Calcite Minerals Research Articles

Hydrogen underground storage potential in sandstone formation: A thorough study utilizing surface complexation modelling

This research focuses on the geochemical aspects of hydrogen underground storage, with particular emphasis on surface complexation modelling and its impact on surface potential and surface charge. The primary objective is to develop the first comprehensive surface complexation model specifically tailored for sandstone rocks, emphasizing key minerals such as quartz, kaolinite, and calcite, which are suitable for hydrogen underground storage applications. This model is intended to serve as a benchmark for more research in this field, providing a solid foundation for investigating and improving predictions related to wettability alteration. Additionally, the model has been integrated with hydrogen solubility to accurately capture changes in surface charge. The study identified six brine compositions with various minerals to examine the effect of monovalent and divalent ions. The results showed an increase in solubility with an overall reduction in salinity, and a decrease in divalent ions. The homogeneous surface complexation model demonstrated a neutral surface potential, attributed to an increased mole fraction of positively charged >SiOH+and a decreased in negatively charged >SiO-. Similar trends were observed in kaolinite and calcite minerals. The influence of pH was also explored, revealing a significant impact on the homogeneous quartz case, where an increase in pH shifted the surface potential from neutral to more negative. The heterogeneous cases exhibited less negative behavior as the quartz content increased per case, mainly due the increasing presence of positively charged species such as >SiOH+ and >AlOH+, and the reduction of the negatively charged >AlO-. Increasing the salinity of the solution resulted in less negative surface potential, attributed to the abundance of positive divalent and monovalent ions boosted by increasing salinity, thus the formation of positive surface complexes.

Controlling factors of fluid mobility in the tuff reservoirs of the Huoshiling formation, Dehui fault depression, southeastern Songliao Basin: insights from micro-nano pore structures

This study addresses the unclear understanding of the primary factors controlling fluid mobility in the tuff reservoirs of the Huoshiling Formation from the Dehui Fault Depression, southeastern Songliao Basin. Through physical property analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thin section (TS), pressure-controlled porosimetry (PCP), rate-controlled porosimetry (RCP), and nuclear magnetic resonance experiments (NMR) on ten tuff samples, we conducted a comprehensive and in-depth exploration of the influencing factors that control the mobility of reservoir fluids. The results indicate: 1) The primary mineral types in the tuff reservoirs are quartz, feldspar, and clay minerals, with porosity predominantly characterized by dissolution pores and intergranular pores; 2) Based on the morphology of PCP intrusion curves, the tuff samples from the study area can be categorized into three types, with reservoir quality progressively deteriorating from Type I to Type III; 3) Compared to the movable fluids saturation (MFS), movable fluids porosity (MFP) is more suitable for characterizing fluid mobility. The mobility of fluids is influenced by various factors such as mineral composition, physical property, pore-throat connectivity, pore type and heterogeneity. MFS and MFP show a positive correlation with permeability, the content of quartz and feldspar, median pore-throat radius (R50), average throat radius (ATR), average pore-throat radius ratio (APT), T2 cutoff value (T2-C), average throat radius (RT), sorting coefficient (SC), and intergranular pore dominate space (Inter-DS), while a negative correlation with the content of calcite and clay minerals, average pore-throat radius ratio, and the fractal dimension from NMR (DNMR). This study elucidates the influencing factors of fluid mobility in tuff reservoirs, which has important reference significance for the scientific development of this type of gas reservoir.

Performance augmentation of fiber reinforced concrete through in situ mineralization of polycrystalline calcium carbonate on fiber surfaces

Enhancing the performance of fiber-reinforced concrete through the meticulous regulation of interfacial microstructure and interaction mode stands as a pivotal area of research. Notably, there are significant differences in the microstructure of several polycrystalline forms of calcium carbonate, which can profoundly influence the interaction behavior between them and the matrix. However, the tailored modulation of calcium carbonate polymorphism for the purpose of fiber surface modification remains unreported. In this paper, polycrystalline mineralization was induced by polydopamine on the surface of polyvinyl alcohol fiber by biomimetic method, and the fiber surface was modified by calcite and aragonite. The cubic calcite and acicular aragonite minerals notably roughened the fiber surface, enhancing interfacial properties between PVA fibers and cement matrix. The damaged form of the interface changed from adhesion failure to cohesive failure. Quantitative assessment of fiber-matrix interfacial interactions via single-fiber pullout tests revealed aragonite's unique morphology and exceptional mechanical attributes yielding higher frictional resistance against pullout loads. The good bonding between calcite and the cement matrix improves the strain-hardening behavior of fiber pullout and significantly enhances energy dissipation. In addition, enhanced interfacial properties bolster composites' mechanical strength. The acicular and cubic mineralized layers increased the flexural strength of the fiber cementitious materials by 35 % and 41 %, respectively. The energy absorbed in resisting the impact of a falling ball increased by 25 % and 36 %, respectively. Analysis reveals calcite promotes hydration more significantly at comparable particle sizes, bolstering interfacial bond strength with cement, and offering superior reinforcement over aragonite for fiber matrix bridging. This research provides a theoretical basis for promoting the application of polycrystalline CaCO3 and the sustainable development of high-performance fiber-reinforced concrete.

The Structural and Thermal properties of Badarashma Pishti

BackgroundLapis judaicus, or Jews stone (Badarashma), has been used in treating kidney and bladder stones since ancient times by Ayurvedic and Unani medicinal practitioners. A limited number of studies have been carried out using Ayurvedic preparations derived from gems or precious stones that were used traditionally. In Ayurveda, Rasa Shastra includes the fabrication of Bhasmas and Pishti. ObjectiveThis study aimed to prepare and characterize Badarashma Pishti formulation (Lapis judaicus microparticles) and investigate its structural and thermal properties. Materials and methodsThe microparticles were prepared by subjecting purified powder of Lapis judaicus to a wet levigation (Bhavana) process. Characterizations were done using Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), thermo-gravimetry analysis (TGA), energy-dispersive X-ray (EDAX) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis. Physicochemical characterization, elemental analysis, particle size distribution study, and identification of heavy metals were also performed. ResultsA standard operating procedure was developed to formulate Badarashma Pishti. The obtained microparticles were irregularly shaped with a size of 4.290 ± 0.472 μm, confirmed in SEM images. The FTIR and XRD of prepared Badarashma Pishti samples revealed the presence of calcite, quartz, and aragonite minerals. The results of EDAX also confirmed the presence of Ca, Mg, O, and Si elements. ConclusionThe proposed study results reveal great insights for determining the authenticity, purity, and standardization parameters of inorganic mineral drugs, proving to be a useful delivery system for treating renal calculi.

Experimental and Molecular Dynamics Evaluation of the Effect of a Sulfate Surfactant on the Shale’s Methane Sorption

Shale gas has shown a great potential for exploration and development via advanced horizontal drilling and multistage hydraulic fracturing. Slickwater is a major type of fracking fluid, containing various chemical additives, water, and sand. In this matter, surfactant additives play a significant role in regulating the optimal performance of slickwater. The implication of the change in gas adsorption/desorption behavior of shale rocks and their individual minerals has rarely been experimentally investigated. In this study, the effect of a sulfate surfactant on methane adsorption capacity of a Marcellus shale was evaluated. Molecular dynamics simulation was also applied for gas adsorption assessment on major minerals in shales. Accordingly, the significant alteration of the adsorption energy of illite, quartz, and calcite minerals treated by a surfactant was investigated. Conclusively, the methane sorption capacity of the treated shale sample was reduced and correspondingly, the gas diffusion coefficient increased. Experimentally, the methane sorption analysis showed that the diffusion of the surfactant resulted in significant methane desorption. Besides, the major mineral constituents of shale behaved differently as unveiled by molecular simulation. The methane adsorption energy of calcite was reduced more significantly than quartz and illite when treated with surfactant. And, at the molecular level, the number of adsorbed methane molecules on illite reduced by half after a sulfate surfactant treatment.

EFFECT OF CLAY MINERALS, CALCITE, AND ORGANIC MATTER ON ADSORPTION AND DESORPTION OF CADMIUM AND LEAD

A Factorial experiment of CRD was conducted, to study and evaluate the effectiveness of Calcite, Bentonite, and Kaolinite minerals, as well as organic matter, on adsorption and desorption of Pb and Cd. Bentonite and kaolinite clay minerals were treated by adding of 20 % calcite and 5 % organic matter of the weight of the mineral, so that the final weight became 100 g per treatment. Treatments were incubated for 180 days after that, and treated with five concentrations of Pb and Cd, (0, 10, 20, 30, 40, and 50 μg ml-1) as PbCl2 and CdSo4 respectively, The results showed the superiority of bentonite mineral over kaolinite in the maximum adsorption Xm and binding energy K by 137, 312.5, 20, and 193.5 % for Pb and Cd respectively. In the case of calcite mineral with both minerals, an increase in the binding energy and the greater adsorption were observed in the case of Cd and a decrease in the case of Pb with bentonite. In case of presence of organic matter with kaolinite, the maximum adsorption Xm for cadmium increased, as it was 204.08 μg g-1, while in the case of bentonite with organic matter it was 111.1 μg g-1. In the case of Pb, it reached 93.46 and 208.3 μg gm-1 for both minerals betonies and kaolinite, respectively. Regarding collective release, the results showed that the order of the treatment for the released Cd was as follows: M2 + O.M + C = M2 +O.M < M2 < M2 +C < M1 + C < M1 < M1 +O.M + C < M1 + O.M In the case of released Pb, the order of treatment was as follows: M1 < M1 + C = M1 + O.M < M1 + O.M + C < M2 + O.M + C < M2 + C < M2 + O.M < M2.

Effect of Chloride Solution on Liquid Limit, and Plasticity Index of Soil in Selected Sites in Erbil /North Iraq

This study is an attempt to investigate the effect of NaCl, CaCl2, KCl, and NH4Cl solutions with different concentrations (2.5%, 5%, 7.5%) on the liquid limit, plastic limit, and plasticity index of Sarbasty and Mamwastayan soil samples /Erbil Governorate. The soil samples' liquid and plastic limits were found by using the cone penetrometer method. The Results showed that the soil's liquid, plastic limits, and Plasticity index decreased with increasing salt solution concentration. Maximum reduction of liquid limit and plastic limit in Sarbasty was from 53.6 to 34.3 and in Mamwastayan from 35.9 to 27.2, both accomplished by adding a concentration of 7.5% of KCl and CaCl2 respectively. According to the Unified Soil Classification System, the Sarbasty soils were classified as high plasticity clay (CH), and Mamwastayan low plasticity clay (CL). After adding different concentrations of salt solution to the soil, the Sarbasty soil classification changed from CH to CL. Mineralogically these soils are composed of non-clay minerals of calcite and quartz and clay minerals consisting of Montmorillonite, Chlorite, swelling Chlorite, Kaolinite, Illite, Palygorskite, and Illite- Chlorite. Sarbasty soil was the most effective salt chloride solution than the Mamwastayan soil sample swelling.

From loose sand to sandstone: An experimental approach on early calcite precipitation in sands of siliciclastic and mixed carbonate-siliciclastic composition.

Artificially cemented sandstones were produced to assess the impact of detrital texture and composition on the precipitation and distribution of early calcite cement, and cement-related degradation in porosity. To simulate early-calcite cementation, loose sediment of variable composition (siliciclastic and calcareous) and grain size was exposed to a calcite supersaturated solution for 35 to 58 days at 23°C. Identification and distribution of the newly precipitated crystals was performed with high resolution 2D optical and scanning electron microscopy. The experimental results show the precipitation of grain-coating, pore-bridging and pore-filling granular calcite cement with up to 100 μm crystal size. Despite a positive correlation between the amount of detrital carbonate grains and calcite crystals, calcite cement does not preferentially nucleate on bioclast surfaces, irrespectively of their favourable mineralogy. Siliciclastic grains show high calcite cement coverage with altered feldspar, particularly plagioclase, displaying coverage of 94.3%. Grain size variations within the sand packs have influence on the precipitation pattern of calcite with coarse-grained layers (500-710 μm) showing minor calcite cementation (6.3%), while medium- (250-500 μm) to fine-grained layers (125-250 μm) comprise average calcite cement contents of 16.3% and 28.2%, respectively. The findings of this study enhance our knowledge regarding the precipitation processes of calcite in porous material with heterogeneous reacting mineral phases, shapes and pore connectivity.

Evolution of pore structure and cement composition during weathering of conglomerate at Mogao Grottoes in alkaline and arid regions, NW China

Numerous conglomerate grottoes have been excavated and preserved in the arid and alkaline regions of NW China. After millennia of weathering, these conglomerate grottoes have suffered from various weathering issues (such as seepage and collapse) that are internally governed by the distribution of pore networks and the degree of cementation. However, studies on conglomerate weathering have mostly been reported in humid and tropical climates, where intensive chemical weathering occurs. Additionally, characterizations of pore evolution during conglomerate weathering have been restricted due to limitations in detecting pore size and pore type using a single pore characterization method. To fill this gap, this study jointly used mercury intrusion porosimetry (MIP) and computed tomography (CT) to characterize the pore evolution process during conglomerate weathering at Mogao Grottoes, a world heritage site in NW China. Mineralogical, hydrological, mechanical and microscopic characterization were also conducted to understand the changes in compositions of bulk samples and cements during weathering. Results revealed that the majority of pores in conglomerate are concentrated in macropores > 5 μm, followed by mesopores and micropores. During weathering, volume fraction of macropores significantly increases and that of micropores decreases, with median/average pore diameters experiencing an 8- to 10-fold increase. Permeability, porosity and fractal dimension exhibited strong positive linear correlations with median/average pore diameters. Throughout weathering, the abundances of calcite and clay minerals show notable decrease, particularly in cements, resulting in an enrichment of feldspars. Frequently occurring sand-carrying wind activities and salt weathering in arid regions are inferred to be responsible for the major cement loss and porosity generation through physical processes. Our combined MIP-CT method for pore network characterization is also applicable to other lithologies with a wide range of pore sizes. The proposed mechanism of pore evolution and cementation failure provides a scientific base for protecting stone heritages in arid zones.

Circular economy strategies in sedimentary phosphate mine reclamation: Development of technosol from phosphate waste rock

Proper management of mine waste plays a crucial role in minimizing environmental impacts. One potential solution to tackle this problem involves transforming mine waste rock into soil to facilitate the process of mine restoration. The aim of this study was to assess the mineralogical, chemical, and physical characteristics of technosol derived from phosphate mine waste dumps. Following this evaluation, a novel rehabilitation strategy was proposed. For this purpose, a total of 32 samples were systematically collected across a 4 ha area of technosols, which had been established in accordance with the waste rock soil rehabilitation strategy involving geomorphic reshaping. According to the findings, phosphate mining left the soil with a sandy texture, resulting in a degraded soil structure with severely unfavorable crop growth conditions, notably poor stability, and low water retention. The chemistry of the studied soils was characterized by the dominance of CaO (29.02 wt%± 1.01) > SiO2 (27.61 wt% ± 0.61) > P2O5 (11.34 wt% ± 0.23) > MgO (5.97 wt%±0.16). Mineralogically, the samples were mainly formed by quartz, dolomite, calcite, apatite, and clay minerals. The prevalence of dolomite played a significant role in enhancing the accessibility of Mg as an essential nutrient and the occurrence of apatite in the soil resulted in the presence of P2O5. However, the abundance of Ca was linked to three major minerals: calcite, apatite, and dolomite. X-ray fluorescence analyses demonstrated that the concentrations of Fe2O3, K2O, and SO3 did not exceed 2 wt%.Organic matter, represented by SOC <0.2% and N < 0.02%, demonstrated an extraordinary deficiency in the study area. The analysis of element bioavailability confirmed that the soil was rich in Ca (10383,26 mg/kg), Mg (278,47 mg/kg), Zn (12,82 mg/kg), and Cu (3,7 mg/kg) but deficient in other essential nutrients such as P, K, S, Mn, and Fe. Our research results provide a set of recommendations aimed at enhancing existing mine rehabilitation practices applicable to both pre- and post-rehabilitation phases, leveraging automated mineralogy and circular economy principles. Notably, we propose a rehabilitation strategy to be implemented prior to the geomorphic reshaping phase, which is intended to reduce costs and efforts associated with soil reconstitution.

Comparison Study Between Inherited and Biogenic Calcium Carbonate Formation on The Surface Roots of Eucalyptus Trees Using X-Ray Technique and Field Observations

Background: This study aims to explain the mechanism of formation of calcite and it's to shed light on the synthetic carbonate crystallization on the surface of roots due to this mechanism is poorly understood and highly controversial. It is accepted that calcite formed originally from parent rocks and not in soils. Method: The origin of calcite in calcareous soil, in Aldiwaniya city, Iraq was investigated, by selecting two soil samples, one from the contact zone with root surface and the other sample from bulk soil and out of the root system. Results: X-ray diffraction showed that the calcite has two types, first one is well crystallized and ordered, with only minor deviations in lattice unit cell parameters relative to typical calcite. The clay-sized calcite (active calcite) is enriched in A and C-horizons relative to biogenic calcite and this mineral exist in larger size separates, and it's clearly appears in the shape of white crystals around eucalyptus root surfaces as shown in graphs. The results of X-ray showed that the appearance of smectite mineral which was diagnosed by the peak 14.21 A° in air dry magnesium-saturated treatment which expanded to 16.28 A° when saturated with ethylene glycol, where clarity of peak was increased, Also, the results showed that the appearance of peak 14.21 A° in magnesium saturation air dried, as a shoulder on the peak of the mica (10.14 A°). Conclusion: In general, calcite minerals have characteristic x-ray diffraction peaks at the following angles: 29.5, 31.7, 34.5, 35.7, 47.3, 56.4, and 63.4 degrees.

Tracing magmatic footprints: Influence of a CO2-rich melt on the mineral assemblage of the San José del Guaviare Syenite, SE Colombia

A combined optical and electron microscopy (SEM, EDS, and EPMA) study was conducted on ten rock samples from the Proterozoic San José del Guaviare Syenite (SJGS), southeastern Colombia, to utilize minor and trace minerals in interpreting the magmatic evolution of these silica undersaturated rocks. The major minerals of the sampled syenites are nepheline, Fe-rich clinopyroxene, amphibole, alkali feldspar, and biotite. The minor minerals are titanite, calcite, cancrinite, and sodalite. Trace minerals are the niobium- or rare earth element-rich minerals pyrochlore, columbite, euxenite, britholite, ancylite-Ce and wöhlerite. Apatite, rhodochrosite, strontianite, fluorite, zircon, magnetite, ilmenite, and pyrite occur as traces as well. Crystallization started with primary (magmatic) calcite and Nb-rich minerals pyrochlore, columbite, euxenite, and a first generation of apatite, which occur as inclusions in foids, feldspars, and Fe-rich clinopyroxenes. Calcite is enriched in light rare earth elements and Sr, with low Mg concentrations, while primary apatite has high Sr concentrations. Both minerals have a composition typical for minerals crystallized in carbonatites. The presence of calcite and high Fe and low Ti clinopyroxene point to CO2-saturated conditions. During cooling, fluorbritholite-Ce formed as individual grains or by a fluid-enhanced apatite-britholite transformation. The formation of Fe-rich amphibole, often at the expense of Fe-rich clinopyroxene, reveals a decreasing influence of CO2 and temperature. Presumably, the transformation of orthoclase into microcline occurred simultaneously. Perthitic microcline as a second K-feldspar generation indicates slow cooling from high temperatures. A late stage of CO2-rich hydrothermal-metasomatic processes is suggested by the growth of secondary cancrinite, Sr-Mn carbonates and ancylite-Ce. The composition of primary and early crystallized calcite and apatite makes their origin as residues of an early segregated or independently formed mantle-derived carbonatitic melt more likely than crystallization from a CO2-rich syenitic melt. An origin from melted crustal carbonates is unlikely as well. Therefore, the presence of a carbonatitic melt at an early magmatic evolutive stage, as opposed to a non-carbonatitic melt at a late stage, seems possible for the SJGS rocks.

Investigations of the impact of geothermal water reinjection on water-rock interaction through laboratory experiments and numerical simulations

In the quest for sustainable geothermal energy production, the adoption of geothermal reinjection technology has become a crucial element in the development of geothermal resources. However, the processes of injection and extraction can lead to interactions between water and rock within the geothermal reservoir, resulting in pore blockage. This study focuses on the Kaifeng Zhenyu Garden geothermal field as a case study to examine the water-rock interactions that occur during geothermal reinjection, as well as the subsequent changes in mineral composition and porosity within the reservoir. The findings reveal that the primary minerals undergoing dissolution are dolomite and feldspar, with the precipitation of calcite and clay minerals following suit. Additionally, results from field simulations corroborate that dolomite and feldspar are the main minerals dissolving, accompanied by the precipitation of calcite and illite. Notably, significant changes in mineral dissolution and precipitation near the geothermal well have led to a slight reduction in the reservoir's porosity. This investigation provides valuable insights into the water-rock interactions involved in geothermal reinjection processes across various geothermal fields.

Geochemical Modeling and Quality Assessment of the Surface Waters from the Mouhoun River System, Burkina Faso: Implications of Water–Rock Interactions and Anthropogenic Activities

Major ion and heavy metal geochemistry was used to investigate the factors that control the Mouhoun River water quality in western Burkina Faso. Major cation concentrations was in the following decreasing order: Ca2+&gt; Na+&gt; K+&gt; Mg2+, reflecting silicate weathering. However, relatively high HCO3- and SO42- concentrations could be related to dissolution of calcite and sulfide minerals, respectively. The average heavy metal concentrations in the riverine system were in the following order: FeT&gt;Ag&gt;Mn&gt;Zn&gt;Pb&gt;Cu&gt;Ni&gt;AsT&gt;Cr&gt;Hg&gt;Co&gt;Cd with FeT and Ag exceeding the World Health Organization permissible limits. Concentrations of all heavy metals, except Cr, were higher in the Mouhoun system compared to the average world river concentrations. Adsorption and speciation models showed that Zn, Ag, Cd, Co, Cr and Ni are likely to remain in their free ionic forms, and thus posing serious threats to aquatic life and human health. Ag-Hg-Ni-Cd association around Poura and Tenado on the principal component plot suggested that the widespread artisanal gold mining in these areas may have contributed to these metals’ loading. In contrast, NH4+, Pb, Cu, Cr, AsT and Zn were clustered around a densely populated and industrialized Kou watershed, pointing to agricultural and industrial sources of these pollutants. Furthermore, the Kou River had the highest metal index followed by Tenado, Samendeni, Poura and Boromo. Hence, the chemistry of the Mouhoun River and its tributary appears to be mainly controlled by population density and various anthropogenic activities taking place in their drainage basins. The findings could provide avenues for sound and sustainable water resource management in a water scarce semi-arid environment.

Shale Oil Generation Conditions and Exploration Prospects of the Cretaceous Nenjiang Formation in the Changling Depression, Songliao Basin, China

Low-maturity shale oil predominates in shale oil resources. China’s onshore shale oil, particularly the Cretaceous Nenjiang Formation in the Songliao Basin, holds significant potential for low-maturity shale oil, presenting promising exploration and development prospects. This study delves into the hydrocarbon generation conditions, reservoir characteristics, and oil-bearing property analysis of the mud shale from the Nen-1 and Nen-2 sub-formations of the Nenjiang Formation to pinpoint favorable intervals for shale oil exploration. Through the integration of lithology, pressure, and fracture distribution data in the study area, favorable zones were delineated. The Nen-1 sub-formation is widely distributed in the Changling Depression, with mud shale thickness ranging from 30 to 100 m and a total organic content exceeding 2.0%. Type I kerogen predominated as the source rock, while some samples contained type II kerogen. Organic microcomponents primarily comprised algal bodies, with vitrinite reflectance (Ro) ranging from 0.5% to 0.8%. Compared to Nen-1 shale, Nen-2 shale exhibited less total organic content, kerogen type, and thermal evolution degree, albeit both are conducive to low-maturity shale oil generation. The Nen-1 and Nen-2 sub-formations predominantly consist of clay, quartz, feldspar, calcite, and pyrite minerals, with minor dolomite, siderite, and anhydrite. Hydrocarbons primarily reside in microfractures and micropores, including interlayer micropores, organic matter micropores, intra-cuticle micropores, and intercrystalline microporosity, with interlayer and intra-cuticle micropores being dominant. The free oil content (S1) in Nen-1 shale ranged from 0.01 mg/g to 5.04 mg/g (average: 1.13 mg/g), while in Nen-2 shale, it ranged from 0.01 mg/g to 3.28 mg/g (average: 0.75 mg/g). The Nen-1 and Nen-2 sub-formations are identified as potential intervals for shale oil exploration. Considering total organic content, oil saturation, vitrinite reflectance, and shale formation thickness in the study area, the favorable zone for low-maturity shale oil generation is primarily situated in the Heidimiao Sub-Depression and its vicinity. The Nen-2 shale-oil-enriched zone is concentrated in the northwest part of the Heidimiao Sub-Depression, while the Nen-1 shale-oil-enriched zone lies in the northeast part.

The Role of Fe(III) in Selective Adsorption of Pullulan on Calcite Surfaces: Experimental Investigation and Molecular Dynamics Simulation.

The floatability of fluorite and calcite exhibit similar properties, rendering their flotation separation challenging. Macromolecular polysaccharide reagents containing the polyhydroxyl group have shown broad promising application. The selectivity of polysaccharide is relatively low. In this study, the introduction of Fe3+ was employed to enhance the selective adsorption capacity of Pullulan polysaccharide towards fluorite and calcite minerals, thereby achieving effective flotation separation. Furthermore, the mechanism underlying intramolecular interactions was elucidated. The DFT calculation and XPS analysis revealed that the adsorption of Fe3+ on the calcite surface was more favorable, leading to the formation of a Ca-O-Fe structure. The MD simulation, XPS analysis, and Zeta potential analysis revealed that the Fe-OH groups on the surface of calcite reacted with the -OH groups in Pullulan and formed bonds, resulting in the formation of a Calcite-Fe-Pullulan structure. This facilitated the attachment of a significant number of Pullulan molecules to the calcite surface. The formation of a hydrophilic layer on the outer surface of calcite by Pullulan, in contrast to the absence of such layer on fluorite's surface, results in an increased disparity in surface floatability between these two minerals, thereby enhancing the efficiency of flotation separation.

Advanced smectite alteration and the role of accessory reactants at 180 °C: New experimental constraints on the stability of bentonite

Bentonite clay is commonly accepted as an appropriate material for backfilling the space between the radioactive canisters and the host rock of planned underground repository sites for waste disposal. Despite its favourable properties as a hydrodynamic seal, its long-term stability remains a concern. This experimental study of a Bavarian bentonite investigated advanced montmorillonite (smectite) illitisation at 180 °C in the presence of K-oxalate and/or the accessory minerals of pyrite and calcite. The formation of mixed-layered illite-smectite was quantified by X-ray diffraction Rietveld refinement and the crystal chemistry was determined by transmission electron microscopy. The results showed neocrystallisation of a celadonitic illite-smectite (up to 63% illite-layers) after treatment with KCl or K-oxalate with increased Al3+ in the tetrahedral sheets, reduced amounts in the octahedral locations and increased fixation of non-exchangeable K+ ions in response to the increased layer charges. K-oxalate complexation of Al3+ and enhanced dissolution of the smectite resulted in the formation of a possible intermediate amorphous phase and illite-smectite crystallites with additional vacant sites explaining the lower number of octahedral ions (<2 per formula unit). Adding 10% pyrite, 10% calcite, or 5% of each, did influence the degree of alteration to a recognisable degree in the presence of KCl, but the effects on the rate of illitisation were minimal when reacted with K-oxalate, which further increased illitisation by up to 6.4 times. Although batch reactor experiments do have limitations compared to complex repository conditions, our results do indicate that claystone host rocks low in organic matter should be favoured over organic-rich lithologies that are likely to contain oxalate ligands or similar catalysing compounds.

Tiebas Castle’ tuiles vernissées: Characterization, raw clay provenance, and manufacturing technology

Tiebas Castle was built between 1254 and 1264 as a royal residence of the kings of Navarre. The Castle was decorated with architectural luxuries imported from the French court. Some decorative elements of this French style are the polychrome roof tiles, called tuiles vernissées; and the glazed floor tiles, called carreaux de pavement. Both are the unique that have been found in the Iberian Peninsula. Elemental and mineralogical analysis allowed us to distinguish two different types of pastes that were used for both tuiles vernissées and carreaux de pavement: yellowish and reddish. The reddish paste was composed mainly of quartz, and to a lesser extent of haematite and illite. The yellow pastes were very rich in calcite and other calcium-bearing minerals (gehlenite, anorthite, diopside or wollastonite) and poorer in quartz and haematite. The different colour tones of the yellow paste samples allowed them to be classified into five subgroups (YP-1, YP-2, YP-3, YP-4, and YP-5). This classification turned out to coincide with a somewhat different mineral composition. The study of the mineral phases newly formed (gehlenite, anorthite, diopside and wollastonite) or destroyed (illite) during firing allowed us to estimate the maximum firing temperature of each of the subgroups. The temperature ranges for each subgroup were as follows: 750–800 °C (YP-5), 850–900 °C (YP-4), 900–925 °C (YP-3), 925–950 °C (YP-2), and 950–1000 °C (YP-1). The study of its possible raw materials allowed us to identify that the yellow pastes from tuiles vernissées and carreaux de pavement were prepared from a mixture of two clays. One of them was the decalcification clay (A15 clay) with which they also made the reddish pastes. The other component of the mixture was the marl from Castle hill. The proportion that the artisans used of both raw materials was 1:2 (twice as much marl as decalcification clay).

Assessment of the spaceborne EnMAP hyperspectral data for alteration mineral mapping: A case study of the Reko Diq porphyry Cu[sbnd]Au deposit, Pakistan

For over four decades, spaceborne multispectral data have played a crucial role in supporting mineral exploration and geologic mapping. The spaceborne multispectral datasets, however, have a restricted number of bands with coarse spectral resolution and, thus are very limited in mineral mapping. The advent of high-quality spaceborne imaging spectroscopic data like the Environmental Mapping and Analysis Program (EnMAP), has bridged this gap initiating a new era in global hyperspectral mineral mapping. The EnMAP satellite, operational since November 2022, covers the spectral range of 420 and 2450 nm in 224 bands, offering a spatial resolution of 30 m and a mean spectral sampling distance of 8.1 and 12.5 nm in the visible-near infrared and shortwave infrared regions, respectively. In this paper, we demonstrate the enhanced mapping capabilities of EnMAP using datasets acquired over the Reko Diq mining district, a cluster of Miocene porphyries located in Pakistan's Chagai Belt hosting an undeveloped world-class porphyry Cu-Au ± Mo deposit. The EnMAP's Level 2A data product was processed using the polynomial fitting technique to characterize the diagnostic absorption features of the alteration minerals in the Reko Diq porphyry system. This involved retrieving the minimum wavelength, depth, width, and asymmetry parameters for key absorption features and employing them interactively for mineral characterization. A diverse array of minerals were successfully mapped over the study area and validated by ground spectroscopy. This includes abundance/composition maps for white micas, chlorite, epidote, calcite, kaolinite, gypsum, jarosite, and ferric and ferrous iron minerals. The minimum wavelength of white mica was found to vary between 2195 and 2210 nm, with the shorter wavelengths (Al-rich) white mica occurring proximal to the known mineralized zones. The potassic alteration cores and the outer propylitic zones were identified by the ferrous iron and chlorite-epidote-calcite mineral maps, respectively. This study demonstrated the superiority of EnMAP hyperspectral data in delineating the alteration mineralogy and zonation pattern of porphyry copper systems. This capability can potentially contribute to the exploration of new deposits in exposed terrains worldwide.

Effectiveness of Using Calcite as an Aerosol to Remediate the Urban Heat Island

The purpose of this study was to develop analytical tools to find the effectiveness of using aerosols to mitigate the urban heat island effect. Specifically, mineral calcite would be placed in a plume over cities to reflect solar radiation. A secondary goal is to compare the relative efficiencies of releasing the particles from tower heights or from aircraft heights. The aim is to reduce daytime temperatures at the surface. The method was to use a one-dimensional model or a single-column model to predict temperatures and weather conditions at all altitudes over a period of one month. The SCAM6 code was altered to incorporate the new capabilities for introduced aerosols. The pre-existing code considered only windblown dust, so the code was enhanced to handle aerosols that were intentionally produced. The key findings are that calcite as an aerosol does affect the weather. The models predict that in humid regions, calcite is less effective because it interacts with water clouds. In arid regions, calcite should be more effective since there are fewer water clouds to interact with. The result is that it is possible to predict reductions in air temperatures if solar insolation can be reduced. It was shown that temperatures can be reduced by 4 °C in arid regions. The conclusions are that calcite aerosol should be effective at mitigating urban heat islands. However, further work is needed related to economic, health, and ecological concerns.