Tectono-magmatic and kinematic evolution of the Africa-Europe plate boundary: from Cadomian subduction to Western Mediterranean tectonics
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Processes driving orogenic styles and long-term isostatic versus dynamic support of the topography have been largely debated in domains of plate convergence. The tectonic evolution of orogens reflect the interactions between mantle flow driving plates and the inherited rheology and composition of moving plates. Here we show that the tectono-magmatic evolution of the European lithospheric mantle and structure, which inherits past subduction/collision (e.g. Cadomian, Variscan) and rifting events (Tethys/Atlantic), control first-order crust-mantle coupling, plate-mantle coupling, defining Alpine-type orogens. The lack of thermal relaxation needed to maintain rheological contrasts over several hundreds of millions of years requires high mantle heat flux below Central Europe since at least the Permian. A combination of edge-driven convection on craton margins and asthenospheric flow triggered by rift propagation during the Atlantic and Tethys rifting is suggested to be the main source of heat. Timing and rates of exhumation recorded across Western Europe during the Cenozoic convergence reveal an additional control by the architecture of Mesozoic rifted margins that defined a complex array of small continental blocks with European affinity (e.g. S-Iberia, Ebro/Sardinia-Corsica) caught between the East European and West African cratons, and Adria. By 50 Ma the acceleration of orogenic exhumation, from the High Atlas to the Pyrenees, occurred synchronously with the onset of extension and magmatism in the West European Rift. Extension marks the onset of distinct orogenic evolution between Western Europe (Iberia) and the Alps (Adria) in the east, heralding the opening of the Western Mediterranean. While the details of the Cenozoic topographic history of peri-Mediterranean orogens are understood to be controlled by the rheology and architecture of rifted margins combined with changing large-scale kinematic boundary conditions (e.g. Atlas, Betics, Pyrenees, Alps), their post-10 Ma, quaternary to current surface and tectonic evolution appears to illustrate increasing control by magmatism and flow at the asthenosphere-lithosphere boundary.Keywords:
Passive margin
geodynamics
geodynamics
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geodynamics
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Observations suggest that global (plate) tectonics operates on the Earth. The most characteristic features of the global tectonics are ocean floor spreading in mid-ocean ridges and subduction in deep-sea trenches. These processes imply the existence of mantle flow. However, within the framework of the plate tectonics, it is impossible to build a consistent quantitative theory of mantle convection because one cannot answer the question of where the tectonic plate “terminates”. From a mathematical point of view, the difficulty of global tectonics is that there are no boundary and initial conditions that would allow one to consider the evolution of some isolated part of the planet (e. g., the upper mantle). Therefore, to obtain a physically justified answer to the questions about the causes and energy sources of mantle motions, it is necessary to consider an evolution of the planet as a single whole. This formulation of the problem leads to the global geodynamics. Unlike the global tectonics, which in fact ignores the existence of the Earth’s core, for the global geodynamics the liquid outer and solid inner core, as well as the processes at the boundary between them and at the boundary between the core and the mantle, which decisively influence the mantle dynamics, are the main objects of the study. In this review, we confine ourselves to the global heat balance of the Earth. In the coming years, the results of the geoneutrino experiment will make it possible to obtain a reliable estimate of the total rate of radiogenic heat production in the Earth and to estimate the heat flow from the core to the mantle. Even this alone will significantly narrow the choice of models describing processes in the core. An ascertainment of the temperature at the inner/outer core interface and an elucidation of the mixing nature in the outer core will allow one to reduce an uncertainty of the temperature at the base of the mantle and to formulate a boundary condition problem for the mantle flow dynamics. Thus, a bridge from global geodynamics to global tectonics will be thrown and the conceptions of the latter will be put on a firm physical basis.
geodynamics
Hotspot (geology)
Core–mantle boundary
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geodynamics
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Trap (plumbing)
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Mantle plume
geodynamics
Hotspot (geology)
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By 1968, J. Tuzo Wilson had identified three basic elements of geodynamics: plate tectonics, mantle plumes of deep origin, and the Wilson Cycle of ocean opening and closing, which provides evidence of plate tectonic behavior in times before quantifiable plate rotations. My pre-1968 experience disposed me to try to play a part in testing these ideas. Most recently, with colleagues, I have been able to show that deep-seated plumes of the past ∼5.5 × 10 8 years have risen only from narrow plume generation zones (PGZs) at the core-mantle boundary (CMB) mostly on the edges of two Large Low Shear wave Velocity Provinces (LLSVPs) that have been stable, antipodal, and equatorial in their present positions for hundreds of millions of years and perhaps much longer. A need now is to develop an understanding of Earth that embodies plate tectonics, deeply subducted slabs, and stable LLSVPs with plumes that rise from PGZs on the CMB.
geodynamics
Mantle plume
Hotspot (geology)
Convergent boundary
Tectonophysics
Continental drift
Pacific Plate
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