REE geochemical signatures and sedimentary environments of the Lower Cambrian black rock series in southeastern Chongqing and its adjacent areas

The Lower Cambrian black rock series in southeastern Chongqing and its adjacent areas are characterized by less-enriched ΣREE,ΣLREE/ΣHREE ratios ranging between 1.99 and 9.01 with an average of 6.86, relatively Enriched LREE, δEu values ranging between 0.69 and 7.33 with an average of 2.79, and δCe values ranging between 0.70 and 1.01 with an average of 0.85. The results of research in the present paper show that the Lower Cambrian black rock series in the study area resulted from the mixing of the normal seawater and hot seawater deposition in the transitional conditions from the anoxic reducing environments to the weakly oxidized environments on the outer continental shelves.