Granite of Zahedan, Southeastern Iran
Abstract
The late-Eocene-early Oligocene Zahedan granitic rocks are the most important intrusive rocks in the Nehbandan-Khash tectonic zone located in the east of Iran. This zone is composed of oceanic crust rocks such as flysch facies, mafic and ultramafic rocks that are intruded by the Zahedan granitic rocks and extend for a long distant in a narrow zone almost with a north-south trend. Samples of these rocks were taken from Garaghe mountain in the northwest of Zahedan to Bug mountain near to Mirjave city about 200-km length. The Zahedan intrusive rocks occurred as batholiths and stocks on outcrops that are cut by a lot of north-south dykes in some areas. The petrographic studies show some variations in mineralogy, textures and alteration. The granitic rocks are generally medium grain and granular in texture. Other textures are porphyritic, perthitic, granophyric, skeletal, pegmatitic and aplitic. The granitic rocks are composed of orthoclase, plagioclase, quartz, and biotite with or without amphibole and clinopyroxene. Some common accessory minerals are sphene, zircon, and magnetite. Secondary processes formed chlorite, siricite, calcite, clay and epidote group minerals from these granites. Tourmaline, garnet and andalusite are also reported from these rocks. Many mineralogical characteristics are similar as I type granitoids and some of them are similar as S type granitoids. Chemically they are peraliminus and similar S type granitoids. The granitic rocks are generally monzogranite, granodiorite and tonalite in composition and are belong to calc-alkaline magmatic series. Major and trace-element composition of the Zahedan granitic rocks shows similarities to subduction and collisions tectonic settings such as Island-arc, continental-arc, and continent-continent collision settings. However, there are a few volcanic rocks in this area. Consequently, the Zahedan granitic rocks probably formed from partial melting of oceanic-crust rocks such as ophiolites, flysch facies that consist of sandstone, shale and siltstone in a continental-continental collision setting.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....4933B