金沙江—红河富碱侵入岩带含矿与不含矿富碱斑岩Li同位素地球化学特征及其地质意义

Lithium Isotopic Characteristics of Ore-Bearing and Barren Intrusions in the Jinshajiang-Honghe Alkali-Rich Intrusive Belt

Li同位素示踪是近几年发展起来的一种新兴的稳定同位素地球化学方法,它在示踪岩浆源区物质组成微小变化方面非常灵敏。本文首次运用Li同位素地球化学示踪方法对金沙江—红河富碱侵入岩带不含矿的剑川北岩体和含矿的万硐山岩体进行了研究。结果表明剑川北岩体和万硐山岩体的Li/Yb的比值分别为7.20～9.58和11.18～20.0,δ7Li特征分别为+0.3‰～+6.2‰和-6.5‰～+0.1‰;含矿与不含矿岩体δ7Li值存在明显差异,指示含矿岩体的岩浆源区可能遭受过较大程度的板片脱水所释放的具有较低δ7Li值的流体的交代作用。研究结果为进一步揭示金沙江—红河富碱侵入岩带富碱斑岩源区特征提供了重要依据。

Lithium isotope tracing is a new stable isotope geochemical method developing fast in recent years,and can trace tiny changes of magma source region.In this article,lithium isotope geochemistry was used to study ore-bearing Wandongshan intrusion and ore-barren Jianchuanbei intrusion in Jinshajiang-honghe alkaline-rich intrusive belt.Results show that the Li/Yb ratio ranges of Wandongshan intrusion and Jianchuanbei intrusion are 7.20-9.58 and 11.18-20.0,respectively.δ7Li values of Wandongshan intrusion and Jianchuanbei intrusion are ＋0.3‰-＋6.2‰ and-6.5‰-＋0.1‰,respectively.This result may due to the different degrees of slab-derived fluid metasomatism between ore-bearing Wandongshan intrusion and ore-barren Jianchuanbei intrusion.It offers an important clue to further study on the source region of the Jinshajiang-honghe alkaline-rich intrusive belt.