关键词: 火山岩, 稀有金属, 成岩成矿, 挥发分, 结晶分异

Abstract: Volcanic rocks play a fundamental role in transferring materials and energy from the deep Earth to the surface and provide an important link between the Earth’s interior and exterior systems. Because volcanic eruptions are commonly associated with extensive volatile loss, volcanic rocks have traditionally been considered unfavorable source rocks for rare metal mineralization. However, increasing evidence suggests that highly evolved volcanic systems can concentrate economically important rare metals and, under suitable geological conditions, may independently generate ore deposits. This review summarizes the metallogenic characteristics and ore-forming processes of rare metals (e.g., Sn, Be, Nb-Ta, and Li) associated with felsic volcanic rocks. Representative case studies include the Mexican tin-boron metallogenic belt, the Bolivian tin province, fluorinerich volcanic and subvolcanic systems enriched in Sn-Nb-Ta in South China, volcanic-hosted beryllium deposits along the southeastern coast of China, and volcanic-sedimentary lithium deposits. Through comparison of these mineralization styles, the mechanisms responsible for rare metal enrichment in volcanic environments are evaluated. Meanwhile, this review also discusses the potential effects of mantle-derived magmatism on the migration, partitioning and pre-enrichment of niobium (Nb), such as crustal contamination, carbonate components. The results show that intense magmatic differentiation and volatile enrichment are the key factors controlling rare metal mineralization in volcanic rock systems. Additionally, deep recycled carbonates in the source may facilitate the pre-enrichment of rare metals in mantle-derived magmas. Volcanic systems therefore possess the capacity to form rare metal deposits independently rather than merely representing the volcanic equivalents of intrusive ore-forming systems. Moreover, rare metal enrichment in volcanic rocks may provide a direct record of deep magmatic-hydrothermal processes and serve as an effective exploration indicator for concealed ore bodies in covered regions. Recognition of the ore-forming potential of volcanic systems not only refines current models of rare metal metallogenesis but also offers new opportunities for the exploration of concealed rare metal resources.

Key words: volcanic rocks, rare metals, rock-forming and ore-forming processes, volatiles, fractional crystallization