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Feldspar dissolution during the weathering of granite under tropical conditions

Much of Malaysia is composed of granite. Samples ranging from unweathered granite to surface soils from newly exposed cut slopes and drill-holes were analysed using Quantitative X-ray Powder Diffraction (QXRPD), X-ray Fluorescence spectrometry (XRF), Inductively-coupled plasma mass spectrometry (ICP-MS), Scanning Electron Microscopy (SEM) and Optical microscopy. Samples were also sent to commercial laboratories for the determination of geotechnical engineering index and strength properties. The analyses have brought about a categorization of the weathering profiles into 4 ‘zones’: top soil, saprolite, weathering boundary and unweathered granite zones. The reactions within the active weathering boundary zone dictate the formation of secondary minerals. The findings in each different zone have enlightened the understanding of the development of secondary minerals especially clays in a deep weathering profile. The study also confirms and furthers understanding of the way chemical weathering occurs on the K-feldspar grains and is followed by the mechanical collapse of the grains leading to the reduction in the geotechnical strength of the material. The major element mobility study did not show any relation to the degree of weathering within the saprolite. Trace element study did not give conclusive results. However, a rare earth element (REE) study shows that the mobility of REE depends on the degree of weathering. The presence of clay minerals and feldspar grains are related to the geotechnical engineering properties, especially the strength properties which are responsible to the stability of slopes.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:664193
Date January 2008
CreatorsMdyusoff, Zainuddin
PublisherUniversity of Edinburgh
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Sourcehttp://hdl.handle.net/1842/11854

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