摘要： 中国南方网纹红土是在季风气候条件下形成的一种特殊地层,对重建南方第四纪气候环境具有特殊重要的意义,但长期以来对网纹化过程的物化特点缺乏足够的认识。对江西九江、彭泽与湖南岳阳3个剖面的黏土质网纹红土中白色网纹和红色基质分离后进行了地球化学元素、游离铁含量等测试,结果表明:(1)白色网纹中,发生了Fe、Mn、Th、Ga、Cu、Zn、Co、Ni、Cr、 V等元素的显著亏损,SiO₂、Zr、Hf及轻稀土元素的显著富集,游离铁含量较低;红色基质中则完全相反;(2)网纹中Fe²⁺含量较高,基质中含量较低,揭示了网纹倾向于还原环境,基质倾向于氧化环境。研究认为网纹和基质这种氧化还原差异,是Fe、Mn、Co、Ni、Cr、V、Zn、Th、Ga、Cu等元素在网纹中游离淋失,并在基质中的沉淀富集,造成Zr、SiO₂及轻稀土等在网纹中的相对富集、在基质中“稀释”而呈现亏损的主要原因。

关键词: 红色基质, 白色网纹, 元素地球化学, 网纹发育程度, 干湿交替

Abstract: Reticulate red clay in southern China is a kind of special stratum that formed in a monsoon climate condition,which is of great significance to reconstruct the Quaternary climate environment. For a long time,there is a lack of adequate understanding of physical and chemical characteristics of the formation process of reticulated mottles. Three sections of reticulate red clay,which were located in the Jiujiang and Pengze of Jiangxi Province, and Yueyang of Hunan Province, were studied, and the red matrix and the white reticulated mottles were separated and the geochemical elements,free iron content and so on were analysed. The results show that:(1)In the white reticulated mottles, Fe,Mn,Th,Ga,Cu,Zn,Co,Ni,Cr,V elements are outstanding leaching,while Zr,SiO₂,Hf and light rare earth elements are obvious enriched,and the content of free iron are low; in the red matrix, they are reversed. (2)Fe²⁺ content is higher in the white reticulate,while lower in the matrix,which indicates white reticulate tend to be developed in a reductive environment and matrix tend to be developed in an oxidized environment. The difference of oxidation reduction between white reticulated mottles and red matrix is supposed to be the reason why Fe,Mn,Co,Ni,Cr,V,Zn,Th,Ga,Cu are leaching in the white reticulated mottles and enriched in the matrix, which cause Zr,SiO₂ and light rare earth elements relative enriched in the white reticulated mottles and “dilution” in the red matrix.

Key words: red matrix, white reticulated mottles, element geochemistry, development degree of reticulated mottles, alternating wet and dry

中图分类号: 

• P539.7

• P534.63