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The Wildcat Creek Tuff, Eastern Oregon: Co-Eruption Of Crystal-Poor Rhyolite And Fe-Rich Andesite With Implication For Mafic Underpinnings To Voluminous A-Type Rhyolites, Hillarie Jaye Sales
The Wildcat Creek Tuff, Eastern Oregon: Co-Eruption Of Crystal-Poor Rhyolite And Fe-Rich Andesite With Implication For Mafic Underpinnings To Voluminous A-Type Rhyolites, Hillarie Jaye Sales
Dissertations and Theses
The Wildcat Creek Tuff is a thin (~3-12 m), rhyolite to andesitic ash-flow tuff with a minimal extent of 1500 km2 in Malheur county, eastern Oregon. The previously undated tuff yielded a single crystal, anorthoclase 40Ar/39Ar age of 15.49±0.02 Ma and thus is closely related to mafic and silicic volcanism of the Columbia River Province. The tuff texturally stands out by its high proportion of co-mingled mafic inclusions appearing as dark, scoriaceous, and phenocryst-poor fragments, and their proportion dictate bulk tuff compositions ranging from rhyolite (74% SiO2) to andesite (59% SiO2). Glass analyses confirm …