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华北断块区中、新生代地质构造特征及岩石圈动力学模型

THE MESOZOIC AND CENOZOIC GEOTECTONIC CHARACTERISTICS AND DYNAMICAL MODEL OF THE LITHOSPHERE IN NORTH CHINA FAULTBLOCK REGION

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【作者】 张文佑张抗赵永贵蔡新平王信和徐贵忠吴海威韩贝传曾湘山

【Author】 Zhang Wenyou;Zhang Kang;Zhao Yonggui;Cai Xinping;Wang Xinhe;Xu Guizhong;Wu Haiwei;Han Beichuan;Zeng Xiangshan Institute of Geology, Academia Sinica

【机构】 中国科学院地质研究所中国科学院地质研究所

【摘要】 <正> 华北断块区是我国最古老的岩石圈断块。它经历了前古生代的形成及古生代的平稳发展阶段而进入中、新生代的激发阶段。我们运用地质历史分析与地质力学分析相结合的方法,在新的地质和地球物理资料基础上进一步研究了该区中、新生代的建造和改造历程、地壳和岩石圈结构,探讨了构造应力场的演化,建立了岩石圈动力学模型。

【Abstract】 Essential change in tectonic features of North China had taken place during Mesozoicand Cenozoic in contrast with the steady development in Palaeozoic ear. The great unifiedfault-block region had gradually disrupted to form a series of large grabens. Corresponding-ly, the thicknesses of the crust and lithosphere as well as their modes of movements hadalso changed. This process is difficult to be interpreted simply by the underthrusting of Pa-cific plate underneath the Asian continent, for it might evolve through causes attributive to the change in speed of earth’s rotation and the thermal activity within lithosphere and asthe-nosphere, resulting in the manifestation of block-faulting movement, both horizonal andvertical. In the early Mesozoic, tectonic pattern in present region inherited the Palaeozoic era.Later, the great sedimentary basins gradually reduced in their size and disrupted, and theeast-west differentiation began to predominate. Since the Jurassic period, a series of grabensin various drections had developed in uplifted areas, in which volcanic and detrital rocksof great thickness were accumulated. The great sedimentary basins vanished after the earlyCretaceous, and grabens in dominant NNE and EW directions occurred, making up rhom-bic configurations. The reginal magmatism had its peculiar characteristics. Temporally, it started from the Triassic, and reached its climax during J3-K1. Spatially, the marginal and the internal tectono-magmatic associations can be recognized. The former consists of granitoids and intermedi-ate-acidic rocks, the latter formed along three continent-rift zones. Geochronologically, rocksbecome younger sideward from axes of these zones, with the alkalinity (especially, K2O)correspondingly increasing. The Eogene magmatic rocks are mainly tholeiitic, distributed in graben areas, whereasthe Neogene and Quaternary ones are alkalic basalts distributed in uplifed areas and inter-block fracture zones. Compated with the Cenozoic magmatic rocks, the Mesozoic ones aremore alkalic. The development of the sedimentary and magmatic formations had obviously beencontrolled by the activities of the crustal fractures. Some of intensely active grabens are ofthe nature of continental refts. The mean thickness of the regional lithosphere is about 80 km. On the whole, the li-thosphere is thicker in the western part than that in the eastern part. The thickness of thecrust also has the same features. The lithospheric thickness in present region is comparablewith the mean thickness in Mesozoic folded and reactivated regions over the world. Ascompared with the Precambrian stable platforms, howevert, he lithosphere had undergonean evolutional process of thinning during the Mesozoic and Cenozoic, with a lithosphericattenuation of about 100km. This process accounted for the reactivation of preceding frac-tures, controlling the development of various graben systems. In correspondence with the development of formations, the evolution of the regionalstress fields may be divided into three stages. In early stage, the regional stress field result-ed mainly from the compression of Siberian Fault-block Region toward the south, strongerin the west and weaker in the east. There fore, the lithosphere of the present region, as avisco-elastic body creeped to the south-east, and resulted in its impacting and interactionwith Pacific. Lithosphere Fault-block Region. In the later stage, the direction of the inter-action changed from SE to EW. Moreover, the material of the asthenosphere beneath theuplifted area of the lithosphere continued spreading, causing the stretching, thinning andfracturing of the lithosphere. In the last stage, during the Neogene and Quarternary, the ac-tions of Pacific Fault-block Region futher strengthened. Simultaneously, the North ChinaFault-block Region is compressed by Qinghai-Tibet Fault-block Region. Thus, the stress field of the region shows some variations.

  • 【文献出处】 地质学报 ,Acta Geological Sinica , 编辑部邮箱 ,1983年01期
  • 【被引频次】115
  • 【下载频次】578
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