Geochemistry of the Wufeng–Longmaxi black shales in the NW Middle Yangtze Basin: implications for provenance, paleoenvironment, and heterogeneity of organic matter

作者：Weiqing Liu, Yu Qiao, Wei Wu, Chuanlong Mou, Luqi Chen · 发表于：Geomechanics and Geophysics for Geo-Energy and Geo-Resources · 年份：2025 · DOI：10.1007/s40948-025-01035-0 · 被引用次数：6 · 研究领域：Geochemistry and Elemental Analysis、Hydrocarbon exploration and reservoir analysis、Geochemistry and Geologic Mapping

Understanding shale deposition processes and the mechanisms controlling organic matter enrichment is crucial for analyzing lithofacies genesis, reservoir heterogeneity, and identifying shale gas exploration targets, yet these aspects remain insufficiently understood. In this study, the Wufeng–Longmaxi black shales from the Yangtze Basin were systematically analyzed to reconstruct sedimentary conditions and evaluate the impact of paleoenvironmental factors on organic matter accumulation. Major and trace element geochemistry (e.g., Th/Sc, Co/Th, La/Sc, Fe₂O₃/TiO₂, and Al₂O₃/(Al₂O₃ + Fe₂O₃)) indicates that the Wufeng–Longmaxi shales were derived from a felsic igneous provenance within a continental margin setting. Paleoclimate proxies (CIA, αAlE), primary productivity indicators (P/Al ratios), and Co(ppm) × Mn(%) values suggest a predominantly semi-warm to warm climate with moderate productivity during intervals A and B. In contrast, interval C experienced climatic cooling and elevated primary productivity associated with enhanced upwelling, whereas interval D was marked by rapid warming, reduced productivity, and weakened upwelling. The results demonstrate that paleoclimate influenced primary productivity by modulating oceanic upwelling intensity. Cross-plots of Co(ppm) × Mn(%) and Cd/Mo ratios reveal that organic matter enrichment in interval A was mainly driven by high productivity, while preservation conditions played a dominant role during intervals B and D. Although coolin...