锂同位素在稀有金属成矿过程的分馏机制——以川西打枪沟为例

Fractionation Mechanism of Lithium Isotopes in the Ore-forming processes of Rare Metals:A Case Study from Daqianggou,Western Sichuan

本文首次尝试将锂同位素研究应用于打枪沟锂铍矿床岩浆演化与热液作用研究中。对打枪沟与伟晶岩有关的中-酸性岩体进行了系统的采样、测试,结果表明,岩体δ7Li值主要分布于-1.16‰^+1.59‰,伟晶岩δ7Li值分布于-4.55‰^+12.4‰,表明锂的两种同位素在岩浆演化阶段未发生明显的分馏,而在形成伟晶岩的熔体相-流体相之间交代作用阶段表现出在不同矿物中差异化的分配行为,热液交代作用为锂同位素分馏的主控因素。

This study utilizes lithium isotopes for the first time in an attempt to trace the magmatic evolution and hydrothermal processes of Daqianggou deposit.Systematic sampling were conducted on ore-related intermediatefelsic plutons and pegmatites.Consequently,theδ7Li values range from-1.16 to+1.59‰for felsic plutons,-4.55 to+12.4‰for pegmatites,indicating slight lithium fractionation in the magmatic evolutionary stage and strong lithium fractionation in the hydrothermal metasomatism stage.We propose that hydrothermal metasomatism might be a main controlling factor in lithium fractionation.