锂同位素及其在四川甲基卡伟晶岩型锂多金属矿床研究中的应用

摘要

As a useful geochemical tracer, lithium isotope system has been used to study some important geological or geochemical issues.This paper summarizes the recent advances in research on lithium isotopes and its application to Jiajika pegmatite type lithium polymetallic deposit in Sichuan.The Jiajika deposit is the largest pegmatite type Li-polymetallic deposit in China.Samples from Jiajika deposit were analysed by MC-ICP-MS in the University of Maryland.Two samples of spodumene contain 33592 × 10-6 and 34264 × 10-6 Li and have δ7 Li values of -0.6 ‰ and -0.4‰.One sample of biotite in two-mica granite contains 7350 × 10-6 Li and has δ7Li value of +0.6‰.They are consistent in the uncertainty range.Therefore, following interpretations of published data of C, H and O isotopes, fluid inclusions and chronology, we consider that spodumenes in the lithium polymetallic deposit may have originated from the granite, suggesting that ore-forming fluids were also derived from the granite.%锂同位素在地质学、地球化学研究中有着广阔的应用前景.简单介绍了锂同位素研究已取得的进展,并在四川甲基卡伟晶岩型锂多金属矿床研究中开展应用.研究表明,四川甲基卡锂矿床中2件锂辉石的锂含量非常高,分别为33 592×10-6和34 264×10-6,相应的δKu值分别为-0.6‰和-0.4‰,平均值为-0.5‰,而二云母花岗岩中黑云母的锂含量为7 350×10-6,δ7Li值为+0.6‰,两者在误差范围内具有非常好的一致性,证明锂辉石来源于二云母花岗岩,这与其他包裹体、同位素地球化学和年代学证据等相一致.