Migration of a volcanic front inferred from <scp>K</scp>–<scp>A</scp>r ages of late <scp>M</scp>iocene to <scp>P</scp>liocene volcanic rocks in central <scp>J</scp>apan

<jats:title>Abstract</jats:title><jats:p><jats:styled-content style="fixed-case">K</jats:styled-content>–<jats:styled-content style="fixed-case">A</jats:styled-content>r ages have been determined for 14 late <jats:styled-content style="fixed-case">M</jats:styled-content>iocene to <jats:styled-content style="fixed-case">P</jats:styled-content>liocene volcanic rocks in the north of the <jats:styled-content style="fixed-case">K</jats:styled-content>anto <jats:styled-content style="fixed-case">M</jats:styled-content>ountains, <jats:styled-content style="fixed-case">J</jats:styled-content>apan, for tracking the location of the volcanic front through the time. These samples were collected from volcanoes located behind the trench–trench–trench (<jats:styled-content style="fixed-case">TTT</jats:styled-content>) triple junction of the <jats:styled-content style="fixed-case">P</jats:styled-content>acific, <jats:styled-content style="fixed-case">P</jats:styled-content>hilippine <jats:styled-content style="fixed-case">S</jats:styled-content>ea, and <jats:styled-content style="fixed-case">N</jats:styled-content>orth <jats:styled-content style="fixed-case">A</jats:styled-content>merican plates. This junction is the site of subduction of slabs of the <jats:styled-content style="fixed-case">P</jats:styled-content>acific and the <jats:styled-content style="fixed-case">P</jats:styled-content>hilippine <jats:styled-content style="fixed-case">S</jats:styled-content>ea plates, both of which are thought to have influenced magmatism in this region. The stratigraphy and <jats:styled-content style="fixed-case">K</jats:styled-content>–<jats:styled-content style="fixed-case">A</jats:styled-content>r ages of volcanic rocks in the study area indicate that volcanism occurred between the late <jats:styled-content style="fixed-case">M</jats:styled-content>iocene and the <jats:styled-content style="fixed-case">P</jats:styled-content>liocene, and ceased before the <jats:styled-content style="fixed-case">P</jats:styled-content>leistocene. Volcanism in adjacent areas of the southern <jats:styled-content style="fixed-case">NE J</jats:styled-content>apan and northern <jats:styled-content style="fixed-case">I</jats:styled-content>zu–<jats:styled-content style="fixed-case">B</jats:styled-content>onin arcs also occurred during the <jats:styled-content style="fixed-case">P</jats:styled-content>liocene and ceased at around 3 Ma with the westward migration of the volcanic front, as reported previously. Combining our new age data with the existing data shows that before 3 Ma the volcanic front around the <jats:styled-content style="fixed-case">TTT</jats:styled-content> junction was located about 50 km east of the preset‐day volcanic front. We suggest that northward subduction of the <jats:styled-content style="fixed-case">P</jats:styled-content>hilippine <jats:styled-content style="fixed-case">S</jats:styled-content>ea <jats:styled-content style="fixed-case">P</jats:styled-content>late slab ended at ∼3 Ma as a result of collision between the northern margin of the plate with the surface of the <jats:styled-content style="fixed-case">P</jats:styled-content>acific <jats:styled-content style="fixed-case">P</jats:styled-content>late slab. This collision may have caused a change in the subduction vector of the <jats:styled-content style="fixed-case">P</jats:styled-content>hilippine <jats:styled-content style="fixed-case">S</jats:styled-content>ea <jats:styled-content style="fixed-case">P</jats:styled-content>late from the original north‐directed subduction to the present‐day northwest‐directed subduction. This indicates that the post ∼3 Ma westward migration of the volcanic front was a result of this change in plate motion.</jats:p>