Provenance of Cenozoic sediments in the northeastern Gonghe Basin and its geological significance

Gonghe Basin records a series of complex and diverse tectonic, magmatic, metamorphic and sedimentary events of the Qinling, Qilian and Kunlun orogenic systems around it, and it is a key position to study the tectonic-sedimentary evolution of the northern Tibetan Plateau. Combined with regional geological survey data in this area, and based on systematic analyses of the lithologies and rock assemblages, detrital-zircon geochronology, sandstone components, heavy mineral compositions together with sedimentary facies of the Cenozoic strata from drilling cores, we reconstructed the stratigraphic correlation framework of the strata and discussed the tectonic-sedimentary evolution and sedimentary provenance in the Gonghe sag of the Gonghe Basin during Cenozoic. The chronological analysis of detrital zircons of the Cenozoic sandstones (sediments) in Gonghe sag shows that they have age peaks of 200 similar to 300Ma, 400 similar to 500Ma, 750 similar to 1000Ma, 1800 similar to 2000Ma and 2400 similar to 2550Ma, respectively, and they are mainly concentrated in between 250 similar to 300Ma and 400 similar to 500Ma, which means that the Triassic intrusive rocks and low-grade metamorphic rocks are the main provenance. The analysis results of sandstone components and heavy minerals recorded a transition of tectonic environment in between the Xianshuihe Formation and Linxia Formation in the northeastern part of the Gonghe Basin. The sources of the Cenozoic sediments in the Gonghe sag were from its NEE direction during the sedimentation of the Xining Formation-Xianshuihe Formation, while those were from the NNE direction during the sedimentation of the Linxia Formation. Based on previous research and provenance analysis results of this study, it is believed that the uplift of the Qinghai Nanshan occurred during the Late Miocene-Pliocene, separating the Qinghai Lake Basin and the Gonghe Basin.