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近年来风化过程中镁同位素的研究取得了一系列重要进展,这些进展不仅有利于准确理解河流中镁同位素组成变化的机理,还为深入探讨镁同位素地球化学循环奠定了基础。河流既是风化过程中镁的汇,也是海洋中镁的源。流域河水的镁同位素组成主要与物源和迁移过程中镁同位素分馏有关。河水的镁主要来源于流域的岩石,也受风尘沉积、地下水、植物残骸、降雨降雪等因素的影响。河水迁移过程中镁同位素分馏过程主要为碳酸盐矿物沉淀和溶解、硅酸盐矿物水解、矿物或胶体物质的吸附作用以及植物的吸收作用。此外,水体中次生矿物的形成还可能反映了河流水化学参数(主量元素、CO2溶解度、p H等)的突变。因此,分析河水的镁同位素组成,探讨其主要的分馏过程,不仅是应用镁同位素示踪地表物质循环的基础,还对深入认识镁同位素的地球化学循环具有重要意义。
In recent years, a series of important progresses have been made in the study of magnesium isotopes during the weathering process. These advances are not only helpful to accurately understand the mechanism of magnesium isotope composition in rivers, but also lay a foundation for further exploration of the magnesium isotope geochemical cycle. The river is both a source of magnesium in the ocean and a source of magnesium in the ocean. The magnesium isotope composition of river waters is mainly related to the magnesium isotope fractionation during the source and migration process. River water mainly comes from magnesium in the watershed, and is also affected by such factors as dust deposition, groundwater, plant wreckage and rainfall and snowfall. The process of magnesium isotope fractionation during river water migration mainly involves the precipitation and dissolution of carbonate minerals, the hydrolysis of silicate minerals, the adsorption of minerals or colloids, and the absorption of plants. In addition, the formation of secondary minerals in water may also reflect the abrupt change of chemical parameters (major elements, CO2 solubility, p H, etc.) of river water. Therefore, analyzing the magnesium isotope composition of the river and discussing its main fractionation process are not only the basis for the application of magnesium isotopes to trace the surface material circulation, but also important for understanding the geochemical cycle of magnesium isotopes.