Perpustakaan Digital ITB

Tangkuban Perahu and nearby areas are the most important geothermal prospect in West Java that believed to be a volcano-hosted geothermal system. Recharge of and geothermal fluid evolution have not yet been fully understood. This is due to complexities of fluid origin, subsurface processes and variations of series of manifestations around the prospect. This study describes the origin, processes and evolution of geothermal fluids in relation to recharge and conceptual model of the Tangkuban Perahu Geothermal Systems (TPGS). The investigation involved sampling and analysis of 9 geothermal waters samples, 4 rainwater and 6 gases collected in fumaroles and other manifestations of the Tangkuban Perahu. The deuterium (?2H) and oxygen isotope (?18O) employed together with conservative elements such as B, Cl and rare alkali metals analyses to determine the origin and subsurface processes as the fluid migrates to the surface as discharge. The isotopic values (?18O and ?2H) of thermal and rainwater indicates deep-circulating meteoric origin, at an infiltration altitude ranges between 753-850m above sea level in low terrain. Meanwhile the high standing terrain indicates the recharge zone to be around the wall of the caldera and mountain slopes. Chondrite normalized patterns exhibit an overall negative slope that suggest enrichment of Lower Rare Earth Elements (LREEs). The non-atmospheric gases origin was diagnosed by the lower N2/Ar (? 38) and is characterized of meteoric source origin. The idea that the geothermal water mixes with shallow groundwater is substantiated using different mixing models and geoindicator analysis. The positive ?18O shifts from Kancah (KC), Batu Gede (BG) and Domas crater (KwD) thermal waters relative to the local meteoric lines were considered to be primarily due to interaction with host rocks or magmatic influx. In this geothermal systems, geothermal fluids are heating by heat source and geothermal gradient, followed by partly discharge as thermal springs and fumaroles to the surface along faults and fractures that act as hydrothermal conduits. By integrating with the surface geology and faults trends the geothermal conceptual model was developed for geothermal fluids flow system in the region.