Five samples were analysed, one from the northern part of the Loess Plateau, one from each of the Tengger, Mu Us, Otindog and Horquin deserts. The location of these samples is shown in the map below.
The stars represent the sample sites, the dashed line shows the boundary of the North China craton, the boundary with Mongolia is also shown. The oval shows the approximate extent of the Chinese Loess Plateau.
Zircon were separated from the samples and were dated U-Pb on a LA ICPMS at UCL. The results are plotted on probability plots below, with some observations about the relative abundances of the various ages.
Click the title for a larger image:
The implications of this study show that zircon U-Pb ages can be used to distinguish between potential source areas. The loess sample shows zircon ages that could be associated with tectonic events in northern and western China. More specifically the Qilian Mountains and the Qaidam basin which have Paleozoic aged granitoids which would explain the significant number of Paleozoic aged grains within the loess sample. It also suggests that no one sandy land or desert is acting as a holding area for the loess.
This project moves on from the pilot study described here by adding various techniques like heavy mineral analysis and zircon fission track dating in order to determine the source(s) of the loess. As many of the crust forming events in north China overlap in time it is important to use several techniques to compliment zircon U-Pb dating to obtain as full a picture as possible.
Keep posted for more results to come soon!