First Advisor

Robert Perkins

Term of Graduation

Fall 2020

Date of Publication

1-13-2021

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Geology: Geohydrology

Department

Geology

Language

English

DOI

10.15760/etd.7516

Physical Description

1 online resource (xi, 102 pages)

Abstract

Reservoir temperatures of hydrothermal systems in the Pacific Northwest reflect the feasibility of geothermal energy production and the tectonic framework of the region. Multicomponent geothermometry techniques were applied to new and historic water chemistry data in the north-central Oregon Western Cascades and the lower Wind River Valley in southern Washington in order to recalculate reservoir temperatures. Revised reservoir temperatures, water chemistry, and isotope data were used to determine relationships between hot springs in the north-central Oregon Cascades. Geothermal reservoir temperatures were estimated for the lower Wind River Valley (98.44 ± 0.96°C) and for Austin and Bagby Hot Springs (100.10 ± 1.04°C and 65.29 ± 2.74°C, respectively) using RTEst software and mineral suites reflective of the host rock geology. The estimated reservoir temperature for Austin Hot Springs is lower than previous estimates (180 - 186°C; Ingebritsen et al., 1992; Mariner et al., 1993). The resulting calculated hydrothermal heat output of 48 MW for Austin Hot Springs is lower than the previous estimate of 85 MW (Ingebritsen and Mariner, 2010). Isotopic evidence indicates that Austin and Breitenbush Hot Springs, located ~27 km apart, are recharged at similar elevations along the crest of the Cascades and may be part of a common hydrothermal system. The data further indicate a component of "andesitic water" (4-8%) in waters discharged from Austin and Breitenbush Hot Springs as well as from hot springs and geothermal wells in Wind River Valley, WA. This, along with extensional structures extending from the central Oregon Western Cascades to the lower Wind River Valley suggest similar mechanisms for the heating and movement of deep circulating hydrothermal waters near the volcanic arc. Waters from Bagby Hot Springs, which lie ~15 km further west and away from the arc than Austin Hot Springs, do not have the same isotopic signature. Lower estimated reservoir temperatures and recharge elevations, differences in water chemistry, and the lack of an andesitic water signature indicate that the Bagby Hot Springs represent a discreet, localized hydrothermal flow system.

Note: Appendices are included as supplemental files.

Appendix A: Ion chemistry

Appendix B: Ion and Isotope QAQC

Appendix C: RTEst and GWB files

Rights

© 2020 Aaron Alexander Orr

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/34672

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