摘要
长江与黄河沉积物中磁铁矿的元素组成揭示,两者的FeO与Fe2O3及一些置换元素的含量差异明显。长江磁铁矿中FeO与Fe2O3含量稍高于黄河磁铁矿，而Ti、V、Si、Al、Cr、Mg及Mn等元素含量明显地低于黄河磁铁矿，元素含量变化显著小于黄河磁铁矿。这反映长江磁铁矿中Fe2＋及Fe3＋的类质同象置换较少，主要为均质相单矿物颗粒。而黄河磁铁矿中元素含量变化大，既有均质相的颗粒，也存在一些Fe2＋及Fe3＋类质同象置换普遍的磁铁矿，其中发育钛磁铁矿、钛铁晶石或钛铁矿的出溶交生相。长江与黄河磁铁矿不同的元素组成特征揭示了长江与黄河沉积物不同的物质来源。由于碎屑磁铁矿在表生环境中具有相当高的稳定性，因此磁铁矿可以作为一种特征的标型矿物，根据其含量、元素组成与晶相特点来区分长江与黄河沉积物，用以研究边缘海中长江与黄河的物质混合与扩散问题。
Magnetites from the Yangtze River and the Yellow River sediments have different chemical compositions with distinct FeO, Fe2O3 and trace elemental concentrations. The Yangtze magnetite has slightly higher FeO and Fe2O3 contents than that in the Yellow river sediment (Huanghe magnetite), whereas replacement elements, such as Ti, V, Al, Si, Mg, Mn and Cr bear obviously lower contents and little compositional variation in the Yangtze magnetite than in the Huanghe magnetite. This indicates that isomorphic replacements of Fe2＋ and Fe3＋ by other elements are rare in the Yangtze magnetite, and the magnetites are homogeneous. On the contrary, the Huanghe magnetites show different cases, in which some grains are homogeneous and other grains heterogeneous with distinct trellis- type intergrowth, reflecting many isomorphic replacements of Fe2＋ and Fe3＋ . Different characters of chemical and crystal structure in the Yangtze and Huanghe magnetites reflect their different sediment sources. Due to high stability in hypergene environment, magnetite can be used as indicator based on its chemical composition and crystal structure to distinguish and trace the Yangtze River and the Yellow River sediments, furthermore, to study diffusion and mixture of both sediments in shallow seas.
出处
《地球化学》
CAS
CSCD
北大核心
2000年第5期480-484,共5页
Geochimica
基金
国家自然科学基金!(49976016)
南京大学成矿作用国家重点实验室资助
同济大学海洋地质教育部重点实验室资助项目
关键词
磁铁矿
标型矿物
沉积物
长江
黄河
magnetite
typomorphic mineral
Yangtze River
Yellow River
chemical composition
