Provenance study of the sediments in Wei River using the detrital zircon U-Pb dating

The Weihe Basin is a Cenozoic intracontinental faulted basin owing its origin to the evolution of the Qinling Orogenic belt. It receives a large amount of clastic deposits from the Qinling mountain. To establish the sediment "source to sink" system for the basin is important to the understanding of the relationship between the basin and the mountain and to the investigation of the tectono-sedimentary evolution of this region. We, in this paper, studied 11 sediment samples collected from both the mainstream and the major tributaries of the Wei River using the detrital zircon U-Pb dating as the mean. Results show that there are five zircon age groups in the mainstream of the Wei River, i.e. 100~300Ma, 300~500Ma, 700~1000Ma, 1700~2000Ma and 2100~2500Ma, dominated by the groups of 100~300Ma and 300~500Ma, suggesting that the sediments mainly come from the northern Qinling Orogenic belt. The content of the zircon age groups of 1700~2000Ma and 2100~2500Ma occur mainly in the upstream sediments indicating the exposure of the Proterozoic rocks in the upper reach. The tributaries of the Wei River show clearly differences in the sediment zircon ages. For examples, the Jing River and the Luo River drained through the Loess Plateau have the similar age groups of 200~300 Ma、400~500 Ma、800~1100 Ma、1800~2000 Ma and 2400~2550 Ma. And the ages of the Ba River sediment obviously inherit the characteristic of the northern Qinling Orogenic belt. According to the provenance analysis, it is concluded that the Jing River is the major contributor of sediment to the mainstream of the Wei River, the Luo River has a certain extent influence on it, whereas the Ba River contributes little to the mainstream. The proportion of zircon age groups from the sediments of the Yellow River before and after its confluence with the Wei River shows a sharp change, indicating the great contribution of the Wei River to the Yellow River.