Lithium isotope traces magmatic fluid in a seafloor hydrothermal system.
Lithium isotope traces magmatic fluid in a seafloor hydrothermal system.
复制标题
锂同位素追踪海底热液系统中的岩浆流体
DOI：
10.1038/srep13812
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发表时间：
2015-09-08
影响因子：
4.6
通讯作者：
Fu Q
中科院分区：
文献类型：
--
作者：
Yang D;Hou Z;Zhao Y;Hou K;Yang Z;Tian S;Fu Q
中国大型火山成因块状硫化物矿床的流体包裹体和脉石石英的锂同位素组成为岩浆流体输入三叠纪海底热液系统提供了有力的证据。对于流体包裹体，δ7Li 结果从+4.5‰到+13.8‰变化；对于寄生脉石石英（9个含有原生流体包裹体的脉石石英样品），δ7Li结果从+6.7‰到+21.0‰变化。这些数据证实了热液石英和流体之间随温度变化的锂同位素分馏（即 Δδ7Liquartz-fluid= –8.9382 × (1000/T) + 22.22(R2= 0.98; 175 °C–340 °C)），这表明流体包裹体与它们含有石英，因此可以使用 δ7Liquartz 数据确定流体的成分。据此，我们估计，在 175–340 °C 温度下，成矿流体的 δ7Li 范围为 -0.7‰ 至 +18.4‰。该 δ7Li 范围与 Li-O 模型一起表明岩浆流体在矿石形成中发挥了重要作用。这项研究表明，锂同位素可以有效地用于追踪海底热液系统中的岩浆流体，并具有监测流体混合和成矿过程的潜力。
Lithium isotopic compositions of fluid inclusions and hosted gangue quartz from a giant volcanogenic massive sulfide deposit in China provide robust evidence for inputting of magmatic fluids into a Triassic submarine hydrothermal system. The δ7Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions). These data confirm the temperature-dependent Li isotopic fractionation between hydrothermal quartz and fluid (i.e., Δδ7Liquartz-fluid= –8.9382 × (1000/T) + 22.22(R2= 0.98; 175 °C–340 °C)), which suggests that the fluid inclusions are in equilibrium with their hosted quartz, thus allowing to determine the composition of the fluids by using δ7Liquartzdata. Accordingly, we estimate that the ore-forming fluids have a δ7Li range from −0.7‰ to +18.4‰ at temperatures of 175–340 °C. This δ7Li range, together with Li–O modeling , suggest that magmatic fluid played a significant role in the ore formation. This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.