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通过分析长江干流及主要支流表层悬浮物的环境磁学参数特征(类型、含量及粒度)及其空间变化,探讨环境磁学对河流物源示踪的意义。结果表明,长江悬浮物磁性矿物特征以磁铁矿为主,含有少量赤铁矿及针铁矿。上游不完整反铁磁性矿物含量高于中下游,反映四川盆地广泛分布的紫红色砂页岩的影响。受攀枝花钒钛磁铁矿影响,干流磁性矿物含量上游高于中下游,表现为在攀枝花处迅速增加,向下游逐渐降低并在经过三峡后显著降低,说明三峡大坝对上游磁性矿物有明显的拦截作用。支流中雅砻江、汉江及湘江较高的磁性矿物含量分别受控于流域出露的源岩及工农业等人为影响。长江悬浮物x_(fd)%大于5%,表明样品中含有超顺磁颗粒。受流域地势及气候影响,磁性颗粒的粒径从上游至下游逐渐变细。长江悬浮物磁性特征能够在一定程度上反映物源特征,但长江地质条件复杂,气候类型空间变异大,且流域人为影响较大(三峡大坝等),使得利用磁性矿物特征示踪物源受到限制。
By analyzing the characteristics of environmental magnetic parameters (type, content and grain size) and their spatial variations, the paper discusses the significance of environmental magnetism on river source tracing. The results show that the magnetic minerals in the Yangtze River are mainly magnetite and contain a small amount of hematite and goethite. The incomplete upper antiferromagnetic mineral content is higher than the middle and lower reaches, reflecting the influence of purple sand shale widely distributed in Sichuan Basin. Affected by the vanadium-titanium magnetite in Panzhihua, the magnetic mineral content in the mainstream is higher than that in the middle and lower reaches, showing a rapid increase in Panzhihua, a decrease to the downstream and a significant decrease after passing through the Three Gorges, indicating that the Three Gorges Dam has obvious Intercept function. The higher levels of magnetic minerals in the Yalong River, Han River and Xiang River in the tributaries are controlled by man-made influences such as source rocks and industrial and agricultural practices exposed in the basin. The Yangtze River suspended matter x_ (fd)% greater than 5%, indicating that the sample contains superparamagnetic particles. Influenced by the topography and climate of the basin, the particle size of magnetic particles tapers from upstream to downstream. The magnetic characteristics of the suspended matter in the Yangtze River can reflect the characteristics of provenance to a certain extent. However, the geological conditions of the Yangtze River are complex, the climate type has large spatial variability, and the man-made impact on the basin is large (such as the Three Gorges Dam). Therefore, limit.