--> Tectono-Thermal Reconstruction of the Western Bohai Bay Basin (East China) and Its Implication for Hydrocarbon Generation and Migration

AAPG ACE 2018

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Tectono-Thermal Reconstruction of the Western Bohai Bay Basin (East China) and Its Implication for Hydrocarbon Generation and Migration

Abstract

The shortage of studies on the tectono-thermal evolution of the western Bohai Bay Basin (WBBB), including Jizhong Sub-basin and Cangxian Uplift, is unfavorable for further petroleum exploration and exploitation. This study aims to reconstruct the tectono-thermal history of the WBBB based on the combination of 125 vitrinite reflectance (Ro), 7 apatite fission track (AFT) and 9 apatite (U-Th)/He (AHe) data. The effective AFT ages range from 60.3 Ma to 97.0 Ma with mean track lengths of 10.86~12.64 μm. Moreover, the dispersion of the single-grain AFT ages is caused by the parameter Dpar. The effective AHe data varies between 21.1 Ma and 75.0 Ma. Two rapid cooling events revealed by the thermal modeling results occurred in Early Cretaceous-Late Cretaceous (130-90 Ma) and late Eocene-Early Miocene (40 Ma~18 Ma). The first cooling event resulted from the extension-detachment caused by the doming of the Fuping Complex, which was related to the subduction of the Izanagi Plate. The second one was caused by the subduction of the Pacific Plate in the middle Eocene-early Miocene (43~23 Ma) and the collision of the Indian and Eurasian plates and the rollback of the subducting Pacific Plate during early Miocene (23-18 Ma). The WBBB experienced two heat flow peaks with ~75 mW/m2 and ~80mW/m2 in the Early Cretaceous and Late Eocene, respectively. During the late Eocene-early Miocene, the rapid subsidence in the Baxian Depression, coupled with the rapid uplift in the Cangxian Uplift, caused the Shahejie Formation to generate gas in early Miocene. Meanwhile, the tectonic movement in the early Miocene also made faults became the migration paths as revealed by homogenization temperature. This study provide new insights for the tectonic evolution and hydrocarbon evolution of the WBBB.