`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.


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

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