gtcrustГеодинамика и тектонофизикаGeodynamics & Tectonophysics2078-502XInstitute of the Earth's crust of the Russian Academy of Sciences, Siberian Branch10.5800/GT-2018-9-1-0348gtcrust-532Research ArticleТЕКТОНОФИЗИКАTECTONOPHYSICSГИДРОДИНАМИКА И ТЕПЛОМАССООБМЕН В ГРИБООБРАЗНОЙ ГОЛОВЕ ТЕРМОХИМИЧЕСКОГО ПЛЮМАHYDRODYNAMICS AND HEAT AND MASS TRANSFER IN MUSHROOM-SHAPED HEADS OF THERMOCHEMICAL PLUMESКирдяшкинА. Г.KirdyashkinA. G.

Анатолий Григорьевич Кирдяшкин, докт. техн. наук, в.н.с.  

Новосибирск.

Anatoly G. Kirdyashkin, Doctor of Technical Sciences, Lead Researcher.

agk@igm.nsc.ruКирдяшкинА. А.KirdyashkinA. A.

Алексей Анатольевич Кирдяшкин, докт. геол.-мин. наук, профессор.   

Новосибирск.

Alexei A. Kirdyashkin, Doctor of Geology and Mineralogy, Professor of RAS, Head of Laboratory. 

Novosibirsk.

aak@igm.nsc.ruИнститут геологии и минералогии им. В.С. Соболева СО РАН.РоссияS. Sobolev Institute of Geology and Mineralogy, Siberian Branch of RAS.Russian FederationИнститут геологии и минералогии им. В.С. Соболева СО РАН; Новосибирский национальный исследовательский государственный университет.РоссияS. Sobolev Institute of Geology and Mineralogy, Siberian Branch of RAS; Novosibirsk National Research State University.Russian Federation20182403201891263286Copyright © Кирдяшкин А.Г., Кирдяшкин А.А., 20182018Кирдяшкин А.Г., Кирдяшкин А.А.Kirdyashkin A.G., Kirdyashkin 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/532

Описана модель мантийного термохимического плюма, и представлена схема его зарождения на границе ядро–мантия. Приведены основные соотношения для определения тепловой мощности термохимического плюма и диаметра его канала. Плюмы с грибообразной головой имеют относительную тепловую мощность 1.9<Ka<10. После прорыва расплава из канала плюма на поверхность происходит плавление вдоль подошвы массива коры над кровлей плюма и образуется грибообразная голова плюма, т.е. формируется крупное интрузивное тело (корневой батолит). На основе данных лабораторного и теоретического моделирования представлена тепловая и гидродинамическая структура термохимического плюма с грибообразной головой. Определены основные параметры некоторых плюмов, ответственных за образование батолитов Северной Азии. Гидродинамика и теплообмен в грибообразной голове плюма рассмотрены на основе модели плоского горизонтального слоя жидкости. Оценены величины изменения температуры и скорости течения в расплаве головы плюма. Расчеты состава расплава в грибообразной голове плюма проведены в два этапа: 1) после осаждения тугоплавких минералов на подошву головы плюма; 2) после осаждения плагиоклаза в расплаве, образовавшемся после первого этапа и содержащем 61.5 % плагиоклазового компонента. Результаты расчетов приведены в виде таблиц, представляющих процентное весовое содержание оксидов, а также нормативный минералогический состав расплава при температуре Tр=1410 °C и Tр=1380 °C. Расчеты толщины слоя остаточного расплава проведены для Хэнтэйского плюма, у которого толщина головы l=d=29 км (d – диаметр канала плюма). На основе предложенной модели плюма с грибообразной головой в результате расчетов может быть получен нормативный состав расплава, близкий к составу нормальных гранитов.

The model of a thermochemical mantle plume is described. The scheme of origination of the plume from the core-mantle boundary is presented. The basic ratios for determining the thermal power and the diameters of thermochemical plumes are given. After eruption of the melt from the plume conduit to the surface, melting occurs along the base of the crustal block above the plume roof, resulting in the formation of a mushroom-shaped head of the plume, which means that a large intrusive body (deep-rooted batholith) is formed. The relative thermal power of such plumes is 1.9<Ka<10. Based on the laboratory and theoretical modeling results, we present the thermal and hydrodynamic structure of the thermochemical plume with the mushroom-shaped head. The parameters of some plumes, that are responsible for formations of batholiths in North Asia, are estimated from the geological data, including the age intervals and the extent of magmatism. Relying on the model of the flat horizontal liquid layer, hydrodynamics and heat transfer of the mushroom-shaped plume head are considered. The variations in temperature and flow velocity in the melt of the plume head are assessed. The compositional changes in the melt of the plume head are determined by stages: (1) after settling of refractory minerals; (2) after settling of plagioclase in the melt resulting from the first stage. The tables show the calculation data, including the weight contents of oxides and the normative compositions for the melts at Tmelt=1410 °C and Tmelt=1380 °C. The thickness of the residual melt is estimated for the case of the Khentei plume. Its head’s thickness (l) is equal to the plume conduit diameter (d): l=d=29 km. The proposed model of the plume with the mushroom-shaped head was used to calculate the normative composition of the melt with a chemical composition similar to that of normal granites.

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