The basal unit of the Early Cambrian black shale sequence of South China hosts sulfide-rich polymetallic units, non-sulfidic vanadium-rich black shales, sapropelic alginite (combustible shale), barite, and phosphorite. This rock spectrum occurs in a paleoceanographic similar, and stratigraphically correlated, transgressive upwelling setting on the passive continental margin of the Neoproterozoic Yangtze Platform. Several centimeter-thick polymetallic sulfidic units (3–13 wt% Mo+Ni, 100–600 ppm U) have relatively light Mo (δ^98/95Mo = 1.1 ± 0.2‰) and relatively heavy U isotope composition (δ^238/235U = 0.2 ± 0.1‰). Several meter-thick V-rich shales with multiple ore-grade layers (0.1–0.8 wt% V, < 100 ppm U, Mo and Ni ~ 100 ppm) have isotopically lighter Mo (δ^98/95Mo = 0.3 ± 0.4‰) and heavier U composition (δ^238/235U = 0.4 ± 0.2‰ and up to 0.7‰). The inverse Mo versus U isotope correlation suggests that both metals were enriched by removal from anoxic to strongly euxinic bottom water in restricted basins along the rifted continental margin. Metal replenishment probably occurred via the cycling of Fe–Mn-oxyhydroxide particles across the redox boundary, with sorption/desorption of Mo (and likely Ni) in a stratified water column. In contrast, V enrichment with much lower Mo, Ni, and U contents, but more fractionated Mo and U isotope composition, reflects non-sulfidic anoxic depositional conditions in a partly open system with higher bottom water renewal rates. While Mo isotope fractionation likely occurred in the water column, U isotope fractionation may dominantly have occurred at the water-sediment interface, perhaps in a benthic organic flocculent layer. These findings indicate that local hydrodynamic control and stratified water column redox conditions may explain the observed variation of metal enrichment (Mo–Ni versus V) in the black shales. Furthermore, the high δ^98/95Mo values up to 2.6‰ of the black shales studied and the correlated U and Mo isotope data suggest that Early Cambrian seawater was at least episodically broadly similar to modern seawater.

华南早寒武世黑色页岩层序基底发育富硫化物多金属单元、非硫化物富钒黑色页岩、腐泥褐藻岩（可燃页岩）、重晶石、磷矿等。该岩石谱出现在新元古代扬子地台被动大陆边缘的古海洋学相似且地层相关的海侵上升流环境中。几个厘米厚的多金属硫化物单元（3–13 wt% Mo+Ni，100–600 ppm U）具有相对轻的 Mo（δ ^98/95 Mo = 1.1 ± 0.2‰）和相对重的 U 同位素组成（δ ^238/235 ） U=0.2±0.1‰）。几米厚的富钒页岩具有多个矿石品位层（0.1–0.8 wt% V，< 100 ppm U、Mo 和 Ni ~ 100 ppm），其同位素较轻 Mo (δ ^98/95Mo = 0.3 ± 0.4‰) 和较重的 U 成分 (δ ^238/235U = 0.4 ± 0.2‰ 至 0.7‰）。钼与铀同位素反比关系表明，这两种金属是通过从裂谷大陆边缘受限盆地的缺氧到强缺氧底层水的去除而富集的。金属补充可能是通过 Fe-Mn-羟基氧化物颗粒穿过氧化还原边界的循环发生的，伴随着分层水柱中 Mo（以及可能的 Ni）的吸附/解吸。相比之下，Mo、Ni和U含量低得多的V富集，但Mo和U同位素组成的分馏更多，反映了具有较高底水更新率的部分开放系统中的非硫化物缺氧沉积条件。虽然钼同位素分馏可能发生在水柱中，但铀同位素分馏可能主要发生在水-沉积物界面，也许在底栖有机絮凝层中。这些发现表明，局部水动力控制和分层水柱氧化还原条件可以解释观察到的黑色页岩中金属富集（Mo-Ni 与 V）的变化。此外，高 δ^{研究的黑色页岩的98/95} Mo 值高达 2.6‰，相关的 U 和 Mo 同位素数据表明，早寒武世海水至少在某些情况下与现代海水大致相似。