Mineralogical Analyses Research Articles

One-part alkali-activated soil stabilization with sodium metasilicate: Mechanical-geochemical-mineralogical characterization

A shift towards environmental sustainability is an emerging trend in the modern construction industry, and soil stabilization is no exception. Environmental and economic constraints associated with traditional cement have led to a renewed research focus, particularly on the development of alkali-activated materials (AAMs), a cost-effective and environmentally sustainable stabilization method. Traditional AAM synthesis involves the activation of industrial byproducts in an alkaline solution, which poses challenges in transporting, storing, and handling large quantities of liquid alkaline activators in the field. To address these challenges and enable the large-scale application of AAM-based soil stabilization, a one-part alkali-activation method is proposed, utilizing a dry powdered alkaline activator. This study aims to evaluate the potential of dry sodium metasilicate (SM), used in conjunction with Class C fly ash, Class F fly ash, and ground granulated blast-furnace slag, to stabilize weak clayey soils with medium-to-high initial moisture content. Towards that end, five stabilizer mixes with and without SM were designed to stabilize natural soil at different initial moisture states. The engineering properties of these blends were assessed through unconfined compressive strength (UCS) testing, and a relationship between the initial water content of the soil, stabilizer dosage, and the desired UCS for the alkali-activated mixtures was developed. Furthermore, the microstructure of these blends was characterized through geochemical and mineralogical analyses, including pH measurement, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), and scanning electron microscope (SEM) imaging. This study demonstrates the feasibility of using dry SM to create one-part AAM, which holds promise for stabilizing weak soils in various transportation infrastructure systems, including roadways, airfield pavements, and railways.

Quaternary alluvial paleosols of the Atbara River, eastern Sudan: description and paleoenvironments

ABSTRACTQuaternary climatic changes in the Nile Basin and their effects on the evolution of African mammals and vegetation are poorly understood, particularly for the last 1 Ma. Pleistocene (~230 to <17 ka) alluvial sediments exposed along the middle stretches of the Atbara River in eastern Sudan are rich in fossil vertebrates and are ideal for paleoenvironmental reconstruction during this time interval. We performed petrographic, mineralogical and geochemical analyses on the middle Atbara paleosols to reconstruct the paleoclimate and paleolandscape. We describe Aridisols/Calcisols characterized by calcretes and containing gypsum and halite, and Vertisols with pedogenic slickensides and a relatively large amount of smectite. The paleosols indicate that the study area transitioned from an arid to semi‐arid climate during Marine Isotope Stage (MIS)7/6, to a more humid climate during MIS5, and then a return to more arid conditions during MIS2. The studied paleosols likely supported a range of grassland and wooded grassland savanna habitats. Our study confirms that the Atbara River Valley provided favorable living conditions for Pleistocene large mammal communities including Homo, potentially facilitating dispersals out of Africa through the Nile corridor.

Assessment of heavy metal contamination of sediments in popular tourist beaches of the Kerala State, southern India: Implications on textural and mineralogical affinities and mitigation

Beaches form one of the most contaminated sedimentary environments by a myriad variety of anthropogenic activities, including tourism and recreational activities. The concentrations of metals and their pollution levels were studied for four tropical tourist beaches in Kerala state, Southern India. Bulk geochemical and mineralogical analyses of 16 sediment samples were performed to determine the environmental status and the environmental risk level using various geochemical indices. Based on the enrichment of TiO2 and SiO2 concentrations, the samples were grouped into ilmenite-rich samples (IRS) and quartz-rich samples (QRS) respectively and the geochemical signatures are significantly different. Mineralogically, the IRS group is dominated by ilmenite, quartz, sillimanite, zircon and rutile while the QRS group consists of quartz, spinel and calcite and garnets are common in both groups of sediments. Despite the variation in the trends of pollution indices, it has been found that Kovalam beach sediments are enriched with W, Th and U where, IRS with enrichment of W, U and Th while QRS only enriched with W and Th and not U. The mineralogical affinity of W with secondary tungsten-bearing minerals has been documented by the XRD analysis and these metals are mainly controlled by the geogenic sourced minerals. However, in terms of ecological risk, Pb, As and Cu have a considerable to moderate risk in both groups of sediments. Overall, both group of sediments shows a moderate risk. Based on the biological effect assessment the elements of concern are Pb and Zn in IRS and possible effect by the Cr, Cu and As in IRS and only by Cu in QRS. Though the prevalence of geogenic and anthropogenic processes and influences of metal enrichments are documented by the study, their relative influences, mobility and bioavailability need to be systematically studied.

Incomplete sulfide oxidation under sub-oxic conditions: Rates and aqueous sulfur speciation

The oxidative dissolution of sulfide minerals consumes oxygen and can generate redox gradients in mine wastes that affect the mobility of redox-sensitive solutes. However, the controls of oxygen depletion on sulfide reactivity and sulfur mobilization remain poorly constrained, complicating the long-term assessment of drainage quality dynamics. We investigated pyrite and Fe-rich sphalerite weathering using aqueous S speciation and quantitative mineralogical analyses under controlled, ambient versus sub-oxic, conditions at 6 < pH < 9. Titration assays revealed that oxidation rates for pyrite (up to 10−10 mol m−2 s−1) were higher than for sphalerite (up to 10−11 mol m−2 s−1) and, for both minerals, decreased by two orders-of-magnitude under sub-oxic (<50 ppm O2) conditions. Precipitation of secondary S-bearing minerals was restricted to elemental S, with no sulfate- or thiosulfate-salts detectable >0.01 wt%. Sulfate was the dominant aqueous S species produced in all experiments, but significant amounts of thiosulfate, tetrathionate, and sulfite were also found. These dissolved intermediate S species were abundant under both sub-oxic and oxic conditions, and broadly in line with known sulfide oxidation mechanisms, even though the weathering of pyrite produced several factors less incompletely oxidized S than that of sphalerite, under otherwise comparable conditions. This work shows that a range of intermediate S species may be produced even in low-reactivity conditions and may help optimize the management of such mine waste materials.

New insights into sedimentological and geochemical conditions of marine Pleistocene sediments in the Tangier region (Morocco): First implications for paleoenvironmental and paleoclimatic reconstructions

The Pleistocene period is characterized by important periodic climatic variations, marked by alternating arid and humid phases. This work aims to reconstruct the prevailing Pleistocene paleoenvironment and paleoclimate in the Tangier area based on a multidisciplinary study of a marine formation dating from 125 ka. Field investigations and sedimentological, micropaleontological, mineralogical, and geochemical analyses were carried out on samples from the Pleistocene Achakkar formation. The granulometric study, combined with a morphoscopic, exoscopic analysis of quartz grains and evidence for diverse benthic foraminifera, suggests a low-energy marine depositional environment, most likely foreshore to shoreface. Moreover, analysis of clay minerals and major elements suggests mineralogical evolution, indicating an arid climate. The sedimentary successions of the Pleistocene Achakkar littoral are progressively more and more coarse; emplacement was subject to several interactive factors, such as climatic and eustatic responsible for reconstituting the geological history of the Tangier Peninsula.

Valorization of waste concrete powder (WCP) through silica fume incorporation to enhance the reactivity and hydration characteristics

The aim of this study is to utilize the bulk proportion of waste concrete powder (WCP) as cementitious material in the fabrication of binder, and to investigate the impact of silica fume on the reactivity and hydration characteristics of thermomechanical activated WCP. A 29 Silicon Nuclear Magnetic Resonance (NMR) analysis confirmed the presence of reactive silica in the activated WCP. Various blends were prepared with a 50%–80% substitution of type CEM I 52.5 N cement. The combination of activated WCP and silica fume improved the reactivity of the binder blend and achieved a compressive strength comparable to cement. Mineralogical analysis revealed the development of secondary C–S–H gels in mixtures containing silica fumes and activated WCP, which is the result of a secondary hydration reaction between portlandite and reactive silica. The use of life cycle analysis software for the replacement of 60 wt % of cement with activated WCP was found to reduce carbon dioxide emissions by 80.42% due to the use of less cement, an environmentally friendly WCP activation process, even when considering the addition of 10% silica fume. This innovative approach not only enhances WCP reactivity and mechanical strength but also significantly contributes to the reduction of carbon emissions. By elucidating the formation mechanisms and environmental benefits, this study paves the way for a more eco-conscious and efficient construction methodology, promoting the vision of a greener future.

Micromechanical and mineralogy analyses on extremely ductile engineered geopolymer composites with different activator pretreatments

In this study, the effects of activator pretreatments on properties of fly ash-based extremely ductile engineered geopolymer composites (ED-EGCs) were investigated. Two ED-EGC mixtures were designed using the same binder system and polyethylene fiber reinforcement, but different pretreated activators. A sequence of experiments including mechanical testing, micromechanical analysis, and chemical characterization was performed. The test results indicate that ED-EGCs were lightweight with density values lower than 1.7 g/cm3, had moderate compressive strengths over 21 MPa, and exhibited extremely ductile behavior with tensile strain capacities over 11 %. Overall, the warming pretreatment was beneficial to improve strengths but less effective to enhance tensile ductility of ED-EGCs. In contrast, the ED-EGC mixture adopting the cooling pretreatment showed tensile strain capacity up to 18.6 %, which has been unprecedented in the literature. The micromechanical analysis explained the extremely ductile behavior of ED-EGCs. SEM observation also confirmed that the fibers were robustly embedded into the geopolymer matrix. Through chemical analysis using EDS, it was found that N-A-S-H gel was the dominant geopolymeric product of ED-EGCs.

Anthropogenic disturbances influence mineral and elemental constituents of freshwater lake sediments.

Lake sediments can provide valuable insights into anthropogenic disturbances such as intensive aquaculture and land use changes. These disturbances often manifest as elevated levels of nutrients and elements within the sediments. This paper uses several analytical techniques, i.e., FTIR (Fourier-transform infrared spectroscopy), XRD (X-ray diffraction), EDS (energy-dispersive X-ray spectroscopy), and SEM (scanning electron microscopy), to examine the elemental constituents of lake sediments, along with their relative mineral abundances and surface morphology. The selected freshwater lakes are from the Central Gangetic Plain. The analysis provides a "fingerprint" of geogenic and biogenic mineral constituents of the sediments. Physicochemical, mineralogical, and elemental analysis shows that intensive aquaculture activities in lake alter the sediment chemistry as evidenced by the increase in pH, organic carbon, organic matter, and total phosphorus which is not observed in the lake where aquaculture is prohibited. Freshwater lake sediment is characterized by a high content of biogenic silica and carbonate minerals. The variations in sediment nutrients and mineral fluxes of the selected lakes are mainly attributed to diverse anthropogenic pressures, differences in lake productivity, and the overall ecological condition of the lakes. In the selected three lakes, major variation was reported in the autochthonous sediments in comparison to the allochthonous sediments. The study concludes that catchment and biotic deposit variations in the lakes cannot be evened out by in-lake mixing mechanisms due to variations in the terrigenous and pelagic deposits of the lake. The results highlight the importance of studying annual fluctuations and spatial variations in geogenic and biogenic mineral particle fluxes in lakes. Such investigations provide valuable insights into the annual dynamics of minerals within lakes, contributing to a more comprehensive understanding of their behavior and distribution.

Influence of Adding Jordanian Scoria on the Properties of Clay-based Geopolymer

This work aims to investigate the influence of adding Jordanian scoria on the characteristics of clay-based geopolymer. The clay deposit and scoria were gotten from north-east Jordan. The chemical, mineralogical, and microstructural properties of the used materials were examined. Scoria was added to clay-based geopolymer mixtures in different ratios: 0%, 10%, 20%, 30%, 40%, and 50%. Comprehensive experimental tests were conducted to assess the effect of adding scoria on the properties of the produced geopolymer. The results revealed decreased compressive strength and dry density, whereas porosity, water absorption, cation exchange capacity, and specific surface area increased as the ratio of scoria increased. The mineralogical and microstructural analysis of the geopolymers after adding scoria indicates the formation of mineral phases, namely hydroxy-sodalite and hydroxy-cancrinite in addition to the gel phase.

First results of electron microscopic study of sandstones of the Salikhovo Formation Vendian (The East-European platform)

For the first time, for the platform Vendian deposits, along with lithological and petrographic methods of studying rocks in sections and quantitative mineralogical analysis of the heavy fraction of concentrate, a study was carried out by scanning electron microscopy in thin sections. The use of scanning electron microscopy made it possible to significantly refine the mineral composition of rock-forming, secondary and accessory minerals. For the first time, it was indicated that the sandstones have their own minerals of rare earth elements (monazite and xenotime) and thorium (torite), and some geochemical features of REE concentrator minerals (apatite and zircon) have been identified. Additional information on the mineral and geochemical composition of the rocks of the Salikhov Formation can be used in the future to reconstruct the composition of the feeding provinces and the conditions for the formation of sedimentary paleobasins.

Archaeometric Analyses of dolia of the Final Bronze Age/Early Iron Age Found at Gagliato (CZ)–Calabria–Southern Italy

In the hinterland of Soverato (in the Catanzaro province CZ) in Calabria, Italy, in the territory of Gagliato, on a series of terraced plains, the remains of an extensive settlement have been identified with archaeological evidence that includes the various phases of the protohistoric period and the Greek age. In the settlement, numerous protohistoric ceramic finds consisting in fragments of vascular shapes of various sizes and large dolia were recovered. This paper presents the preliminary results of the mineralogical, petrographic and paleontological analyses performed on dolia samples selected on the basis of the typology and the characteristics of the ceramic impasto. The dolia analyses were obtained through various analytical techniques. Petrographic and micropaleontological studies were performed using polarized optical microscopy (POM). The mineralogical analyses were carried out using X-ray diffractometry (XRD), both on selected ceramics and on the clayey and sandy sediments sampled for comparison around the settlement area. Furthermore, micromorphological observations have been performed, using scanning electron microscopy (SEM), on selected foraminiferal tests picked up from the clay sediments collected in the study area. Data highlight the remarkable compatibility between the mineralogical composition of the dolia and the sampled sediments, and they confirm that the raw materials for ceramic production may have occurred in an area not far from the settlement, as assumed by archaeologists.

The Petrology and Geochemistry of REE-Enriched, Alkaline Volcanic Rocks of Ambitle Island, Feni Island Group, Papua New Guinea

Ambitle in the Feni Island Group is located within the NW trending Tabar–Lihir–Tanga–Feni (TLTF) volcanic island chain, Melanesian Arc, northeastern Papua New Guinea. The TLTF chain is renowned for its alkaline magmatism, geothermal activity, copper–gold mineralization, and world-class gold mining. Although its geochemical patterns indicate island arc signatures (i.e., high LILE and depleted HFSE), TLTF volcanism is not directly related to the older Melanesian Arc subduction system. However, it may have been influenced by source mantle metasomatism linked to the older subduction. The purpose of this study is to (1) present and interpret the petrographic, mineralogical, and geochemical data from Feni within the context of the tectonic evolution of the TLTF and (2) propose a geodynamic, petrogenetic model for the Feni volcanic rocks. The key methodologies used in this study are field mapping and sampling, petrographic analysis using the optical microscope, whole-rock geochemical analysis via XRF and ICP MS, and mineralogical analysis using an electron microprobe. The main rock types sampled in this study include feldspathoid-bearing basalt, trachybasalt, phonotephrite, trachyandesite, and trachydacite. Minerals identified include forsteritic olivine, diopside, augite, labradorite, andesine, anorthitic plagioclase, nepheline, and leucite in the primitive mafic suites, whereas the more evolved intermediate and felsic hypabyssal suites contain amphibole, albite, orthoclase, biotite, and either rare quartz or feldspathoids. Amphibole composition is primarily magnesiohastingsite with minor pargasite formed under polybaric conditions. Accessory minerals include apatite, titanite, and Ti-magnetite. We propose that limestone assimilation followed by fractional crystallization are plausible dominant processes in the geochemical evolution of the Ambitle volcanics. Clinopyroxene fractionation is dominant in the mafic volcanics whereas hornblende fractionation is a major petrologic process within the intermediate suites proven by the enrichment of LREE and depletions in MREE and HREE. Feni magmas are also highly enriched in REEs relative to neighboring arcs. This study is globally significant as alkaline magmas are important sources of Cu, Au, and REE as critical elements for green energy and modern technology.

Geochemistry and mineralogy of muds and thermal waters from mud volcanoes in the NW Caribbean Coast of Colombia and their potential for pelotherapy

Mud volcanoes in northwestern Colombia are used by local people as inexpensive recreation and wellness centres, especially for pelotherapy. However, the potential therapeutic value of the muds and thermal waters released by these volcanoes has not been fully investigated. The main objective of this research is to determine the potential therapeutic value of the solid and liquid fractions of the muds sampled from nine mud volcanoes located along the northwestern Caribbean coast of Colombia through geochemical and mineralogical analysis. An evaluation of the granulometric characteristics was also carried out. The presence of a hypertonic saline environment created by secondary volcanic processes is indicated by the thermal fluid fraction. The mineral composition of the muds is dominated by quartz, phyllosilicates (kaolinite, smectite, illite and chlorite), feldspar, carbonates (dolomite, calcite) and a significant amorphous component. Based on the composition of the clay fraction, three distinct groups can be distinguished: (i) kaolinite-rich, (ii) illite-rich, and (iii) chlorite-rich. These muds are suitable for use by the local population due to the extremely low levels of contaminants harmful to human health, such as potentially toxic elements, nitrates, nitrites or fluorides. The results of this study suggest that the muds and thermal waters released by these mud volcanoes have potential therapeutic value. Further research is needed to confirm these findings and to investigate the specific mechanisms by which these muds and waters can be used in medical practice.

Chemical and Mineralogical Characterisation of Clayey Sands from the Ivorian Serimentaru Basin in Road Construction

In Ivory Coast, particularly in the south, most paved and unpaved roads are made of clayey sand, given its availability. The early degradation of roads is related to a strong sensitivity of certain materials to the environment (climate, geology, and degrees of alteration) and a poor knowledge of the geotechnical properties could slow down their use in road construction. Within this framework, this paper focuses on determining the chemico-mineralogical nature of the clayey sands of the localities of Bingerville and Samo, in the South-East of Ivory Coast. Tests were conducted based on the chemical and mineralogical analyses. Chemical elements were determined by atomic absorption spectrometry, colorimetry, complexometry, and gravimetry. Organic matter was determined using the Rock-Eval 6 pyrolysis method, while the mineralogical composition was determined using a Bruker D8 ADVANCE diffractometer. The chemico-mineralogical analyses reveal that the clayey sands from Bingerville and Samo are more enriched in silica oxide (SiO2) but less enriched in iron oxide (Fe2O3). All the soils studied have a degree of laterization greater than 2, which suggests that they are non-lateritic soils. The low Total Organic Carbon (TOC) values lies between 0.1 and 0.15% by weight, which reflects the extremely low amount of organic matter in these soils. This indicates the possibility of treating these soils with hydraulic binders. The mineralogy of the studied soils denotes that they are composed of kaolinite and illite.

Thermal influence of sills on the chemostratigraphy and mineralogy of carbonate rocks from the Irati formation, Paraná basin

Carbonate rocks and shales are prominent lithologies in atypical petroleum systems. In these settings, the thermal effects of sills play a crucial role leading to mineralogical and geochemical alteration in the host rocks and in the maturation process of the associated organic matter. While extensive research has been conducted on shales within atypical systems, the understanding of the petrophysical and geochemical properties of carbonate rocks remains uncertain in numerous basins. In this study, we selected the Irati Formation (Paraná Basin) to investigate the thermal effects caused by diabase sills on the chemostratigraphic and lithologic features of carbonate rocks. We conducted mineralogical analyses, examined oxygen and carbon stable isotopes, and analyzed inorganic geochemical data from two distinct sections of the formation: one with diabase sills intruding the sequence and the other without identified intrusions in the area. Widespread recrystallization of minerals is observed throughout the studied rock wall, resulting in the formation of marbles and calc-silicate rocks, where dolomite is mainly replaced by calcite. The carbonate bank, located 5–7 m below the sill, is marked by brucite and chrysotile, while the rocks up to 1 m below and above the intrusion show the presence of tremolite, diopside, and antigorite. Substantial variations in elemental data are observed, including a significant increase in SiO2 and K2O below the sill, as well as elevated MgO levels within the carbonate bank. Additionally, stable isotopic signatures of oxygen and carbon display a negative shift influenced by decarbonation and intense fluid flow controlling the reactions. The contact aureole resulting from the intrusion is identified at least 7 m above and below the sill based on mineralogical and inorganic geochemical data.

Meteoric diagenesis influenced by East Asian Summer Monsoon: A case study from the Pleistocene carbonate succession, Xisha Islands, South China Sea

The East Asian Monsoon (EAM) has significantly influenced various depositional and diagenetic processes in carbonate sediments in much of East and South Asia during the Cenozoic. The relationship between the EAM and marine carbonate platforms, which are widely developed in this region, however, remains largely unknown. Based on petrographic, mineralogical, and geochemical analyses of the carbonate succession (∼237 m thick) on the Xisha Islands, South China Sea, meteoric diagenesis and its relationship with the East Asian Summer Monsoon (EASM) during the Pleistocene were studied. Various petrographic features, stable isotopes (δ13C, δ18O), and trace elements (Sr, Fe, Mn, Rare Earth Elements and Y) indicate that this succession was extensively altered by meteoric diagenesis, producing four exposed surfaces embedded in the shallow coral reef sediments. Given this data, we suggest that the meteoric diagenesis that affected this succession occurred during periods of low sea-level, and was potentially related to the relative intensity of the EASM. During strong EASM periods, particularly during the Mid-Pleistocene Transition ∼0.9 Ma, meteoric diagenesis was intense, as suggested by the complete alteration of unstable minerals, extreme dissolution, the presence of reddish-brown iron oxides, and a large negative excursion of δ13C (−6.2‰). The influence of the EASM on meteoric diagenesis of Pleistocene carbonate platforms can be identified throughout the South China Sea. This study sheds light on the relationship between meteoric diagenesis and paleo-climate conditions in carbonate platform regions that are influenced by monsoons.

Influence of the material composition of the original ore on the quality of the iron ore concentrate.

In recent years, improvement of blast-furnace process efficiency is largely associated with an increase in the iron content in iron ore concentrates – the feedstock for agglomeration. The study of the material composition of ores, their features makes it possible to adjust the scheme of preparation of raw materials and determine the optimal content of iron in the concentrate for further processing. When studying the material composition, it was found that the sample of iron ore is represented by ferruginous quartzites of the silicate-magnetite type in combination with magnetite. In the original ore sample, magnetite dominates among ore minerals, and quartz and amphiboles dominate among rock-forming minerals. The coarseness and shape of the isolation of magnetite in all varieties of rocks are generally favorable for enrichment; the mineral is characterized by clear rectilinear and slightly sinuous contours, which contributes to its selective isolation. It should be noted that the magnetite content remains constant as the coarseness of the sample material decreases. Automated mineralogical analysis established that 87.36% of iron is associated with magnetite (with fluctuations in size classes from 86.23 to 91.37%); the rest of the iron is associated with rock-forming minerals. The theoretical content of magnetite in iron ore concentrate, achievable by enriching the original ore of the studied sample, according to automated mineralogical analysis, will be 95.83%, which, in turn, will provide the maximum possible iron content in magnetite concentrate of 68.57%. The existing technology of mining and enrich-ment using 4 types of ores from the Stoilenskoye deposit, with a planned increase in iron to 70%, will result to fluctua-tions of this component in the concentrate from 68.0 to 70.0%.

Impact-related chemical modifications of the Chang’E-5 lunar regolith

Impact events on the Moon have been recognized as modifying the composition of surface materials through processes such as shock metamorphism and mixing with exotic components. Previous studies have indicated that the regolith sampled by the Chinese Chang’E-5 mission was primarily evolved from local mare basalts, likely originating from a single episode of effusive volcanism. The relatively simple and monotonic protolith of the Chang’E-5 regolith presents a unique opportunity to investigate the chemical modifications induced by impact events. In this study, we conducted detailed petrographic and mineralogical analyses on a diverse set of lunar regolith samples, including thirty-three small impact glass particles (39–227 μm), one large agglutinate (∼1.6 mm), and sixteen basaltic clasts (0.1–1.6 mm). Numerical modeling was also conducted to quantitatively assess the melting behavior of basaltic clasts under different impact conditions. Our primary objective was to evaluate the chemical variations of impact glass in relation to lithic clasts. While the majority of homogeneous impact glass spherules and larger basaltic clasts (≥1 mm) exhibit similar bulk compositions (e.g., Al2O3, CaO and FeO) to the local regolith, we recognize additional effects of impact processes, including impact comminution, impact melting and crystallization, differential volatilization, and potentially selective melting. These processes have modified the texture and geochemistry of lunar regolith components. The chemical signatures of small clasts in the Chang’E-5 regolith indicate that the fine size fractions (e.g., those with diameters of ≤ 300 μm) are predominantly composed of lithic and monomineralic fragments with a substantial proportion being dominated by mesostasis. Melting of these sub-millimeter fractions may lead to the formation of impact glass with chemical compositions deviating from the average local regolith. These results have implications for understanding the compositional evolution of the Chang’E-5 regolith. Notably, our study suggests that impact glasses spherules with different major (e.g., TiO2, MgO) and minor (e.g., REEs, Zr, Th and U) element compositions could be derived from the same protolith of local mare basalts, instead of being exclusively attributed to exotic impact ejecta. In this case, small-scale local impacts may have played a crucial role in the impact history of the Chang'E-5 landing site.

The Impact of Restricting Air Intake in Self-Aspirated Flotation Cells at Los Pelambres Concentrator

This article describes the impact of restricting the air intake in industrial 250 m3 WEMCO flotation cells at Los Pelambres concentrator. The influence of air restriction on the hydrodynamic and metallurgical performance of this type of machine was evaluated. The experiments were conducted in single flotation cells and entire rougher banks. In all cases, the gas holdup was measured to estimate the effectiveness of the obstruction system to decrease the air concentration. In single cells, axial profiles for solid percentage and particle size were evaluated. In addition, mass balances were conducted to assess the copper recoveries and concentrate features. In individual cells, air restriction led to a decrease in the gas holdup. However, this slight change was enough to obtain a more stable froth zone and a better solid suspension. The latter was observed as: (i) a higher P80 below the pulp–froth interface, (ii) a less diluted pulp at this level, (iii) a slightly higher Cu recovery, and (iv) a coarser concentrate product. A mineralogical analysis of the concentrate sample also showed the presence of coarser liberated Cu-sulfide particles. The results in single cells suggested an improvement in the recovery of coarse particles via more intense solid suspension. The air intake was also restricted in three rougher banks to assess the impact of air obstruction on the overall performance of the respective circuit. Eleven out of fourteen cells were operated with air restriction, which led to a significant improvement in recovery of 0.9%–1.6% (absolute), at a 95% confidence level. Size-by-size mass balances were also conducted for the rougher circuits, which proved that the recovery improvements were justified by the simultaneous increase in the recovery of coarse and fine particles. Thus, a restriction in the air intake showed that a decrease in the gas holdup (and in the bubble surface area flux) was compensated by better solid suspension and a higher collision efficiency in the draft tube. The former promoted the recovery of coarse particles in the quiescent zone, whereas the latter improved the interaction between bubbles and fine particles. Further developments are being made to implement a regulatory control strategy for the air intake in self-aspirated flotation cells and to use this approach for optimizing industrial flotation banks.

Integrated methodology to link geochemical and geophysical-lab data in a geophysical investigation of a slag heap for resource quantification

The increasing need to find alternative stocks of critical raw materials drives to revisit the residues generated during the former production of mineral and metallic raw materials. Geophysical methods contribute to the sustainable characterization of metallurgical residues inferring on their composition, zonation and volume(s) estimation. Nevertheless, more quantitative approaches are needed to link geochemical or mineralogical analyses with the geophysical data. In this contribution, we describe a methodology that integrates geochemical and geophysical laboratory measurements to interpret geophysical field data solving a classification problem. The final aim is to estimate volume(s) of different types of materials to assess the potential resource recovery. We illustrate this methodology with a slag heap composed of residues from a former iron and steel factory. First, we carried out a 3D field acquisition using electrical resistivity tomography (ERT) and induced polarization (IP), based on which, a sampling survey was designed. We conducted laboratory measurements of ERT, IP, spectral induced polarization (SIP), and X-ray fluorescence analysis, based on which, 4 groups of different chemical composition were identified. Then we carried out a 3D probabilistic classification of the field data, based on 2D kernel density estimators (for each group) fitted to the inverted data collocated with the samples. The estimated volumes based on the classification model were: 4.17 × 103 m3 ± 12 %, 1.888 × 105 m3 ± 12 %, 59.4 × 103 m3 ± 19 %, and 2.30 × 104 m3 ± 21% for the groups ordered with an increasing metallic content. The uncertainty ranges were derived from comparing the volumes with and without considering the probabilities associated to the classification. We found that a representative sampling and the definition of the KDE bandwidths are defining elements in the classification and ultimately the estimation of volumes. This methodology is suitable to quantitatively interpret geophysical data in terms of the geochemical composition of the materials, integrating uncertainties both in the classification and the estimation of volumes. Furthermore, several crucial elements in the investigation of metallurgical residues could be applied in a real case study, e.g., geophysical field acquisition, sampling and lab measurements.