| Title | Geochemical Analysis of Thermal Fluids from the Mount Meager Geothermal Field, British Columbia, Canada |
|---|---|
| Authors | Katherine HUANG, Andri STEFÃNSSON |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | geochemistry, conservative elements, geothermometry, WATCH, PHREEQC, Canada, Mount Meager |
| Abstract | Thermal fluids from springs and wells in the southern Mount Meager geothermal field were analyzed to understand the fluid origin, assess controls on chemistry from effects of mixing and water-rock interaction, and determine the reservoir temperature and composition. Chloride and boron concentrations range from 100 to 3300 ppm and 0.3 to 28 ppm, respectively. These very high conservative element concentrations cannot alone be explained by rock dissolution and are instead likely supplied by a single magmatic source. Calculated reservoir compositions suggest that se1ect deep wells have experienced significant CO2 degassing from reservoir to the surface, and high SO4 content present from surface samples is traced down to the reservoir. These data corroborate the hypothesis that a magmatic component exists and contributes to B, Cl, CO2 and SO4 fluid composition, although CO2 and SO4 may have alternate sources. Select geothermometers calculated reservoir temperatures of up to 283 °C for central deep wells. Like many high-temperature geothermal systems, the compositions of thermal fluids appear to be controlled by the equilibrium between the fluid and observed secondary minerals. Hot springs and wells on the eastern and northern sides of the reservoir are of low temperature and likely define the boundaries of peripheral waters. Wells to the southeast contain anomalously high Cl and SO4, suggesting a possible magmatic input of these components which may be controlled by the east-west running Meager Creek Fault Zone. There is a significant source of hot, Cl- and CO2-rich thermal waters supplying deep wells MC-1, MC-2, MC-6 and MC-8, and possibly MC-3. These NaCl waters likely define the high temperature, central location of the geothermal reservoir. |