Sedimentary Environment and Mechanisms of Differential Organic Matter Enrichment of the Lucaogou Formation in the Eastern Junggar Basin

The Middle Permian Lucaogou Formation in the Junggar Basin hosts a suite of organic‐rich fine‐grained sedimentary succession of continental lacustrine facies, whose deposition was prominently governed by volcanic‐hydrothermal activities. Most prior investigations have predominantly focused on deciphering the dominant controls on organic matter (OM) enrichment in the vertical profile, whereas systematic research on the sedimentary settings and differential OM enrichment mechanisms of the Lucaogou Formation source rocks across distinct sags remains poorly documented. To fill this critical research gap, this study reconstructs the sedimentary paleoenvironments of the Lucaogou Formation source rocks in the Dongdaohaizi Sag, Fukang Sag, and Jimsar Sag of the Junggar Basin and clarifies the driving mechanisms of differential OM enrichment in these sags, using an integrated dataset of organic geochemical, major and trace element analyses. Our results demonstrate that the source rocks in the Jimsar Sag are classified as high‐quality intervals with strong hydrocarbon generation potential, whereas those in the Fukang and Dongdaohaizi sags are generally of moderate to poor quality. In terms of paleoenvironmental conditions, all three sags were characterized by an arid to semi‐humid paleoclimatic background, formed in a deep lacustrine depositional environment, and maintained high paleoproductivity levels during the Lucaogou Formation depositional period. Specifically, the Jimsar Sag featured higher water salinity and stronger reducing conditions, whereas the Dongdaohaizi Sag recorded higher paleoproductivity than the other two sags, which is attributed to more intense volcanic‐hydrothermal alteration. Furthermore, two distinct OM enrichment models, namely, the high productivity‐anoxic preservation model and the high productivity‐oxidative consumption model, are proposed under the synergistic effect of volcanic‐hydrothermal activities and lacustrine water salinization. This model framework reveals the intrinsic mechanism of differential OM enrichment among different sags and provides a novel theoretical basis for high‐quality source rock evaluation and hydrocarbon exploration in intracontinental rift lacustrine basins affected by volcanic‐hydrothermal activities.