华北克拉通构造演化

华北克拉通是中国大陆的主要构造单元,从早期到中生代以来的地质记录较完整,受到国际关注,是大陆形成和演化研究的天然实验室。华北克拉通的构造演化可以分为八个大的阶段:陆核形成阶段;陆壳巨量生长阶段;微陆块拼合与克拉通化;古元古代大氧化事件与地球环境剧变;古元古代活动带构造与高级麻粒岩相变质作用;中-新元古代多期裂谷与地球中年调整期;古生代边缘造山;中生代构造转折与去克拉通化。华北克拉通的大陆演化显示了地球的进化和不可逆过程,特别是热体制的演变。早期陆核的成因仍存在争议,但是陆壳由小到大、多阶段生长的过程是明确的。25亿年前后的克拉通化是最具显示度的地质事件,微陆块的拼合是大陆聚合和形成稳定克拉通的主要过程,已经被揭示。但是由绿岩带-高级区构成的穹隆-龙骨构造并不遵从板块构造的基本构造样式。经历了太古宙与元古宙分界时期的"静寂期"之后,华北克拉通记录了与全球休伦冰期以及大氧化事件相关的地质活动。古元古代活动带则记录了裂谷-俯冲-碰撞的过程,具有显生宙造山带的某些特征,伴有高级麻粒岩岩相的变质作用,暗示了早期板块构造的出现。从约18~8亿年长达十亿年或更长的时限里,华北克拉通一直处于伸展环境,发育多期裂谷,有多期陆内岩浆活动,是岩石圈结构和下地壳组成的关键调整期。从古生代起,华北的南、北缘都经历了现代板块构造意义的造山事件,显示了华北克拉通古陆通过古蒙古洋和古秦岭洋与相邻陆块之间的构造活动,分别称为兴蒙造山带和秦岭-大别造山带。中生代的华北克拉通出现构造体制的转折和地壳活化,表现为岩石圈减薄和大量壳熔花岗岩的出现。古太平洋板块的活动显然是重要因素之一,但周边其它陆块的作用也是重要的,克拉通破坏机制及其内涵的研究还有进一步深化的空间。华北克拉通的构造演化有其特点,也具有全球意义。 

TECTONIC EVOLUTION OF THE NORTH CHINA CRATON

The North China Craton (NCC) is a major tectonic unit of China. It is brought into focus to international Earth scientists, because of its complicated and complete geological records from Early Archean to Mesozoic. The tectonic evolution of the NCC can be classified into eight stages, which are as follows:Continental nuclei generation; Major growth of continental crust; Amalgamation of micro-blocks and cratonization; Great Oxygenation Event (GOE) and Paleo-Earth environment change; Paleoproterozoic mobile belt event and metamorphism of high-grade granulite facies; Proterozoic multi-stage rifting and Earth''s Middle Age adjustment period; Paleozoic orogeneses along the margins of the NCC; Mesozoic tectonic regime inversion and de-cratonization. The tectonic evolution of the NCC as an example shows the Earth''s irreversible evolution process with, specially, heat regime change. Although remaining controversial to mechanism of nuclei generation, it is undisputed that the continental crust grew from small to large in scale with multi-stages.~2.5 Ga cratonization is the most important event, and the amalgamation of micro-blocks is a fundamental process to accomplish stabilization. However, the amalgamation complied the dome-keel tectonic model (tectonic style of high-grade region and greenstone belt) is different from the Plate tectonics. After "the quiet period" during the Archean-Proterozoic boundary, the NCC recorded geological presentations of the Huronian Glaciation and GOE. The Paleoproterozoic mobile belt event includes rift-subduction-collision processes with metamorphism of high-grade granulite facies, indicating tectonic regime change from early heat tectonics to Early Plate Tectonics. The NCC was in an extensional tectonic setting over a long to 1.0 Ga critical epoch from~1.8 Ga to <0.8 Ga, during which main geological activities included multi-stage rifting, multi-intracontinental magmatism and adjustment of lithosphere and texture between crust and mantle. The Paleozoic orogeneses occurred along the margins of the NCC, showing the tectonic activities between the Siberia, North China and South China blocks related to the Paleo-Mongolia Ocean and Paleo-Qinling Ocean. The Mesozoic tectonic regime inversion and basement reworking were shown by lithospheric thinning and a vast amount of crust-partial melting granites. The subduction of the Paleo-Pacific Ocean Plate to the NCC is considered as a main governing factor, but interaction with other circumjacent geological blocks are also considerable. The study on tectonic evolution of the NCC has global significance.