The rare earth elements (REEs) provide significant geological information and serve as a reliable indicator for predicting the paleoclimate, paleoenvironment, and paleotectonic evolution of sedimentary rocks. The REEs, major elements, and trace elements of 75 marine shale samples collected from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region were analyzed. The results revealed that the major elements Al₂O₃, K₂O, and TiO₂ were primarily influenced by clay minerals associated with terrigenous detrital, whereas SiO₂ and Na₂O were not affected by clay minerals. The ΣREE values obtained from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region were found to be lower than those of the Post-Archean Average Shale (PAAS) (184.8 μg/g). The study of REE indicators related to the source, redox conditions, and tectonic settings led to the following conclusions: (a) ΣREE showed strong positive correlations with TiO₂, Al₂O₃, K₂O, and Na₂O, but exhibited relatively weak correlations with Fe₂O₃ and P₂O₅, suggesting that REEs were mainly associated with clay minerals, but were also influenced by pyrite, phosphates, and other minerals; (b) The high values of Ce/Ce*, Mo_EF, U_EF, and C_org/P were mainly concentrated in Stages I, II, III and V of the Dalong Formation at the FTS and PTL sections, and the corresponding strong anoxic environment was more conducive to the preservation of organic matter; (c) The diagram between La/Yb and ΣREE, Al₂O₃-TiO₂, TiO₂-Zr, and La/Th-Hf bivariate diagrams indicated that the provenance of the rocks from the Dalong formations was primarily felsic igneous rocks; (d) Discriminant-function diagrams and La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 triangular diagrams show that the clastic sediments of the Dalong formations were derived most likely from continental island arcs. This study corresponds to the background of the transition from continental margin to continental collision structure in South China during the Late Permian.

The evolutional process of palaeoceanic environment and its effect on the accumulation of organic matter during the Ordovician–Silurian transition in Lower Yangtze region has been overlooked compared to that in Upper Yangtze region of South China, although their paleogeographic settings were expected to be discrepant. This paper documents the marine depositional environment, paleoclimate, and sediment supply changes, and discusses their roles in controlling the organic matter enrichment in sedimentary rocks within the Ordovician–Silurian transition of the Lower Yangtze region, using the latest geochemical data of the continuous drilling core. The stratigraphic framework of the Ordovician–Silurian transition in the Lower Yangtze region is composed of two third-order sequences, each of which can be subdivided into a lower TST (transgressive systems tract) and an upper RST (regressive systems tract). TST1 represented an evident depositional transition stage which was marked by the ending of the underlying carbonate sediments and the initiation of the terrigenous clastic-dominated sediments. Geochemical proxies indicate that the relatively low productivity, dysoxic water column condition, and high sediment supply flux collectively resulted in inadequate organic matter hosted in deposits of the TST1. During the depositional period of RST1, the global sea level declined due to the Hirnantian glaciation age. The icehouse also caused the decrease in overall river flux and, thus, the terrigenous clastic sediment supply. The icehouse also strengthened the upwelling that occurred in the Lower Yangtze sea. The upwelling boosted the marine algae explosion through the delivery of abundant nutrients, which not only enhanced paleoproductivity but also led to an anoxic environment by oxygen consumption. Such high paleoproductivity, anoxic water column environment, and low sediment supply flux caused the deposition of organic-rich shale. The sea level rose during the TST2 due to the ending of an ice age. The relatively large water depth and high paleoproductivity associated with volcanic eruptions are the main factors that caused the enrichment of organic matter during this stage. During the deposition of RTS2, the increase of sediment supply flux resulted in a decrease in accommodation space and water depth and the dilution of organic matter in deposits, which was the primary constraint of organic matter accumulation.

The Kungurian Stage in the early Permian was a transitional glacial age between the late Paleozoic icehouse and the early Mesozoic super-greenhouse period This stage offers an excellent opportunity to study the co-evolution between global carbon cycles and environments. This study presents facies and carbon isotope variations in a new carbonate section in the Lower Yangtze region of South China in order to understand the linkage between carbon cycle fluctuation, sedimentary environment, and climate change. Based on the sedimentary facies analyses of the Chihsia Formation (Kungurian), seven facies types were identified and grouped into lower slope, upper slope, and platform facies associations. The facies analyses show that the Kungurian Stage experiences two transgressive-regressive cycles; paleoclimatic changes controlled the sedimentary records and sea level fluctuations. Early Kungurian carbonate rocks record the presence of the short-lived Kungurian carbon isotopic event (KCIE). The rapid negative carbon isotope of the KCIE was closely related to the huge CO₂ emission. A warming climate could have slowed down oceanic ventilation rates and accelerated stratification of seawater. The resulting anoxic environment led to a sharp decline in biological species. In the middle Kungurian, the intensity of volcanic activity gradually weakened and the climate turned cold, which accelerated oceanic ventilation rates and led to increased oxygenation of deep-shelf water masses. The higher Δ¹³C values supported enhanced primary productivity and photosynthesis, which promote the prosperity of biological species. This study provides a new perspective for better understanding the links between marine carbon cycle fluctuations, climate change, and environments during the icehouse to greenhouse conversion period.

Helium is a critical, scarce, and strategic resource, often found in association with natural gas. This study reports the first discovery of overpressured helium-rich natural gas in the Lower Yangtze Region of Eastern China, with helium concentrations reaching as high as 4.5%, significantly surpassing the commercial extraction threshold of 0.1%. Comprehensive geochemical analyses, including helium isotopes ratios, carbon isotope compositions of CH4 and CO2, and gas compositional data, indicate that the helium in this region is predominantly crustal in origin. This finding contrasts with the mantle-derived helium commonly observed in the Mesozoic and Cenozoic lacustrine rift basins of Eastern China. These results suggest that helium exploration in Eastern China should account for both crustal and mantle-derived sources, challenging previous assumptions that focused primarily on mantle-originated helium. Key geological factors contributing to the observed helium enrichment include: (1) the presence of an ancient Proterozoic granite basement as the primary helium source rock; (2) large and deep fault systems acting as vertical migration pathways; (3) thick gypsum layers functioning as effective caprock seals; and (4) the simple stratigraphic architecture of the central transition belt, which provides favorable conditions for large-scale gas accumulation and preservation. These findings suggest that the central transition belt of the Lower Yangtze Region has significant potential for helium resource development. Future research will prioritize helium reserve estimation and the evaluation of economic extraction feasibility within this area.

Lithium­(Li)-rich brines represent an increasingly important strategic resource and are commonly associated with evaporites. Their formation has traditionally been mainly attributed to evaporation-driven concentration under arid paleoclimatic conditions. This study investigates the genetic mechanism of the thick anhydrite deposits and associated lithium-rich brines in the Middle Triassic Zhouchongcun Formation of the Lower Yangtze region. Through integrating petrographic, elemental, and isotopic geochemistry and fluid inclusion analyses, combined with reconstruction of the stratigraphic burial-thermal history, we demonstrate that the formation and evolution of these evaporates are closely linked to multiple tectonic-thermal events. Petrographic characteristics and carbon–oxygen isotopic data indicate that the anhydrite initially formed in a restricted evaporative environment during the Middle Triassic, with δ¹³C ranging from −2.9 to −0.4‰ and δ¹⁸O values from −8.1 to −5.6‰, showing a significant positive correlation. Fluid inclusion data reveals subsequent complex hydrothermal overprinting. Primary inclusions record homogenization temperatures of 181.3–210.2 °C, corresponding to the peak paleo-temperature reached during early deep burial. In contrast, secondary inclusions yield lower homogenization temperatures of 135.8–174.3 °C, consistent with hydrothermal activity associated with the Yanshanian tectonic-thermal event. Burial–thermal history reconstruction indicates significant heating during the Middle Jurassic, with maximum temperature reached between approximately 150–170 Ma, coinciding with regional magmatic-tectonic activity. These results indicate that the anhydrite underwent intense reworking by medium- to high- temperature hydrothermal fluids during the Yanshanian period, superimposed upon its primary evaporative sedimentary origin. Geochemical data further shows that both fluid inclusions within anhydrite and the formation brines belong to a mixed sodium sulfate-sodium chloride hydrochemical type, supporting a common fluid source The lithium content in secondary inclusions is more than 4.8 times higher than that in primary inclusions, which the lithium content in regional intrusive rocks is 9.4 times higher than background levels, indicating a dominant contribution from Yanshanian magmatic-hydrothermal fluids. Micro-Raman spectroscopy combined with brine ion composition analysis jointly provides additional evidence for substantial hydrothermal input of lithium. Based on these observations, a three-stage genetic model is proposed: (1) sedimentary foundation, characterized by anhydrite precipitation and initial brine formation in a closed evaporative basin during the Middle Triassic; (2) lithium addition via hydrothermal reworking, whereby lithium-rich magmatic–hydrothermal fluids ascended during the Yanshanian event (∼150 Ma), modifying pre-existing anhydrite and enriching brines at temperatures of 150 °C; and (3) structural adjustment and accumulation, involving lithium migration and concentration within anhydrite–dolostone anticline traps during post–Late Cretaceous uplift and cooling under extensional tectonic conditions. This model highlights the key controlling role of medium-low temperature hydrothermal events in the formation of evaporite-type lithium resources and provides a new genetic framework and exploration guide for lithium-rich brines in evaporite basins.

The Late Permian witnessed a Permian Chert Event (PCE) and distinctive oceanic geochemical fluctuations, such as an ocean acidification event, large-scale volcanic eruption, and rapid global warming. However, the links between siliceous rock formation mechanism, ocean, and climate changes are rarely discussed. In this article, two well-preserved deeper-water sections of the Dalong Formation from the Lower Yangtze region in southeast China are selected for analysis. To document the coeval oceanic changes, we present thin section authentication, scanning electron microscope (SEM) observation, and multiple geochemical proxies, including total organic carbon contents (TOC), major element contents, trace element contents, and rare earth element contents (REEs). The results show that siliceous rocks are mainly of biological origin in this region. The low content of MgO (0.10-0.94%, mean = 0.36%) in the Fantiansi section of Tongling area indicates that it is affected by regional hydrothermal fluids. The correlation between Al2O3/TiO2, Al2O3 versus SiO2 /Al2O3, and TiO2/sigma REEs indicates that the Late Permian was greatly influenced by the continuous input of terrigenous materials. The correlations of MnO/TiO2, LaN/CeN, Ce/Ce*, and LREE/HREE imply that the Dalong Formation siliceous rocks were deposited in a continental margin setting. Redox geochemical data (EFU, EFMo, and EFV) imply the water column experienced widespread anoxic/euxinic during the Late Permian, which aided in the preservation of organic matter following biological decay. The accumulation of siliceous rocks is related to South China experiencing a hot tropical climate, coastal upwelling and continental weathering-enriched marine nutrients, fostering high primary productivity, and benefiting abundant siliceous zooplankton. Volcanic and regional hydrothermal activity further enhanced nutrient flux, and the simultaneous ocean acidification event provided favorable chemical conditions for the preservation of silica, leading to the formation of siliceous rocks in the Dalong Formation.