Mineral Resources

Sorption in shales is a key process controlling their gas storage capacity. It is, however, a complex phenomenon due to the broad and variable petrophysical characteristics of shales. This complexity is further compounded by the simultaneous occurrence of gas adsorption on mineral and organic surfaces and absorption processes within sedimentary organic matter. In this study, gravimetric sorption experiments were conducted on three geologically distinct shales at 40 °C and pressures ranging from 2 to 15 MPa. We examined both pristine powdered shale samples and their solvent-extracted counterparts to investigate the dominant controls and sorption mechanisms of hydrogen (H 2 ) and carbon dioxide (CO 2 ) - two gases central to energy transition. The sorption capacity of H 2 is shown to be independent of the total organic carbon (TOC) content and is rather governed by the available pore volume in the shale, with thermal maturity exerting a positive influence on porosity development, particularly in samples exhibiting contrasting maturities. Conversely, the CO 2 sorption capacity is controlled by both TOC content and available pore volume. An increase in either parameter enhances the sorption capacity. Comparisons of H 2 and CO 2 sorption capacities among samples possessing relatively similar textural properties and contrasting TOC content indicate that the contribution of H 2 absorption in organic matter becomes increasingly significant at elevated pressures, while CO 2 absorption is shown to increase the total sorption capacity at all investigated pressures. This study provides the first experimental evidence on the role of H 2 and CO 2 absorption in increasing the sorption capacity of immature organic-rich shales. • H 2 retention occurs via adsorption, governed mainly by textural properties. • At high pressure and in TOC-rich shales, absorption enhances H 2 sorption. • CO 2 sorption is enhanced by larger textural properties and/or higher TOC content.

Spent neodymium–iron–boron (NdFeB) magnets represent a valuable secondary source of rare earth elements (REEs). This study presents an innovative process for recovering Neodymium (Nd) from spent NdFeB magnets using inorganic Al(NO 3 ) 3 ·9H 2 O solution composed of aluminium nitrate nonahydrate (Al(NO 3 ) 3 ·9H 2 O) and water referred to as a “green Brønsted solvent.” Hammett acidity measurements confirm that concentrated solutions of Al(NO 3 ) 3 ·9H 2 O and H 2 O exhibit strong Brønsted acidity, enabling the selective leaching of Nd from NdFeB magnet sample roasted at 660 °C. A high separation factor of 4150 for Nd over iron (Fe) was achieved. This Al(NO 3 ) 3 ·9H 2 O solution offers significant advantages, including non-volatility, safety, high solubility, and excellent selectivity for REEs. Under optimal conditions (80 °C, solid-to-liquid ratio of 1:20, and leaching time of 150 min), 96.9% of Nd was leached, while Fe leaching was limited to just 0.9%. The dissolved Nd 3+ was subsequently recovered from the leachate by precipitation with oxalic acid, followed by oxidative roasting, yielding Nd 2 O 3 with a purity greater than 95%. This high selectivity and product purity demonstrate the feasibility of this process for producing high-quality Nd 2 O 3 suitable for reuse in NdFeB magnet manufacturing. Moreover, the approach minimizes impurity incorporation and downstream processing requirements, offering an environmentally friendly strategy for REEs recovery from secondary resources. • Green Brønsted solvent enables selective Nd leaching from spent NdFeB magnets. • Roasting of NdFeB at 660 °C significantly enhances the selective recovery of Nd. • High Nd/Fe separation factor of 4150 achieved with Al(NO 3 ) 3 ·9H 2 O and H 2 O solution. • Optimised leaching yielded 96.9% Nd recovery with only 0.9% Fe co-leached. • Nd 3+ recovered as >95% pure Nd 2 O 3 via oxalic acid precipitation and roasting.

Grinding environment strongly influences chalcopyrite surface reactivity and flotation, but direct dry-wet comparisons are often confounded by size and liberation effects. This study presents a mechanistically controlled comparison of dry and wet grinding effects on chalcopyrite by achieving closely matched particle size distributions and comparable liberation for both a model mineral and a low-grade copper ore. Under these controlled conditions, pronounced differences in surface chemistry and electrochemical reactivity were observed. Dry-ground particles exhibited higher oxygen demand, indicating highly reactive, minimally passivated surfaces, whereas wet-ground particles showed greater surface oxidation, which intensified with increasing temperature due to galvanic interactions and oxyhydroxide formation. These surface modifications directly translated into flotation behaviour: dry grinding consistently yielded higher copper recoveries and grades, while wet grinding particularly at elevated temperatures led to reduced collector adsorption and flotation performance. Grinding additives had negligible effects on the model mineral and only modestly improved recovery in the real ore, without altering dominant oxidation trends. Overall, the results demonstrate that, under equivalent liberation conditions, chalcopyrite flotation performance is governed primarily by grinding-induced surface chemistry rather than bulk mineral exposure. • Bulk surface chalcopyrite liberation is similar under both grinding environment. • Dry grinding forms reactive surfaces; wet grinding reduces reactivity at all T, GA negligible. • Flotation efficiency is governed by surface chemistry under comparable liberation.

ABSTRACT The high‐precision multi‐scale fracture network model serves as the crucial geometric prerequisite for studying the permeability of fractured zones and ensuring the safety of urban underground rail projects. However, the practical application of multi‐scale fracture networks is hindered by challenges in cross‐scale integration. This study examines the three‐dimensional structure of a fractured zone at a metro station in Guangzhou, using borehole core data and CT images. A macro–micro data coupling method for 3D geological structure reconstruction is proposed, integrating multi‐point statistics (MPS) and deep learning techniques. The macroscopic model is constructed using an Adaptive Fully‐Connected Deep Neural Network (AFCDNN) and MPS, while a multi‐scale Expectation Maximisation (EM)‐like iterative optimisation method resolves issues such as stratigraphic sequence disruption and boundary ambiguity. U‐Net networks identify fractures in core CT images, while a quaternion rotation matrix corrects borehole disturbances, restoring fracture topology under real in situ stress conditions and constructing a microscopic DFN model. By coupling the meshed macroscopic model with the upscaled DFN model, a refined 3D geological model is created. The results demonstrate that this method generates high‐precision models with a 1‐m resolution, clearly depicting the spatial distribution of fault zones (e.g., soil‐like fractured zones, block‐like fractured zones and moderately weathered fault rock) and bedrock characteristics (exhibiting a ‘west‐low, east‐high’ pattern). After rotation correction, the DFN model's fracture orientations, initially scattered, clustered into three dominant groups. Given the significant variation in fracture volume, Lambert W transformation was applied to preserve the characteristics of both large and small fractures. This method improved the goodness of fit of the fracture volume distribution from 0.68 to 0.96. The macro–micro coupling method proposed in this study overcomes the limitations of traditional single‐scale modelling. It addresses previous constraints where large‐scale simulations used only homogeneous media, while heterogeneous media were limited to small‐scale simulations. This approach avoids the homogenisation of macroscopic models for microscopic fractures, overcomes the challenges of scaling microscopic models to engineering applications, and provides crucial technical support for deep rock mass heterogeneous modelling and metro engineering safety management.

Abstract Regolith-hosted rare earth element (REE) deposits in South China supply most of the world’s heavy REE (HREE), but the parent minerals that liberate HREE during weathering remain uncertain because commonly invoked accessory phases are refractory. Here we recognize that fluorite is the dominant HREE host in the granitic bedrock of the world’s largest deposit (Shitouping; ~174,000 t HREE oxides). Fluorite occurs in the Early Cretaceous syenogranite at a concentration of ~0.8 wt.% and contains 4.7 wt.% REE with a LREE/HREE ratio of 0.3, accounting for 82% of the bulk-rock HREE budget. During supergene weathering, fluorite dissolves almost completely (> 99%), releasing HREE that adsorb onto clay minerals in the overlying saprolite, whereas refractory phases such as xenotime persist. Mass-balance modelling confirms that HREE ions liberated from primary magmatic fluorite constitute the principal source of the economic ore. Extreme magmatic fractionation enriches residual melts in fluorine and HREE, driving fluorite crystallization and preferential HREE incorporation. Our results imply that regolith-hosted HREE deposits require bedrocks enriched in easily weathered HREE phases (notably fluorite) and depleted in refractory HREE hosts (e.g., xenotime and titanite), guiding exploration to F-rich, highly fractionated granites low in P and Ti.

Abstract Pattern formation in geological materials is commonly described using analogies to Turing‐type reaction–diffusion systems, yet a unifying thermodynamic explanation remains elusive. Here we develop a multiscale, thermodynamically consistent framework for pattern‐forming instabilities in porous media undergoing coupled thermo–hydro–mechanical–chemical–electrical processes. By extending irreversible thermodynamics to include configurational degrees of freedom and Onsager–Casimir reciprocal couplings, we show that morphing patterns emerge as universal non‐equilibrium instabilities rather than system‐specific bifurcations. Part I establishes the theoretical foundations and stability criteria; applications are presented in Part II.

Abstract A series of earthquakes along the East Anatolian Fault Zone (EAFZ) started with the January 24, 2020, Sivrice (Elazığ) Earthquake (M W 6.8) and culminated in the the catastrophic Kahramanmaraş Earthquakes (M W 7.8 and M W 7.6) on February 6, 2023. This study explores how the 2020 Sivrice event influenced the 2023 Kahramanmaraş earthquakes using field surveys and seismotectonic analyses. The 2020 earthquake, occurring in the northeastern part of Pütürge Segment, was followed by field surveys and Differential interferometry (DInSAR) analysis to determine fault geometry and slip distribution. Seismological studies, including moment tensor solutions, stress tensor analysis, and Coulomb stress changes, provided insights into the fault dynamics. Surface deformations were observed in a 50 km section of the Pütürge segment, showing R, R’, T, P, and Y fractures typical of a left-lateral deformation zone. The moment tensor analysis revealed a left-lateral strike-slip fault trending N65°E, with a minor normal component. The timing and location of the earthquakes, suggest that the rupture progresses bilaterally. The analysis of Coulomb stress changes showed that the 2020 event transferred stress to the Arıkonak sub-segment, the Yarpuzlu restraining double-bend, the Erkenek Segment of the EAFZ, as well as the Gerger and Narince Segments of the Southeastern Anatolian Thrust Zone. These areas were further stressed by the 2020 earthquake, setting the stage for the February 2023 Kahramanmaraş events. Thus, the 2020 Sivrice earthquake served as a trigger for the catastrophic 2023 earthquakes. The Arıkonak sub-segment, Gerger, and Narince segments are still potential sources of earthquake hazard.

Mapping the internal structure of sedimentary basins basement depth can be used for a variety of geological applications, particularly the identification of natural resources such as groundwater, minerals, or the geological structures associated with