Home – Home – Jornals – Russian Geology and Geophysics 2002 number 1

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 (PH₂0 = 0,7-1,0P_tot) 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 Kfs Q + Sph + Ap + Ilm 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.