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Full-Text Articles in Geology
Shared Roots: A Geochemical Investigation Of Basaltic Andesites To Understand Magmatic Cogenesis At The Middle Sister And South Sister Volcanoes, Central Oregon, Sean Francis Halstead
Shared Roots: A Geochemical Investigation Of Basaltic Andesites To Understand Magmatic Cogenesis At The Middle Sister And South Sister Volcanoes, Central Oregon, Sean Francis Halstead
WWU Honors College Senior Projects
The Middle Sister and South Sister volcanoes, near Bend, Oregon, are overlapping, active Cascade Arc stratovolcanoes which share a complex, contemporaneous eruptive history. This history is characterized by an extreme compositional diversity of lavas erupted in alternating phases of high activity from one neighboring volcano to the other, with both vents producing material ranging from basaltic andesite to rhyolite. This system is understood to be predominantly fed by basaltic andesites fractionated from partial mantle melts within the lower crust, but magma compositions are additionally impacted by mixing, assimilation, and crustal contamination while in transit to the surface. Thus, the subterranean …
Using Two Coeval Andesites From Middle Sister And South Sister, Oregon, As Clues To Understanding Connectivity Between Adjacent, Coincident Stratovolcanoes, James Peale
Geology Graduate and Undergraduate Student Scholarship
The Three Sisters Volcanic Complex in central Oregon is a cluster of three primary stratovolcanoes and a mafic periphery which lies at the intersection of the Cascade volcanic arc and the Basin and Range extensional province. This project focuses on the two youngest stratovolcanoes, Middle Sister and South Sister. Middle Sister experienced a period of frequent eruptive activity from approximately 27 ka to 14 ka, during which it erupted dacites, andesites, and basaltic andesites. South Sister experienced an intense period of eruptive activity from approximately 36 ka to 22 ka, during which it erupted a diverse suite of magmas ranging …
Understanding Potential Reservoir Interconnectivity Between Two Contemporaneous Volcanoes During The Onset Of Cone-Building Activity, Middle Sister And South Sister, Central Oregon, Emma Calvert
Geology Graduate and Undergraduate Student Scholarship
Klah Klanee (Three Points) is located in the central Cascades near Bend, Oregon. The Three Sisters Volcanic Complex (TSVC) lies at a tectonically complex intersection of the Cascade Subduction Zone, the Basin and Range Province, and the High Lava Plains. The TSVC is a compositionally diverse volcanic field consisting of four stratovolcanoes and numerous periphery cones and vents. Middle Sister and South Sister are the youngest of the stratovolcanoes and they share a largely contemporaneous and semi-alternating episodic eruptive history. These parallel histories could indicate a complex, interconnected magmatic root system within the crust below the TSVC and the surrounding …
Excess Silica In Omphacite And The Formation Of Free Silica In Eclogite, H. W. Day, Sean R. Mulcahy
Excess Silica In Omphacite And The Formation Of Free Silica In Eclogite, H. W. Day, Sean R. Mulcahy
Geology Faculty Publications
Silica lamellae in eclogitic clinopyroxene are widely interpreted as evidence of exsolution during decompression of eclogite. However, mechanisms other than exsolution might produce free silica, and the possible mechanisms depend in part on the nature and definition of excess silica. ‘Excess’ silica may occur in both stoichiometric and non-stoichiometric pyroxene. Although the issue has been debated, we show that all common definitions of excess silica in non-stoichiometric clinopyroxene are internally consistent, interchangeable, and therefore equivalent. The excess silica content of pyroxene is easily illustrated in a three-component, condensed composition space and may be plotted directly from a structural formula unit …