中国南方网纹红土的形成机制及网纹成熟度研究

发布时间：2018-05-22 10:10

本文选题：网纹红土 + 第四纪　；参考：《江西师范大学》2015年硕士论文

【摘要】：网纹红土是发育在我国南方的独特地层,广泛的存在于红土风化壳中,因红色粘土层内含有网纹状、管状、蠕虫状浅色(白色,黄白色等)斑点(reticulated mottles)而得名。关于这套地层,前人在其物质组成,分布规律,土体形态,时代及其环境意义等方面做了大量工作,研究成果众多。但是仍存在以下悬而未决的问题:1)对网纹红土中网纹的形成原因和发育机制,尚不能全面系统的阐述。即对网纹红土的驱动机制及其发育过程还存在争议。2)对网纹的持续发育,没有清晰的认识,从而对网纹红土的气候环境的指示意义,尚不明确。本文在前人研究的基础上,结合多次野外实地勘探,选择长江中下游沿岸岳阳港口大道(YY)、黄石西塞山(XXS)、九江王家竹林(JSW)以及彭泽土塘(TT)四个地点的不同发育程度的十个网纹红土样品,将其浅色网纹与红色基质分离后,分别进行粒度、常量元素、微量元素、含水量、pH值、Eh值测试及游离铁、Fe3+/Fe2+值等测试。结果表明:网纹红土中,孔隙及其造成的含水量的差异性分布可能是网纹红土最初形成的内在驱动机制。在粘土质地的网纹红土中,相对于基质部分,网纹部分的细粘土颗粒少,含水量高,pH(4.96-5.73)、Eh(297-338mv)都较低,说明网纹处于酸性还原环境中。而基质,因铁质胶膜的发育,填充了孔隙,含水量变低,处在偏氧化环境中(335-384mv),pH(5.82-6.31)接近中性。酸性偏还原环境,使得Fe、Mn、Co、Ni、Cr、V、Ti等过渡金属元素在网纹中被强烈淋溶,在基质中,这些高场强元素强烈富集,铁质胶膜发育。这使二氧化硅、Zr等稳定矿物或元素在网纹中相对富集。由于铁质胶膜在基质中的发育和网纹部分细粘质性颗粒的减少,基质中孔隙率减小,而网纹中孔隙率增加。进而扩大了网纹与基质之间的含水量差异,进一步促进元素物质在网纹中的淋溶迁移和在基质中的沉淀积累。这是一个正反馈过程,只要土体反复干湿交替,网纹在一定的时间内,气候排水量不为零,这个过程就能促进元素物质在网纹中淋溶迁移,在基质中沉淀积累,从而促进网纹不断发育,网纹的成熟度也就会越高。随着基质中以Fe为主的过渡金属元素的富集,基质的颜色不断变深;网纹则由于Fe元素的流失和稳定元素的富集,颜色越浅,从而使网纹与基质色度差增大。而色度差异越大,说明上述物质淋溶与淀积过程进行的也就越充分,网纹也就越发育,网纹成熟度也越高。网纹成熟度,可用网纹与基质的色度差异表示(△E=[(△a)2+(△b)2+(△L)2]1/2)。研究认为,干湿交替的土体环境和温暖湿润的气候环境,是网纹化过程的外在环境驱动机制。研究进一步分析了中国南方大量网纹红土地层的时代后,认为亚热带季风区干湿交替的季风气候特点,是中国南方网纹红土在早更新世晚期产生并持续发育的气候环境条件。网纹红土是古土壤,并且是正在形成的古土壤。在季风区,网纹的形成与发育是个普遍的土壤环境现象,网纹是土壤新生体。本研究从机理上,回答了网纹红土形成的成因机制和外部环境条件,解释了以前未能解决的网纹红土的众多现象与特点。为基于网纹红土的中国南方第四纪研究,提供了新的思路和方法,具有较为重要的现实意义和理论意义。
[Abstract]:Reticulated red soil is a unique stratum developed in the south of China. It is widely found in the weathered crust of the red soil. It is named after the reticulated, tubular, vermicular light color (white, yellow white) spots in the red clay layer (reticulated mottles). A great deal of work has been done in the fields of righteousness, but there are still many outstanding achievements. However, there are still unresolved questions: 1) the reasons for the formation and development mechanism of the net pattern in the reticulated red soil can not be fully systematically expounded. That is, the driving mechanism and the development process of the reticulated red soil are still in dispute.2), and there is no clear understanding of the continuous development of the reticulated reticulated soil. It is not clear that the climatic environment of the reticulated red soil is not clear. On the basis of previous studies, this paper selects ten reticulated red lines in four locations of Yueyang port Avenue (YY) along the middle and lower reaches of the Yangtze River, XXS, Jiujiang's Wangjia bamboo forest (JSW) and Pengze soil pond (TT) on the basis of previous studies. The soil sample, after separating the light color mesh with the red matrix, carries out the particle size, the constant element, the trace element, the water content, the pH value, the Eh value test, the free iron and the Fe3+/Fe2+ value. The results show that the difference distribution of the pore and the water content in the reticulated red soil may be the internal driving mechanism of the original formation of the reticulated red soil. In the reticulated red soil of the earth, the fine clay particles in the reticulated part are less, the water content is high, pH (4.96-5.73) and Eh (297-338mv) are low, indicating that the mesh is in the acid reduction environment. The matrix, due to the development of the iron glue film, fills the pores, the water content is low, in the partial oxidation environment (335-384mv), and pH (5.82-6.31) close to the medium. The acid partial reduction environment makes the transition metal elements such as Fe, Mn, Co, Ni, Cr, V, Ti are strongly leached in the mesh. In the matrix, these high field elements are enriched and the iron film develops. This makes the stable minerals and elements of silicon dioxide, Zr and other elements relatively rich in the mesh. Due to the development of the iron colloid in the matrix and the mesh part of the fine clay The decrease of sex particles, the decrease in porosity in the matrix and the increase of porosity in the mesh, and further increase the water content difference between the mesh and the matrix, further promote the leaching and migration of elements in the mesh and the accumulation of precipitation in the matrix. This is a positive feedback process, as long as the soil is repeatedly dry and wet alternately, the mesh is in a certain time, The amount of water in the climate is not zero. This process can promote the leaching and migration of elements in the mesh, precipitate and accumulate in the matrix, thus promote the growth of the mesh and the higher the maturity of the mesh. With the enrichment of the transition metal elements with Fe as the main element in the matrix, the color of the matrix is deepened, and the net pattern is due to the loss and stability of the Fe element. The enrichment of the fixed elements, the lighter the color, and the difference in the chromaticity between the mesh and the matrix. The greater the chromaticity difference, the more fully the leach and deposition process of the above material, the more mature the reticle and the higher the ripening of the mesh. The mesh maturity can be expressed by the difference of the chromaticity between the mesh and the matrix (delta E=[(Delta a) 2+ (delta b) 2+ (delta L) 2]1/2). It is considered that the alternation of dry and wet soil environment and the warm and humid climate environment are the external environment driving mechanism of the reticulated process. After the further analysis of the time of the large number of reticulated red soil strata in southern China, it is considered that the dry and wet monsoon climate in the subtropical monsoon region is produced in the late Early Pleistocene. The reticulated red soil is the paleosol and it is an ancient soil formed. In the monsoon area, the formation and development of the net pattern is a universal soil environment phenomenon, and the mesh is a new soil new body. This study answered the mechanism of the formation of the reticulated red soil and the external environment conditions, and explained the previous failure. Many phenomena and characteristics of reticulated red soil can be solved. It provides new ideas and methods for the Quaternary study in southern China based on reticulated red soil, which has more important practical significance and theoretical significance.
【学位授予单位】：江西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S151

【参考文献】