Search Results (58)

Glauconite-rich sands can generate authigenic clays during burial, as glauconite breaks down and supplies material for smectite that may subsequently transform into illite. The smectite-to-illite transformation is a key burial diagenetic reaction that strongly influences sandstone reservoir quality; however, the reaction pathways and resulting textures in glauconite-rich sands remain insufficiently documented. To better constrain illitization in glauconitic systems, we conducted four hydrothermal batch experiments using glauconitic greensand from the Arnager Greensand Formation (Bornholm Island, Denmark), reacted with Red Sea water at 80 °C, 150 °C, 200 °C, and 250 °C for 21 days. Reaction products were characterized using bulk and clay-fraction XRD, XRF, and SEM–EDS, together with pre- and post-reaction fluid chemistry. At 80 °C, early dissolution of glauconite and other detrital components (K-feldspar, muscovite and calcite) was observed, resulting in increased concentrations of dissolved ions in the fluid but no authigenic clay formation. Authigenic smectite first developed at 150 °C, occurring primarily as grain-coating clay. With further heating to 200 °C, smectite began to transform into mixed-layer illite–smectite, accompanied by the first clear development of illite textures. At 250 °C, illitization advanced significantly, and the reacted products were dominated by wavy to fibrous illite. The resulting clay minerals and their grain-coating morphologies are comparable to coatings reported from buried sandstone reservoirs. These findings suggest that glauconite alteration can generate grain-coating clays that may help limit quartz cement growth and preserve porosity. However, the development of wavy/fibrous illite may also obstruct pore spaces and reduce permeability. Overall, glauconite-derived clay evolution may preserve porosity while still degrading permeability, and the net reservoir effect depends on the morphology and distribution (thickness and coverage) of the newly developed clay minerals. Full article

Meeting future material needs requires expanding metal supply while reducing environmental footprints and improving the efficiency of exploration and resource assessment. The Wadi El-Muweih area, located north of the Aswan region in Egypt’s Eastern Desert, hosts significant iron ore potential within the Late Cretaceous Nubia sandstone (Taref Formation). This study provides a systematic, integrated approach for delineating ironstone extensions to support more targeted field campaigns and responsible development pathways. Remote sensing enabled the rapid screening and mapping of iron-bearing zones, subsequently validated through field observations and mineralogical and geochemical analyses. The iron-bearing middle member of the Taref Formation consists of glauconitic/chamositic and ferruginous sandstones, with ironstone bands occurring in three fining-upward cycles. The mineralogical results indicate chamosite, hematite, and goethite as primary constituents, with detrital quartz and apatite in varying proportions. The geochemical data show high Fe₂O₃ (avg. 68.83%) and SiO₂ (avg. 13.13%), with elevated Al₂O₃, CaO, and P₂O₅ compared to Aswan’s oolitic ironstones. The study confirms that massive, oolitic, and conglomeratic ironstone facies formed in a near-shore environment during transgressive–regressive cycles. By combining remote sensing with ground-based validation, the workflow supports sustainable metal technologies by improving discovery efficiency, reducing unnecessary disturbance, and strengthening the geoscientific basis for future iron resource planning. Full article

The Cretaceous dinosaur record from Normandy, in NW France, is reviewed. It includes several enigmatic specimens that were briefly mentioned in short notes published during the 19th and 20th centuries that have since then been destroyed in World War II or lost. Since they were neither described in detail nor illustrated, their identification must remain uncertain, but some may have been ankylosaur remains, while another specimen may have belonged to a bird or a non-avian theropod. Specimens that were properly described and are kept in museums in Normandy come from Albian and Cenomanian horizons in the coastal cliffs of Seine-Maritime. The Albian record, from Cape La Hève (Le Havre) includes an incomplete titanosaurian sauropod skeleton, described as Normanniasaurus genceyi, and an isolated caudal vertebra from the same provenance, probably belonging to that taxon. The Cenomanian record is limited to a group of bones and a tooth of the furileusaurian abelisaurid theropod Caletodraco cottardi from the glauconitic Chalk at Saint-Jouin-Bruneval. All these specimens come from marine sediments and are in all likelihood derived from floating carcasses that drifted over a fairly long distance from an emergent land area corresponding to the Armorican massif in the west. Although scanty, the record from Normandy sheds some light on the poorly known dinosaurs that inhabited north-western Europe during the middle part of the Cretaceous, some of which apparently had Gondwanan affinities. Full article

This paper highlights the findings of the emergency excavation carried out at Avenida Miguel de Cervantes No. 35 in Écija, conducted in two phases between 1999 and 2000 and in 2003. The investigation revealed a domus featuring valuable decorative elements, including pictorial wall paintings and two high-quality mosaics. Stylistic analysis of the wall decorations identified a scheme composed of wide and narrow panels, with a predominance of bright green in the central zone, along with traces of figurative representations. The evidence suggests a second construction phase in the latter half of the 2nd century AD, followed by renovations in the 3rd and 4th centuries. The use of green prevailing monochromy appears to be associated with high-status representational spaces. A total of six samples from the wall paintings and mortars were analysed. X-ray diffraction (XRPD) and X-ray fluorescence (XRF) were employed for a minimally destructive preliminary study of the mortars, while confocal microscopy was used to observe the sequence in which the pigments were applied, and Raman spectroscopy enabled the identification of the pigments, notably highlighting glauconite as the green pigment. Full article

This review provides a comprehensive analysis of the petrophysical controls influencing greensand reservoirs, with an emphasis on the role of glauconite and associated clay minerals in determining porosity, permeability, and water saturation. Greensands contain iron-rich clay minerals that exert paramagnetic and conductive effects, challenging conventional well-log interpretations and often leading to biased estimates of reservoir parameters. Several challenges for petrophysical property measurements are faced in the laboratory due to clay-induced pore-throat obstruction and microporosity, which underscores the importance of tailored interpretation workflows and data integration. In this paper we highlight the necessity of integrated approaches such as combining core analysis, spectral gamma-ray, and nuclear magnetic resonance (NMR) logging with conventional well logs to calibrate petrophysical models using shale–sand water saturation models, such as Waxman–Smits and Simandoux, to better characterise economical pay zones. Finally, future research directions are indicated, which include refining the calibration of saturation and permeability models, advancing rock-typing methodologies, and understanding mineralogical influences on reservoir quality to optimise hydrocarbon recovery from greensand reservoirs. Full article

The Cenomanian Bahariya Formation exposed at Gebel El Dist in the Western Desert of Egypt provides valuable surface analogues for evaluating the reservoir quality of subsurface Bahariya sandstones. The formation was analyzed using 27 oriented samples and 91 core plugs from quartz arenite (QA) and quartz wacke (QW) facies. Analyses included XRD, petrography, SEM, helium porosity–permeability, and capillary tests, as well as measurements of pore-throat radii (R) at 35% and 36% mercury saturation. X-ray diffraction analyses reveal a heterogeneous mineral composition dominated by quartz, feldspars, dolomite, pyrite, siderite, goethite, hematite, clay minerals, glauconite, and gypsum. QA displays higher porosity and permeability than QW, along with larger pore radii, and lower specific surface area per unit pore volume (Spv) and per unit grain volume (Sgv). Multivariate regression equations, specific to each facies, were developed to convert standardized XRD mineral percentages directly into pore-system and flow attributes (ϕ, k, r, Spv, Sgv, R35, R36), quantifying capillary-based recovery contrasts between facies. Across both facies, regressions linking mineralogy to ϕ, k, r, Spv, Sgv, R35, and R36 are strong (R² = 0.78–1.00). The established predictive equations provide a low-cost method to estimate reservoir quality from mineralogy alone, enabling rapid screening of Cenomanian Bahariya analogues and similar clastic reservoirs where core data are limited. Full article

Historically, clays have been widely used for the treatment of wounds and to stop hemorrhaging. The aim of this study was to combine four natural clay minerals (kaolinite, glauconite, montmorillonite, and bentonite) with magnetite (Fe₃O₄) nanoparticles to produce Fe₃O₄–clay complexes with enhanced antimicrobial properties and chemopreventive activity against melanoma. The magnetite–clay complexes were synthesized by the chemical co-precipitation method and characterized using XRD, TEM, STEM-EDS, SEM, and SQUID magnetometer. Antimicrobial properties were determined by evaluation of MIC values. The most promising materials were also subjected to direct contact antibacterial test according to the OECD standard for porous materials. Cytotoxicity of the complexes towards melanoma cells and normal human skin fibroblasts was assessed by MTT assay. We performed XRD, which confirmed the formation of Fe₃O₄–clay complex materials. It was also proven that complexes exhibited superparamagnetic properties. Microbiological experiments clearly revealed that modification of natural clays with magnetite significantly boosted their antimicrobial properties. Fe₃O₄–montmorillonite and Fe₃O₄–bentonite showed the strongest antimicrobial activity. Moreover, the mentioned complexes had the ability to reduce the viability of melanoma cells by 35–40%, while exhibiting no cytotoxicity against the normal human fibroblast (BJ) cell line, which is an extremely desirable feature. Thus, it may be concluded that Fe₃O₄–montmorillonite and Fe₃O₄–bentonite complexes hold promise for use in the management of infected wounds and wounds after melanoma excision. Full article

Multiple ironstone beds formed during the Callovian-Oxfordian times as a consequence of intense continental weathering, upwelling, and hydrothermal activity. This study examines the compositional differences between core and rim, and the origin of iron ooids along the northwestern margin of the Neo-Tethys Ocean to highlight sea-level fluctuations, redox conditions, and elemental influx. An integrated sedimentological study, including petrography, mineralogy, micro-texture, and mineral chemistry, was carried out to explain the origin and implications of ironstones. The ~14 m thick Callovian-Oxfordian, marginal marine deposits in the Kutch Basin, in western India, exhibit iron ooids, predominantly formed in oolitic shoals during transgression, associated with lagoonal siliciclastics. Callovian shoals interbedded with lagoonal facies record minor sea-level fluctuations, whereas the Oxfordian deposit records a major transgression and condensation, resulting in extensive ironstone deposits. The ooid cortices and nuclei exhibit distinctive mineralogy and micro-textures: glauconitic smectite exhibits poorly-developed rosettes, chamosite displays flower-like, and goethite shows rod-like features. Three types of ooids are formed: (i) monomineralic ooids are entirely of chamosite or goethite, (ii) quartz-nucleated ooids, and (iii) composite ooids with either chamosite core and goethite rim, or chamosite core and glauconitic smectite rim. The assemblages within iron ooids reflect variation in depositional redox conditions: glauconitic smectite develops under suboxic lagoonal flank, chamosite forms in anoxic central lagoon, and goethite precipitates on oxic shoals. Full article

Glauconite, a diagenetic sedimentary phyllosilicate mineral, holds significant importance in soil science, as it is commonly used in soil characterization (as in greensands) and can be identified in the field by its color and morphology. It is a potential fertilizer, rich in essential macronutrients like potassium, phosphorus, calcium, and numerous micronutrients such as manganese, zinc, copper, cobalt, and nickel. In this meticulously conducted study, we extracted five individual elements (potassium, calcium, magnesium, sodium, and zinc) from washed glauconite samples separated into five different size fractions using a suite of acids. The acids employed were nitric acid, hydrochloric acid, acetic acid, and phosphoric acid, each prepared at the same molarity of 0.1 M. Water was used as the control solubilizing medium. The extractant behavior of the acids was assessed by measuring concentrations of each element by the ICP-OES device. The results demonstrate that nitric acid consistently exhibits the highest efficacy in releasing elements, followed by hydrochloric acid and phosphoric acid, while acetic acid results in the lowest release of these nutrients. These findings support the use of acidification treatment of glauconite, enhancing elemental release and potentially reducing the amount of glauconite needed as an alternative fertilizer, thus adding economic value. Full article

Routine core permeability and porosity are crucial in assessing flow units within a reservoir because they define a reservoir’s storage and flow capacities. A limited amount of work has been conducted on the lower cretaceous (Barremian to Valanginian) sandstones in the Bredasdorp Basin, offshore South Africa, focusing on the flow zones and the possible effect of diagenetic minerals on the individual flow zones, limiting understanding of reservoir quality and fluid flow behavior across the field. Nine hundred routine core analysis datasets were used to determine the flow units within the reservoir from three wells (F-A10, F-A13, and F-O2) from independent methods, namely: the Pore Throat Radius, Flow Zone Indicator, Stratigraphic Modified Lorenz Plot, and Improved Stratigraphic Modified Lorenz Plot. The results showed six flow units: fracture, super-conductive, conductor, semi-conductor, baffle, and semi-barrier. The super-conductive flow units contributed the most flow, whereas the semi-barrier and baffle units contributed the least flow. Petrography analyses revealed that the diagenetic minerals present were smectite, illite, glauconite, siderite, micrite calcite, and chlorite. The pore-filling minerals reduced the pore spaces and affected pore connectivity, significantly affecting the flow contribution of the baffle and semi-barrier units. Micrite calcite and siderite cementation in FU5 of F-A13 and FU9 of F-O2 significantly reduced the intergranular porosity by filling up the pore spaces, resulting in tight flow units with impervious reservoir quality. It was noted that where the flow unit was classified as super-conductive, authigenic clays did not significantly affect porosity and permeability as they only occurred locally. However, calcite and silica cementation significantly affected pore connectivity, where the flow unit was classified as a very low, tight, semi-barrier, or barrier. Full article

The full potential of glauconite-based nanocomposites as micronutrient fertilizers remains underexplored, particularly their interaction with Zn, Cu, and B. Despite the promising applications, the mechanisms of nutrient sorption and their effects on plant growth require further investigation, especially concerning structural changes and nutrient delivery efficiency. This study investigates the modification of glauconite with Zn, Cu, and B solutions to create multifunctional nanocomposites with enhanced properties. It was established that the activation process preserves the primary globular–lamellar morphology of glauconite while introducing structural changes. Nanocomposites were synthesized using chemical activation and characterized using XRD, SEM-EDS, TEM, FTIR, and BET analyses. Agrochemical tests evaluated their effects on oat growth under controlled conditions. Nanocomposites with zinc sulfate exhibited an increase in specific surface area and mesoporosity, enhancing sorption capacity and facilitating the formation of inner-sphere complexes on the mineral’s basal surface. Modification with copper led to the formation of secondary phases, such as sulfates, on the surfaces of microflakes and globules while preserving the crystalline structure with inner-sphere coordination of Cu²⁺. Boron-modified nanocomposites were characterized by localized restructuring, pore channeling, and an increase in mesopore diameter, along with the formation of outer-sphere complexes relative to the basal surface of glauconite. Thermogravimetric and calorimetric analyses with mass spectrometry revealed specific endothermic and exothermic effects, particularly in Zn-modified samples, confirming changes in dehydration energetics. Agricultural tests on oats (Avena sativa) demonstrated the effectiveness of Cu- and B-modified nanocomposites in improving plant growth parameters, including a 7% increase in plant height and a 6.4% increase in dry weight. Zn-modified nanocomposites showed high germination rates (up to 100%) at low dosages but require optimization to avoid phytotoxicity at higher concentrations. The findings highlight the potential of adapting nanocomposites for targeted nutrient release. Additionally, glauconite nanocomposites have potential applications in restoring degraded soils, treating polluted runoff, and developing slow-release agrochemical systems. Full article

This paper aims to explore the current status and development trend of glauconite research through CiteSpace (version 6.2.R3) software tools. Based on the literature records from 1980 to 2024 in the Web of Science Core Collection database, this study visualizes the countries/regions, institutions, authors, journals, literature, and keywords related to glauconite. The results show that the United States, Russia, India, France, and England are the main contributing countries to glauconite research, the Russian Academy of Sciences is the institution with the largest number of publications, and Santanu Banerjee and Gilles S. Odin are the most influential authors. The field of glauconite has a high degree of international cooperation and multidisciplinary cross-disciplinary nature. The research hotspots of glauconite are also identified, including origin, basin, sediments, geochemistry, sandstone, and climate, and emerging research frontiers such as fertilizer, removal, provenance, composition characteristics, and Fe are pointed out. Glauconite research is not only of great significance in the field of geology, but its application potential in environmental management and agricultural development is also gradually being recognized, indicating that this field has broad research and application prospects in the future. Full article

Territorial inventories of geosites remain on the international agenda, and they can help in acquiring information for solving pure geological research tasks. New field investigations in the northern part of Mountainous Adygeya (geoheritage-rich territory in the western Greater Caucasus) permitted us to extend our knowledge of its geosites. Five geosites were described qualitatively and assessed semi-quantitatively, namely the Polkovnitskaya River Valley (ammonite-bearing concretions of Aptian glauconitic sandstones), the Little Khadzhokh River Valley (Aptian glauconitic sandstones with fossils and trace fossils), the Shakhan and Middle Khadzhokh River Valley (Upper Jurassic variegated siliciclastics, Hauterivian fluvial and deltaic sandstones, mixed ancient and modern clastic material), the Big Khadzhoh Waterfall (splendid waterfall and exposures of locally folded Oxfordian–Kimmeridgian limestones), and the Verblyud Mountain (small, camel-shaped cuesta’s remnant). They were ranked nationally (one geosite), regionally (three geosites), and locally (one geosite). Close examination of the considered geosites permitted to register pure geological peculiarities (changes in the dip direction between sedimentary packages), which indicate the tectonic activity across the Jurassic–Cretaceous transition. Additionally, complex accessibility patterns were established in some geosites, and these patterns should be addressed in further refinements of the semi-quantitative approaches to geosite assessment. Full article

Many historic buildings and monuments on the Salento Peninsula (Apulia, southern Italy) were built from locally quarried Miocene calcarenites belonging to the Pietra Leccese Formation (Late Burdigalian–early Messinian). The main facies consists of a homogeneous and porous biomicrite, pale yellow in colour and fine- to medium-grained, very rich in planktonic Foraminifera and massive or thick-bedded in outcrop. Additionally, there are other facies, among which Piromafo stands out for its aesthetic appearance, enhanced by its greenish-brown or greenish-grey colours. Piromafo occurs in the upper part of the Pietra Leccese Fm. and is represented by a fine- to medium-grained glauconitic and phosphatic biomicrite with macrofossils, especially Bivalves and Gastropods. Despite its important historical use as a building and ornamental material, especially in Roman and Baroque architecture, a research gap exists in the scientific literature describing the properties of the stone and their correlation. Therefore, the aim of this paper is to present a wide range of properties useful in explaining the in situ behaviour and damage susceptibility of the stone in monuments and buildings, but also to assist in selecting preservation treatments and strategies. An overall assessment of the main petrophysical and mechanical properties, especially for restoration/conservation purposes, was performed using both standard and unconventional techniques. Starting with rock fabric inspection, particular attention was given to the relationship between the pore size distribution and the hydraulic and thermal properties of the material. Unconfined compressive strength, flexural strength, and indirect tensile strength were also estimated. The findings reveal a significant correlation between the pore size distribution and the hydraulic and thermal properties of Piromafo, impacting its durability and suitability for use in conservation. Specifically, the thermal properties, influenced by the mineral composition and fabric, indicate the potential for using Piromafo as an effective refractory and insulation material, which justifies the origin of its name and confirms what is already stated in the specific literature. Additionally, correlations were proposed among the various mechanical parameters evaluated, including the Schmidt hammer rebound values with compressive strength and tangent modulus. The mechanical analysis shows that the material possesses adequate properties for structural applications. Full article

Studies of the mineralogical composition were carried out, and the features of the clays from the deposits of Kazakhstan were established using Mössbauer spectroscopy (MS) and X-ray diffraction analysis (XRD). According to the XRD results, all the samples were mixed-layer clays of the kaolinite–illite type. The lattice parameters of the kaolinite were determined, and it was shown that its structure was disordered and contained a certain amount of impurity in some of the clay samples. A special feature of two of the samples was the additionally identified muscovite polytype 2M₁. The spectra of the iron-containing clays were amenable to being resolved into separate components, with similar Mössbauer parameters of the kaolinite, muscovite, illite, and glauconite. The oxidation state of the iron was determined using MS. The predominant part of paramagnetic iron in most samples was in the trivalent state. The primary minerals contributing to Fe²⁺ were illite and muscovite. The results obtained during the study of the clay samples with complex mineralogical compositions using MS and XRD methods both complemented one another and were found to be in good agreement. Full article