Hydrothermal Fluids and Where to Find Them: Using Seismic Attenuation and Anisotropy to Map Fluids Beneath Uturuncu Volcano, Bolivia. Issue 5 (28th February 2023)

• Record Type: Journal Article
• Authors: Hudson, T. S.; Kendall, J. M.; Blundy, J. D.; Pritchard, M. E.; MacQueen, P.; Wei, S. S.; Gottsmann, J. H.; Lapins, S.
• Is Part Of: Geophysical research letters. Volume 50:Issue 5(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-28
• Subjects: seismology -- volcanoes -- geothermal -- mineral exploration -- hydrothermal fluids -- attenuation; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL100974
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Mapping fluid accumulation in the crust is pertinent for numerous applications including volcanic hazard assessment, geothermal energy generation, and mineral exploration. Here, we use seismic attenuation tomography to map the distribution of fluids in the crust below Uturuncu volcano, Bolivia. Seismic P wave and S wave attenuation, as well as their ratio ( Q P / Q S ), constrain where the crust is partially and fully fluid‐saturated. Seismic anisotropy observations further constrain the mechanism by which the fluids accumulate, predominantly along aligned faults and fractures in this case. Furthermore, subsurface pressure‐temperature profiles and conductivity data allow us to identify the most likely fluid composition. We identify shallow regions of both dry and H2 O/brine‐saturated crust, as well as a deeper supercritical H2 O/brine column directly beneath Uturuncu. Our observations provide a greater understanding of Uturuncu's transcrustal hydrothermal system, and act as an example of how such methods could be applied to map crustal fluid pathways and hydrothermal/geothermal systems elsewhere. Plain Language Summary: Locating where water/brines, gas, and molten rock are in the crust is important various applications, including assessing volcanic hazard, generating geothermal energy, and exploring for critical metals. Here, we map how seismic energy is absorbed (or attenuated) in Earth's crust, in order to look for fluids in the subsurface. We do this at Uturuncu volcano, Bolivia. This allows us to imagine whether the crust is partly or fully saturated with fluids. We also use seismic anisotropy to help us understand how the seismic energy is absorbed. We then use other data, including pressure, temperature, and electrical conductivity data to identify what fluids can be found where. We find that we can map where water/brines are and whether they contain carbon dioxide (i.e., are "sparkling") or not (i.e., "still"). Key Points: Seismic attenuation tomography can map crustal fluids and elucidate whether fluids are compressible, incompressible, or supercritical S wave velocity anisotropy suggests that crustal fluids at Uturuncu migrate and/or accumulate along fractures Seismic attenuation combined with temperature, pressure, and conductivity measurements can provide constraint on fluid composition