The study of tourmalinization and related textures in granites, aplites and pegmatites of Faghireh-Khakoo area (South of Hamadan)

Category Other
Group GSI.IR
Location 20th symposium on geosciences
Holding Date 16 April 2008

     The study area is a part of the Alvand intrusive complex which is located in the Sananadaj-Sirjan zone. This complex comprises various basic to acid (mafic to felsic) plutonic and hypabyssal rocks and veins which tourmalinization is common in their granites, aplites and pegmatites so that resulted in spectacular structures and textures. In addition to prismatic tourmaline crystals, tourmalinization is occurred in 3 various forms:
1-extensive tourmalinization as generation of tourmaline nodules (cocards) in aplites,
2- vein and veinlet tourmalinization,
3-tourmaline-feldspar intergrowth, causing exclusive intergrowth texture in pegmatites of study area.
The tourmalinization in granites of this area is occurred in pneumatolitic stage due to boron rich fluids in rock fractures. In aplites, probably due to gas (pneumatolitic) differentiation in silicic boron rich fluids of late stage crystallization, tourmalinization is occurred as tourmaline rich nodules. In pegmatites, tourmaline emplacement has begun from margins, fractures and weak planes of lattice of feldspars (such as cleavage and twining) and extended to other parts of crystals so that various stages of tourmalinization is simply recognizable.