Search

Oceanic lithosphere is generated at divergent plate boundaries and disappears at convergent plate boundaries. Seafloor spreading and plate subduction together constitute the physical coupling and mass conservation relationships to the movement of lithospheres on Earth. Subduction zones are a key site for the transfer of both matter and energy at converging plate boundaries, and their study has been the hot spot and frontier of Earth system science since the development of plate tectonics theory. As far as the dynamic regime and geothermal gradient of convergent plate margins are concerned, they have different properties in different stages of the subduction zone evolution. In general, the early low-angle subduction leads to compressional tectonism dominated by low geothermal gradients at the plate interface, and the late high-angle subduction results in extensional tectonism dominated by high geothermal gradients at the plate interface and its hanging wall. Active rifts are produced along suture zones through not only slab rollback or slab breakoff in the terminal stage of oceanic subduction but also foundering and thinning of the lithosphere in the post-subduction stage. Due to the differences and changes in the geometric and thermobaric structures of convergent plate margins, a series of changes in the type of metamorphism and magmatism can occur in active and fossil subduction zones. Dehydration and melting of the subducting oceanic crust are prominent at subarc depths, giving rise to fluids that dissolve different concentrations of fluid-mobile incompatible elements. The subduction zone fluids at subarc depths would chemically react with the overlying mantle wedge peridotite, generating metasomatites as the mantle sources of mafic magmas in oceanic and continental arcs. However, these metasomatites did not partially melt immediately upon the fluid metasomatism to trigger arc magmatism, and they did not melt until they were heated by asthenospheric convection due to rollback of the subducting slab. Therefore, recognition of the changes in the dynamic regime and geothermal gradient of subduction zones in different stages of plate convergence not only provides insights into geodynamic mechanisms of the tectonic evolution from subduction zones to orogenic belts, but also places constraints on the formation and evolution of different types of metamorphic and magmatic rocks within the advanced framework of plate tectonics. [ABSTRACT FROM AUTHOR]

In order to better understand the role of post-collisional mafic magmatism at convergent plate boundaries in revealing the earth's evolution, this paper has systematically summarized the research history of post-collisional mafic magmatism, different types of collision and their influence on the nature of orogenic mantle, the concept and implication of post-collisional magmatism, and the relationship between post-collisional mafic magmatism and orogenic mantle evolution and mineralization. Post-collisional mafic igneous rocks are not only the direct records for studying the nature and evolution of orogenic mantle, but also the important carriers for regional mineralization. However, the type and quantity of the crustal materials involved in modifying the overlying lithospheric mantle during collisional orogeny, the process and mechanism of such modification, and the major control factors and mechanism of mafic magmatism-related mineralization during the post-collisional period are the main contents and direction of future researches in this field. Therefore, the study of post-collisional mafic magmatism is of significant implications for developing the theory of plate tectonics. [ABSTRACT FROM AUTHOR]

Crustal subduction and continental collision is the core of plate tectonics theory. Understanding the formation and evolution of continental collision orogens is a key to develop the theory of plate tectonics. Different types of subduction zones have been categorized based on the nature of subducted crust. Two types of collisional orogens, i.e. arc-continent and continent-continent collisional orogens, have been recognized based on the nature of collisional blocks and the composition of derivative rocks. Arc-continent collisional orogens contain both ancient and juvenile crustal rocks, and reworking of those rocks at the post-collisional stage generates magmatic rocks with different geochemical compositions. If an orogen is built by collision between two relatively old continental blocks, post-collisional magmatic rocks are only derived from reworking of the old crustal rocks. Collisional orogens undergo reactivation and reworking at action of lithosphere extension, with inheritance not only in the tectonic regime but also in the geochemical compositions of reworked products (i.e., magmatic rocks). In order to unravel basic principles for the evolution of continental tectonics at the post-collisional stages, it is necessary to investigate the reworking of orogenic belts in the post-collisional regime, to recognize physicochemical differences in deep continental collision zones, and to understand petrogenetic links between the nature of subducted crust and post-collisional magmatic rocks. Afterwards we are in a position to build the systematics of continental tectonics and thus to develop the plate tectonics theory. [ABSTRACT FROM AUTHOR]