Dissolution and deposition of chemicals takes place when geothermal fluids interact with the host rocks around the reservoir.
It is thought that the distribution of each geothermal water (alkali-neutral Cl type hot water, acid SO4 type hot water etc.) as well as its flowing path can be estimated by the analysis of the chemical composition of main and trace component of alteration mineral.

West JEC joined forces with NEDO for the development of these techniques aiming at secondary quartz or pyrite as measuring probes and carrying out precision measurement using the Inductively coupled plasma mass-spectrometer ICP-MS (Fig.6-1) equipment.
The selection of these secondary quartz or pyrite minerals is for the purpose of eliminating the influence rock difference and that of the degree of geothermal alteration.
Secondary quartz and pyrite are depositions and crystallizations of chemicals in the geothermal hot water. Therefore, the changes of these secondary components (Fig. 6-2) seem to show the difference of geothermal waters and temperature. West JEC pursues to make use of this knowledge to disclose the horizontal and vertical distribution of the different reservoirs.


Click to image
Fig.6-1 Inductively coupled plasma mass-spectrometer(ICP-MS)
Fig.6-2 Variation of minor chemical composition in pyrite

 

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