Meso-Cenozoic Thermal Regime And Lithospheric Thinning In The Bohai Bay Basin

Bohai Bay Basin?BBB?is located in the destabilized center of the North China Craton?NCC?.Based on the thermal history,thermal lithosphere thickness and the thermal-rheological structure of the lithosphere can provide geothermic basis and constraints for the destruction of NCC and determined the geodynamic mechanisms.We reconstructed the Meso-Cenozoic thermal history for Jizhong and Linqing sub-basin using method of apatite fission track and Easy%R_o,combining previous research and comparing the thermal history evolution of different tectonic units in the BBB.The Meso-Cenozoic evolution of the thermal lithospheric thickness and the lithospheric thermal-rheological structure in different tectonic units were calculated by combining the crustal structural and thermal parameters.We discussed the relationship between thermal regime and lithospheric thinning of the BBB and determined the geodynamic mechanisms.Studies have shown that the Meso-Cenozoic thermal history,thermal lithospheric thickness and lithospheric strength of major tectonic units of BBB have a similar general evolutionary trend,but have differences in different tectonic units.Generally,the western Linqing and Jizhong sub-basin are“cold”and have low heat flow,thick lithosphere and strong lithospheric strength,while the eastern Jiyang and Bozhong sub-basin are“hot”and have high heat flow,thin lithosphere and weak lithospheric strength.Early Cretaceous to Late Cretaceous is characterized by the first heat-flow peak?85 mW/m²⁹0 mW/m²?,the first lithosphere thin peak?55 km-65 km?,the first lithospheric strength weak peak(1.5×10¹² N/m².5×10¹² N/m),banana split thermal-rheological structure,strong crust and weak mantle.Paleogene to Eocene is characterized by the second heat-flow peak?80 mW/m²⁸5 mW/m²?,the second lithosphere thin peak?46 km⁵9 km?,the second lithospheric strength weak peak(1.4×10¹² N/m².5×10¹² N/m),crème br?lée thermal-rheological structure,strong crust and weak mantle.Two heat-flow peaks are corresponding to the destabilization peak of NCC and the extensional period of BBB,respectively.We reconstructed the thermal history and the thermal lithospheric thickness of the eastern North China,Wyoming,and Siberian cratons by using xenolith and thermal indicator data.Researches from three cratons demonstrate that heat-flow values of the eastern North China Craton and Wyoming Craton?WC?have increased exceeding 20 mW/m² in the Meso-Cenozoic and the thermal lithospheric thickness has decreased by>100 km because of the cratonic destabilization.However,the thermal history variation of the stable Siberian Craton?SC?is small about 5 mW/m²,the lithosphere has remained stable and it has experienced relatively little lithospheric thinning<100 km.The differences of the thermal regime between stable and destabilized cratons are related to the breakup of the Pangea supercontinent and the plate subduction caused by it is the major factor of cratonic destabilized.The BBB located on the active continental margin and underriding by the Pacific plate,our research on thermal history,thermal lithosphere thickness,lithospheric thermal-rheological structure and the lithospheric strength since Mesozoic is in good agreement with the destabilized process of the NCC.The results show that the subduction of Pacific plate is the geodynamic mechanism of the destruction of the eastern North China Craton.