Thermochemical Mantle Convection with Drifting Deformable Continents: Main Features of Supercontinent Cycleстатья
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Дата последнего поиска статьи во внешних источниках: 10 февраля 2021 г.
Аннотация:We employ 2D Cartesian geometry model of thermochemical
convection with non-Newtonian rheology and phase
transitions, in the presence of floating deformable continents. Using
a mantle model with continental crust, lithosphere and the material
of the oceanic crust that can be subjected to eclogitization we study
the stages of supercontinent cycle: assembly, evolution of supercontinent,
its breakup and divergence of continents. Our results
show that cold downgoing flows aggregate continents into a
supercontinent. After its formation, the convection pattern changes:
the subduction zones at the edges of the supercontinent and typical
relatively narrow mantle plumes in the subcontinental mantle arise.
The lifetime of the supercontinent is about 550 Ma. Typical
velocities for continents before collision are 3–10 cm/year, for
supercontinent 0.5–1.5 cm/year and after the breakup 4–8 cm/year.
Despite the small mobility of the supercontinent, there is no significant
warming up of the subcontinental mantle. The temperature
anomaly under supercontinent is less than 50 K and the superplume
does not arise. We obtain that the phase transitions at
410 km and 660 km and the eclogitization of the subducted
oceanic crust affects the supercontinent cycle significantly. Our
results demonstrate certain irregularity of supercontinent cycle. The
typical shear stresses in the mantle are less than 30 MPa; in the
subduction zones and on the continent borders they are
100–250 MPa. Before the breakup maximum shear stress generated
in the supercontinent can reach 200 MPa.