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Variations in the recovery of platinum group metals (PGMs) are often attributed to mineralogical and other natural ore-type variations. To increase the recovery of PGMs by the flotation process, a comprehensive understanding of gangue and valuable minerals is essential for optimising the extraction and processing of metals. Recoveries may be improved if the questions of how, where, and why losses occur can be answered with a certain degree of confidence. A requirement is the availability of statistically reliable mineralogical data. The PGMs of MG-1–4 chromite tailings dumps of the western limb of the Bushveld complex (BC) were studied in detail to unravel the PGMs and the nature of the platinum group minerals in the sample. Characterisation of the chromite tailings via deportment analysis revealed that the sample contained a significant amount of 3E PGM + Au (Pt, Pd, Ru, and Au) and was concentrated in the -25 µm fraction. The results of automated mineralogical analysis showed that the sample was composed of the PGE-sulphides group, comprising 63.6 vol%, PGE-sulfarsenides 10.4 vol%, PGE-arsenides 1.3 vol%, PGE-bismuth tellurides 3.3 vol%, PGMs-alloy 4.1 vol%, and Laurite comprising 17.3 vol% of the total PGE population. The sample was composed of 66.5 vol% of liberated PGMs, 0.2 vol% attached to liberated BMS, 27.3 vol% of PGMs attached to or locked within silicate or oxide gangue composite particles, 0.2 vol% of PGMs associated with BMS attached to silicate or oxide gangue particles, and a low proportion (5.8 vol%) of PGMs reported being locked within gangue or oxide particles. The majority of PGM grains observed were reported in the fast-floating category (64.4 vol%), 27.6 vol% in the slow-floating 1 category, 2.2 vol% in the slow-floating 2 category, and 5.8 vol% to the non-floating category. The results of the study revealed that the PGMs of MG 1–4 chromite tailings were liberated; however, the low liberation index (<0.2) suggested that a significant portion of PGMs remained trapped within gangue, hindering their recovery. This highlights the need for effective comminution (crushing and grinding) to achieve better liberation. The sample contained fine particles that were more prone to being lost in the tailings and to lowering recovery due to the slimes coating valuable minerals. The recovery of the PGMs from this complex's polymetallic bodies of low-grade and complex mineralogy will be insufficient with traditional methods and thus innovation is needed. Innovation like advanced comminution, novel flotation equipment or reagents, selective leaching and bioprocessing can overcome these challenges. [ABSTRACT FROM AUTHOR]

Baoshan is a world-class skarn Cu-polymetallic deposit located at the junction of the Nanling and Qin-Hang metallogenic belts in China. While there has been extensive research on the mineralogy and geochemistry of skarn deposits, studies on the fluid characteristics and evolutionary history from the early to late skarn stages in such deposits are still limited. In this study, we analyzed garnet and pyroxene from the early skarn stage and scheelite from the late skarn stage of the Baoshan deposit. We distinguished two generations of garnet (Grt1 and Grt2), one generation of pyroxene, and three generations of scheelite (Sch I, Sch II, and Sch III) on the basis of mineral assemblages and microscopic characteristics. Grt1 appears coarse-grained, and Grt2 cuts through Grt1 as veinlets. In Grt1, the andradite end-member increases from the core to the rim, while the grossular portion decreases (Ad35–36Gr59–61Sp3–4 to Ad59–61Gr36–37Sp2–3), and in Grt2, the andradite end-member significantly increases (Ad41–73Gr25–55Sp2–3). Grt1 and Grt2 have similar trace element compositions, with enrichment in Zr and depletion in Nb and Hf, depletion in LREE, enrichment in HREE, and weak negative Eu anomalies. Pyroxene coexists with Grt1 and is similarly cut by Grt2, with its composition mainly being diopside (Di82–99Hd0.6–15Jo0–3.2). Sch I and Sch II appear as anhedral to subhedral grains, while Sch III is predominantly found in veinlets. In Sch I and Sch II, most REEs enter the scheelite lattice via the Na-REE coupled substitution mechanism, with a smaller portion substituting Ca vacancies. In Sch III, the substitution mechanism involving Ca site vacancies may dominate. During the early skarn stage, the oxygen fugacity of the fluid gradually decreased from Grt1 and pyroxene to Grt2. In the late skarn stage, fluid oxygen fugacity remains stable from Sch I and Sch II to Sch III in shallow parts but significantly decreases in deeper parts. The garnet and pyroxene from the Baoshan deposit align with typical skarn Cu deposit compositions, while scheelite in the late skarn stage shows Sch I, Sch II, and shallow Sch III as skarn-type and deep Sch III as vein-type scheelite. Early skarn stage fluids were weakly acidic. Sch I, Sch II, and Sch III originated from fluids related to the Baoshan granite porphyry, with Sch III also showing evidence of water–rock interaction. This study reconstructed the fluid evolution history from the early to late skarn stages at the Baoshan deposit, providing insights into the ore-forming processes of other skarn deposits. [ABSTRACT FROM AUTHOR]

The Xuanwei Formation's claystones in the Dian-Qian District of Southwest China are rich in rare-earth elements (REEs), suggesting their potential as a source of medium and heavy rare earths. However, the REE content in these rocks is lower than other types of rare-earth deposits, and the interrelationship among clay minerals is intricate. There is no direct evidence indicating the mineralization of REEs, limiting their beneficiation and extraction. The objective of this study is the characterization of REE distribution in the Dian-Qian District. The sedimentary rocks in this district are mainly composed of kaolinite, boehmite, quartz, rutile, and pyrite. The results of continuous chemical extraction of REE-rich claystone and transmission electron microscope (TEM) observations have confirmed that REEs occurred as florencite in the rocks, and that the ion-absorption state makes only a negligible contribution to the REE content. A close relationship between florencite and kaolinite makes traditional mineral processing operations very difficult. Combined with the properties of kaolinite, roasting-acid leaching was the efficacious approach for rare-earth resources extracted from the rare earth-rich clay rocks of the Xuanwei Formation. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the mineralogical and chemical composition of zinc and lead metallurgical slags. These slags contain numerous elements, including toxic metals, which form conglomerates or multiphase intergrowths. The phase composition of slags is one of the main factors that determine their behaviour in weathering environments, that is, their ability to release metals when exposed to atmospheric factors. In this paper, the release of elements from slags and their mobility in a hypergenic environment is determined based on the results of leachability tests and on geochemical modelling, thus assessing the environmental impact of landfilled slags. The elements released from slags in the largest quantities are zinc and lead. Zn is leached out over a long period of time. It was found that after 12 years, the concentration of Zn in the eluate exceeds by 40 times the permissible value of 200 mg/kg for hazardous waste. The degree of leaching of lead from slags as a function of time (after 12 years), despite its significant solubility in water, is much lower than the degree of leaching of zinc. The most mobile phase components of slags in the studied hypergenic environment are the lead phases (anglesite and galena) and, to a lesser extent, the zinc phases (sphalerite and willemite). Anglesite and galena in almost the entire Eh-pH range, along with admixtures of elements, decompose into ionic forms: PbCl42−, Pb2+, and PbOH+. Sphalerite in the soil and water environment (oxidizing and acidic conditions) will decompose into the mobile ionic form Zn2+. Willemite, which is resistant to weathering, will undergo similar decomposition. It can therefore be assumed that the carriers of toxic metals are primarily lead sulphides and sulphates, zinc sulphides, and, less frequently, zinc, lead, and iron oxides. [ABSTRACT FROM AUTHOR]

The Libyan territory is made of a heterogeneous geologic bodies including intrusive igneous, metamorphic, volcanic rocks, and marine and continental sedimentary formations, Archean to Quaternary in age. It makes part of the "Saharan Metacraton" built up by the pre-Neoproterozoic continental crust between the Hoggar to the west, the Congo Craton to the South, and the Arabian–Nubian Shield to the East. This territory includes heterogeneous mineralogies and lithologies engendered by various geological processes that established appropriate conditions for geo-resources occurrence. Libya has indeed an interesting hydrocarbon potential and the potential to enhance the production and the development of many others geological resources. Unfortunately, trusted official data describing the true state of the geo-resources sector in Libya including production, demand, and market balance are missing for the post 2010 period due to the no effective governance resulting from the political-military instability. Accordingly, this short report is mainly based on the analysis of relevant multisource data and information from published research and available documentation. It constitutes a general diagnosis and a synthesis of the state of the art of the geo-resources of Libya from a combined geological and economic point of view and exposes the opportunities and the challenges their future development faces. [ABSTRACT FROM AUTHOR]

Atomic force microscopy coupled with infrared spectroscopy (AFM-IR) is one of the most effective and widely employed mixed techniques capable of providing direct access to infrared spectroscopic imaging and chemical analysis at the nanoscale spatial resolution. In this communication, AFM-IR was applied to the evaluate the in-situ nanoscale mineralogy and to characterize the organic structure of shale. Significant chemical and microstructural heterogeneity could be observed on the mirror-like surface of naturally deformed shale. It was also apparent that slickensides formed on the mirror-like surface potentially influence the spatial distribution of organic matter. This technique provides an effective combination for direct and in-situ studies of the morphology and physicochemical properties of geological rocks at the nanoscale, opening a new avenue for investigations to help reveal some complex geological phenomena, such as organic carbon graphitization and mineral transformation during fault deformation. Furthermore, this technique makes it possible to determine the chemical composition, molecular structure and functional group information of shale organic matter, which is crucial information for investigating the hydrocarbon generation potential, maturity evaluation, and oil and gas migration mechanisms in shale. [ABSTRACT FROM AUTHOR]

A microfine-grained complex refractory gold ore in Henan has a grade of 1.2 g/t, but the recovery rate by beneficiation is low. To improve the recovery rate and economic benefits, a process mineralogy study was conducted on the flotation tailings. The study revealed that the gold-bearing minerals in the tailings are primarily pyrite, followed by silicate minerals such as quartz and feldspar. The pyrite particles are mostly smaller than 0.038 mm, typically occurring as fine particles intergrown with gangue minerals or encapsulated within them, with occasional monomeric occurrences. The monomer liberation degree is only 4. 60%, indicating that increasing the grinding fineness could further recover the gold from the tailings. Open-circuit and closed-circuit tests showed that when the grinding fineness was increased to 0.074 mm accounting for about 85%, and the flotation reagent regime was optimized and adjusted, the recovery rate increased to 85.86%, leading to significant economic benefits. [ABSTRACT FROM AUTHOR]

The characterisation of the thickness and geology of cover sequences significantly improves targeting for mineral exploration in buried terrains. Audio-frequency Magnetotelluric (AMT) data is applicable to characterise cover sequences, where their conductivity (inverse resistivity) can be differentiated. We present a regional study from the under-cover East Tennant region in the Northern Territory (Australia) where we have applied deterministic and probabilistic inversion methods to derive 2D and 1D resistivity models. We integrated these models with information of co-located basement penetrating boreholes (lithological and geophysical logs) to ground-truth and validate the models and to improve geophysical interpretations. In the East Tennant region, borehole lithology and wireline logging demonstrate that the modelled AMT response is largely controlled by the mineralogy of the cover and basement rocks. The bulk conductivity is due primarily to bulk mineralogy and the success of using the AMT models to predict cover thickness is shown to be dependent on whether the bulk mineralogy of cover and basement rocks are sufficiently different to provide a detectable conductivity contrast. Our investigation of a range of geological scenarios that differ in thickness, complexity and geology of the cover and basement rocks suggests that in areas where there is sufficient difference in bulk mineralogy and where the stratigraphy is relatively simple, AMT models predict the cover thickness with high certainty. In more complex scenarios interpretation of AMT models may be more ambiguous and requires integration with other data (e.g. drilling, wireline logging, potential field modelling). Overall, we conclude that the application of the method has been validated and the results compare favourably with borehole stratigraphy logs once geological (i.e. bulk mineralogical) complexity is understood. This demonstrates that the method is capable of identifying major litho-stratigraphic units with resistivity contrasts. Our results have assisted with the planning of regional drilling programs and have helped to reduce the uncertainty and risk associated with intersecting targeted stratigraphic units in covered terrains. [ABSTRACT FROM AUTHOR]

Internal erosion by suffusion within a sand–clay mixture may occur as detachment of clay particles, which is induced by a decrease in ionic concentration (IC) along with application of a high hydraulic gradient. Through designed laboratory soil-column experiments, this study investigates the impact of the IC gradient (stepwise or gradual decrease), clay mineralogy, sand particle size and hydraulic gradient on the suffusion of a sand–clay mixture. The observed breakthrough concentration of clay particles revealed the substantial suffusion of a sand–clay mixture caused by a stepwise decrease in the IC for kaolinite and illite, while similar filtrated quantities of bentonite were observed for stepwise and gradual decreases in IC. In addition, the small-grained sand showed a relatively high susceptibility to suffusion by a stepwise decrease in IC, most likely because of the low reattachment of detached clay particles. The mass of filtrated clay particles evaluated from the area of the observed breakthrough curves in this study provides a clear insight into the need to incorporate the IC gradient when assessing the susceptibility to the suffusion of clay-containing soils. [ABSTRACT FROM AUTHOR]

Reliable reconstructions of tephrostratigraphy and emplacement mechanisms of Early to Middle Miocene volcaniclastic deposits across the Alpine-Mediterranean region may yield important clues as to the nature, spread, volume, magnitude and frequency of large silicic eruptions of the Carpathian-Pannonian Region. Here we report on a sequence of Middle Miocene volcaniclastic deposits intercalated with lacustrine strata from the Livno-Tomislavgrad Basin, part of the Dinaride Lake System. We applied a multi-proxy approach to elucidate their source, decipher their emplacement mechanism, and evaluate their basin-scale and regional correlativity. New high-precision zircon geochronology (~ 14.32 Ma) reveals their simultaneity with numerous volcaniclastic deposits (and their alteration products) widely spread across the Alpine-Mediterranean region. Additionally, their correlativity is confirmed at the scale of the Livno-Tomislavgrad Basin, based on similar lithostratigraphy, mineralogy and volcanic glass geochemistry. Newly obtained zircon Hf isotope data imply that Livno-Tomislavgrad Basin distal volcaniclastic deposits and ~ 14.36 Ma Harsány ignimbrite of the Carpathian-Pannonian Region had shared a parental eruptive center. However, different volcanic glass geochemistry, bolstered by the high-precision geochronology, suggests distinct eruption events, implying more frequent explosive volcanism of the Carpathian-Pannonian Region during Middle Miocene than previously recognized. We suggest that the ~ 14.32 Ma fine fallout tephra, deposited in the distal basin in the Dinarides (> 400 km from the source), was likely re-mobilized by water-driven hillside erosion from the extensive paleo-relief, and further transported via land-derived gravity flows. Upon entering the lake, the gravity flows likely transformed into subaqueous sediment density flows. These deposited ~ 1 to 7-m-thick overall graded volcaniclastic turbidites, thinning away from the presumed source of tephra re-mobilization. Although over-thickened, the ~ 14.32 Ma Livno-Tomislavgrad Basin volcaniclastic deposits can still serve as a reliable tephro- and tectono-stratigraphic markers due to their rapid mode of accumulation. Schematic illustration of the formation of studied ~14.32 Ma volcaniclastic successions of the SE Livno-Tomislavgrad Basin, Dinaride Lake System [ABSTRACT FROM AUTHOR]

The Koum Basin is a North Cameroonian intracontinental basin that is part of the upper Benue Trough, notably the Yola arm. The sediments of this basin were examined to determine paleoenvironmental and paleoclimatic interpretations, which were based mostly on sedimentology and mineralogical evolution in its central part. The examined materials are dominated by claystone and siltstones of varied colours, which are, for the most part, carbonated, and a few layers of fine to medium sandstone and conglomerate. The bulk organic geochemistry enabled the designation of type III kerogen, indicating a terrestrial origin of organic matter, which shows predominantly immature issues. The bulk mineralogy development exhibits no significant changes and is dominated by phyllosilicate (25.66%), calcite (24.5%), plagioclase (19.36%), and quartz (19.31%). Smectite, illite, and vermiculite dominate clay mineral fraction, with only low quantities of kaolinite and chlorite. The diagenesis influence is low to moderate, as shown by moderate illitization and chloritization as well as Tmax values. The deposition occurred in a globally semi-arid climate, as evidenced by the permanent occurrence of smectite, punctuated by short periods of drier and humid weather. [ABSTRACT FROM AUTHOR]

Nickel is a strategic element whose production and consumption in over a decade has increased to over 39% and 71%, respectively. Generally, due to their complex mineralogy, laterites, the current attractive source of Ni, are subjected to hydrometallurgy and pyrometallurgy techniques without enrichment in order to extract Ni. Therefore, numerous investigations in vogue on laterite enrichment performed spanning from 1964 to date were reviewed in this article, and the future directions were proposed through critical synthesis. The possibilities of obtaining both higher recoveries and increase in grade for Ni were noticed using selective comminution-classification method followed by flocculation-flotation strategy. Hence, in order to improve on the reported Ni yields from selective comminution-classification process, one of the ways could be to subject the ore to a multi-stage selective comminution-classification method followed by subjecting the obtained concentrate to flocculation-flotation technique. Therefore, the findings of this investigation would aid in upscaling the production to meet the demand. Properties of goethite and serpentine were explored. Physical and flotation methods for laterite enrichment were reviewed. Future directions for laterite beneficiation were proposed. [ABSTRACT FROM AUTHOR]

We combine published and new mineralogical data on most major taxa of brachiopods from all over the world, to investigate patterns and controls on brachiopod carbonate mineralogy. Measurements of 1726 specimens in 162 species (including 56 fossil species) ranged from 79°N to 74°S and from intertidal to almost 4000 m deep. Calcareous brachiopods mostly create strong resilient valves of very low-Mg calcite ($\bar{\chi }$ χ ¯ = 1.3 wt% MgCO3). The substrate-cemented Craniida ($\bar{\chi }$ χ ¯ = 8.9 wt% MgCO3) and Thecideida ($\bar{\chi }$ χ ¯ = 6.5 wt% MgCO3) are unusual in precipitating calcite with higher Mg content. This is the first study to find bimineralic brachiopods; a few species show a combination of low-Mg ($\bar{\chi }$ χ ¯ = 0.8 wt% MgCO3) and intermediate-Mg calcite ($\bar{\chi }$ χ ¯ = 7.2 wt% MgCO3) (sensu Smith AM, Key MM Jr, Gordon DP. 2006. Skeletal mineralogy of bryozoans: taxonomic and temporal patterns. Earth-Science Reviews. 78:287–306.). While Mg in calcite varies systematically among valve layers and sometimes along the growth axis, we found no consistent difference between valves of the same individual. A weak latitudinal signal indicates some overall temperature control of Mg, but in general, brachiopods are active calcifiers, precipitating low-Mg calcite even when Mg:Ca ratio in seawater is high. The drivers on brachiopod mineralogy are individual, environmental, and phylogenetic – resulting in complex variability. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Cultural Studies / Kültür Araştırmaları Dergisi is the property of Journal of Cultural Studies / Kultur Arastirmalari Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The socio-economical importance of geological heritage (geoheritage) makes it a geological resource. New minerals are reported regularly, and their type specimens and localities are ex-situ and in-situ constituents of geoheritage, respectively. The present study focuses on the contemporary dynamics of these specific resources. For this purpose, the information about new minerals reported during the past five years is analyzed. The attention is paid to the distribution of the new mineral specimens (holotypes and cotypes) and their type localities by country; the transboundary replacement of new minerals is also considered. It is established that the new minerals-related geoheritage resources are accumulated in dozens of countries. The ex-situ geoheritage (specimens in museum collections) is represented twice narrower than the in-situ geoheritage (localities as geosites). About half of new minerals are replaced to the other countries and often to the other parts of the world. The registered patterns are explained by the peculiarities of the contemporary mineralogical research. The outcomes of the present analysis permit to make recommendations for the development of the optimal geoheritage policy. [ABSTRACT FROM AUTHOR]

This article examines the clay mineralogy of twelve representative soils developed from gypsum-rich parent materials on several geomorphic positions. These soils were classified as Haploxerept, plus one profile as Humixerept and another as Xerorthent. The clay mineralogy, determined by X-ray diffraction, showed quite a similar clay composition in all profiles, with mica, chlorite, and smectite, from most to less abundant. Mica and chlorite are deemed inherited, while smectite—appearing in minor proportions—could result from both transformation and/or neoformation, because the leaching of bases by free drainage does not favor the transformation of mica to smectite. Therefore, the differences in clay mineralogy appeared to be lithogenic rather than pedogenic. These compositional data are an advance in the basic knowledge of the studied soils. [ABSTRACT FROM AUTHOR]

This paper presents a gravimetric method for the quantification of total organic carbon by ignition at 1100°C and carbonates by acid dissolution in rock samples containing coal. Two minerals (CM-1 and CM-2) and a subbituminous coal (SBC) were used in the study. The mineralogical characterization of the samples was performed by X-ray diffraction and scanning electron microscopy. This revealed the presence of calcite in samples CM-1 (20.4%) and CM-2 (74.7%), dolomite in CM-2 (0.7%), and graphite in sample SBC (42.6%). To eliminate carbonates, the samples were treated with 4 mol/L HCl, which allowed quantification. Results of the carbonate gravimetric quantification were compared with those obtained with a calcimeter. A significant difference was observed for the sample CM-2 (70.3% versus 63.4% by calcimetry, p-value = 0.0042). For the sample without carbonates, no differences were observed for loss on ignition without and with the acid treatment, so this is not necessary for this type of sample. A morphological study showed no significant surface change after acid treatment, but fracture of iron oxide particles was observed in CM-1 and CM-2 after heat treatment. In this study it was demonstrated that rock mineralogy is essential to correctly analyze organic and inorganic carbon content. [ABSTRACT FROM AUTHOR]

Thermal soil treatment is a well-established remediation method to remove organic contaminants from soils in waste management. The co-contamination with heavy metals raises the question if thermal soil treatment affects heavy metal mobility in soils. In this study, four contaminated soils and a reference sample were subjected to thermal treatment at 105°C, 300°C and 500°C for 7 day. Thermogravimetry and differential scanning calorimetry were used to understand the reactions, and resulting gases were identified by Fourier-transformed infrared spectroscopy. Treated and untreated samples were characterised by X-ray diffraction (XRD) and electron microprobe analysis and subjected to pH-dependent leaching tests, untreated samples additionally by X-ray-fluorescence (XRF) and inductively coupled plasma mass spectroscopy (ICP-MS). Leachates were analysed using ICP-MS and ion chromatography. Maximum available concentrations were used for hydrogeochemical modelling using LeachXS/Orchestra to predict leaching control mechanisms. Leaching experiments show that thermal treatment tends to decrease the mobility at alkaline pH of Pb, Zn, Cd, As and Cu, but to increase the mobility of Cr. In the acidic to neutral pH range, no clear trend is visible. Hydrogeochemical modelling suggests that adsorption processes play a key role in controlling leaching. It is suggested that the formation of minerals with a more negatively charged surface during thermal treatment are one reason why cations such as Pb2+, Zn2+, Cd2+ and Cu2+ are less mobile after treatment. Future research should focus on a more comprehensive mineralogical investigation of a larger number of samples, using higher resolution techniques such as nanoscale secondary ion mass spectrometry to identify surface phases formed during thermal treatment and/or leaching. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The geoenergy industry has challenging demands on cements used as downhole materials. Once placed in the annular space, the cement sheath must be very low permeability and mechanically durable. Its characteristics are strongly influenced by its microstructure. A holistic approach, including combined mineralogical, physical, and mechanical investigations, provides a better understanding of how these characteristics interplay. Class G cement was investigated and compared to cement formulations containing carbon black or silica fu me, trying to tailor its performance. The addition of carbon black and silica fume has some effect on the modal and chemical phase composition and results in a much denser microstructure. Furthermore, porosity is reduced while the pore size distribution remains similar. Samples containing carbon black have a reduced Young's modulus, indicating a more plastic behavior. The addition of silica fume increased both mechanical strength and permeability. However, comparable results can also be achieved by carefully tuning the water/cement ratio of the initial slurry. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Magnetite is a widespread ore mineral in skarn systems and usually hosts a wide variety of inclusions. Micro- to nano-sized solid inclusions in magnetite are unique tools to track the evolutionary processes of its host mineral and, subsequently, to constrain the timing of the mineralization event. In this study, we characterize micro- to nano-sized solid inclusions in magnetite from the La Víbora magnesian skarn (Málaga, Spain) using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM energy-dispersive X-ray spectrometry (EDS) analyses and compositional mapping expose two types of nano-inclusions oriented along the (111) of magnetite: type 1 includes dolomite, spinel, and Mg–Fe–Al silicate, and type 2 is made up of Mg–Fe–Al silicates enveloping the Mg-bearing amorphous silica phase. High-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), and fast Fourier transform (FFT) patterns reveal that the majority of the solid inclusions display non-oriented matrices compared to the host magnetite, precluding the possibility of sub-solidus processes. Instead, these inclusions are thought to preserve skarn mineral assemblages that were entrapped during the growth of magnetite. However, the local supersaturation of fluids trapped in the boundary layer of crystallizing magnetite is evidenced by coherent lattice orientation of precipitated and host magnetite and by the occurrence of an Mg-bearing amorphous silica phase. Our findings reveal that skarn reactions observed at field and microscopic scales are also recorded in nano-sized inclusions within magnetite. These observations underscore the significance of micro- to nano-scale solid inclusions in magnetite to decipher overprinted skarn reactions as well as constraining the timing of Fe mineralization events in skarns.

Kamafugites are rare volcanic igneous rocks, characterized by the presence of kalsilite and variable amounts of leucite, nepheline, melilite, clinopyroxene, olivine and phlogopite, which may not necessarily be present all together. Kamafugites are silica-poor (moderately ultrabasic to basic), CaO- and alkali-rich (mostly ultrapotassic) lithologies, generated from strongly metasomatized and heterogeneous mantle sources, with abundant phlogopite and little or no orthopyroxene. Melting of phlogopite- and carbonate-bearing veins is often invoked as being responsible for the ultrapotassic and ultracalcic signatures observed in many kamafugites. Nevertheless, many questions still persist about their mantle sources, such as the paragenesis of the metasomatic veins within the lithospheric mantle and the degree of interaction between the initial melts and the peridotite matrix. We experimentally investigated four natural kamafugite samples to determine the mantle assemblages that were in equilibrium with these melts at the onset of partial melting and their genesis. The kamafugites were collected from the three known areas where they occur: Uganda, Italy and Brazil. Near-liquidus experiments were carried out at 1 to 2 GPa and temperatures from 1250 to 1380 °C. These experiments provide information on the mineralogy of the potential mantle sources in each of the volcanic provinces, also allowing a comparison among them. The experiments confirm the common presence of clinopyroxene and phlogopite as the main near-liquidus phases, with olivine joining the near-liquidus phase assemblage in one Italian sample (San Venanzo) and in the Brazilian kamafugite. Other minor phases (apatite and Fe–Ti oxides) also crystallized in near-liquidus conditions, highlighting their importance for at least the Ugandan and Brazilian kamafugites. Our results demonstrate that various amounts of clinopyroxene (∼40 % in Italy and 50 %–60 % in Uganda and Brazil), phlogopite (∼20 %–30 % in Brazil, ∼40 % in Uganda and ∼60 % in Italy) and accessory phases (up to 4 % titanite in Uganda, up to 3 % apatite in Uganda and up to 5 % oxides in Uganda and Brazil) are required for the formation of kamafugite melts. The contribution of olivine differs among the four samples, being negligible for the Ugandan kamafugites and in one of the Italian kamafugites but up to 5 % in the second Italian kamafugite and 10 % in Brazil.

Amid the scarcity of lunar meteorites and the imperative to preserve their scientific value, non-destructive testing methods are essential. This translates into the application of microscale rock mechanics experiments and scanning electron microscopy for surface composition analysis. This study explores the application of Machine Learning algorithms in predicting the mineralogical and mechanical properties of DHOFAR 1084, JAH 838, and NWA 11444 lunar meteorites based solely on their atomic percentage compositions. Leveraging a prior-data fitted network model, we achieved near-perfect classification scores for meteorites, mineral groups, and individual minerals. The regressor models, notably the K-Neighbor model, provided an outstanding estimate of the mechanical properties—previously measured by nanoindentation tests—such as hardness, reduced Young’s modulus, and elastic recovery. Further considerations on the nature and physical properties of the minerals forming these meteorites, including porosity, crystal orientation, or shock degree, are essential for refining predictions. Our findings underscore the potential of Machine Learning in enhancing mineral identification and mechanical property estimation in lunar exploration, which pave the way for new advancements and quick assessments in extraterrestrial mineral mining, processing, and research.

Lunar soil simulants (LSS) have been pivotal in the success of past and current lunar missions. They have enhanced the design of lander and rover wheels through interaction studies on the lunar testbed under simulated environmental conditions. They have also been used to evaluate the geotechnical, geomechanical, and dynamic characteristics of the lunar soil (LS), which is vital for future lunar outposts. While most simulants have focused on either the chemical and mineralogical or geotechnical properties, developing a comprehensive LSS that mimics the lunar soil is of paramount importance for lander and rover soft-landing and future lunar habitation. This article presents the significant development and characterization of the new LSS NYUAD-1, the first regional soil simulant tailored for the planned Emirates lunar missions. The material and geotechnical properties of NYUAD-1, including chemical composition, mineralogy, particle size, morphology, specific gravity, density, shear strength, and compressibility behaviors, were assessed through laboratory tests conducted per ASTM standards. Comparative analysis with authentic lunar regolith and various regolith simulants confirms the significance and applicability of NYUAD-1 for lunar-based research, offering a promising step toward future lunar habitation.

Millimeter-sized crystals of mimetite and pyromorphite, and polymineralic mimetite-pyromorphite-vanadinite crystals occur in quartz-baryte vein within paragneisses of the Sowie Mts, SW Poland. Three morphologically different mimetite crystals and a polymineralic crystal were examined by electron probe micro-analysis (EPMA), back-scattered electrons (BSE) imaging, Raman microspectroscopy, and X-ray composition mapping. Mimetite occurs as well-developed crystals, crystals built up of sub-parallel individuals due to autoepitaxial growth, and crystals extensively etched. All of the mimetite crystals are zoned with respect to pyromorphite molecule content with sharp increase up to 23 mol% in the outermost zones. The apparent vanadinite crystal actually consists of oscillatory-zoned pyromorphite + minor vanadinite core, intermediate zones composed of pyromorphite, two mimetite zones intercalated by a band of oscillatory pyromorphite and minor vanadinite, and vanadinite mantle. EPMA data show a limited miscibility between all three minerals in the polymineralic crystal. Most analyzes cluster around 10 mol% of ternary solid solution with the maximum value of ca. 30 mol%. X-ray elemental maps reveal sharp boundaries between compositionally contrasting zones in the crystal core. In mimetite zones, the substitution of As by P does not exceed 0.43 atoms per formula unit (apfu). In the vanadinite mantle, As + P does not exceed 0.30 apfu. The distribution of Pb is uniform throughout the crystal with the highest Ca/Pb ratio of 0.03. The observed sequence of crystallization in the polymineralic crystal can be explained by the relative changes in ions concentrations at the crystal/solution interface, i.e. within the diffusion boundary layer, in accord with the models of the autocatalytic crystal growth. The authors hypothesize that kinetically driven fast growth of the polymineralic crystals resulted in precipitation of discrete mineral phases with very limited anionic substitutions.

Volcanic rocks in the Pieniny Klippen Belt (PKB) of the Western Carpathians have been the focus of geologists for over a century (e.g. Uhlig, 1890; Małkowski, 1921). Miocene volcanism is most common in the PKB. However, there are infrequent occurrences of Cretaceous volcanic rocks. Several magmatic bodies of Cretaceous age have already been described in the PKB, including basalts at Hanigovce and Biała Woda, as well as peperites at Vršatec, and Velykyi Kamenets. The magmatic body in Vršatec occurs within the Upper Cretaceous marlstones of the Lalinok Formation, the age of which was previously determined to be younger than 100 Ma (Spišiak et al., 2011). Our new U-Pb zircon dating indicates the magmatic age to be ca. 80 Ma. This new age can be used as a benchmark for the forthcoming provenance studies of the surrounding clastic rocks in the PKB and the Outer Carpathians flysch.

Bituminous sand is an important geomaterial due to its numerous engineering applications and great economic potentials. The occurrence is diverse in nature and therefore, it is very crucial to study the engineering behaviour and understand the inherent variability in the engineering parameters needed in exploitation, design and construction in and/or on them. This study presents laboratory investigations into the engineering behaviour and the inherent variability in bituminous sand considering index, physical, fabric and geochemistry, mineralogy, oedometer and strength characteristics on the samples in the intact and reconstituted states. The findings can be summarised as follows: (1) The gradings are characterised by different particle sizes and hence, the bituminous sands are well-graded, (2) The fabrics are heterogeneous and isotropic and composed majorly of bituminous materials coated particles aggregation to clusters with inter- and intra- particle/cluster voids, (3) Silica and quartz dominate the composition and mineralogy with other elements and minerals in lesser proportions, (4) Bituminous sands have convergent behaviour and the compressibility is dependent of fines content, (5) Intact behaviour shows the presence of significant structure and (6) The inherent variability is high in some engineering grading descriptors, clay mineral, yield stress and strength, and low in the fines content, quartz mineral, compressibility and in situ specific volume and (7) Depending on the properties needed by the practitioners, interpolation and extrapolation from one point/location to the other could be made in these geomaterials.

Characterizing fluid circulation in orogens is key to understanding orogenic processes because fluid–rock interaction modifies the physical properties of rocks, hence their response to deformation and, for example, their suitability for radioactive waste storage. Fluid circulation can be dated by applying geochronological methods to fluid-precipitated minerals. Fluid sources and associated pathways can be traced using isotope data measured in the same or in other cogenetic minerals. We applied this concept to the Aar Massif (central Swiss Alps), which was part of the former European passive continental margin that was deformed and exhumed during the (Cenozoic) Alpine orogeny. Newly collected epidote from veins and from one cleft at several localities in meta-granitoids in the Aar Massif yielded U–Pb ages ranging from 27.7 ± 3.4 to 12.4 ± 1.9 Ma, which complement previously published geochronological data revealing Permian (278 ± 29, 251 ± 50, and 275 ± 18 Ma) and Miocene (19.2 ± 4.3 and 16.9 ± 3.7 Ma) epidote veins. We used Pb–Sr–O–H isotope geochemistry of epidote to evaluate fluid sources and pathways during Permian rifting and the Miocene compressional phases of Alpine orogeny. Strontium isotope data of Permian epidote are consistent with previous work suggesting meteoric water infiltration along syn-rift faults and through syn-rift sediments. A more-complex structural framework existed in the Miocene, when a sedimentary lid covered the Aar Massif. Strontium, O, and H isotope data of Miocene epidote-forming fluids indicate (1) meteoric water, mixing with (2) fluids derived from sedimentary units being compacted during orogenesis and/or (3) metamorphic water. All three fluid endmembers may have been circulating and mixing in the Aar Massif during Miocene deformation. Strontium isotope data further indicate that Miocene fluids contributed to imprinting a highly radiogenic Sr isotope composition onto Alpine shear zones or that the fluids inherited a highly radiogenic Sr isotope component by dissolving the Rb-rich, high 87Sr / 86Sr biotite therein. Both possibilities can coexist, and they imply that external fluids could modify the chemical composition of the post-Variscan granitoids hosting the studied epidote veins by fluid–rock interaction processes during deformation. Lead, Sr, and H isotopic differences among Miocene samples further suggest complexity of large-scale fluid circulation. Our work supports the fact that the reconstruction of multifaceted and multi-stage fluid circulation in highly deformed rocks benefits from extracting geochronological and isotope data from the same mineral.

Karlseifertite (IMA 2024-007, International Mineralogical Association), Pb(Ga2Ge)(AsO4)2(OH)6, is a new member of the dussertite group, from Tsumeb, Namibia. It is a secondary oxidation-zone mineral found on fracture surfaces in germanite–chalcocite ore. Karlseifertite occurs in rosettes of thin, yellow, hexagonal plates up to about 0.2 mm in diameter and usually less than 0.01 mm thick. The mineral has a pale-yellow streak, subadamantine lustre, Mohs hardness of ∼ 4, brittle tenacity, irregular fracture, perfect cleavage on {001} and a calculated density of 4.993 g cm−3. Optically, karlseifertite crystals are uniaxial (+), with ω=1.890(5) and ε=1.894(calc) (white light). The empirical formula from electron probe microanalyses is Pb0.992+(Ga1.603+Ge0.684+Fe0.573+Al0.123+)Σ2.97[(As0.765+S0.156+W0.096+)Σ1.00O4]2(OH0.99)6. Karlseifertite is trigonal with space group R3‾m and unit-cell parameters a=7.2814(7), c=17.1077(12) Å, V=785.50(15) Å3 and Z=3. The mineral has an alunite-supergroup structure (R1=0.0591 for 248 reflections with I>2σI).

The rock composition and ore mineralization of the Malenkiy site located within the Khengur gabbro-dolerite complex of the Pay-Khoy were examined. Petrogeochemical analysis revealed two varieties of the studied rocks: fine-crystalline quartz and medium- and coarse-crystalline quartz containing metagabbro-dolerite. The Y, Zr, and Nb contents suggest that metagabbro-dolerites formed in an intraplate setting from enriched mantle sources during the melting of garnet peridotite, with a small contribution from the melt source of ancient continental crust. Two types of ore mineralization were distinguished: nest- and veinlet-disseminated sphalerite-chalcopyrite-pyrrhotite (type I) and veinlet-disseminated cobaltite-pentlandite-chalcopyrite-pyrrhotite (type II). The most efficient ore mineralization was type II, which is characterized by the presence of both high-temperature cobalt- and nickel-bearing sulfide minerals, as well as low-temperature tellurides of palladium (kotulskite) and silver (hessite).

The occurrence of Cr-bearing oxide phases as inclusions in diamonds and in extraterrestrial materials has the potential to serve as an indicator of formation conditions. However, such an application requires detailed knowledge of phase stabilities and the influence that Cr may have on its stability. To this end, the incorporation of Cr in high-pressure post-spinel Fe–Mg oxide phases was experimentally investigated at pressures of 14–22 GPa and temperatures between 1100 and 1600 °C using a multi-anvil press. We find that neither the Fe3Cr2O6 nor the Mg3Cr2O6 endmember composition is stable over the expected range of pressure and temperature where Fe5O6 itself is known to be stable. Further experiments along the Fe32+Fe23+O6–Fe32+Cr2O6 binary indicate only small amounts of Cr substitution are possible: ∼ 0.12 cations Cr per formula unit or ∼ 6 mol % Fe32+Cr2O6 component. In contrast, complete solid solution is apparent across both the Fe22+(Cr,Fe3+)2O5 and the Mg2(Cr,Fe3+)2O5 binaries, and there are indications of complete solution in the entire (Mg,Fe2+)2(Cr,Fe3+)2O5 quaternary system. The O5-structured phase usually coexists with (Fe,Mg)O. At 16–20 GPa, a post-spinel phase with O4 stoichiometry was occasionally encountered, having either a modified Ca-ferrite- (mCF-FeCr2O4) or a Ca-titanate-type (CT-MgCr2O4) structure. In one high-temperature experiment at 1600 °C, an unquenchable Mg-rich phase with a reconstructed Mg4Fe23+O7 stoichiometry occurred together with Mg2(Cr,Fe3+)2O5. In one experiment at 1100 °C and 16 GPa with a bulk composition of Mg2(Cr0.6,Fe0.43+)2O5, an assemblage of O5 phase + eskolaite–hematite solid solution + periclase was obtained together with minor amounts of the CT-type phase and a β-(Cr,Fe)OOH phase. The occurrence of these two minor phases in this low-temperature experiment is an indicator of variable reaction kinetics amongst the starting materials, which caused chemical heterogeneities to develop at the onset of the experiment. The structural systematics of Fe22+(Cr,Fe3+)2O5 and (Fe2+,Mg)2(Cr,Fe3+)2O5 solid solutions were investigated. It is notable that the Fe3+ and Cr endmembers have somewhat different crystal structures, belonging to space groups Cmcm (no. 63) and Pbam (no. 55), respectively. The phase transition occurs around the midpoint of the Fe3+–Cr joins. In spite of complexities in the behavior of the unit-cell parameters, the variation in molar volume with composition deviates only slightly from linearity. Wüstite and periclase coexisting in our experiments reveal the incorporation of up to 9 wt % and 25 wt % Cr2O3, respectively. This is consistent with the minor Cr contents reported for some ferropericlase inclusions in natural diamond. The limited solubility of other cations in Fe5O6 limits the likelihood of it being an accessory phase in the Earth's deep upper mantle and transition zone, except in Fe-rich environments. In contrast, the O5 phase appears to be more flexible in accommodating a range of divalent and trivalent cations, suggesting that this phase is more likely to be stabilized, potentially where redox reactions related to diamond formation occur.

The new mineral bonacinaite (IMA2018-056), Sc(AsO4) ⚫ 2H2O, was found on the dumps of the Varenche Mine (Saint-Barthélemy, Nus, Aosta Valley, Italy), an old manganese mine, where it occurs as a low-temperature hydrothermal mineral associated mainly with quartz, granular braunite, undefined manganese oxides, arseniopleite, manganberzeliite and thortveitite. Bonacinaite forms colourless (with faint to distinct violet tints), pseudohexagonal, thick tabular crystals, up to 0.25 mm in size, sometimes with annular internal zones showing violet tinges, or as small, faintly violet lath-shaped crystals. The crystals are transparent and brittle, with vitreous lustre. The calculated density of an almost pure bonacinaite crystal is 2.82 g cm−3. Optically, bonacinaite is biaxial negative, α=1.598(4), β=1.618(3), and γ=1.638(3) (measured with a Na light source, 589 nm); 2V (measured) is large, and 2V (calculated) = −88.9°. The empirical formula, based on six O atoms per formula unit is (Sc0.90Mn3+0.08Fe3+0.01Pb0.01)Σ1.00[(As0.95P0.06)Σ1.01O4] ⚫ 2H2O. Bonacinaite has monoclinic symmetry, with space group P21/n and unit-cell parameters (single-crystal data / powder diffraction data) a=5.533(1)/5.521(1), b=10.409(2)/10.336(3), c=9.036(2)/9.059(4) Å, β=91.94(3)/91.97(4), V=520.1(2)/516.7(3) Å3 and Z=4. The crystal structure was refined from single-crystal intensity data obtained from a distinctly Al- and P-bearing crystal to R1(F) = 3.7 % for 1178 reflections. Bonacinaite is isotypic with the other members of the metavariscite group: kolbeckite, metavariscite and phosphosiderite.

Sulfide- and sulfate-rich hydrothermal vents are involved in Earth's major geochemical cycles. An outstanding scientific question consists of finding out whether certain minerals found in hydrothermal chimneys are influenced more or less directly by microorganisms living at high temperatures (thermophiles or hyperthermophiles) in these environments. Here we report the morphological, textural and chemical characterization of pyrite crystals collected across a section of a chimney from the Trans-Atlantic Geotraverse hydrothermal site, sampled from the inner, hotter portion to the external, cooler portion, providing a promising approach to the search for hyperthermophilic biosignatures. The internal and middle portions of the chimney mainly harbour cube-shaped pyrite containing low quantities of hydrocarbons and thermally matured organic compounds. In contrast, the samples from the external portion contain pyrite spherules composed of a mosaic of slightly disoriented domains that include large amounts of organic material chemically consistent with thermally matured biogenic organic compounds. These characteristics make them comparable but not identical to pyrite spherules produced in the laboratory in the presence of hyperthermophilic archaea of the order Thermococcales. Differences include larger crystalline domains and more thermally matured organic compounds. Such features could be consistent with the thermal transformation of pyrite spherules produced by (or at least in the presence of) living cells. However, it remains impossible to completely rule out an abiotic origin without further isotopic investigation and experimental studies on the abiotic production of pyrite spherules in the presence of organic compounds and under hydrothermal conditions.

The current climate emergency and the related energy transition require the development of technology producing zero-carbon energy. One viable option entails the utilization of recyclable metal fuels. The primary energy stored by the reduction in metal oxides can be transported and later released by metal combustion. Mg is among the most promising metal as a regenerable energetic vector, having an energy density of 25 MJ kg−1. The exploitation of the Mg oxidation and reduction loop has recently been demonstrated, and the loop combustion products are made of metal oxides. The mineralogical characterization of the MgO crystals generated by the Mg combustion is of utter importance for the optimization of the particle trapping capacity in the combustion system during the closed oxidation and reduction loop. In this paper we characterize MgO particles generated in a swirl-stabilized Mg flame by using powder X-ray diffraction, transmission electron microscopy and selected area electron diffraction, and atomic-resolution microscopy combined with energy-dispersive X-ray spectroscopy and dual-electron energy-loss spectroscopy. The MgO combustion products were chemically homogeneous at this level of investigation. Three representative morphologies (cubic, truncated octahedron, and spherical) and two isostructural phases were identified in the MgO combustion product. These findings may contribute to the optimization of system development, particularly in terms of the collection efficiency of the combustion end product.

The study of rock chemistry is a milestone in understanding fluid–rock interactions and fluid migration in subduction zones. When combined with thermodynamic models, it can provide direct insight into fluid composition, metasomatic reactions, and pressure–temperature (P–T) conditions, as well as their role in rock deformation. Here, a shear zone – located in the Mont Avic area of the Zermatt-Saas zone (Western Alps) – is analyzed. This shear zone consists of several blocks of different lithotypes, including a Ca-rich metasomatite block embedded in a serpentinite mylonitic matrix, and structurally underlies a coherent eclogitic mafic unit. This work aims to estimate the pressure–temperature conditions of the Ca-rich metasomatism and the amount of fluid involved. The brecciation exhibits mosaic breccia textures with clasts comprising ∼80 vol % of garnet, together with omphacite, epidote, titanite, rutile, and apatite hosted in an omphacite matrix. Quantitative chemical mapping of the garnet reveals primary garnet cores with embayment and lobate edges with a chemical composition similar to unaltered reference eclogite garnet. These primary garnet cores are overlain by Ca-rich metasomatic garnet rims with oscillatory chemical zoning. The oscillatory chemical zoning, together with the morphology of the primary garnet cores, suggests repeated influxes of external Ca-rich fluid that destabilized the primary garnet cores and promoted the growth of Ca-rich rims. Mass balance calculations between precursor metabasite and Ca-metasomatite indicate multiple fluid sources involving dehydrated serpentinite, calcic metasediments, and metabasites with time-integrated fluid fluxes calculated between 11.5×103 and 5.5×104 mfluid3 mrock-2, consistent with channelized fluid flow in an open system. Thermodynamic modeling of garnet from unbrecciated and non-metasomatized metabasites – from the Savoney eclogitic mafic unit – indicates peak metamorphic conditions of 2.5±0.1 GPa and 535±40 °C, consistent with regional estimates. Pressure–temperature conditions of metasomatism were constrained using P–X and T–X phase modeling (where X represents changes in bulk CaO and Na2O composition) between 2.6–2.2 GPa and 570–500 °C, showing that Ca-rich fluid percolation occurred close to the metamorphic peak (i.e., prograde to the peak or early exhumation path).

Selected crystals of natural K-bearing tourmalines, extracted from a quartzofeldspathic rock from the Kumdy-Kol microdiamond deposit (an ultrahigh-pressure region of Kokchetav Massif, northern Kazakhstan), were characterized using a scanning electron microscope, an electron microprobe and single-crystal X-ray diffraction to investigate the impact of K uptake on the tourmaline structure. All the studied crystals belong to the maruyamaite–oxy-dravite/dravite compositional field, with K contents ranging from 0.03 to 0.47 apfu (atoms per formula unit), and contain a minor fluor-uvite component that increases towards oxy-dravite and dravite. The compositional variability of our samples can be expressed as a sequence of substitutions ranging from maruyamaite to oxy-dravite, dravite and fluor-uvite (or vice versa). Specifically, the substitutions that lead from maruyamaite to oxy-dravite to dravite are (1) XK + AlTOT + O1O ↔ XNa + MgTOT + O1O and (2) XNa + MgTOT + O1O ↔ XNa + MgTOT + O1OH, respectively. Conversely, the substitutions that lead from oxy-dravite to dravite to fluor-uvite are (1) XNa + MgTOT + O1O ↔ XNa + MgTOT + O1OH and (2) XNa + MgTOT + O1OH ↔ XCa + MgTOT + O1F, respectively. By analysing the difference between the bond valence sum and mean formal charge at the X site, we show that an increase in the K content (K > 0.21 apfu) results in the compression of X–O bonds (overbonded cation). Conversely, lower K contents lead to the stretching of the bonds (underbonded cation). Compared to the K-dominant analogues with ZFeO6 povondraite-type framework, K-bearing tourmalines with a smaller ZAlO6 framework such as maruyamaite should only be stable at higher-pressure conditions, as pressure is necessary to squeeze the relatively large K cation into the tighter X cavity. In both cases, the essential condition for the formation of K-dominant tourmalines is the extremely high K activity in the crystallization fluid. The K-tourmaline from the Kokchetav Massif may have crystallized under high-pressure (HP) conditions, with an upper limit between 3.5–7 GPa, during retrograde metamorphism following the ultrahigh-pressure (UHP) metamorphic peak.

In today's global market, the movement of raw materials and goods in the free global market can lead to unintended consequences. One significant concern is the potential presence of contaminants and carcinogens, particularly when products originate from regions with less strict regulations and enforcement. This issue is particularly pertinent in the natural raw materials utilized in the global building materials market, where contamination by asbestos minerals can occur. Therefore, the screening of natural raw materials for asbestos content is crucial to mitigate the risk of exposure to carcinogens for both workers and the general public. In this study, we examine a challenging case involving a smectite–kaolinite clay from Gomsiqe–Puka, Albania, possibly containing mineral fibres. Detection and quantification of asbestos in this material push the boundaries of current experimental methods. Using transmission electron microscopy (TEM), micro-Raman spectroscopy, and electron probe microanalysis (EPMA), we identified the presence of asbestos tremolite, along with a rare fibrous variety of diopside. EPMA data allowed the advancement of some speculations on the origin of the observed tremolites, showing that Al-rich tremolites are typical of oceanic settings and Al-poor tremolites are more similar to continental tremolites. We also investigated the impact of milling on the detection and quantification of mineral fibres, testing different milling times. This investigation is crucial as it can influence the classification of the raw material as asbestos-containing material or not. Our findings indicate that tremolite, cleavage fragments, and elongated particles break down into smaller World Health Organization (WHO) fibres with increasing milling times (1–5 min). However, prolonged milling (10 min) leads to overgrinding, resulting in a decrease in the number of counted WHO fibres with a length exceeding 5 µm.

Lascar volcano, located in northern Chile, is among the most active volcanoes of the Andean Central Volcanic Zone (CVZ). Its activity culminated in the last major explosive eruption in April 1993. Lascar andesites which erupted in April 1993 have a phase assemblage composed of plagioclase, clinopyroxene, orthopyroxene, Fe–Ti oxides, and rhyolitic glass. To better constrain storage conditions and mechanisms of magmatic differentiation for andesitic magmas in a thick continental crust, crystallization experiments were performed in internally heated pressure vessels at 300 and 500 MPa, in the temperature (T) range of 900–1050 °C, at various water activities (aH2O) and oxygen fugacities (logfO2 between QFM+1.5 and QFM+3.3 at aH2O =1; QFM is quartz–fayalite–magnetite oxygen buffer). The comparison of experimental products with natural phase assemblages, phase compositions, and whole-rock compositions was used to estimate magma storage conditions and to reconstruct the magma plumbing system. We estimate that Lascar two-pyroxene andesitic magmas were stored at 975±25 °C, 300±50 MPa, and logfO2 of QFM+1.5±0.5, under H2O-undersaturated conditions with 2.5 wt % to 4.5 wt % H2O in the melt. The geochemical characteristics of the entire suite of Lascar volcanics indicates that a fractionating magmatic system located at a depth of 10–13 km is periodically replenished with less evolved magma. Some eruptive stages were dominated by volcanic products resulting most probably from the mixing of a mafic andesitic magma with a felsic component, whereas compositional variations in other eruptive stages are better explained by crystal fractionation processes. The relative importance of these two mechanisms (mixing vs. crystal fractionation) may be related to the amount and frequency of magma recharge in the reservoir.

The socio-economical importance of geological heritage (geoheritage) makes it a geological resource. New minerals are reported regularly, and their type specimens and localities are ex-situ and in-situ constituents of geoheritage, respectively. The present study focuses on the contemporary dynamics of these specific resources. For this purpose, the information about new minerals reported during the past five years is analyzed. The attention is paid to the distribution of the new mineral specimens (holotypes and cotypes) and their type localities by country; the transboundary replacement of new minerals is also considered. It is established that the new minerals-related geoheritage resources are accumulated in dozens of countries. The ex-situ geoheritage (specimens in museum collections) is represented twice narrower than the in-situ geoheritage (localities as geosites). About half of new minerals are replaced to the other countries and often to the other parts of the world. The registered patterns are explained by the peculiarities of the contemporary mineralogical research. The outcomes of the present analysis permit to make recommendations for the development of the optimal geoheritage policy.

A Dauphiné twin (DT) in a deformed quartz was visualized for the first time by using orientation-optimized electron channelling contrast imaging (ooECCI) under Bragg conditions of the rhombohedral planes. The visualization in backscattered electron (BSE) imaging with a scanning electron microscope (SEM) is possible due to the electron excitations of positive and negative rhombohedral planes from respective twin domains. Those diffraction planes have different structure factors and scattering amplitudes in electron diffraction and are exchanged in a pair of DT domains. The large-angle convergent beam diffraction (LACBED) patterns on the <011‾0> zone axis were displayed with the absence of two-fold symmetry axis along the [0001] direction in an individual twin domain but with a 180° rotation relation along the c direction between a pair of the twin domains. Related to the DT law, the LACBED pattern across a DT boundary showed the higher six-fold rotation symmetry, which is the same as that of the high-temperature β quartz. The off-axis LACBED patterns displaying Bragg lines demonstrated no angular misfit over the twin boundary. This non-orientation misfit on the twin domains allows us to confirm the visualization mechanism of DT in ECCI. The different contrast of a pair of DT domains in the BSE images originates not from a misorientation between the two domains but from different diffraction intensities between positive and negative rhombohedral planes in quartz. The observation procedure from ECCI with SEM to LACBED with TEM (transmission electron microscope) imaging presented here is indispensable for a deep understanding of the role of twinning, ranging spatially from the micrometre scale for a SEM of the bulk specimen to the nanometre scale for a TEM of the interaction with crystal defects in deformation because of their optical invisibility in a conventional petrological microscopy. Following this procedure, dislocations on a rhombohedral plane were characterized in the vicinity of DTs in naturally deformed quartz. This result implies that non-basal slips, e.g. a rhombohedral slip system, i.e. 1/3<1‾1‾20>{101‾1} ({r}) and 1/3<11‾20>{101‾2} ({π}), were activated in the vicinity of DTs. The activity of dislocations on a non-basal plane resulted from the interaction between DTs and dislocations during plastic deformation.

Strongly peraluminous (SP) leucogranite typical of Himalayan-type collision orogen is reported from Kottayam, the western Madurai block, Southern Granulite Terrane (SGT). Low concentration of mafics (average ≈ 5%), consistently high A/CNK (≥1.1), and invariable presence of garnet and normative corundum (1.24–2.12 wt.%) qualify Kottayam granite (KG) as SP leucogranite. Geochemically, KG is ferroan to magnesian (F* = 0.79–0.90), alkali-calcic to calc-alkali (MALI = 6.64–7.54), peraluminous (ASI = 1.19–1.26) and plot in peraluminous leucogranite field. Further, all the KG samples fall within the 'SP granite quadrilateral,' defined by the Al2O3/TiO2 and CaO/Na2O ratios of SP granites from orogens around the world. The REE pattern is akin to SP granites from the Himalayas and the Hercynides. Various tectonic discrimination criteria and plots indicate that KG formed in a Himalayan-type collisional orogeny. Source discrimination norms, together with zircon εHf values (−6.62 to −4.02), strongly point to a crustal source comprising an admixture of metapelites and meta-greywacke. U–Pb analyses of zircons define a concordia age of 741 ± 12 Ma, which coincides with the timing of the breakup of the Rodinia supercontinent. Mineralogical, geochemical, and isotopic evidence, thus, demonstrate that KG exemplifies crustal recycling during the Tonian period. Research highlights: Strongly peraluminous (SP) leucogranite distinctive of Himalayan-type collision orogens is reported from Kottayam, Kerala, which forms part of the western Madurai block, Southern granulite terrane (SGT), southern India. Mineralogy, geochemistry, and isotope data substantiate that this SP leucogranite formed in Himalayan-type collision orogeny. Geochemical and isotope indices show that present SP leucogranite formed from a pelite-psammite mixed source, signifying crustal recycling, during the Tonian period in SGT. Chemical proxies and geochronology data suggest that this SP leucogranite is probably associated with the post-collisional phase of collision orogeny, contemporaneous with Rodinia rifting. [ABSTRACT FROM AUTHOR]

The heating potential of microwave-heated bituminous mixtures depends on the heating characteristics of aggregates. This study focused on understanding the effect of mineral, chemical, and dielectric properties of aggregates on the rate of heating of aggregates, with special emphasis on the effect of the power level of microwave energy. Properties of the aggregates collected from 18 different sources were evaluated using X-ray diffraction, X-ray fluorescence spectroscopy, and a microwave vector network analyzer. Heating studies were conducted on the aggregates using a microwave oven at four different power levels (330, 525, 630, and 700 W). Thermal images, captured using a forward-looking infrared (FLIR) thermal camera, were used to obtain the heating characteristics, such as heating time, rate and nonuniformity of heating. The rate of heating of aggregates (0.212°C/s−1.007°C/s), nonuniformity of heating (0.059°C–0.218°C), and time of heating to 100°C (40–520 s) varied widely with the source of aggregate. In general, the heating rate and the degree of nonuniformity of the aggregates increased with increase in microwave power. Bulk mineralogy and chemical composition of aggregates significantly influenced the dielectric response of aggregates (adjusted R-squared values of 0.75 and 0.70, respectively) and the sensitivity of heating parameters to microwave power (adjusted R-squared values of 0.83 and 0.92, respectively). Two different predictive models were developed for estimation of heating rate of aggregates with (1) power, density, and dielectric loss factor, and (2) power, density, and aggregate chemical indices as independent variables. The adjusted R-squared values of these two predictive models were 0.84 and 0.92, respectively. [ABSTRACT FROM AUTHOR]

The varicoloured compacted black shale of the Duwi Formation at Mohamed Rabah, Wasief, and Umm El-Huwitat mines is part of the huge black shale belt extending from the Egyptian western desert to the Red Sea coast in the east. Egypt’s black shale has been the focus of multiple studies to investigate its potential as a future energy resource due to its organic content. However, in the this study, the focus has been on the mineralogy and geochemistry of the inorganic content of these bearing shale mines, investigated to determine their chemical characteristics. These shales mainly comprise clay minerals, calcite, quartz, orthoclase, gypsum, and anhydrite. The studied clay fraction reveals that the clay minerals are represented by montmorillonite, kaolinite, and illite. Analysed black shales are recognized by their total organic carbon (TOC) content (0.14–2.52 wt%) and are rich in SiO2 (50.83 wt%), followed by Al2O3 (14.7 wt%) and CaO (2.04 wt%). The chemical composition of these shales shows general enrichment of immobile elements and is associated with terrigenous influx, such as SiO2, Al2O3, and TiO2. Due to the oxidation and weathering of the organic matter, the geochemical composition shows that the studied black shales have high concentrations of V (1400 ppm), Sr (389.8 ppm), Zn (325.8 ppm), and Zr (258.3 ppm). The geochemical classification revealed that the studied black shale samples were related to siliceous and aluminous rocks due to the high SiO2 and Al2O3 contents and were deposited in marine environment. The studied black shale is enriched in V, Sr, Zn, and Zr and is an important source of these elements. U at Wasief exists in high concentrations due to the richness of its black shale in organic matter. These black shales were deposited in a marine environment, derived from felsic igneous as source rocks, and affected by intense chemical weathering. [ABSTRACT FROM AUTHOR]

The Jiadi and Damaidi gold deposits in southwest Guizhou Province are the largest basalt-hosted Carlin-type gold deposits recently discovered in China. This study uses the Tescan Integrated Mineral Analyzer, supported by detailed field investigations, regional geological data, and extensive sample collections, including mineralized ore, altered wall rock, and unaltered basalt samples, for ore-bearing and geochemical analyses. Comparative analysis between altered and unaltered basalt samples revealed a mineral assemblage of sericite, quartz, and pyrite. This mineral composition forms through the hydrothermal alteration of unaltered basalt, originally containing feldspar, pyroxene, and ilmenite. The wall rock primarily features sericite, quartz, and hematite. During the alteration process, major, trace, and rare earth elements notably migrate. In the Jiadi deposit, K2O, Rb, Au, and REE significantly increase, while Na2O, CaO, MgO, and MnO decrease. SiO2, Al2O3, and Fe2O3 levels remain relatively stable. In the Damaidi deposit, K2O, Rb, and Au enrich, contrasting with the depletion of Na2O, CaO, MgO, and MnO, while SiO2, Fe2O3, Al2O3, TiO2, and REE show no significant changes. In the wall rock, TiO2, Al2O3, K2O, and REE increase, while Na2O, CaO, MgO, and MnO decrease; SiO2 and Fe2O3 content remains unchanged. The mineralization process likely originated from mid- to low-temperature, reductive magmatic hydrothermal fluids rich in CO2, CH4, N2, H+, S2−, HS−, H3AsO3, and [Au(HS)2]−. These fluids migrated to tectonically weak zones in the Lianhuashan area, where Emeishan basalts are present. They reacted with Fe-bearing minerals in the basalt, such as ferro-hornblende and ilmenite, forming pyrite, arsenic-bearing pyrite, and arsenopyrite, thus enriching Au in these minerals. Additionally, K+ and H+ in the fluid reacted with plagioclase in the basalt, forming sericite and quartz. As the fluid entered the wall rock from structural weak zones, its oxidation increased, leading to the complete or partial reaction of Fe-bearing minerals in the wall rock, resulting in the formation of hematite or magnetite. This mineralization process is similar to that observed in carbonate-hosted Carlin-type gold deposits in southwest Guizhou, with the primary distinction being the iron source. In carbonate deposits, iron originates from ferridolomite within the wall rock, while in basalt-hosted deposits, it derives from ferripyroxene and ilmenite. [ABSTRACT FROM AUTHOR]

The lamprophyric rocks are uncommon volatile-rich melanocratic porphyritic rocks which contain only mafic phenocrysts. The felsic minerals are confined in the groundmass. They occur as dikes, sills and diatremes. The lamprophyric rocks are sometimes associated with diamond deposits. This review article discusses the ongoing debate in igneous petrology regarding the classification of lamprophyric rocks, specifically the Lamprophyre clan vs Lamprophyre facies problem. The background of this debate is rooted in conflicting interpretations of the classification of these rocks, with some researchers grouping them into a super-group called the “Lamprophyre clan” while others emphasize the distinction between the different types of these rocks (Lamprophyre facies). The aim of this study is to provide a comprehensive analysis of relevant literature and propose a more inclusive petrological classification system for lamprophyric rocks by considering the geological setting, petrography, texture, mineralogy, whole-rock geochemistry and isotopic analysis of the various kimberlites, orangeites, lamproites, para-lamproites, calc-alkaline, alkaline and ultramafic lamprophyres. Lastly, the diamond potential is also taken into account. The implications of this study are significant for the international geological community. It proposes the adoption by the IUGS TGIR of both the Lamprophyre clan (as updated by Kamvisis & Phani, 2022, i.e. genetically interrelated rocks) and Lamprophyre facies (as suggested by Mitchell, 1994, i.e. rocks that formed under volatile-rich conditions) concepts to achieve a more widespread consensus among igneous petrologists. Both terms can be correct but they represent different perspectives in the study of these exotic rocks.