@article{ae1a8916b95e42db9f96d84a7031ac64,
title = "Petit-spot volcanoes on the oldest portion of the Pacific plate",
abstract = "The formation of a petit-spot volcano involves the ascent of an asthenospheric melt to the outboard part of a plate subduction zone where flexure of the plate has taken place in the outer trench swell. On the Pacific Plate, the only previously known examples of such volcanoes were in the vicinity of the Japan Trench. We describe here a newly discovered petit-spot submarine volcano that formed in one of the oldest parts of the Pacific Plate among a cluster of small conical knolls to the southeast of Minamitorishima (Marcus) Island. Geochronological data indicate that this petit-spot volcanic eruption occurred less than 3 million years ago. The volcano erupted on the eastern slope of the outer rise, and it is at an unusually large distance from the Mariana trench axis (~800 km) because this rise, near the older part of the Pacific Plate, is wider than those of other subduction systems.",
keywords = "Alkali-basalt, Outer-rise, Pacific plate, Petit-spot, Seamount",
author = "Naoto Hirano and Shiki Machida and Hirochika Sumino and Kenji Shimizu and Akihiro Tamura and Taisei Morishita and Hideki Iwano and Shuhei Sakata and Teruaki Ishii and Shoji Arai and Shigekazu Yoneda and Tohru Danhara and Takafumi Hirata",
note = "Funding Information: Shipboard multibeam data were obtained during the research cruise of R/V YOKOSUKA (YK10-05) that was funded by the Japan Agency for Marine–Earth Science and Technology (JAMSTEC), Yokosuka, Japan. The data are available at the website of the Deep Sea Research Database ( http://www.jamstec.go.jp/e/database/ ). We used the {\textquoteleft}SeaBeam{\textquoteright} system built by L-3 Communications SeaBeam Instruments to produce the wide-swath contour maps of the seafloor at surveying speeds of 8–12 knots. Two dives (6K#1203 and 6K#1206) by the submersible SHINKAI6500 revealed a knoll ~450 m in height at the north of the central part of the field, and it has ridges that extend ~4.2 km to the northeast and 5.5 km to the south ( Fig. 2 ). The submersible dives climbed the knoll along the northern and southern ridges, respectively. The dives mainly observed highly elongate pillow tubes covered by a thin layer of pelagic sediment ( Fig. 2 A–C, E, H). Sampled pillow tubes contained pelagic mud as seen in cross-sections cut onboard ( Fig. 2 D). The terminations of the lava flows were inflated, mainly on the seafloor where the slope was gentler, thereby producing spherical features ( Fig. 2 A). A sheet flow with ropy structures on the surface was observed to cover a relatively steep slope ( Fig. 2 G). The orientations of the lava flows are roughly down-slope ( Fig. 2 ). Such clear observations designate the lavas as young, with thin coverings of pelagic sediment and thin ferromanganese crusts ( Azami et al., 2018 ). 3.2 Funding Information: We thank Captains H. Tanaka and T. Sakurai, and the crews of the R/V Yokosuka and the submersible SHINKAI 6500 , as well as the onboard scientific party. The Kyoto University Research Reactor Institute, and the International Research Center for Nuclear Materials Science, the Institute for Materials Research, Tohoku University are gratefully acknowledged in their assistance of undertaking the radiometric dating. This study was financially supported in part by the Toray Science and Technology Grant, Toray Science Foundation, Japan (# 11-5208 ) and by the Japan Society for the Promotion of Science, Japan (# 24654180 , # 17K05715 , # 18H03733 ). Shipboard multibeam data are available at the Deep Sea Research Database's website ( http://www.jamstec.go.jp/e/database/ ). Geochemical and geochronological data are all available in supporting information. Appendix A Funding Information: We thank Captains H. Tanaka and T. Sakurai, and the crews of the R/V Yokosuka and the submersible SHINKAI 6500, as well as the onboard scientific party. The Kyoto University Research Reactor Institute, and the International Research Center for Nuclear Materials Science, the Institute for Materials Research, Tohoku University are gratefully acknowledged in their assistance of undertaking the radiometric dating. This study was financially supported in part by the Toray Science and Technology Grant, Toray Science Foundation, Japan (#11-5208) and by the Japan Society for the Promotion of Science, Japan (#24654180, #17K05715, #18H03733). Shipboard multibeam data are available at the Deep Sea Research Database's website (http://www.jamstec.go.jp/e/database/). Geochemical and geochronological data are all available in supporting information. Publisher Copyright: {\textcopyright} 2019 Elsevier Ltd",
year = "2019",
month = dec,
doi = "10.1016/j.dsr.2019.103142",
language = "English",
volume = "154",
journal = "Deep-Sea Research Part I: Oceanographic Research Papers",
issn = "0967-0637",
publisher = "Elsevier Ltd.",
}