Electronic Theses and Dissertation

Penelitian ini menggunakan metode spektroskopi inframerah untuk menganalisis komposisi mineral dan pengaruh ukuran butir terhadap karakteristik spektra reflektansi inframerah sampel batuan dari kawasan geotermal Ie Su’um dan Ie Jue. Spektra reflektansi inframerah dari sampel batuan tersebut diukur menggunakan Spektroradiometer FieldSpec4 Hi-Res dari panjang gelombang visible and near-infrared (VNIR) sampai shortwave infrared (SWIR) (350-2500 nm). Komposisi mineral sampel batuan diidentifikasi dengan membandingkan kemiripan spektra hasil pengukuran dengan database spektra mineral dari United State Geological Survey (USGS). Pengklasifikasian kemiripan spektra pada panjang gelombang SWIR (2000–2500 nm) menggunakan metode Spectral Angle Mapper (SAM), Spectral Feature Fitting (SFF) dan Binary Encoding (BE). Hasil penelitian menunjukkan bahwa variasi sampel batuan dari kawasan geotermal tersebut dan fraksi ukuran butir mempengaruhi nilai reflektansi dan karakteristik spektra inframerah. Kedalaman fitur-fitur absorpsi spektra reflektansi dari sampel batuan dipengaruhi oleh fraksi ukuran butir. Komposisi mineral sampel batuan dari kawasan geotermal Ie Su’um dan Ie Jue didominasi oleh mineral illite, montmorillonite, kaolinite dengan campuran smectite, chlorite, gypsum dan calcite. Berdasarkan penelitian ini dapat disimpulkan bahwa metode spektroskopi inframerah merupakan sebuah metode yang efektif untuk mengidentifikasi komposisi mineral pada batuan dari kawasan geotermal.

Kata Kunci: Kawasan Geotermal, Spektroskopi Inframerah, Batuan, Komposisi Mineral, Ie Su’um, Ie Jue

This study uses infrared spectroscopy method to analyze mineral composition and the effect of grain sizes on the characteristics of infrared reflectance spectra of rock samples, collected from the Ie Su'um and Ie Jue geothermal areas. The infrared reflectance spectra of rock samples were measured using a FieldSpec4 Hi-Res Spectroradiometer from visible and near-infrared (VNIR) to shortwave infrared (SWIR) (350-2500 nm) wavelength regions. Mineral composition of rock samples were identified by analyzing the similarity of the measured spectra with mineral spectral database from the United State Geological Survey (USGS). The spectral similarity classification at the SWIR wavelength range (2000–2500 nm) was computed by using Spectral Angle Mapper (SAM), Spectral Feature Fitting (SFF) and Binary Encoding (BE) methods. The results showed that the variation of rock samples from the geothermal area and grain size fractions affected the reflectance value and the characteristics of infrared reflectance spectra. The depth of spectral absorption features of rock samples is influenced by grain size fractions. The mineral composition of rock samples from the Ie Su'um and Ie Jue geothermal areas were dominated by illite, montmorillonite, kaolinite with a mixture of smectite, chlorite, gypsum and calcite minerals. Based on this research, it can be concluded that the infrared spectroscopy method is an effective approach in identifying mineral composition of rocks from the geothermal area. Keywords: Geothermal Area, Infrared Spectroscopy, Rock, Mineral Composition, Ie Su'um, Ie Jue