* Astronomy

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RE: Tibetan Plateau

Blobrana · L

Tibet becomes warmer and wetter

The "roof of the world" has become warmer and wetter, according to a report jointly released Friday by the climate center of southwest China's Tibet Autonomous Region and the regional remote sensing applications research center.
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Title: Displacement along the Karakoram fault, NW Himalaya, estimated from LA-ICP-MS U-Pb dating of offset geologic markers
Authors: P.H. Leloup, R.F. Weinberg, B.K. Mukherjee, P. Tapponnier, R. Lacassin, E. Boutonnet, f, M.-L. Chevalierg, F. Valli, H. Li, N. Arnaud, J.-L. Paquette

The magnitude of fault offset, a key parameter of fault geometry and kinematics, provides critical information on the role of the Karakoram fault (KKF) in accommodating deformation of the Tibetan crust. Geologic markers used for estimating the magnitude of offset along the KKF include: (1) geomorphologic features, (2) correlative stratigraphic sequences, (3) ophiolite melange belts, (4) igneous bodies, and (5) regional fault systems. The debated offsets of the KKF range from 40km to as much as 1000km. Conflicting offsets may result from a lack of available offset correlations based on quantitative measurements. The Kunsha granite and the Ayilari granite provide another set of potential markers for estimating the offset along the KKF. U-Pb zircon ages and textural observations provide the basis for correlating these granites. Zircon U-Pb ages show that both the Kunsha granite and the South Ayilari granite crystallized around 50Ma ago, whereas the North Ayilari granite formed mostly around 20Ma ago. Reconstruction of batholiths on two sides of the Namru-Menshi basin, as well as the Yalung-Zangbo suture and the trace of the South Kailas thrust, show the offset along the KKF to be about 52±2km. The chronologic data appear to preclude a 100km offset, based on the correlation between the North Ayilari granite and the Kunsha granite. Our data further disproves the conjecture that the North Ayilari granite is synkinematic granite of the KKF, and thus contradicts a 280-400km ophiolite melange belt offset, since it is based on the an incorrect fault initiation time. We calculate a slip rate of 4.5±0.1mm/yr since 12Ma, which implies that the average long-term slip rate is low. This does not support the lateral extrusion model, which predicts a high slip rate. It does support the concept that the collision between India and Eurasia proceeded by distributed deformation rather than lateral extrusion along faults that bound a rigid Tibet.

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Title: Comment on "Displacement along the Karakoram fault, NW Himalaya, estimated from LA-ICP-MS U-Pb dating of offset geologic markers"published by Shifeng Wang et al. in EPSL, 2012

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Tibetan Plateau may be older than previously thought

The growth of high topography on the Tibetan Plateau in Sichuan, China, began much earlier than previously thought, according to an international team of geologists who looked at mountain ranges along the eastern edge of the plateau. The Indian tectonic plate began its collision with Asia between 55 and 50 million years ago, but "significant topographic relief existed adjacent to the Sichuan Basin prior to the Indo-Asian collision," the researchers report online in Nature Geoscience.
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Two More Weather Stations for Tibet Plateau

China will set up two more comprehensive weather- monitoring stations on the Qinghai-Tibet Plateau, another step toward the goal of establishing 23 stations on the plateau, said Yao Tandong, director of the Institute of Tibetan Plateau Research under the Chinese Academy of Sciences.
Sometimes called "the third pole", the Qinghai-Tibet Plateau has gained growing attention because of its significant role in global atmospheric circulation and its sensitivity to climate change.
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Third Pole Environment

Despite its distance from the region in question, in late August Reykjavik hosted the third workshop on the Third Pole Environment (TPE) - a region centred on the Tibetan Plateau and the Himalayas that boasts the largest store of ice outside the Arctic and Antarctic.
Ólafur Ragnar Grímsson, Iceland's president, talks to Nature about why the TPE workshop was held in Iceland and the importance of scientific cooperation between his country and China.
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New Caltech Research Suggests Strong Indian Crust Thrust Beneath the Tibetan Plateau

For many years, most scientists studying Tibet have thought that a very hot and very weak lower and middle crust underlies its plateau, flowing like a fluid. Now, a team of researchers at the California Institute of Technology (Caltech) is questioning this long-held belief and proposing that an entirely different mechanism is at play.

"The idea that Tibet is more or less floating on a layer of partially molten crust is accepted in the research community. Our research proposes the opposite view: that there is actually a really strong lower crust that originates in India" - Jean-Philippe Avouac, professor of geology and director of Caltechs Tectonics Observatory.

These insights lead to a better understanding of the processes that have shaped the Himalaya Mountains and Tibet - the most tectonically active continental area in the world.

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