CHEMICAL CHARACTERISTICS OF HOTSPRINGS AND FUMAROLES OF PAPANDAYAN VOLCANO AND ITS RELATION TO THE VOLCANIC ACTIVITY

• Main Author: PRIMULYANA, SOFYAN
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/20535
• Institution: Institut Teknologi Bandung

Chemical characteristics of geothermal manifestations on the surface are very useful for studying magmatic hydrothermal systems. Changes in chemical characteristics over time provide valuable information for monitoring volcanic activity. Geothermal manifestations in the Papandayan volcano consist of hot springs, hot mud pools, acid crater lake, and fumaroles. Hot springs have temperature between 32 and 96C, pH between 0.8 and 3.0 (strong acid) and are classified as acid sulphate water type formed by condensation of magmatic gases of primarily oSO2, H2S, dan HCl into the shallow groundwater. Fumaroles have temperature between 90 and 300C, consist mostly of HO (96 to 99%), CO (0.9 to 2.9%), total sulfur o22(SO and HS) from 0.10 to 1.0%, HCl is less than 0.24%, N is less than 0.06%, 222O is less than 0.003%, and CH, H, He, and Ar are less than 0.002%. 242HS content is higher than SO and total sulfur content (St) is higher than HCl 22reflecting low to medium temperature fumaroles. Gas content shows characteristics of volcanic andesitic gases associated with convergent tectonic environment and influenced by the presence of hydrothermal system and the mixing of meteoric water. Increase in volcanic activity during 2000-2002 was marked by the increasing of temperature, pH, chemical contents and ?S of sulphates, and the increasing of K/Na ratio and Cl/SO ratio of hot springs. Decrease in volcanic activity since 2003-2009 was marked by decreasing temperature, pH, chemical contents and ?S of sulphates and the decreasing ratio of K/Na and the ratio Cl/SO in hot springs and supported by lower ratio of 344344SO/HS in fumaroles. 22The changes of chemical compositions are strongly influenced by the increasing supply of magmatic gases, mainly HCl and SO2 at the time of increase in volcanic activity. iii Increasing of CO2/St and St/HCl ratios at fumaroles since 2003-2009 is due to decreasing magmatic gases supply and absorption of HCl and SO2 into hydrothermal systems. The increasing of temperature, chemical contents, isotopic of ?34S (SO4), ratio of Cl/SO4 in hot water and increasing the ratio of SO2/H2S in fumaroles can be used as geochemical parameters for monitoring of future changes in the activity of the Papandayan volcano.