Geologic evidence for a magma chamber beneath Newberry Volcano, Oregon
Article first published online: 20 SEP 2012
This paper is not subject to U.S. copyright. Published in 1988 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 93, Issue B9, pages 10067–10079, 10 September 1988
How to Cite
1988), Geologic evidence for a magma chamber beneath Newberry Volcano, Oregon, J. Geophys. Res., 93(B9), 10067–10079, doi:10.1029/JB093iB09p10067., and (
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 28 MAR 1988
- Manuscript Received: 5 OCT 1987
At Newberry Volcano, central Oregon, more than 0.5 m.y. 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 years ago, with repose periods of 2000–3000 years 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 (U.S. 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.