The aim of the present study was to investigate the oxygen isotopic composition of the Ediacaran weathering material from the western margin of the East European Craton. This area presents a unique opportunity to investigate the Ediacaran strata with a minimum diagenetic overprint. Paleosol intervals, containing material formed during the most advanced weathering stages, rich in kaolinite and iron (hydr)oxides, and corresponding sedimentary rocks were investigated. Bulk material and separated clay fractions were subjected to reactions with hot dithionite-citrate-bicarbonate solution in order to remove free iron (hydr)oxides. The obtained material was characterized by X-ray diffraction, chemical analysis, thermogravimetric analysis, and the measurement of oxygen isotope composition. Comparison of the isotopic compositions of iron (hydr)oxides and phyllosilicates, extracted from the natural and dithionite-citrate-bicarbonate treated samples, bulk, and clay fractions, leads to the conclusion that these compounds are in isotopic disequilibrium in the investigated samples. Disequilibrium is caused by the presence of diagenetic illite, originating from the Caledonian and Variscan hydrothermal pulses. The average isotopic composition of kaolinite was extracted from the phyllosilicate data by extrapolation. The temperature estimate, based on the average isotopic composition of iron (hydr)oxide and kaolinite, depends strongly on the hematite-water fractionation factor used in the calculation but qualitatively agrees with the expected tropical weathering conditions. The complex approach needed to extract these data from multicomponent mineral mixtures results in large analytical error if precise error propagation analysis is applied.

本研究的目的是调查东欧克拉通西缘的埃迪卡拉安风化物质的氧同位素组成。该地区提供了一个独特的机会来调查具有最小成岩作用叠印的Ediacaran地层。研究了古土壤层段，其中包含在最高级的风化阶段形成的物质，富含高岭石和（铁）氧化物，以及相应的沉积岩。使大块物料和分离出的粘土级分与热的连二亚硫酸盐-柠檬酸盐-碳酸氢盐溶液进行反应，以除去游离的铁（氢）氧化物。通过X射线衍射，化学分析，热重分析和氧同位素组成的测量来表征所获得的材料。从天然和连二亚硫酸氢盐-碳酸氢盐-碳酸氢盐处理过的样品，大块和粘土馏分中提取的氢氧化铁和页硅酸盐的同位素组成的比较得出结论，这些化合物在所研究的样品中处于同位素不平衡状态。不平衡是由于成岩伊利石的存在而引起的，这种成岩的伊利石来自加里东和瓦里斯坎热液脉冲。通过外推法从页硅酸盐数据中提取高岭石的平均同位素组成。温度估算值基于氧化铁和高岭石的平均同位素组成，在很大程度上取决于计算中使用的赤铁矿-水分馏因子，但在质量上与预期的热带风化条件相符。