渤海西南海域中生代构造演化、动力学机制及其对华北克拉通破坏的启示

渤海西南海域自中生代以来历经多期构造活动,记录了华北克拉通的破坏过程。为了明晰渤海西南海域中生代构造演化与区域构造间的关系,以研究区三维地震资料以及深层钻井资料为基础,结合区域构造背景,厘定了研究区中生代构造特征,恢复了中生代构造演化过程,并探讨了其动力学机制及其对华北克拉通破坏的响应。结果表明:(1)不同于渤海湾盆地陆上油区NEE向的构造面貌,渤海西南海域发育多走向、多类型构造,三维地震资料揭示中生代发育NWW向负反转裂陷、NEE向走滑逆冲、挤压褶皱等异于新生代伸展样式的特殊构造,其中尤以NWW向负反转构造占主导。(2)渤海西南海域中生代以来经历了印支期逆冲褶皱成山、燕山早期左旋逆冲改造、燕山中期裂陷反转以及燕山晚期褶皱等多期变形过程, 其中印支期逆冲褶皱是潜山形成的关键时期,而燕山中期反转是构造体制发生变革的关键时期。(3)NWW向构造的形成与印支期华南板块与华北板块的碰撞有关,燕山早期左旋走滑是太平洋板块NWW向俯冲于华北板块之下的结果,代表太平洋构造域接替古特提斯构造域控制华北板块变形;燕山中期的裂陷反转与区域大规模中基性岩浆活动相对应,是华北克拉通大规模破坏的浅层响应。印支期NWW向先存构造燕山中期反转裂陷模式的提出,丰富了传统华北克拉通破坏形成NEE向盆地的简单构造模式。

Mesozoic tectonic evolution of the southwestern Bohai Sea and its dynamic mechanism: Implications for the destruction of the North China Craton

Mesozoic of the southwestern Bohai Sea experienced multi-stage tectonic activities and records in detail the destruction process of the North China Craton. Here, to clarify the relationship between Mesozoic tectonic evolution in the southwestern Bohai Sea and regional tectonic setting, the structural characteristics of the Mesozoic are determined, its formation and evolutionary processes are restored, and its dynamic mechanism and response to the destruction of the North China Craton are discussed based on the 3D seismic and deep drilling data, combined with regional tectonic background. As results show, (1) differing from the NEE-trending structure of the onshore oil area of the Bohai Bay Basin, the southwestern Bohai Sea develops multi-strike, multi-type structures. The 3D seismic data reveal negative-inversion, strike-slip thrusting, and folding structures that are different from the Cenozoic extensional structures; among them, the NWW-trending negative-inversion structure dominates. (2) Mesozoic of the Bohai Sea undergoes multi-stage deformation, which includes formation of the Indonesian thrust fold, sino-lateral thrust transformation in the Early Yanshan period, negative inversion in the Middle Yanshan period, and fold in the late Yanshan period; among them, thrust fold during the Indosinian movement was the key stage for the buried-hill formation, and the middle Yanshan negative-inversion stage was the key stage for the tectonic transformation. (3) Formation of the NWW-trending structure is related to the South-North China collision during the Indonesian period. The sinistral strike-slip in the early Yanshan period is the result of the NWW-ward subduction of the Pacific plate, which signifies the replacement of the Paleo-Tethys domain by the Pacific domain for controlling the deformation of the North China plate. The negative inversion in the middle Yanshan period corresponds to the large-scale regional magmatic activity, which is the shallow response to the large-scale destruction of the North China Craton. The proposed model of a NWW-trending negative-inversion towards the preexisting structure of the Indosinian in the middle Yanshanian enriches the simple traditional structural model for the destruction of the North China Craton to form the NEE-trending basins.