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Since the Paleozoic, the tectonic evolution of northeastern Eurasia has been primarily influenced by the Paleo-Asian Ocean and the Paleo-Pacific tectonic domains. However, the spatial and temporal frameworks, as well as the timing of the tectonic transition between these two oceanic domains, remain unclear. For addressing these issues, we present petrological, geochronological, and geochemical data for andesite and sandstone samples from the Seluohe Group along the Jilin-Yanji Suture between the Jiamusi Khanka Block and the North China Craton. The geochemical results indicate that the andesite sample is high-Mg andesite. Its magma source was generated by the metasomatized mantle wedge influenced by f luids derived from the subducted slab in a continental island arc setting. The high-Mg andesite gives the crystallization ages of Early Triassic (249±3 Ma). The sandstone is immature greywacke with a maximum depositional age of Early Triassic (247±1 Ma), and its sediments primarily originate from concurrent magmatic rocks within a juvenile continental arc. Based on our new findings, we propose that the Seluohe Group represents an Early Triassic volcanic-sedimentary association with continental island arc characteristics associated with the southwestward subduction of the Heilongjiang Ocean. We identified a sedimentary basin intimately associated with one or more continental arcs along the northeastern edge of the North China Craton. We suggest that the southwestward subduction of the Jilin-Heilongjiang Ocean in the Early Mesozoic accounts for this continental arc setting. There is a distinct temporal gap between the closure of the Paleo-Asian Ocean (ca. 260 Ma) and the onset of Paleo-Pacific plate subduction (234–220 Ma), which is essentially coeval with the southwestward subduction of the Jilin-Heilongjiang Ocean between 255 Ma and 239 Ma.

A genus within the family Douvillinidae of the order Strophomenida from the Erdaogou Member of the Xibiehe Formation in the Early Devonian of central Jilin has been re-examined, with consideration

To determine the geological age, petrogenesis, and tectonic setting of Mesozoic volcanic rocks in the Ningyuancun Formation in Xunke area, Lesser Hinggan Range, the zircon U-Pb geochronology, petrographic observations, and geochemical analyses of major and trace elements were conducted in this study. Zircon U-Pb dating showed that the volcanic rocks of the Ningyuancun Formation were formed in the Early Cretaceous (112.97±0.90 Ma). Major element analyses revealed that the content of SiO? weighted from 74.14% to 76.54%, indicating the volcanic rocks to be high-silica and felsic. The content of AlO varies from 12.48% to 13.65%. A total alkali content of the volcanic rocks range between 8.46% and 9.56%, with Na?O/K?O ratios from 0.69 to 0.89. This indicated that the volcanic rocks belonged to a highly differentiated calc-alkaline series. Additionally, A/CNK values range from 0.950 to 1.015, and A/NK values vary between 0.999 and 1.127, suggesting a peraluminous characteristic. Trace element analysis showed a right-sloping “V-shaped” REE pattern, with the enrichment in light REEs and a prominent negative anomaly of Eu. The volcanic rocks are enriched in Rb, Th, U, La, and Ce, while Ba, Sr, and Ti are depleted. Rb/Sr ratio ranges from 10.01 to 12.46, Ti/Y ratio is from 51.14 to 95.72, and Ti/Zr ratio is from 5.78 to 6.41. It is suggested that the magma was derived from the partial melting of crustal rocks. This evidenced that the Early Cretaceous high-silica rhyolites were formed in an intra continental extension in eastern Northeast China during the northwestward subduction of the Pacific Plate. The crustal extension, asthenospheric mantle upwelling and underplating of mantle-derived magmas resulted in the residual crystalline mush in Early Cretaceous mafic magma chambers to erupt.

The quest for enrichment model of continental shale oil in the Zhanhua Sag of the Jiyang Depression in the Bohai Bay Basin to provide reference for exploration and development requires a comprehensive approach. Therefore, this study employs rock pyrolysis, Scanning Electron Microscopy (SEM), X-Ray diffraction analysis (XRD), Nuclear Magnetic Resonance (NMR), and other experiments to analyze the conditions for shale oil enrichment and establish its patterns. The results show that favorable hydrocarbon generation potential and appropriate thermal maturation degree control “in situ enrichment”; while the storage capacity and the mobility of shale oil determine “migration enrichment.” In the process, the TOC governs the oil-generating capacity of shale with medium to large pores and microfractures serving as the main enrichment spaces and migration pathways for shale oil. Based on the deposition model, the study area can be divided into five lithofacies stages (I-algal limestone, II-laminated marl, III-laminated recrystallized limestone, IV-laminated mudstones, and IV-blocky calcareous mudstones). Integrating the geochemical parameters into the sedimentary patterns makes it clear that the study area underwent two phases of hydrocarbon expulsion during the thermal evolution of source rocks (Stage II: 3 060–3 120 m and Stage IV: 3 020–3 040 m). However, judging by the observed TOC (2% to 5.6%), thermal maturity (Ro>0.8%), S1 (>2 mg/g) and OSI (>100 mg/g) as well as moderate basin size, climate, and quantity of terrestrial input, the blocky calcareous mudstones (Stage IV) have better oil-prone characteristics and potential to generate a substantial quantity of hydrocarbons at this stage. More so, with a brittleness index exceeding 60%, it exhibits favorable fracturability accounting for the main controlling factors and enrichment patterns of shale oil in the area. Hence, this study further enriches and develops the theoretical understanding of shale oil enrichment in the area, provides valuable insights for future exploration of continental shale oil in eastern China and other similar basin around the world.

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