MAGMA RESIDENCE AND STORAGE CONDITIONS AT LARGE VOLUME DOMES IN THE ANDEAN CENTRAL VOLCANIC ZONE, CHILE

The Andean Central Volcanic Zone (CVZ), home to large silicic volcanic systems like the Chao Dacite and Chillahuita Dome, offers a unique natural laboratory to investigate the magmatic processes responsible for explosive volcanism and extensive dome formations. These silicic systems, characterized by their high phenocryst content and compositional homogeneity, reflect prolonged magma residence in subvolcanic reservoirs and dynamic thermal and chemical evolution. The aim of this research is to quantify the magma residence times and storage conditions by examining the diffusion rates of Strontium (Sr) and Magnesium (Mg) in plagioclase phenocrysts, thereby elucidating the thermal and compositional evolution of these magmatic systems. To achieve this, we analyze plagioclase samples from both Chao and Chillahuita dome by Electron Probe Microanalysis (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). These data will be applied to forward diffusion models to calculate timescales of Sr and Mg diffusion. The trace and major element zoning profiles from EPMA and LA-ICPMS will be used to reconstruct the magmatic history beneath the domes. The expected results from this research work include evidence of extended magma storage at near-solidus temperatures, insights into magmatic processes such as fractional crystallization, magma mixing, and convection, and a comparative framework linking dome-forming events to regional ignimbrite eruptions at the CVZ. The findings from this research will enhance our understanding of the magmatic processes driving the evolution of these silicic domes, with implications for volcanic petrology and mineralogy, volcanic eruption forecasting, and volcanic risk mitigation in one of the most volcanically active regions of South America.