A black rock series occurs in Xiamaling Formation, eastern Yanshan area, North China. Major and trace element compositions of the representative rocks were analyzed in this paper. Five samples have varying major element oxides (e.g., SiO₂=53.00%～78.83%, A1₂O₃=1.20%～17.57%). Their PAAS-normalized REE patterns are HREE-enriched with positive negative Ce anomalies, which is the typical feature of modern seawater. These samples show high A1₂O₃ and TiO₂ values (1.31%～18.48%); their U concentrations (averaging 3.95×10^-6), Th/Sc ratios (0.97～1.26), Th/U ratios (averaging 3.50), and chondrite-normalized REE and continental crust-normalized trace element patterns indicate that terrigenous detrital materials significantly contributed to the deposition. The Ba/Sr ratios (9.28～22.79), Co/Zn ratios (0.01～0.29) and related diagrams show that the black rock series was evidently influenced by marine hydrothermal activities during its precipitation. However, the proportion of hydrothermal fluid in original solution was less than 0.1%. The major and trace element ratios, Ce/Ce^* ratios (0.82～0.93) and tectonic discrimination diagrams also indicate that this black rock series was probably deposited in the deep-water anoxic environment of a continental arc setting.