Black chert of Early Cambrian age (Niutitang Formation or equivalents), in South China, show high TOC. The origin of the chert was controversial and poorly understood. The black chert of the Lower Cambrian Niutitang Formation from the Zhalagou section in Sandu County, Guizhou Province, contains high concentrations of trace metals. Three possibilities may have caused enrichment in the trace elements, including euxinic seawater, upwelling and hydrothermal fluids. The moderate to large negative Ce anomalies suggest a semi-oxic environment and thus argue against the euxinic seawater as the source of the trace elements. Upwelling is also less possible due to the lack of positive relationships of Ba, Zn, Cu, Ni, Cd and P to TOC. In contrast, the most likely source for the trace elements are hydrothermal fluids as is evidenced by ternary diagram of Al-Fe-Mn, the ratio of Al2O3/(Fe2O3 + Al2O3) and REY distribution patterns. Compared with modern organic matter-rich sediments from euxinic basin and Peruvian upwelling, Early Cambrian chert shows significant difference in trace element enrichment factors, suggesting that it is unlikely for a unique seawater source to have the metal anomalies. In contrast, the trace elements must have added from a non-seawater source. By further comparison with time-equivalent neighbouring deep basin and slope facies chert successions, it can be found that the deep basin seawater components during the Early Cambrian had nothing in common with the slope environment in terms of enrichment of trace elements, such as Ba, Zn, Cu, Ni and Cd. By contrast, hydrothermal fluids vented from syndepositional fault along the margin-to-slope of Yangtze platform may have played a key role in trace elements enrichment in South China.
