November Meeting: Geophysical Imaging of Yellowstone’s Hydrothermal Plumbing System (Carol Finn, USGS)

Geophysical Imaging of Yellowstone’s Hydrothermal Plumbing System

Carol Finn, USGS

Abstract:

The nature of Yellowstone National Park’s plumbing system linking deep thermal fluids to its legendary thermal features is virtually unknown. The prevailing concepts of Yellowstone hydrology and chemistry are that fluids reside in reservoirs with unknown geometries, flow laterally from distal sources and emerge at the edges of lava flows. Here we present a high-resolution synoptic view of pathways of the Yellowstone hydrothermal system derived from electrical resistivity and magnetic susceptibility models of airborne geophysical data. Groundwater and thermal fluids containing appreciable total dissolved solids significantly reduce resistivities of porous volcanic rocks and are differentiated by their resistivity signatures. Clay sequences mapped in thermal areas and boreholes typically form at depths of less than 1,000 metres over fault controlled thermal fluid and/or gas conduits. We show that most thermal features are located above high-flux conduits along buried faults capped with clay that has low resistivity and low susceptibility. Shallow subhorizontal pathways feed groundwater into basins that mixes with thermal fluids from vertical conduits. These mixed fluids emerge at the surface, controlled by surficial permeability, and flow outwards along deeper brecciated layers. These outflows, continuing between the geyser basins, mix with local groundwater and thermal fluids to produce the observed geochemical signatures. Our high fidelity images inform geochemical and groundwater models for hydrothermal systems
worldwide.

Speaker Bio:

Dr. Carol Finn graduated with a BA in Geology from Wellesley College and a MS and Ph.D. in geophysics from the University of Colorado. She is a research geophysicist at the U. S. Geological
Survey, a past president and past General Secretary (Treasurer) of AGU. Her research interests are quite broad, but currently focus on the application of magnetic and gravity data, along with other geophysical techniques, to identify the subsurface distribution of hydrothermal alteration, sub-volcanic intrusions as well as ground water as they relate to both landslide hazard assessment and systematics of hydrothermal systems; find crystalline basement related to global mineral resource assessments (Algeria, Mauritania, Afghanistan, South Africa, Canada, Russia, United States);
and model the 3-D geometry and internal structure of layered mafic intrusions, including the Bushveld, Stillwater and Duluth complexes, in support of assessments of platinum group element potential. She is a Fellow of the Geological Society of America, has received Department of the Interior Meritorious and Special Service Awards and fellowships from Japan and Australia. When not working, she is skiing, hiking, jogging, rafting and “moming” her 12 year old son.

Timing: 

5:30 to 6:30 PM – Happy Hour in Vallecito Room

6:30 – 8:00 PM – Business Meeting and speaker presentation, with raffle to follow