Using the Sr isotope compositions of feldspars and glass to distinguish magma system components and dynamics

The individual components of magmatic rocks are being increasingly targeted to gain insight into volcanic systems. Here we demonstrate the use of Sr isotope microsampling to distinguish distinct populations of glass and plagioclase that represent the sources of components (liquids and crystals) within each erupted magma batch. We analyzed glasses and plagioclase feldspar crystal cores to characterize crystal cargoes and host liquids from pumice-fall units from the Minoan cycle, Santorini, Greece. Using this approach, we identify the magmatic components that interacted prior to eruption and formation of pumice clasts, allowing us to interpret the magma dynamics associated with each eruption. Varying degrees of complexity can be identified, from relatively simple cases where the crystals are in isotopic equilibrium with the glass, to more complex, such as the large caldera-forming Minoan eruption, which is characterized by at least two liquid components and three different crystal provenances.