Crystal and melt inclusion timescales reveal the evolution of magma migration before eruption

Abstract

Volatile element concentrations measured in melt inclusions are a key tool used to understand magma migration and degassing, although their original values may be affected by different re-equilibration processes. Additionally, the inclusion-bearing crystals can have a wide range of origins and ages, further complicating the interpretation of magmatic processes. To clarify some of these issues, here we combined olivine diffusion chronometry and melt inclusion data from the 2008 eruption of Llaima volcano (Chile). We found that magma intrusion occurred about 4 years before the eruption at a minimum depth of approximately 8 km. Magma migration and reaction became shallower with time, and about 6 months before the eruption magma reached 3–4 km depth. This can be linked to reported seismicity and ash emissions. Although some ambiguities of interpretation still remain, crystal zoning and melt inclusion studies allow a more complete understanding of magma ascent, degassing, and volcano monitoring data.

Mafic glass compositions: a record of magma storage conditions, mixing and ascent

“…There is also evidence of both assimilation (low TiO 2 , K 2 O and high Al 2 O 3 ) and fractionation at a high modal abundance of plagioclase (high TiO 2 , P 2 O 5 , K 2 O and low Al 2 O 3 , CaO). Taken together, the preserved melt compositions in Llaima samples support interpretations [114,116,117] of relatively shallow magma storage, rapid syn-eruptive evacuation of the volcanic conduit, and entrainment of crystals from parts of the system that have experienced different amounts of fractionation and assimilation.…”

Fast ascent rate during the 2017–2018 Plinian eruption of Ambae (Aoba) volcano: a petrological investigation

“…Crystals with the stronger reverse zoning also show rounded edges indicative of dissolution. Reverse zoning can be interpreted as reflecting either magma mixing (Ruth et al 2018) or reheating of a magma reservoir.…”

The potential for aqueous fluid-rock and silicate melt-rock interactions to re-equilibrate hydrogen in peridotite nominally anhydrous minerals

“…Thermally driven diffusion in igneous minerals is now widely used to quantify the timescales of geologic processes operating in diverse tectonic settings (e.g., Costa and Dungan 2005;Shea et al 2015a;Ruth et al 2018). Hydrogen diffusion chronometry has classically been applied at high temperatures (e.g., 1000-1200°C), where it records short-lived processes such as magma ascent Peslier and Luhr 2006;Denis et al 2015;Lloyd et al 2016) and melt inclusion re-equilibration during degassing/decompression of melts (e.g., Le Voyer et al 2014).…”