HYDROGEOCHEMISTRY AND ITS IMPLICATIONS ON 3D CONCEPTUAL MODEL OF GEOTHERMAL SYSTEMS IN THE KENDENG CALDERA COMPLEX

• Main Author: Aris Widyaminudiin, Masdukhan
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53382
• Institution: Institut Teknologi Bandung

Kendeng Caldera Complex is a caldera that hosts geothermal systems in East Java. The existence of geothermal systems in the caldera characterized by surface manifestations. In general, a caldera with complex volcanism will have intense surface manifestations. However, the manifestations in Kendeng Caldera were limited to Ijen craters and Blawan and do not show intense surface manifestations. The two manifestation groups have different geological control and manifestation characteristic. These differences show that there is more than one geothermal system in the Kendeng Caldera. These studies intend to understand the correlation between the manifestations and distribution of the geothermal system in the Kendeng Caldera. The method used in this research consists of hydrogeochemical studies and modeling of geothermal system components. Hydrogeochemical studies based on water chemistry data from field observations and previous research, while geothermal modeling uses geological and geophysical data from previous studies. Results of hydrogeochemical studies and modeling of geothermal system will be integrated and created in a 3D conceptual model. The results showed that Ijen crater and Blawan had different geothermal systems based on hydrogeochemical studies and modeling. Based on hydrogeochemical studies, Blawan and Ijen Crater manifestations have differences in physical parameters, especially in the pH, EC, and TDS values. The results of the Cl-Li-B and Cl-F-B diagrams show that these two manifestations originate from different reservoirs. This result is supported by mixing model and water isotope analysis that shows the different fluid origins and processes between Ijen craters and Blawan manifestations. The differences between the two systems indicated by the thickened clay cap layer between the Ijen crater and Blawan in the models. This clay cap layer separates Ijen crater and Blawan reservoir. The modeling results also show the geothermal system associated with cinder cones in the Kendeng Caldera. This system does not show surface manifestations such as Blawan or Ijen crater. It is due to an impermeable layer under the surface that blocks the thermal fluid from reaching the surface.