Thermal and hydrodynamic conditions of magma chamber and melting conduit formation in the subduction zone
A.A. Kirdyashkin, A.G. Kirdyashkin, V.E. Distanov, I.N. Gladkov
Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk,Russia
Keywords: free convective flows, subduction zone, plume conduit, melt, primary chamber, heat power
Abstract
A model of a thermochemical plume in the subduction zone is presented here, based on experimental modeling and theoretical analysis, as well as geological and geophysical data. A thermochemical plume originates at the boundary between the upper and lower mantle when a chemical additive is present in the crustal layer of the subducting oceanic lithospheric plate, which lowers the melting point of the crustal layer substance. The structure of thermal gravitational flows in the plume conduit melted out in the crustal layer was established due to experimental modeling. The heat power at the plume base and the heat power transferred by the plume conduit to the surrounding mantle were determined. The depth of location of a primary magma chamber, from which the thermochemical plume originates and rises to the surface of the continent, where the volcano is formed, was determined depending on the crustal layer thickness, the rate of subduction, and the angle of subducting lithospheric plate inclination. The primary magma chamber is formed in a region where the rates of subduction and melting of the crustal layer are equal in magnitude and directed oppositely. A model of the origin of a thermochemical plume on the primary chamber roof is presented, and the conditions of the plume conduit outcrop are determined. Based on theoretical modeling, geological and geophysical data on the depth of the primary chamber origin, the thermal and hydrodynamic conditions for the existence of a thermochemical plume incipient from the primary chamber and responsible for volcano formation on the surface were found.
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