Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (4): 206-218.DOI: 10.13745/j.esf.sf.2023.6.20

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Tectono-thermal mechanism and hydrocarbon generation action in the North Yellow Sea Eastern Sub-basin

LIU Jinping1,2(), WANG Gaiyun1,2,*(), JIAN Xiaoling1,2, ZHU Chuanqing3, HU Xiaoqiang1,2, YUAN Xiaoqiang1,2, WANG Chao1,2   

  1. 1. Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources, Guangzhou 511458, China
    2. Guangzhou Marine Geological Survey, Guangzhou 511458, China
    3. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China
  • Received:2023-05-26 Revised:2023-06-29 Online:2024-07-25 Published:2024-07-10

Abstract:

The North Yellow Sea Eastern Sub-basin is a typical Meso-Cenozoic small superimposed faulted basin, currently in its early exploration phase. Comprehensive studies on the complex tectonic-thermal evolution in this region are lacking. By integrating vitrinite reflectance (Ro) and apatite fission track (AFT) analysis, the thermal history and geothermal gradient of the Meso-Cenozoic era have been reconstructed in this basin, alongside assessments of erosion thickness and processes. These investigations have enabled an analysis of the thermal evolution history of Middle-Upper Jurassic source rocks. Results indicate that paleo-heat flow peaked at 75-90 mW/m2 during 120-100 Ma, decreased to 60 mW/m2 at 40 Ma, and then rose to 70 mW/m2 at present. Correspondingly, temperatures declined gradually from 100-70 Ma but rapidly dropped during 70-40 Ma, with the geothermal gradient shifting from 34-36 ℃/km to 23 ℃/km before rising to 28 ℃/km. Overall, paleo-geothermal gradient and heat flow were higher before the Late Cretaceous, aligning with the transition from a faulted basin to a depression basin. Intense uplift and erosion occurred during the Late Cretaceous-Eocene, resulting in an erosion thickness of approximately 1.0-1.5 km. Deposition slowed or ceased during 100-90 Ma, with significant uplift occurring during 85-40 Ma, especially rapid during 70-40 Ma. The tectonic-thermal history has influenced hydrocarbon generation, with both Middle and Upper Jurassic source rocks experiencing early hydrocarbon generation during the Late Jurassic-Early Cretaceous. In the central depression, erosion thickness was thinner in the Lower Cretaceous-Eocene, while deposition thickness was thicker in the Oligocene-Quaternary, leading to higher present-day strata temperatures and favoring late hydrocarbon generation. Exploration efforts for potential accumulation should focus on areas surrounding hydrocarbon generation depressions.

Key words: Eastern Sub-basin, apatite fission track, vitrinite reflectance, tectonic-thermal history, hydrocarbon generation action

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