Abstract

• The present research is carried out laterite and lateritic soils of the Hpa-an Township, Kayin State. In this area, Taungnyo Formation (Carboniferous to Early Permian), Moulmein Limestone (Middle to Late Permian) are exposed covering with older alluvium (Pleistocene) and younger alluvium (Holocene). Laterite altered from all kind of rocks such as igneous, sedimentary and metamorphic rocks. Geochemical analysis of lateritic soil samples is tested with EDXRF to differentiate the laterite type and lateritization processes. Geochemical study of laterite in Hpa-an area suggest that it is made up of within 24% - 64% of SiO2 , between 16 % and 50 % of Fe2O3 , from 13 % to 27 % of Al2O3. Others oxides such as K2O, MnO and CaO are composed of small amount. Trace elements are shown that S, Sr, Cr, V, Zr Cu, Zn,Y, Nb and Rb. The identification and analysis of laterites were made by Molar Ratio of laterite which is based on the ratios of sesquioxides (Fe2O3 + Al2O3) to silica (SiO2). Molar ratio less than 1.33 is true laterite, between 1.33 and 2 is lateritic soil and greater than 2 is non-lateritic soil. Ternary Diagram is used to explore degree of lateritization. Four stages of alteration are recognized in lateritization process: (i) kaolinitization, (ii) weak lateritization, (iii) moderate lateritization and (iv) strong lateritization. Based on the results, Taunggalay and Myaing-gale areas have less than 1.33 in Molar ratio and moderate lateritization. Vicinity of Hpaan and Ya-The Byan Taung display between 1.33 and 2 in Molar ratio. These areas pronounced lateritic soil and lied in weak lateritization zone. Southern parts of the study area show greater than 2 in Molar ration where it is non-lateritic soil zone and kaolinization stage.