Tracking caldera cycles in the Aso magmatic system – Applications of magnetite composition as a proxy for differentiation

Caldera-forming eruptions are among the most hazardous natural events on Earth and pose a significant risk for global consequences in future. Recent petrological re-evaluations of pre-, syn-, post-caldera deposits several volcanic systems worldwide suggest cyclic behavior evolution subvolcanic reservoirs feeding these eruptions. Such caldera cycles usually subdivided into maturation, fermentation recovery phases, each characterized by distinct features (e.g. variations mineral glass compositions). Combined with trends intensive parameters geophysical information about eruptive system, characteristics can be used to determine current state reservoir within cycle framework. Here, we test application this model Aso complex Central Kyushu (Japan) analyzing activity between Aso-4 Aso-3 evaluate recent based geochemistry. Widely overlapping compositions minerals (here plagioclase orthopyroxene) melt, as well similar ranges magmatic H2O content), make it difficult pinpoint chemical differences pre- or Tracing MnO/Al2O3 ratio titanomagnetite, other hand, appears useful proxy trace level differentiation prior eruption. Titanomagnetite is an abundant phase known chemically re-equilibrate fast melt hence records “average” conditions prevailing just eruption, MnO showing typical incompatible during magma evolution, while Al2O3 typically compatible. The assessment different case studies revealed clear evolutionary patterns common all low Mn (associated levels differentiation) recovery, progressively increasing culminating at highest (and associated phase, right before next caldera-forming event. titanomagnetite analytically easy quick electron microprobe, gives valuable position system Based evaluation products context activity, conclude that presently still after massive Depending supply from depth, either enter renewed maturation could decline leading cessation system.