Magma mingling recorded in "B'-scoria fall deposit" from Maekake stage, Asama volcano.

Magma mingling recorded in "B'-scoria fall deposit" from Maekake stage, Asama volcanoThe eruptive products from Asama volcano, central Japan, often show textural heter ogeneities.Especially, the pyroclastic materials of "B'-scoria fall deposit", which erupted between the 1108 and the 1783 eruptions, show remarkable textural heterogeneities in various scale.B' is constituted of scoria, pumice, heterogeneous scoria and some banded pumice.The bulk rock composition of these materials are andesitic (58 wt% SiO2) to dacitic (63 wt%).These materials show remarkable textural heterogeneities such as the patchy or the banding texture in various scale.These textural heterogeneities are due to the coexistence of four petrographically different groundmass glass parts.Petrographical features and mineralogical data suggest that the mixing of different types of magmas produced these groundmass glass parts.Furthermore, the patchy and the banding texture indicate that the four parts were mingled with one another.These features may be interpreted by the mixing model; magma mixing, producing heteroge neous mixed magma (having four magma parts), and then the mingling of these four magma parts, which erupted finally and became various pyroclastic materials such as heterogeneous scoria, scoria, pumice and banded pumice.