近些年表生环境中镁同位素分馏取得了一系列重要研究进展,这些新认识为深入理解表生环境中镁同位素地球化学循环奠定了基础。表生环境中镁同位素的地球化学循环主要涉及风化、河流搬运、碳酸盐沉淀、水岩反应等重要地质过程。风化过程中镁同位素发生显著分馏,硅酸盐风化产物中富集重的镁同位素,轻的镁同位素易进入水体。河流搬运过程中,镁同位素不发生分馏,但外源输入可能影响水体的镁同位素组成。河水汇入海洋后,碳酸盐沉淀过程可导致轻的镁同位素以碳酸盐的形式从海水中移出。在海底高温水岩反应过程中,海水中绝大多数的镁(80%~87%)都进入岩石,循环后的热液可能富集轻的镁同位素。海底低温水岩反应过程中海水的镁可以进入岩石并形成次生矿物,此过程的镁同位素分馏主要与次生矿物的形成有关。此外,海水中的镁易与黏土矿物发生交换反应,此过程黏土矿物倾向于吸附轻的镁同位素。总之,在表生环境中上地壳的镁(δ26Mg约为-0.22‰)经历风化作用、河流搬运、海洋贮存,最终以碳酸盐岩(δ26Mg一般小于-1‰)或与玄武岩发生反应的形式重新回到岩石圈。 In recent years, a series of important research progresses have been made in the isotopic fractionation of magnesium in epigenetic environments. These new understandings have laid the foundation for further understanding of the magnesium isotope geochemical cycles in epiphytic environments. The geochemical cycles of magnesium isotopes in epigenetic environments mainly involve important geological processes such as weathering, river handling, carbonate precipitation and water-rock reactions. Magnesium isotopes are significantly fractionated during the weathering process. Silicate weathering products are enriched with heavy magnesium isotopes and light magnesium isotopes are readily accessible to the water. Magnesium isotopes do not fractionate during river handling, but exogenous inputs may affect the magnesium isotope composition of the water body. After the water has been introduced into the oceans, the carbonate precipitation process can lead to the removal of light magnesium isotopes from seawater as carbonates. During the reaction of high-temperature water and rock on the seabed, most of the magnesium in the seawater (80% -87%) enters the rock, and the hydrothermal fluid after recycle may be enriched in light magnesium isotopes. During the process of seafloor low temperature water-rock reaction, magnesium in seawater can enter the rock and form secondary minerals. The magnesium isotope fractionation in this process is mainly related to the formation of secondary minerals. In addition, magnesium in seawater easily exchanges with clay minerals. In this process, clay minerals tend to adsorb light magnesium isotopes. In summary, magnesium in the upper crust (δ26Mg approximately -0.22 ‰) undergoes weathering in the supergene environment and is transported by rivers and stored in the ocean. Finally, carbonate (δ26Mg generally less than -1 ‰) or a form of reaction with basalts Back to the lithosphere.