Bestämning av kvartshalt i sandprov : metodutveckling med OSL-, SEM- och EDS- analys

Sammanfattning: Quartz is one of the most common minerals on Earth and is found in both lose sediment, sedimentary rock and bedrock. The maturity grade of sediments can be determined by the amount of quartz it contains. This is used when interpreting the sediments’ geological history and reconstructing paleoenvironments. The purpose of this thesis is to analyze and develop methods for determining the quartz content in sediment, for which the following techniques have been used; energy dispersive spectrometry analysis (EDS) in scanning electron microscope (SEM), optically stimulated luminescence (OSL) and interpretation of backscatter images from SEM. It has been examined whether the luminescence and electron attributes can be used to estimate the actual quartz content in a sediment sample. Synthetically prepared samples with known content of quartz, potassium, feldspar and plagioclase were analyzed and interpreted in associated programs. The results show that it is possible to determine the amount of quartz in the samples by mapping the elements with an EDS analysis in SEM. However, it is not likely that the method will be widely applied since it is very time consuming. OSL analysis showed that it is not possible to estimate the quartz content in sand by luminescence. This because the OSL signal from quartz was drowned by the OSL signal from feldspar. Backscatter analysis from SEM showed that best results were obtained after the sediment samples were cast in epoxy and polished. The grayscale in the received backscatter images were interpreted in the computer program NIS Elements. The results showed that the error of the most reliable estimations (three picked samples) of the quartz content amounted to ± 4%. This study shows that out of the three tested methods the backscatter method generates the best results and is most reasonable to implement.