Despite growing interest in mine tailings valorization, most previous studies on thermally induced mineral transformations have focused on monomineralic systems, leaving the behavior complex, multimineral mine residues comparatively unexplored. Thermal treatment of fine-grained mining wastes is proposed as a method to enhance their reuse within the mining industry itself or in other related industries like civil and chemical engineering. Four fine-grained mining wastes (three mine tailings and one sludge from an acid mine water treatment plant) were chemically and mineralogically characterized across a temperature range of 40 °C to 950 °C using a combined TGA, XRD and SEM-EDS approach. The three mine tailings correspond to deposits classified as IOCG-type (iron‑copper‑gold oxides), volcanogenic massive sulfides (MSS), and carbonatites. Depending on their initial mineralogy, one or more of the following mineral transformations were observed: 1) conversion of gypsum to bassanite and anhydrite within the ranges of 100–200 °C and 850–950 °C, respectively; 2) a two-steps transformation of chlorite (i.e. chamosite) into a diffraction X-ray-amorphous phase, tentatively termed “meta-chlorite” by analogy with meta-kaolinite, between 650 °C and 800 °C and a concomitant neoformation of hematite and a Si-rich matrix; 3) transformation of carbonates (i.e., calcite and dolomite) into oxides (i.e., lime and periclase) within the 800–950 °C range. These mineral transformations confer greater reactivity to the residues, showing strong potential as low-cost precursors for alkali-activated cementation processes, thereby supporting the valorization of mine residues within a circular economy framework, with direct applications in underground mine galleries backfilling, construction materials (plasters and 3D-printing pastes), and other industrial uses as alkaline reagents.
Exploration geochemistry, while extraordinarily successful for magmatic-hydrothermal deposits in mountainous terrains, has demonstrated lower discovery rates for supergene deposits that form in depositional sinks after long-distance transport. This paper argues that this ‘effectiveness paradox’ is not a failure of geochemical exploration, but a cognitive-methodological mismatch: reverse-tracing principles optimized for source-type mineralization have been persistently applied to sink-type deposits—including evaporites, placers, weathering-leached REE, and sandstone-hosted uranium—that require fundamentally different tracing strategies. To resolve this mismatch, we develop a holistic source-to-sink (S2S) exploration framework that explicitly links erosional sources, transport pathways, and depositional sinks within a unified process-based architecture. The framework is grounded in a synthesis of advances in climatology, geomorphology, regolith science, pedology, hydrology, and critical zone research—disciplines that collectively govern element release, transport, and accumulation at the Earth's surface. Four Chinese case studies—Tarim (potash), Boziguer (zircon placer), Honghe (ion-adsorption REE), and Qaidam (sandstone-hosted uranium)—validate the framework by demonstrating that source-specific proxies (total K, heavy mineral fingerprints, U₀/Th/U) and sink-specific proxies (soluble K+, heavy mineral enrichment, exchangeable REE, U6+/U4+/TOC) are systematically distinct. International examples from diverse tectonic and climatic settings—including the Lithium Triangle, Klondike, Jos Plateau, Dongqiao, Frome, Wyoming, and Esperance—further demonstrate global transferability.The framework operationalizes three principal transitions—from reverse-tracing to whole-chain tracing; from total-element-dominated proxy suites to tiered systems incorporating process-sensitive dynamic proxies; and from empirical targeting to quantitative coupling assessment—through a dual-proxy system and a four-stage workflow, with numerical terrain analysis (ksn, χ, VeSi_val, DeDi_val) serving as the initial step to enable systematic identification of erosional versus depositional domains prior to geochemical sampling. The S2S framework is offered not as a universal solution, but as a systematic approach to a specific class of problems—exploration for supergene deposits in depositional sinks—complementing rather than replacing existing exploration techniques.
Rising greenhouse gas (GHG) emissions have intensified the need for effective carbon mitigation strategies, making carbon capture, utilization and storage (CCUS) a key technology for achieving long-term decarbonization. Future deployment of CCUS projects is expected to be supported by the Paris Agreement's Article 6 mechanisms, together with India's emerging domestic carbon market and carbon-pricing frameworks. Owing to its extensive sedimentary basins, India possesses significant geological potential for long-term CO2 storage. This review provides a comprehensive assessment of the geological CO2 storage potential of major subsurface formations in India and evaluates their suitability for long-term geological CO2 storage and future CCUS development. A systematic review of the published literature from 2000 to 2025 was conducted using peer-reviewed journal articles, conference proceedings, books, government reports, and publications from internationally recognized organizations. The review critically evaluates geological storage options, storage-capacity estimation approaches, reservoir characteristics, monitoring strategies, uncertainty assessment, and recent policy developments. In addition, a bibliometric analysis based on the Scopus database was performed to identify publication trends and emerging research directions. The bibliometric analysis identified 1138 publications, demonstrating a substantial increase in geological CO2 storage research, particularly after 2020. India comprises approximately 3.4 million km2 of sedimentary basins with an estimated national geological CO2 storage potential of 400–500 Gt CO2. Deep saline aquifers constitute the largest storage resource (300–400 Gt CO2), followed by basalt formations (200–400 Gt CO2), while depleted oil and gas reservoirs (5–10 Gt CO2) and unmineable coal seams (∼5 Gt CO2) provide additional storage opportunities. The review also proposes an Integrated Geological Storage Potential Framework (IGSPF) for comparative screening and prioritization of Indian sedimentary basins based on storage capacity, reservoir quality, injectivity, caprock integrity, geological maturity, and data availability. Deep saline aquifers are identified as the most promising option for long-term geological CO2 storage in India, while basalt formations offer additional potential through mineral carbonation. Overall, the findings highlight the need for standardized storage-capacity assessment, detailed reservoir characterization, robust monitoring and risk management, and supportive policy frameworks. As the storage-capacity estimates presented in this review are derived from published literature, future CCUS deployment will require site-specific characterization, reservoir modelling, and pilot-scale validation before field-scale implementation.
