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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 958

Last Page: 958

Title: Overview of Geothermal Exploration on Western Slopes of Mt. Hood, Oregon: ABSTRACT

Author(s): H. Jack Meyer, John W. Hook

Article Type: Meeting abstract


Since 1977, Northwest Geothermal Corp., the U.S. Geological Survey, the Oregon Dept. of Geology and Mineral Industries, and the U.S. Dept. of Energy have cooperatively explored the western slopes of Mt. Hood, Oregon, for geothermal water suitable for direct utilization. The high regional heat flow of the Cascade Mountains provided the impetus for the exploration. A possible magma chamber associated with Mt. Hood enhanced the prospect. The anticipated resource is deep circulating meteoric waters.

The stratigraphic history of the western Mt. Hood area is one of andesitic volcanism from late Oligocene to Holocene. The Miocene basalts of the Columbia River Group interrupt and locally interfinger with this sequence. A large quartz diorite stock of questionable age is exposed immediately southwest of Mt. Hood.

The regional structural setting has been interpreted to be a right lateral wrench tectonic system resulting from north-south compression. Major northwest-trending right lateral faults with some vertical component, and northeast-trending antithetic faults were mapped. Low amplitude en-echelon west-northwest-trending folds are present in the younger rocks. An older northeast-trending fold pattern, coupled with thrusting, was mapped in the basalts of the Columbia River Group.

The exploratory drilling program was designed to develop stratigraphic, structural, and hydrologic information, as well as to establish the geothermal gradient. The initial 564-m observation well in the Old Maid Flat area of Mt. Hood yielded a conductive gradient of 67°C/km. Gradients on the western side range from 20 to 83°C/km. Two deep tests (1,220 m and 1,837 m), funded by DOE, have been drilled. Both wells, while finding no fluids, have conductive gradients to total depth.

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Copyright 1997 American Association of Petroleum Geologists