T109 The Legacy of Kenneth L. Pierce: Interdisciplinary Studies along the Track of the Yellowstone Hotspot and Beyond II

Monday, 10 October 2022
1:30 PM - 5:30 PM
605

YELLOWSTONE LAKE HYDROTHERMAL FLUIDS: SYSTEMATIC VARIATIONS IN CHEMICAL AND PHYSICAL PROPERTIES CONTROL SEDIMENT ALTERATION AND HYDROTHERMAL EXPLOSIONS

Paper number: T109-15
Program: Technical Sessions
Time: 4:55 PM – 5:10 PM

Authors

Abstract

Yellowstone Lake is an extremely active hydrothermal area on the Yellowstone Plateau with very high heat flow, multiple large (>100 m diameter) hydrothermal explosion craters, dozens of hydrothermal domes, and hundreds of active and currently inactive subaqueous hydrothermal vents. Hydrothermally altered muds from the active and deepest (~119 m depth) hydrothermal vent area in the lake (the Stevenson Island Deep Hole) and an active hydrothermal dome in the northern lake both have low-Cl vent fluids, less than average lake water at 140 µm/L (5 mg/L). Their alteration mineral assemblages of smectite, kaolinite, chlorite, boehmite, pyrite, anhydrite, and quartz are typical of vapor-dominated alteration in Yellowstone. Stable isotope (δD and δ18O) values of vent and pore fluids in the Deep Hole vent field are consistent with hot, ascending vapor-dominated fluids (H2O, CO2, and H2S) mixing with lake water trapped during sedimentation or entrained during venting.

In contrast, hydrothermal explosion deposits from the large Elliott’s Crater and Mary Bay explosion craters are related to liquid-dominated, Cl-rich fluids (called alkaline-chloride) that carry high dissolved silica concentrations due to water-rock interaction at high temperatures at depth. The explosion deposits contain chalcedony, quartz, albite, smectite, chlorite, pyrite, and anhydrite and lack kaolinite. The δ18O values of bulk sediment indicate pre-explosion alteration temperatures of 150-300oC.

Hydrothermal alteration studies indicate low- and high-Cl fluids produce distinctly different mineral assemblages and produce hydrothermal explosions of systematically variable power. Alkaline-Cl fluids flashing from liquid to steam in the Elliott’s Crater and Mary Bay systems produced the largest hydrothermal explosion craters and deposits known on Earth. Vapor-dominated systems in Yellowstone Lake explode by simple expansion of the steam phase, producing less voluminous and less extensive deposits.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-382205

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.