Provenance Analysis of Middle Yanchang Formation in the Southeastern Ordos Basin and Its Indications for the Uplift of the Qinling Orogenic Belt

In order to clarify the provenance of the southeastern part of the Ordos Basin and distinct the initiation time of the Qinling orogenic belt uplift during the middle Yanchang Formation, detrital zircon U-Pb dating method was used to analyze the provenance of the Jinsuoguan, Xiashiwan, Huangling and Huanglong areas, which is part of the Ordos Basin. The age assemblages of detrital zircons in Jinsuoguan area are 2200～2700 Ma, 1700～2100 Ma, 900～1200 Ma, 400～500 Ma and 205～382 Ma. The detrital zircon age assemblages in Huanglong, Xiasiwan and Huangling are 2200～2700 Ma, 1700～2100 Ma and 205～382 Ma. Comprehensive study found: ① The lacustrine depositional center divides two different areas inside the southeastern study area of the middle Yanchang Formation basin, south of lake basin center of jinsuoguan main stem from the south of the southern margin of the north China craton basin and north Qinling tectonic belt. The provenance of the huanglong, Huangling and Xiashiwan areas which are located at the north of lake center is mainly derived from the Yinshan block、the Konzi rock belt and hercynian indosinian thermal event magmatic rocks in the north Margin of the North China Craton. ② The sediments have a good sedimentary response to the Qinling orogenic belt in Jinsuoguan during in chang 7, the youngest zircon grains reflect that the orogenic belt began to uplift around (234.7±4) Ma.