Fluid Fluxing and Accumulation Drive Decadal and Short-Lived Explosive Basaltic Andesite Eruptions Preceded by Limited Volcanic Unrest

Abstract Some volcanoes are known for repeatedly producing explosive but short-lived eruptions (< half a day) every decade or so. These often preceded by limited unrest signals and short run-up times to eruption (a few hours months), thus they difficult anticipate. well-documented examples the 1990 2014 of Kelud volcano in Indonesia, 2015 Calbuco Chile. Here we interrogate rock record obtain insights into processes pre-eruptive conditions that led eruption, which integrate with monitoring data (seismicity, lake temperature hydro-acoustics, sulfur emissions) towards conceptual model this type events. Mineral-melt geothermobarometers indicate basaltic andesite magma carried crystal cargo from as deep 15–19 km, reached volatile saturation at 4–9 km 2–4 wt.% water melt. The textures compositional zoning orthopyroxene plagioclase do not support intrusion more primitive driver instead propose fluid accumulation high-temperature fluxing depth (likely dominated CO2) played major role priming occur. Such gas is also supported mass balance calculation emitted excess SO2 gas. Mg-Fe diffusion profiles reversely zoned pyroxenes constrain timescales weeks months before addition reservoir, such events may be recorded signals, especially change hydroacoustics temperature, probably seismic swarms. We exsolution shallow reservoir plays crucial modulating triggering brief other worldwide.