Research on the evaluation of centimeter-scaled heterogeneity of the shale

Shale serves as a critical carrier for recording geological evolution. It preserved essential information of paleoenvironments, elemental cycling, and hydrocarbon resources.However, the centimeter-scaled heterogeneity of shale may affect the accuracy of geological interpretations. This study investigates thecentimeter-scaled heterogeneity of four representative shale samples from China by integrating the XRF scanning and rock pyrolysis analysis. The results indicate that inorganic element contents and organic geochemical parameters of shales can vary dramatically—by several to tens of times—within centimeter-scaled intervals. There is a significant correlation between the organic carbon content and the distribution of certain inorganic elements, reflecting that they were jointly controlled by the sedimentary environments and hydrodynamic conditions of shales. It is recommended that the geochemical studies of shales in the future should be concentrated on the potential influence of centimeter-scaled heterogeneity of shales. By leveraging the respective advantages of desktop and handheld XRF technologies in sampling strategies and experimental design, the distortion of geological information caused by the data processing such as the ″sample misalignment comparison″ or the ″mixed homogenization″ can be avoided, there by the reliability of data interpretation and the scientific validity of geological conclusions can be enhanced.