Earth connections in 50 years of ocean drilling toward mantle drilling

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Author(s): Michibayashi, Katsuyoshi
Author Affiliation(s): Primary:
Nagoya University, Nagoya, Japan
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Hard-rock drilling in 50 years of ocean drilling are briefly summarized with special emphases on mantle drilling in order to understand deep processes and their impacts to the surface environments of our planet. Drilling into mantle has been a long-time aspiration since the first Mohole project in 1961. The (Moho-to-Mantle) M2M proposal, submitted to IODP in 2012, addressed the reachable goals of sampling the in situ upper mantle peridotite and investigating the nature of the Mohorovicic seismic discontinuity (Moho) with the drilling vessel Chikyu. The science of M2M proposal was positively reviewed by the science evaluation panel (SEP) and the proposal identified as the flagship project of Chikyu. The growing technology can accomplish the proposed drilling through ∼6,000 m of igneous oceanic crust formed from a fast-spreading ridge, and an additional ∼500 m into the ocean lithosphere mantle. However, the project faces difficulty in preparing its action plan due to postponement of the site survey for its three candidate drill sites. This exciting big science project may need to wait for major financial support before it is realized. A few past IODP expeditions tried to drill into fresh mantle at large oceanic core complexes in slow-spreading ridges. In these locations, igneous lower crust and lithospheric mantle are exhumed in the footwall of a detachment fault and can be exposed on the seafloor. Expeditions 304 and 305 aimed to drill pristine mantle in the Atlantis Massif of the Mid-Atlantic Ridge, but recovered gabbroic rocks. Expedition 360 finished the first leg of a multiphase drilling project by drilling into a gabbroic body at the ultraslow-spreading Southwest Indian Ridge. Drilling into the mantle has yet been achieved even in the slow spreading ridges, although a future expedition after Exp. 360 may drill through the crust/mantle boundary and investigate the nature of Moho in a mid-ocean ridge setting.
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 18 Geophysics, Solid-Earth; Crust; International Ocean Discovery Program; Lithosphere; Mantle; Mohole Project; Mohorovicic discontinuity; Oceanic crust; Oceanic lithosphere
Record ID: 2019050454
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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