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Title: Geology and geothermal resources of the Santiam Pass area of the Oregon Cascade Range, Deschutes, Jefferson and Linn Counties, Oregon

Technical Report ·
DOI:https://doi.org/10.2172/7018867· OSTI ID:7018867

This open-file report presents the results of the Santiam Pass drilling program. The first phase of this program was to compile all available geological, geophysical and geothermal data for the Santiam Pass area and select a drill site on the basis of these data (see Priest and others, 1987a), A summary of the drilling operations and costs associated with the project are presented in chapter 1 by Hill and Benoit. An Overview of the geology of the Santiam Pass area is presented by Hill and Priest in chapter 2. Geologic mapping and isotopic age determinations in the Santiam Pass-Mount Jefferson area completed since 1987 are summarized in chapter 2. One of the more important conclusions reached in chapter 2 is that a minimum of 2 km vertical displacement has occurred in the High Cascade graben in the Santiam Pass area. The petrology of the Santiam Pass drill core is presented by Hill in chapter 3. Most of the major volcanic units in the core have been analyzed for major, minor, and trace element abundances and have been studied petrographically. Three K-Ar ages are interpreted in conjunction with the magnetostratigraphy of the core to show that the oldest rocks in the core are approximately 1.8 Ma. Geothermal and geophysical data collected from the Santiam Pass well are presented by Blackwell in chapter 4. The Santiam Pass well failed to penetrate beneath the zone of lateral groundwater flow associated with highly permeable Quaternary volcanic rocks. Calculated geothermal gradients range from about 50[degree]C/km at depth 700-900 m, to roughly 110[degree]C/km from 900 m to the bottom of the well at 929 m. Heat-flow values for the bottom part of the hole bracket the regional average for the High Cascades. Blackwell concludes that heat flow along the High Cascades axis is equal to or higher than along the western edge of the High Cascades.

Research Organization:
Oregon State Dept. of Geology and Mineral Industries, Portland, OR (United States)
Sponsoring Organization:
USDOE; USDOE, Washington, DC (United States)
DOE Contract Number:
FG07-89ID12834
OSTI ID:
7018867
Report Number(s):
DOE/ID/12834-13; USGS-OFR-0-92-3; ON: DE93008762
Country of Publication:
United States
Language:
English