The Collision: New insight into the formation of the Himalayas

AsianScientist (April 5, 2022)– The High Himalayas and the Tibetan Plateau were formed when the Eurasian and Indian continental plates collided. These plates are large areas moving independently of the Earth’s surface. A new study reports that the Indian continental plate is likely tilting downward under the Asian plate. Posted in Proceedings of the National Academy of Sciences, these results, based on a helium signature found in more than 200 hot springs across the Tibetan Plateau, oppose a widely held model for mountain building, according to which the Indian plate simply lies flat beneath the plate. Asian. A better idea of ​​the arrangement of these plates will help scientists understand the continental collision of eons ago.

About 50 million years ago, the Indian and Asian continental plates collided, resulting in the formation of the Himalayas and, soon after, the Tibetan Plateau. But how the plates interface has long been debated. In the early 1920s, several theories were proposed, but two became the most important. In the first, the Indian plate is thought to lie flat beneath Tibet, which is part of the Asian plate. While the other model says the Indian plate is tilting below the Asian plate, tilting down below Tibet.

Researchers from the United States and China, led by Simon Klemperer of Stanford University’s Department of Geophysics, wanted to see which of the two models accurately explains how the tallest mountains came to be.

Over many years, Klemperer’s team sampled water and gas from 196 geothermal springs on the Tibetan Plateau and included previously reported data from 29 other Tibetan springs. Ranging from hot to cool, the springs were scattered across the plateau. They bring water from tens of kilometers underground to the surface. Along with water, they carry elements such as helium. The researchers trapped the water and gas from these springs in copper tubes, through which the helium cannot escape.

Helium gas is a good “process proxy” for geological changes in Tibet, said Shyam Rai of the Indian Institute of Science Education and Research in Pune. Asian scientist. Rai who is a professor emeritus in the institute’s Department of Earth and Climate Sciences was not involved in the study.

Heavier than hydrogen, helium has two natural forms, helium-3 and helium-4. Both forms move rapidly through the Earth’s mantle and crust. “Essentially all of Earth’s helium-3 was created when Earth condensed from the solar nebula,” Klemperer said. Asian scientist. “And that helium-3 has been slowly leaking out of Earth ever since.” If this form of noble gas was found, it must have traveled from the mantle. Rather, the more abundant Helium-4 is a product of constant radioactivity in the planet’s crust. So, depending on the type of helium the researchers find in the hot spring sample, they can tell where it might have come from – the Earth’s crust or mantle.

Klemperer and his colleagues noted a clear distinction in the helium signal from the hot springs – the helium in the north came from the mantle and the crustal helium in the south. This helium boundary mirrored the boundary between the Tibetan mantle and the Indian crust several kilometers below the Earth’s surface. From these signatures, the researchers interpreted that, although the Indian plate is in contact with Tibet to the south, it is moving away from and dipping downward relative to the Asian plate on the northern side of Tibet – at what point remains to be discovered. “What’s new here is the collection of such a large data set in Tibet that allows us to map this border,” Klemperer said.

Such data collection for the Tibetan region is certainly a first, Rai agreed. But the helium signature must be analyzed in the context of other data on geological processes in the region, Rai added. While the Indian plate certainly appears to tilt below the Asian plate in this stretch, it remains to be seen whether this placement is true east or west of this region, according to Rai.

Klemperer wants to follow this distinct border between the two continental places to the east and west to see what new data might reveal.

Source: Stanford Land; Photo: Ping Zhao

The article can be found at Klemperer et al. (2022). India’s limited sub-thrust under Tibet: 3He/4Hot springs analysis locates mantle suture in continental collision

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