New evidence for Jurassic continental rifting in the northern Sanandaj Sirjan Zone,western Iran: the Ghalaylan seamount,southwest Ghorveh |
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| Authors: | Hossein Azizi Fatemeh Nouri Robert J Stern Marie Azizi Federico Lucci Yoshihiro Asahara |
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| Institution: | 1. Mining Department, Faculty of Engineering, University of Kurdistan , Sanandaj, Iran azizi1345@gmail.com https://orcid.org/0000-0001-5686-4340;3. Mining Department, Faculty of Engineering, University of Kurdistan , Sanandaj, Iran;4. Geosciences Department, University of Texas at Dallas , Richardson, TX, USA;5. Earth Sciences Department, Faculty of Basic Sciences, University of Kurdistan , Sanandaj, Iran;6. Dipartimento di Scienze, Università Roma Tre , Roma, Italy;7. Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University , Nagoya, Japan |
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| Abstract: | ABSTRACT We address the growing controversy about the tectonic setting in which Jurassic magmatism of Iran occurred: arc or continental rift. In the Ghorveh area of the northern Sanandaj Sirjan zone (SaSZ), the Ghalayan metabasites are interlayered with marble and schist and locally cut by acidic dikes. Zircon U-Pb dating of the metabasitic rocks shows that these crystallized at ca. 145–144 Ma ago in the Late Jurassic (Tithonian). This complex was metamorphosed in the lower greenschist facies, however, some protolithic structures such as pillow lava and primary minerals are preserved. The metabasites are tholeiites with low SiO2 (45.6–50.5 wt.%), moderate Al2O3 (11.3–17.0 wt.%), and high TiO2 (0.7–2.9 wt.%) and Fe2O3 (9.4–14.1 wt.%). The Ghalayan metabasites are enriched in Light rare earth elements (LREEs) without significant Nb, Ta, Pb, Sr and Ba anomalies, similar to modern continental intra-plate tholeiitic basalts such as Afar and East African rifts. The Ghalaylan metabasites show wide ranges for 87Sr/86Sr(i) (0.7039–0.7077) and positive εNd(t) values (+0.1 to +4.6). These isotopic compositions are similar to those expected for slightly depleted subcontinental lithospheric mantle sources. Independently built discrimination diagrams indicate an intra-continental rifting regime for the source of Jurassic metabasites in the northern SaSZ. Geochemical and tectonic evidence suggests that rifting or a mantle plume was responsible for volcanic activity in the Upper Jurassic SaSZ. Considering the variation of ages of basaltic volcanism along the SaSZ, we suggest that Ghalayan basaltic magmatism reflected a submarine volcano that formed as part of the late stage continental rift, similar to Afar in the East African Rift system. Our results indicate that an extensional tectonic regime dominated SaSZ tectonics in the Middle to Late Jurassic. |
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https://orcid.org/0000-0001-5686-4340;3. Mining Department, Faculty of Engineering, University of Kurdistan , Sanandaj, Iran;4. Geosciences Department, University of Texas at Dallas , Richardson, TX, USA;5. Earth Sciences Department, Faculty of Basic Sciences, University of Kurdistan , Sanandaj, Iran;6. Dipartimento di Scienze, Università Roma Tre , Roma, Italy;7. Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University , Nagoya, Japan