University of Twente Student Theses


Using Thermal Infrared Spectroscopy to Reveal Feldspars Mineralogy and Chemistry

Wardhana, Asyari Ismail (2009) Using Thermal Infrared Spectroscopy to Reveal Feldspars Mineralogy and Chemistry.

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Abstract:Mapping feldspar composition and mineralogy is important in identifying alteration zones. Conventional analysis techniques such as XRD and microprobe could yield the mineral composition and mineral chemistry of feldspars. How ever, these techniques have a limitation; they are very time consuming and require high cost for the analysis. The thermal infrared (TIR or 8-12μm) has great potential for remote mineral mapping. The main objective of this research is to develop a methodology to determine feldspar composition and mineralogy from thermal infrared spectra, to assist alteration mapping on airborne TIR data. The study was conduct in the Yerington area, Nevada, USA. The area is approximately 250,000 m2. Yerington area especially Mc Arthur mine site, where post ore-tilting during extreme crustal extension in Late Tertiary rotated the Jurassic porphyry copper deposit. This condition creates the exposure from various alteration zones on the surface of the study area and Tertiary volcanic rocks. The methods that conducted in this research were divided into two categories in order to answer the specific problems, they are 1. Determining the diagnostic wavelength region in TIR for feldspars identification using USGS spectral library and 2. Rock samples TIR measurement in laboratory. The result shows the important wavelength for feldspar identification occurs in the range of 8- 10 μm. Plagioclase feldspar was influenced by percentage of anorthite. From the USGS spectral library analysis, the feldspar members that are idecntified are albite, oligoclase, andesine, labradorite, bytownite, microcline, sanidine and orthoclase. It was shown in the TIR data, the alkali feldspar group, could be analyzed using band depth absorption calculation. The results showing the decreasing of spectral absorption band depth from Ca rich feldspar to K-rich feldspar in alkali feldspars group. Analysis of field samples reveals classification of mineralogy in the study area. There are three members of feldspar was resulted from 51 samples that were measured in TIR wavelengths. Those feldspar members are albite, andesine and sanidine. The variations of feldspars member were present in the various alteration zones.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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