QE293 : U-Pb dating of North Zahedan granitoid plutons, SE Iran
Thesis > Central Library of Shahrood University > Geosciences > MSc > 2016
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Abstarct: The NE Zahedan granitoids (Lakhshak, Zargoli and Gapdan plutons) with 280 Km2 are parts of Zahedan-Saravan granitic belt. These granitoids represent Cenozoic magmatism in eastern Iran. They are granodiorite and biotite granite in compositions with granular texture which were cut by numerous dykes. The NE Zahedan granitoids mainly consist of plagioclase, K-feldspar, quartz, hornblende and biotite with subordinate zircon, apatite and allanite and opaque minerals. Dykes are the youngest igneous rocks in the study area and have NE-SW strikes. They consist of plagioclase, quartz, sanidine, hornblende and biotite. Their accessory minerals are zircon, apatite and Fe-Ti oxides. Field studies, petrographic and dating show that granodiorite intrusive rocks of Gapdan, Zargoli, South Zargoli and Lakhshak were crystallized in 43, 42, 43/1 and 29 Ma ago; and they are located in 51, 52, 57 and 75 Kilometers from ophiolites, respectively. The initial 87Sr/86Sr and 143Nd/144Nd ratios show systematic changes and decrease toward the East like what was observed in Sierra Nevada Batholith (North America). These ratios show that the parent magma of Gapdan, Zargoli and South Zargoli plutons are more likely to crustal materials while the parent magma of Lakhshak pluton show a participation of oceanic lithosphere, mantle and crustal melts. The trace elements can be useful to determine the origin of the parent magma. Chondrite-normalized REE patterns indicate the depth and consequently the source of magma formation of the Oligocene igneous rocks were more than Eocene igneous rocks; because the later ones show less slip in REE pattern in compare with Oligocene igneous rocks suggestion that the formed in deeper levels. Considering that Garnet is stable in depths more than 35 km, it seems that the parent magma of Oligocene rocks was derived from depths of more than 35 km in a subduction environment. These results are also consistent with EPMA analyses, in which the reservoir deep of the Eocene magmas (~18km for example Zargoli pluton) was less than Oligocene magmas (for example ~25 km for Lakhshak pluton). The chonderite normalized REE patterns of Eocene igneous rocks show upward trend which represent that their parent magmas were derived from an amphibolites source. This is also confirmed by binary diagram of (La/Yb)N versus YbN, while the Oligocene igneous rocks plot within the garnet amphibolite filed which means they were derived from deeper depths.
Keywords:
#U-Pb dating #Zircon #Titanite #Granodiorite #Sistan Zone #Iran Link
Keeping place: Central Library of Shahrood University
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Keeping place: Central Library of Shahrood University
Visitor: