关键词: 物源, 地球化学, 稀土, 晚二叠世, 贵州

Abstract: Geochemical characteristics and sources of ore-forming material of different lithological sections of the rare earth element (REE)-rich rock series at the base of the first member of the Late Permian Xuanwei Formation in the western Guizhou region are still unclear. This study conducts geochemical analyses of major, trace, and REEs of typical profiles in the western Guizhou and Qixi regions, and explores the geochemical characteristics and sources of ore-forming material of different lithological sections of REE-rich rock series. The results show that the REE-rich rock series can be divided into iron rock section, aluminum rock section, and clastic rock section from bottom to top. Among them, the aluminum clay rock section shows the highest rare earth content, up to 0.76%. The REE-rich rock series is mainly composed of SiO2, Al2O3, FexOy, and TiO2 with a total content of 83.93% to 87.24%; Large ion lithophile elements such as Cs, Rb, Ba, V are depleted, while high-field strength elements such as Zr, Hf, Nb, Ta are stable; The REE distribution patterns are all displayed as right dipping with different lithological sections being characterized by moderate differentiation of light and heavy REEs in the iron rock section, no δCe anomalies, and weak negative δEu anomalies; The degree of differentiation between light and heavy REEs in the aluminum rock section is significant, showing negative δCe and δ Eu anomalies; The light and heavy REE fractionation in the clastic rock section is moderate with a weak positive δCe anomaly and a negative δ Eu anomaly. Based on the ICV values of the samples, La/Sc-Co/Th diagrams, and REE distribution patterns, it is determined that the main sources of the aluminum clay rock section and the clastic rock section are moderately acidic volcanic rocks (not volcanic ash) that were eroded, transported, and deposited, while the source of the iron rock section is nearby basalts.

Key words: source, geochemistry, rare earth element, Late Permian, Guizhou