| Title | Geochemistry Model of Chloride Springs Origin Near Sea Coastal Area: Case Study from Rajabasa Geothermal Field |
|---|---|
| Authors | Wildan MUSSOFAN, Tom POWELL, Lukman SUTRISNO, Mauliate A. SIHOTANG |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | hot springs, sea water, Rajabasa, conceptual model |
| Abstract | The purpose of this paper is to evaluate the likelihood of outflow of geothermal water to shoreline hot springs at Rajabasa and the implications of this outflow to conceptual models. Two different models have been proposed to explain the chemistry of the Gunung Botak shoreline hot spring; a mixed seawater – geothermal water and purely steam – heated seawater. The steam – heated seawater model is based solely upon a similarity in Cl/B ratios between the springs and seawater, which are much higher than in the usual liquid geothermal system. Hot springs distant from the shoreline show high Cl/B ratio, however, suggesting that this is a characteristic of the system. The model for a mixed seawater – geothermal water origin proposes an elaborate model of boiling, seawater mixing and repeated boiling, which is testable by modelling fumarole gas chemistry. It was found that the majority of the gas chemistry of the inland Way Merak and seaside Gunung Botak fumaroles can be matched with a boiling-mixing-boiling model, but with surpluses of hydrogen and ammonia at Gunung Botak. The hydrogen surplus appears to be due to regeneration after first boiling, whereas the ammonia surplus remains unexplained. In any case, the modelling supports the existence of a geothermal component in the Gunung Botak hot springs, consistent with the expectation of shoreline hot springs at an on-shore liquid geothermal system. This information refines the conceptual model of a liquid dominated system which has upflow just north of the high elevation Pangkul fumaroles then flows to the southward to the Way Merak fumaroles and Gunung Botak hotsprings. |