Secondary Minerals Research Articles

Modern River-Sand Geochemical Mapping in the Manufahi Municipality and Its Surroundings, Timor-Leste: Implications for Provenance

A geochemical mapping of regional modern river-sand is performed to clarify geological information in the study area of Timor-Leste. Several areas of Timor-Leste including the study area in particular have limited geological information due to limited accessibility and dense vegetation coverage, and deformed, weathered, and erosion-covered materials. A total of 53 modern river sand samples were collected and analyzed. Ten major elements were determined by using wavelength-dispersive X-ray fluorescence. Areas characterized by clastic sedimentary rocks are recognized clearly by elevated concentrations of SiO2, Al2O3, and K2O. Meanwhile, areas covered by carbonate sedimentary rocks are detected by significant concentrations of CaO and MnO. The occurrences of the altered clastic and carbonate sedimentary rocks of the Wailuli and Aitutu Formations due to metamorphic, silicification and other alteration processes were responsible for the elevated concentrations and positive correlation between SiO2, CaO, K2O, and MnO, and CaO, TiO2, and MnO in the midstream and near the downstream areas of the Clerec and Sahe River catchments. The positive correlation observed between TiO2, CaO and MnO may be ascribed to the presence of carbonate components associated with secondary Ti-bearing minerals, which are potentially formed through hydrothermal alteration processes.

Thermal springs associated with the Melilla-Fès-Smaala-Oulmès fault (Morocco): The role of fluid geochemistry in identifying a major active geodynamic structure

The thermal springs form a hydrothermal system implanted on the active tectonic structure of the Melilla - Fès - Smaala - Oulmès fault (MFSO). This fault forms a multiple play tectonic corridor generally oriented NE-SW parallel to the Nekor fault. It crosses two structural domains, the Meseta, to the South, and the Rif, to the North, forming a highly complex deep shear zone. The thermal waters from these springs have chloride-sodium facies and sodium-calcium bicarbonate facies with emergence temperatures between 24.4 and 53.6 °C. Along this fault, the pH of these waters varies centrifugally, with acidic values in the South and North and neutral values in the intermediate sector. Important information about the origin of thermal waters and the characteristics of the reservoirs is provided by the chemical compositions (chemical elements, isotopes, and gases) of these waters involving rock-water-gas interaction during their circulation in depth and flow to the surface, through different types of reservoirs intersected by the fracture networks associated to the MFSO. These reservoirs correspond to the crystalline basement and its Triassic evaporitic clay, Jurassic carbonate, Cretaceous marl, and Miocene saliferous cover, whose temperatures have been estimated between 100 and 200 °C. The stable isotopic compositions (−8.39 to −5.2‰ for δ18O and −51.2 to 30.1‰ for δ2H) indicate a meteoric origin of these waters, whose recharge areas are located in the Rif and Atlas reliefs. The gas phase present in the waters shows δ13Cco2 (−19.3 ‰ to −4,25 ‰) and 3He/4He (0.203–3.864 Ra) with mantellic signature, implying that the fault is deeply rooted. The mantellic helium content decreases progressively in these waters from SE to NE, following the direction of the MFSO fault, from the emergencies in the Palaeozoic basement to the springs in the secondary and Tertiary formations of the Prerif and Mesorif. This decrease results probably from the mixing with gases derived from the thick secondary and Tertiary sedimentary cover. These waters would also collect these gases during their interactions with these sedimentary formations. Towards the NE, these waters, which rise within the formations of the Mediterranean arc, are also influenced by gases derived from the sediments of volcanic arcs.The MFSO fault, which is permeable due to its fracture network, favours the diffusion of heat and the upwelling of mantle gases, which are collected by the fluids that will interact with the rocks during their circulation at depth and flow to the surface. Its hydraulic character, highlighted in the North by seismic tomographic sections, confirms the presence of fluids at a depth of 5 km. This hydraulic character is continuous towards the South, implying the intimate association of the springs studied with this active tectonic structure. The pressure generated by these fluids and the precipitation of secondary clay minerals will weaken this fault, giving it an aseismic character.

Seasonal variations in lithium and magnesium isotopic composition of the Nujiang River water at the Daojieba Hydrological Station: Implications for chemical weathering

The response of chemical weathering to climate could be examined in a way by investigating seasonal changes in river geochemistry. Here, we determined the major elements, δ13C of DIC, 87Sr/86Sr, δ7Li, and δ26Mg of monthly time-series water samples at the Daojieba Hydrological Station in lower reach of the Nujiang River over a hydrological year. During high-flow seasons, the dissolved 87Sr/86Sr, δ7Li, and δ26Mg exhibit comparatively high values. 87Sr/86Sr ratio, together with δ13C of DIC, Si/Ca ratio, and pH value of river water, indicate an enhanced silicate weathering contribution to river dissolved load, and river δ7Li is impacted by secondary mineral formation-related fractionation during these periods. Similar to the 87Sr/86Sr ratio, δ26Mg of river water is indicative of a dominant source control. The positive relationship between Mg/Na ratio and δ26Mg value suggests that the prior weathering of Mg-rich silicate minerals could be important for elevated δ26Mg and Mg/Na molar ratio during high-flow seasons, while the Mg isotope fractionation signal can be seen when runoff increases dramatically. During low-flow seasons, river 87Sr/86Sr and δ26Mg values evolve to a carbonate weathering signal, whereas river δ7Li reflects a more congruent silicate weathering, and these changes point to the obvious influence of geothermal water in these periods. The covariations of δ7Li, δ26Mg, and discharge are observed. Changes in runoff can significantly impact the isotopic composition of Li and Mg by changing the hydrological flow path, in which dominant reactions of mineral dissolution and secondary mineral formation vary. This study highlights the hydrological control on Li and Mg isotopic compositions of the Nujiang River water, which could be considered the dominant control of monsoon climate on weathering processes in high-relief river basins at a short-term scale.

Mineralogy and geochemistry of altered Emeishan basaltic volcaniclastics with respect to their critical element mineralization

Research on the mineralogical and geochemical characteristics of altered end-Guadalupian basaltic volcanoclastic rocks can increase the understanding of the alteration history of the overlying stratabound Nb(Ta)-Zr(Hf)-REY-Ga mineralization in the Late Permian coal-bearing sequences. In this paper, based on petrographic observations in addition to XRD, XRF, and ICP-MS analyses, we present and discuss in detail the relationships between primary and secondary minerals and outline the distribution of major and trace element chemistry in the middle/Late Permian basaltic volcaniclastics from the ELIP's zone, western Guizhou, southwest China. The primary clastic suite consists of plagioclase-group minerals, clinopyroxenes, feldspathoids, spinels, and basaltic glasses. Fragments of mafic and, less commonly, felsic and alkaline volcanic rocks are minor components of the studied samples. The alteration products are represented by various chlorite-group minerals (including abundant chamosite), quartz, calcite, albite, analcime, barite, and pyrite, along with relatively minor amounts of titanite, sanidine, magnetite, rutile, and copiapite. The mineralogical and geochemical characteristics of the studied volcaniclastics provide strong evidence correlating them with the high-Ti basalt group, widely distributed within the inner Emeishan large igneous province (ELIP) and coeval rift zone of the middle and outer ELIP. After deposition, the volcaniclastics reacted with complex solutions including heated meteoric waters and were periodically infiltrated by seawater and ascending hydrothermal fluids. As a result, the primary volcanic rocks partly lost alkalis, titanium, silica, and most of the trace elements. These elements, especially the incompatible elements, were probably enriched in the overlying tuffaceous and coal-bearing sequences in the middle and outer ELIP.

Wpływ właściwości dielektrycznych na ogrzewanie rud siarczkowych w polu elektromagnetycznym

Microwave heating is a form of high-frequency electromagnetic radiation. The heating of primary and secondary mineral raw materials in the microwave field depends primarily on their dielectric and thermal properties. The condition is the absorption of microwave radiation. Dielectric heating of materials occurs immediately after placing them in an electric high-frequency field. Knowledge of the dielectric characteristics of mineral raw materials is an important assumption for the use of electromagnetic radiation at the intensification of technological treatment methods. Most mined minerals consist of several mineral components that have different dielectric properties. Most sulphides are well heated in a microwave field. Conversely, tailings components of ores, such as quartz, are transmission materials. The study of dielectric properties involves measurements of the complex relative permittivity ε*, which consists of a real and an imaginary part. The imaginary part of permittivity “loss factor” represents the measure of dielectric losses in the material. Microwave heating of sulphide ores and concentrates such are chalcopyrite, tetrahedrite, galena depends on their chemical composition and content of impurities. The article describes the influence of dielectric properties on heating of chalcopyrite in microwave field. SEM analyses of studied samples are presented.

Effect of biochar-derived DOM on contrasting redistribution of chromate during Schwertmannite dissolution and recrystallization

Biochar-derived dissolved organic matter (BDOM), is extensively involved in the recrystallization of minerals and the speciation alteration of associated toxic metals. This study investigates how BDOM extracted from tobacco petiole (TP) or tobacco stalk (TS) biochar influences the speciation repartitioning of Cr(VI) in environments impacted by acid mine drainage (AMD), focusing on interactions with secondary minerals during Schwertmannite (Sch) dissolution and recrystallization. TP-BDOM, rich in lignin-like substances, slowed down the Cr-Sch dissolution and Cr release under acidic conditions compared to TS-BDOM. TP-BDOM's higher O/C component exerts a delayed impact on Cr-Sch stability and Cr(VI) reduction. In-situ ATR-FTIR and 2D-COS analysis showed that carboxylic and aromatic N-OH groups in BDOM could interact with Cr-Sch surfaces, affecting sulfate and Cr(VI) release. It was also observed that slight recrystallization occurred from Cr-Sch to goethite, along with increased Cr incorporation into secondary minerals within TS-BDOM. This enhances our understanding of BDOM's role in Cr(VI) speciation changes in AMD-contaminated sites.

Legacy copper/nickel mine tailings potentially harbor novel iron/sulfur cycling microorganisms within highly variable communities.

The oxidation of sulfide-bearing mine tailings catalyzed by acidophilic iron and sulfur-oxidizing bacteria releases toxic metals and other contaminants into soil and groundwater as acid mine drainage. Understanding the environmental variables that control the community structure and metabolic activity of microbes indigenous to tailings (especially the abiotic stressors of low pH and high dissolved metal content) is crucial to developing sustainable bioremediation strategies. We determined the microbial community composition along two continuous vertical gradients of Cu/Ni mine tailings at each of two tailings impoundments near Sudbury, Ontario. 16S rRNA amplicon data showed high variability in community diversity and composition between locations, as well as at different depths within each location. A temporal comparison for one tailings location showed low fluctuation in microbial communities across 2 years. Differences in community composition correlated most strongly with pore-water pH, Eh, alkalinity, salinity, and the concentration of several dissolved metals (including iron, but not copper or nickel). The relative abundances of individual genera differed in their degrees of correlation with geochemical factors. Several abundant lineages present at these locations have not previously been associated with mine tailings environments, including novel species predicted to be involved in iron and sulfur cycling.IMPORTANCEMine tailings represent a significant threat to North American freshwater, with legacy tailings areas generating acid mine drainage (AMD) that contaminates rivers, lakes, and aquifers. Microbial activity accelerates AMD formation through oxidative metabolic processes but may also ameliorate acidic tailings by promoting secondary mineral precipitation and immobilizing dissolved metals. Tailings exhibit high geochemical variation within and between mine sites and may harbor many novel extremophiles adapted to high concentrations of toxic metals. Characterizing the unique microbiomes associated with tailing environments is key to identifying consortia that may be used as the foundation for innovative mine-waste bioremediation strategies. We provide an in-depth analysis of microbial diversity at four copper/nickel mine tailings impoundments, describe how communities (and individual lineages) differ based on geochemical gradients, predict organisms involved in AMD transformations, and identify taxonomically novel groups present that have not previously been observed in mine tailings.

Modeling the geochemical evolution of mine waters during mixing

This study focuses on assessing the hydrogeochemical processes influencing the mobility of dissolved metal and metalloid species during mine effluent mixing. Field samples were collected to characterize effluents at an active gold mine located in the Abitibi Greenstone belt in western Québec, Canada. Controlled laboratory mixing experiments were further performed with real effluents. In situ physicochemical parameters, concentrations of major dissolved ions and trace elements were analyzed. Mineralogical analyses were also performed on precipitates from the laboratory mixtures. The data were used for statistical analyses and for modeling the geochemical evolution of effluents using PHREEQC with the wateq4f.dat database (with modifications). The results suggest that the formation of secondary minerals such as schwertmannite, Fe(OH)3, and jarosite could significantly affect the concentrations of trace elements in effluents. The precipitation of secondary minerals immobilized trace elements through coprecipitation and sorption processes. The main limitations of the modeling approach used here include the evaluation of the ion balance for low pH samples with high Fe and Al concentrations and the omission of biological processes. The approach provides insights into the geochemical evolution of mine effluents and could be adapted to several mining sites as a tool for improving water management.

A Pore-Scale Phase Field Model for CO2-Fluid-Basalt Interactions.

Basalt is a suitable target area for CO2 storage. Clarifying the evolution of the pore structure during CO2-fluid-basalt interactions is a crucial element in the preparation of a CO2 geologic storage operation. In this study, a pore-scale phase field model is proposed to simulate the CO2-fluid-basalt interaction process of Snake River Plain basalt. Our model is suitable for complex multimineral natural rocks, and the initial mineral distribution before the reaction can be completely based on a real 3D rock image without the need to simplify the mineral geometry. The simulation results demonstrate that after 120 days of dissolution-precipitation reaction, the volume of secondary minerals (3.75%) exceeds that of dissolved minerals (2.01%), leading to a reduction in porosity by 1.74%. The pore structure of the basalt changes significantly, and the connectivity is obviously reduced. The effects of temperature and pressure on the reaction rate were examined to guide site selection for CO2 sequestration. The results show that increasing temperature and pressure can accelerate the reaction rate, but the impact of pressure on the reaction rate is negligible compared to the significant influence of temperature. Therefore, an area with a high geothermal gradient is conducive to geological sequestration.

High‐resolution cathodoluminescence of calcites from the Cold Bokkeveld chondrite: New insights on carbonatation processes in CM parent bodies

AbstractCarbonates, as secondary minerals found in CM chondrites, have been widely employed for reconstructing the composition of the fluids from which they precipitated. They also offer valuable insights into the hydrothermal evolution of their parent bodies. In this study, we demonstrate that high‐resolution cathodoluminescence (HR‐CL) analyses of calcites derived from the brecciated Cold Bokkeveld CM2 chondrite can effectively reveal subtle compositional features and intricate zoning patterns. We have identified two distinct types of cathodoluminescence (CL) centers: a blue emission band (approximately 375–425 nm), associated with intrinsic structural defects, and a lower energy orange extrinsic emission (around 620 ± 10 nm), indicating the presence of Mn cations. These compositional variations enable discrimination between the calcite grain types previously designated as T1 and T2 in studies of CM chondrites. T1 calcites exhibit variable CL and peripheral Mn enrichments, consistently surrounded by a rim composed of Fe‐S‐rich serpentine–tochilinite assemblage. Conversely, T2 calcites display homogeneous CL and more abundant lattice defects. These polycrystalline aggregates of calcite grains, devoid of serpentine, contain Fe‐Ni sulfide inclusions and directly interface with the matrix. We propose that changes in the Mn content of calcite (indicated by the intensity of orange CL emission) are influenced by variations in redox potential (Eh) and pH of the fluid phase. This proposed hydrothermal evolution establishes a parallel between terrestrial serpentinization followed by carbonation processes and the aqueous alteration of CM chondrites, warranting further exploration and investigation of this intriguing similarity.

Coupled redox cycling of arsenic and sulfur regulates thioarsenate enrichment in groundwater

High‑arsenic groundwater is influenced by a combination of processes: reductive dissolution of iron minerals and formation of secondary minerals, metal complexation and redox reactions of organic matter (OM), and formation of more migratory thioarsenate, which together can lead to significant increases in arsenic concentration in groundwater. This study was conducted in a typical sulfur- and arsenic-rich groundwater site within the Datong Basin to explore the conditions of thioarsenate formation and its influence on arsenic enrichment in groundwater using HPLC-ICPMS, hydrogeochemical modeling, and fluorescence spectroscopy. The shallow aquifer exhibited a highly reducing environment, marked by elevated sulfide levels, low concentrations of Fe(II), and the highest proportion of thioarsenate. In the middle aquifer, an optimal ∑S/∑As led to the presence of significant quantities of thioarsenate. In contrast, the deep aquifer exhibited low sulfide and high Fe(II) concentration, with arsenic primarily originating from dissolved iron minerals. Redox fluctuations in the sediment driven by sulfur‑iron minerals generated reduced sulfur, thereby facilitating thioarsenate formation. OM played a crucial role as an electron donor for microbial activities, promoting iron and sulfate reduction processes and creating conditions conducive to thioarsenate formation in reduced and high‑sulfur environments. Understanding the process of thioarsenate formation and the influencing factors is of paramount importance for comprehending the migration and redistribution of arsenic in groundwater systems.

Laboratory Experiments and Geochemical Modeling of Gas–Water–Rock Interactions for a CO2 Storage Pilot Project in a Carbonate Reservoir in the Czech Republic

The aim of this study was to characterize the influence of CO2 in geological structures on mineralogical changes in rocks and assess the sequestration capacity in mineral form and solution of a potential pilot storage site in the Czech Republic. Rock samples from a dolomite reservoir and the overburden level, as well as the corresponding pore water, were used. The most important chemical process occurring in the reservoir rock is the dissolution of carbonate minerals and feldspars during the injection of CO2 into the structure, which increases the porosity of the structure by approximately 0.25 percentage points and affects the sequestration capacity of the reservoir rock. According to the results of geochemical modeling, the secondary carbonate minerals (dolomite, siderite, and ephemeral dawsonite) were present only during the first 50 years of storage, and the porosity at this stage decreased by 1.20 pp. In the caprocks, the decomposition of K-feldspar and calcite resulted in an increase in porosity by 0.15 percentage points at the injection stage only, while no changes in porosity were noted during storage. This suggests that their insulation efficiency can be maintained during the injection and post-injection periods. However, further experimental research is needed to support this observation. The results of this study indicate that the analyzed formation has a low potential for CO2 sequestration in mineral form and solution over 10,000 years of storage, amounting to 5.50 kg CO2/m3 for reservoir rocks (4.37 kg CO2/m3 in mineral form and 1.13 kg CO2/m3 in dissolved form) and 3.22 kg CO2/m3 for caprock rocks (3.01 kg CO2/m3 in mineral form and 0.21 kg CO2/m3 in dissolved form). These values are lower than in the case of the depleted Brodské oil field, which is a porous reservoir located in the Moravian part of the Vienna Basin.

IDENTIFIKASI MINERAL SEKUNDER UNTUK MENILAI POTENSI TANAH LAHAN PERTANIAN CABE HIYUNG DI DESA HIYUNG KABUPATEN TAPIN KALIMANTAN SELATAN

Hiyung Village is part of Tapin Tengah District, Tapin Regency, South Kalimantan. Besides rice, superior agricultural commodities in this village is Hiyung Cayenne Pepper. High demand and prices have caused more and more cayenne pepper to be cultivated. Hiyung Cayenne Pepper Cultivation is expected to increase farmers' income, so efforts are needed so that agricultural activities can continue. The sustainability of agricultural can be maintained if they are managed well. Appropriate management actions can be implemented if the soil and land characteristics are known. Soil is one of the things that really determines the success of an agricultural business, especially the availability of nutrients. Analysis of the secondary mineral composition of soil (sand) is very important in order to determine the nutrient reserves in the soil. Information about nutrient reserves in the soil can be used as a basis for good soil management so that it meets plant needs and does not cause damage to the soil and the environment. The specific aim of this research is to determine the composition of primary minerals (sand) to identify nutrient reserves in the soil. This research was carried out using a survey method to obtain data or information on soil and land characteristics and current management. Observations and soil sampling in the field were carried out at 5 locations with a distance of 1 km between locations. Sand mineral analysis uses a polarizing microscope to determine the mineral composition. Primary minerals (sand) at the research location are dominated by rock fragments and quartz. The weatherable mineral content is very small so the potential for nutrient reserves is very small.

Studies of radioactive minerals and geochemistry of uranium at the granitic rocks of Wadi Um Shillman Area, South Eastern Desert, Egypt

The northwestern part of Gabal Um Ara granitic pluton is represents a good example for uranium occurrence in the southeastern desert of Egypt. Among the different lithologies in the study area, the granitic rocks attract attention for more detailed geological, geochemical and radiometrical studies. Um Ara granitic masses cover an oval outline area of about 300 km2, which is characterised by moderate topography. The granitic rocks are classified as monzogranite and alkali feldspar granite. Both of them belong to the post-orogenic younger granite magmatic activity that intruded the Egyptian shield between 620 and 530 Ma. The intrusion of Um Ara monzogranite and alkali feldspar granite appears to have been controlled by deep-seated tectonic zones and block faulting. The studied area lies at southeast of Aswan City between 22ͦ 38′ 12˝–22ͦ 38′ 34˝ N and 33ͦ 47′ 27˝–33ͦ 48′ 14˝ E. Geochemically, the average concentration of the elements in North Um Ara granite shows that the relative abundance decreases gradually with decreasing incompatibility from Rb to Y. The common features are enrichment in more mobile elements Rb, Th and U. The monzogranite shows the lowest U and Th content, whereas the alkali-feldspar shows an enhanced contents of both elements, with average Th/U ratio = 3.0. the alkali-feldspar exhibits an expanded enrichment of Th relative to U. The U of the alkali-feldspar may be included within the structure of the refractory accessory minerals. The northern part of the Um Ara granitoids has subjected to different types of alterations. The radiometric survey of the northwestern part of Gabal Um area granitic pluton revealed the presence of several radioactive anomalies near the contact with the Dokhan volcanic and metavolcanic rocks in the north. Some visible uranium mineralisation of uranium minerals occur mainly along the NW, NE, E-W and N-S joints, of a highly sheared alkali feldspar-granite. Uranophane is visible secondary uranium mineral, characterised by bright yellow lemon colours and occurs mainly as filling fractures and joints associated with violet fluorite, iron and manganese oxides. The radioactive and accessory minerals studying and X-ray diffraction analysis that of the mineralised alkali feldspar-granite granite in the northwestern part of Gabal Um Ara granitic pluton revealed include the presence of fluorite, zircon, columbite, spessartine garnet whereas, the secondary uranium minerals are represented by uranophane, β-uranophane and kasolite. The hydrothermal origin was proposed as two possible alternatives for this uranium mineralisation.

Research on the influence of mineral heterogeneity under different CO2 injection schemes in low permeability reservoirs

In the pursuit of sustainable oil and gas resource extraction, the innovative integration of carbon capture, utilization, and storage (CCUS) technology has emerged as the most promising approach. During the CCUS process, intricate physicochemical interactions between the injected CO2, facilitated through various injection strategies (Water Alternative Gas: WAG/Continue Gas Injection: CGI) and the formation fluids and heterogeneous mineral assemblages within the reservoir trigger alterations in mineral structures, consequently impacting permeability and recovery factors, constituting a pivotal aspect. Precisely delineating and quantifying these interactions is paramount for optimizing process design and evaluating reservoir dynamics in the successful implementation of CCUS operations. This study has carried out qualitative and quantitative characterization of mineral heterogeneity, different pore types, and mineral combination characteristics from a low-permeability sandstone reservoir. Additionally, the effect on the physical properties of minerals from different development methods (WAG/CGI) was investigated using numerical simulation for CCUS applications. The results indicate that the saturated CO2 fluid selectively dissolves the potassium feldspar (orthoclase) in intergranular pores, while the intergranular pores are filled with illite and secondary precipitated clay minerals. It initially dissolves the sensitive mineral (ankerite) in the intergranular pores. The decrease of ankerite and increase of illite result from the prolonged contact period between saturated CO2 and minerals, which changes the mineral cementation to argillaceous type, thus affecting permeability in the context of CCUS. The spatial impact on reservoir physical properties depends on the spatial heterogeneity of the original sensitive minerals (ankerite, anorthite, illite, etc.) distributed in the study area. In the WAG scheme, the physicochemical interaction between saturated CO2 and reservoir minerals is more intense than in the CGI scheme for CCUS operations, significantly impacting cumulative production.

Environmental behaviour of iron and steel slags in coastal settings

Iron and steel slags have a long history of both disposal and beneficial use in the coastal zone. Despite the large volumes of slag deposited, comprehensive assessments of potential risks associated with metal(loid) leaching from iron and steel by-products are rare for coastal systems. This study provides a national-scale overview of the 14 known slag deposits in the coastal environment of Great Britain (those within 100 m of the mean high-water mark), comprising geochemical characterisation and leaching test data (using both low and high ionic strength waters) to assess potential leaching risks. The seaward facing length of slag deposits totalled at least 76 km, and are predominantly composed of blast furnace (iron-making) slags from the early to mid-20th Century. Some of these form tidal barriers and formal coastal defence structures, but larger deposits are associated with historical coastal disposal in many former areas of iron and steel production, notably the Cumbrian coast of England. Slag deposits are dominated by melilite phases (e.g. gehlenite), with evidence of secondary mineral formation (e.g. gypsum, calcite) indicative of weathering. Leaching tests typically show lower element (e.g. Ba, V, Cr, Fe) release under seawater leaching scenarios compared to deionised water, largely ascribable to the pH buffering provided by the former. Only Mn and Mo showed elevated leaching concentrations in seawater treatments, though at modest levels (<3 mg/L and 0.01 mg/L, respectively). No significant leaching of potentially ecotoxic elements such as Cr and V (mean leachate concentrations <0.006 mg/L for both) were apparent in seawater, which micro-X-Ray Absorption Near Edge Structure (μXANES) analysis show are both present in slags in low valence (and low toxicity) forms. Although there may be physical hazards posed by extensive erosion of deposits in high-energy coastlines, the data suggest seawater leaching of coastal iron and steel slags in the UK is likely to pose minimal environmental risk.

Monitoring air fluxes in caves using digital flow metres

Precise measurements of airflow within caves are increasingly demanded to assess heat and mass transfers and their impacts on the karst environment, including subsurface ecosystems, hydrochemistry of karst water and secondary mineral precipitates. In this study, we introduce a new, low-cost and lightweight device adapted to monitoring air fluxes in caves which addresses the need for reliable measurements, low power consumption, durability and affordability. The device was calibrated in a wind tunnel, showing the high accuracy and precision of the device. Field-related uncertainties were further investigated in a ventilated cave to determine the effect of local airflow conditions on the inferred mass flux. Comparing measured values with a 3-D air velocity distribution modelled on a surveyed cave section suggests that most of the uncertainties in estimating the airflow result from the relative position of the instrument in the streamlines rather than from the accuracy of the device.

Mineralogy and weathering of REE minerals in the Liuchen granite, Guangxi, southern China: Implications for HREE enrichment in the granite regolith

Regolith-hosted ion-adsorption REE deposits (IARDs) in southern China were derived predominantly from the weathering of granitoids. However, the role of primary REE minerals in the formation of a REE-rich regolith during weathering of the granites has not been fully understood. To investigate the formation process of IARDs, fresh granite samples and regolith samples from different horizons (i.e., fully-, highly-, and semi-weathered horizons) in the Liuchen (LC) super-large IARD of Guangxi Province, southern China were collected and studied the compositions of the REE minerals. Allanite-(Ce), monazite, apatite, and zircon are major primary LREE-bearing minerals in the LC granite, and xenotime-(Y) is the major host of HREEs, including Gd, Dy, Er, Yb and Y (up to 38.68 wt%). Altered anhedral xenotimes are observed recrystallized as a result of the breakdown of apatite. These xenotimes have elevated contents of HREEs compared with their precursors. The sizes of these altered xenotimes are significantly smaller (mostly 0.5–5 μm) compared to the primary xenotimes (>50 μm). The increased surface-to-volume ratio for smaller particle sizes of these altered xenotimes make them more susceptible to weathering during supergene alteration. Except for zircon, the volume of primary REE minerals is reduced in zones of intense weathering (fully- and highly-weathered horizons) in the granite regolith, but relics of xenotime which covered by biofilms on their surfaces were observed in the incipient zones of weathering (e.g., in the semi-weathered horizon). Dissolution that begins at their surfaces from nano-scale was observed in these mineral relics. Microbial solubilization of this previously thought insoluble REE phosphate is likely to control the mobilization REE content, especially Y, in the LC granite regolith. Secondary cerianite-(Ce) and LREE- and HREE-bearing phosphates, mainly rhabdophane and florencite, were identified in the regolith, and this is evidence that HREE minerals such as xenotime-(Y) that were undergoing bio-weathering were an important source of materials for the formation of REE-bearing secondary minerals. This may provide new insights into the formation of so-called “ion-adsorption” REE deposits.

Quantitative analysis of the Permian sediments of Karoo Basin of South Africa using combined petrophysical and X-ray analytical techniques

This study quantifies the petrophysical parameters and determines the impact of mineralogy on the petrophysical parameters of the Permian sediments of the main Karoo Basin, South Africa. Conventional well logs from KDD-01 well, thirty-two and forty-two samples are investigated for mineral and composition analyses using X-ray diffraction and fluorescent techniques, respectively. Three intervals of Abrahamskraal Formation (500–513m), dolerite sill that intruded the Abrahamskraal Formation (513–530m), and Waterford Formation (1014–1048m) are investigated. The results show that the average porosity of the Abrahamskraal Formation is 2.9%, the dolerite interval has an average value of 1.8%, whereas the Waterford Formation has an average value of 2.1%. The average permeability for the Abrahmaskraal Formation is 0.05mD, dolerite 0.04mD, and the Waterford Formation is 0.08mD, respectively. No hydrocarbon was detected. The low values of petrophysical properties may be associated with the pore network, which is poorly connected, intense precipitation of secondary minerals, and pore infilling during burial diagenesis. Quartz mineral dominates in the Abrahamskraal Formation, with an average value of 47% and 61% in the Waterford Formation.In comparison, plagioclase is the main mineral constituent in the dolerite, with an average of 44%. Based on the combined petrophysical and geochemistry classification scheme, the formations evaluated belong to the type III pore structure. The type III pore structure is a poor and ineffective reservoir, with rock porosity usually less than 6% and a permeability of less than 0.15mD. However, regarding the mineral elemental ratio, the Abrahamskraal and the Waterford Formations meet the type II pore structure criteria, while the dolerite is type III. This paper has produced a helpful rock classification scheme based in the Karoo Basin, South Africa, using petrophysical and geochemical data for the first time.

Sequestration of Labile Organic Matter by Secondary Fe Minerals from Chemodenitrification: Insight into Mineral Protection Mechanisms.

Labile organic matter (OM) immobilized by secondary iron (Fe) minerals from chemodenitrification may be an effective way to immobilize organic carbon (OC). However, the underlying mechanisms of coupled chemodenitrification and OC sequestration are poorly understood. Here, OM immobilization by secondary Fe minerals from chemodenitrification was investigated at different C/Fe ratios. Kinetics of Fe(II) oxidation and nitrite reduction rates decreased with increasing C/Fe ratios. Despite efficient sequestration, the immobilization efficiency of OM by secondary minerals varied with the C/Fe ratios. Higher C/Fe ratios were conducive to the formation of ferrihydrite and lepidocrocite, with defects and nanopores. Three contributions, including inner-core Fe-O and edge- and corner-shared Fe-Fe interactions, constituted the local coordination environment of mineral-organic composites. Microscopic analysis at the molecular scale uncovered that labile OM was more likely to combine with secondary minerals with poor crystallinity to enhance its stability, and OM distributed within nanopores and defects had a higher oxidation state. After chemodenitrification, high molecular weight substances and substances high in unsaturation or O/C ratios including phenols, polycyclic aromatics, and carboxylic compounds exhibited a stronger affinity to Fe minerals in the treatments with lower C/Fe ratios. Collectively, labile OM immobilization can occur during chemodenitrification. The findings on OM sequestration coupled with chemodenitrification have significant implications for understanding the long-term cycling of Fe, C, and N, providing a potential strategy for OM immobilization in anoxic soils and sediments.