Preliminary research of magma mixing and explosive mechanism of the Millennium eruption of Tianchi volcano.

Studies on magma evolution and on geophysical observations indicate that there are two magma chambers beneath Tianchi volcano.Continuous basaltic magma influx from mantle chamber to crust chamber are essential to the keep Tianchi volcano active over a million years,and are also important to interpret the magma evolution of Tianchi volcano.In this paper,we present evidence of magma influx and magma mixing from the gray pumice of the Millennium eruption of Tianchi volcano.The breccias in the gray pumice and the banded structures indicate the occurrence of magma mixing.The petrological,mineralogical and chemical studies of these samples reveal the story of magma influx and mixing,which may trigger the Millennium eruption of Tianchi volcano.