[S-CG41] Hard-Rock Drilling Science: From Continental to Deep Sea Drilling, and Oman Project

[SCG41-10] New Developments in Hard Rock Drilling Project: Horoman and Forearc Mantle drilling

*Katsuyoshi Michibayashi¹, Eiichi Takazawa², Tomoaki Morishita³, Mikiya Yamashita^4,5, Gou Fujie⁴, Shigeaki Ono⁴ (1.Nagoya University, 2.Niigata University, 3.Kanazawa University, 4.JAMSTEC, 5.AIST)

Keywords:Horoman Peridotite, Oman ophiolite, Forearc Mantle Drilling

Plate tectonics, which is the paradigm of modern earth science, has been based on the assumption of a homogeneous and dry oceanic plate. However, rapid progress in ocean bottom exploration in the last 20 years strongly suggests that oceanic plates are diverse and quite wet (water-bearing). The Oman Drilling Expedition (2016-2018) has clearly demonstrated that the oceanic plate is not only poorly understood, but also that a major feature of the oceanic plate is that it can be far more hydrous than currently thought. However, while the Oman drilling experiment is revealing the full picture of the wet oceanic plate, our understanding of the dry case is still lacking. The Horoman peridotite body, located near Cape Erimo in the southernmost part of the Hidaka Mountains in Hokkaido, Japan, is one of the rare dry oceanic plate fragments in the world. We are now planning to carry out Horoman peridotite drilling experiments to recover continuous samples of dry oceanic plate material. We will compare our results with those of the recent Oman ophiolite drilling experiments to develop a new lithostratigraphic model that accounts for the entire oceanic plate, taking into account magma production and water content. In addition, the results of the geophysical survey of the Ogasawara Trench performed on December 19, 2020 will be briefly presented for the forearc Mantle drilling project.