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`Himalayas pushed India deep into Earth`s mantle`

Last Updated: Sunday, May 30, 2010 - 09:47

New Delhi: The collision of continents that
formed the Himalayas, the highest mountain range in the world,
also pushed India up to 200 km deep into the Earth`s mantle, a
team of Indo-British researchers has claimed.

A new study by geologists at Delhi University and the
UK-based National Oceanography Centre found that when India
and Asia collided some 90 million years ago, the continental
crust of the Indian tectonic plate was forced down under the
Asian plate.

Scientists believe that the subduction of the continental
crust to such depth was never reported earlier.

"The subduction of continental crust to this depth has
never been reported in the Himalayas and is also extremely
rare in the rest of world," lead researcher Anju Pandey of the
National Oceanography Centre in Southampton said.

The new findings, published this month in `Geology`
journal, are expected to alter several fundamental parameters
of Himalayan tectonics, such as the rate of rise of the
mountain range, its angle, and further subduction of the
Indian plate.

Pandey and her colleagues Preeti Singh and Pramod Verma
of the University of Delhi, used sophisticated analytical
techniques to demonstrate the occurrence of relict majorite, a
variety of mineral garnet, in rocks collected from the
Himalayas.

Majorite is stable only under ultra-high pressure
conditions and is believed to have been formed deep down in
the Earth`s crust, before it was exhumed millions of years
later, they said.

"Our findings are significant because researchers have
disagreed about the depth of subduction of the Indian plate
beneath Asia," said Pandey.

In fact, the previous depth estimates conflicted with
estimates based on computer models. The new results suggest
that the leading edge of the Indian plate sank to a depth
around double that of previous estimates.

"Our results are backed up by computer modelling and will
radically improve our understanding of the subduction of the
Indian continental crust beneath the Himalayas," Pandey said.

The formation of the Himalayas was a result of movement
of continental drift and the subsequent collision of India
with Asia.

PTI



First Published: Sunday, May 30, 2010 - 09:47

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