New information about how Himalayas were formed

Aug 05, 2010 by Denize Springer
Geologists based their findings on samples taken from eclogites (the dark portions of rock) in northwest India near Tibet.

Evidence of the mineral majorite in Himalayan rocks have overturned scientific theory about the birth of the tallest mountains on Earth.

Geologists have long debated aspects of the collision between Asian and Indian landmasses that formed the Himalayas about 57 million years ago. When the continents collided they closed an ocean between them. The Asian plate forced the Indian plate, still connected to the denser ocean crust, down toward the Earth's mantle in a process called subduction.

Assistant Professor of Geosciences Mary Leech was part of a team of researchers who examined the content of metamorphic rocks that were caught up in the collision between the Asian and Indian landmasses. They examined thin sections of rocks known as eclogites. Collected in the Ladakh region of northwest India near Tibet at an altitude of about 15,000 feet, these samples contained garnet. The garnets held chemical evidence of majorite, which is formed only under extreme pressure at depths of 185 to 200 kilometers. This is more than twice the distance previously accepted (90 kilometers) regarding the depth the Indian crust sank during the continental collision.

"This is the first evidence of the mineral majorite in eclogite rocks found in the Himalayas," Leech said. "Current computer models do not indicate that rocks like those we examined got to such depths and came back up to the surface."

Eclogites are metamorphic rocks formed in subduction zone complexes in mountain belts where two continents come together. Minerals found in the eclogites and formed by extreme pressure give geologists clues to the movement and history of mountain formation. As mountains continue to develop over millions of years, the eclogites move back up to the surface where geologists can easily access samples.

Leech said that the findings will radically change scientific models regarding the age of the mountains and the rate and angle at which the Indian plate continues to collide with the Asian plate while forcing up the Himalayas.

The study, titled "Evidence of former majoritic garnet in Himalayan eclogite points to 200-km-deep subduction of Indian continental crust," was published in the May 2010 issue of the journal Geology. Principal investigator of the study was Anju Pandey of the National Oceanography Centre in Southampton, England.

Leech, a recipient of the prestigious National Science Foundation CAREER grant, studies the chemical aspects of mountain formation and has conducted field work in Himalayan mountain belts as well the Dabie-Sulu belt in eastern China, the Scandinavian Caledonides of Norway, the Urals in Russia and the Kokchetav Massif in Kazakhstan. Her research focuses on eclogite found in these mountain belts.

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

More information: geology.gsapubs.org/content/38/5.toc

Related Stories

Jade sheds light on Guatemala's geologic history

Jul 27, 2009

The shifting of tectonic plates in Central America has been poorly understood -- until now. New research on jade found along fault lines in Guatemala is helping geologists piece the puzzle of the past 130 million years.

Plate tectonics may take a break

Jan 03, 2008

Plate tectonics, the geologic process responsible for creating the Earth’s continents, mountain ranges, and ocean basins, may be an on-again, off-again affair. Scientists have assumed that the shifting of crustal plates ...

Earth's crust melts easier than previously thought

Mar 18, 2009

A University of Missouri study published in Nature this week has found that the Earth's crust melts easier than previously thought. In the study, researchers measured how well rocks conduct heat at differ ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Nik_2213
not rated yet Aug 06, 2010
Fascinating ! We may be due a re-run as the Australian plate slams into SE Asia.

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...