This study examines a lower Cambrian pyrite-bearing black shale–graywacke succession in the Czech Republic interpreted as infill of a deep-marine, extensional trench-slope basin on top of an accretionary wedge that developed during subduction of an oceanic plate beneath the northern margin of Gondwana. The new U–Pb detrital zircon geochronology of the graywacke constrains the maximum age of deposition to 533 +5/−6 Ma, whereas the Re–Os dating of pyrite yielded a younger age of 507 ± 16 Ma. Distribution of major and trace elements and calculated enrichment factors (EF) indicate that this succession was deposited under changing redox conditions over a short time span and that the basin was presumably controlled by tectonic subsidence and varying supply of terrigenous arc-derived material. This depositional setting is reflected by largely variable EFs and δ⁹⁸Mo and δ⁵³Cr values. Euxinic conditions detected at the base of the sampled black shale interval are documented by the highest values of EFs of redox-sensitive metals (e.g., Mo, U, V, Ni, Co, As) and also the C_org/P (>1000) and DOP_T (>0.7) values. Black shales show lower δ⁵⁶Fe values due to the excess of authigenic pyrite-Fe with a mean δ⁵⁶Fe value of −0.02‰ over detrital Fe in graywacke with a mean δ⁵⁶Fe value of +0.25‰. However, the Fe isotopic signatures of the black shales are not consistent with iron shuttling, mixing of authigenic and detrital sources, or hydrothermal metal enrichment. Instead, they most likely resulted from partial oxidation of pyrite through the syndepositional oxidizing hydrothermal fluids (Si–Ba enrichment), which resulted in precipitation of isotopically heavy Fe-oxyhydroxides. We propose that our maximal recorded δ⁹⁸Mo value (+ 0.98‰) might represent the best estimate for the ancient local seawater Mo composition at around 533 Ma and argues against deep-ocean oxygenation in the early Cambrian. On the other hand, the Se/Co ratios of synsedimentary pyrite indicate a mean atmosphere O₂ value of ~27%.

这项研究考察了捷克共和国下一个含寒武纪的含黄铁矿的黑色页岩-灰色瓦克层序，解释为在增生的楔形物上充填了深海的，伸展的沟槽-斜坡盆地，该楔形物是在北缘以下的大洋板块俯冲时形成的。冈瓦纳。Graywacke的新的U–Pb碎屑锆石年代学将最大沉积年龄限制为533 + 5 / −6 Ma，而黄铁矿的Re–Os测年产生了507±16 Ma的更年轻年龄。主要元素和痕量元素的分布以及计算的富集因子（EF）表明，该演替是在短时间内跨变化的氧化还原条件下沉积的，该盆地可能受构造沉降和陆源弧源物质供应的变化控制。⁹⁸ Mo和δ ^53个Cr值。氧化还原敏感金属（例如，Mo，U，V，Ni，Co，As）的EF最大值以及C _org / P（> 1000 ）记录了在采样的黑色页岩间隔底部检测到的富氧条件）和DOP _T（> 0.7）值。黑色页岩显示出较低的δ ⁵⁶的Fe的值由于过量自生黄铁矿的Fe，平均δ ⁵⁶铁-0.02‰在硬砂岩，平均δ值超过碎屑的Fe ⁵⁶Fe值为+ 0.25‰。但是，黑色页岩的铁同位素特征与铁穿梭，自生和碎屑源混合或热液金属富集不一致。取而代之的是，它们很可能是由于黄铁矿通过同沉积氧化性热液（Si-Ba富集）而部分氧化的结果，这导致了同位素重铁氢氧化物的沉淀。我们建议记录δ我们最大的⁹⁸莫值（+ 0.98‰）可能代表大约533毫安的古海水本地莫组成的最佳估计数，并反驳了在寒武纪早期的深海氧。另一方面，副沉积黄铁矿的Se / Co比值表明平均大气O ₂值为〜27 ％。