Geology is a science that mainly studies the surface layer of solid crust or lithosphere. The research content mainly includes the material composition, internal structure and formation and evolution history of the solid earth, and reveals the objective laws of various geological processes and processes of the earth from different angles. In the branch of geology, tectonics plays an important role. By synthesizing the data of various branches of geology, it summarizes the geological evolution history of regions or regions and even the whole world, thus establishing the dynamic relationship between various geological processes and helping people to correctly and reasonably understand the evolution of the earth. The process of regional geological evolution directly controls the changes of regional topography, landforms and climate, the distribution of mineral resources and the occurrence of some geological disasters. Therefore, the study of regional structure and evolution history is of great theoretical and practical significance for deepening geological research, deeply understanding the changes and laws of natural resources and environment closely related to human life, and providing resource guarantee and environmental support for the sustainable development of human society.
Tectonics is one of the most active subjects in geological research in China. Since the late19th century, the study of China geotectonics has a history of 100 years. Ren Jishun, Yang et al. This paper makes a wonderful summary of the history of geotectonic research in China, and divides the process of geotectonic research in China into the following stages [1 2]: 1949 years ago was the founding and foundation period; 1949 ~ 1976 is a period of development, and a hundred schools of thought contend; 1976 to the end of the 20th century was the period when plate tectonics prevailed, and it went through the stages of reflection and urgent pursuit in the 1970s, integration with the international community in the 1980s, and in-depth study of major geological problems in continental lithosphere in the 1990s. Since 2 1 century, it has entered a new voyage of structural research. The new topic of "Beyond Plate Tectonics" put forward by American scientists in "A New Journey of Tectonic Geology and Continental Dynamics" is undoubtedly an important starting point for the new voyage. Chinese mainland has many tectonic units, complex geological evolution history and many unique geological phenomena, which is an ideal place to study the formation and evolution process of the continent and its dynamic mechanism. More than a century of geological research history, especially large-scale regional geological mapping, has accumulated rich data, which has laid a solid foundation for summing up the laws of regional geological evolution and further studying and discussing continental dynamics. In this new period, the main tasks of regional geotectonic research in China should be to clear up the existing regional data in detail, summarize the laws of regional evolution, incorporate regional geotectonic research into the scientific research of the earth's surface, and explore the formation and evolution history and its dynamic mechanism of Chinese mainland from the perspective of studying the evolution and development of global continents, so as to serve the national economic construction.
1. 1.2 plate tectonic theory and continental dynamics
The theory of plate tectonics originated from the study of the ocean, and its basic idea is that the upper layer of solid earth can be divided into two spheres with significantly different physical properties in the vertical direction, namely, the rigid lithosphere in the upper layer and the plastic asthenosphere in the lower layer; The rigid lithosphere can be divided into several plates with different sizes in the lateral direction, and the boundaries between the plates are the mid-ocean ridge, the trench and the transform fault. The plates float on the plastic asthenosphere for large-scale movement, which makes the plates disperse, converge and slip, leading to ocean expansion, continental disintegration and reorganization, and earthquake and volcanic activity at the plate boundary. The interior of the plate is relatively stable, and the edge of the plate becomes a zone with strong tectonic activity due to the interaction of adjacent plates; The interaction between plates fundamentally controls the process of various geological processes and also determines the basic pattern of global lithospheric movement and evolution. It is generally believed that the motive force of plate movement comes from mantle convection and submarine expansion.
Although the plate tectonic theory perfectly describes the mechanism of submarine expansion and subduction of ocean plate dynamics, and better explains the dynamics of ocean opening and closing evolution and continental division and reorganization, it has encountered considerable difficulties in explaining the complex process of continental material growth and decrease and the geological evolution within the continent because it emphasizes horizontal movement and ignores vertical movement and mantle convection, and ignores the interaction between different layers of the earth. Many scholars believe that there is a huge dynamic difference between the continent and the ocean, at least in the depth of the upper mantle, and the existing plate tectonic theory can not simply explain the dynamic process of the continent. With the increasingly severe problems of resources, environment and geological disasters faced by human society, it has become a great challenge and opportunity for geologists to explore the characteristics and genetic mechanism of geological processes in the mainland, especially after the collision, so that earth science can better serve the development of human society.
For a long time, the origin and evolution of continents have been the focus of geologists' attention. With the in-depth study of solid earth science theory, people's understanding of the mainland is entering a new height, that is, from the partial understanding of the shallow continental crust to the overall understanding of the continental crust-mantle system. With the increase of geoscience information and the development of lithosphere plan, the study of lithosphere structure and evolution is turning to the establishment of global dynamics and continental dynamics theory. On the one hand, this makes the theory of plate tectonics perfect and develop, on the other hand, it also questions and refutes the basic principle of plate theory and the action process of plate movement. At the same time, structural theoretical models such as viscous flow model, back plate structure, surge structure [3] and mantle plume structure [4] have been put forward one after another, and the dynamic mechanism model of continental evolution is developing towards diversification. Therefore, whether from further deepening the plate tectonic theory or developing new geodynamics, exploring continental dynamics has become one of the important topics of solid earth science research at present and in the future.
1. 1.3 continental dynamics and its role in continental tectonic research
Continental dynamics is an important scientific problem and research field based on plate tectonic theory. This paper mainly studies the dynamic mechanism related to the formation and evolution of the continent, and expounds how the continent interacts with the whole earth system by studying various basic problems such as the formation process and evolution history of the continent. This concept is put forward based on the obtained data, which shows that the lithosphere and even the upper mantle structure of the mainland and the ocean are different. The formation, preservation and extinction of continental lithosphere is much more complicated than the growth and extinction of marine lithosphere described by plate tectonics.
Continental dynamics obviously inherits and develops the basic theory of plate tectonics, but it is beyond the research scope of plate tectonics in depth and breadth. In depth, it tries to refine the process of plate movement, explore and reveal the formation mechanism and process of orogenic belt structure, magma, metamorphism and other products in the process of plate movement, unlike the previous plate tectonic theory, which is limited to the description of various structural deformation characteristics and rock assemblage characteristics in the plate tectonic environment. Broadly speaking, it has studied many important problems that have not been involved in plate tectonics before, such as the formation of the rheological layer in the crust and its influence on the strain of the upper crust, the coupling between the mantle and the deep crust, the formation mechanism of Moho surface, the influence of fluid and heat on the stress field, the large-scale fluid migration and its consequences during orogeny, the exchange and recycling of crust and mantle materials, and the stripping process of deep rocks. Judging from the evolution of orogenic belts, the focus of previous plate tectonics research is to determine whether there is an ocean and what kind of ocean it is. Did you dive? What kind of continental margin? What is the way of plate collision and when will it end? Basically, it does not involve the history after the collision and the geological process within the continent. The study of continental dynamics focuses on the study of continental interior, including the main processes of lithospheric thickening and uplift, and the emplacement and denudation of rocks in orogenic belts, that is, the expression of extrusion, strike-slip and extension during the formation of orogenic belts, and their relationship with the stress caused by plate movement and buoyancy caused by continental crust thickness, as well as the formation, emplacement and denudation of granite, mafic and ultramafic rocks and deep metamorphic rocks. [5] and geological processes and their internal continents.
The study of continental dynamics does not oppose the theory of plate tectonics. Although plate tectonics theory has its limitations, it can better explain the evolution process of ancient oceans and the continental assembly process during the formation of continents, while continental dynamics explores the evolution and dynamics of continents before and after the formation of ancient oceans. Can the continental crust really circulate? The answer is yes. Denudation and redeposition, deep lava magmatism and metamorphism are constantly transforming the ancient continent into a young continent. Just as we found few fragments of ancient marine lithosphere on the mainland, which shows that most of the marine lithosphere has returned to the mantle, the reason why there are few ancient lithospheres on the mainland is probably that they have been transformed into young continental crust. The question is what is the mechanism of this transformation, and how long is the time limit, which we still need to pursue tirelessly. When the original characteristics of continental dynamics were fully revealed and organically combined with plate tectonics, the real global tectonic theory was born [6].
Since 1990s, international geosciences have attached great importance to the study of continental dynamics, and the focus of international lithosphere plan has shifted from the structure, structure and evolution of lithosphere to process and dynamics, among which continental lithosphere, deep process and dynamics have become two of the four main fields of international lithosphere plan. The National Science Foundation, the Geological Survey and the Department of Energy jointly put forward and implemented the "Continental Dynamics Plan" for 30 years (1990 ~ 2020), aiming at establishing the dynamic evolution models of the continent at different scales, and providing a new basis for earthquake dynamics prediction, three-dimensional prediction of oil, gas and metal minerals and large-scale ecological environment change prediction. The geoscience strategy report (1994 ~ 2000) of the Natural Environment Research Council of the United Kingdom also listed continental dynamics as its key research field, and focused on four issues, such as the deep structure and composition of the continent, the structure of the continental margin, the role of vertical crustal movement in the rock cycle and its relationship with the surface action. In addition, the "European Lens" project initiated by 16 European countries aimed at the origin and evolution of the continent was implemented from 1992 to 2/kloc-0 at the beginning of the century, aiming at improving the understanding of the evolution and control of the earth's crust and mantle structure and its dynamic process with time.
Chinese mainland's dynamics research is almost in step with the international research [7]: In the early 1990s, China geologists began to discuss the dynamics of Chinese mainland, and listed continental dynamics as a priority research field in the ninth five-year plan for basic research. For this purpose, the Ministry of Science and Technology has established major scientific projects such as "Continental Scientific Drilling" and "Modern Crustal Movement Observation Network" and national key basic research and development projects such as "Formation and evolution of the Qinghai-Tibet Plateau and its environmental and resource effects" and "Continental Deep Dive". By setting up a series of major, key and general projects, the National Natural Science Foundation of China supports experts to carry out multidisciplinary research on the lithospheric structure and evolution of the main structural units (orogenic belt, basin and shield) in Chinese mainland. China Academy of Sciences, Ministry of Land and Resources, Seismological Bureau of China and other departments have also deployed related large-scale observation, investigation and research projects on continental dynamics. Through the above work, we have gained a lot of new knowledge about the lithospheric structure and evolution of the main orogenic belts and other tectonic units in China, and accumulated a lot of valuable geological, geophysical and geochemical data, which laid a good foundation for our further systematic planning and continental dynamics research.
The geological structure of Shandong Province is quite complicated. The formation of Archean TTG rock series, the formation and exhumation of Sulu ultrahigh-pressure metamorphic belt, the development of alkaline granites in different periods (Proterozoic, Neoproterozoic and Mesozoic), the genesis and denudation of large-scale granites in Mesozoic, the explosive enrichment of alkaline calc-alkaline volcanic rocks in Mesozoic mainland, the eruption of gold elements in Jiaobei and Cenozoic mantle-derived basalts are all typical geological tectonic events in China and even the world, and they are also classic plate structures. It can be said that Shandong land area is one of the best areas to solve the problem of continental dynamics, and it is a natural laboratory for continental dynamics research. At the same time, studying the geological structure pattern and continental crust evolution in Shandong Province will certainly help to solve the problems of resources, environment and geological disasters faced by Shandong Province.