Tectonic environment of Ordovician carbonate-cherts in the Shihuigou area, North Qilian orogen
北祁连石灰沟奥陶纪碳酸盐岩—硅质岩形成的构造环境

Ordovician cherts, mudstone, greywacke, calcarenite, bioclastic limestone, reef limestone and alkaline basalts, ignimbrite, pyroclastic rocks represent the lithological associations of a seamount/oceanic island in the Shihuigou, North Qilian orogenic belt. The cherts contain abundant early-middle Ordovician conodonts, and mudstone and sandstone contain middle-late Ordovician Trilobita and graptolite fossils. Geochemical analysis of these chert samples indicates that they contain some detrital components from source area with distinctive character of LREE enrichment and negative Eu*CNanomalous; they deposited in the continental margin rather than in the open sea or near the spreading ridge setting.