Rapid transition from continental breakup to igneous oceanic crust in the South China Sea

Creators: Larsen, H. C.; Stock, J.; Hinojosa, J.

Abstract

Continental breakup represents the successful process of rifting and thinning of the continental lithosphere, leading to plate rupture and initiation of oceanic crust formation. Magmatism during breakup seems to follow a path of either excessive, transient magmatism (magma-rich margins) or of igneous starvation (magma-poor margins). The latter type is characterized by extreme continental lithospheric extension and mantle exhumation prior to igneous oceanic crust formation. Discovery of magma-poor margins has raised fundamental questions about the onset of ocean-floor type magmatism, and has guided interpretation of seismic data across many rifted margins, including the highly extended northern South China Sea margin. Here we report International Ocean Discovery Program drilling data from the northern South China Sea margin, testing the magma-poor margin model outside the North Atlantic. Contrary to expectations, results show initiation of Mid-Ocean Ridge basalt type magmatism during breakup, with a narrow and rapid transition into igneous oceanic crust. Coring and seismic data suggest that fast lithospheric extension without mantle exhumation generated a margin structure between the two endmembers. Asthenospheric upwelling yielding Mid-Ocean Ridge basalt-type magmatism from normal-temperature mantle during final breakup is interpreted to reflect rapid rifting within thin pre-rift lithosphere.

Additional Information

© 2018 Springer Nature Limited. Received 11 November 2017; Accepted 04 July 2018; Published 20 August 2018. The authors acknowledge the Chinese National Offshore Oil and Gas Company (CNOOC) for providing access for Z.S. and H.C.L. to work on their large regional database of seismic reflection data, which CNOOC subsequently amended with acquisition of new data to document our selected drill sites. The authors thank the RV JOIDES Resolution crew and the IODP technical staff. The IODP–China office supported international workshops to develop the original drilling proposal. Co-principal investigators of the drilling proposal, P. Wang and C.-F. Li, are acknowledged for their contributions to planning. This research used data and samples provided by the International Ocean Discovery Program. A.K. and C.A.-Z. acknowledge support from NSF award no. OCE-1326927. D.Z. was supported by the Korean IODP program (KIODP). Author Contributions: H.C.L. was co-principal investigator (co-PI) for the original drilling proposal and interpretation of seismic data, co-chief scientist of expeditions 367/368, and directed the writing of the paper. G.M. is principal co-author, developed the geodynamic model jointly with H.C.L. and M.N. and was a shipboard scientist (structural geology) at expedition 368. M.N. was a shipboard scientist (structure/sedimentology) at expedition 367, carried out structural interpretation of syn-rift sedimentation, and contributed to model development and graphics. Z.S was co-PI for the original drilling proposal, interpretation of seismic data, and was co-chief scientist of expeditions 367/368. J.S. was co-chief scientist of expeditions 367/368 and co-proponent of the original drilling proposal. Z.J. was co-chief scientist of expeditions 367/368 and coordinated biostratigraphic interpretations. A.K. was expeditions 367/368 project manager. C.A.A.-Z. was expeditions 367/368 project manager and performed biostratigraphy. J.B., A.B., Y.C., M.D., A.F., J.H., T.W.H., K.H., B.H., X.H., B.J., C.Lei., L.L., Z.L., A.L., C.Lupi, A.McC., M.N., C.R., I.S., C.S., X.S., R.X., R.Y., L.Y., C.Z., J.Z., Y.Z., N.Z. and L.Z. collected the drilling data during IODP expedition 367 and participated in the writing of the paper. S.B., D.C., K.D., W.D., E.F., F.F., A.G., E.H., S.J., H.J., R.K., B.L., Y.L., J.L. (co-PI)., Chang Liu, Chuanlian Liu, L.N., N.O., D.W.P., P.P., N.Q., S.Sa., J.C.S., S.St., L.T., F.M.vdZ., S.W., H.W., P.S.Y. and G.Z. collected the drilling data during IODP expedition 368 and participated in writing of the paper. Roles on board are detailed in https://iodp.tamu.edu/scienceops/precruise/southchinasea2/participants.html. The authors declare no competing interests. Data availability: The data that support the findings of this study are available from the IODP Proceedings of Expeditions 367/368 (http://iodp.tamu.edu/publications/bibliographic_information/367368cit.html) to be published 28 September 2018. All IODP data from any expeditions can be obtained from https://doi.org/10.14379/iodp.proc.367368.2018. Further questions can be directed to the corresponding authors.

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