Writers : Esmaeili,Valizade,Hasanzade,Blown,Herve
Refference : Geosciences Scientific Quarterly Journal,No.41_42
Publishing Year : 1381

Abstract :
Shah-Kuh granitic massif (South of Birjand) is mainly composed of monzograrnte- granodiorite and syenogranite units which enclose large microgranitic bodies. Small outcrups of greisenized granites, occurred in the eastern part. The massif is cut by dacitic, andesitic, and aplitic dykes and mineralized quartz- tourmaline veins.
The Presence of magnetite, magmatic allanite, amphibole and the lack of muscovite, alurninosilicates and pegniatitic veins attests to the I-type affiliation of these rocks. The monzogranite- granodiorite unit is distinct from syenogranites by the lack of amphibole, lower Xmg of biotites and lower An% of plagioclase in the later.
Based on thin section studies, four types of microstructures including magmatic, submagmatic, high temperature subsolidus and low temperature subsolidus (mylonitic) are recognized.
Hydrothernial alteration effects on the pluton can be summarized as:
1-Formation of K-feldspar megactysts; 2- Alteration of biotite to muscovite (or K-feldspar) + rutile + sulfides; 3- Formation of pale green biotite from magmatic biotite; 4-Chloritization of biotite; and 5-Complete destruction of biotite and feldspar during greisenization.
K-Ar dating was performed 13 biotite separates from main rock types. This gives an age of 165+- 3.1 Ma (middle Jurassic) for the Shah- Kuh granite. With an average age of 168.3+_ 3.17 Ma, the microgranites represent the oldest unit among the dated samples. Monzogranite - grandiorite and syenogranite unites, which have been dated 165.23.1 (Ma)and 161.6 + 2.5 (Ma), respectively, are somewhat younger unites. It can be concluded that all of the granitic rock types in the suite, formed in a very short period of time.
Subject List : Geochronology, Granitoeid