新疆阿尔泰协库斯特伟晶岩中锂的矿物学行为及其启示  

Mineralogical Behavior of Lithium and Its Implications from the Xiekusite Pegmatite, Altay, Xinjiang

作　　者：徐遥辰 卢奂 饶灿 XU Yaochen;LU Huan;RAOCan(School of Earth Sciences, Zhejiang University, Hangzhou 310027,China)

机构地区：[1]浙江大学地球科学学院

出　　处：《高校地质学报》2019年第3期321-332,共12页Geological Journal of China Universities

基　　金：国家自然科学基金项目(41472036;41772031);国家级大学生创新创业训练计划项目(201710335006)联合资助

摘　　要：协库斯特伟晶岩位于新疆阿尔泰可可托海镇,属于典型的Li-Cs-Ta(LCT)伟晶岩,发育大量锂的磷酸盐矿物和硅酸盐矿物。文章利用电子探针和X射线衍射等分析手段,结合野外观察,系统研究了协库斯特伟晶岩中锂的矿物学行为,探讨花岗质岩浆—热液过程中锂矿物的结晶演变与热液蚀变过程。研究表明:协库斯特伟晶岩中锂矿物结晶于两个阶段,花岗质岩浆阶段,锂矿物主要有锂辉石、磷锂铝石与磷锰锂矿,而锂电气石、多硅锂云母、锂白云母等形成于岩浆—热液过渡阶段至热液阶段。磷锰锂矿与羟磷锂铝石团块包体反映协库斯特伟晶岩中锂的磷酸盐熔体与硅酸盐熔体的不混溶机制。磷锰锂矿逐渐蚀变形成黄白色—红色的结构相似的矿物相,揭示了磷锰锂矿的氧化过程以及锂的释放过程。早期锂辉石、磷锰锂矿、磷锂铝石等锂矿物热液蚀变释放出Li进入热液,这种富Li热液作用形成了次生富锂矿物,显示了协库斯特伟晶岩内部Li的地球化学循环过程。Xiekusite pegmatite, a typical Li-Cs-Ta(LCT) pegmatite, is located in the Koktokay county of Altay, Xinjiang, and hosts a large amounts of lithium minerals of phosphate and silicate. In this paper, in combination with field observations, the mineralogical behavior of Li from the Xiekusite pegmatite has been studied for crystallization evolution and hydrothermal alteration of Li minerals during magmatic to hydrothermal stages by electron micro-probe and X-ray diffraction analyses. The results show that (1) Li minerals from the Xiekusite pegmatite crystallized through two stages, spodumene, montebrasite and lithiophylite formed during the magmatic stage;while elbaite, polylithionite and trilithionite crystallized from the magmatic-hydrothermal transition stage to hydrothermal stage.(2) The rock-inclusions of montebrasite-lithiophylite association reflect an immiscibility mechanism between Li phosphate melt and Li silicate melt in the Xiekusite pegmatite.(3) Lithiophyllite was altered to a series of minerals which have similar structures but different colors (from light yellowish to deep red ), suggestive of the oxidation and Li-leaching processes of lithiophyllite.(4) Li was leached into fluids by hydrothermal alteration of Li minerals such as spodumene, montebrasite and lithiophylite, and secondary Li-bearing minerals crystallized from the Li-rich fluids, these processes reflect the geochemical cycle of Li in the Xiekusite pegmatite.

关 键 词：锂矿物 锂的地球化学循环 矿物学行为 伟晶岩 阿尔泰 

分 类 号：P618.71[天文地球—矿床学]