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Wairakite: A Potential Indicator of Fluid Mixing

Conference ·
OSTI ID:15014666
Wairakite is a common geothermal mineral. Detailed paragenetic studies indicate that wairakite typically forms after the deposition of epidote {plus_minus} prehnite and later anhydrite + calcite. Epidote and prehnite are interpreted as products of early, high temperature alteration associated with upswelling reservoir fluids whereas calcite and anhydrite are related to descending acidic condensates. Calculated stability relationships among the calc silicate minerals indicates that cooling and/or decreasing pH will lead to the deposition of wairakite instead of epidote, whereas decreasing pH favors wairakite over prehnite. We infer, from the petrographic relationships, that these changes occur when descending condensate mixes with the in-situ reservoir fluids during the waning stages of geothermal activity. Fluid inclusion measurements indicate wairakite is commonly deposited between temperatures of {approx}235 and 300 C.
Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA
Sponsoring Organization:
USDOE
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
15014666
Report Number(s):
UCRL-CONF-209297
Country of Publication:
United States
Language:
English