References

gtcrust

Геодинамика и тектонофизика

Geodynamics & Tectonophysics

2078-502X

Institute of the Earth's crust of the Russian Academy of Sciences, Siberian Branch

10.5800/GT-2018-9-1-0349

gtcrust-533

Research Article

ТЕКТОНОФИЗИКА

TECTONOPHYSICS

ДВИЖУЩИЕСЯ ДЕФОРМИРУЕМЫЕ КОНТИНЕНТЫ, СМОДЕЛИРОВАННЫЕ АКТИВНЫМИ МАРКЕРАМИ: ЗАКРЫТИЕ И РАСКРЫТИЕ ОКЕАНОВ, РЕЦИРКУЛЯЦИЯ ОКЕАНИЧЕСКОЙ КОРЫ

MODELING OF MOVING DEFORMABLE CONTINENTS BY ACTIVE TRACERS: CLOSING AND OPENING OF OCEANS, RECIRCULATION OF OCEANIC CRUST

Бобров

А. М.

Bobrov

A. M.

Александр Марович Бобров, канд. физ.-мат. наук, в.н.с.

Москва.

Alexandr M. Bobrov, Candidate of Physics and Mathematics, Lead Researcher.

Moscow.

a_m_bobrov@yahoo.com

Баранов

А. А.

Baranov

A. A.

Алексей Андреевич Баранов, канд. физ.-мат. наук, в.н.с.

Москва.

Aleksei A. Baranov, Candidate of Physics and Mathematics, Lead Researcher.

Moscow.

Baranov@ifz.ru

Институт физики Земли им. О. Ю. Шмидта РАН.РоссияO.Yu. Schmidt Institute of Physics of the Earth of RAS.Russian Federation

Институт физики Земли им. О. Ю. Шмидта РАН; Институт теории прогноза землетрясений и математической геофизики РАН.РоссияO.Yu. Schmidt Institute of Physics of the Earth of RAS; Institute of Earthquake Prediction Theory and Mathematical Geophysics of RAS.Russian Federation

2018

24032018

91287307

2018

Бобров А.М., Баранов А.А.

Bobrov A.M., Baranov A.A.

Данная работа распространяется под лицензией Creative Commons Attribution 4.0.

This work is licensed under a Creative Commons Attribution 4.0 License.

https://www.gt-crust.ru/jour/article/view/533

В численных экспериментах изучена эволюция системы мантия – движущиеся деформируемые континенты. Континенты движутся самосогласованно с мантийными течениями термокомпозиционной конвекции. Определены основные черты глобальной геодинамики – схождение и сжатие континентов, возникновение и исчезновение зон субдукции, бэкроллинг зон субдукции, перестройка мантийных течений и растяжение континентов с их последующим расхождением, раскрытие и закрытие океанов, а также рециркуляция океанической коры в мантии. Континентальная кора смоделирована активными маркерами, имеющими добавочную вязкость и плавучесть, тогда как континентальная литосфера – маркерами только с повышенной вязкостью, имеющими нейтральную плавучесть. Океаническая кора, в свою очередь, смоделирована активными маркерами, имеющими плавучесть. Принципиальный результат – соответствие численных расчетов реальной двухмодовости динамики Земли: океаническая кора, несмотря на свою положительную плавучесть у поверхности, погружается в зонах субдукции и уходит глубоко в мантию. (Часть океанической коры остается налипшей на окраинах континентов и не тонет, сохраняясь на длительное время.) В отличие от нее, континентальная кора не субдуцирует в зонах субдукции. Континентальная литосфера, несмотря на свою нейтральную плавучесть, за счет вязкости и сцепления с континентальной корой также остается на поверхности. При этом при «наезде» континента на зону субдукции происходит ее исчезновение и локальная перестройка течений в мантии. Изучено влияние перехода базальт – эклогит в океанической коре на структуру мантийных течений и движение континентов. Установлено, что включение в модель эффекта этого перехода существенно меняет картину мантийных течений и положения континентов. Кроме того, появляется новый эффект – возникновение скоплений остатков океанической коры на дне мантии. Вещество океанической коры накапливается на дне мантии неоднородно, образуя несколько скоплений. Поднимаясь вместе с плюмами, вещество океанической коры вновь оказывается на поверхности Земли.

The evolution of the ‘mantle – moving deformable continents’ system has been studied by numerical experiments. The continents move self-consistently with the mantle flows of thermo-compositional convection. Our model (two-dimensional mantle convection, non-Newtonian rheology, the presence of deformable continents) demonstrates the main features of global geodynamics: convergence and divergence of continents; appearance and disappearance of subduction zones; backrolling of subduction zones; restructuring of mantle flows; stretching, breakup and divergence of continents; opening and closing of oceans; oceanic crust recirculation in the mantle, and overriding of hot mantle plumes by continents. In our study, the continental crust is modeled by active markers which transfer additional viscosity and buoyancy, while the continental lithosphere is marked only by increased viscosity with neutral buoyancy. The oceanic crust, in its turn, is modeled by active markers that have only an additional buoyancy. The principal result of our modeling is a consistency between the numerical calculations and the bimodal dynamics of the real Earth: the oceanic crust, despite its positive buoyancy near the surface, submerges in subduction zones and sinks deep into the mantle. (Some part of the oceanic crust remains attached to the continental margins for a long time.) In contrast to the oceanic crust, the continental crust does not sink in subduction zones. The continental lithosphere, despite its neutral buoyancy, also remains on the surface due to its viscosity and coupling with the continental crust. It should be noted that when a continent overrides a subduction zone, the subduction zone disappears, and the flows in the mantle are locally reorganized. The effect of basalt-eclogite transition in the oceanic crust on the mantle flow pattern and on the motion of continents has been studied. Our numerical experiments show that the inclusion of this effect in the model considerably alters the pattern of mantle flows and leads to distinct changes in the evolution of continents. Moreover, a new effect arises – bulging of heavy material (eclogitized former oceanic crust) at the core-mantle boundary, wherefrom it arises with the mantle plumes on the surface of the Earth.

численное моделированиетермокомпозиционная конвекцияконтинентмаркерокеаническая корарециркуляциябэкроллинг

numerical modelingthermo-compositional convectioncontinenttraceroceanic crustrecirculationbackrolling

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The authors declare that there are no conflicts of interest present.