovative methodology based on synchrotron 2D micro X-ray diffraction (2D-µXRD) to map relevant parameters related to the organisation of all types of soil clay minerals, i.e. relative diffracted intensities, degree of preferential orientation, mean deviation angle from the surface. Our methodological strategy was first validated on a laboratory-made model sample, composed of various pure clay phases with clear preferential orientations. Then, a vertical section of soil crust from long-term bare fallow (LTBF) experiment of the France's National Research Institute for Agriculture, Food and Environment (INRAE, Versailles, France) was studied. Micromorphological features of the soil crust were first described by using conventional scanning electron microscopy. Synchrotron 2D-µXRD analyses were then successfully applied on the same region of interest. The in-depth analysis provided by the synchrotron 2D-µXRD approach revealed the presence of clay microlayers that were not observed on SEM images. Additionally, clay mineralogy as well as preferred clay-particle orientation and overall alignment highlighted specific quantitative structural signatures. These signatures involved the discrimination between clay microlayers associated to the settling of clay particles in microdepressions and clayey microaggregates resulting from transportation of pre-existing soil crusts. This new technique has led to re-interpretation of the deposition mechanisms in the natural soil investigated here and opens wide perspectives for in-depth detailed characterization of clay mineralogy in soil crusts.

Automated Quantitative Mapping of Ore Minerals by Multispectral Reflected-light Microscopy

ABSTRACT An innovative multispectral reflected-light microscopy system is able to automatically identify ore minerals by measuring their specular reflectance with non-polarized light in a number of spectral bands, and comparing the values obtained with a reference database. In this way it can provide quantitative mineralogical mapping comparable to that obtained from automated mineralogy systems based on SEM-EDS (Scanning Electron Microscopy with Energy-Dispersive X-Ray Spectroscopy), at a fraction of the cost and with less stringent environmental and operational requirements. The new system, called AMCO (for Automated Microscopic Characterization of Ores), consists of an instrument and two proprietary software applications: amcoCapture, to acquire multispectral images of a polished section prepared from an ore sample, and amcoAnalysis, to process these images and extract different types of mineralogical information from them.

Geological and Mineralogical Mapping Based on Statistical Methods of Remote Sensing Data Processing of Landsat-8: A Case Study in the Southeastern Transbaikalia, Russia

The work considers the suitability of using multispectral satellite remote sensing data Landsat-8 for conducting regional geological and mineralogical mapping of the territory of south-eastern Transbaikalia (Russia) based on statistical methods for processing remote sensing data in conditions of medium–low-mountain relief and continental climate. The territory was chosen as the object of study due to its diverse metallogenic specialization (Au, U, Mo, Pb-Zn, Sn, W, Ta, Nb, Li, fluorite). Diversity in composition and age of ore-bearing massifs of intrusive, volcanogenic, and sedimentary rocks are also of interest. The work describes the initial data and considers the procedure for their pre-processing, including radiometric and atmospheric correction. Statistical processing algorithms to increase spectral information content of satellite data Landsat-8 were used. They include: principal component analysis, minimum noise fraction, and independent component analysis. Eigenvector matrices analyzed on the basis of statistical processing results and two-dimensional correlation graphs were built to compare thematic layers with geological material classes: oxide/hydroxide group minerals containing transition iron ions (Fe3+ and Fe3+/Fe2+); a group of clay minerals containing A1-OH and Fe, Mg-OH; and minerals containing Fe2+ and vegetation cover. Pseudo-colored RGB composites representing the distribution and multiplication of geological material classes are generated and interpreted according to the results of statistical methods. Integration of informative thematic layers using a fuzzy logic model was carried out to construct a prediction scheme for detecting hydrothermal mineralization. The received schema was compared with geological information, and positive conclusions about territory suitability for further remote mapping research of hydrothermally altered zones and hypergenesis products in order to localize areas promising for identifying hydrothermal metasomatic mineralization were made.