Writers : Ghalamghndi.J, Vosoughi AbedinI.M, Herve Bellon , EmRmi.M. H , Pourmali.M and IL Rasbid
Refference : Geosciences Scientific Quarterly Journal,No.:47-48,P.:16
Publishing Year : 1382

Abstract :
Oshnaviyeh plutonic complex (OPC), the western member of Urumiyeh-Golpayehgan intrusive plutons is located in northern part of Sanandaj-Sujan Zone. OPC, exposing in an area of about 700 km2, comprises 10 plutons that can be divided into three suites, i.e., diorite, granite and alkali syenite -alkali granite. Dioritic bodies are the oldest intrusive rocks of the region, which on the basis of the field study , their relative age of emplacement is estimated to be Post- Jurassic and Pre-Miocene. However, with respect to the age of other similar intrusive bodies in Nagbadeh area, they are most likely of Post Early Cretaceous - Pre Miocene age. Hybrid intrusive rocks, occurring at the contact of dioritic and granitic rocks may suggest a simultaneous emplacement of both magmas. Syemtic pluton from alkali syemte -alkali granite suite has intruded dioritic and granitic rocks, in contrast, flourine bearing alkali granite pluton from this suite shows no contact with other igneous rocks in he area.
K-Ar age detenninations obtained on amphibole specimens from diorite suite are 91.9±2.3, 94.1±2.3 and 100±2.4 Ma, and on iotite specimens from granite suite are 100±1.5 to 98.9±1.5 Ma. Chronology study using same method on arfvedsonite specimens from syenite pluton shows 78.9±3.1, 79.6±19 and 81.7±2.0 Ma and on K-fledspar samples of flourine bearing alkal granite pluton from the alkali syenite -alkali granite suite presents 76±3.4 and 77.1±1.8. Therefore, based on field evidence anc K/Ar age dating, OPC presumably formed during two episodes: granite and diorite suites formed simultaneously at about lO( Ma, then plutons of alkali syenite -alkali granite suite emplaced at about 80 Ma.
Subject List : Geochronology