This Wyoming volcanic field has undergone repeated eruption of rhyolitic magma strongly depleted in 18O. Large calderas subsided 2.0, 1.3 and 0.6 m.y. ago on eruption of ash-flow sheets. More than 60 other rhyolite lavas and tuffs permit reconstruction of the long-term chemical and isotopic evolution of the silicic system. Narrow delta 18O ranges in the ash-flow sheets contrast with wide delta 18O variation in post-caldera lavas. The earliest post-collapse lavas are 3-6per mille lighter than the preceding ash-flow sheets. The 18O depletions were short-lived events that immediately followed caldera subsidence and sequences of post-caldera lavas record partial recovery toward pre-caldera delta 18O values. Contemporaneous extra-caldera rhyolites show no effects of the repeated depletions. Although some contamination by foundering roof rocks seems to be required, water was probably the predominant contaminant.-W.H.B.
Citation Information
Publication Year | 1984 |
---|---|
Title | Catastrophic isotopic modification of rhyolitic magma at times of caldera subsidence, Yellowstone plateau volcanic field. |
Authors | W. Hildreth, R. L. Christiansen, J. R. O'Neil |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Journal of Geophysical Research |
Index ID | 70013144 |
Record Source | USGS Publications Warehouse |