Abstract
Yellowstone Lake hydrothermal vent systems have been studied using ROV assets to better understand the chemical and mineralogical evolution of the sublacustrine sediments through which the hot spring fluids discharge to the lake floor. Here we focus on the deposits/alteration and coexisting vent fluid chemistry associated with the Deep Hole on the lake floor, east of Stevenson Island. Remote in its location, at 120 m below the lake surface, this region in the northeast portion of Yellowstone Lake is associated with numerous hydrothermal vents and hot springs, providing evidence of high-temperature fluid-mineral interaction and phase separation phenomena. Vapor-dominated hydrothermal fluids issuing from Deep Hole vents attain temperatures in excess of 150 °C and are enriched in magmatically derived H2S and CO2. Upon mixing with lake water in the root zone of the hydrothermally active vents, the dissolved gases render the mixed fluid, both acidic and reducing, effectively transforming diatomaceous sediment, with detritally sourced Al and Fe components, to an alteration assemblage dominated by kaolinite, pyrite, and lesser boehmite. These alteration processes have been modeled by computer based simulations, coupling fluid flow and mineral dissolution kinetics, to provide insight on the temporal evolution of the vent system. Results predict rapid dissolution of amorphous silica. The magnitude and rate of silica loss, facilitated by the continuous influx of acidic source fluids, yields an increasingly silica poor alteration mineral sequence with time, characterized by quartz, followed by kaolinite and ultimately boehmite. These data are consistent with the observed decrease in SiO2/Al2O3 ratio of the vent deposits with increasing abundance of trace immobile elements, suggesting significant mass loss with reaction progress. Pyrite is predicted to form from sulfidation of magnetite, with noteworthy decrease in magnetic intensity, as measured for hydrothermally altered sediment in the near-field vent environment. Moreover, hydrogen isotope compositional data for kaolinite, together with δD vent fluid data, suggest temperatures in keeping with the high temperatures measured for the vent deposits and discharging fluid, while supporting the potential use of kaolinite as a geothermometer. The predicted and observed transformation of silica-rich protolith to kaolinite, boehmite, and pyrite underscores the large scale dissolution and removal of silica, with possible implications for the temporal evolution of vent deposits on the lake floor in the Stevenson Island Deep-Hole region.
| Original language | English (US) |
|---|---|
| Article number | 107231 |
| Journal | Journal of Volcanology and Geothermal Research |
| Volume | 414 |
| DOIs | |
| State | Published - Jun 2021 |
Bibliographical note
Funding Information:This work was funded by NSF grants EAR 1515377 and OCE 1434798 (W.E. Seyfried) . D.I. Foustoukos acknowledges the NSF grant EAR 1761388 . The Institute for Rock Magnetism is funded by the NSF Division of Earth Sciences, Instruments and Facilities program, and by the University of Minnesota. This is IRM contribution #2007.The authors thank Dave Lovalvo, the engineers onboard R/V Annie, and the Global Foundation for Ocean Exploration for their efforts that contributed to the successful outcome of the project. We also thank Dr. Rob Sohn and members of the HD-YLAKE research team for constructive advice and invaluable assistance during the three year field program. All work in Yellowstone National Park was completed under an authorized Yellowstone research permit ( YELL-2018-SCI-7018 ).
Funding Information:
This work was funded by NSF grants EAR 1515377 and OCE 1434798 (W.E. Seyfried). D.I. Foustoukos acknowledges the NSF grant EAR 1761388. The Institute for Rock Magnetism is funded by the NSF Division of Earth Sciences, Instruments and Facilities program, and by the University of Minnesota. This is IRM contribution #2007.The authors thank Dave Lovalvo, the engineers onboard R/V Annie, and the Global Foundation for Ocean Exploration for their efforts that contributed to the successful outcome of the project. We also thank Dr. Rob Sohn and members of the HD-YLAKE research team for constructive advice and invaluable assistance during the three year field program. All work in Yellowstone National Park was completed under an authorized Yellowstone research permit (YELL-2018-SCI-7018).
Publisher Copyright:
© 2021
Keywords
- Hydrothermal deposits
- Mineral alteration
- Reaction rates
- Vent fluid chemistry
- Yellowstone Lake
