湖南香花岭地区花岗岩中锂对成岩成矿的制约

锂（Li）是一种战略关键金属，岩浆阶段主要在花岗质岩石中得到富集和结晶。由于具有不相容和富挥发性等性质，锂对花岗岩的成岩成矿具有重要的制约。文章利用电子探针、LA-ICP-MS 等分析手段，对湖南香花岭地区癞子岭和尖峰岭花岗岩进行系统岩相学、主微量和矿物学研究，结果表明：（1）花岗质岩浆结晶分异过程中，Li 含量逐渐升高，大幅度降低了熔体粘度，增大了结晶温度区间，花岗质岩浆得到充分结晶分异，导致花岗岩的垂直分带；（2）花岗岩中Li 与稀有金属含量呈正相关关系，Li 与Ta、Nb、Sn 等稀有金属具有协同成矿作用；（3）花岗岩中云母类矿物具有向富Li 演化的趋势，以铁锂云母为主，随着铁锂云母的结晶，Nb、Ta、Sn 等稀有金属相继析出，导致晚期云母中Ta、Nb 等含量降低。熔体中H2O、F 等对花岗质岩浆的性质和结晶分异有较大影响，但不足以致使花岗岩呈垂直分带。

Constraints of Lithium on the Petrogenesis and Mineralization of Granite in Xianghualing Area,Hunan Province

Lithium(Li),one of strategic key metals,is mainly concentrated and crystallized in granitic rocks during magmatic stage.Owing to its incompatibility and volatile properties,Li has an important restriction on the petrogenesis and mineralization of granite.In this paper,the petrography,major-trace elements and mineralogy of Laiziling and Jianfengling granites in Xianghualing area(Hunan province),were systematically studied by means of electron microprobe analysis and LA-ICP-MS analysis.The results show:(1)during the crystallization differentiation of granitic magmas,the Li content increases gradually,which greatly reduces melt viscosity and increases crystallization temperature range,and granitic rocks were thus fully differentiated,resulted in the vertical zonation of granite;(2)in the granites Li contents have positive relationships with rare-metals’contents,and Li has synergistic mineralization with Ta,Nb and Sn etc.;(3)mica group minerals evolved to Li-rich phase(mainly zinnwaldite),with the crystallization of zinnwaldite,Nb,Ta and Sn etc.are successively precipitated,leading to decreasing contents of Ta and Nb in late mica.Although H2O,F,etc.in the melt have great influence on the properties and crystallization differentiation of granitic magma,but they are not enough to cause granite to be vertical zonation.