Textural and compositional analyses of plagioclase phenocrysts in volcanic rocks have been utilized widely to decipher magmatic processes, in particular magma mixing. The features of plagioclase phenocrysts can also be used to correlate separate but potentially related deposits in volcanic terranes. This study focuses on plagioclase phenocrysts from two dacitic ash-flow tuffs (Qdt and Qto) exposed on the east side of Newberry Volcano. To explore possible petrogenetic relationships between the tuffs, the phenocrysts were characterized in terms of occurrence, morphology, disequilibrium textures, and zoning patterns. Plagioclase crystals from Qdt and Qto display similar textural attributes but differ with respect to compositional zoning types. The textural similarities suggest that the tuffs are comagmatic, but the difference in zoning patterns implies separate eruptive events. Further detailed studies of plagioclase phenocrysts from these ash-flow tuffs will provide greater insights into magmatic processes occurring at Newberry Volcano.
Fisher, Kara. "Examining Petrologic Linkages between Dacitic Ash-Flow Tuffs at Newberry Volcano through Textural and Compositional Analysis of Plagioclase Phenocrysts." Poster presentation at the Academic Excellence Showcase, Western Oregon University, May 31, 2012.
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