C5+ HYDROCARBONS IN FUMAROLIC GASES FROM THE KAKKONDA (TAKINOUE) GEOTHERMAL AREA, JAPAN

Three fumarolic gases, both gas and liquid phases, from the Kakkonda ( Takinoue) geothermal area, northern Japan, were analyzed with a gas ch romatograph-mass spectrometer to confirm the presence of C5+ hydrocarb ons in the geothermal fluid of this area. C5+ hydrocarbons found in th e analyses were mainly alkanes (C-5-C-15), aromatics (C-6-C-12) and cy cloalkanes (C-6-C-8). Alkanes in the gas phase of one of the three sam ples show C-10-C-11 predominance, which has not been observed in other geothermal fields before. This clearly shows that compositions of hea vier hydrocarbons from fumaroles in this area are not uniform. The var iety suggests that up-flows in this geothermal circulation system take hydrocarbons with various degrees of thermal degradation up to the su rface.