Thermobarometry and tectonic setting interpretation of blue schist facies rocks from the Asalem metamorphic complex (NW Rasht)


1 قزوین-دانشگاه بین المللی امام خمینی-دانشکده علوم پایه-گروه زمین شناسی

2 گروه زمین شناسی دانشگده علوم پایه دانشگاه بین المللی امام خمینی

3 Department of Geology, Faculty of Sciences, Imam Khomeini International University, Qazvin, Iran


A metamorphic complex containing green schist, mica schist and serpentinite exposed in the Asalem area (NW Rasht). The occurrence of blue schist facies rocks in this complex are reported here for the first time. Mineralogical paragenesis of metabasitic blueschists consists of glaucophane, epidote, chlorite and phengite while there are garnet, phengite, chloritoide and feldspar in the metapelitic rocks. The metamorphic conditions of these rocks calculated by THERMOCALC software, petrogenetic grids and conventional thermobarometrs, are 7 to 12 Kb and 350 to 550 ºC for pressure and temperature, Pressure and temperature conditions of metamorphism and protolith diversity (metapelite, marble, metabasite, serpentinite) of the Asalem metamorphic complex indicate that they were created in the Pacific Ocean-type accretionary prisms (B-type blueschists). The studied metamorphic complex likely originated along the Paleotethys suture zone, as a result of the subduction onset of the Paleotethys oceanic basin beneath the southern margin of Luarasia during Carboniferous.