A study of REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which is...A study of REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which is lower than that of sedimentary rocks from the whole world(230 μg/g) and approximately resembles to that of sedimentary rocks from the platforms(129 μg/g). Among different lithologies, average total REE concentration of shales is the highest(230 μg/g), that of limestones is the lowest(18 μg/g) and that of sandstones and siltstones is in between(213 μg/g) .REE concentrations of strata of different geologic ages are controlled by lithology.REE concentrations of Ordovician and Triasaic strata consisting mostly of carbonate rocks are the lowest(40 and 44 μg/g, respectively), and those of Silulian and Devonian strata consisting mainly of terrestrial detrital rocks are the highest (231 and 248 μg/g, respectively). Sedimentary rocks studied show very similar REE patterns with LREE enrichment and negative Eu anomaly regardless of lithology and stratigraphic age. Samples are plotted in a confined area in Σ(La～Nd)-Σ(Sm～Ho)-Σ(Er～Lu) ternary plot, suggesting homogeneity of REE composition and a stable environment for the studied region. Similarity between REE compositions of sedimentary rocks from the studied region and that from typical platforms of the world suggests the platform character of the studied region during Sinica to Triassic. Results of this study suggests that the provenance of the studied sedimentary rocks is not the Jiangnanian old land mass, but the old continent(s) from the north.展开更多
文摘A study of REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which is lower than that of sedimentary rocks from the whole world(230 μg/g) and approximately resembles to that of sedimentary rocks from the platforms(129 μg/g). Among different lithologies, average total REE concentration of shales is the highest(230 μg/g), that of limestones is the lowest(18 μg/g) and that of sandstones and siltstones is in between(213 μg/g) .REE concentrations of strata of different geologic ages are controlled by lithology.REE concentrations of Ordovician and Triasaic strata consisting mostly of carbonate rocks are the lowest(40 and 44 μg/g, respectively), and those of Silulian and Devonian strata consisting mainly of terrestrial detrital rocks are the highest (231 and 248 μg/g, respectively). Sedimentary rocks studied show very similar REE patterns with LREE enrichment and negative Eu anomaly regardless of lithology and stratigraphic age. Samples are plotted in a confined area in Σ(La～Nd)-Σ(Sm～Ho)-Σ(Er～Lu) ternary plot, suggesting homogeneity of REE composition and a stable environment for the studied region. Similarity between REE compositions of sedimentary rocks from the studied region and that from typical platforms of the world suggests the platform character of the studied region during Sinica to Triassic. Results of this study suggests that the provenance of the studied sedimentary rocks is not the Jiangnanian old land mass, but the old continent(s) from the north.
