SUPERSUBDUCTION ANATECTIC GRANITOIDS OF THE URALS
G. B. Fershtater, F. Bea, N. S. Borodina, E. A. Zin'kova, P. Montero, and E. S. Shagalov
Keywords: Subduction, anatexis, fluid, magmatism, substratum, restite, melt, Urals
Pages: 42-56
Abstract
The most intense supersubduction anatexis in the Urals occurred in the late Early Carboniferous (340-320 Ma ago). It is characterized by high water saturation ( PH 20 = 0,7-1,0 Ptot) of the generated melts, caused by additional supply of water into the zone of anatexis. Anatexis occurs in the zone of stability of main hydroxyl-bearing minerals - biotite and hornblende accumulated in restite. Anatectic melt is either of tonalite or granodiorite composition. This composition of melt is due to a basite substratum whose degree of melting provides about 40% of melt sufficient for separation from the substratum. Outmelting of granitoid melts is accompanied by water basite magmatism. The products of this magmatism are represented by high-Sr hornblende gabbros, which are the source of heat and matter (substratum) for anatexis. Gabbroids and products of crystallization of anatectic melt share the mineral composition: Hbl + Bt + An 20-45 + Ep ![](http://www.sibran.ru/biblio/plusmin.gif) Kfs ![](http://www.sibran.ru/biblio/plusmin.gif) Q + Sph + Ap + Ilm ![](http://www.sibran.ru/biblio/plusmin.gif) Mt Prolonged basite magmatism inecreased the crust thickness from below, thus causing its underplating in a suture megablock, in the adjacent island-arc zones, and in the regions of development of supersubduction tonalite-granodiorite massifs in the continent-marginal zones.
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