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Geology, Alteration And Mineralization Of A Silicic Volcanic Center, Glass Buttes, Oregon, Michael James Johnson
Geology, Alteration And Mineralization Of A Silicic Volcanic Center, Glass Buttes, Oregon, Michael James Johnson
Dissertations and Theses
Glass Buttes, a Pliocene silicic volcanic complex within the High Lava Plains province of Oregon, was erupted approximately 5.0 to 5.8 million years ago. Geologic mapping revealed that the eastern portion of the complex is underlain by rhyolitic glass domes, flows and rare pyroclastis flows. Basalt flows are interlayered with and onlap the silicic glass. Younger basalt flows, erupted from local vents, overlie silicic glass and onlapping basalts.
The eastern end of Glass Buttes is hydrothermally altered at the surface; a weak geothermal anomaly coincides with the altered areas. Alteration, localized by northwest trending normal faults, occurs primarily as opalite …