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.
Highlights
Volatile element concentrations measured in melt inclusions are a key tool used to understand magma migration and degassing, their original values may be affected by different re-equilibration processes
We focus on the zoning patterns and melt inclusions from olivine crystals sourced from the 2008 eruption of Llaima volcano (Southern Chile)
The classic open system degassing trends observed in the melt inclusion dataset from the 2008 eruption are likely a record of the background persistent degassing rather than a record of magmatic processes related to the 2008 eruption[28]
Summary
Volatile element concentrations measured in melt inclusions are a key tool used to understand magma migration and degassing, their original values may be affected by different re-equilibration processes. Studying the chemical gradients of crystals and modelling them with diffusion laws has provided evidence for crystals being sourced from different parts of the plumbing system with timescales ranging from a few hours to years within a single eruption deposit[19,20,21,22,23,24,25,26] It is currently not straightforward how melt inclusion data can be related to the processes of magma migration and evolution that may precede the eruption. We use the chemical diffusion laws in the host crystals as a proxy to estimate the minimum time between the melt inclusions’ last re-equilibration depth and the eruption This provides a firstorder approximation of the progressive ascent, mixing, and overall shallow accumulation of magma prior to eruption
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