A multimineral approach to decipher pre-eruptive magma dynamics: the case of the 2010 eruption of Kizimen (Kamchatka, Russia)

Abstract

Volcanic mineral texture and compositional zoning offer crucial insights into magmatic processes and their timing preceding an eruption. Each mineral may capture different aspects of the pre-eruptive magmatic processes. Here we use a multimineral (plagioclase, orthopyroxene, and magnetite) approach to decipher the magma dynamics prior the 2010 magmatic eruption of Kizimen volcano (Kamchatka). The eruption comprised explosive episodes generating pyroclastic density currents followed by the extrusion of a thick lava flow. We combined crystal system analysis with diffusion chronometry on plagioclase and magnetite, together with the orthopyroxene data of Ostorero et al. (3:290, 2022). Plagioclase crystals record up to four different magmatic environments which include two distinct magma mixing events. The first one involved the injection of mafic magma into an initially dacitic reservoir. The magma intrusion led to significant environmental changes within the reservoir which became thermally and compositionally zoned, with remnant dacitic magma at the top and newly created andesitic magma at its base. Both plagioclase and orthopyroxene record the interaction between the dacitic and andesitic magmas during a second mixing event at their interface. This event can be linked to a seismic crisis approximately 1.5 years before the eruption, and is also recorded by Fe–Mg diffusion chronometry in orthopyroxene. Magnetite zoning recorded a final heating event of a few days, potentially marking magma ascent and storage in the lava dome. The compositional zoning plagioclase and magnetite crystals is consistent with the spatio-temporal interpretations made from orthopyroxene crystals zoning and timescales. Plagioclase serves as a reliable yet more complex archive compared to orthopyroxene. Correlating different mineral records enables a more precise reconstruction of magmatic history. Combining petrological and monitoring data provides a more robust understanding of pre-eruptive reactivation.