Some aspect of petrography and geochemistry of the western Avaj gabbros

Category Petrology
Group GSI.IR
Location 23th symposium on geosciences
Holding Date 05 May 2008

      The Mesozoic very low to low grade regionally metamorphic rocks of the Razan zone in the west of Avaj had intruded comparative their foliation by several small-elongated intrusions, with NW-SE direction. The intrusive rocks show a gabbroic composition and fine to medium grain granular texture with a predominant plagioclase, clinopyroxene and variable amount of hornblende and Fe-Ti oxides. The gabbros in their chilled margin have textures that vary from porphyritic to ophitic and subophitic with phenocrysts of euhedral plagioclase and clinopyroxene set in a microcrystalline to hypocrystalline groundmass characterized by plagioclase, clinopyroxene and opaques.
   The gabbros and chilled margin samples, analyzed from the different parts of pluton, have same restricted major element composition and are silica saturated. The Mg# rang for the gabbros are between 0.4 and 0.65, thus suggesting that the Avaj gabbros represent an evolved composition instead a primary melt. The gabbros have similar MgO and FeOt (total iron as FeO) contents indicating that they were generated at similar depths and temperatures.

tags: QAZVIN