SPATIAL PROVENANCE DIFFERENCE OF THE LOESS ON LOESS PLATEAU BASED ON DETRITAL ZIRCON U-PB AGE

The Loess Plateau covers a vast area in the central part of China. Our predecessors have used a variety of research methods to study the provenance of the loess from different points of view. However, systematic researches are still lacking on the spatial difference in provenance of the loess, which is critical important to the explanation of transport mechanism of the dust. A total of 17 samples are collected by the authors from both the Loess Plateau and its surrounding areas for detrital zircon U-Pb dating. Results show that there are seven zircon age groups, i.e. 0-100 Ma, 100-350 Ma, 350-600 Ma, 600-1 100 Ma, 1 100-1 500 Ma, 1 500-2 300 Ma and 2 300-2 800 Ma. After comparison of the zircon U-Pb age spectra of the 17 samples, it is found that the loess from the plateau has certain similarities, and the main reasons for the similarity are multiple redeposition and thorough mixing. However, there are still differences in some areas. For examples, the loess in the northern part of the plateau lacks zircons younger than 100 Ma, which may come from the southern margin of the Ordos Basin, while the western Xining loess is short of zircon with a peak value of about 2 000 Ma comparing to the eastern Mangshan loess. The Mangshan loess is mainly from the floodplain of the Yellow River, which may suggest that the Yellow River has played an important role in the formation of Loess Plateau. The loess Plateau has multiple provenances and different genesis, and the composition of the loess is dominated by its nearest source area. Therefore, the regional sedimentary environment should be fully considered when the provenance analysis of Loess Plateau is carrying out.