Abstract
Using the CL images and Ti concentrations of quartz, we estimate magma temperatures. (1)We compare the Obirakiyama tuff mainly contains two types of quartz bearing pumice clast (Bt-type and Hb-type; Kudo et al.,2007). CL images of Bt-type quartz crystals are almost uniform (710C). In contrast, Hb-type quartz crystals has darker core (750C) with brighter rim(800C). It is concluding that only Hb-type magma has recharged mafic magma its triggered eruption. (2)There is a across arc variation of the caldera forming felsic magma. Chijimisawa tuff (volcanic front region) has higher temperature (40-90C) than Obirakiyama tuff (back arc region).