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|Title:||Pedogenic alteration of illite in subtropical China|
|Citation:||Clay Minerals: journal of the European Clay Groups, 2014; 49(3):379-390|
|Publisher:||The Mineralogical Society|
|W. Han, H. L. Hong, K. Yin, G. J. Churchman, Z. H. Li, and T. Chen|
|Abstract:||Pedogenic alteration of illite from red earth sediments in Jiujiang in subtropical China was investigated using X –ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Illite, hydroxy-interlayered vermiculite (HIV), kaolinite and mixed-layer illite-HIV (I-HIV) are present in the soils. The characteristic reflections of the clay phases were 14 Å, 10 –14 Å, 10 Å, and 7 Å, respectively. After Mg-glycerol saturations, the 14 Å peak of the samples did not expand, and after heating at 350°C and 550°C it shifted to 13.8 Å and 12 Å respectively, with no residual 14 Å reflection, suggesting the occurrence of hydroxy-interlayered vermiculite. The randomly interstratified I-HIV clays were characterized by a broad peak at 10 –14 Å, which did not change its position after Mg-glycerol saturation, but collapsed to 10 Å after heating at 350°C and 550°C. HRTEM analysis showed different lattice fringes of 12 Å, 10 Å and 7 Å. Mixed-layer I-HIV, HIV-K and illite-kaolinite (I-K) were observed in the HRTEM images which represented the intermediate phases during illite alteration. The merging of two 10 Å illite layers into a 12 Å HIV layer, lateral transformation of one HIV layer into one kaolinite layer and alteration of one illite layer into two kaolinite layers illustrated the mechanisms of illite-to-HIV, HIV-to-kaolinite and illite-to-kaolinite transformation, respectively. The proposed pedogenic alteration of illite and the weathering sequence of the clay minerals in Jiujiang is illite → I-HIV → HIV→ HIV-K → kaolinite. In addition, illite may transform directly to kaolinite.|
|Keywords:||pedogenic alteration; illite; mixed-layer clay; high-resolution transmission electron microscopy (HRTEM); red earth|
|Rights:||© 2014 The Mineralogical Society|
|Appears in Collections:||Agriculture, Food and Wine publications|
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