CORRELATING MT. YANA LAVAS WITH TUSCAN FORMATION BRECCIAS: SHOWCASING GEOLOGIC RESEARCH IN PUBLIC OUTREACH WITH THE MYANA EXPLORER FIELD TRIP APP

Mt. Yana is an approximately 3 Ma stratovolcano of the ancestral Cascades (1), located 40 km south of the Lassen Volcanic Center. Extensive erosion of the edifice offers easy access to the interior of Mt. Yana to investigate products of the growth and erosion of the volcano. New research builds on unpublished mapping and data (2) to investigate whether specific lava flows of Mt. Yana can be traced to erosional volcaniclastic breccias in the Tuscan Formation, located 70 km downslope, in Chico, CA. Proximal andesite outcrops within the eroded edifice of Mt. Yana host pyroxene phenocrysts that we compared to pyroxene-phyric andesite clasts of the Tuscan Formation. Image analyses of hand samples (using ImageJ) indicate that the area percent of pyroxene crystals in Tuscan formation clasts (3-12%) are similar to those in Mt. Yana samples (10-13%). Preliminary thin section and SEM-EDS analyses indicate that both Mt. Yana and Tuscan Formation samples contain orthopyroxenes (opx) and clinopyroxenes (cpx), and zoned pyroxene crystals (with both opx and cpx). Electron Microprobe analyses will be used to compare pyroxene compositions in samples from Mt. Yana outcrops and Tuscan Formation debris flow deposits. To engage the public in learning about ancient Mt. Yana, we have developed the MYana Explorer app, which guides users in an exploration of the interior of the eroded volcano and the research used to reconstruct physical and petrogenetic processes of Mt. Yana. A guided day-hike includes 12 stops that explore volcano growth processes such as volcanic dike emplacement, lava flows, columnar jointing, and hyaloclastite deposits of glassy magma fragments that were quenched from water/ice interactions. Erosional features in the app include proximal breccias deposited by debris flows. Stops in Chico guide users in observing distal erosional remnants of Mt. Yana at breccia outcrops of the Tuscan Formation. (1) Clynne & Muffler, 2010; (2) Clynne personal communication.