Mineralogy of kaolin clays in different forest ecosystems of southern Western Ghats, India

摘要

Random X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to identify 1 : 1 clay minerals in soils of five different forest ecosystems such as moist deciduous forests, evergreen forests, shola forests, grasslands and scrub jungles in the southern Western Ghats, India. The study sites experience a humid tropical climate with intense leaching and weathering, except scrub jungle which lies in the rain shadow area of the Western Ghats. XRD analyses of air-dried samples, confirmatory tests using formamide intercalation and SEM could establish kaolinite-halloysite coexistence in clay fractions of three different ecosystems of the Western Ghats. Earlier studies on clay mineralogy in the region failed to establish such coexistence because of the relative metastable nature of halloysite with respect to kaolinite. The identification of soil systems with metastable minerals like halloysite presents interesting possibilities of further studies vis-a-vis soil genesis and management in the tropics.