Spinel crystals in mantle ultramafic xenoliths as the source of P-T conditions of alteration above the magma chamber beneath the Avacha Volcano (Kamchatka)

Abstract

This study focuses on the ability of spinel crystals in ultramafic xenoliths, like zircon, to store the primary composition and structure when exposed to magma fluid flows or the thermal heating of ultramafic fragments in magma flows during volcanic eruptions. Mantle ultramafic rock xenoliths from explosives of the Avacha Volcano in Kamchatka have different facies of their metasomatic changes above the magma chamber. An alternative hypothesis of their source is from fragments of layered mafic intrusions containing spinels, which store initial petrogenetic records of the original magma melt. Experiments were conducted to prove this idea using a Budker Institute of Nuclear Physics (INP SB RAS) unit. Large scales of change in the composition and structure of spinel crystals were caused by the hot fluids from melted xenolith sites.