Clay mineral composition of some volcanogenous soils in Indonesia and the Philippines

Abstract

Abstract Clay fractions of three Andosols and a Latosol occurring in Indonesia, and two Alluvial Soils derived from pyroclastic sediments in the Philippines were examined by means of chemical analyses, X-ray diffraction, differential thermal analysis, thermogravimetry, infrared absorption spectroscopy, and electron microscopy. The results are summarized as follows. Allophane is a dominant clay mineral of young volcanogenous soils occurring in the tropics. Small amounts of halloysite, gibbsite, and imogolite are also found in some of the young volcanogenous soils. Halloysite and imogolite are relatively abundant in the surface soil, while gibbsite is more abundant in the subsoil. In the clay fraction of the young volcanogenous soils in the tropics, α-cristobalite is often present, but quartz occurs rarely. Small amounts of feldspars are also present in the Philippine soils. 2 : 1-type minerals are found to a small extent in some of the sample soils. The above results agree well with the results for Japanes...