PROCESSING TECHNOLOGIES FOR RARE EARTH ELEMENTS FROM PERALKALINE IGNEOUS DEPOSITS: A SYSTEMATIC REVIEW
DOI:
https://doi.org/10.61164/p8v9aq27Keywords:
peralkaline igneous rocks; eudialyte; steenstrupine; loparite; Zr–Nb–REE deposits; hydrometallurgy; roasting; chloride leaching.Abstract
Peralkaline igneous deposits have gained increased attention as strategic sources of heavy rare earth elements (HREEs) and critical metals such as Zr, Nb, and Hf, providing a potential alternative to carbonatite and ion-adsorption clay deposits within a diversified global supply chain. Their processing remains technologically challenging due to complex silicate mineralogy—dominated by eudialyte-group minerals and steenstrupine—slow dissolution kinetics, and the widespread formation of silica gel during leaching, all of which require specialized “chemical-cracking” methods, including acid baking, dry digestion, sulfation or chloride roasting, and alkali fusion. Significant progress has been made in beneficiation (e.g., improved magnetic and gravity separation, enhanced mineral liberation through automated mineralogy) and hydrometallurgical processing, especially in approaches that prevent silica polymerization, boost selectivity for HREEs, and lower reagent use through optimized thermochemical decomposition. Recent research also includes innovations in solvent extraction, residue stabilization strategies, and life-cycle assessments, highlighting both improved technical feasibility and changing environmental considerations. Compared to carbonatites, which generally contain more acid-soluble LREE phases, peralkaline deposits demand more energy-intensive processing flowsheets; however, they provide significantly higher HREE concentrations than ion-adsorption clays, supporting long-term supply resilience. Overall, these advancements indicate that many of the historical metallurgical challenges associated with peralkaline REE ores are becoming increasingly manageable, positioning these deposits as promising sources for future REE production.
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