Daisen is a volcanic field in the Southwest Japan Arc, where the Philippine Sea Plate is subducted beneath the Eurasian Plate.  Daisen consists of a ~1.2 Ma basaltic lava flow partially overlain by an andesite-dacite series that ranges in age from 500 Ka to 17 Ka.  The Daisen andesite-dacite suite exhibits particular trace element characteristics such as high Sr/Y and La/Yb that suggest fractional crystallization of garnet.  Such magmas are often referred to as “adakites” due to their resemblance to lavas found at Adak Island in the Aleutian Arc.  Slab melting may or may not be involved.
Daisen 大山
Misen: youngest volcanic feature at Daisen (17 Ka)
Misen dacite
Kabutogasen and Yahazugasen: Daisen lava flows, ~400 Ka
Kabutogasen dacite
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