江西泰和第四纪红色粘土的矿物特征
MINERALOGICAL PROPERTIES OF THE QUATERNARY RED CLAYS IN TAIHE REGION, JIANGXI PROVINCE
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摘要: 第四纪红色粘土在我国南方分布很广,最典型的分布在华中岗地上,土层较厚,上部土质均匀,下部具有红白网纹并含砾石,大都是中更新世的洪积—冲积或残积—坡积物,笔者认为可能是间冰期比较暖热气候条件下的产物。熊毅早就指出:各地环境殊异,地形复杂,母岩不同,其理化特征将随之而异。第四纪红色粘土来自不同的堆积相,和经受不同的风化和成土过程,这将在矿物组成方面反映出来。土壤普查的结果表明,第四纪红色粘土按其分布的地形部位,成因和物质来源,可分成两类:一类是残积坡积相，为中更新世较早的暗红色沉积物，即Q2另一类是冲积相，为中更新世较晚的红化程度较轻的淡红色沉积物。它们都经历了中更新世至今的成土过程1)”。为了查明它们的差异，并有助于第四纪沉积物的研究，笔者用部分标本进行矿物分析，并对初步结果进行讨论。Abstract: The Quaternary red clays which may probably belong to respective sedimentary facies are widely dispersed in South China. The period of the Quaternary red clays has been divided in middle Pleistocene ( Q 2 ) . They are charecterized by red color, clayey texture, mottling in the bottom layer and boulder in the lower part. According to the geomorphology, the genesis and origin of materials, the Quaternary red clay sediments in the Taihe region,Jiangxi Province, may be divided into two types; one ( profile 1 , 2 ) is dark red material of residual and slope deposits of early middle Pleistocene which sedimented earlierj the other ( profile 3,4) is light red alluvial material,which sedimented later, Both of them have undergone-a soil-forming process since middle Pleistocene until now. It can be seen from the composition of heavy minerals in-the 10-50 μm fractions that the dark red clay sediments contain 7 -10% hornblende and 17-20% tourmaline, while the contents of the two minerals in light red ones are 17-22% and 9-14% respectively. It can also be seen from the composition of the minerals of the2μm fractions that the dark red sediments have little more kaolinite and free iron oxides, less 14λ transitional minerals and noncrystalline materials than the light red ones.The activity of free iron oxide, the dispersity and specific surface area are greater in 'light red sediments than those in dark red ones. The X-ray diffraction patterns of the clay particles in mottling layer ofter the treatment of removing iron indicate that the mineral composition in mottling layer ( 2μ) is similar to the soil in the upper layer and that the difference in the colour of the mottles only reflects the various contents of free iron oxide. According to the study of mineralogy, there is a difference in the degree of weathering and soil forming between the two sediments of Quaternary red clays,the weathering degree of dark red sediments is greater than that in the other. The red clay must be compared with the soils which were developed from igneous rock, when a thorough investigation is made,
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[1] (1)熊毅，1944，江西更新统枯土之性质及其生成，地质论评，9卷1-2期，109-1200
(2)熊毅，1952,由更新统沉积物的胶体矿物分析试论第四纪气候，地质学报，32卷,26-410
(3)Alexiades, C. A, and Jackson, M, I.，1966: Quantitative clay mineralogical
analysis of soils and sediments, Clays Clay Miner. 14, 35-52
(4)Jackson, M, L,，1964: Soil clay mineralogical analysis in C, L. Rich and G, W, Kunze(eds)。Soil Clay Mineralogy, p.245-294, The University of North Carolona Press Chapel Hill,
(5)Herrera, R. Garcia, Miragaya, J, and Mayorga, O, 1980e Effect. of the removal of free iron oxides 0n the cation exchange capacity at
various pH"s and surface area of two alfisols and oxisol from Venezuela, Agrochimica Vol. 24: p. 5-6, 403-409. -
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