镁铁-超镁铁质岩成岩成矿过程中的锂同位素地球化学:回顾与展望

Retrospects and Prospects on Li Isotope Geochemistry during Petrogenesis and Mineralization of Mafic-Ultramafic Rocks

锂(Li)同位素体系是示踪镁铁-超镁铁质岩成岩成矿过程(如结晶分异、地壳混染和熔/流体-矿物相互作用等)的全新工具.通过实例研究综述了原位Li同位素在镁铁-超镁铁质岩中应用的主要进展,主要包括:(1)美国Yellow Hill阿拉斯加型杂岩体Li同位素研究揭示弧岩浆早期堆晶过程可发生明显的Li同位素分馏;(2)土耳其和西藏蛇绿岩的Li同位素研究证明其在示踪蛇绿岩地幔序列岩石成因及豆荚状铬铁矿演化过程中的潜力;(3)Stillwater层状岩体超镁铁岩带Li同位素研究揭示流体对于大型层状岩体各矿物形成及铬铁岩中矿物元素交换的作用;(4)橄榄石Li含量与同位素分析在揭示岩浆铜镍矿床成矿过程的应用.

In-situ Li isotope geochemistry has been better utilized to trace many complex processes including fractional crystallization, crust contamination and melt/fluid-mineral reaction during the petrogenesis and mineralization of mafic-ultramafic rocks. This study summarizes the major progresses in Li isotope geochemistry during petrogenesis and mineralization of maficultramafic intrusions based on case studies. Firstly, the Li isotope study of Yellow Hill Alaskan-type intrusion reveal Li isotope fractionation during magma differentiation. Secondly, the studies on ophiolites from Turkey and Tibet indicate that Li isotope systematics have potential to constrain genesis of ophiolitic mantle section and evolution of chromitites. Thirdly, the Li isotope study of the ultramafic zone of the Stillwater complex demonstrates that hydrous fluids constrained mineral composition and acted as a critical medium of chemical exchange between minerals in the chromitites. Finally, Li isotope fractionation behavior in the formation of magmatic Ni-Cu sulfide deposits has been investigated.