西昆仑含锂盐湖卤水蒸发成矿机理初探

A Preliminary Study on the Evaporative Mineralization Processes and Mechanisms of Lithium-Bearing Salt Lake Brines in the West Kunlun

摘要: 西昆仑位于青藏高原北缘，区内富锂花岗伟晶岩和长英质岩石广泛发育，深大断裂、封闭山间盆地及高寒干旱气候在空间上耦合，为盐湖卤水型锂资源形成提供了有利地质条件。本文综合国内外含锂盐湖研究成果，从区域锂源、水文输运、水化学演化、蒸发结晶分异及锂赋存转化等方面，系统总结西昆仑含锂盐湖卤水蒸发富集与成矿机制。现有认识表明，盐湖锂富集并非单纯由水分蒸发控制，而是源区岩石风化与深循环流体供锂、断裂和水系输导、封闭盆地汇聚、蒸发与冻结浓缩、主要盐类选择性结晶以及晚期母液保存共同作用的结果。不同水化学类型决定卤水的析盐顺序和锂迁移路径：氯化物型卤水在石盐大量析出后通常表现为Li、K、Mg和B向残余母液富集；硫酸盐型卤水受石膏、芒硝及复硫酸盐沉淀控制，锂的富集效率与硫酸根去除程度和固相夹带密切相关；碳酸盐型卤水则受碱度、pH及碳酸盐矿物沉淀制约。综合区域资料，可将西昆仑盐湖锂成矿过程概括为“多源供锂–构造输导–流域汇聚–蒸发/冻结分异–晚期母液储集”。当前研究仍存在锂源贡献比例、水盐平衡、地下孔隙卤水分布及气候变化响应等方面的不足。未来应加强流域尺度连续监测、多同位素联合示踪、矿物–卤水反应模拟和地下卤水调查，以建立可量化、可检验的区域成矿模式。

Abstract: The West Kunlun region is located along the northern margin of the Qinghai-Xizang Plateau, where lithium-rich granitic pegmatites and felsic rocks are widely developed. The spatial coupling of deep-seated faults, closed intermontane basins, and a cold-arid alpine climate provides favorable geological conditions for the formation of lithium resources in salt lake brines. Based on a comprehensive review of studies on lithium-bearing salt lakes in China and elsewhere, this paper systematically summarizes the evaporative enrichment and metallogenic mechanisms of lithium-bearing salt lake brines in the West Kunlun region, with emphasis on regional lithium sources, hydrological transport, hydrochemical evolution, evaporative crystallization and differentiation, and the occurrence and transformation of lithium. Current understanding indicates that lithium enrichment in salt lakes is not controlled solely by water evaporation, but results from the combined effects of lithium supply through weathering of source rocks and deep-circulating fluids, transport through fault systems and drainage networks, accumulation within closed basins, evaporative and cryogenic concentration, selective crystallization of major salts, and preservation of late-stage residual brines. Different hydrochemical types determine the sequence of salt precipitation and the migration pathways of lithium. In chloride-type brines, Li, K, Mg, and B are generally concentrated in the residual mother liquor following extensive halite precipitation. In sulfate-type brines, lithium enrichment is controlled by the precipitation of gypsum, mirabilite, and complex sulfate salts, and its enrichment efficiency is closely related to the extent of sulfate removal and the entrapment of brine or lithium by solid phases. In carbonate-type brines, lithium behavior is primarily constrained by alkalinity, pH, and the precipitation of carbonate minerals. Integrating the available regional data, the metallogenic process of lithium in West Kunlun salt lakes can be summarized as a sequential process of “multi-source lithium supply - tectonic transport - catchment-scale accumulation - evaporation/freezing-induced differentiation - late-stage residual brine storage”. Nevertheless, significant uncertainties remain regarding the relative contributions of different lithium sources, basin-scale water-salt balance, the distribution of subsurface pore brines, and the response of lithium enrichment to climatic change. Future studies should therefore strengthen continuous monitoring at the catchment scale, integrated multi-isotope tracing, mineral-brine reaction modeling, and systematic investigation of subsurface brines, with the aim of establishing a quantitative and testable regional metallogenic model.