Electronic Theses and Dissertation

Penelitian ini bertujuan untuk mengkarakterisasi endapan vulkanik Gunung Seulawah Agam melalui integrasi analisis FTIR, XRD, dan XRF untuk memahami komposisi material, zonasi geokimia, serta ciri khas sistem vulkaniknya. Sampel diambil pada delapan titik yang mewakili empat sektor yaitu utara, barat, selatan, dan timur dengan tiga interval kedalaman. Hasil FTIR menunjukkan dominasi pita Si–O dan Si–O–Si pada kisaran 970–1015 cm⁻¹ di seluruh sektor, yang menandakan kerangka silikat sebagai komponen utama endapan. Analisis XRD mengidentifikasi kristobalit dan kuarsa sebagai fase kristalin dominan, dengan hematit dan magnetit sebagai fase oksida minor hingga menengah, serta kalsit dalam jumlah terbatas tanpa kehadiran mineral alterasi hidrotermal. Hasil XRF menunjukkan komposisi unsur mayor didominasi oleh SiO₂ sekitar 38–66%, Al₂O₃ 6–20%, dan Fe₂O₃ 10–41%, sehingga Seulawah Agam diklasifikasikan sebagai sistem vulkanik menengah silika. Unsur minor dan jejak seperti ZrO₂, SrO, Y₂O₃, dan Eu₂O₃ terdeteksi konsisten pada lintas sektor, dengan ZnO dan CuO hadir pada kadar jejak rendah. Secara lateral, Sektor Utara mencerminkan karakter silika menengah, Sektor Barat menunjukkan oksidasi paling kuat, Sektor Selatan memiliki kandungan silika tertinggi, dan Sektor Timur memperlihatkan silikat primer yang paling homogen. Integrasi FTIR–XRD–XRF menunjukkan bahwa variasi geokimia lebih dikontrol oleh faktor struktural dan zonasi sektoral daripada perbedaan sumber magma. Ciri khas Gunung Seulawah Agam ditandai oleh dominasi silikat kristalin yang stabil, komposisi unsur mayor yang seimbang, serta sidik jari unsur minor–jejak yang konsisten.

This study aimed to characterize the volcanic deposits of Mount Seulawah Agam through an integrated analysis of FTIR, XRD, and XRF to elucidate the material composition, geochemical zoning, and distinctive characteristics of the volcanic system. Samples were collected from eight locations representing four sectors (north, west, south, and east) across three depth intervals. FTIR results indicate the dominance of Si–O and Si–O–Si absorption bands within the 970–1015 cm⁻¹ range across all sectors, reflecting a silicate framework as the principal component of the deposits. XRD analysis identified cristobalite and quartz as the dominant crystalline phases, accompanied by hematite and magnetite as minor to intermediate oxide phases and minor calcite, with no evidence of hydrothermal alteration minerals. The XRF results show that the major element composition is dominated by SiO₂ at approximately 38–66%, Al₂O₃ at 6–20%, and Fe₂O₃ at 10–41%, classifying Seulawah Agam as an intermediate-silica volcanic system. Minor and trace elements such as ZrO₂, SrO, Y₂O₃, and Eu₂O₃ were consistently detected across all sectors, whereas ZnO and CuO were present at low trace levels. Laterally, the northern sector exhibited intermediate silica characteristics, the western sector recorded the strongest oxidation signature, the southern sector displayed the highest silica content, and the eastern sector was characterized by the most homogeneous primary silicate assemblage. The integration of FTIR, XRD, and XRF indicates that geochemical variations are primarily controlled by structural factors and sectoral zoning rather than differences in the magma source. The distinctive character of Mount Seulawah Agam is defined by the stable dominance of crystalline silicates, balanced major element composition, and consistent minor–trace element geochemical fingerprint.