Fig. 5

Schematic diagrams showing a the state before the Aso-4 event started. Amphibole- and Cpx-free crystal mush underlying the 4I-1 melt chamber and overlying two-pyroxene-bearing crystal mush with a local amphibole-bearing part; b the mafic magma started intrusion into the 4I-1 melt chamber. The initially intruded mafic magma was mixed with the 4I-1 melt to form small volume of hybrid magma, which crystallized Al-enriched amphiboles. In addition, the intrusion induced partial collapse of the crystal mush; c the hybrid magma and crystals derived from the collapsed mush were incorporated into and mixed with the 4I-1 melt, and the magma erupted to form the 4I-1 pyroclastic flow; d large volume of the mafic magma intruded into and mixed with the residual 4I-1 melt to form abundant hybrid magma, which erupted in the later stage of Aso-4 eruption; e after Aso eruption ended, low-density breccias and residual crystal mush acted as density barrier for ascending mafic magma, resulting in formation of mafic magma reservoir at the depth similar to the Aso-4 magma reservoir; f in post-caldera stage, mafic magmas derived from the new mafic magma reservoir have erupted