Graduate Thesis Or Dissertation
 

DyhrmanRichardF1976.pdf

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5d86p290p

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  • The thesis area is located southwest of Portland, Oregon, in the Western Cascades. In the area are volcaniclastic rocks and lava flows that range in composition from basaltic andesite to dacite. The dominant volcaniclastic rock type is thin intracanyon ash-flow tuff. The dominant lava flows are a thick sequence of basaltic andesites to dacites that account for 60 percent of those found in the thesis area. Within this group is an intracanyon flow of basaltic andesite that contains double pheriocrystic stages of clinopyroxene and plagioclase. Quartz is also present and surrounded by a reaction rim of clinopyroxene. This unit is an example of magmatic mixing. The most distinctive unit is a cliff-forming horublende ignimbrite found in two isolated locations. This unit contains large hornblende crystals, collapsed pumice lumps, and sanidine granite inclusions. There are four andesite intrusions in the thesis area; two are dikes and two are irregular discordant bodies. The most distinctive is Pin Creek andesite with large embayed quartz phenocrysts. Variation diagrams based on chemical data follow normal trends as expected for calc-alkaline or calcic rocks. Rocks from the thesis area are calcic, due to abundant calcic plagioclase phenocrysts and intense alteration. The thesis area lies along the western flank of a broad northeast-plunging anticline. All units consistently dip 8 to 11° in a westerly direction or northerly direction depending upon their location with respect to the nose of the anticline. Two distinct groups of faults occur. One group trending north-northwest, the other east-west. It is the northern fault of the east-west-trending group that has served as a zone of crustal weakness for the intrusion of a dike system and the conduit of hot water supplying Bagby Hot Springs. Bagby Hot Springs lies in a broad, deeply-glaciated valley used primarily for recreational activities. The projected geothermal reservoir temperature of 127°C and the low flow rate do not make this area a good potential reservoir for generation of electricity.
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file details DyhrmanRichardF1976.pdf 2017-08-14 Público Descargar