| Title | Aquifer Chemistry of Thermal Waters in Obama Geothermal Field, Japan- Between 1984 and 2001 |
|---|---|
| Authors | H. Saibi, S. Ehara, Y. Fujimitsu & J. Nishijima |
| Year | 2004 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | |
| Abstract | Thermal waters hosted by volcanic rocks emerge along the faults lineaments in the Obama geothermal area (Western part of Kyushu Island, Japan). All thermal waters belong to Na-Cl facies. Those waters are slightly alkaline and have high dissolved contents with total dissolved solids around 8404 mg/kg in 1984 and 8196 mg/kg in 2001. The chemical-isotope geothermometers, silica-carbonate and enthalpy-chloride mixing models suggest a reservoir temperature is around 190 oC in 1984 and 210 oC in 2001. The chloride composition of the parent fluid is 6200 mg/kg in 1984 and 3800 mg/kg in 2001. The silica composition of the parent fluid is 310 mg/kg in 1984 and 400 mg/kg in 2001. The Obama hot waters are products of mixing of three phases: sea water, meteoric water and magmatic water. The Obama geothermal field is in a recovery state with rising in the water temperature and decreasing in the salinity. |