汞同位素地球化学研究及其在矿床学中的应用进展

汞作为一种重要的成矿元素,广泛分布于不同地质体中,并参与成岩成矿作用。随着质谱技术的飞跃发展,汞同位素地球化学研究取得引人瞩目的进展。汞同位素被广泛地应用于示踪地球表生生物地球化学过程及汞污染等。近年来,汞同位素又被应用于揭示行星的演化过程、识别地质历史时期大火成岩省及示踪矿床成矿物质来源等方面。本文在前人研究的基础上,对不同地质储库汞同位素组成进行了系统总结。陨石、岩浆岩、变质岩、沉积岩、火山气体等地质储库汞同位素组成变化较大,部分样品还显示非质量分馏信息。本文着重阐述了低温热液矿床(现代热泉、汞矿床、铅锌矿床、锑矿床、金矿床)汞的赋存状态及同位素组成特征,构筑了汞同位素体系的基本格架。结合最新的研究成果,较全面地总结了矿床成矿过程中可能会发生的汞同位素分馏机制。热液矿床中汞同位素的质量分馏可能由流体挥发或者沸腾作用、冷凝作用、氧化还原反应、硫化物沉淀等引起。岩矿石中汞同位素的非质量分馏信息可能是地质历史时期汞光化学作用的产物,或者是继承某一特定的源岩信息所致。因此,未来汞同位素在示踪低温热液矿床的成矿物质来源、刻画成矿流体演化过程方面具有较大的应用潜力。

Advances in the Study on Mercury Isotope Geochemistry and Its Application in Mineral Deposits

BACKGROUND: As an important mineralization element, mercury is widely distributed in different geological bodies and participates in diagenesis and mineralization. With the rapid development of mass spectrometry technology, the field of mercury isotope geochemistry has made remarkable progress. Mercury isotopes have been widely used to trace the biogeochemical processes of the earth''s surface and mercury pollution. In recent years, mercury isotopes have been applied to reveal the evolution of planets, identify large igneous provinces in geological history, and trace the sources of mineral deposits.
OBJECTIVES: To summarize the mercury isotope compositions of different geological reservoirs (meteorites, terrestrial rocks, coal, sediments, volcanic emissions, epithermal deposits) and investigate the factors controlling the Hg isotope fractionation during ore-forming processes in epithermal deposits.
METHODS: Literature reviewed that included published data from this research group and others.
RESULTS: Based on previous studies, the isotope composition of mercury in different geological reservoirs was systematically studied. The mercury isotopic composition of geological reservoirs such as meteorites, magmatic rocks, metamorphic rocks, sedimentary rocks, and volcanic gases varied greatly, and some samples also contained non-mass fractionation information. The occurrence and isotopic composition characteristics of low-temperature hydrothermal deposits (modern hot springs, mercury deposits, lead-zinc deposits, antimony deposits, gold deposits) was the focus of this review, and the basic framework of the mercury isotope system construction. Combined with the latest research results, a comprehensive summary of the mercury isotope fractionation mechanism that may have occurred in the mineralization process of the deposit was carried out. The mass fractionation of mercury isotopes in hydrothermal deposits may be caused by fluid volatilization or boiling, condensation, redox reactions, and sulfide precipitation. The non-mass fractionation of mercury isotopes in rocks and ores may be the product of mercury photochemistry during the geological history, or the inheritance of a specific source rock information.
CONCLUSIONS: In the future, mercury isotope has great application potential in tracing the ore-forming source of low-temperature hydrothermal deposits and characterizing the evolution of ore-forming fluids.