HYDROGEOCHEMICAL AND ISOTOPES STUDY OF THERMAL WATER LIKUPANG TIMUR AREA AND ITS CORRELATION TO THE SURROUNDING GEOTHERMAL SYSTEM AND POTENTIAL

• Main Author: Vina Febrim, Dwi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/40527
• Institution: Institut Teknologi Bandung

The study area is located in Likupang Timur, North of Sulawesi. This area is composed by Quaternary Young Volcanic Rocks. Likupang Timur is developed in a tectonically-active setting and controlled by a north-northwest–south-southeast (NNW-SSE) local fault trend. This structure acts as conduits for the hydrothermal fluids to ascend from a deeper system toward the surface. In this research, chemical composition of the reservoir water was analyzed and classified using Piper Diagram, Cl-SO4-HCO3 and Cl-Li-B triangular diagrams. A Na-K-Mg triangular diagram was used to classify waters according to the state of equilibrium at given temperatures. Kation geothermometers were used to predict reservoir temperature. Isotopes ?18O, ?D (?2H) and ?13C were used to trace and determine the origin of groundwater. The hot springs are sodium-chloride type with neutral pH, and sourced from old geothermal systems. The reservoir temperatures were estimated by kation geothermometers and validated by fluid-mineral equilibrium calculations. Some of thermal fluid is in equilibrium with reservoir rocks. The estimated reservoir temperature is in the range of 195.29 - 117.16oC and 145.78 - 75.48oC. Based on result of these geothermometer calculations supported by sulfate concentration (SO42-) and Cl/B value, the geothermal system in study area are thought to consist of two different systems. All the hot water samples are plotted near local meteoric water line (?2H =8.82 ?18O + 18.8) indicating that the thermal waters are of meteoric origin. The isotopic composition of hot springs presents enrichment in ?18O and ?2H are affected by evaporation process and water-rock interaction processes which are characterized by a positive shift of the ?18O values. Enrichment of ?13C values in hot springs can be explained by input of magmatic CO2.