PARAMETERS OF PLUMES OF NORTH ASIA
A.G. Kirdyashkin1, A.A. Kirdyashkin1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Experimental and theoretical modeling, thermochemical plumes, free-convection flows, thermal power, large igneous provinces, batholiths, rift zones
Abstract
This paper presents the thermal and hydrodynamic structure of the conduit of a thermochemical mantle plume based on the results of experimental and theoretical modeling of thermochemical plumes. The basic relations for determining the thermal power and diameter of plumes are given. Depending on the geodynamic setting of eruption, the following types of plumes are distinguished: plumes responsible for the formation of large igneous provinces (LIP); plumes with a mushroom-shaped head, responsible, in particular, for batholith formation; and plumes producing rift zones. Using geological data (extent of magmatism, age of igneous provinces, and sizes of igneous areas), we estimated the parameters of plumes in Siberia and its folded framing: mass flow rate of melt, thermal power, depth of origin, and diameters of plume conduits and heads. The plumes responsible for the formation of the Siberian LIP (relative thermal power Ka = 114.9) and the West Siberian rift system (Ka = 37.8 for each of the three plumes) originated at the core-mantle boundary and discharged in the presence of a refractory layer in the lithosphere. The Vilyui plume (Ka = 27.3) originated at the core-mantle boundary and caused the formation of a rift system in the absence of a refractory layer. The plumes that produced the Hangayn (Ka = 6.8) and Henteyn (Ka = 5.5) batholiths were initiated at the core-mantle boundary and had mushroom-shaped heads. The plumes responsible for the formation of rift zones might have originated at the 670 km discontinuity.
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