Characterisation of iron nodules in a Ultisol of central Taiwan

摘要: The chemical and physical properties, clay mineralogy, 14C radiocarbon age of iron nodules found in a Ultisol located on low elevation terrace Taiwan were investigated. results indicated that the amount size increase with soil depth. Free contents markedly higher than surrounding matrix. Feo/Fed ratio was all nodules, indicating predominant form free crystalline. Al-substituted goethite as oxide mineral Al substitution ranged from 16 to 24% mole. Illite hydroxy-interlayered vermiculite kaolinite dominant minerals nodules. X-ray fluorescence (XRF) analysis are composed primarily Fe, Si, Al, minor amounts Mn. Based similarity mineralogical compositions dating ages, it is suggested major driving force promoting formation situ weathering saprolite by frequent wetting/drying cycles. We speculate illuviated played only role their formation.