Magmatic volatile contents and explosive cinder cone eruptions in the High Cascades: Recent volcanism in Central Oregon and Northern California

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dc.contributor.author Ruscitto, Daniel M., 1981-
dc.date.accessioned 2011-06-13T22:25:40Z
dc.date.available 2011-06-13T22:25:40Z
dc.date.issued 2011-03
dc.identifier.uri http://hdl.handle.net/1794/11262
dc.description xvi, 182 p. : col. ill. en_US
dc.description.abstract Volatile components (H 2 O, CO 2 , S, Cl) dissolved in magmas influence all aspects of volcanic activity from magma formation to eruption explosivity. Understanding the behavior of volatiles is critical for both mitigating volcanic hazards and attaining a deeper understanding of large-scale geodynamic processes. This work relates the dissolved volatile contents in olivine-hosted melt inclusions from young volcanics in the Central Oregon and Northern California Cascades to inferred magmatic processes at depth and subsequent eruptive activity at the surface. Cinder cone eruptions are the dominant form of Holocene volcanism in the Central Oregon segment of the High Cascades. Detailed field study of deposits from three cinder cones in Central Oregon reveals physical and compositional similarities to explosive historic eruptions characterized as violent strombolian. This work has important implications for future hazard assessments in the region. Based on melt inclusion data, pre-eruptive volatile contents for seven calc-alkaline cinder cones vary from 1.7-3.6 wt.% H 2 O, 1200-2100 ppm S, and 500-1200 ppm Cl. Subarc mantle temperatures inferred from H 2 O and trace elements are similar to or slightly warmer than temperatures in other arcs, consistent with a young and hot incoming plate. High-magnesium andesites (HMA) are relatively rare but potentially important in the formation of continental crust. Melt inclusions from a well-studied example of HMA from near Mt. Shasta, CA were examined because petrographic evidence for magma mixing has stimulated a recent debate over the origin of HMA magmas. High volatile contents (3.5-5.6 wt.% H 2 O, 830-2900 ppm S, 1590-2580 ppm Cl), primitive host crystals, and compositional similarities with experiments suggest that these inclusions represent mantle-derived magmas. The Cascades arc is the global end member, warm-slab subduction zone. Primitive magma compositions from the Cascades are compared to data for arcs spanning the global range in slab thermal state to examine systematic differences in slab-derived components added to the mantle wedge. H 2 O/Ce, Cl/Nb, and Ba/La ratios negatively correlate with inferred slab surface temperatures predicted by geodynamic models. Slab components become increasingly solute-rich as slab surface temperatures increase from ∼550 to 950°C at 120 km depth. This dissertation includes previously published and unpublished co-authored material. en_US
dc.description.sponsorship Committee in charge: Dr. Paul J. Wallace, Chair and Advisor; Dr. Katharine Cashman, Member; Dr. Ilya Bindeman, Member; Dr. Richard Taylor, Outside Member en_US
dc.language.iso en_US en_US
dc.publisher University of Oregon en_US
dc.relation.ispartofseries University of Oregon theses, Dept. of Geological Sciences, Ph. D., 2011;
dc.subject Cascade Range en_US
dc.subject Cinder cones en_US
dc.subject Melt inclusions en_US
dc.subject Volatiles en_US
dc.subject Explosive volcanism en_US
dc.subject Geology en_US
dc.subject Petrology en_US
dc.subject Geochemistry en_US
dc.subject Volcanism -- Oregon
dc.subject Volcanism -- California, Northern
dc.subject Volcanism -- Cascade Range
dc.title Magmatic volatile contents and explosive cinder cone eruptions in the High Cascades: Recent volcanism in Central Oregon and Northern California en_US
dc.title.alternative Recent volcanism in Central Oregon and Northern California en_US
dc.type Thesis en_US


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