ASSESSING CRUSTAL STORAGE THROUGHOUT THE ERUPTIVE HISTORY OF AUGUSTINE VOLCANO

Augustine (Sugpiaq: Utakineq; Dena'ina: Chu Nula) Volcano, located in the Cook Inlet of the Aleutian volcanic arc in Alaska, is known for its complex magmatic system that supplies frequent volcanic activity, with a history of eight eruptions in the past two centuries. The Augustine magmatic system is particularly intriguing as it lacks a central magma chamber and instead consists of a plexus of dikes, which inhibit mixing and chemical homogenization. Newly modeled spatially resolved concentration profiles in plagioclase and pyroxene crystals support a multi-stage magmatic plumbing system, with timescales of magma assembly on the order of 100 to 1,000 years, suggesting a vertically extensive volcanic system containing both warm- and cold- storage regions. Such characteristics raise questions about the timescales of magma storage, intricate processes of magma movement within the volcano, and the plumbing system's vertical extent. To address these questions, diffusion chronometry techniques are employed, utilizing multiple mineral phases that initiate crystallization at varying depths and temperatures, focused on the largest historical eruptions of 1883, 1976, 1986, and 2006. Additionally, as Augustine’s volcanic activity began relatively recently in the late Holocene, the Augustine magmatic system offers valuable insights into the maturation process and changing storage conditions of a volcanic system over time. Therefore, Augustine Volcano storage dynamics may present a typical model for how younger complex magmatic systems mature to store vertically extensive large volumes of magma, potentially assembling for caldera-forming events.