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A new chemical index of weathering for metamorphic silicate rocks in tropical regions: A study from Sri Lanka |
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| Authors: | U de S Jayawardena Eiji Izawa |
| Institution: | aDepartment of Civil Engineering, Faculty of Engineering, University of Peradeniya, Peradeniya, Sri Lanka bDepartment of Mining, University of Kyushu, Kyushu, Japan |
| Abstract: | Weathered and fresh samples of metamorphic rocks from Sri Lanka were collected from various localities and analysed for major elements by XRF method (RIGAKU, KG-X System, Japan). The content of water was determined by the ignition method. The XRF results, obtained from these samples form the basis of a new index of chemical weathering, particularly for Sri Lanka, which is named the Silica-Titania Index, and is calculated as follows: Silica-Titania Index = {(SiO2/TiO2)/(SiO2/TiO2) × (Al2O3/TiO 2) × (SiO2/Al2O3)]} × 100(molecular proportions). The index can be used to determine the degree of weathering in chemically weathered silicate rocks of other countries in tropical regions. A triangular diagram plots the position of this index. The point load strengths of fresh rocksand weathered rocks with different degrees of weathering were correlated with the values of this new chemical index. The relative variation in strengths of fresh rocks and weathered rocks clearly indicates its suitability and usefulness for engineering geologists. |
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