阿尔金羌河三区伟晶岩的锂富集机制OA

The Qianghesanqu deposit hosts a composite"pegmatitic-hydrothermal"lithium deposit with giant re-source potential.Given its complex pegmatite zoning and the previously ambiguous metallogenic stages and lith-ium enrichment mechanisms,this study presents a systematic investigation integrating detailed field geological surveys,mineral chemistry,and geochronological analyses.This research innovatively proposes a"two-stage,multi-unit"zoning evolution model.Unlike the traditional model,this new model emphasizes the critical role of late-stage hydrothermal overprinting in the formation of the distinctive zoning texture.During the early stage of pegmatite evolution,Li+was primarily sequestered into minerals such as spodumene via melt crystallization.Subsequently,the late-stage ore-forming fluids transitioned from a high-temperature,weakly alkaline state to a medium-low-temperature,F-rich,and weakly acidic state.These fluids intensely leached the early-formed spod-umene,leading to the substantial mobilization and migration of Li.The mobilized Li was then highly enriched by incorporating into the lepidolite crystal lattice via elemental substitution.A protracted time span of～13 Ma between the columbite-tantalite U-Pb age((466.5±4.2)Ma)and the lepidolite Rb-Sr ages(460.7～453.4 Ma)not only corroborates the presence of prolonged hydrothermal superposition but also reveals the tectonic setting.Specifically,the magmatic and hydrothermal stages correspond to the tectonic transition from syn-collisional slab thickening to a late-collisional extensional regime,respectively.This new zoning model not only enriches the theoretical framework for the zonation of LCT-type pegmatites but also provides a new paradigm for under-standing the metallogenesis process of highly evolved pegmatite systems with significant hydrothermal superpo-sition worldwide.