EARLY PERMIAN CHERT RECORDED HYDROTHERMAL EVENT ON A CARBONATE PLATFORM IN NORTH CHINA

Petrologic and geochemical data from nodular chert in an Early Permian limestone from North China reveal the origin and process of silica deposition in the carbonate platform. In Jiaozuo and Yuzhou section (Henan province) of the Taiyuan Formation, centimeter-size nodular cherts are scattered within shallow marine limestone beds. The cherts are composed of cryptocrystalline quartz, chalcedony, minor calcite, and silicified calcareous fossils. Major and trace element data of chert samples are similar to those of hydrothermal cherts of other ages. Silicon and oxygen isotopes suggest that the chert originated from hydrothermal silica. Moreover, while nodular cherts were emplaced in the limestones due to hydrothermal activity during marine transgression, volcanic ashes were deposited in the Taiyuan Formation during marine regression. In sum, these Early Permian cherts record a unique depositional signal of submarine hydrothermal event, and shed light on late Paleozoic tectonics of the North China Craton.