Evidence for the reversal of gradients in the uppermost parts of silicic magma reservoirs

W. A. Duffield, J. Ruiz

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


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

Original languageEnglish (US)
Pages (from-to)1115-1118
Number of pages4
Issue number12
StatePublished - 1992

ASJC Scopus subject areas

  • Geology


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