Applying stand-off LIBS to paleoclimatic research: A case study on geochemical content of carbonate rocks

摘要

Carbonate rocks, mainly limestone and dolostone, have made up 10% to 15% of sedimentary rocks in the Earth. Geochemical contents of carbonate rocks could reflect a series of key geological information of ancient environment, such as temperature, precipitation, salinity and geologic event. Stand-off LIBS provides an approach to rapidly, accurately and nondestructively determine the elemental concentrations in difficult carbonate rock samples, such as cliff rocks, small reefs and karst caves. In this study, we have determined Mg/Ca ratio and Sr/Ca ratio in either limestones from Xinjiang, Guangdong, Hunan or dolostones from Yunnan at a distance of 15 meters. 2D Mapping data of Mg/Ca and Sr/Ca ratios of rocks from Yunnan clearly exhibit spatial variation of geochemical contents. These variations are correlated to the temperature changes along the geologic times, which has been proved to influence the Magnesium incorporation of rocks.