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Geological Society, London, Special Publications; 1984; v. 16; p. 173-181;
DOI: 10.1144/GSL.SP.1984.016.01.13
© 1984 Geological Society of London

Western Pacific Region

Heat flow and magmatism in the NW Pacific back-arc basins

P. M. Sychev & A. Y. Sharaskin

Sakhalin Complex Scientific Research Institute, Far East Science Centre, U.S.S.R. Academy of Sciences, Novoalexandrovsk 694050, Sakhalin, U.S.S.R.
Vernadsky Institute of Geochemistry, Academy of Sciences of the U.S.S.R., Vorobyevskoe Shausse 47-a, 117334, Moscow B-334, U.S.S.R.

High heat flow is a characteristic feature of a number of back-arc basins of the NW Pacific Ocean. Temperature calculations related to the geological and geophysical data reveal that the sources of the high heat flow are located at shallow depths in the upper mantle and probably are zones of partial melting. From the location of these zones, the character and composition of magmas, and the evolution of the basins, it is proposed that injection of magmas, by a magmafracting (magmarupture) mechanism, is the main deep process within the back-arc basins. It is assumed that ‘primitive’ ultrabasic magma rises from great depths in the mantle along vertical or sub-vertical channels and is then distributed nearly horizontally close to the lower boundary of the crust, under the back-arc basins. The initial cause of the magmatic process is apparently a stepped gravity differentiation, beginning perhaps on the core-mantle boundary, and not the supposed subduction of oceanic lithosphere.