The Youjiang basin, located on the southwestern margin of the Yangtze Block, is an important part of the large- scale low- temperature metallogenic domain in China.However, the metal sources and enrichment processes of the low- temperature Au, Sb, and Hg deposits in the basin remain poorly understood. Previous studies have shown that the Lower Cambrian black shale series are enriched with low- temperature metallogenic elements (such as As, Sb, and Au), which may provide a material basis for low- temperature mineralization in the Youjiang basin. To further elucidate the relationship between the Cambrian polymetallic black shale series and low- temperature mineralization in the Youjiang basin, this study carried out elemental geochemistry, laser ablation inductively coupled plasma mass spectrometry (LA- ICP- MS) for in- situ trace element analysis, and fluid inclusion analysis on the Lower Cambrian (Niutitang Formation and Gezhongwu Formation) black shale (phosphorus- bearing rock formations) and their later hydrothermal veins. The results showed that: ① Sb and As concentrations in the Lower Cambrian strata are significantly higher than those in the upper crust (enrichment coefficient ranging from 2 to 69). The lg(U)- lg(Th) relationship indicates that Sb- As enrichment in the hydrothermal vein- bearing phosphorite rocks of the Lower Cambrian Gezhongwu Formation is mainly affected by hydrothermal fluids. ② Temperatures of fluid inclusions in the later hydrothermal quartz veins range from 137.4 to 260℃, with salinities ranging from 0.18% to 5.11%NaCleq. These values are consistent with those of low- temperature ore- forming fluids in the Youjiang Basin (140~270℃, 1.5%~7.0%NaCleq). ③ Two types of apatite are developed in the hydrothermal vein- bearing phosphorite rocks: sedimentary apatite (Fap1) and hydrothermal apatite (Fap2). Fap1 exhibits a typical bioclastic structure, while Fap2 displays a flat surface and is mainly found near late hydrothermal quartz veins. Electron probe microanalysis (EPMA) and LA- ICP- MS analysis reveal that Fap2 is more enriched in low- temperature elements (Sb, As, and Cu) and depleted in rare earth elements compared to Fap1. Based on these findings, we propose that Fap1 represents typical biosedimentary apatite, serving as the main carrier of rare earth elements in phosphorites. In contrast, Fap2 is hydrothermal apatite formed during later stages, exhibiting significant enrichment in low- temperature mineralizing elements (Sb, Cu, and As).The lower content of these elements in Fap1 reveals that the Lower Cambrian strata alone are insufficient to provide the material basis for low- temperature mineralization. Instead, late hydrothermal fluids (such as Carlin- type mineralizing fluids) originating from deeper sources (e.g., metamorphic basement or magma) may be one of the reasons for the anomalous enrichment of low- temperature mineralizing elements in the Lower Cambrian black shales.