Remnant of Rodinia Supercontinent Identified in Mauritius

A Precambrian microcontinent in the Indian Ocean

Authors:

1. Trond H. Torsvik (a,b,c,d,e,j)
2. Hans Amundsen (f)
3. Ebbe H. Hartz (a,g)
4. Fernando Corfu (d)
5. Nick Kusznir (h)
6. Carmen Gaina (a,b,d,j)
7. Pavel V. Doubrovine (a,b,j)
8. Bernhard Steinberger (a,b,i)
9. Lewis D. Ashwal (e)
10. Bjørn Jamtveit (a)

Affiliations:

a. Physics of Geological Processes, University of Oslo, 0316 Oslo, Norway

b. Center of Advanced Study, Norwegian Academy of Science and Letters, 0271 Oslo, Norway

c. Geodynamics, NGU, N-7491 Trondheim, Norway

d. Geosciences, University of Oslo, 0316 Oslo, Norway

e. School of Geosciences, University of Witwatersrand, WITS 2050, South Africa

f. EPX, Jacob Aalls Gate 44b, N-0364 Oslo, Norway

g. Det norske oljeselskap, Postboks 2070 Vika, 0125 Oslo, Norway

h. Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 3BX, UK

i. Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Heinrich-Mann-Allee 18/19, 14473 Potsdam, Germany

j. Present address: Centre for Earth Evolution and Dynamics, University of Oslo, 0316 Oslo, Norway

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 years^{2, 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.