Image: © GFZ/Steinberger
HIDDEN MICRO-CONTINENT FOUND IN THE INDIAN OCEAN
Beneath the islands of Reunion and Mauritius lies a hitherto undiscovered microcontinent. The continental fragment Mauritia is believed to have detached about 60 million years ago, while Madagascar and India were drifting apart. The fragment was hidden under huge masses of lava.
Continental break-up is usually associated with mantle plumes, which is where giant blobs of hot rock rise from the mantle, intruding tectonic plates until the plates break apart at the hot spots. The ancient supercontinent Gondwana began to break apart in this fashion about 184 Mya (million years ago). This break up was accompanied by massive eruptions of basalt lava, when East Gondwana (Antarctica, Madagascar, India and Australia), started to separate from Africa. About 130 Mya South America started drifting westward from Africa and the South Atlantic Ocean; this resulted in open marine conditions by 110 Mya. About 120 Mya East Gondwana began to separate, as India started moving northward.
Mantle plumes currently underneath the islands of Marion and Reunion may well have played a role in the formation of the Indian Ocean. If the zone of the rupture is situated at the edge of a landmass, then fragments of the land may separate off; the Seychelles are a prime example of this.
A team of geoscientists from Norway, South Africa, Britain and Germany studied lava sand grains from the Mauritius beach. Their study suggested there were more continental fragments. The sand grains contained zircons aged between 660 and 1970 million years; the lava carried these zircons when it pushed through subjacent continental crust of the same age.
This dating method was supplemented by recalculating the hotspot trail. This showed the position of the plates relative to the two hotspots at the time of rupture, and also showed that the continent fragments continued to wander over the Reunion plume; this explained how they were covered with volcanic rock. What had previously been thought of as the trail of the Reunion hotspot turned out to be continent fragments. This research suggests micro-continents occur ore frequently than previously realised.
The coloured track (left colour scale) west of Reunion in the image is the calculated movement of the Reunion hotspot. The black lines with yellow circles and the red circle indicate the corresponding calculated track on the African plate and the Indian plate, respectively. The numbers in the circles are ages in millions of years. The areas with topography just below the sea surface are now regarded as continental fragments.
-TEL
http://www.gfz-potsdam.de/
Trond H. Torsvik, Hans Amundsen, Ebbe H. Hartz, Fernando Corfu, Nick Kusznir, Carmen Gaina, Pavel V. Doubrovine, Bernhard Steinberger, Lewis D. Ashwal, Bjørn Jamtveit. A Precambrian microcontinent in the Indian Ocean. Nature Geoscience, 2013; DOI:10.1038/NGEO1736
HIDDEN MICRO-CONTINENT FOUND IN THE INDIAN OCEAN
Beneath the islands of Reunion and Mauritius lies a hitherto undiscovered microcontinent. The continental fragment Mauritia is believed to have detached about 60 million years ago, while Madagascar and India were drifting apart. The fragment was hidden under huge masses of lava.
Continental break-up is usually associated with mantle plumes, which is where giant blobs of hot rock rise from the mantle, intruding tectonic plates until the plates break apart at the hot spots. The ancient supercontinent Gondwana began to break apart in this fashion about 184 Mya (million years ago). This break up was accompanied by massive eruptions of basalt lava, when East Gondwana (Antarctica, Madagascar, India and Australia), started to separate from Africa. About 130 Mya South America started drifting westward from Africa and the South Atlantic Ocean; this resulted in open marine conditions by 110 Mya. About 120 Mya East Gondwana began to separate, as India started moving northward.
Mantle plumes currently underneath the islands of Marion and Reunion may well have played a role in the formation of the Indian Ocean. If the zone of the rupture is situated at the edge of a landmass, then fragments of the land may separate off; the Seychelles are a prime example of this.
A team of geoscientists from Norway, South Africa, Britain and Germany studied lava sand grains from the Mauritius beach. Their study suggested there were more continental fragments. The sand grains contained zircons aged between 660 and 1970 million years; the lava carried these zircons when it pushed through subjacent continental crust of the same age.
This dating method was supplemented by recalculating the hotspot trail. This showed the position of the plates relative to the two hotspots at the time of rupture, and also showed that the continent fragments continued to wander over the Reunion plume; this explained how they were covered with volcanic rock. What had previously been thought of as the trail of the Reunion hotspot turned out to be continent fragments. This research suggests micro-continents occur ore frequently than previously realised.
The coloured track (left colour scale) west of Reunion in the image is the calculated movement of the Reunion hotspot. The black lines with yellow circles and the red circle indicate the corresponding calculated track on the African plate and the Indian plate, respectively. The numbers in the circles are ages in millions of years. The areas with topography just below the sea surface are now regarded as continental fragments.
-TEL
http://www.gfz-potsdam.de/
Trond H. Torsvik, Hans Amundsen, Ebbe H. Hartz, Fernando Corfu, Nick Kusznir, Carmen Gaina, Pavel V. Doubrovine, Bernhard Steinberger, Lewis D. Ashwal, Bjørn Jamtveit. A Precambrian microcontinent in the Indian Ocean. Nature Geoscience, 2013; DOI:10.1038/NGEO1736
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