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The study of the chemical and mineralogical composition of the agricultural soils is essential to know its process of formation. and the characteristics associated to the fertility and to the retention of nutrients as foundations for conduct its use and management. With this objective are evaluated Brown sialitic and Vertisols soils representative of the eastern region of Cuba. The technique of X-rays diffraction (DRX) was used for determine the mineralogical and chemistry composition of the predominant soils. Were calculated the oxides SiO2, Al2O3, Fe2O3 and the molecular relations SiO2 / Al2O3, SiO2 / Fe2O3 and SiO2 / R2O3 for characterize the soils. The predominant minerals in the Brown soils were in that order: calcite, quartz, montmorillonite and anortite. In the Vertisols were detected quartz, albite and vermiculite that are very resistant to the meteorism. The vertical distribution of the minerals show a degree of evolution uniform of the parent rocks. The sequence of free oxides (SiO2> Al2O3> Fe2O3) corroborated the sialitic origin of the soil profiles, associated with the predominance of minerals in a relation 2:1. The uniform distribution of the total of elements in all the profiles shows a lithogenic origin. [ABSTRACT FROM AUTHOR]

A mineralogical and mineral chemistry study was carried out in the San Luis Alta telluride-rich gold deposit, mid-south Peru, to contribute towards determining its formation and improving the ore processing. The San Luis mineralization is considered an intrusion-related gold deposit located in the Arequipa segment of the Coastal Batholith. The mineralization occurs in quartz veins hosted in diorites and granodiorites from the Tiabaya Super-Unit. These veins are sulfide-rich in the deep areas and contain abundant iron oxides. Sulfides are mainly pyrite with minor chalcopyrite and galena. Native gold and telluride minerals are abundant. Mineral chemistry was determined using an electron microprobe. The mineralogy of veins was classified into four stages. Gold occurs in the three last stages either in large grains, visible to the naked eye, or, more frequently, in grains of less than 10 µm. Gold appears as grains encapsulated in pyrite, Fe oxides, quartz and filling fractures. The first stage is characterized by the deposition of quartz and massive pyrite, which does not contain gold. During the second stage, hessite, calaverite, petzite and altaite are formed. Additionally, Bi-tellurides, mainly volynskite, rucklidgeite, kochkarite and tellurobusmuthine, are formed. Some of these minerals occur as blebs encapsulated in pyrite, suggesting that a Bi-Te-rich melt was formed from the ore-forming hydrothermal fluid and transported the Au and Ag elements. This stage was followed by a fracturing event and tellurobismuthite, tetradymite and montbrayite precipitated. In the last stage, a supergene replacement formed covellite, bornite and goethite. Te-Bi minerals do not appear in this stage, but selenium minerals occur in minor amounts. Chlorargyrite and iodargyrite occur and are associated with gold. [ABSTRACT FROM AUTHOR]

Different ore deposit types may evolve from a common magmatic-hydrothermal system. Establishing a genetic link between different deposit types in an ore cluster can not only deepen the understanding of the magmatic-hydrothermal mineralization process but can also guide exploration. Both the Nihe iron-oxide–apatite (IOA) deposit and the Shaxi porphyry Cu–Au deposit in the Lower Yangtze Valley, Anhui, Southeast China, formed in the Luzong Cretaceous volcanic basin at ~130 Ma. We examined a temporal–spatial and potential genetic link between these deposits based on stratigraphic lithofacies sections, biotite and clinopyroxene mineralogical chemistry, zircon chronology, Hf isotopes, and trace elements. Stratigraphy, petrology, mineralogical chemistry, and available fluid inclusion results support that the emplacement depth of the Nihe ore-related porphyry is shallower than that of the Shaxi porphyry. The magmatic zircon and hydrothermal zircon from Nihe provided U–Pb ages of 130.6 ± 0.7 Ma and 130.7 ± 0.7 Ma, respectively. The magmatic zircon U–Pb age (130.0 ± 0.8 Ma) of Shaxi overlaps with its molybdenite Re–Os age (130.0 ± 1.0 Ma). The agreement between the mineralization and porphyry emplacement ages of Nihe and Shaxi indicates a temporal coincidence and supports a possible genetic link between the two deposits, considering their close spatial relationship (in the same ore district, 15 km). The zircon Hf isotopes and trace elements support the evolution of both deposits from an enriched lithospheric mantle, although the Shaxi deposit may have experienced contamination of the Jiangnan-type basement. Both deposits lie above the fayalite-magnetite-quartz buffer, but the Nihe magmatic zircons are of lower temperature and less oxidized than that of Shaxi. The much higher Eu/Eu* and Yb/Dy values of zircons from Shaxi are likely caused by the suppression of early plagioclase crystallization and the prevalence of amphibole fractionation, thus indicating more hydrous content of the Shaxi ore-related magma. Additionally, the Shaxi ore-related porphyry has higher zircon Hf concentrations, suggesting that the porphyry Cu–Au deposit has experienced a greater degree of magma fractionation. Our study highlights that the Nihe IOA deposit and the Shaxi porphyry Cu–Au deposit have a common magma source, while different extent of crust contamination, magma oxidation state, hydrous content, and degree of magma fractionation collectively result in the two distinct ore deposits. This possible genetic link suggests a great potential of porphyry Cu–Au-PGE mineralization in the Middle–Lower Yangtze River metallogenetic belt, especially in the deep part of the IOA district in the Luzong Cretaceous volcanic basin. [ABSTRACT FROM AUTHOR]

Sediment-derived granites (S-type) can provide detailed information about continental crust reworking processes and tectonic regimes through time. Their compositions reflect the nature of sedimentary rocks that melted to form them. Inherited accessory minerals in these granites can provide information regarding the age and nature of the crustal rocks that contributed to the formation of their sedimentary source rock. In addition, S-type granites typically form during collisional stages in modern orogens, and their Precambrian records can provide clues about ancient tectonics. In this contribution, we present a detailed petrogenesis of the Cupim Pluton, located in the Paleoproterozoic Mineiro Belt (Brazil). The Cupim pluton is composed of two-mica and garnet-bearing leucogranites that are strongly peraluminous (ASI > 1.1), high-K (K 2 O/Na 2 O > 1), low MgO + FeO + TiO 2 (<2 wt%). Its composition is similar to that of melts experimentally produced by muscovite/biotite dehydration melting reactions. Rb/Sr and Rb/Ba ratios suggest that these leucogranites are formed by the melting of heterogeneous sedimentary source(s). Zircon crystals from the Cupim Pluton unveil a protracted crustal melting period (2.01–1.98 Ga) hitherto unknown in the Mineiro Belt, which itself discloses a late collisional orogenic stage in southern São Francisco Craton. Igneous zircon crystals exhibit εHf (t) between −16.4 and − 0.6, and δ30Si between −1.16 and − 0.26 ‰, which is typical for zircon from sediment-derived granites. Hafnium isotope variations reflect mixing between at least two crustal sources, which is in line with inherited zircon cores that evidence major Archean and minor Paleoproterozoic sediment contributions. The emplacement of the Cupim Pluton leucogranites ends a subduction-collision cycle, following a long period of TTG-sanukitoid magma production, and promoted the stabilization of the southern São Francisco Craton. [Display omitted] • Cupim Pluton is composed of sediment-derived (two-mica and garnet-bearing) granites. • Whole-rock and mineralogical chemistry diversity point to source heterogeneity. • 2000 Ma zircons mark the collisional event in the Southern São Francisco Craton. • Inherited zircons reveal Archean contribution to Paleoproterozoic sedimentary basins. • Zircon Hf-Si isotope compositions attest to crust reworking and source mixing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantitative reconciliation of mineralogical data with leachate dynamic. • Investigation of mine waste rock water content on weathering. • Decrease in leachate pH at lower water saturation. • Carbonate phase size reduction with increase in water saturation. Water content plays a critical yet ambivalent role in the physical and geochemical stability of mine tailings and waste rock, but its effects on individual chemical weathering reactions (dissolution and precipitation) and bulk water quality remain poorly understood. We experimented with synthetic waste rock to quantitatively reconcile modal and textural mineralogical parameters (mineral size, association, and liberation) with leachate quality at different water saturation levels (5–100%). Leachate pH consistently decreased from a 13-week average of 6.14 at 100% saturation to 5.37 at 5% saturation. Simultaneously, mineralogical analyses revealed a reduction in the size of carbonate phases over the course of weathering, decreasing from 200 µm to 145 µm as water saturation increased from 5% to 100%, which could be a contributing factor to more alkaline pH in samples with higher water saturation. Total concentrations of iron (Fe) and copper (Cu) in solution increased with lower moisture, with Cu concentrations increasing 24-fold in samples at 5% saturation compared to full saturation. In contrast, arsenic (As) concentration increased with higher moisture levels, which we attribute to reduced galvanic protection of As-bearing pyrite from oxidation. Multivariate statistical evaluation allowed us to uncover correlations between water chemistry and mineralogical data (i.e., sulfide associations or phase perimeters) and to explain chemical differences between samples, particularly those at 100% and 5% water saturation. Our findings underscore the importance of conducting quantitative mineralogical investigations on mine waste materials and considering their stored water content in the formulation of mine waste management strategies. [ABSTRACT FROM AUTHOR]

Keywords: Phyllosilicates; glauconite; nontronite; peak shift EN Phyllosilicates glauconite nontronite peak shift 1080 1090 11 06/01/22 20220601 NES 220601 Introduction Raman spectroscopy found widespread application in the rapid and non-destructive characterization of silicate minerals ([26]; [8]; [35]; [34]; [44]; [31]; [1]; [45], 2015; [30]). Concluding remarks In this study, Raman spectroscopy analysis of nontronite and glauconite-nontronite mixed-layer phases from deep-sea hydrothermal fields reveals that these phyllosilicates have diagnostic Raman spectral features that include a series of strong peaks in the low wavenumber region (<700 cm SP -1 sp ) and the hydroxyl domain (3500-3700 cm SP -1 sp ). To fill these knowledge gaps, this study reports a comprehensive Raman spectral characterization of nontronite and glauconite-nontronite mixed-layer phases (i.e., vertical mixing/interstratification of glauconite and nontronite layers) from seafloor hydrothermal fields. Chemistry/structure-dependent Raman spectral features of glauconite and nontronite For the analyzed nontronite and glauconite-nontronite mixed-layer samples, the covariations between Raman spectral properties and octahedral chemistry (Table 2; Figs. [Extracted from the article]

We conducted outcrop‐to‐nanoscale structural observations on a principal slip zone (PSZ) of the Yangsan fault, a major strike‐slip fault in southeast Korea, and some high‐velocity rotary shear tests on the PSZ gouges to understand shear localization and physico‐chemical processes in the PSZ during earthquakes. At the fault outcrop, the PSZ appears 1–2 cm thick. At smaller scales, the PSZ is subdivided into Units 1 to 4 based on their microstructures. Microscopic observations confirmed the shear localization in Units 1 (20–500 μm in thickness) and 3 (0.8–3 mm in thickness). Further localization was observed in several μm‐thick shear bands. Various structural and mineralogical features that recorded physico‐chemical processes in slip zones were found in the PSZ, including gouge fluidization structures relevant to thermal pressurization, solidified frictional melt of clay‐rich gouge, and mineralogical changes by frictional heating‐induced illitization. The gouge melting and mineralogical changes were reproduced in our experiments at 1.3 m s−1. The gouge fluidization has been observed in previous tests at seismic slip rates. Thus, the observations from the natural and experimental faults indicate that the shear localization in the PSZ was coseismic. In a cataclasite zone next to the PSZ, altered veins of pseudotachylyte were found. All these observations indicate temporal changes of the PSZ materials (e.g., formation of solidified melt, alteration of the melt into clay minerals, friction‐induced mineralogical changes). Associated with such changes, coseismic slip zone processes and dominant weakening mechanisms may also vary, even at the same location on a fault. Plain Language Summary: Shear strain may be localized into narrow zones of tectonic faults in short‐term and long‐term scales. We conducted outcrop‐to‐nanoscale structural observations on a principal slip zone (PSZ) of the Yangsan fault in southeast Korea and shear tests on fault rocks taken from the fault at 1.3 m s−1 to understand the short‐term shear localization in the fault during earthquakes. Frictional heating‐related geological records such as gouge injection structures, solidified frictional melt, and mineralogical changes were found in the principal slip zone. The frictional gouge melting and mineralogical changes were reproduced in our experiments, and the gouge injection structures were observed in previous shear tests at seismic slip rates. Thus, the natural and experimental observations indicate that the shear localization into the PSZ, which is several tens of μm to several mm in thickness, occurred during earthquakes. Further localization was also observed in several μm‐thick shear bands in the PSZ. This study gives us an idea of shear localization zone thickness in natural fault zones. Also, it shows, with changes in slip zone materials, physical and chemical processes in fault slip zones during earthquakes may vary with time, even at the same location of a fault. Key Points: Shear localization occurred in natural slip zones as thin as several μm to tens of μmGeologic records of clay‐rich gouge melting, gouge fluidization, and friction‐induced illitization indicate coseismic shear localizationWith changes in slip zone materials, coseismic slip zone processes and dominant weakening mechanisms may vary with time [ABSTRACT FROM AUTHOR]

[Display omitted] • Initial timing of the extensional environment of the EKOB was not later than 428 Ma. • No genetic relation between highly evolved rhyolite and trachyte at Haidewula. • Strongly peraluminous volcanic rocks are favorable U-sources for mineralization. Zircon U–Pb-Hf isotopic compositions, mineralogical chemistry, and whole-rock geochemistry analyses were performed on rhyolite and trachyte from the Haidewula deposit in the East Kunlun Orogen Belt (EKOB). These analyses aimed to elucidate the genetic relationship between trachyte and rhyolite and to investigate the role of these volcanic rocks in uranium mineralization. Zircon U–Pb isotope dating indicates that the Haidewula rhyolite and trachyte were contemporaneous with emplacement ages of 421 Ma to 428 Ma, respectively. The trachyte samples exhibit high K 2 O/Na 2 O and Fe# [FeO/(FeO + MgO)] ratios, and belong to metaluminous, ferroan volcanic rock; the rhyolite samples display high A/CNK and Fe# ratios, elevated high field strength element contents, and can be classified as strongly peraluminous A 2 -type magma. Trace and major elemental geochemical signatures demonstrate that the Haidewula trachyte originated from the high-temperature partial melting of a mafic lower crust, followed by fractional crystallization of plagioclase, pyroxene, magnetite, and/or K-feldspar. On the other hand, the rhyolite was likely generated by high-temperature melting of granodiorite in a low water and mid-crust pressure environment, followed by fractional crystallization of feldspar and ilmenite. The occurrence of A-type volcanic rocks at Haidewula suggests that the initial timing of crustal extension in the EKOB was not later than 428 Ma. Overall, Paleozoic igneous rocks in the EKOB revealed that a post-collisional extensional regime, resulting from the rewelding of the microcontinents in eastern Gondwana, was responsible for intensive magmatism during the Late Silurian period. In comparison to other volcanic complexes hosting uranium deposits in eastern China, the relatively U-rich rhyolite and trachyte had the potential to contribute to the formation of U mineralization. In particular, the rhyolitic tuffaceous U-rich glassy volcanic rocks in the Haidewula deposit may represent favorable U-source rocks for mineralization, with uranium released through volcanic glass devitrification processes and leaching by oxidizing hydrothermal fluids. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mineralogical and geochemical analysis of Taiji-2 subseafloor samples on the SMAR were conducted. • Mineralogical and pyrite chemistry differences between stockwork and semi-massive sulfide samples were revealed. • w and logf S2 decrease from subseafloor stockwork to semi-massive sulfide zone. • Three distinct mineralization stages were identified. In modern seafloor hydrothermal mineralization systems, subseafloor deposits are crucial alongside seafloor massive sulfides, consisting mainly of stockwork at the periphery and semi-massive sulfides at the central of subseafloor ore bodies. These two ore types exhibit contrasting mineralogical and elemental compositions, and the difference between their formation processes are unclear due to sampling challenges. The mafic-hosted Taiji-2 hydrothermal field, located on the Southern Mid-Atlantic Ridge, presents pyrite-enriched subseafloor sulfides on the seafloor, providing a good research opportunity. Our study included comprehensive analyses of mineralogy, pyrite chemistry, and in-situ sulfur isotopes through LA-MC-ICP-MS method on Taiji-2 subseafloor samples. Our findings suggest: (1) a hybrid source of ore-forming materials, (2) increased seawater involvement and decreased temperature and sulfur fugacity from the periphery to the central of subseafloor deposits, and (3) multistage of subseafloor ore-forming activities. Additionally, we characterized the seafloor alteration of Taiji-2 subseafloor sulfides. These results enhance our understanding of subseafloor mineralization in seafloor hydrothermal field. [ABSTRACT FROM AUTHOR]

The ExoMars rover, scheduled to be launched in 2020, will be equipped with a novel and diverse payload. It will also include a drill to collect subsurface samples (from 0‐ to 2‐m depth) and deliver them to the rover analytical laboratory, where it will be possible to perform combined science between instruments. For the first time, the exact same sample target areas will be investigated using complementary analytical methods—infrared spectrometry, Raman spectrometry, and laser desorption mass spectrometry—to establish mineralogical and organic chemistry composition. Fundamental for implementing this cooperative science strategy is the Raman Laser Spectrometer (RLS) calibration target (CT). The RLS CT features a polyethylene terephthalate disk used for RLS calibration and verification of the instrument during the mission. In addition, special patterns have been recorded on the RLS CT disk that the other instruments can detect and employ to determine their relative position. In this manner, the RLS CT ensures the spatial correlation between the three analytical laboratory instruments: MicrOmega, RLS, and MOMA. The RLS CT has been subjected to a series of tests to qualify it for space utilization and to characterize its behavior during the mission. The results from the joint work performed by the RLS and MicrOmega instrument teams confirm the feasibility of the "combined science" approach envisioned for ExoMars rover operations, whose science return is optimized when complementing the RLS and MicrOmega joint analysis with the autonomous RLS operation. [ABSTRACT FROM AUTHOR]

The purpose of this study was to carry out a mineralogical, chemical, petrographic and physical-mechanical characterization of the two kinds of slate rocks from Tchihingue deposit in Angola in order to make a good use of them as industrial rocks. The characterization was carried out using Atomic Absorption Spectrometry, thin section petrographic analysis and X-ray diffraction. Determining physical-mechanical properties of the rock was carried out through the abrasion test, and resistance to flexion and compression. It was determined that slates have a majority chemical composition of silicon, aluminum, iron and potassium oxides. Both types have a very fine texture on a sericite matrix, which classifies them as sericitic slates. They are essentially composed of muscovite and quartz. Kaolinite is identified on the yellow slate and hematite on the brown slate as accessory minerals, distinctive features of each slate. Brown slate is richer in micaceous minerals and yellow slate has higher quartz content. The technological properties of these slates are suitable for application as an industrial rock, with little significant difference in flexural strength. The selection of its potential can be given from the aesthetic point of view. [ABSTRACT FROM AUTHOR]

Analyses of the zircon U—Pb age, mineralogical chemistry and whole-rock geochemistry of the Jiling pluton along the southern margin of the Alxa Block were conducted. The results of these analyses will provide crucial information for investigations of Paleozoic crust-mantle interactions in the North Qilian Orogenic Belt (NQOB) and explorations of the transition age from a compressional to extensional environment during the collision between the Alxa Block and the Qilian-Qaidam Block. The zircon dating results reveal that the Jiling pluton is composed of Early Silurian granitoids (435–442 Ma) with contemporaneous mafic microgranular enclaves (MMEs). Most granitoids contain amphibole and titanite and have A/CNK values <1, illustrating that they belong to amphibolite-rich calc-alkaline granitoids (ACGs) and K-rich and K-feldspar porphyritic calc-alkaline granitoids (KCGs). Both the granitoid and MME samples display variable initial Sr and Nd isotopic compositions. We suggest that the Jiling pluton was formed by crust-mantle-derived magma mixing. The high HFSE content of the MMEs indicates that the mantle-derived magmas were derived from melting of the mantle wedge metasomatized by adakitic magma, and the crustal-derived magmas were derived from melting of Paleoproterozoic meta-basaltic rocks in the Longshoushan Group. The discovery of the Jiling granitoids indicates that the NQOB was dominated by a compressional environment during Middle Ordovician-Early Silurian in response to the collision between the Qilian-Qaidam Block and the Alxa Block, and the initial extensional environment began before 442 Ma. • The Jiling granitoids and MMEs were emplaced at Early Silurian (442–435 Ma). • The Jiling granitoids were formed by crustal-mantle-derived magma mixing. • Transition from compression to extensional environment started before 442 Ma in the NQOB. [ABSTRACT FROM AUTHOR]

Zisha stoneware is a distinctive pottery tradition unique to China. This ceramic tradition was highly popularized during the Ming Dynasty (1368–1644 CE), and continues to be manufactured through the present day. Throughout history, Zisha stoneware vessels have been highly desirable objects used mainly by high status individuals, and by the early 17th century was exported to Europe as trade items. Soon thereafter, European imitations of Zisha stonewares were produced in the Netherlands at Delft, and in England and Germany. Today, authentic Zisha wares are difficult to discern from imitations using the naked eye alone, which poses problems for provenance, authenticity of antiquities, and reconstructing ancient ceramic technologies developed in China. The goal of this study was to determine the elemental and mineralogical properties of Zisha clays and to evaluate their suitability for archaeological provenance study. This study used petrographic thin-section analysis and neutron activation analysis to characterize multiple distinct types of Zisha clays, as well as other regional clays, from deposits around Huanglong Mountain (Yixing City, China). Representative samples of each clay type were sub-divided into untreated raw clays and processed and fired ceramics for comparison. The results show clays from each major collection area have unique compositional signatures based on their trace element chemistries and mineralogical properties. Additionally, those characteristics are stable and not significantly altered by preparation or firing processes. We propose that Zisha clays have high potential for archaeological provenance studies of Zisha stoneware antiquities. • Zisha stoneware is representative of cultural heritage in China • Clay samples measured using neutron activation analysis (NAA) • Geochemical characteristics examined by statistical analysis • Comparison between fired samples and raw clay materials provides reliable provenance information [ABSTRACT FROM AUTHOR]

The Paraná deposit, located at Southwestern Rio Grande do Norte state, in Brazil, is one of the few emerald deposits found at Borborema Province. The mineralization occurs in phlogopite schists and actinolite-phlogopite schists associated with pegmatites and albitites within the Portalegre Shear Zone. Unlike other well-known Brazilian emerald deposits, the mineralogy of Paraná emeralds has remained poorly investigated for the last 40 years. In this study, we conducted mineralogical characterization of theses emeralds through gemological testing, mineral chemistry, absorption and reflectance spectroscopy, and thermal analysis. The Paraná emeralds are bluish-green colored, characterized by high refractive index, several two-phase fluid inclusions and mica is the main mineral inclusion. Electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry analyses detected the presence of Fe2+ (0.43-1.94 wt.% FeO) and Cr3+ (0.04-0.14 wt.% Cr2O3) as the main chromophores replacing octahedral Al3+ in the crystal structure. In addition, substantial amounts of MgO (0.40-2.72 wt.%), Na2O (0.50-1.81 wt.%), and Cs2O (0.07-0.44 wt.%) were also identified. The main causes for its coloration were attributed to Cr3+ absorption features in visible spectral range, which were corroborated by absorption and reflectance spectra. The presence of types I and II H2O at channel-sites was recorded in Fourier-transform infrared spectra and demonstrated by dehydration processes observed in different thermal and thermogravimetric analyses. [ABSTRACT FROM AUTHOR]

Highlights • A new optical pathway was developed for images acquisition in the UV-band (365 nm). • Multispectral images analysis is proven to differentiate six various sulfides. • Six common sulfides were automatically identified and quantified by cluster analysis. • Procedures can be developed for sulfides quantification by optical microscopy. Abstract The mining industry needs effective techniques to meet the future challenges of resources extraction. As the deposits become more and more complex, a very good knowledge of an orebody is necessary. Mineralogical characterization is an essential contribution to improve the knowledge on the ore and wastes for a given mining project. It could bring major advances in ore extraction, mineral processing, and integrated waste management. However, mineralogical analyses can be very tedious, when done manually. Consequently, automated mineralogy was developed during the last three decades to improve the rapidity of mineralogical characterization, so that mineralogical information can be routinely obtained. Nowadays, the systems commonly used are based on expensive equipment including scanning electron microscopes (SEM) with energy dispersive X-ray analyzers (EDX). Optical Microscopy (OM) is neglected, although this route can provide reliable and quick results, yet cheaper. In this study, the possibility of using optical microscopy in reflected light mode to automatically characterize opaque minerals is explored. The identification and quantification of six common sulfides from polymetallic ores (arsenopyrite, chalcopyrite, galena, pyrite, pyrrhotite, and sphalerite) were automatically accomplished on a polished section by optical microscopy. Six spectral images were acquired for multispectral image analysis. Five of them were acquired under a white light source, equipped with four different excitation filters (436 nm, 480 nm, 605 nm, and 650 nm). The sixth image was acquired under an UV-light source at 365 nm, after modifying the optical pathway to detect the reflectance of the minerals in the UV-spectrum without changing the acquiring camera. Two image analysis software solutions were then tested to automatically classify and quantify the six sulfide minerals. The classification was systematically done on the acquired multispectral images by grey thresholding with the Clemex Vision PE® software. The GOCAD® software used principal component analysis (PCA) analysis and a supervised K-means clustering method to classify the minerals. Then, the obtained results were compared to the SEM-EDS quantification, considered here as the reference. The differences between the computed surface areas were mainly due to the artifacts of the polished sections preparation. The two software solutions present promising results and could be fully exploited to proceed to other mineralogical analyses, such as mineral liberation, mineral associations, textures identification, and particle size distribution. This study is an initial step towards differentiate and identify sulfides via an optical route arguably reliable and cheaper to characterize mine products. [ABSTRACT FROM AUTHOR]

Abstract The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics. Highlights • We investigated the Belessa kaolin deposit of Central Main Ethiopian Rift. • Chemical Index of Alteration showed that the host rocks are intensively altered. • The kaolin deposit is formed through supergene alteration of acidic volcanic rocks. • The dominant clay mineral identified in the kaolin ore is kaolinite. • The kaolin is found to be appropriate for ceramics, paper coating and filler. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Lower Carboniferous Jiujialu Fm at Zunyi, northern Guizhou, contains 110 m of Kazakhstan-subtype karst bauxite deposits. • Alternating bauxite ore and bauxitic claystone layers having different petrological, mineralogical and geochemical compositions. • A total of seven cycles developed in response to fluctuating groundwater table levels, controlled by LPIA glacio-eustasy. Abstract The Lower Carboniferous Jiujialu Formation bauxite deposits at Zunyi, northern Guizhou are distinguished by their great thickness (to 110 m) and cyclic alternation of bauxite ore and bauxitic claystone layers. These features are typical of the Kazakhstan subtype of karst bauxite deposits, although the genesis of this type of deposit is poorly understood. Here, we undertook a petrological, mineralogical, and geochemical study of the Zunyi deposit in drillcore ZK5600 to gain insights into its formation history. The Zunyi profile contains seven bauxite cycles, as recorded by petrological, mineralogical and geochemical features, indicating a multistage formation history. Each cycle is composed of a lower bauxitic claystone layer and an upper bauxite ore layer. The bauxite ore is characterized by high Al 2 O 3 , high Al-mineral (diaspore), and low SiO 2 content. Positive Ce anomalies, high CIA values (>90), and strong depletion of major elements indicate that the bauxite ore formed through intense chemical weathering and leaching in a well-drained soil environment. The bauxitic claystone is characterized by relatively lower Al 2 O 3 and higher SiO 2 and clay mineral (mostly illite) content. This lithology exhibits both negative and positive Ce anomalies, moderate CIA values (70–80), and enrichment of some elements (e.g., Fe, K), indicating formation through moderate chemical weathering in a poorly drained soil environment. Secular variations in chemical weathering intensity and soil drainage conditions were linked to regional hydrologic changes. During the early Carboniferous, the Zunyi area was located in a karstified coastal upland setting, and its hydrologic system was affected by glacio-eustatic fluctuations. High groundwater table elevations during eustatic highstands led to formation of bauxitic claystone layers, whereas low groundwater table elevations during eustatic lowstands led to formation of bauxite ore layers. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ca-enriched silicates and carbonates in the endo and exocontact of granites. • Carbonate and calcsilicate minerals are very much responsive. • Physical-chemical regime of Ca-enriched mineral assemblages. • Marker mineral assemblages for crustal and subcrustal impact. • Ca-enriched silicates and carbonates and the geodynamic setting. Abstract Metacarbonate rocks (marble, calcsilicate rock, skarn) hosting strata- and structurebound Fe-, As-Sb, Bi-, Ni-Co, Cu-Pb-Zn, U-, W- ore minerals as well as talc, clay minerals, barite and fluorite are widespread in the country rocks south of the collisional calc-alkaline felsic to intermediate intrusive rocks of the Fichtelgebirge Pluton, Germany. At its western rim, thrustbound and vein-type mineral assemblages with Au-As-Sb and F-Ba minerals associated with carbonate gangue minerals developed. Only recently, a calcite-hosted Sb mineralization was encountered in a deep-seated lineamentary fault zone cutting through metaultrabasic rocks along the northern edge of the granites. The same structure zone forms the loci of calcite-bearing U episyenite situated within this pluton. A composite geological, mineralogical and chemical (major and trace elements, REE, C- and O isotopes) study has been conducted to distinguish the heat and element source in subcrustal or deep-seated crustal areas and in the largely exposed granite complex. Only Sn-W skarn deposits are genetically related to the highly fractionated granitic members of the Variscan pluton. Pegmatite skarn has a strong subcrustal component as to the heat source and the provenance of rare elements and a moderate crustal one as far as the silicates are concerned. Deep-seated fault zones were active over a rather long period of time and acted as conduits venting magmas and hydrothermal fluids from the waning stages of the Variscan deformation through the Neogene. Calcsilicate and carbonate mineral assemblages are an efficacious tool to constrain the physico-chemical regime in this mineral province, covering the temperature range from 745 °C down to 53 °C in a medium to low pressure regime at strongly varying redox conditions. The major and trace elements, the REE variation, the Ce and Eu anomalies as well as carbon and oxygen isotopes of the various mineral assemblages enable us to identify the fluid sources and depict the element concentration processes, e.g., mixing of fluids, connate fluid and meteoric fluid interaction. From the economic point of view, the mineralizing system is most prospective for rare element deposits, talc, kaolinite-group minerals, iron, and uranium. Accumulations of fluorite and barite are subeconomic in mineral assemblages inside as well as outside the granites, while base metals and precious metals are only of mineralogical interest. [ABSTRACT FROM AUTHOR]

Abstract Eastern United States loess mapped by the U.S. Department of Agriculture, National Resources Conservation Service (USDA-NRCS) mostly occurs near major river systems like the Delaware and Susquehanna Rivers. The proximity of loess along major river valleys suggests late-Quaternary glacial meltwater sediments were dominant sediment sources for loess. Based on differing lithologies of meltwater deposits in these systems, we hypothesize that loess in each river system has a unique geochemical and mineralogical signature. To test this hypothesis, we examined pedons developed in loess parent materials, and adjacent to either the Delaware or West-Branch of the Susquehanna River, both of which carried large amounts of Wisconsinan outwash. Soils were analyzed for particle size distribution, clay mineralogy, and coarse and fine silt particle density, mineralogy, and geochemistry. Results show that while the pedons are similar in morphology, substantial differences exist in the pedons' textures, mineralogies, and geochemical compositions. We attribute the differences to parent material differences that stem from lithologically distinct sediment sources for loess from the two river systems. Susquehanna River loess has a higher particle density, and lower abundance of minerals such as Zr, base oxides (such as CaO), and rare earth elements. Discriminant analysis results suggest that developing a "loess fingerprint" for each river system based on major, minor and rare earth elements is possible, and likely to be useful in differentiating sources; however coarse silts may be a more effective fraction (than fine silts) for sediment sourcing, especially if rare earth elements are used. Highlights • We examined pedons developed in loess parent materials. • Soils were analyzed for particle size, mineralogy, and geochemistry. • Results suggest major, minor and rare earth elements can differentiate loess sources. [ABSTRACT FROM AUTHOR]

Abstract The characterization of ceramic materials from archaeological sites is of great importance to learn about the human traditions and regional History. In this work, 12 pieces of ceramics of the Cuatrovitas Archaelogical Site (Bollullos de la Mitación, Seville, Spain) were studied to approach the provenance of the raw material and the firing temperature. In addition, raw materials, from possible sources areas used for the manufacture of those ceramics, were also studied. Mineralogical characterization by XRD and chemical analyses of major, trace and rare earth elements were performed on both raw and ceramic materials. Thin sections, SEM-EDS analyses and micro-XRF mapping were carried out to complete the mineralogical and chemical characterization. The results show that there are two types of ceramic materials, probably prepared by mixtures of different clays and sandy materials. A feasible source area for those raw materials could be the alluvial of the Guadiamar River. According to the mineralogy of the high-temperature phases found in the ceramic pieces, two firing temperatures can be approached: one at 800–850 °C owing to the presence of calcite, and another at 900–950 °C because of the presence of diopside and gehlenite. Highlights • Guadiamar River alluvial is a possible area for raw material in Cuatrovitas Site. • Diopside and gehlenite suggest firing temperatures above 900–950 °C. • Calcite and absence of high temperatures phases suggests firing below 800–850 °C. [ABSTRACT FROM AUTHOR]

Abstract The Dongyang gold deposit is located in Fujian Province in southeastern China, mainly hosted by a NW–SE trending Late Jurassic porphyritic rhyolite, and classified as a low-sulfidation epithermal gold deposit. The units associated with the gold mineralization in this area are highly altered and have undergone sericitic and argillic alteration as well as silicification, with the latter two types of alteration especially associated with gold enrichment. The deposit contains pyrite, marcasite, and arsenopyrite, with lesser amounts of chalcopyrite, galena, sphalerite, and silver minerals. The sulfides and silver minerals within the deposit provide insight into the evolution of the ore-forming fluid and the processes that caused the gold enrichments to form in the study area. In addition, the geochemical similarity of gold and silver means these elements tend to migrate and precipitate simultaneously, in turn indicating that sulfides and silver minerals can provide insights into the processes that concentrate gold. Here, we present chemical compositional, and crystal structural data for sulfides and silver minerals within the Dongyang gold deposit by scanning electron microscopy (SEM), electron microprobe analyser (EMPA), X-ray diffraction (XRD) and laser Raman microprobe, and use these data to gain insights into the characteristics and evolution of the fluids that formed the deposit. We also outline key concepts for future gold deposit exploration in this region. Four types of pyrite in the deposit are recognized based on arsenic content and crystal morphology, evolving from early As-poor pyrite (Py1) to As-rich pyrite (Py2) and/or arsenopyrite, to non-cubic As-poor pyrite (Py3), and finally to cubic As-poor pyrite (Py4), with an inverse correlation between sulfur and arsenic concentrations. Pyrite crystal morphologies vary from earlier pentagonal dodecahedron forms to later cube forms, indicating a decrease in degree of supersaturation (as controlled by the activity of dissolved Fe and sulfide) and/or temperature conditions for pyrite growth. In addition, the presence of As-poor marcasite associated with early pyrite (Py1) suggests that the early ore-forming fluid was relatively acidic. Arsenopyrite is generally concentrated in the shallower parts of the deposit, indicating that later hydrothermal fluids were enriched in arsenic. This study also identified a number of key silver mineral phases that formed in a sequence from chalcopyrite, to a galena–fahlore–allargentum–dyscrasite–polybasite–electrum assemblage, to stephanite, and finally to chlorargyrite. Chalcopyrite replaced by fahlore suggests increased oxygen fugacity and decreased temperature. Fahlore Sb / (As + Sb) (>90%) and Ag / (Ag + Cu) ratios (6%–27%) are indicative of relatively high temperatures (>200 °C), and allargentum is thought to form in elevated pH conditions (pH > 7). Stephanite and chlorargyrite precipitated under relatively low temperature (<200 °C). Finally, the presence of chlorargyrite suggested that silver was transported as chloride complexes, indicating relatively high oxygen fugacity. The sequence of silver mineral precipitation suggests that the ore-forming fluids showed a temporal increase in pH and oxygen activity, and a decrease in temperature and sulfur fugacity. This indicates that the hydrothermal fluids that formed the deposit can be divided into early and late stage fluids, with the former being a relatively higher-temperature and higher‑sulfur fugacity fluid compared with the lower-temperature and higher‑oxygen-fugacity late-stage fluid. Finally, the presence of silver minerals with high gold contents (up to 2 wt%), as well as arsenian pyrite and arsenopyrite, may be useful indicators of prospective areas for gold exploration in this region. Highlights • Components and morphology of pyrite indicated decreased supersaturation and/or temperature. • Silver minerals indicated decreased temperature and sulfur fugacity, and increased pH and oxygen fugacity. • Ore-forming fluids are divided into early stage of reduced and high-temperature and late stage of oxidized and low-temperature. [ABSTRACT FROM AUTHOR]

Abstract Historical Cu-Slags located at former industrial sites in Poland are exposed to weathering that may trigger release of metallic contaminants to the surrounding soils. However, the extent to which different metals are leached depends on the mineral composition of the slags and the conditions of their deposition. Historical slags are often crystalline and composed of phases with a variable response to weathering. Also, weathering of crystalline slags (CS) is different from that of amorphous slags (AS). To understand how the slag phase composition triggers weathering and the ultimate release of metallic elements, we studied the leaching of historical crystalline and amorphous slag. A combined geochemical and mineralogical approach determined the weathering sequence(s) of slag components subjected to different conditions of specific slag disposal. In detail, experiments under: i) various pH conditions in the range of 2–13 in a batch mode simulated slag deposition within a deep soil profile, whereas ii) exposure to solutions of artificial root exudates (ARE) in a dynamic experimental system simulated slag deposition within topsoil. The results demonstrated that crystalline phases in the order Leucite > Plagioclase > Pyroxene are preferentially dissolved in inorganic conditions of a pH ≤ 7, in contrast to glass, which is preferentially dissolved in alkaline conditions (pH > 7). Also, inorganic conditions better promote the dissolution of metal-bearing phases (sulphides and metals) when compared to silicates. In contrast, artificial root exudates do not show preferential dissolution of any phase and cause the strongest leaching in all of the analyzed conditions. We show that reconstructing the susceptibility of complex crystalline slags to weathering requires a specific approach including analyses and interpretation of all major components such as Ca, Mg and K, not merely a focus on Si and metals. Highlights • Mg, Ca and Cu/Mg, Cu/Ca track preferential dissolution of slag phases. • Acidic artificial root exudates (ARE) promote severe dissolution of bulk slag. • Phase stability for inorganic acidic conditions: Cu phases > silicates > glass. • Phase stability for inorganic alkaline conditions: Cu phases > glass > silicates. • Cu release in ARE and inorganic conditions (pH 2–3) is environmentally relevant. [ABSTRACT FROM AUTHOR]

Abstract—Layer-by-layer chemical and mineralogical analysis was carried out to consider the evolution of the Fe-Mn crusts in different tectonic settings in the South Atlantic Ocean. The ferromanganese crust in the rift valley of the Mid-Atlantic Ridge was formed owing to the hydrothermal-hydrogenetic supply. The formation of crust in the Transform Fracture zones of the Angola Basin was related to the halmyrolysis of magmatic rocks and subsequent hydrogenetic supply, which affected the proportions of goethite and vernadite, the Mn/Fe ratio, and Ce anomaly, as well as the content of some elements (Co, Cu, Al, REE). It is revealed that the Fe-Mn crusts taken in the abyssal part and on the seamount top in the Cape Basin are hydrogenetic in origin and consist of vernadite significantly enriched in Co, Ce, Tl, and Pt. The relationship of trace elements with manganese minerals is estimated by leaching of crusts by reagents, which either completely dissolve manganese oxyhydroxides (1 M NH2OH · HCl + 25%CH3COOH) or no (3.5 N H2SO4). It was shown that 100% Co and only 28% Ce are incorporated in the manganese minerals, while REE, Y, Sr, and U form a sorption complex of oxhyhydroxides. To estimate the chemical peculiarities of the hydrogenetic Fe-Mn crusts of the Atlantic Ocean, they were compared with the crusts of the Pacific Ocean. It is shown that the crusts of the Pacific Ocean have higher manganese and cobalt contents. The additional manganese could be derived from a hydrothermal source. [ABSTRACT FROM AUTHOR]

This paper reports mineral and whole‐rock geochemical data (major and trace elements, Sr–Nd isotopes, and in situ plagioclase Sr‐isotope analysis) for Cenozoic volcanic rocks from Sabeto, NW Fiji, with the aim of constraining the origin of Cenozoic shoshonitic rocks found throughout Fiji. The most mafic shoshonitic lavas (absarokites) exhibit porphyritic textures and massive structure with phenocrysts of olivine (Fo = 76–78), clinopyroxene (Mg# = 73.9–80.0), and plagioclase (An = 71.9–92.1). Major element geochemical data include SiO2 = 47.31–48.46 wt%, MgO = 4.20–5.76 wt%, Mg# = 49–51, Al2O3 = 17.64–18.93 wt%, and (Na2O + K2O) = 5.12–7.01 wt%. The trace element geochemistry is typically arc like, with enrichment in the large ion lithophile elements (LILEs), the light rare earth elements (LREEs), and P, along with depletion in the heavy rare earth elements (HREEs) and high‐field‐strength elements (HFSEs; e.g., Nb, Ta, Zr, Hf, and Ti). Whole‐rock (87Sr/86Sr)i ratios and εNd(t) values vary from 0.7037 to 0.7039 and from +7.62 to +8.45, respectively. The former is near equal to the 87Sr/86Sr ratios of plagioclase phenocrysts (0.7034–07039). Based on these geochemical data and the results of previous studies, we propose that the Sabeto shoshonitic primary magma was derived from partial melting of the depleted lithospheric mantle, modified by subduction‐related fluids. The thermobarometric calculation indicates that the P–T conditions of Fiji shoshonitic magma chamber are ~1100 °C and ~2.8 GPa (~90 km depth), with an average H2O fraction of ~6 wt%. In addition, the shoshonitic melts experienced fractional crystallization of clinopyroxene, olivine, and plagioclase during magma evolution. These volcanic rocks formed in an extensional setting following collision of the Vitiaz arc and the Ontong Java Plateau during the Pliocene. [ABSTRACT FROM AUTHOR]

Abstract The role of secondary minerals in controlling the migration of arsenic and selected metals (Cu, Pb, Zn) has been investigated in voluminous mining waste dumps at Kaňk (northern part of the Kutná Hora ore district, Czech Republic). These wastes initially contained a large amount of Fe sulfides and arsenopyrite and have been exposed to atmosphere for approximately 500 years. The long-term weathering under acidic conditions caused dissolution of almost all sulfides and significant alteration of primary silicate minerals, producing deeply weathered As-, Fe-, and S-rich waste material (As: 13 g kg−1; Fe: 74 g kg−1; S: 44 g kg−1) with large proportion of clayey matrix filling the space between rock fragments. Detailed mineralogical investigation (powder X-ray diffraction, electron microprobe, Raman spectroscopy) and sequential extraction revealed that arsenic in these wastes is principally stored in reactive but not highly soluble minerals such as poorly-crystalline Fe (oxyhydr)oxides, bukovskýite, and X-ray amorphous hydrated ferric arsenate (HFA). Lesser fraction of As is contained in schwertmannite and less reactive scorodite, jarosite, and well-crystalline Fe (oxyhydr)oxides (especially goethite). Fe (oxyhydr)oxides also appear to be the main reservoirs of Cu and Zn; Pb is principally stored in jarosite. Acidic pore waters (pH ≈ 2.8) collected after rainfall events contain much Al (113 mg L−1), As (2.5 mg L−1), Ca (500 mg L−1), Cu (24 mg L−1), Fe (58 mg L−1), Si (44 mg L−1), SO 4 2− (2170 mg L−1) and Zn (16 mg L−1). Geochemical modeling revealed that most of these elements (Al, Ca, Cu, SO 4 2−, Zn) are controlled by ephemeral Al-Ca-Cu-Zn sulfates (e.g. gypsum, aluminite), which form at the surface of the waste dumps as a result of evaporation of pore solutions during dry seasons. Despite the fact that bukovskýite and other interesting Fe(III) (sulfo)arsenate minerals store a major part of As in the mining wastes, geochemical modeling supported the notion that mobility of As and Fe is controlled by the unspectacular poorly-crystalline As-bearing Fe (oxyhydr)oxides. The data show that the Fe(III) (oxyhydr)oxides, (sulfo)arsenates and hydroxysulfates in the 500-year-old mining waste dump retain arsenic efficiently but not completely. Monitoring wells installed at the site before our research recorded up to 1440 mg L−1 As in shallow groundwater. They argue, however, that this aquifer is disconnected from the larger groundwater bodies at the site and hence does not represent arsenic accumulation of environmental concern. Highlights • Speciation of As in medieval mining waste dumps was determined by combination of mineralogical and geochemical methods. • A multiple As-hosting phases (mainly bukovskýite, HFA, HFO) were identified. • As and Fe solubility is controlled by As-HFO. [ABSTRACT FROM AUTHOR]

Recent investigations found that hydrothermal activity and sulfide mineralization occurs along the Southwest Indian Ridge (SWIR). The Longqi and Duanqiao hydrothermal fields between 49° E and 53° E of the SWIR are two prospective mineralization areas discovered by Chinese scientists. With the aim to determine the mineralogical and chemical characteristics of sulfide minerals, we have conducted detailed studies for samples from the two areas using an optical microscope, X‐ray diffractometer, scanning electron microscope, and electron microprobe. The mineralization processes in the Longqi area are divided into three main stages: (1) the low‐medium‐temperature stage: colloform pyrite (Py I) + marcasite → euhedral pyrite (Py II), (2) the high‐temperature stage: isocubanite (±exsolved chalcopyrite) + pyrrhotite → coarse‐grained chalcopyrite (Ccp I), and (3) the medium–low‐temperature stage: sphalerite + fine‐grained chalcopyrite inclusions (Ccp II) → aggregates of anhedral pyrite (Py III) ± marcasite → Fe‐oxide (‐hydroxide) + amorphous silica. The mineralization processes in the Duanqiao area are divided into two main stages: (1) the medium–high‐temperature stage: subhedral and euhedral pyrite (Py I′) → coarse‐grained chalcopyrite (Ccp I′) and (2) the medium–low‐temperature stage: sphalerite → fine‐grained chalcopyrite (Ccp II′) + chalcopyrite inclusions (Ccp II′) → silica‐cemented pyrite (Py II′) + marcasite → Fe‐oxide + amorphous silica. We suggest that the fine‐grained chalcopyrite inclusions in sphalerite from Longqi and Duanqiao were formed by co‐precipitation and replacement mechanisms, respectively. Primary sphalerites from both fields are enriched in Fe (avg. 5.84 wt% for the Longqi field vs. avg. 3.69 wt% for the Duanqiao field), Co (avg. 185.56 ppm for the Longqi field vs. 160.53 ppm for the Duanqiao field), and Cd (avg. 1950 ppm for the Longqi field vs. avg. 525.26 ppm for the Duanqiao field). Cu contents in pyrite from the Duanqiao field (Py I′: avg. 849.23 ppm and Py II′: avg. 1191.11 ppm) tend to be higher than those from the Longqi field (Py I: avg. 26.67 ppm, Py II: avg. 445 ppm, and Py III: avg. 179.29 ppm). Chalcopyrite from both fields is enriched in Zn (Ccp I: avg. 3226.67 ppm, Ccp II: avg. 9280 ppm, Ccp I′: avg. 848 ppm, Ccp II′ (inclusions): avg. 1098 ppm, and Ccp II′ (fine‐grained): avg. 1795 ppm). The varying contents of Zn in the different pyrite and chalcopyrite generations may result from the zone refining process. An integrated study of the mineralogy and mineralogical chemistry suggests that the hydrothermal fluids of the Longqi area are likely conditioned with higher temperatures and relatively lower fO2 and fS2 than those of the Duanqiao area, but in contrast to the former, the latter is much affected by the compositions of the surrounding rocks. [ABSTRACT FROM AUTHOR]

Persistence and bioavailability of heavy metals in soils adjacent to ancient Cu mines continues to be a possible threat to human health. However, there have been very few studies to determine this risk. Asturias (Northwest of Spain) is a Cu metallogenic province with abundant epithermal-type deposits, whose paragenetic sequences also include As, Co, Ni, Sb and Hg minerals. Several Cu mines have been worked in this region since prehistoric times and the six most significant ones are studied in this work to provide new insights into the potential for both contemporary and past contamination due to Cu mining to impact human health. The main characteristics of each deposit were defined by means of optical and scanning-electron microscopy, X-ray diffraction and Electron Probe Micro Analysis. These characteristics were used to better interpret the environmental results, obtained from samples of mining wastes, soils and waters, which were analyzed by means of X-ray fluorescence and ICP-MS. Many of these mines are almost forgotten, but their negative effects will endure over time, since they were abandoned long before the introduction of environmental regulations to control metal release. An inheritance of derelict mine facilities and spoil heaps still remains in the sites of this district. The spoil heaps are the main pollution sources and concentrations of up to 2.1% Cu and 0.4% As, among others, were found in the surrounding soils. The potential adverse health effects of the exposure to these elements have been assessed, finding significant risks for potential receptors, such as farmers or local residents. [ABSTRACT FROM AUTHOR]

The ceramic properties of clay materials heated at high temperature are largely dependent on the mineral reactions, which usually are followed by XRD analysis on pressed pieces that are heated at different temperatures. Nevertheless, the use of “in-situ” high temperature X-ray diffraction (HTXRD) to follow the evolution of the crystalline phases under controlled temperature provides more precision. In this paper, the mineralogical changes produced during firing (RT-1000 °C) of two clay materials of very different mineralogical composition, frequently used in the manufacture of bricks in the SE Spain, have been studied by XRD classical procedure and with HTXRD, and the results obtained were compared. Although the phases identified by both X-ray analyses were the same, temperatures for the mineralogical reactions seem to be different, probably due to the experimental conditions. The patterns obtained by ex-situ XRD were at a higher speed than those by in-situ HTXRD, and probably the equilibrium was not achieved for the most reactions. Because of the expansion of the mineral structure parameters occurred during heating the mineral reflections do not match with those found in the database JPCDS, neither the position nor intensities of some stable phases at high temperature. For the optimization of the interpretation of the HTXRD patterns, and to facilitate the kinetics of the new phases, it is necessary to work at a high integration time per step and a slow heating rate. The in-situ HTXRD investigations of ceramic materials can save time respect to the classical XRD study of test-pieces heated at different temperatures, and lead immediate information of the transformation occurring on heating, which can be useful to improve the most suitable firing temperature in the industry. [ABSTRACT FROM AUTHOR]

Sulfuric acid minerals are important clues to identify the speleogenetic phases of hypogene caves. Italy hosts ~25% of the known worldwide sulfuric acid speleogenetic (SAS) systems, including the famous well-studied Frasassi, Monte Cucco, and Acquasanta Terme caves. Nevertheless, other underground environments have been analyzed, and interesting mineralogical assemblages were found associated with peculiar geomorphological features such as cupolas, replacement pockets, feeders, sulfuric notches, and sub-horizontal levels. In this paper, we focused on 15 cave systems located along the Apennine Chain, in Apulia, in Sicily, and in Sardinia, where copious SAS minerals were observed. Some of the studied systems (e.g., Porretta Terme, Capo Palinuro, Cassano allo Ionio, Cerchiara di Calabria, Santa Cesarea Terme) are still active, and mainly used as spas for human treatments. The most interesting and diversified mineralogical associations have been documented in Monte Cucco (Umbria) and Cavallone-Bove (Abruzzo) caves, in which the common gypsum is associated with alunite-jarosite minerals, but also with baryte, celestine, fluorite, and authigenic rutile-ilmenite-titanite. In addition, the core of alunite and jarosite, from these two systems, results enriched in PO43-, clearly suggesting hypogene hydrothermal origin. Santa Cesarea Terme, Capo Palinuro, and Acqua Mintina caves show important native sulfur deposits, which abundantly cover walls, ceilings, and speleothems. Abundant copiapite, pickeringite, tamarugite, hexahydrate assemblages have been observed in the Calabrian systems; their association with pyrite and hematite would suggest they formed in very acidic conditions with pH ranging between 0 and 4. [ABSTRACT FROM AUTHOR]

Mineralogical studies indicate that two major phase transitions occur near the depth of 660 km in the Earth's pyrolitic mantle: the ringwoodite (Rw) to perovskite (Pv) + magnesiowüstite (Mw) and the majorite (Mj) to perovskite (Pv) phase transitions. Seismological results also show a complicated phase boundary structure at this depth in plume regions. However, previous geodynamical modeling has mainly focused on the effects of the Rw–Pv+Mw phase transition on plume dynamics and has largely neglected the effects of the Mj–Pv phase transition. Here, we develop a 3-D regional spherical geodynamic model to study the combined influence of these two phase transitions on plume dynamics. Our results show the following: (1) A double phase boundary occurs in the high-temperature center of the plume, corresponding to the double reflections in seismic observations. Other plume regions feature a single, flat uplifted phase boundary, causing a gap of high seismic velocity anomalies. (2) Large amounts of relatively low-temperature plume materials can be trapped in the transition zone due to the combined effects of phase transitions, forming a complex truncated cone shape. (3) The Mj–Pv phase transition greatly enhances the plume penetration capability through 660-km phase boundary, which has a significant influence on the plume dynamics. Our results provide new insights which can be used to better constrain the 660-km discontinuity variations, seismic wave velocity structure and plume dynamics in the mantle transition zone. The model can also help to estimate the mantle temperature and Clapeyron slopes at the 660 km phase boundary. [ABSTRACT FROM AUTHOR]

The central portion of the Canaã dos Carajás domain, located in the northern part of the Carajás province was originally marked by the occurrence of undifferentiated rocks belonging to the Xingu complex and Plaque suite, as well as greenstone belts, mafic rocks of the Pium diopside-norite and high K calc-alkaline leucogranites (Boa Sorte and Cruzadão granites). A semi-detailed geological mapping (1:100.000) was carried out in the Vila União area and allowed the identification of several deformed granite bodies intrusive in the Mesoarchean units. They correspond to the most expressive unit of the studied area and are composed predominantly of monzogranites with chemical and mineralogical affinity with the Neoarchean A-type granites of the Planalto and Vila Jussara suites. The variable felsic and ferromagnesian minerals contents, as well as the different proportions between them, allowed to distinguish four major groups of granitoids: (i) biotite-hornblende monzogranites (BtHblMzG); (ii) biotite granites and leucogranites (BtLG); (iii) biotite-hornblende tonalites (BtHblTn); and (iv) quartz diorites (QD). The tectonic foliation of these rocks follows the regional E-W trend and exhibits high angles (70–85°). Well-developed core and mantle structures in quartz and feldspar crystals, as well as the presence of serrated and irregular contacts between these crystals suggest that dynamic recrystallization occurred at relatively high temperatures (>500 °C). These rocks exhibit a wide variation in silica content (57.20–75.91 wt%), are metaluminous to slightly peraluminous and show affinity with A-type (high HFSE) and ferroan granites. Based on magnetic petrology studies it was possible to distinguish two groups of rocks: (1) granites containing only ilmenite with low magnetic susceptibility values (MS; <0.570 × 10 −3 SI), and (2) granites with magnetite as the main iron and titanium oxide mineral and higher MS values (>1.437 × 10 −3 SI). Textural and compositional evidences indicate that magnetite and ilmenite are early-crystallized phases and titanite has magmatic origin. Amphiboles are calcic and classified as hastingsite, whereas biotites are magnesian to ferroan. The relatively high Fe/(Fe + Mg) ratios found in the amphiboles of the BtHblMzG and BtHblTn varieties indicate that these granitoids were formed under low to moderate f O 2 conditions, whereas in the BtLG the lower values of this ratio suggest more oxidizing conditions. Geothermometers point to crystallization temperatures between 830 and 930 °C in the different facies. The high total Al content in the amphibole crystals suggests crystallization at pressures between 400 and 800 MPa, indicating that these granitoids were emplaced at different crustal depths. [ABSTRACT FROM AUTHOR]

Abstract: Intrusion of quartz‐monzodioritic igneous bodies of Oligocene age into Eocene lithic crystal tuffs and trachy‐basalts resulted in the occurrence of a widespread argillic alteration zone in the Jizvan district (northern Iran). Mineralogically, the argillic alteration zone includes minerals such as kaolinite, quartz, smectite, pyrophyllite, muscovite‐illite, alunite, rutile, calcite, feldspar, chlorite, hematite and goethite. Therefore, the non‐CHARAC behaviour for trace elements in the argillic samples is reflected in the non‐chondritic Y/Ho and Zr/Hf ratios and the irregular REE patterns, which appear related to the tetrad effect phenomenon. The chondrite‐normalized REE distribution patterns indicate both concave (W‐shaped) and convex (M‐shaped) tetrad effects in the argillic samples. Based on the field evidence and the results from geochemical studies, it can be concluded that the samples from the argillic alteration zone having high fourth tetrad effect values (>0.30) were developed in the fault and breccia zones. The results indicate that factors such as preferential scavenging by Mn‐oxides, crystallization of clay minerals, fluid‐rock interaction, overprint of hypogene mineral assemblage by supergene ones, and the structural control, have all played an important role in the occurrence of tetrad effects in samples of the argillic zone in the Jizvan district. [ABSTRACT FROM AUTHOR]

The Bukit Botol volcanic-hosted massive sulphide (VHMS) deposit is located in the Central Belt of Peninsular Malaysia. The deposit occurs in a package of Permian-aged coherent felsic volcanic and volcaniclastic rocks which have a geochemical signature indicative of a volcanic arc tectonic setting. Mineralisation shows distinct ore zonation, forming a stringer to massive sulphide zone at the footwall followed by barite lenses and exhalite layers (Fe-Mn ore) at the top. Mineralogy is characterised by pyrite as the major sulphide mineral, with minor chalcopyrite, sphalerite, and rare galena; traces of gold, silver- and tin-bearing minerals also occur in the massive sulphide and barite ores. Laser ablation inductively coupled plasma mass spectrometry (LA−ICP−MS) analysis combined with the textural characteristics of pyrite provides evidence for significant variations of trace elements in different pyrite types at Bukit Botol, having three types of pyrite in the paragenetic sequence. The concentrations of As, Se, Te, Cu, Zn and Pb decrease from the early pyrite 1 to the late stage pyrite 3, and the Co/Ni ratios vary for the three pyrite types. The combined textural and compositional data of pyrite suggest that the hydrothermal fluid responsible for mineralisation evolved from an early, high temperature, reduced, low pH and desulphurized fluid to more S-rich, oxidized, high pH and cooler fluid. Available sulphur isotope data from the Bukit Botol deposit point to reduced seawater, along with a possible magmatic contribution, as the most probable sources for the ore-forming fluids. [ABSTRACT FROM AUTHOR]

The influence of different rock mineralogical compositions on element leaching and bio-weathering processes is poorly understood. Here, the role of basalt composition on nutrient leaching (calcium, iron, phosphorus or magnesium) and subsequent support of Cupriavidus metallidurans CH34 growth was evaluated. Seven different basalts were examined. In iron-limiting media, growth could be restored for all basalts tested, while only two basalts could restore growth in magnesium-limiting medium. Only for magnesium growth complementation was correlated with the composition of the basalts tested. Our results showed that basalt composition can affect leaching and availability of different elements, in turn, affecting bacterial growth. [ABSTRACT FROM AUTHOR]

The extraction of copper from black shales associated with fine-grained and complex base metal ore mineralization traditionally using pyrometallurgy becomes increasingly uneconomic, because one of the most significant cost factors is the high energy consumption. Thus, energy-saving alternative mineral processing methods are to be considered to improve the metal recovery route economically and environmentally. In this study, a milled, organic carbon-rich black shale ore from the Sangerhausen mining district in central Germany has been pre-treated by ethanol prior to the froth flotation tests to gain a copper concentrate marked by an increased copper content and more efficient copper recovery. The flotation product (15.3% Cu) was used for biohydrometallurgically batch tests to extract copper and associated trace metals. SEM-based automated particle analyses on the comminuted black shale ore, flotation product as well as tailings, bioleaching residues and abiotic leaching residues were used to trace the recovery performance particularly of copper sulfides. The black shale ore is characterized by high contents of bornite (2.8 wt%) and chalcopyrite (1.3 wt%) associated with a high grade of pyrite (5.8 wt%). Considerable enrichments were achieved in the flotation product for bornite (20.7 wt%) and chalcopyrite (10.3 wt%) as well as for galena and sphalerite, while pyrite was successfully depressed in the tailings. Compared to abiotic chemical leaching, the bioleaching test of the bornite- and chalcopyrite-rich copper concentrate was particular efficient in the recovery of bornite and chalcocite. However, chalcopyrite was leached insufficiently in both, abiotic and microbial leaching tests, and presents a common component in the residues. [ABSTRACT FROM AUTHOR]

Fe(III) hydroxysulfate minerals are secondary minerals commonly found in acid mine drainage (AMD) sites and have a major impact on water and soil quality in these environments. While previous studies showed that the Fe(III) hydroxysulfate mineral transformation could be mediated by some bacterial strains under laboratory conditions, the role of indigenous microbial activity in Fe(III) hydroxysulfate mineral transformation in natural environment has received little attention. In this study, microcosms were constructed with AMD-affected river water and sediment from the Dabaoshan Mine that was either left unamended or enriched with nutrients (lactate, nitrogen, and phosphorus (LNP)) and biosynthetic minerals (schwertmannite or jarosite). The results show that microbial activity played a decisive role in the mineralogical transformation of schwertmannite/jarosite in the AMD-contaminated site when organic carbon was available. The accumulation of Fe(II) and sulfide in microcosms amended with LNP indicates that schwertmannite/jarosite transformation is mediated by microbial reduction. XRD, SEM and FTIR analyses suggest that schwertmannite was completely transformed to goethite in the Sch-LNP microcosms at the end of their incubation. Jarosite in the Jar-LNP microcosms was also transformed to goethite, but at a much slower rate than schwertmannite. Bacterial community analysis reveals that the stimulated indigenous bacteria promote the mineralogical transformation of schwertmannite/jarosite. Most of these bacteria, including Geobacter , Desulfosporosinus , Geothrix , Desulfurispora , Desulfovibrio , and Anaeromyxobacter , are known to reduce iron and/or sulfate. The mineralogical transformation of schwertmannite and jarosite exerts significant control on the geochemistry of AMD-contaminated systems. [ABSTRACT FROM AUTHOR]

Molybdenum is an essential element for life, with growing production due to a constantly expanding variety of industrial applications. The potentially harmful effects of Mo on the environment, and on human and ecosystem health, require knowledge of Mo behavior in mining-affected environments. Mo is usually present in trace amounts in ore deposits, but mining exploitation can lead to wastes with very high Mo concentrations (up to 4000 mg/kg Mo for tailings), as well as soil, sediments and water contamination in surrounding areas. In mine wastes, molybdenum is liberated from sulfide mineral oxidation and can be sorbed onto secondary Fe(III)-minerals surfaces (jarosite, schwertmannite, ferrihydrite) at moderately acidic waters, or taken up in secondary minerals such as powellite and wulfenite at neutral to alkaline pH. To date, no Mo-metabolising bacteria have been isolated from mine wastes. However, laboratory and in-situ experiments in other types of contaminated land have suggested that several Mo-reducing and -oxidising bacteria may be involved in the cycling of Mo in and from mine wastes, with good potential for bioremediation. Overall, a general lack of data is highlighted, emphasizing the need for further research on the contamination, geochemistry, bio-availability and microbial cycling of Mo in mining-affected environments to improve environmental management and remediation actions. [ABSTRACT FROM AUTHOR]

Atmospheric leaching (AL) of low-grade nickel laterite ores often produces leach liquor containing significant amounts of trivalent iron, aluminium and chromium ions. These impurities are normally removed by increasing the leach liquor pH to precipitate these metals before the recovery of nickel, cobalt and other metal values. This paper documents an investigation of the removal of iron, aluminium and chromium from both synthetic and real nickel laterite AL leach solutions using single- and multi-stage precipitation methods. Single-stage precipitation experiments performed using synthetic leach solutions containing Fe(III) + Ni(II) + Al(III), Fe(III) + Ni(II) + Cr(III), and Fe(III) + Ni(II) + Al(III) + Cr(III) showed that greater losses of nickel to solids occurred in the presence of aluminium and chromium. Increasing the pH value of the solution and the precipitation temperature favoured the removal of iron, aluminium and chromium, but at a cost of greater nickel losses. However, by carefully controlling pH and temperature using a multi-stage precipitation process, the iron, aluminium and chromium can be rejected effectively by precipitation with minimal nickel loss and desirable sludge properties. The optimum conditions for a multi-stage precipitation process were found to be pH 3.0 and 55 °C in the first stage and pH 3.0 and 85 °C in the second stage. Using this approach, as much as 95% iron and chromium together with more than 80% aluminium can be removed; the level of nickel loss to the solid can be reduced to below 1%. The sludge showed a fast settling rate of 5.05 m/h following the addition of a cationic flocculant. Similar satisfactory results were also obtained when performing this multi-stage precipitation procedure with real leach solutions. [ABSTRACT FROM AUTHOR]

In this paper, submicron spinel-containing calcium aluminate (SP-CA) cements were prepared at temperatures of 1200 °C (RA12), 1300 °C (RA13), and 1450 °C (RA14) using reactive alumina, magnesium hydroxide, and calcium carbonate as raw materials. The microstructural characteristics and high temperature properties of refractory castables bonded by SP-CA cement were investigated. The results indicated that the mineralogical compositions of SP-CA were spinel (MgAl 2 O 4 , MA) and CaAl 2 O 4 (CA). The spinel phases presented no definite borders or shapes, with average size ranging from 0.1 μm to 1.2 µm at different sintering temperatures. After heating alumina-spinel castables, the submicron spinel particles bonded with corundum and hibonite (CA 6 ) grains could strengthen the castable body. However, the large sized (< 88 µm) spinel did not form links between spinel and alumina in the castable with added preformed spinel (castable AS). Submicron spinel can decrease the pore sizes of refractory castables from 2 µm to 0.5 µm. Extended finite element method (XFEM) calculations showed that smaller pores prevent stress concentration and result in increased deformation with limited crack propagation. Hence, large numbers of 0.5 µm pores can act as crack-stoppers to improve the thermal shock resistance of castables with added SP-CA cements. Thermal shock resistance tests showed that R '''' of castable RA12 was 39.7 m, which is significantly higher than that of castable AS (19.8 m). The corrosion rate of castable RA12 was 5 mm 2 /min, which is significantly lower than that of castable AS (7.4 mm 2 /min). Small pore size and submicron spinel played relevant roles in corrosion behavior. [ABSTRACT FROM AUTHOR]

Tajikistan has abundant copper-tin resources. In this study, mineralogical analysis of copper-tin ores from the Mushiston deposit of Tajikistan indicates that tin mainly occurred in mushistonite, cassiterite, and stannite, while copper mainly occurred in mushistonite, malachite, azurite, and stannite. The total grades of tin (Sn) and copper (Cu) were 0.65% and 0.66%, respectively, and the dissemination size of copper-tin minerals ranged from 4 μm to over 200 μm. Coarse particles of copper-tin minerals were partially recovered by shaking table concentrators with a low recovery rate. Based on the mineralogical analysis, flotation recovery was used for the first time on the fine particles of copper-tin minerals, including mushistonite, from shaking table tailings. Single factor flotation experiments, open circuit flotation tests, and closed circuit flotation tests were performed to determine the optimized flotation conditions. Results indicated that benzohydroxamic acid (C6H5CONHOH) and lead nitrate could effectively recover the mushistonite, cooperating with other depressants. The final concentrate contained 13.28% Sn, with a recovery rate of 61.56%, and 18.51% Cu, with a recovery rate of 86.52%. This method proved effective for the exploitation and use of this type of copper-tin resource in Tajikistan. [ABSTRACT FROM AUTHOR]

Despite of significant efforts in the last decades towards utilization of steel slag in the construction industry, steel slag stockpiling and landfilling operations do not seem to be declining in steel-producing countries. Use of steel slag as a construction material requires understanding of its engineering properties and development of a methodology to address its swelling potential. This paper focuses on the results of a series of laboratory tests (grain-size analysis, X-ray diffraction, specific gravity, compaction, maximum and minimum dry unit weight, direct shear, and long-term swelling tests) performed on samples of electric-arc-furnace ladle (EAF(L)) steel slag to assess its potential to be used as a geo-material. Direct shear test results indicated that the EAF(L) steel slag exhibits comparable frictional properties to angular crushed sand. Based on the leachate concentration levels from TCLP analyses, the EAF(L) steel slag tested was classified as Type III Solid Waste. The long-term, one-dimensional (1D) swelling test results showed continued volumetric expansion even after more than 16 months of monitoring. Replacing 5–10% by weight of EAF (L) steel slag with Class C fly ash reduced the 1D swelling to negligible levels. [ABSTRACT FROM AUTHOR]

There are several metasomatic uranium deposits in the area around Mount Isa in Queensland, containing a total of 56,400 t of uranium. Many of these ores are refractory in nature, meaning that relatively high leach temperatures (> 75 °C) and reagent dosages (> 50 g/L H 2 SO 4 ) are needed to effectively extract the uranium from them. Also, these ores are hosted in alkaline rock which means that acid leaching is unlikely to be economical. While refractory uranium ores are not typically leached in alkaline media, previous work has shown that uranium can be extracted from brannerite in alkaline media, albeit slowly. The same leaching conditions previously shown to be effective for the extraction of uranium from brannerite were repeated with a sample of refractory uranium ore from a deposit near Mount Isa in north western Queensland. Mineralogical analysis with a Tescan Integrated Mineralogical Analyser (TIMA) showed that the uranium was present as brannerite (51%) and coffinite (49%). The ore was leached in sodium carbonate media for 24 h. Leach temperatures of 50, 70 and 90 °C, and sparging with oxygen, air and nitrogen were tested. The effect of adding ferricyanide chemical oxidant was also tested. Similar initial uranium extraction rates were observed for the Mount Isa uranium ore compared with Sierra Albarrana brannerite leached under the same conditions in earlier work. The final extractions were lower however, due to the fine-grained nature of the uranium mineralisation in the ore. TIMA analysis on a residue produced under the most intense set of leaching conditions (90 °C, O 2 sparged) showed that the extent of coffinite dissolution was greater than that of brannerite dissolution during leaching. Likewise, the TIMA analyses showed that the extent of apparent uranium liberation decreased during leaching, due to poorly liberated particles remaining undissolved. These results indicate that alkaline leaching could be a viable method for the processing of these long overlooked ores provided that the uranium is sufficiently liberated. [ABSTRACT FROM AUTHOR]

The new mineral roymillerite PbMg(SiAlO)(SiO)(BO)(CO)(OH)O, related to britvinite and molybdophyllite, was discovered in a Pb-rich assemblage from the Kombat Mine, Grootfontein district, Otjozondjupa region, Namibia, which includes also jacobsite, cerussite, hausmannite, sahlinite, rhodochrosite, barite, grootfonteinite, Mn-Fe oxides, and melanotekite. Roymillerite forms platy single-crystal grains up to 1.5 mm across and up to 0.3 mm thick. The new mineral is transparent, colorless to light pink, with a strong vitreous lustre. Cleavage is perfect on (001). Density calculated using the empirical formula is equal to 5.973 g/cm. Roymillerite is optically biaxial, negative, α = 1.86(1), β ≈ γ = 1.94(1), 2 V (meas.) = 5(5)°. The IR spectrum shows the presence of britvinite-type tetrahedral sheets, $${\text{CO}}_{3}^{2 - }$$ , $${\text{BO}}_{3}^{3 - }$$ , and OH groups. The chemical composition is (wt%; electron microprobe, HO and CO determined by gas chromatography, the content of BO derived from structural data): MgO 4.93, MnO 1.24, FeO 0.95, PbO 75.38, BO 0.50, AlO 0.74, CO 5.83, SiO 7.90, HO 1.8, total 99.27. The empirical formula based on 83 O atoms pfu (i.e. Z = 1) is PbMgMnFeBAlCSiHO. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is triclinic, space group P $$\bar{1}$$ , with a = 9.315(1), b = 9.316(1), c = 26.463(4) Å, α = 83.295(3)°, β = 83.308(3)°, γ = 60.023(2)°, V = 1971.2(6) Å. The crystal structure of roymillerite is based built by alternating pyrophyllite-type TOT-modules Mg(OH)[(Si,Al)O] and I-blocks Pb(OH)O(CO)(BO,SiO). The strongest lines of the powder X-ray diffraction pattern [ d, Å (I, %) ( hkl)] are: 25.9 (100) (001), 13.1 (11) (002), 3.480 (12) (017, 107, −115, 1-15), 3.378 (14) (126, 216), 3.282 (16) (−2-15, −1-25), 3.185 (12) (−116, 1-16), 2.684 (16) (031, 301, 030, 300, 332, −109, 0-19, 1-18), 2.382 (11) (0.0.-11). Roymillerite is named to honor Dr. Roy McG. Miller for his important contributions to the knowledge of the geology of Namibia. [ABSTRACT FROM AUTHOR]

Paleoclimatic/environmental changes of northern Mongolia were investigated by chemical and mineralogical analyses of sediment cores from Lake Hovsgol and Lake Erhel back to 18.9 and 34.3 cal ka BP, respectively. The climate of this region was dry in the glacial period, and wet in the Holocene. Desalination of Lake Hovsgol occurred at 13.2–11.6 cal ka BP, i.e., during the transition from the late glacial to early Holocene. At the same time, ca. 12.82 cal ka BP, deposition in the Lake Erhel area changed from fluvial to lacustrine. Climate of northern Mongolia was humid during the late glacial to the early Holocene period (ca. 10.57–7.24 cal ka BP for the Hovsgol and from ca. 12.82 to 7–8 cal ka BP for the Erhel). This reconstruction differs from that for the more northern Lake Baikal region, which humidification continued from the last glacial period until mid-Holocene. This difference could be attributed to longer period of glacier melting and permafrost thawing around the Baikal and on its watershed, associated with increased summer insolation. [ABSTRACT FROM AUTHOR]

A thermodynamic model is developed for pyroxenes in the chemical (mineralogical) system CaMgSi2O6 (diopside, Di, 1) - CaTiAlSiO6 (grossmanite, Gr, 2) - CaMg1/2 Ti1/2AlSiO6 (alumino - buffonite, AlBf, 3) - CaAl2SiO6 (Calcium Aluminum Tschermaks, CATS, 4), aka fassaites. It is formulated for the assumptions of molecular mixing between AlBf and Di, Gr and CATS components, and that the reduction in configurational entropy resulting from short - range Al - Si ordering on tetrahedral sites may be described using, as a proxy, a long-range, convergent ordering parameter for ordering of Al and Si between A and B tetrahedral sites on the AlBf - free tetrahedral sublattice. Nine out of sixteen independent thermodynamic parameters are calibrated to be consistent with calorimetric measurements of Benisek and others (2007), spectroscopic and statistical mechanical constraints on tetrahedral Al - Si ordering in pyroxenes on the Di - CATS binary (Cohen, 1986; Vinograd, 2001; Warren and others, 2001), and phase equilibrium constraints on Di - AlBf miscibility gaps in the Di - AlBf - CATS ternary subsystem (Yang 1975, 1976). The remaining seven independent parameters (for Gr - bearing fassaites) are constrained to be consistent with the distribution of fassaite compositions in calcium - aluminum - rich inclusions in carbonaceous chondrites (CAIs), experimental determinations of fassaite single - phase regions produced at the extremely low oxygen fugacities prevailing during their primary condensation/crystallization (for example, Beckett, ms, 1986), and the assumption that secondary fassaites in Wark - Lovering rims enclosing CAIs were in local equilibrium with the outer surface layers of the earlier (canonical) AlBf - rich fassaites at their layer contacts at temperatures of around 1473 K (Wark and Lovering, 1982; Meeker and others, 1983; Murrell and Burnett, 1987; Ruzicka, 1997; Dyl and others, 2011). In this model there is a miscibility gap between Di-rich and AlBf-rich fassaites on the Di - AlBf join which displays only very limited extension into the fassaite tetrahedron. On the Di - AlBf - CATS face of this tetrahedron there is a second miscibility gap (upper buffonite gap, UBG) with 0.08 < X4fas < 0.22 and 0.06 < X4fas < 0.25 at 1505 and 1473 K. This gap is modestly ellipsoidal with its long axis roughly radial to AlBf and it is roughly symmetrically disposed between Di and AlBf at 1505 K. At 1473 K this gap extends to the AlBf - CATS binary, intersecting it at very low and intermediate X4fas, with most of its CATS - rich binode being metastable with respect to assemblages composed of the minerals melilite, spinel, anorthite, perovskite and CATS - poor fassaite. A third miscibility gap extends from the CATS-rich portion of the AlBf - CATS binary, and occupies most of the CATS - rich portion of this ternary at 1505 and 1473 K. It is metastable with respect to assemblages composed of melilite, spinel, anorthite, perovskite and hibonite, and, has a CATS - rich binode that is virtually coincident with the Di-CATS binary at high CATS contents, in accordance with compositions of metastable, virtually AlBf-free CATS-rich fassaites (kushiroites) found in hibonite ≈ grossite + fassaite spherules in CAIs (for example, Krot and others, 1999). Within the fassaite tetrahedron at 1473 K the UBG is rapidly destabilized with addition of the Gr component, diminishing in dimension and collapsing to a critical endpoint at X2fas < 0.06. With further increase in Ti(Al)-1 exchange potential, the third miscibility gap in Di - AlBf - CATS fassaites (where it is metastable) becomes less extensive, and, it separates into an interior gap and one emanating from the Gr - AlBf - CATS ternary at a Ti(Al)-1 exchange potential corresponding to a reference Gr - CATS fassaite with X2fas (=Xref2) ≈ 0.22. Both of these gaps continue to decrease in size with further increases in Ti(Al)-1 exchange potential, with the gap emanating from the Gr - AlBf - CATS ternary terminating there in a critical point at X2 ref ≈ 0.30. With further increase in Ti(Al)-1 exchange potential the more Di-rich gap continues to move toward the Di - Gr - CATS ternary until X2 ref ≈ 0.50. At higher Ti(Al)-1 exchange potentials there is complete miscibility in quaternary fassaites, except in the immediate vicinity of the Di - AlBf binary, and, at very high Ti(Al)-1 exchange potentials, in fassaites near the Di - Gr binary. Evaluating the Ti(Al)-1 exchange potentials at which the extensive gap that is metastable in the diopside - alumino - buffonite - CATS ternary subsystem becomes stable in the quaternary system at given temperatures awaits development of a comprehensive database for CAI fassaites and their associated minerals, particularly the solid solutions melilite and hibonite (for example, Waldbaum, 1973; Waldbaum and Woodhead, 1975; Doyle and others, 2014). The model for fassaite thermochemistry is used to develop a Ti3+ - Ti4+ fassaite oxygen cosmobarometer based on experimental constraints (for example, Beckett, ms, 1986). Values of oxygen fugacity calculated with this cosmobarometer for fassaites and melilites, judged by Grossman and others (2008) to be coeval in refractory CAIs from the Allende carbonaceous chondrite, are more than three orders of magnitude below that of a gas of solar composition. [ABSTRACT FROM AUTHOR]

This paper presents the mineralogical and geochemical compositions of coal benches and non-coal (carbonaceous rock benches, parting, roof and floor) samples from the No. 1 Coal in the Longtan Formation of the Permian-Lopingian epoch from the Shugentian Coalfield, eastern Yunnan Province, southwestern China. The coal is rich in Nb, Ta, Zr, and Hf, which were derived from the Kangdian Upland with the dominant compositions of the Emeishan basalt. The minerals identified in the samples include mixed-layer illite-smectite, kaolinite, quartz, siderite, and minor calcite, pyrite, anatase and ankerite. Albite and chamosite occur in the roof and floor samples. The parting sample (SGT1-2p) is characterized by abundant siderite (64.9%) and calcite (20.1%), and one carbonaceous rock sample SGT1-11 contained a large amount of pyrite (26.1%). Four factors were responsible for the geochemical and mineralogical compositions in the samples; namely, the terrigenous detrital materials transported from the Kangdian Upland, direct volcanic ash inputs, multi-stage inputs of hydrothermal fluids, and marine influences. The co-existence of siderite and pyrite was attributed to a continental-marine transitional environment. [ABSTRACT FROM AUTHOR]

Although CO 2 storage in deep saline aquifers is now accepted as a potential option for atmospheric CO 2 mitigation, the chemico-mineralogical property alterations in the aquifer formation associated with CO 2 /brine/rock mineral interactions, the corresponding influence on formation hydro-mechanical properties and the effect of rock mineral structure, are not yet fully understood. This study was therefore conducted to obtain a comprehensive understanding of the effect of long-term CO 2 exposure on the chemico-mineralogical structure and corresponding strength characteristics of saline aquifer rock formations using silicate cement (SS) and carbonate cement (CS) Hawkesbury sandstone samples collected from the Sydney basin. Sandstone samples were first reacted with brine+CO 2 under different injection pressures (both sub-critical (4, 6 MPa) and super-critical (8, 10 MPa)) under a constant temperature of 35 °C. A comprehensive chemico-mineralogical analysis (ICP-AES and XRD) was first conducted on both the rock mass pore fluid and the rock matrix over the saturation period of one year, giving special attention to the alteration of dominant rock minerals (quartz, calcite and kaolinite). The overall influence after 12 months of saturation with brine and CO 2 on the strength characteristics of the two types of sandstones (SS and CS) was then investigated and correlated with the chemico-mineralogical reaction, in order to understand the coupled process. According to the test results, compared to the silicate cement-dominant mineral structure (SS), the presence of a carbonate cement-dominant mineral structure (CS) in the aquifer rock formation creates more significant alterations in the formation's chemico-mineralogical structure upon CO 2 injection. This is because calcite mineral reactions occur at much greater rates compared to quartz mineral reactions in CO 2 -exposed environments. In addition, although some minor precipitation of kaolinite minerals may also occur upon CO 2 injection, the effect may not be significant. Overall, rock mineral changes in deep saline aquifers upon CO 2 injection have a significant influence on the strength characteristics of the reservoir rock mass, depending on the aquifer mineral structure, and CS formations are subject to much greater strength property changes upon exposure to CO 2 than SS formations. Interestingly, CO 2 injection causes a strength gain in SS sandstone and a strength reduction in CS sandstone. These mechanical property alterations in aquifer rock formations are also dependent on the CO 2 injection pressure and phase, and increasing the injecting CO 2 pressure significantly enhances the changes, due to the highly acidic environment created by the enhanced CO 2 solubility process. Changing the CO 2 phase from sub- to super-critical condition also accelerates the reaction mechanisms, due to the greater chemical potential of super-critical CO 2 . However, overall SS sandstone exhibits more stable chemical-mineralogical and mechanical characteristics upon CO 2 injection than CS sandstone, and exhibits more suitable characteristics for CO 2 sequestration. [ABSTRACT FROM AUTHOR]

Soundless cracking demolition agents (SCDAs) have emerged as a potential method for underground rock fragmentation. However, the application of SCDAs in deep earth formations requires them to be modified to suit each application. Basic understanding of the hydration mechanism and the expansive pressure generation of SCDAs is of paramount importance in the process of adapting SCDAs to such applications. Therefore, the microstructural, mineralogical and mechanical morphology of SCDA during the hydration process was studied through a series of experiments (Uniaxial compressive strength (UCS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis) carried out on SCDA specimens at different degrees of hydration. Experimental results suggest that mechanical properties of hydrating SCDA are dependent on the confinement provided to the SCDA during the hydration process and the porosity of aging SCDA reduce during hydration if the volume expansion is restrained. The pressure generation mechanism was explained using a spherical expansion model, and SEM images obtained for hydrating SCDA confirm this hypothesis. XRD analysis of SCDA indicates that expansive pressure is generated by a combination of Ca(OH) 2 and Ettringite formation in the system, although it is dominated by Ca(OH) 2 . The early strength gain in SCDA was found to be related to the calcium silicate hydrate formation in the compound. The relationships observed between the microstructure, mineralogy and the mechanical properties of SCDA with increasing expansive pressure aids to improve the current understanding of SCDA. [ABSTRACT FROM AUTHOR]