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Subduction initiation and ophiolite crust: new insights from IODP drilling

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posted on 2017-01-16, 13:18 authored by Mark K. Reagan, Julian A. Pearce, Katerina Petronotis, Renat R. Almeev, Aaron J. Avery, Claire Carvallo, Timothy Chapman, Gail L. Christeson, Eric C. Ferré, Marguerite Godard, Daniel E. Heaton, Maria Kirchenbaur, Walter Kurz, Steffen Kutterolf, Hongyan Li, Yibing Li, Katsuyoshi Michibayashi, Sally Morgan, Wendy R. Nelson, Julie Prytulak, Marie Python, Alastair H.F. Robertson, Jeffrey G. Ryan, William W. Sager, Tetsuya Sakuyama, John W. Shervais, Kenji Shimizu, Scott A. Whattam

International Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis.

Funding

We thank the USSSP for initial funding of US scientists, and NSF grants OCE1558608 (Nelson), OCE1558647 (Reagan), OCE1558689 (Shervais), and OCR1558855 (Ryan), for continued funding. Julian Pearce thanks NERC (UK) for financial support through grant NE/M012034/1). J. Prytulak was supported by NERC grant NE/M010643. S. Kutterolf thanks the German Research Foundation (KU-2685/4-1), and R. Almeev thanks the German Science Foundation (DFG Project AL 1189/8) for financial support. W. Kurz was supported by the Austrian Academy of Sciences and by the Austrian Science Fund (FWF Project P27982-N29). K. Michibayashi was supported by the Japan Society for the Promotion of Science (JSPS: 16H06347) and the Japan Drilling Earth Science Consortium. H.Y. Li acknowledges the support from the State Oceanic Administration (GASI-GEOGE-02). T. Chapman was funded by ANZIC.

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