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Geologic evidence for a magma chamber beneath Newberry Volcano, Oregon

Journal of Geophysical Research

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Abstract

At Newberry Volcano, central Oregon, more than 0.5 my of magmatic activity, including caldera collapse and renewed caldera-filling volcanism, has created a structural and thermal chimney that channels magma ascent. Holocene rhyolitic eruptions 1) have been confined mainly within the caldera in an area 5 km in diameter, 2) have been very similar in chemical composition, phenocryst mineralogy, and eruptive style, and 3) have occurred as recently as 1300 yr ago, with repose periods of 2000-3000 yr between eruptions. Holocene basaltic andesite eruptions are widespread on the flanks but are excluded from the area of rhyolitic volcanism. Basaltic andesite in fissures at the edge of the rhyolite area has silicic inclusions and shows mixed basalt-rhyolite magma relations. These geologic relations and the high geothermal gradient that characterizes the lower part of a drill hole in the caldera (US Geological Survey Newberry 2) indicate that a rhyolitic magma chamber has existed beneath the caldera throughout the Holocene. Its longevity probably is a result of intermittent underplating by basaltic magma. -Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geologic evidence for a magma chamber beneath Newberry Volcano, Oregon
Series title:
Journal of Geophysical Research
Volume
93
Issue:
B9
Year Published:
1988
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research
First page:
10067
Last page:
10079