QE548 : Isotopic geochemistry, petrogenesis and emplacement mechanism of the Garagheh granitoid pluton (East of Iran)
Thesis > Central Library of Shahrood University > Geosciences > PhD > 2023
Authors:
Nazanin Sarhadi [Author], Mehdi Rezaei-Kahkhaei[Supervisor], Habibolah Ghasemi[Advisor]
Abstarct: The Garagheh granitoid pluton is located 90 km northwest of Zahedan and elliptically in the northwest of the Zahedan-Saravan magmatic belt in the Suture Zone Sistan. The intrusion of the pluton into the flysch sediment (Eocene) has caused contact mextamorphism in the surroundings. The Garagheh granitoid pluton with SiO2 between 63 and 76 wt% has two magmatic pulses biotite granite (mextamorphosed) and granodiorite (less mextamorphosed). The dioritic dykes have slightly penetrated the rocks with EW and NS trends. Tectonic processes during and after the placement of the pluton have caused low to moderate deformations in the rocks of the region. The constituent minerals of the Garagheh pluton include plagioclase, biotite, quartz, K-feldspar, iron-titanium oxides, zircon, apatite and allanite. The dominant texture of the rocks of The Garagheh pluton is granular type and textures such as poikilitic, perthitic and myrmekite are also observed in them. This pluton is high potassium calc-alkaline, mextalaluminous to slightly peraluminous and type I. Also, geochemical data show that; The rocks are enriched in LIL and LREE elements, while they are depleted in HREE elements. According to the spider diagram, the granitoids show negative anomalies of Ti, Nb, Ba and also positive Pb anomalies. Therefore, Garagheh granitoid pluton are formed from the melting of amphibolite rocks with crustal contamination. The dykes show negative P and Nb anomalies and positive Pb anomalies which are the result of mixing mantle melt and melt from the lower crust. Thermobarometric studies show the stopping temperature and exchange and final equilibrium of biotite in granite biotite rocks at a temperature of 615-673±12 °C and a pressure of 1.1-1.5-5 kbar and in granodiorites. It is at a temperature of 682-692±12 °C and a pressure of 0.5-0.7±0.3 kbar. The clinopyroxenes in the dikes are of diopside type and baxsed on thermobarometry, clinopyroxenes were formed at temperatures of 1053-1110±11 °C and pressures of 5.5±0.92 to 8.2±0.82. The U-Th-Pb analyses performed by SIMS method shows that biotite granites were emplaced in 44.5±0.7 Ma and granodiorites in 44.3±0.6 Ma. baxsed on the data obtained from the magnetic susceptibility anisotropy (AMS), the average magnetic susceptibility values are between 10.28 µSI and 301 µSI. Their deformation factor (P) varies between 0.8 and 15.5 percent. The value of the shape factor in most samples has positive values and a cookie shape. Magnetic orientations throughout the pluton are on average between 31 and 60.8 degrees and show the trend of northwest-southeast. The parallelism of the foliations with the margin of the pluton and the presence of nearby mextamorphic rocks shows that during the injection of magma, biotite, granites and granodiorites were placed under the host rock parallel to the schistosity in the form of laccolith with a slope of 45° in the north-east direction.
Keywords:
#Sistan Suture Zone #Zahedan-Saravan magmatic belt #Garagheh granitoid pluton #Mineral chemistry #U-Pb data #Anisotropy of Magnetic Susceptibility. Keeping place: Central Library of Shahrood University
Visitor: