HYDRODYNAMIC PROCESSES ASSOCIATED WITH PLUME RISE AND CONDITIONS FOR ERUPTION CONDUIT FORMATION
A.A. Kirdyashkin, N.L. Dobretsov, A.G. Kirdyashkin, I.N. Gladkov, and N.V. Surkov
United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the RAS,
3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Thermochemical plume, laboratory modeling, pressure distribution, shear stress, critical thickness of above-plume massif, eruption conduit, high-melting layer
Pages: 869-885
Abstract
We present results of laboratory modeling of thermochemical plumes rising from the core-mantle boundary. Laboratory modeling of plume rise based on the laboratory experiments shows that a plume keeps the same diameter till its eruption to the surface if the melting temperature of the ambient material remains invariable but develops a mushroom-shaped head if impinges on a high-melting layer.
Using theoretical modeling, we obtained pressure distribution in a rising plume and estimated an excess of pressure in the melt beneath the plume roof over the lithostatic pressure. The critical thickness of above-plume massif at which eruption conduit forms is compared with the available estimates from geological data.
A high-melting layer can occur in the upper mantle between 400 and 650 km at a certain relation between the melting curve of natural peridotite KLB-1 and melt temperature at the plume roof. The structure of a plume impinging on a high-melting layer is predicted in the reported model.
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