Testing EQ3/6 and GEMBOCHS using fluid-mineral equilibria in the wairakei geothermal system
The ability of the EQ3 and EQ6 geochemical modeling codes and the GEMBOCHS thermodynamic data bases to simulate geochemical changes in the post-emplacement environment at the potential Yucca Mountain, Nevada repository is being tested using observed mineral-fluid relations in the Taupo Volcanic Zone of New Zealand. In this report, comparisons between observed equilibria and simulations of field relations in the Wairakei geothermal system are used to test the codes and data bases in high temperature systems. Analysis of trends in water and gas chemistries and well discharge characteristics with time were used to identify a set of representative water and gas analyses from zones producing at about 250{degrees}C. The most common vein minerals at this temperature are: wairakite, adularia, epidote, quartz, albite, chlorite, calcite, prehnite, and pyrite. Calculations were carried out using version 7.2a R134 of EQ3 and version 7.2a R130 of EQ6 and the SUPCRT and COM subsets of the R24 version of GEMBOCHS. Thermodynamic data bases using different data for Al aqueous species were sued to identify the data set which produced the best matches between observed and calculated equilibria. The simulations described in this paper suggest that EQ6 can be used to identify facies of minerals that will be stable in various environments, but can not be used to predict the exact phase assemblage that is in equilibrium with a given water.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Civilian Radioactive Waste Management, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 641095
- Report Number(s):
- UCRL-ID-129280; R&D Project: MOL206; ON: DE98057729; CNN: W-7405-Eng-48
- Resource Relation:
- Other Information: PBD: 28 Aug 1995
- Country of Publication:
- United States
- Language:
- English
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