A Precambrian microcontinent in the Indian Ocean

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Abstract

The Laccadive–Chagos Ridge and Southern Mascarene Plateau in the north-central and western Indian Ocean, respectively, are thought to be volcanic chains formed above the Réunion mantle plume1 over the past 65.5 million years2,3. Here we use U–Pb dating to analyse the ages of zircon xenocrysts found within young lavas on the island of Mauritius, part of the Southern Mascarene Plateau. We find that the zircons are either Palaeoproterozoic (more than 1,971 million years old) or Neoproterozoic (between 660 and 840 million years old). We propose that the zircons were assimilated from ancient fragments of continental lithosphere beneath Mauritius, and were brought to the surface by plume-related lavas. We use gravity data inversion to map crustal thickness and find that Mauritius forms part of a contiguous block of anomalously thick crust that extends in an arc northwards to the Seychelles. Using plate tectonic reconstructions, we show that Mauritius and the adjacent Mascarene Plateau may overlie a Precambrian microcontinent that we call Mauritia. On the basis of reinterpretation of marine geophysical data4, we propose that Mauritia was separated from Madagascar and fragmented into a ribbon-like configuration by a series of mid-ocean ridge jumps during the opening of the Mascarene ocean basin between 83.5 and 61 million years ago. We suggest that the plume-related magmatic deposits have since covered Mauritia and potentially other continental fragments.

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Figure 1: Crustal thickness map based on gravity inversion and the Réunion hotspot chain.
Figure 2: U–Pb concordia diagram.
Figure 3: Late Cretaceous to Eocene plate reconstructions.

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Acknowledgements

We thank E. R. Neuman for discussions, and C. Mac Niocaill for constructive comments. The European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Advanced Grant Agreement Number 267631 (Beyond Plate Tectonics), the Norwegian Research Council (Topo-4D) and the Centre for Advanced Study are acknowledged for financial support.

Author information

T.H.T., H.A. and B.J. developed the conceptual idea for the study, H.A. and E.H. sampled the Mauritius rocks, F.C. dated the samples, N.K. calculated the crustal thickness map, C.G. and T.H.T developed detailed reconstructions, P.D. and B.S. developed global plate motion frames, and L.D.A. and B.J. handled geochemical aspects. All authors contributed to discussions and writing of the manuscript.

Correspondence to Trond H. Torsvik or Carmen Gaina or Pavel V. Doubrovine.

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Torsvik, T., Amundsen, H., Hartz, E. et al. A Precambrian microcontinent in the Indian Ocean. Nature Geosci 6, 223–227 (2013) doi:10.1038/ngeo1736

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