Magmatic Speedometry Using R-coded Fitted Elemental Diffusion (M-SURFED) Model: Insights into the Augustine Magmatic System

Diffusion chronometry modeling is an emerging approach for establishing magmatic timelines, with potential resolution down to months and days. Existing user-friendly programs are limited to mineral-specific diffusion, specific processing platforms, Microsoft Excel computational power, or the number of parameters set in the model, such as temperature and activation energy of elements within a mineral. Such constraints have the potential to misrepresent all possible solutions for calculating magmatic speedometry through the limitation of storage conditions. In an effort to remove these restrictions, the Magmatic Speedometry Using R-coded Fitted Elemental Diffusion (M-SURFED) model was created. This model is operated using R, a freely available computational software that can run across multiple operations systems. M-SURFED allows for user input of a range of temperatures or activation energies to be used in the model and is therefore only limited to solving magmatic pacing times by sample size or individual elemental profiles within a crystal. The M-SURFED model provides a more quantitative approach for fitting diffusion chronometry timescales and has been used to evaluate large datasets across multiple mineral compositions to answer questions of how magma is stored within a system and how it has evolved over time. Results from M-SURFED modeling across eruptive cycles have been compared to investigate distinctions across the 120-year eruptive history of Augustine volcano (Sugpiaq: Utakineq; Dena'ina: Chu Nula). Augustine volcano, a late Pleistocene stratovolcano located in the Cook Inlet in southern Alaska, remains one of the most active in the Aleutian volcanic arc. Newly modeled spatially resolved Mg and Ti concentration data in plagioclase and pyroxene crystals support a multi-stage magmatic plumbing system, with timescales on the order of 100 years, suggesting a vertically extensive volcanic system, with both warm- and cold-storage dominating regions.