The concept of "geodynamics" has a long history. Scheidegger( 1958, 1963, 1982) discussed this concept earlier, emphasizing the relationship between the characteristics of the earth's surface and the driving forces inside the earth. As for the study of the deep structure of the earth, it has always been a difficult point in the geological-geophysical subject. In the late 1980s, the seismic tomography technology based on the analysis of natural seismic data made a major breakthrough, revealing the image of the deep structure of the earth (Woodhouse et al., 1984), and giving an intuitive image of the earth structure from a macro perspective. Maruyama et al. developed the concept of mantle plume based on these images, put forward a conceptual model of mantle plume structure, and explained the driving force of plate movement with super mantle plume, nuclear-mantle interaction and mantle convection (Xie, 1995, 1997). Since the 1990s, many scholars have explored the deep structure of the earth and made a series of significant achievements. For example, Song Xiaodong discovered and confirmed that the rotation speed of the earth's inner core is about 1 degree faster than the overall rotation speed of the earth every year, which is regarded as a major scientific discovery in contemporary times. Mao Heguang and other high-pressure test devices using giant diamonds and other technologies have provided some data on the properties of core-mantle boundary materials. The global geoscience transect (GGT) spans a series of important orogenic belts and basins, providing systematic information about its deep structure, and has also made important achievements in China (Wu, 199 1).

Hunan Province belongs to the circum-Pacific tectonic domain, located at the southeast edge of the North-South orogenic belt of Daxing 'anling-Taihang Mountain-Wulingshan (Liu Guangding, 1992, 1993), and has a structural pattern of "three horizontals, two verticals and two triangles" proposed by Academician Liu Guangding. In this tectonic domain, there is a long strip of Mesoproterozoic metamorphic rock series, which runs from northern Guangxi and eastern Guizhou across the border of Hunan, Hubei and Jiangxi to Anhui and Zhejiang, but it does not integrate the metamorphic Devonian system. Huang (1980) called it "Jiangnan ancient land". Hunan is located in the middle of Jiangnan ancient land, between the Yangtze block and the South China fold belt, and is the secondary structure of the South Plate. Therefore, the evolution history of the southern plate and the stress characteristics of each tectonic development stage directly control the characteristics of tectonic activity in this area. To study the structural evolution characteristics of Hunan Province, we must consider the active history of the whole southern plate, especially the structural history analysis of the Yangtze block and the Cathaysian ancient continental margin.

There are disputes about the structural attributes of Hunan, and there are different opinions. From the viewpoint of geomechanics, Li Siguang discussed the "Cathaysian multi-character structure", "Hunan mountain structure", "Nanling east-west structure" and "Wuling multi-character structure" involving Hunan, and preliminarily analyzed the structural system of Hunan. From the perspective of geological and historical development, while summarizing the main geological structural characteristics in China, Huang determined the "Qiyang Arc" protruding from central Hunan to the west, which was called a "beautiful, almost arc-shaped" arc structure; Wu et al. established "Wei Zi spiral structure" and "Dayishan syncline structure" and named "Qiyang arc" as "Qiyangshan font" (Hunan Bureau of Geology and Mineral Resources,1988); Tian Qi published the Relationship between the Axis of Xuefeng Mountain in Hunan and Paleozoic transgression, expounded the tectonic position, nature and significance of Hunan, and created the term "Xuefeng Movement". Chen (1992) published a series of articles from the viewpoint of diwa theory, analyzed the structural characteristics of Hunan, and applied this theory to the study of metallogenic regularity of gold deposits in Hunan and tin polymetallic deposits in South China, especially in the research and application of structure and gold deposits, and made many major breakthroughs; During the period of 1977, Zhao Hengsheng and Zhu Zhenmin, the dispatching teams of Hunan Province, studied the contact relationship between Permian and Triassic in Qixingjie, Lianyuan, and proved that they were continuous deposits with rich paleontological and petrological data, which changed the traditional view of false integration. In addition, according to the characteristics of sedimentary types and sedimentation, they put forward a new understanding of "Jiangnan ancient land" (Geology of Nanling Granite edited by Chen Xincai and Mo Zhusun 1980), and systematically summarized the structural characteristics and metallogenic model of Nanling granite. After 1980s, with the deepening of nappe structure research, many ancient lands were suspected. In particular, Xu Jinghua (1980, 1987) put forward many new understandings of South China's geotectonics. He believes that the ancient land in the south of the Yangtze River is an Indosinian collision orogenic belt, and that Fan Jingshan and Jiuwandashan in northern Guangxi are paleozoic with sporadic Feilai and Xuefeng peaks. In this way, whether "Jiangnan ancient land" (including Xuefeng ancient land) is in situ, quasi-in situ or an alien body has become a focus of structural research in this area, and there are still different opinions.

199 1 year, Chen Xincai and others studied the structural properties and evolution of Xuefeng Mountain and its adjacent areas, and discussed the tectonic evolution background of South China. It was found that there were three large ductile shear zones in different directions in Hunan, which refreshed the content of structural research in Hunan. Among them, the different mechanisms of structural deformation in the three major tectonic stages, that is, the deformation mechanisms in Wuling stage and Caledonian stage are flattening and ductile-brittle ductile shear. The discovery of ductile shear zone is of great significance to the search and prediction of gold deposits. The Indosinian-Yanshanian tectonic deformation mechanism is strike-slip brittle shear, and brittle shear deformation is mainly concentrated in the main section, forming a long-distance nappe thrust, thus opening up a new way to find hidden minerals under nappe.

During 1999, Liang Xinquan and others proposed that the thickening and thinning of lithosphere caused by convergent mantle creep and divergent mantle creep were the fundamental reasons for Mesozoic tectonic deformation and activation in this area. It is considered that there are two sets of opposite thrust-shear nappe tectonic systems in Xuefeng Mountain structural belt in Mesozoic, which are the products of multi-directional crustal movement and deformation in different evolution periods.

It can be seen that it is of practical significance to strengthen the deep geological research in Hunan Province. In recent years, Wu, 1995, 1999 and other research results on post-orogenic extensional structures and basins show that post-orogenic extensional structures and basins are common in many orogenic belts. At the same time, the formation and evolution of sedimentary basins are also the products of various rheological dynamic processes in the lithosphere, and are the places where different mineral resources gather. The main changes of basin tectonic development occurred simultaneously with the changes of continental margin and continental interior. There are many interdependent relationships between orogeny and basin formation, such as dynamic environment (stretching, squeezing and shearing), material environment (deep compensation, shallow direct erosion and giving), fluid interaction (interlayer flow), stress participation (direct participation and stress transfer) and so on. Therefore, the mutual restriction between horizontal tension and compression and vertical subsidence, the change of magmatic-thermal history and tectonic stress field, and the migration of subsidence center of sedimentary basin are all important components of the unity and organic connection between orogenic belt and basin research.

Orogenic belt and basin are two tectonic units alternately distributed in continental block, which are important aspects of continental dynamics and even geology research. The combination of orogenic belt and basin research is the key to the development of continental resources, geotectonic theory and other geological theories, and it is also a new growth point of geological science research in the future.

As one of the key research objects in the field of earth science and tectonic geology, the study of orogenic belt has a history of nearly a hundred years, and it is currently in the central stage from scientific practice exploration to new theoretical creation and generalization. As early as the middle and late19th century, some famous geologists at that time, such as Gilbert, de Lapprand and Dana, discussed the process and types of orogeny, the difference between orogeny and land-building, orogeny and the formation of mountains. Hall and Dana put forward the word geosyncline through the investigation and study of Appalachian mountains, which is an early classical exposition on geosyncline and orogenic belt. It involves geosyncline subsidence, sedimentation, magmatic activity, deformation, metamorphism and lateral compressive stress, which makes folds uplift and form orogenic belts. These understandings have always been generally accepted by geologists. By the beginning of the 20th century, it was still pointed out that "regional angle unconformity" was an episodic (cyclic) process, which indicated that the tectonic movement in the orogenic belt changed the stratigraphic combination and deformation. In the late 1960s, the rise of plate tectonics theory provided a new idea for the study of orogeny. That is to say, the formation and evolution of orogenic belts reflect the process of lithospheric plates from dissociation (opening of ocean basins of different scales) to convergence (closing of ocean basins). In space, orogenic belts are often suture zones between plates or marginal zones where plates converge. With the help of plate theory, it has played a certain deepening role in explaining the formation mechanism of orogenic belts-the correlation between horizontal movement (ocean basin expansion) and vertical movement (ocean basin subduction), the temporal and spatial relationship of various magmatic activities in orogenic belts and the classification of orogenic belts (Wu, 1999). By the late 1980s, with the further development of various testing methods, geologists had a certain understanding of the deformation, metamorphism and dynamic characteristics of the earth's continent, but the theory of plate tectonics could not provide an exact explanation for the dynamic effects of the continent (such as various deformations, large-scale strike-slip and thrust faults after orogeny). Therefore, according to the behavior, function, history and evolution of the mainland, combined with the harmonious relationship between man and nature and human needs, continental dynamics aimed at promoting social development was born.

In the mid-1950s, Chen pointed out that the continental tectonic system in eastern China had undergone a fundamental change after Mesozoic, and made a typical analysis of the tectonic development history and metallogenic characteristics of Yinshan in the north and southeast coast of China, concluding that these two areas were neither platform areas nor geosyncline areas as mentioned in historical documents. Under the background of late Paleozoic-early Mesozoic-China platform, general tectonic-magmatic activation began to appear, and the regional geological characteristics were different from platform stage and geosyncline stage. Therefore, the concepts of "platform activation" and "activation zone" were put forward, and the theory was applied to the study of metallogenic regularity of gold deposits in southern Hunan and tin polymetallic deposits in southern China, especially in the research and application of structure and gold deposits, and many major breakthroughs were made (Chen Xincai, Chen Guo,/. Therefore, the research on the evolution, dynamic mechanism and effect of orogenic belt since Mesozoic and Cenozoic can provide more direct scientific basis for the current social needs such as developing resources, solving environmental degradation and predicting frequent disasters.