Researchers from the Northwest Institute of Eco-Environmental Resources of the Chinese Academy of Sciences (CAS) and their collaborators have revealed the uranium isotopic composition (234U/238U isotope ratio) and its constraints on the provenance of the Qinghai-Tibet Plateau's surface dust.
Related results were published in Journal of Geophysical Research-Earth Surface on March 1.
The Uranium (U) isotope signatures in Qinghai-Tibet Plateau's dust are distinct and thus can be used as an effective tracer of dust provenance.
As the 234U/238U isotope ratio of fine particles (smaller than 50 μm) reflects the time elapsed since their separation from bedrock, the uranium comminution age method can be used to trace a series of intermediate phases such as dust production, transportation and deposition.
In the study, the researchers investigated the 234U/238U isotope ratios of surface dust samples collected at various locations on the Tibetan Plateau and nearby glaciers, and revealed that these ratios reflected the influence of regional tectonic evolution, landscape dynamics, and glacier erosion processes.
The study also showed that dust collected from nearby glacial areas with rugged terrain (e.g., the Qilian and Himalayan Mountains) had higher 234U/238U values than those collected in the topologically flat non-glacial areas. This is consistent with elevated erosion rates and dust comminution-transport processes in glacial areas, which yield a major source for large quantities of fresh comminuted particles.
Besides, the researchers found that the 234U/238U isotope values of TP dust tended to fall between those of the high-elevation sites and the dust sinks, indicating the combined influence of short comminution times (tectonics, landscape dynamics, and glacial erosion) and long residence time on the Tibetan Plateau.
This study is the first to measure the 234U and 238U isotopic composition of surface dust in the cryospheric regions of the Tibetan Plateau and to use the uranium comminution age method to reveal the spatial distribution and variation of 234U/238U values and dust evolution processes. It provides new insights into the Tibetan Plateau dust emissions and transport.
52 Sanlihe Rd., Xicheng District,
Beijing, China (100864)