Environmental and Earth Sciences

Abstract: Accurate prediction of gold enrichment is critical for mineral exploration and resource evaluation, particularly in data-limited environments where only geochemical information is available. This study evaluates machine learning (ML) models against linear baselines for predicting relative gold enrichment defined as ln(Au/G10), where G10 represents the geometric mean of ten predictor elements (S, Fe, Al, Si, Mn, Sr, Ni, Cu, K, Ti). A total of 53,126 samples from a sulphide-hosted orogenic gold system were subjected to compositional data analysis (CoDA) preprocessing, including multiplicative replacement of below-detection values, closure to a constant sum, centred log-ratio (CLR) transformation of predictor variables, and robust outlier filtering using the Minimum Covariance Determinant (MCD) method. After screening, 41,626 samples were retained for modelling. Comparative modelling included linear baselines—Ordinary Least Squares (OLS), Ridge, Lasso, and Huber—and non-linear ML algorithms: Random Forest (RF), Support Vector Regression (SVR), k-Nearest Neighbours (kNN), and Multi-Layer Perceptron (MLP). Under the non-circular formulation, nonlinear models consistently outperformed linear baselines. Random Forest achieved the strongest validation performance (R2 ≈ 0.51), followed closely by MLP and SVR, while linear models remained substantially weaker (R2 ≈ 0.31). SHapley Additive exPlanations (SHAP) applied to the Random Forest model identified sulphur (S) and iron (Fe) as the most influential predictors, consistent with sulphide-controlled gold mineralization processes in orogenic systems. The model predicts relative gold enrichment based solely on multielement geochemistry, providing a robust and interpretable proxy for mineralization intensity in data-constrained environments. This study demonstrates that machine learning models, when combined with CoDA-correct preprocessing and a non-circular target formulation, can provide geologically meaningful and methodologically robust predictions of gold enrichment. The workflow offers a transparent and reproducible framework for early-stage exploration targeting using multielement geochemistry.

Abstract: This study investigates the provenance, weathering history, and tectono-sedimentary evolution of Lower Ediacaran siliciclastic rocks of the Imiter Formation (Saghro Group, Imiter Sub-inlier, Anti-Atlas, Morocco) deposited along the northern margin of Gondwana. An integrated approach combining petrography, whole-rock major and trace element geochemistry, rare earth elements (REE), Sm–Nd isotopes, and organic geochemistry (TOC and δ¹³Cₒᵣg) was used to constrain sediment sources and deposi-tional conditions. Geochemical proxies, including Th/Sc, La/Sc, and Zr/Sc ratios, to-gether with REE distribution patterns, indicate that the sediments were mainly derived from felsic to intermediate rocks of the upper continental crust, with only minor sedi-ment recycling. The negative εNd(t) values (−8.5 to −6.2) and Paleoproterozoic Nd model ages (1.6–2.1 Ga) further suggest erosion of evolved crustal sources related to the West African Craton. Weathering indices (CIA, CIW, PIA) suggest weak to moder-ate chemical weathering under predominantly arid conditions. Redox-sensitive proxies (V–Ni, V/Cr, V/(V+Ni)) and low TOC contents (0.1–0.3 wt.%) indicate deposition under mainly oxic to dysoxic conditions with only transient reducing episodes. Tectonic dis-crimination diagrams, supported by regional magmatism, point to sedimentation within an extensional basin evolving from active margin to continental rift conditions during the late Pan-African orogeny. The Imiter Formation records a system dominat-ed by crustal recycling, syn-rift tectonics, and dynamic redox conditions in a shallow marine environment.

Abstract: To reveal the solute sources, migration and enrichment mechanisms of water bodies in the endorheic lake region of the Qiangtang Plateau, Tibetan Plateau, and to clarify the hydrogeochemical cycling patterns in alpine arid zones, this study took typical en-dorheic lake areas in the region as the research object, conducted a systematic hydro-geological survey, collected 28 groups of water samples of various types (including springs, rivers, thermal springs, freshwater lakes, salt lake brines, atmospheric precip-itation and glacial meltwater), tested their major ions, trace elements and physical properties, and comprehensively investigated the hydrogeochemical characteristics, evolution laws and solute sources of water bodies, quantified the dominant control-ling factors and established a conceptual hydrogeochemical model by combining methods such as PHREEQC modeling, principal component analysis (PCA) and Pear-son correlation analysis; the results show that water bodies in the study area exhibit a distinct evolutionary gradient, from the low-salinity HCO₃-Ca recharge end-member, through transitional HCO₃·SO₄-Ca(Mg) water, to highly mineralized Cl-Na(SO₄·Cl-Na) salt lake brine, with synchronous enrichment of Li, B, As and other elements; solute sources are controlled by a ternary coupling mechanism of evaporative concentration, rock weathering and leaching, and deep geothermal fluid input, while cation ex-change and mineral dissolution-precipitation further regulate ionic ratios; As, Li, B and Cl⁻ display conservative migration in non-hydrothermal waters, whereas thermal springs show unique geochemical signatures due to the input of deep-seated fluids; PCA reveals that evaporative concentration (contribution rate 55.39%) is the dominant controlling factor, rock weathering (17.09%) provides the basic solute load, and the coupled process of deep fluid mixing and carbonate precipitation (14.21%) regulates elemental fractionation, and this study constructs a conceptual model of "multi-source recharge–water–rock interaction–evaporative concentration", which clarifies the evo-lutionary laws of regional water bodies and provides a scientific basis for water cycle research and green exploration of strategic mineral resources in salt lakes of the en-dorheic regions on the plateau.

Abstract: Geochemical anomaly detection plays a critical role in mineral exploration, yet conven-tional methods are often limited by compositional effects, sensitivity to outliers, and in-sufficient consideration of spatial relationships. To address these issues, this study pro-poses an integrated analytical framework that combines compositional data analysis and spatial statistics for robust geochemical anomaly identification. The framework incor-porates isometric log-ratio (ILR) transformation to eliminate the closure effect, robust principal component analysis (RPCA) to extract stable geochemical patterns, local indi-cators of spatial association (LISA) to characterize spatial clustering, and compositional balance analysis (CoBA) to enhance anomaly signals. The method is applied to the Barkol Lake area in the Eastern Tianshan, a key metallogenic belt within the Central Asian Orogenic Belt. The results reveal significant geochemical anomalies characterized by Cu-associated element assemblages (e.g., Cu–Ni–Cr), which are spatially correlated with major fault zones and volcanic–intrusive complexes. The identified anomalies show strong consistency with known mineral occurrences and delineate several prospective targets for copper polymetallic mineralization. Compared with conventional approaches, the proposed framework demonstrates improved robustness to outliers, enhanced sensi-tivity to weak anomalies, and better integration of compositional and spatial constraints. These advantages highlight its effectiveness for geochemical anomaly detection and mineral prospectivity mapping in complex geological settings.

Abstract: The Late Triassic Bolila Formation in the central Qiangtang Basin is a critical carbonate succession, yet its depositional age and reservoir‑forming mechanisms have long been contentious. This study presents an integrated sedimentological, detrital zircon U–Pb geochronological, carbon‑oxygen isotopic, and reservoir petrological investigation of the Quemudongda section. Detrital zircon ages constrain the deposition to 225.7–235.7 Ma (Carnian–Norian), correcting its previous Jurassic assignment. Stable carbon and oxygen isotope signatures (δ¹³C up to +4.0‰, δ¹⁸O as low as –14.3‰) corroborate the Late Triassic age and indicate a warm, humid paleoenvironment. The section reveals a steep‑rimmed platform‑margin association dominated by hexactinellid‑calcareous sponge reefs intercalated with seven slump‑breccia layers, recording three evolutionary stages from reef initiation to decline. Reservoir properties are controlled by the interplay of sedimentation, dolomitization, and fracturing. Early dolomitization generated intercrystalline porosity, but subsequent high‑temperature burial recrystallization produced xenotopic textures that severely reduced matrix porosity (average 2.8%). Tectonic microfractures provide the main permeability pathways (0.001–8.5 mD), resulting in a fracture–pore dual‑porosity system. Breccia dolostone exhibits significantly better physical properties (average porosity 3.71%, permeability 2.412 mD) than reef dolostone. The platform‑margin reef‑shoal complex, overlain by Bagong Formation source rocks, forms a favorable lower‑reservoir / upper‑source assemblage. The breccia dolostone–fracture overlap zone represents the sweet spot for hydrocarbon exploration. These findings offer new insights into carbonate platform‑margin evolution and provide a scientific basis for reservoir prediction in the Qiangtang Basin.

Abstract: We present a new whole-rock geochemical dataset for intrusive rocks of the late Variscan Serre batholith (Calabria, southern Italy), a well-exposed section of tilted con-tinental crust emplaced between ~305 and 292 Ma. The dataset includes major, trace and rare earth element (REE) analyses for 74 samples collected from the main plutonic units, ranging from tonalites and quartz-diorites at deeper structural levels to peraluminous granites at shallower levels, as well as leucosomes from associated migmatitic metase-diments. Analytical data were obtained using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). The dataset integrates new and previously published geochemical data into a con-sistent and reusable format, including sample locations (WGS84), lithological classification and stratigraphic attribution. Sampling sites are also provided as a downloadable geo-spatial (.kmz) file for visualization in GIS platforms. The dataset is made available as a supplementary Excel file. These data are intended to support a wide range of applications, including petro-genetic studies of granitoid magmatism and investigations of water–rock interaction processes in crystalline aquifers. The dataset represents a valuable resource for both fundamental and applied geoscientific research.

Abstract: With growing global REE demand, the investigation of cryptic clay-hosted rare earth element (REE) enrichment provides a better understanding of potential new prospects. This study is focused on novel REE enrichment (up to 1.38 wt.% TREO) identified in the regolith overlying the Doradilla Sn skarn prospect, northern New South Wales, Australia. The REE mode of occurrence was investigated through petrographic, field emission scanning electron microscopy (FE-SEM), micro-X-ray fluorescence (µ-XRF), and Laser Raman analyses. Secondary REE-bearing phosphate minerals are the dominant host of the REE in the regolith at Doradilla. The presence of water identified through Laser Raman confirms these minerals as rhabdophane-(La) (La(LREE,Ca)(PO₄)·_nH₂O), hosting most LREE, and churchite-(Y) (Y(HREE,Ca)(PO₄)·2H₂O), hosting most HREE. Through confirming the majority of REE being hosted in hydrated, and therefore, secondary minerals, this cryptic REE-enrichment is confirmed to be the result of secondary mineralization driven entirely by regolith-derived processes. This study highlights the importance of detailed mineral characterization in confirming the deportment of REEs in clay-hosted settings, and suggests that new protoliths (in this case a Sn skarn) have the potential to form significant, secondary REE enrichment in the overlying clay-hosted, regolith environment.

Abstract: Debris avalanche deposits related to the edifice collapse of the summit area of Zao Volcano have been identified for the first time at the volcano’s eastern foot. These deposits extend approximately 11–15 km from the summit. Based on their spatial distribution and clast petrology, the deposits are interpreted to have originated from the Umanose caldera. Deposit thickness ranges from 20–30 m in the western and northern parts to over 50 m in the eastern part, with an estimated volume of approximately 0.3 km³, comparable to that of the summit caldera depression. Matrix facies occur at most outcrops, whereas block facies are found at only three sites. The vertical drop-to-runout distance ratio (H/L) is less than 0.09, which falls within the typical range for debris avalanches but indicates relatively high mobility. Based on its volume and stratigraphic relationships, the collapse is interpreted to have been caused either by a phreatic eruption or by a non-eruptive large-scale failure of a hydrothermally altered zone beneath the summit area. The collapse is considered to mark the onset of the latest activity stage of Zao Volcano, and the petrological characteristics of the magma differ markedly from those of the preceding stage.

Abstract: The Paleozoic rocks of Egypt's Western Desert remain under limited exploration. Complex subsurface structures create stratigraphic challenges that hinder petroleum exploration. Organic microfacies analysis offers a precise and effective tool to address these challenges and enhance our understanding of environmental changes. The Faghur-1X well penetrated the Devonian Zeitoun Formation, yielding numerous successful core recoveries. Seven of these cores were analyzed to delineate lithological and stratigraphical variations. Three distinct organic microfacies types were identified within the studied section. These organic microfacies reveal significant paleoenvironmental shifts that represent key correlative events within the Devonian. These include liptinite-dominated-medium organic density distal facies (A) (cores 19-A, 18-B, 17-A); vitrinite-dominated-high organic density proximal facies (B) (cores 14-A, 20-A/Band 20-C); ironstone rich and low organic density condensed section/distal facies (cores 18-A, 16-A, 15-A, 15-B). These organic facies exhibit unique characteristics resulting from the interaction of organic matter with the rock matrix and environmental processes. These unique characteristics facilitate intra-basinal stratigraphic correlation. While commonly applied to hydrocarbon source rock evaluation, this study investigates the stratigraphic significance of organic microfacies for resolving subsurface geological problems.

Abstract: The origin of uranium-series imbalance and radiogenic lead excess has long been a subject of debate. Here, based on a novel theory of neutrino oscillation-induced radioactive decay and magma formation, a unified mechanism is proposed to explain uranium-series imbalance, radiogenic lead excess, and excess argon formation. This mechanism indicates that magma originates from the upper mantle, formed by the melting of its constituent materials due to accelerated radioactive decay induced by atmospheric neutrino oscillations. During magma formation, radioactive decay rates typically increase due to Mikheyev-Smirnov-Wolfenstein (MSW) resonance perturbations from neutrino oscillations. This effect causes radioactive isotopes to decay over a shorter period than their normal half-lives would suggest, resulting in overestimated ages based on decay laws. Consequently, radioactive daughter isotopes and radiogenic isotopes become enriched relative to their parent isotopes. The accelerated melting of radioactive materials due to increased decay rates means that both the excess of radioactive daughter isotopes and radiogenic isotopes accompany the magma formation process. When using radiometric dating, careful consideration of the mineral's formation environment is essential. Generally, minerals formed in the crust or at the Earth's surface exhibit relatively normal radiometric ages, whereas minerals formed in the mantle or glassy materials solidified from magma tend to show radiometric ages that are older to varying degrees.

Abstract: The Upper Campanian phosphorite series in Egypt, which overlies the Nubian Group, exhibits pronounced lateral lithological variations. Glauconitic, dolomitic, calcareous, and cherty sediments, together with bituminous shales, form diverse lithofacies associations that reflect the region's complex depositional environments. These lithofacies, associated with the Duwi Formation, are marine deposits originally formed in anoxic, organic-rich environments and later reworked into shallower, oxygenated settings during sea-level fluctuations. This study presents a detailed geological, petrographic, and geochemical characterization of these phosphorite deposits in North Aswan, Egypt, across five localities: Wadi Hilal, East Sibaiya, Um Higarah, Um Salama, and Um Tundbah. The lithostratigraphic succession is dominated by the Upper Cretaceous Duwi Formation, which unconformably overlies the Middle-Campanian Qusseir shale and conformably underlies the Middle-Maastrichtian Dakhla shale. Petrographically, the phosphorites comprise phosphatic grains (pellets and bioclasts such as bone fragments and shark teeth), non-phosphatic grains (quartz), and cements of silica, calcite, and iron oxides. Geochemically, P₂O₅ content ranges from 17.4 to 31.24%, uranium concentrations vary between 40.59 and 245.84 ppm, and total rare earth elements (∑REEs) range from 47.83 to 270.37 ppm. The studied phosphorites are suitable for phosphoric acid production, with potential for uranium recovery as a by-product.

Abstract: The Idrija mercury deposit represents one of the largest mercury formations globally, ranking second only to the Almadén deposit in Spain. The deposit has been exploited for more than five centuries and represents one of the most historically significant and extensively studied mercury mines worldwide. The Karoli orebody is characterized by a high abundance of pyrite (from 50 to 90%) and exceptionally rich cinnabar mineralization, with mercury contents locally reaching up to 78%. This study aims to provide a preliminary yet detailed characterization of the ores from the Idrija mercury deposit and to establish their textural and genetic characteristics. We implemented microscopic examination of thin sections, complemented by LA-ICP-MS trace element analyses of pyrite. Three different pyrite types were identified: fine-grained framboidal Py1, subhedral to euhedral Py2, and larger, well-developed euhedral Py3. LA-ICP-MS analysis of Py3 pyrite grains revealed low trace element concentrations, with maximum values remaining below 100 ppm. These observations suggest that the hydrothermal fluids were mercury-rich but of low salinity, which may have limited the incorporation of trace elements into pyrite. Our research provides new insights into the formation of the Karoli orebody. We envision that further investigations of fluid composition, salinity, and fluid inclusions could significantly enhance understanding of the Idrija mercury formation and evolution.

Abstract: The Wailukum area in North Maluku Province, Indonesia, is an ultramafic rock complex with a high degree of serpentinization. The mineral composition of ultramafic and mafic rocks strongly influences scandium (Sc) distribution and enrichment during lateritization. This study aims to analyze the element distribution, mineral composition, and rock identification in three types of geological materials in a lateritic profile which contains Sc, specifically bedrock, saprolite, and limonite. The analytical methods used are petrography, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). Results show that in the bedrock, Sc is mainly associated with clinopyroxene minerals such as augite and diopside. In the saprolite, Sc content decreases due to higher mobility but remains partly associated with clinopyroxene. In the limonite zone, Sc reaches maximum enrichment. Among rock types, gabbro contains the highest absolute Sc concentration (23.25 ppm in bedrock and up to 58.5 ppm in limonite), while wehrlite records the greatest enrichment ratio, with a 9.18-fold increase from bedrock to limonite. In contrast, gabbro shows the lowest enrichment ratio (2.52-fold) despite its high initial Sc content. These patterns indicate that Sc enrichment is controlled by clinopyroxene as the primary host in bedrock, its relative stability during weathering.

Abstract:

Post-collisional Cu-Au-Ni-Co-Pt-Pd-Sc porphyry, [Duck Creek porphyry system (DCPS)], with overlying Au-Te-Bi-W-HRE epithermal mineralisation, [Highway epithermal system (HES)] has been discovered in the core of the Mitakoodi anticline, southwest of Cloncurry. Xenotime and monazite geochronology indicates mineralisation occurred between ~1490 and 1530 Ma. Host rock lithologies show widespread potassic and/or propylitic to phyllic alteration. Paragenesis of porphyry sulphides indicate early crystallisation of pyrite, followed by chalcopyrite, with bornite forming by hydrothermal alteration chalcopyrite. Cu sulphides also show the effect of supergene oxidation alteration with rims of covellite, digenite and chalcocite. Redox conditions deduced from V/Sc systematics indicate that the DCPS contains both highly oxidized (typical of porphyries) and reduced lithologies, typical of plume generated tholeiitic and alkaline suites. Ni/Te and Cu/Te systematics plot within the fields defined by epithermal and porphyry deposits. Duck Creek chalcophile and highly siderophile element (Cu, MgO and Pd) systematics resemble data from porphyry mineral systems, at Cadia, Bingham Canyon, Grasberg, Skouries, Kalmakyr, Elaisite, Assarel and Medet. SAM geophysical inversion models suggest the presence of an extensive porphyry system below the HES. A progressive increase in molar Cu/Au ratios with depth from the HES to the DCPS, supports this conclusion. Three metal sources contributed to the DCPS-HES viz., tholeiitic ferrogabbro, potassic ultramafic to mafic system and a Fe and Ca-rich alkaline system. The latter two imparted non-crustal superchondritic Nb/Ta ratios that are characteristic of many deposits in the eastern Mount Isa Block. The associated tholeiite and alkaline magmatism reflect mantle plume upwelling through a palaeo-slab window that had accreted below the eastern flank of the North Australian craton following west verging collision by the Numil Terrane. Discovery of this linked mineral system provides a new paradigm for mineral exploration in the region.

Abstract: Papua New Guinea is one of the least studied regions in the Southwest Pacific, and large areas of the country, such as the Fly Plat-form, remain poorly understood due to limited exposure and access constraints. This study presents the first documentation of basaltic volcanism on the Fly Platform, based on new field discoveries at Mea-hill and Yemsigi, two areas located approximately 25 km apart. Inte-grated field observations, petrography, mineral chemistry, and whole-rock geochemistry show that both basalt suites were derived from a similar magma source but record contrasting emplacement histories. Meahill basalts, which include welded tuffs and highly ve-sicular basalt units, reflect rapid magma ascent, vigorous degassing, and locally explosive activity. In contrast, the massive, less vesicular porphyritic basalts at Yemsigi preserve a quieter emplacement history, but with more extensive post-magmatic alteration. Geochemical sig-natures from least altered rocks of both suites support an intraplate origin with similarities to Pliocene-Pleistocene lava fields of Northeast Queensland. The origin of the intra-plate basaltic magmatism is enig-matic, but both young volcanic provinces correlate spatially with a lower mantle anomaly that may represent residual slab material and a seated-seated magma source. These findings provide further insight into the tectono-magmatic evolution of the Fly Platform region and highlight the need for continued geological investigation in this underexplored district.

Abstract: ligocene rocks and fluids of A-1X well were conducted for source rock and fluid characterization and implying the suitable geological sites for CO2 storage from high-salinity water in sandstone reservoirs based on Rock-Eval pyrolysis, vitrinite reflectance measurement, bitumen extraction, hydrocarbon fractionation, gas chromatography, stable carbon isotope, formation water and X-Ray Diffraction analyses. Shale source rocks reveal fairly good potential of hydrocarbon generation. Compositions of gas sample in gas-related zones 1010-1110m are mainly composed of CH4, following C2+, N2, and a little content of CO2 and no noticeable of H2S. Carbon isotopes of oil and gas samples reveal the organic matters mainly derived from sapropelic and little humic sources, entering the mature stage to oil window phases. The formation water is classified as Calcium-Chloride type that contain high concentrations of total dissolved solid, salinity, and K+, Na+ and Cl- cations. This formation water is associated with deep source, and close system that are effective conditions for a large pool with good sealing capacity and not impacted by dissolution of the salt rock around. Most sandstones comprise very high visual porosities including high quartz, plagioclase and calcite minerals that are favorable conditions for subsurface pore space and CO2 injection in over saturated fluids. The popular presence of brittle minerals in the upper part of strongly fractured basement indicates this could be a good sandstone reservoir. The finding is identification of suitable candidate for storing CO2 in the saline aquifer under the active petroleum system with current oil and gas accumulations.

Abstract: Geochemical, petrographic, and geochronological analyses of granitoids from Kan-chanaburi Province, western Thailand, reveal key insights into magmatic evolution and metallogenesis within the Western Granite Belt. U–Pb zircon dating identifies two main magmatic episodes: Late Triassic (227-214 Ma), and Late Cretaceous (79-68 Ma). The granitoids, including quartz monzonite, granodiorite, and quartz-rich gran-ite, are composed of quartz, plagioclase, K-feldspar, and biotite, with minor horn-blende and accessory minerals such as titanite, zircon, magnetite, ilmenite, and garnet. Magnetic susceptibility values (0.0001 × 10-3 to 0.0199 × 10-3 SI units) indicate pre-dominantly ilmenite-series granitoids, with localized magnetite-series occurrences. Geochemical data classify these intermediate to felsic plutonic rocks as calc-alkaline to shoshonitic, with a peraluminous, S-type affinity. U-Pb cassiterite and wolframite ages of 80-77 Ma suggest that W-Sn mineralization occurred during the Late Cretaceous at early-stage magmatism. The temporal and spatial distribution of these granitoids is closely linked to Pb–Zn–W–Sn mineralization, reflecting the influence of post-collisional magmatism on regional metallogenesis in the Sibumasu Terrane. This study refines the tectono-magmatic framework of western Thailand and underscores the importance of granitoid emplacement timing in controlling mineral deposit for-mation.

Abstract:

Water quality assessment is crucial for the sustainable use and management of groundwater resources. This study was carried out in the irrigated plains of Vehari District, Punjab, Pakistan, to evaluate groundwater suitability for a managed aquifer recharge (MAR) project. Twenty-three groundwater samples were collected in June 2021 from an area of 1,522 km² and analyzed for major physicochemical parameters including electrical conductivity (EC), total dissolved solids (TDS), pH, turbidity, calcium (Ca), magnesium (Mg), chloride (Cl), alkalinity (Alk), bicarbonate (HCO₃⁻), hardness, potassium (K), sulphate (SO₄²⁻), sodium (Na), and nitrate (NO₃⁻). Water quality was assessed using WHO and PID standards, alongside derived hydrochemical indices such as sodium percentage (%Na), Kelley’s ratio (KR), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and the water quality index (WQI). The dataset was interpreted using geo-statistical, geospatial, multivariate, and correlation analyses. Cation and anion dominance followed the order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > SO₄²⁻ > Cl⁻ > NO₃⁻. WQI results showed that 35% of samples indicate “poor,” 50% “very poor,” and 15% “unsuitable” drinking-water quality. However, irrigation suitability indices confirmed that groundwater is generally acceptable for agricultural use, though unfit for drinking. The outcomes of this study provide essential insights for groundwater management in the region, where the Punjab Irrigation Department (PID) has initiated a MAR project. Considering that the irrigation sector is the major groundwater consumer in the area, the compatibility of groundwater and surface water quality supports the implementation of MAR to enhance agricultural sustainability.

Abstract: Detailed geochemical modelling of the potential groundwater impacts of CO2 geo-sequestration requires site-specific knowledge of how mobile elements are hosted within rocks. We present a simple sequential extraction procedure analogous to pH conditions produced by different partial pressures of carbon dioxide (CO2) in contact with water. The procedure consists of three sequential steps: Water at pH 7; acetic acid–ammonium acetate at pH 5 and then at pH 3, with the amounts of specific elements extracted by each step considered with respect to whole-rock total element abundance. Our purpose in developing this procedure is three-fold: 1) identify readily mobilised suites of elements for groundwater baseline and monitor bore studies; 2) provide insights regarding the mode/s of occurrence of easily extracted elements within rock samples; and 3) suggest possible mechanisms for the mobilisation of rock-sourced elements into groundwater under neutral to moderately acidic pH that can inform reactive transport modelling of carbon storage sites. In our case study, the second step extracted most of the main mobile elements of interest.

Abstract: Birnessite is a layered manganese oxide with strong oxidizing ability, but the electronic reason for this property is still unclear. In this work, eight birnessite samples with different interlayer cations and Mn(III)/Mn(IV) ratios were studied to explore how electron affinity (EA) affects oxidation behavior. The samples were examined by XRD, XPS, SEM and UPS, and oxidation tests were carried out with Fe(II) and phenol under controlled pH and temperature. The electron affinity values ranged from 5.52 to 5.93 eV, increasing from Na⁺- to K⁺-, Ca²⁺- and Mg²⁺-birnessite. Samples with higher EA showed faster oxidation, and the Fe(II) removal rate was about 2.1 times higher than that of low-EA samples. The relationship between EA and rate constant followed an exponential trend (R² = 0.96). Surface and spectral data showed that samples with higher EA had slower Mn(IV) loss and later surface passivation. These results show that electron affinity controls the oxidizing ability of birnessite and can be used to predict and improve the performance of manganese oxides in pollutant removal and catalytic oxidation.