Dissertation
AN EVALUATION OF THE HYDROTHERMAL SYSTEM IN SEVEN MILE HOLE, YELLOWSTONE NATIONAL PARK
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2024
DOI:
https://doi.org/10.7273/000006576
Abstract
The Yellowstone hydrothermal system is an exceptional natural laboratory that acts as a modern analog for extinct epithermal systems as well as a pristine example of economically important geothermal fields. The Yellowstone hydrothermal system has been ongoing for at least 400,000 years. This age, however, comes from travertine mounds outside of the caldera, and post-collapse rhyolitic flows have likely covered evidence of the older system inside the caldera. In the Grand Canyon of the Yellowstone River, erosion has exposed a 154 ka hydrothermal system hosted by the Tuff of Sulphur Creek, allowing an excellent opportunity to study older hydrothermal alteration in situ, including the fluid pathways and consequences of hydrothermal alteration. This area is especially interesting as it allows an investigation into a dynamic portion of the greater Yellowstone hydrothermal system, where the water table has lowered over time and the area has been altered by the two end-member fluid chemistries in the caldera: alkaline-chloride and acid-sulfate. Hydrothermal alteration in the Seven Mile Hole area drove the production of seven hydrothermal mineral assemblages. These mineral assemblages indicate the area has been altered in a multistage process, starting with alkaline-chloride fluids and transitioning to acid-sulfate fluids with an expansion of the steam-heated zone. Temperature estimates for the system are largely bounded by a pure water hydrostatic boiling point curve based on the 2500 m modern elevation of the rim of the Grand Canyon of the Yellowstone River and one with an additional 460 m of hydraulic head. These bounding curves demonstrate the dynamic subsurface conditions created by the two major glaciations and the incision of the Grand Canyon of the Yellowstone River. Given these estimates, the δ18O of the altering fluid falls in the range of -21.6 to -5.5 per mil, fitting well with the isotopic signature of the modern thermal fluids discharging in Yellowstone. Vein, erosion resistant ridges, and trends of siliceous sinter indicate altering fluids permeated the Tuff of Sulphur Creek along joints created by a combination of volcanic-related stresses and regional Basin and Range extension. The diverse chemistry of the altering fluids increased porosity due to acid attack and decreased porosity due to mineralization, as well as mobilizing constituents, such as Ba, from magmatic phases to secondary minerals like barite and alunite supergroup minerals.
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Details
- Title
- AN EVALUATION OF THE HYDROTHERMAL SYSTEM IN SEVEN MILE HOLE, YELLOWSTONE NATIONAL PARK
- Creators
- Jarred Lee Zimmerman
- Contributors
- Peter B Larson (Chair)Sean P Long (Committee Member)Johannes Haemmerli (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 208
- Identifiers
- 99901121535501842
- Language
- English
- Resource Type
- Dissertation