中国东北白垩纪盆地从伸展到挤压的构造转换过程及其大地构造意义

It has been widely accepted that Cretaceous basins in Northeast China experienced a transition from tectonic extension to compression, however, the time and process of this tectonic switch and its geodynamic mechanism still remain controversial. In this research proposal the Cretaceous basins in Northeast China are taken into consideration as an organic whole, and the basins in the eastern Heilongjiang, the Songliao and Hailar basins are emphasized, focusing on the structral and sedimentary responses for the teconic switch from extension to contraction and the discussion on its tectonic significance. The significant geological surface reflecting tectonic switch can be identified and dated by means of the integrated analysis of unformormity，switching of sedimentary system and provenance, and syn-tectonic growth strata. The detailed anatomy of the key basins and regional seismic-geological profile and sequential balanced restoration is conducted to clarify the zonality, the amount of shortening and propagation patterns of compressive deformation. The study on source to sink systems of key basins during the tectonic switching period will be conducted in order to clarify transition responses of sedimentary systems and provenances, and their temporo-spatial migration patterns. Based on the above studies, structrual sketch and temporal-spatial evolution of the basin and range system can be reconstructed and discussed. Late Cretaceous basin system and type in Norheast China can be determined in order to reveal its dynamic process. Finally, combined with records of plate subducting and collisional events in Northeast Asia, the relationship between the switch of tectonic system and plate interactions surrounding Northeast China can be investigated, which may provide important constraints on understanding the Cretaceous tectonic process in Northeast Asia.

白垩纪时期，中国东北经历了从伸展到挤压的构造体制转换，这一盆地构造演化的框架已成为学界的普遍共识，但对转换的时间、过程及动力学机制仍有争议。本申请将中国东北白垩纪盆地作为一个有机关联的整体，以黑龙江东部盆地群、松辽盆地和海拉尔盆地为重点，通过不整合面、沉积体系与沉积物源的变化和同构造生长地层的综合研究，识别构造转换的关键地质界面并厘定转换时间，明确其转换时间的空间变化；通过重点盆地精细构造解释和地震-地质大剖面的构建与构造平衡恢复，厘定挤压构造变形的分带性、变形的缩短量和变形的扩展规律；开展重点盆地构造转换时期的源-汇体系研究，阐明构造转换背景下沉积体系、物源的变化响应与时空迁移规律。在此基础上探讨构造转换时期的盆-岭构造格局及其演变，厘定晚白垩世盆地系统和盆地类型，揭示其成盆动力学过程，探讨构造体制转变与东北亚周边板块俯冲、碰撞等作用的关系，为认识东北亚白垩纪地球动力学过程提供重要制约。

中国东北白垩纪盆地群可以划分为东部、中部和西部三个近平行的NNE向的盆地发育带。通过对这三个白垩纪盆地带关键构造转换界面识别和时代厘定，发现早白垩世裂陷作用具有西早东晚、依次向东迁移变新的规律，而盆地从伸展到挤压的转换时间则呈现出东早西晚，依次向西扩展变新规律。厘定了吉林东部汪清地区发育一套早白垩世晚期安山岩-埃达克岩和富铌玄武岩组合，为俯冲弧岩浆成因，结合早白垩世岩浆和裂陷作用向东迁移变新特点，提出早白垩世松辽盆地及其以东陆壳伸展和岩浆活动受古太平洋板块俯冲后撤主导。以三江盆地等为代表的东部盆地，其上白垩统缺失下部和顶部地层，构造变形样式以挤压的冲断-褶皱为主；同时盆地充填经历了早白垩世东部和西部双向充填向晚白垩世单一向西充填的转变。以松辽盆地为代表的中部盆地，其发育了完整的上白垩统，最大厚度超过5 km，挤压构造变形主要集中在松辽盆地的东部，以褶皱变形为主，与东部带相比变形强度相对较弱；晚白垩世的沉积充填特征和物源体系存在重要转变，即Campanian以后，盆地水系从环形水系转变为向西单向水系，同时沉积中心变为近南北狭长状并不断向西迁移。以海拉尔盆地为代表的西部盆地，晚白垩世则基本处于隆升缺失阶段，仅在Maastrichtian期经历了小幅坳陷沉降和弱的挤压。基于上述白垩纪盆地构造-沉积响应特征和时空规律，提出了中国东北经历了早白垩世伸展到晚白垩世构造挤压的转换，时间约为90 Ma。同时，盆地的性质也发生了根本性的改变。晚白垩世东北盆地群属于一个统一的大型弧后前陆盆地系统，即东部带属于前陆褶皱-冲断带，中部带对应与前渊坳陷单元，大兴安岭和西部带则分别属于前隆和隆后坳陷单元。中国东北白垩纪盆地构造转换过程指示了东北亚陆缘从早白垩世“西太平洋型”俯冲向“安第斯型”俯冲的重大转变，改变白垩纪盆地主要受控于伸展的传统观点，很好解释了晚白垩世盆地空间分异演化的动力学机理，并为该地区非常规油气勘探开发提供重要地质依据。

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