OS024-0005
Introducing the revised IODP proposal to reveal the nature of back-arc basin lower crust and upper mantle at the Godzilla Megamullion

Thursday, 10 December 2020
Poster
Yasuhiko Ohara, Hydrographic and Oceanographic Department of Japan, Tokyo, Japan; Japan Agency for Marine-Earth Science and Technoloty, Yokosuka, Japan, Katsuyoshi Michibayashi, Nagoya University, Nagoya, Japan, Jonathan E Snow, Louisiana State University, Baton Rouge, LA, United States, Henry J Dick, Woods Hole Oceanographic Institution, Woods Hole, MA, United States, Yumiko Harigane, Geological Survey of Japan, Tsukuba, Japan and Alessio Sanfilippo, University of Pavia, Pavia, Italy
Abstract:
Oceanic core complexes (OCCs) or megamullions are domal bathymetric highs characterized by axis-normal surface corrugations and exposures of serpentinized peridotite and gabbroic rocks which are interpreted as exhumed footwalls of low-angle detachment faults. OCCs provide a valuable opportunity to directly study the architecture of oceanic lithosphere, together with the tectono-magmatic processes associated with its formation and evolution.

The Godzilla Megamullion, located in the extinct Parece Vela Basin in the Philippine Sea, is the largest known OCC (areal dimensions ~125 km × 55 km). A significant fraction of the ocean floor is created in back-arc basins, where water plays a major role in generating back-arc basin basalts, a significant contrast to magmatic process at mid-ocean ridges. Furthermore, much of our understanding of all ocean crust comes from ophiolites, which are largely attributed to supra-subduction zone environments. A better understanding of the architecture of back-arc basin crust is a necessary contribution that will bridge the results of ophiolite analog studies and the overall geology of oceanic crust. However, there is no single long section of lower oceanic crust and uppermost mantle from a back-arc basin to understand the differences that characterize the architecture and composition of ocean lithosphere in this key tectonic setting. Godzilla Megamullion is arguably the best place in the world to study the architecture of back-arc basin lithosphere and it’s crust/mantle boundary.

We initially submitted an IODP Proposal to drill the Godzilla Megamullion in 2003, which was deactivated in 2011. We submitted a new IODP Proposal in 2017, incorporating the progress of the Godzilla Megamullion study. Following the interactions with the Science Evaluation Panel (SEP) of IODP, the revised Godzilla proposal has matured and address the five challenges of IODP 2013-2023 Science Plan, addressing tectono-magmatic and biological themes. Here, we share the general scheme of the improved proposal with the community.

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