Physical Sciences and Mathematics Commons^™

Revisiting Volcanology And Composition Of Rhyolites And Associated Ree Rich Mafic Clasts Of The Three Fingers Caldera, Se Oregon, Phillip Ira Marcy

Dissertations and Theses

Two adjacent caldera systems, the Mahogany Mountain and the Three Fingers caldera constitute voluminous rhyolitic volcanic deposits on the eastern margin of the Oregon-Idaho graben during the middle-Miocene. Both calderas are part of the Lake Owyhee volcanic field that in turn is part of widespread rhyolite deposits associated with the Columbia River Basalt province. We focus on establishing relationships between intracaldera units of Three Fingers caldera and caldera-forming tuff of Spring Creek and surveying the distribution of entrained mafic clasts which often display anomalous concentrations of rare earth elements.

Previous mapping identified two intra-caldera facies and one outflow facies of …