四川甲基卡锂矿区二长花岗岩的地球化学、氢氧同位素组成及其地质意义  

Geochemistry and Hydrogen-Oxygen Isotope Compositions of Jiajika Two-mica Granite,Sichuan Province,and Their Geological Significance

作　　者：侯江龙[1] 李建康[1] 王登红[1] 代鸿章 刘丽君 HOU Jianglong;LI Jiankang;WANG Denghong;DAI Hongzhang;LIU Lijun(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing100037,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing100083,China)

机构地区：[1]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《现代地质》2020年第5期1058-1066,共9页Geoscience

基　　金：国家重点研发计划项目“我国锂能源金属成矿规律、靶区优选与重点查证”(2017YFC0602701);中国地质调查局“战略性新兴产业矿产调查”工程项目“松潘-甘孜成锂带锂铍多金属大型资源基地综合调查评价”(DD20190173);中国地质调查局“大宗急缺矿产和战略性新兴产业矿产调查”工程项目“川西甲基卡大型锂矿资源基地综合调查评价”、“中国矿产地质志”(DD20160055,DD20160056,DD20160346,DD20190379)。

摘　　要：四川甲基卡锂矿床为超大型锂矿床,矿区南部呈岩株状产出的二云母花岗岩与稀有金属伟晶岩在时间、空间及成因上具有密切关系。通过对该岩体元素地球化学特征和氢氧同位素组成的研究,探讨了其在稀有金属成矿过程中的作用。研究结果表明,甲基卡二云母花岗岩为富硅、高钾、钙碱性、强过铝质S型花岗岩,其稀土总量较低,岩浆来源为三叠系西康群砂泥岩为代表的地壳物质的部分熔融,流体来源可能是岩浆水和变质水的混合水。岩体微量元素R型聚类分析显示,与稀有金属成矿最密切的元素为Li、Rb、Ti、W、Mn,而岩体稀有元素含量的变化规律指示岩体北侧成矿效率高于南侧,是下一步找矿工作的重点。综合地球化学、氢氧同位素及前人研究,认为花岗岩浆在底辟侵入过程中可能发生了不混溶作用,由此分离出的伟晶岩浆在运移过程中稀有金属得到不断富集,最终形成伟晶岩型稀有金属矿床。Jiajika is a superlarge lithium deposit in Sichuan Province.The two-mica granite in the southern Jiajika orefield is closely related to rare metal pegmatites in space,time and origin.In this study,geochemical and hydrogen-oxygen isotope analyses of the granite were carried out to understand the rare metal metallogenic process.The results show that the Jiajika two-mica granite is S-type with high SiO2,high-K calc-alkaline and peraluminous.The total rare earth composition of the granite is very low.The magma source of the granite may have been partial melting of the Triassic Xikang Group sandy-mudstone,and the fluid source may have been a mixture of magmatic and metamorphic water.R cluster analysis of trace elements shows that Li,Rb,Ti,W and Mn are closely related to rare metal metallogeny.Changes in the rare element contents suggest that ore-forming efficiency in the north was higher than in the south.Therefore,future prospecting work should focus on the northern part of the granite.Results of geochemistry,hydrogen-oxygen isotopes and previous studies reveal immiscibility in the diapirism of granitic magma.Pegmatitic magma segregated from the granitic magma may have concentrated the rare metals,and eventually formed the pegmatitic rare metal deposit.

关 键 词：二云母花岗岩 地球化学 氢氧同位素 稀有金属 伟晶岩 甲基卡 

分 类 号：P588.1[天文地球—岩石学] P595[天文地球—地质学]