Ioan Vasile Sanislav

The Elaine Dorothy Cu-Au deposit, located in the Mary Kathleen Domain of the Mount Isa Inlier, Australia, records the interaction of Paleoproterozoic skarn metasomatism, fluid evolution, and deformation. The deposit is hosted by carbonate- and calc-silicate-rich rocks of the Corella Formation and comprises diopside–garnet–scapolite–wollastonite ± amphibole assemblages associated with pyrrhotite–chalcopyrite–pyrite mineralisation. Field relationships and mineral textures indicate that sulphide deposition began during or shortly after prograde skarn formation and subsequently evolved from disseminated and vein-controlled to semi-massive, massive, and shear-zone-hosted mineralisation. LA-ICP-MS analyses of pyrite, pyrrhotite, chalcopyrite, and magnetite record systematic variation in trace-element compositions during this evolution. Early Py1 is enriched in Co and Se and displays Co/Sb–Se/As characteristics consistent with a magmatic-hydrothermal contribution. Se-in-pyrite thermometry yields formation temperatures of up to 544 ± 36 °C for the earliest stage, decreasing to approximately 323–417 °C in later Py1 and 342 ± 11 °C for Py2. The transition from Co-rich Py1 to Co-poor, Ni-enriched Py2, together with pyrrhotite-dominated assemblages and cross-cutting chalcopyrite–pyrrhotite textures, records progressive changes in fluid chemistry and conditions of sulphide stability. Variable magnetite trace-element compositions and brecciation further indicate repeated modification during continued fluid circulation. Structural relationships demonstrate that deformation enhanced permeability along the Mary Kathleen structural architecture, promoting fluid focusing, sulphide redistribution, and local concentration within retrograde alteration zones. We interpret Elaine Dorothy as a deformation-enhanced Paleoproterozoic calcic skarn that evolved toward a skarn–IOCG transitional system, rather than as a classic IOCG end member. The deposit demonstrates how deformation, fluid–rock interaction, and evolving redox–sulphur-fugacity conditions progressively modify an early calcic skarn framework, enhancing permeability and fluid focusing, and generating IOCG-affinity characteristics through continued hydrothermal reworking rather than a discrete IOCG-forming event. This provides a process-based framework for recognising structurally reworked skarn systems in Proterozoic mineral provinces.

This study presents a synthetic proof-of-concept surrogate-assisted simulation–optimisation framework for identifying potentially mineralised locations using groundwater copper-isotope observations. The methodology adapts established groundwater contaminant-source characterisation principles, in which unknown source release histories are reconstructed from down gradient concentration measurements, to the investigation of concealed copper mineralisation. An isotope-informed MODFLOW–MT3DMS model was used to generate synthetic groundwater concentrations of Cu_Tot (total copper), ⁶³Cu, and ⁶⁵Cu for hypothetical mineralisation scenarios. Model responses were evaluated at 20 observation wells over five stress periods. These synthetic data were used to train, validate, and test a Gaussian Process Regression (GPR) surrogate model. The GPR model replicates the numerical simulator responses during testing. The test results show R² values exceeding 0.9998 and corresponding RMSE and MAE values of 0.03022 and 0.00571, respectively, indicating high predictive accuracy within the simulated parameter space. The trained surrogate was subsequently coupled with an Adaptive Simulated Annealing (ASA) algorithm to solve the inverse source-characterisation problem. The optimisation formulation contained 20 decision variables, representing time-varying source fluxes at four predefined candidate locations over five stress periods. Three candidates represented active synthetic mineral sources, whereas the fourth was intentionally assigned as an inactive dummy location to evaluate whether the framework could distinguish active from non-mineralised candidates. The optimisation converged in approximately 1080 s under the reported computational configuration. The reconstructed flux histories identified the three active candidates while assigning a near-zero flux to the dummy candidate. These results demonstrate that, under controlled synthetic conditions, isotope-informed inverse modelling can discriminate between predefined active and inactive candidate locations and reconstruct their temporal source strengths. However, the results do not constitute validation of a field-ready mineral-exploration method, because both the training and evaluation data were generated using the same underlying numerical framework. Subject to validation with independent field observations and more realistic geological, hydrogeochemical, and uncertainty representations, the proposed methodology could provide a computational screening and hypothesis-testing tool for prioritising prospective mineralised zones for further investigation.

Granitic magmatism is widely recognised as a fundamental driver of many hydrothermal ore systems, because evolving magmas supply heat, fluids and metals to the upper crust (Hedenquist & Lowenstern,...

Ductile shear zones act as transient pathways for crustal fluids, yet the conditions under which their connected porosity becomes sufficient to conduct are not well constrained. We present a porosity balance in which connected porosity evolves under three competing processes: creation by creep cavitation, creation by metamorphic reaction, and thermally activated closure. The model is constrained by existing experimental data, and permeability is linked to porosity through a percolation law with a sharp threshold. Within this constrained model, creep cavitation alone produces a steady‐state porosity orders of magnitude below the threshold at natural strain rates. A net reaction‐driven porosity source resolves this gap, and the critical net porosity‐production rate required to reach the threshold is geologically reasonable. Ductile shear‐zone permeability is therefore likely transient and reaction‐gated, with deformation alone unable to sustain connectivity at natural rates.

1. The Georgetown Inlier and the adjacent Croydon Province form the easternmost exposure of Proterozoic basement within the North Australian Craton and host a wide range of mineral systems spanning...

Accurate digital elevation models (DEMs) are essential for hydrological modelling and floodplain analysis, particularly in low-relief floodplains where small elevation errors can significantly affect flow routing and inundation extent. This study evaluated the vertical accuracy of six freely available global DEMs across the Flinders River catchment, North Queensland, Australia, using 30,916,100 quality-filtered ICESat-2 ATL06 elevation points for regression-based bias correction and airborne LiDAR datasets from five benchmark regions for independent validation. The evaluated DEMs included TANDEM-X, Copernicus DEM, ALOS AW3D30, SRTM, ASTER GDEM, and the Hydrological DEM. Vertical accuracy was assessed using mean error (ME), root mean square error (RMSE), and residual dispersion before and after calibration. Results showed substantial pre-calibration bias in the Hydrological DEM (ME = −2.93 m) and SRTM (ME = −2.66 m), whereas Copernicus DEM showed minimal initial bias (ME = −0.01 m). Regression-based correction reduced mean errors to within ±0.13 m across all DEMs. SRTM showed the largest improvement, with RMSE decreasing from 3.20 m to 0.55 m, while TANDEM-X achieved the highest post-calibration accuracy (RMSE = 0.14 m). Independent LiDAR validation confirmed improved vertical accuracy while preserving terrain morphology and river gradients.

Lithological mapping is essential for geological studies, mineral exploration, and environmental assessment. Satellite remote sensing combined with machine learning provides a scalable, cost-effective approach for regional lithological discrimination. This study evaluates hyperspectral and multispectral satellite imagery for lithological mapping in a geologically complex region of northwestern Queensland, Australia. The study area, within the Mount Isa Inlier, comprises diverse sedimentary, volcanic, intrusive, and metamorphic lithologies. PRISMA hyperspectral and ASTER multispectral imagery were analyzed using supervised classification algorithms, including Support Vector Machine (SVM), Mahalanobis Distance (MaDC), Minimum Distance (MDC), and Maximum Likelihood (MLC). Image-derived endmembers from representative lithologies were used as training data. Classification accuracy was assessed using confusion matrices, Overall Accuracy (OA), and the Kappa coefficient. PRISMA imagery outperformed ASTER data. SVM achieved the highest performance for PRISMA (OA = 82.03%, Kappa = 0.81), whereas MLC achieved the highest performance for ASTER (OA = 33.29%, Kappa = 0.30). Classification accuracy was evaluated using an independent set of validation ROIs that were spatially separated from the training samples, providing a more reliable estimate of model performance. These results highlight the benefits of hyperspectral remote sensing with machine learning for lithological discrimination in complex terrain and emphasise the importance of spatially independent validation. The approach demonstrates strong potential for regional-scale applications and may support more efficient mineral exploration and geological mapping workflows.

The Gebel Shalman-Wadi Biarn (GSh-WB) area in Egypt’s South Eastern Desert hosts NYF-type rare-metal pegmatites with significant U, Th, Nb-Ta, and REEs mineralization. This study integrates field observations, petrography, mineralogy, whole-rock geochemistry, and gamma-ray spectrometry to characterize these pegmatites and evaluate their economic potential. The pegmatites occur as veins, dykes, and zoned pockets hosted entirely within syenogranites. Petrography, pegmatites, and syenogranites are primarily composed of K-feldspar, albite, and quartz with trace amounts of biotite and muscovite. The environmental scanning electron microscope (ESEM) revealed the presence of the following minerals: autunite, kasolite, thorite, monazite-(Ce), parisite, xenotime-(Y), ferrocolumbite, hydroxyplumbobrtafite, aeschynite-(Y), and zircon, which are the major U-Th, Nb-Ta, and REE-bearing minerals. Additionally, gold, cassiterite, wolframite, pyrrhotite, chalcopyrite, and brass alloy were identified as sources of precious and base metals. Both groups’ chondrite-normalized REE patterns, which display slightly elevated LREE patterns and negative Eu anomalies, point to fractional crystallization involving plagioclase fractionation. Consequently, pegmatite and syenogranites are believed to have mostly formed from the partial melting of a reconstituted juvenile crust and its weathered sediments associated with Neoproterozoic magmatism. The marginally positive Ce anomaly in the (GSh-WB) pegmatites (1.02–0.98) may be associated with monazite crystallization resulting from enhanced fractionation. The Th and U levels range from 101 to 28.6 ppm and from 51 to 5.8 ppm, respectively. The magnitude of the tetrad effect in the rare earth elements of the analyzed rocks exceeds one (T1 = 1.12–1.02, T3 = 0.92–1.08, and T1,3 = 1.01–1.05), suggesting an M-type tetrad effect. The presence of this tetrad effect is indicative of granite that has been significantly altered by hydrothermal processes and is extensively fractionated. Chondrite-normalized REE patterns of the pegmatites (average ΣREE = 439 ppm) and their host syenogranites (average ΣREE = 192 ppm) show similar trends characterized by enrichment of light rare earth elements (LREEs) relative to heavy rare earth elements (HREEs) and pronounced negative Eu anomalies (Eu/Eu* = 0.09–0.22). These features, together with negative Sr and Ba anomalies, likely reflect extensive fractional crystallization of feldspars and feature anorogenic rocks. Spectrometric analysis reveals eU values of 2.0–288 ppm and eTh values of 7.0–455 ppm in pegmatite samples, with eU/eTh ratios (0.49–0.39) exceeding the typical continental crust value of 0.25, indicating uranium enrichment. Both magmatic and hydrothermal processes contributed to the observed radioactivity. The spatial distribution of uranium shows lithological and structural controls. The GSh-WB pegmatites represent a potential target for uranium exploration.

This study investigates the dyke swarms of the Um Dwiela area in the southern Egyptian Shield through a combined approach of remote sensing, field investigations and laboratory analyses, including mineralization and radioactive prospecting. Radioelements laboratory measurements and optical remote sensing datasets are combined to detect the bostonite rocks and their radioactive mineralization. The processing of Landsat-8, Sentinel-2 and ASTER data effectively delineated the country rocks, bostonite dykes and structural elements. Field observations indicate that the dykes trend NE-SW, extending approximately 12 km with widths ranging from 1 to 13 m. These dykes have experienced multiple alteration phases, pointing to the influence of hydrothermal fluids. Uranium mineralization is structurally controlled, occurring within fractures at the contact between bostonite and metasedimentary rocks. Average measurements obtained using a NaI(Tl) analyzer reveal elevated and variable radionuclide concentrations [²³²Th (442.25 Bq/kg), ²³⁸U (608.43 Bq/kg), and ⁴⁰K (1141.41 Bq/kg)], all exceeding internationally permissible safety limits. Multiple radiological hazard indices further indicate a substantial radiation risk, with all values classified as high according to global standards. Consequently, the associated gamma radiation exposure poses an elevated radiological hazard concern.

Celestine (SrSO₄) is the principal ore of Sr and a sensitive tracer of diagenetic fluid–rock interaction in carbonate–evaporite successions. This study presents integrated petrographic mineral chemistry and Sr–S isotopic data for epigenetic celestine hosted by Asmari carbonates at Jabal Hafit, Al Ain (UAE), to constrain fluid source, and mechanisms of SrSO₄ precipitation during basin diagenesis. Field and SEM observations show celestine as stratabound, vug- and fracture-filling euhedral to subhedral crystals within dolomitised limestone, suggesting precipitation after initial lithification during early-to-mid burial diagenesis. Electron microprobe analyses show nearly stoichiometric SrSO₄ (55.15–57.30 wt.% SrO; 42.43–44.35 wt.% SO₃) with very low Ba and Ca. The characteristically high Sr/Ba signature of the celestine reflects a complex diagenetic history driven by efficient Sr remobilisation during carbonate recrystallisation within an inherently Ba-poor marine sequence. Measured ⁸⁷Sr/⁸⁶Sr ratios are tightly clustered (0.707841–0.707854) with a high degree of isotopic homogeneity, which indicates a stable, well-buffered fluid reservoir, while the absolute values align with an Oligocene marine signature. Sulphur isotope values (δ³⁴S = +27.3 to +29.1‰) are enriched relative to coeval marine sulphate, which could be attributed to closed-system Rayleigh fractionation driven by bacterial sulphate reduction. We propose that celestine precipitated from stable, marine-buffered burial brines, where supersaturation was achieved through coupled Sr enrichment from carbonate diagenesis and microbial modification of the sulphate reservoir.