QE270 : Petrology and geochemistry of Asbkeshan granitoidic intrusion
Thesis > Central Library of Shahrood University > Geosciences > MSc > 2015
Authors:
Abstarct: The study area is located in 290 km away SE of Shahrood. Asbkeshan and Gandab granitoidic plutons cropped out in east of Asbkeshan village and in 9 km west of Garmab village, respectively. The mentioned area is a part of north of Central Iran structural zone or in Sabzevar subzone in detail. Asbkeshan and Gandab granitoidic plutons intruded in Upper Cretaceous volcanocedimentary rocks. These plutons have NE-SW general trend. Lithological composition of these plutons vary from diorite to tonalite. These rocks show granular, granophyry and poikilitic textures. Plagioclase, quartz and orthoclase are essential rock forming minerals of these rocks. Among the mentioned minerals, plagioclase has the highest frequency. These rocks have hornblend but don't have biotite (as the minor rock forming minerals). The investigated rocks have calk alkaline nature. Their variation trends of major element oxides and trace element versus SiO2 indicate that these plutons originated by the same petrological mechanisms. baxsed on geochemical diagrams, fractional crystallization has been the main processes during the formation and evolution of these granitoidic plutons. The studied granitoidic rocks are belong to I-type granitoids and in tectonic-setting discrimination diagrams plot in volcanic arc of active continental margin.In spider diagrams, the studied granitoidic rocks depleted in P,Ti,Nb and Ta and enriched in K and Ba.These features are charactristics of volcanic arc magmatism. Magma forming of these plutons produced from partial melting of Sabzevar- Darouneh branch of subducted oceanic lithosphere beneath of Sabzevar subzone and then ascent to upper levels of crust from deep fractures and emplaced in Upper Cretaceous volcanosedimentary sequence in Eocene time.
Keywords:
#I-type granitoid #Subduction #Calk-alkaline #Cretaceous #Eocene #Asbkeshan #Gandab #Sabzevar Link
Keeping place: Central Library of Shahrood University
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Keeping place: Central Library of Shahrood University
Visitor: