新疆柯鲁木特伟晶岩脉中石榴子石组成对岩浆-热液过程及Li矿化的制约  

Magmatic-Hydrothermal Evolution and Li Mineralization in Pegmatite:Constraints from Composition of Garnet from Kelumute No.112 Pegmatite,Xinjiang Autonomous Region,China

作　　者：吕正航[1] 张辉[1] 赵景宇 

机构地区：[1]中国科学院地球化学研究所地球内部物质高温高压院重点实验室,贵州贵阳550081 [2]宿州学院,安徽宿州234000

出　　处：《矿物学报》2017年第3期247-257,共11页Acta Mineralogica Sinica

基　　金：国家自然科学基金(编号:41403016;41372104);贵州省科技项目(编号:2015GZ77802)

摘　　要：利用EMPA研究新疆阿尔泰柯鲁木特112号伟晶岩脉中5个结构带内的石榴子石化学组成。结果表明,112号脉中石榴子石属于铁铝榴石-锰铝榴石系列,主要为锰铝榴石。相同结构内不同石榴子石具有相近的化学组成,不同结构带中的石榴子石的化学组成显著差异:相比早期结构带中的石榴子石,晚期结构中的石榴子石Fe含量增加,Mn含量降低。结合铌钽族矿物中相似的Mn-Fe演化趋势,我们提出岩浆-热液过程中富F流体相出溶可能是晚期结构带中石榴子石显示高Fe、低Mn组成的机理。112号脉中锰铝榴石比例较高,变化于64%~90%范围,集中在稀有金属花岗伟晶岩中的锰铝榴石组成范围,由此我们认为伟晶岩中高Mn O含量的锰铝榴石是伟晶岩内部Li矿化的矿物学标志。The Kelumute No. 112 pegmatite hosts a complex Li-Be-Nb-Ta ore deposits which ranges in the secondary scale in Altay, Xinjiang Autonomous Region, China. Compositions of garnet from its five mineral assemblage zones have been determinated by electron probe microanalysis （EPMA）in this work. Results reveal that all garnet from No. 112 pegmatite belongs to almandite-spessartite series with high proportion of spessartite. Composition of garnet shows similarity in the same zone and discrepancies in different zones with an increasing trend of Fe and a decreasing trend of Mn from early to late formation. Combined with the similar variation trend of Fe and Mn in apatite and columbitetantalite, exsolution of the F-rich fluid phase from the evolved silicate melt during the magmatichydrothermal stage inducing variation in composition of garnet was identified in No. 112 pegmatiteforming melt. Garnets from the five zones of No. 112 pegmatite show a high spessartite proportion of 64% -90%, which is consistent with compositions of spessartites from super large and large scale worldwidely pegmatitic Li ore deposits, we thus to conclude that spessartite with high MnO eontent could be an effective mineral indicator for exploring pegmatitic Li ore deposits.

关 键 词：石榴子石 岩浆-热液演化 Li矿化 伟晶岩 新疆 

分 类 号：P574.2[天文地球—矿物学] P595[天文地球—地质学]