Thermobarometry, geochemistry and tectonic setting interpretation of migmatitic metabasites of Soltan Abad metamorphic complex (NE Sabzevar)

Soltan Abad metamorphic complex is located in NE of the Sabzevar ophiolites. Migmatitic metabasites are exposed next to the trondhjemitic body, in the western part of this metamorphic complex. Thermobarometric calculations of these metabasites indicate that the metamorphic process has taken place at temperature higher than 650°C and pressure more than 15 Kb. Under these conditions, migmatitic structures have been created by partial melting process as Grt-hornblenditic melanosome and tonalitic-trondhjemitic leucosome with adakitic characteristics. Rare earth elements pattern of melanosome as positive slope and heavy rare earth elements enrichment and amphibole-bearing leucosome as negative slope and light rare earth elements depletion indicating partial melting event has occurred at high pressure garnet stability conditions as well. Upward convex of rare earth elements pattern in the amphibole-rich leucosome and middle rare earth elements enrichment are compatible with amphibole accumulation. Adakitic composition of leucosome in the migmatitic metabasites and the age of their generation are similar to the adjacent tonalitic-trondhjemitic bodies. Probable scenario for the migmatitic metabasites contain metamorphism and partial melting of subducted oceanic slab at depth higher than 50 Km in a hot subduction zone and the creation of garnet-hornblenditic melanosome and tonalitictrondhjemitic leucosome with adakitic characteristics.