The mantle sources of mid-ocean ridge basalts beneath the Indian and Pacific oceans have distinct isotopic compositions with a long-accepted boundary at the Australian–Antarctic Discordance along the Southeast Indian Ridge. This boundary has been widely used to place constraints on large-scale patterns of mantle flow and composition in the Earth’s upper mantle. Sampling between the Indian and Pacific ridges, however, has been lacking, especially along the remote 2,000 km expanse of the Australian–Antarctic Ridge. Here we present Sr, Nd, Hf and Pb isotope data from this region that show the Australian–Antarctic Ridge has isotopic compositions distinct from both the Pacific and Indian mantle domains. These data define a separate Zealandia–Antarctic domain that appears to have formed in response to the deep mantle upwelling and ensuing volcanism that led to the break-up of Gondwana 90 million years ago, and currently persists at the margins of the Antarctic continent. The relatively shallow depths of the Australian–Antarctic Ridge may be the result of this deep mantle upwelling. Large offset transforms to the east may be the boundary with the Pacific domain.

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This study was supported by KOPRI grant nos PP13040 and PE18050 to S.-H.P. Support at Harvard, Wyoming, Woods Hole and Tulsa was provided by the National Science Foundation (OCE1259916). J.B.-T. was supported by the French Agence Nationale de la Recherche through grant no. ANR-10-BLAN-0603 (M&Ms—Mantle Melting—Measurements, Models, Mechanisms). S.-S.K. was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1D1A1A02018632). J.L. was also supported by the CAS through grant no.Y4SL021001 and NSFC through grant no. 91628301. We thank the captain and crew of the icebreaker RV Aaron for support under difficult sea conditions. We appreciate the constructive reviews by J. Morgan and P. Kempton.

Author information


  1. Korea Polar Research Institute, Incheon, Republic of Korea

    • Sung-Hyun Park
    • , Hakkyum Choi
    •  & Yun-Seok Yang
  2. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA

    • Charles H. Langmuir
  3. Department of Geology and Geophysics, University of Wyoming, Laramie, WY, USA

    • Kenneth W. W. Sims
    •  & Sean R. Scott
  4. Laboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon and Université Claude Bernard Lyon 1, CNRS UMR 5276, Lyon, France

    • Janne Blichert-Toft
  5. Department of Geology and Earth Environmental Sciences, Chungnam National University, Daejeon, Republic of Korea

    • Seung-Sep Kim
  6. Departement of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

    • Jian Lin
  7. Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China

    • Jian Lin
  8. Department of Geosciences, University of Tulsa, Tulsa, OK, USA

    • Peter J. Michael


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S-H.P. led the KOPRIDGE project, which included three cruises, interpreted the data and wrote the first draft of the manuscript. C.H.L. contributed to the initial stage of cruise planning, geochemical interpretations and manuscript preparation and editing, and participated in the 2011 cruise. K.W.W.S. oversaw the isotopic analyses by S.R.S. and contributed to the geochemical interpretations and manuscript preparation and editing. J.B.-T. oversaw and participated in the Hf isotopic analyses by S.R.S. and contributed to the geochemical interpretations and manuscript preparation and editing. S.-S.K. contributed to the cruise design, performed geophysical data analyses and interpretations, and contributed to manuscript writing and editing. S.R.S. performed the Sr, Nd, Hf and Pb isotopic analyses and contributed to the table preparation, geochemical interpretations and manuscript editing. J.L. contributed to the cruise design, performed geophysical data analyses and interpretations, participated in the 2011 cruise and contributed to manuscript editing. H.C. and Y.-S.Y. contributed to the cruises and produced the relevant figures and maps. P.J.M. was involved in the cruise planning, geochemical interpretation and manuscript editing. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Sung-Hyun Park.

Supplementary information

  1. Supplementary data Table 1

    Sr-Nd-Pb-Hf isotope data from KR1 and KR2

  2. Supplementary data table 2

    Standard and reference material data

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