Itinome-gataa nd Sannome-gatav olcanoes,n ortheasternJ apan, are characterizedb y the
eruption of mafic to salic andesite of the calc-alkaline series and high-alumina basalt, both
of which contain small amounts of high-pressure diopside and forsterite megacrysts,
lherzolite and websterite derived from the upper mantle, and gabbro and amphibolite
xenoliths from the lower crust (about 20 to 30 km in depth). It seems likely that this is the
first discovery of upper mantle peridotite xenoliths in calc-alkaline andesite. This andesite
is characterizedb y presenceo f hornblendea nd biotite phenocrysts