An analysis of Late Carboniferous sedimentary tectonic setting and provenance of North Qaidam area:Evidence from Well Shiqian 1

Based on the knowledge of sedimentology, geochemistry and global tectonics, the authors systematically analyzed the well core samples of Keluke and Zhabusagaxiu Formations from Well Shixian 1 located in the Shihuigou area on the northern margin of the Qaidam Basin. The content of major and trace elements and the relevant discrimination diagrams demonstrate that the clastic rocks of Keluke and Zhabusagaxiu Formations from Well Shixian 1 were formed in the passive continental margin, and their geochemical characteristics are extremely different from clastic rocks with other tectonic histories. The sandy conglomerates of Keluke and Zhabusagaxiu Formations were highly recycled(or the igneous rocks of the study area were highly differentiated) and experienced moderate to high weathering. The clastic rocks were sourced from Post Archean Eon crust dominated by acidic igneous rocks. On the basis of the geochemical study of the clastic rocks and previous study results, the northern margin of the Qaidam Basin is regarded as a passive margin cratonic basin controlled by Zongwulong trough expansion in the north. The clastic rocks were sourced from the base of the Paleozoic orogenic belt in the northern Qaidam. The transgression was from north to south and the depositional systems were distributed from south to north, showing an overall pattern with mountains in the south and oceans in the north.