| Abstract: | Evidence from large-volume ignimbrites indicates that the source-magma reservoirs for most of these voluminous silicic pyroclastic deposits contained monotonic vertical chemical gradients at the time of eruption. However, gradients from a large-volume magma reservoir that produced a group of penecontemporaneous silicic lava domes, but no ignimbrite, show a reversal of the usual ignimbrite pattern. This reversal originated by modification of the usual pattern through minor assimilation of partially melted roof rocks. Eruptions that produced these domes apparently just tapped the uppermost part of their source reservoir. They thereby provide a high-resolution instantaneous view of this variably contaminated part of the magma system. The long-standing paradigm for monotonic zoning in large-volume reservoirs of silicic magma may require modification. -from Authors |
| Genre: | Article |
| ProdID: | 70017105 |
| Citation Author: | Duffield, W. A.; Ruiz, J. |
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| Citation End Page: | 1118 |
| Citation Issue: | 12 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geology |
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| Citation Number Of Pages: | 4 |
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| Citation Search Results Text: | Evidence for the reversal of gradients in the uppermost parts of silicic magma reservoirs; 1992; Article; Journal; Geology; Duffield, W. A.; Ruiz, J. |
| Citation Start Page: | 1115 |
| Citation Volume: | 20 |
| Citation Year: | 1992 |
| Type: | citation/reference |
| Text: | Evidence for the reversal of gradients in the uppermost parts of silicic magma reservoirs; 1992; Article; Journal; Geology; Duffield, W. A.; Ruiz, J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 1992 00:00 -0600 |
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