title: Volcanism in response to plate flexure.
abstract: Volcanism on Earth is known to occur in three tectonic settings: divergent plate boundaries (such as mid-ocean ridges), convergent plate boundaries (such as island arcs), and hot spots. We report volcanism on the 135 million-year-old Pacific Plate not belonging to any of these categories. Small alkalic volcanoes form from small percent melts and originate in the asthenosphere, as implied by their trace element geochemistry and noble gas isotopic compositions. We propose that these small volcanoes erupt along lithospheric fractures in response to plate flexure during subduction. Minor extents of asthenospheric melting and the volcanoes' tectonic alignment and age progression in the direction opposite to that of plate motion provide evidence for the presence of a small percent melt in the asthenosphere.
authors.affiliation: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan. nhirano@ucsd.edu
authors.forename: Naoto
authors.initials: N
authors.lastname: Hirano
authors.forename: Eiichi
authors.initials: E
authors.lastname: Takahashi
authors.forename: Junji
authors.initials: J
authors.lastname: Yamamoto
authors.forename: Natsue
authors.initials: N
authors.lastname: Abe
authors.forename: Stephanie P
authors.initials: SP
authors.lastname: Ingle
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kaneoka
authors.forename: Takafumi
authors.initials: T
authors.lastname: Hirata
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Kimura
authors.forename: Teruaki
authors.initials: T
authors.lastname: Ishii
authors.forename: Yujiro
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Shiki
authors.initials: S
authors.lastname: Machida
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Suyehiro