Petrography, Geochemistry, and Geochronology of the Green Mountain Shield Volcano, Oregon

Abstract

Green Mountain (GM) is a small (~25km) shield volcano located in central Oregon. The ~740,000 year old shield, and associated young (~13,000 ya; Mackey et al., 2014) lava fields, are approximately ~50 km southeast of the Newberry Caldera on the northwest side of an age progressive trend of bi-model volcanism from southeastern Oregon to Newberry (Jordan, 2004). In a previous study(Friedrichs and Castonguay, 2014), XRF results were reported and interpreted as evidence of a single magma chamber that had undergone fractional crystallization and a significant magma recharge event before the most recent volcanism. This study aims to expand on this existing knowledge by applying geochronology, detailed petrographic analysis, and additional XRF analysis.