Microstructural Analysis of Dry-Stacked Kiriburu Iron Ore Mine Tailings: Relevance to Dust Emission and Stability

Mining and beneficiation of hematite ore at Kiriburu iron mine, eastern India, generates large volumes of fine tailings that are stored in dry-stacked facilities. Dry stacking, although adopted as a geotechnically safer alternative to conventional hydraulic impoundments, introduces complex surface–atmosphere interactions that govern both Aeolian entrainment and long-term structural evolution. The present investigation elucidates the microstructural and compositional heterogeneity of dry-stacked tailings. Representative samples from the surface (0–50 cm), midlayer (150 cm), and bottom (300 cm) were subjected to particle size analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDS) under bulk, line-scan, and elemental-mapping modes, complemented by X-ray diffraction mineralogical profiling. The results delineate stratification of particle size and mineralogy. Finely ground, loosely packed clays and aged iron oxides produce a separable matrix on top. Hematite/goethite enrichment (Fe = 28.9%), coarser particle sizes, and partial cementation in the midlayer reduce erodibility. The well-compacted, coarse-grained, mineralogically stable bottom layer provides structural stability. Consequently, the surface layer shows the highest susceptibility to wind-driven particle detachment and fugitive dust emission, whereas deeper layers display reduced availability of detachable fines due to enhanced packing and cementation. These depth-dependent microstructural traits provide a mechanistic basis for identifying dust-prone horizons in dry-stacked tailings and prioritizing surface mitigation. Integration of microstructural and surface-chemical results indicates that dust emission with depth establishes a link between mineral surface chemistry and environmental behavior. Collectively, all these observations demonstrate that the surface layer has the highest dust emission potential, overlying a consolidated, hematitic–siliceous layer that imparts structural resilience.