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GLOBAL SHEAR ZONES, EXTENSION QUADRANTS AND MANTLE SUPERPLUMS

GLOBAL SHEAR ZONES, EXTENSION QUADRANTS AND MANTLE SUPERPLUMS. 1 Leonid Rastsvetaev , 1 Tatiana Tveritinova 1 Geological faculty, Moscow state University.

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GLOBAL SHEAR ZONES, EXTENSION QUADRANTS AND MANTLE SUPERPLUMS

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  1. GLOBAL SHEAR ZONES, EXTENSION QUADRANTS AND MANTLE SUPERPLUMS 1 LeonidRastsvetaev,1 Tatiana Tveritinova1Geological faculty, Moscow state University

  2. Many structural pattern’s features of the tectonosphere are associated with the astronomical features of the Earth as a rotating planetary body. The effective viscosity and density, the shape and internal structure of this body are in hydrodynamic equilibrium with the angular velocity of its rotation. Geodetic data indicate that the geoid is a three-axis ellipsoid.Its small axis coincides with the rotation axis of the Earth, the large and middle axes lie in the Equatorial plane. Temperatures, Heat, and Energy in the Mantle of the Earth http://preprod-scitec.liveperformancesales.com/geophysics-images-june/

  3. The main planetary deformation of the Earth as an ellipsoid of rotation The critical circles and the centers of deformations in asymmetric-triaxial Earth ellipsoid (by Catterfeld [1962] with the addition the global shear zones (by Rastsvetaev [Problems of Global correlation, 1980]) 1 – critical parallels, 2 – critical meridiams, 3 – critical diagonals (shear zones), 4 – deformation centers

  4. The shear zones and tensile structures of the triaxial strain ellipsoid(schematic model)

  5. A global zone of shear, tension and compression on the geoid surface in the Mercator projection The meridional compression and latitudinal extension are expressed by the near-Equatorial zone of Alpine folding and the meridional rift and spreading zones, as well as by two conjugate global shear zones ("critical diagonals" of the geoid), dividing the globe into conjugate quadrants of compression and extension (by Rastsvetaev [Problems of Global correlation, 1980] 1 – ancient platforms (Aв–Australian, Aф–African, ВЕ–East European, И–Indian, Ки–Chinese, С–Siberian, СА–North American, ЮА–South American); 2 – young platforms; 3 – Alpine foldbelt: a–more intense, b–less intense; 4-6 – the main disjunctive systems on the continents (a) and in the oceans (b): 4 – thrusts and reverse faults, 5 – shears and zones of shear deformations, 6 – spreading and normal-fault-graben systems; 7 – zones of global shearing of a geoid and nodes of their intersection

  6. Global shear zonesare oriented approximately at 45 degrees to the plane of the Equator and intersect along the minor Equatorial axis of the triaxial earth's ellipsoid. They separate tectonosphere into four quadrants (two quadrants of compression and two extension). In low and middle latitudes these planetary disjunctive systems are expressed by zones of shear deformations (right – NW and left – NE strike); in middle and high latitudes they turn out to be arc-shaped systems of deep vertical faults, reverse or normal faults [Rastsvetaev,1991]. 1-2 – rift zones of oceans (1), continents and marginal seas (2); 3-5 – shear fault systems: on the continents (3), in the structures of the ocean floor (4-5); 6 – compression zones: thrust and convrgent disjunctive-folded systems; 7 – areas of dynamic influence of global shear zones; 8 – exits to the Earth’s surface of the big (a) and small (b) Equatorial axes of the earth ellipsoid;

  7. Temperatures, Heat, and Energy in the Mantle of the Earthhttp://preprod-scitec.liveperformancesales.com/geophysics-images-june/

  8. Tomographic models of transverse wave velocities for depths of 500 km and 2850 km.The color indicates the speed change values from -2% (red) to +2% (blue)(Ritsema, van Heijst, and Woodhouse (1999). Complex shear wave velocity structure imaged beneath Africa and Iceland, Science 286, no. 5446) and hot spot distribution (black circles)(Courtillot, Davaille, Besse, and Stock (2003) Three distinct types of hotspots in the Earth’s mantle. Earth and Planetary Science Letters 205)

  9. Regions of low seismic wave speeds in the mantle tend to geoid sectors around the large Equatorial axes of the Earth. Areas of high seismic wave speedstend to geoid sectors around the polar and small Equatorial axes. This pattern could be due to pressure drop and partial melting of the material in the extension quadrants of the earth's deformation ellipsoid. Comparison "areas of low pressure" at depths of 500 km and 2850 km show a decrease their area with depth, that is, their conical shape. The anomal decompressed zones in lower mantle tend to the zone of Equatorial swelling of the earth ellipsoid and are localized in the Central regions of the African and Pacificextension quadrants fixing the pressure decrease in the depth of these quadrants (along the axis A of the strain ellipsoid).

  10. Hot spots in the system of axes and quadrants of the geoid as the deformation ellipsoid 1–projection of deep extension zones in the centers of African and Pacific plumes 2 – projection of the deep polar zones of compression 3 – the most compressed zone of the Earth (mainland zone) 4 – exits to the surface areas of the global shear (Courtillot, Davaille, Besse, and Stock (2003) Three distinct types of hotspots in the Earth’s mantle. Earth and Planetary Science Letters 205)

  11. Centers of deep extension zones in the global shear zone system Orange coloris the depth of 2850 km, the red lines indicate the anomaly at a depth of 500 km

  12. Schematic CrossSection of the Geoid The New Model Red zone at a depth of 2850km–the main zone of extension and decompression In the center of the zone originate primary superplumes (African and Pacific) Along the planes of the global shear zones, additional decompression conditions can be realized and secondary plumes can arise that contribute to the process of lithosphere extension Under the conditions of complex changes in the mantle matter, other plumes can also arise under tension

  13. Conclusions • Planet Earth is a three-axis ellipsoid of rotation working as natural ellipsoid of deformation. Global shear zones (among all planetary disjunctive systems) play the most important role in the geoid structure. They divide it into four sectors – two compression quadrants (North and South) and two extension quadrants (Pacific and African (Indo-Atlantic)). Seismic tomography data suggest that this division is traced to the entire depth of the active tectonosphere. • Due to the decrease in the total lithostatic pressure partial melting of the mantle material occurs in the deep zones of the extension quadrants, and lower mantle foci of the Pacific and African global superplums and smaller hot spots of the lower and middle latitudes appear. Smelting volatile and low-melting components of the mantle material in zones of the total decompression and in extension quadrants leads to the formation and rise of fluid flows and "actinolite jets“ and includes mechanisms of thermo-gravitational and thermo-chemical convection. • The study of planetary systems of shear, extension and compression is one of the most interesting tasks of global structural Geology. The data obtained indicate the important role of rotation as a factor of global structure formation at different deep levels of our rotating planet.

  14. Thank You for attention!

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