Petrography and geochemistry of Lingbi Qingyun stone in northern Anhui Province

Abstract：Qingyun stone of Lingbi County is a type of microcrystalline limestone lying in Sinian Zhangqu Formation, characterized by black color, dense texture and bronze-like sound. It can be used as an ornament or musical instrument. The rock is dominated by euhedral microcrystalline calcite, up to 10 μm in size, with abundant organic matter. It has high CaO and low MgO, SiO2, Fe2O3, Al2O3, shows low REE concentrations, and is enriched in Sr, Cu, Mn and Ba. Based on a comparison of the petrographic and geochemical features between the Qingyun stone and the common microcrystalline limestone in the study area, the authors hold that the characteristics of the bronze-like sound produced by the Qingyun stone can be attributed to its single mineral assemblage, uniform grain size, dense texture, very small pore size and high organic matter abundance. The Qingyun stone was genetically associated with the global high CO2 concentrations and regional extraordinary geological events in Sinian period, being the combined result of the CaCO3 oversaturated sedimentary environments and the complex geological events.